Peroxidase-Based Toxicity In Hypereosinophilic States.'

描述（由申请人提供）：嗜酸粒细胞1（EO）吞噬细胞可以消灭寄生虫，但也可以损伤宿主组织。尽管过敏是 EO 介导的病理学最常见的例子，但嗜酸性粒细胞增多综合征 (HES) 是最引人注目的。 HES 是一种全身性血液疾病，其特征是多器官系统受累，是心脏病的一种典型特征，通常是致命的。嗜酸性粒细胞性心脏病 (EHD) 发生在各种嗜酸性粒细胞增多状态，无论其原因如何。EO 特异性颗粒蛋白（其中最丰富的是嗜酸性粒细胞过氧化物酶 (EPO)）在心内膜和心肌沉积，被认为介导 EHD 中的心脏毒性。尽管 EPO 丰富且 EO 呼吸爆发强劲，但关于 EPO 介导的氧化损伤对病理学的贡献知之甚少。我们发现，在 H2O2 存在的情况下，三种不常见的底物 - 溴化物 (Br-)、亚硝酸盐 (NO2-) 和硫氰酸盐 (SCN-) - 会竞争被 EPO 氧化，分别产生 HOBr、NO2 和 HOSCN。这些氧化剂对人体细胞的相对毒性为 HOBr> NO2 >> HOSCN；但 EPO 优先氧化 SCN。 > NO2 - > Br- 我们假设 SCN “缓冲”EPO 产生的更具细胞毒性的 N02 和 Br 基氧化剂，因此血清 SCN 水平（由饮食决定）可能会调节 EPO 毒性。我们提出的工作的总体目标是检验以下假设：EPO 产生的氧化剂以底物决定的方式对哺乳动物细胞和组织造成损害，从而导致 EHD 的发病机制。第一个具体目标是检验 HOBr 和 N02 通过与膜成分反应破坏膜完整性而导致坏死性细胞死亡的假设，而 HOSCN 施加硫氢基靶向细胞内氧化应激，可以影响组织因子基因表达并诱导细胞凋亡。通过新开发的敏感底物特异性氨基酸“生物标志物”评估 EHD 的发生与 EPO 特异性蛋白质氧化损伤的平行积累。第三个具体目标是测试 EPO 有助于 IL.5 转基因小鼠系中 EHD 发病机制的假设，我们将比较 IL-5 转基因系和与 EPO“敲除”系杂交的 IL-S 转基因系中的 EHD 严重程度、寿命和 EPO 生物标志物水平。第四个具体目标是测试这样的假设：在IL-5转基因小鼠中，增加血清SCN-抑制和减少SCN-促进EPO介导的蛋白质氧化损伤和EHD的严重程度。这些研究如果成功，将建立HES和EHD的小鼠模型，证明EPO介导的氧化损伤在EHD发病机制中的作用，并提出一种简单的治疗策略（即膳食补充廉价的SCN-），该策略甚至可以应用于EHD。贫困社区以及预防更常见的过敏性疾病，例如哮喘。

DESCRIPTION (provided by applicant): Eosinophi1 (EO) phagocytes destroy parasites but can also damage host tissue. Although allergies are the most common example of EO-mediated pathology, the hypereosinophilic Syndrome (HES) is the most striking. HES is a systemic hematologic disorder characterized by multi-organ system involvement, preeminently a characteristic, usually lethal form of heart disease. Eosinophilic heart disease (EHD occurs in a variety of hypereosinophilic states, irrespective of their cause. Endocardial and myocardial deposition of EO specific granule proteins, of which eosinophil peroxidase (EPO) is the most abundant, is proposed to mediate cardiotoxicity in EHD. Despite the abundance of EPO and the vigor of the EO respiratory burst, little is known about the contribution of EPO-mediated oxidative damage to the pathology of eosinophilic inflammatory states. We find that three unusual substrates - bromide (Br-), nitrite (NO2-), and thiocyanate (SCN-) - compete for oxidation by EPO in physiologic fluids in the presence of H202, yielding, respectively, HOBr, NO2., and HOSCN. The relative toxicity of these oxidants for human cells is HOBr> NO2>> HOSCN; yet EPO preferentially oxidizes SCN > NO2 - > Br-. We hypothesize that SCN "buffers" against generation by EPO of the more cytotoxic N02- and Br- based oxidants and consequently serum SCN- levels, which are dietarily determined, may modulate EPO toxicity. The overall goal of our proposed work is to examine the hypothesis that that EPO-generated oxidants impose damage in a substrate-determined manner to mammalian cells and tissue that contributes to the pathogenesis of EHD, which we propose as a paradigm for any organ damage occurring in eosinophil inflammatory states. The first specific aim is to test the hypothesis that whereas HOBr and N02 cause necrotic cell death by reacting with membrane components to destroy membrane integrity, HOSCN imposes sulfhydryl-targeted intracellular oxidative stress that can influence tissue factor gene expression and induce apoptosis. The second specific Aim is to test the hypothesis that an interleukin-5 (IL.5) transgenic mouse line will develop progressive functional, anatomic, and histologic manifestations of EHD with a parallel accumulation of EPO-specific protein oxidative damage as assessed by newly developed sensitive, substrate-specific amino acid "biomarkers." The third specific aim is to test the hypothesis that EPO contributes to the pathogenesis of EHD in the IL.5 transgenic mouse line. We will compare EHD severity, longevity, and EPO biomarker levels in the IL-5 transgenic line with that of an IL-S transgenics crossbred with an EPO 'knockout" line. The fourth specific aim is test the hypothesis that increasing serum SCN- inhibits, and decreasing SCN- promotes, EPO-mediated protein oxidant damage and the severity of EHD in IL-5 transgenic mice. These studies, if successful, will establish a murine model for HES and EHD, prove a mole for EPO-mediated oxidant damage in the pathogenesis of EHD, and suggest a simple strategy fur its treatment, (i.e., dietary supplementation with inexpensive SCN-), that could be applied even in impoverished communities as well as against more common allergic diseases, such as asthma.