The colon-selective spasmolytic otilonium bromide inhibits muscarinic M(3) receptor-coupled calcium signals in isolated human colonic crypts

Susanne Lindqvist, James Hernon, Paul Sharp, Neil Johns, Sarah Addison, Mark Watson, Richard Tighe, Shaun Greer, Jean Mackay, Michael Rhodes, Michael Lewis, William Stebbings, Chris Speakman, Stefano Evangelista, Ian Johnson, Mark Williams

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33 Citations (Scopus)

Abstract

1. Otilonium bromide (OB) is a smooth muscle relaxant used in the treatment of irritable bowel syndrome. Otilonium bromide has been shown to interfere with the mobilization of calcium in intestinal smooth muscle, but the effects on other intestinal tissues have not been investigated. We identified the muscarinic receptor subtype coupled to calcium signals in colonic crypt derived from the human colonic epithelium and evaluated the inhibitory effects of OB. 2. Calcium signals were monitored by fluorescence imaging of isolated human colonic crypts and Chinese hamster ovary cells stably expressing the cloned human muscarinic M(3) receptor subtype (CHO-M(3)). Colonic crypt receptor expression was investigated by pharmacological and immunohistochemical techniques. 3. The secretagogue acetylcholine (ACh) stimulated calcium mobilization from intracellular calcium stores at the base of human colonic crypts with an EC(50) of 14 micro M. The muscarinic receptor antagonists 4-DAMP, AF-DX 384, pirenzepine and methroctamine inhibited the ACh-induced calcium signal with the following respective IC(50) (pK(b)) values: 0.78 nM (9.1), 69 nM (7.2), 128 nM (7.1), and 2510 nM (5.8). 4. Immunohistochemical analyses of muscarinic receptor expression demonstrated the presence of M(3) receptor subtype expression at the crypt-base. 5. Otilonium bromide inhibited the generation of ACh-induced calcium signals in a dose dependent manner (IC(50)=880 nM). 6. In CHO-M(3) cells, OB inhibited calcium signals induced by ACh, but not ATP. In addition, OB did not inhibit histamine-induced colonic crypt calcium signals. 7. The present studies have demonstrated that OB inhibited M(3) receptor-coupled calcium signals in human colonic crypts and CHO-M(3) cells, but not those induced by stimulation of other endogenous receptor types. We propose that the M(3) receptor-coupled calcium signalling pathway is directly targeted by OB at the level of the colonic epithelium, suggestive of an anti-secretory action in IBS patients suffering with diarrhoea.
Original languageEnglish
Pages (from-to)1134-1142
Number of pages9
JournalBritish Journal of Pharmacology
Volume137
Issue number7
DOIs
Publication statusPublished - Dec 2002

Keywords

  • Acetylcholine
  • Animals
  • Atropine
  • CHO Cells
  • Calcium
  • Calcium Signaling
  • Colon
  • Cricetinae
  • Dose-Response Relationship, Drug
  • Humans
  • Muscarinic Antagonists
  • Parasympatholytics
  • Piperidines
  • Pirenzepine
  • Quaternary Ammonium Compounds
  • Receptor, Muscarinic M3
  • Receptors, Muscarinic
  • Time Factors
  • Vasodilator Agents

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