Toxicity and carcinogenicity studies of 4-methylimidazole in F344/N rats and B6C3F1 mice

Cytotoxicity and mutagenicity of cola and grape flavored soft drinks in bone marrow cells of rodents

Due to the large consumption of soft drinks in Brazil and worldwide in recent years and considering that some of the components present in their composition pose potential risks to human health, the aim of this study was to evaluate the cytotoxic and mutagenic potential of specific cola and grape-flavored soft drink brands. Bone marrow cells of Wistar rats were initially treated by gavage with one single dose of Cola or Grape soft drink, which was next offered ad libitum (instead of water) for 24 hours. A negative control treatment was performed by administering one single dose of water and a positive control administering cyclophosphamide intraperitoneally. Statistical analysis showed that the Cola and Grape soft drinks studied were not cytotoxic. However, the Cola soft drink proved mutagenic in this experiment treatment time. Therefore, this study serves as a warning about the consumption of Cola-flavored soft drink and for the need for further subchronic and chronic studies on soft drinks in order to evaluate the long term mutagenic and cytotoxic effects of these substances.

Carcinogenic 4(5)-methylimidazole found in beverages, sauces, and caramel colors: chemical properties, analysis, and biological activities

Since the National Toxicology Program (NTP) identified 4(5)-methylimidazole [4(5)-MI] as a cancer causing chemical in 2007 and the State of California added it to the Proposition 65 list of compounds as a carcinogen on January 7, 2011, many researchers and regulatory agencies have become focused on the presence of 4(5)-MI in foods and beverages. 4(5)-MI has been known to form in the Maillard reaction system consisting of a sugar and ammonia-a typical caramel-color preparation method for beverages. 4(5)-MI is identified in various beverages and sauces, which are colored with caramel, as well as in caramel color itself. Analysis of 4(5)-MI is extremely difficult due to its high water solubility, but the analytical method for 4(5)-MI has progressed from conventional paper chromatography, gas chromatography, and gas chromatography-mass spectrometry to the most advanced high-performance liquid chromatography-mass spectrometry. Various studies indicate that caramel colors and carbonated beverages contain 4(5)-MI in levels ranging from 0 to around 1000 ppm and from 0 to about 500 ppm, respectively. Reports of the toxicity of 4(5)-MI at relatively high levels suggest that it may cause some adverse effects on human consumers.

Carcinogenicity and regulation of caramel colorings

2- and 4-methylimidazoles are present as contaminants in caramel colorings manufactured with ammonia catalysts. Both contaminants have been shown to induce cancer in animals and may be present in caramel colorings in amounts that exceed federal guidelines. California requires warning notices on products that could lead to consumption of more than 30 micrograms per day. The US Food and Drug Administration should bar the use of excessively contaminated caramel coloring in food.

Formation of carcinogenic 4(5)-methylimidazole in Maillard reaction systems

4(5)-Methylimidazole has received the attention of federal and state regulatory agencies because of its carcinogenicity and common presence in foods and beverages. In the present study, the formation of 4(5)-methylimidazole in Maillard reaction model systems consisting of D-glucose/NH(3), L-rhamnose/NH(3), methylglyoxal/NH(3), and methylglyoxal/formaldehyde/NH(3) was investigated. 4(5)-Methylimidazole was formed at levels ranging from 0.49 to 0.71 mg/mL in the d-glucose/NH(3) model system. The formation of 4(5)-methylimidazole was slightly higher in the L-rhamnose/NH(3) system (0.91 mg/mL) than in the d-glucose/NH(3) system (0.71 mg/mL) under the conditions used in the present study. A methylglyoxal/NH(3) system produced significantly higher levels of 4(5)-methylimidazole (5.70 mg/mL), suggesting that methylglyoxal is an important precursor of 4(5)-methylimidazole. Ammonolysis of methylglyoxal, which is one of the glucose degradation products, was proposed to form formamide, which subsequently reacted with 2-aminopropanal (α-aminocarbonyl intermediate) formed from methylglyoxal to give 4- or 5-methylimidazole. The levels of 4(5)-methylimidazole found in commercial cola soft drinks range from 0.30 μg/mL (brand 3) to 0.36 μg/mL (brands 1 and 5).

Early toxicology signal generation in the mouse

The rat has been the preferred rodent toxicology species since before regulatory requirements have been in place, and there exists in the pharmaceutical industry and the regulatory agencies a significant amount of historical data for the rat. The resulting experience base with the rat makes the possibility of replacing it with the mouse for regulated toxicology studies untenable for all but the most extreme circumstances. However, toxicologists are very familiar with the mouse as a model for chronic carcinogenicity studies, and there exist multiple preclinical mouse models of disease. The authors evaluated the use of the mouse for early in vivo toxicology signal generation and prioritization of small molecule lead compounds prior to nomination of a development candidate. In five-day oral gavage studies with three test agents in the mouse, the authors were able to identify the same dose-limiting toxicities as those identified in the rat, including examples of compound-mediated hemolysis as well as microscopic lesions in the alimentary canal, kidney, and pancreas. Performing early signal generation studies in the mouse allows for earlier assessment of the safety liabilities of small molecules, requires significantly less compound, and allows evaluation of more compounds earlier in the project's life cycle.

Effects of 4-methylimidazole on cerebral glutamate decarboxylase activity and specific GABA receptor binding in mice

4-Methylimidazole (4MeI) is a tremorogenic and convulsive agent of concern both in human and veterinary toxicology. The in vitro effects of 4MeI (5 μM–20 mM) on cerebral glutamate decarboxylase (GAD) activity and (in concentrations up to 50 mM) on binding of [³H]GABA to cerebral GABA receptors were tested in brain tissue from B6D2 mice. The effects of 1-methylimidazole (1MeI), 2-methylimidazole (2MeI), 4-methylhydroxy-imidazole (4MeOHI), imidazole-4-aceticacid (4AcI) (all in concentrations of 5–20 mM) and imidazole (20 mM) on GAD activity were also tested. In addition, the effect of a lethal dose of 4MeI (250 mg/kg ip) to B6D2 mice in vivo on the postmortem concentrations of γ-aminobutyric acid (GABA) and glutamate in their brains were measured. In all experiments, student's t-test was used for statistical comparison. 4MeI in concentrations of 2 mM and above did inhibit GAD activity significantly in vitro, but glutamate and GABA concentrations in mouse brains after lethal 4MeI poisoning were not significantly different from control values. The effect of 2MeI on GAD activity was stronger than the effect of 4MeI. Binding of [³H]GABA to cerebral GABA receptors in vitro was significantly inhibited only at 4MeI concentrations of 5 mM and above. The results indicate that neither inhibition of GABA synthesis nor competitive inhibition of the binding of GABA to its receptors are likely mechanisms for the excitation and convulsions seen in 4MeI poisoning in animals.