title: Benzimidazolone activators of chloride secretion: potential therapeutics for cystic fibrosis and chronic obstructive pulmonary disease.
abstract: The diseases of cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) are characterized by mucus-congested airways. Agents that stimulate the secretion of Cl- are anticipated to facilitate mucociliary clearance and thus be of benefit in the treatment of CF and COPD. Recently 1-EBIO (1-ethyl-2-benzimidazolinone or 1-ethyl-1,3-dihydro-2H-benzimidazol-2-one) was shown to stimulate chloride secretion albeit at relatively high concentrations (0.6-1 mM). The studies reported here were undertaken to develop a more potent benzimidazolone. Structure activity studies with 30 benzimidazolone derivatives revealed that ethyl and hydrogen groups at the 1 and 3 nitrogen positions, respectively, were critical for the activation of hIK1 K+ channels and that other alkyl groups were not tolerated at these positions without some loss in potency. Substitutions at the 5 and 6 positions improved the potency of 1-EBIO. Compared with 1-EBIO, the most potent of these derivatives, DCEBIO (5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one) was severalfold better in a 86Rb+ uptake assay, 20-fold better in short circuit current measurements on T84 monolayers, and 100-fold better in patch-clamp assays of hIK1 activity. Short circuit current studies revealed DCEBIO stimulates Cl- secretion via the activation of hIK1 K+ channels and the activation of an apical membrane Cl- conductance. The improved potency of DCEBIO strengthens the possibility that compounds in this class may be of therapeutic benefit in the treatment of CF and COPD.
authors.affiliation: Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: S
authors.initials: S
authors.lastname: Singh
authors.forename: C A
authors.initials: CA
authors.lastname: Syme
authors.forename: A K
authors.initials: AK
authors.lastname: Singh
authors.forename: D C
authors.initials: DC
authors.lastname: Devor
authors.forename: R J
authors.initials: RJ
authors.lastname: Bridges
mesh_terms: D000818:Animals; D001562:Benzimidazoles / Q000138:chemical synthesis / Q000494:pharmacology* / Q000627:therapeutic use*; D065101:Chloride Channel Agonists; D018118:Chloride Channels / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D003550:Cystic Fibrosis / Q000188:drug therapy*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000188:drug therapy*; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism; D012414:Rubidium Radioisotopes; D013268:Stimulation, Chemical; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured; D014982:Xenopus laevis
chemical_list: D001562:Benzimidazoles; C505032:CFTR protein, human; D065101:Chloride Channel Agonists; D018118:Chloride Channels; D002712:Chlorides; D015221:Potassium Channels; D012414:Rubidium Radioisotopes; D019005:Cystic Fibrosis Transmembrane Conductance Regulator