Impact of Insufficient Vascular EC-SOD in Pulmonary Hypertension

描述（由申请人提供）：氧化应激和活性氧信号现在被认为在肺动脉高压（PH）的发病机制中起关键作用。抗超氧化物（O2.-）的唯一胞外酶防御是抗氧化剂胞外超氧化物歧化酶（EC-SOD或SOD3）。虽然EC-SOD在大多数组织中只占总SOD活性的一小部分，但它是动脉中含量最多的SOD亚型。在初步数据和迄今为止少数的人类研究中，EC-SOD的表达和活性在终末期PH中下降。在PH动物模型中EC-SOD活性的丧失会使结果恶化，尽管其机制尚不清楚。我们假设，定位于肺动脉（PA）壁的EC-SOD对防止血管炎症和重塑至关重要，因为它可以阻止细胞外

DESCRIPTION (provided by applicant): Oxidative stress and reactive oxygen species signaling are now recognized to have a critical role in the pathogenesis of pulmonary hypertension (PH). The sole extracellular enzymatic defense against superoxide (O2.-) is the antioxidant extracellular superoxide dismutase (EC-SOD or SOD3). Though EC-SOD constitutes a small fraction of total SOD activity in most tissues, it is the most abundant SOD isoform in arteries. In preliminary data and the few human studies to date, EC-SOD expression and activity are decreased in end- stage PH. Loss of EC-SOD activity in animal models of PH worsens outcome, though the mechanisms are poorly understood. We hypothesize that EC-SOD localized to the pulmonary artery (PA) wall is critical to the protection against vascular inflammation and remodeling because it prevents extracellular redox-sensitive events in the matrix that can activate important signaling pathways in PA cells. We will test this hypothesis using novel mouse models, primary PASMC and macrophages, potent molecular tools and a targeted EC-SOD replacement. Our first Aim will test the contribution of insufficient vascular EC-SOD to the development of PH; and whether its prominent vascular localization can be translated into a more effective therapeutic strategy by targeting EC-SOD replacement to the PA. We will test mouse strains with a generalized loss of EC-SOD versus a preferential loss of vascular EC-SOD, measure redox state, inflammation, pulmonary vascular remodeling and PH; and test if the effects can be reversed by targeted EC-SOD replacement. Our second Aim will test if insufficient vascular EC-SOD, as a result of impaired scavenging of extracellular O2.-, activates TGF-ß; and if this is responsible for ERK1/2 activation, Egr-1 expression and the subsequent changes in growth, inflammation and synthetic properties of PASMC. This aim will use in vivo and in vitro models to systematically test if low vascular EC-SOD, increases O2.---dependent activation of the key growth factor, TGF-ß, and if this is responsible for ERK1/2-dependent up-regulation of the transcription factor, early growth response-1, leading to changes in the growth, inflammatory, and synthetic properties of PASMC in PH. In the third Aim, we will test if low vascular EC-SOD results in oxidative fragmentation of matrix component, HA, leading to NLRP3 inflammasome activation in macrophages. This aim will focus on a specific matrix component, hyaluronan, susceptible to superoxide-mediated fragmentation and implicated in PH. The aim will test if insufficient vascular EC-SOD leads to oxidative fragmentation of hyaluronan and its activation of the NLRP3 inflammasome, a protein platform that processes pro-inflammatory cytokines IL-1ß and IL-18 in macrophages. This proposal provides direct translational relevance by establishing the foundation to develop novel antioxidant therapies appropriately targeted to a specific vascular compartment. These findings will have important implications in a wide range of lung diseases to ultimately improve health outcome for patients with these serious problems.