title: Toll-like receptor 2 regulates intestinal inflammation by controlling integrity of the enteric nervous system.
abstract: OBJECTIVE
  In the intestines, Toll-like receptor 2 (TLR2) mediates immune responses to pathogens and regulates epithelial barrier function; polymorphisms in TLR2 have been associated with inflammatory bowel disease phenotype. We assessed the effects of TLR2 signaling on the enteric nervous system (ENS) in mice.
  
  
  METHODS
  TLR2 distribution and function in the ileal neuromuscular layer of mice were determined by immunofluorescence, cytofluorimetric analysis, immunoprecipitation, and immunoblot analyses. We assessed morphology and function of the ENS in Tlr2(-/-) mice and in mice with wild-type Tlr2 (wild-type mice) depleted of intestinal microbiota, using immunofluorescence, immunoblot, and gastrointestinal motility assays. Levels and signaling of glial cell line-derived neurotrophic factor (GDNF) were determined using quantitative reverse transcriptase polymerase chain reaction, immunohistochemistry, and immunoprecipitation analyses. Colitis was induced by administration of dextran sulfate sodium or 2,4 dinitrobenzensulfonic acid to Tlr2(-/-) mice after termination of GDNF administration.
  
  
  RESULTS
  TLR2 was expressed in enteric neurons, glia, and smooth muscle cells of the intestinal wall. Tlr2(-/-) mice had alterations in ENS architecture and neurochemical profile, intestinal dysmotility, abnormal mucosal secretion, reduced levels of GDNF in smooth muscle cells, and impaired signaling via Ret-GFRα1. ENS structural and functional anomalies were completely corrected by administration of GDNF to Tlr2(-/-) mice. Wild-type mice depleted of intestinal microbiota had ENS defects and GDNF deficiency, similar to Tlr2(-/-) mice; these defects were partially restored by administration of a TLR2 agonist. Tlr2(-/-) mice developed more severe colitis than wild-type mice after administration of dextran sulfate sodium or 2,4 dinitrobenzensulfonic acid; colitis was not more severe if Tlr2(-/-) mice were given GDNF before dextran sulfate sodium or 2,4 dinitrobenzensulfonic acid.
  
  
  CONCLUSIONS
  In mice, TLR2 signaling regulates intestinal inflammation by controlling ENS structure and neurochemical coding, along with intestinal neuromuscular function. These findings provide information as to how defective TLR2 signaling in the ENS affects inflammatory bowel disease phenotype in humans.
authors.affiliation: Department of Molecular Medicine, University of Padova, Padova, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Brun
authors.forename: Maria Cecilia
authors.initials: MC
authors.lastname: Giron
authors.forename: Marsela
authors.initials: M
authors.lastname: Qesari
authors.forename: Andrea
authors.initials: A
authors.lastname: Porzionato
authors.forename: Valentina
authors.initials: V
authors.lastname: Caputi
authors.forename: Chiara
authors.initials: C
authors.lastname: Zoppellaro
authors.forename: Serena
authors.initials: S
authors.lastname: Banzato
authors.forename: Alessia Rosaria
authors.initials: AR
authors.lastname: Grillo
authors.forename: Lisa
authors.initials: L
authors.lastname: Spagnol
authors.forename: Raffaele
authors.initials: R
authors.lastname: De Caro
authors.forename: Daniela
authors.initials: D
authors.lastname: Pizzuti
authors.forename: Vito
authors.initials: V
authors.lastname: Barbieri
authors.forename: Antonio
authors.initials: A
authors.lastname: Rosato
authors.forename: Giacomo Carlo
authors.initials: GC
authors.lastname: Sturniolo
authors.forename: Diego
authors.initials: D
authors.lastname: Martines
authors.forename: Giovanni
authors.initials: G
authors.lastname: Zaninotto
authors.forename: Giorgio
authors.initials: G
authors.lastname: Palù
authors.forename: Ignazio
authors.initials: I
authors.lastname: Castagliuolo
mesh_terms: D000818:Animals; D001557:Benzenesulfonates / Q000009:adverse effects; D003092:Colitis / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology*; D016264:Dextran Sulfate / Q000009:adverse effects; D004195:Disease Models, Animal; D017615:Enteric Nervous System / Q000187:drug effects / Q000503:physiopathology*; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000378:metabolism / Q000494:pharmacology; D007249:Inflammation / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009457:Neuroglia / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D051195:Toll-Like Receptor 2 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*
chemical_list: D001557:Benzenesulfonates; D051100:Glial Cell Line-Derived Neurotrophic Factor; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; C001073:2,4-dinitrobenzenesulfonic acid; D016264:Dextran Sulfate
keywords: 2,4 dinitrobenzensulfonic acid; DNBS; EGC; ENS; GDNF; GFAP; IBD; Immune Regulation; Innate Immunity; LMMP; Microbe; TLR2; Toll-like receptor 2; Ulcerative Colitis; WT; enteric glial cells; enteric nervous system; glial cell line-derived neurotrophic factor; glial fibrillary acidic protein; inflammatory bowel diseases; longitudinal smooth muscle-myenteric plexus; mRNA; messenger RNA; nNOS; neuronal nitric oxide synthase; rGDNF; recombinant histidine-tagged GDNF; wild type