Gene-environment interaction in preterm delivery with special reference to organochlorine pesticides

Abstract

We investigated the association between glutathione S-transferases mu1 (GSTM1), theta 1 (GSTT1), Cytochrome P450IA1-T6235C (rs4646903, CYP1A1m1) and CYP1A1-1462V (rs1048943, CYP1A1m2) gene polymorphisms, and organochlorine pesticides (OCPs) level with risk of preterm delivery (PTD). Maternal and cord blood samples of PTD (n = 156) cases and subjects of full-term delivery (FTD, n = 151) were collected at the time of delivery/after delivery. Women occupationally exposed to OCPs and other high-risk factors such as anemia, hypertension and dietary habit were excluded. The OCP levels were estimated by gas chromatography, and polymorphic analysis of GSTM1/GSTT1 and CYP450 genes was carried out using multiplex PCR and PCR-restriction fragment length polymorphism, respectively. The frequency of GSTM1/GSTT1 (null) genotype was significantly higher in PTD cases than in the controls. Significantly high levels of α-hexachlorocyclohexane (HCH), γ-HCH and Dichlorodiphenyldichloroethylene (p'p'-DDE) were observed in maternal blood, while significantly high levels of p,p'-dichlorodiphenyltrichloroethane and p'p'-DDE were found in the cord blood of PTD cases compared with the controls. A significant association was seen between β-HCH and GSTM1 genotype when interaction between GSTM1 gene polymorphism, maternal blood OCP levels and period of gestation (POG) was ascertained. A significant reduction in POG was observed. Similarly, cord blood dieldrin levels were significantly associated with CYP1A1m2 (Aa/aa) with reduction in POG. Our observations indicate that higher levels of OCPs in pregnant women may be associated with increased risk of 'idiopathic' PTD. Furthermore, this study shows that the interaction between high OCPs levels and polymorphism in CYP1A1m2 and GSTM1 null genotypes may magnify the risk of PTD, thus providing evidence for a gene-environment interaction in pregnant women.