Interactions between cholinergic and prostaglandin signaling elements in the urothelium: role for muscarinic type 2 receptors.

OBJECTIVE: To characterize the interactions between the cholinergic and prostaglandin signaling systems within the urothelium-lamina propria of the guinea pig and elucidate the role of muscarinic receptors in these interactions.
METHODS: The urothelium-lamina propria was isolated from guinea pig bladders, cut into strips (5×10 mm), and maintained in vitro. The tissue was either stretched or left unstretched but exposed to 2'(3')-O-(4-benzoylbenzoyl)adenosine-5'-triphosphate tri(triethylammonium) salt, arecaidine, and prostaglandin E2 (PGE2). Acetylcholine and PGE2 release was measured using a GeneBLAzer M3 CHO-K1-bla cell reporter assay and an enzyme immunoassay, respectively. The role of the muscarinic type 2 and 3 (M2 and M3, respectively) receptors and nitric oxide in mediating PGE2 release was determined in the presence of the muscarinic antagonists 11-[(2-[(diethylamino)methyl]-1-piperidinyl)acetyl]-5,11-dihydro-6H-pyrido[2,3b][1,4] benzodiazepin-6-one and darafenicin and a nitric oxide donor (NONOate).
RESULTS: Acetylcholine release was detected in response to stretch and in the unstretched preparations exposed to PGE2 or the adenosine triphosphate analog 2'(3')-O-(4-benzoylbenzoyl)adenosine-5'-triphosphate tri(triethylammonium) salt. The cholinergic agonist arecaidine induced a concentration-dependent production of PGE2 (half-maximal concentration 75 nM). The arecaidine stimulation of PGE2 production was inhibited in a dose-dependent manner by the antagonist AFDX-116 (M2>M3; half-maximal inhibition 110 nM) but not darifenacin (M3>>M2). Finally, in the presence of the nitric oxide donor, NONOate, arecaidine-stimulated PGE2 production was inhibited.
CONCLUSION: These observations demonstrate that complex signal interactions occur within the urothelium involving acetylcholine, adenosine triphosphate, nitric oxide, and PGE2. In addition, the data have demonstrated a role for muscarinic M2 receptors and nitric oxide in the cholinergic regulation of PGE2 production in the bladder wall.