Ascorbate uptake enables tubular mitophagy to prevent septic AKI by PINK1-PARK2 axis.

Abstract

Ascorbate (Vitamin C) has been proposed as a promising therapeutic agent against sepsis in clinical trials, but there is little experimental evidence on its anti-septic efficacy. We report that Toll-like receptor 4 (TLR4) activation by LPS stimuli augments ascorbate uptake in murine and human tubular cells through upregulation of two ascorbate transporters SVCT-1 and -2 mediated by Fn14/SCFFbxw7α cascade. Ascorbate restriction, or knockout of SVCT-1 and -2, the circumstance reminiscent to blockade of ascorbate uptake, endows tubular cells more vulnerable to the LPS-inducible apoptosis, whereas exogenous administration of ascorbate overrides the ruin execution, for which the PINK1-PARK2, rather than BNIP3-NIX axis is required. Ascorbate increases, while SVCT-1 and -2 knockout or ascorbate restriction dampens tubular mitophagy upon LPS stimuli. Treatment of endotoxemic mice with high-dose ascorbate confers mitophagy and substantial protection against mortality and septic acute kidney injury (AKI). Our work provides a rationale for clinical management of septic AKI with high doses of ascorbate.