The effect of NOx pollution on oxidative stress in pregnant women living in Durban, South Africa.

Abstract

Introduction: Ambient air pollution and associated oxidative stress has been implicated in many pathological conditions; including adverse birth outcomes. Optimum glutathione-S-transferase (GST) P1 activity is essential for efficient detoxification of reactive oxygen and nitrogen species limiting DNA adduct (8-OHdG) formation. We aim to investigate the effect oxides of nitrogen (NOx) have on the induction of oxidative stress in pregnant women, and low birth weight. Method: Participants (n=113) were recruited from communities in Durban, South Africa, as part of the Mother and Child in the Environment (MACE) birth cohort. Land use regression models were developed to characterise exposure and obtain NOx levels. Serum samples were analysed for the 8-OHdG adduct using the OxiSelect™ Oxidative DNA Damage ELISA Kit. Isolated DNA from whole blood were used for single-nucleotide polymorphism (SNP) genotyping of the GSTP1 SNP using polymerase chain reaction and restriction fragment length polymorphism. Statistical data analysis included, ANOVA and student t test. Results: The 8-OHdG adduct concentration increased concomitantly with NOx (intervals 1-20, 20-40, 40-60 µg/m3: *p=0.0162). Subjects with wild type (AA) GSTP1 genotype had lower levels of 8-OHdG adducts than subjects with the variant (AG+GG) genotype at NOx 1-20µg/m3 whilst at higher NOx intervals (20-40 and 40-60µg/m3), the 8-OHdG concentration was higher for AA subjects than AG+GG (*p=0.028). Conclusion: The results show that increasing NOx levels induced increasing oxidative stress in pregnant women as observed through increased 8-OHdG adduct formation. The GSTP1 wildtype differentially influences oxidative stress with protective effects in low NOx areas and adverse effects with high NOx levels in ambient air. The effect on birth outcomes and stress markers are currently being investigated.