Repeated-dose liver and gastrointestinal tract micronucleus assays with CI Solvent Yellow 14 (Sudan I) using young adult rats

Toxic effects of Arianor Ebony hair dye on human cells

To evaluate the risks of hair dye exposure, we investigated cellular and molecular effects of Arianor Ebony dye, which is a mixture of azo and anthraquinone dyes, used in the composition of the black color. Cytotoxicity, genotoxicity, and gene expression of relevant molecules of apoptotic and oxidative stress mechanisms were investigated in HepG2 cells exposed to Arianor Ebony. Results showed that the dye did not induce cytotoxicity to exposed cells at a concentration up to 50 µg/mL compared to the negative control. However, genotoxic assays indicated that the dye was able to damage the genetic material at a concentration of 25 µg/mL, with induction factor values of exposed cells two- to five-fold higher than those recorded for the negative control. Moreover, the lowest observed effect concentration was 12.5 µg/mL. For gene expression, relevant changes were observed in cytochrome c and caspase 9, which decreased in cells incubated with the dye in a dose-dependent manner when compared with the negative control. In parallel, the expression of genes for antioxidant enzymes was increased in exposed cells, suggesting the presence of metabolic routes that protect cells against the toxic effect of the dye, avoiding exacerbated cellular death. Results suggested that the dye disrupted cellular homeostasis through mitochondrial dysfunction, which may be hazardous to human health. Thus, further investigations are necessary to deeply understand the mechanisms of action of the dye, considering its toxic potential found in our ex vivo assays.

Detection of hepatocarcinogens by combination of liver micronucleus assay and histopathological examination in 2-week or 4-week repeated dose studies

Background

Currently, revisions to the ICH S1 guidance on rodent carcinogenicity testing are being proposed. Application of this approach would reduce the use of animals in accordance with the 3Rs principles (reduce/refine/replace). The method would also shift resources to focus on more scientific mechanism-based carcinogenicity assessments and promote safe and ethical development of new small molecule pharmaceuticals. In the revised draft, findings such as cellular hypertrophy, diffuse and/or focal cellular hyperplasia, persistent tissue injury and/or chronic inflammation, preneoplastic changes, and tumors are listed as histopathology findings of particular interest for identifying carcinogenic potential. In order to predict hepatocarcinogenicity of test chemicals based on the results from 2- or 4-week repeated dose studies, we retrospectively reanalyzed the results of a previous collaborative study on the liver micronucleus assay. We focused on liver micronucleus induction in combination with histopathological changes including hypertrophy, proliferation of oval cells or bile duct epithelial cells, tissue injuries, regenerative changes, and inflammatory changes as the early responses of hepatocarcinogenesis. For these early responses, A total of 20 carcinogens, including 14 genotoxic hepatocarcinogens (Group A) and 6 non-liver-targeted genotoxic carcinogens (Group B) were evaluated.

Results

In the Group A chemicals, 5 chemicals (NPYR, MDA, NDPA, 2,6-DNT, and NMOR) showed all of the 6 early responses in hepatocarcinogenesis. Five chemicals (DMN, 2,4-DNT, QUN, 2-AAF, and TAA) showed 4 responses, and 4 chemicals (DAB, 2-NP, MCT, and Sudan I) showed 3 responses. All chemicals exhibited at least 3 early responses.

Contrarily, in the Group B chemicals (6 chemicals), 3 of the 6 early responses were observed in 1 chemical (MNNG). No more than two responses were observed in 3 chemicals (MMC, MMS, and KA), and no responses were observed in 2 chemicals (CP and KBrO3).

Conclusion

Evaluation of liver micronucleus induction in combination with histopathological examination is useful for detecting hepatocarcinogens. This assay takes much less time than routine long-term carcinogenicity studies.

Evaluation of the novel liver micronucleus assay using formalin-fixed tissues

Background

The repeated-dose liver micronucleus (RDLMN) assay is an effective and important in vivo test for detecting genotoxic compounds, particularly for those that require metabolic activation to show genotoxicity. In a collaborative study by the Collaborative Study Group for the Micronucleus Test (CSGMT)/The Japanese Environmental Mutagen Society (JEMS) – Mammalian Mutagenicity Study Group (MMS), micronucleus induction of 22 chemicals with the RDLMN assay employing the collagenase digestion method was examined and reported on. Recently, we have developed a method which enables retrospective evaluation of micronucleus induction in formalin-fixed liver tissues (the formalin-fixed method) obtained in general toxicity studies completed in the past. Using this method, we were able to easily evaluate clastogenic potential of chemicals from the formalin-fixed tissues obtained in the general toxicity studies.

In this study, to evaluate the usefulness of the formalin-fixed method, we have conducted a liver micronucleus assay using the formalin-fixed liver samples obtained from the above collaborative study (18 of 22 test chemicals) and carried out a comparison with the results obtained by the collagenase digestion method.

Results

Comparison of the collagenase digestion and formalin-fixed methods was conducted using the results of the micronucleus assays with a total of 18 test chemicals which included 12 genotoxic hepatocarcinogens (Group A), 4 genotoxic carcinogens but not liver targeted (Group B), and 2 nongenotoxic hepatocarcinogens (Group C). The formalin-fixed method obtained the similar results as the collagenase digestion method in 10 out of the 12 chemicals of Group A, and all chemicals of Group B and Group C. Although the results were statistically contradictive due to different levels of concurrent negative control, the 2 other chemicals of Group A showed comparable responses between the two methods.

Conclusion

The present study shows that the formalin-fixed method is capable of detecting liver carcinogens with sensitivity equal to or higher than that of the collagenase digestion method. We recommend use of the formalin-fixed method because of its capability of enabling retrospective evaluation of micronucleus induction in the formalin-fixed liver tissues obtained in general toxicity studies completed in the past.

Adsorption behavior of Sudan I-IV on a coastal soil and their forecasted biogeochemical cycles

Sudan I-IV as synthetic azo dyes have been concerned worldwide and ever caused a panic on food safety because of illegal addition into foodstuffs. In the past decades, various methods are being developed to identify and determine Sudan dyes in foodstuffs. However, relevant studies about their biogeochemical behaviors and potential environmental effects are rarely reported, although it is of great importance and necessity accounting for their potential environmental contamination from various sources. In this work, the experimental studies on adsorption behavior of Sudan I-IV acting on soil (10, 25, 50, 75, and 100 mg/L) were carried out, and their transport in soil compartments and between soil-water, and air-soil interfaces were discussed. Results showed that the amount of Sudan I-IV adsorbed on soil increased accordingly with the increasing concentration of Sudan dyes in aqueous solution, and Sudan II and IV were more likely adsorbed on the tested soils than Sudan I and III based on their maximum adsorption amount. However, for Sudan I, III, and IV, in some high concentrations (under the treatment of 75 mg/L for Sudan III, 100 mg/L for Sudan I and IV), the adsorption was significantly increased, and then came back to the "normal" level (under the treatment of 100 mg/L for Sudan III). It is expected that relevant researches on their biogeochemical behaviors in soil compartments, and between soil-water and air-soil interfaces would be concerned and addressed.