2-(4-(2-carboxyethyl)phenethylamino)-5--n-ethylcarboxamidoadenosine and Inflammation

The adenosine A2a receptor agonist CGS21680 has been suggested to act as an anti‑inflammatory agent that protects against cardiopulmonary bypass (CPB)‑induced organ injury. However, the therapeutic effects of CGS21680 for CPB‑induced lung injury have not been comprehensively evaluated. Using a juvenile rat model, the present study was designed to evaluated whether CGS21680 attenuates CPB‑induced lung injury. Our juvenile rat CPB model was established by 60 min CPB with or without CGS21680 pretreatment (100 µg/kg, in the CPB priming solution). Rats in the Sham group only underwent cannulation and heparinization. Serum and pulmonary levels of inflammatory markers and histological features of pulmonary tissues were analyzed. All juvenile rats survived following CPB. Significantly elevated serum levels of tumor necrosis factor‑α (TNF‑α), myeloperoxidase (MPO) and interleukin‑1β (IL‑1β), and decreased glutathione peroxidase (GSH‑PX) levels were observed in the CPB group compared to the Sham group (all P<0.05). TNF‑α, MPO and IL‑1β were significantly decreased, while GSH‑PX was markedly increased in the CGS group when compared to the CPB group. Consistently, pulmonary tissues from rats in the CPB group showed considerable amounts of damaged pneumocytes, severe edema, and increased alveolar macrophages, and significantly higher lung injury scores compared to the controls. Collectively, these changes were all further attenuated by CGS21680. Pretreatment with CGS21680 before CPB attenuated pulmonary injury, which may be related to the anti‑inflammatory effects of CGS21680 downstream of A2a receptor activation.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Animals; Cardiopulmonary Bypass; Disease Models, Animal; Humans; Inflammation; Interleukin-1beta; Lung; Lung Injury; Peroxidase; Phenethylamines; Rats; Rats, Sprague-Dawley; Receptor, Adenosine A2A; Tumor Necrosis Factor-alpha

Adenosine is the final product of ATP metabolism, mainly derived from the action of 5'-nucleotidase cleavage of AMP. Cellular production of adenosine is greatly enhanced in inflamed tissues, ischemic tissues, and under hypoxia, where ATP is released from damaged cells. Much evidence has been accumulated on adenosine anti-inflammatory effects mediated through A

Topics: Adenosine; Adenosine A2 Receptor Agonists; Animals; Carrageenan; Cytokines; Edema; Fibroblast Growth Factor 2; Gene Expression Regulation; Hindlimb; Inflammation; Male; Phenethylamines; Rats; Rats, Wistar; Receptor, Adenosine A2A

The mobilization and homing of endothelial progenitor cells (EPCs) contribute to the rapid endothelialization of tissue engineering blood vessel (TEBV). Inflammation can affect TEBV patency, and monocytes/macrophages (MM) are the main effector cells. But it is not clear how EPCs interact with MM after TEBV transplantation. Our results showed acellular materials would not directly cause acute and severe inflammatory responses but activate E-selectin expression in homing EPCs, gradually promoting the polarization of MM to the M1. Adenosine A2a receptor agonist CGS21680 promoted the secretion of more proangiogenic factors from MM, inducing EPC migration and mobilization. CGS21680 could inhibit MM polarization to the M1 type through the down-regulation of EPC proinflammatory molecules, such as E-selectin. Chitosan/(2-hydroxypropyl)-β-cyclodextrin nanoparticles were prepared to control the release of CGS-21680 and then modified to TEBVs through layer-by-layer assembly. Animal experiments showed that this TEBV can maintain patency for 6 months and good endothelialization was observed. In summary, our results showed the regulation of EPC pro-inflammatory activities is a new approach to enhance TEBV patency. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2634-2642, 2018.

Topics: 2-Hydroxypropyl-beta-cyclodextrin; Adenosine; Animals; Blood Vessel Prosthesis; Cell Count; Cell Movement; Computed Tomography Angiography; Delayed-Action Preparations; Endothelial Progenitor Cells; Inflammation; Lipopolysaccharides; Macrophages; Monocytes; Nanoparticles; Phenethylamines; Rats, Wistar; Tissue Engineering; Vascular Patency

Topics: Adenosine; Animals; Disease Progression; Enzyme Activation; Hepatocytes; Inflammation; Lipids; Male; Mice, Inbred C57BL; Non-alcoholic Fatty Liver Disease; Phenethylamines; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Receptor, Adenosine A2A; Signal Transduction; T-Lymphocytes, Helper-Inducer; T-Lymphocytes, Regulatory

Dendritic cells (DCs) exposed to various oxygen tensions under physiopathological conditions are the critical immune cells linking innate and adaptive immunity. We have previously demonstrated that reoxygenation of hypoxia-differentiated DCs triggers complete DCs activation and inflammatory responses, so restraining the activation of reoxygenated DCs is important to suppress inflammatory responses in diseases caused by oxygen redelivery such as ischemia-reperfusion injury. In the current study, we showed that reoxygenation of hypoxia-differentiated DCs led to predominant expression of high levels of adenosine receptor A2AR on reoxygenated DCs as compared to those on hypoxic or normoxic DCs. Agonist CGS21680 targeting A2AR could effectively inhibit the maturation and activation of reoxygenated DCs through downregulating the expression of MHC class II molecules and CD86. In response to CGS21680 treatment, reoxygenated DCs exhibited a decrease in proinflammatory cytokines IL-1β, IL-6 and TNF-α, and an increase in immune-regulatory cytokine TGF-β. These data suggest the critical role of A2AR signaling pathway in inhibiting the maturation and proinflammatory function of reoxygenated DCs, thereby proposing A2AR as a potential valuable target for controlling reoxygenated DCs-triggered inflammation.

Topics: Adenosine; Animals; Cell Differentiation; Cytokines; Dendritic Cells; Female; Inflammation; Inflammation Mediators; Mice, Inbred C57BL; Models, Biological; Molecular Targeted Therapy; Oxygen; Phenethylamines; Phenotype; Receptor, Adenosine A2A; RNA, Messenger; Signal Transduction; Up-Regulation

Regulatory T cells have various mechanisms to suppress the inflammatory response, among these, the modulation of the microenvironment through adenosine and with the participation of CD39, CD73 and A2A. The aim of this study was to assess the expression of CD73 and A2A in immune cells and the effect of activation of A2A by an adenosine analogue on apoptosis in patients with obesity and type 2 diabetes mellitus (T2D). CD73 and A2A expression were analyzed by flow cytometry in lymphocyte subpopulations from patients with obesity (n = 22), T2D (n = 22), and healthy subjects (n = 20). Lymphocytes were treated with the selective A2A antagonist (ZM241385) or the selective A2A agonist (CGS21680), and apoptotic cells were detected by Annexin V. We found an increased expression of CD39 coupled to a decrease in CD73 in the patient groups with obesity and T2D compared to the control group in the different studied lymphocyte subpopulations. A2A expression was found to be increased in different subpopulations of lymphocytes from T2D patients. We also detected positive correlations between CD39+ cells and age and BMI. Meanwhile, CD73+ cells showed negative correlations with age, WHR, BMI, FPG, HbAc1, triglycerides and cholesterol. Moreover, an increase in the percentage of apoptotic cells from T2D patients with regard to the groups with obesity and control was observed. In addition, the CD8+ T cells of patients with T2D exhibited decreased apoptosis when treated with the A2A agonist. In conclusion, our data suggest a possible role for CD73 and A2A in inflammation observed in patients with T2D and obesity mediated via apoptosis.

Topics: 5'-Nucleotidase; Adenosine; Adult; Antigens, CD; Apoptosis; Apyrase; Body Mass Index; CD8-Positive T-Lymphocytes; Diabetes Mellitus, Type 2; Gene Expression Regulation; GPI-Linked Proteins; Humans; Inflammation; Lymphocyte Subsets; Lymphocytes; Obesity; Phenethylamines; Receptor, Adenosine A2A; Triazines; Triazoles

The nucleoside adenosine is a known regulator of immunity and inflammation that mediates, at least in part, the anti-inflammatory effect of methotrexate, an immunosuppressive agent widely used to treat autoimmune inflammatory diseases. Adenosine A2A receptors play a key role in the inhibition of the inflammatory process besides promoting wound healing. Therefore, we aimed to determine the topical effect of a selective agonist, CGS-21680, on a murine model of skin hyperplasia with a marked inflammatory component. Pretreatment with either CGS-21680 (5 μg per site) or the reference agent dexamethasone (200 μg/site) prevented the epidermal hyperplasia and inflammatory response induced by topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA, 2 nmol/site) for three consecutive days. The histological analysis showed that both CGS-21680 and dexamethasone produced a marked reduction of inflammatory cell infiltrate, which correlated with diminished myeloperoxidase (MPO) activity in skin homogenates. Both treatments reduced the levels of the chemotactic mediators LTB4 and CXCL-1, and the inflammatory cytokine TNF-α, through the suppression of NFκB phosphorylation. The immunohistochemical analysis of the hyperproliferative markers cytokeratin 6 (CK6) and Ki67 revealed that while both agents inhibit the number of proliferating cells in the epidermis, CGS-21680 treatment promoted dermal fibroblasts proliferation. Consistently, increased collagen deposition in dermis was observed in tissue sections from agonist-treated mice. Our results showed that CGS 21680 efficiently prevents phorbol-induced epidermal hyperplasia and inflammation in mice without the deleterious atrophic effect of topical corticosteroids.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Administration, Topical; Animals; Anti-Inflammatory Agents; Cell Proliferation; Collagen; Cytokines; Dexamethasone; Disease Models, Animal; Epidermis; Female; Hyperplasia; Inflammation; Mice; Peroxidase; Phenethylamines; Skin Diseases; Tetradecanoylphorbol Acetate

Adenosine mediates its effects through activation of a family of four G-protein-coupled receptors, named A1 , A2A , A2B and A3 . This nucleoside plays an important role in immunity and inflammation, and the A2A adenosine receptor subtype has a key role in the inhibition of inflammatory processes besides promoting wound healing. In this issue of Experimental Dermatology, Arasa et al. show that the topical application of a selective A2A agonist, CGS 21680, to mouse skin reduced epidermal hyperplasia as well as skin inflammation, similarly to topical corticoids, without side effects like skin atrophy. Rigorously following up this work is important for the development of novel treatment strategies for chronic hyperproliferative inflammatory dermatoses, such as targeting the A2A adenosine receptor family.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Animals; Epidermis; Female; Inflammation; Phenethylamines; Skin Diseases

Activation of the adenosine 2A receptor (A2AR) reduces inflammation in models of acute injury but contribution in development of chronic abdominal aortic aneurysms (AAAs) is unknown. Elastase perfusion to induce AAA formation in A2AR-knockout (A2ARKO) and C57BL6/J wild-type (WT) mice resulted in nearly 100% larger aneurysms in A2ARKO compared to WT at d 14 (P<0.05), with evidence of greater elastin fragmentation, more immune cell infiltration, and increased matrix metallatoproteinase (MMP) 9 expression (P<0.05). Separately, exogenous A2AR antagonism in elastase-perfused WT mice also resulted in larger aneurysms (P<0.05), while A2AR agonism limited aortic dilatation (P<0.05). Activated Thy-1.2(+) T lymphocytes from WT mice treated in vitro with A2AR antagonist increased cytokine production, and treatment with A2AR agonist decreased cytokine production (P<0.05 for all). Primary activated CD4(+) T lymphocytes from A2ARKO mice exhibited greater chemotaxis (P<0.05). A2AR antagonist increased chemotaxis of activated CD4(+) cells from WT mice in vitro, and A2AR agonist reduced this effect (P<0.05). A2AR activation attenuates AAA formation partly by inhibiting immune cell recruitment and reducing elastin fragmentation. These findings support augmenting A2AR signaling as a putative target for limiting aneurysm formation.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Adenosine A2 Receptor Antagonists; Animals; Aortic Aneurysm, Abdominal; CD4-Positive T-Lymphocytes; Cytokines; Humans; Inflammation; Male; Matrix Metalloproteinase 9; Mice; Mice, Inbred C57BL; Mice, Knockout; Pancreatic Elastase; Phenethylamines; Phenotype; Receptors, Adenosine A2; Triazines; Triazoles

Chronic obstructive pulmonary disease (COPD) is a neutrophilic inflammatory disorder that is weakly responsive to glucocorticoids. Identification of ways to enhance the anti-inflammatory activity of glucocorticoids is, therefore, a major research objective. Adenosine receptor agonists that target the A2B-receptor subtype are efficacious in several cell-based assays and preclinical models of inflammation. Accordingly, the present study was designed to determine if a selective A2B-receptor agonist, 2-[6-amino-3,5-dicyano-4-[4-(cyclopropylmethoxy)phenyl]pyridin-2-ylsulphanyl]acetamide (Bay 60-6583), and a glucocorticoid, dexamethasone, in combination display putative anti-inflammatory activity that is superior to either drug alone. In BEAS-2B human airway epithelial cells stably transfected with cAMP-response element (CRE) and glucocorticoid response element (GRE) reporter constructs, Bay 60-6583 promoted CRE-dependent transcription and enhanced GRE-dependent transcription by an adenosine A2B-receptor-mediated mechanism that was associated with cAMP formation and abolished by an inhibitor of cAMP-dependent protein kinase. Analysis of the concentration-response relationship that described the enhancement of GRE-dependent transcription showed that Bay 60-6583 increased the magnitude of response without affecting the potency of dexamethasone. Bay 60-6583 and dexamethasone also induced a panel of genes that, collectively, could have benefit in COPD. These were categorized into genes that were induced in a positive cooperative manner (RGS2, p57(kip2)), an additive manner (TTP, BRL-1), or by Bay 60-6583 (CD200, CRISPLD2, SOCS3) or dexamethasone (GILZ) only. Thus, the gene induction "fingerprints" produced by Bay 60-6583 and dexamethasone, alone and in combination, were distinct. Collectively, through their actions on gene expression, an adenosine A2B-receptor agonist and a glucocorticoid administered together may have utility in the treatment of inflammatory disorders that respond suboptimally to glucocorticoids as a monotherapy.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Algorithms; Aminopyridines; Calcium; Cell Line; Cyclic AMP; Cyclic AMP Response Element Modulator; Cytosol; Dexamethasone; Epithelial Cells; Humans; Inflammation; Phenethylamines; Pulmonary Disease, Chronic Obstructive; Real-Time Polymerase Chain Reaction; Receptor, Adenosine A2B; Receptors, Glucocorticoid; Respiratory Mucosa; RNA, Messenger; Transfection

Morning stiffness and increased symptoms of inflammatory arthritis are among the most common manifestations of rheumatoid arthritis (RA). Tumor necrosis alpha (TNF-α), an important mediator of inflammation in RA, regulates the circadian expression of clock proteins, and adenosine A(2A) receptors (A(2A)R) mediate many of the anti-inflammatory and antirheumatic actions of methotrexate, the cornerstone drug in the treatment of RA. We found that A(2A)R activation and TNF-α activated the clock core loop of the human monocytic THP-1 cell line. We further observed that interleukin (IL)-10, but not IL-12, mRNA expression fluctuates in a circadian fashion and that TNF-α and A(2A)R stimulation combined increased IL-10 expression. Interestingly, TNF-α, but not CGS21680, dramatically inhibited IL-12 mRNA expression. The demonstration that A(2A)R and TNF-α regulate the intrinsic circadian clock in immune cells provides an explanation for both the pathologic changes in circadian rhythms in RA and for the adverse circadian effects of methotrexate, such as fatigue.

Topics: Adenosine; ARNTL Transcription Factors; Arthritis, Rheumatoid; Cell Line; Circadian Clocks; Circadian Rhythm; CLOCK Proteins; Cryptochromes; Fatigue; Humans; Inflammation; Interleukin-1; Interleukin-10; Methotrexate; Monocytes; Period Circadian Proteins; Phenethylamines; Receptor, Adenosine A2A; RNA, Messenger; Tumor Necrosis Factor-alpha

A(2A) adenosine receptors (ARs) play a key role in the inhibition of the inflammatory process. The purpose of this study was to evaluate the modulation of A(2A)ARs in rheumatoid arthritis (RA) patients after different pharmacological treatments and to investigate the effect of A(2A)AR stimulation in a rat model of arthritis. We investigated A(2A)AR density and functionality in RA progression by using a longitudinal study in RA patients before and after methotrexate (MTX), anti-TNFα agents or rituximab treatments. A(2A)ARs were analyzed by saturation binding assays in lymphocytes from RA patients throughout the 24-month study timeframe. In an adjuvant-induced arthritis model in rats we showed the efficacy of the A(2A)AR agonist, CGS 21680 in comparison with standard therapies by means of paw volume assessment, radiographic and ultrasonographic imaging. Arthritic-associated pain was investigated in mechanical allodynia and thermal hyperalgesia tests. IL-10 release following A(2A)AR stimulation in lymphocytes from RA patients and in serum from arthritic rats was measured. In lymphocytes obtained from RA patients, the A(2A)AR up-regulation was gradually reduced in function of the treatment time and the stimulation of these receptors mediated a significant increase of IL-10 production. In the same cells, CGS 21680 did not affected cell viability and did not produced cytotoxic effects. The A(2A)AR agonist CGS 21680 was highly effective, as suggested by the marked reduction of clinical signs, in rat adjuvant-induced arthritis and associated pain. This study highlighted that A(2A)AR agonists represent a physiological-like therapeutic alternative for RA treatment as suggested by the anti-inflammatory role of A(2A)ARs in lymphocytes from RA patients. The effectiveness of A(2A)AR stimulation in a rat model of arthritis supported the role of A(2A)AR agonists as potential pharmacological treatment for RA.

Topics: Adenosine; Animals; Anti-Inflammatory Agents; Antibodies, Monoclonal, Murine-Derived; Antirheumatic Agents; Arthritis, Experimental; Arthritis, Rheumatoid; Disease Models, Animal; Humans; Inflammation; Longitudinal Studies; Lymphocytes; Male; Methotrexate; Phenethylamines; Purinergic P1 Receptor Agonists; Rats; Receptors, Purinergic P1; Rituximab; Tumor Necrosis Factor-alpha; Up-Regulation

C-C chemokine receptor 7 (CCR7) and its chemoattractant agonist CCL21 promote cell migration and expression of pro-inflammatory proteins in an atherogenic environment. Since A(2A) adenosine receptor activation reduces migration and inflammatory effects, we examined its effect on CCR7 expression and migration. CCR7 protein expression decreased by about a third in macrophages treated with A(2A) receptor agonist CGS 21680 (p = 0.028, n = 7) and was reversed with antagonist, although mRNA levels increased twofold (p = 0.001, n = 3). Furthermore, macrophages treated with CGS 21680 showed a significant decrease in migration (p = 0.0311, n = 7). These results suggest that A(2A) adenosine receptor activation not only modulates CCR7 expression in both normal and inflammatory environments but also regulates macrophage migration to CCR7-specific chemoattractants.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Adenosine A2 Receptor Antagonists; Cell Line; Cell Movement; Chemokine CCL21; Humans; Inflammation; Macrophages; Phenethylamines; Receptors, Adenosine A2; Receptors, CCR7; RNA, Messenger; Triazines; Triazoles

Prosthesis loosening, associated with wear particle-induced inflammation and osteoclast-mediated bone destruction, is a common cause for joint implant failure, leading to revision surgery. Adenosine A(2A) receptors (A(2A)Rs) mediate potent anti-inflammatory effects in many tissues and prevent osteoclast differentiation. We tested the hypothesis that an A(2A)R agonist could reduce osteoclast-mediated bone resorption in a murine calvaria model of wear particle-induced bone resorption. C57BL/6 and A(2A)R knockout (A(2A)R KO) mice received ultrahigh-molecular weight polyethylene particles and were treated daily with either saline or the A(2A)R agonist CGS21680. After 2 weeks, micro-computed tomography of calvaria demonstrated that CGS21680 reduced particle-induced bone pitting and porosity in a dose-dependent manner, increasing cortical bone and bone volume compared to control mice. Histological examination demonstrated diminished inflammation after treatment with CGS21680. In A(2A)R KO mice, CGS21680 did not affect osteoclast-mediated bone resorption or inflammation. Levels of bone resorption markers receptor activator of nuclear factor κB (RANK), RANK ligand, cathepsin K, CD163, and osteopontin were reduced after CGS21680 treatment, together with a reduction in osteoclasts. Secretion of interleukin-1β (IL-1β) and tumor necrosis factor-α was significantly decreased, whereas IL-10 was markedly increased in bone by CGS21680. These results in mice suggest that site-specific delivery of an adenosine A(2A)R agonist could enhance implant survival, delaying or eliminating the need for revision arthroplastic surgery.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Animals; Cells, Cultured; Female; Humans; Inflammation; Mice; Mice, Inbred C57BL; Mice, Knockout; Osteolysis; Phenethylamines; Prosthesis Failure; Receptor, Adenosine A2A

Adenosine is considered as a potent endogenous anti-inflammatory and immunosuppressive molecule. We examined the roles of A2A-adenosine receptor (A(2A)R) in the progression of lupus nephritis.. MRL/lpr mice were given a selective A(2A)R agonist, CGS21680 (0.4 mg/kg per day, i.p.) while control mice received saline only. After 8 weeks of treatment, mice were sacrificed for assessment of functional and histological parameters as well as inflammatory infiltration in the kidneys. MCP-1, IFN-γ, MHC-II and A(2A)R mRNA expression was evaluated by RT-PCR. Expression of A(2A)R and nuclear NFκB p65 protein was determined by Western blot analysis. Levels of anti-dsDNA antibody and IFN-γ were measured by ELISA.. CGS21680 treatment resulted in significant decrease in proteinuria, blood urea and creatinine as well as improvement in renal histology. Renal macrophage and T-cell infiltration were significantly attenuated in association with suppressed expression of MCP-1, IFN-γ and MHC-II. CGS21680 treatment reduced the level of serum anti-dsDNA and renal immune complex deposition. CGS21680 inhibited the activation of NFκB and suppressed the expression of IFN-γ, MCP-1 and MHC-II in MRL/lpr splenocytes.. A(2A)R activation suppressed inflammation in the kidneys of MRL/lpr mice and can be considered as a novel therapeutic approach for human lupus nephritis.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Animals; Blotting, Western; Disease Models, Animal; Disease Progression; Female; Gene Expression; Inflammation; Lupus Erythematosus, Systemic; Lupus Nephritis; Mice; Mice, Inbred MRL lpr; Phenethylamines; Receptor, Adenosine A2A; Reverse Transcriptase Polymerase Chain Reaction; RNA

Permanent functional deficits following spinal cord injury (SCI) arise both from mechanical injury and from secondary tissue reactions involving inflammation. Enhanced release of adenosine and glutamate soon after SCI represents a component in the sequelae that may be responsible for resulting functional deficits. The role of adenosine A2A receptor in central ischemia/trauma is still to be elucidated. In our previous studies we have demonstrated that the adenosine A2A receptor-selective agonist CGS21680, systemically administered after SCI, protects from tissue damage, locomotor dysfunction and different inflammatory readouts. In this work we studied the effect of the adenosine A2A receptor antagonist SCH58261, systemically administered after SCI, on the same parameters. We investigated the hypothesis that the main action mechanism of agonists and antagonists is at peripheral or central sites.. Spinal trauma was induced by extradural compression of SC exposed via a four-level T5-T8 laminectomy in mouse. Three drug-dosing protocols were utilized: a short-term systemic administration by intraperitoneal injection, a chronic administration via osmotic minipump, and direct injection into the spinal cord.. SCH58261, systemically administered (0.01 mg/kg intraperitoneal. 1, 6 and 10 hours after SCI), reduced demyelination and levels of TNF-α, Fas-L, PAR, Bax expression and activation of JNK mitogen-activated protein kinase (MAPK) 24 hours after SCI. Chronic SCH58261 administration, by mini-osmotic pump delivery for 10 days, improved the neurological deficit up to 10 days after SCI. Adenosine A2A receptors are physiologically expressed in the spinal cord by astrocytes, microglia and oligodendrocytes. Soon after SCI (24 hours), these receptors showed enhanced expression in neurons. Both the A2A agonist and antagonist, administered intraperitoneally, reduced expression of the A2A receptor, ruling out the possibility that the neuroprotective effects of the A2A agonist are due to A2A receptor desensitization. When the A2A antagonist and agonist were centrally injected into injured SC, only SCH58261 appeared neuroprotective, while CGS21680 was ineffective.. Our results indicate that the A2A antagonist protects against SCI by acting on centrally located A2A receptors. It is likely that blockade of A2A receptors reduces excitotoxicity. In contrast, neuroprotection afforded by the A2A agonist may be primarily due to peripheral effects.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Adenosine A2 Receptor Antagonists; Animals; Inflammation; Infusion Pumps, Implantable; JNK Mitogen-Activated Protein Kinases; Male; Mice; Motor Activity; Phenethylamines; Pyrimidines; Spinal Cord; Spinal Cord Injuries; Triazoles

We aimed to elucidate the role of alpha(1)-adrenoceptors in adenosine analgesia in the formalin test. Formalin was injected into the hind paw of male CD-1 mice after injection of adenosine A(1) or A(2a) receptor agonists, CPA, [N(6)-cyclopentyladenosine], and CGS21680 [2-p-(2-carboxyethyl)-phenylethylamino-5'-N-ethylcarboxamidoadenosine hydrochloride]. In the behavioral experiment, alpha(1)-adrenoceptors were blocked by an alpha(1)-adrenoceptor antagonist prazosin, 0.01 mg/kg i.p., and the time mice spent paw licking was recorded for the early (0-15 min) and late (15-60 min) phase of formalin pain. In the neurochemical experiments, mice were killed 15 or 45 min after formalin injection. The density of alpha(1)-adrenoceptors was assessed in various brain areas and in the lumbar spinal cord by [(3)H]prazosin autoradiography. Adenosine agonists produced analgesia in both phases of formalin pain, while prazosin showed a tendency to pronociceptive action in the late phase, and antagonized the effect of CGS21680. After formalin injection, alpha(1)-adrenoceptor density was elevated in some brain areas, mainly in the late phase (some contralateral amygdaloid and ipsilateral thalamic nuclei) and depressed in others (early phase in the ipsilateral spinal cord and late phase in both ipsi- and contralateral sensorimotor cortex). Elevation of alpha(1)-adrenoceptor density, which may be interpreted as a defensive response, did not develop in several cases of CPA-pretreated mice. This suggests that the analgesic effect of adenosine A(1) receptor activation renders the defensive response unnecessary. The depression of alpha(1)-adrenoceptors may suggest development of hypersensitivity in a given structure, and this was antagonized by CGS21680, suggesting the role of A(2a) receptors in control of inflammatory formalin pain.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Adenosine A2 Receptor Antagonists; Analgesics; Animals; Autoradiography; Central Nervous System; Disease Models, Animal; Inflammation; Male; Mice; Nociceptors; Pain; Pain Measurement; Phenethylamines; Prazosin; Receptor, Adenosine A2A; Receptors, Adrenergic, alpha-1

To investigate the effects of adenosine A2A receptor (A2AR) activation on inflammatory responses in small-for-size liver transplantation.. A rat orthotopic liver transplantation model was established using 35% grafts. Expression of A2AR in liver grafts was assessed using Western blot analysis. Recipients were given either saline solution (control group) or CGS21680 (A2AR agonist) or ZM241385 (A2AR antagonist) immediately after and 12 hours after reperfusion. Proinflammatory factors (tumor necrosis factor-alpha [TNF-alpha], macrophage inflammatory protein-2 [MIP-2], and intercellular adhesion molecule-1 [ICAM-1]) were analyzed using an enzyme-linked immunosorbent assay; neutrophil infiltration was assessed using a myeloperoxidase activity assay and hematoxylin-eosin staining; and nuclear factor-kappaB (NF-kappaB) was assessed using Western blot analysis and an electrophoretic mobility shift assay.. Expression of A2AR was increased after reperfusion, peaking at 6 to 12 hours after transplantation. Compared with controls, A2AR activation decreased TNF-alpha, MIP-2, and ICAM-1 expression, reduced MIP-2 activity, inhibited IkappaB phosphorylation, and suppressed NF-kappaB activation.. Expression of A2AR is increased after transplantation, and suppresses inflammatory responses by blocking NF-kappaB activation in small-for-size grafts.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Adenosine A2 Receptor Antagonists; Alanine Transaminase; Animals; Chemokine CXCL2; Cytokines; Enzyme-Linked Immunosorbent Assay; Inflammation; Intercellular Adhesion Molecule-1; Liver; Liver Transplantation; Male; NF-kappa B; Organ Size; Peroxidase; Phenethylamines; Phosphorylation; Rats; Rats, Inbred Lew; Receptor, Adenosine A2A; Triazines; Triazoles; Tumor Necrosis Factor-alpha

Here we studied the role of peripheral adenosine A(2A) receptors in mechanical hyperalgesia during inflammation using mice lacking the A(2A) receptors. Unilateral s.c. administration of the local inflammatory agent λ-carrageenan induced profound mechanical hyperalgesia 24 h after administration in the ipsilateral hind paw in wild-type mice. In homozygous mice lacking the A(2A) receptors, carrageenan-induced hyperalgesia was significantly reduced compared to wild type controls. The reduction in inflammatory hyperalgesia seen in A(2A) receptor knock-out mice was not associated with changes in paw edema. CGS 21680, a selective A(2A) receptor agonist, produced significantly more mechanical hyperalgesia in wild type females than in wild type males upon direct s.c. injection into the hindpaw whereas it had no effect upon systemic administration. The hyperalgesic effect of CGS 21680 was markedly reduced in the A(2A) knock-out mice of both sexes. Subcutaneous ZM-241,385, a selective A(2A) receptor antagonist, injected into the hindpaw reduced the mechanical hyperalgesia following carrageenan in female mice, but not in males. The results indicate that activation of peripheral adenosine A(2A) receptors during inflammation is associated with mechanical hyperalgesia, and that this effect is more prominent in females than in males.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Adenosine A2 Receptor Antagonists; Animals; Carrageenan; Female; Ganglia, Spinal; Hyperalgesia; Inflammation; Injections, Intraperitoneal; Injections, Subcutaneous; Male; Mice; Mice, Knockout; Pain; Pain Threshold; Phenethylamines; Receptor, Adenosine A2A; Sex Characteristics; Triazines; Triazoles

Adenosine is formed in injured/ischemic tissues, where it suppresses the actions of essentially all cells of the immune system. Most of the anti-inflammatory actions of adenosine have been attributed to signaling through the G(s) protein-coupled A(2A) adenosine receptor (AR). Here, we report that the A(3)AR is highly expressed in murine neutrophils isolated from bone marrow. Selective activation of the A(3)AR with (2S,3S,4R,5R)-3-amino-5-[6-(2,5-dichlorobenzylamino)purin-9-yl]-4-hydroxytetrahydrofuran-2-carboxylic acid methylamide (CP-532,903) potently inhibited mouse bone marrow neutrophil superoxide generation and chemotaxis induced by various activating agents. The selectivity of CP-532,903 was confirmed in assays using neutrophils obtained from A(2A)AR and A(3)AR gene "knockout" mice. In a model of thioglycollate-induced inflammation, treating mice with CP-532,903 inhibited recruitment of leukocytes into the peritoneum by specifically activating the A(3)AR. Collectively, our findings support the theory that the A(3)AR contributes to the anti-inflammatory actions of adenosine on neutrophils and provide a potential mechanistic explanation for the efficacy of A(3)AR agonists in animal models of inflammation (i.e., inhibition of neutrophil-mediated tissue injury).

Topics: Adenosine; Animals; Bone Marrow Cells; Cell Separation; Chemotaxis; Furans; Gene Expression Regulation; Humans; Inflammation; Mice; Mice, Inbred C57BL; Mice, Knockout; N-Formylmethionine Leucyl-Phenylalanine; Neutrophil Activation; Neutrophils; Peritonitis; Phenethylamines; Purines; Receptor, Adenosine A2A; Receptor, Adenosine A2B; Receptor, Adenosine A3; RNA, Messenger; Superoxides

The aim of the present study was to investigate the potential role of adenosine A(2A) receptor (A(2A)R) activation in small-for-size liver transplantation. A rat orthotopic liver transplantation model was performed by using 40% (range: 36-46%) liver grafts. Recipients were given either saline (control group) or CGS 21680 (2-p-(2-Carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine hydrochloride, a selective A(2A)R agonist), or CGS 21680+ ZM 241385 (a selective A(2A)R antagonist) immediately after reperfusion for 3 h. Compared with control group, CGS 21680 used at both low dose (0.05 microg/kg/min) and high dose (0.5 microg/kg/min) increased the survival rate from 16.7% (2/12) to 83.3% (10/12) and 66.7% (8/12), respectively. These effects correlated with improved liver function and preserved hepatic architecture. CGS 21680 effectively decreased neutrophil infiltration, suppressed pro-inflammatory (TNF-alpha, IL-1beta and IL-6) expression, promoted expression of antiapoptotic molecules, and inhibited apoptosis. The effects of CGS 21680 were prevented when ZM 241385 was co-administrated. In conclusion, the present study showed that A(2A)R activation alleviated portal hypertension, suppressed inflammatory response, reduced apoptosis, and potentiated the survival of small-for-size liver grafts. Our findings provide the rationale for a novel therapeutic approach using A(2A)R activation to maximize the availability of small-for-size liver grafts.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Animals; Apoptosis; Cytokines; Graft Survival; Inflammation; Liver; Liver Transplantation; Male; Models, Animal; Peroxidase; Phenethylamines; Rats; Rats, Sprague-Dawley; Receptor, Adenosine A2A; Reperfusion; Transplantation, Isogeneic

Hemorrhagic shock and resuscitation trigger a global ischemia/reperfusion phenomenon, in which various inflammatory processes critically contribute to the ensuing tissue damage. Adenosine is an endogenous nucleoside that is released during shock. Activation of adenosine A(2A) receptors can broadly inactivate inflammatory cascades. The current study was designed to evaluate the effect of A(2A) receptor activation on organ injury and inflammation in the setting of global ischemia/reperfusion elicited by trauma/hemorrhagic shock and resuscitation.. Prospective animal study with concurrent control.. Small animal laboratory.. Adult male Sprague-Dawley rats.. The rats were subjected to a laparotomy (trauma) and 90 mins of hemorrhagic shock or trauma/sham shock. The selective A(2A) receptor agonist CGS-21680 (2-p-(2-carboxyethyl) phenethylamino-5'-N-ethyl-carboxamidoadenosine; 0.5 mg/kg) or its vehicle was injected 30 mins before shock or immediately after resuscitation. At 3 hrs following resuscitation, animals were killed and tissue was harvested for analysis. Lung permeability and pulmonary myeloperoxidase levels were used to quantitate lung injury. Intestinal injury was determined by histologic analysis of terminal ileum. Red blood cell deformability was measured by a laser-assisted ektacytometer. In this assay, a decrease in the elongation index is a marker of decreased red blood cell deformability.. Pretreatment with CGS-21680 protected the lung but not the gut against shock-induced injury and prevented the shock-induced decrease in red blood cell deformability. Posttreatment with CGS-21680 ameliorated shock-induced lung injury but failed to prevent gut injury and preserve red blood cell deformability.. A(2A) receptor agonists may represent a novel therapeutic approach in preventing organ injury following trauma/hemorrhagic shock.

Topics: Adenosine; Adenosine A2 Receptor Agonists; Animals; Inflammation; Lung Diseases; Male; Phenethylamines; Rats; Rats, Sprague-Dawley; Receptor, Adenosine A2A; Reperfusion Injury; Resuscitation; Shock, Hemorrhagic; Shock, Traumatic

Loss of function of the peritoneal membrane is associated with peritonitis. Adenosine levels in sites of inflammation were shown to increase and exhibit immunoregulatory effects. Our aim was to elucidate the regulatory role of adenosine during peritonitis and to test the involvement of peritoneal mesothelial cells (PMC) in adenosine regulation. In a mice model of Escherichia coli peritonitis, the adenosine A(2A) receptor (A(2A)R) agonist (CGS21680) prevented leukocyte recruitment and reduced tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) levels. Peritonitis induced the elevation of adenosine with a peak at 24 h. Analysis of adenosine receptor levels on peritoneum showed that A(1) receptor (A(1)R) protein levels peak at 12 h after inoculation and then return to baseline at 24 h, whereas high affinity A(2A)R protein levels peak at 24 h concomitantly with the peak of adenosine concentration. Low affinity A(2B) receptor (A(2B)R) levels elevated slowly, remaining elevated up to 48 h. In human PMC (HPMC), the early cytokines, IL-1-alpha, and TNF-alpha upregulated the A(2B) and A(2A) receptors. However, interferon-gamma (IFN-gamma) upregulated the A(2B)R and decreased A(2A)R levels. Treatment with the A(2A)R agonist reduced IL-1-dependent IL-6 secretion from HPMC. In conclusion, the kinetics of adenosine receptors suggest that at early stage of peritonitis, the A(1)R dominates, and later its dominance is replaced by the G stimulatory (Gs) protein-coupled A(2A)R that suppresses inflammation. Early proinflammatory cytokines are an inducer of the A(2A)R and this receptor reduces their production and leukocyte recruitment. Future treatment with adenosine agonists should be considered for attenuating the damage to mesothelium during the course of acute peritonitis.

Topics: Adenosine; Adenosine A1 Receptor Agonists; Adenosine A2 Receptor Agonists; Adenosine A2 Receptor Antagonists; Animals; Antihypertensive Agents; Cells, Cultured; Disease Models, Animal; Down-Regulation; Epithelium; Escherichia coli; Female; Humans; Inflammation; Interleukin-6; Leukocytes; Mice; Mice, Inbred Strains; Peritonitis; Phenethylamines; Purinergic P1 Receptor Agonists; Purinergic P1 Receptor Antagonists; Receptor, Adenosine A1; Receptor, Adenosine A2A; Receptors, Purinergic P1; RNA, Messenger; Theobromine; Tumor Necrosis Factor-alpha; Up-Regulation; Xanthines

Topics: Adenosine; Adenosine A2 Receptor Agonists; Animals; Blood Pressure; Erythrocyte Deformability; Humans; Immunologic Factors; Inflammation; Lung Diseases; Phenethylamines; Rats; Reperfusion Injury; Shock, Hemorrhagic; Shock, Traumatic; Time Factors; Toll-Like Receptor 4; Vasodilator Agents

To evaluate the direct effect of adenosine on cytokine-polarized effector T cells, murine type 1 helper T cells (Th1) and type 1 cytotoxic T lymphocytes (Tc1) and Th2/Tc2 cells were generated using an antigen-presenting cell (APC)-free method. Tc1 and Tc2 cells had similar adenosine signaling, as measured by intracellular cyclic AMP (cAMP) increase upon adenosine A(2A) receptor agonism by CGS21680 (CGS). CGS greatly reduced Tc1 and Tc2 cell interleukin 2 (IL-2) and tumor necrosis factor alpha (TNF-alpha) secretion, with nominal effect on interferon gamma (IFN-gamma) secretion. Tc2 cell IL-4 and IL-5 secretion was not reduced by CGS, and IL-10 secretion was moderately reduced. Agonist-mediated inhibition of IL-2 and TNF-alpha secretion occurred via A(2A) receptors, with no involvement of A(1), A(2B), or A(3) receptors. Adenosine agonist concentrations that abrogated cytokine secretion did not inhibit Tc1 or Tc2 cell cytolytic function. Adenosine modulated effector T cells in vivo, as CGS administration reduced CD4(+)Th1 and CD8(+)Tc1 cell expansion to alloantigen and, in a separate model, reduced antigen-specific CD4(+) Th1 cell numbers. Remarkably, agonist-mediated T-cell inhibition was abrogated by in vivo IL-2 therapy. Adenosine receptor activation therefore preferentially inhibits type I cytokine secretion, most notably IL-2. Modulation of adenosine receptors may thus represent a suitable target primarily for inflammatory conditions mediated by Th1 and Tc1 cells.

Topics: Adenosine; Animals; Antigen-Presenting Cells; CD28 Antigens; CD3 Complex; CD4-Positive T-Lymphocytes; CD8-Positive T-Lymphocytes; Cells, Cultured; Cyclic AMP; Dose-Response Relationship, Drug; Flow Cytometry; Inflammation; Interferon-gamma; Interleukin-10; Interleukin-2; Mice; Mice, Inbred C57BL; Mice, Transgenic; Phenethylamines; Receptor, Adenosine A2A; Signal Transduction; T-Lymphocytes, Cytotoxic; Th1 Cells; Tumor Necrosis Factor-alpha

Recently, adenosine has been proposed to be a "metabolic" switch that may sense and direct immune and inflammatory responses. Inflammation and pro-inflammatory cytokine production are important in development of HIV-1 associated dementia, a devastating consequence of HIV-1 infection of the CNS. The HIV-1 protein Tat induces cell death in the CNS and activates local inflammatory responses partially by inducing calcium release from the endoplasmic reticulum. Because activation of adenosine receptors decreases production of the pro-inflammatory cytokine TNF-alpha in several experimental paradigms both in vitro and in vivo, we hypothesized that adenosine receptor activation would control both increased intracellular calcium and TNF-alpha production induced by Tat. Treatment of primary monocytes with Tat significantly increased the levels of intracellular calcium released from IP3 stores. Activation of adenosine receptors with CGS 21680 inhibited Tat-induced increases of intracellular calcium by 90 +/- 8% and was dependent on protein phosphatase activity because okadaic acid blocked the actions of CGS 21680. Tat-induced TNF-alpha production was inhibited 90 +/- 6% by CGS 21680 and concurrent treatment with okadaic acid blocked the inhibitory actions of CGS 21680. Using a model monocytic cell line, CGS 21680 treatment increased cytosolic serine/threonine phosphatase. Together, these data indicate that A2A receptor activation increases protein phosphatase activity, which blocks IP3 receptor-regulated calcium release and reduction of intracellular calcium inhibits TNF-alpha production in monocytes.

Topics: Adenosine; Calcium; Cells, Cultured; Gene Products, tat; HIV-1; Humans; Inflammation; Monocytes; Phenethylamines; Phosphoprotein Phosphatases; Receptor, Adenosine A2A; Signal Transduction; tat Gene Products, Human Immunodeficiency Virus; Tumor Necrosis Factor-alpha; U937 Cells

We have investigated the effect of 2(4-((2-carboxymethyl)phenyl)ethylamino)-5'-N-ethylcarboxamidoadenosine (CGS 21680), a potent and selective agonist at adenosine A2A receptors, on pulmonary inflammation induced by allergen challenge in the ovalbumin-sensitised, Brown Norway rat. Aerosol administration of ovalbumin (5 mg x ml(-1) for 60 min; calculated dose 0.4 mg x kg(-1)) induced increases in bronchoalveolar lavage fluid leukocyte numbers, protein content and myeloperoxidase and eosinophil peroxidase activities measured 24 h post challenge. CGS 21680 (10 and 100 microg x kg(-1) given intratracheally (i.t.) 30 min before and 3 h after allergen challenge) inhibited dose-dependently all the parameters of inflammation. Qualitatively similar results were obtained with the glucocorticosteroid, budesonide (0.1, 1 and 10 mg x kg(-1) given 3 h prior to ovalbumin challenge). CGS 21680 given i.t. reduced blood pressure in anaesthetised rats at similar doses to those at which anti-inflammatory effects were manifested. Both the anti-inflammatory and hypotensive responses to CGS 21680 were blocked by pretreatment with the selective adenosine A2A receptor antagonist, 4-(2-(7-amino-2-(2-furyl)(1,2,4)triazolo(2,3-a(1,3,5)triazin-5-yl amino)ethyl)phenol (ZM 241385), 3 mg x kg(-1) p.o., 1 h prior to the agonist. Thus, CGS 21680 manifests broad-spectrum anti-inflammatory activity in a model of allergic asthma in the Brown Norway rat through activation of adenosine A2A receptors. The striking similarity to budesonide, a clinically used anti-inflammatory agent, suggests that adenosine A2A receptor agonists may be useful alternatives to glucocorticosteroids in the treatment of asthma.

Topics: Adenosine; Allergens; Animals; Anti-Inflammatory Agents; Asthma; Blood Pressure; Budesonide; Dose-Response Relationship, Drug; Inflammation; Lung; Male; Ovalbumin; Phenethylamines; Purinergic P1 Receptor Agonists; Rats; Rats, Inbred BN; Receptor, Adenosine A2A; Triazines; Triazoles; Vascular Resistance

The ubiquitous neuromodulator adenosine inhibits the production of several proinflammatory cytokines through activation of specific cell-surface adenosine receptors. We demonstrated recently that antisense oligonucleotides to tumor necrosis factor-alpha (TNF-alpha) are neuroprotective in a rat model of intracerebral hemorrhage. Therefore, we hypothesized that activation of adenosine receptors would provide protection against intracerebral hemorrhage-induced TNF-alpha production and inflammatory events. In vitro experiments showed that adenosine A1, A2A, and A3 receptor subtypes were present on U937 cells, and activation of these subtypes inhibited TNF-alpha production with a rank order of A2A > > A1 > A3. Prolonged treatment of U937 cells with the A2A receptor agonist 2-p-(carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine hydrochloride (CGS 21680) desensitized adenosine A2A, A1, and A3 receptors. CGS 21680 administration directly into the striatum immediately prior to the induction of intracerebral hemorrhage inhibited TNF-alpha mRNA and, 24 hours following induction, reduced parenchymal neutrophil infiltration (p < 0.001) and TUNEL-positive cells (p < 0.002) within and bordering the hematoma. These results suggest that pharmacological strategies targeting A2A receptors may provide effective inhibition of acute neurotoxic proinflammatory events that occur following intracerebral hemorrhage.

Topics: Adenosine; Adenylyl Cyclases; Animals; Apoptosis; Cerebral Hemorrhage; Chemotaxis, Leukocyte; Humans; In Situ Nick-End Labeling; Inflammation; Injections, Intraventricular; Male; Neutrophils; Phenethylamines; Phytohemagglutinins; Purinergic P1 Receptor Agonists; Rats; Rats, Sprague-Dawley; Receptor, Adenosine A2A; Receptor, Adenosine A3; Receptors, Purinergic P1; RNA, Messenger; Tetradecanoylphorbol Acetate; Tumor Necrosis Factor-alpha; U937 Cells

We have identified a mechanism, mediated by the epsilon isozyme of protein kinase C (PKCepsilon) in peripheral neurons, which may have a role in chronic inflammatory pain. Acute inflammation, produced by carrageenan injection in the rat hindpaw, produced mechanical hyperalgesia that resolved by 72 hr. However, for up to 3 weeks after carrageenan, injection of the inflammatory mediators prostaglandin E(2) or 5-hydroxytryptamine or of an adenosine A(2) agonist into the same site induced a markedly prolonged hyperalgesia (>24 hr compared with 5 hr or less in control rats not pretreated with carrageenan). A nonselective inhibitor of several PKC isozymes and a selective PKCepsilon inhibitor antagonized this prolonged hyperalgesic response equally. Acute carrageenan hyperalgesia could be inhibited by PKA or PKG antagonists. However, these antagonists did not inhibit development of the hypersensitivity to inflammatory mediators. Our findings indicate that different second messenger pathways underlie acute and prolonged inflammatory pain.

Topics: Adenosine; Animals; Carrageenan; Dinoprostone; Enzyme Inhibitors; Hindlimb; Hyperalgesia; Inflammation; Isoenzymes; Male; Nociceptors; Pain; Phenethylamines; Protein Kinase C; Protein Kinase C-epsilon; Protein Kinase Inhibitors; Purinergic P1 Receptor Agonists; Rats; Rats, Sprague-Dawley; Serotonin; Time Factors

We have investigated the effects of the adenosine A(2A) receptor agonist CGS 21680 (0.01 - 1 microM) on reactive oxidant production by, and elastase release from FMLP-activated human neutrophils, as well as on cytosolic Ca(2+) fluxes and intracellular concentrations of cyclic AMP. Oxidant production, elastase release and cyclic AMP were assayed using lucigenin-enhanced chemiluminescence, colourimetric and radioimmunoassay procedures respectively, while cytosolic Ca(2+) fluxes were measured by fura-2 spectrofluorimetry in combination with radiometric procedures which distinguish between net efflux and influx of the cation. Treatment of neutrophils with CGS 21680 did not affect the FMLP-activated release of Ca(2+) from intracellular stores, but resulted in dose-related acceleration of the rate of decline in fura-2 fluorescence, as well as decreases in both efflux and store-operated influx of Ca(2+), compatible with enhancement of resequestration of the cation by the endo-membrane Ca(2+)-ATPase. These effects on neutrophil Ca(2+) handling were associated with increased intracellular cyclic AMP and with inhibition of oxidant production and release of elastase. In contrast, treatment of neutrophils with the selective A(2A) receptor antagonist, ZM 241385 (2.5 microM), prevented the transient increase in cyclic AMP in FMLP-activated neutrophils which was associated with delayed sequestration of incoming Ca(2+) during store-operated influx. The CGS 21680-mediated reduction of Ca(2+) efflux from FMLP-activated neutrophils was also antagonized by pretreatment of the cells with ZM 241385 (2.5 microM), as well as by thapsigargin (1 microM), an inhibitor of the endo-membrane Ca(2+)-ATPase. ZM 241385 also neutralized the cyclic AMP-elevating and anti-inflammatory interactions of CGS 21680 with neutrophils. We conclude that A(2A) receptors regulate the pro-inflammatory activities of human neutrophils by promoting cyclic AMP-dependent sequestration of cytosolic Ca(2+).

Topics: Adenosine; Calcium; Calcium Radioisotopes; Cyclic AMP; Cytosol; Dose-Response Relationship, Drug; Fura-2; Humans; Inflammation; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Pancreatic Elastase; Phenethylamines; Purinergic P1 Receptor Agonists; Purinergic P2 Receptor Antagonists; Superoxides; Thapsigargin; Triazines; Triazoles

The effect of spinal adenosine receptor ligation on peripheral leukocyte accumulation was studied in two rat models of inflammation. Neutrophil infiltration into dermal inflammatory sites was signficantly reduced by adenosine A1 receptor agonists injected through intrathecal catheters. These effects were reversed by N-methyl-D-aspartate (NMDA), and were mimicked by (+/-)-2-amino-5-phosphonopentanoic acid (AP-5), a glutamate NMDA receptor antagonist. Peripheral adenosine levels, as measured in air pouch exudates, decreased markedly in inflamed pouches but remained near normal after intrathecal treatment with AP-5. Moreover, the antiinflammatory effects of intrathecal A1 receptor agonists and AP-5 were reversed by an adenosine A2 receptor antagonist administered intraperitoneally. Hence, central NMDA receptor activity can regulate neutrophil accumulation in peripheral inflammatory sites by reducing local levels of adenosine, an antiinflammatory autacoid which inhibits neutrophil function through A2 receptor activation. This represents a previously unknown pathway by which the central nervous system influences inflammatory responses.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Adenosine; Adenosine-5'-(N-ethylcarboxamide); Animals; Anti-Inflammatory Agents; Carrageenan; Catheterization; Central Nervous System; Dexamethasone; Excitatory Amino Acid Antagonists; Inflammation; N-Methylaspartate; Neutrophils; Peroxidase; Phenethylamines; Propionates; Purinergic P1 Receptor Antagonists; Rats; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate; Receptors, Purinergic P1; Signal Transduction; Skin; Spinal Cord; Theobromine