(PQ9) Directed and unbiased studies of synaptic injuries as sequelae of radiotherapy: mapping, sex-dependence, and reversal

摘要 脑癌是一个可怕的诊断，代表了相对较大的儿童癌症部分，但 由于治疗方面的巨大进步，儿童的存活率现在超过80%。这些积极的临床 结果需要使用放射治疗（RT），但与其他治疗方式一样，RT会导致显著的长期- 长期神经认知后遗症不仅影响癌症幸存者，而且影响他们的护理网络， 社会接受RT治疗脑癌的成年人也有类似的症状， 改善或消除RT的神经认知效应。理论上，RT诱导的脑损伤更容易 治疗比其他脑损伤，鉴于损伤的时间是已知的，预处理是可行的。然而，在这方面， RT诱导的脑损伤的性质不清楚是这样做的主要障碍。放射治疗诱导脑损伤的研究 损伤集中在分裂的神经前体（NP）细胞上，从这些细胞中产生一小部分出生后的“成年- “天生”神经元产生于齿状回，因为海马体（齿状回是海马体的一部分） 对辐射特别敏感。当然，NP细胞损伤有助于RT诱导的后遗症。然而，在这方面， 我们和其他人最近发现，终末分化的神经元，长期以来被认为是抵抗 辐射，经历突触改变以响应辐射。这一观察对以下方面具有重大意义： 治疗放射治疗引起的后遗症，因为它表明，损害可能发生在整个 大脑，而不限于出生后神经元形成的小的、离散的部位。在这份提案中，我们提出 我们关于这一现象的最新数据显示，治疗剂量的辐射导致异位 突触发生和突触增强在RT的1小时内。女性比男性更受此影响 损伤和抑制谷氨酸信号既阻止突触扩张， 突触丧失然而，许多问题仍然没有答案：损伤的局部程度如何？伤口是否 传播沿着神经回路？大脑的某些区域是否更容易受到伤害？如何 这些参数是否受接受RT的个体的性别影响？RT介导的突触缺陷 逆转？这些都是至关重要的问题，需要合理设计治疗方法来解决 RT诱发的神经认知后遗症。我们建议定义急性RT诱导的突触损伤的性质， 通过（i）使用用于神经元的荧光探针在小鼠脑中创建RT介导的突触损伤的图谱， 活动和突触增强，先进的成像技术和多维分析，（ii）测试 年龄和性别对受试者对RT的反应的影响，和（iii）操纵细胞信号传导以试图 逆转RT介导的突触损伤。我们提出了一种新颖的多学科方法来解剖 RT介导的突触损伤在分子、突触、细胞和生物体上的性质，即行为， 程度.这一翻译提案的结果有可能极大地、积极地影响 所有年龄段的癌症幸存者，我们的技术可以用来研究其他类型的脑损伤。

Abstract Brain cancer is a terrifying diagnosis representing a relatively large segment of childhood cancer, yet thanks to great advances in treatment, survival rates among children now exceed 80%. These positive clinical outcomes require the use of radiotherapy (RT), but like other treatment modalities, RT causes significant long- term neurocognitive sequelae impacting not only cancer survivors, but also their caregiver networks and society. Adults receiving RT for brain cancers also suffer similar symptoms and would benefit from the amelioration or elimination of the neurocognitive effects of RT. In theory, RT-induced brain injury is easier to treat than other brain injuries, given that the time of injury is known and pretreatment is feasible. However, the unclear nature of RT-induced brain damage is a major obstacle to doing so. Research on RT-induced brain injury has focused on the dividing neuroprogenitor (NP) cells from which a small pool of postnatal, “adult- born” neurons arises in the dentate gyrus, as the hippocampus (of which the dentate gyrus is part) is particularly sensitive to radiation. Certainly, NP cell damage contributes to RT-induced sequelae. However, we and others have recently shown that terminally differentiated neurons, long thought to be resistant to radiation, undergo synaptic alterations in response to radiation. This observation has major implications for the treatment of RT-induced sequelae because it suggests that the damage could happen throughout the entire brain and not be limited to the small, discrete sites of postnatal neuron formation. In this proposal, we present our most recent data on this phenomenon, showing that therapeutic doses of radiation lead to ectopic synaptogenesis and synapse potentiation within 1 hr of RT. Females are more affected than males by this insult, and suppressing glutamate signaling prevents both synapse expansion and subsequent long-term synapse loss. Many questions remain unanswered, however: How localized is the injury? Does the injury promulgate along neuronal circuits? Are some regions of the brain more or less susceptible to the injury? How are these parameters affected by the sex of the individual undergoing RT? Can RT-mediated synaptic defects be reversed? These are critical questions whose answers are required to rationally design therapies to combat RT-induced neurocognitive sequelae. We propose to define the nature of acute RT-induced synaptic damage at by (i) creating at atlas of RT-mediated synaptic injury in the mouse brain using fluorescent probes for neuronal activity and synaptic potentiation, advanced imaging techniques and multidimensional analysis, (ii) testing the influences of age and sex on subject response to RT, and (iii) manipulating cellular signaling to attempt to reverse RT-mediated synaptic damage. We propose a novel and multidisciplinary approach to dissecting the nature of RT-mediated synaptic damage at the molecular, synaptic, cellular, and organismal, i.e. behavioral, levels. The results of this translation proposal have the potential to greatly and positively impact the health of cancer survivors of all ages, and our techniques could be used to investigate other types of brain injuries.