Asthma Increases Vaso-occlusion in Sickle Cell Disease

描述（由申请人提供）：哮喘是一种增加镰状细胞病（SCD）患儿发病率和死亡率的合并症。最近，我们报道了由卵清蛋白（OVA）致敏的SCD小鼠引起的实验性哮喘，其肺部炎症和胶原沉积的增加程度远高于OVA致敏的对照小鼠。初步结果显示，与ova致敏的对照组相比，ova致敏对SCD小鼠气道阻力的增加程度更大。此外，ova致敏可增加SCD小鼠的促炎高密度脂蛋白（HDL）水平，表明来自SCD+哮喘小鼠的HDL比来自SCD小鼠的HDL更大程度上被氧化修饰。在缺乏载脂蛋白A-I （HDL中的主要抗炎载脂蛋白）的小鼠中进行的组织学和气道反应研究进一步证明了HDL在预防肺部炎症中起重要作用。通过apoA-I缺失导致的HDL基因缺失会显著增加肺部炎症和胶原沉积，即使没有OVA致敏也会增加气道阻力。基于这些发现，我们假设哮喘和SCD诱导的氧化应激协同增加HDL氧化，从而损害HDL功能。此外，我们假设HDL功能的丧失（直接或间接）增加了肺血管内皮细胞的活化（增加VCAM-1表达），这反过来又增加了SCD+哮喘小鼠在缺氧/再灌注（H/R）损伤时对肺血管闭塞的易感性。为了验证这些假设，我们提出了三个目标。目的1将确定哮喘和SCD合并是否会增加HDL的氧化，从而增加HDL的功能，以及是否针对黄嘌呤氧化酶（XO）诱导的氧化应激；2)髓过氧化物酶（MPO）；3)游离血红蛋白（Hb）；4)氧化脂质可防止哮喘SCD小鼠体内HDL和其他脂蛋白的氧化。目的2将确定哮喘合并SCD是否会损害肺动脉血管舒张，增加肺动脉高压（PAH）并增加气道高反应性。这些研究将揭示靶向氧化应激（即XO、MPO、游离Hb和氧化脂质）是否真的能改善HDL功能并恢复肺和气道功能。Aim 3将确定VCAM-1（和ICAM-1）介导SCD+哮喘小鼠红细胞血管充血的程度；是否针对氧化酶活性，游离Hb或氧化脂质减轻肺部炎症和减少血管充血；最后，用apoa - 1治疗是否能减少肺部炎症和血管充血。如果我们的假设是正确的，恢复HDL功能应该减少肺部炎症并减轻SCD+哮喘小鼠肺部的血管闭塞。我们的研究结果将揭示哮喘增加SCD气道高反应性和多环芳烃的炎症和氧化机制。新的治疗策略将用于确定哮喘在多大程度上增加这四种不同的氧化途径，从而诱导SCD的肺部炎症、气道高反应性和血管闭塞。

DESCRIPTION (provided by applicant): Asthma is a co-morbid condition that increases morbidity and mortality of children who have sickle cell disease (SCD). Recently, we reported that experimental asthma induced by ovalbumin (OVA) sensitization of SCD mice increases pulmonary inflammation and collagen deposition in SCD mice to a much greater extent than in OVA-sensitized control mice. Preliminary Results show that OVA-sensitization also increases airway resistance in SCD mice to a greater degree than in OVA-sensitized controls. Additionally, OVA-sensitization increases proinflammatory high-density lipoprotein (HDL) levels in SCD mice, indicating that HDL from SCD+asthma mice is oxidatively modified to a greater extent than HDL from SCD mice. Further proof that HDL plays an important role in preventing pulmonary inflammation comes from histology and airway response studies in mice lacking apolipoprotein A-I (apoA-I), the major anti- inflammatory apolipoprotein in HDL. Genetic loss of HDL via apoA-I deletion dramatically increases pulmonary inflammation and collagen deposition and increases airway resistance even without OVA sensitization. On the basis of these findings, we hypothesize that the oxidative stress induced by asthma and SCD synergize to increase HDL oxidation, which then impairs HDL function. Further, we hypothesize that the loss of HDL function (either directly or indirectly) increases endothelial cell activation (increased VCAM-1 expression) in pulmonary vessels, which in turn, increases the susceptibility of SCD+asthma mice to pulmonary vaso-occlusion when subjected to hypoxia/reperfusion (H/R) injury. To test these hypotheses we propose 3 aims. Aim 1 will determine if the combination of asthma and SCD increases oxidation of HDL and therefore HDL function and if targeting oxidative stress induced by 1) xanthine oxidase (XO); 2) myeloperoxidase (MPO); 3) cell free hemoglobin (Hb); and, 4) oxidized lipids prevents oxidation of HDL and other lipoproteins in the SCD mice with asthma. Aim 2 will determine if the combination of asthma plus SCD impairs pulmonary artery vasodilatation, increases pulmonary arterial hypertension (PAH) and increases airway hyperresponsiveness. These studies will reveal whether targeting oxidative stress (i.e., XO, MPO, free Hb and oxidized lipids) actually improves HDL function and restores pulmonary and airway function. Aim 3 will determine the extent to which VCAM-1 (and ICAM-1) mediates red cell vascular congestion in SCD+asthma mice; whether targeting oxidative enzyme activity, free Hb or oxidized lipids attenuates pulmonary inflammation and reduces vaso-congestion; and finally, whether treatments with apoA-I can reduce pulmonary inflammation and vaso-congestion. If our hypotheses are correct, restoring HDL function should decrease pulmonary inflammation and attenuate vaso-occlusion in the lungs of SCD+asthma mice. Findings from our studies will reveal new insight into the inflammatory and oxidative mechanisms by which asthma increases airway hyperresponsiveness and PAH in SCD. Novel therapeutic strategies will be used to determine the extent to which asthma increases these four different oxidative pathways to induce pulmonary inflammation, airway hyperresponsiveness and vaso-occlusion in SCD. PUBLIC HEALTH RELEVANCE: Asthma increases morbidity and mortality in individuals afflicted with sickle cell disease. We want to determine why asthma increases inflammation and red cell vascular congestion in lungs of sickle cell mice. We think that the oxidative stress induced by asthma coupled with oxidative stress induced by sickle cell disease team up to oxidize high-density lipoprotein (HDL). Oxidation changes "good cholesterol" into "bad cholesterol," which can no longer clean up blood vessels and airways. Thus, lung tissues bind more white blood cells causing the airways to shrink, which restricts airflow. This decreases blood and oxygen exchange in the lung, which in turn, increases red cell sickling and vaso-occlusion in sickle cell disease. We plan to reduce oxidative stress and decrease HDL oxidation by using a combination of standard and novel drug therapies. If we are correct, then our drug therapies should improve blood vessel function and decrease airway resistance in SCD mice with experimental asthma.