Succinate accumulates during myocardial ischemia and is rapidly oxidized during reperfusion, leading to reactive oxygen species (ROS) production through reverse electron transfer (RET) from mitochondrial complex II to complex I, and favoring cell death. Given that connexin 43 (Cx43) modulates mitochondrial ROS production, we investigated whether Cx43 influences RET using inducible knock-out Cx43^{Cre−ER(T)/fl} mice. Oxygen consumption, ROS production, membrane potential and coenzyme Q (CoQ) pool were analyzed in subsarcolemmal (SSM, expressing Cx43) and interfibrillar (IFM) cardiac mitochondria isolated from wild-type Cx43^fl/fl mice and Cx43^{Cre−ER(T)/fl} knock-out animals treated with 4-hydroxytamoxifen (4OHT). In addition, infarct size was assessed in isolated hearts from these animals submitted to ischemia–reperfusion (IR), and treated or not with malonate, a complex II inhibitor attenuating RET. Succinate-dependent ROS production and RET were significantly lower in SSM, but not IFM, from Cx43-deficient animals. Mitochondrial membrane potential, a RET driver, was similar between groups, whereas CoQ pool (2.165 ± 0.338 vs. 4.18 ± 0.55 nmol/mg protein, p < 0.05) and its reduction state were significantly lower in Cx43-deficient animals. Isolated hearts from Cx43^{Cre−ER(T)/fl} mice treated with 4OHT had a smaller infarct size after IR compared to Cx43^fl/fl, despite similar concentration of succinate at the end of ischemia, and no additional protection by malonate. Cx43 deficiency attenuates ROS production by RET in SSM, but not IFM, and was associated with a decrease in CoQ levels and a change in its redox state. These results may partially explain the reduced infarct size observed in these animals and their lack of protection by malonate.

琥珀酸在心肌缺血期间积累，并在再灌注过程中迅速氧化，导致通过反向电子转移 （RET） 从线粒体复合物 II 到复合物 I 产生活性氧 （ROS），并有利于细胞死亡。鉴于连接蛋白 43 （Cx43） 调节线粒体 ROS 的产生，我们使用诱导型敲除 Cx43^{Cre-ER（T）/fl} 小鼠研究了 Cx43 是否影响 RET。分析野生型 Cx43 fl/fl 小鼠和用 4-羟基他莫昔芬 （4OHT） 处理的野生型 Cx43^fl/fl 小鼠和 Cx43^{Cre-ER（T）/fl} 敲除动物的肌膜下 （SSM，表达 Cx43） 和纤维间 （IFM） 心脏线粒体的耗氧量、ROS 产生、膜电位和辅酶 Q （CoQ） 库。此外，在接受缺血再灌注 （IR） 治疗的这些动物的离体心脏中评估了梗死面积，并用丙二酸盐（一种减弱 RET 的复合物 II 抑制剂）治疗或不治疗。来自 Cx43 缺陷动物的琥珀酸盐依赖性 ROS 产生和 RET 在 SSM 中显着降低，但在 IFM 中未降低。线粒体膜电位（一种 RET 驱动因素）在各组之间相似，而辅酶 Q 库 （2.165 ± 0.338 vs. 4.18 ± 0.55 nmol/mg 蛋白，p < 0.05）及其还原状态在 Cx43 缺陷动物中显着降低。与 Cx43^fl/fl 相比，用 4OHT 处理的 Cx43^{Cre-ER（T）/fl} 小鼠的离体心脏在 IR 后梗死面积更小，尽管缺血结束时琥珀酸盐浓度相似，并且丙二酸盐没有额外的保护。Cx43 缺陷减弱了 SSM 中 RET 产生的 ROS，但不会减弱 IFM，并且与 CoQ 水平的降低和氧化还原状态的变化有关。 这些结果可能部分解释了在这些动物中观察到的梗塞面积减小以及它们缺乏丙二酸盐的保护。