Pathogenesis of Oxidative Stress in Chagas Disease

描述(申请人提供)：恰加斯病是由原生动物克氏锥虫引起的，是全球第三大热带疾病负担。恰加斯病管理每年的总费用估计为80亿美元。近年来，人畜共患寄生虫的存在以及人口流动性的增加、通过输血传播、先天性感染和器官移植增加了美国查加斯人感染病例。然而，目前尚无疫苗或安全药物可用于治疗美国约30万名患者和流行国家的1000万名患者。该项目的研究将确定查加西克心肌病的治疗靶点。我们首次提出这一假说，认为克氏锥虫通过三种不同的机制损伤心脏组织：(1)ICa+2应激是由入侵的寄生虫引起的，它导致mt膜电位的改变，并启动活性氧物种(ROS)的释放；(2)寄生虫分子的直接作用促进受损宿主细胞的存活和细胞重塑；(3)炎症诱导的免疫病理的持续，特别是由于活性氧中间体。这些通路汇聚在一起，导致病理性肥大，导致心力衰竭。支持我们假设的主要初步观察结果包括：(1)抗氧化剂的克氏锥虫表达增强了寄生虫的毒力；(2)宿主承受着慢性氧化/炎症应激，这是导致Chagas病进展过程中左心功能受损的原因；(3)ROS诱导的DNA氧化加合物和多聚腺苷二磷酸核糖聚合酶1(PARP-1)的激活在感染的心肌细胞中发出炎症细胞因子反应的信号。我们将利用PI实验室建立的尖端分子、生化和免疫学工具来实现以下三个目标-(1)检验TC-抗氧化剂阻止受损细胞正常内稳清除的假说，并建立有利于纤维化的环境；(2)检验PARP-1/PAR解除对Nrf1/2途径的调控并在心脏慢性氧化/炎症状态中发挥关键作用的假说；以及(3)检验抑制PARP-1将在防止心肌病进展方面提供治疗益处的假说。创新之处在于，寄生虫(抗氧化剂)和宿主(PARP-1/Nrf1/2)分子通过心肌细胞中丰富的线粒体相互作用是导致心肌病慢性演变的关键事件。这些研究意义重大，将证明针对寄生虫(抗氧化剂)和宿主(PARP-1/PAR)因子的治疗药物将在治疗急性感染和保护慢性感染患者的心功能方面提供最大益处。 公共卫生相关性：这项建议将阐明克氏毛滴虫感染的致病原因和机制以及心肌病后果，并提供治疗目标，以预防与拉丁美洲流行国家和发达国家的发病率和心力衰竭相关死亡有关的慢性炎症/氧化病理，这些国家的感染者迁徙增加。

DESCRIPTION (provided by applicant): Chagas disease is caused by the protozoan Trypanosoma cruzi, and represents the third greatest tropical disease burden globally. The total annual cost of Chagas disease management is estimated at >8 billion US dollars. The zoonotic presence of parasite and increased population mobility, transmission through blood transfusion, congenital infection and organ transplantation has, in recent years, increased the human cases of Chagas in the US. However, no vaccines or safe drugs are available for treatment of an estimated >300,000 patients in the US and >10 million patients in endemic countries. The studies in this project will identify therapeutic targets for the treatment of Chagasic cardiomyopathy. We pioneer the hypothesis that T. cruzi damages the heart tissue via three distinct mechanisms: (1) iCa+2 stress is caused by invading parasites, which results in alteration of mt membrane potential and initiates reactive oxygen species (ROS) release, (2) direct effects of parasite molecules promote survival of damaged host cells and cellular remodeling, and (3) persistence of inflammation-induced immunopathology, particularly due to reactive oxygen intermediates. These pathways converge, resulting in pathological hypertrophy leading to heart failure. The major preliminary observations that provide support to our hypothesis include (1) T. cruzi expression of antioxidants enhanced parasite virulence, (2) host sustains chronic oxidative/inflammatory stress that was contributory to impaired LV function during the progression of Chagas disease, and (3) ROS induced DNA oxidative adducts and poly(adenosine diphosphate ribose) polymerase 1 (PARP-1) activation signaled inflammatory cytokine response in infected cardiomyocytes. We will employ cutting-edge molecular, biochemical and immunological tools, established in the PI's laboratory, to achieve the following three aims - (1) Test the hypothesis that Tc-antioxidants prevent the normal homeostatic clearance of the damaged cells, and establish an environment conducive to fibrosis, (2) Test the hypothesis that PARP-1/PAR deregulates Nrf1/2 pathway and play a key role in chronic oxidative/inflammatory state of chagasic heart, and (3) Test the hypothesis that inhibition of PARP-1 will provide therapeutic benefits in preventing progression of chagasic cardiomyopathy. The innovation lies in the idea that the interaction of parasite (antioxidants) and host (PARP-1/Nrf1/2) molecules via abundant mitochondria in the cardiomyocytes is the key event resulting in chronic evolution of chagasic cardiomyopathy. These studies are significant and will demonstrate that therapeutic drugs against parasite (antioxidants) and host (PARP-1/PAR) factors will provide the most benefit in treatment of acute infection and preservation of heart function in chronically infected patients. PUBLIC HEALTH RELEVANCE: This proposal will shed light on the cause and mechanisms of pathogenesis and cardiomyopathy outcome of infection by T. cruzi, and provide therapeutic targets to prevent the chronic inflammatory/oxidative pathology that is associated with morbidity and heart failure related deaths in endemic countries in Latin America and developed countries where migration of infected individuals has increased.