Nitric oxide-dependent ethanol stimulation of ciliary motility is linked to cAMP-dependent protein kinase (PKA) activation in bovine bronchial epithelium.
BACKGROUND
The first line of protection in the lung from the outside environment is provided by the mucociliary apparatus, which continually clears the airways of inhaled microorganisms, dust, and debris. Because alcohol is known to impair airway host defenses, we have examined the effects of ethanol on mucociliary function. In earlier studies, we found that ethanol rapidly and transiently stimulates ciliary motility through a nitric oxide-dependent mechanism. Because many agonists stimulate ciliary motility through activation of cyclic nucleotide-dependent protein kinases, we hypothesized that ethanol stimulates ciliary motility by activating protein kinases.


METHODS
Protein kinase activity and ciliary beat frequency (CBF) were assayed in primary cultures of bovine bronchial epithelial cells after exposure to ethanol.


RESULTS
Ethanol markedly activated cyclic adenosine monophosphate (cAMP)-dependent protein kinase [protein kinase A (PKA)] at biologically relevant concentrations (20-100 mM), with activation detectable after 15 min and persisting up to 4 hr. Ethanol's PKA activation was blocked by nitric oxide synthase inhibitors, indicating a nitric oxide-dependent pathway, and was also specifically blocked by PKA inhibitors. Ethanol did not directly activate cyclic guanosine monophosphate (cGMP)-dependent protein kinase [protein kinase G (PKG)] in bovine bronchial epithelial cells, but inhibitors of PKG attenuated PKA activation, suggesting a link between PKA activation and PKG activation during ethanol exposure. CBF increased in parallel to PKA activation, suggesting tight coupling between stimulated CBF and PKA activation.


CONCLUSIONS
We conclude that ethanol stimulates CBF through activating PKA in bovine bronchial epithelial cells and we suggest a cooperative mechanism involving PKA and nitric oxide.
Sisson
J H
JH
Department of Internal Medicine, University of Nebraska Medical Center, Omaha 68198-5300, USA. jsisson@unmc.edu
May
K
K
Wyatt
T A
TA
D000818:Animals; D001980:Bronchi / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002417:Cattle; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D002923:Cilia / Q000187:drug effects / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D000431:Ethanol / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052250:Nitric Oxide Synthase Type III; D019323:omega-N-Methylarginine / Q000494:pharmacology
D002492:Central Nervous System Depressants; D004791:Enzyme Inhibitors; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D000431:Ethanol; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D017868:Cyclic AMP-Dependent Protein Kinases