Sirt3 suppresses calcium oxalate-induced renal tubular epithelial cell injury via modification of FoxO3a-mediated autophagy.

High oxalic acid and calcium oxalate (CaOx)-induced renal tubular epithelial cell (TEC) injury plays a key role in nephrolithiasis. However, the mechanism remains unknown. Gene array analysis of the mice nephrolithiasis model indicated significant downregulation of sirtuin 3 (Sirt3) and activation of mitogen-activated protein kinase (MAPK) pathway. Kidney biopsy tissues of renal calculi patients also showed decreased Sirt3 expression. Silencing Sirt3 exacerbated oxidative stress and TEC death under CaOx stimulation. Restoring Sirt3 expression by overexpression or enhancing its activity protected renal function and reduced TEC death both in vitro and in vivo. Inhibiting the MAPK pathway resulted in upregulation of Sirt3 expression, preservation of renal function and decreased cell death both in vitro and in vivo. Furthermore, Sirt3 could upregulate FoxO3a activity post-translationally via deacetylation, dephosphorylation and deubiquitination. FoxO3a was found to interact with the promoter region of LC3B and to increase its expression, enhancing TEC autophagy and suppressing cell apoptosis and necrosis. Taken together, our results indicate that the MAPK/Sirt3/FoxO3a pathway modulates renal TEC death and autophagy in TEC injury.