Abstract
Adenosine receptors A1 (A1AR) and A2a (A2aAR) play an important role in regulating glutamate uptake to avoid glutamate accumulation that causes excitotoxicity in the brain; however, the precise mechanism of the effects of A1AR and A2aAR is unclear. Herein, we report that expression of the A1AR protein in the astrocyte membrane and the level of intracellular glutamate were decreased, while expression of the A2aR protein was elevated in cells exposed to oxygen-glucose deprivation (OGD) conditions. Coimmunoprecipitation (Co-IP) experiments showed that A1AR interacts with A2aAR under OGD conditions. The activation of A1AR and inactivation of A2aAR by 2-chloro-N6-cyclopentyladenosine (CCPA) and SCH58251, respectively, partly reversed OGD-mediated glutamate uptake dysfunction, elevated EAAT2, and PPARγ protein levels, and suppressed the expression of Ying Yang 1 (YY1). Both the silencing of YY1 and the activation of PPARγ upregulated EAAT2 expression. Moreover, YY1 silencing elevated the PPARγ level under both normal and OGD conditions. Histone deacetylase (HDAC)1 was found to interact with YY1, and HDAC1 silencing improved PPARγ promoter activity. Taken together, our findings suggest that A1AR-A2aAR heteromers regulate EAAT2 expression and glutamate uptake through the YY1-mediated recruitment of HDAC1 to the PPARγ promoter region.
Highlights
Ischemic stroke, the most common subtype of stroke, seriously threatens public health in China, with up to 2.5 million new stroke cases reported every year and high rates of mortality [1, 2]
Western blotting showed that the expression of A1AR on the cell surface was decreased after oxygen-glucose deprivation (OGD) treatment, whereas A2aAR protein levels were elevated
The intracellular glutamate level was significantly decreased after cells were subjected to OGD for 1 and 6 h compared to 0 h (p < 0:05) (Figure 1(e))
Summary
The most common subtype of stroke, seriously threatens public health in China, with up to 2.5 million new stroke cases reported every year and high rates of mortality [1, 2]. The exposure of astrocytes to oxygen-glucose deprivation (OGD) conditions induces dysfunction of glutamate clearance and inflammatory mediator release, resulting in excitotoxic neuronal death during the ischemic process [3,4,5,6,7]. EAAT2, the most abundant GluT in the brain [15], plays a major role in the uptake of extracellular glutamate [16,17,18]. Further studies reported that EAAT2/GLT1 expression is regulated at the transcriptional and translational levels through a complex mechanism that involves factors such as PI3K-Akt [19], NF-κB [20], and the epigenetic modifiers histone deacetylase (HDAC) I and II [21]. The mechanism of EAAT2 regulation has not been fully clarified
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