Early oxidative stress in testis and epididymal sperm in streptozotocin-induced diabetic mice: its progression and genotoxic consequences

Experimental induction of diabetes mellitus in animal models using chemical diabetogens is demonstrated to impair testicular function progressively leading to decreased fertility. Although, both steroidogenic and spermatogenic dysfunctions have been reported, the role of oxidative stress mechanism/s has been less understood. We have investigated the induction of oxidative damage during early diabetic phase in testis and epididymal sperm (ES) in mice administered an acute dose of streptozotocin (STZ). Our results show enhanced lipid peroxidation in testis (cytosol and mitochondria) and ES and increased ROS production as early as 5 days. Further, significant perturbations in the activities of antioxidant enzymes in testis/ES and enhanced protein carbonyl content were suggestive of increased oxidative stress during early diabetic phase. STZ-induced oxidative damage in both compartments was amenable for attenuation by treatment with oral supplements of either ascorbic acid (10 mg/(kg(bw) day)) or taurine (1 g/(kg(bw) day)). Furthermore, the oxidative impairments in testis/ES were persistent during the progressive phase (as measured at 2 and 4 weeks of sampling) and were associated with significant increase DNA damage (testis) and higher incidence of abnormal sperms. Interestingly, mating of STZ treated males sequentially for a period of 5 weeks with virgin untreated females resulted in a significant increase in the male-mediated dominant lethal-type mutations during the first 3 weeks, indicating a stage-specific genotoxic effect on post-meiotic germ cells. Based on the occurrence of oxidative impairments in STZ-treated mice both during both early and progressive phase, it is hypothesized that oxidative stress mechanisms may be wholly or in part contribute towards the development of testicular dysfunction and degeneration under situations of experimentally induced diabetes in animal models.     

Biomonitoring Hospital Effluents by the <Emphasis Type="Italic">Allium cepa</Emphasis> L. Test

Hospital effluents are serious problems in developing countries like Brazil, and when not treated adequately, can cause mutagenic effects on live organisms. Biomonitors, like Allium cepa L., which is one of the most used plant species when monitoring effluent genotoxicity, have been used to alert the world population about environmental contamination and genotoxic chemical emissions. The Allium cepa test was used to evaluate the genotoxicity of a hospital effluent in Santa Maria, Rio Grande do Sul State, Brazil. During the study, chromosomal disruptions, anaphasic bridges, and micronuclei during telophase were observed, indicating environmental toxicity risk.     

Genotoxicity studies on a high-purity rebaudioside A preparation

Rebaudioside A (Reb A) is a steviol glycoside isolated from the leaves of the Stevia rebaudiana plant. This non-nutritive, natural sweetener is reported to be 250–450 times sweeter than sucrose and has potential for wide use in the US diet, and is used in Japan and South America today. The safety of Reb A has been investigated in several recently published studies and information on genotoxicity is described herein. Reb A was investigated for its potential to induce genotoxicity in three in vitro and two in vivo assays (conducted according to OECD guidelines). Reb A was non-mutagenic in an Ames test using Salmonella typhimurium and Escherichia coli, in a chromosomal aberration test using Chinese Hamster V79 cells and in a mouse lymphoma assay using L5178Y+/− cells, all studies were conducted at concentrations up to 5000 μg/ml, with and without metabolic activation. Also, Reb A was non-genotoxic in a bone marrow micronucleus test in mice at doses up 750 mg/kg bw and in an unscheduled DNA synthesis test in rats at 2000 mg/kg bw. These studies provide additional evidence that Reb A is not genotoxic at the doses tested and further support the generally recognized as safe determination of Reb A.     

Cytotoxic, mutagenic and genotoxic effects of new anti-T. cruzi 5-phenylethenylbenzofuroxans. Contribution of phase I metabolites on the mutagenicity induction

5-Phenylethenylbenzofuroxans have displayed in vitro and in vivo activity against Trypanosoma cruzi, the etiologic agent of American Trypanosomiasis. On the basis of benzofuroxans pre-clinical studies we evaluated the potential of six 5-phenylethenyl derivatives to induce cytotoxicity, mutagenicity and genotoxicity using different in vitro models. Cytotoxic effects were evaluated using a set of cells, mammal pre-monocytic macrophages, V-79 lung fibroblast from Chinese hamster, and colorectal adenocarcinoma Caco-2 cells, in the MTT viability assay. Mutagenicity was tested in the Ames assay using Salmonella typhimurium TA98 strain with and without metabolic activation by S9-rat liver homogenate. The genotoxic potentials were evaluated with the alkaline single cell gel electrophoresis (comet assay) in V-79 cells. In view of the Ames test results we study whether the main mammals’ phase I metabolites, the corresponding o-nitroanilines, are involved in the mechanism of mutagenicity. These metabolites are produced by NADPH-dependent enzymes in cytosol and by xanthine oxidase and cytochrome P450 in microsomes from rat liver. Among them, the electronic property of phenyl substituent seems to be responsible for this effect. It could be pointed out that the equimolecular mixture of compounds 1 and 2 (5E- and 5Z-(2-phenylethenyl)benzofuroxan, respectively) could be used in further clinical studies as anti-T. cruzi drug.     

Application of toxicogenomics to study mechanisms of genotoxicity and carcinogenicity

Specific genotoxic events such as gene mutations and/or chromosome damage are considered hallmarks of cancer. The genotoxicity testing battery enables relatively simple, rapid and inexpensive hazard identification, namely by assessing a chemical's ability to cause genetic damage in cells. In addition, the 2-year rodent carcinogenicity bioassay provides an assessment of a risk associated with the chemical to develop cancer in animals. Although the link between genotoxicity and carcinogenicity is well documented, this relationship is complicated due to the impact of non-genotoxic mechanisms of carcinogenesis and by character of the in vitro genotoxicity assays and specific endpoints making the interpretation of test results in light of human risk and relevance difficult. In particular, the specificity of test results has been questioned. Therefore, the development of novel scientific approaches bridging genotoxicity and carcinogenicity testing via understanding underlying mechanisms is extremely important for facilitating cancer risk assessment. In this respect, toxicogenomics approaches are considered promising as these have the potential of providing generic insight in molecular pathway responses. The goal of this report thus is to review recent progress in the development and application of toxicogenomics to the derivation of genomic biomarkers associated with mechanisms of genotoxicity and carcinogenesis. Furthermore, the potential for application of genomic approaches to hazard identification and risk assessment is explored.     

Genotoxicity and composition of particulate matter from biomass burning in the eastern Brazilian Amazon region

In the present study Tradescantia pallida micronucleus (Trad-MCN) bioassay was used to assess the genotoxicity of particulate matter with a mass median aerodynamic diameter less than 10 μm (PM₁₀) in Tangara da Serra (MT), a Brazilian Amazon region that suffers the impact of biomass burning. The levels of PM (coarse and fine size fractions) and black carbon (BC) collected were also measured. Furthermore, the alkanes and polycyclic aromatic hydrocarbons (PAHs) were identified and quantified in the samples taken during the burning period by gas chromatography with flame ionization detection (GC-FID). The PM and BC results for both fractions indicate a strong correlation (p<0.001). The analysis of alkanes indicates an anthropic influence. Retene was the most abundant PAH found, an indicator of biomass burning, and 12 other PAHs considered to be potentially mutagenic and/or carcinogenic were identified in this sample. The Trad-MCN bioassay showed a significant increase in micronucleus frequency during the period of most intense burning, possibly related to the mutagenic PAHs that were found in such extracts. This study demonstrated that Trad-MCN was sensitive and efficient in evaluating the genotoxicity of organic compounds from biomass burning. It further emphasizes the importance of performing chemical analysis, because changes in chemical composition generally have a negative effect on many living organisms. This bioassay (ex situ), using T. pallida with chemical analysis, is thus recommended for characterizing the genotoxicity of air pollution.     

Aquilegia vulgaris extract protects against the oxidative stress and the mutagenic effects of cadmium in Balb/c mice

Cadmium (Cd) is a non-essential element and is a widespread environmental pollutant. Exposure to cadmium can result in cytotoxic, carcinogenic and mutagenic effects. The aim of the current work was to evaluate the protective effect of Aquilegia vulgaris extract against the oxidative stress and the genotoxicity induced by Cd using the chromosomal aberrations in somatic and germ cells assay and random amplified polymorphism DNA (RAPD-PCR) analysis. Forty male Balb/c mice were divided into four groups including the control group, Cd-treated group and the groups treated with the extract alone or plus Cd. The results indicated that Cd increased serum ALT, AST, urea, LDH, CK, lipid peroxidation in liver tissue accompanied with a significant decrease in GPX and SOD. Cd also increased the number of chromosomal aberrations in bone marrow and spermatocytes including structural and numerical aberrations. Animals treated with the extract alone were comparable to the control regarding all the tested parameters. The extract succeeded in preventing or diminishing the oxidative stress and the clastogenic effects of Cd. It could be concluded that Aquilegia vulgaris extract is a promising protective agent against oxidative stress and genotoxicity during the exposure to Cd.     

The Maillard reaction--illicite (bio)chemistry in tissues and food

We present a review of our early work on the Maillard reaction, at the interface of food chemistry and tissue biochemistry, as well as the reinterpretation of our early findings in the light of recent advances in the chemistry of the involved reactions. These concern specifically the role of lower aldehydes, produced during the glycolytic pathways and especially acetaldehyde. We also review some of our recent findings on the cytotoxic and genotoxic aspect of these “illicit” organic reactions, taking place in tissues (and also in food products) besides the genetically “programmed” metabolic pathways. Some recent results in organic-pharmaceutical chemistry confirm the potential importance of the reviewed reactions both in food chemistry and in tissues as well as the pathological importance of reactions taking place in tissues.     

Acute, subacute toxicity and genotoxic effect of a hydroethanolic extract of the cashew (Anacardium occidentale L.)

Anacardium occidentale L. (Anacardiaceae), popularly known as cajueiro is a native plant to Brazil, and largely used in popular medicine to treat ulcers, hypertension and diarrhea. In the present study, acute, 30-day subacute toxicity and genotoxicity assays were carried out. The crude extract did not produce toxic symptoms in rats in doses up to 2000 mg/kg. Based on biochemical analyses of renal and hepato-biliary functions, such as the level of urea, creatinine, transaminases and alkaline phosphatase, we determined that the extract is generally tolerated by rats. This was also confirmed by hematological and histopathological exams. Genotoxicity was accessed by the Ames test in Salmonella typhimurium strains TA97, TA98, TA100, TA102 and by the bone marrow micronucleus test in mice. The extract was shown to induce frameshift, base pair substitution and damage to the chromosomes. However, this effect was less deleterious than the clastogenic effect of ciclophosphamide.     

无患子皂苷遗传毒性的研究

目的：评价无患子皂苷的急性毒性和遗传毒性,为无患子皂苷的日常应用提供毒理学依据。方法通过急性经口毒性试验、哺乳动物红细胞微核试验、细菌回复突变试验和体外哺乳动物细胞染色体畸变试验,检测无患子皂苷对原核生物和真核生物在基因水平和染色体水平的诱变性。结果无患子皂苷的雌雄小鼠急性经口毒性LD50均为4640 mg/kg,可见流涎和黏液便等中毒体征。小鼠骨髓细胞微核试验各剂量组与阴性对照组比较,差异均无统计学意义（ P〉0.05）;Ames试验在加或不加S9各剂量组及菌株条件下的回变菌落数均未超过自发回变菌落数（阴性对照）的2倍以上,未观察到剂量-效应关系;染色体畸变试验无患子皂苷对CHL的IC50为75μg/mL,各剂量组与阴性对照组比较,差异均无统计学意义（ P〉0.05）。在上述各试验中,阳性对照组与阴性对照组比较,差异均有统计学意义（ P〈0.01）。结论在本实验条件下,无患子皂苷不具有遗传毒性。