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Abstract #8844 Published in IGR 5-1
Bradykinin enhancement of PGE2 signalling in bovine trabecular meshwork cells
Webb JG; Shearer TW; Yates PW; Mukhin YV; Crosson CEExperimental Eye Research 2003; 76: 283-289
Kinins and prostaglandins activate signalling pathways in cells of the trabecular meshwork and have opposing effects on outflow resistance to aqueous humor. Consequently, interactions between these pathways may be important in the regulation of intraocular pressure. In the present study, the influence of bradykinin on PGE2 signalling was examined in primary cultures of bovine trabecular meshwork cells. Incubation of cells with bradykinin produced a concentration-dependent (EC50 = 3.6 ± 0.7 n) elevation of intracellular free Ca2+. At a maximal concentration of 100 n, the increase in Ca2+ was rapid, peaking in 30 seconds, and then slowly returned to baseline. This effect was completely inhibited in cells pretreated with the selective B2 kinin receptor antagonist, Hoe-140. Treatment of trabecular meshwork cells with PGE2, in comparison, had no effect on cellular Ca2+ but produced a concentration-dependent increase in adenosine 3', 5'-cyclic monophosphate (cAMP) formation. Bradykinin had no effect on basal cAMP. However, incubation of cells with PGE2 in combination with bradykinin resulted in a three- to five-fold enhancement of PGE2-stimulated cAMP production. Bradykinin enhancement of cAMP stimulation was concentration-dependent with an EC50 of 3.6 ± 1.8 n. Treatment of cells with bradykinin increased the response maximum for PGE2 signalling, while the EC50 for PGE2 was not changed. This action of bradykinin was again blocked in cells pretreated with Hoe-140. Bradykinin also produced a two- to three-fold increase in isoproterenol and cholera toxin-stimulated cAMP accumulation. However, when adenylyl cyclase was stimulated directly with forskolin, bradykinin failed to alter cAMP production. These results indicate that bradykinin activates B2 kinin receptors in trabecular meshwork cells to amplify PGE2-stimulated cAMP formation by facilitating the interaction between activated Gs and the catalytic unit of adenylyl cyclase.
Dr. J.G. Webb, Department of Cell and Molecular Pharmacology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA. webbj@musc.edu
Classification:
2.5 Meshwork (Part of: 2 Anatomical structures in glaucoma)
3 Laboratory methods
