Assessment of chromosomal aberration in the bone marrow cells of Swiss Albino mice treated by 4-methylimidazole

A systematic approach to evaluate plausible modes of actions for mouse lung tumors in mice exposed to 4-methylimidozole

The National Toxicology Program (NTP) reported that chronic dietary exposure to 4-methylimidazole (4-MeI) increased the incidence of lung adenomas/carcinomas beyond the normally high spontaneous rate in B6C3F1 mice. To examine plausible modes of action (MoAs) for mouse lung tumors (MLTs) upon exposure to high levels of 4-MeI, and their relevance in assessing human risk, a systematic approach was used to identify and evaluate mechanistic data (in vitro and in vivo) in the primary and secondary literature, along with high-throughput screening assay data. Study quality, relevance, and activity of mechanistic data identified across the evidence-base were organized according to key characteristics of carcinogens (KCCs) to identify potential key events in known or novel MLT MoAs. Integration of these evidence streams provided confirmation that 4-MeI lacks genotoxic and cytotoxic activity with some evidence to support a lack of mitogenic activity. Further evaluation of contextual and chemical-specific characteristics of 4-MeI was consequently undertaken. Due to lack of genotoxicity, along with transcriptomic and histopathological lung changes up to 28 and 90 days of exposure, the collective evidence suggests MLTs observed following exposure to high levels of 4-MeI develop at a late stage in the mouse chronic bioassay, albeit the exact MoA remains unclear.

Caramel colors in terms of scientific research, with particular consideration of their toxicity

Caramel colors, the most common food additives in the world, are divided into four classes (IIV), marked with the symbols E150 a-d, respectively. Individual classes of caramel colors differ from each other in physico-chemical properties and the method of preparation, which affects the formation of various compounds that are important for the assessment of food safety A number of studies on all caramel classes of have been performed, including toxicokinetic, genotoxic, carcinogenic and reproductive and developmental toxicity studies, which have not shown harmful effects of these additives at doses not exceeding ADI. However, there is an increasing number of scientific reports of the possible toxic effects present in caramels of low-molecular compounds. Currently, three compounds are considered to be toxicologically important and resulting from the possible concentration in the final product: 5-HMF (present in all classes), 4(5)-MeI (present in caramel classes III and IV) or THI (present in caramel class III). 4(5)-MeI has a neurotoxic effect and was considered in 2011 as a possible human carcinogen (class 2B, according to IARC). In the case of THI, studies have confirmed its lymphopenic activity, probably secondary to its immunosuppressive effect. Consequently, in the 1980s, JECFA set acceptable levels 4(5)-MeI and THI, for the caramel classes in which these compounds may be present. The toxicity of 5-HMF has not been confirmed unequivocally, but studies have shown that this compound is not neutral to living organisms. Currently, most international organizations and scientific institutes recognize these additives as safe for consumers, but at the same time scientists emphasize the need for further research.

A weight of evidence assessment of the genotoxic potential of 4-methylimidazole as a possible mode of action for the formation of lung tumors in exposed mice

4-Methylimidazole (4-MeI) is a byproduct formed during the cooking of foods containing carbohydrates and amino acids, including the production of flavors and coloring substances, e.g., class III and IV caramel colors, used in many food products with extensive human exposure. Two-year rodent bioassays via oral exposure conducted by the National Toxicology Program reported evidence of carcinogenicity only in B6C3F₁ mice (increased alveolar/bronchial neoplasms). In 2011, the International Agency for Research on Cancer classified 4-MeI as Group 2B, "possibly carcinogenic to humans". An expert panel was commissioned to assess the genotoxic potential of 4-MeI and the plausibility of a genotoxic mode of action in the formation of lung tumors in mice when exposed to high doses of 4-MeI. The panel defined and used a weight-of-evidence (WOE) approach that included thorough evaluation of studies assessing the genotoxic potential of 4-MeI. The panelists categorized each study, consisting of study weight, degree of technical performance, study reliability, and contribution to the overall WOE. Based on the reviewed studies' weighted contribution, the panel unanimously concluded that the WOE supports no clear evidence of in vivo genotoxicity of 4-MeI and no association for a genotoxic mode of action in the formation of mouse lung tumors.

Food Safety and Nutraceutical Potential of Caramel Colour Class IV Using In Vivo and In Vitro Assays

Nutraceutical activity of food is analysed to promote the healthy characteristics of diet where additives are highly used. Caramel is one of the most worldwide consumed additives and it is produced by heating natural carbohydrates. The aim of this study was to evaluate the food safety and the possible nutraceutical potential of caramel colour class IV (CAR). For this purpose, in vivo toxicity/antitoxicity, genotoxicity/antigenotoxicity and longevity assays were performed using the Drosophila melanogaster model. In addition, cytotoxicity, internucleosomal DNA fragmentation, single cell gel electrophoresis and methylation status assays were conducted in the in vitro HL-60 human leukaemia cell line. Our results reported that CAR was neither toxic nor genotoxic and showed antigenotoxic effects in Drosophila. Furthermore, CAR induced cytotoxicity and hipomethylated sat-α repetitive element using HL-60 cell line. In conclusion, the food safety of CAR was demonstrated, since Lethal Dose 50 (LD₅₀) was not reached in toxicity assay and any of the tested concentrations induced mutation rates higher than that of the concurrent control in D. melanogaster. On the other hand, CAR protected DNA from oxidative stress provided by hydrogen peroxide in Drosophila. Moreover, CAR showed chemopreventive activity and modified the methylation status of HL-60 cell line. Nevertheless, much more information about the mechanisms of gene therapies related to epigenetic modulation by food is necessary.

Evaluation of in vitro and in vivo genotoxic and antigenotoxic effects of Rhus coriaria

Rhus coriaria has been important in the treatment of many diseases in traditional use. In this content, the genotoxic, antigenotoxic, and oxidative stress effects of methanol extract of R. coriaria (RCE) were investigated in this study. Two hundred fifty, 500, or 750 µg/mL concentrations of RCE were not found to have DNA damaging effect on pET22-b(+) plasmid and were unable to induce micronuclei in human lymphocytes (24 or 48 h treatment period). However, it did not inhibit the genotoxic effect of mitomycin-c (0.25 µg/mL). Cytotoxic effects of RCE were investigated using mitotic index (MI) and nuclear division index (NDI). Five hundred, 1000, and 2000 mg/kg concentrations of RCE did not induce chromosome aberrations in rat bone marrow cells for 12 or 24 h treatment period. In addition, 2000 mg/kg concentration of RCE showed an antigenotoxic effect by decreasing to genotoxic effect of 400 mg/kg urethane at 12 and 24 h treatment periods. RCE showed cytotoxic effects by significantly decreasing NDI. Moreover, RCE increased cytotoxic effect of Mitomycin C (MMC). However, RCE did not induce cytotoxicity in rat bone marrow cells. The highest concentration of RCE reduced total oxidant level in 12 h treatment. Interestingly, the lowest total oxidant level was found in rats blood treated with the lowest concentration RCE and urethane together. Thousand and 2000 mg/kg concentrations of RCE decreased total antioxidant levels of rat blood at 24 h treatment period. Our results showed that RCE possess cytotoxic effect in short-term treatments in vitro. However, it does not demonstrate genotoxic or cytotoxic effects in vivo.