The Role of TRPC6 in Renal Ischemia/Reperfusion and Cellular Hypoxia/Reoxygenation Injuries

Renal ischemia/reperfusion (I/R), a major cause of acute kidney injury (AKI), is a serious clinical event in patients during post-renal transplantation. I/R is associated with renal dysfunction and tubular Apoptosis, and calcium (CA²⁺) overload has been reported to be a crucial factor on tubular Apoptosis in I/R injury (IRI). The canonical transient receptor potential channel 6 (TRPC6), a type of non-selective CA²⁺ channel, is involved in many renal diseases. Our earlier study identified that TRPC6-mediated CA²⁺ influx plays a novel role in suppressing cytoprotective Autophagy triggered by oxidative stress in primary tubular epithelial cells (TECs). This study explored the potential beneficial impact of TRPC6 knockout (TRPC6^-/-) and the relevant cellular mechanisms against I/R-induced AKI in mice. Measuring changes of renal function, apoptotic index, and Autophagy in mouse kidneys that suffered 24 h reperfusion after 40 min ischemia and working in vitro with TECs that suffered 24 h reoxygenation after 24 h hypoxia, we found that 1) IRI tissues had increased TRPC6 expression and TRPC6 knockout significantly ameliorated renal damage induced by IRI; 2) TRPC6 knockout enhanced the level of Autophagy and alleviated the depolarization of mitochondrial membrane potential (ψm, MMP) and apoptotic changes upon IRI; and 3) IRI tissues had increased p-AKT and p-ERK1/2 expressions, while TRPC6 knockout could markedly reduce the phosphorylation of Akt and ERK1/2. These discoveries suggest that, by reducing CA²⁺ overload, the underlying protective mechanism of TRPC6^-/- may be involved in down-regulation of PI3K/Akt and ERK signaling, which is likely to provide a new avenue for future AKI therapies.