Atypical astrocytes in the aging cortex

老化皮质中的非典型星形胶质细胞

• 批准号: 10552699
• 负责人: Chris G Dulla
• 金额: $ 20.63万
• 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 2025-01-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10552699
• 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 Acid Transporter 1; Excitatory Amino Acids; Fluorescent in Situ Hybridization; Frequencies; Funding; GLAST Protein; Genetic Transcription; Glial Fibrillary Acidic Protein; Global Change; Glutamate Transporter; Glutamates; Hippocampus; Homeostasis; Image; Immunohistochemistry; Impaired cognition; Impairment; Individual; Mediating; Messenger RNA; Modeling; Morphology; Myelin Basic Proteins; Neurons; Oligodendroglia; Phenotype; Play; Potassium; Prefrontal Cortex; Prevalence; Process; Property; Proteins; Publishing; Reporting; Risk; Rodent; Role; Shapes; Somatosensory Cortex; Synapses; Synaptic Transmission; Testing; Work; age related; aged; cognitive function; executive function; extracellular; immunoreactivity; inward rectifier potassium channel; male; nervous system disorder; neural circuit; neuropathology; normal aging; novel; reconstruction; single-cell RNA sequencing; spatial memory; timeline; 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.

概括。 在正常衰老过程中，星形胶质细胞会改变其转录和功能特性。星形胶质细胞发挥中枢作用 通过表达兴奋性氨基酸转运蛋白（EAAT：GLT-1）来塑造神经元功能 和 GLAST），介导谷氨酸吸收，内向整流 K+ 通道 Kir4.1，缓冲 细胞外K+。虽然我们知道 EAAT 和 Kir4.1 的表达受到发育调节，但我们知之甚少 关于它们在正常衰老中的作用。该提案是建立在我们的新颖发现之上的，即逐渐更多 星形胶质细胞在衰老过程中失去 EAAT 和 Kir4.1 表达。令人惊讶的是，这种损失并不是渐进的、全球性的 变化，但发生在逐个细胞的基础上，单个星形胶质细胞表达最少的 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 压后皮质和前额皮质（RSC 和 PFC），但不在海马或体感皮质中。 非典型星形胶质细胞在雄性中更为丰富，并且随着动物年龄的增长其数量也会增加。到 1 岁为止，直至 这些区域 15% 的星形胶质细胞是非典型的。有趣的是，非典型星形胶质细胞不具有反应性，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呈 Sox9 阳性，表明它们处于 事实上星形胶质细胞。它们也不标记 NG2（OPC 标记）、MBP（少突胶质细胞标记）或 NeuN（神经元标记） 标记）。非典型星形胶质细胞通常与血管相关，但血管变化是否有助于 他们的出现尚不清楚。根据初步数据，我们假设非典型星形胶质细胞 正常衰老期间在 RSC 和 PFC 中积累，导致谷氨酸和 K+ 域受损 吸收。这很重要，因为这些区域在空间记忆和执行功能中发挥着重要作用。 如果我们的假设正确，谷氨酸和 K+ 吸收的丧失可能会导致与年龄相关的认知能力下降 与这些区域相关的功能。此外，衰老过程中 EAAT 和 Kir4.1 的联合损失可能 会特别有害。我们最近发表了> 30 Hz 的神经元活动爆发驱动突触特异性 抑制谷氨酸的吸收。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所致。 驱动 EAAT 功能的电压依赖性抑制的过程。使用基因编码电压指示器 （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 对于缓冲细胞外至关重要 K+，其衰老过程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 抑制谷氨酸的吸收。在这里，我们将使用电生理学、谷氨酸和 GEVI 成像，以及 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 老化过程中的情况以及这是否会导致谷氨酸吸收和 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是否 导致与年龄相关的突触和认知功能障碍。