IL-6 accelerates renal fibrosis after acute kidney injury via DNMT1-dependent FOXO3a methylation and activation of Wnt/β-catenin pathway

Maladaptive repair following acute kidney injury (AKI) can trigger inflammation and fibrosis, while progressive renal interstitial fibrosis is critical for the transition of AKI to chronic kidney disease. The aim of this study was to investigate the effect of pro-inflammatory IL-6 on the renal fibrosis after AKI as well as the underlying mechanism. Bioinformatics analysis was performed to identify potential genes related to renal fibrosis. An in vitro model of AKI was established by hypoxia-reoxygenation (H/R) in mouse renal tubular epithelial cells (mRTECs). Gain- and loss-of-function approaches were employed to identify the effects of IL-6/FOXO3a on the renal fibrosis following AKI. The methylation level of FOXO3a promoter was assessed by methylation specific PCR. An AKI mouse model was established by ischemia-reperfusion. Adenovirus-packaged shRNA targeting IL-6 or FOXO3a was utilized for further exploration of their roles in vivo. IL-6 was highly expressed in H/R-exposed mRTECs and kidney tissues of AKI mice rendered with renal fibrosis. Knockdown of IL-6 slowed the renal fibrosis after AKI. IL-6 induced DNMT1 to promote FOXO3a promoter methylation and thus inhibited FOXO3a expression. This inhibition led to promotion of renal fibrosis through activating the Wnt/β-catenin pathway. Further in vivo results verified that loss of IL-6 disrupted the Wnt/β-catenin pathway through reversing DNMT1-mediated inhibition of FOXO3a and consequently attenuated renal fibrosis. All in all, these results suggest that targeting IL-6 contributes to protection against renal fibrosis after AKI through mediating the DNMT1/FOXO3a/Wnt/β-catenin axis, which may serve as promising target for the treatment of AKI and prevention against chronic kidney disease.