Exosomes - novel mediators of direct and bystander radiation effects on the brain

我的NSERC项目的首要目标是了解生物（哺乳动物）如何在分子水平上对低剂量电离辐射做出反应，并确定小泡（外泌体）在辐射反应中的作用，重点是哺乳动物的大脑辐射反应。背景：该计划是基于我们最近的基础研究，这些研究已经改变了辐射生物学的范式，并证明了大脑对低剂量辐射（LDR）暴露高度敏感。最近，我们报道了头部LDR暴露导致受辐射动物前额皮质DNA损伤和基因表达的影响。我们也证明了肝辐照后大脑中存在旁观者效应。头部和肝脏照射均降低了脊柱密度、树突复杂性和树突长度，并改变了行为。此外，分级暴露还会导致DNA损伤，改变整体基因组甲基化并诱导行为改变。虽然已经报道了大脑中直接和旁观者LDR效应的发生，但这一现象的分子机制尚未得到研究。细胞释放大量的微囊泡，包括被称为外泌体的纳米颗粒（50100纳米），进入细胞外空间。外泌体可能在辐射暴露引起的一系列脑副作用中起重要作用。理论和假设：在这里，我们假设外泌体可能参与体内的直接和旁观者辐射效应，并提出了一种新的LDR脑现象的外泌体理论，即LDR对大脑影响的机制是通过外泌体信号传导介导的。为了验证我们的理论，我们提出了以下假设：直接和旁观者LDR暴露会影响脑和血液中的外泌体特征，并影响外泌体货物。外泌体信号与体内LDR对大脑的影响有关，外泌体构成真正的旁观者信号。环境富集将至少部分逆转ldr诱导的外泌体介导效应。我将聘请一组受训人员，我们将首次分析ldr暴露大鼠的大脑和血清中的外泌体，并将它们与未治疗动物的外泌体进行比较。我们将共同分析外泌体的DNA， RNA，小RNA和蛋白质含量，并将尝试通过应用新的环境富集技术来积极改变外泌体模式来减轻LDR对大脑的影响。预期结果：这项研究和培训计划致力于LDR对大脑的生物学效应的基础研究。它将解决一个根本性的重要问题：小剂量的LDR对生物体是否有危险？它们是否会影响大脑？生物体是否能够适应环境中的LDR暴露？了解暴露的细胞和生物体中发生的分子变化可能有助于制定预防低致病性辐射有害影响的措施。

The overarching goal of my NSERC program is to understand how organisms (mammals) respond to low-dose ionising radiation on a molecular level and to determine the role of small vesicles (exosomes) in radiation responses, with a focus on mammalian brain radiation responses.Background: The program is based on our most recent fundamental studies that have shifted the paradigm of radiation biology and proved that the brain is highly sensitive to low dose radiation (LDR) exposure. Recently, we reported that head LDR exposure induced DNA damage and affected gene expression in the prefrontal cortex of irradiated animals. We also proved that bystander effects exist in the brain after liver irradiation. Both head and liver irradiation reduced spine density, dendritic complexity and dendritic length and altered behavior. Moreover, fractionated LDR exposure also caused DNA damage, altered global genomic methylation and induced behavioral changes.While the occurrence of direct and bystander LDR effects in the brain was reported, the molecular mechanisms of this phenomenon are under-investigated. Cells release a wide array of microvesicles, including nanoparticles (50100 nm) called exosomes, into the extracellular space. Exosomes may be important in a wide array of brain side effects of radiation exposure.Theory and Hypotheses: Here, we hypothesise that exosomes may be involved in direct and bystander radiation effects in vivo and propose a new exosomal theory of the LDR brain phenomenon, whereby the mechanisms that underlie the LDR's effects on the brain are mediated via exosomal signaling.The following hypotheses are proposed to test our theory:1. Direct and bystander LDR exposures affect exosome profiles in the brain and blood and influence exosome cargo.2. Exosome signaling is implicated in LDR effects in vivo on the brain and exosomes constitute bona fide bystander signals.3. Environmental enrichment will at least partly reverse the LDR-induced exosome-mediated effects.I will engage a team of trainees who we will for the first time analyse exosomes in the brains and serum of LDR-exposed rats and compare them with the exosomes of untreated animals. Together, we will analyse DNA, RNA, small RNA and protein content of the exosomes, and will attempt to mitigate the effects of LDR on the brain by applying novel environmental enrichment techniques to positively alter exosome patterns.Expected outcomes: This research and training program is devoted to fundamental studies on the biological effects of LDR on the brain. It will address a fundamentally important issue: are small doses of LDR dangerous for living organisms, do they affect the brain, and are organisms capable of adapting to environmental LDR exposures? Understanding the molecular changes that occur in exposed cells and organisms may assist in the development of measures to prevent the deleterious effects of LDR.