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.

琥珀酸盐在心肌缺血期间积聚，并在再灌注期间迅速氧化，通过从线粒体复合物 II 到复合物 I 的反向电子转移 (RET) 导致活性氧 (ROS) 产生，并有利于细胞死亡。鉴于连接蛋白 43 (Cx43) 调节线粒体 ROS 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。对从野生型 Cx43 ^fl/fl小鼠和 Cx43 ^Cre−ER(T)分离的肌膜下（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)池进行分析^/fl基因敲除动物用 4-羟基他莫昔芬 (4OHT) 治疗。此外，还评估了这些动物的离体心脏的梗塞面积，这些心脏进行了缺血再灌注（IR），并用丙二酸（一种减弱 RET 的复合物 II 抑制剂）进行了治疗或未治疗。在 Cx43 缺陷动物的 SSM 中，琥珀酸依赖性 ROS 产生和 RET 显着降低，但 IFM 中则不然。线粒体膜电位（RET 驱动因素）在各组之间相似，而 CoQ 池（2.165 ± 0.338 与 4.18 ± 0.55 nmol/mg 蛋白质，p  < 0.05）及其还原状态在 Cx43 缺陷动物中显着较低。与 Cx43 ^fl/fl相比，用 4OHT 处理的Cx43 ^{Cre−ER(T)/fl}小鼠离体心脏在 IR 后梗塞面积更小，尽管缺血结束时琥珀酸浓度相似，且丙二酸没有额外保护。 Cx43 缺陷会减弱 SSM 中 RET 产生的 ROS，但不会减弱 IFM，并且与 CoQ 水平降低和氧化还原状态变化相关。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的保护。