The role of various biomarkers in the evaluation of styrene genotoxicity

P. Vodicka PhDa, P. Soucek PhDb, Mikko Koskinen PhDc, R. Stetina PhDd, L. Vodicková MDb, K. Hemminki MD PhDe

a Inst. Exper. Medicine, Acad. Sci. Czech Rep., Prague, Czech Republic, b Natl. Inst. Publ. Health, Prague, Czech Republic, c Orion Pharma Corp., Espoo, Finland, d Purkynje Military Med. Acad., Hradec Králové, Czech Republic, e Dept. Biosci., Karolinska Inst., Huddinge, Sweden

Aim: Styrene, an important industrial chemical, is classified as a possible human carcinogen. DNA and haemoglobin adducts, single-strand breaks (SSB) in DNA, chromosomal aberrations (CA) and HPRT mutant frequencies (MF) in styrene-exposed workers were analysed to understand mechanisms of genotoxic effects. The data on biomarkers were related to the data on genotyping xenobiotic-metabolising enzymes (CYP1A1, 2E1, EPHX, GSTM1, GSTP1 and GSTT1). The role of DNA repair capacities in styrene-exposed workers is discussed. Methods: The complexity of markers required multiple methodological approach, including 32P-postlabelling/HPLC assay, PCR methods for genotyping, cytogenetic analysis, T-cell cloning assay, comet assay, tests for DNA repair capacity and statistics. Results: Haemoglobin and O6 styrene guanine adducts, SSB and CA were significantly higher in the exposed group as compared to controls. These biomarkers correlated significantly with the external and internal exposure, significant relationship between individual biomarkers was found. Although HPRT MF were significantly higher in the exposed workers than in controls (P=0.039), the only significant correlation was with the cumulative styrene exposure (R=0.558, P=0.001). Our studies revealed that SSB may be associated with heterozygosity in CYP2E1 (5´-flanking region and intron 6, r2=0.614). Individuals with low and medium activity EPHX genotypes (exon 3 Tyr/His and exon 4 His/Arg) exhibited higher frequencies of CA than those with high activity genotypes (P=0.044). MF at the HPRT gene were significantly associated with heterozygosity in CYP2E1 (intron 6, P=0.001) and GSTP1 (exon 5, P=0.038). The distribution of the deduced EPHX activity and the frequency of Ala/Val genotype in GSTP1, exon 5, were significantly different in exposed workers than in controls (P=0.041 and P=0.025, resp.). Styrene-exposed laminators exhibited significantly increased DNA repair capacity as compared to control individuals. The detection of 1-adenine DNA adducts in styrene-exposed workers provides an excellent tool for assessing an integral measure of DNA damage (reflecting individual exposure, metabolism and DNA repair). Conclusions: The whole battery of biomarkers did not reveal simple mechanistic relationships between the exposure and biological effect. Markers of individual susceptibility and DNA repair as well as data on the population showing processes of adaptation and selection may contribute to our understanding genotoxic and/or carcinogenic effects of xenobiotics.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Environment and Occupation.