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 Ca²⁺-dependent K⁺ (BK) channel (Slo 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 μmol/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 β₁-subunit was co-expressed, being concentration-dependent with an EC₅₀ of 28.4 μmol/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 β₁-subunit-dependent mechanism that requires SMC integrity leads to HCTZ-induced BK channel activation.

中文翻译：

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氢氯噻嗪激活人平滑肌BK通道需要细胞完整性和BKβ1亚基的存在。

类噻嗪类利尿剂是治疗动脉高血压的最常用药物，其功效与其慢性血管舒张作用有关。先前的研究表明，大电导电压依赖性和Ca ²⁺依赖性K ⁺（BK）通道（Slo 1，MaxiK通道）的激活是噻嗪诱导的血管舒张作用的原因。但是，缺乏支持这种说法的直接电生理证据。BK通道可以与一个小配件β亚单位（β相关联₁ -β ₄）赋予当前表型特定的生物物理和药理学特性。β1亚基主要在平滑肌细胞（SMC）中表达。在这项研究中，我们研究了氢氯噻嗪（HCTZ）对人脐动脉（HUASMC）和表达BK通道（有和没有β1-亚基）的HEK293T细胞的天然SMC中BK通道活性的影响。使用全细胞配置记录时，HCTZ的浴液应用（10μmol/ L）显着增加了HUASMCs中的BK电流，但不影响HUASMCs中BK通道的单位电导率和打开概率（由内而外配置） ，表明需要细胞完整性的间接机制。在表达BK通道的HEK293T细胞，HCTZ-增强BK通道活性只观察时，β ₁-亚基共表达，浓度依赖性，EC ₅₀为28.4μmol/ L，而膜电位不影响浓度关系。此外，HCTZ不会影响由内而外配置评估的HEK293T电池中的BK通道电流，但会显着增加与电池连接的配置中的打开概率。我们的数据表明，一个β ₁，需要SMC完整性导致HCTZ诱导的BK通道活化亚基依赖性机制。