Janssen Y M, Marsh J P, Absher M P, Gabrielson E, Borm P J, Driscoll K, Mossman B T
Department of Pathology, University of Vermont, Burlington 05405.
Am J Respir Crit Care Med. 1994 Mar;149(3 Pt 1):795-802. doi: 10.1164/ajrccm.149.3.8118652.
The generation of oxidants is a proposed mechanism of cell injury by asbestos fibers. To determine whether human pleural mesothelial cells (HMC) respond to asbestos and active oxygen species (AOS) by induction of antioxidant enzymes, cells obtained from pleural effusion were exposed to crocidolite or chrysotile asbestos or xanthine/xanthine oxidase (X/XO), a chemical-generating system of AOS. Gene expression of manganese-containing superoxide dismutase (MnSOD) and heme oxygenase (HO), endogenous enzymes involved in cell defense against oxidant stresses, was then determined. Dosage-dependent increases in steady-state mRNA levels of MnSOD and HO were observed in HMC exposed to asbestos or X/XO. However, increases in gene expression of MnSOD or HO did not occur in HMC after exposure to particulates such as polystyrene beads or riebeckite, the nonfibrous analog of crocidolite asbestos. Comparative experiments with human adult lung fibroblasts (HAL) showed less striking increases in mRNA levels of MnSOD and HO in response to asbestos, but steady-state mRNA levels for HO were increased more than fivefold in response to X/XO. To determine whether increases in mRNA levels of MnSOD were translated into protein, Western blot analyses were performed on HMC and HAL cells exposed to asbestos or X/XO. Slight increases in MnSOD immunoreactive protein were observed in HMC in response to both agents. In contrast, X/XO caused striking elevations in MnSOD protein levels in HAL cells. These results suggest that certain antioxidant enzymes are inducible in HMC after exposure to asbestos and other oxidants.
氧化剂的产生是石棉纤维导致细胞损伤的一种推测机制。为了确定人胸膜间皮细胞（HMC）是否通过诱导抗氧化酶来响应石棉和活性氧（AOS），将从胸腔积液中获取的细胞暴露于青石棉或温石棉或黄嘌呤/黄嘌呤氧化酶（X/XO，一种AOS化学产生系统）。然后测定参与细胞抗氧化应激防御的内源性酶——含锰超氧化物歧化酶（MnSOD）和血红素加氧酶（HO）的基因表达。在暴露于石棉或X/XO的HMC中观察到MnSOD和HO的稳态mRNA水平呈剂量依赖性增加。然而，在暴露于聚苯乙烯珠或钠闪石（青石棉的非纤维类似物）等颗粒后的HMC中，MnSOD或HO的基因表达并未增加。用人成人肺成纤维细胞（HAL）进行的对比实验表明，HAL对石棉的反应中，MnSOD和HO的mRNA水平增加不太显著，但对X/XO的反应中，HO的稳态mRNA水平增加了五倍以上。为了确定MnSOD的mRNA水平增加是否转化为蛋白质，对暴露于石棉或X/XO的HMC和HAL细胞进行了蛋白质印迹分析。在HMC中，两种试剂均导致MnSOD免疫反应蛋白略有增加。相比之下，X/XO导致HAL细胞中MnSOD蛋白水平显著升高。这些结果表明，暴露于石棉和其他氧化剂后，HMC中某些抗氧化酶是可诱导的。
