KLF15 deficiency contributes complement activation and podocyte injury in IgA nephropathy via regulating p300/ NF-κB axis

Abstract

Krüppel-Like Factor 15 (KLF15) is a member of the Krüppel-like subfamily of zinc finger transcription factors, involved in a diverse renal physiology and diseases. The exact roles of KLF15 in IgA nephropathy (IgAN) have not been fully investigated. To address the issue of KLF15 expression and its exact roles in IgAN, IgAN mouse models and IgA-treated podocytes MPC-5 were established. Co-immunoprecipitation (Co-IP) assay was conducted to detect the interaction between KLF15 and p300. Levels of genes and complement factors were determined by Western blot, immunofluorescence, immunohistochemistry and ELISA assays. Podocytes apoptosis was detected with flow cytometry. KLF15 expression was downregulated in both renal tissues of IgAN mouse models and IgA-treated podocytes. This suppression coincided with elevated levels of complement components C3a and C5a, along with increased complement factor H (CFH) expression, collectively suggesting activation of the complement activation in IgA nephropathy. Besides, NF-κB was activated in IgAN, evidenced by the elevated levels of NF-κB p65 and its acetylation at lysine 310 as well as IκBα phosphorylation in IgAN models and IgA-treated podocyte. KLF15 overexpression alleviated complement activation and IgAN podocyte injury, characterized by improved cell viability, reduced apoptotic cells and apoptotic proteins expression (Bax/Bcl-2 and cleaved-caspase3), upregulated expression of nephrin and podocin, and suppressed complement components. In terms of mechanism, KLF15 overexpression could inhibit NF-κB activation by interacting with p300 to decrease p300 level, which was further confirmed by using p300 activator CTB or NF-κB activator PMA. These results indicate that KLF15 protects against podocyte injury in IgA nephropathy by suppressing complement system activation and modulating the p300/NF-κB signaling axis.