Benzo[a]pyrene induces apoptosis in RL95-2 human endometrial cancer cells by cytochrome P450 1A1 activation.
Benzo[a]pyrene (B[a]P) has been shown to be an inducer of apoptosis in some cell types. To date, due to the lack of an appropriate model system, studies of the cellular and biochemical mechanism(s) by which B[a]P induces apoptosis have been focused on Hepa1c1c7 cells. Moreover, the precise relationship between the bioactivation of B[a]P by CYP1A1 or CYP1B1 and the occurrence of cytotoxicity-mediated apoptosis requires further elucidation. In the present study, we showed that B[a]P-induced apoptosis in RL95-2 cells is accompanied by the activation of caspases. In addition, the mitochondrial changes, including the decrease of mitochondrial potential and the release of mitochondrial cytochrome c and second mitochondria-derived activator of caspases/direct inhibitor of apoptosis protein binding protein with low PI (Smac/DIABLO) into the cytosol, support the suggestion that the mitochondrial pathway is robustly associated with B[a]P-evoked apoptosis. This study showed the involvement of the nuclear translocation of mitochondrial apoptosis-inducing factor in B[a]P-induced apoptosis of RL95-2 cells. Exposure to B[a]P up-regulates aryl hydrocarbon receptor, heat-shock protein 90, cytochrome P450 1A1 (CYP1A1), cytochrome P450 1B1 (CYP1B1), and epoxide hydrolase significantly, which might be prerequisites for the conversion of B[a]P to B[a]P-7,8-dihydroxy-9,10-epoxide. Although both CYP1A1 and CYP1B1 proteins were up-regulated significantly by B[a]P, only CYP1A1 exhibited activity. Thus, CYP1A1 is believed to be a central oxidative enzyme that is ultimately required for formation of B[a]P-7,8-dihydroxy-9,10-epoxide from B[a]P in RL95-2 cells. Altogether, our data showed that RL95-2 cells are susceptible to apoptosis by exposure to B[a]P and that B[a]P-evoked apoptosis is mediated predominantly by the activation of CYP1A1. Here we suggest that RL95-2 cells are an excellent model for the investigation of xenobiotic mechanisms associated with CYP1A1 as well as CYP1B1.
Kim
Ji Young
JY
Department of Anatomy and Cell Biology, College of Medicine, Dong-A University, Dongdaeshin-dong 3-1, Seo-gu, Busan 602-714, Korea.
Chung
Jin-Yong
JY
Park
Ji-Eun
JE
Lee
Seung Gee
SG
Kim
Yoon-Jae
YJ
Cha
Moon-Seok
MS
Han
Myung Seok
MS
Lee
Hye-Jeong
HJ
Yoo
Young Hyun
YH
Kim
Jong-Min
JM
D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D001564:Benzo(a)pyrene / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D016889:Endometrial Neoplasms / Q000201:enzymology / Q000503:physiopathology*; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D008928:Mitochondria / Q000187:drug effects / Q000648:ultrastructure; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism; D015854:Up-Regulation
D018336:Receptors, Aryl Hydrocarbon; D001564:Benzo(a)pyrene; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D019363:Cytochrome P-450 CYP1A1; D020169:Caspases