Mechanism of hypoxia mediated radiation lung injury

描述（由申请人提供）：不可接受的放射（RT）引起的肺损伤的风险仍然是目前治疗累及胸部区域肿瘤的一个重要限制因素。尽管正常组织放射生物学的进展表明，电离辐射引发一系列遗传和分子事件，从而导致肺损伤，但目前尚不清楚如何在辐射结束后持续数月至数年对损伤的长期反应。对rt诱导的肺损伤机制的理解不足阻碍了适当介入方法的发展，以防止这一严重问题。目前的建议是基于我们最近的发现，即缺氧是rt诱导肺损伤发展的一个重要因素。我们认为，缺氧是由两个因素引起的：1)激活的巨噬细胞消耗的氧气增加，同时产生活性氧（ROS）和细胞因子；2)由于血管损伤导致灌注减少，向组织输送的氧气减少。我们假设缺氧介导了一个连续的、巨噬细胞相关的ROS产生和促纤维原细胞因子和促纤维原细胞因子的表达/激活周期。这一过程导致了痛苦。本研究的目的是确定肺照射后缺氧的时间开始，并确定缺氧与照射后不同时间点巨噬细胞活性（ROS和细胞因子的产生）和血管损伤之间的关系。肺缺氧将使用EF5缺氧标志物来确定。巨噬细胞活化将通过免疫组织化学评估。ROS将通过电子自旋共振（ESR）光谱和自旋捕获来检测。放射性核素灌注试验将用于评估肺灌注。在描述了缺氧、巨噬细胞激活和RT后血管损伤之间的关系后，我们将尝试通过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。其次，通过氯化钆（gadolinium chloride, GdCI3）抑制巨噬细胞活性，可以间接靶向ROS介导的损伤。如果成功，该项目可能直接导致临床应用策略的发展，以降低rt诱导肺损伤的风险，并试图在不增加肺部并发症风险的情况下向胸部肿瘤提供更高剂量的辐射。

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.