Rapid non-genomic inhibition of ATP-induced Cl- secretion by dexamethasone in human bronchial epithelium.
A non-genomic antisecretory role for dexamethasone at low concentrations (0.1 nM to1 microM) is described in monolayers of human bronchial epithelial cells in primary culture and in a continuous cell line (16HBE14o- cells). Dexamethasone produced a rapid decrease of [Ca(2+)](i) (measured with fura-2 spectrofluorescence) to a new steady-state concentration. After 15 min exposure to dexamethasone (1 nM), [Ca(2+)](i) was reduced by 32 +/- 11 nM (n = 7, P < 0.0001) from a basal value of 213 +/- 36 nM (n = 7). We have shown previously that aldosterone (1 nM) also produces a rapid fall in [Ca(2+)](i); however, after the decrease in [Ca(2+)](i) induced by dexamethasone, subsequent addition of aldosterone did not produced any further lowering of [Ca(2+)](i). The rapid response to dexamethasone was insensitive to pretreatment with cycloheximide and unaffected by the glucocorticoid type II and mineralocorticoid receptor antagonists RU486 and spironolactone, respectively. The rapid [Ca(2+)](i) decrease induced by dexamethasone was inhibited by the Ca(2+)-ATPase pump inhibitor thapsigargin (1 microM), the adenylate cyclase inhibitor MDL hydrochloride (500 microM) and the protein kinase A inhibitor Rp-adenosine 3',5'-cyclic monophosphorothioate (200 microM), but was not affected by the protein kinase C inhibitor, chelerythrine chloride (0.1 microM). Treatment of 16HBE14o- cell monolayers with dexamethasone (1 nM) inhibited the large and transient [Ca(2+)](i) increase induced by apical exposure to ATP (10(-4) M). Dexamethasone (1 nM) also reduced by 30 % the Ca(2+)-dependant Cl(-) secretion induced by apical exposure to ATP (measured as the Cl(-)-sensitive short-circuit current across monolayers mounted in Ussing chambers). Our results demonstrate, for the first time, that dexamethasone at low concentrations inhibits Cl(-) secretion in human bronchial epithelial cells. The rapid inhibition of Cl(-) secretion induced by the synthetic glucocorticoid is associated with a rapid decrease in [Ca(2+)](i) via a non-genomic mechanism that does not involve the classical glucocorticoid or mineralocorticoid receptor. Rather, it is a result of rapid non-genomic stimulation of thapsigargin-sensitive Ca(2+)-ATPase, via adenylate cyclase and protein kinase A signalling.
Urbach
V
V
INSERM U454, CHU A. de Villeneuve, 34295 Montpellier Cedex 05, France. urbach@montp.inserm.fr
Walsh
D E
DE
Mainprice
B
B
Bousquet
J
J
Harvey
B J
BJ
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D001980:Bronchi / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002712:Chlorides / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology*; D004848:Epithelium / Q000378:metabolism; D005938:Glucocorticoids / Q000494:pharmacology*; D006727:Hormone Antagonists / Q000494:pharmacology; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D015735:Mifepristone / Q000494:pharmacology; D000451:Mineralocorticoid Receptor Antagonists / Q000494:pharmacology; D009994:Osmolar Concentration; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D013148:Spironolactone / Q000494:pharmacology; D013997:Time Factors
D002712:Chlorides; D005938:Glucocorticoids; D006727:Hormone Antagonists; D000451:Mineralocorticoid Receptor Antagonists; D011500:Protein Synthesis Inhibitors; D013148:Spironolactone; D015735:Mifepristone; D003907:Dexamethasone; D000255:Adenosine Triphosphate; D003513:Cycloheximide; D002118:Calcium