Cyclic helix B peptide ameliorates renal tubulointerstitial fibrosis induced by unilateral ureter obstruction via inhibiting NLRP3 pathway

Background: Renal fibrosis is the inevitable outcome of all progressive chronic kidney diseases (CKD) and leads to a gradual loss of renal function. We previously reported cyclic helix B peptide (CHBP), a novel synthesized peptide derived from erythropoietin, had shown effective renoprotection. In this study, we investigated the anti-fibrotic and renoprotective effect of CHBP in a murine renal tubulointerstitial fibrosis model induced by unilateral ureter obstruction (UUO). Methods: Mice were subjected to the UUO model and CHBP was given intraperitoneally. To assess the therapeutic effects of CHBP, pathological injury, deposition of extracellular matrix (ECM) and the progression of epithelial-mesenchymal transition (EMT) were examined in vivo. The anti-fibrotic effects of CHBP was validated in vitro using TCMK-1 cells treated with TGF-beta 1. Involvement of the NLRP3 pathway was demonstrated both in vivo and in vitro. Results: CH BP significantly ameliorated renal tubulointerstitial injury and fibrosis in terms of ECM deposition. The EMT process was also alleviated after CHBP treatment. Similar therapeutic effects of CHBP were also observed in vitro in TGF-beta 1 treated tubular epithelial cells (TECs). NLRP3/caspase-1/IL-1 beta pathway was involved and activated upon injury, both in vivo and in vitro. While the activation of the NLRP3 pathway was found to be in negative correlation with CHBP treatment. CHBP could suppress the activation of NLRP3 and its downstream inflammatory mediators even with addition of extracellular ATP, a direct activator of the NLRP3 inflammasome. Conclusions: Our results suggest that CHBP could effectively protect the kidney from renal tubulointerstitial fibrosis in the UUO model via counteracting the NLRP3/caspase-1/IL-1 beta pathway.