Influence of retinoids on the mutagenicity of cigarette-smoke condensate in Salmonella typhimurium TA98

Experimental databases on inhibition of the bacterial mutagenicity of 4-nitroquinoline 1-oxide and cigarette smoke

Two antimutagenicity databases were prepared by applying a co-treatment procedure to the Salmonella reversion assay. Ninety compounds belonging to various chemical classes were quantitatively tested for antimutagenicity towards the direct-acting mutagen 4-nitroquinoline 1-oxide (4NQO) in strain TA100 of S. typhimurium and 63 of them were additionally tested for antimutagenicity towards unfractionated mainstream cigarette smoke (CS) in strain TA98, in the presence of S9 mix. Twelve compounds (13.3%) inhibited 4NQO mutagenicity by at least 50%, with a MID50 (dose inhibiting 50% of mutagenicity) varying over a 1226-fold range. Twenty-six compounds (41.3%) inhibited CS mutagenicity, with a MID50 varying over a 520-fold range. Three compounds only, i.e., bilirubin, curcumin and myricetin, were capable of inhibiting the mutagenicities of both 4NQO and CS. However, myricetin and the other flavonoid rutin were at the same time mutagenic by inducing frameshift mutations following metabolic activation. There was a rather rigorous selectivity of antimutagenicity data depending on the chemical class of inhibitors and it was possible to discriminate protective effects within several pairs or series of structurally related compounds. For instance, all eight thiols and aminothiols inhibited 4NQO mutagenicity, which contrasted with the inactivity of the remaining 17 sulfur compounds tested, all of them lacking a free sulfhydryl group. The mutagenicity of CS was consistently inhibited by the majority of phenols (eight out of 10 tested) and by all two isothiocyanates, two dithiocarbamates, three indole derivatives, three tetrapyrrole compounds and three flavonoids tested. Although the results obtained cannot be extrapolated to other mutagens or test systems, they may provide a useful source of information for research in the area of antimutagenesis and for the development of chemopreventive agents.

gamma-L-glutamyl-taurine (Litoralon) prevents the micronucleus formation induced by mitomycin C

We have examined whether gamma-L-glutamyl-taurine (Litoralon) could prevent the genotoxic action of mitomycin C (MMC) in the rat bone marrow cells using the micronucleus test. Litoralon (0.83 mg/kg) administered concurrently with MMC (0.75 mg/kg) did not exhibit any protective action. Pretreatment with a single dose (0.83 mg/kg) of Litoralon 24 h before the administration of MMC (0.75 mg/kg) prevented the micronucleus-inducing effect of MMC. There was no difference between the efficiencies of a single and multiple Litoralon pretreatments. Since Litoralon is known to exhibit vitamin A-like activity and stimulation of poly-ADP-ribose synthesis, it is presumed that either one of these 2 properties separately, or both in conjunction, can be responsible for the inhibition of micronucleus formation.