Prevention of oxidant-induced cell death in Caco-2 colon carcinoma cells after inhibition of poly(ADP-ribose) polymerase and Ca2+ chelation:: Involvement of a common mechanism

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 mu M 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 Ca2+ is an activating factor in PARP-mediated cell killing. (C) 1998 Elsevier Science Inc.