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Schuetz JD, Swaan PW, Tweedie DJ. The role of transporters in toxicity and disease. Drug Metab Dispos 2014; 42:541-5. [PMID: 24598705 PMCID: PMC3965901 DOI: 10.1124/dmd.114.057539] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 02/07/2014] [Indexed: 01/19/2023] Open
Abstract
The significance of transporters in the disposition, metabolism, and elimination of drugs is well recognized. One gap in our knowledge is a comprehensive understanding of how drug transporters change functionality (their amount and activity) in response to disease and how disease and its inevitable pathology change transporter expression. In this issue of Drug Metabolism and Disposition a series of review and primary research articles are presented to highlight the importance of transporters in toxicity and disease. Because of the central role of the liver in drug metabolism, many of the articles in this theme issue focus on transporters in the liver and how pathology or alterations in physiology affects transporter expression. The contributing authors have also considered the role of transporters in drug interactions as well as drug-induced liver injury. Noninvasive approaches to assessing transporter function in vivo are also described. Several articles highlight important issues in oncology where toxicity must be balanced against efficacy. In total, this theme issue will provide a stepping-stone to future studies that will establish a more comprehensive understanding of transporters in disease.
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Affiliation(s)
- John D Schuetz
- Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee (J.D.S); Department of Pharmaceutical Sciences, University of Maryland, Baltimore, Maryland (P.W.S); and Department of Drug Metabolism and Pharmacokinetics, Boehringer Ingelheim, Ridgefield, Connecticut (D.J.T.)
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Kosters A, Felix JC, Desai MS, Karpen SJ. Impaired bile acid handling and aggravated liver injury in mice expressing a hepatocyte-specific RXRα variant lacking the DNA-binding domain. J Hepatol 2014; 60:362-9. [PMID: 24120911 PMCID: PMC3946967 DOI: 10.1016/j.jhep.2013.09.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Revised: 09/20/2013] [Accepted: 09/30/2013] [Indexed: 12/19/2022]
Abstract
BACKGROUND & AIMS Retinoid X Receptor α (RXRα) is the principal heterodimerization partner of class II Nuclear Receptors (NRs), and a major regulator of gene expression of numerous hepatic processes, including bile acid (BA) homeostasis through multiple partners. Specific contributions of hepatic RXRα domains in heterodimer function in response to either BA load or ductular cholestasis are not fully characterized. METHODS Wild-type (WT) mice and mice expressing a hepatocyte-specific RXRα lacking the DNA-Binding-Domain (hs-RxrαΔex4(-/-)), which retains partial ability to heterodimerize with its partners, were fed a 1% cholic acid (CA) diet for 5 days, a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet for 3 weeks, or control diet. RESULTS Serum ALT (6.5-fold; p<0.05), AST (9.3-fold; p=0.06) and BA (2.8-fold; p<0.05) were increased in CA-fed hs-RxαΔex4(-/-) mice compared to CA-fed WT mice, but were equally induced between genotypes by DDC-feeding. CA-feeding elevated total (4.4-fold; p=0.06) and unconjugated (2.2-fold; p<0.02) bilirubin levels in hs-RxrαΔex4(-/-) mice compared to WT mice, but not in DDC-fed hs-RxrαΔex4(-/-) mice. Increased necrosis and inflammation was observed in CA-fed, but not in DDC-fed hs-RxrαΔex4(-/-) mice. Apoptotic markers DR5, CK8, CK18 RNA were increased in CA- and DDC-fed hs-RxrαΔex4(-/-) mice. Cleaved caspase 3, CK18 and p-JNK protein were elevated in CA-fed but not in DDC-fed hs-RxrαΔex4(-/-) mice. Induction of Ostβ and Cyp2b10 RNA was impaired in CA-fed and DDC-fed hs-RxrαΔex4(-/-) mice. Surprisingly, DDC-fed hs-RxrαΔex4(-/-) mice showed attenuated fibrosis compared to DDC-fed WT mice. CONCLUSIONS These two models of cholestasis identify common and injury-specific roles for RXRα heterodimers and the functional relevance of an intact RXRα-DBD in the hepatocytic adaptive cholestatic response.
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Affiliation(s)
- Astrid Kosters
- Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, Emory University School of Medicine, Atlanta GA, 30322
| | - Julio C. Felix
- Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030
| | - Moreshwar S. Desai
- Division of Critical Care Medicine, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030
| | - Saul J. Karpen
- Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, Emory University School of Medicine, Atlanta GA, 30322
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Hrycay E, Forrest D, Liu L, Wang R, Tai J, Deo A, Ling V, Bandiera S. Hepatic bile acid metabolism and expression of cytochrome P450 and related enzymes are altered in Bsep (-/-) mice. Mol Cell Biochem 2014; 389:119-32. [PMID: 24399466 DOI: 10.1007/s11010-013-1933-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 12/18/2013] [Indexed: 02/06/2023]
Abstract
The bile salt export pump (BSEP/Bsep; gene symbol ABCB11/Abcb11) translocates bile salts across the hepatocyte canalicular membrane into bile in humans and mice. In humans, mutations in the ABCB11 gene cause a severe childhood liver disease known as progressive familial intrahepatic cholestasis type 2. Targeted inactivation of mouse Bsep produces milder persistent cholestasis due to detoxification of bile acids through hydroxylation and alternative transport pathways. The purpose of the present study was to determine whether functional expression of hepatic cytochrome P450 (CYP) and microsomal epoxide hydrolase (mEH) is altered by Bsep inactivation in mice and whether bile acids regulate CYP and mEH expression in Bsep (-/-) mice. CYP expression was determined by measuring protein levels of Cyp2b, Cyp2c and Cyp3a enzymes and CYP-mediated activities including lithocholic acid hydroxylation, testosterone hydroxylation and alkoxyresorufin O-dealkylation in hepatic microsomes prepared from female and male Bsep (-/-) mice fed a normal or cholic acid (CA)-enriched diet. The results indicated that hepatic lithocholic acid hydroxylation was catalyzed by Cyp3a/Cyp3a11 enzymes in Bsep (-/-) mice and that 3-ketocholanoic acid and murideoxycholic acid were major metabolites. CA feeding of Bsep (-/-) mice increased hepatic Cyp3a11 protein levels and Cyp3a11-mediated testosterone 2β-, 6β-, and 15β-hydroxylation activities, increased Cyp2b10 protein levels and Cyp2b10-mediated benzyloxyresorufin O-debenzylation activity, and elevated Cyp2c29 and mEH protein levels. We propose that bile acids upregulate expression of hepatic Cyp3a11, Cyp2b10, Cyp2c29 and mEH in Bsep (-/-) mice and that Cyp3a11 and multidrug resistance-1 P-glycoproteins (Mdr1a/1b) are vital components of two distinct pathways utilized by mouse hepatocytes to expel bile acids.
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Affiliation(s)
- Eugene Hrycay
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC, V6T1Z3, Canada
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Abstract
Enterohepatic circulation is responsible for the capture of bile acids and other steroids produced or metabolized in the liver and secreted to the intestine, for reabsorption back into the circulation and transport back to the liver. Bile acids are secreted from the liver in the form of mixed micelles that also contain phosphatidylcholines and cholesterol that facilitate the uptake of fats and vitamins from the diet due to the surfactant properties of bile acids and lipids. Bile acids are synthesized in the liver from cholesterol by a cascade of enzymes that carry out oxidation and conjugation reactions, and transported to the bile duct and gall bladder where they are stored before being released into the intestine. Bile flow from the gall bladder to the small intestine is triggered by food intake in accordance with its role in lipid and vitamin absorption from the diet. Bile acids are further metabolized by gut bacteria and are transported back to the circulation. Metabolites produced in the liver are termed primary bile acids or primary conjugated bile salts, while the metabolites generated by bacterial are called secondary bile acids. About 95% of bile acids are reabsorbed in the proximal and distal ileum into the hepatic portal vein and then into the liver sinusoids, where they are efficiently transported into the liver with little remaining in circulation. Each bile acid is reabsorbed about 20 times on average before being eliminated. Enterohepatic circulation is under tight regulation by nuclear receptor signaling, notably by the farnesoid X receptor (FXR).
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Affiliation(s)
- Frank J Gonzalez
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.
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Takigawa T, Miyazaki H, Kinoshita M, Kawarabayashi N, Nishiyama K, Hatsuse K, Ono S, Saitoh D, Seki S, Yamamoto J. Glucocorticoid receptor-dependent immunomodulatory effect of ursodeoxycholic acid on liver lymphocytes in mice. Am J Physiol Gastrointest Liver Physiol 2013; 305:G427-38. [PMID: 23868404 DOI: 10.1152/ajpgi.00205.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Although ursodeoxycholic acid (UDCA) has long been used for patients with chronic cholestatic liver diseases, particularly primary biliary cirrhosis, it may modulate the host immune response. This study investigated the effect of UDCA feeding on experimental hepatitis, endotoxin shock, and bacterial infection in mice. C57BL/6 mice were fed a diet supplemented with or without 0.3% (wt/vol) UDCA for 4 wk. UDCA improved hepatocyte injury and survival in concanavalin-A (Con-A)-induced hepatitis by suppressing IFN-γ production by liver mononuclear cells (MNC), especially NK and NKT cells. UDCA also increased survival after lipopolysaccharide (LPS)-challenge; however, it increased mortality of mice following Escherichia coli infection due to the worsening of infection. UDCA-fed mice showed suppressed serum IL-18 levels and production of IL-18 from liver Kupffer cells, which together with IL-12 potently induce IFN-γ production. However, unlike normal mice, exogenous IL-18 pretreatment did not increase the serum IFN-γ levels after E. coli, LPS, or Con-A challenge in the UDCA-fed mice. Interestingly, however, glucocorticoid receptor (GR) expression was significantly upregulated in the liver MNC of the UDCA-fed mice but not in their whole liver tissue homogenates. Silencing GR in the liver MNC abrogated the suppressive effect of UDCA on LPS- or Con-A-induced IFN-γ production. Furthermore, RU486, a GR antagonist, restored the serum IFN-γ level in UDCA-fed mice after E. coli, LPS, or Con-A challenge. Taken together, these results suggest that IFN-γ-reducing immunomodulatory property of UDCA is mediated by elevated GR in the liver lymphocytes in an IL-12/18-independent manner.
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Affiliation(s)
- Toshimichi Takigawa
- Dept. of Immunology and Microbiology, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama, 359-8513 Japan.
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Chaudhry AS, Thirumaran RK, Yasuda K, Yang X, Fan Y, Strom SC, Schuetz EG. Genetic variation in aldo-keto reductase 1D1 (AKR1D1) affects the expression and activity of multiple cytochrome P450s. Drug Metab Dispos 2013; 41:1538-47. [PMID: 23704699 PMCID: PMC4162005 DOI: 10.1124/dmd.113.051672] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Accepted: 05/23/2013] [Indexed: 02/02/2023] Open
Abstract
Human liver gene regulatory (Bayesian) network analysis was previously used to identify a cytochrome P450 (P450) gene subnetwork with Aldo-keto reductase 1D1 (AKR1D1) as a key regulatory driver of this subnetwork. This study assessed the biologic importance of AKR1D1 [a key enzyme in the synthesis of bile acids, ligand activators of farnesoid X receptor (FXR), pregnane X receptor (PXR), and constitutive androstane receptor (CAR), known transcriptional regulators of P450s] to hepatic P450 expression. Overexpression of AKR1D1 in primary human hepatocytes led to increased expression of CYP3A4, CYP2C8, CYP2C9, CYP2C19, and CYP2B6. Conversely, AKR1D1 knockdown decreased expression of these P450s. We resequenced AKR1D1 from 98 donor livers and identified a 3'-untranslated region (UTR) (rs1872930) single nucleotide polymorphism (SNP) significantly associated with higher AKR1D1 mRNA expression. AKR1D1 3'-UTR-luciferase reporter studies showed that the variant allele resulted in higher luciferase activity, suggesting that the SNP increases AKR1D1 mRNA stability and/or translation efficiency. Consistent with AKR1D1's putative role as a driver of the P450 subnetwork, the AKR1D1 3'-UTR SNP was significantly associated with increased hepatic mRNA expression of multiple P450s (CYP3A4, CYP2C8, CYP2C9, CYP2C19, and CYP2B6) and CYP3A4, CYP2C8, CYP2C19, and CYP2B6 activities. After adjusting for multiple testing, the association remained significant for AKR1D1, CYP2C9, and CYP2C8 mRNA expression and CYP2C8 activity. These results provide new insights into the variation in expression and activity of P450s that can account for interindividual differences in drug metabolism/efficacy and adverse drug events. In conclusion, we provide the first experimental evidence supporting a role for AKR1D1 as a key genetic regulator of the P450 network.
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Affiliation(s)
- Amarjit S Chaudhry
- Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
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Staudinger JL, Woody S, Sun M, Cui W. Nuclear-receptor-mediated regulation of drug- and bile-acid-transporter proteins in gut and liver. Drug Metab Rev 2013; 45:48-59. [PMID: 23330541 DOI: 10.3109/03602532.2012.748793] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Adverse drug events (ADEs) are a common cause of patient morbidity and mortality and are classically thought to result, in part, from variation in expression and activity of hepatic enzymes of drug metabolism. It is now known that alterations in the expression of genes that encode drug- and bile-acid-transporter proteins in both the gut and liver play a previously unrecognized role in determining patient drug response and eventual clinical outcome. Four nuclear receptor (NR) superfamily members, including pregnane X receptor (PXR, NR1I2), constitutive androstane receptor (NR1I3), farnesoid X receptor (NR1H4), and vitamin D receptor (NR1I1), play pivotal roles in drug- and bile-acid-activated programs of gene expression to coordinately regulate drug- and bile-acid transport activity in the intestine and liver. This review focuses on the NR-mediated gene activation of drug and bile-acid transporters in these tissues as well as the possible underlying molecular mechanisms.
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Affiliation(s)
- Jeff L Staudinger
- Department of Pharmacology and Toxicology, University of Kansas, Lawrence, Kansas 66045, USA.
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Influence of CYP3A5 and MDR1 Genetic Polymorphisms on Urinary 6β-Hydroxycortisol/Cortisol Ratio After Grapefruit Juice Intake in Healthy Chinese. J Clin Pharmacol 2013; 50:775-84. [DOI: 10.1177/0091270009354997] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Gardès C, Chaput E, Staempfli A, Blum D, Richter H, Benson GM. Differential regulation of bile acid and cholesterol metabolism by the farnesoid X receptor in Ldlr -/- mice versus hamsters. J Lipid Res 2013; 54:1283-99. [PMID: 23431047 DOI: 10.1194/jlr.m033423] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Modulating bile acid synthesis has long been considered a good strategy by which to improve cholesterol homeostasis in humans. The farnesoid X receptor (FXR), the key regulator of bile acid synthesis, was, therefore, identified as an interesting target for drug discovery. We compared the effect of four, structurally unrelated, synthetic FXR agonists in two fat-fed rodent species and observed that the three most potent and selective agonists decreased plasma cholesterol in LDL receptor-deficient (Ldlr (-/-)) mice, but none did so in hamsters. Detailed investigation revealed increases in the expression of small heterodimer partner (Shp) in their livers and of intestinal fibroblast growth factor 15 or 19 (Fgf15/19) in mice only. Cyp7a1 expression and fecal bile acid (BA) excretion were strongly reduced in mice and hamsters by all four FXR agonists, whereas bile acid pool sizes were reduced in both species by all but the X-Ceptor compound in hamsters. In Ldlr (-/-) mice, the predominant bile acid changed from cholate to the more hydrophilic β-muricholate due to a strong repression of Cyp8b1 and increase in Cyp3a11 expression. However, FXR agonists caused only minor changes in the expression of Cyp8b1 and in bile acid profiles in hamsters. In summary, FXR agonist-induced decreases in bile acid pool size and lipophilicity and in cholesterol absorption and synthesis could explain the decreased plasma cholesterol in Ldlr (-/-) mice. In hamsters, FXR agonists reduced bile acid pool size to a smaller extent with minor changes in bile acid profile and reductions in sterol absorption, and consequently, plasma cholesterol was unchanged.
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Affiliation(s)
- Christophe Gardès
- Cardiovascular and Metabolic Diseases DTA, F. Hoffmann-La Roche AG, Basel, Switzerland.
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Aleksunes LM, Xu J, Lin E, Wen X, Goedken MJ, Slitt AL. Pregnancy represses induction of efflux transporters in livers of type I diabetic mice. Pharm Res 2013; 30:2209-20. [PMID: 23319174 DOI: 10.1007/s11095-013-0981-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Accepted: 01/07/2013] [Indexed: 01/13/2023]
Abstract
PURPOSE To determine whether down-regulation of transcription factor signaling during pregnancy disrupts the induction of efflux transporters in type I diabetic mice. METHODS Type I diabetes was induced in female C57BL/6 mice with multiple low dose intraperitoneal injections of streptozotocin (STZ) at least 2 weeks prior to mating with normoglycemic male mice. On gestation day 14, livers were collected from vehicle- and STZ-treated non-pregnant and pregnant mice for quantification of efflux transporter and transcription factor signaling. RESULTS STZ treatment up-regulated expression of Mrp1-5, Mdr1, Abcg5, Abcg8, Bcrp, and Bsep mRNA and/or protein in the livers of non-pregnant mice. Interestingly, little to no change in transporter expression was observed in STZ-treated pregnant mice compared to vehicle- and STZ-treated non-pregnant mice. CONCLUSIONS This study demonstrates the opposing regulation of hepatobiliary efflux transporters in response to diabetes and pregnancy and points to PPARγ, Nrf2, and FXR as candidate pathways underlying the differential expression of transporters.
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Affiliation(s)
- Lauren M Aleksunes
- Department of Pharmacology and Toxicology, Rutgers University Ernest Mario School of Pharmacy, Piscataway, New Jersey, USA.
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Chu X, Bleasby K, Evers R. Species differences in drug transporters and implications for translating preclinical findings to humans. Expert Opin Drug Metab Toxicol 2012; 9:237-52. [DOI: 10.1517/17425255.2013.741589] [Citation(s) in RCA: 208] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Wang J, Jiang Z, Ji J, Li Y, Chen M, Wang Y, Zhang Y, Tai T, Wang T, Zhang L. Evaluation of hepatotoxicity and cholestasis in rats treated with EtOH extract of Fructus Psoraleae. JOURNAL OF ETHNOPHARMACOLOGY 2012; 144:73-81. [PMID: 22954498 DOI: 10.1016/j.jep.2012.08.028] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Revised: 07/21/2012] [Accepted: 08/16/2012] [Indexed: 06/01/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Fructus Psoraleae (FP) has been widely used to heal skin diseases as well as osteoporosis, osteomalacia, and bone fracture. There also exist many clinical reports about FP-induced hepatotoxicity associated with acute cholestatic hepatic injury. However, the FP-induced hepatotoxicity and the underlying mechanisms remain unclear. AIMS OF THE STUDY The present study aims to determine the hepatotoxicity of FP in Sprague-Dawley (SD) rats and to investigate the underlying mechanisms. MATERIALS AND METHODS Sprague-Dawley rats of both sexes were intragastrically administered with the EtOH extract of FP (EEFP) at doses of 1.875, 1.25 and 0.625 g/kg for 28 day. Body weight, relative liver weight, biochemical analysis, histopathology, the mRNA and protein expression of Cholesterol 7α-hydroxylase (CYP7A1), farnesoid X receptor (FXR), bile-salt export pump (BSEP), multidrug resistance-associated protein 2 (MRP2), multidrug resistance-associated protein 3 (MRP3) were evaluated to study the EEFP-induced hepatotoxicity and its underlying mechanisms. RESULTS Many abnormalities were observed in the EEFP-treated groups including suppression of weight gain and food intake, change of some parameters in serum biochemistry, increased weight of liver, and decreased concentration of bile acid in bile. The mRNA and protein expression of CYP7A1, MRP3, MRP2, BSEP increased and the expression of FXR decreased in EEFP-treated female groups; the mRNA and protein of FXR and CYP7A1 decreased and that of the others remained the same in EEFP-treated male groups. CONCLUSION In conclusion, we provide evidence for the first time that EEFP can induce sex-related cholestatic hepatotoxicity, and that female rats are more sensitive to EEFP-induced hepatotoxicity, which involves the destruction of the biosynthesis and transportation of bile acid. Further investigation is still needed to uncover the mechanism of the sex-dimorphic EEFP-induced hepatotoxicity.
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Affiliation(s)
- Jiaying Wang
- Jiangsu Provincial Center for Drug Screening, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing 210009, PR China
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63
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Wang YG, Zhou JM, Ma ZC, Li H, Liang QD, Tan HL, Xiao CR, Zhang BL, Gao Y. Pregnane X receptor mediated-transcription regulation of CYP3A by glycyrrhizin: A possible mechanism for its hepatoprotective property against lithocholic acid-induced injury. Chem Biol Interact 2012; 200:11-20. [DOI: 10.1016/j.cbi.2012.08.023] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Revised: 08/17/2012] [Accepted: 08/27/2012] [Indexed: 10/27/2022]
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Attinkara R, Mwinyi J, Truninger K, Regula J, Gaj P, Rogler G, Kullak-Ublick GA, Eloranta JJ. Association of genetic variation in the NR1H4 gene, encoding the nuclear bile acid receptor FXR, with inflammatory bowel disease. BMC Res Notes 2012; 5:461. [PMID: 22929053 PMCID: PMC3517390 DOI: 10.1186/1756-0500-5-461] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Accepted: 08/01/2012] [Indexed: 12/15/2022] Open
Abstract
Background Pathogenesis of inflammatory bowel diseases (IBD), ulcerative colitis (UC) and Crohn’s disease (CD), involves interaction between environmental factors and inappropriate immune responses in the intestine of genetically predisposed individuals. Bile acids and their nuclear receptor, FXR, regulate inflammatory responses and barrier function in the intestinal tract. Methods We studied the association of five variants (rs3863377, rs7138843, rs56163822, rs35724, rs10860603) of the NR1H4 gene encoding FXR with IBD. 1138 individuals (591 non-IBD, 203 UC, 344 CD) were genotyped for five NR1H4 genetic variants with TaqMan SNP Genotyping Assays. Results We observed that the NR1H4 SNP rs3863377 is significantly less frequent in IBD cases than in non-IBD controls (allele frequencies: P = 0.004; wild-type vs. SNP carrier genotype frequencies: P = 0.008), whereas the variant rs56163822 is less prevalent in non-IBD controls (allele frequencies: P = 0.027; wild-type vs. SNP carrier genotype frequencies: P = 0.035). The global haplotype distribution between IBD and control patients was significantly different (P = 0.003). This also held true for the comparison between non-IBD and UC groups (P = 0.004), but not for the comparison between non-IBD and CD groups (P = 0.079). Conclusions We show that genetic variation in FXR is associated with IBD, further emphasizing the link between bile acid signaling and intestinal inflammation.
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Affiliation(s)
- Ragam Attinkara
- Department of Clinical Pharmacology and Toxicology, University Hospital, Zurich, Switzerland
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Jonker JW, Liddle C, Downes M. FXR and PXR: potential therapeutic targets in cholestasis. J Steroid Biochem Mol Biol 2012; 130:147-58. [PMID: 21801835 PMCID: PMC4750880 DOI: 10.1016/j.jsbmb.2011.06.012] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2011] [Revised: 05/17/2011] [Accepted: 06/17/2011] [Indexed: 12/17/2022]
Abstract
Cholestatic liver disorders encompass hepatobiliary diseases of diverse etiologies characterized by the accumulation of bile acids, bilirubin and cholesterol as the result of impaired secretion of bile. Members of the nuclear receptor (NR) family of ligand-modulated transcription factors are implicated in the adaptive response to cholestasis. NRs coordinately regulate bile acid and phospholipid transporter genes required for hepatobiliary transport, as well as the phases I and II metabolizing enzymes involved in processing of their substrates. In this review we will focus on FXR and PXR, two members of the NR family whose activities are regulated by bile acids. In addition, we also discuss the potential of pharmacological modulators of these receptors as novel therapies for cholestatic disorders.
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Affiliation(s)
- Johan W. Jonker
- Center for Liver, Digestive and Metabolic Diseases, Department of Pediatrics, University Medical Center Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
- Corresponding author. Tel.: +31 050 361 1261; fax: +31 050 361 1746
| | - Christopher Liddle
- Storr Liver Unit, Westmead Millennium Institute and University of Sydney, Westmead Hospital, Westmead, NSW 2145, Australia
| | - Michael Downes
- Gene Expression Laboratory, The Salk Institute for Biological Studies, Howard Hughes Medical Institute, 10010 Torrey Pines Road, La Jolla, CA 92037, USA
- Corresponding author. Tel.: +1 858 453 4100; fax: +1 858 455 1349
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Chen Y, Tang Y, Guo C, Wang J, Boral D, Nie D. Nuclear receptors in the multidrug resistance through the regulation of drug-metabolizing enzymes and drug transporters. Biochem Pharmacol 2012; 83:1112-26. [PMID: 22326308 PMCID: PMC3339266 DOI: 10.1016/j.bcp.2012.01.030] [Citation(s) in RCA: 167] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 01/23/2012] [Accepted: 01/25/2012] [Indexed: 01/18/2023]
Abstract
Chemotherapy is one of the three most common treatment modalities for cancer. However, its efficacy is limited by multidrug resistant cancer cells. Drug metabolizing enzymes (DMEs) and efflux transporters promote the metabolism, elimination, and detoxification of chemotherapeutic agents. Consequently, elevated levels of DMEs and efflux transporters reduce the therapeutic effectiveness of chemotherapeutics and, often, lead to treatment failure. Nuclear receptors, especially pregnane X receptor (PXR, NR1I2) and constitutive androstane activated receptor (CAR, NR1I3), are increasingly recognized for their role in xenobiotic metabolism and clearance as well as their role in the development of multidrug resistance (MDR) during chemotherapy. Promiscuous xenobiotic receptors, including PXR and CAR, govern the inducible expressions of a broad spectrum of target genes that encode phase I DMEs, phase II DMEs, and efflux transporters. Recent studies conducted by a number of groups, including ours, have revealed that PXR and CAR play pivotal roles in the development of MDR in various human carcinomas, including prostate, colon, ovarian, and esophageal squamous cell carcinomas. Accordingly, PXR/CAR expression levels and/or activation statuses may predict prognosis and identify the risk of drug resistance in patients subjected to chemotherapy. Further, PXR/CAR antagonists, when used in combination with existing chemotherapeutics that activate PXR/CAR, are feasible and promising options that could be utilized to overcome or, at least, attenuate MDR in cancer cells.
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Affiliation(s)
- Yakun Chen
- Department of Medical Microbiology, Immunology, and Cell Biology, Southern Illinois University School of Medicine, Springfield, IL 62794, United States
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Endogenous bile acid disposition in rat and human sandwich-cultured hepatocytes. Toxicol Appl Pharmacol 2012; 261:1-9. [PMID: 22342602 DOI: 10.1016/j.taap.2012.02.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 01/10/2012] [Accepted: 02/02/2012] [Indexed: 01/08/2023]
Abstract
Sandwich-cultured hepatocytes (SCH) are used commonly to investigate hepatic transport protein-mediated uptake and biliary excretion of substrates. However, little is known about the disposition of endogenous bile acids (BAs) in SCH. In this study, four endogenous conjugated BAs common to rats and humans [taurocholic acid (TCA), glycocholic acid (GCA), taurochenodeoxycholic acid (TCDCA), and glycochenodeoxycholic acid (GCDCA)], as well as two BA species specific to rodents (α- and β-tauromuricholic acid; α/β TMCA), were profiled in primary rat and human SCH. Using B-CLEAR® technology, BAs were measured in cells+bile canaliculi, cells, and medium of SCH by LC-MS/MS. Results indicated that, just as in vivo, taurine-conjugated BA species were predominant in rat SCH, while glycine-conjugated BAs were predominant in human SCH. Total intracellular BAs remained relatively constant over days in culture in rat SCH. Total BAs in control (CTL) cells+bile, cells, and medium were approximately 3.4, 2.9, and 8.3-fold greater in human than in rat. The estimated intracellular concentrations of the measured total BAs were 64.3±5.9 μM in CTL rat and 183±56 μM in CTL human SCH, while medium concentrations of the total BAs measured were 1.16±0.21 μM in CTL rat SCH and 9.61±6.36 μM in CTL human SCH. Treatment of cells for 24h with 10 μM troglitazone (TRO), an inhibitor of the bile salt export pump (BSEP) and the Na⁺-taurocholate cotransporting polypeptide (NTCP), had no significant effect on endogenous BAs measured at the end of the 24-h culture period, potentially due to compensatory mechanisms that maintain BA homeostasis. These data demonstrate that BAs in SCH are similar to in vivo, and that SCH may be a useful in vitro model to study alterations in BA disposition if species differences are taken into account.
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A novel heterozygous NR1H4 termination codon mutation in idiopathic infantile cholestasis. World J Pediatr 2012; 8:67-71. [PMID: 21633855 DOI: 10.1007/s12519-011-0299-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Accepted: 05/04/2010] [Indexed: 02/05/2023]
Abstract
BACKGROUND This study aimed to evaluate the genetic effect of the NR1H4 gene in the pathogenesis of idiopathic infantile cholestasis of Chinese subjects in Guangxi, China. METHODS Seventy-eight patients with idiopathic infantile cholestasis served as a study group and 95 infants without cholestasis as controls. Genomic DNA was extracted from peripheral venous blood leucocytes by phenol chloroform procedures. Polymerase chain reaction (PCR) was used to amplify all coded exons of NR1H4, and single-strand conformation polymorphism (SSCP) was used to analyze all amplification fragments. The PCR products with abnormal bands in SSCP were sequenced using an ABI 3100 sequencer. RESULTS A novel heterozygous termination codon mutation in NR1H4 exon 5 (NR1H4 R176X, CGA-TGA) was found in one of the 78 patients. The patient with mutation R176X had high levels of bilirubin, alanine aminotransferase, γ-glutamyltransferase, cirrhosis and ascites despite biliary tract flushing procedures and drug therapy. In the other patients and controls, no mutation was detected. CONCLUSIONS Heterozygous termination codon mutation of NR1H4 R176X was found in idiopathic infantile cholestasis. The novel mutation is useful to establish particular characteristics for differential diagnosis of idiopathic infantile cholestasis and to determine the influence of such gene defects in the prognosis.
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Fidler AE, Holland PT, Reschly EJ, Ekins S, Krasowski MD. Activation of a tunicate (Ciona intestinalis) xenobiotic receptor orthologue by both natural toxins and synthetic toxicants. Toxicon 2011; 59:365-72. [PMID: 22206814 DOI: 10.1016/j.toxicon.2011.12.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2011] [Revised: 12/04/2011] [Accepted: 12/06/2011] [Indexed: 12/21/2022]
Abstract
Vertebrate xenobiotic receptors are ligand-activated nuclear receptors (NRs) that bind exogenous biologically active chemicals before activating the transcription of genes involved in xenobiotic metabolism and excretion. Typically, xenobiotic receptors have ligand binding domains (LBDs) that can accommodate a structurally diverse array of molecules and in addition display high levels of inter-taxa sequence diversity suggestive of positive selection. Pursuing the idea that xenobiotic receptors may adaptively evolve to bind toxic chemicals commonly present in an organism's environment/diet, we examined ligand binding by a xenobiotic receptor orthologue of a marine filter-feeding organism. The solitary tunicate Ciona intestinalis (Phylum Chordata) genome encodes an orthologue of the vertebrate pregnane X receptor (PXR) and vitamin D receptor (VDR), here denoted CiVDR/PXRα. In a luciferase reporter assay the CiVDR/PXRα was activated, at nanomolar concentrations, by two of four natural marine microalgal biotoxins tested (okadaic acid, EC50 = 18.2 ± 0.9 nM and pectenotoxin-2, EC50 = 37.0 ± 3.5 nM) along with 1 of 11 synthetic toxicants (esfenvalerate: EC50 = 0.59 ± 0.7 μM). Two related C. intestinalis NRs, orthologous to vertebrate farnesoid X receptor and liver X receptors, respectively, along with the PXR of a freshwater fish (zebrafish, Danio rerio), were not activated by any of the 15 chemicals tested. In contrast, human PXR was activated by okadaic acid at similar concentrations to CiVDR/PXRα (EC50 = 7.2 ± 1.1 nM) but not by pectenotoxin-2. A common features pharmacophore developed for the CiVDR/PXRα ligand consisted of an off-center hydrogen bond acceptor flanked by two hydrophobic regions. The results of this study are consistent with the original hypothesis that natural toxins, present in the diet of filter-feeding marine invertebrates, may have acted as selective agents in the molecular evolution of tunicate xenobiotic receptors. Bioassays based on tunicate xenobiotic receptor activation may find application in marine environmental monitoring and bioprospecting.
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Affiliation(s)
- Andrew E Fidler
- Cawthron Institute, Private Bag 2, Nelson 7012, New Zealand.
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Sodani K, Patel A, Kathawala RJ, Chen ZS. Multidrug resistance associated proteins in multidrug resistance. CHINESE JOURNAL OF CANCER 2011; 31:58-72. [PMID: 22098952 PMCID: PMC3777468 DOI: 10.5732/cjc.011.10329] [Citation(s) in RCA: 192] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Multidrug resistance proteins (MRPs) are members of the C family of a group of proteins named ATP-binding cassette (ABC) transporters. These ABC transporters together form the largest branch of proteins within the human body. The MRP family comprises of 13 members, of which MRP1 to MRP9 are the major transporters indicated to cause multidrug resistance in tumor cells by extruding anticancer drugs out of the cell. They are mainly lipophilic anionic transporters and are reported to transport free or conjugates of glutathione (GSH), glucuronate, or sulphate. In addition, MRP1 to MRP3 can transport neutral organic drugs in free form in the presence of free GSH. Collectively, MRPs can transport drugs that differ structurally and mechanistically, including natural anticancer drugs, nucleoside analogs, antimetabolites, and tyrosine kinase inhibitors. Many of these MRPs transport physiologically important anions such as leukotriene C4, bilirubin glucuronide, and cyclic nucleotides. This review focuses mainly on the physiological functions, cellular resistance characteristics, and probable in vivo role of MRP1 to MRP9.
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Affiliation(s)
- Kamlesh Sodani
- Department of Pharmaceutical Sciences, St. John's University, Queens, NY 11439, USA
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Ursodeoxycholic acid in cholestasis: linking action mechanisms to therapeutic applications. Clin Sci (Lond) 2011; 121:523-44. [PMID: 21854363 DOI: 10.1042/cs20110184] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
UDCA (ursodeoxycholic acid) is the therapeutic agent most widely used for the treatment of cholestatic hepatopathies. Its use has expanded to other kinds of hepatic diseases, and even to extrahepatic ones. Such versatility is the result of its multiple mechanisms of action. UDCA stabilizes plasma membranes against cytolysis by tensioactive bile acids accumulated in cholestasis. UDCA also halts apoptosis by preventing the formation of mitochondrial pores, membrane recruitment of death receptors and endoplasmic-reticulum stress. In addition, UDCA induces changes in the expression of metabolizing enzymes and transporters that reduce bile acid cytotoxicity and improve renal excretion. Its capability to positively modulate ductular bile flow helps to preserve the integrity of bile ducts. UDCA also prevents the endocytic internalization of canalicular transporters, a common feature in cholestasis. Finally, UDCA has immunomodulatory properties that limit the exacerbated immunological response occurring in autoimmune cholestatic diseases by counteracting the overexpression of MHC antigens and perhaps by limiting the production of cytokines by immunocompetent cells. Owing to this multi-functionality, it is difficult to envisage a substitute for UDCA that combines as many hepatoprotective effects with such efficacy. We predict a long-lasting use of UDCA as the therapeutic agent of choice in cholestasis.
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Henkel AS, Kavesh MH, Kriss MS, Dewey AM, Rinella ME, Green RM. Hepatic overexpression of abcb11 promotes hypercholesterolemia and obesity in mice. Gastroenterology 2011; 141:1404-11, 1411.e1-2. [PMID: 21726512 PMCID: PMC3186850 DOI: 10.1053/j.gastro.2011.06.062] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2010] [Revised: 05/24/2011] [Accepted: 06/17/2011] [Indexed: 12/12/2022]
Abstract
BACKGROUND & AIMS ABCB11 is a canalicular transport protein that controls the rate-limiting step in hepatic bile acid secretion. Its expression levels vary in humans, and it is not clear how these variations affect lipid metabolism. We investigated whether overexpression of Abcb11 in mice increases lipid absorption in the intestine and affects the development of obesity or hypercholesterolemia. METHODS Transgenic mice that overexpress Abcb11 in liver (TTR-Abcb11) and FVB/NJ mice (controls) were fed a high-cholesterol or high-fat diet for 12 weeks. Intestinal lipid absorption was measured by the dual fecal isotope method. Energy expenditure was measured by indirect calorimetry. The bile acid pool was analyzed by high-performance liquid chromatography. RESULTS TTR-Abcb11 mice had a nearly 2-fold increase in intestinal cholesterol absorption compared with controls. TTR-Abcb11 mice fed a high-cholesterol diet had greater increases in plasma and hepatic levels of cholesterol and became more obese than controls; they also had increased intestinal absorption of fatty acids and decreased energy expenditure. In the TTR-Abcb11 mice, the sizes of plasma and total bile acid pools were reduced; the bile acid pool contained more species of hydrophobic bile acids compared with controls. CONCLUSIONS Hepatic overexpression of Abcb11 in mice promotes diet-induced obesity and hypercholesterolemia; increased intestinal cholesterol absorption by hydrophobic bile acids might cause these features. Increased absorption of fatty acids in the intestine and reduced expenditure of energy could increase weight gain in TTR-Abcb11 mice. In humans, variations in expression of ABCB11 might confer genetic susceptibility to diet-induced hyperlipidemia and obesity.
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Chennamsetty I, Claudel T, Kostner KM, Baghdasaryan A, Kratky D, Levak-Frank S, Frank S, Gonzalez FJ, Trauner M, Kostner GM. Farnesoid X receptor represses hepatic human APOA gene expression. J Clin Invest 2011; 121:3724-34. [PMID: 21804189 DOI: 10.1172/jci45277] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Accepted: 06/01/2011] [Indexed: 12/31/2022] Open
Abstract
High plasma concentrations of lipoprotein(a) [Lp(a), which is encoded by the APOA gene] increase an individual's risk of developing diseases, such as coronary artery diseases, restenosis, and stroke. Unfortunately, increased Lp(a) levels are minimally influenced by dietary changes or drug treatment. Further, the development of Lp(a)-specific medications has been hampered by limited knowledge of Lp(a) metabolism. In this study, we identified patients suffering from biliary obstructions with very low plasma Lp(a) concentrations that rise substantially after surgical intervention. Consistent with this, common bile duct ligation in mice transgenic for human APOA (tg-APOA mice) lowered plasma concentrations and hepatic expression of APOA. To test whether farnesoid X receptor (FXR), which is activated by bile acids, was responsible for the low plasma Lp(a) levels in cholestatic patients and mice, we treated tg-APOA and tg-APOA/Fxr-/- mice with cholic acid. FXR activation markedly reduced plasma concentrations and hepatic expression of human APOA in tg-APOA mice but not in tg-APOA/Fxr-/- mice. Incubation of primary hepatocytes from tg-APOA mice with bile acids dose dependently downregulated APOA expression. Further analysis determined that the direct repeat 1 element between nucleotides -826 and -814 of the APOA promoter functioned as a negative FXR response element. This motif is also bound by hepatocyte nuclear factor 4α (HNF4α), which promotes APOA transcription, and FXR was shown to compete with HNF4α for binding to this motif. These findings may have important implications in the development of Lp(a)-lowering medications.
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Affiliation(s)
- Indumathi Chennamsetty
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Graz, Austria
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Role of nuclear receptors for bile acid metabolism, bile secretion, cholestasis, and gallstone disease. Biochim Biophys Acta Mol Basis Dis 2011; 1812:867-78. [DOI: 10.1016/j.bbadis.2010.12.021] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 12/21/2010] [Accepted: 12/22/2010] [Indexed: 12/12/2022]
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González R, Cruz A, Ferrín G, López-Cillero P, Fernández-Rodríguez R, Briceño J, Gómez MA, Rufián S, Mata MDL, Martínez-Ruiz A, Marin JJG, Muntané J. Nitric oxide mimics transcriptional and post-translational regulation during α-tocopherol cytoprotection against glycochenodeoxycholate-induced cell death in hepatocytes. J Hepatol 2011; 55:133-44. [PMID: 21145864 DOI: 10.1016/j.jhep.2010.10.022] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 10/07/2010] [Accepted: 10/12/2010] [Indexed: 12/11/2022]
Abstract
BACKGROUND & AIMS Reactive oxygen species (ROS) and nitric oxide (NO) exert a relevant role during bile acid-induced hepatotoxicity. Whether α-Tocopherol regulates oxidative and nitrosative stress, bile acid transporter expression and their NO-dependent post-translational modifications, and cell death were assessed in vitro and in vivo. METHODS α-Tocopherol and/or NO donors (DETA-NONOate or CSNO, and V-PYRRO/NO) were administered to glycochenodeoxycholic acid (GCDCA)-treated cultured human hepatocytes or to bile duct obstructed rats. Cell injury, superoxide anion (O⁻₂) production, as well as inducible nitric oxide synthase (NOS-2), cytochrome P4507A1 (CYP7A1), heme oxygenase-1, (HO-1) and bile acid transporter expression were determined. Cysteine S-nitrosylation and tyrosine nitration of Na(+)-taurocholate co-transporting polypeptide (NTCP), as well as taurocholic acid (TC) uptake were also evaluated. RESULTS GCDCA-induced cell death was associated with increased (O⁻₂) production, NTCP and HO-1 expression, and with a reduction of CYP7A1 and NOS-2 expression. α-Tocopherol reduced cell death, (O⁻₂) production, CYP7A1, NTCP, and HO-1 expression, as well as increased NOS-2 expression and NO production in GCDCA-treated hepatocytes. α-Tocopherol and NO donors increased NTCP cysteine S-nitrosylation and tyrosine nitration, and reduced TC uptake in hepatocytes. α-Tocopherol and V-PYRRO/NO reduced liver injury and NTCP expression in obstructed rats. CONCLUSIONS The regulation of CYP7A1, NTCP, and HO-1 expression may be relevant for the cytoprotective properties of α-Tocopherol and NO against mitochondrial dysfunction, oxidative stress and cell death in GCDCA-treated hepatocytes. The regulation of NO-dependent post-translational modifications of NTCP by α-Tocopherol and NO donors reduces the uptake of toxic bile acids by hepatocytes.
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Affiliation(s)
- Raúl González
- Instituto Maimónides para la Investigación Biomédica de Córdoba, Reina Sofia University Hospital, Córdoba, Spain
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Yang J, MacDougall ML, McDowell MT, Xi L, Wei R, Zavadoski WJ, Molloy MP, Baker JD, Kuhn M, Cabrera O, Treadway JL. Polyomic profiling reveals significant hepatic metabolic alterations in glucagon-receptor (GCGR) knockout mice: implications on anti-glucagon therapies for diabetes. BMC Genomics 2011; 12:281. [PMID: 21631939 PMCID: PMC3130710 DOI: 10.1186/1471-2164-12-281] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 06/01/2011] [Indexed: 02/07/2023] Open
Abstract
Background Glucagon is an important hormone in the regulation of glucose homeostasis, particularly in the maintenance of euglycemia and prevention of hypoglycemia. In type 2 Diabetes Mellitus (T2DM), glucagon levels are elevated in both the fasted and postprandial states, which contributes to inappropriate hyperglycemia through excessive hepatic glucose production. Efforts to discover and evaluate glucagon receptor antagonists for the treatment of T2DM have been ongoing for approximately two decades, with the challenge being to identify an agent with appropriate pharmaceutical properties and efficacy relative to potential side effects. We sought to determine the hepatic & systemic consequence of full glucagon receptor antagonism through the study of the glucagon receptor knock-out mouse (Gcgr-/-) compared to wild-type littermates. Results Liver transcriptomics was performed using Affymetric expression array profiling, and liver proteomics was performed by iTRAQ global protein analysis. To complement the transcriptomic and proteomic analyses, we also conducted metabolite profiling (~200 analytes) using mass spectrometry in plasma. Overall, there was excellent concordance (R = 0.88) for changes associated with receptor knock-out between the transcript and protein analysis. Pathway analysis tools were used to map the metabolic processes in liver altered by glucagon receptor ablation, the most notable being significant down-regulation of gluconeogenesis, amino acid catabolism, and fatty acid oxidation processes, with significant up-regulation of glycolysis, fatty acid synthesis, and cholesterol biosynthetic processes. These changes at the level of the liver were manifested through an altered plasma metabolite profile in the receptor knock-out mice, e.g. decreased glucose and glucose-derived metabolites, and increased amino acids, cholesterol, and bile acid levels. Conclusions In sum, the results of this study suggest that the complete ablation of hepatic glucagon receptor function results in major metabolic alterations in the liver, which, while promoting improved glycemic control, may be associated with adverse lipid changes.
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Affiliation(s)
- Jianxin Yang
- Pfizer Global Research and Development, Groton, CT, USA.
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Trauner M, Halilbasic E. Nuclear receptors as new perspective for the management of liver diseases. Gastroenterology 2011; 140:1120-1125.e1-12. [PMID: 21334334 DOI: 10.1053/j.gastro.2011.02.044] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Nuclear receptors (NRs) are ligand-activated transcription factors that act as sensors for a broad range of natural and synthetic ligands and regulate several key hepatic functions including bile acid homeostasis, bile secretion, lipid and glucose metabolism, as well as drug deposition. Moreover, NRs control hepatic inflammation, regeneration, fibrosis, and tumor formation. Therefore, NRs are key for understanding the pathogenesis and pathophysiology of a wide range of hepatic disorders. Finally, targeting NRs and their alterations offers exciting new perspectives for the treatment of liver diseases.
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Affiliation(s)
- Michael Trauner
- Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Austria.
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Krasowski MD, Ni A, Hagey LR, Ekins S. Evolution of promiscuous nuclear hormone receptors: LXR, FXR, VDR, PXR, and CAR. Mol Cell Endocrinol 2011; 334:39-48. [PMID: 20615451 PMCID: PMC3033471 DOI: 10.1016/j.mce.2010.06.016] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 04/28/2010] [Accepted: 06/29/2010] [Indexed: 12/17/2022]
Abstract
Nuclear hormone receptors (NHRs) are transcription factors that work in concert with co-activators and co-repressors to regulate gene expression. Some examples of ligands for NHRs include endogenous compounds such as bile acids, retinoids, steroid hormones, thyroid hormone, and vitamin D. This review describes the evolution of liver X receptors α and β (NR1H3 and 1H2, respectively), farnesoid X receptor (NR1H4), vitamin D receptor (NR1I1), pregnane X receptor (NR1I2), and constitutive androstane receptor (NR1I3). These NHRs participate in complex, overlapping transcriptional regulation networks involving cholesterol homeostasis and energy metabolism. Some of these receptors, particularly PXR and CAR, are promiscuous with respect to the structurally wide range of ligands that act as agonists. A combination of functional and computational analyses has shed light on the evolutionary changes of NR1H and NR1I receptors across vertebrates, and how these receptors may have diverged from ancestral receptors that first appeared in invertebrates.
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Affiliation(s)
- Matthew D Krasowski
- Department of Pathology, University of Iowa Hospitals and Clinics, RCP 6233, 200 Hawkins Drive, Iowa City, IA 52242, USA.
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Abstract
Interindividual differences in drug transporter expression can result in variability in drug response. This variation in gene expression is determined, in part, by the actions of nuclear hormone receptors that act as xenobiotic- and endobiotic-sensing transcription factors. Among the ligand-activated nuclear receptors, signaling through the pregnane X receptor (PXR), constitutive androstane receptor (CAR), farnesoid X receptor (FXR), and vitamin D receptor (VDR) constitute major pathways regulating drug transporter expression in tissues. Hence, these endobiotic- and xenobiotic-sensing nuclear receptors are intrinsically involved in environmental influences of drug response. Moreover, because nuclear receptor genes are polymorphic, these transcription factors are also thought to contribute to heritability of variable drug action. In this chapter, the molecular aspects of drug transporter gene regulation by ligand-activated nuclear receptors will be reviewed including their clinical relevance.
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Režen T. The impact of cholesterol and its metabolites on drug metabolism. Expert Opin Drug Metab Toxicol 2011; 7:387-98. [PMID: 21320036 DOI: 10.1517/17425255.2011.558083] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
INTRODUCTION Global prevalence of Western-type diet has increased in the last decades resulting in occurrence of certain chronic diseases. This type of diet is also linked to high-cholesterol intake and increase in blood cholesterol. Many of the molecular mechanisms of dealing with increased levels of cholesterol and its metabolites have been elucidated in animal models and humans. It is also evident that cholesterol metabolism is closely connected to drug metabolism. Cholesterol/bile acids and drugs share many transporters, enzymes and regulatory proteins which are key points in the crosstalk. AREAS COVERED This review presents an overview of the effect of cholesterol and its metabolites on drug metabolism with special emphasis on species-specific differences. The article focuses on the role of nuclear receptors farnesoid X receptor, vitamin D receptor and liver X receptor in the regulation of drug metabolism genes and the role of cholesterol biosynthesis intermediates, oxysterols and bile acids in the induction of drug metabolism through pregnane X receptor. EXPERT OPINION Studies show that the regulation of drug metabolism by sterols is multileveled. Many species-dependent differences were observed which hinder the transfer of findings from model animals to humans. As of now, there is little evidence available for cholesterol impact on drug metabolism in vivo in humans. There is also the need to confirm the results obtained in animal models and in vitro analyses in human cells but this is very difficult given the current lack of tools.
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Affiliation(s)
- Tadeja Režen
- Faculty of Medicine, University of Ljubljana, Institute of Biochemistry, Vrazov Trg 2, SI-1000 Ljubljana, Slovenia.
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Krasowski MD, Ai N, Hagey LR, Kollitz EM, Kullman SW, Reschly EJ, Ekins S. The evolution of farnesoid X, vitamin D, and pregnane X receptors: insights from the green-spotted pufferfish (Tetraodon nigriviridis) and other non-mammalian species. BMC BIOCHEMISTRY 2011; 12:5. [PMID: 21291553 PMCID: PMC3042382 DOI: 10.1186/1471-2091-12-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Accepted: 02/03/2011] [Indexed: 12/23/2022]
Abstract
Background The farnesoid X receptor (FXR), pregnane X receptor (PXR), and vitamin D receptor (VDR) are three closely related nuclear hormone receptors in the NR1H and 1I subfamilies that share the property of being activated by bile salts. Bile salts vary significantly in structure across vertebrate species, suggesting that receptors binding these molecules may show adaptive evolutionary changes in response. We have previously shown that FXRs from the sea lamprey (Petromyzon marinus) and zebrafish (Danio rerio) are activated by planar bile alcohols found in these two species. In this report, we characterize FXR, PXR, and VDR from the green-spotted pufferfish (Tetraodon nigriviridis), an actinopterygian fish that unlike the zebrafish has a bile salt profile similar to humans. We utilize homology modelling, docking, and pharmacophore studies to understand the structural features of the Tetraodon receptors. Results Tetraodon FXR has a ligand selectivity profile very similar to human FXR, with strong activation by the synthetic ligand GW4064 and by the primary bile acid chenodeoxycholic acid. Homology modelling and docking studies suggest a ligand-binding pocket architecture more similar to human and rat FXRs than to lamprey or zebrafish FXRs. Tetraodon PXR was activated by a variety of bile acids and steroids, although not by the larger synthetic ligands that activate human PXR such as rifampicin. Homology modelling predicts a larger ligand-binding cavity than zebrafish PXR. We also demonstrate that VDRs from the pufferfish and Japanese medaka were activated by small secondary bile acids such as lithocholic acid, whereas the African clawed frog VDR was not. Conclusions Our studies provide further evidence of the relationship between both FXR, PXR, and VDR ligand selectivity and cross-species variation in bile salt profiles. Zebrafish and green-spotted pufferfish provide a clear contrast in having markedly different primary bile salt profiles (planar bile alcohols for zebrafish and sterically bent bile acids for the pufferfish) and receptor selectivity that matches these differences in endogenous ligands. Our observations to date present an integrated picture of the co-evolution of bile salt structure and changes in the binding pockets of three nuclear hormone receptors across the species studied.
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Affiliation(s)
- Matthew D Krasowski
- Department of Pathology, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, USA.
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82
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He H, Mennone A, Boyer JL, Cai SY. Combination of retinoic acid and ursodeoxycholic acid attenuates liver injury in bile duct-ligated rats and human hepatic cells. Hepatology 2011; 53:548-57. [PMID: 21274875 PMCID: PMC3069505 DOI: 10.1002/hep.24047] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Accepted: 10/11/2010] [Indexed: 12/12/2022]
Abstract
UNLABELLED Cholestasis leads to liver cell death, fibrosis, cirrhosis, and eventually liver failure. Despite limited benefits, ursodeoxycholic acid (UDCA) is the only Food and Drug Administration-approved treatment for cholestatic disorders. Retinoic acid (RA) is a ligand for nuclear receptors that modulate bile salt homeostasis. RA also possesses immunomodulatory effects and is used to treat acute promyelocytic leukemia and inflammatory disorders such as psoriasis, acne, and rheumatoid arthritis. To test whether the supplementation of RA with UDCA is superior to UDCA alone for treating cholestasis, male Sprague-Dawley rats underwent common bile duct ligation (BDL) for 14 days and were treated with phosphate-buffered saline (PBS), UDCA, all-trans retinoic acid (atRA), or UDCA and atRA by gavage. Treatment with UDCA and atRA substantially improved animal growth rates, significantly reduced liver fibrosis and bile duct proliferation, and nearly eliminated liver necrosis after BDL. Reductions in the bile salt pool size and liver hydroxyproline content were also seen with treatment with atRA or atRA and UDCA versus PBS and UDCA. Furthermore, atRA and UDCA significantly reduced liver messenger RNA and/or protein expression of transforming growth factor β1 (Tgf-β1), collagen 1a1 (Col1A1), matrix metalloproteinase 2 (Mmp2), cytokeratin 19, α-smooth muscle actin (α-SMA), cytochrome P450 7A1 (Cyp7a1), tumor necrosis factor α, and interleukin-β1. The molecular mechanisms of this treatment were also assessed in human hepatocytes, hepatic stellate cells, and LX-2 cells. atRA alone or in combination with UDCA greatly repressed CYP7A1 expression in human hepatocytes and significantly inhibited COL1A1, MMP2, and α-SMA expression and/or activity in primary human hepatic stellate cells and LX-2 cells. Furthermore, atRA reduced TGF-β1-induced Smad2 phosphorylation in LX-2 cells. CONCLUSION Our findings indicate that the addition of RA to UDCA reduces the bile salt pool size and liver fibrosis and might be an effective supplemental therapy with UDCA for cholestatic diseases.
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Affiliation(s)
- Hongwei He
- Yale Liver Center, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
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83
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Anakk S, Watanabe M, Ochsner SA, McKenna NJ, Finegold MJ, Moore DD. Combined deletion of Fxr and Shp in mice induces Cyp17a1 and results in juvenile onset cholestasis. J Clin Invest 2011; 121:86-95. [PMID: 21123943 PMCID: PMC3007143 DOI: 10.1172/jci42846] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Accepted: 10/13/2010] [Indexed: 12/17/2022] Open
Abstract
Bile acid homeostasis is tightly regulated via a feedback loop operated by the nuclear receptors farnesoid X receptor (FXR) and small heterodimer partner (SHP). Contrary to current models, which place FXR upstream of SHP in a linear regulatory pathway, here we show that the phenotypic consequences in mice of the combined loss of both receptors are much more severe than the relatively modest impact of the loss of either Fxr or Shp alone. Fxr-/-Shp-/- mice exhibited cholestasis and liver injury as early as 3 weeks of age, and this was linked to the dysregulation of bile acid homeostatic genes, particularly cytochrome P450, family 7, subfamily a, polypeptide 1 (Cyp7a1). In addition, double-knockout mice showed misregulation of genes in the C21 steroid biosynthesis pathway, with strong induction of cytochrome P450, family 17, subfamily a, polypeptide 1 (Cyp17a1), resulting in elevated serum levels of its enzymatic product 17-hydroxyprogesterone (17-OHP). Treatment of WT mice with 17-OHP was sufficient to induce liver injury that reproduced many of the histopathological features observed in the double-knockout mice. Therefore, our data indicate a pathologic role for increased production of 17-hydroxy steroid metabolites in liver injury and suggest that Fxr-/-Shp-/- mice could provide a model for juvenile onset cholestasis.
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Affiliation(s)
- Sayeepriyadarshini Anakk
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA.
Department of Internal Medicine, School of Medicine, Keio University, Shinjuku-ku, Tokyo, Japan.
Department of Pathology, Baylor College of Medicine, Houston, Texas, USA
| | - Mitsuhiro Watanabe
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA.
Department of Internal Medicine, School of Medicine, Keio University, Shinjuku-ku, Tokyo, Japan.
Department of Pathology, Baylor College of Medicine, Houston, Texas, USA
| | - Scott A. Ochsner
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA.
Department of Internal Medicine, School of Medicine, Keio University, Shinjuku-ku, Tokyo, Japan.
Department of Pathology, Baylor College of Medicine, Houston, Texas, USA
| | - Neil J. McKenna
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA.
Department of Internal Medicine, School of Medicine, Keio University, Shinjuku-ku, Tokyo, Japan.
Department of Pathology, Baylor College of Medicine, Houston, Texas, USA
| | - Milton J. Finegold
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA.
Department of Internal Medicine, School of Medicine, Keio University, Shinjuku-ku, Tokyo, Japan.
Department of Pathology, Baylor College of Medicine, Houston, Texas, USA
| | - David D. Moore
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA.
Department of Internal Medicine, School of Medicine, Keio University, Shinjuku-ku, Tokyo, Japan.
Department of Pathology, Baylor College of Medicine, Houston, Texas, USA
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84
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Gachon F, Firsov D. The role of circadian timing system on drug metabolism and detoxification. Expert Opin Drug Metab Toxicol 2010; 7:147-58. [PMID: 21192771 DOI: 10.1517/17425255.2011.544251] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
INTRODUCTION It has been known for a long time that the efficiency and toxicity of drugs change during a 24-h period. However, the molecular mechanisms involved in these processes have started to emerge only recently. AREAS COVERED This review aims to highlight recent discoveries showing the direct role of the molecular circadian clock in xenobiotic metabolism at the transcriptional and post-transcriptional levels in the liver and intestine, and the different ways of elimination of these metabolized drugs via biliary and urine excretions. Most of the related literature focuses on transcriptional regulation by the circadian clock of xenobiotic metabolism in the liver; however, the role of this timing system in the excretion of metabolized drugs and the importance of the kidney in this phenomenon are generally neglected. The goal of this review is to describe the molecular mechanisms involved in rhythmic drug metabolism and excretion. EXPERT OPINION Chronopharmacology is used to analyze the metabolism of drugs in mammals according to the time of day. The circadian timing system plays a key role in the changes of toxicity of drugs by influencing their metabolisms in the liver and intestine in addition to their excretion via bile flow and urine.
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Affiliation(s)
- Frédéric Gachon
- University of Lausanne, Department of Pharmacology and Toxicology, CH-1005 Lausanne, Switzerland.
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85
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Misaka S, Kurosawa S, Uchida S, Yoshida A, Kato Y, Kagawa Y, Yamada S. Evaluation of the pharmacokinetic interaction of midazolam with ursodeoxycholic acid, ketoconazole and dexamethasone by brain benzodiazepine receptor occupancy. J Pharm Pharmacol 2010; 63:58-64. [DOI: 10.1111/j.2042-7158.2010.01176.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Abstract
Objectives
To clarify whether alterations in midazolam pharmacokinetics resulting from changes in cytochrome P450 3A (CYP3A) activity lead to changes in its pharmacodynamic effects, benzodiazepine receptor occupancy was measured in the brain of rats after oral administration of midazolam.
Methods
Receptor occupancy was measured by radioligand binding assay in rats pretreated with ursodeoxycholic acid (UDCA), ketoconazole and dexamethasone, and the plasma concentration of midazolam was simultaneously determined.
Key findings
There was a significant increase in the apparent dissociation constant and decrease in the maximum number of binding sites for specific [3H]flunitrazepam binding after oral administration of midazolam at pharmacologically relevant doses, suggesting that midazolam binds significantly to brain benzodiazepine receptors. Pretreatment with UDCA significantly enhanced the binding. This correlated well with significant enhancement by UDCA of the plasma midazolam concentration. The brain benzodiazepine receptor binding of oral midazolam was significantly enhanced by pretreatment with ketoconazole, a potent inhibitor of CYP3A, whereas it was significantly reduced by treatment with dexamethasone, an inducer of this enzyme. These effects paralleled changes in the plasma concentration of midazolam.
Conclusions
The results indicate that pharmacokinetic changes such as altered CYP3A activity significantly influence the pharmacodynamic effect of midazolam by affecting occupancy of benzodiazepine receptors in the brain. They also suggest in-vivo or ex-vivo time-dependent measurements of receptor occupancy by radioligand binding assay to be a tool for elucidating the pharmacokinetic interaction of benzodiazepines with other agents in pre-clinical and clinical evaluations.
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Affiliation(s)
- Shingen Misaka
- Department of Pharmacokinetics and Pharmacodynamics, Global Center of Excellence (COE), Practical Pharmacy and Clinical Pharmaceutics, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
| | - Souhei Kurosawa
- Department of Pharmacokinetics and Pharmacodynamics, Global Center of Excellence (COE), Practical Pharmacy and Clinical Pharmaceutics, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
| | - Shinya Uchida
- Department of Pharmacokinetics and Pharmacodynamics, Global Center of Excellence (COE), Practical Pharmacy and Clinical Pharmaceutics, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
| | - Akira Yoshida
- Department of Pharmacokinetics and Pharmacodynamics, Global Center of Excellence (COE), Practical Pharmacy and Clinical Pharmaceutics, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
| | - Yoshihisa Kato
- Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Tokushima, Japan
| | - Yoshiyuki Kagawa
- Department of Pharmacokinetics and Pharmacodynamics, Global Center of Excellence (COE), Practical Pharmacy and Clinical Pharmaceutics, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
| | - Shizuo Yamada
- Department of Pharmacokinetics and Pharmacodynamics, Global Center of Excellence (COE), Practical Pharmacy and Clinical Pharmaceutics, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
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86
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Meyer Zu Schwabedissen HE, Böttcher K, Chaudhry A, Kroemer HK, Schuetz EG, Kim RB. Liver X receptor α and farnesoid X receptor are major transcriptional regulators of OATP1B1. Hepatology 2010; 52:1797-807. [PMID: 20827719 DOI: 10.1002/hep.23876] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
UNLABELLED Organic anion transporting polypeptide 1B1 (OATP1B1) is a liver-enriched transporter involved in the hepatocellular uptake of many endogenous molecules and several structurally divergent drugs in clinical use. Although OATP1B1 coding region polymorphisms are known to make an impact on substrate drug disposition in humans, little is known regarding the mechanisms underlying the transcriptional regulation of this transporter. In this study, we note that messenger RNA (mRNA) expression of OATP1B1 in a large human liver bank exhibited marked interindividual variability that was not associated with coding region polymorphisms. Accordingly, we hypothesized that such variability in expression is reflective of nuclear receptor-mediated transcriptional regulation of this transporter. We tested prototypical ligands for the nuclear receptors pregnane X receptor (PXR), constitutive androstane receptor (CAR), liver X receptor (LXR) α, and farnesoid X receptor (FXR) in a human hepatoma-derived cell line and noted induction of OATP1B1 mRNA when the cells were treated with LXRα or FXR ligands. To confirm a direct role for LXRα and FXR to OATP1B1 expression, we performed detailed promoter analysis and cell-based reporter gene assays resulting in the identification of two functional FXR response elements and one LXRα response element. The direct interaction between nuclear receptors with the identified response elements was assessed using chromatin immunoprecipitation assays. Using isolated primary human hepatocytes, we show that LXRα or FXR agonists, but not PXR or CAR agonists, are capable of OATP1B1 induction. CONCLUSION We note that OATP1B1 transcriptional regulation is under dual nuclear receptor control through the oxysterol sensing LXRα and the bile acid sensor FXR. Accordingly, the interplay between OATP1B1 and nuclear receptors may play an important and heretofore unrecognized role during cholestasis, drug-induced liver injury, and OATP1B1 induction-related drug interactions.
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87
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Regulation of drug-metabolizing enzymes by xenobiotic receptors: PXR and CAR. Adv Drug Deliv Rev 2010; 62:1238-49. [PMID: 20727377 DOI: 10.1016/j.addr.2010.08.006] [Citation(s) in RCA: 272] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 08/09/2010] [Accepted: 08/10/2010] [Indexed: 12/24/2022]
Abstract
Drug-metabolizing enzymes (DMEs) and transporters play pivotal roles in the disposition and detoxification of numerous foreign and endogenous chemicals. To accommodate chemical challenges, the expression of many DMEs and transporters is up-regulated by a group of ligand-activated transcription factors namely nuclear receptors (NRs). The importance of NRs in xenobiotic metabolism and clearance is best exemplified by the most promiscuous xenobiotic receptors: pregnane X receptor (PXR, NR1I2) and constitutive androstane/activated receptor (CAR, NR1I3). Together, these two receptors govern the inductive expression of a largely overlapping array of target genes encoding phase I and II DMEs, and drug transporters. Moreover, PXR and CAR also represent two distinctive mechanisms of NR activation, whereby CAR demonstrates both constitutive and ligand-independent activation. In this review, recent advances in our understanding of PXR and CAR as xenosensors are discussed with emphasis placed on the differences rather than similarities of these two xenobiotic receptors in ligand recognition and target gene regulation.
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88
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Lu H, Gonzalez FJ, Klaassen C. Alterations in hepatic mRNA expression of phase II enzymes and xenobiotic transporters after targeted disruption of hepatocyte nuclear factor 4 alpha. Toxicol Sci 2010; 118:380-90. [PMID: 20935164 DOI: 10.1093/toxsci/kfq280] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Hepatocyte nuclear factor 4 alpha (HNF4a) is a liver-enriched master regulator of liver function. HNF4a is important in regulating hepatic expression of certain cytochrome P450s. The purpose of this study was to use mice lacking HNF4a expression in liver (HNF4a-HNull) to elucidate the role of HNF4a in regulating hepatic expression of phase II enzymes and transporters in mice. Compared with male wild-type mice, HNF4a-HNull male mouse livers had (1) markedly lower messenger RNAs (mRNAs) encoding the uptake transporters sodium taurocholate cotransporting polypeptide, organic anion transporting polypeptide (Oatp) 1a1, Oatp2b1, organic anion transporter 2, sodium phosphate cotransporter type 1, sulfate anion transporter 1, sodium-dependent vitamin C transporter 1, the phase II enzymes Uridine 5'-diphospho (UDP)-glucuronosyltransferase (Ugt) 2a3, Ugt2b1, Ugt3a1, Ugt3a2, sulfotransferase (Sult) 1a1, Sult1b1, Sult5a1, the efflux transporters multidrug resistance-associated protein (Mrp) 6, and multidrug and toxin extrusion 1; (2) moderately lower mRNAs encoding Oatp1b2, organic cation transporter (Oct) 1, Ugt1a5, Ugt1a9, glutathione S-transferase (Gst) m4, Gstm6, and breast cancer resistance protein; but (3) higher mRNAs encoding Oatp1a4, Octn2, Ugt1a1, Sult1e1, Sult2a2, Gsta4, Gstm1-m3, multidrug resistance protein (Mdr) 1a, Mrp3, and Mrp4. Hepatic signaling of nuclear factor E2-related factor 2 and pregnane X receptor appear to be activated in HNF4a-HNull mice. In conclusion, HNF4a deficiency markedly alters hepatic mRNA expression of a large number of phase II enzymes and transporters, probably because of the loss of HNF4a, which is a transactivator and a determinant of gender-specific expression and/or adaptive activation of signaling pathways important in hepatic regulation of these phase II enzymes and transporters.
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Affiliation(s)
- Hong Lu
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
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89
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Gu X, Manautou JE. Regulation of hepatic ABCC transporters by xenobiotics and in disease states. Drug Metab Rev 2010; 42:482-538. [PMID: 20233023 DOI: 10.3109/03602531003654915] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The subfamily of ABCC transporters consists of 13 members in mammals, including the multidrug resistance-associated proteins (MRPs), sulfonylurea receptors (SURs), and the cystic fibrosis transmembrane conductance regulator (CFTR). These proteins play roles in chemical detoxification, disposition, and normal cell physiology. ABCC transporters are expressed differentially in the liver and are regulated at the transcription and translation level. Their expression and function are also controlled by post-translational modification and membrane-trafficking events. These processes are tightly regulated. Information about alterations in the expression of hepatobiliary ABCC transporters could provide important insights into the pathogenesis of diseases and disposition of xenobiotics. In this review, we describe the regulation of hepatic ABCC transporters in humans and rodents by a variety of xenobiotics, under disease states and in genetically modified animal models deficient in transcription factors, transporters, and cell-signaling molecules.
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Affiliation(s)
- Xinsheng Gu
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, 06269, USA
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90
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Wallace K, Cowie DE, Konstantinou DK, Hill SJ, Tjelle TE, Axon A, Koruth M, White SA, Carlsen H, Mann DA, Wright MC. The PXR is a drug target for chronic inflammatory liver disease. J Steroid Biochem Mol Biol 2010; 120:137-48. [PMID: 20416375 PMCID: PMC2937210 DOI: 10.1016/j.jsbmb.2010.04.012] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 04/13/2010] [Accepted: 04/16/2010] [Indexed: 12/17/2022]
Abstract
UNLABELLED PXR activators are used to treat pruritus in chronic inflammatory liver diseases such as primary biliary cirrhosis (PBC). The aims of this study were to determine whether PXR activators could have an additional benefit of inhibiting inflammation in the liver, and determine whether cyclosporin A - which more effectively prevents PBC recurrence in transplanted patients than FK506 - is a PXR activator. In SJL/J mice (which have constitutively high levels of hepatic portal tract inflammatory cell recruitment), feeding a PXR activator inhibited inflammation, TNFalpha and Il-1alpha mRNA expression in SJL/J-PXR(+/+), but not SJL/J-PXR(-/-). Monocytic cells - a major source of inflammatory mediators such as TNFalpha - expressed the PXR and PXR activators inhibited endotoxin-induced NF-kappaB activation and TNFalpha expression. PXR activation also inhibited endotoxin-stimulated TNFalpha secretion from liver monocytes/macrophages isolated from PXR(+/+) mice, but not from cells isolated from PXR(-/-) mice. To confirm that PXR activation inhibits NF-kappaB in vivo, 3x-kappaB-luc fibrotic mice (which express a luciferase gene regulated by NF-kappaB) were imaged after treatment with the hepatotoxin CCl(4). PXR activator inhibited the induction of hepatic NF-kappaB activity without affecting CCl(4) toxicity/hepatic damage. Using a PXR reporter gene assay, cyclosporin A - but not FK506 - was shown to be a direct PXR activator, and also to induce expression of the classic PXR-regulated CYP3A4 gene in human hepatocytes and in a cell line null for the FXR, a nuclear receptor with similar properties to the PXR. CONCLUSION PXR activation is anti-inflammatory in the liver and the effects of cyclosporin A in PBC disease recurrence may be mediated in part via the PXR. Since PXR activation promotes hepatocyte growth and is also anti-fibrogenic, the PXR may be an excellent drug target for the treatment of chronic inflammatory liver disease.
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Key Words
- alt, alanine aminotransferase
- csa, cyclosporin a
- gt, gliotoxin
- gapdh, glyceradehyde 3 phosphate dehydrogenase
- hyp, hyperforin
- ikk2-in, iκb kinase 2 inhibitor
- lps, lipopolysaccharide
- metyr, metyrapone
- mts, ([3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2h-tetrazolium salt
- pbc, primary biliary cirrhosis
- pcn, pregnenolone 16α carbonitrile
- pti, portal tract inflammation
- pparγ, peroxiome proliferator activated receptor γ
- pxr, pregnane x receptor
- rif, rifampicin
- sulf, sulfasalazine
- tlr4, toll-like receptor 4
- tnfα, tumour necrosis factor-α
- pregnane x receptor
- sxr
- nf-κb
- rifampicin
- hyperforin
- tnfα
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MESH Headings
- Animals
- Cell Line
- Cyclosporine/therapeutic use
- Female
- Gene Expression Regulation
- Hepatitis, Chronic/drug therapy
- Hepatitis, Chronic/genetics
- Hepatitis, Chronic/metabolism
- Humans
- Liver Cirrhosis, Biliary/drug therapy
- Liver Cirrhosis, Biliary/genetics
- Liver Cirrhosis, Biliary/metabolism
- Mice
- Mice, Knockout
- NF-kappa B/metabolism
- Pregnane X Receptor
- Receptors, Steroid/deficiency
- Receptors, Steroid/genetics
- Receptors, Steroid/metabolism
- Tumor Necrosis Factor-alpha/genetics
- Tumor Necrosis Factor-alpha/metabolism
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Affiliation(s)
- Karen Wallace
- Institute of Cellular Medicine, University of Newcastle, Newcastle, Upon Tyne, UK
| | - David E. Cowie
- Institute of Cellular Medicine, University of Newcastle, Newcastle, Upon Tyne, UK
| | | | - Stephen J. Hill
- Institute of Cellular Medicine, University of Newcastle, Newcastle, Upon Tyne, UK
| | | | - Andrew Axon
- Institute of Cellular Medicine, University of Newcastle, Newcastle, Upon Tyne, UK
| | - Matthew Koruth
- Institute Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Steven A. White
- Institute of Cellular Medicine, University of Newcastle, Newcastle, Upon Tyne, UK
| | | | - Derek A. Mann
- Institute of Cellular Medicine, University of Newcastle, Newcastle, Upon Tyne, UK
| | - Matthew C. Wright
- Institute of Cellular Medicine, University of Newcastle, Newcastle, Upon Tyne, UK
- Corresponding author at: Institute of Cellular Medicine, Level 2 William Leech Building (M2.125), Medical School, Framlington Place, University of Newcastle Upon Tyne NE2 4HH. Tel.: +44 191 222 7094.
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91
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Abstract
Mammalian UDP-glycosyltransferases (UGTs) are divided into four families: UGT1, UGT2, UGT3, and UGT8. UGT3 is the last of the gene families to be identified, and until relatively recently, little was known about the function of these enzymes. In this article, we present new analyses of the UGT3 family genes, including the structure of the UGT3A locus, interspecies sequence conservation, single nucleotide polymorphisms, and splice variants. We also review recently published work that has revealed that one member of this family, UGT3A1, has a unique enzymatic function: N-acetylglucosaminidation. Finally, we discuss the possible biological significance of the UGT3A enzymes.
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Affiliation(s)
- Robyn Meech
- Department of Clinical Pharmacology, Flinders University of South Australia, Bedford Park, South Australia, Australia.
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92
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Blaas L, Kornfeld JW, Schramek D, Musteanu M, Zollner G, Gumhold J, van Zijl F, Schneller D, Esterbauer H, Egger G, Mair M, Kenner L, Mikulits W, Eferl R, Moriggl R, Penninger J, Trauner M, Casanova E. Disruption of the growth hormone--signal transducer and activator of transcription 5--insulinlike growth factor 1 axis severely aggravates liver fibrosis in a mouse model of cholestasis. Hepatology 2010; 51:1319-26. [PMID: 20162728 PMCID: PMC2976853 DOI: 10.1002/hep.23469] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
UNLABELLED Growth hormone (GH) resistance and low serum levels of insulinlike growth factor 1 (IGF-1) are common features in human liver fibrosis and cirrhosis. Signal transducer and activator of transcription 5 (STAT5) controls several vital functions in the liver, including GH-mediated transcription of IGF-1. To investigate the role of STAT5 in liver fibrogenesis, we specifically deleted the Stat5a/b locus both in hepatocytes and cholangiocytes in the multidrug resistance gene 2 knockout (Mdr2(-/-)) mouse model of cholestasis. Double knockout mice develop an early and severe liver fibrosis phenotype, accompanied by perturbed expression of key regulators of bile acid homeostasis. Deletion of Stat5 resulted in GH resistance, and IGF-1 levels in serum were undetectable. We could observe reduced expression of important hepatoprotective genes, such as epidermal growth factor receptor (Egfr), hepatocyte nuclear factor 6 (Hnf6), prolactin receptor (Prlr), and leukemia inhibitory factor receptor (Lifr) as well as increased numbers of apoptotic hepatocytes. CONCLUSION Our data suggest that loss of STAT5 sensitizes hepatocytes to bile acid-induced damage and apoptosis caused by disruption of GH-induced transcription of Igf-1 and down-regulation of hepatoprotective genes. These findings could contribute to the understanding of liver fibrosis and future treatment strategies for liver fibrosis.
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Affiliation(s)
- Leander Blaas
- Ludwig Boltzmann Institute for Cancer Research (LBICR), Vienna, Austria
| | | | - Daniel Schramek
- Institute of Molecular Biology of the Austrian Academy of Sciences (IMBA), Vienna, Austria
| | - Monica Musteanu
- Ludwig Boltzmann Institute for Cancer Research (LBICR), Vienna, Austria
| | - Gernot Zollner
- Laboratory of Experimental and Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine, Medical University of Graz, Austria
| | - Judith Gumhold
- Laboratory of Experimental and Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine, Medical University of Graz, Austria
| | - Franziska van Zijl
- Department of Medicine I, Institute of Cancer Research, Medical University of Vienna, Austria
| | - Doris Schneller
- Department of Medicine I, Institute of Cancer Research, Medical University of Vienna, Austria
| | - Harald Esterbauer
- Department of Medical and Chemical Laboratory Diagnostics, Medical University of Vienna, Austria
| | - Gerda Egger
- Clinical Institute of Pathology, Medical University of Vienna, Austria
| | - Markus Mair
- Ludwig Boltzmann Institute for Cancer Research (LBICR), Vienna, Austria
| | - Lukas Kenner
- Ludwig Boltzmann Institute for Cancer Research (LBICR), Vienna, Austria
- Clinical Institute of Pathology, Medical University of Vienna, Austria
| | - Wolfgang Mikulits
- Department of Medicine I, Institute of Cancer Research, Medical University of Vienna, Austria
| | - Robert Eferl
- Ludwig Boltzmann Institute for Cancer Research (LBICR), Vienna, Austria
| | - Richard Moriggl
- Ludwig Boltzmann Institute for Cancer Research (LBICR), Vienna, Austria
| | - Josef Penninger
- Institute of Molecular Biology of the Austrian Academy of Sciences (IMBA), Vienna, Austria
| | - Michael Trauner
- Laboratory of Experimental and Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine, Medical University of Graz, Austria
| | - Emilio Casanova
- Ludwig Boltzmann Institute for Cancer Research (LBICR), Vienna, Austria
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93
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Castaño G, Burgueño A, Fernández Gianotti T, Pirola CJ, Sookoian S. The influence of common gene variants of the xenobiotic receptor (PXR) in genetic susceptibility to intrahepatic cholestasis of pregnancy. Aliment Pharmacol Ther 2010; 31:583-92. [PMID: 19958310 DOI: 10.1111/j.1365-2036.2009.04210.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND The xenobiotic nuclear pregnane X receptor is implicated in many physiological pathways and diseases, including bile acid detoxification and cholestasis. Aim To estimate the contribution of common gene variants of the xenobiotic receptor (pregnane X receptor, PXR) to genetic susceptibility to intrahepatic cholestasis of pregnancy. METHODS A total of 101 intrahepatic cholestasis of pregnancy patients and 171 healthy pregnant women in the third trimester of their pregnancies were included. Four tag single nucleotide polymorphisms (SNPs) (rs12488820 C/T, rs2472671 C/T, rs2461823 A/G, and rs1054191 A/G) encompassing 36 kb in chromosome 3, with a minor allele frequency > or =0.10 and representing 33 polymorphic sites were genotyped. Besides these, three additional SNPs (rs3814057, rs6785049, and rs7643645) were included because they showed previous evidence of functionality. RESULTS Genotypic test for single SNPs showed that rs2461823 genotypes were significantly associated with intrahepatic cholestasis of pregnancy (P < 0.0069), OR per G allele: 1.44, 95% CI: 1.01-2.05, P < 0.042. The Cochran-Armitage test for trend and the allelic test showed a significant association with disease status (P < 0.04 and 0.03 respectively), G being the risk allele. A positive association between rs2461823 and ALT, AST, and bilirubin concentrations was observed. Neonate birth weight adjusted by the Capurro index was significantly associated with rs2461823 (P < 0.05); the proportion of the total variation attributed to rs2461823 genotypes was 7.8%. CONCLUSION Common PXR polymorphisms may contribute to the genetic susceptibility to intrahepatic cholestasis of pregnancy.
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Affiliation(s)
- G Castaño
- Research Council in Health, Government of City of Buenos Aires, Ciudad Autónoma de Buenos Aires, Argentina
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94
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Fickert P, Fuchsbichler A, Wagner M, Silbert D, Zatloukal K, Denk H, Trauner M. The role of the hepatocyte cytokeratin network in bile formation and resistance to bile acid challenge and cholestasis in mice. Hepatology 2009; 50:893-9. [PMID: 19585611 DOI: 10.1002/hep.23068] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
UNLABELLED The intermediate filament cytoskeleton of hepatocytes is composed of keratin (K) 8 and K18 and has important mechanical and nonmechanical functions. However, the potential role of the K8/K18 network for proper membrane targeting of hepatocellular adenosine triphosphate-binding cassette transporters and bile formation is unknown. We therefore designed a comparative study in K8 and K18 knockout mice and respective wild-type controls to test the hypothesis that intermediate filaments of hepatocytes play a role in normal bile formation. In addition, we challenged mice either with a 1% cholic acid-supplemented diet or a diet containing the porphyrinogenic xenobiotic 3,5-diethoxycarbonyl-1,4-dihydrocollidine to determine the effect of K8/K18 loss on bile flow/composition and liver injury under different physiological and toxic stress stimuli. Protein expression levels and membrane localization of various transporters and anion exchangers were compared using western blotting and immunofluorescence microscopy, respectively, and bile flow and composition were determined under various experimental conditions. Our results demonstrate that loss of the intermediate filament network had no significant effect on bile formation and composition, as well as expression levels and membrane targeting of key hepatobiliary transporters under baseline and stress conditions. However, loss of K8 significantly increased liver injury in response to toxic stress. CONCLUSION The intermediate filament network of hepatocytes is not specifically required for proper bile formation in mice.
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Affiliation(s)
- Peter Fickert
- Laboratory of Experimental and Molecular Hepatology, Division of Gastroenterology and Hepatology, Medical University of Graz, Graz, Austria
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95
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Wang R, Chen HL, Liu L, Sheps JA, Phillips MJ, Ling V. Compensatory role of P-glycoproteins in knockout mice lacking the bile salt export pump. Hepatology 2009; 50:948-56. [PMID: 19650158 DOI: 10.1002/hep.23089] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
UNLABELLED Bile salt export pump (BSEP; ATP-binding cassette, subfamily B, member 11) mutations in humans result in progressive familial intrahepatic cholestasis type 2, a fatal liver disease with greatly reduced bile flow. However in mice, Bsep knockout leads only to mild cholestasis with substantial bile flow and up-regulated P-glycoprotein genes (multidrug resistance protein 1a [Mdr1a] and Mdr1b). To determine whether P-glycoprotein is responsible for the relatively mild phenotype observed in Bsep knockout mice, we have crossed mouse strains knocked out for Bsep and the two P-glycoprotein genes and generated a triple knockout mouse. We found that a knockout of the three genes leads to a significantly more severe phenotype with impaired bile formation, jaundice, flaccid gallbladder, and increased mortality. The triple knockout mouse is the most severe genetic model of intrahepatic cholestasis yet developed. CONCLUSION P-glycoprotein functions as a critical compensatory mechanism, which reduces the severity of cholestasis in Bsep knockout mice.
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Affiliation(s)
- Renxue Wang
- British Columbia Cancer Research Centre, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
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96
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Yumoto R, Hamada S, Okada K, Kato Y, Ikehata M, Nagai J, Takano M. Effect of ursodeoxycholic acid treatment on the expression and function of multidrug resistance-associated protein 2 in rat intestine. J Pharm Sci 2009; 98:2822-31. [DOI: 10.1002/jps.21628] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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97
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Deo AK, Bandiera SM. 3-Ketocholanoic Acid Is the Major in Vitro Human Hepatic Microsomal Metabolite of Lithocholic Acid. Drug Metab Dispos 2009; 37:1938-47. [DOI: 10.1124/dmd.109.027763] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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98
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Zollner G, Trauner M. Nuclear receptors as therapeutic targets in cholestatic liver diseases. Br J Pharmacol 2009; 156:7-27. [PMID: 19133988 DOI: 10.1111/j.1476-5381.2008.00030.x] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Cholestasis results in intrahepatic accumulation of cytotoxic bile acids, which cause liver damage ultimately leading to biliary fibrosis and cirrhosis. Cholestatic liver injury is counteracted by a variety of adaptive hepatoprotective mechanisms including alterations in bile acid transport, synthesis and detoxification. The underlying molecular mechanisms are mediated mainly at a transcriptional level via a complex network involving nuclear receptors including the farnesoid X receptor, pregnane X receptor, vitamin D receptor and constitutive androstane receptor, which target overlapping, although not identical, sets of genes. Because the intrinsic adaptive response to bile acids cannot fully prevent liver injury in cholestasis, therapeutic targeting of these receptors via specific and potent agonists may further enhance the hepatic defence against toxic bile acids. Activation of these receptors results in repression of bile acid synthesis, induction of phases I and II bile acid hydroxylation and conjugation and stimulation of alternative bile acid export while limiting hepatocellular bile acid import. Furthermore, the use of nuclear receptor ligands may not only influence bile acid transport and metabolism but may also directly target hepatic fibrogenesis and inflammation. Many drugs already used to treat cholestasis and its complications such as pruritus (e.g. ursodeoxycholic acid, rifampicin, fibrates) may act via activation of nuclear receptors. More specific and potent nuclear receptor ligands are currently being developed. This article will review the current knowledge on nuclear receptors and their potential role in the treatment of cholestatic liver diseases.
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Affiliation(s)
- Gernot Zollner
- Laboratory of Experimental and Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine, Medical University of Graz, Graz, Austria
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99
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di Masi A, De Marinis E, Ascenzi P, Marino M. Nuclear receptors CAR and PXR: Molecular, functional, and biomedical aspects. Mol Aspects Med 2009; 30:297-343. [PMID: 19427329 DOI: 10.1016/j.mam.2009.04.002] [Citation(s) in RCA: 213] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Accepted: 04/28/2009] [Indexed: 12/31/2022]
Abstract
Nuclear receptors (NRs) are ligand-activated transcription factors sharing a common evolutionary history and having similar sequence features at the protein level. Selective ligand(s) for some NRs is not known, therefore these NRs have been named "orphan receptors". Whenever ligands have been recognized for any of the orphan receptor, it has been categorized and grouped as "adopted" orphan receptor. This group includes the constitutive androstane receptor (CAR) and the pregnane X receptor (PXR). They function as sensors of toxic byproducts derived from endogenous metabolites and of exogenous chemicals, in order to enhance their elimination. This unique function of CAR and PXR sets them apart from the steroid hormone receptors. The broad response profile has established that CAR and PXR are xenobiotic sensors that coordinately regulate xenobiotic clearance in the liver and intestine via induction of genes involved in drug and xenobiotic metabolism. In the past few years, research has revealed new and mostly unsuspected roles for CAR and PXR in modulating hormone, lipid, and energy homeostasis as well as cancer and liver steatosis. The purpose of this review is to highlight the structural and molecular bases of CAR and PXR impact on human health, providing information on mechanisms through which diet, chemical exposure, and environment ultimately impact health and disease.
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Affiliation(s)
- Alessandra di Masi
- Department of Biology, University Roma Tre, Viale Guglielmo Marconi 446, I-00146 Roma, Italy
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100
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Zhang B, Xie W, Krasowski MD. PXR: a xenobiotic receptor of diverse function implicated in pharmacogenetics. Pharmacogenomics 2009; 9:1695-709. [PMID: 19018724 DOI: 10.2217/14622416.9.11.1695] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The pregnane X receptor (PXR; NR1I2), a member of the nuclear receptor superfamily, regulates the expression of drug-metabolic enzymes and transporters involved in the responses of mammals to their chemical environment. The same enzyme and transporter systems are also involved in the homeostasis of numerous endogenous chemicals. The regulatory function of PXR is implicated in normal physiology and diseases, such as drug-drug interactions, hepatic steatosis, vitamin D homeostasis, bile acids homeostasis, steroid hormones homeostasis and inflammatory bowel diseases. As such, any genetic variations of this receptor could potentially have widespread effects on the disposition of xenobiotics and endobiotics. Knowledge concerning the genetic polymorphisms of PXR may help to understand the variations in human drug response and ensure safe drug use. The correlation of PXR genetic polymorphisms with several disease conditions also suggests that this receptor may represent a valid therapeutic for hepato-intestinal disorders such as inflammatory bowel disease and primary sclerosing cholangitis.
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Affiliation(s)
- Bin Zhang
- Center for Pharmacogenetics, University of Pittsburgh, Pittsburgh, PA 15261, USA
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