Enhancing effects of carbon tetrachloride on in vivo mutagenicity in the liver of mice fed 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx)

Abstract

-Chronic stimulus subsequent to cell injury plays an important role in cancer development, but the precise mechanisms remain unknown partly because appropriate animal models are lacking. In the present study, the effects of hepatotoxicant carbon tetrachloride (CCl 4 ) on in vivo mutagenicity were investigated using gpt delta mice with or without p53. Female B6C3F 1 p53-proficient or -deficient gpt delta mice were given a diet containing 300 ppm of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) for 13 weeks, concurrently with intraperitoneal injection of 1 ml/kg CCl 4 solution once a week. Mutant frequencies of gpt and red/gam in p53-proficient mice fed MeIQx were both significantly elevated by CCl 4 co-treatment. Enhancing effects of CCl 4 treatment were also noted in p53-deficient mice. In the mutation spectra analysis of gpt mutant colonies, G:C to T:A transversions were predominantly observed regardless of CCl 4 injection, and clonal expansion of gpt colonies were increased in the co-treated group as compared with MeIQx alone group. The present data showing no significant changes in mRNA expression levels of CYP1A2 and GSTa4 between MeIQx-treated groups with and without CCl 4 . In the Western blotting analysis, CYP1A2 protein levels were significantly decreased in the co-treated group as compared to MeIQx alone group, and GSTα protein levels were not changed among any groups. It is suggested that the mutant frequency by co-treatment with CCl 4 might result from some factors other than p53 or MeIQx metabolism/excretion. Thus, our data clearly demonstrate that this model could be a powerful tool for identifying the mechanisms underlying combinatorial effects on carcinogenesis.

Gene expression profiling using DNA microarray analysis of the cerebellum of mice treated with methylmercury

“…The total RNA from the cerebellum samples was isolated using the Isogen kit (Nippon gene, Tokyo, Japan) according to the manufacturer's protocol (Okamura et al, 2010). The first strand of cDNA was synthesized using the PrimeScript TM RT reagent kit (Takara, Shiga, Japan).…”

Mutagenicity of carcinogenic heterocyclic amines in Salmonella typhimurium YG strains and transgenic rodents including gpt delta

“…CCl 4 treatments enhanced MF even in the p53-deficient background. [ 138 ] 9-(4′-aminophenyl)-9 H -pyrido[3,4- b ]indole (aminophenylnorharman, APNH) C57 BL6/J mice male diet for 12 weeks gpt and Spi − liver 10 ppm + G:C to T:A transversions, followed by G:C to A:T transitions, were the most frequent mutations detected by gpt assay. Single G deletions in run sequences were detected by Spi − selection.…”

Possible Carcinogenic Mechanisms Underlying Renal Carcinogens in Food

“…Such assays are promising tools for investigating the relationship between chemical genotoxicity and carcinogenicity. As additional analyses, various factors related to chemical carcinogenesis, such as DNA modifications, oxidative stress, cell proliferation and metabolic enzyme activities can also be measured in transgenic rodents [4][5][6][7][8][9][10][11] . This review focuses on reported renal carcinogens found in natural products such as d-limonene and aristolochic acid (AA), food additives such as potassium bromate (KBrO 3 ) and madder color (MC), and mycotoxins such as ochratoxin A (OTA) and citrinin (CTN).…”