Induction of Parkinsonian-Like Changes via Targeted Downregulation of Astrocytic Glutamate Transporter GLT-1 in the Striatum

Abstract

Background: Previous investigations have suggested that decreased expression of glutamate transporter-1 (GLT-1) is involved in glutamate excitotoxicity and contribute to the development of Parkinson’s disease (PD), GLT-1 is decreased in animal models of PD. GLT-1 is mainly expressed in astrocytes, and the striatum is a GLT-1-rich brain area. Objective: The aim was to explore the function and mechanism of astrocytic GLT-1 in PD-like changes. Methods: In the study, PD-like changes and their molecular mechanism in rodents were tested by a behavioral assessment, micro-positron emission tomography/computed tomography (PET/CT), western blotting, immunohistochemical and immunofluorescence staining, and high performance liquid chromatography pre-column derivatization with O-pthaldialdehida after downregulating astrocytic GLT-1 in vivo and in vitro. Results: In vivo, after 6 weeks of brain stereotactic injection of adeno-associated virus into the striatum, rats in the astrocytic GLT-1 knockdown group showed poorer motor performance, abnormal gait, and depression-like feature; but no olfactory disorders. The results of micro-PET/CT and western blotting indicated that the dopaminergic system was impaired in astrocytic GLT-1 knockdown rats. Similarly, tyrosine hydroxylase (TH) positive immune-staining in neurons of astrocytic GLT-1 knockdown rats showed deficit in cell count. In vitro, knockdown of astrocytic GLT-1 via RNA interference led to morphological injury of TH-positive neurons, which may be related to the abnormal calcium signal induced by glutamate accumulation after GLT-1 knockdown. Furthermore, the GLT-1 agonist ceftriaxone showed a protective effect on TH-positive neuron impairment. Conclusion: The present findings may shed new light in the future prevention and treatment of PD based on blocking glutamate excitotoxicity.