Imaging Activated Macrophages in the Lungs

描述（由申请人提供）：肺巨噬细胞在启动对微生物和环境刺激的先天免疫反应，解决急性炎症和促进损伤后修复方面至关重要。持续或失调的巨噬细胞激活在多种肺部疾病的发病机制中起重要作用；然而，研究人类肺部疾病中多效巨噬细胞群的表型由于目前需要获得足够数量的细胞的侵入性方法而变得复杂。非侵入性鉴定活化巨噬细胞的新方法的发展有助于提高对炎症性肺部疾病的理解和治疗选择。炎症部位的巨噬细胞亚群表达高水平的叶酸受体？(FR吗?)我们在小鼠中的初步数据表明FR？在正常、静止的肺中不表达，但在气管内或全身用大肠杆菌脂多糖（LPS）治疗后，在巨噬细胞亚群中特异性上调。我们还鉴定了FR？肺巨噬细胞在支气管肺发育不良（BPD）、肺纤维化和慢性肺阻塞性疾病（COPD）小鼠模型中的表达。此外，我们发现COPD、特发性肺纤维化（IPF）和BPD患者的肺巨噬细胞表达FR？而在健康人巨噬细胞中表达量极少。基于该受体的表达，我们发现我们可以使用叶酸衍生物与荧光探针结合，在小鼠肺中成像活化的巨噬细胞。在这项提议中，我们假设发展分子成像技术来识别活化巨噬细胞的功能亚群，将促进对炎症性肺部疾病的理解，并可能导致新的巨噬细胞靶向治疗。虽然我们的初步研究采用了光学成像技术，但为了适用于人类，我们计划开发正电子发射断层扫描（PET）技术来成像活化的肺巨噬细胞。具体目标是：1)识别和表征活化肺巨噬细胞上存在的特定细胞表面标记物；2)验证临床前成像方法，以观察体内巨噬细胞的活化；3)开发基于pet的体内活化肺巨噬细胞成像策略。总之，这些研究将优化基于FR？活化巨噬细胞表面新成像靶点的表达与探索。这些新策略可以应用于人类炎症性肺病的研究。

DESCRIPTION (provided by applicant): Lung macrophages are critical for initiating the innate immune response to microbial and environmental stimuli, resolving acute inflammation, and promoting repair following injury. Persistent or dysregulated macrophage activation plays an important role in the pathogenesis of multiple lung diseases; however, studying the phenotype of the pleiotropic macrophage population in human lung disease is complicated by the invasive methods currently required to obtain sufficient quantities of cells. Development of new methodologies to non- invasively identify activated macrophages could facilitate improved understanding and treatment options for inflammatory lung diseases. A subset of macrophages at sites of inflammation expresses high levels of the folate receptor ? (FR?). Our preliminary data in mice demonstrate that FR? is not expressed in normal, quiescent lungs but is up-regulated specifically in a subset of macrophages after intratracheal or systemic treatment with E. coli lipopolysaccharide (LPS). We also identified FR? expression in lung macrophages in mouse models of bronchopulmonary dysplasia (BPD), lung fibrosis, and chronic pulmonary obstructive disease (COPD). Further, we found that lung macrophages from humans with COPD, idiopathic pulmonary fibrosis (IPF), and BPD express FR?, whereas expression in healthy human macrophages is minimal. Based on expression of this receptor, we have found that we can image activated macrophages in mouse lungs using a folate derivative conjugated with a fluorescent probe. In this proposal, we hypothesize that developing molecular imaging techniques to identify functional subsets of activated macrophages will advance understanding of inflammatory lung diseases and could lead to novel, macrophage-targeted therapies. Although our preliminary studies have employed optical imaging techniques, for applicability to humans we plan to develop positron emission tomography (PET) techniques to image activated lung macrophages. Specific aims are to: 1) identify and characterize specific cell-surface markers present on activated lung macrophages, 2) validate pre-clinical imaging approaches to visualize macrophage activation in vivo, and 3) develop PET-based strategies for imaging activated lung macrophages in vivo. Together, these studies will optimize imaging probes based on FR? expression and explore new imaging targets present on the surface of activated macrophages. These new strategies can then be applied to the study of inflammatory lung diseases in humans.