Inhibition of Oxidative Stress in HeLa Cells by Chemopreventive Agents 1
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چکیده
12-O-Tetradecanoylphorbol.13-acetate (TPA)-mediated oxidative stress in HeLa cells and its inhibition were studied by fluorometric measurement of H2Oz and by 3H-postlabeling of the oxidized bases 8-hydroxyl-2'-deoxyguanosine (8-OHdG) and 5-hydroxymethyl-2'-deoxyuridine (HMdU). TPA treatment (10 fmol/cell) caused "~7-fold increase in H202 levels (0.1 nmol TPA/ml), and 5-10-fold increase in 8-OHdG and HMdU (10 nmol TPA/ml). Naturally occurring compounds [caffeic acid phenethyl ester (CAPE), (-).epigallocatechin gaUate (EGCG), penta-O-galloyl-jB-D-glucose (PGG) and sarcophytol A (Sarp A)] and the anticancer drug tamoxifen (TAM) were tested as potential chemopreventive agents. These agents dose-dependently inhibited TPA-induced H202, 8-OHdG and HMdU. The doses required for a 50% decrease in H202 were ~2.5/tM for TAM; 5 ~M for CAPE, EGCG and PGG; and 75/tM for Sarp A. TAM and PGG (10 ~M), EGCG (25/~M), and CAPE (50/XM) abolished TPA-mediated H202 production, even below the normal cellular levels. TAM (2.5-20/tM) decreased TPA-mediated HMdU and 8-OHdG formation 2-29 times. Maximum inhibition occurred at 20/tM TAM, which caused an "~95 % decline in HMdU and 8-OHdG. CAPE was effective at 0.5-50/tM. CAPE (25/~M) decreased 8-OHdG 95% and HMdU 58%, while Sarp A (250/zM) reduced 8-OHdG by 93% and HMdU by 78%. EGCG (1-25/xM) and PGG (1-10 /tM) inhibited formation of 8-OHdG and HMdU dose-dependently. However, higher doses (50 and 100 ~M) decreased the efficacy of that inhibition. Of those agents tested, TAM appears to be the most and Sarp A the least effective. Our results point to these 5 compounds as being potential chemopreventive agents, which at very low doses decrease the tumor promoter-mediated oxidative processes.
منابع مشابه
Inhibition of oxidative stress in HeLa cells by chemopreventive agents.
12-O-Tetradecanoylphorbol-13-acetate (TPA)-mediated oxidative stress in HeLa cells and its inhibition were studied by fluorometric measurement of H2O2 and by 3H-postlabeling of the oxidized bases 8-hydroxyl-2'-deoxyguanosine (8-OHdG) and 5-hydroxymethyl-2'-deoxyuridine (HMdU). TPA treatment (10 fmol/cell) caused approximately 7-fold increase in H2O2 levels (0.1 nmol TPA/ml), and 5-10-fold incre...
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