Involvement of UDP-Glucuronosyltransferases UGT1A9 and UGT2B7 in Ethanol Glucuronidation, and Interactions with Common Drugs of Abuse

Abstract

Ethyl glucuronide (EtG) determination is increasingly used in clinical and forensic toxicology to document ethanol consumption. The enzymes involved in EtG production, as well as potential interactions with common drugs of abuse, have not been extensively studied. Activities of human liver (HLM), kidney (HKM), and intestinal (HIM) microsomes, as well as of 12 major human recombinant UDP-glucuronosyltransferases (UGTs), toward ethanol (50 and 500 mM) were evaluated in vitro using liquid chromatography-tandem mass spectrometry. Enzyme kinetic parameters were determined for pooled microsomes and recombinant UGTs with significant activity. Individual contributions of UGTs were estimated using the relative activity factor approach, proposed for scaling activities obtained with cDNA-expressed enzymes to HLM. Interaction of morphine, codeine, lorazepam, oxazepam, nicotine, cotinine, cannabinol, and cannabidiol (5, 10, 15 mg/l) with ethanol (1.15, 4.6, 11.5 g/l; i.e., 25, 100, 250 mM) glucuronidation was assessed using pooled HLM. Ethanol glucuronidation intrinsic clearance (Cl int ) was 4 and 12.7 times higher for HLM than for HKM and HIM, respectively. All recombinant UGTs, except UGT1A1, 1A6, and 1A10, produced EtG in detectable amounts. UGT1A9 and 2B7 were the most active enzymes, each accounting for 17 and 33% of HLM Cl int , respectively. Only cannabinol and cannabidiol significantly affected ethanol glucuronidation. Cannabinol increased ethanol glucuronidation in a concentrationdependent manner, whereas cannabidiol significantly inhibited EtG formation in a noncompetitive manner (IC 50 = 1.17 mg/l; inhibition constant (K i ) = 3.1 mg/l). UGT1A9 and 2B7 are the main enzymes involved in ethanol glucuronidation. In addition, our results suggest that cannabinol and cannabidiol could significantly alter ethanol glucuronidation.

Telomerase reverse transcriptase mutations in plasma DNA in patients with hepatocellular carcinoma or cirrhosis: Prevalence and risk factors

“…Several uridine diphosphoglucuronate‐glucuronosyltransferases (UGTs), including UGT1A6, UGT2B7, and UGT1A5, were up‐regulated in HCCs with TERT mutations. Glucuronidation by UGTs represents a minor detoxifying pathway for ethanol 28. Alcohol treatment up‐regulates UGT1A5 expression in hepatocytes29 and moderate to severe alcohol consumption is associated with increased levels of UGT1A6 in liver 30.…”

Clinical Sensitivity and Specificity of Meconium Fatty Acid Ethyl Ester, Ethyl Glucuronide, and Ethyl Sulfate for Detecting Maternal Drinking during Pregnancy

“…This may be explained by our low EtS LOQ compared to other markers, although our EtS LOQ was higher than previously reported (13). EtG-negative meconium also may have resulted from reduced maternal EtG formation due to genetic UGT polymorphisms (37) or liver damage from heavy alcohol consumption. UGT polymorphism studies indicated cannabinoids, specifically cannabidiol, negatively impacted ethanol glucuronidation activity (37).…”

Probe substrate and enzyme source-dependent inhibition of UDP-glucuronosyltransferase (UGT) 1A9 by wogonin

“…UGT1A9 is one of the most important UGT isoforms in liver, kidney and intestine, and take part in the metabolism of many xenobiotics. For example, UGT1A9 is the major UGT isoform involved in the ethanol glucuronidation 19 . UGT1A9 showed extensive activity towards the glucuronidation of acetaminophen 20 .…”