Whole DNA methylome profiling in mice exposed to secondhand smoke

A large body of evidence has linked secondhand smoke (SHS) to lung cancer in nonsmokers. Yet, the underlying mechanisms of SHS carcinogenicity in nonsmokers' lung cancer remain elusive. Recently, we have demonstrated a genotoxic mode of action for SHS, based on the ability of this carcinogen to induce adduct-driven mutagenesis in transgenic Big Blue® mice. In the present study, we have expanded this investigation to determine whether SHS can also cause epigenetic effects through aberrations of DNA methylation. Here, we have globally profiled DNA methylation in the lung of Big Blue® mice exposed to SHS for a duration of 4-months, both immediately after the termination of exposure and at several intervals post-exposure. We have used a genome-wide microarray-based approach to catalogue DNA methylation profile in the lung of mice exposed to SHS and at various recovery periods from the time of exposure. Mice exposed to clean air, for comparable amount of times, were used as controls. Mice that were injected intraperitoneally with chronic doses of B(a)P (a powerful carcinogen in SHS) or DMSO (sham) were used for comparison purposes .

大量研究证据表明，二手烟（secondhand smoke, SHS）与非吸烟者的肺癌发生密切相关。然而，二手烟诱导非吸烟者肺癌的潜在致癌机制仍未明确。近期，本研究基于该致癌物可在转基因Big Blue®小鼠中诱导加合物驱动的诱变效应，证实了二手烟具有遗传毒性作用模式。本研究将该研究方向进一步拓展，旨在探究二手烟是否可通过DNA甲基化异常引发表观遗传效应。本研究对暴露于二手烟达4个月的Big Blue®小鼠肺部组织开展了全基因组DNA甲基化谱分析，采样时点分别为暴露结束即刻及暴露后的多个时间区间。本研究采用基于全基因组微阵列的技术手段，对暴露于二手烟后不同恢复阶段的小鼠肺部组织的DNA甲基化谱进行了编录分析。暴露于洁净空气且暴露时长匹配的小鼠作为对照组。此外，本研究还设置了两组对照用于对比分析：一组为腹腔注射慢性剂量苯并(a)芘（benzo(a)pyrene, B(a)P，二手烟中的强效致癌物）的小鼠，另一组为腹腔注射二甲基亚砜（dimethyl sulfoxide, DMSO，假处理组）的小鼠。