Leveraging mitochondrial function to combat radiation therapy-induced microvascular disease

大约20万退伍军人在退伍军人健康管理机构接受癌症治疗。使用 提高许多癌症的存活率，癌症对心血管的长期有害副作用 治疗方法已经变得越来越明显。对于退伍军人中经常发生的许多癌症， 放射治疗(RT)是治疗中不可或缺的组成部分。尽管在技术上有所改进，但 靶向RT的肿瘤组织，一些辐射总是到达周围的正常组织。内皮损伤 小血管内或“放射性内皮病”一直被认为是RT的主要原因- 致正常组织损伤。许多辐射后综合征都被归因于辐射 内皮病。其中之一是认知能力下降，据估计，多达90%的患者会受到影响 脑放疗后。从机制上讲，放射性内皮病变被认为是由线粒体损伤引起的， 导致多年的慢性氧化应激和内皮功能障碍。因此，在 放射治疗的时间可能对减少放射性内皮病变及其后遗症，包括认知功能下降至关重要。 发现有效的缓释剂将需要对RT相关的途径有一个统一的看法 线粒体损伤影响了这一进程的各个步骤，但到目前为止还没有实现这一点。 该项目的目标是确定线粒体损伤促进作用的机制。 放射性内皮病变，并测试线粒体损伤的保护是否防止不良的短暂性和 放射治疗对小血管的远期疗效。RT诱导线粒体DNA损伤，扰乱ATP 产生，提高线粒体膜电位、钙摄取和活性氧(ROS) 制作。线粒体钙单转运体(MCU)调节线粒体基质对钙的摄取，并 最近被报道为氧化还原依赖。线粒体Ca~(2+)增加ROS生成促进 进一步的线粒体功能障碍。因此，我们假设内皮细胞(ECs)中的MCU驱动前馈 线粒体ROS回路，导致RT的长期不良影响，包括认知功能下降 脑RT。事实上，我们实验室公布的数据表明，阻止线粒体钙摄取 足以减少线粒体ROS的产生，保护EC屏障功能。因此，我们的中央 假设MCU介导的线粒体钙摄取是过量ROS所必需的 RT后产生，从而用于慢性线粒体DNA损伤，血脑屏障(BBB) 精神崩溃，毛细血管丢失，认知能力下降。这一假设得到了我们强大的飞行员的进一步支持 在RT过程中抑制ECs中MCU可消除体外线粒体DNA损伤并保护作用 在体内防止血脑屏障的分解。我们新颖的工具和分析方法使我们处于完美的位置，可以执行 建议的研究。其中包括可以选择性地模拟线粒体钙摄取的遗传模型。 在ECs中，最先进的放射设备，微血管功能障碍和活体行为的分析，以及 创新的基于纳米颗粒的工具，用于在RT时选择性地靶向内皮细胞。我们的目标是：1.剖析 线粒体钙摄取驱动内皮细胞损伤机制的RT，2.检验 抑制内皮细胞线粒体钙摄取对RT诱导的在体损伤具有保护作用。 确定纳米颗粒介导的MCU抑制剂对RT-R的保护程度 致内皮细胞损伤。 我们提议的研究的基本原理是，对辐射机制的更好的理解 内皮病将使有效治疗的发展成为可能。当工程顺利完成后，我们会 已经建立了MCU促进辐射后线粒体损伤的机制，以及如何 MCU抑制剂的内皮选择性递送可能是迈向开发的第一步 有效缓解放射性内皮病，将使我们的退伍军人受益。

Approximately 200,000 veterans receive cancer treatment at Veterans Health Administration facilities. With improving survival rates for many cancers, the deleterious long-term cardiovascular side effects of cancer therapies have become increasingly apparent. For many of the cancers that frequently occur among veterans, radiation therapy (RT) is an integral component of treatment. Despite improvements in the techniques used to target RT to the cancer tissue, some radiation always reaches surrounding normal tissue. Endothelial damage within the small blood vessels or “radiation endotheliopathy” has been postulated as a major cause of RT- induced injury of normal tissue. Many post-radiation syndromes have been attributed to radiation endotheliopathy. One of them is cognitive decline, which is estimated to affect as many as 90% of patients after brain RT. Mechanistically, radiation endotheliopathy is believed to be initiated by mitochondrial injury, leading to chronic oxidative stress and endothelial dysfunction over a period of years. Thus, intervention at the time of RT is likely critical for reducing radiation endotheliopathy and its sequelae, including cognitive decline. The discovery of effective mitigators will require a unified view of the pathways by which RT-related mitochondrial injury influences various steps in this progression; this has not been achieved to date. The objective of the proposed project is to identify the mechanisms by which mitochondrial injury promotes radiation endotheliopathy, and to test whether protection from mitochondrial injury prevents adverse short- and long-term effects of RT in small blood vessels. RT induces mitochondrial DNA damage, perturbs ATP production, enhances the mitochondrial membrane potential, Ca2+ uptake and reactive oxygen species (ROS) production. The mitochondrial Ca2+ uniporter (MCU) regulates Ca2+ uptake into the mitochondrial matrix and was recently reported as being redox-dependent. Mitochondrial Ca2+ augments ROS production that promotes further mitochondrial dysfunction. Thus, we posit that MCU in endothelial cells (ECs) drives a feed-forward circuit with mitochondrial ROS that leads to long-term adverse effects of RT, including cognitive decline after brain RT. Indeed, published data from our laboratory demonstrate that blocking mitochondrial Ca2+ uptake is sufficient to reduce mitochondrial ROS production and protect EC barrier function. Thus, our central hypothesis is that MCU-mediated Ca2+ uptake by mitochondria is required for excessive ROS production after RT, and thus for chronic mitochondrial DNA damage, blood brain barrier (BBB) breakdown, capillary loss, and cognitive decline. This hypothesis is further supported by our strong pilot data that inhibition of MCU in ECs during RT abolishes mitochondrial DNA damage in vitro and protects against BBB breakdown in vivo. Our novel tools and assays put us in the perfect position to perform the proposed study. These include genetic models in which mitochondrial Ca2+ uptake can be modeled selectively in ECs, state-of-the-art radiation equipment, assays of microvessel dysfunction and behavior in vivo, and innovative nanoparticle-based tools for selectively targeting ECs at the time of RT. Our aims are to 1. dissect the mechanisms by which mitochondrial Ca2+ uptake drives endothelial injury by RT, 2. test whether inhibition of mitochondrial Ca2+ uptake in ECs protects against RT-induced injury in vivo and 3. determine the extent to which nanoparticle-mediated delivery of MCU inhibitors protects against RT- induced EC injury. The rationale of our proposed studies is that an improved understanding of the mechanisms of radiation endotheliopathy will enable the development of effective therapies. Upon its successful completion, we will have established mechanisms by which MCU promotes mitochondrial injury after radiation, and how endothelial-selective delivery of an MCU inhibitor might be implemented as a first step towards developing effective mitigators of radiation endotheliopathy that will benefit our veterans.