Cardiac stress-responsive mechanism and its theraprutic application

在缺血应激反应中，氧自由基是一个重要的介导因子，它可以诱导腺苷和Mn-SOD等抗氧化剂的产生，这一过程可以解释缺血预处理是如何对缺血应激产生保护作用的。我们的目的是确定外源性应激如何诱导心脏的保护作用。(1)心肌细胞抗应激机制的研究以大鼠心肌细胞、血管内皮细胞和平滑肌细胞为细胞模型，分别进行缺血再灌注、热休克和牵张应激处理。治疗后，我们通过测定其蛋白表达和活性来检测效应分子如外-5 '-核肽酶和Mn-SOD。这些分子的蛋白质和活性均增加。当心肌细胞过表达这些分子中的每一种时，过表达分子的细胞显示出对各种应激的抗性。(2)心肌细胞对应激反应的细胞内信号通路利用荧光分析系统测定了被认为是应激反应的主要机制的氧自由基，发现在各种类型的应激后，细胞质中的氧自由基增加。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激酶在诱导应激反应信号中起重要作用。因此，这些分子应该是增加最终效应物如Mn-SOD。总之，我们确定了参与应激反应的细胞内信号通路。P38和S6激酶被确定为该过程中的关键介质。

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.