benzofurans and Hepatoblastoma

Usnic acid, a natural botanical product, is a constituent of some dietary supplements used for weight loss. It has been associated with clinical hepatotoxicity leading to liver failure in humans. The present study was undertaken for metabolism and toxicity evaluations of usnic acid in human hepatoblastoma HepG2 cells in culture. The cells were treated with the vehicle control and usnic acid at concentrations of 0-100 µm for 24 h at 37 °C in 5% CO2 . Following the treatment period, the cells were evaluated by biochemical and toxicogenomic endpoints of toxicity that included cytochrome P450 activity, cytotoxicity, oxidative stress, mitochondrial dysfunction and changes in pathway focused gene expression profiles. Usnic acid exposure resulted in increased P450 activity, cytotoxicity, oxidative stress and mitochondrial dysfunction in HepG2 cells. The pathway-focused gene expression analysis resulted in significantly altered expression of six genes out of a total of 84 genes examined. Of the six altered genes, three genes were up-regulated and three genes down-regulated. A marked up-regulation of one gene CCL21 associated with inflammation, one gene CCNC associated with proliferation and carcinogenesis and one gene UGT1A4 associated with metabolism as well as DNA damage and repair were observed in the usnic acid-treated cells compared with the vehicle control. Also a marked down-regulation of one gene CSF2 associated with inflammation and two genes (CYP7A1 and CYP2E1) associated with oxidative metabolic stress were observed in the usnic acid-treated cells compared with the control. The biomarkers used in this study demonstrate the toxicity of usnic acid in human hepatoblastoma HepG2 cells, suggesting an oxidative mechanism of action.

Topics: Anti-Infective Agents; Anti-Obesity Agents; Benzofurans; Biomarkers; Cell Survival; Cytochrome P-450 Enzyme System; Gene Expression; Hep G2 Cells; Hepatoblastoma; Hepatocytes; Humans; Liver Neoplasms; Membrane Potential, Mitochondrial; Mitochondria, Liver; Mitochondrial Diseases; Oxidative Stress

To identify the novel inhibitor of de novo lipogenesis in hepatocytes, we screened for inhibitory activity of triglyceride (TG) synthesis using [14C]acetate in the human hepatoma cell line, HepG2. Using this assay system we discovered the novel compound, benzofuranyl alpha-pyrone (TEI-B00422). TEI-B00422 also inhibited the incorporation of acetate into the triglyceride (TG) fraction in rat primary hepatocytes. In HepG2 cells, the incorporation of oleate into TG was unaffected. TEI-B00422 inhibited rat hepatic acetyl-CoA carboxylase (ACC), K(i)=3.3 microM, in a competitive manner with respect to acety-CoA but not fatty acid synthase and acyl-CoA transferase/diacylglycerol. Thus, these results suggest that the inhibition of TG synthesis by TEI-B00422 is based on the inhibitory action of ACC. The structure of TEI-B00422 is totally different from the known inhibitors of ACC and may be useful in the development of therapeutic agents to combat a number of metabolic disorders.

Topics: Acetyl Coenzyme A; Animals; Benzofurans; Cell Line; Enzyme Inhibitors; Fatty Acids; Hepatoblastoma; Hepatocytes; Humans; Liver Neoplasms; Pyrones; Rats