JNK exacerbates ischemia/reperfusion injury in hyperglycemic subjects.

描述(申请人提供)：美国急性心肌梗死患者平均再通时间为3-4小时。在此期间，缺血组织内的代谢活动是预后的主要决定因素，并受受试者的血糖和胰岛素反应状态的严重影响。葡萄糖刺激的胰岛素分泌不足和/或肌肉和肝脏的胰岛素抵抗会导致高血糖。我们推测，在高血糖受试者中伴随心肌缺血/再灌流的加重损伤至少部分是由于c-jun-N末端激酶(JNK)功能从支持生存到支持死亡的早期转换的结果。我们先前在培养的心肌细胞中描述了JNK功能的能量依赖开关。当心肌细胞的ATP水平下降到50%以下时，这种转变就会发生，这种情况会使心肌细胞对氧化应激敏感，同时胰岛素受体底物-1(IRS-1)在抑制丝氨酸-307上的磷酸化增加。我们现在已经证实，当心肌受到缺血/再灌注并遇到类似的代谢应激时，该开关也在体内起作用。在体内的效果是显著的，在长时间的缺血期间抑制JNK可以减少~50%的细胞凋亡和脑梗塞，但是对短时间的缺血施加的同样的抑制使细胞凋亡和脑梗塞增加3倍和2倍。由于严重缺血/再灌流造成的损伤中有50%是由JNK调节的，这种转换可能是急性心肌梗死预后的主要因素。在这一修订的应用中，我们将确定高血糖的病因对JNK代谢转换的影响程度，表征介导转换的代谢信号，并确定受影响的死亡/生存途径。在目标1中，我们将通过高清晰度超声心动图和微型MRI来确定随着时间的推移而发生的梗塞和重构。这将在3种高血糖模型中实施：(I)db/db小鼠，具有肥胖和胰岛素抵抗的单基因易感性。(Ii)具有肥胖和胰岛素抵抗多基因易感性的NONcNZO10小鼠。(Iii)注入脂质以诱导胰岛素抵抗和高血糖的野生型小鼠。在目标2中，我们将使用先进的成像技术，包括微型核磁共振/核磁共振来确定精确的代谢参数，这些参数调节正常和高血糖心脏缺血/再灌注后JNK的转换。在目标3中，我们将确定JNK开关影响的死亡途径，以及对受影响心肌区域重塑和基因表达的长期影响。公共卫生相关性：在动物模型和患者中，空腹高血糖与心肌梗死增加有关。空腹高血糖也与胰岛素抵抗有关。高血糖患者发生急性心肌梗死预后不良的机制尚不清楚。在这里，我们提出了一个新的假说，即应激激酶在接受急性心肌梗死的高血糖患者中被特异性地激活，并导致不良结局。有人提议在小鼠模型上进行实验来验证这一假设。如果我们的假设是正确的，我们将描述这种情况的分子基础，并开始开发新的治疗方法。

DESCRIPTION (provided by applicant): The mean time to reperfusion of acute myocardial infarction patients in the USA is 3-4h. The metabolic activity within the ischemic tissue over this period is a major determinant of outcome and is critically influenced by the glycemic and insulin responsive status of the subject. Inadequate glucose-stimulated insulin production and/or insulin resistance of muscle and liver cause hyperglycemia. We hypothesize that the exacerbated injury that accompanies myocardial ischemia/reperfusion in hyperglycemic subjects is at least in part the consequence of an early switch in the function of c-Jun-N-terminal kinase (JNK) from pro-survival to pro-death. We previously described an energy-dependent switch in the function of JNK in cultured cardiac myocytes. The switch occurred when cardiac myocyte ATP level fell by below 50%, a condition that sensitized myocytes to oxidative stress, and coincided with increased phosphorylation of the insulin receptor substrate-1 (IRS-1) on the inhibitory serine-307. We have now confirmed that the switch also operates in vivo when the myocardium is subjected to ischemia/reperfusion and encounters similar metabolic stress. The in vivo effect is dramatic, JNK inhibition during prolonged ischemia reduced both apoptosis and infarction by ~50%, but the same inhibition imposed on a short ischemic episode increased apoptosis >3-fold and infarct >2-fold. Because >50% of injury caused by severe ischemia/reperfusion is regulated by JNK, the switch is potentially a major contributor to the outcome of AMI. In this revised application we will determine the degree to which the etiology of hyperglycemia affects JNK metabolic switching, characterize the metabolic signals that mediate switching and determine the death/survival pathways that are affected. In Aim 1 we will determine infarction and remodeling over time by high-definition echocardiography and micro-MRI. This will be implemented in 3 models of hyperglycemia: (i) db/db mice with monogenetic susceptibility to obesity and insulin resistance. (ii) NONcNZO10 mice with polygenic susceptibility to obesity and insulin resistance. (iii) Wild type mice infused with lipid to induce insulin resistance and hyperglycemia. In Aim 2 we will use advanced imaging techniques including micro-NMR/MRI to determine the precise metabolic parameters that regulate JNK switching in normal and hyperglycemic hearts subjected to ischemia/reperfusion. In Aim 3 we will define the death pathways that are affected by the JNK switch and the long-term effects on remodeling and gene expression in the affected region of the myocardium. PUBLIC HEALTH RELEVANCE: Fasting hyperglycemia is associated with increased myocardial infarction in both animal models and patients. Fasting hyperglycemia is also associated with insulin resistance. The mechanism for the poor outcome of hyperglycemic patients to acute myocardial infarction is not known. Here we present a new hypothesis where stress kinases are activated specifically in hyperglycemic patients undergoing AMI and cause poor outcome. Experiments are proposed to test this hypothesis in mouse models. If our hypothesis is correct we will described the molecular basis for this an begin to develop new approaches for treatment.