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当前治疗胸部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，电离辐射会触发一系列遗传和分子事件，从而导致肺损伤，但目前仍不清楚，在辐射结束后，对损伤的长期反应如何能够持续数月至数年。由于缺乏对放射治疗所致肺损伤机制的了解，阻碍了预防这一严重问题的适当介入方法的发展。目前的建议是基于我们最近的发现，即低氧是导致RT诱导的肺损伤的一个重要因素。我们认为缺氧是由两个因素造成的：1)激活的巨噬细胞消耗的氧气增加，并伴随着活性氧物种(ROS)和细胞因子的产生；2)由于血管损伤导致组织的氧输送减少，导致灌注量减少。我们假设，低氧介导了巨噬细胞相关的ROS的持续产生以及纤维原和原细胞因子的表达/激活。这一过程导致L紊乱血管生成、内皮细胞死亡和胶原沉积，导致持续低氧，从而进一步促进肺组织损伤和纤维化。本研究的目的是确定肺照射后一过性低氧的发生时间，并确定低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)和血管损伤的关系。肺缺氧将使用EF5缺氧标志物来确定。巨噬细胞的活化将通过免疫组织化学进行评估。ROS将使用电子自旋共振(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血流灌注。在确定了低氧、巨噬细胞激活和放疗后血管损伤之间的关系之后，我们将尝试通过两种方式来破坏这一损伤循环。首先，ROS将直接以超氧化物歧化酶(SOD)模拟物为靶点。第二，ROS介导的损伤将通过用GdCl3抑制巨噬细胞的活性来间接靶向。如果成功，该项目可能直接导致临床适用的策略的开发，以降低放射治疗引起的肺损伤的风险，试图允许向胸部肿瘤提供更高剂量的辐射，而不会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.