Radiation-induced astrocyte dysfunction and cognitive decline

全脑照射(WBI)导致50%长期存活的脑肿瘤患者出现进展性痴呆。 治疗结束后，至少部分原因是脑血流量调节失调。尽管WBI的具体机制- 引起的CBF下降和认知能力下降尚不清楚，有越来越多的证据表明， 神经血管单位起着至关重要的作用。这一建议的目的是阐明 辐射所致认知损害中的星形胶质细胞功能障碍。中心假设是辐射 导致星形胶质细胞衰老和随后的功能障碍，改变血管扩张介质的产生 和损害神经血管偶联(NVC)反应。由此导致的神经血管功能障碍导致 脑血流量下降和认知障碍。拟议中的工作是新颖的，因为它将是第一个展示 辐射诱导的星形胶质细胞衰老是WBI对大脑影响的关键驱动因素。结果将会是 可能确定特定的机制并揭示能够改善脑血液的潜在疗法 补充和恢复学习和记忆。提出了以下目标：1)阐明细胞 WBI导致NVC反应损害的潜在机制。工作假说是WBI对两者都有损害 二十烷类化合物介导的NVC反应的嘌呤能成分。为了在临床上检验这一假设 相关的小鼠WBI模型，将使用激光散斑来评估促进NVC反应的通路 对比成像、药理学工具和基于LC/MS/MS的神经胶质递质释放的测量。这个 药物上调NVC反应对WBI治疗小鼠认知功能的影响 下定决心。2)确定辐射诱导的衰老如何改变星形胶质细胞的功能和表型。它是 预测辐射会导致星形胶质细胞衰老，从而损害细胞的能量代谢和 产生/释放三磷酸腺苷，改变细胞分泌模式，失调血管活性合成 脂类调节剂。为了验证这些假设，将从WBI处理的小鼠中分离衰老的星形胶质细胞，并 原代培养的人类星形胶质细胞将在体外受到辐射。我们将结合先进的细胞成像技术 研究细胞能量学、基因表达和生物化学的技术和前沿蛋白质组学和生物化学 分泌组特征、三磷酸腺苷释放的调节和脂质介体的合成。3)确定 消除衰老细胞是否能改善WBI治疗的小鼠的NVC和认知功能。这是假设的 依赖p16的细胞衰老程序的激活与WBI诱导的神经血管有关 功能障碍和认知障碍。预计衰老细胞的消除，无论是通过基因 手法(p16-3MR小鼠模型)或通过药物手段恢复神经血管功能和 改善WBI治疗小鼠的认知能力。总之，拟议的研究将确定一个基本的机制 管理与WBI相关的神经血管功能障碍最终导致认知障碍。

Whole brain irradiation (WBI) leads to progressive dementia in ~50% of brain tumor patients who survive long- term after treatment, at least in part, due to dysregulation of CBF. Although the specific mechanisms for WBI- induced deceases in CBF and cognitive decline are not yet known, there is increasing evidence that alterations of the neurovascular unit play a crucial role. The objective of this proposal is to elucidate the mechanistic role of irradiation-induced astrocyte dysfunction in cognitive impairment. The central hypothesis is that irradiation causes astrocyte senescence and subsequent dysfunction, altering the production of vasodilator mediators and impairing neurovascular coupling (NVC) responses. The resulting neurovascular dysfunction contributes to decline in CBF and cognitive impairments. The proposed work is novel in that it will be the first to demonstrate that radiation-induced astrocyte senescence is a key driver of the effects of WBI on the brain. The results will likely identify specific mechanisms and reveal potential therapies that are capable of improving cerebral blood supply and restoring learning and memory. The following aims are proposed: 1) Elucidate the cellular mechanisms underlying WBI-induced impairment of NVC responses. The working hypothesis is that WBI impairs both eicosanoid-mediated and purinergic components of NVC responses. To test this hypothesis in a clinically relevant mouse model of WBI, pathways contributing to NVC responses will be assessed using laser speckle contrast imaging, pharmacological tools and LC/MS/MS-based measurement of gliotransmitter release. The impact of pharmacological up-regulation of NVC responses on cognitive function of WBI-treated mice will be determined. 2) Determine how irradiation-induced senescence alters astrocyte function and phenotype. It is predicted that irradiation induces senescence in astrocytes, which impairs cellular energy metabolism and the production/release of ATP and alters the cellular secretory profile, dysregulating the synthesis of vasoactive lipid mediators. To test these hypotheses senescent astrocytes will be isolated from WBI-treated mice and primary human astrocyte cultures will be irradiated in vitro. We will combine advanced cellular imaging techniques and cutting-edge proteomics and biochemistry to investigate cellular energetics, gene expression and secretome signatures, the regulation of ATP release and the synthesis of lipid mediators. 3) Determine whether elimination of senescent cells improves NVC and cognitive function in WBI-treated mice. It is hypothesized that activation of p16-dependent cellular senescence programs is responsible for WBI-induced neurovascular dysfunction and cognitive impairment. It is expected that elimination of senescent cells, either through genetic manipulation (p16-3MR mouse model) or by pharmacological means will restore neurovascular function and improve cognition in WBI-treated mice. Together, the proposed studies will identify a fundamental mechanism governing WBI-related neurovascular dysfunction eventually leading to cognitive impairment.