Effect of cigarette smoke on placental antioxidant enzyme expression

Abstract

Cigarette smoking is associated with systemic oxidative stress leading to an upregulation of antioxidant systems [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and heme oxygenase (HO)] in some tissues, but the response in the human placenta is unknown. The aim of this study was to determine the effect of cigarette smoke exposure on placental antioxidant expression in vivo, as well as the effect on antioxidant expression in the human trophoblast choriocarcinoma (HTR)-8SVNeo cell line. In the in vivo experiment, normal-term placentas were obtained following elective caesarean section. The chorionic villi (CV), anchoring villi (AV), and basal plate (BP) were dissected, and Western blot analysis was carried out for HO-1, HO-2, SOD, CAT, and GPx. In vitro experiment, a cigarette smoke extract (CSE) was prepared by bubbling the smoke form three cigarettes through 15 ml of RPMI. This 100% CSE was syringe filtered and diluted to 0.1, 0.5, 1, 2, 5, and 10% concentrations. HTR-8SVNeo cells were cultured with the CSE for 48 h. The cells were harvested, protein was extracted, and run on SDS-PAGE gels, and Western blot analysis was carried out for HO-1, HO-2, SOD, and CAT. Immunofluorescence for HTR-8SVNeo cells HO-1 was carried out following increasing concentrations of CSE. In the in vivo experiment, HO-1 and HO-2 expression was increased in the BP of placentas from smokers compared with nonsmokers. CAT, GPx, and SOD levels in all placental regions, as well as HO-1 and HO-2 expression in the AV and CV were unchanged. In the in vitro experiment, The 5%, 10%, and 20% dilutions were toxic to the cells. The 0.1% CSE solution did not significantly alter HO-1 expression. Treatment with the 0.5%, 1% and 2% CSE solutions resulted in a dose-dependent increase in HO-1 expression. None of the CSE treatments resulted in a significant alteration in HO-2, SOD, GPx, or CAT expression. HO-1 immunoflourescence confirmed the HO-1 expression studies. Cigarette smoke exposure increases HO-1 and HO-2 expression in the placental basal plate and increases HO-1 expression in the HTR-8SVNeo cell line. Increased HO-1 and HO-2 protein expression may increase the production of the antioxidants biliverdin and bilirubin, which are products of heme metabolism. This could function to reduce the oxidative load that is released into the maternal plasma from the preeclamptic placenta and may contribute to the observed decreased incidence of preeclampsia in smokers.