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局接受癌症治疗。与 提高许多癌症的存活率，癌症的有害的长期心血管副作用， 治疗变得越来越明显。对于退伍军人中经常发生的许多癌症， 放射治疗（RT）是治疗的一个组成部分。尽管在技术上有所改进， 尽管将RT靶向癌组织，但一些辐射总是到达周围的正常组织。内皮损伤 在小血管内或“放射性内皮病”已被假定为RT的主要原因， 导致正常组织损伤。许多辐射后综合征都归因于辐射 内皮病其中之一是认知能力下降，据估计，这会影响多达90%的患者 在脑RT后。从机制上讲，放射性内皮病被认为是由线粒体损伤引发的， 导致多年的慢性氧化应激和内皮功能障碍。因此， RT的时间对于减少放射性内皮病及其后遗症，包括认知能力下降可能是至关重要的。 有效缓解剂的发现将需要对逆转录病毒相关的途径有一个统一的看法。 线粒体损伤影响该进程中的各个步骤;这一点迄今尚未实现。 该项目的目的是确定线粒体损伤促进细胞凋亡的机制。 放射性内皮病变，并测试是否保护线粒体损伤防止不良的短， RT对小血管的长期影响。RT诱导线粒体DNA损伤，干扰ATP 产生，增强线粒体膜电位，Ca 2+摄取和活性氧（ROS） 生产线粒体Ca 2+单向转运体（MCU）调节Ca 2+摄取到线粒体基质中， 最近被报道为依赖于氧化还原。线粒体Ca 2+增加ROS的产生， 线粒体功能障碍。因此，我们认为内皮细胞中的MCU驱动前馈 与线粒体ROS的回路，导致RT的长期不良影响，包括认知下降后， 事实上，我们实验室发表的数据表明，阻断线粒体Ca 2+摄取是 足以减少线粒体ROS产生并保护EC屏障功能。因此，我们的中央 一种假说认为，线粒体对MCU介导的Ca 2+摄取是过量ROS所必需的， RT后的生产，并因此慢性线粒体DNA损伤，血脑屏障（BBB） 毛细血管损失和认知能力下降。这一假设得到了我们强大的飞行员的进一步支持 在RT期间抑制EC中的MCU在体外消除线粒体DNA损伤并保护线粒体DNA。 体内抗血脑屏障破坏。我们的新工具和分析使我们处于完美的位置， 建议的研究。这些包括遗传模型，其中可以选择性地模拟线粒体Ca 2+摄取 在EC中，最先进的放射设备，体内微血管功能障碍和行为的测定，以及 创新的纳米粒子为基础的工具，选择性地针对内皮细胞在RT的时间。我们的目标是1。解剖 线粒体Ca 2+摄取通过RT驱动内皮损伤的机制，2.测试是否 抑制内皮细胞线粒体Ca 2+摄取可在体内保护RT诱导的损伤; 3. 确定纳米颗粒介导的MCU抑制剂递送保护免受RT的程度。 导致EC损伤。 我们提出研究的理由是，更好地了解辐射机制 内皮病将使有效治疗的发展成为可能。在计划成功完成后，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以作为开发MCU抑制剂的第一步来实施。 放射性内皮病变的有效缓解剂，这将有利于我们的退伍军人。

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.