Adenosine A1 Receptor Research Articles

Microglial depletion exacerbates motor impairment and dopaminergic neuron loss in a 6-OHDA model of Parkinson's disease

6-hydroxydopamine (6-OHDA) is a common neurotoxin used to induce Parkinson's disease (PD) in mice, exerting neurotoxic effects through the production of reactive oxygen species and microglial activation. However, the role of microglia in PD is still not clear, with contradictory reports showing neuroprotection or exacerbation of neuronal death. Microglial depletion aggravates motor coordination impairments and reduces tyrosine hydroxylase positive neurons in the substantia nigra pars compacta. Moreover, MeCP2 and Adora1 genes expression were downregulated, suggesting they may be involved in the neurodegenerative process. This study highlights that microglia plays a protective role in dopaminergic neuron survival during the initial phase of PD, and the investigation of the mechanisms of this effect in future studies will help elucidate the pathophysiology of PD.

Adenosine receptor stimulation inhibits methamphetamine-associated cue seeking.

Methamphetamine (METH) is a psychostimulant drug that remains a popular and threatening drug of abuse with high abuse liability. There is no established pharmacotherapy to treat METH dependence, but evidence suggests that stimulation of adenosine receptors reduces the reinforcing properties of METH and could be a potential pharmacological target. This study examines the effects of adenosine receptor subtype stimulation on METH seeking using both a cue-induced reinstatement and cue-craving model of relapse. Male and female rats were trained to self-administer METH during daily 2-h sessions. Cue-induced reinstatement of METH seeking was evaluated after extinction training. A systemic pretreatment of an adenosine A1 receptor (A1R) or A2A receptor (A2AR) agonist was administered prior to an extinction or cue session to evaluate the effects of adenosine receptor subtype stimulation on METH seeking. The effects of a systemic pretreatment of A1R or A2AR agonists were also evaluated in a cue-craving model where the cued-seeking test was conducted after 21 days of forced home-cage abstinence without extinction training. Cue-induced reinstatement was reduced in both male and female rats that received A1R or A2AR agonist pretreatments. Similarly, an A1R or A2AR agonist pretreatment also inhibited cue craving in both male and female rats. Stimulation of either adenosine A1R or A2AR subtypes inhibits METH-seeking behavior elicited by METH-associated cues. These effects may be attributed to the ability of A1R and A2AR stimulation to disrupt cue-induced dopamine and glutamate signaling throughout the brain.

Mast Cell-Associated Serotonin in Acupoint Contributes to Acupuncture Analgesia in Arthritis Rats by Mediating ATP Release.

The activation of subcutaneous mast cells (MCs) helps to trigger the analgesic effect induced by acupuncture (AP), a traditional oriental therapy, that has been gradually accepted worldwide. This work aimed to reveal whether the serotonin (5-hydroxytryptamine, 5-HT) released from MCs plays an important role in this process, which has a controversial effect in the mechanism of pain. In vivo tests, a 20-min session of AP was applied at Zusanli acupuncture point (acupoint) of acute ankle arthritis rats. Pain thresholds of the injured hindpaw were assessed to reflect the pain state, and the targeting substances in the interstitial space of the treated acupoint were sampled by microdialysis. In vitro experiments, exogenous 5-HT (exo-5-HT) was introduced to mediate adenosine triphosphate (ATP) release from cultured MCs. Needling promoted 5-HT accumulation at the Zusanli acupoint, which was prevented by sodium cromolyn. AP's analgesic effect was suppressed by the inhibition of 5-HT receptors at the acupoint, especially 5-HT1A subtype. In vitro tests, mechanical perturbation mimicking needling stimulation induced MCs to release 5-HT. 1 μM and 10 μM of exo-5-HT facilitated ATP release, which was restrained by blocking of 5-HT1 receptors rather than 5-HT3 receptors. As 5-HT, ATP and adenosine were also transiently accumulated in the treated acupoint during needling. Promoting ATP hydrolysis or activation adenosine A1 receptors duplicated AP analgesic effect. Finally, the inhibition of ATP receptors by suramin or pyridoxal phosphate-6-azo tetrasodium salt hydrate (PPADS) prevented AP analgesic effect. Our results suggest that MC-associated 5-HT release at acupoints contributes to AP analgesia, and the mediation of ATP secretion through 5-HT1A receptors might be the underlying mechanism at play. ATP could facilitate adenosine production or the propagation of needling signals.

Cordycepin improved the cognitive function through regulating adenosine A2A receptors in MPTP induced Parkinson's disease mice model

BackgroundParkinson's disease (PD), the most common neurodegenerative disorder, primarily affects dopaminergic neurons in the substantia nigra (SN). In addition to severe motor dysfunction, PD patients appear apparent cognitive impairments in the late stage. Cognitive dysfunction is accompanied by synaptic transmission damage in the hippocampus. Cordycepin has been reported to alleviate cognitive impairments in neurodegenerative diseases. PurposeThe study aimed to estimate the protection roles of cordycepin on cognitive dysfunction in PD model and explore the potential mechanisms. Methods1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was used to establish the PD model in vivo and in vitro experiments. In the in vivo experiments, the C57BL / 6 mice were intraperitoneally injected with MPTP and intragastric administration with cordycepin. Open field test (OFT) was used to estimate the exercise ability. Spontaneous alternation behavioral (SAB) and morris water maze (MWM) tests were used to evaluate the learning and memory abilities. The hippocampal slices from C57BL / 6 and Kunming mice in the in vitro experiments were used to record field excitatory postsynaptic potential (fEPSP) by electrophysiological methods. Western blotting was used to examine the level of tyrosine hydroxylase (TH) in the in vivo experiments and the levels of adenosine A1 and A2A receptors (A1R and A2AR) in the in vitro experiments, respectively. The drugs of MPTP, cordycepin, DPCPX and SCH58261 were perfused through dissolving in artificial cerebrospinal fluid. ResultsCordycepin could significantly reduce the impairments on motor, exploration, spatial learning and memory induce by MPTP. MPTP reduced the amplitude of LTP in hippocampal CA1 area but cordycepin could improve LTP amplitudes. Cordycepin at dosage of 20 mg/kg also increased the TH level in SN. In the in vitro experiments, MPTP inhibited synaptic transmission in hippocampal Schaffer-CA1 pathway with a dose-dependent relationship, while cordycepin could reverse the inhibition of synaptic transmission. Furthermore, the roles of cordycepin on synaptic transmission could been attenuated in the presence of the antagonists of A1R and A2AR, DPCPX and SCH58261, respectively. Interestingly, the level of A2AR rather than A1R in hippocampus was significantly decreased in the cordycepin group as compared to the control. ConclusionThe present study has showed that cordycepin could improve cognitive function in the PD model induced by MPTP through regulating the adenosine A2A receptors. These findings were helpful to provide a new strategy for the dementia caused by Parkinson's disease.

Effects of Chronic Caffeine Consumption on Synaptic Function, Metabolism and Adenosine Modulation in Different Brain Areas.

Adenosine receptors mainly control synaptic function, and excessive activation of adenosine receptors may worsen the onset of many neurological disorders. Accordingly, the regular intake of moderate doses of caffeine antagonizes adenosine receptors and affords robust neuroprotection. Although caffeine intake alters brain functional connectivity and multi-omics analyses indicate that caffeine intake modifies synaptic and metabolic processes, it is unclear how caffeine intake affects behavior, synaptic plasticity and its modulation by adenosine. We now report that male mice drinking caffeinated water (0.3 g/L) for 2 weeks were behaviorally indistinguishable (locomotion, mood, memory) from control mice (drinking water) and displayed superimposable synaptic plasticity (long-term potentiation) in different brain areas (hippocampus, prefrontal cortex, amygdala). Moreover, there was a general preservation of the efficiency of adenosine A1 and A2A receptors to control synaptic transmission and plasticity, although there was a tendency for lower levels of endogenous adenosine ensuring A1 receptor-mediated inhibition. In spite of similar behavioral and neurophysiological function, caffeine intake increased the energy charge and redox state of cortical synaptosomes. This increased metabolic competence likely involved a putative increase in the glycolytic rate in synapses and a prospective greater astrocyte-synapse lactate shuttling. It was concluded that caffeine intake does not trigger evident alterations of behavior or of synaptic plasticity but increases the metabolic competence of synapses, which might be related with the previously described better ability of animals consuming caffeine to cope with deleterious stimuli triggering brain dysfunction.

Role of cardiac β1-adrenergic and A1-adenosine receptors in severe arrhythmias related to Parkinson's disease

AimsAlthough reduced life expectancy in Parkinson's Disease (PD) patients has been related to severe cardiac arrhythmias due to autonomic dysfunctions, its molecular mechanisms remain unclear. To investigate the role of cardiac β1-Adrenergic (β1AR) and A1-Adenosine (A1R) receptors in these dysfunctions, the pharmacological effects of stimulation of cardiac β1AR (isoproterenol, ISO), in the absence and presence of cardiac β1AR (atenolol, AT) or A1R (1,3-dipropyl-8-cyclopentyl xanthine, DPCPX) blockade, on the arrhythmias induced by Ischemia/Reperfusion (CIR) in an animal PD model were studied. MethodsPD was produced by dopaminergic lesions (confirmed by immunohistochemistry analysis) caused by the injection of 6-hydroxydopamine (6-OHDA, 6 μg) in rat striatum. CIR was produced by a surgical interruption for 10 min followed by reestablishment of blood circulation in the descendent left coronary artery. On the incidence of CIR-Induced Ventricular Arrhythmias (VA), Atrioventricular Block (AVB), and Lethality (LET), evaluated by Electrocardiogram (ECG) analysis, the effects of intravenous treatment with ISO, AT and DPCPX (before CIR) were studied. ResultsVA, AVB and LET incidences were significantly higher in 6-OHDA (83%, 92%, 100%, respectively) than in control rats (58%, 67% and 67%, respectively). ISO treatment significantly reduced these incidences in 6-OHDA (33%, 33% and 42%, respectively) and control rats (25%, 25%, 33%, respectively), indicating that stimulation of cardiac β1AR induced cardioprotection. This response was prevented by pretreatment with AT and DPCPX, confirming the involvement of cardiac β1AR and A1R. ConclusionPharmacological modulation of cardiac β1AR and A1R could be a potential therapeutic strategy to reduce severe arrhythmias and increase life expectancy in PD patients.

Problems and prospects for finding new pharmacological agents among adenosine receptor agonists, antagonists, or their allosteric modulators for the treatment of cardiovascular diseases.

A1-adenosine receptors (A1AR) are widely distributed in the human body and mediate many different effects. They are abundantly present in the cardiovascular system, where they control angiogenesis, vascular tone, heart rate, and conduction. This makes the cardiovascular system A1AR an attractive target for the treatment of cardiovascular diseases (CVD). The review summarizes the literature data on the structure and functioning of A1AR, and analyzes their involvement in the formation of myocardial hypertrophy, ischemia-reperfusion damage, various types of heart rhythm disorders, chronic heart failure, and arterial hypertension. Special attention is paid to the role of some allosteric regulators of A1AR as potential agents for the CVD treatment.

Role of cytochrome P450-epoxygenase and soluble epoxide hydrolase in the regulation of vascular response.

The role of cytochrome P450-epoxygenase has been seen in cardiovascular physiology and pathophysiology. The aberration in CYP450-epoxygenase genes occur due to genetic polymorphisms, aging, or environmental factors, that increase susceptibility to cardiovascular diseases (CVDs). The actual role played by the CYP450-epoxygenases is the metabolism of arachidonic acid (AA) and linoleic acid (LA) into epoxyeicosatrienoic acids (EETs) and epoxyoctadecaenoic acid (EpOMEs) metabolites (oxylipins) and others, which is involved in vasodilation and myocardial-protection. But the genetic polymorphisms in CYP450-epoxygenases lose their beneficial cardiovascular effects of oxylipins, and the soluble epoxide hydrolase (sEH) antagonizes beneficial oxylipins into diols. Like sEH converts EETs into dihydroxyeicosatrienoic acid (DHETs), EpOMEs into dihydroxyoctadecaenoic acid (DiHOMEs), and reverses its beneficial effects, and the sEH gene (Ephx2) polymorphisms cause the enzyme to become overactive and convert epoxy-fatty acids into diols, making them vulnerable to CVDs, including hypertension. Other, enzymes like ω-hydroxylases (CYP450-4A11 & CYP450-4F2)-derived oxylipins from AA, ω-terminal-hydroxyeicosatetraenoic acids (19-, 20-HETE), lipoxygenase-derived oxylipins, mid-chain hydroxyeicosatetraenoic acids (5-, 11-, 12-, 15-HETEs), and the cyclooxygenase-derived prostanoids (prostaglandins: PGD2, PGF2α; thromboxane: Txs, oxylipins) are involved in vasoconstriction, hypertension, inflammation, and cardiac toxicity. Also, there are significant interactions were seen between adenosine receptors [adenosine A2A receptor (A2AAR) and adenosine A1 receptor (A1AR)] with CYP450-epoxygenases, ω-hydroxylases, sEH, and their derived oxylipins in the regulation of the cardiovascular response. Moreover, polymorphisms exist in CYP450-epoxygenases, ω-hydroxylases, sEH, and the adenosine receptor genes in populations associated with CVDs. This chapter will discuss the role of oxylipins' interactions with adenosine receptors in cardiovascular function/dysfunction in mice and humans.

Ultrasonic-induced synthesis of novel diverse arylidenes via Knoevenagel condensation reaction. Antitumor, QSAR, docking and DFT assessment.

A series of arylidenes derivatives was synthesized under ultrasonic methodology via Knoevenagel condensation reaction of cyanoacetohydrazide derivative with the appropriate aldehydes and/or ketone. The anticancer properties of the newly synthesized compounds were tested against four different human cancer cell lines (HEPG-2, MCF-7, HCT-116, and PC-3); compounds 5d and 6 demonstrated the greatest anticancer activity against all cancer cell lines. The MLR technique was used to create the QSAR model using five molecular descriptors (AATS6p, AATS7p, AATS8p, AATS0i, and SpMax4_Bhv). The examination of the constructed QSAR model equations revealed that the selected descriptors influence the tested compound's anti-proliferative activity. The descriptors identified in this work by QSAR models can be utilized to predict the anticancer activity levels of novel arylidenes derivatives. This will allow for significant cost savings in the drug development process and synthesis at pharmaceutical chemistry laboratories. According to the physicochemical properties, the results revealed that all of these compounds comply with Lipinski's Rule of Five, indicating that they may have high permeability across biological membranes and reveal drug-relevant properties. The Swiss Target Prediction webtool was used to assess the probable cellular mechanism for the promising candidate compounds (5d and 6), and the results revealed that adenosine A1 receptor (ADORA1) was a common target for both compounds. ADORA1 is involved in the regulation of cell metabolism and gene transcription. ADORA1 overexpression has been linked to a variety of cancers, including colon cancer, breast cancer, leukemia, and melanoma. The docking study of tested compounds 5d and 6 revealed that their binding scores to ADORA1 are more favorable than those of its co-crystalized ligand (DU172, selective ADORA1 antagonist) and adenosine (ADORA1 endogenous agonist), implying that they may hold great promise as an anti-cancer therapy. Density functional theory (DFT) with a (B3LYP)/6-31G (d,p) basis set was used to calculate the physicochemical parameters of these compounds. The theoretical data from the DFT computation was found to be in good agreement with the experimental values.

PS-BPB06-1: GLOMERULAR HEMODYNAMIC CHANGES WITH SGLT2 INHIBITION IN TYPE 2 DIABETIC RATS USING IN VIVO IMAGING

Background and aim: Clinical trials have shown that sodium-glucose co-transporter 2 inhibitor (SGLT2i) not only reduce the risk of heart failure and cardiovascular events in people with type 2 diabetes, but also inhibit DKD progression. Improvement of glomerular hyperfiltration via tubuloglomerular feedback (TGF) is considered to be one of the possible pathways for renal protection with SGLT2i in DKD. However, the mechanisms responsible for kidney protection, especially in the setting of T2D, remain incompletely understood. In previous work, we established a method for measuring single nephron GFR (SNGFR) in mice using in vivo imaging and found that the adenosine/adenosine A1 receptor (A1aR) pathway is central for tubuloglomerular feedback (TGF) signaling and the pathogenesis of glomerular hyperfiltration in animal models of type 1 diabetes (Kidokoro K. et al. Circulation 2019). The mechanism of development of glomerular hyperfiltration, and improvement of glomerular hyperfiltration by SGLT2i may, however, be different in type 1 vs type 2 diabetes and related DKD. However, the detailed regulatory mechanism of GFR have not yet been elucidated in DKD related to T2D. Methods: Zucker lean (ZL) rats and Zucker diabetic fatty (ZDF) rats were used. In the first experiment, SNGFR and diameters of glomerular afferent/efferent arterioles were measured in both groups. Next, we examined the change of SNGFR and diameters of glomerular afferent/efferent arterioles, as well as urinary excretions of glucose and sodium in ZDF after a single-dose administration of SGLT2i (luseogliflozin; 10 mg/kg, gavage) for 120 minutes, which generated the following three groups: SGLT2i group, SGLT2i + adenosine A1 receptor (A1aR) antagonist (8-cyclopentyl-1,3-dipropylxanthine, 1 mg/kg) group, and insulin group. Results: SNGFR, afferent and efferent arteriole diameter were significantly increased in ZDF compared to ZL, with greater afferent vs. efferent dilatation. SGLT2i treatment resulted in correction of afferent arteriole vasodilation, with post-SGLT2i diameter that was comparable to baseline levels (p > 0.05). Post-SGLT2i SNGFR was also similar compared to baseline levels. Changes in efferent arteriole diameter were not significant. The inhibitory effect on hyperfiltration by SGLT2i was abolished by the concomitant use of an A1aR antagonist. In contrast, urinary sodium and urinary glucose in SGLT2 inhibitor group increased significantly regardless of adenosine A1 receptor antagonist use. In response to SGLT2i, urinary adenosine and PGE2 increased significantly (p > 0.05), while urine NOx did not change. Conclusion: Regulation of afferent arteriolar tone with SGLT2i is dependent on adenosine/ A1aR signaling an experimental model of T2D related hyperfiltration, regardless of ARB use.

PS-BPB06-7: NOVEL MOLECULAR MECHANISMS OF CARDIO-RENAL INTERACTION MEDIATED BY INCREASED SERUM MODIFIED NUCLEOSIDES ASSOCIATED WITH RENAL FAILURE

Objective: The number of patients with chronic kidney disease (CKD) continues to rise by population aging. Moreover, CKD patients progress to end-stage renal failure and require renal replacement therapy. Many cohort studies have shown that impaired renal function itself is a risk factor for the development of cardiovascular disease, rather than comorbidities such as diabetes or hypertension. However, the molecular mechanisms are not fully understood. We focused on chemical modifications in RNA and their pathophysiological significance. Previously, we have shown that modified nucleosides, the metabolites of modified RNA, have unique physiological effects. For example, we reported that N6-methyladenosine is a true ligand for the A3 adenosine receptor, and that 1-methylguanosine promotes Zika virus replication in the host. In addition, it was found that a number of modified nucleosides are present in serum and excreted into extracellular spaces like urine. Therefore, we hypothesized that the decreased urinary excretion of modified nucleosides upon renal failure may cause abnormally high levels of modified nucleosides in the blood, which may exert detrimental effects on the heart and vasculature. Methods and Results: First, serum samples were collected from 210 CKD patients, and the correlation between serum modified nucleoside levels and eGFR was investigated. The results showed that several modified nucleosides such as 5-methylcytidine and pseudouridine were inversely correlated with renal function (r2 = -0.76, p < 0.0001; r2 = -0.78, p < 0.0001, respectively). Moreover, we found that 1-methylinosine was inversely correlated with renal function and positively correlated with BNP, a typical marker for heart failure (r2 = -0.82, p < 0.0001 vs. eGFR; r2 = 0.41, p = 0.010 vs. BNP). Next, to explore the possibility of cardiovascular injury associated with this elevation of 1-methylinosine, we examined its effect on vascular endothelial cells. We found that the addition of 1-methylinosine significantly increased cell proliferation using cultured human aortic endothelial cells (p = 0.004, n = 6). Conclusions: Through this study, we found that multiple modified nucleosides are significantly elevated in serum of CKD patients. Furthermore, the elevation of 1-methylinosine in serum can induce abnormal proliferative signals in vascular endothelial cells, which may thereby lead to endothelial damage. In conclusion, these results suggest that the elevated blood levels of modified nucleosides could be a novel marker for vascular injury, and might become a potential target for drug intervention in the cardio-renal interaction.

Pequeñas moléculas: nuevos horizontes terapéuticos en la psoriasis

Psoriasis is a chronic immune-mediated skin disease frequently associated with different comorbidities, among which psoriatic arthritis stands out, with a high impact on the quality of life of patients. We have an important therapeutic arsenal that includes topical agents, phototherapy and systemic drugs. In recent years, biological therapy has brought about a true revolution in the treatment of moderate to severe psoriasis, due to its great efficacy and safety. However, it has some limitations such as its exclusively parenteral administration, its high cost and the lack of efficacy and tolerance in some cases. Therefore, based on a better knowledge of the pathophysiology of psoriasis, new therapeutic options have emerged: the small molecules. They represent an enrichment for the clinician in the therapeutic management of psoriasis. Some of those have approved indication and others under investigation. The objective of this review is to analyze the efficacy and safety data of these molecules that include phosphodiesterase inhibitors (apremilast), Janus kinase inhibitors (tofacitinib, baricitinib), selective tyrosine kinase 2 inhibitors (deucravacitinib), agonists G protein-associated A3 adenosine receptor (piclidenoson), orphan T-gamma receptor inverse agonists (vimirogant), and sphingosine-1-phosphate receptor antagonists (ponesimod). In addition, new molecular targets are discussed. In short, the frontline of new systemic treatment for psoriasis.

Clues from a missense mutation of the adenosine A1 receptor gene associated with early-onset Parkinson's disease.

Clues from a missense mutation of the adenosine A1 receptor gene associated with early-onset Parkinson's disease.

The role of adenosine A1 receptor in the analgesia induced by myofascial reorganization technique in mice with peripheral inflammation

The role of adenosine A1 receptor in the analgesia induced by myofascial reorganization technique in mice with peripheral inflammation

A2AR and traumatic brain injury.

Accumulating evidence has revealed the adenosine 2A receptor is a key tuner for neuropathological and neurobehavioral changes following traumatic brain injury by experimental animal models and a few clinical trials. Here, we highlight recent data involving acute/sub-acute and chronic alterations of adenosine and adenosine 2A receptor-associated signaling in pathological conditions after trauma, with an emphasis of traumatic brain injury, including neuroinflammation, cognitive and psychiatric disorders, and other severe consequences. We expect this would lead to the development of therapeutic strategies for trauma-related disorders with novel mechanisms of action.

Exercise attenuates neuronal degeneration in Parkinson's disease rat model by regulating the level of adenosine 2A receptor.

Parkinson's disease occurs due to loss of dopaminergic neurons, which alters the behavioural changes. The present study evaluates the effect of exercise on neurodegeneration against Parkinson's disease (PD) rat model and postulates its effect on novel molecular pathway. Rotenone was administered at 1 mg/kg s.c. every 48 h for 18 days for the in-duction of PD and exercise was given to rats for a period of 2 weeks after the confirmation of PD. Moreover, PD rats also received CGS 21680 (adenosine A2A receptor agonist, 0.5 mg/kg, i.p.) with exercise for a period of 2 weeks after confirmation of PD. The effect of exercise was assessed for motor and cognitive function in PD rats. The level of inflammatory cytokines and neurotransmitters was estimated in brain tissue of PD rats. Data of investigation reveal that exercise attenuates cognitive and motor function in PD rats, the exercise + CGS 21680 group shows reverse in the behavioural changes compared to exercise-treated PD rats. The level of inflammatory cytokines and neurochemical level ameliorated in the exercise-treated group compared to the PD group of rats, which is reversed in the exercise + CGS 21680 group. In conclusion, exercise protects neurodegeneration in PD rats by reducing aggregation of a-synuclein and activity of adenosine 2A receptor.

Species dependence of A3 adenosine receptor pharmacology and function.

Efforts to fully understand pharmacological differences between G protein-coupled receptor (GPCR) species homologues are generally not pursued in detail during the drug development process. To date, many GPCRs that have been successfully targeted are relatively well-conserved across species in amino acid sequence and display minimal variability of biological effects. However, the A3 adenosine receptor (AR), an exciting drug target for a multitude of diseases associated with tissue injury, ischemia, and inflammation, displays as little as 70% sequence identity among mammalian species (e.g., rodent vs. primate) commonly used in drug development. Consequently, the pharmacological properties of synthetic A3AR ligands vary widely, not only in binding affinity, selectivity, and signaling efficacy, but to the extent that some function as agonists in some species and antagonists in others. Numerous heterocyclic antagonists that have nM affinity at the human A3AR are inactive or weakly active at the rat and mouse A3ARs. Positive allosteric modulators, including the imidazo [4,5-c]quinolin-4-amine derivative LUF6000, are only active at human and some larger animal species that have been evaluated (rabbit and dog), but not rodents. A3AR agonists evoke systemic degranulation of rodent, but not human mast cells. The rat A3AR undergoes desensitization faster than the human A3AR, but the human homologue can be completely re-sensitized and recycled back to the cell surface. Thus, comprehensive pharmacological evaluation and awareness of potential A3AR species differences are critical in studies to further understand the basic biological functions of this unique AR subtype. Recombinant A3ARs from eight different species have been pharmacologically characterized thus far. In this review, we describe in detail current knowledge of species differences in genetic identity, G protein-coupling, receptor regulation, and both orthosteric and allosteric A3AR pharmacology.

Microglia regulate neuronal and behavioural functions under physiological and pathological conditions.

Microglia are immune cells in the central nervous system that engulf unnecessary synapses during development. In vivo imaging has substantially improved in recent years, besides the development of tools for manipulating microglia and neurons. These techniques reveal the novel functions of microglia. Microglia regulate neuronal activity to prevent synchronization. This neuron-microglia interaction is mediated by adenosine triphosphate-P2Y12 and adenosine-adenosine A1 receptor signalling in the striatum. Moreover, microglia release inflammation-related molecules that suppress neuronal activity, thus leading to lipopolysaccharide-induced aversion. Prostaglandin E2 (PGE2)-PGE receptor 1 signalling in the striatum underlies this behavioural alteration. Chronic stress activates microglia through toll-like receptor (TLR) 2 and TLR4 to release pro-inflammatory cytokines in the medial prefrontal cortex, thereby causing social avoidance. Microglia play multiple functions under physiological conditions, as well as pathological and psychological stress.

Repeated topical paeoniflorin attenuates postoperative pain and accelerates cutaneous fibroblast proliferation in mice

This study investigated whether the repeated topical paeoniflorin inhibits postoperative pain in mice. An incision of the plantar skin and underlying muscle of the hind paw elicits acute postoperative pain. Repeated topical paeoniflorin inhibited postoperative pain. An adenosine A1 receptor antagonist (DPCPX) attenuated the analgesic effect of paeoniflorin. Paeoniflorin treatment accelerated wound healing at the surgical site. Paeoniflorin accelerated fibroblast proliferation, which inhibited by DPCPX. These results suggest that the repeated topical paeoniflorin attenuates postoperative pain and accelerated wound healing through fibroblast proliferation, and the activation of adenosine A1 receptor is involved in the action of paeoniflorin.

Reversing the negative effect of adenosine A1 receptor-targeted immunometabolism modulation on melanoma by a co-delivery nanomedicine for self-activation of anti-PD-L1 DNAzyme

The metabolite adenosine plays critical roles in tumor progression, metastasis and chemoresistance, and the adenosine pathway has been regarded as an important therapeutic target in cancer. Here, we found that adenosine A1 receptor (ADORA1) was overexpressed in melanoma tissue and had a positive association with tumor malignance and advancement from clinical patient samples. The inhibition of ADORA1 could damage melanoma cells with high specificity and induce tumor cells immunogenic cell death (ICD), while PD-L1 was also elevated significantly at cell surface after treatment, indicating a negative effect on tumor immunotherapy. To compensate this drawback, we designed and fabricated a hybrid nanomedicine with DPCPX (an ADORA1 inhibitor) loaded PLGA core and metal-organic framework (MOF) shell via Fe3+/Mn2+-tannic acid (TA) coordination for anti-PD-L1 DNAzyme (Dz) encapsulation. The nanosystem was not only a carrier to co-deliver DPCPX and Dz, but also a metal reservoir to release Mn2+ for self-activation of the metal-dependent Dz for PD-L1 mRNA cleavage. As a result, a co-inhibition of ADORA1 and PD-L1 was realized to strengthen the ICD immune response, thus promoting dendritic cell (DC) maturation, CD8+ T lymphocyte infiltration and activation, and memory T cells production for enhanced immunotherapy. Such combinatorial therapy could effectively control both primary and distal tumor growth with full biocompatibility. This study provides a novel strategy to induce tumor selective ICD, and highlights the benefits of combining ADORA1 inhibitor with PD-L1 blockage via self-active nanomedicine to enhance the melanoma immunotherapy.