m⁶A methyltransferase ZC3H13 improves pulmonary fibrosis in mice through regulating Bax expression

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease. N6-methyladenosine (m⁶A) is a reversible RNA modification that was shown to be associated with IPF development. The present study aimed to explore the function and potential mechanism of the m⁶A methylation enzyme zinc finger CCCH-type containing 13 (ZC3H13) in IPF. In the study, bioinformatic screening yielded a differentially expressed m⁶A gene, ZC3H13, which was down-regulated in GEO microarrays, BLM-induced mouse models, and cellular models. Overexpression of ZC3H13 reduced histopathological damage of lung tissues in mice, mitigated fibrosis (including reduced α-SMA, collagen Ⅰ, and Vimentin levels, and elevated E-cadherin levels), decreased lung/body weight ratio and lung hydroxyproline levels, reduced oxidative stress (increased SOD activity and GSH-Px activity and decreased MDA levels), suppressed apoptosis within lung tissues and MLE-12 cells, promoted Bcl-2 expression, and inhibited Bax expression. Bax expression was found to be negatively correlated with ZC3H13 expression by correlation analysis. ZC3H13 could bind Bax mRNA and promote its m⁶A methylation through reading protein YTHDC1, thereby inhibiting its stability. Bax inhibition ameliorated BLM-induced MLE-12 cell dysfunction and partially abrogated the inhibition of MLE-12 cell function by ZC3H13 downregulation. In conclusion, m⁶A methyltransferase ZC3H13 impedes lung epithelial cell apoptosis and thus improves pulmonary fibrosis by promoting Bax mRNA m⁶A methylation and down-regulating Bax expression through reading protein YTHDC1.