title: Rapid effects of dexamethasone on intracellular pH and Na+/H+ exchanger activity in human bronchial epithelial cells.
abstract: Glucocorticoids have been shown to produce rapid nongenomic responses in airway epithelia. By using an intracellular pH (pH(i)) spectrofluorescence imaging system and the NH4Cl acid-loading technique, we have shown that the synthetic glucocorticoid,dexamethasone, accelerated intracellular pH recovery after an acid load in a human bronchial epithelial cell line (16HBE14o- cells). Exposure to NH4Cl (20 mm) elicited an intracellular acidification, followed by a pH(i) recovery. Inhibition of the Na+/H+ exchanger decreased the steady-state pH(i) and antagonized the dexamethasone stimulation of pH(i) regulation. The rapid effect of dexamethasone on pH(i) was neither affected by the inhibitor of transcription, cycloheximide, nor by the classical glucocorticoid and mineralocorticoid receptors antagonists, RU486 and spironolactone, respectively. The dexamethasone effect on pH(i) regulation was reduced by inhibitors of adenylate cyclase, cAMP-dependent protein kinase and mitogenactivated protein kinase (ERK1/2). By using a PepTag assay system and Western blotting, we have shown that dexamethasone stimulated cAMP-dependent protein kinase and mitogen-activated protein kinase activities. Taken together our results provide evidence for the rapid stimulation of Na+/H+ exchange activity by glucocorticoids in bronchial epithelial cells via a nongenomic mechanism involving cAMP-dependent protein kinase and mitogen-activated protein kinase ERK1/2 pathways.
authors.affiliation: INSERM U454, Centre Hospitalier Universitaire Arnaud de Villeneuve, 34295 Montpellier, France.
authors.forename: Valia A
authors.initials: VA
authors.lastname: Verrière
authors.forename: Darina
authors.initials: D
authors.lastname: Hynes
authors.forename: Sheila
authors.initials: S
authors.lastname: Faherty
authors.forename: James
authors.initials: J
authors.lastname: Devaney
authors.forename: Jean
authors.initials: J
authors.lastname: Bousquet
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Harvey
authors.forename: Valérie
authors.initials: V
authors.lastname: Urbach
mesh_terms: D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D001980:Bronchi / Q000166:cytology* / Q000473:pathology; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D004847:Epithelial Cells / Q000166:cytology*; D005938:Glucocorticoids / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D020935:MAP Kinase Signaling System; D015735:Mifepristone / Q000494:pharmacology; D008901:Mineralocorticoids / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D037342:Pertussis Toxin / Q000494:pharmacology; D010766:Phosphorylation; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013256:Steroids / Q000378:metabolism; D013997:Time Factors
chemical_list: D000893:Anti-Inflammatory Agents; D005938:Glucocorticoids; D008901:Mineralocorticoids; D017923:Sodium-Hydrogen Exchangers; D013256:Steroids; D015735:Mifepristone; D003907:Dexamethasone; D000242:Cyclic AMP; D037342:Pertussis Toxin; D017868:Cyclic AMP-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D002118:Calcium