Characterization of dibenzo[ a,l pyrene- trans -11,12-diol (dibenzo[ def,p chrysene) glucuronidation by UDP-glucuronosyltransferases

Kristine C. Olson, Dongxiao Sun, Gang Chen, Arun Sharma, Shantu Amin, Ira Ropson, Thomas Spratt, Philip Lazarus

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Abstract

Dibenzo[a,lpyrene (DB[a,lP) (dibenzo[def,pchrysene) is a highly carcinogenic polycyclic aromatic hydrocarbon (PAH) that has been identified in tobacco smoke and is found in our environment due to incomplete combustion of organic matter. Its metabolites are known to form stable DNA adducts in bacteria and mammalian cells, and can lead to tumors in animal models. Glucuronidation of major metabolites of DB[a,lP by the uridine-5′-diphosphate glucuronosyltransferase (UGT) family of enzymes is an important route of detoxification of this pro-carcinogen. The focus of the current study was to characterize the glucuronidation of the pro-carcinogenic enantiomers DB[a,lP-(+)-trans-11S,12S-diol and DB[a,lP-(-)-trans-11R,12R-diol. Glucuronidation assays with HEK293 cell lines overexpressing individual human UGT enzymes demonstrated that UGTs 1A1, 1A4, 1A7, 1A8, 1A9, 1A10, and 2B7 glucuronidated one or both DB[a,lP-trans-11,12-diol enantiomers. Three glucuronide conjugates were observed in activity assays with UGTs 1A1 and 1A10, while two glucuronides were formed by UGTs 1A7, 1A8, and 1A9, and one glucuronide was made by UGT1A4 and UGT2B7. Enzyme kinetic analysis indicated that UGT1A9 was the most efficient UGT at forming both the (+)-DB[a,lP-11-Gluc and (-)-DB[a,lP-11-Gluc products, while UGTs 1A1 and 1A10 were the most efficient at forming the (+)-DB[a,lP-12-Gluc product (as determined by k cat/K M). Incubations with human liver microsomes showed the formation of three diastereomeric glucuronide products: (+)-DB[a,lP-11-Gluc, (+)-DB[a,lP-12-Gluc, and (-)-DB[a,lP-11-Gluc, with an average overall ratio of 31:32:37 in four liver specimens. Human bronchus and trachea tissue homogenates demonstrated glucuronidation activity against both DB[a,lP-trans-11,12-diol enantiomers, with both tissues producing the (+)-DB[a,lP-11-Gluc and (+)-DB[a,lP-12-Gluc with little or no formation of (-)-DB[a,lP-11-Gluc. These results indicate that multiple UGTs are involved in the stereospecific glucuronidation of DB[a,lP-trans-11,12-diol in a pattern consistent with their expression in respiratory tract tissues and that glucuronidation may be an important first-line detoxification mechanism of DB[a,lP metabolites.

Original languageEnglish (US)
Pages (from-to)1549-1559
Number of pages11
JournalChemical Research in Toxicology
Volume24
Issue number9
DOIs
StatePublished - Sep 19 2011

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Glucuronosyltransferase
Glucuronides
Uridine Diphosphate
Enantiomers
Diphosphates
Uridine
Metabolites
Detoxification
Tissue
Liver
Assays
Enzymes
Cells
Enzyme kinetics
Tobacco
DNA Adducts
HEK293 Cells
Polycyclic Aromatic Hydrocarbons
Liver Microsomes
Bronchi

All Science Journal Classification (ASJC) codes

  • Toxicology

Cite this

@article{5dbc854b155f42a99f91d3c35e2b6062,
title = "Characterization of dibenzo[ a,l pyrene- trans -11,12-diol (dibenzo[ def,p chrysene) glucuronidation by UDP-glucuronosyltransferases",
abstract = "Dibenzo[a,lpyrene (DB[a,lP) (dibenzo[def,pchrysene) is a highly carcinogenic polycyclic aromatic hydrocarbon (PAH) that has been identified in tobacco smoke and is found in our environment due to incomplete combustion of organic matter. Its metabolites are known to form stable DNA adducts in bacteria and mammalian cells, and can lead to tumors in animal models. Glucuronidation of major metabolites of DB[a,lP by the uridine-5′-diphosphate glucuronosyltransferase (UGT) family of enzymes is an important route of detoxification of this pro-carcinogen. The focus of the current study was to characterize the glucuronidation of the pro-carcinogenic enantiomers DB[a,lP-(+)-trans-11S,12S-diol and DB[a,lP-(-)-trans-11R,12R-diol. Glucuronidation assays with HEK293 cell lines overexpressing individual human UGT enzymes demonstrated that UGTs 1A1, 1A4, 1A7, 1A8, 1A9, 1A10, and 2B7 glucuronidated one or both DB[a,lP-trans-11,12-diol enantiomers. Three glucuronide conjugates were observed in activity assays with UGTs 1A1 and 1A10, while two glucuronides were formed by UGTs 1A7, 1A8, and 1A9, and one glucuronide was made by UGT1A4 and UGT2B7. Enzyme kinetic analysis indicated that UGT1A9 was the most efficient UGT at forming both the (+)-DB[a,lP-11-Gluc and (-)-DB[a,lP-11-Gluc products, while UGTs 1A1 and 1A10 were the most efficient at forming the (+)-DB[a,lP-12-Gluc product (as determined by k cat/K M). Incubations with human liver microsomes showed the formation of three diastereomeric glucuronide products: (+)-DB[a,lP-11-Gluc, (+)-DB[a,lP-12-Gluc, and (-)-DB[a,lP-11-Gluc, with an average overall ratio of 31:32:37 in four liver specimens. Human bronchus and trachea tissue homogenates demonstrated glucuronidation activity against both DB[a,lP-trans-11,12-diol enantiomers, with both tissues producing the (+)-DB[a,lP-11-Gluc and (+)-DB[a,lP-12-Gluc with little or no formation of (-)-DB[a,lP-11-Gluc. These results indicate that multiple UGTs are involved in the stereospecific glucuronidation of DB[a,lP-trans-11,12-diol in a pattern consistent with their expression in respiratory tract tissues and that glucuronidation may be an important first-line detoxification mechanism of DB[a,lP metabolites.",
author = "Olson, {Kristine C.} and Dongxiao Sun and Gang Chen and Arun Sharma and Shantu Amin and Ira Ropson and Thomas Spratt and Philip Lazarus",
year = "2011",
month = "9",
day = "19",
doi = "10.1021/tx200178v",
language = "English (US)",
volume = "24",
pages = "1549--1559",
journal = "Chemical Research in Toxicology",
issn = "0893-228X",
publisher = "American Chemical Society",
number = "9",

}

TY - JOUR

T1 - Characterization of dibenzo[ a,l pyrene- trans -11,12-diol (dibenzo[ def,p chrysene) glucuronidation by UDP-glucuronosyltransferases

AU - Olson, Kristine C.

AU - Sun, Dongxiao

AU - Chen, Gang

AU - Sharma, Arun

AU - Amin, Shantu

AU - Ropson, Ira

AU - Spratt, Thomas

AU - Lazarus, Philip

PY - 2011/9/19

Y1 - 2011/9/19

N2 - Dibenzo[a,lpyrene (DB[a,lP) (dibenzo[def,pchrysene) is a highly carcinogenic polycyclic aromatic hydrocarbon (PAH) that has been identified in tobacco smoke and is found in our environment due to incomplete combustion of organic matter. Its metabolites are known to form stable DNA adducts in bacteria and mammalian cells, and can lead to tumors in animal models. Glucuronidation of major metabolites of DB[a,lP by the uridine-5′-diphosphate glucuronosyltransferase (UGT) family of enzymes is an important route of detoxification of this pro-carcinogen. The focus of the current study was to characterize the glucuronidation of the pro-carcinogenic enantiomers DB[a,lP-(+)-trans-11S,12S-diol and DB[a,lP-(-)-trans-11R,12R-diol. Glucuronidation assays with HEK293 cell lines overexpressing individual human UGT enzymes demonstrated that UGTs 1A1, 1A4, 1A7, 1A8, 1A9, 1A10, and 2B7 glucuronidated one or both DB[a,lP-trans-11,12-diol enantiomers. Three glucuronide conjugates were observed in activity assays with UGTs 1A1 and 1A10, while two glucuronides were formed by UGTs 1A7, 1A8, and 1A9, and one glucuronide was made by UGT1A4 and UGT2B7. Enzyme kinetic analysis indicated that UGT1A9 was the most efficient UGT at forming both the (+)-DB[a,lP-11-Gluc and (-)-DB[a,lP-11-Gluc products, while UGTs 1A1 and 1A10 were the most efficient at forming the (+)-DB[a,lP-12-Gluc product (as determined by k cat/K M). Incubations with human liver microsomes showed the formation of three diastereomeric glucuronide products: (+)-DB[a,lP-11-Gluc, (+)-DB[a,lP-12-Gluc, and (-)-DB[a,lP-11-Gluc, with an average overall ratio of 31:32:37 in four liver specimens. Human bronchus and trachea tissue homogenates demonstrated glucuronidation activity against both DB[a,lP-trans-11,12-diol enantiomers, with both tissues producing the (+)-DB[a,lP-11-Gluc and (+)-DB[a,lP-12-Gluc with little or no formation of (-)-DB[a,lP-11-Gluc. These results indicate that multiple UGTs are involved in the stereospecific glucuronidation of DB[a,lP-trans-11,12-diol in a pattern consistent with their expression in respiratory tract tissues and that glucuronidation may be an important first-line detoxification mechanism of DB[a,lP metabolites.

AB - Dibenzo[a,lpyrene (DB[a,lP) (dibenzo[def,pchrysene) is a highly carcinogenic polycyclic aromatic hydrocarbon (PAH) that has been identified in tobacco smoke and is found in our environment due to incomplete combustion of organic matter. Its metabolites are known to form stable DNA adducts in bacteria and mammalian cells, and can lead to tumors in animal models. Glucuronidation of major metabolites of DB[a,lP by the uridine-5′-diphosphate glucuronosyltransferase (UGT) family of enzymes is an important route of detoxification of this pro-carcinogen. The focus of the current study was to characterize the glucuronidation of the pro-carcinogenic enantiomers DB[a,lP-(+)-trans-11S,12S-diol and DB[a,lP-(-)-trans-11R,12R-diol. Glucuronidation assays with HEK293 cell lines overexpressing individual human UGT enzymes demonstrated that UGTs 1A1, 1A4, 1A7, 1A8, 1A9, 1A10, and 2B7 glucuronidated one or both DB[a,lP-trans-11,12-diol enantiomers. Three glucuronide conjugates were observed in activity assays with UGTs 1A1 and 1A10, while two glucuronides were formed by UGTs 1A7, 1A8, and 1A9, and one glucuronide was made by UGT1A4 and UGT2B7. Enzyme kinetic analysis indicated that UGT1A9 was the most efficient UGT at forming both the (+)-DB[a,lP-11-Gluc and (-)-DB[a,lP-11-Gluc products, while UGTs 1A1 and 1A10 were the most efficient at forming the (+)-DB[a,lP-12-Gluc product (as determined by k cat/K M). Incubations with human liver microsomes showed the formation of three diastereomeric glucuronide products: (+)-DB[a,lP-11-Gluc, (+)-DB[a,lP-12-Gluc, and (-)-DB[a,lP-11-Gluc, with an average overall ratio of 31:32:37 in four liver specimens. Human bronchus and trachea tissue homogenates demonstrated glucuronidation activity against both DB[a,lP-trans-11,12-diol enantiomers, with both tissues producing the (+)-DB[a,lP-11-Gluc and (+)-DB[a,lP-12-Gluc with little or no formation of (-)-DB[a,lP-11-Gluc. These results indicate that multiple UGTs are involved in the stereospecific glucuronidation of DB[a,lP-trans-11,12-diol in a pattern consistent with their expression in respiratory tract tissues and that glucuronidation may be an important first-line detoxification mechanism of DB[a,lP metabolites.

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U2 - 10.1021/tx200178v

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