Role of oxyradicals in mutagenicity and DNA damage induced by crocidolite asbestos in mammalian cells

Crocidolite, one of the most carcinogenic forms of asbestos, is mutagenic i n cultured mammalian cells when assayed using a system that can detect mult ilocus deletions. In the present study, we examined the effect of buthionin e sulfoximine (BSO) on mutation frequency and the formation of 8-hydroxydeo xyguanosine (8-OHdG) in human-hamster hybrid (A(L)) cells induced by crocid olite fibers in an attempt to determine the role of oxyradicals: in mediati ng fiber mutagenesis, BSO, a competitive inhibitor of the enzyme gamma-glut amyl cysteine synthetase, depleted nonprotein sulfhydryls to <5% of control within 24 h at a nonmutagenic dose of 25 mu m. In cells pretreated with BS O for 24 h, the mutation yield at the CD59 locus induced by a 4 mu g/cm(2) dose of crocidolite fibers was increased by more than 3-fold (P < 0.05). Us ing immunoperoxidase staining with a monoclonal antibody specific for 8-OHd G, we demonstrated that crocidolite fibers induced a dose-dependent increas e in oxidative DNA damage in A(L) cells. Furthermore, addition of DMSO, a w ell-established hydroxyl radical (OH.) scavenger, dramatically suppressed 8 -OHdG induction (P < 0.005). Our results definitely demonstrate, that react ive oxygen species mediate fiber-induced DNA damage mutagenesis in A(L) cel ls in a concentration-dependent manner.