The large conductance Ca²⁺-activated K⁺ (BK) channels, composed of the pore-forming α subunits (BK-α, encoded by KCNMA1 gene) and the regulatory β1 subunits (BK-β1, encoded by KCNMB1 gene), play a unique role in the regulation of coronary vascular tone and myocardial perfusion by linking intracellular Ca²⁺ homeostasis with excitation-contraction coupling in coronary arterial smooth muscle cells (SMCs). The nuclear factor erythroid 2-related factor 2 (Nrf2) belongs to a member of basic leucine zipper transcription factor family that regulates the expression of antioxidant and detoxification enzymes by binding to the antioxidant response elements (AREs) of these target genes. We have previously reported that vascular BK-β1 protein expression was tightly regulated by Nrf2. However, the molecular mechanism underlying the regulation of BK channel expression by Nrf2, particularly at transcription level, is unknown. In this study, we hypothesized that KCNMA1 and KCNMB1 are the target genes of Nrf2 transcriptional regulation. We found that BK channel protein expression and current density were diminished in freshly isolated coronary arterial SMCs of Nrf2 knockout (KO) mice. However, BK-α mRNA expression was reduced, but not that of BK-β1 mRNA expression, in the arteries of Nrf2 KO mice. Promoter-Nrf2 luciferase reporter assay confirmed that Nrf2 binds to the ARE of KCNMA1 promoter, but not that of KCNMB1. Adenoviral expression and pharmacological activation of Nrf2 increased BK-α and BK-β1 protein levels and enhanced BK channel activity in coronary arterial SMCs. Hence, our results indicate that Nrf2 is a key determinant of BK channel expression and function in vascular SMCs. Nrf2 facilitates BK-α expression through a direct increase in gene transcription, whereas that on BK-β1 is through a different mechanism.

大电导的Ca ²⁺激活的K ⁺（BK）通道发挥作用，该通道由成孔的α亚基（BK-α，由KCNMA1基因编码）和调节性β1亚基（BK-β1，由KCNMB1基因编码）发挥作用通过连接细胞内Ca ²⁺在调节冠状动脉血管张力和心肌灌注中发挥独特作用冠状动脉平滑肌细胞（SMCs）中具有兴奋-收缩偶联的体内稳态。核因子类胡萝卜素2相关因子2（Nrf2）属于基本亮氨酸拉链转录因子家族的成员，该家族通过与这些靶基因的抗氧化剂响应元件（ARE）结合来调节抗氧化剂和解毒酶的表达。我们先前曾报道过，血管BK-β1蛋白的表达受到Nrf2的严格调控。但是，尚不清楚由Nrf2调节BK通道表达的分子机制，特别是在转录水平。在这项研究中，我们假设KCNMA1和KCNMB1是Nrf2转录调控的目标基因。我们发现在Nrf2基因敲除（KO）小鼠的新鲜分离的冠状动脉SMC中BK通道蛋白表达和电流密度降低。但是，在Nrf2 KO小鼠的动脉中，BK-αmRNA表达降低，但BK-β1mRNA表达却没有降低。启动子-Nrf2荧光素酶报告基因测定证实Nrf2结合KCNMA1启动子的ARE ，但不结合KCNMB1。Nrf2的腺病毒表达和药理激活增加冠状动脉SMC中的BK-α和BK-β1蛋白水平并增强BK通道活性。因此，我们的结果表明，Nrf2是血管平滑肌细胞中BK通道表达和功能的关键决定因素。Nrf2通过直接增加基因转录来促进BK-α表达，而BK-β1上的表达则是通过不同的机制。