Angiopoietin-like 4 exacerbates renal tubular epithelial cell pyroptosis in acute kidney injury via integrin β5/FAK signaling pathway.

Abstract

Angiopoietin-like 4 (Angptl4) is a secreted protein that participates in multiple biological processes. Our previous study on the effect of Angptl4 in minimal change disease (MCD) unexpectedly indicated a close correlation between Angptl4 and kidney function, especially in MCD patients combined with AKI, implying a possible function of Angptl4 in AKI. However, the role and molecular mechanism of Angptl4 in AKI are undetermined. Biopsy tissue and serum of patients with AKI were analyzed by ELISA and immunohistochemistry to evaluate ANGPTL4 expression and its correlation with kidney function. For in vitro study, ANGPTL4 overexpressed and knocked down HK-2 cells were used to determine the effect of ANGPTL4 on cell pyroptosis. For in vivo study, Angptl4 global and conditional knockout mice were generated to study AKI using cisplatin- or ischemia/reperfusion-induced AKI mouse models. Additionally, we used various experimental approaches to investigate how ANGPTL4 induces tubular cell injury via interaction with integrin β. Angptl4 was up regulated in kidney tubular epithelial cells of multiple AKI models and correlated with kidney function. ANGPTL4 aggravated tumor suppressor GSDME-dependent cell pyroptosis in vitro. In genetic mice, overexpression of Angptl4 worsened kidney function, inflammation, and cell pyroptosis, whereas ablation of Angptl4 attenuated kidney injury in AKI. Mechanistically, ANGPTL4 interacted with integrin β5 and activated focal adhesion kinase (FAK), promoting kidney tubular pyroptosis through the caspase 3/GSDME signaling pathway. Inhibition of integrin β5 or FAK alleviated kidney tubular pyroptosis and kidney dysfunction. Moreover, ANGPTL4 promoted the secretion of cytokines MCP-1 and RANTES by kidney tubular epithelial cells, enhancing macrophage recruitment. Our results reveal that Angptl4 triggers pyroptosis and worsened kidney injury in AKI and offers a potential target for the diagnosis and treatment of AKI.