The Role of Poly(ADP–Ribose) Polymerase in the Nuclear and Mitochondrial Genomes of the Retinal Pigment Epithelium Against Oxidative and Alkylation Stress

Abstract

Purpose: : To investigate the role of Poly(ADP)polymerase (PARP) in the nDNA and mtDNA of the RPE against oxidative (H₂O₂) and alkylation (MMS) damage.

Methods: : : Cellular sensitivity of ARPE–19 to oxidative induced–H₂O₂ and alkylation induced–MMS stress was determined by the MTT assay. PARP ribosyl(ation) activity was inhibited by supplementation of 3–aminobenzamide (competitive PARP inhibitor). The susceptibility and repair capacities of nuclear and mitochondrial genomes were assessed by QPCR.

Results: : This study demonstrated that cells lacking ribosyl(ation) activity had a significantly lower lesion repair capacity in both nDNA and mtDNA (P<0.05) which culminated in reduced cell viability post–treatment after H₂O₂ exposure only (P<0.05). Furthermore, the mtDNA demonstrated a significantly greater sensitivity compared to nDNA to both oxidative and alkylation damage (P<0.05).

Conclusions: : PARP activity has an important function in protecting both the nuclear and mitochondrial genomes of the RPE against a wide array of genotoxic damage. Furthermore, we hypothesize PARP plays a substantial role in providing the RPE with the high oxidative tolerance required for this cell type to survive the constant ROS attack it has to endure in vivo for many decades.

Keywords: oxidation/oxidative or free radical damage • retinal pigment epithelium • cell survival