The G‐Protein‐coupled bile acid receptor, Gpbar1 (TGR5), negatively regulates hepatic inflammatory response through antagonizing nuclear factor kappa light‐chain enhancer of activated B cells (NF‐κB) in mice

Gpbar1 (TGR5), a membrane‐bound bile acid receptor, is well known for its roles in regulation of energy homeostasis and glucose metabolism. TGR5 also displays strong attenuation of macrophage reactivity in vitro, but the physiological roles of TGR5 in inflammatory response, and its mechanism, is unknown. Here, we demonstrate that TGR5 is a negative modulator of nuclear factor kappa light‐chain enhancer of activated B cells (NF‐κB)‐mediated inflammation. TGR5 activation suppresses the phosphorylation of nuclear factor of kappa light polypeptide gene enhancer in B‐cells inhibitor, alpha (IκBα), the translocation of p65, NF‐κB DNA‐binding activity, and its transcription activity. Furthermore, TGR5 activation enhances the interaction of IκBα and β‐arrestin2. Suppression of NF‐κB transcription activity and its target gene expression by TGR5 agonist are specifically abolished by the expression of anti‐β‐arrestin2 small interfering RNA. These results show that TGR5 suppresses the NF‐κB pathway by mediation of the interaction between IκBα and β‐arrestin2. In a lipopolysaccharide (LPS)‐induced inflammation model, TGR5−/− mice show more severe liver necroses and inflammation, compared with wild‐type (WT) mice. Activation of TGR5 by its agonist ligand inhibits the expression of inflammatory mediators in response to NF‐κB activation induced by LPS in WT, but not TGR5−/−, mouse liver. Conclusion: These findings identify TGR5 as a negative mediator of inflammation that may serve as an attractive therapeutic tool for immune and inflammatory liver diseases. (HEPATOLOGY 2011;)

[1]  A. Ohta,et al.  Role of G-protein-coupled adenosine receptors in downregulation of inflammation and protection from tissue damage , 2001, Nature.

[2]  R. Lefkowitz,et al.  β-Arrestin inhibits NF-κB activity by means of its interaction with the NF-κB inhibitor IκBα , 2004 .

[3]  R. Lefkowitz,et al.  beta-Arrestin inhibits NF-kappaB activity by means of its interaction with the NF-kappaB inhibitor IkappaBalpha. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[4]  M. Andrassy,et al.  Diabetes-associated sustained activation of the transcription factor nuclear factor-kappaB. , 2001, Diabetes.

[5]  B. M. Forman,et al.  Farnesoid X receptor antagonizes nuclear factor κB in hepatic inflammatory response , 2008, Hepatology.

[6]  Y. Ben-Neriah,et al.  NF-κB functions as a tumour promoter in inflammation-associated cancer , 2004, Nature.

[7]  H. Davis,et al.  Targeted deletion of Gpbar1 protects mice from cholesterol gallstone formation. , 2006, The Biochemical journal.

[8]  Hongyan Zhong,et al.  Role of A2B adenosine receptor signaling in adenosine-dependent pulmonary inflammation and injury. , 2006, The Journal of clinical investigation.

[9]  S. Fiorucci,et al.  Bile-acid-activated receptors: targeting TGR5 and farnesoid-X-receptor in lipid and glucose disorders. , 2009, Trends in pharmacological sciences.

[10]  D. Häussinger,et al.  The G‐protein coupled bile salt receptor TGR5 is expressed in liver sinusoidal endothelial cells , 2007, Hepatology.

[11]  R. Ye.  Regulation of nuclear factor κB activation by G‐protein‐coupled receptors , 2001, Journal of leukocyte biology.

[12]  Michael Karin,et al.  NF-kappaB: linking inflammation and immunity to cancer development and progression. , 2005, Nature reviews. Immunology.

[13]  D. Häussinger,et al.  Expression and function of the bile acid receptor TGR5 in Kupffer cells. , 2008, Biochemical and biophysical research communications.

[14]  S. Morris,et al.  Bcl10 plays a critical role in NF-κB activation induced by G protein-coupled receptors , 2007, Proceedings of the National Academy of Sciences.

[15]  Yiwei Li,et al.  NF-kappaB: a potential target for cancer chemoprevention and therapy. , 2008, Frontiers in bioscience : a journal and virtual library.

[16]  Yue Sun,et al.  Identification of beta-arrestin2 as a G protein-coupled receptor-stimulated regulator of NF-kappaB pathways. , 2004, Molecular cell.

[17]  Michael Karin,et al.  NF-κB in cancer: from innocent bystander to major culprit , 2002, Nature Reviews Cancer.

[18]  J. Olefsky,et al.  SIRT1 inhibits inflammatory pathways in macrophages and modulates insulin sensitivity. , 2010, American journal of physiology. Endocrinology and metabolism.

[19]  B. M. Forman,et al.  Farnesoid X receptor alleviates age‐related proliferation defects in regenerating mouse livers by activating forkhead box m1b transcription , 2009, Hepatology.

[20]  R. Lefkowitz,et al.  The role of beta-arrestins in the termination and transduction of G-protein-coupled receptor signals. , 2002, Journal of cell science.

[21]  M. Karin,et al.  Regulation and function of NF-kappaB transcription factors in the immune system. , 2009, Annual review of immunology.

[22]  M. Menger,et al.  Impact of leukocytes and platelets in mediating hepatocyte apoptosis in a rat model of systemic endotoxemia. , 2004, American journal of physiology. Gastrointestinal and liver physiology.

[23]  H. Miyoshi,et al.  Targeted disruption of G protein-coupled bile acid receptor 1 (Gpbar1/M-Bar) in mice. , 2006, The Journal of endocrinology.

[24]  B. Aggarwal,et al.  Nuclear factor-kappaB: the enemy within. , 2004, Cancer cell.

[25]  J. Auwerx,et al.  Bile acids and the membrane bile acid receptor TGR5--connecting nutrition and metabolism. , 2008, Thyroid : official journal of the American Thyroid Association.

[26]  R. Seifert,et al.  Constitutive activity of G-protein-coupled receptors: cause of disease and common property of wild-type receptors , 2002, Naunyn-Schmiedeberg's Archives of Pharmacology.

[27]  K. Wellen,et al.  Inflammation, stress, and diabetes. , 2005, The Journal of clinical investigation.

[28]  A. Manning,et al.  Role of IKK1 and IKK2 in Lipopolysaccharide Signaling in Human Monocytic Cells* , 1998, The Journal of Biological Chemistry.

[29]  M. Soley,et al.  Liver injury after an aggressive encounter in male mice. , 2007, American journal of physiology. Regulatory, integrative and comparative physiology.

[30]  T. Huang,et al.  Activation of Kupffer cells and caspase-3 involved in rat hepatocyte apoptosis induced by endotoxin. , 1999, Journal of hepatology.

[31]  Jianping Ye,et al.  Shilianhua extract inhibits GSK-3beta and promotes glucose metabolism. , 2009, American Journal of Physiology. Endocrinology and Metabolism.

[32]  Rinat Abramovitch,et al.  NF-kappaB functions as a tumour promoter in inflammation-associated cancer. , 2004, Nature.

[33]  Michael Karin,et al.  NF-kappaB in cancer: from innocent bystander to major culprit. , 2002, Nature reviews. Cancer.

[34]  Georg Kraal,et al.  Inhibition of NF-kappaB activation in macrophages increases atherosclerosis in LDL receptor-deficient mice. , 2003, The Journal of clinical investigation.

[35]  G. Hotamisligil,et al.  Inflammation and metabolic disorders , 2006, Nature.

[36]  C. Sabin,et al.  Transgenic human C-reactive protein is not proatherogenic in apolipoprotein E-deficient mice. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[37]  F. D’Acquisto,et al.  From willow bark to peptides: the ever widening spectrum of NF-κB inhibitors , 2006 .

[38]  J. Auwerx,et al.  TGR5-mediated bile acid sensing controls glucose homeostasis. , 2009, Cell metabolism.

[39]  Ya-Xiong Tao,et al.  Constitutive activation of G protein-coupled receptors and diseases: insights into mechanisms of activation and therapeutics. , 2008, Pharmacology & therapeutics.

[40]  G. Hotamisligil,et al.  Nutrient sensing and inflammation in metabolic diseases , 2008, Nature Reviews Immunology.

[41]  B. Aggarwal,et al.  Nuclear factor-kappa B and cancer: its role in prevention and therapy. , 2002, Biochemical pharmacology.

[42]  M. Karin,et al.  NF-κB and STAT3 – key players in liver inflammation and cancer , 2011, Cell Research.

[43]  G. Hotamisligil,et al.  Inflammation and endoplasmic reticulum stress in obesity and diabetes , 2008, International Journal of Obesity.

[44]  J. Auwerx,et al.  Bile acids induce energy expenditure by promoting intracellular thyroid hormone activation , 2006, Nature.

[45]  Courtney M. Lappas,et al.  Adenosine A2A agonists in development for the treatment of inflammation , 2005, Expert opinion on investigational drugs.

[46]  F. D’Acquisto,et al.  From willow bark to peptides: the ever widening spectrum of NF-kappaB inhibitors. , 2006, Current opinion in pharmacology.

[47]  J. Linden.  New insights into the regulation of inflammation by adenosine. , 2006, The Journal of clinical investigation.

[48]  H. Thorlacius,et al.  Allopurinol inhibits CXC chemokine expression and leukocyte adhesion in endotoxemic liver injury , 2003, Inflammation Research.

[49]  T. Sugiyama,et al.  Lipopolysaccharide triggered TNF-alpha-induced hepatocyte apoptosis in a murine non-alcoholic steatohepatitis model. , 2009, Journal of hepatology.

[50]  Yue Sun,et al.  Identification of β-Arrestin2 as a G Protein-Coupled Receptor-Stimulated Regulator of NF-κB Pathways , 2004 .

[51]  Michael Karin,et al.  NF-kappaB and cancer-identifying targets and mechanisms. , 2008, Current opinion in genetics & development.

[52]  Masataka Harada,et al.  A G Protein-coupled Receptor Responsive to Bile Acids* , 2003, The Journal of Biological Chemistry.

[53]  J. Auwerx,et al.  Nongenomic actions of bile acids. Synthesis and preliminary characterization of 23- and 6,23-alkyl-substituted bile acid derivatives as selective modulators for the G-protein coupled receptor TGR5. , 2007, Journal of Medicinal Chemistry.