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PLoS ONE 01/2013; 8(1). · 4.09 Impact Factor
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ABSTRACT: BACKGROUND: Toll like receptors (TLRs) sense the intestinal microbiota and regulate the innate immune response. A dysregulation of TLRs function participates into intestinal inflammation. Farnesoid X Receptor (FXR) is a nuclear receptor and bile acid sensor highly expressed in entero-hepatic tissues. FXR regulates lipid metabolism and innate immunity. METHODOLOGY/PRINCIPAL FINDINGS: In this study we have investigated whether FXR gene expression/function in the intestine is modulated by TLRs. We found that in human monocytes activation of membrane TLRs (i.e. TLR2, 4, 5 and 6) downregulates, while activation of intracellular TLRs (i.e. TLR3, 7, 8 and 9) upregulates the expression of FXR and its target gene SHP, small heterodimer partner. This effect was TLR9-dependent and TNFα independent. Intestinal inflammation induced in mice by TNBS downregulates the intestinal expression of FXR in a TLR9-dependent manner. Protection against TNBS colitis by CpG, a TLR-9 ligand, was lost in FXR(-/-) mice. In contrast, activation of FXR rescued TLR9(-/-) and MyD88(-/-) mice from colitis. A putative IRF7 response element was detected in the FXR promoter and its functional characterization revealed that IRF7 is recruited on the FXR promoter under TLR9 stimulation. CONCLUSIONS/SIGNIFICANCE: Intestinal expression of FXR is selectively modulated by TLR9. In addition to its role in regulating type-I interferons and innate antiviral immunity, IRF-7 a TLR9-dependent factor, regulates the expression of FXR, linking microbiota-sensing receptors to host's immune and metabolic signaling.
PLoS ONE 01/2013; 8(1):e54472. · 4.09 Impact Factor
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Hollie Swanson,
Taira Wada,
Wen Xie,
Barbara Renga,
Angela Zampella, Eleonora Distrutti,
Stefano Fiorucci,
Bo Kong,
Ann M Thomas,
Grace L Guo,
Ramesh Narayanan,
Muralimohan Yepuru,
James Dalton,
John Y L Chiang
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ABSTRACT: This article is a report on a symposium sponsored by the American Society for Pharmacology and Experimental Therapeutics and held at the Experimental Biology 12 meeting in San Diego, CA. The presentations discussed the roles of a number of nuclear receptors in regulating glucose and lipid homeostasis, the pathophysiology of obesity-related disease states and the promise associated with targeting their activities to treat these diseases. While many of these receptors, in particular constitutive androstane receptor and pregnane X receptor and their target enzymes have been thought of as regulators of drug and xenobiotic metabolism, this symposium highlighted the advances made in our understanding of the endogenous functions of these receptors. Similarly, the advances made in our understanding of the mechanisms underlying bile acid signaling pathways in the regulation of body weight and glucose homeostasis illustrates the importance of using complementary approaches to elucidate this fascinating network of pathways. The observations that some receptors, like the farnesoid X receptor can function in a tissue specific manner via well defined mechanisms has important clinical implications particularly in the treatment of liver diseases. Finally, the novel findings that agents that selectively activate estrogen receptor β can effectively inhibit weight gain in a high-fat diet model of obesity identifies a new role for this member of the steroid superfamily. Taken together, this symposium has revealed a number of significant findings that illustrate the promise associated with targeting a number of nuclear receptors for the development of new therapies to treat obesity and other metabolic disorders.
Drug metabolism and disposition: the biological fate of chemicals 10/2012; · 3.74 Impact Factor
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ABSTRACT: Background and Purpose: Low doses of acetyl-salicylic acid (ASA) and nonsteroidal anti-inflammatory drugs (NSAIDs) increase the risk for gastrointestinal bleeding. GPBAR-1 is a bile acid receptor expressed in the gastrointestinal tract. Here, we have investigated whether GPBAR1 is required for mucosal protection in models of gastrointestinal injury caused by ASA and NSAIDs. Experimental Approch: GPBAR1(+/+) and GPBAR1(-/-) mice were administered ASA, 10 to 50 mg.kg(-1) and naproxen and gastric and intestinal mucosal damage assessed by measuring lesion scores. Key Results: Expression of GPBAR1, mRNA and protein, was detected in the in mouse stomach. Mice lacking GPBAR1were more sensitive to gastric and intestinal injury caused by ASA and NSAIDs and had a severe reduction in the expression of cystathionine-γ-liase (CSE), cysteine b-synthase (CBS) and endothelial nitric oxide synthase, i.e. enzymes required for generation of hydrogen sulphide (H(2) S) and nitric oxide, in the stomach. Administering GPBAR1(+/+) mice with two GPBAR1 agonists, ciprofloxacin and betulinic acid, rescued mice from gastric injury caused by ASA and NSAIDs. The protective effect of these agents was lost in GPBAR1(-/-) mice. Inhibition of CSE by DL-propargylglycin completely reversed protection afforded by ciprofloxacin in wild type mice, while administering mice with an H(2) S donor restored the protective effects of ciprofloxacin in GPBAR1(-/-) mice. GPBAR1 deletion alters small intestinal morphology and increases the sensitivity to injury caused by naproxen. Conclusions And Implications: GPBAR1 is essential to maintain gastric and intestinal mucosal integrity. GPBAR1 agonists protect against gastrointestinal injury caused by ASA and NSAIDs by a COX-independent mechanism. © 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.
British Journal of Pharmacology 08/2012; · 4.41 Impact Factor
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ABSTRACT: The glucocorticoid receptor (GR) is a master gene orchestrating the activation of gluconeogenic genes in the liver in response to food withdrawal. Mechanisms of GR regulation by other nuclear receptors, however, are poorly defined. Here, we report that the farnesoid X receptor (FXR), a bile acid sensor, activates gluconeogenic pathways in the liver and regulates GR expression and activity. FXR-null mice are hypoglycemic in the unfed state and exhibit both a reduced hepatic production of glucose in response to the pyruvate challenge and a decreased expression of two rate-limiting enzymes involved in gluconeogenesis, phosphoenolpyruvate carboxykinase (PEPCK), and glucose-6-phosphatase (G6Pase), along with blunted liver expression of GR. Treating wild-type mice with a semisynthetic FXR ligand (6E-CDCA) increases the liver expression of GR, PEPCK, and G6Pase. This effect was lost in fed animals, as well as in FXR(-/-) mice. The human and mouse GR promoters contain a conserved FXR-responsive element (an ER-8 sequence) whose activation by FXR ligation leads to GR transcription. GR silencing by siRNA in vitro or its pharmacological antagonism in vivo with mifepristone reverses the effect of FXR activation on expression of gluconeogenic genes. These findings demonstrate that an FXR-GR pathway regulates the activation of hepatic gluconeogenesis in the transition from the unfed to the fed state.
The FASEB Journal 03/2012; 26(7):3021-31. · 5.71 Impact Factor
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ABSTRACT: Invasion and metastasis are critical determinants of gastrointestinal and liver cancers morbidity. Genes and molecules participating in these steps (e.g. growth factors and their receptors, cell cycle regulators, cell adhesion molecules, matrix degrading enzymes) have been progressively clarified. Activated Wnt signaling pathway has been found in these tumors. Mutations in one of the DNA mismatch repair genes, alterations in epigenetics, such as aberrant DNA methylation and histone modifications are associated with the progression of gastrointestinal and control liver neoplasies. Bile acids (BAs), the main constituents of bile, activate a family of nuclear receptors (NRs) that control critical steps in bile acid homeostasis, endo- and xenobiotics detoxification, glucose, lipid metabolism and innate immunity. BAs activated NRs are misregulated in gastrointestinal and liver cancers. The present review provides an overview on the molecular determinants involved in gastrointestinal and liver cancers and focuses on the role of BAs activated NRs in the pathogenesis of these tumors.
Current topics in medicinal chemistry 01/2012; 12(6):625-36. · 4.47 Impact Factor
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ABSTRACT: The farnesoid-x-receptor (FXR), the constitute-androstane-receptor (CAR) and the pregnane-x-receptor (PXR) are ligand regulated nuclear receptors highly expressed in the liver and intestine supervising essential steps in the metabolism of xeno and endo-biotics in entero-hepatic tissues. Primary and secondary bile acids function as receptor agonists/ activators for these receptors. Activation of FXR by steroidal and non steroidal ligands promotes bile acids secretion by activating bile acids transporters in the apical membrane of hepatocytes. These effects are coordinated with a reduction in bile acids uptake at the basolateral membrane. However, FXR agonists interfere with the regulatory activity of CAR on hepatocyte's basolateral transporters. Because these effects might worsen liver injury in a subset of patients with obstructive cholestasis, development of FXR antagonists might be of clinical relevance. Structure-activity relationship studies have shown that available FXR antagonists are poorly specific for FXR, however specific FXR antagonists that are currently used in pre-clinical models of liver injury have been identified from marine organisms. PXR agonists are endowed with a wide array of biological activities but their effects on the expression/activity of phase I and II metabolizing enzymes is likely to limit their pharmacological development. Nevertheless a combination between FXR agonists and CAR and PXR agonists might hold utility in treating subset of patients with liver disorders. In addition, development of tissue specific FXR antagonists is an attractive opportunity to target subsets of genes in the intestine and liver avoiding sideeffects linked to FXR activation.
Current topics in medicinal chemistry 01/2012; 12(6):605-24. · 4.47 Impact Factor
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ABSTRACT: Signals generated by the inflammed intestine are thought to contribute to metabolic derangement. The intestinal microbiota contributes to instructing the immune system beyond the intestinal wall and its modulation is a potential target for treating systemic disorders.
To investigate the pathogenetic role of low grade intestinal inflammation in the development of steatohepatitis and atherosclerosis in a model of genetic dyslipidemia and to test the therapeutic potential of a probiotics intervention in protecting against development of these disorders.
ApoE(-/-) mice were randomized to receive vehicle or VSL#3, a mixture of eight probiotics, at the dose of 20×10(9) colony-forming units/kg/day for three months alone or in combination with 0.2% of dextran sulfate sodium (DSS) in drinking water. Administering DSS to ApoE(-/-) mice failed to induce signs and symptoms of colitis but increased intestinal permeability to dextran FITC and, while had no effect on serum lipids, increased the blood levels of markers of liver injury and insulin resistance. DSS administration associated with low level inflammation of intestinal and mesenteric adipose tissues, caused liver histopathology features of steatohepatitis and severe atherosclerotic lesions in the aorta. These changes were prevented by VSL#3 intervention. Specifically, VSL#3 reversed insulin resistance, prevented development of histologic features of mesenteric adipose tissue inflammation, steatohepatitis and reduced the extent of aortic plaques. Conditioned media obtained from cultured probiotics caused the direct transactivation of peroxisome proliferator-activated receptor-γ, Farnesoid-X-receptors and vitamin D receptor.
Low grade intestinal inflammation drives a transition from steatosis to steatohepatitis and worsens the severity of atherosclerosis in a genetic model of dyslipidemia. VSL#3 intervention modulates the expression of nuclear receptors, corrects for insulin resistance in liver and adipose tissues and protects against development of steatohepatitis and atherosclerosis.
PLoS ONE 01/2012; 7(9):e45425. · 4.09 Impact Factor
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Andrea Mencarelli, Eleonora Distrutti,
Barbara Renga,
Sabrina Cipriani,
Giuseppe Palladino,
Catherine Booth,
Gregory Tudor,
Jan-Hinrich Guse,
Ulrike Hahn,
Micheal Burnet,
Stefano Fiorucci
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ABSTRACT: Inflammation-driven immune dysfunction supports the development of several chronic human disorders including inflammatory bowel diseases and rheumatoid arthritis. Macrolides are effective antibiotics endowed with immunomodulatory effects. In this study we report the chemical synthesis and the pharmacological characterization of CSY0073, a non-antibiotic derivative of azithromycin. CSY0073 was tested for efficacy in two experimental models of colitis induced by administering mice with dextran sulfate (DSS) and trinitrobenzene sulphonic acid (TNBS) and in collagen induced arthritis. Like azithromycin, CSY0073 improved clinical, macroscopic and histopathological scores in mice administered DSS (12.5μmol/kg/day p.o.) and TNBS (45μmol/kg/day p.o.). When administered to TNBS-treated mice, CSY0073 effectively attenuated influx of neutrophils and macrophages into the colonic mucosa and reduced the intestinal expression pro-inflammatory cytokines TNFα, IL-2 and IFNγ. CSY0073 (0.1 to 10μM) counter-regulated TNFα, IFNγ, IL-12 and IL-23 release caused by exposure of mouse spleen monocytes and CD11b+ cells isolated from the colonic lamina propria to endotoxin. CSY0073 (25μmol/kg/day) reduced clinical scores in the collagen induced murine model of rheumatoid arthritis. In myeloid cells, CSY0073 (10μM) prevented the nuclear translocation of the p65 subunit of NF-κB and its binding to canonical NF-κB responsive elements. In summary, we report a novel class of non-antibiotic 14-member macrocycles with anti-inflammatory and immune-modulatory effects. CSY0073, the prototype of this new class of macrolides exerts counter-regulatory activity on NF-κB signaling. This study suggests the exploitation of non-antibiotic macrolides in the treatment of inflammatory disorders characterized by immune dysfunction.
European journal of pharmacology 08/2011; 665(1-3):29-39. · 2.59 Impact Factor
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ABSTRACT: A dysregulated interaction between intestinal epithelial cells (IEC) and components of innate immunity is a hallmark of inflammatory bowel diseases. Rifaximin is a poorly absorbed oral antimicrobial agent increasingly used in the treatment of inflammatory bowel diseases that has been demonstrated to act as a gut-specific ligand for the human nuclear receptor pregnane-X receptor (PXR). In the present study we investigated, whether activation of PXR in IEC by rifaximin, emanates counter-regulatory signals and modulates the expression of cytokines or chemokines mechanistically involved in dysregulated intestinal immune homeostasis documented in inflammatory bowel diseases. Our results demonstrate that primary IEC express PXR that regulate the pattern of cytokines and chemokines expressed. PXR silencing decreases TGF-β and IP-10 while increases the expression of TNF-α, IL-8, Rantes and increase the production of PGE2. This pattern is further exacerbated by treating anti-PXR siRNA cells with bacterial endotoxin (LPS). Exposure to rifaximin caused a robust attenuation of generation of inflammatory mediators caused by LPS and increased the generation of TGF-β. PXR silencing completely abrogated these anti-inflammatory effects of rifaximin. By Western blot analysis we found that rifaximin abrogates the binding of NF-κB caused by LPS. Finally, exposure of human colon biopsies from inflammatory bowel diseases patients to rifaximin reduced mRNA levels of IL-8, Rantes, MIP-3α and TNFα induced by LPS. Collectively, these data establish that rifaximin exerts counter-regulatory activities at the interface between enteric bacteria and intestinal epithelial cells. The ability of rifaximin to activate PXR contributes to the maintenance of the intestinal immune homeostasis.
European journal of pharmacology 07/2011; 668(1-2):317-24. · 2.59 Impact Factor
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ABSTRACT: Hepatic transport and metabolism of glutamate and glutamine are regulated by intervention of several proteins. Glutamine is taken up by periportal hepatocytes and is the major source of ammonia for urea synthesis and glutamate for N-acetylglutamate (NAG) synthesis, which is catalyzed by the N-acetylglutamate synthase (NAGS). Glutamate is taken up by perivenous hepatocytes and is the main source for the synthesis of glutamine, catalyzed by glutamine synthase (GS). Accumulation of glutamate and ammonia is a common feature of chronic liver failure, but mechanism that leads to failure of the urea cycle in this setting is unknown. The Farnesoid X Receptor (FXR) is a bile acid sensor in hepatocytes. Here, we have investigated its role in the regulation of the metabolism of both glutamine and glutamate. In vitro studies in primary cultures of hepatocytes from wild type and FXR(-/-) mice and HepG2 cells, and in vivo studies, in FXR(-/-) mice as well as in a rodent model of hepatic liver failure induced by carbon tetrachloride (CCl(4)), demonstrate a role for FXR in regulating this metabolism. Further on, promoter analysis studies demonstrate that both human and mouse NAGS promoters contain a putative FXRE, an ER8 sequence. EMSA, ChIP and luciferase experiments carried out to investigate the functionality of this sequence demonstrate that FXR is essential to induce the expression of NAGS. In conclusion, FXR activation regulates glutamine and glutamate metabolism and FXR ligands might have utility in the treatment of hyperammonemia states.
Biochimica et Biophysica Acta 07/2011; 1812(11):1522-31. · 4.66 Impact Factor
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ABSTRACT: Low doses of acetyl salicylic acid (ASA) and non-steroidal anti-inflammatory drugs (NSAIDs) cause gastrointestinal damage. The farnesoid X receptor (FXR) is a bile acid sensor essential for maintenance of intestinal homeostasis. Here, we have investigated whether FXR is required for mucosal protection in models of gastrointestinal injury caused by ASA and NSAIDs and if FXR activation has potential in the treatment or prevention of gastrointestinal injury caused by these agents.
FXR(+/+) and FXR(-/-) mice were given ASA (10 to 100 mg·kg(-1) ) or NSAIDs. Gastric and intestinal mucosal damage assessed by measuring lesion scores. FXR were activated by giving mice natural (chenodeoxycholic acid; CDCA) or synthetic (GW4064) FXR agonists.
FXR, mRNA and protein, was detected in human and mouse stomach. FXR(-/-) mice were more prone to develop severe gastric and intestinal injury in response to ASA and NSAIDs and showed a severe reduction in the gastrointestinal expression of cystathionine-γ-lyase (CSE), an enzyme required for generation of hydrogen sulphide. CSE expression was reduced by ≈50% in wild-type mice challenged with ASA. Treating wild-type mice but not FXR(-/-) mice with CDCA or GW4064 protected against gastric injury caused by ASA and NSAIDs, by a CSE-dependent and cycloxygenase- and NO-independent, mechanism. FXR activation by GW4064 rescued mice from intestinal injury caused by naproxen.
FXR was essential to maintain gastric and intestinal mucosal barriers. FXR agonists protected against gastric injury caused by ASA and NSAIDs by a CSE-mediated mechanism.
British Journal of Pharmacology 05/2011; 164(8):1929-38. · 4.41 Impact Factor
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ABSTRACT: Multidrug resistance protein-4 (MRP4) is a member of the multidrug resistance associated gene family that is expressed on the basolateral membrane of hepatocytes and undergoes adaptive up-regulation in response to cholestatic injury or bile acid feeding. In this study we demonstrate that farnesoid X receptor (FXR) regulates MRP4 in vivo and in vitro. In vivo deletion of FXR induces MRP4 gene expression. In vitro treatment of HepG2 cells with FXR ligands, chenodeoxycholic acid (CDCA), cholic acid (CA) and the synthetic ligand GW-4064 suppresses basal mRNA level of the MRP4 gene as well as the co-treatment with CDCA and 6-(4-Chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde-O-(3,4-dichlorobenzyl)oxime (CITCO), an activator of constitutive androstane receptor (CAR). We found in the human MRP4 promoter a CAR responsive element (CARE) embedded within an FXR responsive element (FXRE). We cloned this region and found that FXR suppresses CAR activity in luciferase assay. Finally, we demonstrated that FXR competes with CAR for binding to this overlapping binding site. Our results support the view that FXR activation in obstructive cholestasis might worsen liver injury by hijacking a protective mechanism regulated by CAR and provides a new molecular explanation to the pathophysiology of cholestasis.
Biochimica et Biophysica Acta 02/2011; 1809(3):157-65. · 4.66 Impact Factor
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ABSTRACT: Adipocytes from mesenteric white adipose tissue amplify the inflammatory response and participate in inflammation-driven immune dysfunction in Crohn's disease by releasing proinflammatory mediators. Peroxisome proliferator-activated receptors (PPAR)-α and -γ, pregnane x receptor (PXR), farnesoid x receptor (FXR) and liver x-receptor (LXR) are ligand-activated nuclear receptor that provide counter-regulatory signals to dysregulated immunity and modulates adipose tissue.
To investigate the expression and function of nuclear receptors in intestinal and adipose tissues in a rodent model of colitis and mesenteric fat from Crohn's patients and to investigate their modulation by probiotics.
Colitis was induced by TNBS administration. Mice were administered vehicle or VSL#3, daily for 10 days. Abdominal fat explants obtained at surgery from five Crohn's disease patients and five patients with colon cancer were cultured with VSL#3 medium.
Probiotic administration attenuated development of signs and symptoms of colitis, reduced colonic expression of TNFα, IL-6 and IFNγ and reserved colonic downregulation of PPARγ, PXR and FXR caused by TNBS. Mesenteric fat depots isolated from TNBS-treated animals had increased expression of inflammatory mediators along with PPARγ, FXR, leptin and adiponectin. These changes were prevented by VSL#3. Creeping fat and mesenteric adipose tissue from Crohn's patients showed a differential expression of PPARγ and FXR with both tissue expressing high levels of leptin. Exposure of these tissues to VSL#3 medium abrogates leptin release.
Mesenteric adipose tissue from rodent colitis and Crohn's disease is metabolically active and shows inflammation-driven regulation of PPARγ, FXR and leptin. Probiotics correct the inflammation-driven metabolic dysfunction.
PLoS ONE 01/2011; 6(7):e22978. · 4.09 Impact Factor
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ABSTRACT: GP-BAR1, a member G protein coupled receptor superfamily, is a cell surface bile acid-activated receptor highly expressed in the ileum and colon. In monocytes, ligation of GP-BAR1 by secondary bile acids results in a cAMP-dependent attenuation of cytokine generation.
To investigate the role GP-BAR1 in regulating intestinal homeostasis and inflammation-driven immune dysfunction in rodent models of colitis.
Colitis was induced in wild type and GP-BAR1(-/-) mice by DSS and TNBS administration. Potential GP-BAR1 agonists were identified by in silico screening and computational docking studies.
GP-BAR1(-/-) mice develop an abnormal morphology of colonic mucous cells and an altered molecular architecture of epithelial tight junctions with increased expression and abnormal subcellular distribution of zonulin 1 resulting in increased intestinal permeability and susceptibility to develop severe colitis in response to DSS at early stage of life. By in silico screening and docking studies we identified ciprofloxacin as a GP-BAR1 ligand. In monocytes, ciprofloxacin increases cAMP concentrations and attenuates TNFα release induced by TLR4 ligation in a GP-BAR1 dependent manner. Treating mice rendered colitic by TNBS with ciprofloxacin and oleanolic acid, a well characterized GP-BAR1 ligand, abrogates signs and symptoms of colitis. Colonic expression of GP-BAR1 mRNA increases in rodent models of colitis and tissues from Crohn's disease patients. Flow cytometry analysis demonstrates that ≈90% of CD14+ cells isolated from the lamina propria of TNBS-treated mice stained positively for GP-BAR1.
GP-BAR1 regulates intestinal barrier structure. Its expression increases in rodent models of colitis and Crohn's disease. Ciprofloxacin is a GP-BAR1 ligand.
PLoS ONE 01/2011; 6(10):e25637. · 4.09 Impact Factor
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ABSTRACT: The regulation of hepatic stellate cells (HSCs) by bacterial lipopolysaccharide (LPS) represents a recently-discovered and novel mechanism for hepatic injury and fibrosis. Stimulation of HSCs with LPS results in a rapid and marked induction of interleukin (IL)1β, IL6 and tumor necrosis factor α. These events lead to the development of the activated phenotype in the HSCs associated with fibrosis and inflammation in the injured liver. We have previously demonstrated that farnesoid X receptor (FXR) activation increases transcription of rat peroxisome proliferator-activated receptor-γ (PPARγ) gene in HSCs. We aimed at evaluating the molecular mechanism of the transcriptional regulation of the PPARγ gene by FXR.
Real-time PCR, ELISA, transactivations, EMSA and ChIP experiments were performed in HSC-T6 cells, in primary HSCs, in HEK293T cells and in CCl(4)-treated rats.
In vivo and in vitro activation of FXR downregulates cytokines and collagen(α)1 while inducing PPARγ and small heterodimer partner (SHP). NUBIScan analysis of rat PPARγ promoter revealed the presence of a putative FXR response element. Cotransfection with FXR/retinoic acid receptor significantly enhanced chenodeoxycholic acid-induced luciferase activity. EMSA experiments demonstrated that FXR was able to bind to an inverted repeat-1 sequence and ChIP experiments confirmed that FXR is recruited on the PPARγ promoter.
The present study provides a molecular basis for the physiological cross-talk between FXR and PPARγ pathways in HSCs.
Agents and Actions 01/2011; 60(6):577-87. · 1.59 Impact Factor
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ABSTRACT: The pregnane-X-receptor (PXR) is master gene overseeing detoxification of wide number of xenobiotics and is critical for maintenance of intestinal integrity. The intestinal expression of genes involved in cellular detoxification is down-regulated in patients with inflammatory bowel diseases (IBD). Rifaximin is a non-absorbable antibiotic endowed with a PXR agonistic activity. In the present study we have investigated whether rifaximin activates PXR in primary human colon epithelial cells and human colon biopsies and assessed whether this antibiotic antagonizes the effect of tumor necrosis factor (TNF)-α on expression of PXR and PXR-related genes. Present results demonstrate that primary colon epithelial cells express PXR and that their exposure to rifaximin induces the expression of genes involved in cellular detoxification. Exposure to TNFα reduces the expression of PXR mRNA as well as expression of its target genes. This inhibitory effect was prevented by that co-treatment with rifaximin. Knocking down the expression of PXR in colon epithelial cells by an anti-PXR siRNA, abrogated the counter-regulatory effects exerted by rifaximin on cell exposed to TNFα. Finally, ex vivo exposure of colon biopsies obtained from ulcerative colitis patients to rifaximin increased the expression of genes involved in xenobiotics metabolism. In aggregate, these data illustrate that rifaximin increases the expression of PXR and PXR-regulated genes involved in the metabolism and excretion of xenobiotics and antagonizes the effects of TNFα in intestinal epithelial cells and colon biopsies. These non-antibiotic effects of rifaximin could contribute to the maintenance of the intestinal barrier integrity against xenobiotics and products generated by luminal bacteria.
Biochemical pharmacology 12/2010; 80(11):1700-7. · 4.25 Impact Factor
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ABSTRACT: Although human immunodeficiency virus (HIV)-related morbidity and mortality rates in patients treated with a combination of high active antiretroviral therapy (HAART) have declined, significant metabolic/vascular adverse effects associated with the long term use of HIV protease inhibitors (PIs) have emerged as a significant side effect. Here we illustrate that targeting the bile acid sensor farnesoid X receptor (FXR) protects against dyslipidemia and vascular injury induced HIV-PIs in rodents.
Administration of the HIV PI ritonavir to wild type mice increased plasma triacylglycerols and cholesterol levels and this effect was exacerbated by dosing ritonavir to mice harbouring a disrupted FXR. Dyslipidemia induced by ritonavir associated with a shift in the liver expression of signature genes, Sterol Regulatory Element-Binding Protein (SREBP)-1 and fatty acid synthase. Treating wild type mice with the FXR agonist (chenodeoxycholic acid, CDCA) protected against development of dyslipidemia induced by ritonavir. Administration of ritonavir to ApoE(-/-) mice, a strain that develop spontaneously atherosclerosis, increased the extent of aortic plaques without worsening the dyslipidemia. Treating these mice with CDCA reduced the extent of aortic plaques by 70% without changing plasma lipoproteins or the liver expression of signature genes. A beneficial effect on aortic plaques was also obtained by treating ApoE(-/-) mice with gemfibrozil, a PPARα agonist. FXR activation counter-regulated induction of expression/activity of CD36 caused by HIV-PIs in circulating monocytes and aortic plaques. In macrophages cell lines, CDCA attenuated CD36 induction and uptake of acetylated LDL caused by ritonavir. Natural and synthetic FXR ligands reduced the nuclear translocation of SREBP1c caused by ritonavir.
Activation of the bile acid sensor FXR protects against dyslipidemia and atherosclerotic caused by ritonavir, a widely used HIV PI. From a mechanistic stand point it appears that besides reducing the liver expression of genes involved in fatty acid synthesis, FXR activation counter-regulates the expression/activity of CD36 on monocytes. FXR ligands might hold promise in the treatment dyslipidemia induced by ritonavir.
PLoS ONE 01/2010; 5(10):e13238. · 4.09 Impact Factor
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ABSTRACT: Hydrogen sulphide (H2S) is a gaseous neuro-mediator that exerts analgesic effects in rodent models of visceral pain by activating KATP channels. A body of evidence support the notion that KATP channels interact with endogenous opioids. Whether H2S-induced analgesia involves opioid receptors is unknown.
The perception of painful sensation induced by colorectal distension (CRD) in conscious rats was measured by assessing the abdominal withdrawal reflex. The contribution of opioid receptors to H2S-induced analgesia was investigated by administering rats with selective mu, kappa and delta opioid receptor antagonists and antisenses. To investigate whether H2S causes mu opioid receptor (MOR) transactivation, the neuronal like cells SKNMCs were challenged with H2S in the presence of MOR agonist (DAMGO) or antagonist (CTAP). MOR activation and phosphorylation, its association to beta arrestin and internalization were measured.
H2S exerted a potent analgesic effects on CRD-induced pain. H2S-induced analgesia required the activation of the opioid system. By pharmacological and molecular analyses, a robust inhibition of H2S-induced analgesia was observed in response to central administration of CTAP and MOR antisense, while kappa and delta receptors were less involved. H2S caused MOR transactivation and internalization in SKNMCs by a mechanism that required AKT phosphorylation. MOR transactivation was inhibited by LY294002, a PI3K inhibitor, and glibenclamide, a KATP channels blocker.
This study provides pharmacological and molecular evidence that antinociception exerted by H2S in a rodent model of visceral pain is modulated by the transactivation of MOR. This observation provides support for development of new pharmacological approaches to visceral pain.
Molecular Pain 01/2010; 6:36. · 3.53 Impact Factor
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ABSTRACT: The farnesoid X receptor (FXR) is a bile acid-regulated nuclear receptor expressed in enterohepatic tissues. In this study we investigated whether FXR is expressed by cells of innate immunity and regulates inflammation in animal models of colitis. Acute (7 days) and chronic (8 wk) colitis were induced in wild-type and FXR(-/-) mice by intrarectal administration of trinitrobenzensulfonic acid or by 7-day administration of 5% dextran sulfate in drinking water. The results of this experiment demonstrate that FXR is expressed by and exerts counterregulatory effects on cells of innate immunity. Exposure of LPS-activated macrophages to 6-ethyl chenodeoxycholic acid (6E-CDCA; INT-747) a synthetic FXR ligand, results in a reciprocal regulation of NF-kappaB dependent-genes (TNF-alpha, IL-1beta, IL-6, COX-1, COX-2, and iNOS) and induction of SHP, a FXR-regulated gene. FXR activation stabilizes the nuclear corepressor NCoR on the NF-kappaB responsive element on the IL-1beta promoter. Colon inflammation in Crohn's disease patients and in rodent models of colitis is associated with a reduced expression of FXR mRNA. Using two rodent models of colon inflammation, we show that progression of these immune-mediated disorders is exacerbated in FXR(-/-) mice (p < 0.01). In vivo treatment with INT-747 attenuates organ injury and immune cell activation. FXR activation increased the colon expression of I-BABP, FXR, and SHP while reducing IL-1beta, IL-2, IL-6, TNF-alpha, and IFN-gamma mRNA expression and attenuating disease severity. In aggregate, these findings provide evidence that FXR is an essential component of a network of nuclear receptors that regulate intestinal innate immunity and homeostasis.
The Journal of Immunology 11/2009; 183(10):6251-61. · 5.79 Impact Factor
