Abstract

Adenosine triphosphate (ATP)-dependent potassium channels openers (K_ATP) protect skeletal muscle against function impairment through the activation of the mitochondrial K_ATP channels (mitoK_ATP). Previous reports suggest that modulators of the mitochondrial K_ATP channels have additional effects on isolated mitochondria. To determine whether the K_ATP channel opener nicorandil has non-specific effects that explain its protective effect through the mitochondrial function, chicken muscle mitochondria were isolated, and respiration rate was determined pollarographically. The activity of the electron transport chain (ETC) complexes (I–IV) was measured using a spectrophotometric method. Reactive oxygen species (ROS) levels and lipid peroxidation were assessed using flow cytometry and thiobarbituric acid assay, respectively. Both K_ATP channel opener nicorandil and K_ATP channel blocker 5-hydroxydecanoate (5-HD) decreased mitochondrial respiration; nicorandil increased complex III activity and decreased complex IV activity. The effects of nicorandil on complex III were antagonized by 5-HD. Nicorandil increased ROS levels, effect reverted by either 5-HD or the antioxidant N-2-mercaptopropionyl glycine (MPG). None of these drugs affected lipid peroxidation levels. These findings suggest that K_ATP channel opener nicorandil increases mitochondrial ROS production from complex III. This results by partially blocking electron flow in the complex IV, setting electron carriers in a more reduced state, which is favored by the increase in complex III activity by nicorandil. Overall, our study showed that nicorandil like other mitochondrial K_ATP channel openers might not act through mitoK_ATP channel activation.

Graphic Abstract

中文翻译：

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尼可地尔通过增加骨骼肌线粒体中复合物 III 活性和 ROS 的产生来影响线粒体呼吸链功能。

摘要

三磷酸腺苷 (ATP) 依赖性钾通道开放剂 (K _ATP ) 通过激活线粒体 K _ATP通道 (mitoK _ATP )保护骨骼肌免受功能损害。以前的报告表明，线粒体 K _ATP通道的调节剂对分离的线粒体有额外的影响。确定 K _ATP是否 通道开放剂尼可地尔具有非特异性作用，可以通过线粒体功能解释其保护作用，分离鸡肌肉线粒体，并通过波谱测定确定呼吸速率。使用分光光度法测量电子传递链 (ETC) 复合物 (I-IV) 的活性。分别使用流式细胞术和硫代巴比妥酸测定法评估活性氧 (ROS) 水平和脂质过氧化。K _ATP通道开放剂尼可地尔和 K _ATP通道阻滞剂 5-羟基癸酸酯 (5-HD) 减少线粒体呼吸；尼可地尔增加了复合物 III 的活性并降低了复合物 IV 的活性。尼可地尔对复合物III的作用被5-HD拮抗。尼可地尔增加 ROS 水平，5-HD 或抗氧化剂 N-2-巯基丙酰甘氨酸 (MPG) 可逆转该作用。这些药物均不影响脂质过氧化水平。这些发现表明 K _ATP 通道开放剂尼可地尔增加了复合体 III 中线粒体 ROS 的产生。这是通过部分阻断复合物 IV 中的电子流动，使电子载体处于更还原的状态而产生的，这有利于尼可地尔复合物 III 活性的增加。总体而言，我们的研究表明，尼可地尔与其他线粒体 K _ATP通道开放剂可能不会通过 mitoK _ATP通道激活起作用。

图形摘要