ATP-citrate lyase is essential for high glucose-induced histone hyperacetylation and fibrogenic gene upregulation in mesangial cells

The goal of this study was to address the role of ATP-citrate lyase (ACL), an enzyme that converts citrate to acetyl-CoA, in high glucose (HG)-induced histone acetylation and profibrotic gene expression. Our recent ChIP-Seq studies have demonstrated that HG induces genome-wide histone hyperacetylation in mesangial cells (MCs). Here, we showed that exposure of MCs to HG markedly increased histone acetylation at the H3K9/14 and H3K18 marks and induced the expression of potent profibrotic factors TGF-beta 1, TGF-beta 3, and connective tissue growth factor (CTGF). The induction of these profibrotic factors was further enhanced by histone deacetylase inhibitor but suppressed by histone acetyl-transferase inhibitor, confirming the importance of histone acetylation in this regulation. Interestingly, HG not only upregulated ACL expression but also promoted ACL nuclear translocation, evidenced by increased ACL concentration and activity in the nuclear extracts. Consistent with this observation, transfection of MCs with a plasmid-carrying green fluorescent protein (GFP)-ACL fusion protein led to GFP nuclear accumulation when cultured in HG condition. Silencing ACL with siRNAs alleviated HG-induced histone hyperacetylation, as well as upregulation of TGF-beta 1, TGF-beta 3, CTGF, and extracellular matrix (ECM) proteins fibronectin and collagen type IV, whereas ACL overexpression further enhanced HG induction of histone acetylation, as well as these profibrotic factors and ECM proteins. Collectively, these observations demonstrate that HG promotes ACL expression and translocation into the nucleus, where ACL converts citrate to acetyl-CoA to provide the substrate for histone acetylation, leading to upregulation of fibrogenic genes. Therefore, ACL plays a critical role in epigenetic regulation of diabetic renal fibrosis.