Uptake and Metabolism of 5,7-Dimethoxyflavone, a Potential Chemopreventive Compound, in Fundulus heteroclitus

Petra A. Tsuji¹, Danielle Thiebault¹, Richard N. Winn² and Thomas Walle¹

¹ Marine Biomedicine and Environmental Sciences Center, Medical University of South Carolina, Charleston, SC

 ² Aquatic Biotechnology & Environmental Laboratory, University of Georgia, Athens, GA

Polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (BaP) are ubiquitous environmental pollutants to which humans as well as marine organisms are exposed, and which may result in DNA-binding and tumor formation. Exposure to BaP in fish and recently also in humans has been linked to liver cancer. Since fish and mammals respond similarly to PAHs on a biochemical level, fish, such as Fundulus heteroclitus, a well-investigated small and abundant marine teleost, may be used as sensitive model organisms to investigate biochemical processes involved in chemical carcinogenesis and prevention thereof.

It is our hypothesis that methoxylated flavonoids, such as 5,7-Dimethoxyflavone (DMF), play a chemopreventive role in BaP-induced carcinogenesis by acting on carcinogen-metabolizing enzymes, including cytochrome P450 1A1.

 To determine the protective properties of DMF on BaP-activating enzymes in vitro and in vivo using F. heteroclitus, we first needed to determine uptake, accumulation and potential metabolism of DMF in this species in vivo.

F. heteroclitus were exposed to 20 μM DMF for 8 hours. Uptake and metabolism were investigated using reverse-phase HPLC and LC/MS. Based on comparative HPLC UV-spectra, associated absorption maxima, known molecular weights, retention times and LC/MS data, we conclude that DMF is efficiently taken up and accumulates 40 to 100-fold in tissues of F. heteroclitus. This fish species metabolizes the parent compound DMF in vivo through glucuronidation, excreting two major metabolites in its bile. Fish bile samples were also analyzed for sulfate metabolites; however, none were detected. In our future studies we will expose