Series: 'Current issues in mutagenesis and carcinogenesis.' No. 41. Can a 'relatively simple' screening procedure for the detection of chemicals with aneugenic potential be recommended at the moment?

Effect of cyanidin 3-O-beta-glucopyranoside on micronucleus induction in cultured human lymphocytes by four different mutagens

The anthocyanin cyanidin 3-O-beta-glucopyranoside (Cy-g) is reported to be one of the most effective antioxidants, but little is currently known regarding its potential chemopreventive properties. In this study, we evaluated the ability of Cy-g to protect cultured human lymphocytes from micronucleus (MN) induction by four different mutagens: ethyl methanesulfonate (EMS), colchicine (COL), H(2)O(2), and mitomycin C (MMC). To gain insight into the mechanisms of action of Cy-g, the cultures were treated with the compound before, during, and after treatment with the mutagens; in addition, the cultures were evaluated for the induction of apoptosis. When used by itself, up to 100 microg/ml of Cy-g was nongenotoxic, while 100 microg/ml Cy-g reduced the replicative index of the cells by nearly 50%. In addition, Cy-g was able to reduce the frequency of micronuclei induced by EMS, COL, and H(2)O(2) using all three treatment protocols, but it had no significant effect on MN induction by MMC in any of the protocols. Apoptosis was produced in the cultures treated with Cy-g alone and was increased under conditions in which Cy-g produced anti-genotoxic effects, suggesting that Cy-g mediated-apoptosis may remove highly damaged cells. However, increases in apoptosis were found under conditions in which Cy-g was not significantly anti-genotoxic, indicating that the increases in apoptosis were not sufficient to account for the anti-genotoxicity of Cy-g. Taken together, our findings indicate that Cy-g possesses anti-genotoxic activity in vitro, which suggests its potential use as a chemopreventive agent.

The high production volume chemical challenge program: the relevance of the in vivo micronucleus assay

The in vivo rodent bone marrow micronucleus assay (Mnt) has assumed a pivotal role in screening strategies for the identification of substances potentially carcinogenic to humans. The analysis of the results of the current international 5-year effort to provide toxicological data for high production volume chemicals will play a crucial role in developing future strategies for identifying health hazards. As part of that program, consideration is being given to accepting either in vitro genotoxicity data or results of the Mnt. The present analyses indicate that for hazard identification purposes that, in fact, in vitro genotoxicity test results, such as those derived from the Salmonella mutagenicity assay, may be an acceptable alternative.

Utility of a test for chromosomal malsegregation in Saccharomyces cerevisiae strain D61.M for the detection of antianeugens: test of the model combination of chlorophyllin and nocodazole

Despite the fact that aneuploidy is a major genetic cause of human morbidity and mortality, antimutagenicity studies have used predominantly short-term tests that detect gene mutations, chromosomal aberrations, and micronuclei. Therefore, the major deficiency in the use of short-term tests for antimutagenicity studies is those that detect chromosomal malsegregation leading to aneuploidy. Thus, we initiated a study on the utility of short-term tests for the detection of antianeugenic activity. We selected strain D61.M of Saccharomyces cerevisiae, nocodazole, and chlorophyllin as a model short-term test, aneugen, and antimutagen, respectively, for our initial study. Chlorophyllin strongly inhibited the aneugenic activity of nocodazole, but had no effect on the endpoints when tested alone, in strain D61.M. To our knowledge, this is the first report of an antianeugen. Furthermore, we conclude that strain D61.M can be used as a relatively simple, inexpensive, and rapid short-term test for the study of antianeugenicity.

Direct tubulin polymerization perturbation contributes significantly to the induction of micronuclei in vivo

The computational analysis data presented indicate a significant mechanistic association between the ability of a chemical to cause tubulin polymerization perturbation (TPP), via direct interaction with the protein, and the in vivo induction of micronuclei (MN). Since it is known that TPP is not a genotoxic event, the analyses suggest that the induction of MN by a non-genotoxic mechanism is a significant alternate pathway.

Regulatory Genotoxicity Testing: A Critical Appraisal

This review considers current approaches to regulatory genotoxicity testing, focusing on how the use of animals can be further replaced, reduced and refined. The complementary roles of in vitro and in vivo testing, and the justification for using animals, are discussed in detail. Recommendations are made for improvements and further work, in the light of the considerable current controversy surrounding the composition and deployment of testing strategies, and the interpretation of the data generated, particularly for carcinogenicity prediction. The major problems are the oversensitivity of in vitro tests and the insensitivity of in vivo assays. On the basis of an analysis of some published databases, it is concluded that there is insufficient support for using in vivo genotoxicity assays for screening. Also, it is questionable whether the scientific benefits of using such assays always outweigh the costs to the animals involved. The considerable efforts being made to harmonise in vivo protocols and to develop improved methods for detecting genotoxicity are discussed. It is recommended that more emphasis be placed on characterising genotoxins in vitro, especially for mechanisms of activity, to optimise the benefits of any confirmatory animal tests.. Also, regulatory agencies are urged to require better-designed and more-scientifically sound protocols, in which animal numbers are minimised and data interpretation, particularly that of negative results, is facilitated. Lastly, in the development and validation of transgenic rodent systems, emphasis should be placed on developing protocols in which other acute toxicity and metabolism endpoints can be measured simultaneously with in vivo mutagenesis, while minimising animal numbers.