Heme Oxygenase-1 in Lung Ischemia-Reperfusion Injury

描述(申请人提供)：器官的缺血-再灌注(I-R)或细胞的缺氧-复氧(A-R)会导致细胞死亡、氧化应激和器官功能障碍。肺I-R可能是肺移植/手术、血栓栓子剔除、肺栓塞和再扩张性肺水肿过程中导致急性肺损伤的激发事件，所有这些都会导致临床上严重的呼吸衰竭，但目前还没有针对这些疾病的特定治疗方法。因此，确定保护机制对于制定有效的干预措施至关重要。血红素氧合酶-1(HO-1)是一种重要的保护分子，但其潜在的分子机制和负责的细胞类型(S)却知之甚少。HO-1是血红素加氧酶的高度诱导性亚型，是血红素降解的限速酶。利用肺靶向HO-1 siRNA，我们证实了内源性HO-1诱导在肺内皮细胞和体内具有重要的保护作用。最近，我们发现内皮STAT3在HO-1致死性氧化损伤中的保护作用中起关键作用，并且抗氧化剂分子热休克蛋白Hsp70受到STAT3的调节。我们还建立了内皮靶向的HO-1转基因小鼠和HO-1牙线小鼠，这将成为探索内皮HO-1在体内的特定作用的有价值的工具。这些观察结果使我们提出了一个总体假设，即在A-R/I-R损伤过程中，内皮细胞HO-1通过依赖内皮STAT3-Hsp70的抗氧化途径介导保护。为了验证这一假说，我们将使肺内皮细胞遭受A-R损伤，并使小鼠遭受肺I-R损伤：1)确定STAT3在HO-1对肺内皮细胞和小鼠肺的抗氧化作用中的作用；2)阐明HSP70在介导STAT3和HO-1对肺内皮细胞和小鼠肺的保护作用中的作用；以及3)确定内皮源性HO-1在体内介导保护作用中的特异性作用。研究完成后，我们将对内皮细胞的作用以及HO-1等保护性分子在A-R/I-R损伤中发挥作用的方式获得重要的见解，从而确定新的治疗靶点。项目叙事。我们项目的总体目标是了解肺对损伤的反应和保护自己免受伤害的方式。肺移植后的呼吸衰竭、危及生命的肺血栓清除和其他主要的肺部手术是由于短暂的血流停止，然后重新建立血流(缺血-再灌注)，具有高死亡率和有限的干预选择。我们已经确定了一种新的机制，通过这种机制，我们已经拥有的一种蛋白质，即血红素加氧酶-1，可以预防缺血再灌注肺损伤，并创造了强大的工具，我们可以用来充分探索这些机制，希望将我们的发现应用于设计有效的治疗呼吸衰竭的方法。

DESCRIPTION (provided by applicant): Ischemia-reperfusion (I-R) in organs or anoxia-reoxygenation (A-R) in cells leads to cell death, oxidant stress, and organ dysfunction. Lung I-R is likely the inciting event leading to acute lung injury during lung transplantation/surgery, thromboembolectomy, pulmonary embolism, and re-expansion pulmonary edema, all of which lead to clinically significant respiratory failure but for which no specific therapies exist. Therefore, identifying protective mechanisms will be critical to the development of effective interventions. Heme oxygenase-1 (HO-1) is an important protective molecule but the underlying molecular mechanisms and responsible cell type(s) are poorly understood. HO-1 is the highly inducible isoform of heme oxygenase, the rate-limiting enzyme in heme degradation. Using lung-targeted HO-1 siRNA, we confirmed that endogenous HO-1 induction has important protective effects in lung endothelial cells and in vivo. Recently, we have found that endothelial STAT3 is critical to the protective effects of HO-1 during lethal oxidant injury and that an antioxidant molecule, heat shock protein, Hsp70, is modulated by STAT3. We have also generated endothelial-targeted HO-1 transgenic mice and HO-1 floxed mice, which will serve as valuable tools to explore the specific role of endothelial HO-1 in vivo. These observations have led us to propose the overall hypothesis that endothelial cell HO-1 mediates protection via endothelial STAT3-Hsp70-dependent anti-oxidant pathways during A-R/I-R injury. In order to test this hypothesis we will subject lung endothelial cells to A-R injury and mice to lung I-R injury in the following Specific Aims: 1) Determine the contribution of STAT3 to the anti-oxidant effects of HO-1 in lung endothelial cells and mouse lung, 2) Delineate the role of Hsp70 in mediating the protective effects of STAT3 and HO-1 in lung endothelial cells and mouse lung, and 3) Determine the specific contribution of endothelial-derived HO-1 in mediating protection in vivo. Upon completion of the studies, we will gain important insights into the role of the endothelium and the ways in which protective molecules such as HO-1 exert their effects during A-R/I-R injury and thereby identify novel therapeutic targets. PROJECT NARRATIVE. The overall goal of our project is to understand the ways in which the lung responds to and protects itself against injury. Respiratory failure after lung transplantation, the removal of life-threatening lung clots, and other major lung surgery is due to the transient cessation of blood flow followed by re-establishment of blood flow (ischemia-reperfusion) and carries a high mortality with limited options for intervention. We have identified novel mechanisms whereby a protein that we already possess, heme oxygenase-1, can protect against ischemia-reperfusion lung injury, and have also created powerful tools with which we can explore these mechanisms fully, in the hopes of applying our findings to the design of effective therapies against respiratory failure.