[Dopamine inhibits glutamate-uptake ability of astrocytes via TAAR1-EAAT2 pathway]

Objective To investigate the effect of dopamine (DA) on the glutamate (Glu)-uptake ability of astrocytes, and the role of trace amine-associated receptor 1-excitatory amino acid transporter 2 (TAAR1-EAAT2) signaling pathway in Glu uptake by astrocytes. Methods In the primary cultured astrocytes pretreated with DA, extracellular Glu levels were measured by the Amplex Red glutamic acid assay kit. The levels of TAAR1 and EAAT2 transcriptions were detected by reverse transcription PCR and their protein levels were analyzed by Western blotting. After TAAR1 plasmid and TAAR1 siRNA were separately transfected into the primary astrocytes pretreated by DA, Western blotting was performed to determine the level of EAAT2 and Amplex Red glutamic acid assay kit was used to analyze Glu uptake in primary cultured astrocyte supernatants. Results The expression of EAAT2 in the primary cultured astrocytes significantly decreased in response to DA, and the level of TAAR1 increased. DA significantly enhanced the Glu uptake in primary cultured astrocyte supernatants. After TAAR1 siRNA transfection, EAAT2 expression was upregulated by DA treatment and Glu content in the supernatants was downregulated. On the contrary, after TAAR1 plasmid transfection, EAAT2 expression descended and Glu level ascended in the supernatants. Conclusion DA reduces the Glu-uptake ability of astrocytes through TAAR1-EAAT2 signaling pathway, causes extracellular Glu accumulation, and ultimately destroys the function of astrocytes.