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1.
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
2.
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
3.
Adenosine and its metabolite, inosine, have been described as molecules that participate in regulation of inflammatory response. The aim of this study was to investigate the effect of adenosine and inosine in a mouse model of carrageenan-induced pleurisy as well as the participation of adenosine receptors in this response. Injection of carrageenan into the pleural cavity induced an acute inflammatory response characterized by leukocyte migration, pleural exudation, and increased release of interleukin-1β and tumor necrosis factor-α in pleural exudates. The treatment with adenosine (0.3–100 mg/kg, i.p.) and inosine (0.1–300 mg/kg, i.p.) 30 min before carrageenan injection reduced significantly all these parameters analyzed. Our results also demonstrated that A 2A and A 2B receptors seem to mediate the adenosine and inosine effects observed, since pretreatment with selective antagonists of adenosine A 2A (ZM241385) and A 2B (alloxazine) receptors, reverted the inhibitory effects of adenosine and inosine in pleural inflammation. The involvement of A 2 receptors was reinforced with adenosine receptor agonist {"type":"entrez-protein","attrs":{"text":"CGS21680","term_id":"878113053","term_text":"CGS21680"}}CGS21680 treatment, since its anti-inflammatory effects were reversed completely and partially with ZM241385 and alloxazine injection, respectively. Moreover, the combined treatment with subeffective dose of adenosine (0.3 mg/kg) and inosine (1.0 mg/kg) induced a synergistic anti-inflammatory effect. Thus, based on these findings, we propose that inosine contributes with adenosine to exert anti-inflammatory effects in pleural inflammation, reinforcing the notion that endogenous nucleosides play an important role in controlling inflammatory diseases. This effect is likely mediated by the activation of adenosine A 2 subtype receptors and inhibition of production or release of pro-inflammatory cytokines. 相似文献
4.
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
5.
Subchronic treatment with MAP (4.6 mg/kg, i.p., once daily for 11 days) significantly decreased the K d, but not B max, values of [ 3H]1,3-dipropyl-8-cyclopentylxanthine ([ 3H]DPCPX) binding to adenosine A 1 receptors in the prefrontal cortex and hippocampus, but not striatum, of rat brain. However, subchronic treatment with PCP (10 mg/kg, i.p., once daily for 11 days) did not alter the K d and B max values of [ 3H]DPCPX binding to adenosine A 1 receptors in these three regions. Subchronic treatment with MAP or PCP did not alter the B max and K d values of [ 3H]2-p-(2-carboxyehyl)phenethylamino-5-N-ethylcarboxyamidoadenosine ([ 3H]CGS21680) binding to adenosine A 2A receptors in the striatum. Furthermore, subchronic treatment with MAP or PCP significantly decreased the specific binding of [ 3H]CGS21680 to adenosine A 2A receptors in the hippocampus, but not in the prefrontal cortex. Thus, these results suggest that MAP and PCP may produce differential effects on the adenosine A 2A receptors, but not adenosine A 1 receptors in rat brain. 相似文献
6.
Syntheses and biological activities of imidazo-, pyrimido- and diazepino[2,1- f]purinediones containing N-alkyl substituents (with straight, branched or unsaturated chains) are described. Tricyclic derivatives were synthesized by the cyclization of 8-bromo-substituted 7-(2-bromoethyl)-, 7-(3-chloropropyl)- or 7-(4-bromobutyl)-theophylline with primary amines under various conditions. Compound 22 with an ethenyl substituent was synthesized by dehydrohalogenation of 9-(2-bromoethyl)-1,3-dimethyltetrahydropyrimido[2,1- f]purinedione. The obtained derivatives (5–35) were initially evaluated for their affinity at rat A 1 and A 2A adenosine receptors (AR), showing moderate affinity for both adenosine receptor subtypes. The best ligands were diazepinopurinedione 28 ( Ki = 0.28 μM) with fivefold A 2A selectivity and the non-selective A 1/A 2A AR ligand pyrimidopurinedione 35 ( Ki A 1 = 0.28 μM and Ki A 2A = 0.30 μM). The compounds were also evaluated for their affinity at human A 1, A 2A, A 2B and A 3 ARs. All of the obtained compounds were docked to the A 2A AR X-ray structure in complex with the xanthine-based, potent adenosine receptor antagonist—XAC. The likely interactions of imidazo-, pyrimido- and diazepino[2,1- f]purinediones with the residues forming the A 2A binding pocket were discussed. Furthermore, the new compounds were tested in vivo as anticonvulsants in maximal electroshock, subcutaneous pentylenetetrazole (ScMet) and TOX tests in mice (i.p.). Pyrimidopurinediones showed anticonvulsant activity mainly in the ScMet test. The best derivative was compound 11, showing 100 % protection at a dose of 100 mg/kg without symptoms of neurotoxicity. Compounds 6, 7, 8 and 14 with short substituents showed neurotoxicity and caused death. In rat tests (p.o.), 9 was characterized by a high protection index (>13.3). AR affinity did not apparently correlate with the antiepileptic potency of the compounds. Electronic supplementary materialThe online version of this article (doi:10.1007/s11302-013-9358-3) contains supplementary material, which is available to authorized users. 相似文献
7.
A recently identified novel Gα olf variant, XLGα olf, is shown to functionally couple to the human adenosine A 2A receptor (A 2AR). In Sf9 cells expressing A 2AR, β1, and γ2, co-expression of XLGα olf increased NECA-induced [ 35S]GTPγS binding from approximately 130% to 300% of basal levels. Pharmacological characteristics of A 2AR ligands on these cells were evaluated by using [ 3H]ZM241385- and [ 35S]GTPγS- binding assays. The rank order of the equilibrium binding constants (K d or K i) of adenosine receptor ligands were [ 3H]ZM241385 ≈ CGS15943 < MRS1220 < < CV1808 ≈ NECA < CGS21680 ≈ adenosine < IBMECA < HEMADO ≈ CPA ≈ CCPA. The rank order of EC 50 values for agonists were CV1808 ≈ NECA < adenosine ≈ CGS26180 < IBMECA < HEMADO ≈ CPA ≈ CCPA. This pharmacology is consistent with the literature for A 2AR and suggests that Sf9 cells co-expressing A 2AR, β1, γ2, and XLGα olf could serve as a heterologous expression system for A 2AR drug screening. 相似文献
8.
This study was designed to investigate whether reduced adenosine formation linked to deficits in extracellular ATP hydrolysis by NTPDases contributes to detrusor neuromodulatory changes associated with bladder outlet obstruction in men with benign prostatic hyperplasia (BPH). The kinetics of ATP catabolism and adenosine formation as well as the role of P1 receptor agonists on muscle tension and nerve-evoked [ 3H]ACh release were evaluated in mucosal-denuded detrusor strips from BPH patients ( n = 31) and control organ donors ( n = 23). The neurogenic release of ATP and [ 3H]ACh was higher ( P < 0.05) in detrusor strips from BPH patients. The extracellular hydrolysis of ATP and, subsequent, adenosine formation was slower ( t1/2 73 vs. 36 min, P < 0.05) in BPH detrusor strips. The A 1 receptor-mediated inhibition of evoked [ 3H]ACh release by adenosine (100 μM), NECA (1 μM), and R-PIA (0.3 μM) was enhanced in BPH bladders. Relaxation of detrusor contractions induced by acetylcholine required 30-fold higher concentrations of adenosine. Despite VAChT-positive cholinergic nerves exhibiting higher A 1 immunoreactivity in BPH bladders, the endogenous adenosine tonus revealed by adenosine deaminase is missing. Restoration of A 1 inhibition was achieved by favoring (1) ATP hydrolysis with apyrase (2 U mL −1) or (2) extracellular adenosine accumulation with dipyridamole or EHNA, as these drugs inhibit adenosine uptake and deamination, respectively. In conclusion, reduced ATP hydrolysis leads to deficient adenosine formation and A 1 receptor-mediated inhibition of cholinergic nerve activity in the obstructed human bladder. Thus, we propose that pharmacological manipulation of endogenous adenosine levels and/or A 1 receptor activation might be useful to control bladder overactivity in BPH patients. 相似文献
9.
Exacerbated activation of glutamate receptor-coupled calcium channels and subsequent increase in intracellular calcium ([Ca 2+] i) are established hallmarks of neuronal cell death in acute and chronic neurological diseases. Here we show that pathological [Ca 2+] i deregulation occurring after glutamate receptor stimulation is effectively modulated by small conductance calcium-activated potassium (K Ca2) channels. We found that neuronal excitotoxicity was associated with a rapid downregulation of K Ca2.2 channels within 3 h after the onset of glutamate exposure. Activation of K Ca2 channels preserved K Ca2 expression and significantly reduced pathological increases in [Ca 2+] i providing robust neuroprotection in vitro and in vivo. These data suggest a critical role for K Ca2 channels in excitotoxic neuronal cell death and propose their activation as potential therapeutic strategy for the treatment of acute and chronic neurodegenerative disorders. 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.
Angiogenesis is critical to wound repair due to its role in providing oxygen and nutrients that are required to support the growth and function of reparative cells in damaged tissues. Adenosine receptors are claimed to be of paramount importance in driving wound angiogenesis by inducing VEGF. However, the underlying mechanisms for the regulation of adenosine receptors in VEGF as well as eNOS remain poorly understood. In the present study, we found that adenosine and the non-selective adenosine receptor agonists (NECA) induced tube formation in HMEC-1 in a dose-dependent manner. Adenosine or NECA (10 µmol/L) significantly augmented the number and length of the segments in comparison with the control. Simultaneously, VEGF and eNOS were significantly upregulated following the administration of 10 µmol/L NECA, while they were suppressed after A 2B AR genetic silencing and pharmacological inhibition by MRS1754. In addition, VEGF expression and eNOS bioavailability elimination significantly reduced the formation of capillary-like structures. Furthermore, the activation of A 2B AR by NECA significantly increased the intracellular cAMP levels and concomitant CREB phosphorylation, eventually leading to the production of VEGF in HMEC-1. However, the activated PKA-CREB pathway seemed to be invalidated in the induction of eNOS. Moreover, we found that the elicited PI3K/AKT signaling in response to the induction of NECA assisted in regulating eNOS but failed to impact on VEGF generation. In conclusion, the A 2B AR activation-driven angiogenesis via cAMP-PKA-CREB mediated VEGF production and PI3K/AKT-dependent upregulation of eNOS in HMEC-1. 相似文献
12.
D 1- and D 2-types of dopamine receptors are located separately in direct and indirect pathway striatal projection neurons (dSPNs and iSPNs). In comparison, adenosine A 1-type receptors are located in both neuron classes, and adenosine A 2A-type receptors show a preferential expression in iSPNs. Due to their importance for neuronal excitability, Ca 2+-currents have been used as final effectors to see the function of signaling cascades associated with different G protein-coupled receptors. For example, among many other actions, D 1-type receptors increase, while D 2-type receptors decrease neuronal excitability by either enhancing or reducing, respectively, Ca V1 Ca 2+-currents. These actions occur separately in dSPNs and iSPNs. In the case of purinergic signaling, the actions of A 1- and A 2A-receptors have not been compared observing their actions on Ca 2+-channels of SPNs as final effectors. Our hypotheses are that modulation of Ca 2+-currents by A 1-receptors occurs in both dSPNs and iSPNs. In contrast, iSPNs would exhibit modulation by both A 1- and A 2A-receptors. We demonstrate that A 1-type receptors reduced Ca 2+-currents in all SPNs tested. However, A 2A-type receptors enhanced Ca 2+-currents only in half tested neurons. Intriguingly, to observe the actions of A 2A-type receptors, occupation of A 1-type receptors had to occur first. However, A 1-receptors decreased Ca V2 Ca 2+-currents, while A 2A-type receptors enhanced current through Ca V1 channels. Because these channels have opposing actions on cell discharge, these differences explain in part why iSPNs may be more excitable than dSPNs. It is demonstrated that intrinsic voltage-gated currents expressed in SPNs are effectors of purinergic signaling that therefore play a role in excitability. 相似文献
13.
It has been observed that a cytokine synthesis inhibitor, pentoxifylline, prevents the apoptotic processes taking place in
the amygdala following myocardial infarction. However, it is unknown if the cardioprotective effect of A 2A adenosine receptor agonist, CGS21680, which reduces cytokine synthesis, would lead to such amygdala apoptosis regression.
Thus, this study was designed to investigate whether cardioprotective A 2A adenosine receptor activation reduces apoptosis in the amygdala following myocardial infarction. Anesthetized rats were subjected
to left anterior descending coronary artery occlusion for 40 min, followed by 72 h of reperfusion. The A 2A agonist CGS21680 (0.2 μg/kg/min i.v.) was administered continuously for 120 min, starting (1) five minutes prior to instituting
reperfusion (Early) or (2) five minutes after the beginning of reperfusion (Late). After reperfusion, myocardial infarct size
was determined and the amygdala was dissected from the brain. Infarct size was reduced significantly in the Early compared
to the Control group (34.6 ± 1.8% and 52.3 ± 2.8% respectively; p < 0.05), with no difference com-pared to the Late group (40.1 ± 6.1%). Apoptosis regressi-on was documented in the amygdala
of the Early group by an enhanced phosphatidylinositol 3-kinase-Akt pathway activation and Bcl-2 expression concurrently to
a caspase-3 activation limitation and reduction in TUNEL-positive cells staining. On the other hand, amygdala TUNEL-positive
cell numbers were not reduced in the Late group. Moreover, TNFα was significantly reduced in the amygdala of the Early group
compared to the Control and Late groups. These results indicate that A 2A adenosine receptor stimulation is associated with apoptosis regression in the amygdala following myocardial infarction.
This work was supported by Natural Sciences and Engineering Research Council of Canada (NSERC). 相似文献
14.
BackgroundThis study was inspired by coalescing evidence that magnetic therapy may be a viable treatment option for certain diseases. This premise is based on the ability of moderate strength fields (i.e., 0.1 to 1 Tesla) to alter the biophysical properties of lipid bilayers and in turn modulate cellular signaling pathways. In particular, previous results from our laboratory (Wang et al., BMC Genomics, 10, 356 (2009)) established that moderate strength static magnetic field (SMF) exposure altered cellular endpoints associated with neuronal function and differentiation. Building on this background, the current paper investigated SMF by focusing on the adenosine A 2A receptor (A 2AR) in the PC12 rat adrenal pheochromocytoma cell line that displays metabolic features of Parkinson''s disease (PD). Methodology and Principal FindingsSMF reproduced several responses elicited by ZM241385, a selective A 2AR antagonist, in PC12 cells including altered calcium flux, increased ATP levels, reduced cAMP levels, reduced nitric oxide production, reduced p44/42 MAPK phosphorylation, inhibited proliferation, and reduced iron uptake. SMF also counteracted several PD-relevant endpoints exacerbated by A 2AR agonist {"type":"entrez-protein","attrs":{"text":"CGS21680","term_id":"878113053","term_text":"CGS21680"}}CGS21680 in a manner similar to ZM241385; these include reduction of increased expression of A 2AR, reversal of altered calcium efflux, dampening of increased adenosine production, reduction of enhanced proliferation and associated p44/42 MAPK phosphorylation, and inhibition of neurite outgrowth. Conclusions and SignificanceWhen measured against multiple endpoints, SMF elicited qualitatively similar responses as ZM241385, a PD drug candidate. Provided that the in vitro results presented in this paper apply in vivo, SMF holds promise as an intriguing non-invasive approach to treat PD and potentially other neurological disorders. 相似文献
15.
Binding properties of the subtypes of adenosine A2 receptors in membrane preparations and the effects of adenosine receptor ligands on cAMP accumulation in slices from the optic tectum of neonatal chicks have been investigated. [ 3H]2-[4-(2-p-carboxyethyl)phenylamino]-5'-N-ethylcarboxaminoadenosine (CGS 21680), a selective ligand for adenosine A2a receptors, did not bind to optic tectal membranes, as observed with rat striatal membranes. CGS 21680 also did not induce cyclic AMP accumulation in optic tectum slices. However, 5'-N-ethylcarboxamidoadenosine (NECA), 2-chloro-adenosine or adenosine induced a 2.5- to 3-fold increase on cyclic AMP accumulation in this preparation. [ 3H]NECA binds to fresh non-washed-membranes obtained from optic tectum of chicks, displaying one population of binding sites, which can be displaced by NECA, 8-phenyltheophylline, 2-chloro-adenosine, but is not affected by CGS 21680. The estimated K D value was 400.90 ± 80.50 nM and the B max was estimated to be 2.51 ± 0.54 pmol/mg protein. Guanine nucleotides, which modulate G-proteins activity intracellularly, are also involved in the inhibition of glutamate responses by acting extracellularly. Moreover, we have previously reported that guanine nucleotides potentiate, while glutamate inhibits, adenosine-induced cyclic AMP accumulation in slices from optic tectum of chicks. However, the guanine nucleotides, GMP or GppNHp and the metabotropic glutamate receptors agonist, 1S,3R-ACPD did not alter the [ 3H]NECA binding observed in fresh non-washed-membranes. Therefore, the adenosine A2 receptor found in the optic tectum must be the adenosine A2b receptor which is available only in fresh membrane preparations, and its not modulated by guanine nucleotides or glutamate analogs. 相似文献
16.
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
17.
In previous studies, we have shown that the inactivation of the adenosine A2A receptor exacerbates chronic cerebral hypoperfusion-induced white matter lesions (WMLs) by enhancing neuroinflammatory responses. However, the molecular mechanism underlying the effect of the adenosine A2A receptor remains unknown. Recent studies have demonstrated that cystatin F, a potent endogenous cysteine protease inhibitor, is selectively expressed in immune cells in association with inflammatory demyelination in central nervous system diseases. To understand the expression of cystatin F and its potential role in the effect of A2A receptor on WMLs induced through chronic cerebral hypoperfusion, we investigated cystatin F expression in the WMLs of A2A receptor gene knockout mice, the littermate wild-type mice and wild-type mice treated daily with the A2A receptor agonist {"type":"entrez-protein","attrs":{"text":"CGS21680","term_id":"878113053","term_text":"CGS21680"}}CGS21680 or both {"type":"entrez-protein","attrs":{"text":"CGS21680","term_id":"878113053","term_text":"CGS21680"}}CGS21680 and A2A receptor antagonist {"type":"entrez-protein","attrs":{"text":"SCH58261","term_id":"1052882304","term_text":"SCH58261"}}SCH58261 after chronic cerebral hypoperfusion. The results of quantitative-PCR and western blot analysis revealed that cystatin F mRNA and protein expression were significantly up-regulated in the WMLs after chronic cerebral hypoperfusion. In addition, cystatin F expression in the corpus callosum was significantly increased in A2A receptor gene knockout mice and markedly decreased in mice treated with {"type":"entrez-protein","attrs":{"text":"CGS21680","term_id":"878113053","term_text":"CGS21680"}}CGS21680 on both the mRNA and protein levels. Additionally, {"type":"entrez-protein","attrs":{"text":"SCH58261","term_id":"1052882304","term_text":"SCH58261"}}SCH58261 counteracted the attenuation of cystatin F expression produced by {"type":"entrez-protein","attrs":{"text":"CGS21680","term_id":"878113053","term_text":"CGS21680"}}CGS21680 after chronic cerebral hypoperfusion. Moreover, double immunofluorescence staining revealed that cystatin F was co-localized with the activated microglia marker CD11b. In conclusion, the cystatin F expression in the activated microglia is closely associated with the effect of the A2A receptors, which may be related to the neuroinflammatory responses occurring during the pathological process. 相似文献
18.
6-Hydroxydopamine (6-OHDA) is the most used toxin in experimental Parkinson’s disease (PD) models. 6-OHDA shows high affinity for the dopamine transporter and once inside the neuron, it accumulates and undergoes non-enzymatic auto-oxidation, promoting reactive oxygen species (ROS) formation and selective damage of catecholaminergic neurons. In this way, our group has established a 6-OHDA in vitro protocol with rat striatal slices as a rapid and effective model for screening of new drugs with protective effects against PD. We have shown that co-incubation with guanosine (GUO, 100 μM) prevented the 6-OHDA-induced damage in striatal slices. As the exact GUO mechanism of action remains unknown, the aim of this study was to investigate if adenosine A1 (A1R) and/or A2A receptors (A2AR) are involved on GUO protective effects on striatal slices. Pre-incubation with DPCPX, an A1R antagonist prevented guanosine effects on 6-OHDA-induced ROS formation and mitochondrial membrane potential depolarization, while CCPA, an A1R agonist, did not alter GUO effects. Regarding A2AR, the antagonist SCH58261 had similar protective effect as GUO in ROS formation and mitochondrial membrane potential. Additionally, SCH58261 did not affect GUO protective effects. The A2AR agonist CGS21680, although, completely blocked GUO effects. Finally, the A1R antagonist DPCPX, and the A2AR agonist CGS21680 also abolished the preventive guanosine effect on 6-OHDA-induced ATP levels decrease. These results reinforce previous evidence for a putative interaction of GUO with A1R-A2AR heteromer as its molecular target and clearly indicate a dependence on adenosine receptors modulation to GUO protective effect. 相似文献
19.
Caffeine, a stimulant largely consumed around the world, is a non-selective adenosine receptor antagonist, and therefore caffeine actions at synapses usually, but not always, mirror those of adenosine. Importantly, different adenosine receptors with opposing regulatory actions co-exist at synapses. Through both inhibitory and excitatory high-affinity receptors (A1R and A2R, respectively), adenosine affects NMDA receptor (NMDAR) function at the hippocampus, but surprisingly, there is a lack of knowledge on the effects of caffeine upon this ionotropic glutamatergic receptor deeply involved in both positive (plasticity) and negative (excitotoxicity) synaptic actions. We thus aimed to elucidate the effects of caffeine upon NMDAR-mediated excitatory post-synaptic currents (NMDAR-EPSCs), and its implications upon neuronal Ca2+ homeostasis. We found that caffeine (30–200 μM) facilitates NMDAR-EPSCs on pyramidal CA1 neurons from Balbc/ByJ male mice, an action mimicked, as well as occluded, by 1,3-dipropyl-cyclopentylxantine (DPCPX, 50 nM), thus likely mediated by blockade of inhibitory A1Rs. This action of caffeine cannot be attributed to a pre-synaptic facilitation of transmission because caffeine even increased paired-pulse facilitation of NMDA-EPSCs, indicative of an inhibition of neurotransmitter release. Adenosine A2ARs are involved in this likely pre-synaptic action since the effect of caffeine was mimicked by the A2AR antagonist, SCH58261 (50 nM). Furthermore, caffeine increased the frequency of Ca2+ transients in neuronal cell culture, an action mimicked by the A1R antagonist, DPCPX, and prevented by NMDAR blockade with AP5 (50 μM). Altogether, these results show for the first time an influence of caffeine on NMDA receptor activity at the hippocampus, with impact in neuronal Ca2+ homeostasis. 相似文献
20.
AimsWe investigated the effects induced by exogenous adenosine on the spontaneous contractile activity of the longitudinal muscle of a mouse ileum, the receptor subtypes activated, the involvement of enteric nerves and whether opening of K + channels was a downstream event leading to the observed effects. Main methodsMechanical responses of the mouse ileal longitudinal muscle to adenosine were examined in vitro as changes in isometric tension. Key findingsAdenosine caused a concentration-dependent reduction of the spontaneous contraction amplitude of the ileal longitudinal muscle up to its complete disappearance. This effect induced was markedly reduced by an A 1 receptor antagonist, but not by A 2 and A 3 receptor antagonists and mimicked only by the A 1 receptor agonist. Adenosine uptake inhibitors did not change adenosine potency. A 1 receptor expression was detected at the smooth muscle level. Adenosine responses were insensitive to tetrodotoxin, atropine or nitric oxide synthase inhibitor. Tetraethylammonium and iberiotoxin, BK Ca channel blockers, significantly reduced adenosine effects, whilst 4-aminopyridine, a K v blocker, apamin, a small conductance Ca 2+-activated K + (SK Ca) channel blocker, charybdotoxin, an intermediate conductance Ca 2+-activated K + (IK Ca) and BK Ca channel blocker, or glibenclamide, an ATP-sensitive K + channel blocker, had no effects. The combination of apamin plus iberiotoxin caused a reduction of the purinergic effects greater than iberiotoxin alone. SignificanceAdenosine acts as an inhibitory modulator of the contractility of mouse ileal longitudinal muscle through postjunctional A 1 receptors, which in turn would induce opening of BK Ca and SK Ca potassium channels. This study would provide new insight in the pharmacology of purinergic receptors involved in the modulation of the gastrointestinal contractility. 相似文献
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