Alveolar macrophage apoptosis and Pneumocystis

描述(申请人提供)：卡氏肺孢子虫(人类疾病中的吉罗维氏肺孢子虫)会在免疫功能受损的人中引起严重肺炎，如艾滋病患者。肺孢子虫肺炎患者肺泡巨噬细胞数量减少。在大鼠和小鼠PEP模型中，肺泡巨噬细胞数量减少约60%，主要原因是肺泡巨噬细胞凋亡率增加。在PEP过程中，肺泡和肺泡巨噬细胞中的多胺(亚精胺、乙酰精胺和乙酰亚精胺)水平显著增加。肺泡灌洗液(BAL)能诱导正常肺泡巨噬细胞的凋亡，而这些BAL液中多胺的耗竭使其丧失了诱导细胞凋亡的能力。这项建议将使用类固醇免疫抑制的大鼠和L3T4细胞耗尽的小鼠来检验这一假设，即肺泡巨噬细胞的凋亡直接由多胺引起，或间接由多胺分解代谢产生的活性氧引起。将进行实验以确定PEP期间肺泡和肺泡巨噬细胞中存在的多胺是否来自肺孢子虫、肺泡巨噬细胞和/或肺上皮细胞。将确定诱导肺泡巨噬细胞凋亡所需的每种特定多胺的水平。还将评估肺泡巨噬细胞摄取多胺的变化。将研究活性氧物种水平增加与多胺之间的关系。将识别参与细胞凋亡的促凋亡和抗凋亡因子，并研究多胺对这些因子表达和活性的影响。将通过确定改变线粒体膜电位导致细胞色素c释放到细胞质中的因素以及死亡受体及其配体在细胞凋亡中的作用来研究外在和内在(线粒体)细胞凋亡途径的参与。下调抗凋亡因子对肺泡巨噬细胞对多胺介导的肺泡巨噬细胞、肺孢子虫诱导的凋亡的抵抗力的影响也将被研究。由于在大鼠和小鼠的初步研究表明，抑制肺泡巨噬细胞的凋亡可以减缓疾病的进展，甚至可以解决感染，因此拟议的研究可能会导致治疗肺孢子虫肺炎的新方法。

DESCRIPTION (provided by applicant): Pneumocystis carinii (P. jiroveci in human disease) causes a severe pneumonia in immunocompromised individuals, such as those with AIDS. The number of alveolar macrophages is decreased in humans with Pneumocystis pneumonia (Pep). In rat and mouse Pep models, alveolar macrophage number is decreased by approximately 60% mainly due to the increased rate of apoptosis in alveolar macrophages. During Pep, polyamine (spermidine, acetylspermine, and acetylspermidine) levels are greatly increased in the alveoli and alveolar macrophages. Bronchoalveolar lavage (BAL) fluids from animals with Pep are able to induce apoptosis in normal alveolar macrophages, and depletion of polyamines from these BAL fluids abrogates their ability to induce apoptosis. This proposal will use steroid-immunosuppressed rats and L3T4 cell- depleted mice to test the hypothesis that alveolar macrophages apoptosis is caused directly by polyamines or indirectly by reactive oxygen species that are generated as the result of polyamine catabolism during Pep. Experiments will be performed to determine whether the polyamines present in the alveoli and alveolar macrophage during Pep are derived from Pneumocystis organisms, alveolar macrophages, and/or lung epithelial cells. The levels of each specific polyamine needed to induce apoptosis in alveolar macrophages will be determined. Changes in polyamine uptake by alveolar macrophages will also be assessed. The relationship between increased levels of reactive oxygen species and polyamines will be investigated. Pro- and anti-apoptosis factors that are involved in the apoptosis will be identified, and effects of polyamines on the expression and the activity of these factors will be investigated. The involvement of extrinsic and intrinsic (mitochondrial) apoptosis pathways will be studied by identifying factors that alter mitochondrial membrane potential leading to release of cytochrome c to the cytoplasm and the contribution of death receptors and their ligands to the apoptosis. Effects of down regulation of anti-apoptotic factors on the resistance of alveolar macrophage to polyamine-mediated, Pneumocystis-induced apoptosis will also be investigated. Since preliminary studies in both rats and mice with Pep indicate that inhibition of apoptosis in alveolar macrophages ameliorates disease progression or even resolves the infection, the proposed studies may lead to new treatments for Pneumocystis pneumonia.