Blocking connexin 43 and its promotion of ATP release from renal tubular epithelial cells ameliorates renal fibrosis

Whether metabolites derived from injured renal tubular epithelial cells (TECs) participate in renal fibrosis is poorly explored. After TEC injury, various metabolites are released and among the most potent is adenosine triphosphate (ATP), which is released via ATP-permeable channels. In these hemichannels, connexin 43 (Cx43) is the most common member. However, its role in renal interstitial fibrosis (RIF) has not been fully examined. We analyzed renal samples from patients with obstructive nephropathy and mice with unilateral ureteral obstruction (UUO). Cx43-KSP mice were generated to deplete Cx43 in TECs. Through transcriptomics, metabolomics, and single-cell sequencing multi-omics analysis, the relationship among tubular Cx43, ATP, and macrophages in renal fibrosis was explored. The expression of Cx43 in TECs was upregulated in both patients and mice with obstructive nephropathy. Knockdown of Cx43 in TECs or using Cx43-specific inhibitors reduced UUO-induced inflammation and fibrosis in mice. Single-cell RNA sequencing showed that ATP specific receptors, including P2rx4 and P2rx7, were distributed mainly on macrophages. We found that P2rx4- or P2rx7-positive macrophages underwent pyroptosis after UUO, and in vitro ATP directly induced pyroptosis by macrophages. The administration of P2 receptor or P2X7 receptor blockers to UUO mice inhibited macrophage pyroptosis and demonstrated a similar degree of renoprotection as Cx43 genetic depletion. Further, we found that GAP 26 (a Cx43 hemichannel inhibitor) and A-839977 (an inhibitor of the pyroptosis receptor) alleviated UUO-induced fibrosis, while BzATP (the agonist of pyroptosis receptor) exacerbated fibrosis. Single-cell sequencing demonstrated that the pyroptotic macrophages upregulated the release of CXCL10, which activated intrarenal fibroblasts. Cx43 mediates the release of ATP from TECs during renal injury, inducing peritubular macrophage pyroptosis, which subsequently leads to the release of CXCL10 and activation of intrarenal fibroblasts and acceleration of renal fibrosis.