NAD+ Treatment Can Attenuate the Oxidative Stress‐Induced, PARP‐Mediated ATP Depletion in PC12 Cells

Abstract

NAD+ is a critical factor in multiple biological functions. Poly(ADP‐ribose) polymerase‐1 (PARP‐1), a major NAD+‐consuming enzyme, plays a key role in oxidative stress‐induced cell death. Our previous study has indicated that NAD+ administration can greatly decrease ischemic brain injury, while the mechanisms underlying the effect remain unclear. In this study we tested our hypothesis that NAD+ treatment can attenuate the oxidative stress‐induced, PARP‐mediated ATP depletion, which may underlie the protective effects of NAD+ on brain ischemia. Our study shows that H2O2 treatment can significantly decrease intracellular ATP levels in PC12 cells, which was largely prevented by treatment of NAD+. In contrast, nicotinamide ‐‐‐ the degradation product of NAD+, produce weaker protection against the ATP depletion compared with NAD+, suggesting that NAD+ does not produce its effect on the ATP levels by producing nicotinamide. We also found that PARP inhibitors can prevent the H2O2‐induced ATP depletion, suggesting that NAD+ treatment can prevent the oxidative stress‐induced, PARP‐mediated ATP depletion in PC 12 cells. We also found that neither pyruvate nor antioxidants can attenuate the ATP depletion, arguing against the possibility that NAD+ restores the ATP levels by enhancing antioxidantion capacity of the cells or by increasing glycolysis. Collectively, our study has suggested that NAD+ treatment can restore the ATP levels in cells exposed to oxidative stress, which may at least partially underlie the protective effects of NAD+ on ischemic brain damage. (Supported by a Key Research Grant of Shanghai Municipal Scientific Committee #08JC1415400, and a Shanghai Engineering Center Grant of Equipment and Technology of Physical Therapy for Major Diseases)..