Novel Bioactivation Pathway of Benzbromarone Mediated by Cytochrome P450

ABSTRACT Benzbromarone (BBR) is a hepatotoxic drug, but the detailed mechanism of its toxicity remains unknown. We identified 2,6-dibromohydroquinone (DBH) and mono-debrominated catechol (2-ethyl-3-(3-bromo-4,5-dihydroxybenzoyl)benzofuran; CAT) as novel metabolites of BBR in rat and human liver microsomal systems by comparison with chemically synthesized authentic compounds, and we also elucidated that DBH is formed by cytochrome P450 2C9 and that CAT is formed mainly by CYP1A1, 2D6, 2E1, and 3A4. Furthermore, CAT, DBH, and the oxidized form of DBH are highly cytotoxic in HepG2 compared with BBR. Taken together, our data demonstrate that DBH, a novel reactive metabolite, may be relevant to BBR-induced hepatotoxicity

Licochalcone A Potently Inhibits Tumor Necrosis Factor ␣- Induced Nuclear Factor-B Activation through the Direct Inhibition of IB Kinase Complex Activation

ABSTRACT Glycyrrhiza inflata has been used as a traditional medicine with anti-inflammatory activity; however, its mechanism has not been fully understood. Licochalcone A is a major and biogenetically characteristic chalcone isolated from G. inflata. Here, we found that licochalcone A strongly inhibited tumor necrosis (TNF)-␣-induced nuclear localization, DNA binding activity, and the transcriptional activity of nuclear factor-B (NF-B). Whereas licochalcone A had no effect on the recruitment of receptor-interacting protein 1 and IB kinase ␤ (IKK␤) to TNF receptor I by TNF-␣, it significantly inhibited TNF-␣-induced IB kinase complex (IKK) activation and inhibitor of nuclear factor-B degradation. It is interesting that we found that the cysteine residue at position 179 of IKK␤ is essential for licochalcone A-induced IKK inhibition, because licochalcone A failed to affect the kinase activity of the IKK␤ (C179A) mutant. In contrast, a structurally related compound, echinatin, failed to inhibit TNF-␣-induced IKK activation and NF-B activation, suggesting that the 1,1-dimethy-2-propenyl group in licochalcone A is important for the inhibition of NF-B. In addition, TNF-␣-induced expression of inflammatory cytokines CCL2/ monocyte chemotactic protein-1and CXCL1/KC was clearly inhibited by licochalcone A but not echinatin. Taken together, licochalcone A might contribute to the potent anti-inflammatory effect of G. inflata through the inhibition of IKK activation

A proline-type fullerene derivative inhibits adipogenesis by preventing PPARγ activation

Obesity and its associated metabolic diseases represent some of the most rapidly expanding health issues worldwide, and, thus, the development of a novel chemical compound to suppress adipogenesis is strongly expected. We herein investigated the effects of water-soluble fullerene derivatives: a bis-malonic acid derivative and three types of proline-type fullerene derivatives, on adipogenesis using NIH-3T3 cells overexpressing PPARγ. One of the proline-type fullerene derivatives (P3) harboring three carboxy groups significantly inhibited lipid accumulation and the expression of adipocyte-specific genes, such as aP2, induced by the PPARγ agonist rosiglitazone. On the other hand, the bis-malonic acid derivative (M) and the 2 other proline-type fullerene derivatives (P1, P2), which have two carboxy groups, had no effect on PPARγ-mediated lipid accumulation or the expression of aP2. P3 fullerene also inhibited lipid accumulation induced by the combined stimulation with 3-isobutyl-1-methylxanthine (IBMX), dexamethasone, and insulin in 3T3-L1 preadipocytes. During the differentiation of 3T3-L1 cells into adipocytes, P3 fullerene did not affect the expression of C/EBPδ, C/EBPβ, or PPARγ, but markedly inhibited that of aP2 mRNA. These results suggest that P3 fullerene exhibits anti-obesity activity by preventing the activation of PPARγ