Adenosine A2A Research Articles

Photoresponsive Adenosine Derivatives for the Optical Control of Adenosine A2A Receptors in Living Cells.

The use of photoresponsive ligands to optically control proteins of interest, known as photopharmacology, is a powerful technique for elucidating cellular function in living cells and animals with a high spatiotemporal resolution. The adenosine A2A receptor (A2AR) is a G protein-coupled receptor that is expressed in various tissues; its dysregulation is implicated in severe diseases such as insomnia and Parkinson's disease. A detailed elucidation of the physiological function of A2AR is, therefore, highly desirable. In the present study, we developed two photoswitchable ligands, photoAd(blue) and photoAd(vio), that target A2AR. Using photoAd(vio), we successfully demonstrated the selective activation of A2AR in living cells by violet-light irradiation with high spatiotemporal resolution.

Polydeoxyribonucleotide ameliorates IL-1β-induced impairment of chondrogenic differentiation in human bone marrow-derived mesenchymal stem cells

Osteoarthritis (OA) is a degenerative disease of the joints, prevalent worldwide. Polydeoxyribonucleotide (PDRN) is used for treating knee OA. However, the role of PDRN in IL-1β-induced inflammatory responses in human bone marrow-derived mesenchymal stem cells (hBMSCs) remains unknown. Here, we investigated the role of PDRN in IL-1β-induced impairment of chondrogenic differentiation in hBMSCs. hBMSCs treated with PDRN showed a large micromass, enhanced safranin O and alcian blue staining intensity, and increased expression of chondrogenic genes in IL-1β-induced inflammatory responses, in addition to regulation of catabolic and anabolic genes. In addition, PDRN treatment suppressed the expression of inflammatory cytokines and mitigated IL-1β-induced apoptosis in hBMSCs. Mechanistically, PDRN treatment increased the formation of cyclic adenosine monophosphate (cAMP) and upregulated the phosphorylation of cAMP-dependent protein kinase A (PKA)/cAMP response element binding protein (CREB) through the adenosine A2A receptor in hBMSCs and thus blocked the nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) signaling pathway. Thus, IL-1β-induced expression of inflammatory cytokines in hBMSCs was directly reduced by adenosine A2A receptor activation. Based on our results, we suggest that PDRN may be a promising MSC-based therapeutic agent for OA.

Polynucleotides in Skin Regeneration: Targeting the Adenosine A2A Receptor and Salvage Pathway.

Polynucleotides in Skin Regeneration: Targeting the Adenosine A2A Receptor and Salvage Pathway.

Brain Specific RagA Overexpression Triggers Depressive-Like Behaviors in Mice via Activating ADORA2A Signaling Pathway.

Neuroinflammation hallmarks the pathology of depression although the etiological complexity has not yet been resolved. Previous studies demonstrate that bacterial lipopolysaccharide induces depressive-like behaviors by activating RagA-mTOR-p70S6K signaling pathway. The current project aims to investigate whether and how brain-specific RagA overexpression triggers depressive-like behaviors in mice. Full-length RagA cDNA is cloned into the mammalian expression vector under the control of brain specific promoter, and subsequently overexpressed in the brain of mouse embryos. Indeed, RagA transgenic mice exhibit depressive-like behaviors and memory impairments. RNA-seq profiling of the prefrontal cortex (PFC) transcriptome highlights adenosine A2a receptor (ADORA2A) as a key differentially expressed gene (DEG). Western blotting confirms that ADORA2A and phospho-p70S6K are markedly elevated in RagA transgenic mice. Behavioral assessments demonstrate that ADORA2A inhibitor istradefylline markedly attenuates depressive-like behaviors. Further metabolomics reveals that N-acetylserotonin and several depression-related metabolites are downregulated while proteomic profiling showed that OLIG1 and other proteins are significantly regulated in RagA transgenic mice. Collectively, RagA overexpression alters the expression patterns of signaling proteins and the metabolism of depression-associated metabolites. RagA may cause depressive-like behaviors in mice via activating p70S6K/ADORA2A signaling pathway. Thus, RagA-p70S6K-ADORA2A signaling pathway may be a target for the development of new antidepressant therapies.

An agonist of the adenosine A2A receptor, CGS21680, promotes corneal epithelial wound healing via the YAP signalling pathway.

The adenosine A2A receptor (A2AR) is involved in various physiological and pathological processes in the eye; however, the role of the A2AR signalling in corneal epithelial wound healing is not known. Here, the expression, therapeutic effects and signalling mechanism of A2AR in corneal epithelial wound healing were investigated using the A2AR agonist CGS21680. A2AR localization and expression during wound healing in the murine cornea were determined by immunofluorescence staining, quantitative reverse transcription polymerase chain reaction (RT-qPCR) and western blotting. The effect of CGS21680 on corneal epithelial wound healing in the lesioned corneal and cultured human corneal epithelial cells (hCECs) by modulating cellular proliferation and migration was critically evaluated. The role of Hippo-YAP signalling in mediating the CGS21680 effect on wound healing by pharmacological inhibition of YAP signalling was explored. A2AR expression was up-regulated after corneal epithelial injury. Topical administration of CGS21680 dose-dependently promoted corneal epithelial wound healing in the injured corneal epithelium by promoting cellular proliferation. Furthermore, CGS21680 accelerated the cellular proliferation and migration of hCECs in vitro. A2AR activation promoted early up-regulation and later down-regulation of YAP signalling molecules, and pharmacological inhibition of YAP signalling reverted CGS21680-mediated wound healing effect in vivo and in vitro. A2AR activation promotes wound healing by enhancing cellular proliferation and migration through the YAP signalling pathway. A2ARs play an important role in the maintenance of corneal epithelium integrity and may represent a novel therapeutic target for facilitating corneal epithelial wound healing.

Investigating In Silico and In Vitro Therapeutic Potential of Diosmetin as the Anti-Parkinson Agent.

This study aimed to investigate how diosmetin interacts with seven target receptors associated with oxidative stress (OS) and validate its antioxidant properties for the potential management of Parkinson's disease (PD). In PD, the degeneration of dopaminergic cells is strongly influenced by OS. This stressor is intricately connected to various mechanisms involved in neurodegeneration, such as mitochondrial dysfunction, neuroinflammation, and excitotoxicity induced by nitric oxide. The aim of this research was to establish a molecular connection between diosmetin and OS-associated target receptors was the goal, and it investigated how this interaction can lessen PD. Seven molecular targets - Adenosine A2A (AA2A), Peroxisome Proliferator- Activated Receptor Gamma (PPARγ), Protein Kinase AKT1, Nucleolar Receptor NURR1, Liver - X Receptor Beta (LXRβ), Monoamine Oxidase - B (MAO-B) and Tropomyosin receptor kinase B (TrkB) were obtained from RCSB. Molecular docking software was employed to determine molecular interactions, while antioxidant activity was assessed through in-vitro assays against various free radicals. Diosmetin exhibited interactions with all seven target receptors at their binding sites. Notably, it showed superior interaction with AA2A and NURR1 compared to native ligands, with binding energies of -7.55, and -6.34 kcal/mol, respectively. Additionally, significant interactions were observed with PPARγ, AKT1, LXRβ, MAO-B, and TrkB with binding energies of -8.34, -5.42, -7.66, -8.82, -8.45 kcal/mol, respectively. Diosmetin also demonstrated antioxidant activity against various free radicals, particularly against hypochlorous acid (HOCl) and nitric oxide (NO) free radicals. Diosmetin possibly acts on several target receptors linked to the pathophysiology of PD, demonstrating promise as an OS inhibitor and scavenger.

Activation of adenosine A2a and A2b receptors augments the skin wound healing in juvenile grass carp

Wounded fish skin leads to the impairment of internal tissue homeostasis and provides an opportunity for pathogens to invade, resulting in the occurrence of fish diseases. Accordingly, skin wound healing has been investigated in many fishes. In the present study, we found that the concentration of adenosine increased in grass carp skin wounds and antagonization of adenosine receptors aggravated the skin wound closure, implying that adenosine receptor activation played a role in fish skin wound repair. After the expression of adenosine A2a receptor (A2aR) and A2bR in grass carp skin was verified, the effects of two adenosine analogs, ZM241385 and CGS 21680, on grass carp A2aR and A2bR activation were examined by a dual-luciferase assay. The results showed that 500 nM of ZM241385 could antagonize the activation of both receptors by adenosine and 5–5000 nM of CGS 21680 could stimulate both receptors. In this scenario, these two compounds were administrated to the skin wounds of juvenile grass carp weighting about 8.0 g each, showing that 0.5, 2.5, 12.5 μg/tail of ZM241385 dose-dependently delayed while 0.8 and 2.4 μg/tail of CGS 21680 accelerated closure of the wounds when compared to the control group treated with the solvent. The thickness and cell proliferation of the epithelial layer in the wounds were decreased by 2.5 μg/tail of ZM241385 but increased by 0.8 μg/tail of CGS 21680 at 3 days post wounding compared to the control group. To our knowledge, this is the first report demonstrating the effects of adenosine receptor activation on skin re-epithelization in vertebrates. Moreover, the effects of ZM241385 and CGS 21680 on granulation formation including fibroblast migration and collagen deposition in grass carp skin wounds were also investigated in the present study. The results revealed that these two compounds oppositely regulated fibroblast migration and collagen deposition in grass carp skin wounds. These results implied that activation of grass carp A2aR and A2bR improved granulation formation in the wound, leading to enhancement of skin wound repair in juvenile grass carp. These results provide the new clues and mechanisms on the skin wound healing in fish species.

5,7,3',4',5'-Pentamethoxyflavone, a Flavonoid Monomer Extracted From Murraya paniculata (L.) Jack, Alleviates Anxiety Through the A2AR/Gephyrin/GABRA2 Pathway.

The sedative and hypnotic properties of 5,7,3',4',5'-pentamethoxyflavone (PMF), a monomer extracted from the leaves of Murraya paniculata (L.) Jack, have been reported. However, the role of PMFs in the development of anxiety remains uncertain. An anxiety model was developed using chronic unpredictable mild stimulation (CUMS). Kunming mice were randomly allocated to the following groups: control, CUMS, PMF (50 mg/kg), PMF (100 mg/kg), and diazepam (3 mg/kg). The anxiolytic effects of PMFs were evaluated using elevated plus maze (EPM) test and open field test (OFT). Enzyme-linked immunosorbent assay (ELISA) kits were used to analyze the serum levels of corticosterone (CORT), 5-hydroxytryptamine (5-HT), gamma-aminobutyric acid (GABA), and cyclic adenosine monophosphate (cAMP) in the hippocampus. High-throughput-16S rRNA sequencing was performed to investigate its effect on the composition of the gut microbiota. Subsequently, western blotting was performed to assess the expression of GABAergic synaptic-associated proteins. PMF effectively mitigated CUMS-induced anxiety-like behavior. Further examination revealed that PMF treatment ameliorated dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis and increased 5-HT and GABA levels in the hippocampus. Notably, the ability of PMF to maintain the stability of GABAergic synapses by enhancing the species composition of the gut microbiota and acting on the adenosine a2a receptor (A2AR)/gephyrin/gamma-aminobutyric acid A receptor alpha 2 (GABRA2) pathway revealed a previously unrecognized mechanism for the anxiolytic effect of PMF. These findings suggest that PMF enhances the expression of A2AR, preserves GABAergic synaptic stability, and reduces anxiety by modulating the microbiota composition. Thus, it holds promise as an anxiolytic agent.

Adenosine A2A signaling in mood disorders: How far have we come?

Over the years, evidence has continued to support the role of the adenosinergic system in shaping emotional behavior and its impact on the development of mood disorders. In the 1980s, pioneering studies revealed that tricyclic antidepressants could modulate the levels of adenosine and adenosine metabolism. Moreover, evidence from animal models support a regulation of adenosine receptors in brain regions involved in emotional responses, and the role of pharmacological manipulation of adenosine receptors on behavioral despair, anxiety, locomotion, rewards processing and cognition. Clinical research has focused on the effects of caffeine, a non-selective adenosine receptor antagonist, and in genetic polymorphisms in adenosine receptors on emotional regulation in psychiatric patients. Recently, the approval of Istradefylline as an adjunctive treatment for Parkinson's disease holds great promise to expand our understanding of adenosine A2A receptors (A2AR) blockade in humans. Furthermore, recent advancements in transgenic lines and optogenetic techniques have highlighted the role of adenosine receptors in specific cell types and brain circuits that control emotional behavior. In this review, our focus will be on A2AR, given their strong association to stress-related conditions, mood disorders, and the potential of A2AR antagonists in clinical research. We will discuss the progress achieved in understanding its role in emotional regulation, emphasizing functions across distinct cell types and potential applications as a pharmacological target for mood disorders in the upcoming years.

Minute-timescale free-energy calculations reveal a pseudo-active state in the adenosine A2A receptor activation mechanism

Minute-timescale free-energy calculations reveal a pseudo-active state in the adenosine A2A receptor activation mechanism

Anti-inflammatory effects of polydeoxyribonucleotide and adipose tissue-derived mesenchymal stem cells in a canine cell model of osteoarthritis.

A relatively new therapeutic agent for osteoarthritis (OA), polydeoxyribonucleotide (PDRN), shows potential in treating human OA due to its regenerative and anti-inflammatory effects. However, studies on PDRN for canine OA are limited, and no study has investigated their use with mesenchymal stem cells (MSCs) conventionally used for OA treatment. This study aimed to evaluate the potential of PDRN and explore its combined effect with adipose tissue-derived MSCs (AdMSCs) in treating canine OA. To study the impact of PDRN, canine chondrocytes, synoviocytes, and AdMSCs were exposed to various PDRN concentrations, and viability was assessed using cell counting kit-8. The OA model was created by treating chondrocytes and synoviocytes with lipopolysaccharide, followed by treatment under three different conditions: PDRN alone, AdMSCs alone, and a combination of PDRN and AdMSCs. Using real-time quantitative polymerase chain reaction, the anti-inflammatory effects and mechanisms were investigated by quantitatively assessing pro-inflammatory cytokines, collagen degradation markers, adenosine A2a receptor (ADORA2A), and nuclear factor-kappa B. PDRN alone and combined with AdMSCs significantly reduced the expression of pro-inflammatory cytokines and collagen degradation markers in an OA model. PDRN promoted AdMSC proliferation and upregulated ADORA2A expression. AdMSCs exhibited comprehensive anti-inflammatory effects through paracrine effects, and both substances reduced inflammatory gene expression through different mechanisms, potentially enhancing therapeutic effects. The results indicate that PDRN is a safe and effective anti-inflammatory material that can be used independently or as an adjuvant for AdMSCs. Although additional research is necessary, this study is significant because it provides a foundation for future research at the cellular level.

Targeting the Adenosine A2A Receptor as a Novel Therapeutic Approach for Renal Cell Carcinoma: Mechanisms and Clinical Trial Review.

Renal cell carcinoma (RCC) accounts for nearly 2% of cancers diagnosed worldwide. For metastatic RCC, targeted therapy is one of the most common treatment methods. It can include approaches that target vascular endothelial growth factor (VEGFR) or rely on immune checkpoint inhibitors or mTOR inhibitors. Adenosine A2A receptor (A2AR) is a type of widely distributed G-protein-coupled receptor (GPCR). Recently, an increasing number of studies suggest that the activation of A2AR can downregulate anti-tumor immune responses and prevent tumor growth. Currently, the data on A2AR antagonists in RCC treatment are still limited. Therefore, in this article, we further investigate the clinical trials investigating A2AR drugs in RCC. We also describe the epidemiology and current treatment of RCC, along with the physiological role of A2AR, and the types of A2AR drugs that are associated with tumor treatment.

A2AR regulate inflammation through PKA/NF-κB signaling pathways in intervertebral disc degeneration

BackgroundReduction of inflammatory damage and inhibition of nucleus pulposus (NP) apoptosis are considered to be the main effective therapy idea to reverse the intervertebral disc degeneration (IDD) and alleviate the chronic low back pain. The adenosine A2A receptor (A2AR), as a member of G protein-coupled receptor families, plays an important role in the anti-inflammation and relieving pain. So far, the impact of A2AR on IDD therapy is unclear. The aim of this study was to explore the role of Adenosine A2A receptor (A2AR) in the intervertebral disc degeneration (IDD) and clarify potential mechanism.Materials and methodsIL-1β and acupuncture was used to establish IDD model rats. A2AR agonist CGS-21680 and A2AR antagonist SCH442416 were used to investigate the therapeutical effects for IDD. Histological examination, western blotting analysis and RT-PCR were employed to evaluate the the association between A2AR and cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway.ResultsA2AR activity of the intervertebral disc tissues was up-regulated in feedback way, and cAMP, PKA and CREB expression were also increased. But in general, IL-1β-induced IDD promoted the significant up-regulation the expression of inflammatory factors. The nucleus pulposus (NP) inflammation was exacerbated in result of MMP3 and Col-II decline through activating NF-κB signaling pathway. A2AR agonist CGS-21680 exhibited a disc protective effect through significantly increasing A2AR activity, then further activated cAMP/PKA signaling pathway with attenuating the release of TNF-α and IL-6 via down-regulating NF-κB. In contrast, SCH442416 inhibited A2AR activation, consistent with lower expression levels of cAMP and PKA, further leading to the acceleration of IDD.ConclusionsThe activation of A2AR can prevent inflammatory responses and mitigates degradation of IDD thus suggest a potential novel therapeutic strategy of IDD.

A time‐efficient computational binding affinity estimation protocol with utilization of limited experimental data: A case study for adenosine receptor

AbstractEstimating binding affinity is a crucial step in the drug discovery process. In computer‐aided drug design, this challenge can be divided into two main tasks: finding the correct binding pose and estimating the binding free energy. In this study, we propose a new binding affinity estimation protocol that utilizes molecular docking with limited experimental data and estimates binding affinity using molecular dynamics simulation. A custom scoring function was employed during docking to identify an improved initial binding pose, and the linear interaction energy method with an optimized coefficient was used for binding affinity estimation. The protocol was validated with an external data set and applied to modafinil and its derivatives to rank their binding affinities to adenosine A2A receptors (ADORA2A) as a case study. This approach could be both time‐efficient and valuable for computational drug discovery, particularly when experimental data is limited.

Effect of simultaneous application of adenosine A1 receptor agonist and A2A receptor antagonist on memory, inflammatory factors, and PSD-95 in lipopolysaccharide-induced memory impairment

The potential role of adenosine, a natural neuroprotective agent, and its receptors in the pathogenesis of Alzheimer's disease has been proposed. The present study aims to examine the effect of administering both an A1 receptor agonist and an A2A adenosine receptor antagonist simultaneously on memory, inflammatory factors, and PSD-95 in an LPS-induced Alzheimer's disease model in rats. Fifty-six male Wistar rats were randomly divided into seven groups: Saline, LPS, Saline + Vehicle, LPS + Vehicle, LPS + SCH58261 (A2A receptor antagonist), LPS + CPA (A1 receptor agonist), LPS + SCH58261+CPA. LPS (3 mg/kg/ip) was used to cause memory impairment. Treatment was performed by intraventricular injection of CPA at a dose of 700 μg and SCH-58261 at 40 μg for ten days. Passive avoidance and Y-maze tests were performed to examine animals’ memories. IL-10, TNF-α, and PSD-95 levels were measured in the brain using ELISA and western blot, respectively. Compared to the groups receiving each medication separately, the simultaneous administration of CPA and SCH58261 improved memory (P<0.05). Additionally, compared to the single medication groups, there was a significant increase in IL-10, PSD-95, and a significant decrease in TNF-α in the brain tissue (P<0.05). These findings suggest that the activation of A1 receptors along with A2A receptor inhibition could be a potential therapeutic strategy for Alzheimer's disease. These findings suggest that A1 receptor activation combined with A2A receptor inhibition may be a promising therapeutic approach for Alzheimer's disease.

Novel Quinazoline Derivatives as Highly Effective A2A Adenosine Receptor Antagonists.

The adenosine A2A receptor (A2AR) has been identified as a therapeutic target for treating neurodegenerative diseases and cancer. In recent years, we have highlighted the 2-aminoquinazoline heterocycle as an promising scaffold for designing new A2AR antagonists, exemplified by 6-bromo-4-(furan-2-yl)quinazolin-2-amine 1 (Ki (hA2AR) = 20 nM). Here, we report the synthesis of new 2-aminoquinazoline derivatives with substitutions at the C6- and C7-positions, and the introduction of aminoalkyl chains containing tertiary amines at the C2-position to enhance antagonist activity and solubility properties. Compound 5m showed a high affinity for hA2AR with a Ki value of 5 nM and demonstrated antagonist activity with an IC50 of 6 µM in a cyclic AMP assay. Introducing aminopentylpiperidine and 4-[(piperidin-1-yl)methyl]aniline substituents maintained the binding affinities (9x, Ki = 21 nM; 10d, Ki = 15 nM) and functional antagonist activities (9x, IC50 = 9 µM; 10d, IC50 = 5 µM) of the synthesized compounds while improving solubility. This study provides insights into the future development of A2AR antagonists for therapeutic applications.

A randomized phase 1 study of safety, tolerability, and pharmacokinetics of MK-1088, a novel dual adenosine receptor antagonist, in healthy adult participants.

This phase 1 first-in-human study evaluated the safety, tolerability, and pharmacokinetics of MK-1088, a novel, small-molecule dual inhibitor of adenosine A2A and A2B receptors. Healthy adult participants were enrolled in two panels (n = 8 each) and randomly assigned to receive MK-1088 (n = 6) or placebo (n = 2) orally in each of five treatment periods. Participants in panel A received single ascending doses of MK-1088 at 1, 10, 50, and 150mg or placebo in a fasted or fed (50mg only) state. Participants in panel B received MK-1088 at 3, 25, 100, and 224mg or placebo in a fasted state. Primary objectives were to evaluate safety, tolerability, and plasma pharmacokinetics following a single dose of MK-1088. The secondary objective was to evaluate the effects of a high-fat meal on pharmacokinetics. All participants (n = 16) completed the study (median age: 33 years [range: 20-43]; all were male). Treatment-related adverse events (AEs) occurred in 1 of 6 (17%), 4 of 6 (67%), 4 of 6 (67%), and 2 of 6 (33%) participants after receiving MK-1088 at 3, 25, 100, and 224mg, respectively. No serious AEs or deaths due to any cause occurred. MK-1088 was rapidly absorbed after a single dose; half-life was ~ 11h in the 100-224mg dose range. The target concentration at 12h (> 0.3 µM) was exceeded at the 50-mg dose level. MK-1088 plasma pharmacokinetics increased dose proportionately. A high-fat meal did not significantly affect pharmacokinetics at the 50-mg dose. MK-1088 was well tolerated and demonstrated dose-proportional pharmacokinetic properties that were not affected by a high-fat meal.

Sedum kamtschaticum Exerts Hypnotic Effects via the Adenosine A2A Receptor in Mice.

Insomnia is a common sleep disorder with significant societal and economic impacts. Current pharmacotherapies for insomnia are often accompanied by side effects, necessitating the development of new therapeutic drugs. In this study, the hypnotic effects and mechanisms of Sedum kamtschaticum 30% ethanol extract (ESK) and one of its active compounds, myricitrin, were investigated using pentobarbital-induced sleep experiments, immunohistochemistry (IHC), receptor binding assays, and enzyme-linked immunosorbent assay (ELISA). The pentobarbital-induced sleep experiments revealed that ESK and myricitrin reduced sleep latency and prolonged total sleep time in a dose-dependent manner. Based on c-Fos immunostaining, ESK, and myricitrin enhanced the GABAergic neural activity in sleep-promoting ventrolateral preoptic nucleus (VLPO) GABAergic. By measuring the level of GABA released from VLPO GABAergic neurons, ESK and myricitrin were found to increase GABA release in the hypothalamus. These effects were significantly inhibited by SCH. Moreover, ESK exhibited a concentration-dependent binding affinity for the adenosine A2A receptors (A2AR). In conclusion, ESK and myricitrin have hypnotic effects, and their underlying mechanisms may be related to the activation of A2AR.

Control of Dopamine Signal in High-Order Receptor Complex on Striatal Astrocytes.

The receptor-receptor interaction (RRI) of G protein-coupled receptors (GPCRs) leads to new functional entities that are conceptually distinct from the simple addition of signals mediated by the activation of the receptors that form the heteromers. Focusing on astrocytes, there is evidence for the existence of inhibitory and facilitatory RRIs, including the heteromers formed by the adenosine A2A and the dopamine D2 receptors, by A2A and the oxytocin receptor (OTR), and the D2-OTR heteromers. The possible involvement of these receptors in mosaicism has never been investigated in striatal astrocytes. By biophysical and functional approaches, we focused our attention on the existence of an A2A-D2-OTR high-order receptor complex and its role in modulating cytosolic calcium levels and endogenous glutamate release, when striatal astrocyte processes were stimulated with 4-aminopyridine. Functional data indicate a permissive role of OTR on dopamine signaling in the regulation of the glutamatergic transmission, and an inhibitory control mediated by A2A on both the D2-mediated signaling and on the OTR-facilitating effect on D2. Imaging biochemical and bioinformatic evidence confirmed the existence of the A2A-D2-OTR complex and its ternary structure in the membrane. In conclusion, the D2 receptor appears to be a hotspot in the control of the glutamate release from the astrocytic processes and may contribute to the regulation and integration of different neurotransmitter-mediated signaling in the striatum by the A2A-D2-OTR heterotrimers. Considering the possible selectivity of allosteric interventions on GPCRs organized as receptor mosaics, A2A-D2-OTR heterotrimers may offer selective pharmacological targets in neuropsychiatric disorders and neurodegenerative diseases.

Neuronal A2A receptor exacerbates synapse loss and memory deficits in APP/PS1 mice.

Early pathological upregulation of adenosine A2A receptors (A2ARs), one of the caffeine targets, by neurons is thought to be involved in the development of synaptic and memory deficits in Alzheimer's disease (AD) but mechanisms remain ill-defined. To tackle this question, we promoted a neuronal upregulation of A2AR in the hippocampus of APP/PS1 mice developing AD-like amyloidogenesis. Our findings revealed that the early upregulation of A2AR in the presence of an ongoing amyloid pathology exacerbates memory impairments of APP/PS1 mice. These behavioural changes were not linked to major change in the development of amyloid pathology but rather associated with increased phosphorylated tau at neuritic plaques. Moreover, proteomic and transcriptomic analyses coupled with quantitative immunofluorescence studies indicated that neuronal upregulation of the receptor promoted both neuronal and non-neuronal autonomous alterations, i.e. enhanced neuroinflammatory response but also loss of excitatory synapses and impaired neuronal mitochondrial function, presumably accounting for the detrimental effect on memory. Overall, our results provide compelling evidence that neuronal A2AR dysfunction, as seen in the brain of patients, contributes to amyloid-related pathogenesis and underscores the potential of A2AR as a relevant therapeutic target for mitigating cognitive impairments in this neurodegenerative disorder.