Activation of human smooth muscle BK channels by hydrochlorothiazide requires cell integrity and the presence of BK β1 subunit  

作　　者：Pedro MARTIN Melisa MONCADA Guruprasad KUNTAMALLAPPANAVAR Alex M DOPICO Veronica MILESI 

机构地区：[1]IIFP, UNLP, CONICET - Instituto de estudios Inmunol6gicos y Fisiopatoldgicos, Universidad Nacional de La Plata, Consejo Nacional de Investigaciones Cientfficas y Tecnol6gicas, La Plata, Argentina. 47y 115 S/N, La Plata (1900), Buenos Aires, Argentina [2]Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, 71 South Manassas St, Memphis, TN, 38103, USA

出　　处：《Acta Pharmacologica Sinica》2018年第3期371-381,共11页中国药理学报（英文版）

摘　　要：Thiazide-like diuretics are the most commonly used drugs to treat arterial hypertension, with their efficacy being linked to their chronic vasodilatory effect. Previous studies suggest that activation of the large conductance voltage- and Ca^2＋-dependent K^＋ （BK） channel （Sic 1, MaxiK channel） is responsible for the thiazide-induced vasodilatory effect. But the direct electrophysiological evidence supporting this claim is lacking. BK channels can be associated with one small accessory β-subunit （β1-β4） that confers specific biophysical and pharmacological characteristics to the current phenotype. The β1-subunit is primarily expressed in smooth muscle cells （SMCs）. In this study we investigated the effect of hydrochlorothiazide （HCTZ） on BK channel activity in native SMCs from human umbilical artery （HUASMCs） and HEK293T cells expressing the BK channel （with and without the β1-subunit）. Bath application of HCTZ （10 pmol/L） significantly augmented the BK current in HUASMCs when recorded using the whole-cell configurations, but it did not affect the unitary conductance and open probability of the BK channel in HUASMCs evaluated in the inside-out configuration, suggesting an indirect mechanism requiring cell integrity. In HEK293T cells expressing BK channels, HCTZ-augmented BK channel activity was only observed when the 131-subunit was co-expressed, being concentration-dependent with an ECso of 28.4 pmol/L, whereas membrane potential did not influence the concentration relationship. Moreover, HCTZ did not affect the BK channel current in HEK293T cells evaluated in the inside-out configuration, but significantly increases the open probability in the cell-attached configuration. Our data demonstrate that a {31-subunit-dependent mechanism that requires SMC integrity leads to HCTZ-induced BK channel activation.Thiazide-like diuretics are the most commonly used drugs to treat arterial hypertension, with their efficacy being linked to their chronic vasodilatory effect. Previous studies suggest that activation of the large conductance voltage- and Ca^2＋-dependent K^＋ （BK） channel （Sic 1, MaxiK channel） is responsible for the thiazide-induced vasodilatory effect. But the direct electrophysiological evidence supporting this claim is lacking. BK channels can be associated with one small accessory β-subunit （β1-β4） that confers specific biophysical and pharmacological characteristics to the current phenotype. The β1-subunit is primarily expressed in smooth muscle cells （SMCs）. In this study we investigated the effect of hydrochlorothiazide （HCTZ） on BK channel activity in native SMCs from human umbilical artery （HUASMCs） and HEK293T cells expressing the BK channel （with and without the β1-subunit）. Bath application of HCTZ （10 pmol/L） significantly augmented the BK current in HUASMCs when recorded using the whole-cell configurations, but it did not affect the unitary conductance and open probability of the BK channel in HUASMCs evaluated in the inside-out configuration, suggesting an indirect mechanism requiring cell integrity. In HEK293T cells expressing BK channels, HCTZ-augmented BK channel activity was only observed when the 131-subunit was co-expressed, being concentration-dependent with an ECso of 28.4 pmol/L, whereas membrane potential did not influence the concentration relationship. Moreover, HCTZ did not affect the BK channel current in HEK293T cells evaluated in the inside-out configuration, but significantly increases the open probability in the cell-attached configuration. Our data demonstrate that a {31-subunit-dependent mechanism that requires SMC integrity leads to HCTZ-induced BK channel activation.

关 键 词：THIAZIDE HYDROCHLOROTHIAZIDE BK channel Slol β1-subunit vascular smooth muscle cells human umbilical artery patchclamp electrophysiology 

分 类 号：TP312AD[自动化与计算机技术—计算机软件与理论] X591[自动化与计算机技术—计算机科学与技术]