Abstract
Acetylsalicylic acid (aspirin) is a common nonsteroidal anti-inflammatory drug used for treatment of pain and arthritis. In the body, acetylsalicylic acid is rapidly deacetylated to form salicylic acid. Both compounds have been proposed as anti-inflammatory agents. Major metabolites of salicylic acid are its acyl and phenolic glucuronide conjugates. Formation of these conjugates, catalyzed by UDP-glucuronosyltransferases (UGTs), decreases the amount of pharmacologically active salicylic acid present. We aimed to identify the UGTs catalyzing the glucuronidation of salicylic acid using both heterologously expressed enzymes and pooled human liver microsomes (HLMs) and to develop a liquid chromatographytandem mass spectrometry method to quantify glucuronidation activity of UGTs 1A1, 1A3, 1A4, 1A6, 1A7, 1A8, 1A9, 1A10, 2B4, 2B7, 2B15, and 2B17 Supersomes. All UGTs tested, except 1A4, 2B15, and 2B17, catalyzed salicylic acid phenolic and acyl glucuronidation. Ratios of salicylic acid phenolic to acyl glucuronide formation varied more than 12-fold from 0.5 for UGT1A6 to 6.1 for UGT1A1. These results suggest that all UGTs except 1A4, 2B15, and 2B17 might be involved in the glucuronidation of salicylic acid in vivo. From comparisons of apparent Km values determined in pooled HLMs and in expressed UGTs, UGT2B7 was suggested as a likely catalyst of salicylic acid acyl glucuronidation, whereas multiple UGTs were suggested as catalysts of phenolic glucuronidation. The results of this UGT screening may help target future evaluation of the effects of UGT polymorphisms on response to aspirin in clinical and population-based studies.
Footnotes
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This research was supported by Grant R01 CA94954 from the National Institutes of Health (to J.D.P.). G.E.K. was supported partially by National Cancer Insitute Training Grant T32 CA77116. Presented in part at the American Association for Cancer Research Annual Meeting, Orlando, FL, 27–31 Mar, 2004 (Abstract #3756).
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
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doi:10.1124/dmd.105.005652.
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ABBREVIATIONS: SAPG, salicylic acid phenolic glucuronide; ESI, electrospray ionization; HPLC, high performance liquid chromatography; HLM, human liver microsome; LC, liquid chromatography; MS/MS, tandem mass spectrometry; PMSF, phenylmethylsulfonyl fluoride; TFA, trifluoroacetic acid; SAAG, salicylic acid acyl glucuronide; UGT, UDP-glucuronosyltransferase.
- Received May 26, 2005.
- Accepted October 26, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
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