David Geffen School of Medicine at UCLA, Department of Pathology, Los Angeles, CA, United States; David Geffen School of Medicine at UCLA, Department of Environmental Health, Los Angeles, CA, United States; Pfizer Inc., Experimental Medicine, South San Francisco, California 94080, United States.
Mutat Res. 2013 Sep;749(1-2):58-65. doi: 10.1016/j.mrfmmm.2013.05.003. Epub 2013 Jun 5.
Cigarette smoke causes direct oxidative DNA damage as well as indirect damage through inflammation. Epidemiological studies show a strong relationship between secondhand smoke and cancer; however, the mechanisms of secondhand smoke-induced cancer are not well understood. Animal models with either (i) deficient oxidative DNA damage repair, or (ii) a decreased capacity to combat oxidative stress may help determine the pathways important in mitigating damage caused by smoke. In this study, we used mice lacking Ogg1 and Myh, both of which are involved in base excision repair by removing oxidatively damaged DNA bases. Gclm-deficient mice, which have decreased levels of glutathione (GSH), were used to look at the role of smoke-induced oxidative damage. Ex vivo experiments show significantly elevated levels of DNA single-strand breaks and chromosomal aberrations in peripheral blood lymphocytes from Ogg1(-/-)Myh(-/-) double knockout mice compared to wild type (WT) mice after 24h of exposure to cigarette smoke extract (CSE). The average γH2AX foci per cell was significantly elevated 3h after exposure to CSE in cells from Ogg1(-/-)Myh(-/-) double knockout mice compared to wildtype mice. In vivo we found that all mice had increased markers of DNA damage after exposure to side-stream tobacco smoke (SSTS). Ogg1(-/-)Myh(-/-) and Gclm(-/-) mice had altered levels of peripheral blood glutathione after SSTS exposure whereas wild type mice did not. This may be due to differential regulation of glutathione synthesis in the lung. We also found that Ogg1(-/-)Myh(-/-) mice had a decreased lifespan after oral gavage with benzo[a]pyrene compared to wildtype mice and sham-exposed Ogg1(-/-)Myh(-/-) mice. Our results are important in investigating the roles of oxidative stress and oxidative DNA damage repair in cigarette smoke-induced cancers and characterizing the role of genetic polymorphisms in smoke-related disease susceptibility.
香烟烟雾会直接导致 DNA 氧化损伤，并通过炎症引发间接损伤。流行病学研究表明，二手烟与癌症之间存在很强的关联；然而，二手烟引发癌症的机制尚未得到很好的理解。具有以下两种情况之一的动物模型：（i）氧化 DNA 损伤修复缺陷，或（ii）对抗氧化应激能力下降，可能有助于确定减轻烟雾造成的损伤的重要途径。在这项研究中，我们使用了 Ogg1 和 Myh 缺失的小鼠，它们都参与了通过去除氧化受损的 DNA 碱基来修复碱基切除修复。使用 Gclm 缺失的小鼠来观察与吸烟引起的氧化损伤相关的作用。与野生型（WT）小鼠相比，在香烟烟雾提取物（CSE）暴露 24 小时后，外周血淋巴细胞中的 Ogg1(-/-)Myh(-/-)双敲除小鼠的 DNA 单链断裂和染色体畸变水平显著升高。与野生型小鼠相比，CSE 暴露 3 小时后，Ogg1(-/-)Myh(-/-)双敲除小鼠细胞中的平均 γH2AX 焦点数量显著升高。在体内，我们发现所有小鼠在暴露于侧流烟草烟雾（SSTS）后都有增加的 DNA 损伤标志物。与 SSTS 暴露后的野生型小鼠相比，Ogg1(-/-)Myh(-/-)和 Gclm(-/-)小鼠的外周血谷胱甘肽水平发生了改变。这可能是由于肺部谷胱甘肽合成的差异调节。我们还发现，与野生型小鼠和假暴露的 Ogg1(-/-)Myh(-/-)小鼠相比，Ogg1(-/-)Myh(-/-)小鼠在经口灌胃苯并[a]芘后寿命缩短。我们的研究结果对于研究氧化应激和氧化 DNA 损伤修复在香烟烟雾引发的癌症中的作用以及表征遗传多态性在与吸烟相关疾病易感性中的作用非常重要。
