Na^+/H^+ Exchange Plays a Role in Hypoxia-Reoxygenation induced ICAM-1 expression in CME

Na~+/H~+交换参与了心肌缺血再灌注损伤的机制。虽然心肌细胞一直是本课题广泛研究的对象，但冠脉微血管内皮细胞(CMEC)在心脏再灌注损伤中的作用、Na+/H+交换的激活以及由此产生的细胞内钙超载可能刺激CMEC细胞间黏附分子的合成，从而参与无复流现象。因此，我们研究了Na+/H+交换是否参与细胞间黏附分子-1(ICAM-1)在复氧过程中的表达。从成年大鼠心脏分离的原代培养的CMEC在模拟缺血(pH 6.4低氧灌流)45分钟后，在pH 7.4复氧。在灌流液中加入0.1 mM的Na+/H+交换阻断剂二甲基胺内酯(DMA)。与未处理对照组相比，DMA处理可显著抑制缺氧和复氧过程中[Ca~(2+)]_i的升高(P<0.05)。Northern印迹分析显示复氧3h后ICAM-1m-RNA表达增强，这与免疫细胞化学检测到ICAM-1蛋白表达在复氧后8h达到最高水平有关。DMA可抑制ICAM-1m-RNA和ICAM-1蛋白的表达。结论：Na~+/H~+交换在CMEC复氧时[Ca~(2+)]i超载和ICAM-1表达中起重要作用。

Na^+/H^+ exchange has been implicated in a mechanism for myocardial iscemia-reperfusion injury. Although cardiac myocytes have been a target for extensive resear.ch of this subject, little is known about a role of coronary microvascular endothelial cells (CMEC) in mvocardial reperfusion injury, Activation of Na^+/H^+ exchange and resultant intracellular Ca^<2+> ([Ca^<2+>]i) overload may stimulate intercellular adhesion molecule synthesis in CMEC whitch could paticipate in no reflow phenomenon. We have, therefore, investigated whether Na^+/H^+ exchange is involved in intercellular adhesion molecule-1 (ICAM-1) expression during reoxygenatlon in CMEC.The primary cultures of CMEC Isolated from adult rat hearts were subjected to simulated ischemia (hypoxic perfusion at pH6.4) for 45 minutes followed by reoxygenation at pH7.4. Dimethyl amirolide (DMA), an inhivitor of Na^+/H^+ exchanger, at a concentration of 0.1mM was added to perfusate during hypoxia and reoxygenation. The increase in [Ca^<2+>]i during hypoxia and reoxygenation was inhibited significantly (p<less than or equal>0.05) by the DMA treatment compared with the non-treatment cotrol. Northern blot analysis revealed enhanced expression of ICAM-1 m-RNA after 3 hours of reoxygenation, This was associated with immunocytochemically detected ICAM-1 protein expression which reached a maximum level at 8 hours after reoxygenation. Both ICAM-1 m-RNA and ICAM-1 protein expression were inhibited by DMA treatment. Conclusion : Na^+/H^+ exchange plays an essential role in [Ca^<2+>]i overload and ICAM-1 expression during reoxygenation in CMEC.