Micronuclei in blood lymphocytes and genetic polymorphism for GSTM1, GSTT1 and NAT2 in pesticide-exposed greenhouse workers

Abstract

The frequency of micronuclei (MN) in cultured peripheral lymphocytes was used as a biomarker of genotoxic effects in 34 Italian pesticide-exposed greenhouse workers and 33 unexposed referents matched with the exposed workers for age and smoking habits. The possible influence of the genetic polymorphisms of xenobiotic metabolizing enzymes glutathione S-transferase M1 (GSTM1), T1 (GSTT1), and N-acetyltransferase 2 (NAT2) was also evaluated. To restrict the analysis primarily to cells that have divided once in vitro, MN were scored only in cells showing label after a 42-h incubation with bromodeoxyuridine (BrdU), as detected by immunofluorescence (anti-BrdU technique). Two different concentrations of BrdU (0.5 and 1 μg/ml) were compared. Individual frequencies of micronucleated cells (MNCs) obtained with the two concentrations of BrdU significantly correlated with each other ( r=0.55, P<0.001). Higher mean MNCs frequencies (per 1000 cells) were detected among exposed smokers (9.0 at 0.5 μg/ml BrdU and 7.8 at 1 μg/ml BrdU) than in smoking referents (6.3 and 5.9, respectively). In multiple regression analysis controlling for age, sex, smoking and genotypes, a significant elevation of MNC frequency ( P=0.004 at 1 μg/ml BrdU; P=0.052 at 0.5 μg/ml BrdU) was observed in greenhouse workers with a work history of extensive pesticide spraying ( n=17). Increased MNC frequencies were also associated with ageing at 0.5 μg/ml BrdU, with the GSTM1-positive genotype at both 1 ( P=0.028) and 0.5 ( P=0.056) μg/ml BrdU in all subjects, and with the NAT2 fast acetylator genotype in smokers at 0.5 μg/ml BrdU ( P=0.043). The results indicate that MN rates are increased in greenhouse workers, especially in those involved in pesticide spraying. The GSTM1 positive and NAT2 fast genotypes appear to be associated with elevated MNC frequencies, which contradicts with earlier results on elevated chromosomal aberration rates in GSTM1 null smokers and NAT2 slow subjects.