Mechanism of hypoxia mediated radiation lung injury

描述（由申请方提供）：不可接受的辐射（RT）诱导的肺损伤风险仍然是当前治疗累及胸部区域肿瘤的重要限制因素。尽管正常组织放射生物学的进展表明，电离辐射触发了一系列导致肺损伤的遗传和分子事件，但仍不清楚如何在辐射结束后数月至数年内持续对损伤的长期反应。这种对RT诱导的肺损伤机制的理解不足阻碍了适当的干预方法的发展，以防止这一严重问题。目前的建议是基于我们最近的发现，涉及缺氧作为一个重要的促进因素，在RT诱导的肺损伤的发展。我们认为缺氧是由两个因素引起的：1）活化的巨噬细胞的耗氧量增加，并伴随活性氧（ROS）和细胞因子的产生，2）由于血管损伤导致灌注减少，组织的氧输送减少。我们假设缺氧介导了一个循环的连续，巨噬细胞相关的生产的ROS和表达/激活的profibroqenic和proanqioqenic细胞因子。该过程导致血管生成的失调、内皮细胞死亡和胶原沉积，这导致持续缺氧，其进一步加重肺组织损伤和纤维化。本研究的目的是确定肺照射后缺氧的时间起始。并确定缺氧与巨噬细胞活性的关系（ROS和细胞因子的产生）和血管损伤。将使用EF 5缺氧标志物测定肺缺氧。将通过免疫组织化学评估巨噬细胞活化。将使用电子自旋共振（ESR）光谱和自旋捕获检测ROS。放射性核素灌注测定将用于评估肺灌注。在描述RT后缺氧、巨噬细胞活化和血管损伤之间的关系后，我们将试图以两种方式破坏这种损伤循环。首先，ROS将被超氧化物歧化酶（SOD）模拟物直接靶向。第二，ROS介导的损伤将通过用氯化钆（GdCl 3）抑制巨噬细胞活性来间接靶向。如果成功，该项目可能直接导致临床适用策略的发展，以降低RT诱导的肺损伤的风险，试图允许向胸部肿瘤输送更高剂量的辐射，而不增加肺部并发症的风险。

DESCRIPTION (provided by applicant): The risk of unacceptable radiation (RT)-induced lung injury remains a significant limiting factor in the current treatment of the tumors involving the thoracic region. Despite advances in normal tissue radiobiology demonstrating that ionizing radiation triggers a cascade of genetic and molecular events, which lead to pulmonary injury, it is still unclear how a prolonged response to injury can be sustained for months to years after irradiation has ended. This deficiency in understanding of the mechanisms of RT-induced lung injury has hindered the development of appropriate interventional approaches to prevent this serious problem. The current proposal is based on our recent finding implicating hypoxia as an important contributing factor in the development of RT-induced pulmonary injury. We believe that hypoxia results from two factors: 1) increased oxygen consumption by activated macrophages with associated production of reactive oxygen species (ROS) and cytokines, and 2) decreased oxygen delivery to tissue due to vascular damage causing reduced perfusion. We hypothesize that hypoxia mediates a cycle of continuous, macrophage-associated production of ROS and expression/activation of profibroqenic and proanqioqenic cytokines. This process leads to l disre.qulation of angiogenesis, endothelial cell death, and collagen deposition which result in sustained hypoxia that I_erpetuates further pulmonary tissue damage and fibrosis, The goal of this study is to determine the I temporal onset of hypoxia after lung irradiation, and to define how hypoxia relates to macrophage activity (the production of ROS and cytokines) and vascular damage at different time points after irradiation. Lung hypoxia will be determined using the EF5 hypoxia marker. Macrophage activation will be assessed by immunohistochemistry. ROS will be detected using electron spin resonance (ESR) spectroscopy and spin trapping. A radionuclide perfusion assay will be used to assess pulmonary perfusion. After characterizing the relationship between hypoxia, macrophage activation and vascular damage following RT we will attempt to disrupt this injury cycle in two ways. First, ROS will be targeted directly with superoxide dismutase (SOD) mimetics. Second, ROS mediated injury will be targeted indirectly by inhibiting macrophage activity with gadolinium chloride (GdCI3). If successful, this project may lead directly to the development of clinically applicable strategies to reduce the risk of RT-induced lung injury in an attempt to permit delivery of higher doses of radiation to thoracic tumors without increasing the risk of pulmonary complications.