Epigenome-Wide Analysis of DNA Methylation in Parkinson's Disease Cortex.

Background: Epigenetic factors including DNA methylation contribute to specific patterns of gene expression. Gene−environment interactions can change the methylation status in the brain, and accumulation of these epigenetic changes over a lifespan may be co-responsible for a neurodegenerative disease like Parkinson's disease, which that is characterised by a late onset in life. Aims: To determine epigenetic modifications in the brains of Parkinson's disease patients. Patients and Methods: DNA methylation patterns were compared in the cortex tissue of 14 male PD patients and 10 male healthy individuals using the Illumina Methylation 450 K chip. Subsequently, DNA methylation of candidate genes was evaluated using bisulphite pyrosequencing, and DNA methylation of cytochrome P450 2E1 (CYP2E1) was characterized in DNA from blood mononuclear cells (259 PD patients and 182 healthy controls) and skin fibroblasts (10 PD patients and 5 healthy controls). Protein levels of CYP2E1 were analysed using Western blot in human cortex and knock-out mice brain samples. Results: We found 35 hypomethylated and 22 hypermethylated genes with a methylation M-value difference >0.5. Decreased methylation of cytochrome P450 2E1 (CYP2E1) was associated with increased protein levels in PD brains, but in peripheral tissues, i.e., in blood cells and skin fibroblasts, DNA methylation of CYP2E1 was unchanged. In CYP2E1 knock-out mice brain alpha-synuclein (SNCA) protein levels were down-regulated compared to wild-type mice, whereas treatment with trichloroethylene (TCE) up-regulated CYP2E1 protein in a dose-dependent manner in cultured cells. We further identified an interconnected group of genes associated with oxidative stress, such as Methionine sulfoxide reductase A (MSRA) and tumour protein 73 (TP73) in the brain, which again were not paralleled in other tissues and appeared to indicate brain-specific changes. Conclusions: Our study revealed surprisingly few dysmethylated genes in a brain region less affected in PD. We confirmed hypomethylation of CYP2E1.

DJ-1 is a redox sensitive adapter protein for high molecular weight complexes involved in regulation of catecholamine homeostasis.

DJ-1 is an oxidation sensitive protein encoded by the PARK7 gene. Mutations in PARK7 are a rare cause of familial recessive Parkinson's disease (PD), but growing evidence suggests involvement of DJ-1 in idiopathic PD. The key clinical features of PD, rigidity and bradykinesia, result from neurotransmitter imbalance, particularly the catecholamines dopamine (DA) and noradrenaline. We report in human brain and human SH-SY5Y neuroblastoma cell lines that DJ-1 predominantly forms high molecular weight (HMW) complexes that included RNA metabolism proteins hnRNPA1 and PABP1 and the glycolysis enzyme GAPDH. In cell culture models the oxidation status of DJ-1 determined the specific complex composition. RNA sequencing indicated that oxidative changes to DJ-1 were concomitant with changes in mRNA transcripts mainly involved in catecholamine metabolism. Importantly, loss of DJ-1 function upon knock down (KD) or expression of the PD associated form L166P resulted in the absence of HMW DJ-1 complexes. In the KD model, the absence of DJ-1 complexes was accompanied by impairment in catecholamine homeostasis, with significant increases in intracellular DA and noraderenaline levels. These changes in catecholamines could be rescued by re-expression of DJ-1. This catecholamine imbalance may contribute to the particular vulnerability of dopaminergic and noradrenergic neurons to neurodegeneration in PARK7-related PD. Notably, oxidised DJ-1 was significantly decreased in idiopathic PD brain, suggesting altered complex function may also play a role in the more common sporadic form of the disease.

DNA methylation of the TNF-α promoter region in peripheral blood monocytes and the cortex of human Alzheimer's disease patients.

BACKGROUND: The cytokine tumor necrosis factor-alpha (TNF-α) is elevated in the blood of Alzheimer's disease (AD) patients. Epigenetic DNA modifications of the TNF-α promoter may account for the observed upregulation. METHODS: We analyzed blood samples of 50 AD patients and 55 controls plus 4 AD and 4 control cortex samples using bisulfite sequencing PCR. RESULTS: A significant hypomethylation of the TNF-α promoter was found in AD patients' brains but not in their blood. Cortical TNF-α promoter DNA was higher methylated than blood-derived DNA, both in AD patients and controls. CONCLUSION: In AD patients, epigenetic mechanisms of TNF-α gene regulation, like aberrant DNA methylation, are not relevant in blood.

Reversible multifocal leukoencephalopathy associated with a nocturnal blood pressure non-dipper pattern.

The majority of cases of leukoencephalopathy related to hypertensive crisis show brain lesions predominantly in the posterior lobe. Such cases are usually classified as reversible posterior leukoencephalopathy syndrome (RPLS). A multifocal distribution pattern is also possible, but occurs seldom. Here we report two patients with extensive white matter lesions that affect the entire brain, related to hypertensive crisis associated with a non-dipper pattern of blood pressure during the night as well as renal dysfunction. This nocturnal blood pressure abnormality may be relevant for the distribution pattern of cerebral white matter lesions and underlines the concept that in these cases a 24-h ambulatory blood pressure monitoring is needed.

Different methylation of the TNF-alpha promoter in cortex and substantia nigra: Implications for selective neuronal vulnerability.

Increasing evidence has linked inflammatory processes to neurodegenerative disorders, including Alzheimer's and Parkinson's disease (PD). Tumor necrosis factor alpha (TNF-alpha) is a key inflammatory cytokine and several studies linked increased TNF-alpha to dopaminergic cell death in PD. The TNF-alpha promoter sequence contains several CpG dinucleotides located within or next to transcription factor binding sites. To test the hypothesis whether the methylation state of the TNF-alpha promoter contributes to increased expression of TNF-alpha in PD we compared DNA from different brain regions (substantia nigra pars compacta (SNpc) and cortex) of PD patients and neurologically healthy, age and sex matched controls by bisulfite sequencing of the TNF-alpha promoter region. The TNF-alpha promoter DNA from SNpc was significantly less methylated in comparison to DNA from cortex; however both in PD patients and controls. Although there was a tendency for hypomethylation in PD, our analysis of the 10 CpGs in the TNF-alpha core promoter region (-258 to -35 relative to the TSS) revealed no particular pattern in PD patients compared to control and identified no particular hypomethylated position in cortex or SNpc DNA. Electrophoretic mobility shift and luciferase reporter assays showed that methylation of specific solitary CpG in the TNF-alpha promoter resulted in reduced binding of the transcription factors AP-2 and Sp1, respectively, and suppressed TNF-alpha promoter activity. The brain region specific methylation state of solitary CpG in the TNF-alpha promoter thus determines transcription factor binding efficacy and TNF-alpha expression. A lesser degree of methylation of the TNF-alpha promoter in SNpc cells could underlie the increased susceptibility of dopaminergic neurons to TNF-alpha mediated inflammatory reactions.

Constitutive expression of p55TNFR mRNA and mitogen-specific up-regulation of TNF alpha and p75TNFR mRNA in mouse brain.

Serum tumor necrosis factor (TNF) functions as a mediator of the immune-to-brain axis. Numerous TNF receptor-mediated effects on the nervous system are described but the knowledge about the regional and cellular expression of TNF receptor p55TNFR and p75TNFR in vivo is far from being complete. It is unclear whether TNF mediates its neuroimmune effects alone or in combination with other factors, e.g., bacterial mitogens. Here, we investigated the distribution of TNFalpha, p55TNFR, and p75TNFR in normal mouse brain and examined the stimulus-specific effects of lipopolysaccharide (LPS) and staphylococcal enterotoxin B (SEB) on the expression of the cerebral TNF system. Both mitogens caused enhanced TNFalpha serum levels and induced c-fos mRNA in the paraventricular nucleus but exhibited different effects on the cerebral gene expression of the TNF system. LPS but not SEB rapidly induced TNFalpha mRNA in circumventricular organs (CVOs) followed by spreading of TNFalpha mRNA into brain parenchyma close to the CVOs. The p55TNFR gene was constitutively expressed in many neurons with high levels in brainstem motor nuclei and in neurons of the sensory mesencephalic trigeminal nucleus. Moderate levels of p75TNFR mRNA were seen in single cells scattered throughout the brain in a pattern resembling microglia. Neither LPS nor SEB modulated the p55TNFR gene expression in any region or cell type of the brain, and LPS but not SEB induced p75TNFR mRNA in the CVOs. Thus, enhanced TNF serum levels able to stimulate c-fos mRNA expression in the paraventricular nucleus did not necessarily result in a modulation of the cerebral TNF system.