Chronic stress impairs the aquaporin-4-mediated glymphatic transport through glucocorticoid signaling
The glymphatic system has recently been proposed to function as a brain-wide macroscopic system for the clearance of potentially harmful molecules, such as amyloid beta (e.g., Aβ), from the brain parenchyma. Previous literatures have established that the glymphatic function is dramatically suppressed by aging, traumatic brain injury, and some diseases. However, the effect of chronic stress on the glymphatic function and its underlying mechanism remains largely unknown.
Adult mice were randomly divided into four groups: chronic unpredictable mild stress (CUMS)–treated group, CUMS simultaneously treated with mifepristone (MFP) group, dexamethasone (DEX)-treated group, and control group. Stress response was observed by assessing the change of body weight, plasma corticosterone level, and behavior tests. The level of Aβ42 in cerebral tissue was assessed by ELISA. The glymphatic function was determined by using fluorescence tracer injection. The expression and localization of aquaporin-4 (AQP4) were evaluated by immunohistochemistry and western blot. The transcription level of AQP4 and anchoring molecules was evaluated by real-time PCR.
Compared with control group, CUMS-treated mice exhibited the impairment of global glymphatic function especially in the anterior brain. This change was accompanied by the decreased expression and polarization of AQP4, reduced transcription of AQP4, agrin, laminin, and dystroglycan in the anterior cortex. Similarly, the glucocorticoid receptor (GR) agonist DEX exposure could reduce the glymphatic function and AQP4 expression. Moreover, the GR antagonist MFP treatment could significantly rescue the glymphatic function and reverse the expression and polarization of AQP4 impaired by CUMS.
Chronic stress could impair the AQP4-mediated glymphatic transport in the brain through glucocorticoid signaling. Our results also suggest that GR antagonist could be beneficial to rescue the glymphatic function suppressed by chronic stress.
KeywordsGlymphatic system Chronic stress Aquaporin-4 Cerebrospinal fluid Glucocorticoid receptor
Chronic unpredictable mild stress
This study was supported by the National Natural Science Foundation of China (31871167), China Postdoctoral Science Foundation (No. 2016M601882), Postdoctoral Science Foundation of Jiangsu Province, China (No.1601083C), Suzhou Science and Technology Research Project (No. SYS201669), and Priority Academic Program Development of Jiangsu Higher Education Institutions.
Compliance with ethical standards
All experiments were conducted in accordance with the European Convention for the Protection of Vertebrate Animals used for Experimental and other Scientific Purposes (Council of Europe No. 123, Strasbourg 1985), and all experimental protocols were approved by the Institutional Animal Care and Use Committee of Soochow University.
Conflict of interest
The authors declare that there is no conflict of interest.
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