Glutathione-S-transferase (GSTM1 and GSTT1) polymorphism and lead toxicity in individuals environmentally exposed to lead

Abstract

Genetic variation in enzymes involved in metal detoxification could have influence on susceptibility to lead-induced oxidative stress. The present study aimed at evaluating the effects of genetic variation of Glutathione-S- transferase gene on oxidative stress markers (GSH, SOD, CAT and MDA) among individuals environmentally exposed to lead. GSTM1 and GSTT1 null homozygous genotypes were determined by polymerase chain reaction. Blood lead levels were determined using Microwave Plasma Atomic Emission Spectroscopy (MP- AES-Agilent 4210 USA). Activities of superoxide dismutase, catalase and glutathione levels were assayed using Cayman’s commercial kits. The study found mean blood lead levels of the study subjects of 78.16± 5.79µg/dl with range from 26.6 to 191.0 µg/dl. The frequencies of GSTM1 and GSTT1 null genotypes were 23% and 50.8% respectively. The frequency was high in individuals with blood lead levels greater than 70µg/dl. Significant decreased activity of antioxidant enzymes (SOD and CAT), glutathione levels and concomitant increased of MDA concentrations were observed in individuals with GSTM1 and GSTT1 null genotypes. Therefore, findings from this study were enough to infer a causal relationship between environmental exposure to lead and oxidative stress. Individuals who are homologous null at GSTM1 and GSTT1 loci predispose to increased risk of multi-organs toxicity from environmental exposure to lead.