scholarly journals Differences in Gene Regulation by Dual Ligands of Nuclear Receptors Constitutive Androstane Receptor (CAR) and Pregnane X Receptor (PXR) in HepG2 Cells Stably Expressing CAR/PXR

2016 ◽  
Vol 44 (8) ◽  
pp. 1158-1163 ◽  
Author(s):  
Y. Kanno ◽  
N. Tanuma ◽  
S. Yazawa ◽  
S. Zhao ◽  
M. Inaba ◽  
...  
Keyword(s):  
Gene Regulation ◽  
Nuclear Receptors ◽  
Hepg2 Cells ◽  
Constitutive Androstane Receptor ◽  
Pregnane X Receptor

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.

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 Orphan Nuclear Receptors Constitutive Androstane Receptor and Pregnane X Receptor Share Xenobiotic and Steroid Ligands

2000 ◽  
Vol 275 (20) ◽  
pp. 15122-15127 ◽  
Author(s):  
Linda B. Moore ◽  
Derek J. Parks ◽  
Stacey A. Jones ◽  
Randy K. Bledsoe ◽  
Thomas G. Consler ◽  
...  
Keyword(s):  
Nuclear Receptors ◽  
Constitutive Androstane Receptor ◽  
Pregnane X Receptor ◽  
Orphan Nuclear Receptors

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.

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