Department of Pharmaceutical Sciences, College of Pharmacy, South Dakota State University, Brookings, SD 57007, USA.
Biochem Biophys Res Commun. 2012 Aug 31;425(3):630-5. doi: 10.1016/j.bbrc.2012.07.130. Epub 2012 Jul 27.
Ischemic preconditioning (IPC) is one of the most effective procedures known to protect hearts against ischemia/reperfusion (IR) injury. Tight junction (TJ) barriers occur between coronary endothelial cells. TJs provide barrier function to maintain the homeostasis of the inner environment of tissues. However, the effect of IPC on the structure and function of cardiac TJs remains unknown. We tested the hypothesis that myocardial IR injury ruptures the structure of TJs and impairs endothelial permeability whereas IPC preserves the structural and functional integrity of TJs in the blood-heart barrier. Langendorff hearts from C57BL/6J mice were prepared and perfused with Krebs-Henseleit buffer. Cardiac function, creatine kinase release, and myocardial edema were measured. Cardiac TJ function was evaluated by measuring Evans blue-conjugated albumin (EBA) content in the extravascular compartment of hearts. Expression and translocation of zonula occludens (ZO)-2 in IR and IPC hearts were detected with Western blot. A subset of hearts was processed for the observation of ultra-structure of cardiac TJs with transmission electron microscopy. There were clear TJs between coronary endothelial cells of mouse hearts. IR caused the collapse of TJs whereas IPC sustained the structure of TJs. IR increased extravascular EBA content in the heart and myocardial edema but decreased the expression of ZO-2 in the cytoskeleton. IPC maintained the structure of TJs. Cardiac EBA content and edema were reduced in IPC hearts. IPC enhanced the translocation of ZO-2 from cytosol to cytoskeleton. In conclusion, TJs occur in normal mouse heart. IPC preserves the integrity of TJ structure and function that are vulnerable to IR injury.
缺血预处理（IPC）是保护心脏免受缺血/再灌注（IR）损伤的最有效方法之一。紧密连接（TJ）屏障发生在冠状动脉内皮细胞之间。TJ 提供屏障功能，以维持组织内环境的稳态。然而，IPC 对心脏 TJ 结构和功能的影响尚不清楚。我们假设心肌 IR 损伤会破坏 TJ 的结构并损害内皮通透性，而 IPC 则可以保护血-心屏障中 TJ 的结构和功能完整性。从 C57BL/6J 小鼠中制备 Langendorff 心脏，并使用 Krebs-Henseleit 缓冲液进行灌注。测量心脏功能、肌酸激酶释放和心肌水肿。通过测量心脏血管外腔中 Evans 蓝结合白蛋白（EBA）的含量来评估心脏 TJ 功能。用 Western blot 检测 IR 和 IPC 心脏中 zonula occludens（ZO）-2 的表达和易位。一部分心脏用于透射电子显微镜观察心脏 TJ 的超微结构。在小鼠心脏的冠状动脉内皮细胞之间存在清晰的 TJ。IR 导致 TJ 崩溃，而 IPC 则维持 TJ 的结构。IR 增加了心脏中的血管外 EBA 含量和心肌水肿，但减少了细胞骨架中 ZO-2 的表达。IPC 保持了 TJ 的结构。IPC 心脏中的心脏 EBA 含量和水肿减少，ZO-2 从细胞质易位到细胞骨架增强。总之，正常小鼠心脏存在 TJ。IPC 可维持 TJ 结构和功能的完整性，使其免受 IR 损伤。
