Downregulation of TRPC6 regulates ERK1/2 to prevent sublytic C5b‑9 complement complex‑induced podocyte injury through activating autophagy

Abstract

Idiopathic membranous nephropathy (IMN) is a common glomerular disease, in which 50‑60% of patients can progress to end‑stage renal disease within 10‑20 years, seriously endangering human health. Podocyte injury is the direct cause of IMN. Sublytic C5b‑9 complement complex induces damage in podocytes' structure and function. In sublytic C5b‑9 treated podocytes, the expression of canonical transient receptor potential 6 (TRPC6) is increased. However, the specific mechanism of TRPC6 in sublytic C5b‑9 treated podocytes is unclear. The present study aimed to reveal the effect and mechanism of TRPC6 on sublytic C5b‑9‑induced podocytes. Normal human serum was stimulated using zymosan to form C5b‑9. A lactate dehydrogenase release assay was used to examine C5b‑9 cytotoxicity in podocytes. The RNA and protein expression levels were analyzed using reverse transcription‑quantitative PCR, western blotting and immunofluorescent assay, respectively. Cell Counting Kit‑8 assay and flow cytometry were carried out to test the viability and apoptosis of podocytes, respectively. Transmission electron microscopy was used to observe autophagic vacuole. F‑actin was tested through phalloidin staining. Sublytic C5b‑9 was deposited and TRPC6 expression was boosted in podocytes stimulated through zymosan activation serum. Knockdown of TRPC6 raised the viability and reduced the apoptosis rate of sublytic C5b‑9‑induced podocytes. Meanwhile, transfection of small‑interfering (si)TRPC6 facilitated autophagy progression and enhanced the activation of cathepsin B/L in sublytic C5b‑9‑induced podocytes. The phosphorylation level of ERK1/2 was receded in siTRPC6 and sublytic C5b‑9 co‑treated podocytes. Moreover, the addition of the ERK1/2 activator partially reversed the effect of TRPC6 inhibition on sublytic C5b‑9‑induced podocytes. TRPC6 knockdown reduced the damage of sublytic C5b‑9 to podocytes by weakening the ERK1/2 phosphorylation level to activate autophagy. These results indicated that targeting TRPC6 reduced the injury of sublytic C5b‑9 on podocytes.