Apigenin suppresses the expression of VEGF, an important factor for angiogenesis, in endothelial cells via degradation of HIF-1α protein

AbstractApigenin, a plant-derived flavone, is a potent inhibitor of cell proliferation and angiogenesis, but the mechanisms leading to the pathological anti-angiogenic effects of apigenin are still unclear. In this study, we found that apigenin inhibited the hypoxia-induced expression of vascular endothelial growth factor (VEGF) mRNA in human umbilical artery endothelial cells. Apigenin also suppressed the expression of erythropoietin mRNA, which is a typical hypoxia-inducible gene, via the degradation of hypoxia-inducible factor 1 (HIF-1) α. We investigated the effect of apigenin on the interaction of HIF-1α with heat shock protein 90 (Hsp90), which is reported to be important for the stabilization of HIF-1α, and found that VEGF expression was inhibited via degradation of HIF-1α through interference with the function of Hsp90

CATALYTIC SPECIFICITY OF CYP2D ISOFORMS IN RAT AND HUMAN

ABSTRACT: In rats, six cytochrome P450 (P450) 2D isoforms have been genetically identified. Nonetheless, there is little evidence of catalytic properties of each CYP2D isoform. In this study, using recombinant CYP2D isoforms (rat CYP2D1, CYP2D2, CYP2D3, and CYP2D4 and human CYP2D6) or hepatic microsomes, we investigated the catalytic specificity toward bufuralol, debrisoquine, and propranolol, which are frequently used as CYP2D substrates. Bufuralol was oxidized to three metabolites by rat and human hepatic microsomes. 1-Hydroxybufuralol was the major metabolite. 12-Ethenylbufuralol, one of the others, was identified as a novel metabolite. The formation of 1-hydroxybufuralol and 12-ethenylbufuralol in hepatic microsomes was inhibited by anti-CYP2D antibody, suggesting that these metabolites were formed by CYP2D isoforms. All rat and human recombinant CYP2D isoforms possessed activity for the 1-hydroxylation of bufuralol, indicating that this catalytic property was common to all CYP2D isoforms. However, the 12-ethenylation of bufuralol was catalyzed only by rat CYP2D4 and human CYP2D6. Debrisoquine was oxidized to two metabolites, 3-hydroxydebrisoquine, and 4-hydroxydebrisoquine, by hepatic microsomes. Recombinant CYP2D2 and CYP2D6 had very high levels of activity for the 4-hydroxylation of debrisoquine with low K m values. Only CYP2D1 had a higher level of 3-hydroxylation than 4-hydroxylation activity. Propranolol 4-hydroxylation was catalyzed by CYP2D2, CYP2D4, and CYP2D6. The 7-hydroxylation of propranolol was catalyzed only by CYP2D2. In conclusion, in rats, bufuralol 12-ethenylation activity was specific to CYP2D4 and debrisoquine 4-hydroxylation and propranolol 7-hydroxylation activities were specific to CYP2D2. These catalytic activities are useful as a probe for rat CYP2D isoforms

CYP2A13 expressed in human bladder metabolically activates 4-aminobiphenyl

金沢大学大学院医学系研究科機能分子医薬学金沢大学薬学部authorCigarette smoking is the predominant risk factor for bladder cancer. Aromatic amines such as 4-aminobiphenyl (ABP) is the major carcinogens found in tobacco smoke. Although it is generally accepted that ABP is metabolically activated via N-hydroxylation by CYP1A2 in human liver, previous studies using Cyp1a2-null mice indicated the involvement of other enzyme(s). Here we found that CYP2A13 can metabolically activate ABP to show genotoxicity by Umu assay. The Km and Vmax values for ABP N-hydroxylation by recombinant CYP2A13 in E. coli were 38.5 ± 0.6 μM 7.8 ± 0.0 pmol/min/pmol CYP, respectively. The Km and Vmax values by recombinant CYP1A2 were 9.9 ± 0.9 μM and 39.6 ± 0.9 pmol/min/ pmol CYP, respectively, showing 20-fold higher intrinsic clearance than CYP2A13. In human bladder, CYP2A13 mRNA, but not CYP1A2, is expressed at a relatively high level. Human bladder microsomes showed ABP N-hydroxylase activity (K m = 34.9 ± 4.7 μM and Vmax = 57.5 ± 1.9 pmol/min/mg protein), although the intrinsic clearance was 5-fold lower than that in human liver microsomes (Km = 33.2 ± 2.0 μM and Vmax = 293.9 ± 5.8 pmol/min/mg protein). The activity in human bladder microsomes was prominently inhibited by 8-methoxypsoralen, but not by fluvoxamine, anti-CYP1A2 or anti-CYP2A6 antibodies