Oxidant Regulation of Proteolysis in Acute Lung Injury

描述(申请人提供)：急性肺损伤是危重患者呼吸衰竭的主要原因，其特点是以中性粒细胞为主的炎症反应。炎症损害呼吸道上皮和支持结缔组织，导致微血管渗漏，然后是肺组织纤维化，这是这种疾病的临床特征。因此，调节中性粒细胞和上皮细胞之间的相互作用可能控制着组织修复的基本机制，调节中断可能导致肺损伤。最近的研究表明，在急性肺损伤模型中，中性粒细胞的募集严重依赖于基质金属蛋白酶(MMPs)。在体外和体内肺损伤模型中，MMPs通过从上皮细胞释放强大的趋化物质来募集中性粒细胞。中性粒细胞是活性中间体的主要来源，而氧化剂在体外是MMPs的有效激活剂。此外，许多证据表明，当人类出现急性肺损伤时，氧化应激增加。这些观察表明，反应性中间体可能通过多种机制参与中性粒细胞募集、基质金属蛋白酶的激活以及肺损伤的发病机制。这项建议的总体目标是检验一种假说，即肺炎性细胞产生的活性物质对于调节基质金属蛋白酶活性和介导急性肺损伤至关重要。我们将通过在体外研究MMPs的氧化和激活，分析人类肺样本中的MMPs以寻找氧化损伤的证据，并使用小鼠模型来研究急性肺损伤中的氧化损伤和MMPs的激活，从而解决这个问题。这些互补性研究将使我们能够确定我们在体外发现的基质金属蛋白酶激活机制是否也在体内起作用。

DESCRIPTION (provided by applicant): Acute lung injury is a major cause of respiratory failure in critically ill patients, and it is characterized by a neutrophil-dominated inflammatory response. Inflammation damages the airway epithelium and supporting connective tissue, leading to microvascular leak and then lung tissue fibrosis, the clinical hallmarks of the disorder. Thus, regulation of interactions between neutrophils and epithelial cells likely control fundamental mechanisms of tissue repair, and disrupted regulation may lead to lung injury. Recent studies demonstrate that neutrophil recruitment in a model of acute lung injury depends critically on matrix metalloproteinases (MMPs). MMPs recruit neutrophils by releasing potent chemoattractants from epithelial cells in vitro and in lung injury models in vivo. Neutrophils are a major source of reactive intermediates, and oxidants are potent activators of MMPs in vitro. Also, many lines of evidence suggest that oxidative stress increases when humans develop acute lung injury. These observations indicate that reactive intermediates may contribute to neutrophil recruitment, MMP activation, and the pathogenesis of lung injury by a variety of mechanisms. The overall goal of this proposal is to test the hypothesis that reactive species generated by inflammatory cells of the lung are critical for regulating MMP activity and mediating acute lung injury. We will approach this issue by investigating MMP oxidation and activation in vitro, analyzing MMPs in human lung samples for evidence of oxidative damage, and using mouse models to investigate oxidative damage and MMP activation in acute lung injury. These complementary studies will enable us to determine whether mechanisms of MMP activation that we uncover in vitro also operate in vivo.