Atypical astrocytes in the aging cortex

老化皮质中的非典型星形胶质细胞

• 批准号: 10382048
• 负责人: Chris G Dulla
• 金额: $ 24.75万
• 依托单位: TUFTS UNIVERSITY BOSTON
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-02-01 至 2024-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10382048
• 关键词: 1 year old; ARHGEF5 gene; Age; Age-Months; Age-associated memory impairment; Aging; Amino Acid Transporter; Anatomy; Animals; Appearance; Area; Astrocytes; Astrocytosis; Automobile Driving; Biological Assay; Blood Vessels; Brain; Buffers; CSPG4 gene; Cells; Data; Development; Distal; Electrophysiology (science); Excitatory Amino Acids; Fluorescent in Situ Hybridization; Frequencies; Funding; GLAST Protein; Genetic Transcription; Glial Fibrillary Acidic Protein; Global Change; Glutamate Transporter; Glutamates; Hippocampus (Brain); Homeostasis; Image; Immunohistochemistry; Impaired cognition; Impairment; Individual; Mediating; Messenger RNA; Modeling; Morphology; Myelin Basic Proteins; Neurologic; Neurons; Oligodendroglia; Phenotype; Play; Potassium; Prefrontal Cortex; Prevalence; Process; Property; Proteins; Publishing; Reporting; Risk; Rodent; Role; Shapes; Somatosensory Cortex; Synapses; Synaptic Transmission; Testing; TimeLine; Work; age related; aged; base; cognitive function; executive function; extracellular; immunoreactivity; inward rectifier potassium channel; male; nervous system disorder; neural circuit; normal aging; novel; reconstruction; single-cell RNA sequencing; spatial memory; uptake; voltage

SUMMARY. During normal aging, astrocytes change their transcriptional and functional properties. Astrocyte play a central role in shaping neuronal function through their expression of excitatory amino acid transporters (EAATs: GLT-1 and GLAST), which mediate glutamate uptake, and the inwardly rectifying K+ channel, Kir4.1, which buffers extracellular K+. While we know that EAAT and Kir4.1 expression are developmentally regulated, we know little about their role in normal aging. This proposal is built on our novel finding that progressively more astrocytes lose EAAT and Kir4.1 expression during aging. Surprisingly, this loss is not a gradual, global change but occurs on a cell-by-cell basis with individual astrocytes expressing minimal EAAT and Kir4.1, while neighboring astrocytes remain normal. These “atypical astrocytes” are found predominantly in the retrosplenial and prefrontal cortices (RSC and PFC), but not in the hippocampus or somatosensory cortex. Atypical astrocytes are more abundant in males, and grow in number as animals age. By  1 year of age, up to 15% of astrocytes are atypical in these regions. Interestingly, atypical astrocytes are not reactive, as they lack elevated GFAP immunoreactivity. Importantly, atypical astrocytes are Sox9 positive, showing that they are in fact astrocytes. They also do not label for NG2 (OPC marker), MBP (oligodendrocyte marker), or NeuN (neuronal marker). Atypical astrocytes are often associated with blood vessels, but whether vascular changes contribute to their emergence is unknown. Based on preliminary data, we hypothesize that atypical astrocytes accumulate in the RSC and PFC during normal aging and cause domains of impaired glutamate and K+ uptake. This is significant because these areas play a prominent role in spatial memory and executive function. If our hypothesis is correct, the loss of glutamate and K+ uptake could contribute to age-related losses in cognitive functions associated with these regions. In addition, the combined loss of EAATs and Kir4.1 during aging may be especially detrimental. We recently published that bursts of neuronal activity > 30 Hz drives synapse-specific inhibition of glutamate uptake. We suspect this is due to focal K+-mediated depolarization of astrocyte distal processes driving voltage-dependent inhibition of EAAT function. Using genetically encoded voltage indicators (GEVIs), our preliminary data shows that astrocyte distal processes undergo significant activity-induced depolarization, in line with voltage-dependent EAAT inhibition. Because Kir4.1 is critical to buffering extracellular K+, its loss in aging likely exacerbates activity-induced astrocyte depolarization and increases voltage-dependent suppression of glutamate uptake. Here, we will use electrophysiology, glutamate and GEVI imaging, and anatomical approaches to determine whether RSC and PFC astrocytes lose expression of EAATs and Kir4.1 during aging and whether this leads to disrupted glutamate uptake and K+ buffering. When completed, we will be poised to establish the mechanisms that induce atypical astrocytes and determine whether atypical astrocytes contribute to age-related synaptic and cognitive dysfunction.

摘要 在正常衰老过程中，星形胶质细胞改变其转录和功能特性。星形胶质细胞发挥着核心作用 通过兴奋性氨基酸转运蛋白（EAAT：GLT-1）的表达在塑造神经元功能中的作用 和GLAST），其介导谷氨酸摄取，和内向整流K+通道，Kir4.1，其缓冲 胞外K+。虽然我们知道EAAT和Kir4.1的表达是受发育调控的，但我们所知甚少。 它们在正常衰老中的作用这项提议是建立在我们的新发现之上的， 星形胶质细胞在衰老过程中EAAT和Kir4.1表达缺失。令人惊讶的是，这种损失不是一个渐进的，全球性的， 变化，但发生在细胞与细胞的基础上，个别星形胶质细胞表达最低限度的EAAT和Kir4.1， 而邻近的星形胶质细胞保持正常。这些“非典型星形胶质细胞”主要存在于 压后和前额叶皮质（RSC和PFC），但不是在海马或体感皮质。 非典型星形胶质细胞在雄性中更丰富，并且随着动物年龄的增长而增加。到2001年， 15%的星形胶质细胞在这些区域是非典型的。有趣的是，非典型星形胶质细胞没有反应性，因为它们缺乏 GFAP免疫反应性升高。重要的是，非典型星形胶质细胞是Sox 9阳性的，表明它们在星形胶质细胞中表达。 事实上是星形胶质细胞。它们也不标记NG 2（OPC标记物）、MBP（少突胶质细胞标记物）或NeuN（神经元标记物）。 标记）。非典型星形胶质细胞通常与血管有关，但血管变化是否有助于 他们的出现是未知的。基于初步数据，我们假设非典型星形胶质细胞 在正常衰老过程中在RSC和PFC中积累，并导致受损的谷氨酸和K+ 摄取。这一点很重要，因为这些区域在空间记忆和执行功能中发挥着重要作用。 如果我们的假设是正确的，那么谷氨酸和K+摄取的丧失可能导致与年龄相关的认知功能丧失。 与这些区域相关的功能。此外，在老化过程中EAAT和Kir4.1的联合丢失可能会导致 尤其有害。我们最近发表了一篇文章，神经元活动的爆发> 30 Hz驱动突触特异性 抑制谷氨酸摄取。我们怀疑这是由于局灶性K+介导的星形胶质细胞远端去极化 驱动EAAT功能的电压依赖性抑制的过程。使用基因编码的电压指示器 （GEVI），我们的初步数据表明，星形胶质细胞远端过程经历了显着的活动诱导， 去极化，与电压依赖性EAAT抑制一致。因为Kir4.1对于缓冲细胞外 K+，其在衰老中的损失可能会加剧活动诱导的星形胶质细胞去极化，并增加电压依赖性 抑制谷氨酸摄取。在这里，我们将使用电生理学，谷氨酸和GEVI成像， 确定RSC和PFC星形胶质细胞是否失去EAAT和Kir4.1表达的解剖学方法 以及这是否会导致谷氨酸摄取和K+缓冲中断。完成后，我们将 准备建立诱导非典型星形胶质细胞的机制，并确定非典型星形胶质细胞 导致与年龄相关的突触和认知功能障碍。