The influence of ethanol treatment of cytogenetic effects in bone marrow cells of Chinese hamsters by cyclophosphamide, aflatoxin B1 and patulin

Inhibition of genotoxic effects of mammalian germ cell mutagens

Germ cell mutagens are among the most important chemicals for which chemopreventive agents should be sought and mechanistically defined. These mutagens may include environmental chemicals as well as drugs. In this investigation, the literature was reviewed for substances antimutagenic (or anticlastogenic) to compounds identified as mutagens in at least two germ cell studies. A complete matrix of test results was prepared to identify commonly tested pairs of germ cell mutagens and antimutagens. The categories of antimutagens most tested included vitamins, fatty acids, thiols, tannins and other phenolics. The most frequently studied mutagens were benzo[a]pyrene, cyclophosphamide, mitomycin C, and bleomycin. Based on the availability of the most relevant data, the analysis presented here focused on in vivo tests, specifically on bone marrow cytogenetics. The results indicated that antimutagens commonly found in the diet or endogenously in the body effectively antagonized the cytogenetic damage induced in the bone marrow by most of the germ cell mutagens studied to date. Bone marrow micronucleus and chromosomal aberration assays, which detect systemically active mutagens, may be predictive of similar mitigating effects in germ cells. Test results from antimutagenicity studies in germ cells, though limited, were comparable to the results from studies in the mouse bone marrow micronucleus test.

International Commission for Protection against Environmental Mutagens and Carcinogens. ICPEMC Working Paper No. 15/1. Genetic effects of ethanol

Alcoholics have a higher frequency of chromosomal aberrations and sister-chromatid exchanges (SCEs) in their peripheral lymphocytes. In human and mammalian cells in vitro, ethanol generally does not induce genetic damage, but it induces SCEs in the presence of an exogenous metabolic system. In human lymphocytes in vitro, ethanol induces SCEs in the presence of alcohol dehydrogenase. In animals in vivo, ethanol induces a variety of genetic effects, including SCEs, micronuclei, dominant lethal mutations and aneuploidy in mouse eggs. There is some indication that ethanol may lead to genetic damage in sperm. In bacteria, ethanol is at best marginally active. Ethanol leads to anomalous chromosome segregation in Aspergillus, to mutations in yeast, to chromosomal aberrations and SCEs in plant root tips and to disturbances of meiosis and micronuclei in tetrads in Zea and Tradescantia respectively. The first metabolite of ethanol, acetaldehyde is mutagenic in a variety of test systems. The mutagenic activity of acetaldehyde in bacteria is questionable, but there is no doubt of its mutagenic activity in a variety of eukaryotic test systems in vitro as well as in vivo.

Maternal administration of cyclophosphamide induces chromosomal aberrations and inhibits cell number, histone synthesis, and DNA synthesis in preimplantation mouse embryos

The effects of cyclophosphamide (CPA), administered to pregnant inbred CBA/Ca mice 60 h after copulation, on cell number, mitotic index, chromosome structure, histone synthesis, and DNA synthesis of 84-h blastocysts, and the subsequent development of these blastocysts cultured for a further 120 h in vitro are described. Cyclophosphamide 4, 20, and 40 mg/kg significantly increased the number of chromosomally aberrant cells, chromosomal aberrations, and chromosome breaks in the blastocysts. Chromosomal rearrangements were significantly increased in the CPA 20 and 40-mg/kg treated groups, and in the 40-mg/kg group the number of cells with ring chromosomes was significantly increased. Histone synthesis and DNA synthesis were significantly inhibited in the CPA 20 and 40-mg/kg treated groups. Blastocyst cell number in each of the treated groups was less than the controls. On subsequent culture in vitro, significantly fewer embryos in the CPA 20 and 40-mg/kg groups hatched, attached, developed trophoblast outgrowths, and expanded their inner cell masses. However, the differentiation of inner cell mass into ectoderm and endoderm was impaired by all three doses of the drug. These results demonstrate that CPA administered to pregnant mice 60 h after copulation has a clastogenic effect and interferes with synthesis of DNA and histones in the preimplantation embryo, and that the drug inhibits the subsequent development and differentiation of these embryos. Cytogenetic analysis of preimplantation embryos might be a useful adjunct to the existing methods in the evaluation of the embryotoxicity of drugs and chemicals.

Mutagenic, teratogenic and pharmacokinetic properties of cyclophosphamide and some of its deuterated derivatives

To elucidate which metabolic pathway leads to the ultimate mutagenic and teratogenic metabolite of cyclophosphamide (CPA), the mutagenicity in vitro as well as the teratogenicity in vivo and the pharmacokinetics of CPA and several deuterated analogs (5,5-d2-CPA, 4,4-d2-CPA and 4,4-6,6-d4-CPA) were compared. 5,5-d2-CPA was less mutagenic (isotope effects between 1.7 and 12.3 were found for sister-chromatid exchanges and structural chromosomal aberrations in CHO cells and in the Ames test) and less teratogenic (deuterium isotope effect between 2 and 3) than CPA and the other deuterated analogs. Because the concentrations of 5,5-d2-CPA in pregnant mice and their embryos were equal to or even exceeded those of CPA and the other deuterated analogs, a particular metabolic pathway involving a fission of the C-D or C-H bond on the C-5 rather than the parent drug must be responsible for the isotope effect observed. It had previously been shown (Cox et al., 1976) that the 5,5-d2-CPA has a decreased anti-tumor activity in vivo (isotope effect 7-13) which was accompanied by a decreased formation of phosphoramide mustard and acrolein in vitro (isotope effect 5.3). Our results suggest that phosphoramide mustard is an important proximate metabolite of CPA with regard to the mutagenicity and teratogenicity of the drug. These results show for the first time that labeling of drugs with stable isotopes offers a promising approach to the study of the mechanism of the mutagenic and teratogenic actions of drugs.

Patulin, a further clastogenic mycotoxin, is negative in the SCE assay in Chinese hamster V79-E cells in vitro

Patulin is a potent inducer of chromatid-type aberrations in Chinese hamster V79-E cells, but loses its activity when 9000 g supernatant of rat-liver homogenate is added. The narrow dose range of patulin clastogenicity shows a quantitative relationship between absolute amount of mycotoxin applied and the number of indicator cells treated. Within a dose range permitting survival of V79-E, patulin does not induce an increase of the SCE rate. It is suggested that patulin clastogenicity is caused by interaction with chromosomal proteins and that DNA is not the virtual target of this mycotoxin.

Influence of chronic ethanol uptake and acute acetaldehyde treatment on the chromosomes of bone-marrow cells and peripheral lymphocytes of Chinese hamsters

Chinese hamsters received 10% (v/v) ethanol as their only liquid supply during 46 weeks. At the end of the drinking period the rate of chromosomal aberrations was determined in cultured lymphocytes. The cultures were set up with the blood from the retro-orbital plexus. Bone-marrow metaphases of the same animals were analysed with regard to sister-chromatid exchanges (SCE) after implantation of BrdU tablets in vivo. No cytogenetic effects were found in either test system. Another group of Chinese hamsters received acetaldehyde at 0.01, 0.1 amd 0.5 mg/kg by i.p. injection, and bone-marrow metaphases were analysed with respect to SCE. The SCE frequencies were elevated by acetaldehyde at 0.5 mg/kg, but not by the lower doses.

Simultaneous exposure of Chinese hamsters to ethanol and cigarette smoke: cytogenetic aspects

Chinese hamsters (Cricetulus griseus) were treated with ethanol, with cigarette smoke and with both. During the experimental period of 12 weeks a control group of animals (c) received water ad libitum, another water drinking group received a cigarette smoke treatment during the last 4 weeks (S). Another group received 20% (v/v) ethanol during the whole experimental period as the only liquid supply (E), and one group with the same ethanol treatment was simultaneously treated with cigarette smoke during the last 4 weeks of the experiment (ES). The investigation of bone marrow cells after 12 weeks with regard to chromosomal aberrations and sister chromatid exchanges revealed no effects. A high mitotic activity was found in the smoke treated groups.

Chromosomal analysis in bone-marrow cells of Chinese hamsters after treatment with mycotoxins

Mycotoxins are ubiquitously occurring metabolites of moulds that grow on foodstuffs. They are able to cause toxic diseases in man and animals. Aflatoxin B1 (AFB1), aflatoxin G1 (AFG1) and platulin (PA) induce chromosomal damage in Chinese hamster bone-marrow cells. With respect to the number of induced aberrant mitoses the 3 mycotoxins can be ranked in the order PA greater than AFB1 greater than AFG1.

Chromosomal aberrations in bone marrow of Chinese hamsters exposed to styrene and ethanol

No significant increase was detected in the number of chromosomally damaged cells in bone marrow of Chinese hamsters after either inhalation exposure to 300 ppm styrene or oral intake of 15% ethanol in drinking water (exposure time 4 days or 3 weeks). In combined exposure, a slight increase of chromosomal aberrations was observed in the group exposed for 4 days (2.0% aberrant cells vs. 0.0% in controls). The group exposed for 3 weeks to combined treatment showed no response (0.3% aberrant cells vs. 0.7% in controls).

Mutagenic, cancerogenic and teratogenic effects of alcohol

Alcohol is mutagenic, cancerogenic and teratogenic in man. Ethanol is mutagenic via its first metabolite, acetaldehyde. This is substantiated by the findings that acetaldehyde induces chromosomal aberrations, sister-chromatid exchanges and cross-links between DNA strands. Methanol, a contaminant of many alcoholic beverages, is also mutagenic via its metabolite, formaldehyde. In addition, different indirect pathways may lead to mutations by alcohol. The cancerogenic activity of alcohol remains unverified by modern standard carcinogenicity tests. Ethanol and other alcohols, as well as aldehydes, inhibit RNA synthesis in cells and in cell-free transcriptional systems. A reduction of cellular RNA synthesis may play an important role in the mutagenic, carcinogenic and teratogenic activity of alcohol.