Astrocytic A_2A receptors silencing negatively impacts hippocampal synaptic plasticity and memory of adult mice

Abstract

Astrocytes are wired to bidirectionally communicate with neurons namely with synapses, thus shaping synaptic plasticity, which in the hippocampus is considered to underlie learning and memory. Adenosine A 2A receptors (A 2A R) are a potential candidate to modulate this bidirectional communication, since A 2A R regulate synaptic plastic-

Modification of astrocytic Cx43 hemichannel activity in animal models of AD: modulation by adenosine A2A receptors

“…This A 2A R-mediated control of AD-related dysfunction involves an overfunction of neuronal A 2A R [ 25 , 31 , 67 ], in accordance with the predominant localization of A 2A R in excitatory synapses in the limbic cortex [ 68 , 69 ]. However, A 2A R are also present in astrocytes and the selective manipulation of astrocytic A 2A R has an impact on memory function [ 23 , 29 , 70 ]. Furthermore, A 2A R modulate alterations triggered by Aβ in primary cultures of astrocytes, namely decreased glutamate uptake [ 21 ], altered Ca 2+ dynamics [ 22 ], and increased hemichannel activity and subsequently ATP release [ 20 ], a danger signal in brain disease conditions [ 71 ].…”

“…The selective deletion of A 2A R in astrocytes was accomplished in A 2A R floxed (A 2A flox/flox ) mice through the Cre-lox method. Briefly, an AAV5-GFAP-GFP-CRE viral construct (1 µL from 4.8 × 10 12 particles/mL, obtained from Vector Core, University of North Carolina, USA) was bilaterally administrated into the CA1 region of the dorsal hippocampus (GFAP-CRE-A 2A R mice), whereas control (GFAP-CTR) mice received a similar construct without Cre recombinase, AAV5-GFAP-eGFP (Vector Core, University of North Carolina, USA), as previously described [ 23 ].…”

“…This step was followed by several washes with PBS. Slices were protected from light throughout the entire procedure and were further processed for GFAP immunolabelling, as previously described [ 23 ]. Briefly, hippocampal slices were permeabilized for 30 min with 0.1% Triton X-100 in PBS and then with blocking solution (10% horse serum, 0.1% Triton X-100 in PBS) for 2 h. Slices were then incubated for 2 days at 4 °C with the primary antibody, rabbit anti-GFAP (1:1000, Millipore Cat# AB5804, RRID:AB_2109645) diluted in blocking solution.…”

“…The morphology of astrocytes was studied as previously described [ 23 , 38 , 39 ] by tridimensional reconstruction of astrocytic structures using an open access tool, Simple Neurite Tracer (SNT, RRID:SCR_016566) plugin available in Fiji-ImageJ software. The tridimensional reconstruction of astrocytic processes within the stratum radiatum of the CA1 subregion of the dorsal hippocampus was carried out using Z-stack images as reported above.…”

“…Our group previously showed that cultured astrocytes exposed to Aβ peptides display an enhancement of Cx43 hemichannels and that adenosine A 2A receptors (A 2A R), which are closely associated with Cx43, regulate the levels and activity of hemichannels [ 20 ]. A 2A R modulate key astrocytic functions that are affected by Aβ exposure, such as glutamate uptake [ 21 ], ATP release and hemichannel activity [ 20 ], and Ca 2+ signalling [ 22 ], and we recently showed that the genetic deletion of astrocytic A 2A R in the hippocampus of adult mice impairs synaptic plasticity and cause memory deficits [ 23 ]. Moreover, several studies support the idea that A 2A R are a promising target to manage AD, since the pharmacological or genetic blockade of A 2A R confers neuroprotection [ 24 – 28 ].…”