RT Journal Article
SR Electronic
T1 Suppression of Apoptosis by Bcl-2 to Enhance Benzene Metabolites-Induced Oxidative DNA Damage and Mutagenesis: A Possible Mechanism of Carcinogenesis
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 894
OP 901
VO 55
IS 5
A1 Kuo, Min-Liang
A1 Shiah, Shine-Gwo
A1 Wang, Chau-Jong
A1 Chuang, Shuang-En
YR 1999
UL http://molpharm.aspetjournals.org/content/55/5/894.abstract
AB Apoptosis plays a crucial role in maintaining genomic integrity by selectively removing the most heavily damaged cells from the population. Under that premise, the dysregulation of apoptosis may result in an inappropriate survival of mutated cells. This study demonstrates that ectopic expression of Bcl-2 effectively suppresses benzene-active metabolites, 1,4-hydroquinone- and 1,4-benzoquinone-induced apoptosis in human leukemic HL-60 cells, as evidenced by morphological changes and DNA fragmentation. Although reactive oxygen species production largely contributes to the benzene metabolites-induced apoptotic cell death, Bcl-2 fails to attenuate the benzene metabolites-elicited increase of reactive oxygen species in HL-60 cells, as confirmed by flow cytometry analysis. These data suggest that Bcl-2 prevents benzene metabolites-induced apoptosis at the downstream of oxidative damage events. This study also determines the level of 8-hydroxydeoxyguanosine (8-OH-dGua), an indicator for oxidative DNA damage, in neo- and Bcl-2-overexpressing HL-60 cells after treating with 1,4-hydroquinone or 1,4-benzoquinone. Interestingly, our results indicate that a majority of the 8-OH-dGua is efficiently removed in neocontrol cells within 3 to 6 h, whereas only 25 to 35% of 8-OH-dGua is repaired in Bcl-2 transfectants even for 24 h. Similarly, another oxidative DNA base, thymine glycol, failed to repair and was retained in genomic DNA of Bcl-2 transfectants. The above findings suggest that Bcl-2 may retain benzene metabolites-induced oxidative DNA damage in surviving cells. Indeed, the failure of repairing 8-OH-dGua and thymine glycol in benzene metabolites-treated Bcl-2 survivors increases the number of mutation frequencies at the hprt locus. Results in this study thus provide a novel benzene-induced carcinogenesis mechanism by which up-regulation of Bcl-2 protein may promote the susceptibility to benzene metabolites-induced mutagenesis by overriding apoptosis and attenuating DNA repair capacity. The American Society for Pharmacology and Experimental Therapeutics