The expression profile of type 1 equilibrative nucleoside transporter in aged C57BL/6J mouse brain

The type 1 equilibrative nucleoside transporter (ENT1) is essential for regulating extracellular adenosine levels and has been implicated in various psychiatric disorders. While previous studies have investigated the expression of ENT1 in fetal and neonatal brains, its neuroanatomical distribution in adult and aged mouse brains has not been fully elucidated. Therefore, in this study, we utilize immunohistochemistry and double-immunofluorescence techniques to map the expression of ENT1 across various brain regions. Our findings demonstrate that ENT1-positive cells are widely distributed throughout the brain, with particularly high expression observed in the cerebral cortex and hippocampus. ENT1 is expressed predominantly in neurons, particularly in cholinergic, dopaminergic and glutamatergic neurons. Furthermore, ENT1 is localized primarily to the mitochondria and lysosomes and is expressed to a lesser extent in the Golgi apparatus and endoplasmic reticulum. Notably, we find an age-dependent increase in ENT1 expression in the cerebral cortex, suggesting a potential role in age-related cognitive functions. This study highlights the regionally specific expression of ENT1 in the brain, providing a new morphological basis for understanding its potential roles in brain physiology. Additionally, given its involvement in neurotransmitter regulation, ENT1 may have important implications for neurological and psychiatric disorders. This work lays the groundwork for future studies exploring the implications of ENT1 in neurodegenerative diseases and other aging-related brain disorders.

1型平衡型核苷转运蛋白（type 1 equilibrative nucleoside transporter, ENT1）是调控细胞外腺苷水平的关键蛋白，且已被证实与多种精神疾病存在关联。既往研究虽已探讨了ENT1在胎鼠与新生鼠脑组织中的表达特征，但成年及衰老小鼠脑内的神经解剖学分布尚未完全阐明。本研究采用免疫组织化学与双重免疫荧光染色技术，系统绘制了ENT1在小鼠多个脑区的表达图谱。结果显示，ENT1阳性细胞广泛分布于全脑，其中大脑皮层与海马体的表达水平尤为突出。ENT1主要表达于神经元，尤其富集于胆碱能、多巴胺能及谷氨酸能神经元中。进一步的亚细胞定位分析表明，ENT1主要定位于线粒体与溶酶体，在高尔基体与内质网中仅呈低水平表达。值得注意的是，我们观察到大脑皮层中ENT1的表达随年龄增长呈显著升高趋势，提示其可能在年龄相关性认知功能中发挥潜在作用。本研究明确了ENT1在小鼠脑内的区域特异性表达模式，为理解其在脑生理过程中的潜在功能提供了全新的形态学依据。此外，鉴于ENT1参与神经递质调控，其可能对神经系统疾病及精神类疾病具有重要的潜在意义。本研究为后续探索ENT1在神经退行性疾病及其他衰老相关性脑疾病中的作用奠定了重要基础。