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 increase in 8-OHdG and HMdU (10 nmol TPA/ml). Naturally occurring compounds [caffeic acid phenethyl ester (CAPE), (-).epigallocatechin gallate (EGCG), penta-O-galloyl-beta-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 H2O2, 8-OHdG and HMdU. The doses required for a 50% decrease in H2O2 were approximately 2.5 microM for TAM; 5 microM for CAPE, EGCG and PGG; and 75 microM for Sarp A. TAM and PGG (10 microM), EGCG (25 microM), and CAPE (50 microM) abolished TPA-mediated H2O2 production, even below the normal cellular levels. TAM (2.5-20 microM) decreased TPA-mediated HMdU and 8-OHdG formation 2-29 times. Maximum inhibition occurred at 20 microM TAM, which caused an approximately 95% decline in HMdU and 8-OHdG. CAPE was effective at 0.5-50 microM. CAPE (25 microM) decreased 8-OHdG 95%, and HMdU 58%, while Sarp A (250 microM) reduced 8-OHdG by 93% and HMdU by 78%. EGCG (1-25 microM) and PGG (1-10 microM) inhibited of 8-OHdG and HMdU dose-dependently. However, higher doses (50 and 100 microM) 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.
Bhimani
R S
RS
Department of Environmental Medicine, New York University Medical Center, New York 10016-6451.
Troll
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Grunberger
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Frenkel
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D000080242:8-Hydroxy-2'-Deoxyguanosine; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002109:Caffeic Acids / Q000494:pharmacology; D002392:Catechin / Q000031:analogs & derivatives / Q000494:pharmacology; D004273:DNA, Neoplasm / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000032:analysis; D004224:Diterpenes / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D047348:Hydrolyzable Tannins; D010084:Oxidation-Reduction; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives / Q000494:pharmacology; D013629:Tamoxifen / Q000494:pharmacology; D013634:Tannins / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000633:toxicity*; D013936:Thymidine / Q000031:analogs & derivatives / Q000032:analysis
D016588:Anticarcinogenic Agents; D000970:Antineoplastic Agents; D002109:Caffeic Acids; D004273:DNA, Neoplasm; D004224:Diterpenes; D047348:Hydrolyzable Tannins; D013634:Tannins; D013629:Tamoxifen; C058761:sarcophytol A; C435084:pentagalloylglucose; C018080:5-hydroxymethyl-2'-deoxyuridine; D000080242:8-Hydroxy-2'-Deoxyguanosine; D002392:Catechin; D006861:Hydrogen Peroxide; C045651:epigallocatechin gallate; D003849:Deoxyguanosine; C055494:caffeic acid phenethyl ester; D010626:Phenylethyl Alcohol; D013755:Tetradecanoylphorbol Acetate; D013936:Thymidine