Flavonoids stimulate Cl conductance of human airway epithelium in vitro and in vivo.
The ability of the flavonoids genistein, apigenin, kaempferol, and quercetin to activate cystic fibrosis transmembrane conductance regulator-mediated Cl currents in human airway epithelium was investigated. We used the patch-clamp technique on single Calu-3 cells, transepithelial measurements in Calu-3 monolayers, and in vivo measurements of nasal potential difference. All flavonoids stimulated Cl currents in transepithelial experiments dose dependently. Half-maximal stimulatory concentrations were kaempferol (5.5 +/- 1.7 microM) </= apigenin (11.2 +/- 2.1 microM) </= genistein (13.6 +/- 3.5 microM) </= quercetin (22.1 +/- 4.5 microM). Stimulation of monolayers with forskolin significantly increased their sensitivity to flavonoids: kaempferol (2.5 +/- 0.7 microM) </= apigenin (3.4 +/- 0.9 microM) </= quercetin (4.1 +/- 0.7 microM) </= genistein (6.9 +/- 2.2 microM). Forskolin pretreatment significantly reduced the Hill coefficient (nH) for all flavonoids. Control monolayers showed nH = 2.00 +/- 0.21 (all flavonoids combined), and forskolin-stimulated monolayers showed nH = 1.07 +/- 0.07, which was not different among the flavonoids. These data imply that the activation kinetics and the binding site(s) for flavonoids were significantly altered by forskolin stimulation. In whole cell patch-clamp experiments, maximal flavonoid-stimulated currents (percentage of forskolin-stimulated currents) were apigenin (429 +/- 86%) >/= kaempferol (318 +/- 45%) >/= genistein (258 +/- 20%) = quercetin (256 +/- 26%). Stimulation of the currents was caused by an increase in channel open probability. No other Cl conductances contributed significantly to the flavonoid-activated Cl currents in Calu-3 cells. In vivo, flavonoids significantly stimulated nasal potential difference by, on average, 27.8% of isoproterenol responses.
Illek
B
B
Research Institute, Children's Hospital Oakland, Oakland, California 94609, USA.
Fischer
H
H
D002460:Cell Line; D020843:Chamomile; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology*; D005419:Flavonoids / Q000494:pharmacology*; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D044949:Kaempferols; D007700:Kinetics; D008168:Lung; D008564:Membrane Potentials / Q000187:drug effects; D008954:Models, Biological; D009822:Oils, Volatile / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010946:Plants, Medicinal; D011794:Quercetin / Q000031:analogs & derivatives / Q000494:pharmacology; D013329:Structure-Activity Relationship
D018118:Chloride Channels; D002712:Chlorides; D005419:Flavonoids; D044949:Kaempferols; D009822:Oils, Volatile; D005576:Colforsin; C006552:kaempferol; D011794:Quercetin; D019833:Genistein