An assessment of benzene genotoxicity : DNA adduct formation and its consequence
thesisposted on 15.12.2014, 10:36 by Margaret. Gaskell
The aim of this study was to develop sensitive methods for the analysis of benzene-DNA adducts from benzene-exposed individuals and determine the consequences of such DNA adducts using the supF mutation assay. Benzene-DNA adduct standards, which included a novel DNA adduct characterised and identified as (3', 4'-dihydroxyl)-1, N2-benzetheno-2'-deoxyguanosine 3'-monophosphate, were synthesised and TLC and HPLC systems were developed for the analysed of these adducts following 32P-postlabelling. Attempts were also made to produce an antibody to N2-(4-hydroxyphenyl)-2'-deoxyguanosine 3'-monphosphate, the only benzene-DNA adduct so far identified following in vivo exposure, to be used in an enrichment step prior to 32P-postlabelling. The benzene-DNA adducts formed by the benzene metabolite para-benzoquinone (p-BQ) and the damage induced by hydroquinone (HQ) were assessed for their mutagenic potential in repair proficient and deficient cell lines. Both treatments proved to be mutations following treatment with p-BQ were GCRTMAT transitions, for HQ treatment GCRTMAT transitions predominated, for all cell lines investigated. Application of the 32P-postlabelling assay to the analysis of lymphocyte DNA from petroleum refinery workers resulted in no detectable benzene-DNA adducts, a possible reflection on the low benzene exposure (<2 ppm), the use of an inappropriate surrogate tissue or the detection limit of the assay. Further work in regard to improvement of the assay's sensitivity and selectivity would be necessary prior to any further analysis. The results from the mutation assay indicated that HQ may be the ultimate toxic metabolite, inducing the chromosomal aberrations observed in benzene exposed individuals.