PARTICIPATION OF IRON AND NITRIC-OXIDE IN THE MUTAGENICITY OF ASBESTOS IN HGPRT(-), GPT(-HAMSTER V79 CELLS() CHINESE)

Crocidolite asbestos is known to cause cellular damage, lending to asb estosis, bronchogenic carcinoma, and mesothelioma in humans. The mecha nism responsible for the carcinogenicity of asbestos is not known. Iro n associated with asbestos is thought to play a role by catalyzing the formation of reactive oxygen species, which may cause DNA damage, lea ding to mutations and cancer. Here, we examined whether asbestos can i nduce mutations in Chinese hamster hgprt(+) V79 cells or transgenic hg prt(-1) gpt(+) V79 cells (G12). Treatment with 6 mu g/cm(2) crocidolit e for 24 h caused a 2-fold increase in the mutation frequency at the g pt locus of G12 cells, but no increase at the hgprt locus of V79 cells . The mutation frequency at the gpt locus of G12 cells increased with increasing treatment dose of crocidolite, The mutations induced by cro cidolite appeared to be due to the generation of reactive oxygen speci es catalyzed by iron associated with the fibers, because treatment of G12 cells in iron-free medium with fibers from which redox active iron had been removed with desferrioxamine B prevented all of the gpt(-) m utations above untreated control levels. In addition, treatment of cel ls with a soluble form of iron, 1.5 mM ferric ammonium citrate, result ed in an increase in mutation frequency at the gpt locus of similar to 1.5 fold above that of untreated G12 cells with no increase in mutati ons at the hgprt locus of V79 cells with ferric ammonium citrate. We a lso investigated the effect of nitric oxide on the mutagenicity of cro cidolite in G12 cells. When G12 cells were treated with 3 mu g/cm(2) o f crocidolite in the presence of nitric oxide-generating compound, 200 mu M diethyltriamine/NO, the mutation frequency increased to a level that was more than additive for crocidolite or diethyltriamine/NO trea tment alone. These results strongly suggest that the presence of iron and nitric oxide may either lead to the generation of another reactive , mutagenic species, such as peroxynitrite, or that nitric oxide inhib its a DNA repair enzyme(s). leading to an increase in mutations.