Abstract
Small intestinal mucosal injury is a frequent adverse effect caused by nonsteroidal anti-inflammatory drugs (NSAIDs). The underlying mechanisms are not completely understood, but topical (luminal) effects have been implicated. Many carboxylic acid-containing NSAIDs, including diclofenac (DCF), are metabolized to acyl glucuronides (AGs), and/or ether glucuronides after ring hydroxylation, and exported into the biliary tree. In the gut, these conjugates are cleaved by bacterial β-glucuronidase, releasing the potentially harmful aglycone. We first confirmed that DCF-AG was an excellent substrate for purified Escherichia coli β-d-glucuronidase. Using a previously characterized novel bacteria-specific β-glucuronidase inhibitor (Inhibitor-1), we then found that the enzymatic hydrolysis of DCF-AG in vitro was inhibited concentration dependently (IC50 ∼164 nM). We next hypothesized that pharmacologic inhibition of bacterial β-glucuronidase would reduce exposure of enterocytes to the aglycone and, as a result, alleviate enteropathy. C57BL/6J mice were administered an ulcerogenic dose of DCF (60 mg/kg i.p.) with or without oral pretreatment with Inhibitor-1 (10 μg per mouse, b.i.d.). Whereas DCF alone caused the formation of numerous large ulcers in the distal parts of the small intestine and increased (2-fold) the intestinal permeability to fluorescein isothiocyanate-dextran, Inhibitor-1 cotreatment significantly alleviated mucosal injury and reduced all parameters of enteropathy. Pharmacokinetic profiling of DCF plasma levels in mice revealed that Inhibitor-1 coadministration did not significantly alter the Cmax, half-life, or area under the plasma concentration versus time curve of DCF. Thus, highly selective pharmacologic targeting of luminal bacterial β-d-glucuronidase by a novel class of small-molecule inhibitors protects against DCF-induced enteropathy without altering systemic drug exposure.
Footnotes
This work was supported by the National Institutes of Health National Cancer Institute [Grant CA98468] (to M.R.R.); the Boehringer Ingelheim Endowed Chair in Mechanistic Toxicology; a research grant from Helsinn Healthcare SA, Switzerland (to U.A.B.); the K. A. Nieforth Pharmacy Student Research Fund (to L.B.); and University of Connecticut School of Pharmacy Student Research Scholarship Fund (to L.B.).
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
ABBREVIATIONS:
- GI
- gastrointestinal
- DCF
- diclofenac
- DCF-AG
- diclofenac-1-β-O-acyl glucuronide
- FITC
- fluorescein isothiocyanate
- Inh-1
- Inhibitor-1 [1-((6,8-dimethyl-2-oxo-1,2-dihydroquinolin-3-yl)methyl)-3-(4-ethoxyphenyl)-1-(2-hydroxyethyl)thiourea]
- NSAID
- nonsteroidal anti-inflammatory drug
- LC-MS/MS
- liquid chromatography/tandem mass spectrometry
- COX
- cyclooxygenase
- HPLC
- high-performance liquid chromatography
- NBT
- nitroblue tetrazolium
- AUC
- area under the plasma concentration versus time curve.
- Received December 16, 2011.
- Accepted February 9, 2012.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
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