Prenatal ambient air pollution exposure and SOD2 promoter methylation in maternal and cord blood

Abstract

The evidence is increasing that prenatal air pollutant exposure contributes to elevated oxidative stress in children, but the underlying mechanism is unclear. A pilot study was conducted in China to explore the associations between prenatal ambient air pollution exposure and superoxide dismutase 2 (SOD2) promoter methylation in maternal and cord blood. After detection and analyses, SOD2 promoter methylation levels in umbilical cord blood were elevated as maternal SOD2 promoter methylation levels increased. In addition, the SOD2 promoter methylation levels in umbilical cord blood were positively associated with the particulate matter 10 (PM10) exposure concentrations during the entire pregnancy and the second trimester. In maternal peripheral blood, the SOD2 promoter methylation levels were positively associated with the exposure concentrations of PM10 (during the entire pregnancy and the second trimester) and nitrogen dioxide (NO2) (during the first trimester of pregnancy), whereas the levels were negatively associated with the exposure concentrations of NO2 during the third trimester of pregnancy. Additionally, interaction analyses revealed that the maternal SOD2 promoter methylation level and sulfur dioxide (SO2) exposure (during the entire pregnancy and the third trimester), as well as NO2 exposure (during the third trimester of pregnancy), had an interaction effect on the SOD2 promoter methylation level in umbilical cord blood. Furthermore, mediation analysis revealed that the associations between SOD2 promoter methylation in umbilical cord blood and PM10 exposure during the entire pregnancy and the second trimester were partly mediated by maternal SOD2 promoter methylation. In conclusion, prenatal exposure to air pollutants was significantly associated with SOD2 promoter methylation levels in umbilical cord blood, and this association may be affected by SOD2 promoter methylation levels in maternal peripheral blood. These associations may be one of the mechanisms by which prenatal air pollutant exposure leads to oxidative stress in newborns.