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.

总结。 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。星形胶质细胞扮演着中心角色 兴奋性氨基酸转运体(EAATs：GLT-1)在神经功能塑造中的作用 和GLAST)，它介导谷氨酸的吸收，以及内部整流性K+通道，Kir4.1，它缓冲 胞外K+。虽然我们知道EAAT和Kir4.1的表达是受发育调节的，但我们知道的很少 关于它们在正常衰老中的作用。这项建议是建立在我们的新发现基础上的， 星形胶质细胞在衰老过程中失去EAAT和Kir4.1的表达。令人惊讶的是，这种损失并不是渐进的、全球性的 改变是在逐个细胞的基础上发生的，单个星形胶质细胞表达最小EAAT和Kir4.1， 而邻近的星形胶质细胞则保持正常。这些“非典型星形胶质细胞”主要分布在 脾后皮质和前额叶皮质(RSC和PFC)，但不在海马区或体感皮质。 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而增多。By1岁，最高可达 15%的星形胶质细胞在这些区域是不典型的。有趣的是，非典型星形胶质细胞不是反应性的，因为它们缺乏 GFAP免疫反应增强。重要的是，非典型星形胶质细胞Sox9阳性，表明它们在 事实上是星形胶质细胞。它们也不标记NG2(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。根据初步数据，我们假设非典型星形胶质细胞 在正常老化过程中，在RSC和PFC中积累，并导致谷氨酸和K+受损的区域 领悟。这一点很重要，因为这些区域在空间记忆和执行功能方面发挥着突出的作用。 如果我们的假设是正确的，谷氨酸和K+摄取的丧失可能会导致与年龄相关的认知能力丧失 与这些区域相关联的功能。此外，EAAT和Kir4.1在老化过程中的合计损失可能 尤其有害。我们最近发表了神经元活动的爆发&30赫兹驱动突触特异性 抑制谷氨酸摄取。我们怀疑这是由于局部K+介导的星形胶质细胞远端去极化 驱动电压依赖性抑制EAAT功能的过程。使用遗传编码的电压指示器 (GEVI)，我们的初步数据显示，星形胶质细胞的远端突起经历了显著的活动诱导 去极化，符合电压依赖的EAAT抑制。因为Kir4.1对于缓冲细胞外至关重要 K+，它在衰老过程中的丢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，以及 确定RSC和PFC星形胶质细胞是否失去EAATs和Kir4.1表达的解剖学方法 在衰老期间，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 准备好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。