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

我的NSERC计划的总体目标是在分子水平上了解生物(哺乳动物)对低剂量电离辐射的反应，并确定小囊泡(外体)在辐射反应中的作用，重点是哺乳动物的脑辐射反应。背景：该计划基于我们最近的基础研究，这些研究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照射引起受照动物前额叶皮质DNA损伤并影响基因表达。我们还证实了肝脏照射后脑内存在旁观者效应。头部和肝脏照射都降低了脊椎密度、树突复杂性和树突长度，并改变了行为。此外，分段式LDR暴露还会引起DNA损伤，改变整体基因组甲基化，并诱导行为改变。虽然有报道称在大脑中发生了直接和旁观者的LDR效应，但这种现象的分子机制尚未得到充分的研究。细胞向细胞外空间释放大量的微囊，包括被称为外体的纳米颗粒(50100 Nm)。理论和假设：在此，我们假设外切体可能参与体内的直接和旁观者辐射效应，并提出了一种新的外切体理论，即LDR对大脑的影响的机制是通过外切体信号介导的。提出了以下假设来验证我们的理论：1.直接和旁观者LDR暴露影响脑和血液中的外切体轮廓，并影响外切体的运输。Exosome信号与体内LDR对脑的影响有关，Exosome构成了真正的旁观者信号。环境浓缩将至少部分逆转LDR诱导的外切体介导的效应。我将聘请一个受训团队，他们将首次分析暴露于LDR的大鼠大脑和血清中的外切体，并将它们与未经处理的动物的外切体进行比较。我们将一起分析外切体的DNA、RNA、小RNA和蛋白质含量，并将尝试通过应用新的环境浓缩技术来积极改变外切体模式来减轻LDR对大脑的影响。预期结果：该研究和培训计划致力于LDR对大脑的生物效应的基础研究。它将解决一个根本性的重要问题：小剂量的LDR对生物是否危险，它们是否影响大脑，以及生物是否能够适应环境的LDR暴露？了解暴露在细胞和生物体中发生的分子变化可能有助于制定预防LDR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.