Citrulline protects against cerebral malaria by reducing metabolic encephalopathy

瓜氨酸通过减少代谢性脑病来预防脑型疟疾

• 批准号: 8771391
• 负责人: Irene Gramaglia
• 金额: $ 29.55万
• 依托单位: LA JOLLA INFECTIOUS DISEASE INSTITUTE
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-05-01 至 2016-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8771391
• 关键词: Abbreviations; Address; Affect; African; Alzheimer' s Disease; Amino Acids; Ammonia; Arginine; Astrocytes; Biological Availability; Biological Markers; Blood; Blood - brain barrier anatomy; Blood Vessels; Brain; Brain Edema; Budgets; Cell Adhesion; Cell Adhesion Molecules; Cerebellum; Cerebral Edema; Cerebral Malaria; Cessation of life; Child; Citrulline; Clinical; Clinical Trials; Coagulation Process; Coma; Complex; Consensus; Cytotoxic Brain Edema; Data; Development; Disease; Dose; Double-Blind Method; Endothelial Cells; Erythrocytes; Exhibits; Falciparum Malaria; Foundations; Functional disorder; Funding; Glutamates; Glutamine; Grant; Hemoglobin; Hepatic; Hepatic Encephalopathy; Hepatomegaly; Homeostasis; Human; Hyperammonemia; Immune response; Immune system; Impairment; Individual; Infection; Infectious Agent; Inflammation; Laboratories; Lactic Acidosis; Lead; Link; Liver; Magnetic Resonance Imaging; Malaria; Metabolic Brain Diseases; Modeling; Molecular; Monitor; Morbidity - disease rate; Mus; Nature; Necrosis; Nitric Oxide; Nitrogen; Parasites; Pathogenesis; Pathologist; Pathway interactions; Patients; Performance; Permeability; Phosphatidylserines; Plasmodium; Plasmodium berghei; Plasmodium falciparum; Posture; Process; Prognostic Marker; Regimen; Reporting; Research Infrastructure; Respiratory distress; Secondary to; Signal Transduction; Swelling; TNF gene; Techniques; Uncertainty; Vasogenic Cerebral Edema; Work; arginase; chemotherapy; hemozoin; improved; in vivo Model; innovation; killings; mortality; nitrosative stress; novel; prevent; public health relevance; restoration; theories; tumor; urea cycle

DESCRIPTION (provided by applicant): Cerebral malaria (CM) pathogenesis is due to a complex interaction between the vascular, coagulation and immune systems, and parasite sequestration. About 30% of cerebral malaria (CM) patients die despite adequate anti-parasite therapy, indicating that the host response contributes to pathogenesis and that these patients can be rescued by adjunctive therapy aimed at ameliorating the host response. The fine molecular details required for the development of such adjunctive therapies, however, remain poorly defined. By using the experimental cerebral malaria (eCM) model, we have observed that both citrulline and arginine administration protects all recipients from eCM mortality. The levels of amino acids in the blood during eCM indicate a profound disruption of the urea cycle, suggesting that metabolic encephalopathy (ME) with hyperammonemia is likely present. Hyperammonemia has also been reported in P. falciparum patients, which in turn may contribute to cerebral edema that MRI findings indicate is a hallmark of CM in African children. ME likely functions in concert with P. falciparum-specific processes to elicit CM and mortality because P. vivax patients also exhibit some degree of ME. We therefore propose a limited exploratory grant to determine (i) whether urea cycle dysregulation in blood and brain are indeed contributing to eCM pathogenesis, and (ii) whether eCM-protective citrulline and arginine ameliorate the urea cycle dysregulation. Due to exploratory nature of this R21 proposal and the limited budget, we will use a single in vivo model of CM (namely, Plasmodium berghei ANKA infection of mice). If a link is established in eCM, then the rationale and preliminary data for an RO1 project will have been established to confirm these findings are relevant to humans, other mechanisms, such as arginine effects on the immune system, are not of greater importance, and the verification in expensive clinical trials of CM patients. Our preliminary data indicate tha citrulline protects against eCM pathogenesis in part by restoring the urea cycle homeostasis, and citrulline is a substrate in the urea cycle. We hypothesize that citrulline and arginine ameliorate the dysregulation of substrates in the urea cycle caused by infection with Plasmodium and thereby prevents ME; ME leads, in part, to the breakdown of the BBB, vascular leak, and ultimately CM. To address this hypothesis, we propose in aim 1 to determine the extent to which the urea cycle is impaired in eCM, and whether this impairment contributes to eCM pathogenesis. We will also assess hallmarks of ME, namely astrocyte swelling, development of Alzheimer type II astrocytes, elevated glutamine and low glutamate levels, elevated ammonia levels, and oxidative/nitrosative stress in the brain and then correlate these hallmarks with eCM pathogenesis. In aim 2, we will ameliorate eCM hypoargininemia by citrulline or arginine administration that protects all recipients from the genesis of eCM and partially restores the blood arginine levels. We will determine whether this amelioration of blood arginine levels partially restores the urea cycle, reduces the toxic levels of ammonia in the brain and hence protects against the development of eCM. These studies are significant because they directly address pathogenic mechanisms of an important but often overlooked disease that kills millions of people and defines the mechanisms to target for a potential adjunctive therapy to rescue those presenting with cerebral malaria from their disease. These studies are pre- translational in that they define new mechanisms in CM pathogenesis that are amenable to adjunctive therapies and define biomarkers to validate the efficacy of potential adjunctive therapy. Even though not required for a R21 grant, we have extensive preliminary data to support our hypothesis, established all techniques in our laboratory, and have the infrastructure necessary for performance of the proposed studies. My malaria group colleagues at LIDI all enthusiastically support my work and transition to independence, which this limited R21 grant will facilitate.

描述(申请人提供)：脑型疟疾(CM)的发病机制是由于血管、凝血和免疫系统以及寄生虫隔离之间的复杂相互作用。尽管进行了适当的抗寄生虫治疗，但仍有约30%的脑型疟疾患者死亡，这表明宿主反应在发病机制中起到了作用，通过旨在改善宿主反应的辅助治疗可以挽救这些患者。然而，开发这种辅助疗法所需的精细分子细节仍然不明确。通过使用实验性脑疟疾(ECM)模型，我们观察到瓜氨酸和精氨酸都能保护所有受体免受ECM死亡。ECM期间血液中的氨基酸水平表明尿素循环受到严重破坏，提示可能存在伴有高氨血症的代谢性脑病(ME)。恶性疟原虫患者也有高氨血症的报道，这反过来可能导致脑水肿，MRI结果表明这是非洲儿童CM的一个特征。由于间日疟患者也表现出一定程度的ME，ME可能与恶性疟原虫特异的过程协同作用，导致CM和死亡率。因此，我们提出了一项有限的探索性拨款，以确定(I)血液和脑内尿素循环失调是否确实有助于ECM的发病，以及(Ii)ECM保护性瓜氨酸和精氨酸是否改善尿素循环失调。由于R21提案的探索性和有限的预算，我们将使用单一的CM体内模型(即伯氏疟原虫和小鼠感染)。如果在ECM中建立了链路，则 RO1项目将被建立，以确认这些发现与人类相关，其他机制，如精氨酸对免疫系统的影响，并不是更重要的，以及在昂贵的CM患者临床试验中的验证。我们的初步数据表明，瓜氨酸部分通过恢复尿素循环的动态平衡来预防ECM的发病，而瓜氨酸是尿素循环的底物。我们假设，瓜氨酸和精氨酸改善了由疟原虫感染引起的尿素循环中底物的失调，从而防止了ME；ME在一定程度上导致BBB的崩溃，血管泄漏，并最终导致CM。为了解决这一假设，我们在目标1中建议确定ECM中尿素循环受损的程度，以及这种损害是否有助于ECM的发病。我们还将评估ME的特征，即星形胶质细胞肿胀、阿尔茨海默病II型星形胶质细胞的发展、谷氨酰胺和低谷氨酸水平的升高、脑内氨水平的升高以及氧化/亚硝化应激，然后将这些特征与ECM的发病机制联系起来。在目标2中，我们将通过给予瓜氨酸或精氨酸来改善ECM低精氨酸血症，以保护所有受者免受ECM的发生，并部分恢复血液精氨酸水平。我们将确定这种血液精氨酸水平的改善是否部分恢复了尿素循环，降低了大脑中氨的有毒水平，从而防止了ECM的发展。这些研究意义重大，因为它们直接解决了一种重要但经常被忽视的疾病的致病机制，并确定了潜在的辅助治疗的靶向机制。 把那些患有脑型疟疾的人从疾病中解救出来。这些研究是翻译前的，因为它们定义了CM发病机制中适用于辅助治疗的新机制，并定义了生物标记物来验证潜在的辅助治疗的疗效。尽管不需要R21拨款，但我们有大量的初步数据来支持我们的假设，在我们的实验室建立了所有技术，并拥有执行拟议研究所需的基础设施。我在LIDI的疟疾小组同事都热情地支持我的工作和向独立的过渡，这笔有限的R21赠款将促进这一点。