β-Lapachone-Induced Oxidative Stress Causes PARP-Dependent NAD+-Depletion that Affects the Energy Metabolism of Cultured Primary Rat Astrocytes

Oxidative stress has been connected with many brain pathologies. As brain astrocytes have a strong antioxidative potential, we have investigated the consequences of β-lapachone-induced oxidative stress on the cell metabolism of cultured astrocytes by determining the cellular levels of important components of the cellular redox and energy metabolism. β-Lapachone exposure induced a rapid oxidation of cellular NADH and NADPH followed by a time- and concentration-dependent loss in the total cellular NADx content and an increase in the total cellular NADPx content, while the cell viability was not compromised. In addition, the treated cells were partially depleted of ATP and lost their ability to upregulate glycolytic lactate production after exposure to the respiratory chain inhibitor antimycin A. All these consequences were prevented in the presence of ES936 which inhibits the NQO1-mediated reduction of β-lapachone. Inhibition of poly(ADP-ribose) polymerases (PARPs) by PJ34 or AZD-2461 did not affect the strong cellular accumulation of glutathione disulfide, but significantly lowered the oxidative stress-induced loss in the cellular NADx and ATP contents, maintained the ability of the cells to upregulate glycolytic lactate production during incubation with antimycin A, and doubled the increase in the cellular NADPx content. After removal of the β-lapachone-induced oxidative stress, astrocytes were able to restore their initial cellular content of NADx in the presence of the NAD⁺ precursor nicotinamide. This restoration was accompanied by the reestablishment of the ability to upregulate glycolytic lactate production during antimycin A exposure. The results obtained show that oxidative stress has severe consequences on various fundamental metabolic parameters of astrocytes, but also demonstrate the high potential of these cells to recover after severe oxidative stress.

ATP; Astrocytes; Glutathione; Nicotinamide coenzymes; Oxidative stress; PARP; β-Lapachone.