Inhibition Activities of Fish Oil in iNOs, COX-2, and β-Catenin Expressions in Colorectal Preneoplasia of Mice Induced by Azoxymetane and Dextran Sodium Sulfate

Abstract

Epidemiological studies of the relationship between dietary fish oil and risk of colorectal cancer have been inconsistent. The present study was conducted in order to determine the inhibitory effect of fish oil on inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, and β-catenin expressions in the colorectal preneoplasia development of mice induced by azoxymetane (AOM) and dextran sodium sulfate (DSS). In this study, balb/c mice was injected intraperitoneally by a single dose of 10 mg/kg of body weight AOM followed by administered of 1% DSS during a week in drinking water. Fish oil was administered orally in three different doses (1.5 mg/ low dose, 3 mg/ medium dose and 6 mg/high dose) in each group of mice per day until the mice were terminated. The expression of iNOs, COX-2, and β-catenin were observed in the epithelial cells of colon mucosa crypts. In the second month, the iNOs expression was decreased in the medium and high groups of fish oil. In the third and fourth month, decreasing of the iNOs expression were observed in all groups (p<0.05). The COX-2 expression was decreased in the medium and high groups on the second month. The expression of β-catenin was also decreased in the medium group on the fourth month. The inhibition effect of high dose of fish oil on β-catenin was observed on the third month. In conclusion, administration of medium dose of fish oil in mice induced by AOM/DSS was the most effective dose to decreased the expression of iNOs, COX-2, and β-catenin in the second month.