Yuta Yoshino

DNA methylation changes at SNCA intron 1 in patients with dementia with Lewy bodies

It is difficult to diagnose dementia with Lewy bodies (DLB) because it exhibits clinical and neuropathological overlap with both Alzheimers disease and Parkinsons disease. The α‐synuclein protein is a major component of Lewy bodies, and accumulation of α‐synuclein aggregates causes synaptic dysfunction in DLB. Epigenetic changes at the synuclein alpha ( SNCA ) gene may be involved in DLB pathogenesis.

TREM2 mRNA Expression in Leukocytes Is Increased in Alzheimer’s Disease and Schizophrenia

TREM2 and TYROBP are causal genes for Nasu–Hakola disease (NHD), a rare autosomal recessive disease characterized by bone lesions and early-onset progressive dementia. TREM2 forms a receptor signaling complex with TYROBP, which triggers the activation of immune responses in macrophages and dendritic cells, and the functional polymorphism of TREM2 is reported to be associated with neurodegenerative disorders such as Alzheimer’s disease (AD). The objective of this study was to reveal the involvement of TYROBP and TREM2 in the pathophysiology of AD and schizophrenia. Methods: We investigated the mRNA expression level of the 2 genes in leukocytes of 26 patients with AD and 24 with schizophrenia in comparison with age-matched controls. Moreover, we performed gene association analysis between these 2 genes and schizophrenia. Results: No differences were found in TYROBP mRNA expression in patients with AD and schizophrenia; however, TREM2 mRNA expression was increased in patients with AD and schizophrenia compared with controls (P < 0.001). There were no genetic associations of either gene with schizophrenia in Japanese patients. Conclusion: TREM2 expression in leukocytes is elevated not only in AD but also in schizophrenia. Inflammatory processes involving TREM2 may occur in schizophrenia, as observed in neurocognitive disorders such as AD. TREM2 expression in leukocytes may be a novel biomarker for neurological and psychiatric disorders.

Elevated mRNA Expression and Low Methylation of SNCA in Japanese Alzheimer’s Disease Subjects

Despite the continuing debate about the amyloid hypothesis in Alzheimers disease (AD), the precise pathogenesis is still unclear. Mixed pathology is common and multiple different protein aggregates are seen in human postmortem brains. Aggregates consisting of the alpha-synuclein protein encoded by the Synuclein Alpha gene (SCNA) are common in both dementia with Lewy bodies and AD. We examined SNCA mRNA expression and methylation rates of the CpG island at intron 1 of SNCA in peripheral leukocytes in 50 AD and age- and sex-matched control subjects to verify whether alpha-synuclein pathology affects the AD pathogenesis. SNCA mRNA expression in AD subjects was significantly higher than that in control subjects (1.62±0.73 versus 0.98±0.50, p < 0.001). We found significant differences between AD and control subjects at seven CpG sites (average rate; 8.8±2.7 versus 9.5±2.5, respectively: p = 0.027). The methylation rates tended to be lower in AD subjects at all CpG sites. We conclude that mRNA expression and methylation of SNCA intron 1 are altered in AD, which may be caused by Lewy body pathology in AD.

No abnormal hexanucleotide repeat expansion of C9ORF72 in Japanese schizophrenia patients

Abnormal hexanucleotide repeat expansion of C9ORF72 is known to cause neurodegenerative disorders such as frontotemporal dementia. Additionally, patients with psychotic symptoms are more likely to have abnormal hexanucleotide repeat expansion than are patients without them. We investigated the hexanucleotide repeat sizes of C9ORF72 in 466 Japanese schizophrenia patients. We found no abnormal hexanucleotide repeat expansion. In conclusion, C9ORF72 may not be responsible for schizophrenia susceptibility in the Japanese population.

Gene Expression and Methylation Analysis of ABCA7 in Patients with Alzheimer’s Disease

BACKGROUND/OBJECTIVE The aim of this study was to examine the blood gene expression and methylation of ATP-binding cassette sub-family A member 7 gene (ABCA7) as a biological marker of AD. METHODS AD subjects (n = 50; 11 males, 77.7±6.05 years old) and age- and sex-matched healthy controls (n = 50) were recruited. A single nucleotide polymorphism in ABCA7 (rs3764650), methylation rates of CpG sites in the ABCA7 promoter region, and ABCA7 mRNA expression levels in peripheral blood were examined. RESULTS The distribution of the rs3764650 polymorphism in AD subjects was not different from that of controls. Although the methylation rates of AD subjects were not significantly different from those of controls, the ABCA7 mRNA expression level in AD subjects was significantly higher than that in controls. Additionally, the ABCA7 mRNA expression level in AD subjects was significantly correlated with Mini-Mental State Examination recall, the Alzheimers Disease Assessment Scale total score, and the Clinical Dementia Rating score. We also found a significant correlation between the ABCA7 mRNA expression level and duration of illness. CONCLUSION The ABCA7 mRNA expression level in peripheral blood may be a marker for early stages of AD and disease progression regardless of rs3764650 and the methylation rate of its promoter.

Association Study and Meta-Analysis of Polymorphisms, Methylation Profiles, and Peripheral mRNA Expression of the Serotonin Transporter Gene in Patients with Alzheimer's Disease

Background/Aim: The aim of this study was to elucidate the relationship between Alzheimers disease (AD) and the serotonin transporter gene (SLC6A4). Methods: AD subjects (n = 43) and controls (n = 47) were recruited and evaluated. In leukocytes, we evaluated two polymorphisms in SLC6A4, the serotonin transporter length polymorphic region (5-HTT-LPR) and rs25531, as well as methylation rates of the SLC6A4 promoter region and the SLC6A4 mRNA expression level. We also performed a meta-analysis to examine the relationship between the frequency of the L allele and the risk of AD. Results: The distributions of 5-HTT-LPR and rs25531 polymorphisms in AD subjects were not different from those of controls. Although the methylation rates in AD subjects were not significantly different from those of controls, the expression level in AD subjects was significantly higher than in controls. Additionally, the expression level in AD subjects was significantly correlated with apathy. Meta-analysis revealed that the L/L genotype significantly reduced the risk of AD, but only in the Caucasian population. Conclusion: Higher SLC6A4 mRNA expression in leukocytes in AD was associated with apathy regardless of SLC6A4 genotypes and methylation rates of the promoter region. The L/L genotype may reduce the risk of AD in the Caucasian population.

The nicotinic cholinergic system is affected in rats with delayed carbon monoxide encephalopathy

Delayed carbon monoxide (CO) encephalopathy may occur following recovery from acute CO poisoning. However, the mechanism of delayed neuronal injury remains unknown. The nicotinic acetylcholine receptors (nAChRs) have been suggested to play a role in cognitive status in neurodegenerative diseases, including Alzheimers disease. Therefore, in the current study, we investigated the effect of delayed neuronal CO poisoning on gene expression of nAChRs in the hippocampus of Wistar rats. Behavioral effects (measured by the passive-avoidance test) and histological analyses (hematoxylin-eosin-stained hippocampal cell counts and cell death observations) were also investigated, 21 days after CO exposure for 1h (1000ppm for 40min+3000ppm for 20min). Our findings show cognitive impairment and hippocampal cell death, suggesting our rat model is suitable for studying delayed CO encephalopathy. Expression of nAChR (Chrna3, Chrna4, Chnra7, and Chrnb2) mRNA was assessed using quantitative real-time polymerase chain reaction. Hippocampal Chrna3 expression was significantly decreased, and cerebellar Chrna7 expression significantly increased, in the delayed CO encephalopathy rat model. Thus, the nicotinic cholinergic system may be affected in delayed CO encephalopathy.

Elevated TREM2 mRNA expression in leukocytes in schizophrenia but not major depressive disorder

The pathological mechanisms of schizophrenia (SCZ) have not been clarified, but the microglia hypothesis has recently been discussed. We previously reported that the mRNA for a protein related to activation of microglia, triggering receptor expressed on myeloid cell 2 (TREM2), is expressed higher in peripheral leukocytes in SCZ than controls. In this study, we analyzed TREM2 mRNA expression in leukocytes from both SCZ and major depressive disorder (MDD) patients. We compared 50 SCZ patients and 42 MDD patients with age-matched controls. Levels of TREM2 mRNA in leukocytes were analyzed with quantitative real-time PCR method using TaqMan probe. TREM2 mRNA expression was significantly higher in leukocytes of SCZ subjects than controls, but the expression level was non-significantly different in MDD subjects. We observed a decrease in TREM2 mRNA expression in leukocytes from one SCZ patient after clozapine treatment. The expression did not change following ECT, but the expression level in this patient was still significantly higher than that in controls. We conclude that the high amount of TREM2 mRNA expression in leukocytes is specific to SCZ but not MDD and that changes in TREM2 mRNA expression may be a trait biomarker for SCZ.

Antidepressant action via the nitric oxide system: A pilot study in an acute depressive model induced by arginin.

Nitric oxide (NO) may be a neurotransmitter related to major depressive disorder (MDD) because the selective neuronal NO synthase (NOS) inhibitor, 7-nitroindazole, induces dose-dependent antidepressant-like effects. However, its role in MDD is not yet known. The purpose of our study was to determine if antidepressants improve depression via the NO pathway using an acute depressive rat model induced by L-arginine (AR). Three types of antidepressants were examined, fluoxetine (FLX, 10 mg/kg), milnacipran (MIL, 30 mg/kg), and mirtazapine (MIR, 10 mg/kg), in a depressive model that used AR (750 mg/kg) pretreatment. mRNA expression levels of three NOS subtypes were analyzed by real-time PCR, as well as serum NO levels. Significant increases in iNOS mRNA expression levels were found in brain regions after AR treatment, although the eNOS gene tended to decrease with AR injection. After antidepressant treatment, there were no mRNA expression changes in either nNOS or iNOS. However, eNOS mRNA expression significantly increased with FLX (cerebellum, P=0.011; hippocampus, P=0.011; midbrain, P=0.011; pons, P=0.013; striatum, P=0.011; and thalamus, P<0.001). There was a statistically significant increase in serum NO levels with MIL treatment (P=0.011). We conclude that changes in eNOS mRNA levels in the brain with FLX treatment, and amount of serum NO with MIL treatment may be related to antidepressant effects of both agents, but further experiments are needed to confirm involvement of the NO system in MDD.

Low methylation rates of dopamine receptor D2 gene promoter sites in Japanese schizophrenia subjects.

Abstract Objectives: According to the dopamine hypothesis, several studies on the gene for the dopamine receptor D2 (DRD2) have been conducted. However, no trait biomarkers on DRD2 are available. We examined whether the methylation rates in the upstream region of DRD2 in leukocytes are different in schizophrenia (SCZ) subjects compared to control subjects. Methods: We selected seven CpG sites in the upstream region of DRD2 that may theoretically bind major transcription factors. The methylation rates in these regions of 50 medicated and 18 drug-naïve SCZ subjects were compared with those of age-matched control subjects. Results: The methylation rates were significantly lower in medicated (CpG2, P < 0.0001; CpG4, P = 0.013; CpG7, P < 0.0001; and average: 12.9 ± 1.8 vs. 14.1 ± 2.2, P = 0.005) and drug-naïve SCZ subjects (CpG1, P = 0.006; CpG2, P = 0.001; CpG3, P = 0.001; CpG5, P = 0.02; CpG6, P = 0.015; CpG7, P = 0.027; and average: 9.86 ± 0.9 vs. 11.2 ± 1.3, P = 0.002). Conclusions: We confirmed low methylation rates in the upstream region of DRD2 in both medicated and drug-naïve SCZ subjects. Low methylation rates of DRD2 in leukocytes may be a trait biomarker for SCZ.