Genotoxic and cytotoxic evaluation of venlafaxine in an acute and a subchronic assay in mouse

The present research was made to determine the micronuclei and cytotoxic capacity of the antidepressant venlafaxine in an in vivo acute and subchronic assays in mouse. In the first study, we administered once 5, 50, and 250 mg/kg of the drug, and included a negative and a daunorubicin treated group. Observations were daily made during four days. The subchronic assay lasted 5 weeks with daily administration of venlafaxine (1, 5, and 10 mg/kg) plus a negative and an imipramine administered groups. Observations were made each week. In the first assay results showed no micronucleated polychromatic erythrocytes (MNPE) increase, except with the high dose at 72 h. The strongest cytotoxic effect was found with 250 mg/kg at 72 h (a 51% cytotoxic effect in comparison with the mean control level). In the subchronic assay no MNPE increase was found; however, with the highest dose a significant increase of micronucleated normochromatic erythrocytes was observed in the last three weeks (a mean of 51% respect to the mean control value). A cytotoxic effect with the two high doses in the last two weeks was observed (a polychromatic erythrocyte mean decrease of 52% respect to the mean control value). Results suggest caution with venlafaxine.

Inhibitory effect of mannan on the toxicity produced in mice fed aflatoxin B1 contaminated corn

Aflatoxin B(1) (AFB(1)) is a potent mutagenic and carcinogenic agent found in numerous agricultural and dairy products consumed by humans. Therefore, we evaluated the capacity of mannan to cope with its genotoxic potential. We prepared a diet constituted of corn (90%) plus the recommended amount of other nutrients, as well as with the tested compounds (mannan and/or AFB(1)). Mice were fed this diet during 4 weeks as follows: one group with AFB(1)-contaminated corn (0.25 mg/kg of corn), three groups with mannan (50, 250, and 500 mg/kg of corn) plus AFB(1) (0.25 mg/kg), another group with only mannan (500 mg/kg), and the last group with an uncontaminated diet and no mannan added. We determined the weight, the micronucleated normochromatic erythrocyte rate (MNNE), the polychromatic/normochromatic index, and the sister chromatid exchange rate (SCE). We also examined the recovery response of mice during 4 additional weeks, when they were fed only the normal diet without AFB(1) or mannan. The results in the first period revealed the following: a) mice fed with mannan alone presented values in the range determined for the control group; b) mice fed AFB(1) had a significant weight decrease, as well as a significant increase in the rate of MNNE and SCE; and c) animals fed the combined regimen (AFB(1) plus mannan) presented a 25% weight increase with respect to the animals treated with AFB(1) alone, as well as a significant reduction in the level of MNNE and SCE with the two high doses tested. In the second (recovery) period, the control and the mannan fed groups maintained values similar to those exhibited in the previous phase, and the AFB(1) group as well as the groups fed the regimen combined with mannan showed an improvement in all evaluated parameters; the best response was that found in mice fed AFB(1) plus 500 mg/kg of mannan. Our study established an antigenotoxic effect of mannan that could be due to its adsorbent capacity.

Genotoxic and oxidative damage induced by Helicobacter pylori in Meriones unguiculatus

Infection with Helicobacter pylori has been shown to be at the origin of various gastric pathologies. However, it has not yet been established whether the etiology of such diseases, particularly of gastric cancer, is related to the production of free radicals or to mutagenesis. The aim of this study was to determine whether a six-month infection with Helicobacter pylori increased the amount of lipid peroxidation, nitric oxide, and DNA damage in Mongolian gerbils (Meriones unguiculatus). H. pylori was characterized genotypically and administered orally to the animals. Four tests were applied to identify the presence of bacteria at one, two, four, and six months after the inoculation, namely, isolation and identification in culture, the urease test, the ELISA assay, and immunohistochemical staining of gastric biopsies. The infection was considered to be successful when three of the above-mentioned tests were positive. The infection occurred in 30% of the animals in the first month after the H. pylori inoculation and in 60-70% of the animals in the later stages. Levels of malondialdehyde, nitric oxide, and DNA damage (using the "comet" assay) were determined in the gastric tissue of the animals at one, two, four, and six months. We found statistically significant increases in malondialdehyde and nitric oxide levels from the second month on. The comet assay in animals infected with H. pylori showed a significant increase in the mean tail length throughout the observation period. We conclude that our results support the assumption that oxidative damage and DNA breakage produced by the infection with H. pylori are some of the initial alterations occurring in the development of gastric diseases.

Antigenotoxic effect of Saccharomyces cerevisiae on the damage produced in mice fed with aflatoxin B(1) contaminated corn

The potential of Saccharomyces cerevisiae (Sc) was evaluated for reducing the micronucleated normochromatic erythrocytes (MNNE) rate in mice fed AFB(1) contaminated corn. The study included two groups fed AFB(1) contaminated corn (0.4 and 0.8 mg/kg), a control fed uncontaminated corn, another group fed uncontaminated corn and 0.3% of Sc (1 x 10(8) live cells/g), and two groups fed AFB(1) contaminated corn (0.4 and 0.8 mg/kg) plus 0.3% Sc. Weight and MNNE were determined weekly for six weeks. Subsequently, the same determinations were made for another three-week period, but in mice receiving only a normal diet, without AFB(1) and Sc. Results in the first period revealed the following: control and Sc fed mice had similar constant weight increase, and low MNNE rate; mice fed only AFB(1) showed weight decrease and significant MNNE increase; finally, Sc improved weight gain and reduced MNNE produced by AFB(1). In the second period, results exhibited a tendency similar to that of the previous phase in the control and Sc fed mice; the weight and MNNE values improved in the other groups. We also determined the capacity of Sc for adsorbing and modifying the mycotoxin structure. The mixture was filtered to obtain two phases, and AFB(1) content was measured. Sc revealed a potent adsorbent capacity; however, chromatographic determination suggested no structural modification.