Methylation and expression of nr3c1 gene in thai major depressive disorder patients and effects of antidepressants on crf gene expression

Abstract

Major depressive disorder (MDD) has been associated with hypothalamus-pituitary-adrenal gland (HPA) negative-feedback dysfunction, which is related to DNA methylation in the NR3C1 promoter region. The most common therapy for MDD is the use of antidepressants. This study is divided into two parts. The first part aims to examine glucocorticoid receptor expression and NR3C1 promoter methylation in Thai patients with MDD. This study was performed with 29 MDD patients (9 males, 20 females) and 33 normal controls (7 males, 26 females). Bisulfite pyrosequencing on 7 CpG sites at the NGFI-A binding site in the exon 1F of NR3C1 promoter region showed significant hypermethylation levels at the CpG7 in MDD patients, especially in female samples. However, no significant differences of NR3C1 expression level and cortisol between MDD patients and normal controls were observed. On the other hand, regulation of HPA negative-feedback by endogenous glucocorticoids was shown to occur through inhibition of the CRF gene transcription directly in hypothalamus. The second part aims to investigate the effects of antidepressants on CRF expression in vitro. Results from qRT-PCR showed that antidepressants and psychiatric drugs may directly influence the transcriptional activity of CRF promoter by inhibitory effects of the drugs on forskolin-induced expression of CRF mRNA. These findings revealed that not only neurotransmitters balancing, but the mechanism actions of antidepressants and psychiatric drugs may also act in the HPA negative-feedback regulation by reducing CRF expression in response to stress. Taken together, the results from this thesis suggested that both the NR3C1 and CRF genes may play important roles in the HPA axis stress response systems, which were associated to mental disorders.