title: BK channel regulation by phosphodiesterase type 1: a novel signaling pathway controlling human detrusor smooth muscle function.
abstract: Large-conductance Ca(2+)-activated K(+) (BK) channels are critical regulators of detrusor smooth muscle (DSM) function. We aimed to investigate phosphodiesterase type 1 (PDE1) interactions with BK channels in human DSM to determine the mechanism by which PDE1 regulates human urinary bladder physiology. A combined electrophysiological, functional, and pharmacological approach was applied using human DSM specimens obtained from open bladder surgeries. The perforated whole cell patch-clamp technique was used to record transient BK currents (TBKCs) and the cell membrane potential in freshly isolated human DSM cells in combination with the selective PDE1 inhibitor, 8-methoxymethyl-3-isobutyl-1-methylxanthine (8MM-IBMX). Isometric DSM tension recordings were used to measure spontaneous phasic and electrical field stimulation-induced contractions in human DSM isolated strips. Selective pharmacological inhibition of PDE1 with 8MM-IBMX (10 μM) increased TBKC activity in human DSM cells, which was abolished by subsequent inhibition of protein kinase A (PKA) with H-89 (10 μM). The stimulatory effect of 8MM-IBMX on TBKCs was reversed upon activation of muscarinic acetylcholine receptors with carbachol (1 μM). 8MM-IBMX (10 μM) hyperpolarized the DSM cell membrane potential, an effect blocked by PKA inhibition. 8MM-IBMX significantly decreased spontaneous phasic and nerve-evoked contractions of human DSM isolated strips. The results reveal a novel mechanism that pharmacological inhibition of PDE1 attenuates human DSM excitability and contractility by activating BK channels via a PKA-dependent mechanism. The data also suggest interactions between PDE1 and muscarinic signaling pathways in human DSM. Inhibition of PDE1 can be a novel therapeutic approach for the treatment of overactive bladder associated with detrusor overactivity.
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina; and.
authors.forename: Wenkuan
authors.initials: W
authors.lastname: Xin
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina; and.
authors.forename: Ning
authors.initials: N
authors.lastname: Li
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina; and.
authors.forename: Vitor S
authors.initials: VS
authors.lastname: Fernandes
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina; and.
authors.forename: Biao
authors.initials: B
authors.lastname: Chen
authors.affiliation: Medical University of South Carolina, Charleston, South Carolina.
authors.forename: Eric S
authors.initials: ES
authors.lastname: Rovner
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina; and Medical University of South Carolina, Charleston, South Carolina petkov@cop.sc.edu.
authors.forename: Georgi V
authors.initials: GV
authors.lastname: Petkov
mesh_terms: D000368:Aged; D002217:Carbachol; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004353:Drug Evaluation, Preclinical; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007546:Isoquinolines; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008875:Middle Aged; D018408:Patch-Clamp Techniques; D043264:Phosphodiesterase I / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides; D053201:Urinary Bladder, Overactive / Q000188:drug therapy / Q000378:metabolism*; D014970:Xanthines / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: C119531:8-methoxymethyl-3-isobutyl-1-methylxanthine; D007546:Isoquinolines; D051036:Large-Conductance Calcium-Activated Potassium Channels; D013449:Sulfonamides; D014970:Xanthines; D002217:Carbachol; D017868:Cyclic AMP-Dependent Protein Kinases; D043264:Phosphodiesterase I; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide
keywords: 8MM-IBMX; carbachol; detrusor smooth muscle; muscarinic receptors; phosphodiesterases