Relationship between genotoxicity biomarkers in somatic and germ cells: findings from a biomonitoring study

A biomonitoring study to evaluate chromosome and DNA damage respectively in somatic and germ cells of a group of male workers exposed to styrene by using biomarkers of genotoxicity was carried out. Styrene-exposed workers from three different areas of Tuscany and healthy subjects, of comparable mean age, sex and lifestyle characteristics, as a control group not exposed to chemicals, have been enrolled. In addition to previous reports [L. Migliore, A. Naccarati, A. Zanello, R. Scarpato, L. Bramanti and M. Mariani (2002) Hum. Reprod., 17, 2912-2918; L. Migliore, A. Naccarati, F. Coppede et al. (2006) Pharmacogenet. Genomics, 16, 87-99] we present now data on a cross-sectional investigation involving a homogeneous group of subjects for which data on both somatic and germ cells have been obtained from individuals (42 exposed and 25 controls). Somatic cell genotoxicity was assessed by analysing the frequency of micronucleated binucleated cells (MNBN) in blood lymphocytes. The micronucleus assay was coupled with centromeric fluorescence in situ hybridization (FISH) analysis. Primary DNA damage in germ cells was evaluated by alkaline single-cell gel electrophoresis (Comet assay) and the percentage of the tail DNA (%TD) was used as parameter of Comet evaluation. Moreover, to investigate the frequencies of aneuploidy and diploidy in sperm, we performed multicolour FISH, using DNA probes specific for the centromeric regions of sex chromosomes and chromosome 2, in decondensed sperm nuclei of samples with normal semen parameters in a subgroup of individuals. Mandelic and phenylglyoxylic acids (MAPGA) in end of shift samples were determined as biomarkers of internal dose. MAPGA excretion was consistent with an exposure to styrene above the threshold limit value-time weighted average concentration of 20 p.p.m. Styrene workers showed significantly higher frequency of MNBN as compared to controls (13.8 +/- 5.2 versus 6.2 +/- 5.1; P < 0.001), due to higher proportions of both micronuclei (MN) arising from chromosomal breakage (C-MN) and harbouring whole chromosomes (C+MN). DNA damage in sperm cells was also higher among styrene-exposed, the %TD being 11.02 +/- 2.99 versus 7.42 +/- 2.30 in controls (P < 0.001). The incidence of aneuploidy and diploidy for the tested chromosomes in sperm did not show a statistically significant difference between workers and controls. However, a positive correlation was found between genotoxic damage detected in somatic and in germ cells, even after removing the effect of age (r = 0.475; P < 0.001). Although cytogenetic biomarkers detected both in somatic and germ cells were interrelated, no relationships were apparent with exposure parameters. Styrene exposure may increase the likelihood of both chromosome and DNA damage in somatic and germ cells, thus supporting the hypothesis of an interference on reproductive capacity among exposed workers. This is the first time that a field study shows a correlation between two biomarkers of genotoxicity evaluated at the same time in somatic and germ cells.