Antagonizing EZH2 combined with vitamin D3 exerts a synergistic role in anti‐fibrosis through bidirectional effects on hepatocytes and hepatic stellate cells

Abstract Background and Aim Whether vitamin D3 (VD3) supplementation is associated with improved liver fibrosis is controversial. Methods Liver fibrosis models were treated with VD3, active VD (1,25‐OH 2 Vitamin D3), or collaboration with GSK126 (Ezh2 inhibitor), respectively. Hepatic stellate cells (HSCs) were co‐cultured with hepatocytes and then stimulated with TGF‐β. Autophagy of hepatocytes was determined after the intervention of 1,25‐OH 2 Vitamin D3 and GSK126. Also, the active status of HSCs and the mechanism with 1,25‐OH 2 Vitamin D3 and GSK126 intervention were detected. Results 1,25‐OH 2 Vitamin D3, but not VD3, is involved in anti‐fibrosis and partially improves liver function, which might be associated with related enzymes and receptors (especially CYP2R1), leading to decreased of its biotransformation. GSK126 plays a synergistic role in anti‐fibrosis. The co‐culture system showed increased hepatocyte autophagy after HSCs activation. Supplementation with 1,25‐OH 2 Vitamin D3 or combined GSK126 reduced these effects. Further studies showed that 1,25‐OH 2 Vitamin D3 promoted H3K27 methylation of DKK1 promoter through VDR/Ezh2 due to the weakening for HSCs inhibitory signal. Conclusions VD3 bioactive form 1,25‐OH 2 Vitamin D3 is responsible for the anti‐fibrosis, which might have bidirectional effects on HSCs by regulating histone modification. The inhibitor of Ezh2 plays a synergistic role in this process.