Relationship between xenobiotic toxicity and metabolisn in individuals

由于葡萄糖醛酸化是消除外源生物的重要代谢反应，因此在异构体水平上诱导或抑制udp -葡萄糖醛酸基转移酶（UGT）酶的信息有助于药物治疗和环境化学品的毒理学评估。本研究以主要在人肝脏中表达的UGT1A亚型（UGT1A1、UGT1A6和UGT1A9）为研究对象，研究了β-萘黄酮（BNF）对人肝癌HepG2细胞中UGT1As的诱导作用。用浓度分别为25、50和100 μM的BNF预处理细胞72 h。7-乙基-10-羟基喜树碱（SN-38）葡萄糖醛酸化作为UGT1A1的探针，在对照和bnf预处理的HepG2细胞中表现出s型动力学，Hill系数(n)为1.2-1.3。BNF使V_<max>值显著增加3.6 ~ 4.3倍，而在任何浓度下BNF对S_<50>值均无显著变化。另一方面，作为UGT1A6和UGT1A9探针的4- methylumbellliferone (4-MU) glucuronida…More tion在对照和bnf预处理的HepG2细胞中表现出双相动力学模式，尽管低k_m期的K_<ml>值在对照和bnf预处理的HepG2细胞中相似，但在高k_m期，bnf预处理的liepG2细胞的K_<m2>值降低到对照HepG2细胞的54-69%。低、高K_m相的V_<max>和V_<max2>值在25 μM和/或50μM下显著增加1.9 ~ 2.6倍，而在100 μM下不显著增加。对于V_<max> （V_<max1>和V_<max2>）和V_<max>/K_m (V_<max1>/K_<m1>和V_<max2>/K_<m2>)，在所有检测浓度下BNF均显著增加2.0 ~ 3.2倍。此外，利用TaqMan探针进行实时逆转录聚合酶链反应（RT-PCR）表明，BNF浓度依赖性地诱导了HepG2细胞中UGTIA1的mRNA水平，而不是UGT1A6或UGT1A9的mRNA水平（1.3- 6.0倍）。这些结果表明，BNF对UGT1A亚型在HepG2细胞中的诱导作用不同于以往报道的其他芳烃受体（AhR）激动剂，这将为预测药物-药物相互作用和环境化学物质的毒理学评估提供有用的信息。少

Since glucuronidation is an important metabolic reaction for xenobiotic elimination, information on the induction or suppression of UDP-glucuronosyltransferase (UGT) enzymes at the isoform level is beneficial in drug therapy and the toxicological assessment of environmental chemicals. In this study, we focused on UGT1A isoforms (UGT1A1, UGT1A6 and UGT1A9), mainly expressed in the human liver, and examined the inducibility of UGT1As by β-naphthoflavone (BNF) in human hepatoma HepG2 cells. The cells were pretreated for 72 h with BNF at concentrations of 25, 50 and 100 μM. 7-Ethyl-10-hydroxycamptothecin (SN-38) glucuronidation, used as a probe for UGT1A1, showed sigmoidal kinetics with a Hill coefficient (n) of 1.2-1.3 in control and BNF-pretreated HepG2 cells. The V_<max> values were significantly increased 3.6- to 4.3-fold by BNF, whereas there was no significant change in the S_<50> values by BNF at any concentration examined. On the other hand, 4-methylumbelliferone (4-MU) glucuronida … More tion as a probe for UGT1A6 and UGT1A9 in the control and BNF-pretreated HepG2 cells exhibited a biphasic kinetic pattern Although K_<ml> values for the low-K_m phase were similar between the control and BNF-pretreated HepG2 cells, K_<m2> values for the high-K_m phase of BNF-pretreated liepG2 cells were reduced to 54-69% of control HepG2 cells. The values of V_<max> and V_<max2> for the low- and high-K_m phases, respectively, were significantly increased 1.9- to 2.6-fold by BNF at 25 and/or 50μM but not 100 μM With respect to V_<max> (V_<max1> and V_<max2>) and V_<max>/K_m (V_<max1>/K_<m1> and V_<max2>/K_<m2>), the values were significantly increased 2.0- to 3.2-fold by BNF at all concentrations examined. Furthermore, real-time reverse transcription polymerase chain reaction (RT-PCR) using TaqMan probes demonstrated that BNF concentration-dependently induced mRNA levels of UGTIA1 but not UGT1A6 or UGT1A9 in HepG2 cells (1.3- to 6.0-fold). These results suggest that the inducibility of UGT1A isoforms in HepG2 cells by BNF is different from other aryl hydrocarbon receptor (AhR) agonists previously reported, and should provide useful information for the prediction of drug-drug interactions and toxicological assessment of environmental chemicals. Less