Marsh J P, Mossman B T
Department of Pathology, University of Vermont, College of Medicine, Burlington, 05405.
Cancer Res. 1991 Jan 1;51(1):167-73.
Induction of ornithine decarboxylase (ODC) enzyme activity occurs after exposure of hamster tracheal epithelial (HTE) cells to asbestos and the soluble tumor promoter 12-O-tetradecanoylphorbol-13-acetate. Since active oxygen species are implicated as mediators of asbestos-induced biological responses studies here were designed to examine whether active oxygen species generated by asbestos or oxidants caused increased ODC activity. In confluent HTE cells, significant blockage of chrysotile or crocidolite asbestos-stimulated ODC activity occurred with simultaneous addition of catalase, but not superoxide dismutase, to medium. The addition of xanthine plus xanthine oxidase caused a dose-dependent increase in ODC activity, which was inhibited significantly after addition of catalase or mannitol, indicating that H2O2 was the principal oxidant produced in that reaction. Addition of phenazine methosulfate, a redox reagent used to generate superoxide, resulted in significant elevation of ODC, which was inhibited by addition of superoxide dismutase but not catalase. Hydrogen peroxide added to culture medium also caused a potent increase in ODC activity inhabitable by catalase. Hypochlorous acid caused increases in ODC activity, although the magnitude of this response was less than that observed with other oxidants. Therefore, although all active oxygen species examined triggered ODC, less reduced species (O2- and H2O2) were more proficient than OH or a halogenated oxidant. All oxidants, except HOCl, caused a significant increase in [3H] thymidine incorporation at 24 or 48 h after their addition to HTE cells. In comparative studies, exposure of HTE cells to either asbestos or xanthine plus xanthine oxide increased the level of ODC mRNAs proportionate to oxidant concentration and the extent of enzyme induction. Thus, data indicate that H2O2 plays a major role in asbestos-stimulated ODC induction and proliferation of epithelial cells of the respiratory tract by altering the regulation of a gene critical to proliferation.
仓鼠气管上皮（HTE）细胞暴露于石棉和可溶性肿瘤启动子12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯后，鸟氨酸脱羧酶（ODC）的酶活性会被诱导。由于活性氧被认为是石棉诱导的生物学反应的介质，因此本研究旨在检验石棉或氧化剂产生的活性氧是否会导致ODC活性增加。在汇合的HTE细胞中，当向培养基中同时添加过氧化氢酶而非超氧化物歧化酶时，温石棉或青石棉刺激的ODC活性会受到显著抑制。添加黄嘌呤和黄嘌呤氧化酶会导致ODC活性呈剂量依赖性增加，添加过氧化氢酶或甘露醇后该活性会受到显著抑制，这表明H2O2是该反应中产生的主要氧化剂。添加用于产生超氧化物的氧化还原试剂吩嗪硫酸甲酯会导致ODC显著升高，添加超氧化物歧化酶可抑制该升高，但添加过氧化氢酶则不能。添加到培养基中的过氧化氢也会导致ODC活性显著增加，且可被过氧化氢酶抑制。次氯酸会导致ODC活性增加，尽管该反应的幅度小于其他氧化剂所观察到的幅度。因此，尽管所检测的所有活性氧均能触发ODC，但还原性较低的物种（O2-和H2O2）比OH或卤化氧化剂更有效。除HOCl外，所有氧化剂在添加到HTE细胞后24或48小时均会导致[3H]胸苷掺入显著增加。在比较研究中，HTE细胞暴露于石棉或黄嘌呤加黄嘌呤氧化酶后，ODC mRNA水平会随氧化剂浓度和酶诱导程度成比例增加。因此，数据表明H2O2通过改变对增殖至关重要的基因的调控，在石棉刺激的ODC诱导和呼吸道上皮细胞增殖中起主要作用。
