Glucuronidation of arachidonic and linoleic acid metabolites by human UDP-glucuronosyltransferases

Arachidonic acids (AA) and linoleic acids (LAs) are metabolized, in several tissues, to hydroxylated metabolites that are important mediators of many physiological and pathophysiological processes. The conjugation of leukotriene B4 (LTB4), 5-hydroxyeicosatetraenoic acid (HETE), 12-HETE, 15-HETE, and 13-hydroxyoctadecadienoic acid (HODE) by the human UDP-glucuronosyltransferase (UGT) enzymes was investigated. All substrates tested were efficiently conjugated by human liver microsomes to polar derivatives containing the glucuronyl moiety as assessed by mass spectrometry. The screening analyses with stably expressed UGT enzymes in HK293 showed that glucuronidation of LTB4 was observed with UGT1A1, UGT1A3, UGT1A8, and UGT2B7, whereas UGT1A1, UGT1A3, UGT1A4, and UGT1A9 also conjugated most of the HETEs and 13-HODE. LA and AA metabolites also appear to be good substrates for the UGT2B subfamily members, especially for UGT2B4 and UGT2B7 that conjugate all HETE and 13-HODE. Interestingly, UGT2B10 and UGT2B11, which are considered as orphan enzymes since no conjugation activity has so far been demonstrated with these enzymes, conjugated 12-HETE, 15-HETE, and 13-HODE. In summary, our data showed that several members of UGT1A and UGT2B families are capable of converting LA and AA metabolites into glucuronide derivatives, which is considered an irreversible step to inactivation and elimination of endogenous substances from the body.