Low-dose microcystin-LR antagonizes aflatoxin B1 induced hepatocarcinogenesis through decreasing cytochrome P450 1A2 expression and aflatoxin B1-DNA adduct generation.

Aflatoxin B1 (AFB1) and microcystin-LR (MC-LR) co-existed in food and water, and were associated with hepatocellular carcinoma (HCC). AFB1 induced HCC by activating oxidative stress and generating AFB1-DNA adducts, while MC-LR could promote HCC progression. However, whether they have co-effects in HCC progression remains uncertain. In this study, we found the antagonistic effects of MC-LR on AFB1 induced HCC when they were exposed simultaneously. Compared with single exposure to AFB1, co-exposed to MC-LR significantly repressed the AFB1 induced malignant transformation of human hepatic cells and the glutathione S-transferase Pi positive foci formation in rat livers. MC-LR inhibited AFB1 induced upregulation of cytochrome P450 family 1 subfamily A member 2 (CYP1A2) and reduced the AFB1-DNA adducts generation in both human hepatic cells and rat livers. These results suggest that when co-exposure with AFB1, MC-LR might repress hepatocarcinogenicity of AFB1, which might be associated with its repression on AFB1 induced CYP1A2 upregulation and activation.