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

* 我的NSERC计划的首要目标是了解生物体（哺乳动物）如何在分子水平上对低剂量电离辐射作出反应，并确定小泡（外泌体）在辐射反应中的作用，重点是哺乳动物脑辐射反应。背景资料：该计划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，并证明大脑对低剂量辐射（LDR）暴露高度敏感。最近，我们报道了头部低剂量辐射暴露诱导的DNA损伤和影响基因表达的前额叶皮层的辐射动物。我们还证实了肝照射后脑内存在旁观者效应。头部和肝脏照射降低了棘密度，树突的复杂性和树突的长度和改变的行为。此外，分次LDR暴露也会导致DNA损伤，改变整体基因组甲基化并诱导行为变化。虽然报道了脑中直接和旁观者LDR效应的发生，但该现象的分子机制尚未研究。细胞释放大量的微泡，包括称为外泌体的纳米颗粒（50-100 nm），进入细胞外空间。外泌体可能在辐射暴露的一系列大脑副作用中很重要。理论与假设：在这里，我们假设外泌体可能参与体内直接和旁观者辐射效应，并提出了LDR脑现象的新外泌体理论，其中LDR对脑的影响的机制是通过外泌体信号传导介导的。本文提出了以下假设来检验我们的理论：*1。直接和旁观者LDR暴露影响脑和血液中的外泌体概况并影响外泌体货物。2.外泌体信号传导与脑的体内LDR效应有关，外泌体构成真正的旁观者信号。3.环境富集将至少部分逆转LDR诱导的外来体介导的效应。我将聘请一个培训生团队，我们将首次分析暴露于LDR的大鼠大脑和血清中的外泌体，并将其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，并试图通过应用新的环境富集技术积极改变外泌体模式来减轻LDR对大脑的影响。预期成果：该研究和培训计划致力于低剂量辐射对大脑生物学效应的基础研究。它将解决一个根本性的重要问题：小剂量的低剂量辐射对生物体是否危险，它们是否影响大脑，生物体是否能够适应环境低剂量辐射暴露？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 (50–100 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.***