Molecular expression and pharmacological evidence for a functional role of kv7 channel subtypes in Guinea pig urinary bladder smooth muscle.
Voltage-gated Kv7 (KCNQ) channels are emerging as essential regulators of smooth muscle excitability and contractility. However, their physiological role in detrusor smooth muscle (DSM) remains to be elucidated. Here, we explored the molecular expression and function of Kv7 channel subtypes in guinea pig DSM by RT-PCR, qRT-PCR, immunohistochemistry, electrophysiology, and isometric tension recordings. In whole DSM tissue, mRNAs for all Kv7 channel subtypes were detected in a rank order: Kv7.1~Kv7.2Kv7.3~Kv7.5Kv7.4. In contrast, freshly-isolated DSM cells showed mRNA expression of: Kv7.1~Kv7.2Kv7.5Kv7.3~Kv7.4. Immunohistochemical confocal microscopy analyses of DSM, conducted by using co-labeling of Kv7 channel subtype-specific antibodies and α-smooth muscle actin, detected protein expression for all Kv7 channel subtypes, except for the Kv7.4, in DSM cells. L-364373 (R-L3), a Kv7.1 channel activator, and retigabine, a Kv7.2-7.5 channel activator, inhibited spontaneous phasic contractions and the 10-Hz electrical field stimulation (EFS)-induced contractions of DSM isolated strips. Linopiridine and XE991, two pan-Kv7 (effective at Kv7.1-Kv7.5 subtypes) channel inhibitors, had opposite effects increasing DSM spontaneous phasic and 10 Hz EFS-induced contractions. EFS-induced DSM contractions generated by a wide range of stimulation frequencies were decreased by L-364373 (10 µM) or retigabine (10 µM), and increased by XE991 (10 µM). Retigabine (10 µM) induced hyperpolarization and inhibited spontaneous action potentials in freshly-isolated DSM cells. In summary, Kv7 channel subtypes are expressed at mRNA and protein levels in guinea pig DSM cells. Their pharmacological modulation can control DSM contractility and excitability; therefore, Kv7 channel subtypes provide potential novel therapeutic targets for urinary bladder dysfunction.
Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina, United States of America.
Serge A Y
SA
Afeli
John
J
Malysz
Georgi V
GV
Petkov
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D001569:Benzodiazepines / Q000494:pharmacology; D015153:Blotting, Western; D002219:Carbamates / Q000494:pharmacology; D002478:Cells, Cultured; D004558:Electric Stimulation; D006168:Guinea Pigs; D007124:Immunoenzyme Techniques; D051656:KCNQ Potassium Channels / Q000145:classification / Q000378:metabolism*; D008297:Male; D049990:Membrane Transport Modulators / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010655:Phenylenediamines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D001743:Urinary Bladder / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*
C112297:10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone; D000873:Anthracenes; D002219:Carbamates; D051656:KCNQ Potassium Channels; C113498:L 364373; D049990:Membrane Transport Modulators; D010655:Phenylenediamines; D012333:RNA, Messenger; D001569:Benzodiazepines; C101866:ezogabine; D000109:Acetylcholine