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As susceptibility to carcinogens varies considerably among different strains of experimental animals, evaluation of dose-response relationships for genotoxic carcinogen in different strains is indispensable for risk assessment. Potassium bromate (KBrO3) is a genotoxic carcinogen inducing kidney cancers at high doses in male F344 rats, but little is known about its carcinogenic effects in other strains of rats. The purpose of the present study was to determine dose-response relationships for carcinogenic effects of KBrO3 on N-ethyl-N-hydroxyethylnitrosamine (EHEN)—induced kidney carcinogenesis in male Wistar rats. We found that KBrO3 showed significant enhancement effects on EHEN-induced kidney carcinogenesis at above 250 ppm but not at doses of 125 ppm and below when evaluated in terms of induction of either preneoplastic lesions or tumors in male Wistar rats. Furthermore, KBrO3 significantly increased the formation of oxidative DNA damage at doses of 125 and above but not at doses of 30 ppm and below in kidneys. These results demonstrated that low doses of KBrO3 exert no effects on development of EHEN-initiated kidney lesions and induction of oxidative DNA damage. Taking account of previous similar findings in male F344 rats, it is strongly suggested that a threshold dose exists for enhancement effects of KBrO3 on kidney carcinogenesis in rats. [ABSTRACT FROM PUBLISHER]

We investigated the suppressive effect of lactic acid bacteria (LAB) isolated from traditional South Asian fermented milk 'dahi' on the development of atopic dermatitis (AD) using NC/Nga AD model mice. In the initial evaluation, we confirmed the effect of LAB on serum total IgE using ovalbumin (OVA)-induced type 1 allergy model mice. Forty-one bacterial strains isolated from dahi were evaluated for their ability to induce interleukin (IL)-12 production and suppress IL-4 production in splenocytes obtained from OVA-sensitized mice. Of the 41 strains tested, Lactobacillus delbrueckii subsp. lactis R-037 exhibited the greatest IL-12 induction, suggesting that it is a potent Th1 inducer. Oral administration of heat-treated R-037 significantly suppressed the elevation of serum total IgE in OVA-induced type 1 allergy model mice. In NC/Nga AD model mice, oral administration of heat-treated R-037 reduced inflammatory auricular thickness and alleviated the AD clinical score although the effect on serum total IgE level was unclear. Histopathological findings showed a tendency toward improvement of inflammation. Hyperkeratosis in particular showed improvement in dermatitis skin lesions. These results suggest that oral administration of R-037 may alleviate AD.

Reactive oxygen species cause damage to proteins, lipids and DNA. Coenzyme Q10 (CoQ10) is a compound with mitochondrial bioenergetic functions. The reduced form of CoQ10 shows antioxidant activity. In the present study, effects of CoQ10 on development of azoxymethane (AOM)-induced aberrant crypt foci (ACF) and mucin-depleted foci (MDF) in F344 male rats were investigated. To induce ACF and MDF, 6-week old rats were given two weekly subcutaneous injections of AOM (15 mg/kg body weight) and also received a control diet or experimental diets containing CoQ10 (200 or 500 ppm) for 4 weeks, starting one day before the first dose of AOM. At 10 weeks of age, all animals were sacrificed and their colons were evaluated for numbers and sizes of ACF and MDF. Administration of 200 and 500 ppm CoQ10 resulted in reduction of ACF numbers, to 77% and 68% of the carcinogen control value, respectively. The percentages of ACF consisting of more than 4 crypts in these groups were also significantly lower than in the controls. Treatment with 500 ppm CoQ10 furthermore decreased the number of sialomucin-producing ACF and MDF per colon to 42% and 38% of the carcinogen control value without CoQ10, respectively. These results suggest that CoQ10 may be an effective chemopreventive agent against colon carcinogenesis.