Alterations in DNA methylation and airway hyperreactivity in response toin uteroexposure to environmental tobacco smoke

Abstract

Growing evidence indicates that prenatal exposure to maternal smoking is a risk factor for the development of asthma in children. However, the effects of prenatal environmental tobacco smoke (ETS) exposure on the genome and lung immune cells are unclear. This study aims to determine whether in utero ETS exposure alters DNA methylation patterns and increases airway hyperreactivity (AHR) and inflammation. Pregnant C57BL/6 mice were exposed daily to a concentration of 1.0 mg/m3 ETS. AHR was determined in the 6-week-old offspring by measurement of airway resistance. Global and gene promoter methylation levels in lung DNA from offspring were analyzed by luminometric methylation and pyrosequencing assays, respectively. Offspring exposed to ETS showed a marked increase in the number of alveolar macrophages in the bronchoalveolar lavage fluid and level of IL-13 in the airways compared with offspring of filtered-air exposed dams (controls). ETS exposure significantly augmented AHR compared with controls. In the methylation analysis, ETS-exposed offspring had a significantly lower level of global DNA methylation than the controls. We observed a significant increase in IFN-γ, and significant decrease in IL-13 methylation levels in the ETS group compared with controls. Collectively, these data suggest that in utero ETS exposure increases the risk of pulmonary inflammation and AHR through altered DNA methylation, but additional studies are needed to fully determine the causal link between changes in methylation and cytokines levels, as well as AHR.

The association between environmental tobacco smoke exposure and childhood respiratory disease: a review

“…Epigenetic changes may account for such generational effects [71]. Mice models show alterations in DNA methylation and airway hyperreactivity in response to in utero ETS [72]. Recent human studies have also found smoke-exposure-specific blood DNA methylation changes present in preschool children, which were comparable to those found at birth [73].…”

Reduced mouse allergen is associated with epigenetic changes in regulatory genes, but not mouse sensitization, in asthmatic children

“…We believe these associations are gene specific as there is substantial evidence that epigenetic regulation of both FOXP3 and IFNγ is associated with clinically relevant outcomes (Liu, Ballaney et al 2008, Brand, Kesper et al 2012, Kohli, Garcia et al 2012, Niedzwiecki, Zhu et al 2012, Runyon, Cachola et al 2012, Tang, Levin et al 2012). There is more limited evidence to suggest that differences in global methylation instead may explain outcomes related to exposure to cigarettes and air pollution (Breton, Byun et al 2009, Lee, Jaffar et al 2015, Breton, Yao et al 2016) and allergic sensitization(Sordillo, Lange et al 2013) in some, but not other (Chi, Liu et al 2016), studies.…”

Perinatal exposure to environmental tobacco smoke is associated with changes in DNA methylation that precede the adult onset of lung disease in a mouse model

“…Previously, we reported altered global and gene-specific methylation in 6-week old mice exposed to prenatal ETS that corresponded with alterations in pulmonary inflammation and airway hyperreactivity, suggesting that prenatal ETS exposure can increase disease susceptibility through altered DNA methylation (Lee et al, 2015). However, whether the epigenetic effects of these exposures resolve with age and to what extent these effects may alter the mechanisms involved in adult onset lung pathologies remained unaddressed.…”

“…Breeding and ETS exposure were conducted as previously described (Lee et al, 2015; Brown et al, 2016). Briefly, two female mice were paired with one male mouse to create a timed-pregnant exposure scenario.…”

“…Global DNA methylation was measured via LUMA as previously described (Karimi, Johansson and Ekstrom, 2006; Karimi et al, 2006; Lee et al, 2015). The extent of cleavage within the digested samples was quantified by means of bioluminometric polymerase extension using pyrosequencing on a Pyromark Q96 MD (Qiagen).…”