Vakharia D D, Liu N, Pause R, Fasco M, Bessette E, Zhang Q Y, Kaminsky L S
New York State Department of Health, Wadsworth Center, State University of New York, Albany, New York 12201-0509, USA.
Drug Metab Dispos. 2001 Jul;29(7):999-1006.
Environmental polycyclic aromatic hydrocarbons (PAHs) and metals coexist, and such mixtures could affect the carcinogenicity of PAHs, possibly by modification of PAH induction of the PAH-bioactivating CYP1A. The effect on PAH-mediated CYP1A induction of arsenic, lead, mercury, or cadmium (ranked as the most hazardous environmental metals by the Environmental Protection Agency and the Agency for Toxic Substances and Disease Registry) has thus been investigated. Induction of CYP1A1 by benzo[a]pyrene (BAP), benzo[b]fluoranthene (BBF), dibenzo[a,h]anthracene (DBAHA), benzo[a]anthracene (BAA), or benzo[k]fluoranthene (BKF) was probed by ethoxyresorufin-O-deethylase activity (EROD) in 96-well plates of human HepG2 cells, by immunoblot analysis, and by reverse transcription-polymerase chain reaction. Cells rapidly took up PAHs (BAP, BKF) from medium; by 24 h only 14% remained in the medium, and no detectable PAH bound to well walls. Induction efficiency (relative to dimethyl sulfoxide controls) was in the order BKF (16-fold) > DBAHA (14-fold) > BAA (4-fold) > BAP (3-fold) > BBF (1-fold), all at 5 microM PAH. The metals did not markedly affect cell viability at concentrations of arsenic, 5 microM; lead, 50 microM; mercury, 5 microM; and cadmium, 5 microM. At 5 microM PAH concentration, all of the metals decreased levels of PAH-induced CYP1A1 activities (direct inhibition of EROD activity was excluded) by variable extents and in a PAH-dependent manner. With BAP as inducer decreases in induction were arsenic, 57%; cadmium, 82%; mercury, 4%; and lead, 20%. The decreases were not a consequence of transcriptional down-regulation. One possible conclusion is that these metals could diminish PAH carcinogenic potential by decreasing PAH-mediated induction of their bioactivation by CYP1A1.
环境中的多环芳烃（PAHs）与金属共存，这种混合物可能会影响PAHs的致癌性，可能是通过改变PAH诱导的PAH生物活化细胞色素P450 1A（CYP1A）来实现。因此，研究了砷、铅、汞或镉（被美国环境保护局和有毒物质与疾病登记署列为最危险的环境金属）对PAH介导的CYP1A诱导的影响。通过在人HepG2细胞的96孔板中进行乙氧异吩唑酮-O-脱乙基酶（EROD）活性检测、免疫印迹分析以及逆转录-聚合酶链反应，探究苯并[a]芘（BAP）、苯并[b]荧蒽（BBF）、二苯并[a,h]蒽（DBAHA）、苯并[a]蒽（BAA）或苯并[k]荧蒽（BKF）对CYP1A1的诱导作用。细胞迅速从培养基中摄取PAHs（BAP、BKF）；到24小时时，培养基中仅剩下14%，且未检测到PAH与孔壁结合。诱导效率（相对于二甲基亚砜对照）顺序为BKF（16倍）> DBAHA（14倍）> BAA（4倍）> BAP（3倍）> BBF（1倍），均为5微摩尔PAH浓度。在砷浓度为5微摩尔、铅浓度为50微摩尔、汞浓度为5微摩尔和镉浓度为5微摩尔时，这些金属对细胞活力没有明显影响。在5微摩尔PAH浓度下，所有金属均不同程度地降低了PAH诱导的CYP1A1活性水平（排除了对EROD活性的直接抑制），且呈PAH依赖性。以BAP作为诱导剂时，诱导作用的降低幅度分别为：砷57%、镉82%、汞4%、铅20%。这种降低并非转录下调的结果。一个可能的结论是，这些金属可能通过减少PAH介导的CYP1A1对其生物活化的诱导作用来降低PAH的致癌潜力。
