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1.
The effects of standard adenosine receptor (AR) agonists and antagonists on the proliferation of human T lymphocytes, unstimulated and phytohemagglutinin-stimulated human peripheral blood lymphocytes (PBL), and Jurkat T cells were investigated. Real-time PCR measurements confirmed the presence of all four AR subtypes on the investigated cells, although at different expression levels. A 2A ARs were predominantly expressed in PBL and further upregulated upon stimulation, while malignant Jurkat T cells showed high expression levels of A 1, A 2A, and A 2B ARs. Cell proliferation was measured by [ 3H]-thymidine incorporation assays. Several ligands, including the subtype-selective agonists CPA (A 1), BAY60-6583 (A 2B), and IB-MECA (A 3), and the antagonists PSB-36 (A 1), MSX-2 (A 2A), and PSB-10 (A 3) significantly inhibited cell proliferation at micromolar concentrations, which were about three orders of magnitude higher than their AR affinities. In contrast, further investigated AR ligands, including the agonists NECA (nonselective) and CGS21680 (A 2A), and the antagonists preladenant (SCH-420814, A 2A), PSB-1115 (A 2B), and PSB-603 (A 2B) showed no or only minor effects on lymphocyte proliferation. The anti-proliferative effects of the AR agonists could not be blocked by the corresponding antagonists. The non-selective AR antagonist caffeine stimulated phytohemagglutinin-activated PBL with an EC 50 value of 104 μM. This is the first study to compare a complete set of commonly used AR ligands for all subtypes on lymphocyte proliferation. Our results strongly suggest that these compounds induce an inhibition of lymphocyte proliferation and cell death through AR-independent mechanisms. 相似文献
2.
A 1 adenosine receptors (ARs) reduce, and A 2ARs increase intraocular pressure, partly by differentially altering resistance to aqueous humor outflow. It is unknown whether the opposing effects of A 1AR and A 2AR agonists are mediated at different outflow-pathway cell targets or by opposing actions on a single cell target. We tested whether a major outflow-pathway cell, the trabecular meshwork (TM) cell might constitute the primary AR-agonist target and respond differentially to A 1, A 2A and A 3AR agonists. Receptor activation in human TM cells was identified by applying subtype-selective AR agonists: CPA and ADAC for A 1ARs, CGS 21680 and DPMA for A 2AARs, and Cl-IB-MECA and IB-MECA for A 3ARs. Stimulation of A 1, A 2A and A 3ARs elevated Ca 2+, measured with fura-2. Whole-cell patch clamping indicated that AR agonists activated ion channels non-uniformly, possibly reflecting variability in magnitude of agonist-triggered second-messenger responses. A 1, A 2A and A 3AR agonists all reduced volume, determined by calcein cell imaging. The endogenous source of adenosine delivery to the outflow pathway could be the TM cells since these cells were stimulated to release ATP by hypotonic perfusion. We conclude that: (1) TM cells express functional A 1, A 2A and A 3ARs; and (2) the reported differential effects of AR agonists on aqueous humor outflow are not mediated by differential actions on TM-cell Ca 2+ and volume, but likely by actions on separate cell targets.
Reprint requests should be addressed to: Dr. Mortimer M. Civan, Dept. of Physiology, University of Pennsylvania, Richards Building, Philadelphia, PA 19104-6085. [Tel.: (215)-898-8773; Fax: (215)-573-5851] 相似文献
3.
Chronic granulomatous disease (CGD) is caused by defects in the NADPH oxidase complex and is characterized by an increased susceptibility to infection. Other significant complications of CGD include autoimmunity and non-infectious hyperinflammatory disorders. We show that a gp91 phox deficiency leads to the development of phenotypically altered T lymphocytes in mice and that this abnormal, hyperactive phenotype can be modulated by activation of the adenosine A 2A receptor. T cells isolated from CGD mice produce significantly higher levels of the pro-inflammatory cytokines IFN-γ, IL-2, TNF-α, IL-4 and IL-13 than do WT cells after TCR-mediated activation; treatment with the selective adenosine A 2A receptor agonist, CGS21680, potently inhibits this response. Additionally, the over exuberant inflammatory response elicited by thioglycollate challenge in gp91 phox deficient mice is attenuated by CGS21680. These data suggest that treatment with A 2AR agonists may be an effective therapy by which to regulate the immune system hyperactivity that results from a gp91 phox deficiency. 相似文献
4.
Adenosine receptors (ARs) have emerged as new drug targets. The majority of data on affinity/potency and selectivity of AR ligands described in the literature has been obtained for the human species. However, preclinical studies are mostly performed in mouse or rat, and standard AR agonists and antagonists are frequently used for studies in rodents without knowing their selectivity in the investigated species. In the present study, we selected a set of frequently used standard AR ligands, 8 agonists and 16 antagonists, and investigated them in radioligand binding studies at all four AR subtypes, A 1, A 2A, A 2B, and A 3, of three species, human, rat, and mouse. Recommended, selective agonists include CCPA (for A 1AR of rat and mouse), CGS-21680 (for A 2A AR of rat), and Cl-IB-MECA (for A 3AR of all three species). The functionally selective partial A 2B agonist BAY60-6583 was found to additionally bind to A 1 and A 3AR and act as an antagonist at both receptor subtypes. The antagonists PSB-36 (A 1), preladenant (A 2A), and PSB-603 (A 2B) displayed high selectivity in all three investigated species. MRS-1523 acts as a selective A 3AR antagonist in human and rat, but is only moderately selective in mouse. The comprehensive data presented herein provide a solid basis for selecting suitable AR ligands for biological studies. Electronic supplementary materialThe online version of this article (doi:10.1007/s11302-015-9460-9) contains supplementary material, which is available to authorized users. 相似文献
5.
The theoretical possibility of bivalent binding of a dendrimer, covalently appended with multiple copies of a small ligand, to a homodimer of a G protein-coupled receptor was investigated with a molecular modeling approach. A molecular model was constructed of a third generation (G3) poly(amidoamine) (PAMAM) dendrimer condensed with multiple copies of the potent A 2A adenosine receptor agonist CGS21680. The dendrimer was bound to an A 2A adenosine receptor homodimer. Two units of the nucleoside CGS21680 could occupy the A 2A receptor homodimer simultaneously. The binding mode of CGS21680 moieties linked to the PAMAM dendrimer and docked to the A 2A receptor was found to be similar to the binding mode of a monomeric CGS21680 ligand. 相似文献
6.
Development of diabetes is associated with altered expression of adenosine receptors (ARs). Some of these alterations might be attributed to changes in insulin concentration. This study was undertaken to investigate the possible insulin effect on ARs level, and to determine the signaling pathway utilized by insulin to regulate the expression of ARs in rat B lymphocytes. Western blot analysis of B lymphocytes protein extracts indicated that all four ARs were present at detectable levels in the cells cultured for 24 h without insulin (≤10 ?11 M), although the protein band of A 2A‐AR was barely visible. Inclusion of insulin (10 ?8 M) in the culture medium resulted in an increase of A 1‐AR and A 2A‐AR protein levels and a significant decrease of A 2B‐AR protein, whereas the protein level of A 3‐AR remained unchanged. Alterations in the ARs protein content were accompanied by changes in the ARs mRNA levels. Increase of the insulin concentration from 10 ?11 to 10 ?8 M resulted in 50% decrease of A 2B‐AR mRNA level and two‐, and threefold increase of A 1‐AR and A 2A‐AR mRNA levels, respectively. Pretreatment of B cells with cycloheximide completely blocked the insulin action on A 1‐AR and A 2A‐AR mRNA, but not on A 2B‐AR expression. Detailed pharmacological analysis demonstrated that insulin‐induced A 1‐AR and A 2A‐AR mRNA expression through the Ras/Raf‐1/MEK/ERK pathway. The insulin effect on A 2B‐AR expression was blocked by p38 MAP kinase inhibitor (SB 203580). Concluding, elevated insulin concentration differentially affects the expression of ARs in B lymphocytes in a fashion that might enhance the various immunomodulatory effects of adenosine. J. Cell. Biochem. 109: 396–405, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
7.
The G protein-coupled A 2A adenosine receptor represents an important drug target. Crystal structures and modeling studies indicated that three disulfide bonds are formed between ECL1 and ECL2 (I, Cys71 2.69-Cys159 45.43; II, Cys74 3.22-Cys146 45.30, and III, Cys77 3.25-Cys166 45.50). However, the A 2BAR subtype appears to require only disulfide bond III for proper function. In this study, each of the three disulfide bonds in the A 2AAR was disrupted by mutation of one of the cysteine residues to serine. The mutant receptors were stably expressed in Chinese hamster ovary cells and analyzed in cyclic adenosine monophosphate (cAMP) accumulation and radioligand binding studies using structurally diverse agonists: adenosine, NECA, CGS21680, and PSB-15826. Results were rationalized by molecular modeling. The observed effects were dependent on the investigated agonist. Loss of disulfide bond I led to a widening of the orthosteric binding pocket resulting in a strong reduction in the potency of adenosine, but not of NECA or 2-substituted nucleosides. Disruption of disulfide bond II led to a significant reduction in the agonists’ efficacy indicating its importance for receptor activation. Disulfide bond III disruption reduced potency and affinity of the small adenosine agonists and NECA, but not of the larger 2-substituted agonists. While all the three disulfide bonds were essential for high potency or efficacy of adenosine, structural modification of the nucleoside could rescue affinity or efficacy at the mutant receptors. At present, it cannot be excluded that formation of the extracellular disulfide bonds in the A 2AAR is dynamic. This might add another level of G protein-coupled receptor (GPCR) modulation, in particular for the cysteine-rich A 2A and A 2BARs. 相似文献
8.
Extracellular adenosine is a biologically active signaling molecule that accumulates at sites of metabolic stress in sepsis. Extracellular adenosine has potent immunosuppressive effects by binding to and activating G protein-coupled A2A adenosine receptors (A2AARs) on the surface of neutrophils. A2AAR signaling reproduces many of the phenotypic changes in neutrophils that are characteristic of sepsis, including decreased degranulation, impaired chemotaxis, and diminished ability to ingest and kill bacteria. We hypothesized that A2AARs also suppress neutrophil aging, which precedes cell death, and N1 to N2 polarization. Using human neutrophils isolated from healthy subjects, we demonstrate that A2AAR stimulation slows neutrophil aging, suppresses cell death, and promotes the polarization of neutrophils from an N1 to N2 phenotype. Using genetic knockout and pharmacological blockade, we confirmed that A2AARs decrease neutrophil aging in murine sepsis induced by cecal ligation and puncture. A2AARs expression is increased in neutrophils from septic patients compared to healthy subject but A2AAR expression fails to correlate with aging or N1/N2 polarization. Our data reveals that A2AARs regulate neutrophil aging in healthy but not septic neutrophils. 相似文献
9.
The intent of the present study was to investigate adenosine receptor sites in brain membranes of the saltwater teleost fish, Mullus surmuletus, using the A 1 receptor selective agonist, [ 3H]CHA, and A 2a receptor selective agonist [ 3H]CGS 21680. The A 1 selective agonist, [ 3H]CHA, bound saturably, reversibly and with high affinity to a single-class of binding sites (K d 1.47 nM; B max 100–190 fmol/mg protein, dependent on fish length). The A 2a selective agonist, [ 3H]CGS 21680, also bound saturably, reversibly and with relative high affinity to a single-class of binding sites (K d 44.2 nM; B max 150–300 fmol/mg protein dependent on fish length). In equilibrium competition experiments, adenosine analogous, NECA, CGS 21680, CHA, CPA, S-PIA, R-PIA, CPCA, DPMA, and xanthine antagonists, DPCPX, XAC, and THEO all displaced [ 3H]CHA and [ 3H]CGS 21680 specifically bound to brain membranes from Mullus surmuletus. Specific binding of both [ 3H]CHA and [ 3H]CGS 21680 was inhibited by GDPβS. For [ 3H]CHA the IC 50 value was 2.5 ± 0.1 μM, while for [ 3H]CGS 21680 the IC 50 value was 7.7 ± 0.3 μM. Our results indicate that the high affinity binding sites for [ 3H]CHA have some pharmacological characteristics of mammalian A 1 adenosine receptors, while the binding sites for [ 3H]CGS 21680 appear to be virtually identical to the binding sites for [ 3H]CHA. 相似文献
10.
AbstractThe binding characteristics of radiolabeled N 6-(cyclohexyl)adenosine ([ 3H]CHA), N 6-(R-phenylisopropyl)adenosine ([ 3H]R-PIA), 5′-N-ethylcarboxamidoadenosine ([ 3H]NECA), and 2-[4-(2-carboxyethyl)phenyl]ethyl-amino-5′-N-ethylcarboxamidoadenosine ([ 3H]CGS 21680), to rat testis membranes were investigated. Specific binding of [ 3H]CGS 21680, a selective agonist for the A 2a adenosine receptor, was very modest whilst the nonselective agonist [ 3H]NECA bound to rat testis membranes showing high binding capacity. At least two types of binding sites for [ 3H]NECA could be identified in rat testis membranes: high affinity sites and high capacity sites. Selective agonists for the At adenosine receptor, [ 3H]CHA and [ 3H]R-PIA bound with high affinity to a single class of binding sites. This high affinity binding site showed the typical pharmacological specificity of the A 1 adenosine receptor with a potency order for agonists of CHA R-PIA > NECA > N 6-(S-phenylisopropyl)adenosine (S-PIA). In order to detect the presence of the A 3 adenosine receptor in these membranes we selectively blocked the A 1 receptor with a large molar excess of a xanthine antagonist, either 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) or xanthine amine congener (XAC). In the presence of an antagonist a low affinity binding site for [ 3H]CHA and [ 3H]R-PIA was detected. This low affinity binding site showed a different pharmacological specificity than the high affinity binding site. In fact the potency order for agonists was CHA NECA = R-PIA > S-PIA. This finding suggests that the low affinity binding site represents the A 3 adenosine receptor. 相似文献
11.
The role of the A 2B adenosine receptor (AR) in prostate cell death and growth was studied. The A 2B AR gene expression quantified by real-time quantitative RT-PCR and Western blot analysis was the highest among four AR subtypes (A 1, A 2A, A 2B, and A 3) in all three commonly used prostate cancer cell lines, PC-3, DU145, and LNCaP. We explored the function of the A 2B AR using PC-3 cells as a model. The A 2B AR was visualized in PC-3 cells by laser confocal microscopy. The nonselective A 2B AR agonist NECA and the selective A 2B AR agonist BAY60-6583, but not the A 2A AR agonist CGS21680, concentration-dependently induced adenosine 3′,5′-cyclic monophosphate (cyclic AMP) accumulation. NECA diminished lactate dehydrogenase (LDH) release, TNF-α-induced increase of caspase-3 activity, and cycloheximide (CHX)-induced morphological changes typical of apoptosis in PC-3 cells, which were blocked by a selective A 2B AR antagonist PSB603. NECA-induced proliferation of PC-3 cells was diminished by siRNA specific for the A 2B AR. The selective A 2B AR antagonist PSB603 was shown to inhibit cell growth in all three cell lines. Thus, A 2B AR blockade inhibits growth of prostate cancer cells, suggesting selective A 2B AR antagonists as potential novel therapeutics. 相似文献
12.
Mast cell degranulation triggers hypersensitivity reactions at the body–environment interface. Adenosine modulates degranulation, but enhancement and inhibition have both been reported. Which of four adenosine receptors (ARs) mediate modulation, and how, remains uncertain. Also uncertain is whether adenosine reaches mast cell ARs by autocrine ATP release and ecto-enzymatic conversion. Uncertainties partly reflect species and cell heterogeneity, circumvented here by focusing on homogeneous human LAD2 cells. Quantitative PCR detected expression of A 2A, A 2B, and A 3, but not A 1, ARs. Nonselective activation of ARs with increasing NECA monotonically enhanced immunologically or C3a-stimulated degranulation. NECA alone stimulated degranulation slightly. Selective AR antagonists did not affect C3a-stimulated degranulation. NECA''s enhancement of C3a-triggered degranulation was partially inhibited by separate application of each selective antagonist, and abolished by simultaneous addition of antagonists to the three ARs. Only the A 2A antagonist separately inhibited NECA''s enhancement of immunologically stimulated degranulation, which was abolished by simultaneous addition of the three selective antagonists. Immunological or C3a activation did not stimulate ATP release. NECA also enhanced immunologically triggered degranulation of mouse bone marrow derived mast cells (BMMCs), which was partially reduced only by simultaneous addition of the three antagonists or by the nonselective antagonist {"type":"entrez-protein","attrs":{"text":"CGS15943","term_id":"875345334"}}CGS15943. BMMCs also expressed A 2A, A 2B, and A 3 ARs. but not A 1AR detectably. We conclude that (a) A 1AR is unnecessary for LAD2 degranulation or AR enhancement; (b) A 2A, A 2B, and A 3 ARs all contribute to pharmacologic AR enhancement of LAD2 and BMMC degranulation; and (c) LAD2 cells depend on microenvironmental adenosine to trigger AR modulation. 相似文献
13.
Inter-regulation of adrenergic receptors (ARs) via cross-talk is a long appreciated but mechanistically unclear physiological phenomenon. Evidence from the AR literature and our own extensive studies on regulation of α 2AARs by the scaffolding protein spinophilin have illuminated a potential novel mechanism for cross-talk from β to α 2ARs. In the present study, we have characterized a mode of endogenous AR cross-talk in native adrenergic neurons whereby canonical βAR-mediated signaling modulates spinophilin-regulated α 2AAR endocytosis through PKA. Our findings demonstrate that co-activation of β and α 2AARs, either by application of endogenous agonist or by simultaneous stimulation with distinct selective agonists, results in acceleration of endogenous α 2AAR endocytosis in native neurons. We show that receptor-independent PKA activation by forskolin is sufficient to accelerate α 2AAR endocytosis and that α 2AAR stimulation alone drives accelerated endocytosis in spinophilin-null neurons. Endocytic response acceleration by β/α 2AAR co-activation is blocked by PKA inhibition and lost in spinophilin-null neurons, consistent with our previous finding that spinophilin is a substrate for phosphorylation by PKA that disrupts its interaction with α 2AARs. Importantly, we show that α 2AR agonist-mediated α 2AAR/spinophilin interaction is blocked by βAR co-activation in a PKA-dependent fashion. We therefore propose a novel mechanism for cross-talk from β to α 2ARs, whereby canonical βAR-mediated signaling coupled to PKA activation results in phosphorylation of spinophilin, disrupting its interaction with α 2AARs and accelerating α 2AAR endocytic responses. This mechanism of cross-talk has significant implications for endogenous adrenergic physiology and for therapeutic targeting of β and α 2AARs. 相似文献
14.
A selective agonist radioligand for A 2B adenosine receptors (A 2BARs) is currently not available. Such a tool would be useful for labeling the active conformation of the receptors. Therefore, we prepared BAY 60-6583, a potent and functionally selective A 2BAR (partial) agonist, in a tritium-labeled form. Despite extensive efforts, however, we have not been able to establish a radioligand binding assay using [ 3H]BAY 60-6583. This is probably due to its high non-specific binding and its moderate affinity, which had previously been overestimated based on functional data. As an alternative, we evaluated the non-selective A 2BAR agonist [ 3H]NECA for its potential to label A 2BARs. [ 3H]NECA showed specific, saturable, and reversible binding to membrane preparations of Chinese hamster ovary (CHO) or human embryonic kidney (HEK) cells stably expressing human, rat, or mouse A 2BARs. In competition binding experiments, the AR agonists 2-chloroadenosine (CADO) and NECA displayed significantly higher affinity when tested versus [ 3H]NECA than versus the A 2B-antagonist radioligand [ 3H]PSB-603 while structurally diverse AR antagonists showed the opposite effects. Although BAY 60-6583 is an A 2BAR agonist, it displayed higher affinity versus [ 3H]PSB-603 than versus [ 3H]NECA. These results indicate that nucleoside and non-nucleoside agonists are binding to very different conformations of the A 2BAR. In conclusion, [ 3H]NECA is currently the only useful radioligand for determining the affinity of ligands for an active A 2BAR conformation. 相似文献
15.
Adenosine, through A 2A receptor (A 2AR) activation, can act as a metamodulator, controlling the actions of other modulators, as brain-derived neurotrophic factor (BDNF). Most of the metamodulatory actions of adenosine in the hippocampus have been evaluated in excitatory synapses. However, adenosine and BDNF can also influence GABAergic transmission. We thus evaluated the role of A 2AR on the modulatory effect of BDNF upon glutamate and GABA release from isolated hippocampal nerve terminals (synaptosomes). BDNF (30 ng/ml) enhanced K +-evoked [ 3H]glutamate release and inhibited the K +-evoked [ 3H]GABA release from synaptosomes. The effect of BDNF on both glutamate and GABA release requires tonic activation of adenosine A 2AR since for both neurotransmitters, the BDNF action was blocked by the A 2AR antagonist SCH 58261 (50 nM). In the presence of the A 2AR agonist, {"type":"entrez-protein","attrs":{"text":"CGS21680","term_id":"878113053","term_text":"CGS21680"}}CGS21680 (30 nM), the effect of BDNF on either glutamate or GABA release was, however, not potentiated. It is concluded that both the inhibitory actions of BDNF on GABA release as well as the facilitatory action of the neurotrophin on glutamate release are dependent on the activation of adenosine A 2AR by endogenous adenosine. However, these actions could not be further enhanced by exogenous activation of A 2AR. 相似文献
16.
The release of the inhibitory amino acid taurine is markedly enhanced under ischemic conditions in both adult and developing
brain stem, together with a pronounced increase in the release of the neuromodulator adenosine. We now studied the effects
of adenosine receptor agonists and antagonists on [ 3H]taurine release in the brain stem in normoxia and ischemia, using a superfusion system. Under standard conditions, the adenosine
A 1 receptor agonist N 6-cyclohexyladenosine (CHA) potentiated basal taurine release in adult mice, which response was blocked by the antagonist 8-cyclopentyl-1,3-dipropylxanthine
(DPCPX). CHA and the A 2a receptor agonist 2- p-(2-carboxyethyl)phenylamino-5′- N-ethylcarboxaminoadenosinehydrochloride (CGS 21680) had no effect on the release in developing mice. In ischemia, CHA depressed
both basal and K +-stimulated taurine release in developing mice in a receptor-mediated manner, blocked by DPCPX. The A 2a receptor agonist CGS 21680 was also inhibitory. Taurine and adenosine may thus not cooperate in developing mice to prevent
ischemic neuronal damage. On the other hand, CGS 21680 enhanced taurine release in the adult brain stem in ischemia, both
basal and K +-stimulated release being affected. These effects were abolished by the antagonist 3,7-dimethyl-1-propargylxanthine (DMPX),
indicating a receptor-mediated process. In this case elevated levels of taurine could be beneficial, protecting against hyperexcitation
and excitotoxicity. 相似文献
17.
The anti-inflammatory effect of adenosine was previously found to be mediated via activation of the A 3 adenosine receptor (A 3AR). The aim of the present study was to decipher the molecular mechanism involved with the inhibitory effect of IB-MECA,
an A 3AR agonist, on adjuvant-induced arthritis. 相似文献
18.
The A 2A adenosine receptor (A 2AAR) is a unique G‐protein coupled receptor (GPCR), because besides agonist, its antagonist could also lead to therapeutic relevance. Based on A 2AAR‐antagonist crystal structure, we have studied the binding mechanism of two distinct antagonists, ZM241385 and KW6002, and dynamic behaviors of A 2AAR induced by antagonist binding. Key residues interacting with both antagonists and residues specifically binding to one of them are identified. ZM241385 specifically bound to S67 2.65, M177 5.38, and N253 6.55, while KW6002 binds to F62 2.60, A81 3.29, and H264 7.29. Moreover, interactions with L167 5.28 are found for both antagonists, which were not reported in agonist binding. The dynamic behaviors of antagonist bound holo‐A 2AARs were found to be different from the apo‐A 2AAR in three typical functional switches, (i) the “ionic lock” was in equilibrium between formation and breakage in apo‐A 2AAR, but stayed broken in holo‐A 2AARs; (ii) the “rotamer toggle switch,” T88 3.36/F242 6.44/W246 6.48, adopted different rotameric conformations in apo‐A 2AAR and holo‐A 2AARs; (iii) apo‐A 2AAR preferred α‐helical intracellular loop (IC)2 and flexible IC3, while holo‐A 2AARs had a flexible IC2 and α‐helical IC3. Our results indicated that antagonist binding induced different conformational rearrangements of these characteristic functional switches in apo‐A 2AAR and holo‐A 2AARs. Proteins 2013; 81:1399–1410. © 2013 Wiley Periodicals, Inc. 相似文献
19.
Adenosine can show anti-inflammatory as well as pro-inflammatory activities. The contribution of the specific adenosine receptor
subtypes in various cells, tissues and organs is complex. In this study, we examined the effect of the adenosine A 2A receptor agonist CGS 21680 and the A 2BR antagonist PSB-1115 on acute inflammation induced experimentally by 2,4,6-trinitrobenzenesulfonic acid (TNBS) on rat ileum/jejunum
preparations. Pre-incubation of the ileum/jejunum segments with TNBS for 30 min resulted in a concentration-dependent inhibition
of acetylcholine (ACh)-induced contractions. Pharmacological activation of the A 2AR with CGS 21680 (0.1–10 μM) pre-incubated simultaneously with TNBS (10 mM) prevented concentration-dependently the TNBS-induced
inhibition of the ACh contractions. Stimulation of A 2BR with the selective agonist BAY 60-6583 (10 μM) did neither result in an increase nor in a further decrease of ACh-induced
contractions compared to the TNBS-induced inhibition. The simultaneous pre-incubation of the ileum/jejunum segments with TNBS
(10 mM) and the selective A 2BR antagonist PSB-1115 (100 μM) inhibited the contraction-decreasing effect of TNBS. The effects of the A 2AR agonist and the A 2BR antagonist were in the same range as the effect induced by 1 μM methotrexate. The combination of the A 2AR agonist CGS 21680 and the A 2BR antagonist PSB-1115 at subthreshold concentrations of both agents found a significant amelioration of the TNBS-diminished
contractility. Our results demonstrate that the activation of A 2A receptors or the blockade of the A 2B receptors can prevent the inflammation-induced disturbance of the ACh-induced contraction in TNBS pre-treated small intestinal
preparations. The combination of both may be useful for the treatment of inflammatory bowel diseases. 相似文献
20.
Little is known about the mechanisms that regulate the expression of adenosine receptors during CNS development. We demonstrate here that retinas from chick embryos injected in ovo with selective adenosine receptor ligands show changes in A1 receptor expression after 48 h. Exposure to A1 agonist N 6‐cyclohexyladenosine (CHA) or antagonist 8‐Cyclopentyl‐1, 3‐dipropylxanthine (DPCPX) reduced or increased, respectively, A1 receptor protein and [ 3H]DPCPX binding, but together, CHA+DPCPX had no effect. Interestingly, treatment with A 2A agonist 3‐[4‐[2‐[[6‐amino‐9‐[(2R,3R,4S,5S)‐5‐(ethylcarbamoyl)‐3,4‐dihydroxy‐oxolan‐2‐yl]purin‐2‐yl]amino] ethyl]phenyl] propanoic acid (CGS21680) increased A1 receptor protein and [ 3H]DPCPX binding, and reduced A 2A receptors. The A 2A antagonists 7‐(2‐phenylethyl)‐5‐amino‐2‐(2‐furyl)‐pyrazolo‐[4,3‐e]‐1,2,4‐trizolo[1,5‐c] pyrimidine (SCH58261) and 4‐(2‐[7‐amino‐2‐[2‐furyl][1,2,4]triazolo[2,3‐a][1,3,5]triazo‐5‐yl‐amino]ethyl)phenol (ZM241385) had opposite effects on A1 receptor expression. Exposure to CGS21680 + CHA did not change A1 receptor levels, whereas CHA + ZM241385 or CGS21680 + DPCPX had no synergic effect. The blockade of adenosine transporter with S‐(4‐nitrobenzyl)‐6‐thioinosine (NBMPR) also reduced [ 3H]DPCPX binding, an effect blocked by DPCPX, but not enhanced by ZM241385. [ 3H]DPCPX binding kinetics showed that treatment with CHA reduced and CGS21680 increased the Bmax, but did not affect Kd values. CHA, DPCPX, CGS21680, and ZM241385 had no effect on A1 receptor mRNA. These data demonstrated an in vivo regulation of A1 receptor expression by endogenous adenosine or long‐term treatment with A1 and A 2A receptors modulators. 相似文献
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