Group V Phospholipase A2 and Pulmonary Inflammation

描述(由申请人提供)： 磷脂酶A2(PLA2)能将细胞膜磷脂的sn-2位水解，释放花生四烯酸，花生四烯酸被5-脂氧合酶代谢为白三烯，或被前列腺素过氧化物合成酶(PGHS)代谢为前列腺素和血栓素类。白三烯(LT)和前列腺素(PG)参与多种生理和病理过程。具体地说，肥大细胞的主要二十烷类产物LTC4和PGD2与哮喘有关。我们之前已经描述了小鼠肥大细胞产生二十烷类化合物的即刻和延迟阶段。我们已经证明胞浆磷脂酶A2(CPLA2)对于花生四烯酸在每一阶段的供应是必不可少的。CPLA2也是小鼠巨噬细胞产生二十烷类化合物所必需的。然而，有大量证据表明，cPLA2需要低分子量分泌型PLA2(SPLA2)的协同作用，最有可能的是V组sPLA2。V组sPLA2由肥大细胞和巨噬细胞表达。在转染研究中，它与cPLA2在二十烷类化合物生成的即刻和延迟阶段偶联。V组sPLA2没有特异性的抑制物。这一假设认为，V组sPLA2在肥大细胞和巨噬细胞体外产生二十烷类化合物以及在哮喘中提供LTC4和PGD2方面是必不可少的。为了验证这一假设，我们衍生了编码V组sPLA2基因中断的小鼠。在具体目标1中，我们将使用V组sPLA2纯合中断小鼠的肥大细胞和巨噬细胞，以确定其在不同刺激反应的二十烷类化合物生成的即时和延迟阶段中的作用。在具体目标2中，我们将使用V组sPLA2缺失的小鼠来确定其在日益复杂的炎症反应中的作用。我们将从肥大细胞依赖的被动皮肤过敏反应开始。我们将继续进行积极的皮肤和全身过敏反应，其中V组sPLA2可能还有助于致敏过程。这将导致小鼠哮喘模型，V组sPLA2可能通过不同的机制和不同的细胞过程参与其中。

DESCRIPTION (provided by applicant): Phospholipase A2 (PLA2) hydrolyses the sn-2 position of cell membrane phospholipids to release arachidonic acid, which is metabolized by 5-lipoxygenase to leukotrienes or by prostaglandin endoperoxide synthase (PGHS) to prostaglandins and thromboxane. Leukotrienes (LT) and prostaglandins (PG) have been implicated in diverse physiologic and pathologic processes. Specifically, LTC4 and PGD2, the principal eicosanoid products of the mast cell, have been implicated in bronchial asthma. We have previously described immediate and delayed phases of eicosanoid generation by mouse mast cells. We have demonstrated that cytosolic PLA2 (cPLA2) is essential for the supply of arachidonic acid in each phase. cPLA2 is also required for eicosanoid generation by mouse macrophages. Nevertheless, there is a body of evidence that cPLA2 requires the co-ordinate action of a low molecular weight, secretory PLA2 (sPLA2), most likely group V sPLA2. Group V sPLA2 is expressed by both mast cells and macrophages. In transfection studies, it coupled to cPLA2 in both immediate and delayed phases of eicosanoid generation. There are no specific inhibitors of group V sPLA2. The hypothesis of this proposal is that group V sPLA2 is essential for eicosanoid generation by mast cells and macrophages in vitro, and in the provision of LTC4 and PGD2 in bronchial asthma. To test this hypothesis we have derived mice with disruption of the gene encoding group V sPLA2. In Specific Aim 1 we will use mast cells and macrophages derived from mice with homozygous disruption of group V sPLA2 to determine its role in immediate and delayed phases of eicosanoid generation in response to diverse stimuli. In Specific Aim 2 we will use mice with deletion of group V sPLA2 to determine its role in inflammatory responses of increasing complexity. We will begin with mast cell-dependent passive cutaneous anaphylaxis. We will proceed to active cutaneous and systemic anaphylaxis, in which group V sPLA2 may additionally contribute to the sensitization process. This will lead to mouse models of bronchial asthma in which group V sPLA2 may participate through diverse mechanisms and diverse cellular processes.