Shull S, Heintz N H, Periasamy M, Manohar M, Janssen Y M, Marsh J P, Mossman B T
Department of Biochemistry, Medical School, University of Vermont, Burlington 05405.
J Biol Chem. 1991 Dec 25;266(36):24398-403.
We have demonstrated the selective induction of manganese superoxide dismutase (MnSOD) or catalase mRNA after exposure of tracheobronchial epithelial cells in vitro to different oxidant stresses. Addition of H2O2 caused a dose-dependent increase in catalase mRNA in both exponentially growing and confluent cells. A 3-fold induction of catalase mRNA was seen at a nontoxic dose of 250 microM H2O2. Increase in the steady-state mRNA levels of glutathione peroxidase (GPX) and MnSOD were less striking. Expression of catalase, MnSOD, and GPX mRNA was highest in confluent cells. In contrast, constitutive expression of copper and zinc SOD (CuZnSOD) mRNA was greatest in dividing cells and was unaffected by H2O2 in both exponentially growing and confluent cells. MnSOD mRNA was selectively induced in confluent epithelial cells exposed to the reactive oxygen species-generating system, xanthine/xanthine oxidase, while steady-state levels of GPX, catalase, and CuZnSOD mRNA remained unchanged. The 3-fold induction of MnSOD mRNA was dose-dependent, reaching a peak at 0.2 unit/ml xanthine oxidase. MnSOD mRNA increases were seen as early as 2 h and reached maximal induction at 24 h. Immunoreactive MnSOD protein was produced in a corresponding dose- and time-dependent manner. Induction of MnSOD gene expression was prevented by addition of actinomycin D and cycloheximide. These data indicate that epithelial cells of the respiratory tract respond to different oxidant insults by selective induction of certain antioxidant enzymes. Hence, gene expression of antioxidant enzymes does not appear to be coordinately regulated in these cell types.
我们已经证明，在体外将气管支气管上皮细胞暴露于不同的氧化应激后，可选择性诱导锰超氧化物歧化酶（MnSOD）或过氧化氢酶mRNA的表达。添加H2O2会导致指数生长期和汇合细胞中过氧化氢酶mRNA呈剂量依赖性增加。在250 microM H2O2的无毒剂量下，过氧化氢酶mRNA可诱导3倍增加。谷胱甘肽过氧化物酶（GPX）和MnSOD的稳态mRNA水平的增加不太明显。过氧化氢酶、MnSOD和GPX mRNA的表达在汇合细胞中最高。相比之下，铜锌超氧化物歧化酶（CuZnSOD）mRNA的组成型表达在分裂细胞中最大，并且在指数生长期和汇合细胞中均不受H2O2的影响。在暴露于产生活性氧的系统（黄嘌呤/黄嘌呤氧化酶）的汇合上皮细胞中，MnSOD mRNA被选择性诱导，而GPX、过氧化氢酶和CuZnSOD mRNA的稳态水平保持不变。MnSOD mRNA的3倍诱导是剂量依赖性的，在0.2单位/ml黄嘌呤氧化酶时达到峰值。MnSOD mRNA最早在2小时时增加，并在24小时时达到最大诱导。免疫反应性MnSOD蛋白以相应的剂量和时间依赖性方式产生。添加放线菌素D和环己酰亚胺可阻止MnSOD基因表达的诱导。这些数据表明，呼吸道上皮细胞通过选择性诱导某些抗氧化酶来应对不同的氧化损伤。因此，在这些细胞类型中，抗氧化酶的基因表达似乎不是协调调节的。
