Title: Interception of benzo[a]pyrene-7,8-dione by UDP glucuronosyltransferases (UGTs) in human lung cells.
Authors: Zhang, Li; Huang, Meng; Blair, Ian A; Penning, Trevor M
Published In Chem Res Toxicol, (2013 Oct 21)
Abstract: Polycyclic aromatic hydrocarbons (PAHs) are environmental and tobacco carcinogens. Proximate carcinogenic PAH trans-dihydrodiols are activated by human aldo-keto reductases (AKRs) to yield electrophilic and redox-active o-quinones. Interconversion among benzo[a]pyrene (B[a]P)-7,8-dione, a representative PAH o-quinone, and its corresponding catechol generates a futile redox-cycle with the concomitant production of reactive oxygen species (ROS). We investigated whether glucuronidation of B[a]P-7,8-catechol by human UDP glucuronosyltransferases (UGTs) could intercept the catechol in three different human lung cells. RT-PCR showed that UGT1A1, 1A3, and 2B7 were only expressed in human lung adenocarcinoma A549 cells. The corresponding recombinant UGTs were examined for their kinetic constants and product profile using B[a]P-7,8-catechol as a substrate. B[a]P-7,8-dione was reduced to B[a]P-7,8-catechol by dithiothreitol under anaerobic conditions and then further glucuronidated by the UGTs in the presence of uridine-5'-diphosphoglucuronic acid as a glucuronic acid group donor. UGT1A1 catalyzed the glucuronidation of B[a]P-7,8-catechol and generated two isomeric O-monoglucuronsyl-B[a]P-7,8-catechol products that were identified by RP-HPLC and by LC-MS/MS. By contrast, UGT1A3 and 2B7 catalyzed the formation of only one monoglucuronide, which was identical to that formed in A549 cells. The kinetic profiles of three UGTs followed Michaelis-Menten kinetics. On the basis of the expression levels of UGT1A3 and UGT2B7 and the observation that a single monoglucuronide was produced in A549 cells, we suggest that the major UGT isoforms in A549 cells that can intercept B[a]P-7,8-catechol are UGT1A3 and 2B7.
PubMed ID: 24047243
MeSH Terms: Benzopyrenes/analysis; Benzopyrenes/chemistry*; Benzopyrenes/metabolism*; Catechols/analysis; Catechols/chemistry*; Catechols/metabolism; Cell Line, Tumor; Chromatography, High Pressure Liquid; Dithiothreitol/chemistry; Glucuronides/chemistry; Glucuronides/metabolism; Glucuronosyltransferase/genetics; Glucuronosyltransferase/metabolism*; Humans; Kinetics; Lung/enzymology; Mass Spectrometry; Oxidation-Reduction; Protein Isoforms/genetics; Protein Isoforms/metabolism; Recombinant Proteins/biosynthesis; Recombinant Proteins/genetics