Centre de Biomédecine, Hôpital du Sacré-Coeur de Montréal, 5400 Gouin Ouest Blvd., Montréal, H4J 1C5, QC, Canada.
Pflugers Arch. 2010 Aug;460(3):583-92. doi: 10.1007/s00424-010-0849-6. Epub 2010 Jun 1.
Unapposed connexin 43 hemichannels (Cx43Hc) are present on sarcolemma of cardiomyocytes. Whereas Cx43Hc remain closed during physiological conditions, their opening under ischemic stress contributes to irreversible tissue injury and cell death. To date, conventional blockers of connexin channels act unselectively on both gap junction channels and unapposed hemichannels. Here, we test the hypothesis that Gap26, a synthetic structural mimetic peptide deriving from the first extracellular loop of Cx43 and a presumed selective blocker of Cx43Hc, confers resistance to intact rat heart against ischemia injury. Langendorff-perfused intact rat hearts were utilized. Regional ischemia was induced by 40-min occlusion of the left anterior descendent coronary and followed by 180 min of reperfusion. Gap26 was applied either 10 min before or 30 min after the initiation of ischemia. Interestingly, myocardial infarct size was reduced by 48% and 55% in hearts treated with Gap26 before or during ischemia, respectively, compared to untreated hearts. Additionally, myocardial perfusate flow was increased in both groups during reperfusion by 37% and 32%, respectively. Application of Gap26 increased survival of isolated cardiomyocytes after simulated ischemia-reperfusion by nearly twofold compared to untreated cells. On the other hand, superfusion of tsA201 cells transiently expressing Cx43 with Gap26 caused 61% inhibition of Cx43Hc-mediated currents recorded using the patch clamp technique. In summary, we demonstrate for the first time that Cx43 mimetic peptide Gap26 confers protection to intact heart against ischemia-reperfusion injury whether administered before or after the occurrence of ischemia. In addition, we provide unequivocal evidence for the inhibitory effect of Gap26 on genuine Cx43Hc.
无连接缝隙连接蛋白 43 半通道（Cx43Hc）存在于心肌细胞膜上。虽然在生理条件下 Cx43Hc 保持关闭状态，但在缺血应激下其开放会导致不可逆的组织损伤和细胞死亡。迄今为止，传统的缝隙连接通道阻滞剂对缝隙连接通道和无连接的半通道均无选择性。在这里，我们检验了这样一个假设，即 Gap26，一种源自 Cx43 第一细胞外环的合成结构模拟肽，被认为是 Cx43Hc 的选择性阻滞剂，是否能使完整的大鼠心脏对缺血损伤产生抗性。使用 Langendorff 灌注完整的大鼠心脏。通过左前降支冠状动脉 40 分钟闭塞诱导区域性缺血，随后进行 180 分钟再灌注。Gap26 在缺血开始前 10 分钟或开始后 30 分钟应用。有趣的是，与未处理的心脏相比，在缺血前或缺血期间用 Gap26 处理的心脏，心肌梗死面积分别减少了 48%和 55%。此外，在再灌注期间，两组的心肌灌流流量分别增加了 37%和 32%。与未处理的细胞相比，应用 Gap26 后，模拟缺血再灌注的分离心肌细胞的存活率增加了近两倍。另一方面，用 Gap26 超流转染 Cx43 的 tsA201 细胞会导致用膜片钳技术记录的 Cx43Hc 介导的电流抑制 61%。总之，我们首次证明，Cx43 模拟肽 Gap26 无论是在缺血发生前还是发生后给予，都能使完整心脏免受缺血再灌注损伤。此外，我们提供了确凿的证据证明 Gap26 对真正的 Cx43Hc 具有抑制作用。
