Poly(ADP‐ribose) polymerase‐1 mediated glycolytic inhibition as a mechanism of targeted necrosis following renal ischemia

Abstract

Following ischemic renal injury (IRI), selective damage occurs in the S3 segment of the proximal tubule (PST) due to glycolytic inhibition. However, the exact mechanism by which glycolysis is inhibited is not elucidated. We reported that inhibition of PARP‐1 activity offers protection against necrotic cell death in PSTs following IRI by preserving ATP levels. We hypothesize that discriminating PARP‐1 activation in PSTs following IRI causes poly(ADP‐ribosyl)ation and inhibition of the key glycolytic enzyme GAPDH, leading to inhibition of glycolysis and anaerobic ATP synthesis. We demonstrate using in vitro and in vivo models that GAPDH is poly(ADP‐ribosyl)ated and as a consequence, its activity is inhibited under hypoxic conditions. Inhibition of PARP activity restored GAPDH activity and ATP levels. Supplementation of NAD+ in simulated hypoxia had only a minimal effect on ATP synthesis indicating that glycolytic inhibition is not due to depletion of NAD+ as previously proposed. Inhibition of GAPDH using iodoacetamide, however, exacerbated ATP depletion and necrotic cell death under hypoxic conditions when compared to controls, while inhibition of PARP activity protected the cells. In conclusion, our data indicate that GAPDH‐poly(ADP‐ribosyl)ation and subsequent inhibition of anaerobic respiration exacerbate ATP depletion in PST to induce selective PST cell injury following IRI. AHA and NKF‐Nebraska.