Effect of poly(ADP-ribose) polymerase inhibitors on oxidative stress evoked hydroxyl radical level and macromolecules oxidation in cell free system of rat brain cortex.

Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear enzyme involved in DNA repair, replication and cell cycle. However, its overactivation leads to nicotinamide adenine dinucleotide and ATP depletion and cell death. The inhibitors of PARP-1 were successfully used in the basic studies and in animal models of different diseases. For this reason, it is important to discriminate between specific and non-specific antioxidant properties of PARP-1 inhibitors. The aim of this study was to investigate the effect of PARP-1 inhibitors on the free radical level and oxidation of macromolecules and to compare their properties with the efficacy of antioxidants. Oxidative stress was induced in the brain cortex homogenate by FeCl(2) or CuSO(4) at 25 microM during 15 min incubation at 37 degrees C. PARP-1 inhibitors 3-aminobenzamide (3-AB), 1,5-dihydroxyisoquinoline (DHIQ) and 3,4-dihydro-5-[4-(1-piperidinyl)butoxy]-1(2H)-isoquinolinone (DPQ), and the antioxidants alpha-tocopherol, resveratrol and Tempol were used at 0-5 mM. Free radical contents were estimated by spin-trapping using HPLC. Lipid and protein oxidation were determined by measuring thiobarbituric acid reactive substances and carbonyl groups or using fluorescent probe TyrFluo, respectively. Our data indicate that 3-AB and DHIQ are potent hydroxyl radical scavengers and inhibitors of protein oxidation. DHIQ additionally decreases lipid peroxidation. DPQ has no antioxidant properties and seems to be a specific PARP-1 inhibitor, however, it is a water insoluble compound. Among the investigated antioxidants, the most potent was resveratrol and then alpha-tocopherol and Tempol. These results indicate that 3-A beta, benzamide and DHIQ are potent hydroxyl radical scavengers and antioxidants. These data ought to be taken into consideration when properties of these compounds as PARP inhibitors are evaluated.