Kamp D W, Greenberger M J, Sbalchierro J S, Preusen S E, Weitzman S A
Department of Medicine, Northwestern University Medical School, Veterans Affairs Chicago Health Care System, IL 60611, USA.
Free Radic Biol Med. 1998 Oct;25(6):728-39. doi: 10.1016/s0891-5849(98)00158-0.
Cigarette smoke augments asbestos-induced bronchogenic carcinoma by mechanisms that are not established. Alveolar epithelial cell (AEC) injury due to oxidant-induced DNA damage and depletion of glutathione (GSH) and adenosine triphosphate (ATP) may be one important mechanism. We previously showed that amosite asbestos-induces hydroxyl radical production and DNA damage to cultured AEC and that phytic acid, an iron chelator, is protective. We hypothesized that whole cigarette smoke extracts (CSE) augment amosite asbestos-induced AEC injury by generating iron-induced free radicals that damage DNA and reduce cellular GSH and ATP levels. Asbestos or CSE each caused dose-dependent toxicity to AEC (WI-26 and rat alveolar type I-like cells) as assessed by 51chromium release. The combination of asbestos (5 microg/cm2) and CSE (0.O1-0.1%) caused synergistic injury whereas higher doses of each agent primarily had an additive toxic effect. Asbestos (5 microg/cm2) augmented CSE-induced (0.01-1.0%) AEC DNA damage over a 4 h exposure period as assessed by an alkaline unwinding, ethidium bromide fluorometric technique. These effects were synergistic in A549 cells and additive in WI-26 cells. Asbestos (5 microg/cm2) and CSE (0.5-1.0%) reduced A549 and WI-26 cell GSH levels as assessed spectrophotometrically and ATP levels as assessed by luciferin/luciferase chemiluminescence but a synergistic interaction was not detected. Phytic acid (500 microM) and catalase (100 microg/ml) each attenuated A549 cell DNA damage and depletion of ATP caused by asbestos and CSE. However, neither agent attenuated WI-26 cell DNA damage nor the reductions in GSH levels in WI-26 and A549 cells exposed to asbestos and CSE. We conclude that CSE enhance asbestos-induced DNA damage in cultured alveolar epithelial cells. These data provide additional support that asbestos and cigarette smoke are genotoxic to relevant target cells in the lung and that iron-induced free radicals may in part cause these effects.
香烟烟雾通过尚未明确的机制增强石棉诱导的支气管源性癌。由于氧化剂诱导的DNA损伤以及谷胱甘肽（GSH）和三磷酸腺苷（ATP）耗竭导致的肺泡上皮细胞（AEC）损伤可能是一种重要机制。我们之前表明，铁石棉可诱导培养的AEC产生羟自由基并造成DNA损伤，而铁螯合剂植酸具有保护作用。我们推测，完整香烟烟雾提取物（CSE）通过产生铁诱导的自由基来增强铁石棉诱导的AEC损伤，这些自由基会损伤DNA并降低细胞内GSH和ATP水平。通过51铬释放评估，石棉或CSE各自对AEC（WI - 26和大鼠I型肺泡样细胞）均产生剂量依赖性毒性。石棉（5微克/平方厘米）和CSE（0.01 - 0.1%）的组合导致协同损伤，而每种试剂的更高剂量主要产生相加毒性作用。通过碱性解旋、溴化乙锭荧光技术评估，在4小时暴露期内，石棉（5微克/平方厘米）增强了CSE诱导的（0.01 - 1.0%）AEC DNA损伤。这些效应在A549细胞中是协同的，在WI - 26细胞中是相加的。通过分光光度法评估，石棉（5微克/平方厘米）和CSE（0.5 - 1.0%）降低了A549和WI - 26细胞的GSH水平，通过荧光素/荧光素酶化学发光评估降低了ATP水平，但未检测到协同相互作用。植酸（500微摩尔）和过氧化氢酶（100微克/毫升）各自减轻了石棉和CSE对A549细胞造成的DNA损伤和ATP耗竭。然而，这两种试剂均未减轻WI - 26细胞的DNA损伤，也未减轻暴露于石棉和CSE的WI - 26和A549细胞中GSH水平的降低。我们得出结论，CSE增强了培养的肺泡上皮细胞中石棉诱导的DNA损伤。这些数据进一步支持了石棉和香烟烟雾对肺中的相关靶细胞具有遗传毒性，并且铁诱导的自由基可能部分导致了这些效应。
