Prevention of oxidant-induced cell death in Caco-2 colon carcinoma cells after inhibition of poly(ADP-ribose) polymerase and Ca 2+ chelation: involvement of a common mechanism

Abstract

The human colon carcinoma cell line Caco-2 was exposed to the oxidative stress-inducing agents menadione (MEN), 2,3-dimethoxy-1,4-naphthoquinone, and hydrogen peroxide. All three agents caused DNA damage which was assessed by alkaline unwinding. Further, all three agents induced intensive NAD + depletion, followed by a decrease in intracellular ATP and viability. Inhibition of poly(ADP-ribose) polymerase (PARP, EC 2.4.2.30) by 3-aminobenzamide prevented the depletion of NAD +. These cells had a higher viability and ATP content. The most pronounced effect was observed with 25 μM of MEN, while at higher levels a partial preservation of NAD + was observed with no effect on ATP or viability. The chelation of intracellular calcium by bis-(o-aminophenoxy)-ethane- N, N, N 1, N 1-tetraacidic acid/tetraacetoxymethyl) ester also prevented the dramatic loss of NAD +, demonstrating that Ca 2+ is an activating factor in PARP-mediated cell killing.