Adenosine A_(2A)receptor blockade attenuates excitotoxicity in rat striatal medium spiny neurons during an ischemic-like insult

During brain ischemia,excitotoxicity and peri-infarct depolarization injuries occur and cause cerebral tissue damage.Indeed,anoxic depolarization,consisting of massive neuronal depolarization due to the loss of membrane ion gradients,occurs in vivo or in vitro during an energy failure.The neuromodulator adenosine is released in huge amounts during cerebral ischemia and exerts its effects by activating specific metabotropic receptors,namely:A_(1),A_(2A),A_(2B),and A_(3).The A_(2A)receptor subtype is highly expressed in striatal medium spiny neurons,which are particularly susceptible to ischemic damage.Evidence indicates that the A2Areceptors are upregulated in the rat striatum after stroke and the selective antagonist SCH58261 protects from exaggerated glutamate release within the first 4 hours from the insult and alleviates neurological impairment and histological injury in the following 24 hours.We recently added new knowledge to the mechanisms by which the adenosine A2Areceptor subtype participates in ischemia-induced neuronal death by performing patch-clamp recordings from medium spiny neurons in rat striatal brain slices exposed to oxygen and glucose deprivation.We demonstrated that the selective block of A2Areceptors by SCH58261 significantly reduced ionic imbalance and delayed the anoxic depolarization in medium spiny neurons during oxygen and glucose deprivation and that the mechanism involves voltage-gated K+channel modulation and a presynaptic inhibition of glutamate release by the A2Areceptor antagonist.The present review summarizes the latest findings in the literature about the possibility of developing selective ligands of A2Areceptors as advantageous therapeutic tools that may contribute to counteracting neurodegeneration after brain ischemia.

Adenosine 2A receptor contributes to the facilitation of postinfectious irritable bowel syndrome by γδ T cells via the PKA/CREB/NF-κB signaling pathway

BACKGROUND Immunological dysfunction-induced low-grade inflammation is regarded as one of the predominant pathogenetic mechanisms in post-infectious irritable bowel syndrome(PI-IBS).γδT cells play a crucial role in innate and adaptive immunity.Adenosine receptors expressed on the surface ofγδT cells participate in intestinal inflammation and immunity regulation.AIM To investigate the role ofγδT cell regulated by adenosine 2A receptor(A2AR)in PI-IBS.METHODS The PI-IBS mouse model has been established with Trichinella spiralis(T.spiralis)infection.The intestinal A2AR and A2AR inγδT cells were detected by immunohistochemistry,and the inflammatory cytokines were measured by western blot.The role of A2AR on the isolatedγδT cells,including proliferation,apoptosis,and cytokine production,were evaluated in vitro.Their A2AR expression was measured by western blot and reverse transcription polymerase chain reaction(RT-PCR).The animals were administered with A2AR agonist,or A2AR antagonist.Besides,γδT cells were also injected back into the animals,and the parameters described above were examined,as well as the clinical features.Furthermore,the A2AR-associated signaling pathway molecules were assessed by western blot and RT-PCR.RESULTS PI-IBS mice exhibited elevated ATP content and A2AR expression(P<0.05),and suppression of A2AR enhanced PI-IBS clinical characteristics,indicated by the abdominal withdrawal reflex and colon transportation test.PI-IBS was associated with an increase in intestinal T cells,and cytokine levels of interleukin-1(IL-1),IL-6,IL-17A,and interferon-α(IFN-α).Also,γδT cells expressed A2AR in vitro and generated IL-1,IL-6,IL-17A,and IFN-α,which can be controlled by A2AR agonist and antagonist.Mechanistic studies demonstrated that the A2AR antagonist improved the function ofγδT cells through the PKA/CREB/NF-κB signaling pathway.CONCLUSION Our results revealed that A2AR contributes to the facilitation of PI-IBS by regulating the function ofγδT cells via the PKA/CREB/NF-κB signaling pathway.

Electroacupuncture improves neuropathic pain Adenosine, adenosine 5'-triphosphate disodium and their receptors perhaps change simultaneously

Applying a stimulating current to acupoints through acupuncture needles–known as electroacupuncture–has the potential to produce analgesic effects in human subjects and experimental animals. When acupuncture was applied in a rat model, adenosine 5-triphosphate disodium in the extracellular space was broken down into adenosine, which in turn inhibited pain transmission by means of an adenosine A1 receptor-dependent process. Direct injection of an adenosine A1 receptor agonist enhanced the analgesic effect of acupuncture. The analgesic effect of acupuncture appears to be mediated by activation of A1 receptors located on ascending nerves. In neuropathic pain, there is upregulation of P2X purinoceptor 3 （P2X3） receptor expression in dorsal root ganglion neurons. Conversely, the onset of mechanical hyperalgesia was diminished and established hyperalgesia was significantly reversed when P2X3 receptor expression was downregulated. The pathways upon which electroacupuncture appear to act are interwoven with pain pathways, and electroacupuncture stimuli converge with impulses originating from painful areas. Electroacupuncture may act via purinergic A1 and P2X3 receptors simultaneously to induce an analgesic effect on neuropathic pain.

Attenuation of gastric mucosal inflammation induced by aspirin through activation of A_(2A) adenosine receptor in rats

AIM： To determine whether a specific adenosine A2A receptor agonist （ATL-146e） can ameliorate aspirin-induced gastric mucosal lesions in rats, and reduce neutrophil accumulation and production of pro-inflammatory cytokines. METHODS： Gastric lesions were produced by oral gavage of aspirin （200 mg/kg） and HCI （0.15 mol/L, 8.0 mL/kg）. 4-{3-[6-Amino-9-（5-ethylcarbamoyl-3,4- dihydroxy-tetrahydro-furan-2-yl）-9H-purin-2-yl]-prop-2- ynyl}-cyclohexanecarboxylic acid methyl ester （ATL-146e, 2.5-5μg/kg, IP） was injected 30 min before the administration of aspirin. Tissue myeloperoxidase （MPO） concentration in gastric mucosa was measured as an index of neutrophil infiltration. Gastric mucosal concentrations of tumor necrosis factor-α （TNF-α） and interleukin-1β （IL-1β） were determined by ELISA. Also, we examined the effect of ATL-146e on tissue prostaglandin E2 （PGE2） production and gastric secretion. RESULTS： Intragastric administration of aspirin induced multiple hemorrhagic erosions in rat gastric mucosa. The total length of gastric erosions （ulcer index） in control rats was 29.8±7.75 mm and was reduced to 3.8±1.42 mm alter pretreatment with 5.0 g/kg ATL-146e （P〈 0.01）. The gastric contents of MPO and pro-inflammatory cytokines were all increased after the administration of aspirin and reduced to nearly normal levels by ATL-146e. Gastric mucosal PGE2 concentration was not affected by intraperitoneal injection of ATL-146e. CONCLUSION： The specific adenosine A2A receptor agonist, ATL-146e, has potent anti-ulcer effects presumably mediated by its anti-inflammatory properties.

Upregulated adenosine 2A receptor accelerates post-infectious irritable bowel syndrome by promoting CD4+T cells’T helper 17 polarization

BACKGROUND Post-infectious irritable bowel syndrome(PI-IBS)is generally regarded as a functional disease.Several recent studies have reported the involvement of lowgrade inflammation and immunological dysfunction in PI-IBS.T helper 17(Th17)polarization occurs in IBS.Adenosine and its receptors participate in intestinal inflammation and immune regulation.AIM To investigate the role of Th17 polarization of CD4+T cells regulated by adenosine 2A receptor(A2AR)in PI-IBS.METHODS A PI-IBS model was established by infecting mice with Trichinella spiralis.The intestinal A2AR and CD4+T lymphocytes were detected by immunohistochemistry,and the inflammatory cytokines were detected by enzyme-linked immunoassay.CD4+T lymphocytes present in the animal’s spleen were separated and cultured with or without A2AR agonist and antagonist.Western blotting and real-time quantitative polymerase chain reaction were performed to determine the effect of A2AR on the cells and intestinal tissue.Cytokine production was determined.The protein and mRNA levels of A2AR associated signaling pathway molecules were also evaluated.Furthermore,A2AR agonist and antagonist were injected into the mouse model and the clinical features were observed.RESULTS The PI-IBS mouse model showed increased expression of ATP and A2AR(P<0.05),and inhibition of A2AR improved the clinical features in PI-IBS,including the abdominal withdrawal reflex and colon transportation test(P<0.05).The number of intestinal CD4+T cells and interleukin-17(IL-17)protein levels increased during PI-IBS,which was reversed by administration of the A2AR antagonist(P<0.05).CD4+T cells expressed A2AR and produced IL-17 in vitro,which was regulated by the A2AR agonist and antagonist.The A2AR antagonist increased the production of IL-17 by CD4+T cells via the Janus kinase-signal transducer and activator of transcriptionreceptor-related orphan receptorγsignaling pathway.CONCLUSION The results of the present study suggested that the upregulation of A2AR increases PI-IBS by promoting the Th17 polarization of CD4+T cells.

Changes in A_2Aadenosine receptor parameters in patients affected by bipolar disorders: Correlation with antipsychotic dosage and severity of illness

Typical antipsychotics, potent D2 dopamine receptor antagonists, are the most commonly used drugs in the treatment of bipolar disorders. In the central nervous system, the discovery of antagonistic interactions between A2A adenosine receptors and D2 dopamine receptors suggests that the adenosine system may be involved in the pathogenesis of different psychiatric disorders and in the therapeutic effectiveness of antipsychotic drugs. Previously, we have demonstrated an increase in A2A receptor expression and agonist affinity in platelets from psychotic patients treated with haloperidol. This result suggests that there is also a structural and functional interaction between A2A and D2 receptors in peripheral cells. In this work, we investigated the effect of different doses of typical drugs on A2A adenosine receptor binding and correlated these parameters with the severity of symptoms. We demonstrated, for the first time, that there was a strong correlation between A2A receptor affinity constant values (Kd) and drug doses in psychotic patients with a moderate severity of illness and moderate psychotic symptoms. The correlation was completely lost in patients with severe illness and severe psychotic symptoms. These results demonstrated that in platelets of patients affected by psychosis, typical antipsychotics modulated A2A receptor binding parameters;this regulation is dependent on the degree of D2 receptor occupancy in relation to the severity of psychotic symptoms, suggesting A2A receptors are a peripheral marker for individual therapy effectiveness.

Targeting the adenosine A2A receptor for neuroprotection and cognitive improvement in traumatic brain injury and Parkinson's disease

Adenosine exerts its dual functions of homeostasis and neuromodulation in the brain by acting at mainly 2 G-protein coupled receptors,called A1 and A2A receptors.The adenosine A2A receptor(A2AR)antagonists have been clinically pursued for the last 2 decades,leading to final approval of the istradefylline,an A2AR antagonist,for the treatment of OFF-Parkinson's disease(PD)patients.The approval paves the way to develop novel therapeutic methods for A2AR antagonists to address 2 major unmet medical needs in PD and traumatic brain injury(TBI),namely neuroprotection or improving cognition.In this review,we first consider the evidence for aberrantly increased adenosine signaling in PD and TBI and the sufficiency of the increased A2AR signaling to trigger neurotoxicity and cognitive impairment.We further discuss the increasing preclinical data on the reversal of cognitive deficits in PD and TBI by A2AR antagonists through control of degenerative proteins and synaptotoxicity,and on protection against TBI and PD pathologies by A2AR antagonists through control of neuroinflammation.Moreover,we provide the supporting evidence from multiple human prospective epidemiological studies which revealed an inverse relation between the consumption of caffeine and the risk of developing PD and cognitive decline in aging population and Alzheimer's disease patients.Collectively,the convergence of clinical,epidemiological and experimental evidence supports the validity of A2AR as a new therapeutic target and facilitates the design of A2AR antagonists in clinical trials for disease-modifying and cognitive benefit in PD and TBI patients.

Structural insight into the dual-antagonistic mechanism of AB928 on adenosine A_(2)receptors

The adenosine subfamily G protein-coupled receptors A_(2A)R and A_(2B)R have been identified as promising cancer immunotherapy candidates.One of the A_(2A)R/A_(2B)R dual antagonists,AB928,has progressed to a phaseⅡclinical trial to treat rectal cancer.However,the precise mechanism underlying its dual-antagonistic properties remains elusive.Herein,we report crystal structures of the A_(2A)R complexed with AB928 and a selective A_(2A)R antagonist 2-118.The structures revealed a common binding mode on A_(2A)R,wherein the ligands established extensive interactions with residues from the orthosteric and secondary pockets.In contrast,the cAMP assay and A_(2A)R and A_(2B)R molecular dynamics simulations indicated that the ligands adopted distinct binding modes on A_(2B)R.Detailed analysis of their chemical structures suggested that AB928 readily adapted to the A_(2B)R pocket,while 2-118 did not due to intrinsic differences.This disparity potentially accounted for the difference in inhibitory efficacy between A_(2B)R and A_(2A)R.This study serves as a valuable structural template for the future development of selective or dual inhibitors targeting A_(2A)R/A_(2B)R for cancer therapy.

Unlocking antitumor immunity with adenosine receptorblockers

Tumors survive by creating a tumor microenvironment(TME)that suppresses antitumor immunity.The TME suppresses the immune system by limiting antigen presentation,inhibiting lymphocyte and natural killer(NK)cell activation,and facilitating T cell exhaustion.Checkpoint inhibitors like anti-PD-1 and anti-CTLA4 are immunostimulatory antibodies,and their blockade extends the survival of some but not all cancer patients.Extracellular adenosine triphosphate(ATP)is abundant in inflamed tumors,and its metabolite,adenosine(ADO),is a driver of immunosuppression mediated by adenosine A2A receptors(A2AR)and adenosine A2B receptors(A2BR)found on tumor-associated lymphoid and myeloid cells.This review will focus on adenosine as a key checkpoint inhibitor-like immunosuppressive player in the TME and how reducing adenosine production or blocking A2AR and A2BR enhances antitumor immunity.

P2X7 receptor activation causes phosphatidylserine exposure in canine erythrocytes

AIM To determine if activation of the ATP-gated P2X7 receptor channel induces phosphatidylserine(PS) exposure in erythrocytes from multiple dog breeds.METHODS Peripheral blood was collected from 25 dogs representing 13 pedigrees and seven crossbreeds. ATP-induced PS exposure on canine erythrocytes in vitro was assessed using a flow cytometric Annexin V binding assay.RESULTS ATP induced PS exposure in erythrocytes from all dogs studied. ATP caused PS exposure in a concentrationdependent manner with an EC50 value of 395 μmol/L. The non-P2X7 agonists, ADP or AMP, did not cause PS exposure. The P2X7 antagonist, AZ10606120, but not the P2X1 antagonist, NF449, blocked ATP-induced PS exposure.CONCLUSION The results indicate that ATP induces PS exposure in erythrocytes from various dog breeds and that this process is mediated by P2X7 activation.

P2X7 receptor in skin biology and diseases

The P2X7 receptor is a trimeric ligand-gated cation channel present on immune and other cells. Activation of this receptor by its natural ligand extracellular adenosine triphosphate results in a variety of downstream responses, including the release of pro-inflammatory mediators and cell death. In normal skin, P2X7 is present on keratinocytes, Langerhans cells and fibroblasts, while the presence of this receptor on other cutaneous cells is mainly inferred from studies of equivalent cell types present in other tissues. Mast cells in normal skin however express negligible amounts of P2X7, which can be upregulated in cutaneous disease. This review discusses the potential significance of P2X7 in skin biology, and the role of this receptor in inflammatory skin disorders such as irritant and chronic dermatitis, psoriasis, graft-versus-host disease, as well is in wound healing, transplantation and skin cancer.

Bone-derived MSCs encapsulated in alginate hydrogel prevent collagen-induced arthritis in mice through the activation of adenosine A_(2A/2B)receptors in tolerogenic dendritic cells

Tolerogenic dendritic cells(tol DCs)facilitate the suppression of autoimmune responses by differentiating regulatory T cells(Treg).The dysfunction of immunotolerance results in the development of autoimmune diseases,such as rheumatoid arthritis(RA).As multipotent progenitor cells,mesenchymal stem cells(MSCs),can regulate dendritic cells(DCs)to restore their immunosuppressive function and prevent disease development.However,the underlying mechanisms of MSCs in regulating DCs still need to be better defined.Simultaneously,the delivery system for MSCs also influences their function.Herein,MSCs are encapsulated in alginate hydrogel to improve cell survival and retention in situ,maximizing efficacy in vivo.The three-dimensional co-culture of encapsulated MSCs with DCs demonstrates that MSCs can inhibit the maturation of DCs and the secretion of pro-inflammatory cytokines.In the collagen-induced arthritis(CIA)mice model,alginate hydrogel encapsulated MSCs induce a significantly higher expression of CD39^(+)CD73^(+)on MSCs.These enzymes hydrolyze ATP to adenosine and activate A_(2A/2B)receptors on immature DCs,further promoting the phenotypic transformation of DCs to tol DCs and regulating naive T cells to Tregs.Therefore,encapsulated MSCs obviously alleviate the inflammatory response and prevent CIA progression.This finding clarifies the mechanism of MSCs-DCs crosstalk in eliciting the immunosuppression effect and provides insights into hydrogel-promoted stem cell therapy for autoimmune diseases.

Electroacupuncture stimulating Zusanli(ST36),Sanyinjiao(SP6)in mice with collagen-induced arthritis leads to adenosine A2A receptor-mediated alteration of p38αmitogen-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 p38αMitogen-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.

Prolonged intermittent theta burst stimulation restores the balance between A_(2A)R-and A_(1)R-mediated adenosine signaling in the 6-hydroxidopamine model of Parkinson's disease

An imbalance in adenosine-mediated signaling,particularly the increased A_(2A)R-mediated signaling,plays a role in the pathogenesis of Parkinson's disease.Existing therapeutic approaches fail to alter disease progression,demonstrating the need for novel approaches in PD.Repetitive transcranial magnetic stimulation is a non-invasive approach that has been shown to improve motor and non-motor symptoms of Parkinson's disease.However,the underlying mechanisms of the beneficial effects of repetitive transcranial magnetic stimulation remain unknown.The purpose of this study is to investigate the extent to which the beneficial effects of prolonged intermittent theta burst stimulation in the 6-hydroxydopamine model of experimental parkinsonism are based on modulation of adenosine-mediated signaling.Animals with unilateral 6-hydroxydopamine lesions underwent intermittent theta burst stimulation for 3 weeks and were tested for motor skills using the Rotarod test.Immunoblot,quantitative reverse transcription polymerase chain reaction,immunohistochemistry,and biochemical analysis of components of adenosine-mediated signaling were performed on the synaptosomal fraction of the lesioned caudate putamen.Prolonged intermittent theta burst stimulation improved motor symptoms in 6-hydroxydopamine-lesioned animals.A 6-hydroxydopamine lesion resulted in progressive loss of dopaminergic neurons in the caudate putamen.Treatment with intermittent theta burst stimulation began 7 days after the lesion,coinciding with the onset of motor symptoms.After treatment with prolonged intermittent theta burst stimulation,complete motor recovery was observed.This improvement was accompanied by downregulation of the e N/CD73-A_(2A)R pathway and a return to physiological levels of A_(1)R-adenosine deaminase 1 after 3 weeks of intermittent theta burst stimulation.Our results demonstrated that 6-hydroxydopamine-induced degeneration reduced the expression of A_(1)R and elevated the expression of A_(2A)R.Intermittent theta burst stimulation reversed these effects by restoring the abundances of A_(1)R and A_(2A)R to control levels.The shift in ARs expression likely restored the balance between dopamine-adenosine signaling,ultimately leading to the recovery of motor control.

Role of adenosine in tumor progression: focus on A_(2B) receptor as potential therapeutic target

Adenosine receptors are a family of G-coupled receptors which mediate the anti-inflammatory and immune-suppressive effects of adenosine in a damaged tissue.A large number of evidence indicate that the accumulation of adenosine under hypoxic conditions favors tumor progression,helping cancer cells to evade immune responses.Tumor cells and/or lymphoid and myeloid cells can express the adenosine-generating enzyme CD73 and/or A2A receptor,which in turn strongly suppresses an effective T-cell-mediated response,while promotes the activity of suppressive cells such as Treg and myeloid-derived suppressor cells.CD73 inhibitors and A2A antagonists,either as single agents,or in combination with immune-checkpoints inhibitors such as anti PD-1 monoclonal antibodies,are currently in Phase I clinical trial in cancer patients.Recent studies show that A2B receptor plays an important role in mediating the pro-tumor effects of adenosine,since its selective blockade can inhibit tumor growth in some murine tumor models.Targeting A2B receptor reduces immunosuppression induced by myeloid cells and inhibits the stromal cells activity within the tumor microenvironment,limiting tumor angiogenesis and metastatic processes.Here,the authors review the current data on involvement of A2B receptor in regulating tumor progression and discuss the development of A2B receptor inhibitors as potential therapeutic agents in cancer treatment.

Regulation of epithelial sodium channel ^-subunit expression by adenosine receptor A2a in alveolar epithelial ceils

Background The amiloride-sensitive epithelial sodium channel a-subunit （a-ENaC） is an important factor for alveolar fluid clearance during acute lung injury. The relationship between adenosine receptor A2a （A2aAR） expressed in alveolar epithelial cells and aα-ENaC is poorly understood. We targeted the A2aAR in this study to investigate its role in the expression of αa-ENaC and in acute lung injury.Methods A549 cells were incubated with different concentrations of A2aAR agonist CGS-21680 and with 100 μmol/L CGS-21680 for various times. Rats were treated with lipopolysaccharide （LPS） after CGS-21680 was injected. Animals were sacrificed and tissue was harvested for evaluation of lung injury by analysis of the lung wet-to-dry weight ratio, lung permeability and myeloperoxidase activity. RT-PCR and Western blotting were used to determine the mRNA and protein expression levels of α-ENaC in A549 cells and alveolar type II epithelial cells.Results Both mRNA and protein levels of α-ENaC were markedly higher from 4 hours to 24 hours after exposure to 100μmol/L CGS-21680. There were significant changes from 0.1 umol/L to 100 μmol/L CGS-21680, with a positive correlation between increased concentrations of CGS-21680 and expression of α-ENaC. Treatment with CGS-21680during LPS induced lung injury protected the lung and promoted α-ENaC expression in the alveolar epithelial cells.Conclusion Activation of A2aAR has a protective effect during the lung injury, which may be beneficial to the prognosis of acute lung injury

The plant hormone zeatin riboside inhibits T lymphocyte activity via adenosine A2A receptor activation

Cytokinins are plant hormones that play an integral role in multiple aspects of plant growth and development. The biological functions of cytokinins in mammalian systems are, however, largely uncharacterized. The naturally occurring cytokinin zeatin riboside has recently been demonstrated to activate the mammalian adenosine A2A receptor, which is broadly expressed by various cell types including immune system cells, with the activation of the A2AR playing a role in the regulation of cells involved in both innate and adaptive immunity. We show for the first time that zeatin riboside modulates mammalian immune system activity via an A2AR-dependent mechanism. Specifically, zeatin riboside treatment induces the production of cyclic adenosine monophosphate （cAMP） by T lymphocytes and inhibits the production by CD3^＋CD4^＋ T cells of interferon （IFN）-γ, IL-2, tumor-necrosis factor （TNF）-α, IL-4 and IL-13, and the production by CD3^＋CD8^＋ T cells of IFN-γ, IL-2 and TNF-α. Additionally, the upregulation of CD25, CD69 and CD40L by activated T lymphocytes is modulated by zeatin riboside. Zeatin riboside treatment also potently inhibits thioglycollate-induced peritoneal leukocytosis. The immunomodulatory activities of zeatin riboside are blocked by co-treatment with the selective A2AR antagonist ZM241385. These data suggest that zeatin riboside possesses therapeutic potential as a mammalian immunomodulatory agent.

Adenosine A1 receptor ligands bind toα-synuclein:implications forα-synuclein misfolding andα-synucleinopathy in Parkinson’s disease

Background:Accumulatingα-synuclein(α-syn)aggregates in neurons and glial cells are the staples of many synucleinopathy disorders,such as Parkinson’s disease(PD).Since brain adenosine becomes greatly elevated in ageing brains and chronic adenosine A1 receptor(A1R)stimulation leads to neurodegeneration,we determined whether adenosine or A1R receptor ligands mimic the action of known compounds that promoteα-syn aggregation(e.g.,the amphetamine analogue 2-aminoindan)or inhibitα-syn aggregation(e.g.,Rasagiline metabolite 1-aminoindan).In the present study,we determined whether adenosine,A1R receptor agonist N^(6)-Cyclopentyladenosine(CPA)and antago-nist 8-cyclopentyl-1,3-dipropylxanthine(DPCPX)could directly interact withα-syn to modulateα-syn aggregation and neurodegeneration of dopaminergic neurons in the substantia nigra(SN).Methods:Nanopore analysis and molecular docking were used to test the binding properties of CPA and DPCPX withα-syn in vitro.Sprague-Dawley rats were administered with 7-day intraperitoneal injections of the A1R ligands and 1-and 2-aminoindan,and levels ofα-syn aggregation and neurodegeneration were examined in the SN pars compacta and hippocampal regions using confocal imaging and Western blotting.Results:Using nanopore analysis,we showed that the A1R agonists(CPA and adenosine)interacted with the N-terminus ofα-syn,similar to 2-aminoindan,which is expected to promote a“knot”conformation andα-syn misfolding.In contrast,the A1R antagonist DPCPX interacted with the N-and C-termini ofα-syn,similar to 1-aminoindan,which is expected to promote a“loop”conformation that preventsα-syn misfolding.Molecular docking studies revealed that adenosine,CPA and 2-aminoindan interacted with the hydrophobic core ofα-syn N-terminus,whereas DPCPX and 1-aminoindan showed direct binding to the N-and C-terminal hydrophobic pockets.Confocal imaging and Western blot analyses revealed that chronic treatments with CPA alone or in combination with 2-aminoindan increasedα-syn expression/aggregation and neurodegeneration in both SN pars compacta and hippocampus.In contrast,DPCPX and 1-aminoindan attenuated the CPA-inducedα-syn expression/aggregation and neurodegeneration in SN and hippocampus.Conclusions:The results indicate that A1R agonists and drugs promoting a“knot”conformation ofα-syn can causeα-synucleinopathy and increase neuronal degeneration,whereas A1R antagonists and drugs promoting a“loop”con-formation ofα-syn can be harnessed for possible neuroprotective therapies to decreaseα-synucleinopathy in PD.

Roles and mechanisms of the CD38/cyclic adenosine diphosphate ribose/Ca^(2+) signaling pathway

Mobilization of intracellular Ca2+ stores is involved inmany diverse cell functions, including: cell proliferation;differentiation; fertilization; muscle contraction; secre-tion of neurotransmitters, hormones and enzymes;and lymphocyte activation and proliferation. Cyclic ad-enosine diphosphate ribose(cADPR) is an endogenousCa2+ mobilizing nucleotide present in many cell typesand species, from plants to animals. cADPR is formedby ADP-ribosyl cyclases from nicotinamide adenine di-nucleotide. The main ADP-ribosyl cyclase in mammalsis CD38, a multi-functional enzyme and a type Ⅱ mem-brane protein. It has been shown that many extracel-lular stimuli can induce cADPR production that leadsto calcium release or influx, establishing cADPR as asecond messenger. cADPR has been linked to a widevariety of cellular processes, but the molecular mecha-nisms regarding cADPR signaling remain elusive. Theaim of this review is to summarize the CD38/cADPR/Ca2+ signaling pathway, focusing on the recent advanc-es involving the mechanism and physiological functionsof cADPR-mediated Ca2+ mobilization.

丁酸钠经AMPK/Nrf2/HO-1信号通路调节脂多糖诱导肺泡巨噬细胞极化的作用机制

目的探讨丁酸钠(sodium butyrate,SB)对脂多糖(lipopolysaccharide,LPS)诱导肺泡巨噬细胞极化的影响及其作用机制。方法小鼠肺泡巨噬细胞(MH-S细胞)随机分为对照(Control)组、LPS组、SB组、LPS+SB(LB)组、LPS+SB+腺苷酸活化蛋白激酶(AMPK)抑制剂(Compound C)(LC)组、LPS+SB+核因子E2相关因子2(Nrf2)抑制剂(ML385)(LM)组。通过CCK8检测MH-S细胞活力,筛选出最佳的1000 ng/mL LPS、1 mmol/L SB、10μmol/L Compound C、5μmol/L ML385药物浓度进行后续实验;实时荧光定量(qRT-PCR)检测MH-S细胞白细胞介素-6(IL-6)、肿瘤坏死因子-α(TNF-α)、白细胞介素-1β(IL-1β)、白细胞介素-10(IL-10)、白细胞分化抗原86(CD86)、巨噬细胞甘露糖受体(CD206)、AMPK、Nrf2和血红素加氧酶1(HO-1)的mRNA表达水平;酶联免疫吸附试验(ELISA)检测培养基上清IL-6、TNF-α、IL-1β和IL-10蛋白含量;流式细胞术测定M1和M2型巨噬细胞相关标记物CD86和CD206的表达。各组数据通过单因素方差分析和Tukey法进行检验。结果通过CCK8选取了1000 ng/mL LPS、1 mmol/L SB、10μmol/L Compound C和5μmol/L ML385进行造模和干预。qRT-PCR和ELISA结果一致显示,与LPS组比较,LB组M1型巨噬细胞相关促炎细胞因子IL-6、TNF-α、IL-1β显著降低(均P<0.01),但M2型巨噬细胞相关抑炎细胞因子IL-10显著升高(均P<0.01)。qRT-PCR和流式细胞术结果一致显示,与Control组比较,LPS组CD86水平显著升高(均P<0.01),SB组差异无统计学意义;与LPS组比较,LB组CD86表达水平显著降低(均P<0.01),但M2型巨噬细胞标记物CD206的变化趋势与CD86相反。qRT-PCR结果显示,与LPS组比较,LB组促进AMPK/Nrf2/HO-1的表达(均P<0.05);与LB组比较,LC组降低了AMPK/Nrf2/HO-1的表达(均P<0.05),LM组降低了Nrf2/HO-1的表达(均P<0.05)。流式细胞术结果显示,与LB组比较,LC组和LM组逆转了SB对CD86水平的抑制作用(均P<0.01);M2型巨噬细胞标记物CD206的表达趋势与M1型巨噬细胞标记物CD86相反。结论SB通过激活AMPK/Nrf2/HO-1信号通路,抑制LPS诱导的M1型、促进M2型肺泡巨噬细胞极化,改善了炎症反应。