Cardiac stress-responsive mechanism and its theraprutic application

在对缺血应激的反应中，氧自由基被发现是一个关键的介质，随后诱导了腺苷和锰-超氧化物歧化酶等抗氧化效应物质，这一过程应该解释缺血预适应是如何有益于对缺血应激的保护的。本研究旨在探讨外源性应激对心脏的保护作用。(1)心肌细胞应激抵抗的机制。以大鼠心肌细胞、血管内皮细胞和血管内皮细胞为细胞模型，分别给予缺血再灌注、热休克和牵张应激处理。治疗结束后，通过检测其蛋白表达和活性来检测效应分子ECTO-5‘-核酸酶和锰-超氧化物歧化酶。这些分子的蛋白质和活性都增加了。当这些分子中的每一个过表达时，过表达分子的细胞对不同的应激反应表现出抵抗。(2)细胞内信号转导通路对应激反应的响应。氧自由基被认为是应激反应的主要机制，用荧光分析系统测量，发现在不同类型的应激作用后，胞浆中的氧自由基增加。通过对细胞内信号分子PK-C、MAPK、JNK、P38和S6激酶的生化分析，我们发现JNK、P38和S6激酶在应激反应信号的诱导中起重要作用。总之，我们确定了参与应激反应的细胞内信号转导途径。P38和S6激酶被认为是这一过程中的关键调节因子。

In response to ischemic stress, oxygen radical has been found to be a key mediator, which subsequently induces anti-oxidant effectors such as adenosine, as well as Mn-SOD.This process should explain how ischemic preconditioning is beneficial for the protection against ischemic stress. We aimed to determine how the exogenous stress induces the protective effects in the heart.(1) Mechanism of stress resistance induced in the cardiac myocytes.We used rat cardiac myocytes, endothelial cells and smooth muscle cells as cell model, and treated them with ischemia-reperfusion, heat schock and stretch stress. After treatment, we examined effector molecule such as ecto-5'-nucleatidase and Mn-SOD by measuring their protein expression and activities. Both protein and activities of these molecules were increased. When cardiac cells were overexpressed with each of these molecules, cells over-expressing molecule showed resistance against various stresses.(2) Intracellular signaling pathways in the cardiac cells in response to stresses.Oxygen radicals, proposed to be a major mechanism in stress-response, was measured by using fluorescence assay system, and found to be increased in the cytosol after various types of stresses. By the biochemical analysis of intracellular signal molecules, PK-C, MAPK, JNK, P38, and S6 kinase, we found that JNK, P38, and S6 kinase are important for the induction of stress-response signaling. Thus, the final effector such as Mn-SOD should be increased by these molecules.In conclusion, we determined the intracellular signaling pathway involved in the stress-response. P38 and S6 kinase were identified to be key mediators in this process.