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Mechanical Stimulation-induced Calcium Wave Propagation in Cell Monolayers: The Example of Bovine Corneal Endothelial Cells
Published on: July 16, 2013
Adrenergic regulation of cAMP/protein kinase A pathway in corneal epithelium and endothelium
Matthias Grueb1, Karl Ulrich Bartz-Schmidt, Jens Martin Rohrbach
1University of Tubingen, Department of Ophthalmology, Tubingen, Germany. matthias_grueb@yahoo.de
Purpose:
The G-protein-coupled receptor/cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway is one of the most common and versatile signal pathways in eukaryotic cells. The aim of this study was to characterize subtypes of adrenergic G-protein-coupled receptors and their influence on cAMP concentration and PKA activity in bovine corneal epithelial and endothelial cells.
Procedures:
Adrenergic receptors and PKA were studied using polyclonal antibodies. cAMP concentration was determined with an enzyme immunoassay, and PKA activity was estimated by the kinases consumption of adenosine triphosphate.
Results:
In bovine corneal epithelial and endothelial cells, immunocytochemistry and Western blot were positive for alpha(1)-, alpha(2A)-, beta(1)- and beta(2)-adrenergic receptors. Stimulation of corneal epithelial and endothelial beta-adrenoceptors with isoprenaline led to a dose-dependent increase in cAMP concentration and activation of PKA. Stimulation of corneal alpha(2A)-adrenoceptors with brimonidine resulted in a dose-dependent decrease in cAMP concentration and the inhibition of PKA activity.
Conclusions:
In corneal epithelial and endothelial cells, beta-adrenergic stimulation leads to activation of PKA via stimulation of adenylyl cyclase, and alpha(2A)-adrenoceptor stimulation inhibits PKA activity via inhibition of adenylyl cyclase. Stimulation and inhibition of the corneal cAMP-PKA pathway may play a role in important corneal functions such as wound healing or homeostasis. Long-term therapy with alpha(2A)-agonists or beta-antagonists may influence these functions in a currently unknown way.
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