title: Levamisole inhibits intestinal Cl- secretion via basolateral K+ channel blockade.
abstract: OBJECTIVE
  Phenylimidazothiazoles have recently been shown to activate wild-type and mutant cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels in transfected cells and were proposed as therapy for cystic fibrosis. The aim of this study was to investigate the effects of phenylimidazothiazoles on regulated transepithelial Cl- transport in intact epithelia.
  
  
  METHODS
  T84 intestinal epithelial cells grown on permeable supports and stripped human colonic mucosal sheets were studied by conventional current-voltage clamping. Selective permeabilization of apical or basolateral membranes with the monovalent ionophore nystatin was used to isolate basolateral K+ and apical Cl- channel activity, respectively. 86Rb+ uptake was assessed for Na/K/2Cl cotransporter and Na+,K(+)-adenosine triphosphatase activity.
  
  
  RESULTS
  In T84 monolayers and human colon, levamisole and its brominated derivative bromotetramisole failed to activate transepithelial secretion. In fact, these compounds dose-dependently inhibited secretory responses to the cyclic adenosine monophosphate agonist forskolin and the Ca2+ agonist carbachol. In permeabilized T84 monolayers, phenylimidazothiazoles weakly activated apical Cl- currents (consistent with their reported action on CFTR) and did not affect bumetanide-sensitive or bumetanide-insensitive 86+Rb+ uptake. Instead, they profoundly inhibited the basolateral Ba(2+)-sensitive and Ba(2+)-insensitive K+ currents.
  
  
  CONCLUSIONS
  Phenylimidazothiazoles block K+ channels required for Cl(-)-secretory responses elicited by diverse pathways in model epithelia and native colon, an effect that outweighs their ability to activate apical Cl- channels.
authors.affiliation: Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: E C
authors.initials: EC
authors.lastname: Mun
authors.forename: J M
authors.initials: JM
authors.lastname: Mayol
authors.forename: M
authors.initials: M
authors.lastname: Riegler
authors.forename: T C
authors.initials: TC
authors.lastname: O'Brien
authors.forename: O C
authors.initials: OC
authors.lastname: Farokhzad
authors.forename: J C
authors.initials: JC
authors.lastname: Song
authors.forename: C
authors.initials: C
authors.lastname: Pothoulakis
authors.forename: B J
authors.initials: BJ
authors.lastname: Hrnjez
authors.forename: J B
authors.initials: JB
authors.lastname: Matthews
mesh_terms: D002118:Calcium / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism* / Q000502:physiology; D005576:Colforsin / Q000494:pharmacology; D003106:Colon / Q000187:drug effects / Q000502:physiology; D004553:Electric Conductivity; D006801:Humans; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007978:Levamisole / Q000494:pharmacology*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D028021:Sodium-Potassium-Chloride Symporters; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013773:Tetramisole / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D002352:Carrier Proteins; D002712:Chlorides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D028021:Sodium-Potassium-Chloride Symporters; D005576:Colforsin; D007978:Levamisole; C006226:4-bromotetramisole; D013773:Tetramisole; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium