Electroacupuncture stimulating Zusanli (ST36), Sanyinjiao (SP6) in mice with collagen-induced arthritis leads to adenosine A2A receptor-mediated alteration of p38α mitogen-activated protein kinase signaling and inhibition of osteoclastogenesis.

OBJECTIVE: To observe the effect of electroacupuncture (EA) stimulating Zusanli (ST36), Sanyinjiao (SP6) on inhibition of osteoclastogenesis and the role of the adenosine A2A receptor (A2AR) and the p38α Mitogen-Activated Protein Kinase (MAPK) signaling pathway in mediating this effect. METHODS: Mice with collagen induced arthritis (CIA) received different treatments. Immunohistochemistry and western blotting were used to determine the levels of multiple signaling molecules in these joints [receptor activator of nuclear transcription factor-κB (NF-κB) ligand (RANKL), receptor activator of NF-κB (RANK), tumor necrosis factor receptor associated factor 6 (TRAF6), p38α, NF-κB, and nuclear factor of activated T cells C1 (NFATc1)]. Osteoclasts were identified using tartrate-resistant acid phosphatase (TRAP) staining. RESULTS: The immunohistochemistry results indicated upregulation of p38α, NF-κB, and NFATc1 in the CIA-control and CIA-EA-SCH58261 groups, but reduced levels in the CIA-EA group. Western blotting indicated upregulation of RANKL, RANK, TRAF6, p38α, NF-κB, and NFATc1 in the CIA-control and CIA-EA-SCH58261 groups, but reduced expression in the CIA-EA group. Osteoclasts were more abundant in the CIA-control and CIA-EA-SCH58261 groups than in the CIA-EA group. CONCLUSIONS: EA treatment enhanced the A2AR activity and inhibited osteoclast formation by inhibition of RANKL, RANK, TRAF6, p38α, NF-κB, and NFATc1. SCH58261 reversed the effect of EA. These results suggest that EA regulated p38α-MAPK signaling by increasing A2AR activity, which inhibited osteoclastogenesis.

The ADORA2A TT Genotype Is Associated with Anti-Inflammatory Effects of Caffeine in Response to Resistance Exercise and Habitual Coffee Intake.

Caffeine is an adenosine A2A receptor (ADORA2A) antagonist with ergogenic and anti-inflammatory effects. Previous studies have reported that the ADORA2A gene regulates glutamate metabolism and immune responses, with the ADORA2A rs5751876 TT genotype (with high sensitivity to caffeine) showing larger ergogenic effect following caffeine ingestion. We therefore hypothesized that the TT genotype would be associated with greater anti-inflammatory effects of caffeine in response to exercise, and with higher coffee intake in physically active individuals. The aim of the present study was twofold: (1) to investigate the association of the ADORA2A variant with the anti-inflammatory effects of caffeine in response to intense resistance exercise (RE), and (2) to analyze the association of the rs5751876 with coffee intake in physically active individuals (n = 134). Fifteen resistance-trained athletes participated in a randomized, double-blind, placebo-controlled cross-over study, where they consumed 6 mg/kg of caffeine or placebo one hour prior to performing an RE protocol. Blood samples were taken immediately from the arterial vein before, immediately after, and 15 min after RE for the analysis of inflammatory markers myeloperoxidase (MPO) and acetylcholinesterase (AChE). We found that the ADORA2A TT genotype carriers experienced lower exercise-induced inflammatory responses (p < 0.05 for AchE) when compared to the C allele carriers (i.e., CC/CT) one hour following the ingestion of caffeine. Furthermore, the ADORA2A TT genotype was positively associated with coffee intake (p = 0.0143; irrespective of CYP1A2 rs762551 polymorphism). In conclusion, we found that the ADORA2A gene polymorphism is associated with anti-inflammatory effects of caffeine in response to resistance exercise, as well as with habitual coffee intake in physically active individuals.

Lateral septum adenosine A2A receptors control stress-induced depressive-like behaviors via signaling to the hypothalamus and habenula.

Major depressive disorder ranks as a major burden of disease worldwide, yet the current antidepressant medications are limited by frequent non-responsiveness and significant side effects. The lateral septum (LS) is thought to control of depression, however, the cellular and circuit substrates are largely unknown. Here, we identified a subpopulation of LS GABAergic adenosine A2A receptors (A2AR)-positive neurons mediating depressive symptoms via direct projects to the lateral habenula (LHb) and the dorsomedial hypothalamus (DMH). Activation of A2AR in the LS augmented the spiking frequency of A2AR-positive neurons leading to a decreased activation of surrounding neurons and the bi-directional manipulation of LS-A2AR activity demonstrated that LS-A2ARs are necessary and sufficient to trigger depressive phenotypes. Thus, the optogenetic modulation (stimulation or inhibition) of LS-A2AR-positive neuronal activity or LS-A2AR-positive neurons projection terminals to the LHb or DMH, phenocopied depressive behaviors. Moreover, A2AR are upregulated in the LS in two male mouse models of repeated stress-induced depression. This identification that aberrantly increased A2AR signaling in the LS is a critical upstream regulator of repeated stress-induced depressive-like behaviors provides a neurophysiological and circuit-based justification of the antidepressant potential of A2AR antagonists, prompting their clinical translation.

The Extract of Ilex cornuta Bark Promotes Bone Healing by Activating Adenosine A2A Receptor.

Introduction: Bone fracture is a common reason causing human disability. The delay union and nonunion rates are approximately 5-10% despite patients receiving active treatment. Currently, there is a limited number of drugs directly accelerating bone healing, especially direct extracts from plants. Moreover, the pharmacological effects of Ilex cornuta bark are still unknown. This study aimed to explore the effects and mechanisms of Ilex cornuta bark in bone healing. Methods and Results: First, the promoting effects of Ilex cornuta bark on bone healing were verified by the mice femur fracture model as Ilex cornuta bark increased the callus formation and enhanced the biomechanical stability during the bone healing process. Second, the target gene of Ilex cornuta bark in bone healing identified by bioinformatics analysis and immunofluorescence validation was ADORA2A. Third, 410 main compound compositions of Ilex cornuta bark were explored by a non-target metabolomic analysis, where 190 of them were neg ion mode, and 220 were pos ion mode. Molecular docking was used to predict the regulatory effect of the compounds on adora2a (adenosine A2A receptor), and ursonic acid had the lowest binding energy with adora2a. Finally, nfkb1 was the transcription factor (TF) of adora2a, and ursonic acid also had the lowest binding energy by bioinformatic analysis and molecular docking. Conclusion: Overall, Ilex cornuta bark water extract was a new plant extract on promoting bone healing; in addition, the mechanism of it might be activating adora2a though Nfkb1.

Shenfu Administration Improves Cardiac Fibrosis in Rats With Myocardial Ischemia-Reperfusion Through Adenosine A2a Receptor Activation.

OBJECTIVE: Shenfu injection (SFI) is commonly used for cardiac dysfunction in China. Adenosine receptors have been reported to exert anti-fibrosis effects. The intent of this study was to evaluate that SFI attenuates cardiac fibrosis through activating of adenosine A2a receptor (A2aR) in rats with myocardial ischemia-reperfusion (MI/R). METHODS: Sprague Dawley male rats were randomly divided into five groups, nine rats in each group. Injections in all rat groups were carried out prior to reperfusion, and in the sham and MI/R groups, only vehicle was injected. Injections in the remaining group were as follows: 5 mL/kg in the SFI group; 15 mg/kg nicorandil in the A2R agonist group; and 5 mL/kg SFI plus 5 mg/kg MSX-3 in the SFI + A2aR antagonist group. Changes in cyclic adenosine monophosphate (cAMP) and the development of myocardial infarction and cardiac fibrosis were documented among the groups. Additionally, the levels of A2aR, collagen Ⅰ, collagen Ⅲ, fibronectin, and matrix metalloproteinase-9 (MMP-9) were measured. RESULTS: Following injection with SFI or nicorandil, the cAMP concentration, infarct area, and cardiac fibrosis induced by MI/R injury were significantly decreased (p < 0.05). Additionally, the levels of collagen Ⅰ, collagen Ⅲ, fibronectin, and MMP-9 were clearly suppressed by SFI or nicorandil when compared with the MI/R group (p<0.01). However, the protective effects of SFI were counteracted by MSX-3. A negative correlation between A2aR and collagen I and collagen III was found (p = 0.00). CONCLUSION: SFI activated the A2aR to reduce myocardial fibrosis caused by MI/R injury, which provided an underlying mechanism of action of SFI.

Adenosine A2A Receptor Occupancy by Caffeine After Coffee Intake in Parkinson's Disease.

BACKGROUND: Coffee intake can decrease the risk for Parkinson's disease (PD). Its beneficial effects are allegedly mediated by caffeine through adenosine A2A receptor (A2A R) antagonist action. OBJECTIVE: We aimed to calculate occupancy rates of striatal A2A Rs by caffeine after coffee intake in PD. METHODS: Five patients with PD underwent 11 C-preladenant positron emission tomography scanning at baseline and after intake of coffee containing 129.5 mg (n = 3) or 259 mg (n = 2) of caffeine. Concurrently, serum caffeine levels were measured. RESULTS: The mean serum caffeine level (µg/mL) was 0.374 at baseline and increased to 4.48 and 8.92 by 129.5 and 259 mg of caffeine, respectively. The mean occupancy rates of striatal A2A Rs by 129.5 and 259 mg of caffeine were 54.2% and 65.1%, respectively. CONCLUSIONS: A sufficient A2A R occupancy can be obtained by drinking a cup of coffee, which is equivalent to approximately 100 mg of caffeine. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Parkinsonism-like Disease Induced by Rotenone in Rats: Treatment Role of Curcumin, Dopamine Agonist and Adenosine A2A Receptor Antagonist.

BACKGROUND: Parkinsonism is a neurodegenerative disorder that affects elderly people worldwide. METHODS: Curcumin, adenosine A2AR antagonist (ZM241385) and Sinemet® (L-dopa) were evaluated against Parkinson's disease (PD) induced by rotenone in rats, and the findings were compared to our previous study on mice model. RESULTS: Rats injected with rotenone showed severe alterations in adenosine A2A receptor gene expression, oxidative stress markers, inflammatory mediator, energetic indices, apoptotic marker and DNA fragmentation levels as compared to the control group. Treatments with curcumin, ZM241385, and Sinemet® restored all the selected parameters. The brain histopathological features of cerebellum regions confirmed our results. By comparing our results with the previous results on mice, we noticed that mice respond to rotenone toxicity and treatments more than rats with regards to behavioral observation, A2AR gene expression, neurotransmitter levels, inflammatory mediator and apoptotic markers, while rats showed higher response to treatments regarding oxidative stress and energetic indices. CONCLUSION: Curcumin succeeded in attenuating the severe effects of Parkinson's disease in the rat model and can be considered as a potential dietary supplement. Adenosine A2AR antagonist has almost the same pattern of improvement as Sinemet® and may be considered as a promising therapy against PD. To compare the role of animal species in response to PD symptoms and treatments, our previous report on mice explored the response of mice to rotenone toxicity in comparison with rats, where rats have shown a higher response to treatments. Therefore, no animal model can perfectly recapitulate all the pathologies of PD.

Curcumin by activation of adenosine A2A receptor stimulates protein kinase a and potentiates inhibitory effect of cangrelor on platelets.

Curcumin is a natural polyphenol derived from the turmeric plant (Curcuma longa) which exhibits numerous beneficial effects on different cell types. Inhibition of platelet activation by curcumin is well known, however molecular mechanisms of its action on platelets are not fully defined. In this study, we used laser diffraction method for analysis of platelet aggregation and Western blot for analysis of intracellular signaling mechanisms of curcumin effects on platelets. We identified two new molecular mechanisms involved in the inhibitory effects of curcumin on platelet activation. Firstly, curcumin by activation of adenosine A2A receptor stimulated protein kinase A activation and phosphorylation of Vasodilator-stimulated phosphoprotein. Secondly, we demonstrated that curcumin even at low doses, which did not inhibit platelet aggregation, potentiated inhibitory effect of ADP receptor P2Y12 antagonist cangrelor which partly could be explained by activation of adenosine A2A receptor.

Involvement of the adenosine A1 receptor in the hypnotic effect of rosmarinic acid.

Insomnia, the most common sleep disorder, is characterized by a longer sleep latency, greater sleep fragmentation, and consequent excessive daytime fatigue. Due to the various side effects of prescribed hypnotics, demand for new drugs is still high. Recent studies have suggested the adenosine receptor (AR) as a potential therapeutic target for insomnia, however, clinically useful hypnotics targeting AR are not yet available. In the present study, we evaluated the hypnotic effect of rosmarinic acid, a phenolic compound widely found in medicinal plants, through pentobarbital-induced sleep test, electroencephalography/electromyography (EEG/EMG), and immunohistochemistry in mice. The underlying mechanisms were assessed by pharmacological approach using 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and SCH5826, antagonists for A1R and A2AR, respectively. Receptor-binding assay and functional agonism were also performed. Our study provides a new evidence that rosmarinic acid has a direct binding activity (Ki = 14.21 ± 0.3 µM) and agonistic activity for A1R. We also found that rosmarinic acid significantly decreased sleep fragmentation and onset latency to NREM sleep, and these effects were abolished by DPCPX. The results from c-Fos immunostaining showed that rosmarinic acid decreased the neuronal activity in wake-promoting brain regions, such as the basal forebrain and the lateral hypothalamus, while increasing the neuronal activity in the ventrolateral preoptic nucleus, a sleep-promoting region; all these effects were significantly inhibited by DPCPX. Taken together, this study suggests that rosmarinic acid possesses novel activity as an A1R agonist and thereby exerts a hypnotic effect, and thus it may serve as a potential therapeutic agent for insomnia through targeting A1R.

Attenuation of Tumor Development in Mammary Carcinoma Rats by Theacrine, an Antagonist of Adenosine 2A Receptor.

Caffeine has been reported to induce anti-tumor immunity for attenuating breast cancer by blocking the adenosine 2A receptor. Molecular modeling showed that theacrine, a purine alkaloid structurally similar to caffeine, might be an antagonist of the adenosine 2A receptor equivalent to or more effective than caffeine. Theacrine was further demonstrated to be an effective antagonist of the adenosine 2A receptor as its concurrent supplementation significantly reduced the elevation of AMPK phosphorylation level in MCF-7 human breast cells induced by CGS21680, an agonist of adenosine 2A receptors. In an animal model, the development of mammary carcinoma induced by 7,12-Dimethylbenz[a]anthracene in Sprague-Dawley rats could be attenuated by daily supplement of theacrine of 50 or 100 mg/kg body weight. Both expression levels of cleaved-caspase-3/pro-caspase-3 and granzyme B in tumor tissues were significantly elevated when theacrine was supplemented, indicating the induction of programmed cell death in tumor cells might be involved in the attenuation of mammary carcinoma. Similar to the caffeine, significant elevation of interferon-γ and tumor necrosis factor-α was observed in the serum and tumor tissues of rats after the theacrine supplement of 50 mg/kg body weight. Taken together, theacrine is an effective antagonist of adenosine 2A receptors and possesses great potential to be used to attenuate breast cancer.

Effect of S-Se Bioisosteric Exchange on Affinity and Intrinsic Efficacy of Novel N-acylhydrazone Derivatives at the Adenosine A2A Receptor.

In this work, we evaluated the conformational effect promoted by the isosteric exchange of sulfur by selenium in the heteroaromatic ring of new N-acylhydrazone (NAH) derivatives (3-8, 13, 14), analogues of the cardioactive compounds LASSBio-294 (1) and LASSBio-785 (2). NMR spectra analysis demonstrated a chemical shift variation of the iminic Csp2 of NAH S/Se-isosters, suggesting a stronger intramolecular chalcogen interaction for Se-derivatives. To investigate the pharmacological profile of these compounds at the adenosine A2A receptor (A2AR), we performed a previously validated functional binding assay. As expected for bioisosteres, the isosteric-S/Se replacement affected neither the affinity nor the intrinsic efficacy of our NAH derivatives (1-8). However, the N-methylated compounds (2, 6-8) presented a weak partial agonist profile at A2AR, contrary to the non-methylated counterparts (1, 3-5), which appeared as weak inverse agonists. Additionally, retroisosterism between aromatic rings of NAH on S/Se-isosters mimicked the effect of the N-methylation on intrinsic efficacy at A2AR, while meta-substitution in the phenyl ring of the acyl moiety did not. This study showed that the conformational effect of NAH-N-methylation and aromatic rings retroisosterism changed the intrinsic efficacy on A2AR, indicating the S/Se-chalcogen effect to drive the conformational behavior of this series of NAH.

Identification of anti-Parkinson's Disease Lead Compounds from Aspergillus ochraceus Targeting Adenosin Receptors A2A.

Two novel alkaloids compounds together with fifteen know metabolites were identified from Aspergillus ochraceus. The stereochemistry features of the new molecules were determined via HRESIMS, NMR, ECD, and XRD analyses. Amongst these, compounds two compounds exhibited potential efficacy as anti-Parkinson's disease with the EC50 values of 2.30 and 2.45 µM, respectively. ADMET prediction showed that these compounds owned favorable drug-like characteristics and safe toxicity scores towards CNS drugs. Virtual screening analyses manifested that the compounds exhibited not only robust and reliable interactions to adenosine receptors A2A , but also higher binding selectivity to A2A receptors than to A1 and A3 receptors. Molecular dynamics simulation demonstrated the reliability of molecular docking results and the stability of the complexes obtained with the novel compounds and A2A receptors in natural environments. It is the first time that anti-PD lead compounds have been identified from Aspergillus ochraceus and targeting adenosine A2A receptors.

Structure-Guided Design of G-Protein-Coupled Receptor Polypharmacology.

Many diseases are polygenic and can only be treated efficiently with drugs that modulate multiple targets. However, rational design of compounds with multi-target profiles is rarely pursued because it is considered too difficult, in particular if the drug must enter the central nervous system. Here, a structure-based strategy to identify dual-target ligands of G-protein-coupled receptors is presented. We use this approach to design compounds that both antagonize the A2A adenosine receptor and activate the D2 dopamine receptor, which have excellent potential as antiparkinson drugs. Atomic resolution models of the receptors guided generation of a chemical library with compounds designed to occupy orthosteric and secondary binding pockets in both targets. Structure-based virtual screens identified ten compounds, of which three had affinity for both targets. One of these scaffolds was optimized to nanomolar dual-target activity and showed the predicted pharmacodynamic effect in a rat model of Parkinsonism.

CD39/CD73/A2a Adenosine Metabolic Pathway: Targets for Moxibustion in Treating DSS-Induced Ulcerative Colitis.

Ulcerative Colitis (UC) is a chronic inflammation disease, and the incidence of UC is increasing recently. Both clinical trials and animal experiments show that moxibustion is a complementary and alternative treatment for UC. Previous studies showed that moxibustion can improve UC by regulating the balance of Tregs and Th17 (Sun et al., 2017). Treg cells is one subset of CD4[Formula: see text] T cells that exert the immunosuppressive function. CD39 and CD73, expressed on the surface of Tregs, hydrolyze ATP to AMP and are further involved in the immunosuppressive function of Tregs. In this study, we investigated the effect of moxibustion on CD39[Formula: see text] Tregs and CD73[Formula: see text] Tregs in dextran sulfate sodium (DSS) induced UC mice. The A2a receptor (A2aR), one of the targets of adenosine, was also detected. The results showed that moxibustion could increase the expression of CD39, CD73, and A2aR in colonic tissue and improve the proportion of CD39[Formula: see text] Tregs and CD73[Formula: see text] Tregs in peripheral blood, inguinal draining lymph nodes and spleen in the UC model. Additionally, A2aR agonists enhanced the cell viability of colonic epithelial cells and inhibit the production of cytokines IL-6 and TNF-[Formula: see text] in vitro, which may further influence the pathway of ATP purine signal metabolism and alleviates the gut inflammation of UC mice. Taken together, this study provides supplemental evidence to reveal the immune related mechanism of moxibustion in the treatment of UC.

Electroacupuncture improves neuronal plasticity through the A2AR/cAMP/PKA signaling pathway in SNL rats.

Improvements in neuronal plasticity are considered to be conducive to recovery from neuropathic pain. Electroacupuncture (EA) is regarded as an effective rehabilitation method for neuropathic pain. However, the effects and potential mechanism associated with EA-induced repair of hyperesthesia are not fully understood. Evidence has suggested that the adenosine A2A receptor (A2AR) and the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway play an important role in improving neuropathic pain. Here, we examined the function of EA in promoting neuronal plasticity in spinal nerve ligation (SNL) rats. The A2AR antagonist SCH58261, A2AR agonist 2-p-(2-carboxyethyl)phenethylamino-50-N-ethylcarboxamido adenosine HCl (CGS21680) and A2AR siRNA were used to confirm the relationship between A2AR and the cAMP/PKA pathway as well as the effects of A2AR on EA-induced improvements in neurobehavioral state and neuronal plasticity. Mechanical withdrawal threshold (MWT), thermal withdrawal latency (TWL), HE staining, Western blotting, RT-PCR, immunofluorescence, enzyme-linked immunosorbent assay, Nissl staining, silver staining, Golgi-Cox staining and transmission electron microscopy were used to evaluate the changes in neurobehavioral performance, protein expression, neuronal structure and dendrites/synapses. The results showed that EA and CGS21680 improved the behavioral performance, neuronal structure and dendritic/synaptic morphology of SNL rats, consistent with higher expression levels of A2AR, cAMP and PKA. In contrast to the positive effects of EA, SCH58261 inhibited dendritic growth and promoted dendritic spine/synaptic remodeling. In addition, the EA-induced improvement in neuronal plasticity was inhibited by SCH58261 and A2AR siRNA, consistent with lower expression levels of A2AR, cAMP and PKA, and worse behavioral performance. These results indicate that EA suppresses SNL-induced neuropathic pain by improving neuronal plasticity via upregulating the A2AR/cAMP/PKA signaling pathway.

Adenosine A1 and A2A receptors are involved on guanosine protective effects against oxidative burst and mitochondrial dysfunction induced by 6-OHDA in striatal slices.

6-Hydroxydopamine (6-OHDA) is the most used toxin in experimental Parkinson's disease (PD) models. 6-OHDA shows high affinity for the dopamine transporter and once inside the neuron, it accumulates and undergoes non-enzymatic auto-oxidation, promoting reactive oxygen species (ROS) formation and selective damage of catecholaminergic neurons. In this way, our group has established a 6-OHDA in vitro protocol with rat striatal slices as a rapid and effective model for screening of new drugs with protective effects against PD. We have shown that co-incubation with guanosine (GUO, 100 µM) prevented the 6-OHDA-induced damage in striatal slices. As the exact GUO mechanism of action remains unknown, the aim of this study was to investigate if adenosine A1 (A1R) and/or A2A receptors (A2AR) are involved on GUO protective effects on striatal slices. Pre-incubation with DPCPX, an A1R antagonist prevented guanosine effects on 6-OHDA-induced ROS formation and mitochondrial membrane potential depolarization, while CCPA, an A1R agonist, did not alter GUO effects. Regarding A2AR, the antagonist SCH58261 had similar protective effect as GUO in ROS formation and mitochondrial membrane potential. Additionally, SCH58261 did not affect GUO protective effects. The A2AR agonist CGS21680, although, completely blocked GUO effects. Finally, the A1R antagonist DPCPX, and the A2AR agonist CGS21680 also abolished the preventive guanosine effect on 6-OHDA-induced ATP levels decrease. These results reinforce previous evidence for a putative interaction of GUO with A1R-A2AR heteromer as its molecular target and clearly indicate a dependence on adenosine receptors modulation to GUO protective effect.

Limonene has anti-anxiety activity via adenosine A2A receptor-mediated regulation of dopaminergic and GABAergic neuronal function in the striatum.

BACKGROUND: Limonene, a common terpene found in citrus fruits, is assumed to reduce stress and mood disorders. Dopamine and γ-aminobutyric acid (GABA) have been reported to play an important role in modulating anxiety in different parts of the brain. HYPOTHESIS/PURPOSE: Herein, we report the anxiolytic activity of limonene. In addition, we identified a possible mechanism underlying the effect of limonene on DAergic and GABAergic neurotransmission. STUDY DESIGN: In this study, mice were injected with saline in the control group and limonene in the test group before behavioral analysis. We performed immunoblotting and high-performance liquid chromatography (HPLC) analysis after the behavioral study. RESULTS: The limonene treated group showed increased locomotor activity and open-arm preference in the elevated plus maze experiment. Limonene treatment increased the expression of both tyrosine hydroxylase and GAD-67 proteins and significantly upregulated dopamine levels in the striatum. Furthermore, tissue dopamine levels were increased in the striatum of mice following limonene treatment, and depolarization-induced GABA release was enhanced by limonene pre-treatment in PC-12 cells. Interestingly, limonene-induced anxiolytic activity and GABA release augmentation were blocked by an adenosine A2A receptor (A2AR) antagonist. CONCLUSION: Our results suggest that limonene inhibits anxiety-related behavior through A2A receptor-mediated regulation of DAergic and GABAergic neuronal activity.

Novel curcumin analog (cis-trans curcumin) as ligand to adenosine receptors A2A and A2B: potential for therapeutics.

All four of the adenosine receptor (AR) subtypes mediate pain and have been targeted by pharmacologists to generate new therapeutics for chronic pain. The vanilloid phytochemicals, which include curcumin, capsaicin, and gingerol, have been shown to alleviate pain. However, there is little to no literature on the interaction of vanilloid phytochemicals with ARs. In this study, photochemical methods were used to generate a novel isomer of curcumin (cis-trans curcumin or CTCUR), and the interactions of both curcumin and CTCUR with the two Gs-linked AR subtypes were studied. Competitive binding assays, docking analysis, and confocal fluorescence microscopy were performed to measure binding affinity; cell survival assays were used to measure toxicity; and cAMP assays were performed to measure receptor activation. Competitive binding results indicated that CTCUR binds to both AR A2A and AR A2B with Ki values of 5 µM and 7 µM, respectively, which is consistent with our docking results. Fluorescence microscopy data also shows binding for A2B and A2A. Cell survival results show that CTCUR and CUR are nontoxic at the tested concentrations in these cell lines. Overall, our results suggest that vanilloid phytochemicals may be slightly modified to increase interaction with Gs-ARs, and thereby can be further explored to provide a novel class of non-opioid antinociceptives.

Coffee effectively attenuates impaired attention in ADORA2A C/C-allele carriers during chronic sleep restriction.

Many people consume coffee to attenuate increased sleepiness and impaired vigilance and attention due to insufficient sleep. We investigated in genetically caffeine sensitive men and women whether 'real world' coffee consumption during a simulated busy work week counteracts disabling consequences of chronically restricted sleep. We subjected homozygous C-allele carriers of ADORA2A (gene encoding adenosine A2A receptors) to five nights of only 5 h time-in-bed. We administered regular coffee (n = 12; 200 mg caffeine at breakfast and 100 mg caffeine after lunch) and decaffeinated coffee (n = 14) in double-blind fashion on all days following sleep restriction. At regular intervals four times each day, participants rated their sleepiness and performed the psychomotor vigilance test, the visual search task, and the visuo-spatial and letter n-back tasks. At bedtime, we quantified caffeine and the major caffeine metabolites paraxanthine, theobromine and theophylline in saliva. The two groups did not differ in age, body-mass-index, sex-ratio, chronotype and mood states. Subjective sleepiness increased in both groups across consecutive sleep restriction days and did not differ. By contrast, regular coffee counteracted the impact of repeated sleep loss on sustained and selective attention, as well as executive control when compared to decaffeinated coffee. The coffee also induced initial or transient benefits on different aspects of baseline performance during insufficient sleep. All differences between the groups disappeared after the recovery night and the cessation of coffee administration. The data suggest that 'real world' coffee consumption can efficiently attenuate sleep restriction-induced impairments in vigilance and attention in genetically caffeine sensitive individuals. German Clinical Trial Registry: # DRSK00014379.

Adenosine A2A receptor blockade improves neuroprosthetic learning by volitional control of population calcium signal in M1 cortical neurons.

Volitional control is at the core of brain-machine interfaces (BMI) adaptation and neuroprosthetic-driven learning to restore motor function for disabled patients, but neuroplasticity changes and neuromodulation underlying volitional control of neuroprosthetic learning are largely unexplored. To better study volitional control at annotated neural population, we have developed an operant neuroprosthetic task with closed-loop feedback system by volitional conditioning of population calcium signal in the M1 cortex using fiber photometry recording. Importantly, volitional conditioning of the population calcium signal in M1 neurons did not improve within-session adaptation, but specifically enhanced across-session neuroprosthetic skill learning with reduced time-to-target and the time to complete 50 successful trials. With brain-behavior causality of the neuroprosthetic paradigm, we revealed that proficiency of neuroprosthetic learning by volitional conditioning of calcium signal was associated with the stable representational (plasticity) mapping in M1 neurons with the reduced calcium peak. Furthermore, pharmacological blockade of adenosine A2A receptors facilitated volitional conditioning of neuroprosthetic learning and converted an ineffective volitional conditioning protocol to be the effective for neuroprosthetic learning. These findings may help to harness neuroplasticity for better volitional control of neuroprosthetic training and suggest a novel pharmacological strategy to improve neuroprosthetic learning in BMI adaptation by targeting striatal A2A receptors.