Regulation of ethanol-sensitive EAAT2 expression through adenosine A1 receptor in astrocytes

Abstract

Adenosine-regulated glutamate signaling in astrocytes is implicated in many neurological and neuropsychiatric disorders. In this study, we examined whether adenosine A1 receptor regulates EAAT2 expression in astrocytes using pharmacological agents and siRNAs. We found that adenosine A1 receptor-specific antagonist DPCPX or PSB36 decreased EAAT2 expression in a dose-dependent manner. Consistently, knockdown of A1 receptor in astrocytes decreased EAAT2 mRNA expression while overexpression of A1 receptor upregulated EAAT2 expression and function. Since A1 receptor activation is mainly coupled to inhibitory G-proteins and inhibits the activity of adenylate cyclase, we investigated the effect of forskolin, which activates adenylate cyclase activity, on EAAT2 mRNA levels. Interestingly, we found that forskolin reduced EAAT2 expression in dose- and time-dependent manners. In contrast, adenylate cyclase inhibitor SQ22536 increased EAAT2 expression in dose- and time-dependent manners. In addition, forskolin blocked ethanol-induced EAAT2 upregulation. Taken together, these results suggest that A1 receptor-mediated signaling regulates EAAT2 expression in astrocytes.

Persistent reduction of cocaine seeking by pharmacological manipulation of adenosine A1 and A2A receptors during extinction training in rats

“…Restoration of GLT-1 deficits during withdrawal corresponds with a persistent attenuation of cocaine- and cue-primed reinstatement (Knackstedt et al 2010a; Reissner et al 2013). Interestingly, increasing A1AR transmission in the accumbens results in increased expression of GLT-1 mRNA (Wu et al 2011). Thus, A1AR stimulation may restore cocaine-induced deficits in GLT-1 and basal glutamate to reduce subsequent cocaine seeking, although it is not clear why it would be necessary for A1AR agonists to be administered during extinction training to reveal these lasting effects.…”

Glial and neuroinflammatory targets for treating substance use disorders

“…Adenosine is a purine nucleoside that is increased extracellularly through alcohol-induced inhibition of the adenosine transporter (type 1 equilibrative nucleoside transporter, ENT1) that is expressed on astrocytes (Nagy et al, 1990). This rise in extracellular adenosine consequentially stimulates both adenosine A 1 and A 2A receptors that are also expressed on astrocytes and consequentially reduce GLT1 expression (Matos et al, 2012; Wu et al, 2011). Adenosine also alters synaptic GABA clearance through GABA transporters (i.e., GAT1 and GAT3) located on astrocytes (Minelli et al, 1996, 1995).…”

Glial abnormalities in substance use disorders and depression: Does shared glutamatergic dysfunction contribute to comorbidity?

“…Excessive extrasynaptic glutamate receptor stimulation initiates apoptosis, and the physiological activity of EAAT2/GLT-1 reduces excitotoxicity from synaptic spillover (Hardingham et al 2010). In a rodent model of alcoholism, alcohol upregulates EAAT2/GLT-1 (Wu et al 2011). EAAT2/GLT-1 is also upregulated in the amygdala and cingulate cortex of alcohol-dependent rats, and exposure-induced (but not spontaneously-induced) alcohol use can be antagonized with acamprosate, a glutamatergic neuromodulator (Rimondini et al 2002; Hoffman et al 2003).…”