Cheu J, Talaska G, Miller M, Rice C, Warshawsky D
Department of Environmental Health, University of Cincinnati, OH 45267-0056, USA.
Carcinogenesis. 1997 Jan;18(1):167-75. doi: 10.1093/carcin/18.1.167.
Ferric oxide (Fe2O3) and aluminum oxide (Al2O3) particles are widely encountered in occupational settings. Benzo[a]pyrene (B[a]P), a well-characterized environmental carcinogen, is frequently adsorbed onto particles. It has been shown that B[a]P-coated Fe2O3 particles (B[a]P-Fe2O3) significantly increased lung tumors in the hamster in contrast to B[a]P-coated Al2O3 (B[a]P-Al2O3) or B[a]P alone. In order to determine the genotoxic effects of these particles on the metabolism of B[a]P, pulmonary alveolar macrophages (AM) from male Syrian golden hamsters were incubated with 5 microg (19.8 nmol) B[a]P-coated respirable size (99% < 5 microm) Fe2O3 and Al2O3 particles with loads from 0.5 to 2.0 mg. Intracellular uptake of B[a]P by AM at 24 h was higher with B[a]P-Fe2O3 than that of B[a]P alone (P < 0.05) or B[a]P-Al2O3 (P < 0.05). Total B[a]P metabolism was significantly greater in AM exposed to B[a]P-coated Fe2O3 at 1.0 and 1.5 mg than in the AM exposed to B[a]p-al2O3 (0.5, 1.0 and 1.5 mg) (P < 0.05) or B[a]P alone (P < 0.05). Similar significant differences for Fe2O3 relative to Al2O3 and B[a]P alone were also apparent for total dihydrodiols, quinones and phenolic metabolites. Co-administration of 5 microg alpha-naphthoflavone (alpha-NF, an inhibitor of cytochrome P-4501A1 and P-4501A2) and 10(-3) M cyclohexene oxide (CO, an inhibitor of epoxide hydrolase) significantly reduced B[a]P metabolism in B[a]P-Fe2O3 (P < 0.05) and B[a]P-Al2O3 (P < 0.05) treated groups relative to B[a]P alone. AM were co-cultured with hamster tracheal epithelial cells (HTE) and treated as described above for metabolism studies to assess the DNA binding of B[a]P metabolites in the target cells, using 32P-postlabeling techniques. Two adducts were observed that had chromatographic behavior similar to 7R,8S,9S-trihydroxy-10R-(N2-deoxyguanosyl-3'-phosphate)-7,8,9,10-t etrahydrobenzo[a]pyrene [(+)-anti-BPDE-dG, adduct 1, major adduct representing 70-80% of total adducts] and 7S,8R,9R-trihydroxy-10S-(N2-deoxyguanosyl-3'-phosphate)-7,8,9,10-t etrahydrobenzo[a]pyrene [(-)-anti-BPDE-dG, adduct 2, representing 20-30% of total adducts]. B[a]P-Fe2O3 treatment enhanced the levels of the two B[a]P-DNA adducts in the HTE compared with B[a]P-Al2O3 (P < 0.05) or B[a]P alone. The inhibitors alphaNF and CO significantly reduced total adduct levels in the HTE (P < 0.05) in the B[a]P and B[a]P-Fe2O3 treatments as well as adduct 1 and adduct 2 levels. Our data suggest that the cocarcinogenic effect of B[a]P-Fe2O3 relative to B[a]P-coated Al2O3 can be due to: (i) the enhancement of B[a]P metabolism in AM by Fe2O3 associated with the increased uptake of B[a]P; and (ii) augmentation of DNA adduct formation in epithelial cells.
三氧化二铁（Fe₂O₃）和三氧化二铝（Al₂O₃）颗粒在职业环境中广泛存在。苯并[a]芘（B[a]P）是一种特征明确的环境致癌物，常吸附在颗粒上。研究表明，与B[a]P包被的Al₂O₃（B[a]P - Al₂O₃）或单独的B[a]P相比，B[a]P包被的Fe₂O₃颗粒（B[a]P - Fe₂O₃）显著增加了仓鼠肺部肿瘤的发生。为了确定这些颗粒对B[a]P代谢的遗传毒性作用，将来自雄性叙利亚金仓鼠的肺泡巨噬细胞（AM）与5微克（19.8纳摩尔）B[a]P包被的可吸入粒径（99% < 5微米）的Fe₂O₃和Al₂O₃颗粒一起孵育，颗粒负载量为0.5至2.0毫克。24小时时，AM对B[a]P的细胞内摄取量，B[a]P - Fe₂O₃组高于单独的B[a]P组（P < 0.05）或B[a]P - Al₂O₃组（P < 0.05）。暴露于1.0毫克和1.5毫克B[a]P包被的Fe₂O₃的AM中，B[a]P的总代谢量显著高于暴露于B[a]P - Al₂O₃（0.5、1.0和1.5毫克）（P < 0.05）或单独的B[a]P（P < 0.05）的AM。对于总二氢二醇、醌和酚类代谢物，Fe₂O₃相对于Al₂O₃和单独的B[a]P也有类似的显著差异。共同给予5微克α - 萘黄酮（α - NF，细胞色素P - 4501A1和P - 4501A2的抑制剂）和10⁻³ M环氧环己烷（CO，环氧化物水解酶的抑制剂）显著降低了B[a]P - Fe₂O₃（P < 0.05）和B[a]P - Al₂O₃（P < 0.05）处理组相对于单独的B[a]P组的B[a]P代谢。将AM与仓鼠气管上皮细胞（HTE）共培养，并按上述方法处理进行代谢研究，使用³²P后标记技术评估靶细胞中B[a]P代谢物与DNA的结合。观察到两种加合物，其色谱行为类似于7R,8S,9S - 三羟基 - 10R - （N₂ - 脱氧鸟苷 - 3'-磷酸） - 7,8,9,10 - 四氢苯并[a]芘[（+） - 反式 - BPDE - dG，加合物1，占总加合物的70 - 80%，为主要加合物]和7S,8R,9R - 三羟基 - 10S - （N₂ - 脱氧鸟苷 - 3'-磷酸） - 七氢苯并[a]芘[（ - ） - 反式 - BPDE - dG，加合物2，占总加合物的20 - 30%]。与B[a]P - Al₂O₃（P < 0.05）或单独的B[a]P相比，B[a]P - Fe₂O₃处理增强了HTE中两种B[a]P - DNA加合物的水平。抑制剂αNF和CO显著降低了B[a]P和B[a]P - Fe₂O₃处理组中HTE的总加合物水平（P < 0.05）以及加合物1和加合物2的水平。我们的数据表明，相对于B[a]P包被的Al₂O₃，B[a]P - Fe₂O₃的促癌作用可能归因于：（i）Fe₂O₃增强了AM中B[a]P的代谢，这与B[a]P摄取增加有关；（ii）上皮细胞中DNA加合物形成增加。
