Chemoprevention opens new perspectives in the prevention of
cancer and other degenerative diseases. Use of target-organ
biological models at the histological and genetic levels can markedly facilitate the identification of such potential chemopreventive agents.
Colon cancer is one of the highest incidence rates throughout the world and some evidences have indicated
carotenoids as possible agents that decrease the risk of
colorectal cancer. In the present study, we evaluate the activity of
annatto (Bixa orellana L.), a natural food colorant rich in
carotenoid, on the formation of
aberrant crypt foci (ACF) induced by
dimethylhydrazine (
DMH) in rat colon. Further, we investigate, the effect of
annatto on
DMH-induced DNA damage, by the comet assay. Male Wistar rats were given s.c.
injections of
DMH (40 mg/kg body wt.) twice a week for 2 weeks to induce ACF. They also received experimental diets containing
annatto at 20, 200 or 1000 ppm for five 5 weeks before (pre-treatment), or 10 weeks after (post-treatment)
DMH treatment. In both protocols the rats were sacrificed on week 15th. For the comet assay, the animals were fed with the same experimental diets for 2 weeks. Four hours before the sacrifice, the animals received an s.c. injection of
DMH (40 mg/kg body wt.). Under such conditions, dietary administration of 1000 ppm
annatto neither induce DNA damage in blood and colon cells nor
aberrant crypt foci in rat distal colon. Conversely,
annatto was successful in inhibiting the number of crypts/colon (animal), but not in the incidence of
DMH-induced ACF, mainly when administered after
DMH. However, no antigenotoxic effect was observed in colon cells. These findings suggest possible chemopreventive effects of
annatto through their modulation of the cryptal cell proliferation but not at the initiation stage of colon
carcinogenesis.