title: Exogenous serotonin regulates proliferation of interstitial cells of Cajal in mouse jejunum through 5-HT2B receptors.
abstract: OBJECTIVE
  Interstitial cells of Cajal (ICC) are required for normal gastrointestinal motility. Loss of ICC is associated with several motility disorders. The mechanisms modulating ICC survival and proliferation are poorly understood. This study aimed to establish whether 5-hydroxytryptamine (5-HT) plays a role in regulating ICC proliferation.
  
  
  METHODS
  Expression of 5-HT receptor mRNA was investigated in muscle strips, in purified populations of ICC, and in identified single cells. The effect of 5-HT(2B) receptor ligands on ICC numbers was studied in primary cell cultures. Proliferation of ICC was determined by counting Ki67-positive cells in culture.
  
  
  RESULTS
  Of the 5-HT receptors known to be involved in proliferation, 5-HT(2B) receptor mRNA was detected by reverse transcriptase-polymerase chain reaction (RT-PCR) in jejunal muscle, whereas 5-HT(1A), 5-HT(1D), and 5-HT(2C) receptor mRNAs were not. 5-HT(2B) receptor mRNA was found in single ICC and cells purified by flow cytometry. Exogenous 5-HT (1 micromol/L) increased (66% +/- 9%, P < .005) ICC numbers in culture. The 5-HT(2) receptor antagonist, ritanserin, and the 5-HT(2B) receptor antagonist, SB204741, inhibited the effect of 5-HT. The 5-HT(2B) receptor agonist BW 723C86 induced a concentration-dependent increase in ICC number (50% +/- 6% at 50 nM, P < .04) and increased ICC proliferation (25% +/- 3% vs 19 +/- 1% in controls, P < .03).
  
  
  CONCLUSIONS
  These studies establish that 5-HT(2B) receptors are expressed on ICC. Exogenous 5-HT regulates ICC numbers through 5-HT(2B) receptors in part by increasing ICC proliferation. The 5-HT(2B) receptor may serve as a novel pathway to regulate ICC numbers.
authors.affiliation: Enteric Neuroscience Program, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
authors.forename: Mira M
authors.initials: MM
authors.lastname: Wouters
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Gibbons
authors.forename: Jaime L
authors.initials: JL
authors.lastname: Roeder
authors.forename: Marne
authors.initials: M
authors.lastname: Distad
authors.forename: Yijun
authors.initials: Y
authors.lastname: Ou
authors.forename: Peter R
authors.initials: PR
authors.lastname: Strege
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Szurszewski
authors.forename: Gianrico
authors.initials: G
authors.lastname: Farrugia
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D018920:Coculture Techniques; D007211:Indoles / Q000494:pharmacology; D007583:Jejunum / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008815:Mice, Inbred Strains; D032389:Myocytes, Smooth Muscle / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D044403:Receptor, Serotonin, 5-HT2B / Q000235:genetics / Q000378:metabolism*; D016713:Ritanserin / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology*; D058826:Serotonin 5-HT2 Receptor Agonists; D018490:Serotonin Agents / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013876:Thiophenes / Q000494:pharmacology; D014508:Urea / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: C092430:1-(5-(2-thenyloxy)-1H-indol-3-yl)propan-2-amine; D007211:Indoles; C092756:N-(1-methyl-5-indolyl)-N'-(3-methyl-5-isothiazolyl)urea; D012333:RNA, Messenger; D044403:Receptor, Serotonin, 5-HT2B; D058826:Serotonin 5-HT2 Receptor Agonists; D018490:Serotonin Agents; D012702:Serotonin Antagonists; D013876:Thiophenes; D016713:Ritanserin; D012701:Serotonin; D014508:Urea