Glucuronidation of mono(2-ethylhexyl) phthalate in humans: roles of hepatic and intestinal UDP-glucuronosyltransferases

Nobumitsu Hanioka; Yu Kinashi; Toshiko Tanaka-Kagawa; Takashi Isobe; Hideto Jinno

doi:10.1007/s00204-016-1708-9

Glucuronidation of mono(2-ethylhexyl) phthalate in humans: roles of hepatic and intestinal UDP-glucuronosyltransferases

Arch Toxicol. 2017 Feb;91(2):689-698. doi: 10.1007/s00204-016-1708-9. Epub 2016 Apr 12.

Authors

Nobumitsu Hanioka¹, Yu Kinashi², Toshiko Tanaka-Kagawa³, Takashi Isobe⁴, Hideto Jinno⁵

Affiliations

¹ Laboratory of Xenobiotic Metabolism, Department of Health Pharmacy, Yokohama University of Pharmacy, 601 Matano-cho, Totsuka-ku, Yokohama, 245-0066, Japan. nhanioka@hamayaku.ac.jp.
² Laboratory of Health Chemistry, Faculty of Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama, 700-8530, Japan.
³ Laboratory of Environmental Toxicology, Department of Health Pharmacy, Yokohama University of Pharmacy, 601 Matano-cho, Totsuka-ku, Yokohama, 245-0066, Japan.
⁴ Laboratory of Xenobiotic Metabolism, Department of Health Pharmacy, Yokohama University of Pharmacy, 601 Matano-cho, Totsuka-ku, Yokohama, 245-0066, Japan.
⁵ Laboratory of Hygienic Chemistry, Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya, 468-8503, Japan.

PMID: 27071666
DOI: 10.1007/s00204-016-1708-9

Abstract

Mono(2-ethylhexyl) phthalate (MEHP) is an active metabolite of di(2-ethylhexyl) phthalate (DEHP), which is an endocrine-disrupting chemical. In the present study, MEHP glucuronidation in humans was studied using recombinant UDP-glucuronosyltransferases (UGTs) and microsomes of the liver and intestine. Among the recombinant UGTs examined, UGT1A3, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2B4, and UGT2B7 glucuronidated MEHP. The kinetics of MEHP glucuronidation by UGT1A3, UGT1A7, UGT1A8, UGT1A10, UGT2B4, and UGT2B7 followed the Michaelis-Menten model, whereas that by UGT1A9 fit the negative allosteric model. CL_int values were in the order of UGT1A9 > UGT2B7 > UGT1A7 > UGT1A8 ≥ UGT1A10 > UGT1A3 > UGT2B4. The kinetics of MEHP glucuronidation by liver microsomes followed the Michaelis-Menten model. Diclofenac (20 µM) and raloxifene (20 µM) decreased CL_int values to 43 and 36 % that of native microsomes, respectively. The kinetics of MEHP glucuronidation by intestine microsomes fit the biphasic model. Diclofenac (150 and 450 µM) decreased CL_int values to 32 and 13 % that of native microsomes for the high-affinity phase, and to 28 and 21 % for the low-affinity phase, respectively. Raloxifene (2.5 and 7.0 µM) decreased CL_int values to 35 and 4.1 % that of native microsomes for the high-affinity phase, and to 48 and 53 % for the low-affinity phase, respectively. These results suggest that MEHP glucuronidation in humans is catalyzed by UGT1A3, UGT1A9, UGT2B4, and/or UGT2B7 in the liver, and by UGT1A7, UGT1A8, UGT1A9, UGT1A10, and/or UGT2B7 in the intestine, and also that these UGT isoforms play important and characteristic roles in the detoxification of DEHP.

Keywords: Glucuronidation; Human intestine microsomes; Human liver microsomes; Mono(2-ethylhexyl) phthalate (MEHP); Recombinant human UGT; UDP-glucuronosyltransferase (UGT).

MeSH terms

Diclofenac / pharmacology
Diethylhexyl Phthalate / analogs & derivatives*
Diethylhexyl Phthalate / metabolism
Diethylhexyl Phthalate / pharmacokinetics
Endocrine Disruptors / metabolism
Endocrine Disruptors / pharmacokinetics
Glucuronosyltransferase / genetics
Glucuronosyltransferase / metabolism*
Humans
Intestinal Mucosa / metabolism
Intestines / drug effects
Microsomes / drug effects
Microsomes / metabolism
Microsomes, Liver / drug effects
Microsomes, Liver / metabolism
Models, Theoretical
Raloxifene Hydrochloride / pharmacology
Recombinant Proteins / genetics
Recombinant Proteins / metabolism

Substances

Endocrine Disruptors
Recombinant Proteins
Diclofenac
Raloxifene Hydrochloride
Diethylhexyl Phthalate
Glucuronosyltransferase
mono-(2-ethylhexyl)phthalate