Biomedical subjects

Tohru Kodama

Publications and source records attributed to Tohru Kodama.

7 recordsLinked to original sources

PubMed2025

DNA methylation and multi-omics profiling of T cells uncovers chemotactic pathways and proliferation-linked hypomethylation in narcolepsy type 1.

Narcolepsy type 1 (NT1) is a chronic sleep disorder caused by a loss of orexin-producing cells in the brain and involves autoimmune mechanisms, including the presence of autoreactive T cells. In this study, we performed genome-wide DNA methylation analysis using both CD4+/CD8+ T cells from 42 NT1 patients and 42 controls across discovery and replication cohorts. To identify methylation changes more robustly associated with the disease, we prioritized differentially methylated regions (DMRs) over single-site differentially methylated positions (DMPs). Furthermore, to validate and interpret DMP-level associations, we integrated genome-wide genotype and gene expression data obtained from the same individuals. As a result, the DMR analysis identified 15 reproducible DMRs in CD4+ T cells and 5 in CD8+ T cells, with most DMRs shared between the two cell types. Shared DMRs included regions associated with CCL5 (p = 2.1E-02) and CCR4 (p = 8.3E-03). Integrative analysis with genotype and gene expression data also showed that the DMP related to S100A4, which promotes lymphocyte migration through CCR5 and CXCR3 receptors, was associated with the disease in CD4+ T cells. Pathway analysis of genes identified through both the DMR and integrative analyses indicated enrichment in cell chemotaxis-related pathways, suggesting that aberrant chemokine-mediated cell migration plays a central role in NT1 pathogenesis. Further, NT1-associated methylation changes were predominantly hypomethylation events, significantly enriched in non-promoter, non-CpG island regions (p = 1.74E-102). We further observed that global hypomethylation levels were correlated with hypoSC, a mitotic index estimated from methylation data, highlighting increased T cell proliferation in NT1.

Humans↗

PubMed2004

The loss of circadian PAR bZip transcription factors results in epilepsy.

DBP (albumin D-site-binding protein), HLF (hepatic leukemia factor), and TEF (thyrotroph embryonic factor) are the three members of the PAR bZip (proline and acidic amino acid-rich basic leucine zipper) transcription factor family. All three of these transcriptional regulatory proteins accumulate with robust circadian rhythms in tissues with high amplitudes of clock gene expression, such as the suprachiasmatic nucleus (SCN) and the liver. However, they are expressed at nearly invariable levels in most brain regions, in which clock gene expression only cycles with low amplitude. Here we show that mice deficient for all three PAR bZip proteins are highly susceptible to generalized spontaneous and audiogenic epilepsies that frequently are lethal. Transcriptome profiling revealed pyridoxal kinase (Pdxk) as a target gene of PAR bZip proteins in both liver and brain. Pyridoxal kinase converts vitamin B6 derivatives into pyridoxal phosphate (PLP), the coenzyme of many enzymes involved in amino acid and neurotransmitter metabolism. PAR bZip-deficient mice show decreased brain levels of PLP, serotonin, and dopamine, and such changes have previously been reported to cause epilepsies in other systems. Hence, the expression of some clock-controlled genes, such as Pdxk, may have to remain within narrow limits in the brain. This could explain why the circadian oscillator has evolved to generate only low-amplitude cycles in most brain regions.

Animals↗

PubMed2003

Intravenously administered hypocretin-1 alters brain amino acid release: an in vivo microdialysis study in rats.

We have reported that intravenous administration of hypocretin (Hcrt or orexin) reverses the symptoms of narcolepsy in genetically narcoleptic dogs. We have also reported that the onset of symptoms in canine genetic narcolepsy is accompanied by degenerative changes in forebrain regions, particularly the septal nucleus and amygdala. In the present in vivo microdialysis study we have investigated the effect of intravenous administration of Hcrt-1 (orexin-A) to anaesthetized rats on glutamate and GABA release in the amygdala, a region with moderate Hcrt innervation, and in the cerebellar cortex, a region with sparse or no Hcrt innervation. We found that intravenous Hcrt administration caused a marked (> 60 %) and sustained (> 50 min) increase in glutamate release within the amygdala, but no change in release in the cerebellar cortex. We did not detect a significant change in GABA release. When calcium-free artificial cerebrospinal fluid was used as the microdialysis perfusate, Hcrt-1 no longer produced an increase in glutamate release. Hcrt may act via the calcium-dependent regulation of glutamate release in certain nuclei of the central nervous system.

Amino Acids↗

PubMed2003

[Narcolepsy].

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Adolescent↗

PubMed2002

Differential changes in glutamate concentration in the primate prefrontal cortex during spatial delayed alternation and sensory-guided tasks.

Glutamate is a major neurotransmitter in the mammalian brain and glutamatergic neurotransmission in the frontal cortex is indicated to play important roles in cognitive operations. We previously examined changes in extracellular dopamine in the primate frontal cortex in cognitive tasks, and in this paper we extend this to glutamate. We employed, as cognitive tasks, a delayed alternation task where the animal must retain information in working memory, and a sensory-guided task in which there is no working memory requirement but there may be more sensory processing requirements. Using the in vivo microdialysis method, we examined changes in extracellular glutamate concentration in the dorsolateral, arcuate, orbitofrontal, and premotor areas of the primate frontal cortex. Compared to basal rest levels, we observed significant increases in glutamate concentration in dorsolateral and arcuate areas of the prefrontal cortex during the sensory-guided task, but did not find significant changes in any of the frontal areas examined during the delayed alternation task. When glutamate concentration was compared between the delayed alternation and sensory-guided tasks, difference was observed only in the dorsolateral prefrontal cortex, especially in the ventral lip area of the principal sulcus. The results indicate the importance of glutamate in processing sensory information but not in retaining information in working memory in the primate dorsolateral and arcuate prefrontal cortex. We also compared the concentration of glutamate and dopamine in the tasks. We found a double dissociation in the concentration of glutamate and dopamine in the dorsolateral area: there was an increase in glutamate but no change in dopamine during the sensory-guided task, whereas there was an increase in dopamine but no change in glutamate during the delayed alternation task. It is thus suggested that in the primate dorsolateral prefrontal cortex, increased glutamate tone without dopamine increase facilitates sensory-guided task performance, while increased dopamine tone without glutamate increase is beneficial for working memory task performance.

Animals↗

PubMed2002

Arousal effects of orexin-A correlate with GLU release from the locus coeruleus in rats.

Although orexin was found to promote food intake, recent reports proposed its involvement in the regulation of vigilance. To study the mechanism of how orexin affects arousal, we analyzed glutamate (GLU) release from the locus coeruleus (LC) in rats after systemic injection of orexin-A. Baseline levels of orexin-A in the LC were significantly higher during the dark period than the light period. Intravenous administration of orexin-A increased GLU levels as well as orexin in the LC, simultaneously promoting wakefulness. These results suggest that increases in GLU release may reflect the arousal-inducing effects of orexin.

Animals↗

PubMed2002

Release of neurotransmitters in the monkey frontal cortex is related to level of attention.

Attention is reported to be maintained by monoamines, acetylcholine and amino acids systems. Changes in the releases of these neurotransmitters during the three stages comprising quiet wake (QW) and two arousal states (AW), which are activated from different sources, were investigated. Norepinephrine releases during AW were significantly higher than that during QW. Conversely, the levels of acetylcholine and serotonin that were released did not change significantly among these three stages. The interesting observation was the dissociation of the increase between glutamate and dopamine releases in the two AW states. The results indicate that attention level is related to the amount of norepinephrine release, and that attention quality is related to the interaction between dopamine and glutamate releases.

Animals↗