Liu Jinfeng, Sun Zhongqing, Liu Xin, Chiu Kin, Ma Lan, Wang Jiantao
Shenzhen Eye Hospital, Jinan University, Shenzhen Eye Institute, Shenzhen, China.
Department of Neurology, Xijing Hospital, Fourth Military Medical University, Xi'an, China.
Front Aging. 2025 Jul 31;6:1549848. doi: 10.3389/fragi.2025.1549848. eCollection 2025.
The aging brain shows alterations in microglial function, morphology, and phenotype, reflecting a state of chronic activation. CX3CR1 plays a critical role in regulating microglial chemotaxis, phagocytosis, and activation. However, its exact role in the aging brain is not well understood.
In this study, we examined the expression of CX3CR1 in the brains of middle-aged mice (10 months old) and explored its functional implications by measuring cytokine and scavenger receptor expression, analyzing microglial and astrocyte morphology, conducting proteomic profiling, and assessing synapse density in CX3CR1-deficient mouse brain.
Our results showed that CX3CR1 was upregulated in the hippocampus and frontal cortex of middle-aged mice, with decreased IL-1α and IL-1β levels in the frontal cortex and increased SRA and RAGE levels in the hippocampus. Proteomic analysis revealed an enrichment of differentially expressed proteins (DE-proteins) in the cerebrum of middle-aged mice in GO pathways such as "synapse", "translation", and "ribosome". Following CX3CR1 knockout in the middle-aged mice, TNF-α and IL-1α levels increased, while CD68, SRA, and RAGE levels decreased in the hippocampus. Similarly, CD68, CD36, SRB1, and RAGE levels decreased in the frontal cortex. The absence of CX3CR1 significantly altered microglial morphology, resulting in enlarged cell bodies and shortened processes in the hippocampus and frontal cortex. CX3CR1 deficiency also changed astrocyte morphology, leading to enlarged cell bodies and elongated processes in the hippocampus. Further proteomic analysis indicated that CX3CR1 deficiency affected protein levels in GO pathways such as "glutamatergic synapse" and "RNA splicing." Additionally, we observed a reduction in synaptophysin-positive synapse density in both the hippocampus and frontal cortex of CX3CR1-deficient mice.
Our findings demonstrated that CX3CR1 was upregulated to maintain synaptic homeostasis probably through regulating microglial activation and phagocytosis in the brains of middle-aged mice. CX3CR1 may represent a promising therapeutic target for alleviating the effects of aging and preventing neurodegeneration.
衰老的大脑在小胶质细胞功能、形态和表型方面表现出改变，反映出一种慢性激活状态。CX3CR1在调节小胶质细胞趋化性、吞噬作用和激活中起关键作用。然而，其在衰老大脑中的确切作用尚不清楚。
在本研究中，我们检测了中年小鼠（10个月大）大脑中CX3CR1的表达，并通过测量细胞因子和清道夫受体表达、分析小胶质细胞和星形胶质细胞形态、进行蛋白质组分析以及评估CX3CR1缺陷小鼠大脑中的突触密度来探索其功能意义。
我们的结果显示，CX3CR1在中年小鼠的海马体和额叶皮质中上调，额叶皮质中IL-1α和IL-1β水平降低，海马体中SRA和RAGE水平升高。蛋白质组分析显示，中年小鼠大脑中差异表达蛋白（DE-蛋白）在“突触”、“翻译”和“核糖体”等GO通路中富集。在中年小鼠中敲除CX3CR1后，海马体中TNF-α和IL-1α水平升高，而CD68、SRA和RAGE水平降低。同样，额叶皮质中CD68、CD36、SRB1和RAGE水平降低。CX3CR1的缺失显著改变了小胶质细胞形态，导致海马体和额叶皮质中细胞体增大和突起缩短。CX3CR1缺陷也改变了星形胶质细胞形态，导致海马体中细胞体增大和突起延长。进一步的蛋白质组分析表明，CX3CR1缺陷影响了“谷氨酸能突触”和“RNA剪接”等GO通路中的蛋白质水平。此外，我们观察到CX3CR1缺陷小鼠的海马体和额叶皮质中突触素阳性突触密度降低。
我们的研究结果表明，CX3CR1上调可能通过调节中年小鼠大脑中的小胶质细胞激活和吞噬作用来维持突触稳态。CX3CR1可能是减轻衰老影响和预防神经退行性变的一个有前景的治疗靶点。
