In Vitro Glucuronidation of Wushanicaritin by Liver Microsomes, Intestine Microsomes and Expressed Human UDP-Glucuronosyltransferase Enzymes.

Xiaodan Hong,Hao Gao,Yi Dai,Yuanru Zheng,Frank Gonzalez,Zifei Qin,Xinsheng Yao,Baojian Wu,Zhihong Yao

doi:10.3390/ijms18091983

Abstract

Wushanicaritin, a natural polyphenol compound, exerts many biological activities. This study aimed to characterize wushanicaritin glucuronidation by pooled human liver microsomes (HLM), human intestine microsomes and individual uridine diphosphate-glucuronosyltransferase (UGT) enzyme. Glucuronidation rates were determined by incubating wushanicaritin with uridine diphosphoglucuronic acid-supplemented microsomes. Kinetic parameters were derived by appropriate model fitting. Reaction phenotyping, the relative activity factor (RAF) and activity correlation analysis were performed to identify the main UGT isoforms. Wushanicaritin glucuronidation in HLM was efficient with a high CLint (intrinsic clearance) value of 1.25 and 0.69 mL/min/mg for G1 and G2, respectively. UGT1A1 and 1A7 showed the highest activities with the intrinsic clearance (CLint) values of 1.16 and 0.38 mL/min/mg for G1 and G2, respectively. In addition, G1 was significantly correlated with β-estradiol glucuronidation (r = 0.847; p = 0.0005), while G2 was also correlated with chenodeoxycholic acid glucuronidation (r = 0.638, p = 0.026) in a bank of individual HLMs (n = 12). Based on the RAF approach, UGT1A1 contributed 51.2% for G1, and UGT1A3 contributed 26.0% for G2 in HLM. Moreover, glucuronidation of wushanicaritin by liver microsomes showed marked species difference. Taken together, UGT1A1, 1A3, 1A7, 1A8, 1A9 and 2B7 were identified as the main UGT contributors responsible for wushanicaritin glucuronidation.

Highlights

Xenobiotic metabolism, a ubiquitous natural response to foreign drugs, elicits initiating signals for many pathophysiological events [1]
We aim to characterize the metabolism of wushanicaritin via the glucuronidation pathway and to identify the main uridine diphosphate-glucuronosyltransferase (UGT) enzymes involved in wushanicaritin glucuronidation
The results indicated that the Phase II metabolism glucuronidation was an important pathway for wushanicaritin clearance

Summary

Introduction

Xenobiotic metabolism, a ubiquitous natural response to foreign drugs, elicits initiating signals for many pathophysiological events [1]. According to different drug-metabolizing enzyme systems, xenobiotic biotransformation reactions could be classified to Phase I and Phase II reactions [2,3]. Phase I reactions included oxidation, reduction and hydrolysis, and cytochrome P450s enzymes (CYPs) in liver microsomal were the major Phase I metabolic enzymes [4]. The major conjugation reactions were glucuronidation, acetylation, sulfation and methylation. Uridine diphosphate-glucuronosyltransferase (UGT), acetylase, sulfate transferase and methylase were responsible for Phase II catalytic reactions [7,8]. Phase II reactions were considered as one of the most important detoxification processes due to the obvious increased hydrophilicity of the conjugated metabolites, which could promote the excretion of the drug from the body [9,10]

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Conclusion