Abstract
UDP-glucuronosyltransferases (UGTs) catalyze the addition of UDP-glucuronic acid to endo- and xenobiotics, enhancing their water solubility and elimination. Many exogenous compounds, such as microsomal enzyme inducers (MEIs), alter gene expression through xenobiotic-responsive transcription factors, namely, the aryl hydrocarbon receptor (AhR), constitutive androstane receptor (CAR), pregnane X receptor (PXR), peroxisome proliferator-activated receptor α (PPARα), and nuclear factor erythroid 2-related factor 2 (Nrf2). These transcription factors regulate xenobiotic-inducible expression of hepatic and intestinal biotransformation enzymes and transporters. The purpose of this study was to determine hepatic and intestinal inducibility of mouse Ugt mRNA by MEIs. Male C57BL/6 mice were treated for four consecutive days with activators of AhR [2,3,7,8-tetrachlorodibenzodioxin (TCDD), polychlorinated biphenyl 126, and β-naphthoflavone], CAR [1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP), phenobarbital, and diallyl sulfide], PXR [pregnenolone-16α-carbonitrile (PCN), spironolactone, and dexamethasone], PPARα (clofibrate, ciprofibrate, and diethylhexylphthalate), and Nrf2 (oltipraz, ethoxyquin, and butylated hydroxyanisole), respectively. Ugt1a1 mRNA expression in liver was induced by activators of all five transcription factor pathways, Ugt1a5 by Nrf2 activators, Ugt1a6 by all the pathways except CAR, and Ugt1a9 by all the pathways except Nrf2. Ugt2b35 mRNA in liver was induced by AhR activators and Ugt2b36 by CAR and PPARα activators. Throughout the small and large intestine, the AhR ligand TCDD increased Ugt1a6 and Ugt1a7 mRNA. In small intestine, the PXR activator PCN increased Ugt1a1, Ugt1a6, Ugt1a7, Ugt2b34, and Ugt2b35 mRNA in the duodenum. In conclusion, chemical activation of AhR, CAR, PXR, PPARα, and Nrf2 in mouse results in induction of distinct Ugt gene sets in liver and intestine, predominantly the Ugt1a isoforms.
Footnotes
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This work was supported by the National Institutes of Health National Institute of Environmental Health Sciences [Grants ES09649, ES09716, ES07079].
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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.108.024190.
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ABBREVIATIONS: UGT, UDP-glucuronosyltransferase; MEI, microsomal enzyme inducer; CAR, constitutive androstane receptor; PXR, pregnane X receptor; PB, phenobarbital; TCPOBOP, 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene; PPARα, peroxisome proliferator-activated receptor α; AhR, aryl-hydrocarbon receptor; Nrf2, nuclear factor erythroid 2-related factor 2; NQO1, NADPH quinone oxidoreductase; TCDD, 2,3,7,8-tetrachlorodibenzo-p-dioxin; PCB126, polychlorinated biphenyl 126; OPZ, oltipraz; bDNA, branched DNA; β-NF, β-naphthoflavone; DAS, diallyl sulfide; PCN, pregnenolone-16α-carbonitrile; SPR, spironolactone; DEX, dexamethasone; CLFB, clofibrate; CPFB, ciprofibrate; DEHP, diethylhexylphthalate; ETHOXYQ, ethoxyquin; BHA, butylated hydroxyanisole.
- Received October 28, 2008.
- Accepted January 13, 2009.
- The American Society for Pharmacology and Experimental Therapeutics
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