Relationship between xenobiotic toxicity and metabolisn in individuals

由于葡萄糖醛酸化是消除外源性物质的重要代谢反应，因此在异构体水平诱导或抑制UDP-葡萄糖醛酸基转移酶（UGT）的信息有利于药物治疗和环境化学品的毒理学评估。在这项研究中，我们专注于UGT 1A亚型（UGT 1A 1，UGT 1A 6和UGT 1A 9），主要在人类肝脏中表达，并检查了UGT 1A在人肝癌HepG 2细胞中被β-萘啶酮（BNF）诱导。用浓度为25、50和100 μM的BNF预处理细胞72 h。用作UGT 1A 1探针的7-乙基-10-羟基喜树碱（SN-38）葡萄糖醛酸化在对照和BNF预处理的HepG 2细胞中显示S形动力学，希尔系数（n）为1.2-1.3。BNF使V<max>值显著增加3.6 ~ 4.3倍，而S<50>值在任何浓度下均无显著变化。另一方面，4-甲基伞形酮（4-MU）葡萄糖醛酸 ...更多信息 UGT_（1A 6）和UGT_（1A 9）在对照和BNF预处理的HepG_2细胞中呈双相动力学模式。虽然<ml>对照和BNF预处理的HepG_2细胞低K_m期的K_（10）值相似，但<m2>BNF预处理的liepG_2细胞高K_（10）期的K_（10）值降低到对照HepG_2细胞的54-69%。在<max><max2>25和/或50μM浓度下，BNF使低K_m相和高K_m相的V_和V_分别显著增加1.9- 2.6倍，而在100 μM浓度下则无此作用。在V_<max>（V_<max1>和V_<max2>）和V_<max>/K_m（V_<max1>/K_<m1>和V_<max2>/K_<m2>）方面，BNF使所有浓度下的值显著增加2.0- 3.2倍。此外，使用TaqMan探针的实时逆转录聚合酶链反应（RT-PCR）表明，BNF浓度依赖性地诱导HepG 2细胞中UGTIA 1的mRNA水平，但不诱导UGT 1A 6或UGT 1A 9的mRNA水平（1.3- 6.0倍）。这些结果表明，UGT 1A亚型的诱导HepG 2细胞由BNF是不同于其他芳烃受体（AhR）激动剂以前报道的，并应提供有用的信息，预测药物相互作用和毒理学评价的环境化学品。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