Hypermethylation and downregulation of microRNA219a-2 activates the ALDH1L2/GSH/PAI-1 pathway for fibronectin degradation in renal fibrosis

Epigenetic regulations, such as DNA methylation and microRNAs, play an important role in renal fibrosis. Here, we report the regulation of microRNA-219a-2 by DNA methylation in fibrotic kidneys, unveiling the crosstalk between these epigenetic mechanisms. Through genome-wide DNA methylation analysis and pyro-sequencing, we detected the hypermethylation of microRNA219a-2 in renal fibrosis induced by unilateral ureter obstruction (UUO) or renal ischemia/reperfusion, which was accompanied by a significant decrease in microRNA-219a-5p expression. Functionally, overexpression of microRNA219a-2 enhanced fibronectin induction during hypoxia or TGF-β1 treatment of cultured renal cells. In mice, inhibition of microRNA-219a-5p suppressed fibronectin accumulation in UUO and ischemic/reperfused kidneys. Aldehyde dehydrogenase 1 family member L2 (ALDH1L2) was identified to be the direct target gene of microRNA-219a-5p in renal fibrotic models. MicroRNA-219a-5p suppressed ALDH1L2 expression in cultured renal cells, while inhibition of microRNA-219a-5p prevented the decrease of ALDH1L2 in injured kidneys. Knockdown of ALDH1L2 enhanced plasminogen activator inhibitor-1(PAI-1) induction during TGF-β1 treatment of renal cells, which was associated with fibronectin expression. In conclusion, the hypermethylation of microRNA219a-2 in response to fibrotic stress may attenuate microRNA-219a-5p expression and induce the up-regulation of its target gene ALDH1L2, which reduces fibronectin deposition by suppressing PAI-1.