title: Zinc inhibition of caspase-3 activation does not protect HeLa cells from apoptotic cell death.
abstract: Zinc is proposed to be antiapoptotic for it has been shown to inhibit late events of apoptotic pathways such as Ca(2+)/Mg(2+)-dependent endonuclease cleavage of chromatin DNA, poly-ADP ribose polymerase cleavage, and caspase-3 activity. Because caspase-3 is a critical executioner caspase in apoptosis, this study was undertaken to examine specifically a correlation between zinc inhibition of caspase-3 activation and apoptosis in HeLa cells. Cultured HeLa cells were exposed to 100 microM ZnCl(2) for 1 h prior to 12 h treatment with 1.0 microM doxorubicin (DOX), an important anticancer agent that causes apoptosis in a wide variety of tumor cells. Western blot analysis of HeLa cells treated with DOX for 12 h revealed that DOX caused proteolytic activation of caspase-3 and zinc inhibited this activation. Interestingly, zinc did not inhibit DOX-induced apoptosis as measured by a terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. Furthermore, a microculture tetrazolium assay confirmed that cell death occurred in the presence of zinc. These results demonstrate that zinc specifically inhibits DOX-induced activation of caspase-3 in HeLa cells, but does not suppress DOX-induced apoptosis or otherwise cell death, thus suggesting DOX-induced caspase-3 activation may not play a major role in overall cell death and/or non-caspase-3 pathways are involved in DOX-induced apoptosis in HeLa cells.
authors.affiliation: Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, Kentucky 40202, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Lambert
authors.forename: G W
authors.initials: GW
authors.lastname: Wang
authors.forename: Y J
authors.initials: YJ
authors.lastname: Kang
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006367:HeLa Cells / Q000187:drug effects* / Q000473:pathology; D006801:Humans; D015032:Zinc / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D004317:Doxorubicin; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D015032:Zinc