MUTAGENICITY AND CYTOTOXICITY OF REACTIVE OXYGEN AND NITROGEN SPECIESIN THE MN-11 MURINE TUMOR-CELL LINE

There is increasing evidence that endogenously generated reactive oxyg en (ROS) and reactive nitrogen (RNS) species at sites of inflammation and in tumors may be genotoxic. We have developed a murine tumor model (MN-11) in which mutations at the hypoxanthine phosphoribosyltransfer ase (HPRT) locus, arising both in vitro and in vivo, can be detected. In the present report, we describe an in vitro study of the ability of ROS and RNS to induce mutations in our model system. Cs-137 radiation and radiomimetic drugs caused a dose-dependent increase in mutant fre quency. At D-0, radiation induced about 170 mutants per 10(5) viable c ells, compared to 50 and 95 for streptonigrin and bleomycin, respectiv ely. H2O2 induced a lower frequency of mutants, 20-30 per 10(5) for en zymatically generated or bolus, respectively. For the following treatm ents, mutant frequency at 50% survival is shown. Incubation with human granulocytes induced a low frequency of mutants (about 15 per 10(5)). RNS was tested using a series of NO-donating drugs. Spermine/NO . ind uced cytotoxicity but no mutants while S-nitroso-N-acetylpenicillamine induced a low level, 10 per 10 Both release nitrogen monoxide spontan eously, with a t(1/2) < 3 h. Glyceryl trinitrate and sodium nitropruss ide are two drugs that were slowly metabolized by MN-11 cells (> 12 h) . Glyceryl trinitrate induced about 20 per 10(5) while nitroprusside i nduced 50 per 10(5). Our results indicate that RNS can readily induce mutations detectable in MN-11 cells. At equicytotoxic doses, the induc ed mutant frequency varied considerably for different drugs, suggestin g that different states of nitrogen monoxide (such as NO+ or NO .) may be generated and these may vary in their mutagenic/cytotoxic potentia l. (C) 1997 Elsevier Science B.V.