title: Lactate reduces liver and pancreatic injury in Toll-like receptor- and inflammasome-mediated inflammation via GPR81-mediated suppression of innate immunity.
abstract: OBJECTIVE
  The NACHT, LRR, and pyrin domain-containing protein 3 (NLRP3) inflammasome induces inflammation in response to organ injury, but little is known about its regulation. Toll-like receptors (TLRs) provide the first signal required for activation of the inflammasome and stimulate aerobic glycolysis to generate lactate. We examined whether lactate and the lactate receptor, Gi-protein-coupled receptor 81 (GPR81), regulate TLR induction of signal 1 and limit inflammasome activation and organ injury.
  
  
  METHODS
  Primary mouse macrophages and human monocytes were incubated with TLR4 agonists and lactate and assayed for levels of pro-interleukin (IL)1β, NLRP3, and caspase-1 (CASP1); release of IL1β; and activation of nuclear factor-κB (NF-κB) and caspase-1. Small interfering RNAs were used to reduce levels of GPR81 and arrestin β-2 (ARRB2), and an NF-κB luciferase reporter transgene was transfected in RAW 264.7 cells. Cell lysates were analyzed by immunoprecipitation with an antibody against GPR81. Acute hepatitis was induced in C56BL/6N mice by administration of lipopolysaccharide and D-galactosamine. Acute pancreatitis was induced by administration of lipopolysaccharide and cerulein. Some mice were given intraperitoneal injections of sodium lactate or small interfering RNA against Gpr81. Activation of NF-κB in tissue macrophages was assessed in mice that expressed a reporter transgene.
  
  
  RESULTS
  In macrophages and monocytes, increasing concentrations of lactate reduced TLR4-mediated induction of Il1B, Nlrp3, and Casp1; activation of NF-κB; release of IL1β; and cleavage of CASP1. GPR81 and ARRB2 physically interacted and were required for these effects. The administration of lactate reduced inflammation and organ injury in mice with immune hepatitis; this reduction required Gpr81 dependence in vivo. Lactate also prevented activation of NF-κB in macrophages of mice, and, when given after injury, reduced the severity of acute pancreatitis and acute liver injury.
  
  
  CONCLUSIONS
  Lactate negatively regulates TLR induction of the NLRP3 inflammasome and production of IL1β, via ARRB2 and GPR81. Lactate could be a promising immunomodulatory therapy for patients with acute organ injury.
authors.affiliation: Section of Digestive Diseases, Yale University, New Haven, Connecticut.
authors.forename: Rafaz
authors.initials: R
authors.lastname: Hoque
authors.affiliation: Section of Digestive Diseases, Yale University, New Haven, Connecticut.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Farooq
authors.affiliation: Section of Digestive Diseases, Yale University, New Haven, Connecticut.
authors.forename: Ayaz
authors.initials: A
authors.lastname: Ghani
authors.affiliation: Section of Digestive Diseases, Yale University, New Haven, Connecticut; Section of Digestive Diseases, Department of Veterans Affairs Connecticut Healthcare, West Haven, Connecticut.
authors.forename: Fred
authors.initials: F
authors.lastname: Gorelick
authors.affiliation: Section of Digestive Diseases, Yale University, New Haven, Connecticut; Section of Digestive Diseases, Department of Veterans Affairs Connecticut Healthcare, West Haven, Connecticut. Electronic address: wajahat.mehal@yale.edu.
authors.forename: Wajahat Zafar
authors.initials: WZ
authors.lastname: Mehal
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage / Q000494:pharmacology*; D019390:Arrestins / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002108:Ceruletide; D056486:Chemical and Drug Induced Liver Injury / Q000209:etiology / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D019610:Cytoprotection; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005688:Galactosamine; D006801:Humans; D007113:Immunity, Innate / Q000187:drug effects*; D058847:Inflammasomes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D007274:Injections, Intraperitoneal; D053583:Interleukin-1beta / Q000378:metabolism; D008070:Lipopolysaccharides; D008099:Liver / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009000:Monocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D010179:Pancreas / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D010195:Pancreatitis / Q000139:chemically induced / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D019354:Sodium Lactate / Q000008:administration & dosage / Q000494:pharmacology*; D051197:Toll-Like Receptor 4 / Q000187:drug effects / Q000378:metabolism; D051193:Toll-Like Receptors / Q000187:drug effects* / Q000378:metabolism; D014162:Transfection; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
chemical_list: C000605254:ARRB2 protein, human; D000893:Anti-Inflammatory Agents; C000605258:Arrb2 protein, mouse; D019390:Arrestins; D002352:Carrier Proteins; C533610:HCAR1 protein, human; C529424:Hcar1 protein, mouse; D058847:Inflammasomes; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D016328:NF-kappa B; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; C492716:Nlrp3 protein, mouse; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled; C495345:TLR4 protein, human; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D005688:Galactosamine; D002108:Ceruletide; D019354:Sodium Lactate
keywords: Immune Regulation; Innate Immune Response; Mouse Model; Pancreas