scholarly journals Complementary Roles of Farnesoid X Receptor, Pregnane X Receptor, and Constitutive Androstane Receptor in Protection against Bile Acid Toxicity

2003 ◽  
Vol 278 (46) ◽  
pp. 45062-45071 ◽  
Author(s):  
Grace L. Guo ◽  
Gilles Lambert ◽  
Masahiko Negishi ◽  
Jerrold M. Ward ◽  
H. Bryan Brewer ◽  
...  
Keyword(s):  
Bile Acid ◽  
Constitutive Androstane Receptor ◽  
Pregnane X Receptor ◽  
Farnesoid X Receptor ◽  
Acid Toxicity

Knockdown of ATP8B1 expression leads to specific downregulation of the bile acid sensor FXR in HepG2 cells: effect of the FXR agonist GW4064

2009 ◽  
Vol 296 (5) ◽  
pp. G1119-G1129 ◽  
Author(s):  
Pilar Martínez-Fernández ◽  
Loreto Hierro ◽  
Paloma Jara ◽  
Luis Alvarez
Keyword(s):  
Bile Acid ◽  
Hepg2 Cells ◽  
Target Genes ◽  
Constitutive Androstane Receptor ◽  
Pregnane X Receptor ◽  
Acid Synthesis ◽  
Bile Acid Synthesis ◽  
Bile Secretion ◽  
Farnesoid X Receptor ◽  
Mrna Levels

Farnesoid X receptor (FXR) is a bile acid-sensing nuclear receptor that controls bile acid homeostasis. It has been suggested that downregulation of FXR contributes to the pathogenesis of an inherited disorder of bile secretion caused by mutations in ATP8B1. We have investigated the relationship between ATP8B1 knockdown and FXR downregulation in the human hepatoblastoma cell line HepG2. Transfection of HepG2 cells with ATP8B1 small interfering RNA (siRNA) duplexes led to a 60% reduction in the endogenous levels of ATP8B1 mRNA and protein and a concomitant decrease in FXR mRNA and protein content, as well as in FXR phosphorylation. This decrease was accompanied by a marked reduction in mRNA levels of a subset of FXR targets, such as bile salt export pump ( ABCB11), small heterodimer partner, and uridine 5′-diphosphate-glucuronosyltransferase. ATP8B1 inhibition specifically targeted FXR since mRNA expression of other prominent nuclear receptors, such as pregnane X receptor and constitutive androstane receptor, or liver-enriched transcription factors, such as hepatocyte nuclear factor 1α ( HNF-1α) and HNF-4α, was not altered. The expression of other key genes involved in bile acid synthesis, detoxification, and transport also remained unchanged upon ATP8B1 knockdown. Supporting the specificity of the effect, siRNA-mediated silencing of ABCB11, whose defect is associated with another inherited disorder of bile secretion, did not affect FXR expression. Treatment with the synthetic FXR agonist GW4064 was able to partially neutralize ATP8B1 siRNA-mediated FXR downregulation and fully counteract inhibition of FXR target genes. Collectively these findings indicate that ATP8B1 knockdown specifically downregulates FXR, and this action can be circumvented by treatment with FXR agonists.

scholarly journals Recent advances in understanding bile acid homeostasis

F1000Research ◽  
2017 ◽  
Vol 6 ◽  
pp. 2029 ◽  
Author(s):  
John YL Chiang
Keyword(s):  
Bile Acid ◽  
Bile Acids ◽  
Acid Synthesis ◽  
Bile Acid Synthesis ◽  
Farnesoid X Receptor ◽  
Recent Advances ◽  
Bile Acid Pool Size ◽  
Bile Acid Receptor ◽  
Acid Toxicity ◽  
G Protein Coupled

Bile acids are derived from cholesterol to facilitate intestinal nutrient absorption and biliary secretion of cholesterol. Recent studies have identified bile acids as signaling molecules that activate nuclear farnesoid X receptor (FXR) and membrane G protein-coupled bile acid receptor-1 (Gpbar-1, also known as TGR5) to maintain metabolic homeostasis and protect liver and other tissues and cells from bile acid toxicity. Bile acid homeostasis is regulated by a complex mechanism of feedback and feedforward regulation that is not completely understood. This review will cover recent advances in bile acid signaling and emerging concepts about the classic and alternative bile acid synthesis pathway, bile acid composition and bile acid pool size, and intestinal bile acid signaling and gut microbiome in regulation of bile acid homeostasis.

scholarly journals Pharmacological Activation of PXR and CAR Downregulates Distinct Bile Acid-Metabolizing Intestinal Bacteria and Alters Bile Acid Homeostasis

2018 ◽  
Vol 168 (1) ◽  
pp. 40-60 ◽  
Author(s):  
Joseph L Dempsey ◽  
Dongfang Wang ◽  
Gunseli Siginir ◽  
Qiang Fei ◽  
Daniel Raftery ◽  
...  
Keyword(s):  
Bile Acid ◽  
Gut Microbiota ◽  
Gut Microbiome ◽  
Corn Oil ◽  
Constitutive Androstane Receptor ◽  
Intestinal Bacteria ◽  
Pregnane X Receptor ◽  
Bile Salt Hydrolase ◽  
Dependent Manner ◽  
Germ Free

AbstractThe gut microbiome regulates important host metabolic pathways including xenobiotic metabolism and intermediary metabolism, such as the conversion of primary bile acids (BAs) into secondary BAs. The nuclear receptors pregnane X receptor (PXR) and constitutive androstane receptor (CAR) are well-known regulators for xenobiotic biotransformation in liver. However, little is known regarding the potential effects of PXR and CAR on the composition and function of the gut microbiome. To test our hypothesis that activation of PXR and CAR regulates gut microbiota and secondary BA synthesis, 9-week-old male conventional and germ-free mice were orally gavaged with corn oil, PXR agonist PCN (75 mg/kg), or CAR agonist TCPOBOP (3 mg/kg) once daily for 4 days. PCN and TCPOBOP decreased two taxa in the Bifidobacterium genus, which corresponded with decreased gene abundance of the BA-deconjugating enzyme bile salt hydrolase. In liver and small intestinal content of germ-free mice, there was a TCPOBOP-mediated increase in total, primary, and conjugated BAs corresponding with increased Cyp7a1 mRNA. Bifidobacterium, Dorea, Peptociccaceae, Anaeroplasma, and Ruminococcus positively correlated with T-UDCA in LIC, but negatively correlated with T-CDCA in serum. In conclusion, PXR and CAR activation downregulates BA-metabolizing bacteria in the intestine and modulates BA homeostasis in a gut microbiota-dependent manner.

scholarly journals Bile acid detoxifying enzymes limit susceptibility to liver fibrosis in female SHRSP5/Dmcr rats fed with a high-fat-cholesterol diet

2017 ◽  
Author(s):  
Husna Yetti ◽  
Hisao Naito ◽  
Yuan Yuan ◽  
Xiaofang Jia ◽  
Yumi Hayashi ◽  
...  
Keyword(s):  
Bile Acid ◽  
Nuclear Receptors ◽  
Molecular Mechanisms ◽  
Pregnane X Receptor ◽  
Mature Female ◽  
Farnesoid X Receptor ◽  
Detoxification Enzymes ◽  
Cytochrome P450 Enzymes ◽  
High Fat ◽  
Expression Levels

During middle age, women are less susceptible to nonalcoholic steatohepatitis (NASH) than men. Thus, we investigated the underlying molecular mechanisms behind these sexual differences using an established rat model of NASH. Mature female and male stroke-prone spontaneously hypertensive 5/Dmcr rats were fed control or high-fat-cholesterol (HFC) diets for 2, 8, and 14 weeks. Although HFC-induced hepatic fibrosis was markedly less severe in females than in males, only minor gender differences were observed in expression levels of cytochrome P450 enzymes (CYP)7A1, CYP8B1 CYP27A1, and CYP7B1, and multidrug resistance-associated protein 3, and bile salt export pump, which are involved in fibrosis-related bile acid (BA) kinetics. However, the BA detoxification-related enzymes UDP-glucuronosyltransferase (UGT) and sulfotransferase (SULT) 2A1, and the nuclear receptors constitutive androstene receptor (CAR) and pregnane X receptor (PXR), were strongly suppressed in HFC fed males, and were only slightly changed in HFC-diet fed females. Expression levels of the farnesoid X receptor and its small heterodimer partner were similarly regulated in a gender-dependent fashion following HFC feeding. Hence, the pronounced female resistance to HFC-induced liver damage likely reflects sustained expression of the nuclear receptors CAR and PXR and the BA detoxification enzymes UGT and SULT.

scholarly journals The Decrease in Farnesoid X Receptor, Pregnane X Receptor and Constitutive Androstane Receptor in the Liver after Intestinal Ischemia-Reperfusion

2012 ◽  
Vol 15 (5) ◽  
pp. 616 ◽  
Author(s):  
Jiro Ogura ◽  
Yusuke Terada ◽  
Takashi Tsujimoto ◽  
Takahiro Koizumi ◽  
Kaori Kuwayama ◽  
...  
Keyword(s):  
Western Blotting ◽  
Hepg2 Cells ◽  
Intestinal Ischemia ◽  
Ischemia Reperfusion ◽  
Constitutive Androstane Receptor ◽  
Pregnane X Receptor ◽  
Farnesoid X Receptor ◽  
Expression Levels ◽  
Intestinal Ischemia Reperfusion

Purpose. Intestinal ischemia-reperfusion (I/R) damages remote organs, including the liver, and promotes multi-organ failure (MOF). However, the molecular mechanisms underlying acute liver injury after intestinal I/R have not been completely elucidated. Farnesoid X receptor (FXR), pregnane X receptor (PXR) and constitutive androstane receptor (CAR) regulate metabolizing enzymes and transporters, and coordinately prevent hepatotoxicity reflecting an inability of appropriate excretion of endogenous toxic compounds. In this study, we assessed FXR, PXR and CAR expression levels and their localization levels in nuclei in the liver after intestinal I/R. We also investigated the effect of IL-6 on FXR, PXR and CAR expression levels and their localization levels in nuclei in in vitro experiments. Methods. We used intestinal I/R model rats. Moreover, HepG2 cells were used in in vitro study. Real-time PCR and Western blotting were used to assess mRNA and protein expression levels. Nuclear receptor localization in nuclei was analyzed by Western blotting using nuclear extracts. Results. FXR and PXR expression levels began to be decreased at 3 h, and FXR, PXR and CAR expression levels were decreased at 6 h after intestinal I/R. The localization levels of FXR, PXR and CAR in nuclei began to be decreased at 3 h, and all of them were decreased at 6 h after intestinal I/R. In HepG2 cells, FXR, PXR and CAR expression levels were decreased by 0.5-1 ng/mL, 0.5-100 ng/mL and 100 ng/mL IL-6 treatment for 24 h, respectively. FXR, PXR and CAR localization levels in nuclei were suppressed by 0.5-10 ng/mL, 10-100 ng/mL and 10-100 ng/mL IL-6 treatment for 24 h, respectively. Conclusions. FXR, PXR and CAR expression levels are decreased in the liver after intestinal I/R. IL-6 is one of main causes the decreases in expressions of these receptors. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

scholarly journals Nuclear Receptor Metabolism of Bile Acids and Xenobiotics: A Coordinated Detoxification System with Impact on Health and Diseases

2018 ◽  
Vol 19 (11) ◽  
pp. 3630 ◽  
Author(s):  
Manon Garcia ◽  
Laura Thirouard ◽  
Lauriane Sedès ◽  
Mélusine Monrose ◽  
Hélène Holota ◽  
...  
Keyword(s):  
Transcriptional Control ◽  
Constitutive Androstane Receptor ◽  
Pregnane X Receptor ◽  
Nuclear Hormone Receptor ◽  
Farnesoid X Receptor ◽  
Metabolizing Enzymes ◽  
Functional Studies ◽  
Endogenous Metabolites ◽  
Pathologic Processes

Structural and functional studies have provided numerous insights over the past years on how members of the nuclear hormone receptor superfamily tightly regulate the expression of drug-metabolizing enzymes and transporters. Besides the role of the farnesoid X receptor (FXR) in the transcriptional control of bile acid transport and metabolism, this review provides an overview on how this metabolic sensor prevents the accumulation of toxic byproducts derived from endogenous metabolites, as well as of exogenous chemicals, in coordination with the pregnane X receptor (PXR) and the constitutive androstane receptor (CAR). Decrypting this network should provide cues to better understand how these metabolic nuclear receptors participate in physiologic and pathologic processes with potential validation as therapeutic targets in human disabilities and cancers.

scholarly journals The Xenobiotic-Sensing Nuclear Receptors Pregnane X Receptor, Constitutive Androstane Receptor, and Orphan Nuclear Receptor Hepatocyte Nuclear Factor 4α in the Regulation of Human Steroid-/Bile Acid-Sulfotransferase

2007 ◽  
Vol 21 (9) ◽  
pp. 2099-2111 ◽  
Author(s):  
Ibtissam Echchgadda ◽  
Chung S. Song ◽  
Taesung Oh ◽  
Mohamed Ahmed ◽  
Isidro John De La Cruz ◽  
...  
Keyword(s):  
Bile Acid ◽  
Nuclear Receptors ◽  
Constitutive Androstane Receptor ◽  
Pregnane X Receptor ◽  
Nuclear Factor ◽  
Orphan Nuclear Receptor ◽  
Hepatocyte Nuclear Factor ◽  
Site Mutation ◽  
Composite Element ◽  
Hepatocyte Nuclear Factor 4Α

Abstract The nuclear receptors pregnane X receptor (PXR) and constitutive androstane receptor (CAR) are the primary transcription factors coordinating induced expression of the enzymes and proteins directing oxidative, conjugative, and transport phases of endobiotic and xenobiotic metabolism, whereas hepatocyte nuclear factor 4α (HNF4α), a regulator of hepatic lipid homeostasis, can modify the PXR/CAR response. Steroid- and bile acid-sulfotransferase (SULT2A1) promotes phase II metabolism through its sulfonating action on certain endobiotics, including steroids and bile acids, and on diverse xenobiotics, including therapeutic drugs. This study describes characterization of a PXR- and CAR-inducible composite element in the human SULT2A1 promoter and its synergistic interaction with HNF4α. Inverted and direct repeats of AG(G/T)TCA (IR2 and DR4), both binding to PXR and CAR, define the composite element. Differential recognition of the composite element by PXR and CAR is evident because single-site mutation at either IR2 or DR4 in the natural gene abolished the PXR response, whereas mutations at both repeats were necessary to abrogate completely the CAR response. The composite element conferred xenobiotic response to a heterologous promoter, and the cognate ligands induced PXR and CAR recruitment to the chromatin-associated response region. An HNF4α element adjacent to the −30 position enhanced basal promoter activity. Although functioning as a synergizer, the HNF4α element was not essential for the PXR/CAR response. An emerging role of SULT2A1 in lipid and caloric homeostasis suggests that illumination on the regulatory interactions driving human SULT2A1 expression may reveal new avenues to control certain metabolic disorders.

scholarly journals Molecular cloning and regulation of porcine SULT2A1: relationship between SULT2A1 expression and sulfoconjugation of androstenone

2006 ◽  
Vol 36 (2) ◽  
pp. 301-311 ◽  
Author(s):  
P A Sinclair ◽  
W J Gilmore ◽  
Z Lin ◽  
Y Lou ◽  
E J Squires
Keyword(s):  
Constitutive Androstane Receptor ◽  
Pregnane X Receptor ◽  
Farnesoid X Receptor ◽  
Boar Taint ◽  
Regulatory Control ◽  
Pcr Analysis ◽  
Coding Region ◽  
Positive Role ◽  
Low Levels

Hydroxysteroid sulfotransferase (SULT2A1) is a key enzyme in the testicular and hepatic metabolism of 5α-androstenone, which is a major component of the off-odor and off-flavor in pork known as boar taint. The goals of this study were to determine the role of testicular and hepatic SULT2A1 activity on plasma 5α-androstenone sulfate levels, the accumulation of 5α-androstenone in adipose tissue, and to gain insight into the regulatory control of SULT2A1. Testicular SULT2A1 activity was negatively correlated (r= −0.57; P<0.01) with 5α-androstenone concentrations in fat. The differences observed in SULT2A1 activity warranted investigation into potential genetic variation within porcine SULT2A1. The cDNA sequence of porcine Sult2A1 was determined to be >82% homologous to the human, mouse, and rat Sult2A1 genes. A single nucleotide polymorphism was detected within the coding region of the Sult2A1 from individual testes and liver samples; however, this did not affect the amino acid sequence of the enzyme. Western blot analysis determined that animals with high concentrations of 5α-androstenone in fat and low SULT2A1 activity had corresponding low levels of SULT2A1 protein compared with animals with low levels of 5α-androstenone in fat. Real-time PCR analysis indicated that Sult2A1 mRNA was increased 2.8-fold in animals with high levels of the protein relative to animals with low levels of the protein. Furthermore, we demonstrated the positive role of the nuclear receptors constitutive androstane receptor and pregnane X receptor, as well as the possible role of farnesoid X receptor in the regulation of testicular SULT2A1 activity. Together, the results of this study suggest that differences in SULT2A1 expression can influence 5α-androstenone accumulation in fat.

scholarly journals Xenobiotic Nuclear Receptor Signaling Determines Molecular Pathogenesis of Progressive Familial Intrahepatic Cholestasis

Endocrinology ◽  
2018 ◽  
Vol 159 (6) ◽  
pp. 2435-2446 ◽  
Author(s):  
Kang Ho Kim ◽  
Jong Min Choi ◽  
Feng Li ◽  
Armando Arizpe ◽  
Clavia Ruth Wooton-Kee ◽  
...  
Keyword(s):  
Liver Injury ◽  
Intrahepatic Cholestasis ◽  
Constitutive Androstane Receptor ◽  
Pregnane X Receptor ◽  
Acid Synthesis ◽  
Molecular Pathogenesis ◽  
Farnesoid X Receptor ◽  
Loss Of Function ◽  
Double Knockout ◽  
Progressive Familial Intrahepatic Cholestasis

Abstract Progressive familial intrahepatic cholestasis (PFIC) is a genetically heterogeneous disorder of bile flow disruption due to abnormal canalicular transport or impaired bile acid (BA) metabolism, causing excess BA accumulation and liver failure. We previously reported an intrahepatic cholestasis mouse model based on loss of function of both farnesoid X receptor (FXR; NR1H4) and a small heterodimer partner (SHP; NR0B2) [double knockout (DKO)], which has strong similarities to human PFIC5. We compared the pathogenesis of DKO livers with that of another intrahepatic cholestasis model,Bsep−/−, which represents human PFIC2. Both models exhibit severe hepatomegaly and hepatic BA accumulation, but DKO showed greater circulating BA and liver injury, andBsep−/− had milder phenotypes. Molecular profiling of BAs uncovered specific enrichment of cholic acid (CA)–derived BAs in DKO livers but chenodeoxycholate-derived BAs inBsep−/− livers. Transcriptomic and proteomic analysis revealed specific activation of CA synthesis and alternative basolateral BA transport in DKO but increased chenodeoxycholic acid synthesis and canalicular transport inBsep−/−. The constitutive androstane receptor (CAR)/pregnane X receptor (PXR)–CYP2B/CYP2C axis is activated in DKO livers but not in other cholestasis models. Loss of this axis inFxr:Shp:Car:Pxr quadruple knockouts blockedCyp2b/Cyp2c gene induction, impaired bilirubin conjugation/elimination, and increased liver injury. Differential CYP2B expression in DKO andBsep−/− was recapitulated in human PFIC5 and PFIC2 livers. In conclusion, loss of FXR/SHP results in distinct molecular pathogenesis and CAR/PXR activation, which promotesCyp2b/Cyp2c gene transcription and bilirubin clearance. CAR/PXR activation was not observed inBsep−/− mice or PFIC2 patients. These findings provide a deeper understanding of the heterogeneity of intrahepatic cholestasis.

Multiple mechanisms of ontogenic regulation of nuclear receptors during rat liver development

2005 ◽  
Vol 288 (2) ◽  
pp. G251-G260 ◽  
Author(s):  
N. Balasubramaniyan ◽  
Mohammad Shahid ◽  
Frederick J. Suchy ◽  
M. Ananthanarayanan
Keyword(s):  
Bile Acid ◽  
Nuclear Receptors ◽  
Rat Liver ◽  
Functional Activity ◽  
Pregnane X Receptor ◽  
Farnesoid X Receptor ◽  
Liver Development ◽  
Mrna Levels ◽  
Bile Formation ◽  
Protein Levels

Nuclear receptors (NRs) play pivotal roles in the regulation of genes contributing to hepatobiliary cholesterol and bile acid homeostasis. We have previously shown that transporters involved in bile formation are developmentally regulated and are poorly developed during the fetal stage, but their expression reached gradual maturity during the postnatal period. To define the molecular mechanisms underlying this regulation and the role that class II NRs and associated members [liver receptor homolog-1 (LRH-1) and short heterodimer partner (SHP)] play, we have analyzed the ontogeny of NR expression during liver development. Real-time PCR analysis of hepatic NR expression from fetal day 17 through adult revealed that steady-state mRNA levels for all NRs were very low during the embryonic period. However, mRNA levels peaked close to that of adult rats (>6 wk-old rats) by 4 wk of age for farnesoid X receptor (FXR), pregnane X receptor (PXR), liver X receptor-α (LXRα), peroxisome proliferator-activated receptor-α (PPARα), retinoid acid receptor-α (RARα), LRH-1, and SHP, whereas RXRα mRNA lagged behind. FXR, PXR, LXRα, RARα, and PPARα functional activity in liver nuclear extracts assayed by gel EMSA demonstrated that the activity attained adult levels by 4 wk of age, exhibiting a strict correlation with mRNA levels. Surprisingly, PPARα activity was delayed as seen by EMSA assay. Protein levels for NRs also corresponded to the mRNA and functional activity except for RXRα. RXRα protein levels were higher than message levels, suggesting increased protein stability. We conclude that expression of NRs during rat liver development is primarily regulated by transcriptional mechanisms, which in turn, control the regulation of bile acid and cholesterol metabolic pathways.

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