P88 DNA methylation contributes to cystathionine-γ-lyase downregulation in ox-LDL-treated macrophage.

Hydrogen sulfide (H2S), mainly produced by cystathionine-gamma-lyase (CSE) in vascular system, emerges as a novel gasotransmitter and exerts anti-atherosclerotic effects. Alterations of CSE/H2S pathway may thus be implicated in atherogenesis. However, the cellular and molecular mechanisms remain to be clarified. In this study, we showed that ox-LDL, the major risk factor of atherosclerosis, suppressed CSE promoter activity, and decreased its mRNA and protein expression, as well as H2S generation in macrophage. Exogenous H2S and CSE overexpression reduced TNF-alpha and ICAM-1 generation in ox-LDL-treated macrophage and its adhesion to the endothelial monolayer, whilst CSE knockdown produced opposite effects. Interestingly, ox-LDL increased the expression and activity of DNA methyltransferase (DNMT) and resulted in hypermethylation of CpG islands in the cse gene promoter region, as determined by mehylation-specific PCR and bisulfate sequencing. Moreover, DNMT inhibitor 5-aza-2′-deoxycytidine and DNMT1 siRNA abolished the CSE decrease induced by ox-LDL. More important, the ox-LDL-induced disturbance of CSE and DNMT was confirmed in the peritoneal macrophage isolated from ApoE−/− mice. These results reveal that DNA hypermethylation may be involved in ox-LDL induced CSE downregulation and subsequent H2S reduction in macrophage. We conclude that ox-LDL activates macrophage and triggers vascular inflammation by suppressing CSE transcription via its promoter region hypermethylation. [ABSTRACT FROM AUTHOR]