Microglia and Parkinson

1. Arimoto T, Bing G (2003) Up-regulation of inducible nitric oxide synthase in the substantia nigra by lipopolysaccharide causes Microglial activation and neurodegeneration. Neurobiol.Dis. 12:35-45
   Abstract: The present study was designed to examine whether expression of iNOS was involved in LPS-induced neurodegeneration in rat substantia nigra (SN) and to study the role of NO in the loss of the SN dopaminergic neurons. In Western blot analysis, iNOS was induced in the SN after injection of LPS in a time- and dose-dependent manner. Immunofluorescence and immunohistochemical analyses revealed that the iNOS is located in a fully activated Microglia with the characteristic amoeboid morphology. Furthermore, LPS-induced loss of dopaminergic neurons was significantly inhibited by the administration of L-N(G)-nitroarginine, a selective inhibitor of NOS, and the glucocorticoid dexamethasone. These inhibiting agents for iNOS reduced LPS-induced Microglial activation, suggesting that NO has a role in inflammatory-mediated Microglial activation. These results demonstrate that LPS induces the expression of iNOS in activated Microglia in the SN, and that NO and/or its metabolites may play a crucial role in inflammation-mediated degeneration of dopaminergic neurons

2. Asanuma M, Miyazaki I, Tsuji T, Ogawa N (2003) [New aspects of neuroprotective effects of nonsteroidal anti-inflammatory drugs]. Nihon Shinkei Seishin Yakurigaku Zasshi 23:111-119
   Abstract: Nonsteroidal anti-inflammatory drugs (NSAIDs) exert anti-inflammatory, analgesic and antipyretic activities and are involved in the suppression of prostaglandin synthesis by inhibiting cyclooxygenase (COX), a prostaglandin synthesizing enzyme. It has been recently revealed that NSAIDs also possess inhibitory effects on the generating system of nitric oxide radicals and modulating effects on transcription factors and nuclear receptors which are related to inflammatory reactions. Since it has been reported that inflammatory processes are associated with the pathophysiology of several neurodegenerative diseases and that NSAIDs inhibit amyloid beta-protein-induced neurotoxicity to reduce the risk for Alzheimer's disease, a number of studies have been conducted focusing on the neuroprotective effects of NSAIDs. It has been clarified that the drugs exert neuroprotective effects, which are not related to their COX-inhibiting property, on pathophysiology of various neurological disorders. In this article, new aspects of neuroprotective effects of NSAIDs have been reviewed, especially, in Alzheimer's disease and Parkinson's disease, discussing various pharmacological effects of NSAIDs other than their inhibitory action on COX

3. Beal MF (2003) Mitochondria, oxidative damage, and inflammation in Parkinson's disease. Ann.N.Y.Acad.Sci. 991:120-131
   Abstract: The pathogenesis of Parkinson's disease (PD) remains obscure, but there is increasing evidence that impairment of mitochondrial function, oxidative damage, and inflammation are contributing factors. The present paper reviews the experimental and clinical evidence implicating these processes in PD. There is substantial evidence that there is a deficiency of complex I activity of the mitochondrial electron transport chain in PD. There is also evidence for increased numbers of activated Microglia in both PD postmortem tissue as well as in animal models of PD. Impaired mitochondrial function and activated Microglia may both contribute to oxidative damage in PD. A number of therapies targeting inflammation and mitochondrial dysfunction are efficacious in the MPTP model of PD. Of these, coenzyme Q(10) appears to be particularly promising based on the results of a recent phase 2 clinical trial in which it significantly slowed the progression of PD

4. Cardenas H, Bolin LM (2003) Compromised reactive microgliosis in MPTP-lesioned IL-6 KO mice. Brain Res. 985:89-97
   Abstract: Reactive gliosis, the cellular manifestation of neuroinflammation, is a pathological hallmark of neurodegenerative diseases including Parkinson's disease. The persistent gliosis observed in the Parkinson's disease substantia nigra (SN) and in humans and animals exposed to the neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) may represent a chronic inflammatory response that contributes to pathology. We have previously shown that in the absence of interleukin-6 (IL-6) dopaminergic neurons are more vulnerable to MPTP. Since IL-6 is both an autocrine and paracrine proliferation factor for CNS glia, we investigated reactive gliosis in MPTP-lesioned IL-6 (-/-) mice. While astrogliosis was similar in injured IL-6 (+/+) and IL-6 (-/-) SN pars compacta (pc), microgliosis was severely compromised in IL-6 (-/-) mice. In the absence of IL-6, an acute reactive microgliosis was transient with a complete absence of reactive Microglia at day 7 post-lesion. Extensive reactive microgliosis was observed in the SNpc of MPTP-lesioned IL-6 (+/+) mice. Because glial derived inducible nitric oxide synthase (iNOS) has been implicated in dopaminergic cell death, we examined glial iNOS expression in the IL-6 genotypes to determine if it correlated with the greater vulnerability and reduced microgliosis observed in the MPTP-lesioned IL-6 (-/-) nigrostriatal system. Both reactive Microglia and astrocytes expressed iNOS in the lesioned SNpc. In the IL-6 (-/-) mice, Microglial iNOS expression diminished as reactive microgliosis declined. The data suggest IL-6 regulation of Microglia activation, while iNOS expression appears to be secondary to cell activation

5. Choi SH, Joe EH, Kim SU, Jin BK (2003) Thrombin-induced Microglial activation produces degeneration of nigral dopaminergic neurons in vivo. J.Neurosci. 23:5877-5886
   Abstract: The present study examined whether thrombin-induced Microglial activation could contribute to death of dopaminergic neurons in the rat substantia nigra (SN) in vivo. Seven days after thrombin injection into the SN, tyrosine hydroxylase immunohistochemistry showed a significant loss of nigral dopaminergic neurons. In parallel, thrombin-activated Microglia, visualized by immunohistochemical staining using antibodies against the complement receptor type 3 (OX-42) and the major histocompatibility complex class II antigens were also observed in the SN, where degeneration of nigral neurons was found. Reverse transcription PCR at various time points demonstrated that activated Microglia in vivo exhibited an early and transient expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and several proinflammatory cytokines, including interleukin 1beta (IL-1beta), IL-6, and tumor necrosis factor alpha. Western blot analysis and double-label immunohistochemistry showed an increase in the expression of iNOS and COX-2 and the colocalization of these proteins within Microglia. The thrombin-induced loss of SN dopaminergic neurons was partially inhibited by NG-nitro-L-arginine methyl ester hydrochloride, an NOS inhibitor, and by DuP-697, a COX-2 inhibitor. Additional studies demonstrated that extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) were activated in the SN as early as 30 min after thrombin injection, and that these kinases were localized within Microglia. Inhibition of ERK1/2 and p38 MAPK reduced iNOS and COX-2 mRNA expression and rescued dopaminergic neurons in the SN. The present results strongly suggest that Microglial activation triggered by endogenous compound(s) such as thrombin may be involved in the neuropathological processes of dopaminergic neuronal cell death that occur in Parkinson's disease

6. Collier TJ, Steece-Collier K, McGuire S, Sortwell CE (2003) Cellular models to study dopaminergic injury responses. Ann.N.Y.Acad.Sci. 991:140-151
   Abstract: The study of immature midbrain dopamine (DA) neurons and dopaminergic cell lines in culture provides an opportunity to analyze mechanisms of cell death and avenues of potential intervention relevant to Parkinson's disease (PD) in a controlled environment. Use of cell culture models has provided evidence for different sets of intracellular changes associated with DA neuron death following exposure to the neurotoxins 6-hydroxydopamine and MPP+, supporting roles for oxidative stress and impaired energy metabolism as significant factors endangering these cells. Interference with death of cultured DA neurons has provided an initial test system that has yielded all the identified neurotrophic factors for DA neurons. More recent work suggests that combinations of molecules secreted by myelinating glial cells and their precursors provide even greater neuroprotection for DA neurons. Most recently, culture systems have been used to implicate Microglial activation in DA neuron injury, providing impetus to the investigation of antiinflammatory agents as potential therapeutics for PD. Thus, cell culture models provide an important bidirectional link between mechanistic studies and clinically relevant observations

7. Gao HM, Liu B, Hong JS (2003) Critical role for Microglial NADPH oxidase in rotenone-induced degeneration of dopaminergic neurons. J.Neurosci. 23:6181-6187
   Abstract: Increasing evidence has suggested an important role for environmental toxins such as pesticides in the pathogenesis of Parkinson's disease (PD). Chronic exposure to rotenone, a common herbicide, reproduces features of Parkinsonism in rats. Mechanistically, rotenone-induced dopaminergic neurodegeneration has been associated with both its inhibition of neuronal mitochondrial complex I and the enhancement of activated Microglia. Our previous studies with NADPH oxidase inhibitors, diphenylene iodonium and apocynin, suggested that NADPH oxidase-derived superoxide might be a major factor in mediating the Microglia-enhanced rotenone neurotoxicity. However, because of the relatively low specificity of these inhibitors, the exact source of superoxide induced by rotenone remains to be further determined. In this study, using primary mesencephalic cultures from NADPH oxidase--null (gp91phox-/-) or wild-type (gp91phox+/+) mice, we demonstrated a critical role for Microglial NADPH oxidase in mediating Microglia-enhanced rotenone neurotoxicity. In neuron--glia cultures, dopaminergic neurons from gp91phox-/- mice were more resistant to rotenone neurotoxicity than those from gp91phox+/+ mice. However, in neuron-enriched cultures, the neurotoxicity of rotenone was not different between the two types of mice. More importantly, the addition of Microglia prepared from gp91phox+/+ mice but not from gp91phox-/- mice to neuron-enriched cultures markedly increased rotenone-induced degeneration of dopaminergic neurons. Furthermore, apocynin attenuated rotenone neurotoxicity only in the presence of Microglia from gp91phox+/+ mice. These results indicated that the greatly enhanced neurotoxicity of rotenone was attributed to the release of NADPH oxidase-derived superoxide from activated Microglia. This study also suggested that Microglial NADPH oxidase may be a promising target for PD treatment

8. Gao HM, Hong JS, Zhang W, Liu B (2003) Synergistic dopaminergic neurotoxicity of the pesticide rotenone and inflammogen lipopolysaccharide: relevance to the etiology of Parkinson's disease. J.Neurosci. 23:1228-1236
   Abstract: Parkinson's disease (PD) is characterized by a progressive degeneration of the nigrostriatal dopaminergic pathway resulting in movement disorders. Although its etiology remains unknown, PD may be the final outcome of interactions among multiple factors, including exposure to environmental toxins and the occurrence of inflammation in the brain. In this study, using primary mesencephalic cultures, we observed that nontoxic or minimally toxic concentrations of the pesticide rotenone (0.5 nm) and the inflammogen lipopolysaccharide (LPS) (0.5 ng/ml) synergistically induced dopaminergic neurodegeneration. The synergistic neurotoxicity of rotenone and LPS was observed when the two agents were applied either simultaneously or in tandem. Mechanistically, Microglial NADPH oxidase-mediated generation of reactive oxygen species appeared to be a key contributor to the synergistic dopaminergic neurotoxicity. This conclusion was based on the following observations. First, inhibition of NADPH oxidase or scavenging of free radicals afforded significant neuroprotection. Second, rotenone and LPS synergistically stimulated the NADPH oxidase-mediated release of the superoxide free radical. Third and most importantly, rotenone and LPS failed to induce the synergistic neurotoxicity as well as the production of superoxide in cultures from NADPH oxidase-deficient animals. This is the first demonstration that low concentrations of a pesticide and an inflammogen work in synergy to induce a selective degeneration of dopaminergic neurons. Findings from this study may be highly relevant to the elucidation of the multifactorial etiology of PD and the discovery of effective therapeutic agents for the treatment of the disease

9. Gao HM, Liu B, Zhang W, Hong JS (2003) Synergistic dopaminergic neurotoxicity of MPTP and inflammogen lipopolysaccharide: relevance to the etiology of Parkinson's disease. FASEB J. 17:1957-1959
   Abstract: Parkinson's disease (PD) is a profound movement disorder resulting from progressive degeneration of the nigrostriatal dopaminergic pathway. Although its etiology remains unknown, increasing evidence suggests the involvement of multiple factors such as environmental toxins and genetic susceptibilities in the pathogenesis of PD. In this study using mesencephalic neuron-glia cultures as an in vitro PD model, we demonstrated that the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 0.1-0.5 microM) and an inflammogen lipopolysaccharide (LPS, 0.5 ng/ml) synergistically induced a progressive and selective degeneration of dopaminergic neurons. The synergistic neurotoxicity was observed when both agents were applied either simultaneously or in tandem. The synergistic neurotoxicity was more prominent when lower doses of both agents were applied for a longer period of time. Mechanistically, Microglial NADPH oxidase-mediated generation of reactive oxygen species played a pivotal role in the synergistic neurotoxicity: MPTP and LPS synergistically stimulated the NADPH oxidase-mediated release of superoxide free radical; pharmacological inhibition and genetic inactivation of NADPH oxidase prevented superoxide production and the synergistic neurotoxicity. Additionally, inhibition of nitric oxide synthase afforded significant neuroprotection, suggesting the involvement of nitric oxide in the synergistic neurotoxicity. This study lends strong support for a multifactorial etiology of PD and provides clues for therapeutic interventions

10. Gao HM, Liu B, Zhang W, Hong JS (2003) Novel anti-inflammatory therapy for Parkinson's disease. Trends Pharmacol.Sci. 24:395-401
    Abstract: Parkinson's disease (PD) is a movement disorder that is characterized by progressive degeneration of the nigrostriatal dopamine system. Although dopamine replacement can alleviate symptoms of the disorder, there is no proven therapy to halt the underlying progressive degeneration of dopamine-containing neurons. Recently, increasing evidence from human and animal studies has suggested that neuroinflammation is an important contributor to the neuronal loss in PD. Moreover, the pro-inflammatory agent lipopolysaccharide itself can directly initiate degeneration of dopamine-containing neurons or combine with other environmental factor(s), such as the pesticide rotenone, to exacerbate such neurodegeneration. These effects provide strong support for the involvement of inflammation in the pathogenesis of PD. Furthermore, growing experimental evidence demonstrates that inhibition of the inflammatory response can, in part, prevent degeneration of nigrostriatal dopamine-containing neurons in several animal models of PD, suggesting that inhibition of inflammation might become a promising therapeutic intervention for PD

11. Gao HM, Liu B, Zhang W, Hong JS (2003) Critical role of Microglial NADPH oxidase-derived free radicals in the in vitro MPTP model of Parkinson's disease. FASEB J. 17:1954-1956
    Abstract: 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) damages dopaminergic neurons as seen in Parkinson's disease. Although increasing evidence suggests an involvement of glia in MPTP neurotoxicity, the nature of this involvement remains unclear. Exploiting the advantage of cell culture systems, we demonstrated that Microglia, but not astroglia, significantly enhanced the progression of MPTP-induced dopaminergic neurodegeneration. Characterization of the temporal relationship between neurodegeneration and Microglial activation demonstrates that reactive microgliosis resulting from MPTP-initiated neuronal injury, but not direct activation, underlies the Microglia-enhanced MPTP neurotoxicity. Mechanistically, through the release of NADPH oxidase-derived reactive oxygen species, Microglia contribute to the progressive neuronal damage. Among the factors measured, the production of extracellular superoxide was the most prominent. NADPH oxidase inhibitor, apocynin, attenuated MPTP-induced dopaminergic neurodegeneration only in the presence of glia. More importantly, dopaminergic neurons from mice lacking NADPH oxidase, a key enzyme for superoxide production in immune cells, are significantly more resistant to MPTP neurotoxicity than those from wild-type controls, and Microglia dictate the resistance. This study demonstrates that reactive microgliosis triggered by MPTP-induced neuronal injury and NADPH oxidase-mediated superoxide production in Microglia constitute an integral component of MPTP neurotoxicity. This study also suggests that NADPH oxidase may be a promising target for therapeutic interventions in Parkinson's disease

12. Henningson CT, Jr., Stanislaus MA, Gewirtz AM (2003) 28. Embryonic and adult stem cell therapy. J.Allergy Clin.Immunol. 111:S745-S753
    Abstract: Stem cells are characterized by the ability to remain undifferentiated and to self-renew. Embryonic stem cells derived from blastocysts are pluripotent (able to differentiate into many cell types). Adult stem cells, which were traditionally thought to be monopotent multipotent, or tissue restricted, have recently also been shown to have pluripotent properties. Adult bone marrow stem cells have been shown to be capable of differentiating into skeletal muscle, brain Microglia and astroglia, and hepatocytes. Stem cell lines derived from both embryonic stem and embryonic germ cells (from the embryonic gonadal ridge) are pluripotent and capable of self-renewal for long periods. Therefore embryonic stem and germ cells have been widely investigated for their potential to cure diseases by repairing or replacing damaged cells and tissues. Studies in animal models have shown that transplantation of fetal, embryonic stem, or embryonic germ cells may be able to treat some chronic diseases. In this review, we highlight recent developments in the use of stem cells as therapeutic agents for three such diseases: Diabetes, Parkinson disease, and congestive heart failure. We also discuss the potential use of stem cells as gene therapy delivery cells and the scientific and ethical issues that arise with the use of human stem cells

13. Hirsch EC, Breidert T, Rousselet E, Hunot S, Hartmann A, Michel PP (2003) The role of glial reaction and inflammation in Parkinson's disease. Ann.N.Y.Acad.Sci. 991:214-228
    Abstract: The glial reaction is generally considered to be a consequence of neuronal death in neurodegenerative diseases such as Alzheimer's disease, Huntington's disease, and Parkinson's disease. In Parkinson's disease, postmortem examination reveals a loss of dopaminergic neurons in the substantia nigra associated with a massive astrogliosis and the presence of activated Microglial cells. Recent evidence suggests that the disease may progress even when the initial cause of neuronal degeneration has disappeared, suggesting that toxic substances released by the glial cells may be involved in the propagation and perpetuation of neuronal degeneration. Glial cells can release deleterious compounds such as proinflammatory cytokines (TNF-alpha, Il-1beta, IFN-gamma), which may act by stimulating nitric oxide production in glial cells, or which may exert a more direct deleterious effect on dopaminergic neurons by activating receptors that contain intracytoplasmic death domains involved in apoptosis. In line with this possibility, an activation of proteases such as caspase-3 and caspase-8, which are known effectors of apoptosis, has been reported in Parkinson's disease. Yet, caspase inhibitors or invalidation of TNF-alpha receptors does not protect dopaminergic neurons against degeneration in experimental models of the disease, suggesting that manipulation of a single signaling pathway may not be sufficient to protect dopaminergic neurons. In contrast, the antiinflammatory drugs pioglitazone, a PPAR-gamma agonist, and the tetracycline derivative minocycline have been shown to reduce glial activation and protect the substantia nigra in an animal model of the disease. Inhibition of the glial reaction and the inflammatory processes may thus represent a therapeutic target to reduce neuronal degeneration in Parkinson's disease

14. Liu B, Gao HM, Hong JS (2003) Parkinson's disease and exposure to infectious agents and pesticides and the occurrence of brain injuries: role of neuroinflammation. Environ.Health Perspect. 111:1065-1073
    Abstract: Idiopathic Parkinson's disease (PD) is a devastating movement disorder characterized by selective degeneration of the nigrostriatal dopaminergic pathway. Neurodegeneration usually starts in the fifth decade of life and progresses over 5-10 years before reaching the fully symptomatic disease state. Despite decades of intense research, the etiology of sporadic PD and the mechanism underlying the selective neuronal loss remain unknown. However, the late onset and slow-progressing nature of the disease has prompted the consideration of environmental exposure to agrochemicals, including pesticides, as a risk factor. Moreover, increasing evidence suggests that early-life occurrence of inflammation in the brain, as a consequence of either brain injury or exposure to infectious agents, may play a role in the pathogenesis of PD. Most important, there may be a self-propelling cycle of inflammatory process involving brain immune cells (Microglia and astrocytes) that drives the slow yet progressive neurodegenerative process. Deciphering the molecular and cellular mechanisms governing those intricate interactions would significantly advance our understanding of the etiology and pathogenesis of PD and aid the development of therapeutic strategies for the treatment of the disease

15. Liu B, Hong JS (2003) Role of Microglia in inflammation-mediated neurodegenerative diseases: mechanisms and strategies for therapeutic intervention. J.Pharmacol.Exp.Ther. 304:1-7
    Abstract: Evidence from postmortem analysis implicates the involvement of Microglia in the neurodegenerative process of several degenerative neurological diseases, including Alzheimer's disease and Parkinson's disease. It remains to be determined, however, whether Microglial activation plays a role in the initiation stage of disease progression or occurs merely as a response to neuronal death. Activated Microglia secrete a variety of proinflammatory and neurotoxic factors that are believed to induce and/or exacerbate neurodegeneration. In this article, we summarize recent advances on the study of the role of Microglia based on findings from animal and cell culture models in the pathogenesis of neurodegenerative diseases, with particular emphasis on Parkinson's disease. In addition, we also discuss novel approaches to potential therapeutic strategies

16. Muramatsu Y, Kurosaki R, Watanabe H, Michimata M, Matsubara M, Imai Y, Araki T (2003) Expression of S-100 protein is related to neuronal damage in MPTP-treated mice. Glia 42:307-313
    Abstract: S-100beta is a calcium-binding protein expressed at high levels in brain and is known as a marker of brain damage. However, little is known about the role of S-100beta protein during neuronal damage caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). To determine whether S-100beta protein is induced in glial cells after MPTP treatment, we investigated the expression of S-100 protein immunohistochemically, using MPTP-treated mice. We also examined the change of neurons and glial cells in mice after MPTP treatment. The present study shows that tyrosine hydroxylase (TH) immunoreactivity decreased gradually in the striatum and substantia nigra from 1 day after MPTP treatment. Thereafter, TH-immunopositive cells and fibers decreased in the striatum and substantia nigra at 3 days after MPTP treatment. In contrast, S-100-immunopositive cells and glial fibrillary acidic protein (GFAP)-immunopositive cells increased markedly in the striatum and substantia nigra at 3 days after MPTP treatment. Seven days after MPTP treatment, S-100-immunopositive cells decreased in the striatum and substantia nigra. However, the number of GFAP-immunopositive cells increased in these regions. In double-labeled immunostaining with anti-S-100 and anti-GFAP antibodies, S-100 immunoreactivity was observed only in the GFAP-positive astrocytes. These results provide evidence that astrocytic activation may play a role in the pathogenesis of MPTP-induced degeneration of dopaminergic neurons. Furthermore, the present study demonstrates that S-100 protein is expressed selectively by astrocytes, but not by Microglia, after MPTP treatment. These results provide valuable information for the pathogenesis of the acute stage of Parkinson's disease

17. Piao YS, Mori F, Hayashi S, Tanji K, Yoshimoto M, Kakita A, Wakabayashi K, Takahashi H (2003) Alpha-synuclein pathology affecting Bergmann glia of the cerebellum in patients with alpha-synucleinopathies. Acta Neuropathol.(Berl) 105:403-409
    Abstract: We carried out immunohistochemical examinations of the brains (cerebella) of patients who had suffered from Parkinson's disease (PD), diffuse Lewy body disease (DLBD) or multiple system atrophy (MSA), using antibodies specific for alpha-synuclein. Alpha-synuclein-positive doughnut-shaped structures were found occasionally in the cerebellar molecular layer in some of these patients. Double-labeling immunofluorescence and immunoelectron microscopy studies revealed that these alpha-synuclein-positive doughnut-shaped structures were located in the glial fibrillary acidic protein-positive radial processes of Bergmann glia, corresponding to the outer area of Lewy body-like inclusions, and consisted of granulo-filamentous structures. These findings indicate that, although not frequently, Bergmann glia of the cerebellum are also the targets of alpha-synuclein pathology in alpha-synucleinopathies such as PD, DLBD and MSA

18. Riess O, Berg D, Kruger R, Schulz JB (2003) Therapeutic strategies for Parkinson's disease based on data derived from genetic research. J.Neurol. 250 Suppl 1:I3-10
    Abstract: Following the identification of mutations in alpha-synuclein as the cause of some rare forms of familial Parkinson's disease (PD), genetic research has uncovered numerous gene loci of PD. Meanwhile, several neurodegenerative diseases have been shown to accumulate a-synuclein in neuronal and glial cells summarizing this group of diseases as synucleinopathies. All currently known gene defects causing PD alter the ubiquitin-proteasomal pathway of protein degradation. Identification of these disease mutations allows studying the functional consequences which lead to cellular dysfunction and cell death in cell culture and transgenic animal models, to identify therapeutic targets and to test potential protective strategies in these models

19. Saura J, Pares M, Bove J, Pezzi S, Alberch J, Marin C, Tolosa E, Marti MJ (2003) Intranigral infusion of interleukin-1beta activates astrocytes and protects from subsequent 6-hydroxydopamine neurotoxicity. J.Neurochem. 85:651-661
    Abstract: Activation of glial cells is a prevalent response to neuronal damage in brain disease and ageing, with potential neuroprotective and neurotoxic consequences. We were interested in studying the role of glial activation on dopaminergic neurons of the substantia nigra in an animal model of Parkinson's disease. Thus, we evaluated the effect of a pre-existing glial activation on the dopaminergic neuronal death induced by striatal infusion of 6-hydroxydopamine. We established a model of local glial activation by stereotaxic infusion of interleukin-1beta in the substantia nigra of adult rats. Interleukin-1beta (20 ng) induced a marked activation of astrocytes at days 2, 5 and 10, revealed by heat-shock protein 27 and glial fibrillary acid protein immunohistochemistry, but did not affect the Microglial markers OX-42 and heat-shock proteins 32 or 47. Intranigral infusion of interleukin-1beta 5 days before a striatal injection of 6-hydroxydopamine significantly protected nigral dopaminergic cell bodies, but not striatal terminals from the 6-hydroxydopamine lesion. Also, in the animals pre-treated with interleukin-1beta, a significant prevention of 6-hydroxydopamine-induced reduction of adjusting steps, but not of 6-hydroxydopamine-induced amphetamine rotations, were observed. These data show the characterization of a novel model of local astroglial activation in the substantia nigra and support the hypothesis of a neuroprotective role of activated astrocytes in Parkinson's disease

20. Sherer TB, Betarbet R, Kim JH, Greenamyre JT (2003) Selective Microglial activation in the rat rotenone model of Parkinson's disease. Neurosci.Lett. 341:87-90
    Abstract: Chronic rotenone exposure reproduces features of Parkinson's disease (PD) (Nat. Neurosci. 3 (2000) 1301; Exp. Neurol. 179 (2003) 9). We investigated the role of glial activation in rotenone toxicity in vivo. Male Lewis rats received 2-3 mg/kg rotenone per day for up to 4 weeks. In 50% of surviving rotenone-treated animals, there was nigrostriatal dopaminergic degeneration, marked by reduced tyrosine hydroxylase immunoreactivity). Extensive Microglial activation, determined by OX-42-ir, occurred in striatum and nigra of rotenone-treated animals, and was prominent before anatomical evidence of dopaminergic lesions. Microglia enlarged and developed short, stubby processes in rotenone-treated animals. Rotenone-induced Microglial activation was less pronounced in cortex. Reactive astrocytosis was minimal and limited to a thin rim around the lesion. Marked Microglial activation with minimal astrocytosis is another pathological feature of PD reproduced by rotenone treatment

21. Sugama S, Yang L, Cho BP, DeGiorgio LA, Lorenzl S, Albers DS, Beal MF, Volpe BT, Joh TH (2003) Age-related Microglial activation in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic neurodegeneration in C57BL/6 mice. Brain Res. 964:288-294
    Abstract: Microglial activation was investigated in the brains of young (3 months old) and older (9-12 months old) mice following administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Tyrosine hydroxylase (TH)-positive neuronal loss differed significantly between young and older mice. Importantly, the two groups clearly demonstrated a distinct Microglial activation pattern. In young mice which showed TH neuronal loss at 1 day (33.4%), 3 days (45.1%), 7 days (47.1%) and 14 days (46.9%), Microglial activation was first observed at 1 day, with lesser activation at 3 days and none shown later than 7 days. In contrast, in older mice which showed TH neuronal loss at 1 day (49.6%), 3 days (56.1%), 7 days (71.7%) and 14 days (72.1%), Microglial activation occurred at 1 day, further intensified at 3-7 days, and was largely abated by 14 days. The double immunohistochemistry further demonstrated that the activated Microglia surrounded dopaminergic neurons in older mice at 7 days, which was sharply in contrast to the young mice which were devoid of massive Microglial activation in the SN later than 3 days after MPTP treatment. The present study suggests that age-related Microglial activation in the SN may be relevant to the higher susceptibility to MPTP neurotoxicity in older mice

22. Teismann P, Tieu K, Choi DK, Wu DC, Naini A, Hunot S, Vila M, Jackson-Lewis V, Przedborski S (2003) Cyclooxygenase-2 is instrumental in Parkinson's disease neurodegeneration. Proc.Natl.Acad.Sci.U.S.A 100:5473-5478
    Abstract: Parkinson's disease (PD) is a neurodegenerative disorder of uncertain pathogenesis characterized by the loss of the nigrostriatal dopaminergic neurons, which can be modeled by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Increased expression of cyclooxygenase type 2 (COX-2) and production of prostaglandin E(2) have been implicated in neurodegeneration in several pathological settings. Here we show that COX-2, the rate-limiting enzyme in prostaglandin E(2) synthesis, is up-regulated in brain dopaminergic neurons of both PD and MPTP mice. COX-2 induction occurs through a JNKc-Jun-dependent mechanism after MPTP administration. We demonstrate that targeting COX-2 does not protect against MPTP-induced dopaminergic neurodegeneration by mitigating inflammation. Instead, we provide evidence that COX-2 inhibition prevents the formation of the oxidant species dopamine-quinone, which has been implicated in the pathogenesis of PD. This study supports a critical role for COX-2 in both the pathogenesis and selectivity of the PD neurodegenerative process. Because of the safety record of the COX-2 inhibitors, and their ability to penetrate the blood-brain barrier, these drugs may be therapies for PD

23. Teismann P, Tieu K, Cohen O, Choi DK, Wu dC, Marks D, Vila M, Jackson-Lewis V, Przedborski S (2003) Pathogenic role of glial cells in Parkinson's disease. Mov Disord. 18:121-129
    Abstract: Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the progressive loss of the dopaminergic neurons in the substantia nigra pars compacta (SNpc). The loss of these neurons is associated with a glial response composed mainly of activated Microglial cells and, to a lesser extent, of reactive astrocytes. This glial response may be the source of trophic factors and can protect against reactive oxygen species and glutamate. Alternatively, this glial response can also mediate a variety of deleterious events related to the production of pro-oxidant reactive species, and pro-inflammatory prostaglandin and cytokines. We discuss the potential protective and deleterious effects of glial cells in the SNpc of PD and examine how those factors may contribute to the pathogenesis of this disease

24. Wilms H, Rosenstiel P, Sievers J, Deuschl G, Zecca L, Lucius R (2003) Activation of Microglia by human neuromelanin is NF-kappaB dependent and involves p38 mitogen-activated protein kinase: implications for Parkinson's disease. FASEB J. 17:500-502
    Abstract: It has been suggested that Microglial inflammation augments the progression of Parkinson's disease (PD). However, endogenous factors initiating Microglial activation are largely unknown. We therefore investigated the effects of human neuromelanin (NM) on the release of neurotoxic mediators and the underlying signaling pathways from rat Microglia in vitro. The addition of NM to Microglial cultures induced positive chemotactic effects, activated the proinflammatory transcription factor nuclear factor kappaB (NF-kappaB) via phosphorylation and degradation of the inhibitor protein kappaB (IkappaB), and led to an up-regulation of tumor necrosis factor alpha, interleukin-6, and nitric oxide. The impairment of NF-kappaB function by the IkappaB kinase inhibitor sulfasalazine was paralleled by a decline in neurotoxic mediators. NM also activated p38 mitogen-activated protein kinase (MAPK), the inhibition of this pathway by SB203580 diminished phosphorylation of the transactivation domain of the p65 subunit of NF-kappaB. These findings demonstrate a crucial role of NM in the pathogenesis of PD by augmentation of Microglial activation, leading to a vicious cycle of neuronal death, exposure of additional neuromelanin, and chronification of inflammation. The antagonization of Microglial activation by a pharmacological intervention targeting Microglial NF-kappaB or p38 MAPK could point to additional venues in the treatment of PD

25. Wu DC, Teismann P, Tieu K, Vila M, Jackson-Lewis V, Ischiropoulos H, Przedborski S (2003) NADPH oxidase mediates oxidative stress in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model of Parkinson's disease. Proc.Natl.Acad.Sci.U.S.A 100:6145-6150
    Abstract: Parkinson's disease (PD) is a neurodegenerative disorder of uncertain pathogenesis characterized by a loss of substantia nigra pars compacta (SNpc) dopaminergic (DA) neurons, and can be modeled by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Both inflammatory processes and oxidative stress may contribute to

26. Wullner U, Klockgether T (2003) Inflammation in Parkinson's disease. J.Neurol. 250 Suppl 1:I35-I38
    Abstract: Several studies of Parkinson's disease (PD) patients and experimental models of PD indicate the presence of an inflammatory process in PD. Although the primary cellular mechanisms remain to be clarified, activation of resident Microglia appears to aggravate or even maintain the disease process in PD. Modulation of inflammatory mechanisms could provide a new neuroprotective therapy in PD

27. Al Sarraj S, Maekawa S, Kibble M, Everall I, Leigh N (2002) Ubiquitin-only intraneuronal inclusion in the substantia nigra is a characteristic feature of motor neurone disease with dementia. Neuropathol.Appl.Neurobiol. 28:120-128
    Abstract: Two types of ubiquitinated inclusions have been described in motor neurone disease (MND). (1) Skein or globular ubiquitinated inclusions in the motor neurones (more frequently in the lower motor neurones). This is a characteristic feature of all motor neurone disease categories. (2) Dot-shape or crescentric ubiquitinated inclusions in the upper layers of cortex and dentate gyrus described in cases of motor neurone disease with dementia (DMND). We investigated the substantia nigra (SN) in MND cases; two cases of motor neurone disease inclusion body (MND-IB) dementia, six cases of DMND, 14 cases of MND (including one case from Guam and two cases of familial SOD1 mutation), four cases of Parkinson's disease (PD), and 10 cases of age-matched normal controls. SN and spinal cord sections were stained with ubiquitin (alpha-synuclein, tau, PGM1, SMI-31 and SOD1 antibodies). The neuronal density in SN was quantified by using a computer-based image analysis system. Four out of six DMND cases showed rounded ubiquitin positive inclusions with irregular frayed edges, associated with neuronal loss, reactive astrocytosis and a large number of activated Microglia cells. These inclusions are negative with antibodies to (alpha-synuclein, tau, SMI-31 and SOD1). The SN in cases from MND-IB dementia and MND showed occasional neuronal loss and no inclusions. The ubiquitin-only inclusions in SN of DMND cases are similar (but not identical) to the ubiquitinated inclusions described previously in the spinal cord of MND cases and are distinct from Lewy bodies (LBs). The degeneration of SN is most likely a primary neurodegenerative process of motor neurone disease type frequently involving the DMND cases. MND disease is a spectrum and multisystem disorder with DMND located at the extreme end of a spectrum affecting the CNS more widely than just the motor system

28. Breidert T, Callebert J, Heneka MT, Landreth G, Launay JM, Hirsch EC (2002) Protective action of the peroxisome proliferator-activated receptor-gamma agonist pioglitazone in a mouse model of Parkinson's disease. J.Neurochem. 82:615-624
    Abstract: We examined the effect of pioglitazone, a peroxisome proliferator-activated receptor-gamma (PPARgamma) agonist of the thiazolidinedione class, on dopaminergic nerve cell death and glial activation in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease. The acute intoxication of C57BL/6 mice with MPTP led to nigrostriatal injury, as determined by tyrosine hydroxylase (TH) immunocytochemistry, and HPLC detection of striatal dopamine and metabolites. Damage to the nigrostriatal dopamine system was accompanied by a transient activation of Microglia, as determined by macrophage antigen-1 (Mac-1) and inducible nitric oxide synthase (iNOS) immunoreactivity, and a prolonged astrocytic response. Orally administered pioglitazone (approximately 20 mg/kg/day) attenuated the MPTP-induced glial activation and prevented the dopaminergic cell loss in the substantia nigra pars compacta (SNpc). In contrast, there was little reduction of MPTP-induced dopamine depletion, with no detectable effect on loss of TH immunoreactivity and glial response in the striatum of pioglitazone-treated animals. Low levels of PPARgamma expression were detected in the ventral mesencephalon and striatum, and were unaffected by MPTP or pioglitazone treatment. Since pioglitazone affects primarily the SNpc in our model, different PPARgamma-independent mechanisms may regulate glial activation in the dopaminergic terminals compared with the dopaminergic cell bodies after acute MPTP intoxication

29. Castano A, Herrera AJ, Cano J, Machado A (2002) The degenerative effect of a single intranigral injection of LPS on the dopaminergic system is prevented by dexamethasone, and not mimicked by rh-TNF-alpha, IL-1beta and IFN-gamma. J.Neurochem. 81:150-157
    Abstract: It is becoming widely accepted that the inflammatory response is involved in neurodegenerative disease. In this context, we have developed an animal model of dopaminergic system degeneration by the intranigral injection of lipopolysaccharide (LPS), a potent inductor of inflammation. To address the importance of the inflammatory response in the LPS-induced degeneration of nigral dopaminergic neurones, we carried out two different kinds of studies: (i) the possible protective effect of an anti-inflammatory compound, and (ii) the effect of the intranigral injection of inflammatory cytokines (TNF-alpha, IL-1beta and IFN-gamma) on dopaminergic neurones viability. Present results show that dexamethasone, a potent anti-inflammatory drug that interferes with many of the features characterizing pro-inflammatory glial activation, prevented the loss of catecholamine content, Tyrosine hydroxylase (TH) activity and TH immunostaining induced by LPS-injection and also the bulk activation of Microglia/macrophages. Surprisingly, injection of the pro-inflammatory cytokines failed to reproduce the LPS effect. Taken together, our results suggest that inflammatory response is implicated in LPS-induced neurodegeneration. This damage may be due, at least in part, to a cascade of events independent of that described for TNF-alpha/IL-1 beta/IFN-gamma

30. Cicchetti F, Brownell AL, Williams K, Chen YI, Livni E, Isacson O (2002) Neuroinflammation of the nigrostriatal pathway during progressive 6-OHDA dopamine degeneration in rats monitored by immunohistochemistry and PET imaging. Eur.J.Neurosci. 15:991-998
    Abstract: We investigated the Microglial response to progressive dopamine neuron degeneration using in vivo positron emission tomography (PET) imaging and postmortem analyses in a Parkinson's disease (PD) rat model induced by unilateral (right side) intrastriatal administration of 6-hydroxydopamine (6-OHDA). Degeneration of the dopamine system was monitored by PET imaging of presynaptic dopamine transporters using a specific ligand (11)C-CFT (2beta-carbomethoxy-3beta-(4-fluorophenyl) tropane). Binding of (11)C-CFT was markedly reduced in the striatum indicating dopaminergic degeneration. Parallel PET studies of (11)C-PK11195 (1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3 isoquinoline carboxamide) (specific ligand for activated Microglia) showed increased binding in the striatum and substantia nigra indicative of a Microglial response. Postmortem immunohistochemical analyses were performed with antibodies against CR3 for Microglia/macrophage activation. Using a qualitative postmortem index for Microglial activation we found an initially focal, then widespread Microglial response at striatal and nigral levels at 4 weeks postlesion. These data support the hypothesis that inflammation is a significant component of progressive dopaminergic degeneration that can be monitored by PET imaging

31. Czlonkowska A, Kurkowska-Jastrzebska I, Czlonkowski A, Peter D, Stefano GB (2002) Immune processes in the pathogenesis of Parkinson's disease - a potential role for Microglia and nitric oxide. Med.Sci.Monit. 8:RA165-RA177
    Abstract: It has been known for many years that immune system alterations occur in Parkinson's disease (PD). Changes in lymphocyte populations in cerebrospinal fluid and blood, immunoglobulin synthesis, and cytokine and acute phase protein production have been observed in patients with PD. In this regard, PD patients exhibit a lower frequency of infections and cancer, suggesting that immune system stimulation may occur. This hypothesis is further supported by the observation of T-cell activation leading to the production of interferon gamma in PD. As in other CNS degenerative diseases, in damaged regions in the brains of PD patients, there is evidence of inflammation, characterized by glial reaction (especially Microglia), as well as increased expression of HLA-DR antigens, cytokines, and components of complement. These observations suggest that immune system mechanisms are involved in the pathogenesis of neuronal damage in PD. The cellular mechanisms of primary injury in PD have not been clarified, however, but it is likely that mitochondrial mutations, oxidative stress and apoptosis play a role. Furthermore, inflammation initiated by neuronal damage in the striatum and the substantia nigra in PD may aggravate the course of the disease. These observations suggest that treatment with anti-inflammatory drugs may act to slow progression of PD

32. Gao HM, Hong JS, Zhang W, Liu B (2002) Distinct role for Microglia in rotenone-induced degeneration of dopaminergic neurons. J.Neurosci. 22:782-790
    Abstract: Increasing evidence has suggested an important role for environmental factors such as exposure to pesticides in the pathogenesis of Parkinson's disease. In experimental animals the exposure to a common herbicide, rotenone, induces features of Parkinsonism; mechanistically, rotenone-induced destruction of dopaminergic neurons has been attributed to its inhibition of the activity of neuronal mitochondrial complex I. However, the role of Microglia, the resident brain immune cells in rotenone-induced neurodegeneration, has not been reported. Using primary neuron-enriched and neuron/glia cultures from the rat mesencephalon, we discovered an extraordinary feature for rotenone-induced degeneration of cultured dopaminergic neurons. Although little neurotoxicity was detected in neuron-enriched cultures after treatment for 8 d with up to 20 nm rotenone, significant and selective dopaminergic neurodegeneration was observed in neuron/glia cultures 2 d after treatment with 20 nm rotenone or 8 d after treatment with 1 nm rotenone. The greatly enhanced neurodegenerative ability of rotenone was attributed to the presence of glia, especially Microglia, because the addition of Microglia to neuron-enriched cultures markedly increased their susceptibility to rotenone. Mechanistically, rotenone stimulated the release of superoxide from Microglia that was attenuated by inhibitors of NADPH oxidase. Furthermore, inhibition of NADPH oxidase or scavenging of superoxide significantly reduced the rotenone-induced neurotoxicity. This is the first report demonstrating that Microglia play a pivotal role in rotenone-induced degeneration of dopaminergic neurons. The results of this study should advance our understanding of the mechanism of action for pesticides in the pathogenesis of Parkinson's disease

33. Gao HM, Jiang J, Wilson B, Zhang W, Hong JS, Liu B (2002) Microglial activation-mediated delayed and progressive degeneration of rat nigral dopaminergic neurons: relevance to Parkinson's disease. J.Neurochem. 81:1285-1297
    Abstract: The etiology of sporadic Parkinson's disease (PD) remains unknown. Increasing evidence has suggested a role for inflammation in the brain in the pathogenesis of PD. However, it has not been clearly demonstrated whether Microglial activation, the most integral part of the brain inflammatory process, will result in a delayed and progressive degeneration of dopaminergic neurons in substantia nigra, a hallmark of PD. We report here that chronic infusion of an inflammagen lipopolysaccharide at 5 ng/h for 2 weeks into rat brain triggered a rapid activation of Microglia that reached a plateau in 2 weeks, followed by a delayed and gradual loss of nigral dopaminergic neurons that began at between 4 and 6 weeks and reached 70% by 10 weeks. Further investigation of the underlying mechanism of action of Microglia-mediated neurotoxicity using rat mesencephalic neuron-glia cultures demonstrated that low concentrations of lipopolysaccharide (0.1-10 ng/mL)-induced Microglial activation and production of neurotoxic factors preceded the progressive and selective degeneration of dopaminergic neurons. Among the factors produced by activated Microglia, the NADPH oxidase-mediated release of superoxide appeared to be a predominant effector of neurodegeneration, consistent with the notion that dopaminergic neurons are particularly vulnerable to oxidative insults. This is the first report that Microglial activation induced by chronic exposure to inflammagen was capable of inducing a delayed and selective degeneration of nigral dopaminergic neurons and that Microglia-originated free radicals play a pivotal role in dopaminergic neurotoxicity in this inflammation-mediated model of PD

34. He Y, Le WD, Appel SH (2002) Role of Fcgamma receptors in nigral cell injury induced by Parkinson disease immunoglobulin injection into mouse substantia nigra. Exp.Neurol. 176:322-327
    Abstract: Immune/inflammatory factors have been implicated in the pathogenesis of Parkinson's disease (PD). Immunoglobulin G (IgG) from patients with PD can induce injury of dopaminergic neurons following stereotaxic injection into rat substantia nigra (SN). The PD IgG can be demonstrated in vitro to activate Microglia via the Fcgamma receptor (Fcgamma R) and induce dopaminergic cell injury. To confirm the involvement of Microglia and their Fcgamma R in IgG-induced lesions of SN in vivo we analyzed the tyrosine hydroxylase (TH)-positive cell loss in SN par compacta (SNpc) in mice lacking Fcgamma receptors (Fcgamma R(-/-)) and wild type (Fcgamma R(+/+)). At 1 day after stereotaxic injection of PD IgG into the SN of Fcgamma R(+/+) mice there was a 27% increase in the number of CD11b-positive Microglial cells and no significant loss of TH-positive cells. At 14 days after the stereotaxic injection, the number of Microglial cells was increased by 42%, accompanied by a 40% loss of TH-positive neurons in the SNpc. PD IgG injection in Fcgamma R(-/-) mice resulted in no significant increase of Microglia and no loss of TH-positive cells in the SNpc at any time point. The injection of F(ab')(2) fragments of PD IgG was able to induce TH-positive neuronal loss in the SNpc only when the injected animals raised antibodies against the injected human IgG fragments, which confirmed the importance of the Fcgamma R in Microglial activation and nigral injury

35. Iravani MM, Kashefi K, Mander P, Rose S, Jenner P (2002) Involvement of inducible nitric oxide synthase in inflammation-induced dopaminergic neurodegeneration. Neuroscience 110:49-58
    Abstract: The loss of dopaminergic neurones in the substantia nigra with Parkinson's disease may result from inflammation-induced proliferation of Microglia and reactive macrophages expressing inducible nitric oxide synthase (iNOS). We have investigated the effects of the supranigral administration of lipopolysaccharide on iNOS-immunoreactivity, 3-nitrotyrosine formation and tyrosine hydroxylase-immunoreactive neuronal number, and retrogradely labelled fluorogold-positive neurones in the ventral mesencephalon in male Wistar rats. Following supranigral lipopolysaccharide injection, 16-18 h previously, there was intense expression of NADPH-diaphorase and iNOS-immunoreactivity in non-neuronal, macrophage-like cells. This was accompanied by intense expression of glial fibrillary acidic protein-immunoreactive astrocytosis in the substantia nigra. There were also significant reductions in the number of tyrosine hydroxylase(50-60%)- and fluorogold (65-75%)-positive neurones in the substantia nigra. In contrast, tyrosine hydroxylase-immunoreactivity in the ventral tegmental area was not altered. Pre-treatment of animals with the iNOS inhibitor, S-methylisothiourea (10 mg kg(-1), i.p.), led to a significant reduction of lipopolysaccharide-induced cell death. Similar reduction of tyrosine hydroxylase-immunoreactivity and fluorogold-labelled neurones in the substantia nigra following lipopolysaccharide administration suggests dopaminergic cell death rather than down-regulation of tyrosine hydroxylase. We conclude that the expression of iNOS- and 3-nitrotyrosine-immunoreactivity and reduction of cell death by S-methylisothiourea suggest the effects of lipopolysaccharide may be nitric oxide-mediated, although other actions of lipopolysaccharide (independent of iNOS induction) cannot be ruled out

36. Koutsilieri E, Scheller C, Grunblatt E, Nara K, Li J, Riederer P (2002) Free radicals in Parkinson's disease. J.Neurol. 249 Suppl 2:II1-II5
    Abstract: Although there are a number of hypotheses to explain the pathobiochemistry of Parkinson's disease (PD), the one on oxidative stress (OS) has gained major interest. The evidence for OS participation as a cause of PD can be summarized as follows: 1) OS is involved in physiological aging, 2) there is ample evidence that OS is significantly enhanced in PD compared to age-matched healthy persons, 3) OS is an early feature of PD because OS-dependent aggregation of proteins in the form of advanced glycation end products can be imaged in Lewy bodies at a time in a person's life, when no phenotype of a neurodegenerative disorder is evident, 4) Experimental models of PD show OS and degeneration of dopaminergic neurons. The toxin-induced neurodegeneration can be blocked by antioxidants, and 5) Activated Microglia, known to release free radicals and inflammatory cytokines, are present in brains of Parkinsonian patients.In conclusion, a great body of evidence points to the view that OS is a major component underlying the pathobiochemistry of PD. Together a genetic disposition and endogenous/exogenous toxic events of various origins result in a synergistic cascade of toxicity which leads to dysfunction and finally to cell death of dopaminergic neurons. Again, OS plays a significant role in generating cell death signals including apoptosis

37. Koutsilieri E, Scheller C, Tribl F, Riederer P (2002) Degeneration of neuronal cells due to oxidative stress--Microglial contribution. Parkinsonism.Relat Disord. 8:401-406
    Abstract: Various neurodegenerative disorders including Parkinson's disease, Alzheimer's disease and amyotrophic lateral sclerosis have been causally linked to the generation of free radicals and oxidative stress. In this review, we discuss the implication of oxidative stress in neuronal death and point out the role of intracellular signaling pathways leading to activation of transcription factors associated with cell death and repair. In particular, the impact of Microglia as contributors in promoting oxidative stress in neurodegeneration is highlighted. Finally, pivotal molecular targets for drug therapies of brain disorders are reported

38. Kramer BC, Yabut JA, Cheong J, JnoBaptiste R, Robakis T, Olanow CW, Mytilineou C (2002) Lipopolysaccharide prevents cell death caused by glutathione depletion: possible mechanisms of protection. Neuroscience 114:361-372
    Abstract: Glutathione is an important cellular antioxidant present at high concentrations in the brain. We have previously demonstrated that depletion of glutathione in mesencephalic cultures results in cell death and that the presence of glia is necessary for the expression of toxicity. Cell death following glutathione depletion can be prevented by inhibition of lipoxygenase activity, implicating arachidonic acid metabolism in the toxic events. In this study we examined the effect of glial activation, known to cause secretion of cytokines and release of arachidonic acid, on the toxicity induced by glutathione depletion. Our data show that treatment with the endotoxin lipopolysaccharide activated glial cells in mesencephalic cultures, increased interleukin-1beta in Microglia and caused depletion of glutathione. The overall effect of lipopolysaccharide treatment, however, was protection from damage caused by glutathione depletion. Addition of cytokines or growth factors, normally secreted by activated glia, did not modify L-buthionine sulfoximine toxicity, although basic fibroblast growth factor provided some protection. A large increase in the protein content and the activity of Mn-superoxide dismutase, observed after lipopolysaccharide treatment, may indicate a role for this mitochondrial antioxidant enzyme in the protective effect of lipopolysaccharide. This was supported by the suppression of toxicity by exogenous superoxide dismutase. Our data suggest that superoxide contributes to the damage caused by glutathione depletion and that up-regulation of superoxide dismutase may offer protection in neurodegenerative diseases associated with glutathione depletion and oxidative stress

39. Kurkowska-Jastrzebska I, Babiuch M, Joniec I, Przybylkowski A, Czlonkowski A, Czlonkowska A (2002) Indomethacin protects against neurodegeneration caused by MPTP intoxication in mice. Int.Immunopharmacol. 2:1213-1218
    Abstract: The anti-inflammatory agents are postulated to be effective in treating neurodegenerative disorders. In this study, we showed that indomethacin (IND) in the dose of 1 mg/kg protected neurons against toxic damage caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mice model of Parkinson's disease. IND also diminished Microglial activation and lymphocytic infiltration in the injured areas. These observations suggest that anti-inflammatory properties of IND may play a role in the neuron's protection in this model. However, diminished inflammatory reaction may be secondary to less neuronal damage

40. Lee YB, Nagai A, Kim SU (2002) Cytokines, chemokines, and cytokine receptors in human Microglia. J.Neurosci.Res. 69:94-103
    Abstract: Enriched populations of human Microglial cells were isolated from mixed cell cultures prepared from embryonic human telencephalon tissues. Human Microglial cells exhibited cell type-specific antigens for macrophage-Microglia lineage cells including CD11b (Mac-1), CD68, B7-2 (CD86), HLA-ABC, HLA-DR and ricinus communis aggulutinin lectin-1 (RCA-1), and actively phagocytosed latex beads. Gene expression and protein production of cytokines, chemokines and cytokine/chemokine receptors were investigated in the purified populations of human Microglia. Normal unstimulated human Microglia expressed constitutively mRNA transcripts for interleukin- 1beta (IL-1beta) -6, -8, -10, -12, -15, tumor necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, and monocyte chemoattractant protein-1 (MCP-1), while treatment with lipopolysaccharide (LPS) or amyloid beta peptides (Abeta) led to increased expression of mRNA levels of IL-8, IL-10, IL-12, TNF-alpha, MIP-1alpha, MIP-1beta, and MCP-1. Human Microglia, in addition, expressed mRNA transcripts for IL-1RI, IL-1RII, IL-5R, IL-6R, IL-8R, IL-9R, IL-10R, IL-12R, IL-13R, and IL-15R. Enzyme-linked immunosorbent assays (ELISA) showed increased protein levels in culture media of IL-1beta, IL-8, TNF-alpha, and MIP-1alpha in human Microglia following treatment with LPS or Abeta. Increased TNF-alpha release from human Microglia following LPS treatment was completely inhibited with IL-10 pretreatment, but not with IL-6, IL-9, IL-12, IL-13, or transforming growth factor-beta (TGF-beta). Present results should help in understanding the basic Microglial biology, but also the pathophysiology of activated Microglia in neurological diseases such as Alzheimer disease, Parkinson disease, Huntington disease, amyotrophic lateral sclerosis, stroke, and neurotrauma

41. Lorenzl S, Albers DS, Narr S, Chirichigno J, Beal MF (2002) Expression of MMP-2, MMP-9, and MMP-1 and their endogenous counterregulators TIMP-1 and TIMP-2 in postmortem brain tissue of Parkinson's disease. Exp.Neurol. 178:13-20
    Abstract: We investigated the levels and tissue localization of matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9) in postmortem brain tissue from Parkinson's disease (PD) and age-matched control cases. Using zymography, we found reduced MMP-2 levels in PD cases in the substantia nigra as compared to controls; levels of MMP-2 were not significantly changed in the cortex and the hippocampus. MMP-9 levels were unchanged in the investigated brain regions. Immunohistochemically, MMP-2 was localized primarily in astrocytes and Microglia cells, whereas MMP-9 was predominantly neuronal. Levels of TIMP-1, an endogenous tissue inhibitor of MMPs, were significantly elevated in the substantia nigra, but not in the cortex and hippocampus. TIMP-2 levels were unchanged in PD. To investigate whether increased TIMP-1 levels in the substantia nigra might be due to increased MMP-1 expression, we measured MMP-1 levels using Western blots. MMP-1 levels were unchanged in PD cases compared to controls. Together, these data show alterations of MMP-2 and TIMP-1 in the substantia nigra of PD, consistent with the possibility that alterations in MMPs/TIMPs may contribute to disease pathogenesis

42. McGeer PL, Yasojima K, McGeer EG (2002) Association of interleukin-1 beta polymorphisms with idiopathic Parkinson's disease. Neurosci.Lett. 326:67-69
    Abstract: Activated Microglia surround degenerating substantia nigra neurons in Parkinson's disease (PD). Such Microglia produce high levels of interleukin-1 beta (IL-1 beta) and interleukin-1 alpha (IL-1 alpha). T and C alleles exist for the IL-1 beta-511 regulatory region as well as for the IL-1 alpha-889 regulatory region. The T genotypes of both have been reported to increase the risk of Alzheimer's disease (AD) (Arch. Neurol. 58 (2001) 1790). Since the lesions of PD and AD have similar neuroinflammatory characteristics (Neurology 38 (1988) 1285), we genotyped 100 PD and 100 control postmortem brains for the same polymorphisms. We found a significant increase of the IL-1 beta T genotype in PD cases compared with controls (chi(2)=9.65, P=0.0019). A significant increase was not found for the IL-alpha T genotype (chi(2)=1.32, P=0.23), although there was a trend towards more frequent expression of the T allele

43. Michel PP, Hirsch EC, Agid Y (2002) [Parkinson's disease: cell death mechanisms]. Rev.Neurol.(Paris) 158:24-32
    Abstract: Parkinson disease is a neurodegenerative disorder of aging characterized by a selective and progressive loss of dopaminergic neurons within the substantia nigra. The diagnosis of the disease is made when neuronal cell loss exceeds 50 p. cent indicating that the degenerative process started well before the onset of the first clinical symptoms. Three populations of dopaminergic neurons seem to coexist in the substantia nigra of Parkinsonian patients; (1) senescent neurons that are still spared by the pathological process; (2) sick neurons exhibiting generally a preserved morphology but showing evidence of biochemical and metabolic abnormalities; (3) neurons which have entered into a final state of agony and exhibit the hallmarks of apoptosis, a controlled form of cell death that requires the activation of a particular type of proteases, caspases. In the inherited forms of the disease that are caused by mutations of genes encoding the Parkin, alpha-synuclein and UCHL-1 proteins, the degenerative process results from the dysfunction of an enzymatic complex of proteolysis, the proteasome. This probably leads to the intracellular accumulation of abnormal proteins that become deleterious for dopaminergic neurons. In the sporadic forms of the disease that are the most frequent, causes of the cell demise remain still unknown but neurodegeneration might also result from a decreased activity of the proteasome. A defect in the detoxification of reactive oxygen species or an energy failure caused by inhibition of the mitochondrial respiratory chain, at the complex I level, are other hypothesis that are frequently mentioned. Finally, activated glial cells (astrocytes and Microglia) located around the degenerating dopaminergic neurons might also intervene in the mechanism of degeneration by perpetuating or even amplifying the primary neuronal insult. Proinflammatory cytokines acting on cell death membrane receptors and diffusable messengers such as nitric oxide could be part of this process

44. Michel PP, Hirsch EC, Agid Y (2002) [Parkinson disease: mechanisms of cell death]. Rev.Neurol.(Paris) 158 Spec no 1:S24-S32
    Abstract: Parkinson disease is a neurodegenerative disorder of aging characterized by a selective and progressive loss of dopaminergic neurons within the substantia nigra. The diagnosis of the disease is made when neuronal cell loss exceeds 50 p. 100 indicating that the degenerative process started well before the onset of the first clinical symptoms. Three populations of dopaminergic neurons seem to coexist in the substantia nigra of Parkinsonian patients; (1) senescent neurons that are still spared by the pathological process; (2) sick neurons exhibiting generally a preserved morphology but showing evidence of biochemical and metabolic abnormalities; (3) neurons which have entered into a final state of agony and exhibit the hallmarks of apoptosis, a controlled form of cell death that requires the activation of a particular type of proteases, caspases. In the inherited forms of the disease that are caused by mutations of genes encoding the Parkin, alpha-synuclein and UCHL-1 proteins, the degenerative process results from the dysfunction of an enzymatic complex of proteolysis, the proteasome. This probably leads to the intracellular accumulation of abnormal proteins that become deleterious for dopaminergic neurons. In the sporadic forms of the disease that are the most frequent, causes of the cell demise remain still unknown but neurodegeneration might also result from a decreased activity of the proteasome. A defect in the detoxification of reactive oxygen species or an energy failure caused by inhibition of the mitochondrial respiratory chain, at the complex I level, are other hypothesis that are frequently mentioned. Finally, activated glial cells (astrocytes and Microglia) located around the degenerating dopaminergic neurons might also intervene in the mechanism of degeneration by perpetuating or even amplifying the primary neuronal insult. Proinflammatory cytokines acting on cell death membrane receptors and diffusable messengers such as nitric oxide could be part of this process

45. Orr CF, Rowe DB, Halliday GM (2002) An inflammatory review of Parkinson's disease. Prog.Neurobiol. 68:325-340
    Abstract: The symptoms of Parkinson's disease (PD) were first described nearly two centuries ago and its characteristic pathology identified nearly a century ago, yet its pathogenesis is still poorly understood. Parkinson's disease is the most prevalent neurodegenerative movement disorder and research into its pathogenesis recently accelerated following the identification of a number of causal genetic mutations. The mutant gene products all cause dysfunction of the ubiquitin-proteosome system, identifying protein modification and degradation as critical for pathogenesis. Modified non-degraded intracellular proteins accumulate in certain neuronal populations in all forms of the disease. However, neuronal degeneration is more highly selective and associates with substantial activation of Microglia, the inflammatory cells of the brain. We review the current change in thinking regarding the role of Microglia in the brain in the context of Parkinson's disease and animal models of the disease. Comparison of the cellular tissue changes across a number of animal models using diverse stimuli to mimic Parkinson's disease reveals a consistent pattern implicating Microglia as the effector for the selective degeneration of dopaminergic neurons. While previous reviews have concentrated on the intracellular neuronal changes in Parkinson's disease, we highlight the cell to cell interactions and immune regulation critical for neuronal homeostasis and survival in Parkinson's disease

46. Ryu JK, Shin WH, Kim J, Joe EH, Lee YB, Cho KG, Oh YJ, Kim SU, Jin BK (2002) Trisialoganglioside GT1b induces in vivo degeneration of nigral dopaminergic neurons: role of Microglia. Glia 38:15-23
    Abstract: We recently showed that trisialoganglioside (GT1b) induces cell death of dopaminergic neurons in rat mesencephalic cultures (Chung et al., Neuroreport 12:611-614, 2001). The present study examines the in vivo neurotoxic effects of GT1b on dopaminergic neurons in the substantia nigra (SN) of Sprague-Dawley rats. Seven days after GT1b injection into the SN, immunocytochemical staining of SN tissue revealed death of nigral neurons, including dopaminergic neurons. Additional immunostaining using OX-42 and OX-6 antibodies showed that GT1b-activated Microglia were present in the SN where degeneration of nigral neurons was found. Western blot analysis and double-labeled immunohistochemistry showed that inducible nitric oxide synthase (iNOS) was expressed in the SN, where its levels were maximal at 8 h post-GT1b injection, and that iNOS was localized exclusively within Microglia. GT1b-induced loss of dopaminergic neurons in the SN was partially inhibited by N(G)-nitro-L-arginine methyl ester hydrochloride, an NOS inhibitor. Our results indicate that in vivo neurotoxicity of GT1b against nigral dopaminergic neurons is at least in part mediated by nitric oxide released from activated Microglia. Because GT1b exists abundantly in central nervous system neuronal membranes, our data support the hypothesis that immune-mediated events triggered by endogenous compounds such as GT1b could contribute to the initiation and/or the progression of dopaminergic neuronal cell death that occurs in Parkinson's disease

47. Sriram K, Matheson JM, Benkovic SA, Miller DB, Luster MI, O'Callaghan JP (2002) Mice deficient in TNF receptors are protected against dopaminergic neurotoxicity: implications for Parkinson's disease. FASEB J. 16:1474-1476
    Abstract: The pathogenic mechanisms underlying idiopathic Parkinson's disease (PD) remain enigmatic. Recent findings suggest that inflammatory processes are associated with several neurodegenerative disorders, including PD. Enhanced expression of the proinflammatory cytokine, tumor necrosis factor (TNF)-alpha, has been found in association with glial cells in the substantia nigra of patients with PD. To determine the potential role for TNF-alpha in PD, we examined the effects of the 1-methyl-4-phenyl-1,2,3,4-tetrahydropyridine (MPTP), a dopaminergic neurotoxin that mimics some of the key features associated with PD, using transgenic mice lacking TNF receptors. Administration of MPTP to wild-type (+/+) mice resulted in a time-dependent expression of TNF-alpha in striatum, which preceded the loss of dopaminergic markers and reactive gliosis. In contrast, transgenic mice carrying homozygous mutant alleles for both the TNF receptors (TNFR-DKO), but not the individual receptors, were completely protected against the dopaminergic neurotoxicity of MPTP. The data indicate that the proinflammatory cytokine TNF-alpha is an obligatory component of dopaminergic neurodegeneration. Moreover, because TNF-alpha is synthesized predominantly by Microglia and astrocytes, our findings implicate the participation of glial cells in MPTP-induced neurotoxicity. Similar mechanisms may underlie the etiopathogenesis of PD

48. Tomas-Camardiel M, Sanchez-Hidalgo MC, Sanchez del Pino MJ, Navarro A, Machado A, Cano J (2002) Comparative study of the neuroprotective effect of dehydroepiandrosterone and 17beta-estradiol against 1-methyl-4-phenylpyridium toxicity on rat striatum. Neuroscience 109:569-584
    Abstract: The effects of dehydroepiandrosterone, estradiol and testosterone on 1-methyl-4-phenylpyridium (MPP+)-induced neurotoxicity of the nigrostriatal dopaminergic system were examined in rat. They were subjected to a unilateral intrastriatal infusion of the following treatment conditions: MPP+ alone or co-injection of MPP+ plus each hormone. Four days after injection, concentrations of dopamine and their metabolites were determined from the corpus striatum. To corroborate the neurochemical data an immunohistochemical analysis of tyrosine hydroxylase-immunoreactive fibers and acetylcholinesterase histochemistry in the striatum was performed. Moreover, we performed a dose-response study of the three hormones on the high-affinity dopamine transport system in rat striatal synaptosomes.Rats co-injected within the striatum with MPP+ and either dehydroepiandrosterone or estradiol had significantly greater concentrations of dopamine and less tyrosine hydroxylase-immunoreactive fibers and acetylcholinesterase fiber density loss compared with their respective controls. In addition, 4 days after injection, the brain was fixed and cut into coronal sections, and was immunostained with major histocompatibility complex class II antigens for activated Microglia, and glial fibrillary acidic protein for activated astrocytes. Dehydroepiandrosterone also attenuated Microglial cell activation. In contrast, testosterone showed reductions in dopamine concentrations similar to those obtained by MPP+. The protective effect of dehydroepiandrosterone against the MPP+ neurotoxic dopaminergic system may be produced by its partial prevention of MPP+ inhibition of NADH oxidase activity, whereas the estradiol may function as a neuroprotectant by reducing the uptake of MPP+ into dopaminergic neurons.Our findings we suggest indicate that dehydroepiandrosterone and estradiol by a non-genomic effect may have an important modulatory action, capable of attenuating degeneration within the striatum, and in this way serve as neuroprotectants of the nigrostriatal dopaminergic system

49. Wu DC, Jackson-Lewis V, Vila M, Tieu K, Teismann P, Vadseth C, Choi DK, Ischiropoulos H, Przedborski S (2002) Blockade of Microglial activation is neuroprotective in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of Parkinson disease. J.Neurosci. 22:1763-1771
    Abstract: 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) damages the nigrostriatal dopaminergic pathway as seen in Parkinson's disease (PD), a common neurodegenerative disorder with no effective protective treatment. Consistent with a role of glial cells in PD neurodegeneration, here we show that minocycline, an approved tetracycline derivative that inhibits Microglial activation independently of its antimicrobial properties, mitigates both the demise of nigrostriatal dopaminergic neurons and the formation of nitrotyrosine produced by MPTP. In addition, we show that minocycline not only prevents MPTP-induced activation of Microglia but also the formation of mature interleukin-1beta and the activation of NADPH-oxidase and inducible nitric oxide synthase (iNOS), three key Microglial-derived cytotoxic mediators. Previously, we demonstrated that ablation of iNOS attenuates MPTP-induced neurotoxicity. Now, we demonstrate that iNOS is not the only Microglial-related culprit implicated in MPTP-induced toxicity because mutant iNOS-deficient mice treated with minocycline are more resistant to this neurotoxin than iNOS-deficient mice not treated with minocycline. This study demonstrates that Microglial-related inflammatory events play a significant role in the MPTP neurotoxic process and suggests that minocycline may be a valuable neuroprotective agent for the treatment of PD

50. Wu dC, Tieu K, Cohen O, Choi DK, Vila M, Jackson-Lewis V, Teismann P, Przedborski S (2002) Glial cell response: A pathogenic factor in Parkinson's disease. J.Neurovirol. 8:551-558
    Abstract: Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). The loss of these neurons is associated with a glial response composed mainly of activated Microglial cells and, to a lesser extent, of reactive astrocytes. This glial response may be the source of trophic factors and can protect against reactive oxygen species and glutamate. Alternatively, this glial response can also mediate a variety of deleterious events related to the production of pro-oxidant reactive species, proinflammatory prostaglandin, and cytokines. In this review, the authors discuss the potential protective and deleterious effects of glial cells in the SNpc of PD and examine how these factors may contribute to the pathogenesis of this disease

51. Armstrong RJ, Harrower TP, Hurelbrink CB, McLaughin M, Ratcliffe EL, Tyers P, Richards A, Dunnett SB, Rosser AE, Barker RA (2001) Porcine neural xenografts in the immunocompetent rat: immune response following grafting of expanded neural precursor cells. Neuroscience 106:201-216
    Abstract: Intracerebral neural xenografts elicit a host immune response that results in their rapid rejection. This forms a key barrier to the therapeutic use of xenogeneic tissue transplantation for conditions such as Parkinson's disease. The current study sought to provide insight into the cellular components of donor cell suspensions that are important in stimulating the host rejection response and thereby to suggest rational manipulations of xenogeneic donor tissue that might ultimately enhance its clinical utility. The neural stem cell mitogens, epidermal growth factor and fibroblast growth factor-2, have been used to isolate and expand populations of primordial neural precursor cells from the embryonic pig brain. The immune response elicited by these cells on transplantation into the non-immunosuppressed rat has been fully characterised.In the first experiments, expanded neural precursors were grafted into the hemi-Parkinsonian, non-immunosuppressed Sprague-Dawley rat and graft status and host response examined 10, 21, 35 and 60 days post-transplantation. While equivalent primary tissue grafts were completely eliminated at 35 days, grafts of expanded neural precursors with healthy neurofilament-positive projections were present at all time-points, and two large grafts remained even at 60 days. Some grafts appeared to elicit minimal host immune responses at the time-points they were examined, although most did appear to be undergoing a rejection process since a co-ordinated response involving host cytotoxic T-lymphocytes, Microglia/macrophages, immunoglobulin M and complement could be demonstrated to varying degrees.Subsequent experiments went on to demonstrate further that expanded precursor populations and primary tissue suspensions differed in their immunogenic profile. Firstly, when primary tissue was injected intraperitoneally into immunocompetent rats a vigorous primary humoral response was generated. No such response was detected following injection of expanded neural precursors. Secondly, flow cytometric analysis revealed small but significant levels of class II porcine major histocompatibility complex expression in primary cell suspensions but no such expression in expanded precursor populations.The results of this study therefore demonstrate that the immunogenicity of porcine neural cell suspensions used for intracerebral grafting is reduced when neural stem cell mitogens are used to expand precursor cells. The implications of these findings in the development of novel xenogeneic cellular therapies for neurodegenerative conditions such as Parkinson's disease are discussed

52. Berg D, Gerlach M, Youdim MB, Double KL, Zecca L, Riederer P, Becker G (2001) Brain iron pathways and their relevance to Parkinson's disease. J.Neurochem. 79:225-236
    Abstract: A central role of iron in the pathogenesis of Parkinson's disease (PD), due to its increase in substantia nigra pars compacta dopaminergic neurons and reactive Microglia and its capacity to enhance production of toxic reactive oxygen radicals, has been discussed for many years. Recent transcranial ultrasound findings and the observation of the ability of iron to induce aggregation and toxicity of alpha-synuclein have reinforced the critical role of iron in the pathogenesis of nigrostriatal injury. Presently the mechanisms involved in the disturbances of iron metabolism in PD remain obscure. In this review we summarize evidence from recent studies suggesting disturbances of iron metabolism in PD at possibly different levels including iron uptake, storage, intracellular metabolism, release and post-transcriptional control. Moreover we outline that the interaction of iron with other molecules, especially alpha-synuclein, may contribute to the process of neurodegeneration. Because many neurodegenerative diseases show increased accumulation of iron at the site of neurodegeneration, it is believed that maintenance of cellular iron homeostasis is crucial for the viability of neurons

53. Brevig T, Meyer M, Kristensen T, Zimmer J, Holgersson J (2001) Xenotransplantation for brain repair: reduction of porcine donor tissue immunogenicity by treatment with anti-Gal antibodies and complement. Transplantation 72:190-196
    Abstract: BACKGROUND: Transplantation of embryonic neural tissue is a potential treatment for Parkinson's disease. Because human donor material is in short supply, porcine xenografts are considered a useful alternative. Current immunosuppressive therapies fail, however, to protect intracerebral neural xenografts from host CD4 T lymphocytes. To reduce the immunogenicity of porcine donor tissue, we attempted to remove Microglial cells with antibodies against the alpha-galactosyl epitope (Galalpha1,3Galbeta1,4GlcNAc-R), or anti-Gal, and complement, and studied whether this pretreatment can reduce direct and indirect T-cell responses to the tissue. METHODS: Brain tissue from 27-day-old pig embryos was dissociated and treated with human anti-Gal and rabbit complement. The Microglial content was analyzed by flow cytometry. [3H]thymidine incorporation in cocultures of the brain cells and purified human CD4 T cells was used to determine direct T-cell responses. Indirect T-cell responses were studied by grafting pretreated and control-pretreated (no anti-Gal) nigral tissue into the lesioned striatum of immunocompetent rats with 6-hydroxydopamine-induced hemiParkinsonism. Amphetamine-induced circling behavior was used to measure graft function. RESULTS: Anti-Gal and complement reduced the Microglial content to 11-24% of control and abolished the ability of the brain cells to induce human CD4 T-cell proliferation. Pretreated nigral tissue reduced hemiParkinsonism by more than 50% in five of eight rats at some point during the 10-week follow-up. Rats receiving control-pretreated nigral tissue did not display this degree of improvement. CONCLUSIONS: Pretreatment with anti-Gal and complement can reduce the immunogenicity of porcine neural tissue, and might, therefore, be a valuable alternative or supplement to immunosuppression in neural xenotransplantation

54. Brevig T, Meyer M, Kristensen T, Zimmer J (2001) Neural xenotransplantation: pretreatment of porcine embryonic nigral tissue with anti-Gal antibodies and complement is not toxic for the dopaminergic neurons. Cell Transplant. 10:25-30
    Abstract: The immunogenicity of porcine tissue is a major obstacle to its use as donor material in xenotransplantation for neurodegenerative diseases. We are currently evaluating a novel strategy for reducing the immunogenicity, in which the alpha-galactosyl epitope (Galalpha1,3Galbeta1,4GlcNAc-R) is used as a target for antibody- and complement-mediated removal of Microglia. In the present study, our aim was to determine whether a pretreatment with antibodies against the alpha-galactosyl epitope (anti-Gal) and complement would lyse or otherwise damage dopaminergic neurons in porcine embryonic ventral mesencephalon (VM), the donor tissue for treatment of Parkinson's disease by xenotransplantation. Cell suspensions prepared from VM tissue from 27-day-old pig embryos were incubated with anti-Gal, purified from normal human serum by affinity chromatography, or medium only (control), and subsequently with rabbit complement. After these pretreatments, the cell suspensions were transplanted into the right striatum of 14 adult rats (two groups of 7 animals). The animals were sacrificed 20 days after transplantation, the brains were processed for histology, and the sections were stained for Nissl substance, porcine neurofilament, tyrosine hydroxylase, and rat CD45 to determine graft volume, presence of porcine neurons, content of dopaminergic cells, and leukocyte infiltration, respectively. The VM tissue pretreated with anti-Gal and complement gave rise to dopaminergic grafts that were indistinguishable from those derived from VM tissue given the control pretreatment. In 5 of the 14 animals, the grafts were infiltrated by host leukocytes, but in two of these recipients, the infiltration was only minimal. We conclude that anti-Gal and complement can be applied to porcine embryonic VM tissue without damaging the dopaminergic neurons and their precursors

55. Czlonkowska A, Kurkowska-Jastrzebska I (2001) [Treatment of neurodegenerative diseases: new perspectives]. Neurol.Neurochir.Pol. 35:147-156
    Abstract: The experimental models of neurodegeneration give a possibility to study the inflammatory reaction that starts in response to neuronal death. Inflammation consists of Microglial and astroglial activation, expression of new molecules as cytokines, adhesion molecules and MHC antigens, and is potentially neurotoxic. This article is a summary of a few latest studies that investigate anti-inflammatory agents effect on neuron survival in MPTP mice model of Parkinson's disease. Murine model of Parkinson's disease uses a quite selective toxic effect of MPTP on nigrostriatal system. MPTP causes degeneration of dopaminergic cells bodies in the substantia nigra and of their endings in striatum. Our findings show that anti-inflammatory treatment protects neuronal death. It may indicate that the inflammation contributes to the dopaminergic neuron impairment following MPTP intoxication. However this hypothesis needs further investigation because recent studies suggest that inflammation may have also a protective effect in neurodegentration

56. Fillebeen C, Ruchoux MM, Mitchell V, Vincent S, Benaissa M, Pierce A (2001) Lactoferrin is synthesized by activated Microglia in the human substantia nigra and its synthesis by the human Microglial CHME cell line is upregulated by tumor necrosis factor alpha or 1-methyl-4-phenylpyridinium treatment. Brain Res.Mol.Brain Res. 96:103-113
    Abstract: The presence of the iron-binding protein lactoferrin (Lf) in some specific areas of the central nervous system and particularly in the normal human substantia nigra, where it is found in dopaminergic (DA) neurons and some glial cells, led us to investigate Lf synthesis in this area. Lf mRNA were identified using in situ hybridization and found in small ameboid cells. These cells were identified using immunocytochemistry as activated Microglia since they exhibited macrophage markers such as the CD68 and the CR1 antigens. Double immunofluorescent labeling confirmed that the two Lf immunostained cell populations were activated Microglia and DA neurons. Since activated Microglia contained both Lf and its messenger, these cells are the Lf producing cells. The presence of Lf in DA neurons in which no Lf messengers were visible, might be due to an endocytosis mechanism, DA neurons probably internalizing Lf produced in Microglial cells located in their neighborhood. In neuropathological disorders, such as Alzheimer's and Parkinson's diseases, inflammatory process and oxidative stress are events that contribute to neuronal death. Since Lf concentration increases during these pathologies, we studied the level of Lf expression under these different stresses and showed, using RT-PCR, that the immortalized human embryonic Microglial CHME cell line produced Lf transcripts under tumor necrosis factor alpha or 1-methyl-4-phenylpyridinium treatment whereas untreated cells did not. These data confirm that Lf is produced only when Microglia are activated

57. Fiszer U (2001) Does Parkinson's disease have an immunological basis? The evidence and its therapeutic implications. BioDrugs. 15:351-355
    Abstract: Parkinson's disease (PD) is an age-related neurodegenerative movement disorder of unknown aetiology. Immune abnormalities have been described in PD including the occurrence of autoantibodies against neuronal structures and high numbers of Microglia cells expressing the histocompatibility glycoprotein human leucocyte antigen-DR in the substantia nigra. An infectious cause for PD has been discussed for years. Disturbed cellular and humoral immune functions in peripheral blood of patients with PD have been also reported. An elevated gammadelta(+) T cell population and increased immunoglobulin G immunity in CSF to heat shock proteins have been found in PD. Cytokines and apoptosis-related proteins were elevated in the striatum in patients with PD. Activated glial cells may participate in neuronal cell death in PD by providing toxic substances. We may conclude that the immune system is involved in the pathogenesis of PD. However, we are not able to determine whether the disturbances described above constitute a primary or secondary phenomenon. Immunomodulatory agents may have important applications in the development of new therapies for PD

58. He Y, Appel S, Le W (2001) Minocycline inhibits Microglial activation and protects nigral cells after 6-hydroxydopamine injection into mouse striatum. Brain Res. 909:187-193
    Abstract: To determine the role of immune/inflammatory factors in dopaminergic cell degeneration in Parkinsonian substantia nigra, we assayed tyrosine hydroxylase (TH)-positive immunoreactive neuronal numbers with stereologic techniques and CD11b-positive immunoreactive Microglial profiles following 6-hydroxydopamine (6-OHDA) injection into ipsilateral striatum of mice. We further investigated the effect of minocycline on the inhibition of Microglial activation and subsequent protection of nigral cells. The relative number of Microglial profiles in the substantia nigra (SN) ipsilateral to the injection increased from 31 to 32% 1-3 days after injection, and increased further to 55% by 7 days and 59% by 14 days, compared with the contralateral SN. These changes started prior to the decrease of TH immunoreactivity of 34% on day 7 and of 42% by day 14. In animals treated with minocycline, Microglial activation was inhibited by 47%, and TH positive cells were protected by 21% at day 14 after 6-OHDA injection, compared with those Parkinsonian animals without minocycline treatment. All these results suggest that Microglial activation may be involved in the nigral cell degeneration in 6-OHDA induced Parkinsonian mice

59. Le W, Rowe D, Xie W, Ortiz I, He Y, Appel SH (2001) Microglial activation and dopaminergic cell injury: an in vitro model relevant to Parkinson's disease. J.Neurosci. 21:8447-8455
    Abstract: Microglial activation and oxidative stress are significant components of the pathology of Parkinson's disease (PD), but their exact contributions to disease pathogenesis are unclear. We have developed an in vitro model of nigral injury, in which lipopolysaccharide-induced Microglial activation leads to injury of a dopaminergic cell line (MES 23.5 cells) and dopaminergic neurons in primary mesencephalic cell cultures. The Microglia are also activated by PD IgGs in the presence of low-dose dopa-quinone- or H(2)O(2)-modified dopaminergic cell membranes but not cholinergic cell membranes. The activation requires the Microglial FCgammaR receptor as demonstrated by the lack of activation with PD IgG Fab fragments or Microglia from FCgammaR-/- mice. Although Microglial activation results in the release of several cytokines and reactive oxygen species, only nitric oxide and H(2)O(2) appear to mediate the Microglia-induced dopaminergic cell injury. These studies suggest a significant role for Microglia in dopaminergic cell injury and provide a mechanism whereby immune/inflammatory reactions in PD could target oxidative injury relatively specifically to dopaminergic cells

60. Satoh JI, Kuroda Y (2001) Alpha-synuclein expression is up-regulated in NTera2 cells during neuronal differentiation but unaffected by exposure to cytokines and neurotrophic factors. Parkinsonism.Relat Disord. 8:7-17
    Abstract: Increasing evidence has indicated that proinflammatory cytokines such as TNF-alpha and IL-1beta, produced by activated Microglia and astrocytes, play a key role in progressive degeneration of the nigrostriatal dopaminergic neurons in Parkinson's disease (PD). Since alpha-synuclein is a major component of Lewy bodies in PD brains, we studied the constitutive and cytokine/neurotrophic factor-regulated expression of alpha-synuclein in cultured human neurons by Northern blot and Western blot analyses. The constitutive expression of alpha-synuclein mRNA was identified in a variety of human neural and non-neural cell lines. The levels of alpha-synuclein expression were elevated markedly in NTera2 teratocarcinoma cells following retinoic acid-induced neuronal differentiation, accompanied with an increased expression of synphilin-1, while they were unaltered in NTera2-derived differentiated neurons by exposure to TNF-alpha, IL-1beta, BDNF or GDNF. These results indicate that alpha-synuclein expression in human neurons is up-regulated during differentiation, but is unaffected by a panel of cytokines and neurotrophic factors which are supposed to be involved in the nigral neuronal death and survival

61. Vila M, Jackson-Lewis V, Guegan C, Wu DC, Teismann P, Choi DK, Tieu K, Przedborski S (2001) The role of glial cells in Parkinson's disease. Curr.Opin.Neurol. 14:483-489
    Abstract: Parkinson's disease is a common neurodegenerative disorder characterized by the progressive loss of the dopaminergic neurons in the substantia nigra pars compacta. The loss of these neurons is associated with a glial response composed mainly of activated Microglial cells and, to a lesser extent, of reactive astrocytes. This glial response may be the source of trophic factors and can protect against reactive oxygen species and glutamate. Aside from these beneficial effects, the glial response can mediate a variety of deleterious events related to the production of reactive species, and pro-inflammatory prostaglandin and cytokines. This article reviews the potential protective and deleterious effects of glial cells in the substantia nigra pars compacta of Parkinson's disease

62. Yasojima K, Tourtellotte WW, McGeer EG, McGeer PL (2001) Marked increase in cyclooxygenase-2 in ALS spinal cord: implications for therapy. Neurology 57:952-956
    Abstract: OBJECTIVE: To evaluate the hypothesis that cyclooxygenase-2 (COX-2) is linked to the pathology of ALS by determining whether COX-2 mRNA levels are upregulated in ALS spinal cord. METHODS: Spinal cord from 11 ALS cases and 27 controls consisting of 15 cases of Alzheimer disease (AD), six cases of Parkinson disease (PD), three cases of cerebrovascular disease, and three control cases were analyzed. Total RNA was extracted and reverse transcriptase-PCR analysis performed for the mRNA of COX-2, COX-1, the Microglial marker CD11b, and the housekeeping gene cyclophilin. RESULTS: In ALS compared with non-ALS spinal cord, COX-2 mRNA was upregulated 7.09-fold (p < 0.0001), COX-1 1.14-fold (p = 0.05), and CD11b 1.85-fold (p = 0.0012). COX-2 mRNA levels in AD, PD, cerebrovascular disease, and control cases were each significantly lower than in ALS and were not significantly different from each other. Western blots of the protein products were in general accord with the mRNA data, with COX-2 protein levels being upregulated 3.79-fold compared with non-ALS cases (p = 0.015). CONCLUSIONS: The strong upregulation of COX-2 mRNA in ALS is in accord with studies in the superoxide dismutase transgenic mouse model in which COX-2 upregulation occurs. Taken in conjunction with evidence of a neuroprotective effect of COX-2 inhibitors in certain animal models and in organotypic cultures, the data are supportive of a possible future role for COX-2 inhibitors in the treatment of ALS

63. Grunblatt E, Mandel S, Youdim MB (2000) MPTP and 6-hydroxydopamine-induced neurodegeneration as models for Parkinson's disease: neuroprotective strategies. J.Neurol. 247 Suppl 2:II95-102
    Abstract: The etiology of Parkinson's disease is not known. Nevertheless, a significant body of biochemical data from human brain autopsy studies and from animal models points to an ongoing process of oxidative stress in the substantia nigra, which could initiate dopaminergic neurodegeneration. It is not known whether oxidative stress is a primary or secondary event. Oxidative stress, as induced by the neurotoxins 6-hydroxydopamine and MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), has been used in animal models to investigate the process of neurodegeneration to facilitate the development of antioxidant, neuroprotective drugs. It is apparent in these animal models that radical scavengers, iron chelators, dopamine agonists, nitric oxide synthase inhibitors and certain calcium channel antagonists provide neuroprotection against such toxins if given prior to the insult. Furthermore, recent work from human and animal studies has provided evidence of an inflammatory process. This expresses itself as proliferation of activated Microglia in the substantia nigra, activation and translocation of transcription factors and neurotrophic factor (NF), kappa-beta and elevation of cytotoxic cytokines, tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6. Both radical scavengers and iron chelators prevent lipopolysaccharide (LPS) and iron-induced activation of NF kappa-beta. If an inflammatory response is involved in Parkinson's disease, it would be logical to consider antioxidants and the newly developed, non-steroidal, anti-inflammatory drugs such as cyclo-oxygenase (COX2) inhibitors as a form of treatment. However, to date there has been little or no success in the clinical treatment of neurodegenerative diseases (for example, Parkinson's disease, ischaemia etc.) where neurons die, while in animal models the same drugs provide neuroprotection. This may indicate that either the animal models employed do not reflect the events in neurodegenerative diseases, or that because neuronal death involves a cascade of events, a single neuroprotective drug is not effective. Thus, consideration should be given to multi-neuroprotective drug therapy in Parkinson's disease, similar to the approach taken in AIDS and cancer therapy

64. Grunblatt E, Mandel S, Youdim MB (2000) Neuroprotective strategies in Parkinson's disease using the models of 6-hydroxydopamine and MPTP. Ann.N.Y.Acad.Sci. 899:262-273
    Abstract: The etiology of Parkinson's disease is not known. Nevertheless a significant body of biochemical data from human brain autopsy studies and those from animal models point to an on going process of oxidative stress in the substantia nigra which could initiate dopaminergic neurodegeneration. It is not known whether oxidative stress is a primary or secondary event. Nevertheless, oxidative stress as induced by neurotoxins 6-hydroxydopamine and MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) has been used in animal models to investigate the process of neurodegeneration with intend to develop antioxidant neuroprotective drugs. It is apparent that in these animal models radical scavengers, iron chelators, dopamine agonists, nitric oxide synthase inhibitors and certain calcium channel antagonists do induce neuroprotection against such toxins if given prior to the insult. Furthermore, recent work from human and animal studies has provided also evidence for an inflammatory process. This expresses itself by proliferation of activated Microglia in the substantia nigra, activation and translocation of transcription factors, NF kappa-beta and elevation of cytotoxic cytokines TNF alpha, IL1-beta, and IL6. Both radical scavengers and iron chelators prevent LPS (lipopolysaccharide) and iron induced activation of NF kappa-B. If an inflammatory response is involved in Parkinson's disease it would be logical to consider antioxidants and the newly developed non-steroid anti-inflammatory drugs such as COX2 (cyclo-oxygenase) inhibitors as a form of treatment. However to date there has been little or no success in the clinical treatment of neurodegenerative diseases per se (Parkinson's disease, ischemia etc.), where neurons die, while in animal models the same drugs produce neuroprotection. This may indicate that either the animal models employed are not reflective of the events in neurodegenerative diseases or that because neuronal death involves a cascade of events, a single neuroprotective drug would not be effective. Thus, consideration should be given to multi-neuroprotective drug therapy in Parkinson's disease, similar to the approach taken in AIDS and cancer therapy

65. Herrera AJ, Castano A, Venero JL, Cano J, Machado A (2000) The single intranigral injection of LPS as a new model for studying the selective effects of inflammatory reactions on dopaminergic system. Neurobiol.Dis. 7:429-447
    Abstract: We have injected lipopolysaccharide (LPS) into the nigrostriatal pathway of rats in order to address the role of inflammation in Parkinson's disease (PD). LPS induced a strong macrophage/Microglial reaction in Substantia nigra (SN), with a characteristic clustering of macrophage cells around blood-vessels. The SN was far more sensitive than the striatum to the inflammatory stimulus. Moreover, only the dopaminergic neurons of the SN were affected, with no detectable damage to either the GABAergic or the serotoninergic neurons. The damage to the DA neurons in the SN was permanent, as observed 1 year postinjection. Unlike the direct death of dopaminergic neurons caused by agents as MPP(+) or 6-OHDA, LPS seems to cause indirect death due to inflammatory reaction. Therefore, we suggest that the injection of a single dose of LPS within the SN is an interesting model for studying the selective effects of inflammatory reaction on dopaminergic system and also potentially useful for studying PD

66. Jellinger KA (2000) Cell death mechanisms in Parkinson's disease. J.Neural Transm. 107:1-29
    Abstract: OBJECTIVE: While the causes of neuronal death in Parkinson's disease (PD) and other neurodegenerative disorders are still unknown, several mechanisms are under discussion: programmed vs. passive cell death (apoptosis vs. necrosis), mainly based on conflicting results on the rare presence or absence of DNA fragmentation in substantia nigra neurons using the in situ DNA-labeling (TUNEL) method. DESIGN/METHODS: In 4 cases of Parkinson's disease (PD), 2 cases of Dementia with Lewy bodies (DLB) and 3 age-matched controls, the TUNEL/ISEL method was used to detect DNA fragmentation in substantia nigra locus coeruleus and cerebral cortex [method by Gold et al. (1994)]. In addition, immunohistochemistry was performed for an array of apoptosis-related proteins, i.e. the recently described apoptosis specific protein cJun/AP1 (ASP), the proto-oncogenes c-Jun, c-Jun AP1, Bcl2, Bax, Bcl-x, p53, CD 95 (Fas/Apo-1), activated caspase 3, several heat shock proteins (alpha-B crystallin, ubiquitin), and alpha-synuclein. RESULTS: None of the cases of PD, DLB, and controls showed convincing TUNEL-positivity nor morphologic signs of apoptosis in nigral, locus coeruleus or cortical neurons with or without Lewy bodies but variable numbers of TUNEL-positive astrocytes and Microglial cells in substantia nigra of PD and DLB. There were no significant differences in the expression of c-Jun, ASP, Bcl-2, Bax, and Bcl-x in substantia nigra neurons between PD, DLB, and controls nor between cortical and subcortical neurons with and without Lewy bodies. No expression of p53, and activated caspase 3, or any of the examined stress proteins was seen in neurons, while reactive astroglia and Microglia were decorated by antibodies to Bcl-2, Bax, alpha-B-crystallin and less, to Bcl-x and caspase 3. Lewy bodies, dystrophic neurites and axonal spheroids, all being negative for the applied apoptosis regulating proteins, showed strong expression of the examined stress proteins and of alpha-synuclein. CONCLUSIONS: These findings which are in line with previous results in Alzheimer's disease (Stadelmann et al., 1998) and Parkinson's disease (Banati et al., 1999) suggest that mechanisms distinct from classical apoptosis play a central role in the pathogenesis of PD and related neurodegener