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EN
Poly(ADP-ribose) polymerase (PARP) is a conserved enzyme involved in the regulation of DNA repair and genome stability. The role of PARP during aging is not well known. In this study PARP activity was investigated in nuclear fractions from hippocampus, cerebellum, and cerebral cortex of adult (4 months), old adult (14 months) and aged (24-27 months) rats. Concomitantly, the free radical evoked lipid peroxidation was estimated as thiobarbituric acid reactive substances (TBARS). The specific activity of PARP in adult brain was about 25, 21 and 16 pmol/mg protein per min in hippocampus, cerebellum and cerebral cortex, respectively. The enzyme activity was higher in all investigated parts of the brain of old adults. In aged animals PARP activity was lower in hippocampus by about 50%, and was unchanged in cerebral cortex and in cerebellum comparing to adult rats. The concentration of TBARS was the same in all parts of the brain and remained unchanged during aging. There is no direct correlation between PARP activity and free radical evoked lipid peroxidation during brain aging. The lowered enzyme activity in aged hippocampus may decrease DNA repair capacity which subsequently may be responsible for the higher vulnerability of hippocampal neurons to different toxic insults.
EN
Carvedilol a beta-adrenoreceptor antagonist with potent antioxidant properties raises high expectations in therapy of ischemia. In this study the effect of carvedilol on neuronal survival after transient forebrain ischemia in gerbils was investigated. The role of poly(ADP-ribose) polymerase (PARP-1) in this process was evaluated. Our data indicated that carvedilol administered subcutaneously in a dose of 7 or 70 mg/kg b.w. directly after 5 min of transient forebrain ischemia protects significant population of neurons in hippocampal area CA1, but has no effect after induction of prolonged 10 min ischemia. Carvedilol significantly decreased PARP activity in hippocampus that was markedly increased after both 15 min and 4 days of reperfusion following 5 min of ischemia. Moreover, carvedilol prevented NAD+ depletion after ischemic-reperfusion insult. These results indicated that carvedilol protects neurons against death and suggested that suppression of PARP activity during reperfusion could be involved in this process.
EN
Poly(ADP-ribose) polymerase (PARP-1) is an abundant nuclear protein with a high affinity for single- and double-strand DNA breaks. Its binding to strand breaks promotes catalysis of the covalent modification of nuclear proteins with poly(ADP-ribose) synthesised from NAD+. PARP-1-knockout cells are extremely sensitive to alkylating agents, suggesting the involvement of PARP-1 in base excision repair; however, its role remains unclear. We investigated the dependence of base excision repair pathways on PARP-1 and NAD+ using whole cell extracts derived from normal and PARP-1 deficient mouse cells and DNA substrates containing abasic sites. In normal extracts the rate of repair was highly dependent on NAD+. We found that in the absence of NAD+ repair was slowed down 4-6-fold after incision of the abasic site. We also established that in extracts from PARP-1 deficient mouse cells, repair of both regular and reduced abasic sites was increased with respect to normal extracts and was NAD+-independent, suggesting that in both short- and long-patch BER PARP-1 slows down, rather than stimulates, the repair reaction. Our data support the proposal that PARP-1 does not play a major role in catalysis of DNA damage processing via either base excision repair pathway.
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