Modulation Of Connexin 43 Expression By Histone Acetylation Dependent Mechanisms In Human Bladder Smooth Muscle Cells

We investigated the role of a histone acetylation dependent mechanism in the transcriptional repression of connexin43 (Cx43) in cultured human bladder smooth muscle cells (HBSMCs). Expression of Cx43 mRNA was assessed by RT-PCR and qPCR after treatment of HBSMCs with either the histone deacetylase (HDAC) inhibitor, trichostatin A (TSA) or the histone acetyltransferase (HAT) inhibitor, anacardic acid (AA). Modulation of histone acetylation and recruitment of the transcription factors AP-1 and Sp1 at the Cx43 promoter region in response to TSA or anacardic acid was analyzed by chromatin immunoprecipitation (ChIP) assay. While the treatment with TSA promoted the expression of both the Cx43 mRNA and protein in HBSMCs, the expression of both the Cx43 mRNA and protein were suppressed in the presence of anacardic acid, compared to the levels in the untreated cells. ChIP assays confirmed that TSA-induced transcriptional up-regulation of Cx43 in HBSMCs was associated with increases in the accumulation of acetylated histones H3 and H4 accompanied with the enrichment of accessible AP-1 and Sp1 in the critical promoter region of the Cx43 gene. On the contrary, ChIP assay after treatment with anacardic acid showed that repression of Cx43 in HBSMCs was associated with decreased acetylation levels of histone H3 and H4 accompanied with subsequent reduction in the binding of AP-1 and Sp1. Our finding suggested that TSA-mediated induction and anacardic acid-mediated reduction of Cx43 expression in HBSMCs might be associated with the histone acetylation dependent mechanism linked to the transcription factors AP-1 and Sp1 in the Cx43 promoter.