Complanatuside Ameliorates Renal Injury and Fibrosis in Chronic Kidney Disease by Inhibiting Tubular Cell Apoptosis via Activation of KLK1/BDKRB2.

BACKGROUND: Chronic kidney disease (CKD) is characterized by renal fibrosis as a key pathological feature. Total flavonoids extracted from Astragalus complanatus can effectively alleviate renal fibrosis. However, the anti-fibrotic effect and the underlying specific mechanisms of its main active component, Complanatuside (CPT), remain unclear. This study aims to investigate the role of CPT on apoptosis and fibrosis of kidney in CKD, and the underlying mechanism. METHODS: The protective effects of CPT against CKD were investigated using mouse and cell models of CKD, and its key targets and mechanisms were identified. RESULTS: The results showed that CPT ameliorated renal fibrosis in UUO mice and TGF-β1-induced fibrosis in HK2 cells. Notably, our single-cell RNA sequencing analysis revealed that CPT significantly reduced failed-repair tubular cells and inhibited apoptosis, accompanied by marked activation of KLK1 gene expression. We found that CPT binds to KLK1, activates its expression, reduces PTEC apoptosis, and thereby attenuates renal fibrosis. In line with this, in vitro studies showed that overexpressing KLK1 reduced TGF-β1-induced fibrosis and apoptosis, whereas knocking down KLK1 reversed CPT's renal protective effect. Further bioinformatics analysis indicated that KLK1 promotes BDKRB2 expression. Knocking down BDKRB2 exacerbated TGF-β1-induced fibrosis and apoptosis. Additionally, when investigating the relationship between KLK1 and BDKRB2, we found a direct interaction between them. Furthermore, downregulation of BDKRB2 counteracted the inhibitory effects of KLK1 overexpression on cell apoptosis and renal fibrosis. CONCLUSION: This study reveals that CPT binds to KLK1, promotes BDKRB2 expression, thereby reducing PTEC apoptosis and improving renal fibrosis.