Decreased Expression of Multidrug Resistance-Associated Protein 4 (MRP4/ABCC4) Leads to Reduced Glucuronidation of Flavonoids in UGT1A1-Overexpressing HeLa Cells: The Role of Futile Recycling
详细信息 查看全文
- 作者：Hua Sun ; Xiaotong Zhou ; Xingwang Zhang ; Baojian Wu
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2015
- 出版时间：July 8, 2015
- 年：2015
- 卷：63
- 期：26
- 页码：6001-6008
- 全文大小：385K
- ISSN：1520-5118
文摘
In this study, the role of futile recycling (or deglucuronidation) in the disposition of two flavonoids (i.e., genistein and apigenin) was explored using UGT1A1-overexpressing HeLa cells (or HeLa1A1 cells). Glucuronidation of the flavonoids by HeLa1A1 cell lysate followed the substrate inhibition kinetics (Vmax = 0.10 nmol/min/mg, Km = 0.54 渭M, and Ksi = 2.0 渭M for genistein; Vmax = 0.19 nmol/min/mg, Km = 0.56 渭M, and Ksi = 3.7 渭M for apigenin). Glucuronide was efficiently generated and excreted after incubation of the cells with the aglycone (at doses of 1.25鈥?0 nmol). The excretion rates were 0.40鈥?.69 and 0.84鈥?.1 nmol/min/mg protein for genistein glucuronide (GG) and apigenin glucuronide (AG), respectively. Furthermore, glucuronide excretion and total glucuronidation were significantly reduced in MRP4 knocked-down as compared to control cells. The alterations were well characterized by a two-compartment pharmacokinetic model incorporating the process of futile recycling (defined by a first-order rate constant, Kde). The derived Kde values were 15 and 25 h鈥? for GG and AG, respectively. This was well consistent with the in vitro observation that AG was subjected to more efficient futile recycling compared to GG. In conclusion, futile recycling was involved in cellular glucuronidation, accounting for transporter-dependent glucuronidation of flavonoids.