Urokinase, Defensin and Acute Lung Injury

急性肺损伤（acute lung injury，ALI）的特征是肺泡-毛细血管渗漏和白细胞外渗的渗出期，随后是肺血管重建和肺内分流。虽然血管反应性的改变有助于急性肺损伤的发病率，血管通透性的连续变化的信号转导机制是不完全确定的。我们的研究表明，激活的中性粒细胞分泌的尿激酶纤溶酶原激活物（uPA）和α-防御素通过低密度脂蛋白相关受体（LRP）和整合素α-v-β 3对血管张力产生相反的作用，并且该系统受氧张力调节。基于这些发现，我们将探讨uPA调节血管收缩性并通过与LRP和alpha-v-beta3形成信号转导复合物来影响下游渗透性的假设，该复合物被缺氧失调并被α-防御素破坏。在具体目标1中，我们将研究分子决定因素 uPA、Ovfo和LRP之间形成三元复合物所必需的，其在肺血管中的作用 收缩和防御素的作用。在具体的表达和信号转导将被阐明。在特定目标3中，将在野生型、uPA -/-和防御素转基因小鼠中检查LRP/α-v-β 3在ALI发展中的作用。通过使用血小板特异性启动子的新型uPA和d-kringle uPA转基因小鼠递送系统，将区分uPA对脉管系统的蛋白水解和非蛋白水解作用。综合这些 研究将提供对ALI中uPA对血管张力和通透性的调节的深入了解，并鉴定新的激动剂（uPA和防御素）和新的信号转导途径（LRP/α-v-β 3）作为改善疾病严重程度的潜在位点。

Acute lung injury (ALI) is characterized by an exudative phase of alveolar-capillary leak and leukocyte extravasation followed by pulmonary vasoconstruction and intrapulmonary shunting in response to hypoxia. Although alterations in vasoreactivity contribute to the morbidity of ALI, the signal-transducing mechanism underlying the sequential changes in vascular permeability is incompletely defined. Our studies suggest that urokinase plasminogen activator (uPA) and a-defensins secreted by activated neutrophils exert opposing effects on vascular tone through low-density lipoprotein-related receptor (LRP) and the integrin alpha-v-beta3, and that system is regulated by oxygen tension. Based on these findings, we will explore the hypothesis that uPA regulates vascular contractility and influences downstream permeability by forming a signal-transducing complex with LRP and alpha-v-beta3 that is dysregulated by hypoxia and disrupted by a-defensin. In Specific Aim 1 we will study the molecular determinants required to form ternary complexes between uPA, Ovfo and LRP, its role in pulmonary vascular contraction, and the effect of defensin. In Specific expression and signal transduction will be elucidated. In Specific Aim 3 the role of LRP/alpha-v-beta3 in the development of ALI will be examined in wildtype, uPA -/- and defensin-transgenic mice. Proteolytic and the non-proteolytic effects of uPA on the vasculature will be distinguished through a novel uPA and d-kringle uPA transgenic mouse delivery system using platelet-specific promoters. Taken together these studies will provide insight into the regulation of vascular tone and permeability by uPA in ALI and identify novel agonists (uPA and defensin) and a novel signal-transducing pathway (LRP/ alpha-v-beta3) as potential sites to ameliorate disease severity.