TY - JOUR

T1 - NS19504

T2 - a novel BK channel activator with relaxing effect on bladder smooth muscle spontaneous phasic contractions

AU - Nausch, Bernhard

AU - Rode, Frederik

AU - Jørgensen, Susanne

AU - Nardi, Antonio

AU - Korsgaard, Mads P G

AU - Hougaard, Charlotte

AU - Bonev, Adrian D

AU - Brown, William D

AU - Dyhring, Tino

AU - Strøbæk, Dorte

AU - Olesen, Søren-Peter

AU - Christophersen, Palle

AU - Grunnet, Morten

AU - Nelson, Mark T

AU - Rønn, Lars C B

N1 - Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics.

PY - 2014/9

Y1 - 2014/9

N2 - Large-conductance Ca(2+)-activated K(+) channels (BK, KCa1.1, MaxiK) are important regulators of urinary bladder function and may be an attractive therapeutic target in bladder disorders. In this study, we established a high-throughput fluorometric imaging plate reader-based screening assay for BK channel activators and identified a small-molecule positive modulator, NS19504 (5-[(4-bromophenyl)methyl]-1,3-thiazol-2-amine), which activated the BK channel with an EC50 value of 11.0 ± 1.4 µM. Hit validation was performed using high-throughput electrophysiology (QPatch), and further characterization was achieved in manual whole-cell and inside-out patch-clamp studies in human embryonic kidney 293 cells expressing hBK channels: NS19504 caused distinct activation from a concentration of 0.3 and 10 µM NS19504 left-shifted the voltage activation curve by 60 mV. Furthermore, whole-cell recording showed that NS19504 activated BK channels in native smooth muscle cells from guinea pig urinary bladder. In guinea pig urinary bladder strips, NS19504 (1 µM) reduced spontaneous phasic contractions, an effect that was significantly inhibited by the specific BK channel blocker iberiotoxin. In contrast, NS19504 (1 µM) only modestly inhibited nerve-evoked contractions and had no effect on contractions induced by a high K(+) concentration consistent with a K(+) channel-mediated action. Collectively, these results show that NS19504 is a positive modulator of BK channels and provide support for the role of BK channels in urinary bladder function. The pharmacologic profile of NS19504 indicates that this compound may have the potential to reduce nonvoiding contractions associated with spontaneous bladder overactivity while having a minimal effect on normal voiding.

AB - Large-conductance Ca(2+)-activated K(+) channels (BK, KCa1.1, MaxiK) are important regulators of urinary bladder function and may be an attractive therapeutic target in bladder disorders. In this study, we established a high-throughput fluorometric imaging plate reader-based screening assay for BK channel activators and identified a small-molecule positive modulator, NS19504 (5-[(4-bromophenyl)methyl]-1,3-thiazol-2-amine), which activated the BK channel with an EC50 value of 11.0 ± 1.4 µM. Hit validation was performed using high-throughput electrophysiology (QPatch), and further characterization was achieved in manual whole-cell and inside-out patch-clamp studies in human embryonic kidney 293 cells expressing hBK channels: NS19504 caused distinct activation from a concentration of 0.3 and 10 µM NS19504 left-shifted the voltage activation curve by 60 mV. Furthermore, whole-cell recording showed that NS19504 activated BK channels in native smooth muscle cells from guinea pig urinary bladder. In guinea pig urinary bladder strips, NS19504 (1 µM) reduced spontaneous phasic contractions, an effect that was significantly inhibited by the specific BK channel blocker iberiotoxin. In contrast, NS19504 (1 µM) only modestly inhibited nerve-evoked contractions and had no effect on contractions induced by a high K(+) concentration consistent with a K(+) channel-mediated action. Collectively, these results show that NS19504 is a positive modulator of BK channels and provide support for the role of BK channels in urinary bladder function. The pharmacologic profile of NS19504 indicates that this compound may have the potential to reduce nonvoiding contractions associated with spontaneous bladder overactivity while having a minimal effect on normal voiding.

KW - Animals

KW - Calcium Channel Agonists

KW - Female

KW - Guinea Pigs

KW - HEK293 Cells

KW - Humans

KW - Large-Conductance Calcium-Activated Potassium Channels

KW - Male

KW - Muscle Contraction

KW - Muscle Relaxation

KW - Organ Culture Techniques

KW - Urinary Bladder

U2 - 10.1124/jpet.113.212662

DO - 10.1124/jpet.113.212662

M3 - Journal article

C2 - 24951278

VL - 350

SP - 520

EP - 530

JO - Journal of Pharmacology and Experimental Therapeutics

JF - Journal of Pharmacology and Experimental Therapeutics

SN - 0022-3565

IS - 3

ER -