Polymorphisms in ABC Transporter Genes and Concentrations of Mercury in Newborns - Evidence from Two Mediterranean Birth Cohorts

Background: The genetic background may influence methylmercury (MeHg) metabolism and neurotoxicity. ATP binding cassette (ABC) transporters actively transport various xenobiotics across biological membranes. Objective: To investigate the role of ABC polymorphisms as modifiers of prenatal exposure to MeHg. Methods: The study population consisted of participants (n = 1651) in two birth cohorts, one in Italy and Greece (PHIME) and the other in Spain (INMA). Women were recruited during pregnancy in Italy and Spain, and during the perinatal period in Greece. Total mercury concentrations were measured in cord blood samples by atomic absorption spectrometry. Maternal fish intake during pregnancy was determined from questionnaires. Polymorphisms (n = 5) in the ABC genes ABCA1, ABCB1, ABCC1 and ABCC2 were analysed in both cohorts. Results: ABCB1 rs2032582, ABCC1 rs11075290, and ABCC2 rs2273697 modified the associations between maternal fish intake and cord blood mercury concentrations. The overall interaction coefficient between rs2032582 and log2-transformed fish intake was negative for carriers of GT (beta = -0.29, 95%CI -0.47, -0.12) and TT (beta = -0.49, 95%CI -0.71, -0.26) versus GG, meaning that for a doubling in fish intake of the mothers, children with the rs2032582 GG genotype accumulated 35% more mercury than children with TT. For rs11075290, the interaction coefficient was negative for carriers of TC (beta = -0.12, 95%CI -0.33, 0.09), and TT (beta = -0.28, 95%CI -0.51, -0.06) versus CC. For rs2273697, the interaction coefficient was positive when combining GA+AA (beta = 0.16, 95%CI 0.01, 0.32) versus GG. Conclusion: The ABC transporters appear to play a role in accumulation of MeHg during early development.