Aberrant Histone Modification of TNFAIP3, TLR4, TNIP2, miR-146a, and miR-155 in Major Depressive Disorder

Activated toll-like receptor (TLR) signaling has been well investigated in major depressive disorder (MDD). We previously reported that TNFAIP3, TLR4, TNIP2, miR-146a, and miR-155 play important roles in regulating the toll-like receptor 4 (TLR4) signaling pathway and may serve as novel targets in the pathogenesis of MDD. Recently, aberrant histone modification has been implicated in several psychiatric disorders, including schizophrenia and mood disorder; the most thoroughly studied modification is histone 3 lysine 4 tri-methylation (H3K4me3). In this work, we aimed to explore H3K4me3 differences in the promotors of genes encoding the abovementioned factors in patients with MDD, and whether they were altered after antidepressant treatment. A total of 30 MDD patients and 28 healthy controls were recruited. Peripheral blood mononuclear cells (PBMCs) were collected. The levels of H3K4me3 in the promoters of TNFAIP3, TLR4, TNIP2, miR-146a, and miR-155 were measured through chromatin immunoprecipitation (ChIP) followed by DNA methylation assay. Analysis of covariance was used to evaluate between-group differences after adjusting for age, sex, BMI, and smoking. In comparison with healthy controls, patients with MDD showed significantly lower H3K4me3 levels in the promoters of TNFAIP3, TLR4, TNIP2, miR-146a, and miR-155 in PBMCs. These levels were not significantly altered after completion of a 4-week antidepressant treatment. To explore the association between depression severity and H3K4me3 levels, a multiple linear regression model was generated. The results revealed that levels of H3K4me3 in the TNIP2 promoters a negative correlation with the 17-item Hamilton Depression Rating Scale (HAND-17) score, whereas that of TLR4 had a positive correlation with this score. The present results suggest that decreased H3K4me3 levels in the promoters of the genes encoding TNFAIP3, TLR4, miR-146a, miR-155, and TNIP2 are involved in psychopathology of major depressive disorder.