School of Life Sciences, Center for AI-applied High Efficiency Drug Discovery and Integrated Institute of Biomedical Research (N.L., C.-S.P.) and Department of Chemistry (H.S.P., S.H.P., J.H.A.), Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea; Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, South Korea (B.H.L., K.-S.L., J.S., S.W.L.); and Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, South Korea (T.M.K.).
School of Life Sciences, Center for AI-applied High Efficiency Drug Discovery and Integrated Institute of Biomedical Research (N.L., C.-S.P.) and Department of Chemistry (H.S.P., S.H.P., J.H.A.), Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea; Department of Urology, Samsung Medical Center, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Seoul, South Korea (B.H.L., K.-S.L., J.S., S.W.L.); and Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, South Korea (T.M.K.)
Mol Pharmacol. 2021 Feb;99(2):114-124. doi: 10.1124/molpharm.120.000106. Epub 2020 Dec 2.
The large-conductance calcium-activated potassium channel (BK channel) is expressed on various tissues and is involved in smooth muscle relaxation. The channel is highly expressed on urinary bladder smooth muscle cells and regulates the repolarization phase of the spontaneous action potentials that control muscle contraction. To discover novel chemical activators of the BK channel, we screened a chemical library containing 8364 chemical compounds using a cell-based fluorescence assay. A chemical compound containing an isoxazolyl benzene skeleton (compound 1) was identified as a potent activator of the BK channel and was structurally optimized through a structure-activity relationship study to obtain 4-(4-(4-chlorophenyl)-3-(trifluoromethyl)isoxazol-5-yl)benzene-1,3-diol (CTIBD). When CTIBD was applied to the treated extracellular side of the channel, the conductance-voltage relationship of the channel shifted toward a negative value, and the maximum conductance increased in a concentration-dependent manner. CTIBD altered the gating kinetics of the channel by dramatically slowing channel closing without effecting channel opening. The effects of CTIBD on bladder muscle relaxation and micturition function were tested in rat tissue and in vivo. CTIBD concentration-dependently reduced acetylcholine-induced contraction of urinary bladder smooth muscle strips. In an acetic acid-induced overactive bladder (OAB) model, intraperitoneal injection of 20 mg/kg CTIBD effectively restored frequent voiding contraction and lowered voiding volume without affecting other bladder function parameters. Thus, our results indicate that CTIBD and its derivatives are novel chemical activators of the bladder BK channel and potential candidates for OAB therapeutics. SIGNIFICANCE STATEMENT: The novel BK channel activator CTIBD was identified and characterized in this study. CTIBD directly activates the BK channel and relaxes urinary bladder smooth muscle of rat, so CTIBD can be a potential candidate for overactive bladder therapeutics.
大电导钙激活钾通道（BK 通道）在各种组织中表达，并参与平滑肌松弛。该通道在膀胱平滑肌细胞上高度表达，调节控制肌肉收缩的自发性动作电位的复极化阶段。为了发现 BK 通道的新型化学激活剂，我们使用基于细胞的荧光测定法筛选了包含 8364 种化合物的化学文库。一种含有异恶唑基苯骨架的化合物（化合物 1）被鉴定为 BK 通道的有效激活剂，并通过结构活性关系研究进行了结构优化，得到了 4-(4-(4-氯苯基)-3-(三氟甲基)异恶唑-5-基)苯-1,3-二醇（CTIBD）。当 CTIBD 应用于通道的处理细胞外侧时，通道的电导-电压关系向负值移动，并且最大电导以浓度依赖的方式增加。CTIBD 通过显著减缓通道关闭而不影响通道打开来改变通道的门控动力学。在大鼠组织和体内测试了 CTIBD 对膀胱肌肉松弛和排尿功能的影响。CTIBD 浓度依赖性地减少乙酰胆碱诱导的膀胱平滑肌条的收缩。在乙酸诱导的过度活动膀胱（OAB）模型中，腹腔注射 20mg/kg CTIBD 有效恢复频繁的排尿收缩并降低排尿量，而不影响其他膀胱功能参数。因此，我们的结果表明，CTIBD 及其衍生物是膀胱 BK 通道的新型化学激活剂，是 OAB 治疗的潜在候选药物。
