Gene expression analysis in N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mice model of Parkinson's disease using cDNA microarray: effect of R-apomorphine

Microarray analysis reveals distinct gene expression patterns in the mouse cortex following chronic neuroleptic and stimulant treatment: implications for body weight changes

Atypical neuroleptics are associated with clinical significant weight gain, whereas stimulants are used as anorexiant drugs. The aim of this study was to examine gene expression changes in the mouse frontal cortex following chronic oral treatment with antipsychotics and a stimulant by microarray assessments. Twenty 10-12-week-old male C57BL6 mice received daily for 31 days either the typical neuroleptic haloperidol (1 mg/kg), the atypical neuroleptic clozapine (10 mg/kg) or the stimulant phenylpropanolamine (3 mg/kg). We identified a set of genes that was differently expressed between the neuroleptic-treated groups and the stimulant-treated group. Importantly, we found in the majority of gene alterations down-regulation in genes involved in ATP biosynthesis and lipid metabolism following the stimulant treatment, suggesting these genes as candidates that may regulate body weight. We also identified remarkable expression patterns of genes that encode signalling molecules (e.g. insulin, mitochondrial uncoupling protein 1) that are implicated in the control of food intake and are differently expressed in the neuroleptic groups.

Treatment of Alzheimer's disease: From pharmacology to a better understanding of disease pathophysiology

Alzheimer's disease (AD) is the most common cause of cognitive impairment in older patients and is expected to increase greatly in prevalence in the next future. It is characterized by the development of senile plaques and neurofibrillary tangles, which are associated with neuronal loss affecting to a greater extent cholinergic neurons. A cascade of pathophysiological events is triggered in AD that ultimately involves common cellular signalling pathways and leads to cellular and neural networks dysfunction, failure of neurotransmission, cell death and a common clinical outcome. The process is asynchronous and viable neurons remain an important target for therapeutic intervention at each stage of disease evolution. At present symptomatic drugs inhibiting the degradation of acetylcholine within synapses and more recently glutamate receptor antagonists represent the mainstay of therapy. However, interventions able to halt or slow disease progression (i.e., disease-modifying agents) are necessary. Although much progress has been made in this area, there are currently no clinically approved interventions for AD classed as disease modifying or neuroprotective. This paper reviews the main symptomatic strategies available for treating AD and future strategies for improving our therapeutic approach to AD.

Altered gene expression profiles reveal similarities and differences between Parkinson disease and model systems

Parkinson disease (PD) targets dopaminergic neurons in the substantia nigra, resulting in motor disturbances such as resting tremor, bradykinesia, and rigidity. Pathogenic processes likely occur over several decades, in that an overwhelming percentage of neurons are already dead at the time of clinical diagnosis. For this reason, the usage of animal model systems to discover the early steps in the pathologic cascade is required. These include exposure to the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which selectively kills dopamine neurons in the substantia nigra, and genetic models incorporating mutations in the alpha-synuclein gene that cause disease in human patients. Through the evaluation of these models at multiple time points, it is possible to discover novel gene expression changes that may underlie disease pathogenesis. Specifically, the authors hypothesize that animal models of PD and human PD brains share a gene expression profile that signifies certain aspects of pathogenesis and/or recovery-resistance. To test this and similar hypotheses, the authors and others have utilized new microarray technology that enables the sampling of thousands of genes' expression level in one assay. Because the technology is fairly new and results can vary depending on methods used, results must be evaluated with care. Multiple array and data-mining options can be used to make the most accurate inferences as to differentially expressed genes in each set of samples. The authors developed a fusion classifier approach whereby individual data-mining algorithms generate lists of significant genes. The lists are subsequently queried, and only genes unanimously called significant are retained for further validation. Although the authors' approach identified hundreds of differentially expressed genes in each of three PD systems, only a few were common between the human and animal substantia nigra. These were related to dopamine phenotype, synaptic function, and the mitochondrial metabolism, implicating the presynaptic terminal as a primary site of injury. The time course of the authors' experiments indicates that if the synaptic changes could be prevented, this may alleviate some cell death, in that these changes precede neuronal loss.

The role of oxidative stress in the dysregulation of gene expression and protein metabolism in neurodegenerative disease

There are few examples for which the genetic basis for neurodegenerative disease has been identified. For the majority of these disorders, the key to their understanding lies in knowledge of the molecular changes that contribute to altered gene expression and the translational modification of the protein products. Environmental factors play a role in the development and chronicity of neurodegenerative disorders. Environmental stimuli such as hypoxia, toxins, or heavy metals, increase production of reactive oxygen species and lower energy reserves. Chronic exposure to oxidative radicals can adversely affect gene expression and proteolysis. This review summarizes what is currently known about some of the changes in gene expression and protein metabolism that occur after oxidative stress which contribute to neurodegeneration, and reveals areas where more research is clearly needed.

Gene expression profile of activated microglia under conditions associated with dopamine neuronal damage

Microglia are the resident antigen-presenting cells within the central nervous system (CNS), and they serve immune-like functions in protecting the brain against injury and invading pathogens. By contrast, activated microglia can secrete numerous reactants that damage neurons. The pathogenesis of various neurodegenerative diseases has been associated with microglial activation, but the signaling pathways that program a neuronally protective or destructive phenotype in microglia are not known. To increase the understanding of microglial activation, microarray analysis was used to profile the transcriptome of BV-2 microglial cells after activation. Microglia were activated by lipopolysaccharide, the HIV neurotoxic protein TAT, and dopamine quinone, each of which has been linked to dopamine neuronal damage. We identified 210 of 9882 genes whose expression was differentially regulated by all activators (116 increased and 94 decreased in expression). Gene ontology analysis assigned up-regulated genes to a number of specific biological processes and molecular functions, including immune response, inflammation, and cytokine/chemokine activity. Genes down-regulated in expression contribute to conditions that are permissive of microglial migration, lowered adhesion to matrix, lessened phagocytosis, and reduction in receptors that oppose chemotaxis and inflammation. These results elaborate a broad profile of microglial genes whose expression is altered by conditions associated with both neurodegenerative diseases and microglial activation.

Increased plasma levels of TNF-α but not of IL1-β in MPTP-treated monkeys one year after the MPTP administration

The cause of Parkinson's disease remains unknown although some evidence suggests that an inflammatory reaction, mediated by cytokines such as TNF-alpha and IL-1beta, is related with dopaminergic degeneration in the brain. In the present work we measured the plasma levels of TNF-alpha and IL-1beta in parkinsonian monkeys one year after MPTP administration. TNF-alpha levels were seen to have increased in parkinsonian monkeys reflecting the clinical symptoms observed, while IL-1beta levels remained unchanged. These results suggest that TNF-alpha plays a role in sustaining of dopaminergic degeneration in chronic parkinsonism.

Selective alterations of transcription factors in MPP+-induced neurotoxicity in PC12 cells

MPP(+) (1-methyl-4-phenylpyridinium; the active metabolite of the neurotoxin MPTP (1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine)) depletes dopamine (DA) content and elicits cell death in PC12 cells. However, the mechanism of MPP(+)-induced neurotoxicity is still unclear. In this study, the dose response and time-course of MPP(+)-induced DA depletion and decreased cell viability were determined in nerve growth factor (NGF)-differentiated PC12 cells. The alteration of transcription factors (TFs) induced by MPP(+) from a selected dose level and time point was then evaluated using protein/DNA-binding arrays. K-means clustering analysis identified four patterns of protein/DNA-binding changes. Three of the 28 TFs identified in PC12 cells increased by 100% (p53, PRE, Smad SBE) and 2 decreased by 50% (HSE, RXR(DR1)) of control with MPP(+) treatment. In addition, three TFs decreased within the range of 33-50% (TFIID, E2F1, CREB) and two TFs increased within the range of 50-100% (PAX-5, Stat4). An electrophoretic mobility shift assay (EMSA) was used to confirm the changes of p53 and HSE. The observed changes in TFs correlated with the alterations of DA and cell viability. The data indicates that selective transcription factors are involved in MPP(+)-induced neurotoxicity and it provides mechanistic information that may be applicable to animal studies with MPTP and clinical studies of Parkinson's disease.

Gain-of-function screen identifies a role of the Sec61alpha translocon in Drosophila postmitotic neurotoxicity

To elucidate the intrinsic mechanisms of neurotoxicity induction, including those underlying neural cell death and neurodegeneration, we developed a gain-of-function screen for gene products causing neural cell loss. To identify novel genes with a cell-death-related function in neurons, we screened 4,964 Drosophila GS lines, in which one or two genes from much of the Drosophila genome can be overexpressed. Approximately 0.68% of the GS lines produced phenotypes involving a loss of postmitotic neurons. Of these, we identified and characterized the endd2 gene, which encodes the Drosophila ortholog of Sec61alpha (DSec61alpha), an endoplasmic reticulum protein with protein translocation activity. Ectopic expression of DSec61alpha caused neural cell death accompanied by the accumulation of ubiquitinated proteins, which was mediated by DSec61alpha's translocon activity. This supported our previous observation that the DSec61alpha translocon contributes to expanded polyglutamine-mediated neuronal toxicity, which is also associated with ubiquitinated protein accumulation. These data suggest that the translocon may be a novel component of neural cell death and degeneration pathways. Our approach can be used to identify potential neurotoxic factors within the whole genome, which will increase our understanding of the molecular mechanisms of various types of cell death, including those associated with human neurodegenerative diseases.

Multi-functional drugs for various CNS targets in the treatment of neurodegenerative disorders

Individuals with neurodegenerative diseases such as Parkinson's disease or Alzheimer's disease are benefiting from drugs developed to act on a single molecular target. However, current pharmacological approaches are limited in their ability to modify significantly the course of the disease, and offer incomplete and transient benefit to patients. New therapeutic strategies comprise drug candidates designed specifically to act on multiple neural and biochemical targets for the treatment of cognition impairment, motor dysfunction, depression and neurodegeneration. Examples include the development of single molecular entities that combine two or more of the following properties: (i) cholinesterase inhibition; (ii) activation or inhibition of specific subtypes of acetylcholine receptors or alpha-adrenoceptors; (iii) anti-inflammatory activity; (iv) monoamine oxidase inhibition; (v) catechol-O-methyl transferase inhibition; (vi) nitric oxide production; (vii) neuroprotection; (viii) anti-apoptotic activity; and (ix) activation of mitochondrial-dependent cell-survival genes and proteins. These bi- or multi-functional compounds might provide greater symptomatic efficacy, and better utility as potential neuroprotective disease-modifying drugs.

Triptolide protects dopaminergic neurons from inflammation-mediated damage induced by lipopolysaccharide intranigral injection

Converging lines of evidence suggest that neuroinflammatory processes may account for the progressive death of dopaminergic neurons in Parkinson's disease (PD). Therefore, anti-inflammatory strategies have attracted much interest for their potential to prevent further deterioration of PD. Our previous study showed that triptolide, a traditional Chinese herbal compound with anti-inflammatory and immunosuppressive properties, protected dopaminergic neurons from lipopolysaccharide (LPS)-induced damage in primary embryonic midbrain cell cultures. To examine further if triptolide can protect dopaminergic neurons from inflammation-mediated damage in vivo, microglial activation and injury of dopaminergic neurons were induced by LPS intranigral injection, and the effects of triptolide treatment on microglial activation and survival ratio and function of dopaminergic neurons were investigated. Our results demonstrated that microglial activation induced by a single intranigral dose of 10 mug of LPS reduced the survival ratio of tyrosine hydroxylase-immunoreactive (TH-ir) neurons in the substantia nigra pars compacta (SNpc) to 29% and the content of dopamine (DA) in striatum to 37% of the non-injected side. Intriguingly, treatment with triptolide of 5 mug/kg for 24 days once per day dramatically improved the survival rate of TH-ir neurons in the SNpc to 79% of the non-injected side. Meanwhile, treatment with triptolide of 1 or 5 mug/kg for 24 days once per day significantly improved DA level in striatum to 70% and 68% of the non-injected side, respectively. Complement receptor 3 (CR3) immunohistochemical staining revealed that triptolide treatment potently inhibited LPS-elicited deleterious activation of microglia in SNpc. The excessive production of cytokines, such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta, was significantly abolished by triptolide administration. These results, together with our previous data in vitro, highly suggest the effectiveness of triptolide in protecting dopaminergic neurons against inflammatory challenge.

sgk1, a member of an RNA cluster associated with cell death in a model of Parkinson's disease

In an effort to gain deeper insight into the molecular processes underlying neurodegeneration in Parkinson's disease, we performed gene expression profiling at several early time points after MPTP-injection into old (1-year) mice. We used a PCR-based gene expression profiling method, digital expression pattern display (DEPD), a method of very high sensitivity and reproducibility, which displays almost all transcripts of a tissue. To identify cell death-associated genes, we defined clusters of differentially expressed transcripts with expression behaviour that correlated with the temporal profile of cell death progression and characterized one of these cell death clusters further. We selected one of the strongest regulated genes, the serum and glucocorticoid-regulated kinase 1 (sgk1), and validated its differential expression by Northern blot analysis, semiquantitative PCR and in situ hybridization. Up-regulation of sgk1 (i) coincides with the onset of dopaminergic cell death in both the 8-week acute and 1-year subacute MPTP models, (ii) spans the entire brain, (iii) is attenuated by the l-deprenyl-mediated inhibition of the MPTP conversion to its active metabolite MPP+ and (iv) is not induced by dehydration. This study demonstrated that the combination of the DEPD technology, clustering analysis and a detailed histopathology is a useful tool for elucidating molecular pathways in neurodegenerative diseases.

Genotoxic, neurotoxic and neuroprotective activities of apomorphine and its oxidized derivative 8-oxo-apomorphine

Apomorphine is a dopamine receptor agonist proposed to be a neuroprotective agent in the treatment of patients with Parkinson's disease. Both in vivo and in vitro studies have shown that apomorphine displays both antioxidant and pro-oxidant actions, and might have either neuroprotective or neurotoxic effects on the central nervous system. Some of the neurotoxic effects of apomorphine are mediated by its oxidation derivatives. In the present review, we discuss recent studies from our laboratory in which the molecular, cellular and neurobehavioral effects of apomorphine and its oxidized derivative, 8-oxo-apomorphine-semiquinone (8-OASQ), were evaluated in different experimental models, i.e., in vitro genotoxicity in Salmonella/microsome assay and WP2 Mutoxitest, sensitivity assay in Saccharomyces cerevisiae, neurobehavioral procedures (inhibition avoidance task, open field behavior, and habituation) in rats, stereotyped behavior in mice, and Comet assay and oxidative stress analyses in mouse brain. Our results show that apomorphine and 8-OASQ induce differential mutagenic, neurochemical and neurobehavioral effects. 8-OASQ displays cytotoxic effects and oxidative and frameshift mutagenic activities, while apomorphine shows antimutagenic and antioxidant effects in vitro. 8-OASQ induces a significant increase of DNA damage in mouse brain tissue. Both apomorphine and 8-OASQ impair memory for aversive training in rats, although the two drugs showed a different dose-response pattern. 8-OASQ fails to induce stereotyped behaviors in mice. The implications of these findings are discussed in the light of evidence from studies by other groups. We propose that the neuroprotective and neurotoxic effects of dopamine agonists might be mediated, in part, by their oxidized metabolites.

Quantitative proteomic analysis of mitochondrial proteins: relevance to Lewy body formation and Parkinson's disease

The mechanisms underlying Parkinson's disease (PD) and Lewy body (LB) formation, a pathological hallmark of PD, are incompletely understood; however, mitochondrial dysfunction is likely to be at least partially responsible. To study the processes that might be related to nigral neurodegeneration and LB formation, we employed nonbiased quantitative proteomics with isotope-coded affinity tag (ICAT) to compare the mitochondrial protein profiles in the substantia nigra (SN) between controls and mice treated chronically with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a potent mitochondrial toxicant, and an adjuvant, probenecid (prob), for 5 weeks, which produced selective nigrostriatal neurodegeneration with formation of LB-like cytoplasmic inclusions in the remaining nigral neurons. This method identified a total of more than 300 proteins; of these proteins, more than 100 displayed significant changes in relative abundance in the MPTP/prob-treated mice compared to the controls. We validated one of these proteins, DJ-1, whose mutation has been implicated in familial PD, with Western blot analysis, followed by immunohistochemical studies of its distribution in the SN in relation to cytoplasmic inclusions in mice, as well as in classical LBs in PD patients. The results demonstrated that DJ-1 was not only colocalized with alpha-synuclein in dopaminergic neurons but also to cytoplasmic inclusions in mice treated with MPTP/prob. In addition, DJ-1 was present in the halo but not in the core of classical LBs in patients with PD. Our findings suggested that DJ-1 might play an important role in mitochondrial dysfunction, as well as LB formation in PD.

Genetic and genomic studies of Drosophila parkin mutants implicate oxidative stress and innate immune responses in pathogenesis

Loss-of-function mutations of the parkin gene, which encodes a ubiquitin-protein ligase, are a common cause of autosomal recessive juvenile parkinsonism (ARJP). Previous work has led to the identification of a number of Parkin substrates that implicate specific pathways in ARJP pathogenesis, including endoplasmic reticulum (ER) stress and cell cycle activation. To test the involvement of previously implicated pathways, as well as to identify novel pathways in ARJP pathogenesis, we are using genetic and genomic approaches to study Parkin function in the fruit fly Drosophila melanogaster. In previous work, we demonstrated that Drosophila parkin null mutants exhibit mitochondrial pathology and flight muscle degeneration. To further explore the mechanisms responsible for pathology in parkin mutants, we analyzed the transcriptional alterations that occur during muscle degeneration and performed a genetic screen for parkin modifiers. Results of these studies indicate that oxidative stress response components are induced in parkin mutants and that loss-of-function mutations in oxidative stress components enhance the parkin mutant phenotypes. Genes involved in the innate immune response are also induced in parkin mutants. In contrast, our studies did not reveal evidence for cell cycle or ER stress pathway induction in parkin mutants. These results suggest that oxidative stress and/or inflammation may play a fundamental role in the etiology of ARJP.

Neuroprotective and neurotrophic effect of apomorphine in the striatal 6-OHDA-lesion rat model of Parkinson's disease

We investigated the possible neuroprotective effect of the dopamine (DA) receptor agonist R-apomorphine (R-APO) within the striatal 6-hydroxydopamine (6-OHDA) rat model of Parkinson's disease. In one group of rats, R-APO administration (10 mg/kg/day, s.c.) started 15 min before 6-OHDA-injection. In a second group, R-APO administration started 24 h after lesion induction. Both groups received R-APO chronically for 11 days. Testing was carried out 2 weeks post-lesioning. R-APO treatment, whether started before or after the lesion induction, significantly reduced both the amphetamine-induced ipsiversive rotation and the size of the lesion at the level of the substantia nigra. Moreover, the dopamine cell shape and size resembled that observed in intact animals. R-APO treatment had no effect on the number of cells in the substantia nigra of intact rats, but significantly increased the number of cells in the ventral tegmental area (VTA), suggesting selective neurotrophic properties of R-APO in this region. R-APO treatment significantly attenuated the 6-OHDA-induced striatal DA depletion and DOPAC/DA ratios were normalized. Finally, an acute injection of 10 mg/kg R-APO was unable to scavenge 6-OHDA or MPP(+)-induced hydroxyl radicals as determined with the in vivo salicylate trapping technique. These data provide further evidence of the neurorescuing properties of R-APO. At least at the dose used in this study, this effect possibly occurs via mechanisms other than scavenging of hydroxyl radicals. In intact rats, we also show neurotrophic effects of the R-APO treatment. These seem to be limited to the VTA.

Electro-acupuncture stimulation protects dopaminergic neurons from inflammation-mediated damage in medial forebrain bundle-transected rats

Through producing a variety of cytotoxic factors upon activation, microglia are believed to participate in the mediation of neurodegeneration. Intervention against microglial activation may therefore exert a neuroprotective effect. Our previous study has shown that the electro-acupuncture (EA) stimulation at 100 Hz can protect axotomized dopaminergic neurons from degeneration. To explore the underlying mechanism, the effects of 100 Hz EA stimulation on medial forebrain bundle (MFB) axotomy-induced microglial activation were investigated. Complement receptor 3 (CR3) immunohistochemical staining revealed that 24 sessions of 100 Hz EA stimulation (28 days after MFB transection) significantly inhibited the activation of microglia in the substantia nigra pars compacta (SNpc) induced by MFB transection. Moreover, 100 Hz EA stimulation obviously inhibited the upregulation of the levels of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta mRNA in the ventral midbrains in MFB-transected rats, as revealed by reverse transcriptase polymerase chain reaction (RT-PCR). ED1 immunohistochemical staining showed that a large number of macrophages appeared in the substantia nigra (SN) 14 days after MFB transection. The number of macrophages decreased by 47% in the rats that received 12 sessions of EA simulation after MFB transection. These data indicate that the neuroprotective role of 100 Hz EA stimulation on dopaminergic neurons in MFB-transected rats is likely to be mediated by suppressing axotomy-induced inflammatory responses. Taken together with our previous results, this study suggests that the neuroprotective effect of EA on the dopaminergic neurons may stem from the collaboration of its anti-inflammatory and neurotrophic actions.

Spinal cord molecular profiling provides a better understanding of amyotrophic lateral sclerosis pathogenesis

Research efforts in amyotrophic lateral sclerosis (ALS) have not yet provided a comprehensive explanation of the disease pathogenesis, which is emerging as a complex interaction between multiple factors. Gene expression studies traditionally based on single mRNA specie analysis have recently progressed to allow entire transcriptional profiles of affected tissues to be obtained through array-based methods. This experimental approach has significantly improved our understanding of the molecular changes occurring in ALS, although its limitations in the detection of low-abundance transcripts in tissues with a high level of complexity are becoming increasingly recognized. In this paper, experimental findings based on an expression study in post-mortem spinal cord from sporadic ALS individuals will be discussed in light of recently published data using array analysis in an animal model of the disease. Previous expression data obtained using conventional techniques are also compared. Through the analysis of the information arising from ALS post-mortem and animal model tissues studies, we have identified a pattern of molecular events in which factors implicated in the immune response, cytoprotection and growth-differentiation are differentially regulated in a time-dependent way from early to advanced stages of disease progression.

High throughput approaches in neuroscience

Traditional approaches to understanding biological problems are now being advanced with the use of high throughput technologies, which analyse multiple samples simultaneously, or thousands of analytes in a single sample. The application of these technologies in neurochemistry and neuroscience is beginning to be explored and is assisting in the development of new models of drug action, neuroanatomical investigations, and in identifying molecular pathways involved in neurological and psychiatric disease. Tools such as microarray-based gene expression profiling and 2D and multidimensional proteomic methods are uncovering functional components to a wide variety of neuroscience paradigms and the application of these technologies is set to become standard in analysis.

Expression profile analysis of neurodegenerative disease: advances in specificity and resolution

Microarray technology has become a common tool for developing expression profiles. Initially used in the analysis of cells lines and homogeneous tissues, this platform has been applied to more diverse tissues, such as the brain. Several neural disorders have already been profiled by microarrays using relatively large amounts of tissue. This data has unveiled many genes with differential expression between normal and diseased tissue that could potentially be used as gene markers for these afflictions. Because of the heterogeneity of the CNS, it is likely that small differences between gene expression in these studies would be enhanced by the sampling of a subset of cells based on these newly characterized gene markers. Subtraction of normal, unaffected cells from the sample may also result in a more accurate profile of a diseased cell. Expression profile studies from several neuropathological states are presented, with emphasis placed on those studies using small samples of cellular material and those using specialized methods of cell isolation and RNA amplification.

Prevention of MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) dopaminergic neurotoxicity in mice by chronic lithium: involvements of Bcl-2 and Bax

Lithium has been reported to exert neuroprotective activity in several neuronal cell cultures and in vivo models against glutamate toxicity. Since this action was reported to be associated with alterations in the antiapoptotic Bcl-2 family proteins, the effect of chronic lithium diet on the ability of the parkinsonism neurotoxin, N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to deplete striatal dopamine in mice was determined. Mice were fed for with a diet containing 1.1, 2.2, 3.3, and 4.4 g/kg lithium chloride (LiCl) for 4 weeks, during which time serum levels of lithium were monitored. The 3.3 g/kg lithium diet gave serum level value very similar to what is observed in lithium therapy in man and the 4.4 g/kg well above this. At the end of this period the mice received 24 mg/kg MPTP i.p. once daily for 3 days. A direct relation was established with the increase in serum lithium and its ability to prevent MPTP induced depletion of striatal dopamine (DA) and its metabolites DPOAC and HVA. With the diet containing the highest lithium concentration there was an almost complete prevention of striatal dopamine depletion and the reduction in tyrosine hydroxylase activity and protein and it prevented the increase in dopamine turnover (DOPAC + HVA/DA) normally observed in MPTP treatment. Lithium did not interfere with the metabolism of MPTP, or with its brain uptake, since, the level of its monoamine oxidase (MAO) B derived metabolite, MPP+, in the striata of lithium and non-lithium treated mice were almost identical. Striatal Bcl-2 was significantly decreased, while Bax was increased in MPTP treated mice. Lithium treatment not only increased striatal Bcl-2 in control mice, but also prevented its reduction as induced by MPTP, and an opposing effect was seen with Bax. The neuroprotective action of lithium in this model of Parkinson's disease has been attributed to its antiapoptotic activity which among other factors includes induction of Bcl-2 and reduction of Bax.

Identification of genes regulated by memantine and MK-801 in adult rat brain by cDNA microarray analysis

In this study, we monitored gene expression profiles using cDNA microarrays after an acute systemic administration of the high affinity N-methyl-D-aspartate (NMDA) uncompetitive antagonist MK-801 (1 mg/kg; 4 h), and the clinically used moderate affinity antagonist memantine (25 mg/kg; 4 h) in adult rat brains. From a microarray containing 1090 known genes, 13 genes were regulated by both treatments of which 12 were upregulated and one was downregulated. In addition, 28 and 34 genes were regulated (> or = 1.5- or < or = 0.67-fold change) by either memantine or MK-801, respectively. Genes commonly regulated by both treatments and not previously reported were confirmed by in situ hybridization (ISH) and include regenerating liver inhibitory factor-1 (RL/IF-1), GDP-dissociation inhibitor 1 (GDI-1), neural visinin Ca2+-binding protein 2 (NVP-2), neuromedin B receptor, and Na+/K+ transporting ATPase 2beta. ISH with memantine (5-50 mg/kg) revealed regulation of these genes in other cortical and hippocampal regions. RL/IF-1 induction occurred at 1 h and returned to basal levels by 8 h, consistent with the profile of an immediate early gene. Western blot analysis showed increases (approximately 30-65%) in GDI-1 protein present in both cytosolic and membrane fractions that were significant in the 84-kDa Rab bound form, suggesting that memantine influences Ras-like GTPase function. Genes regulated by a 5 mg/kg dose of memantine might be important in its therapeutic effects. These findings increase the number of known, differentially altered genes after treatment of uncompetitive NMDA receptor antagonists and suggest broader actions of these agents than previously realized.

Genetic ablation of tumor necrosis factor-alpha (TNF-alpha) and pharmacological inhibition of TNF-synthesis attenuates MPTP toxicity in mouse striatum

The impact of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) in the pathology of Parkinson's disease (PD) and in MPTP neurotoxicity remains unclear. Here, male TNF-alpha (-/-) deficient mice and C57bL/6 mice were treated with MPTP (4 x 15 mg/kg, 24 h intervals) and in one series, thalidomide was administered to inhibit TNF-alpha synthesis. Real-time RT-PCR revealed that the striatal mRNA levels of TNF-alpha, of the astrocytic marker glial fibrillary acidic protein (GFAP) and of the marker for activated microglia, macrophage antigen complex-1 (MAC-1), were significantly enhanced after MPTP administration. Thalidomide (50 mg/kg, p.o.) partly protected against the MPTP-induced dopamine (DA) depletion, and TNF-alpha (-/-) mice showed a significant attenuation of striatal DA and DA metabolite loss as well as striatal tyrosine hydroxylase (TH) fiber density, but no difference in nigral TH and DA transporter immunoreactivity. TNF-alpha deficient mice suffered a lower mortality (10%) compared to the high mortality (75%) seen in wild-type mice after acute MPTP treatment (4 x 20 mg/kg, 2 h interval). HPLC measurement of MPP(+) levels revealed no differences in TNF-alpha (-/-), wild-type and thalidomide treated mice. This study demonstrates that TNF-alpha is involved in MPTP toxicity and that inhibition of TNF-alpha response may be a promising target for extending beyond symptomatic treatment and developing anti-parkinsonian drugs for the treatment of the inflammatory processes in PD.

Cell signaling pathways in the neuroprotective actions of the green tea polyphenol (-)-epigallocatechin-3-gallate: implications for neurodegenerative diseases

Accumulating evidence supports the hypothesis that brain iron misregulation and oxidative stress (OS), resulting in reactive oxygen species (ROS) generation from H2O2 and inflammatory processes, trigger a cascade of events leading to apoptotic/necrotic cell death in neurodegenerative disorders, such as Parkinson's (PD), Alzheimer's (AD) and Huntington's diseases, and amyotrophic lateral sclerosis (ALS). Thus, novel therapeutic approaches aimed at neutralization of OS-induced neurotoxicity, support the application of ROS scavengers, transition metals (e.g. iron and copper) chelators and non-vitamin natural antioxidant polyphenols, in monotherapy, or as part of antioxidant cocktail formulation for these diseases. Both experimental and epidemiological evidence demonstrate that flavonoid polyphenols, particularly from green tea and blueberries, improve age-related cognitive decline and are neuroprotective in models of PD, AD and cerebral ischemia/reperfusion injuries. However, recent studies indicate that the radical scavenger property of green tea polyphenols is unlikely to be the sole explanation for their neuroprotective capacity and in fact, a wide spectrum of cellular signaling events may well account for their biological actions. In this article, the currently established mechanisms involved in the beneficial health action and emerging studies concerning the putative novel molecular neuroprotective activity of green tea and its major polyphenol (-)-epigallocatechin-3-gallate (EGCG), will be reviewed and discussed.

Ironing Iron Out in Parkinson's Disease and Other Neurodegenerative Diseases with Iron Chelators: A Lesson from 6-Hydroxydopamine and Iron Chelators, Desferal and VK-28

In Parkinson's disease (PD) and its neurotoxin-induced models, 6-hydroxydopamine (6-OHDA) and N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), significant accumulation of iron occurs in the substantia nigra pars compacta. The iron is thought to be in a labile pool, unbound to ferritin, and is thought to have a pivotal role to induce oxidative stress-dependent neurodegeneration of dopamine neurons via Fenton chemistry. The consequence of this is its interaction with H(2)O(2) to generate the most reactive radical oxygen species, the hydroxyl radical. This scenario is supported by studies in both human and neurotoxin-induced parkinsonism showing that disposition of H(2)O(2) is compromised via depletion of glutathione (GSH), the rate-limiting cofactor of glutathione peroxide, the major enzyme source to dispose H(2)O(2) as water in the brain. Further, radical scavengers have been shown to prevent the neurotoxic action of the above neurotoxins and depletion of GSH. However, our group was the first to demonstrate that the prototype iron chelator, desferal, is a potent neuroprotective agent in the 6-OHDA model. We have extended these studies and examined the neuroprotective effect of intracerebraventricular (ICV) pretreatment with the prototype iron chelator, desferal (1.3, 13, 134 mg), on ICV induced 6-OHDA (250 micro g) lesion of striatal dopamine neurons. Desferal alone at the doses studied did not affect striatal tyrosine hydroxylase (TH) activity or dopamine (DA) metabolism. All three pretreatment (30 min) doses of desferal prevented the fall in striatal and frontal cortex DA, dihydroxyphenylacetic acid, and homovalinic acid, as well as the left and right striatum TH activity and DA turnover resulting from 6-OHDA lesion of dopaminergic neurons. A concentration bell-shaped neuroprotective effect of desferal was observed in the striatum, with 13 micro g being the most effective. Neither desferal nor 6-OHDA affected striatal serotonin, 5-hydroxyindole acetic acid, or noradrenaline. Desferal also protected against 6-OHDA-induced deficit in locomotor activity, rearing, and exploratory behavior (sniffing) in a novel environment. Since the lowest neuroprotective dose (1.3 micro g) of desferal was 200 times less than 6-OHDA, its neuroprotective activity may not be attributed to interference with the neurotoxin activity, but rather iron chelation. These studies led us to develop novel brain-permeable iron chelators, the VK-28 series, with iron chelating and neuroprotective activity similar to desferal for ironing iron out from PD and other neurodegenerative diseases, such as Alzheimer's disease, Friedreich's ataxia, and Huntington's disease.

Oxidative damage in brains of mice treated with apomorphine and its oxidized derivative

Increasing evidence suggests that some of the neurobiological and neurotoxic actions of apomorphine and other dopamine receptor agonists might be mediated by their oxidation derivatives. The aim of the present study was to evaluate the effects of apomorphine and its oxidation derivative, 8-oxo-apomorphine-semiquinone (8-OASQ), on oxidative stress parameters and antioxidant enzyme activity. Adult male CF-1 mice were treated with a systemic injection of apomorphine (0.4, 4.0 or 40.0 mg/kg) or 8-OASQ (0.4, 4.0 or 40.0 mg/kg). Animals were sacrificed by decapitation 24 h after treatment, and the forebrains were collected for analysis of thiobarbituric acid reactive species, protein carbonyls, the total radical-trapping antioxidant parameter, catalase and superoxide dismutase. These treatments did not induce lipid peroxidation at any dose tested. In contrast, apomorphine induced an increase in protein carbonylation and a decrease in total radical-trapping antioxidant parameter at all doses tested. 8-OASQ induced an increase in protein carbonylation and a decrease in total radical-trapping antioxidant parameter only at the higher dose tested. All apomorphine doses tested induced an increase in catalase, but not superoxide dismutase activities. In contrast, 8-OASQ induced a dose-dependent increase in CAT activity. The results suggest that apomorphine and its oxidation product, 8-OASQ, induce differential effects on CNS oxidative parameters.

Neuroprotection by a novel brain permeable iron chelator, VK-28, against 6-hydroxydopamine lession in rats

Significant increase in iron occurs in the substantia nigra pars compacta of Parkinsonian subjects, and in 6-hydroxydopamine (6-OHDA) treated rats and monkeys. This increase in iron has been attributed to its release from ferritin and is associated with the generation of reactive oxygen species and the onset of oxidative stress-induced neurodegeneration. Several iron chelators with hydroxyquinoline backbone were synthesized and their ability to inhibit basal as well as iron-induced mitochondrial lipid peroxidation was examined. The neuroprotective potential of the brain permeable iron chelator, VK-28 (5-[4-(2-hydroxyethyl) piperazine-1-ylmethyl]-quinoline-8-ol), injected either intraventricularly (ICV) or intraperitoneally (IP), to 6-OHDA lesioned rats was investigated. VK-28 inhibited both basal and Fe/ascorbate induced mitochondrial membrane lipid peroxidation, with an IC(50) (12.7 microM) value comparable to that of the prototype iron chelator, desferal, which does not cross the blood brain barrier. At an ICV pretreatment dose as low as 1 microg, VK-28 was able to completely protect against ICV 6-OHDA (250 microg) induced striatal dopaminergic lesion, as measured by dopamine (DA), dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA) levels. IP injection of rats with VK-28 (1 and 5 mg/kg) daily for 10 and 7 days, respectively, demonstrated significant neuroprotection against ICV 6-OHDA at the higher dose, with 68% protection against loss of dopamine at 5mg/kg dosage of VK-28. The present study is the first to show neuroprotection with a brain permeable iron chelator. The latter can have implications for the treatment of Parkinson's disease and other neurodegenerative diseases (Alzheimer's disease, Friedreich ataxia, aceruloplasminemia, Hallervorden Spatz syndrome) where abnormal iron accumulation in the brain is thought to be associated with the degenerative processes.

Neuroprotective strategies in Parkinson's disease : an update on progress

In spite of the extensive studies performed on postmortem substantia nigra from Parkinson's disease patients, the aetiology of the disease has not yet been established. Nevertheless, these studies have demonstrated that, at the time of death, a cascade of events had been initiated that may contribute to the demise of the melanin-containing nigro-striatal dopamine neurons. These events include increased levels of iron and monoamine oxidase (MAO)-B activity, oxidative stress, inflammatory processes, glutamatergic excitotoxicity, nitric oxide synthesis, abnormal protein folding and aggregation, reduced expression of trophic factors, depletion of endogenous antioxidants such as reduced glutathione, and altered calcium homeostasis. To a large extent, the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA) animal models of Parkinson's disease confirm these findings. Furthermore, neuroprotection can be afforded in these models with iron chelators, radical scavenger antioxidants, MAO-B inhibitors, glutamate antagonists, nitric oxide synthase inhibitors, calcium channel antagonists and trophic factors. Despite the success obtained with animal models, clinical neuroprotection is much more difficult to accomplish. Although the negative studies obtained with the MAO-B inhibitor selegiline (deprenyl) and the antioxidant tocopherol (vitamin E) may have resulted from an inappropriate choice of drug (selegiline) or an inadequate dose (tocopherol), the niggling problem that still remains is why these drugs, and others, do work in animals while they fail in the clinic. One reason for this may be related to the fact that in normal human brains the number of dopaminergic neurons falls by around 3-5% every decade, while in Parkinson's disease this decline is greater. Brain autopsy studies have shown that by the time the disease is identified, some 70-75% of the dopamine-containing neurons have been lost. More sensitive reliable methods and clinical correlative markers are required to discern between confoundable symptomatic effects versus a possible neuroprotective action of drugs, namely, the ability to delay or forestall disease progression by protecting or rescuing the remaining dopamine neurons or even restoring those that have been lost.A number of other possibilities for the clinical failure of potential neuroprotectants also exist. First, the animal models of Parkinson's disease may not be totally reflective of the disease and, therefore, the chemical pathologies established in the animal models may not cause, or contribute to, the progression of the disease clinically. Second, because of the series of events occurring in neurodegeneration and our ignorance about which of these factors constitutes the primary event in the pathogenic process, a single drug may not be adequate to induce neuroprotection and, as a consequence, use of a cocktail of drugs may be more appropriate. The latter concept receives support from recent complementary DNA (cDNA) microarray gene expression studies, which show the existence of a gene cascade of events occurring in the nigrostriatal pathway of MPTP, 6-OHDA and methamphetamine animal models of Parkinson's disease. Even with the advent of powerful new tools such as genomics, proteomics, brain imaging, gene replacement therapy and knockout animal models, the desired end result of neuroprotection is still beyond our current capability.

What have we learnt from CDNA microarray gene expression studies about the role of iron in MPTP induced neurodegeneration and Parkinson's disease?

There have been numerous hypotheses concerning the etiology and mechanism of dorsal raphe dopaminergic neurodegeneration in Parkinson's disease and its animal models, MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and 6-hydroxydopamine. The advent of cDNA microarray gene expression where expression of thousands of genes can be globally assessed has indicated that mechanism of neurodegeneration by MPTP is a complex cascade of vicious circles. One of these is the alteration of genes associated with iron metabolism, a transitional metal closely associated with inducing the formation of reactive oxygen species and inducing oxidative stress. cDNA gene expression analyses support the established hypothesis of oxidative induced neurodegeneration involving iron deposition in substantia nigra pars compacta (SNPC) parkinsonian brains. The regulation of cellular iron metabolism has been further enhanced by the recent discovery of two iron regulatory proteins, IRP1 and IRP2 which control the level of iron with in the cell. When the cellular level of iron increases IRP2 is degraded by ubiquitination and no further iron accumulates. The reverse occurs when the level of iron is low within the cell. Knock-out IRP1 and IRP2 mice have shown that in latter mice brain iron accumulation precedes the neurodegeneration, ataxia and bradykinesia observed in these animals. Indeed MPTP treatment, which results in iron accumulation in SNCP, abolishes IRP2 with the concomitant increase in alpha-synuclein. Iron chelators such as R-apomorphine and EGCG, which protect against MPTP neurotoxicity, prevent the loss of IRP2 and the increase in alpha-synuclein. The presence of iron together with alpha-synuclein in SNPC may be detrimental for dopaminergic neurons. Since, iron has been shown to cause aggregation of alpha-synuclein to a neurotoxic agent. The use of iron chelators penetrating the blood brain barrier as neuroprotective drugs has been envisaged.

Chromosomal loci influencing the susceptibility to the parkinsonian neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the dysfunction of the nigrostriatal dopaminergic pathway. Although its etiology is not yet fully understood, an interaction of genetic predisposition and environmental factors is frequently discussed. The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) can evoke PD-like symptoms and neuropathological changes in various species, including mice. It was found repeatedly that mouse strains differ in their susceptibility to MPTP, which might serve as a model for genetic predisposition to neurodegeneration of the nigrostriatal system. In the present study, F2 intercross mice, derived from parental strains with high (C57BL/6J) versus low (BALB/cJ) MPTP susceptibility, were treated with MPTP and phenotyped for dopamine (DA) loss in the neostriatum, a highly sensitive marker of nigrostriatal dysfunction. A subsequent quantitative trait loci analysis revealed a gender-dependent locus for DA loss on chromosome 15 and a putative locus on chromosome 13. A number of potential candidate genes, including the membrane dopamine transporter, are located in the respective areas. Several mechanisms that are possibly involved in the control of the action of MPTP on the nigrostriatal system are discussed.

Effect of 6-hydroxydopamine on striatal GDNF and nigral GFRα1 and RET mRNAs in the adult rat

Exogenous GDNF as well as vectors containing the gene for this trophic factor has been shown to be neuroprotective in animal models of Parkinson's disease. We therefore investigated whether changes in striatal GDNF protein and nigral mRNA levels of its co-receptors GFRalpha1 and RET occur in response to lesions of dopamine (DA) neurons and examined the temporal profile of these changes as they relate to the loss of dopaminergic markers. Rats were lesioned with 6-hydroxydopamine and sacrificed 3 h to 60 days post-infusion. DA tissue levels in the striatum and tyrosine hydroxylase immunoreactivity in the substantia nigra (SN) and ventral tegmental area (VTA) were used to determine the size of the lesions. GDNF protein was measured in the striatum using radioimmunocytochemistry. In situ hybridization was used to determine alterations in the mRNAs of RET and GFRalpha1 in the SN and VTA. We observed no persistent changes in GDNF protein in the striatum in response to 6-hydroxydopamine over the 60-day observation period, suggesting that compensatory changes in this trophic factor do not occur in response to injury. Dramatic decreases in RET and GFRalpha1 were observed in both SN and VTA that were generally correlated with the loss of TH protein and striatal DA content, strongly suggesting that these receptors are located on DA neurons and that the protective effect of GDNF reflects a direct action of the trophic factor on these neurons.

DNA microarray analysis of hippocampal gene expression measured twelve hours after hypoxia-ischemia in the mouse

Cell death from cerebral ischemia is a dynamic process. In the minutes to days after an ischemic insult, progressive changes in cellular morphology occur. Associated with these events is the regulation of competing programs of gene expression; some are protective against ischemic insult, and others contribute to delayed cell death. Many genes involved in these processes have been identified, but individually, these findings have provided only limited insight into the systems biology of cerebral ischemia. Attempts to characterize the coordinated expression of large numbers of genes in cerebral ischemia has only recently become possible. Today, DNA microarray technology provides a powerful tool for investigating parallel expression changes for thousands of genes at one time. In this study, adult mice were subjected to 30 minutes of hypoxia-ischemia (HI), and the hippocampus was examined 12 hours later for differential gene expression using a 15K high-density mouse EST array. The genomic response to HI is complex, affecting approximately 7% of the total number of ESTs examined. Assigning differentially expressed ESTs to molecular functional groups revealed that HI affects many pathways including the molecular chaperones, transcription factors, kinases, and calcium ion binding genes. A comprehensive list of regulated genes should prove valuable in advancing our understanding of the pathogenesis of cerebral ischemia.

Profiling genes related to mitochondrial function in mice treated with N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

Since mitochondrial dysfunction plays an important role in the pathogenesis of dopaminergic neurodegeneration in Parkinson's disease, we determined the expression of genes related to mitochondrial function in the substantia nigra of mice treated with N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) using a cDNA array. MPTP treatment significantly depleted striatal dopamine, but did not result in apparent neuronal loss in the substantia nigra at 3 and 18 days post-treatment. We also examined changes in genes in the hypothalamus, a region containing dopaminergic neurons that are relatively resistant to MPTP. Finally, we confirmed those genes identified by microarrays as differentially expressed in the substantia nigra but not in the hypothalamus using in situ hybridization. Our results demonstrated that MPTP significantly changed the expressions of six genes in nigral neurons, four of which were related to the mitochondrial electron transport chain: the NADH-ubiquinone oxidoreductase 13 kDa B subunit, the NADH-ubiquinone oxidoreductase MNLL subunit, cytochrome c, and the cytochrome c oxidase Va subunit. Two other differentially expressed genes were the dihydropyridine-sensitive L-type calcium channel alpha-2 subunit precursor and type III alpha-1 procollagen. None of these six genes are encoded by mitochondrial DNA. The potential significance of these gene alterations in the context of Parkinson's disease is discussed.

Human neural stem cell transplantation in the MPTP-lesioned mouse

Human neural stem cells have exhibited a remarkable versatility to respond to environmental signals. Their characterization in models of neurotoxic injury may provide insight into human disease treatment paradigms. This study investigates the survival and migration of transplanted human stem cells and tyrosine hydroxylase immunoreactivity in the parkinsonian 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned mouse model, using antisera recognizing human nuclear protein (hNuc) and tyrosine hydroxylase (TH). Our results indicate long-term (up to 90 days) survival of human stem cell xenograft in the MPTP-lesioned mouse and the presence of hNuc-immunoreactive cells at sites distal to the transplant core. Few TH-positive cells are identified in the striatum by immunoperoxidase staining and using immunofluorescent double labeling, infrequent TH-immunoreactive, transplanted cells are identified.

cDNA gene expression profile homology of antioxidants and their antiapoptotic and proapoptotic activities in human neuroblastoma cells

Antioxidants have concentration-dependent neuroprotective and proapoptotic activities in models of Parkinson's disease. The aim of our study was to determine gene-protein pathways of the antioxidants, dopamine (DA), R-apomorphine (R-APO), melatonin, and green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG), in neuroblastoma cells, using a customized cDNA microarray and quantitative reverse transcriptase-polymerase chain reaction gene expression techniques. We demonstrate a concentration-dependent correlation between these compounds and modulation of cell survival/cell death-related gene pathways. High toxic concentration of DA (500 microM), R-APO (50 microM), melatonin (50 microM), and EGCG (50 microM) exhibited a similar profile of proapoptotic gene expression, increasing the level of bax, caspase-6, fas ligand, and the cell-cycle inhibitor gadd45 genes, while decreasing antiapoptotic bcl-2 and bcl-xL. Conversely, the low neuroprotective concentrations (1-10 microM) of these compounds induced an antiapoptotic response. Melatonin displayed an extremely low index of mortality, which may be partially explained by the observation that a high concentration did not significantly affect the expression of mitochondrial Bcl-2 family members, bcl-2 and bax. Protein analysis of Bcl-2, Bax, and activated caspase-3 correlated with the gene expression pattern. Our results provide for the first time new insights into the molecular events involved in the dose-dependent neuroprotective and neurotoxic activities of catechols and indole amine compounds.

Gene and protein expression profiles of anti- and pro-apoptotic actions of dopamine, R-apomorphine, green tea polyphenol (-)-epigallocatechine-3-gallate, and melatonin

Significant evidence has been provided to support the hypothesis that oxidant stress may be responsible for degeneration of dopaminergic neurons in the substantia nigra pars compacta in Parkinson's disease. Dopamine (DA), R-apomorphine (R-APO), green tea polyphenol (-)-epigallocatechine-3-gallate (EGCG), and melatonin are neuroprotective and radical scavenger compounds. The aim of this study was to establish the mechanism of the concentration-dependent neuroprotective and pro-apoptotic action of these drugs via gene expression and protein determination. cDNA microarrays provide new prospects to study and identify various mechanisms of drug action. We employed this technique for the study reported in this paper. Total RNA was extracted from SH-SY5Y cells exposed to low neuroprotective and high toxic concentrations of the drugs, followed by synthesis of cDNA, and hybridization to a microarray membrane related to apoptosis, survival, and cell cycle pathways. We demonstrated a concentration and time-dependent correlation between R-APO, DA, EGCG, and melatonin in modulation of cell survival/cell death-related gene pathways. The results were confirmed by quantitative real-time PCR and protein profiles. Unlike the effects of low concentrations (1-10 micro M), where an antiapoptotic response was manifest, a proapoptotic pattern of gene expression was observed at high toxic concentrations (50-500 micro M) of the antioxidants (e.g., increase in caspases, fas, and gadd45). Our results have provided novel insights into the gene mechanisms involved in both the neuroprotective and proapoptotic activities of neuroprotective drugs. We have shown that DA, R-APO, EGCG, and melatonin exhibit similar gene expression and protein profiles.

Neuroprotective effect of vasoactive intestinal peptide (VIP) in a mouse model of Parkinson's disease by blocking microglial activation

Parkinson's disease (PD) is a common neurodegenerative disorder with no effective protective treatment, characterized by a massive degeneration of dopaminergic neurons in the substantia nigra (SNpc) and the subsequent loss of their projecting nerve fibers in the striatum. To elucidate PD pathogenic factors, and thus to develop therapeutic strategies, a murine PD model based on the administration of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has been used extensively. It has been demonstrated that activated microglia cells actively participate in the pathogenesis of MPTP-induced PD through the release of cytotoxic factors. Because current treatments for PD are not effective, considerable research focused lately on a number of regulatory molecules termed microglia-deactivating factors. Vasoactive intestinal peptide (VIP), a neuropeptide with a potent anti-inflammatory effect, has been found to be protective in several inflammatory disorders. This study investigates the putative protective effect of VIP in the MPTP model for PD. VIP treatment significantly decreases MPTP-induced dopaminergic neuronal loss in SNpc and nigrostriatal nerve-fiber loss. VIP prevents MPTP-induced activation of microglia in SNpc and striatum and the expression of the cytotoxic mediators, iNOS, interleukin 1beta, and numor necrosis factor alpha. VIP emerges as a potential valuable neuroprotective agent for the treatment of pathologic conditions in the central nervous system, such as PD, where inflammation-induced neurodegeneration occurs.

Co-ordinate transcriptional regulation of dopamine synthesis genes by alpha-synuclein in human neuroblastoma cell lines

Abnormal accumulation of alpha-synuclein in Lewy bodies is a neuropathological hallmark of both sporadic and familial Parkinson's disease (PD). Although mutations in alpha-synuclein have been identified in autosomal dominant PD, the mechanism by which dopaminergic cell death occurs remains unknown. We investigated transcriptional changes in neuroblastoma cell lines transfected with either normal or mutant (A30P or A53T) alpha-synuclein using microarrays, with confirmation of selected genes by quantitative RT-PCR. Gene products whose expression was found to be significantly altered included members of diverse functional groups such as stress response, transcription regulators, apoptosis-inducing molecules, transcription factors and membrane-bound proteins. We also found evidence of altered expression of dihydropteridine reductase, which indirectly regulates the synthesis of dopamine. Because of the importance of dopamine in PD, we investigated the expression of all the known genes in dopamine synthesis. We found co-ordinated downregulation of mRNA for GTP cyclohydrolase, sepiapterin reductase (SR), tyrosine hydroxylase (TH) and aromatic acid decarboxylase by wild-type but not mutant alpha-synuclein. These were confirmed at the protein level for SR and TH. Reduced expression of the orphan nuclear receptor Nurr1 was also noted, suggesting that the co-ordinate regulation of dopamine synthesis is regulated through this transcription factor.

Neuroinflammatory processes in Parkinson's disease

Parkinson's disease (PD) is a movement disorder characterized by the progressive degeneration of dopaminergic neurons in the midbrain. To date, its cause remains unknown and the mechanism of nerve cell death uncertain. Apart from the massive loss of dopaminergic neurons, PD brains also show a conspicuous glial reaction together with signs of a neuroinflammatory reaction manifested by elevated cytokine levels and upregulation of inflammatory-associated factors such as cyclooxygenase-2 and inducible nitric oxide synthase. Mounting evidence also suggests a possible deleterious effect of these neuroinflammatory processes in experimental models of the disease. We propose that, in PD, neuroinflammation plays a role in the cascade of events leading to nerve cell death, thus propagating the neurodegenerative process. In this review, we summarize and discuss the latest findings regarding neuroinflammatory aspects in PD.

Using cDNA microarray to assess Parkinson's disease models and the effects of neuroprotective drugs

The remarkable progress made by molecular biology and molecular genetics during the past decade, and the advent of the novel tools of genomics and proteomics, are expected to reveal differential expression profiles of thousands of genes and proteins involved in the degeneration of dopamine-containing cells in Parkinson's disease and allow more focused treatments according to individual genotypes. Of particular interest is the application of microarrays in drug discovery and design to identify 'fingerprints' as potential candidate targets for drug intervention. The major microarray findings relevant to Parkinson's disease and its neurotoxin-induced animal and cell models will be discussed, with particular reference to the neuroprotective therapeutic potential that could arise from the development of drugs 'a la carte'.

Glucose/mitochondria in neurological conditions

Impairments of glucose and mitochondrial function are important causes of brain dysfunction and therefore of brain disease. Abnormalities have been found in association with disease of the nervous system in most of the components of glucose/mitochondrial metabolism. In many, molecular genetic abnormalities have been defined. Brain glucose oxidation is abnormal in common diseases of the nervous system, including Alzheimer disease and other dementias, Parkinson disease, delirium, probably schizophrenia and other psychoses, and of course cerebrovascular disease. Defects in a single component and even a single mutation can be associated with different clinical phenotypes. The same clinical phenotype can result from different genotypes. The complex relationship between biological abnormality in brain glucose utilization and clinical disorder is similar to that in other disorders that have been intensively studied at the genetic level. Genes for components of the pathways of brain glucose oxidation are good candidate genes for disease of the brain. Preliminary data support the proposal that treatments to normalize abnormalities in brain glucose oxidation may benefit many patients with common brain diseases.

Cyclin-dependent kinase activity is required for apoptotic death but not inclusion formation in cortical neurons after proteasomal inhibition

Growing evidence suggests that the proteasome may be dysfunctional in a number of neurodegenerative disorders, including Lewy body diseases. We have reported previously that application of pharmacological inhibitors of the proteasome to cultured cortical neurons leads to apoptotic death and formation of ubiquitinated cytoplasmic inclusions. A number of cell cycle regulatory proteins are known to be degraded by the proteasome. In light of the emerging role of aberrant cell-cycle activation in neuronal cell death, we have assessed the involvement of cell-cycle components in the effects induced by proteasomal inhibitors in cortical neurons. Death and mitochondrial dysfunction induced by lactacystin and other pharmacological inhibitors of the proteasome were prevented by flavopiridol, a specific inhibitor of cyclin-dependent kinases (Cdks). Molecular expression of the Cdk inhibitors p16 or p27, or of dominant-negative Cdk2, Cdk4, or Cdk6 was also protective against lactacystin-induced death. Flavopiridol blocked the induction of retinoblastoma protein (pRb) phosphorylation that occurred after lactacystin application, and expression of a mutant pRb that lacked phosphorylation sites was neuroprotective. These results suggest that in cortical neurons, proteasomal inhibition leads to a cell death pathway that is dependent on Cdk activation and pRb inactivation. Although cyclins D1 and E were sequestered within the ubiquitinated inclusions formed at late time points after lactacystin application, the formation of ubiquitinated inclusions was unaffected by Cdk inhibition. This suggests that there are parallel pathways regulating neuronal death and inclusion formation elicited by proteasomal inhibition in cortical neurons.

Gene discovery and validation for neurodegenerative diseases

Treatment of neurodegenerative diseases, such as Alzheimer's disease, multiple sclerosis, Parkinson's disease and amyotrophic lateral sclerosis (ALS), represents a major challenge for the pharmaceutical industry. These disorders have common and unique molecular pathological characteristics that result in serious reductions in nervous-system functionality. Key to developing novel and efficacious therapeutics is the discovery of new gene targets. Genomic, proteomics and bioinformatic analyses are identifying vast amounts of genes whose expression is associated with the pathology of a specific disease. Extensive validation studies performed in parallel with drug development are crucial for the selection of appropriate target genes. This review outlines some of the current progress in gene discovery for neurodegenerative disease.

Brain sites of movement disorder: genetic and environmental agents in neurodevelopmental perturbations

In assessing and assimilating the neurodevelopmental basis of the so-called movement disorders it is probably useful to establish certain concepts that will modulate both the variation and selection of affliction, mechanisms-processes and diversity of disease states. Both genetic, developmental and degenerative aberrations are to be encompassed within such an approach, as well as all deviations from the necessary components of behaviour that are generally understood to incorporate "normal" functioning. In the present treatise, both conditions of hyperactivity/hypoactivity, akinesia and bradykinesia together with a constellation of other symptoms and syndromes are considered in conjunction with the neuropharmacological and brain morphological alterations that may or may not accompany them, e.g. following neonatal denervation. As a case in point, the neuroanatomical and neurochemical points of interaction in Attention Deficit and Hyperactivity disorder (ADHD) are examined with reference to both the perinatal metallic and organic environment and genetic backgrounds. The role of apoptosis, as opposed to necrosis, in cell death during brain development necessitates careful considerations of the current explosion of evidence for brain nerve growth factors, neurotrophins and cytokines, and the processes regulating their appearance, release and fate. Some of these processes may possess putative inherited characteristics, like alpha-synuclein, others may to greater or lesser extents be endogenous or semi-endogenous (in food), like the tetrahydroisoquinolines, others exogenous until inhaled or injested through environmental accident, like heavy metals, e.g. mercury. Another central concept of neurodevelopment is cellular plasticity, thereby underlining the essential involvement of glutamate systems and N-methyl-D-aspartate receptor configurations. Finally, an essential assimilation of brain development in disease must delineate the relative merits of inherited as opposed to environmental risks not only for the commonly-regarded movement disorders, like Parkinson's disease, Huntington's disease and epilepsy, but also for afflictions bearing strong elements of psychosocial tragedy, like ADHD, autism and Savantism.

Exploiting microarrays to reveal differential gene expression in the nervous system

Microarrays have been used in a wide variety of experimental systems, but realizing their full potential is contingent on sophisticated and rigorous experimental design and data analysis. This article highlights what is needed to get the most out of microarrays in terms of accurately and effectively revealing differential gene expression and regulation in the nervous system.

Neurotrophic factors for the investigation and treatment of movement disorders

Neurotrophic factors (NFs) are proteins that enhance neuronal survival, differentiation, neurotransmitter function and resistance to neurotoxins and lesions. For these reasons the NFs are considered as a new potential therapeutic tool for the treatment of neurodegenerative disorders, a group of diseases that produce the most important cause for disability in the Western world. Some NFs prevent or even reverse the behavioral, biochemical, pharmacological and histological abnormalities observed in several in vitro and in vivo models of neurodegenerative disorders, namely Parkinson's disease. Several NFs have been investigated in primate models of neurological disorders and some of them have been used for patients with these diseases. The results so far obtained in humans have been disappointing for several reasons, including technical problems for delivery, unbearable side effects or lack of efficacy. Future approaches for the use of NFs in humans should include the following: (1) Investigation of the putative compounds in animal models more related to the pathophysiology of each disease, such as in genetic models of neurodegenerative diseases; (2) New methods of delivery including genetic engineering by viral vectors and administration through implantable devices; (3) More precise methods of continuous response evaluation, including the novel neuroimaging techniques; (4) Investigation of the effects of behavioral stimulation and conventional pharmacotherapy on the metabolism of NFs.

Gene expression profiling in the midbrain of striatal 6-hydroxydopamine-injected mice

In order to clarify mechanisms underlying dopaminergic neuronal death in Parkinson's disease (PD), a gene expression profiling study was performed in a rodent model of PD. In this model, mice are intrastriatally injected with 6-hydroxydopamine (6-OHDA) and dopaminergic neurons in the substantia nigra (SN) gradually die by retrograde degeneration. The SN were removed 2 h, 24 h, or 14 days after 6-OHDA administration. Levels of mRNAs related to cell death or survival were quantified using adaptor-tagged competitive PCR (ATAC-PCR). The cyclin D1 gene showed an immediate increase in mRNA expression. After 24 h, when dopaminergic neurons were under intense degeneration, levels of caspase 8 mRNA and p53 apoptosis effecter related to pmp 22 (PERP) mRNA increased and, conversely, FAS mRNA decreased. After 14 days, when the degeneration was attenuated, levels of PERP mRNA and serum- and glucocorticoid-regulated kinase (SGK) mRNA still increased. SGK has a similarity to AKT, which is an important molecule involved in nerve growth factor signal transduction. AKT mRNA levels are low in dopaminergic neurons. These results suggest that an increase in cyclin D1 mRNA triggers dopaminergic neurons to enter an abnormal cell cycle, which leads to neuronal degeneration and cell death, possibly induced by PERP and caspase 8. In addition to cell death-related genes, several survival-related genes are activated. SGK might function as a key enzyme for the survival of dopaminergic neurons.

Gene expression analysis of spontaneously hypertensive rat cerebral cortex following transient focal cerebral ischemia

Identification of novel modulators of ischemic neuronal death helps in developing new strategies to prevent the stroke-induced neurological dysfunction. Hence, the present study evaluated the gene expression changes in rat cerebral cortex at 6 and 24 h of reperfusion following transient middle cerebral artery occlusion (MCAO) by GeneChip analysis. Transient MCAO resulted in selective increased mRNA levels of genes involved in stress, inflammation, transcription and plasticity, and decreased mRNA levels of genes which control neurotransmitter function and ionic balance. In addition to a number of established ischemia-related genes, many genes not previously implicated in transient focal ischemia-induced brain damage [suppressor of cytokine signaling (SOCS)-3, cAMP responsive element modulator (CREM), cytosolic retinol binding protein (CRBP), silencer factor-B, survival motor neuron (SMN), interferon-gamma regulatory factor-1 (IRF-1), galanin, neurotrimin, proteasome subunit RC8, synaptosomal-associated protein (SNAP)-25 A and B, synapsin 1a, neurexin 1-beta, ras-related rab3, vesicular GABA transporter (VGAT), digoxin carrier protein, neuronal calcium sensor-1 and neurodap] were observed to be altered in the ischemic cortex. Real-time PCR confirmed the GeneChip results for several of these transcripts. SOCS-3 is a gene up-regulated after ischemia which modulates inflammation by controlling cytokine levels. Antisense knockdown of ischemia-induced SOCS-3 protein expression exacerbated transient MCAO-induced infarct volume assigning a neuroprotective role to SOCS-3, a gene not heretofore implicated in ischemic neuronal damage.

Microarray analysis of H2O2-, HNE-, or tBH-treated ARPE-19 cells

Oxidative stress plays a key role in aging diseases of the posterior pole of the eye such as age-related macular degeneration. The oxidative stress response of in vitro RPE cells has been studied for a small number of genes. However, a comprehensive transcriptional response has yet to be elucidated. The purpose of this study was to determine if the transcription of a common set of genes is altered by exposure of ARPE-19 cells to three major generators of oxidative stress, hydrogen peroxide (H2O2), 4-hydroxynonenal (HNE), and tert-butylhydroperoxide (tBH). As expected, a common response was observed that included 35 genes differentially regulated by all three treatments. Of these, only one gene was upregulated, and only by one oxidant, while all other responses were downregulation. The majority of these genes fell into five functional categories: apoptosis, cell cycle regulation, cell-cell communication, signal transduction, and transcriptional regulation. Additionally, a large number of genes were differentially regulated by one oxidant only, including the majority of the conventional oxidative stress response genes present on the Clontech Human 1.2 microarray. This study raises questions regarding the generality of results that involve the use of a single oxidant and a single cell culture condition.

DNA array reveals altered gene expression in response to focal cerebral ischemia

The gene expression profile in the cortex was analyzed in a rat model of focal cerebral ischemia by use of cDNA array. It was attempted to monitor changes of gene expression and to profile them into functional classification between ipsilateral and contralateral cortex at 6h after middle cerebral artery (MCA) occlusion. Seventy-one genes out of 1174 genes were significantly modulated by ischemia. Metabolism-, cell communication- and signal transduction-related genes were down-regulated, whereas genes involved in stress response were markedly increased. Besides numerous established ischemia-induced gene products such as macrophage inflammatory protein-1 alpha (MIP-1 alpha), orphan nuclear receptor Nurr 77, secretogranin II (SCG-II), and tumor necrosis factor-alpha (TNF-alpha), several genes were identified which have not previously been shown to be modulated following focal ischemia; these genes include interferon-induced protein (IFN-IP), neurodegeneration-associated protein-1 (NDGAP-1), and neuronal pentraxin receptor (NPR). The RT-PCR analyses of these genes at various time points revealed that mRNA level of IFN-IP was up-regulated, while NDGAP-1 and NPR were transcriptionally down-regulated. The results suggest of the involvement of these genes in neuronal cell damage caused by ischemia and the potential use as targets for the development of preventives/therapeutics of brain stroke.