Secondhand smoke in combination with ambient air pollution exposure is associated with increasedx CpG methylation and decreased expression of <it>IFN-γ</it> in T effector cells and <it>Foxp3</it> in T regulatory cells in children

Abstract

Abstract Background Secondhand smoke (SHS) and ambient air pollution (AAP) exposures have been associated with increased prevalence and severity of asthma and DNA modifications of immune cells. In the current study, we examined the association between SHS and AAP with DNA methylation and expression of interferon-gamma (IFN-γ) and forkhead box protein 3 (Foxp3) in T cell populations. Methods Subjects 7–18 years old were recruited from Fresno (high AAP; n = 62) and Stanford, CA (low AAP; n = 40) and divided into SHS-exposed (Fresno: n = 31, Stanford: n = 6) and non-SHS-exposed (nSHS; Fresno: n = 31, Stanford: n = 34) groups. T cells purified from peripheral blood were assessed for levels of DNA methylation and expression of IFN-γ (in effector T cells) or Foxp3 (in regulatory T cells). Results Analysis showed a significant increase in mean % CpG methylation of IFN-γ and Foxp3 associated with SHS exposure (IFN-γ: FSHS 62.10%, FnSHS 41.29%, p p Foxp3: FSHS 74.60%, FnSHS 54.44%, p p IFN-γ: FSHS 0.75, FnSHS 1.52, p p Foxp3: FSHS 0.75, FnSHS 3.29, p p IFN-γ: FSHS vs. SSHS, p p Foxp3: FSHS vs. SSHS, p p IFN-γ: FSHS vs. SSHS, p p Foxp3: FSHS vs. SSHS, p p IFN-γ: p = 0.15; Foxp3: p = 0.27), nor was Foxp3 expression (p = 0.08); IFN-γ expression was significantly decreased in AAP-only subjects (p Conclusions Exposures to SHS and AAP are associated with significant hypermethylation and decreased expression of IFN-γ in Teffs and Foxp3 in Tregs. Relative contributions of each exposure to DNA modification and asthma pathogenesis warrant further investigation.

Keywords

• Secondhand smoke
• Ambient air pollution
• IFN-γ
• Foxp3
• Methylation
• Epigenetic regulation
• Pediatrics
• T effectors
• T regulatory cells