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Sample records for a2a receptor agonists

  1. Adenosine A2A receptor dynamics studied with the novel fluorescent agonist Alexa488-APEC

    PubMed Central

    Brand, Frank; Klutz, Athena; Jacobson, Kenneth A.; Fredholm, Bertil B.; Schulte, Gunnar

    2009-01-01

    G protein-coupled receptors, such as the adenosine A2A receptor, are dynamic proteins, which undergo agonist-dependent redistribution from the cell surface to intracellular membranous compartments, such as endosomes. In order to study the kinetics of adenosine A2A receptor redistribution in living cells, we synthesized a novel fluorescent agonist, Alexa488-APEC. Alexa488-APEC binds to adenosine A2A (Ki = 149 ± 27 nM) as well as A3 receptors (Ki= 240 ± 160 nM) but not to adenosine A1 receptors. Further, we characterized the dose-dependent increase in Alexa488-APEC-induced cAMP production as well as cAMP response element binding (CREB) protein phosphorylation, verifying the ligand’s functionality at adenosine A2A but not A2B receptors. In live cell imaging studies, Alexa488-APEC induced adenosine A2A receptor internalization, which was blocked by the competitive reversible antagonist ZM 241385 and hyperosmolaric sucrose. Further, internalized adenosine A2A receptors co-localized with clathrin and Rab5, indicating that agonist stimulation promotes adenosine A2A receptor uptake through a clathrin-dependent mechanism to Rab5-positive endosomes. The basic characterization of Alexa488-APEC provided here showed that it provides a usefultool for tracing adenosine A2A receptors in vitro. PMID:18603240

  2. Thermostabilisation of an agonist-bound conformation of the human adenosine A(2A) receptor.

    PubMed

    Lebon, Guillaume; Bennett, Kirstie; Jazayeri, Ali; Tate, Christopher G

    2011-06-10

    The adenosine A(2A) receptor (A(2A)R) is a G-protein-coupled receptor that plays a key role in transmembrane signalling mediated by the agonist adenosine. The structure of A(2A)R was determined recently in an antagonist-bound conformation, which was facilitated by the T4 lysozyme fusion in cytoplasmic loop 3 and the considerable stabilisation conferred on the receptor by the bound inverse agonist ZM241385. Unfortunately, the natural agonist adenosine does not sufficiently stabilise the receptor for the formation of diffraction-quality crystals. As a first step towards determining the structure of A(2A)R bound to an agonist, the receptor was thermostabilised by systematic mutagenesis in the presence of the bound agonist [(3)H]5'-N-ethylcarboxamidoadenosine (NECA). Four thermostabilising mutations were identified that when combined to give mutant A(2A)R-GL26, conferred a greater than 200-fold decrease in its rate of unfolding compared to the wild-type receptor. Pharmacological analysis suggested that A(2A)R-GL26 is stabilised in an agonist-bound conformation because antagonists bind with up to 320-fold decreased affinity. None of the thermostabilising mutations are in the ZM241385 binding pocket, suggesting that the mutations affect ligand binding by altering the conformation of the receptor rather than through direct interactions with ligands. A(2A)R-GL26 shows considerable stability in short-chain detergents, which has allowed its purification and crystallisation. PMID:21501622

  3. Graft versus host disease: New insights into A2A receptor agonist therapy.

    PubMed

    Jones, Karlie R; Kang, Elizabeth M

    2015-01-01

    Allogeneic transplantation can cure many disorders, including sickle cell disease, chronic granulomatous disease (CGD), severe combined immunodeficiency (SCID) and many types of cancers. However, there are several associated risks that can result in severe immunological reactions and, in some cases, death. Much of this morbidity is related to graft versus host disease (GVHD) [1]. GVHD is an immune mediated reaction in which donor T cells recognize the host as antigenically foreign, causing donor T cells to expand and attack host tissues. The current method of treating recent transplant patients with immunosuppressants to prevent this reaction has met with only partial success, emphasizing a need for new methods of GVHD treatment and prevention. Recently, a novel strategy has emerged targeting adenosine A2A receptors (A2AR) through the use of adenosine agonists. These agonists have been shown in vitro to increase the TGFβ-induced generation of FoxP3(+) regulatory T cells (Tregs) and in vivo to improve weight gain and mortality as well as inhibit the release of pro-inflammatory cytokines in GVHD murine models [2,3]. Positive results involving A2AR agonists in vitro and in vivo are promising, suggesting that A2AR agonists should be a part of the management of clinical GvHD. PMID:25709759

  4. Allosteric interactions between agonists and antagonists within the adenosine A2A receptor-dopamine D2 receptor heterotetramer

    PubMed Central

    Bonaventura, Jordi; Navarro, Gemma; Casadó-Anguera, Verònica; Azdad, Karima; Rea, William; Moreno, Estefanía; Brugarolas, Marc; Mallol, Josefa; Canela, Enric I.; Lluís, Carme; Cortés, Antoni; Volkow, Nora D.; Schiffmann, Serge N.; Ferré, Sergi; Casadó, Vicent

    2015-01-01

    Adenosine A2A receptor (A2AR)-dopamine D2 receptor (D2R) heteromers are key modulators of striatal neuronal function. It has been suggested that the psychostimulant effects of caffeine depend on its ability to block an allosteric modulation within the A2AR-D2R heteromer, by which adenosine decreases the affinity and intrinsic efficacy of dopamine at the D2R. We describe novel unsuspected allosteric mechanisms within the heteromer by which not only A2AR agonists, but also A2AR antagonists, decrease the affinity and intrinsic efficacy of D2R agonists and the affinity of D2R antagonists. Strikingly, these allosteric modulations disappear on agonist and antagonist coadministration. This can be explained by a model that considers A2AR-D2R heteromers as heterotetramers, constituted by A2AR and D2R homodimers, as demonstrated by experiments with bioluminescence resonance energy transfer and bimolecular fluorescence and bioluminescence complementation. As predicted by the model, high concentrations of A2AR antagonists behaved as A2AR agonists and decreased D2R function in the brain. PMID:26100888

  5. Allosteric interactions between agonists and antagonists within the adenosine A2A receptor-dopamine D2 receptor heterotetramer.

    PubMed

    Bonaventura, Jordi; Navarro, Gemma; Casadó-Anguera, Verònica; Azdad, Karima; Rea, William; Moreno, Estefanía; Brugarolas, Marc; Mallol, Josefa; Canela, Enric I; Lluís, Carme; Cortés, Antoni; Volkow, Nora D; Schiffmann, Serge N; Ferré, Sergi; Casadó, Vicent

    2015-07-01

    Adenosine A2A receptor (A2AR)-dopamine D2 receptor (D2R) heteromers are key modulators of striatal neuronal function. It has been suggested that the psychostimulant effects of caffeine depend on its ability to block an allosteric modulation within the A2AR-D2R heteromer, by which adenosine decreases the affinity and intrinsic efficacy of dopamine at the D2R. We describe novel unsuspected allosteric mechanisms within the heteromer by which not only A2AR agonists, but also A2AR antagonists, decrease the affinity and intrinsic efficacy of D2R agonists and the affinity of D2R antagonists. Strikingly, these allosteric modulations disappear on agonist and antagonist coadministration. This can be explained by a model that considers A2AR-D2R heteromers as heterotetramers, constituted by A2AR and D2R homodimers, as demonstrated by experiments with bioluminescence resonance energy transfer and bimolecular fluorescence and bioluminescence complementation. As predicted by the model, high concentrations of A2AR antagonists behaved as A2AR agonists and decreased D2R function in the brain. PMID:26100888

  6. The adenosine metabolite inosine is a functional agonist of the adenosine A2A receptor with a unique signaling bias.

    PubMed

    Welihinda, Ajith A; Kaur, Manmeet; Greene, Kelly; Zhai, Yongjiao; Amento, Edward P

    2016-06-01

    Inosine is an endogenous purine nucleoside that is produced by catabolism of adenosine. Adenosine has a short half-life (approximately 10s) and is rapidly deaminated to inosine, a stable metabolite with a half-life of approximately 15h. Resembling adenosine, inosine acting through adenosine receptors (ARs) exerts a wide range of anti-inflammatory and immunomodulatory effects in vivo. The immunomodulatory effects of inosine in vivo, at least in part, are mediated via the adenosine A2A receptor (A2AR), an observation that cannot be explained fully by in vitro pharmacological characterization of inosine at the A2AR. It is unclear whether the in vivo effects of inosine are due to inosine or a metabolite of inosine engaging the A2AR. Here, utilizing a combination of label-free, cell-based, and membrane-based functional assays in conjunction with an equilibrium agonist-binding assay we provide evidence for inosine engagement at the A2AR and subsequent activation of downstream signaling events. Inosine-mediated A2AR activation leads to cAMP production with an EC50 of 300.7μM and to extracellular signal-regulated kinase-1 and -2 (ERK1/2) phosphorylation with an EC50 of 89.38μM. Our data demonstrate that inosine produces ERK1/2-biased signaling whereas adenosine produces cAMP-biased signaling at the A2AR, highlighting pharmacological differences between these two agonists. Given the in vivo stability of inosine, our data suggest an additional, previously unrecognized, mechanism that utilizes inosine to functionally amplify and prolong A2AR activation in vivo. PMID:26903141

  7. Beneficial effects of a novel agonist of the adenosine A2A receptor on monocrotaline-induced pulmonary hypertension in rats

    PubMed Central

    Alencar, Allan K N; Pereira, Sharlene L; Montagnoli, Tadeu L; Maia, Rodolfo C; Kümmerle, Arthur E; Landgraf, Sharon S; Caruso-Neves, Celso; Ferraz, Emanuelle B; Tesch, Roberta; Nascimento, José H M; de Sant'Anna, Carlos M R; Fraga, Carlos A M; Barreiro, Eliezer J; Sudo, Roberto T; Zapata-Sudo, Gisele

    2013-01-01

    Background and Purpose Pulmonary arterial hypertension (PAH) is characterized by enhanced pulmonary vascular resistance, right ventricular hypertrophy and increased right ventricular systolic pressure. Here, we investigated the effects of a N-acylhydrazone derivative, 3,4-dimethoxyphenyl-N-methyl-benzoylhydrazide (LASSBio-1359), on monocrotaline (MCT)-induced pulmonary hypertension in rats. Experimental Approach PAH was induced in male Wistar rats by a single i.p. injection of MCT (60 mg·kg−1) and 2 weeks later, oral LASSBio-1359 (50 mg·kg−1) or vehicle was given once daily for 14 days. Echocardiography was used to measure cardiac function and pulmonary artery dimensions, with histological assay of vascular collagen. Studies of binding to human recombinant adenosine receptors (A1, A2A, A3) and of docking with A2A receptors were also performed. Key Results MCT administration induced changes in vascular and ventricular structure and function, characteristic of PAH. These changes were reversed by treatment with LASSBio-1359. MCT also induced endothelial dysfunction in pulmonary artery, as measured by diminished relaxation of pre-contracted arterial rings, and this dysfunction was reversed by LASSBio-1359. In pulmonary artery rings from normal Wistar rats, LASSBio-1359 induced relaxation, which was decreased by the adenosine A2A receptor antagonist, ZM 241385. In adenosine receptor binding studies, LASSBio-1359 showed most affinity for the A2A receptor and in the docking analyses, binding modes of LASSBio-1359 and the A2A receptor agonist, CGS21680, were very similar. Conclusion and Implications In rats with MCT-induced PAH, structural and functional changes in heart and pulmonary artery were reversed by treatment with oral LASSBio-1359, most probably through the activation of adenosine A2A receptors. PMID:23530610

  8. Spatiotemporal brain dynamics of emotional face processing modulations induced by the serotonin 1A/2A receptor agonist psilocybin.

    PubMed

    Bernasconi, Fosco; Schmidt, André; Pokorny, Thomas; Kometer, Michael; Seifritz, Erich; Vollenweider, Franz X

    2014-12-01

    Emotional face processing is critically modulated by the serotonergic system. For instance, emotional face processing is impaired by acute psilocybin administration, a serotonin (5-HT) 1A and 2A receptor agonist. However, the spatiotemporal brain mechanisms underlying these modulations are poorly understood. Here, we investigated the spatiotemporal brain dynamics underlying psilocybin-induced modulations during emotional face processing. Electrical neuroimaging analyses were applied to visual evoked potentials in response to emotional faces, following psilocybin and placebo administration. Our results indicate a first time period of strength (i.e., Global Field Power) modulation over the 168-189 ms poststimulus interval, induced by psilocybin. A second time period of strength modulation was identified over the 211-242 ms poststimulus interval. Source estimations over these 2 time periods further revealed decreased activity in response to both neutral and fearful faces within limbic areas, including amygdala and parahippocampal gyrus, and the right temporal cortex over the 168-189 ms interval, and reduced activity in response to happy faces within limbic and right temporo-occipital brain areas over the 211-242 ms interval. Our results indicate a selective and temporally dissociable effect of psilocybin on the neuronal correlates of emotional face processing, consistent with a modulation of the top-down control. PMID:23861318

  9. The adenosine A2A receptor antagonist, istradefylline enhances the anti-parkinsonian activity of low doses of dopamine agonists in MPTP-treated common marmosets.

    PubMed

    Uchida, Shin-ichi; Soshiroda, Kazuhiro; Okita, Eri; Kawai-Uchida, Mika; Mori, Akihisa; Jenner, Peter; Kanda, Tomoyuki

    2015-01-15

    The adenosine A2A receptor antagonist, istradefylline, enhances anti-parkinsonian activity in patients with advanced Parkinson׳s disease (PD) already treated with combinations of L-DOPA and dopamine agonist drugs but who are still exhibiting prolonged 'OFF' periods. In contrast, the effects of istradefylline on motor function when administered in combination with low dose dopamine agonist therapy in early PD are unknown. We now investigate whether istradefylline administered with a threshold dose of either the non-ergot dopamine agonist, ropinirole or the ergot dopamine agonist, pergolide enhances anti-parkinsonian activity in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated common marmoset. Both ropinirole (0.01-0.1mg/kg p.o.) and pergolide (0.003-0.1mg/kg p.o.) administered alone produced dose dependent increases in locomotor activity, a reduction in motor disability. Threshold doses of ropinirole (0.025-0.075mg/kg p.o.) and pergolide (0.01-0.075mg/kg p.o.) were then selected that in individual animals caused a small but non-significant anti-parkinsonian effect. Administration of istradefylline (10mg/kg p.o.) alone resulted in a decrease in motor disability and increase in 'ON' time but dyskinesia was not observed. Combined administration of pergolide or ropinirole with istradefylline resulted in an increase in the reversal of motor disability and increase in 'ON' time compared to that produced by either treatment alone but dyskinesia was still not observed. These results show that istradefylline is effective in improving motor function when combined with low dose dopamine agonist treatment. In early PD, this may avoid dose escalation or allow a reduction in dopamine agonist dosage without a loss of efficacy and prevent dopaminergic side-effects from becoming treatment limiting. PMID:25499739

  10. The Adenosine A2A Receptor Agonist, CGS-21680, Blocks Excessive Rearing, Acquisition of Wheel Running, and Increases Nucleus Accumbens CREB Phosphorylation in Chronically Food-Restricted Rats

    PubMed Central

    de Vaca, Soledad Cabeza; Kannan, Pavitra; Pan, Yan; Jiang, Nancy; Sun, Yanjie; Carr, Kenneth D.

    2007-01-01

    Adenosine A2A receptors are preferentially expressed in rat striatum, where they are concentrated in dendritic spines of striatopallidal medium spiny neurons and exist in a heteromeric complex with D2 dopamine (DA) receptors. Behavioral and biochemical studies indicate an antagonistic relationship between A2A and D2 receptors. Previous studies have demonstrated that food-restricted (FR) rats display behavioral and striatal cellular hypersensitivity to D1 and D2 DA receptor stimulation. These alterations may underlie adaptive, as well as maladaptive, behaviors characteristic of the FR rat. The present study examined whether FR rats are hypersensitive to the A2A receptor agonist, CGS-21680. In Experiment 1, spontaneous horizontal motor activity did not differ between FR and ad libitum fed (AL) rats, while vertical activity was greater in the former. Intracerebroventricular (i.c.v.) administration of CGS-21680 (0.25 and 1.0 nmol) decreased both types of motor activity in FR rats, and returned vertical activity levels to those observed in AL rats. In Experiment 2, FR rats given access to a running wheel for a brief period outside of the home cage rapidly acquired wheel running while AL rats did not. Pretreatment with CGS-21680 (1.0 nmol) blocked the acquisition of wheel running. When administered to FR subjects that had previously acquired wheel running, CGS-21680 suppressed the behavior. In Experiment 3, CGS-21680 (1.0 nmol) activated both ERK 1/2 and CREB in caudate-putamen with no difference between feeding groups. However, in nucleus accumbens (NAc), CGS-21680 failed to activate ERK 1/2 and selectively activated CREB in FR rats. These results indicate that FR subjects are hypersensitive to several effects of an adenosine A2A agonist, and suggest the involvement of an upregulated A2A receptor-linked signaling pathway in NAc. Medications targeting the A2A receptor may have utility in the treatment of maladaptive behaviors associated with FR, including substance abuse

  11. Effects of adenosine and adenosine A2A receptor agonist on motor nerve conduction velocity and nerve blood flow in experimental diabetic neuropathy.

    PubMed

    Kumar, Sokindra; Arun, K H S; Kaul, Chaman L; Sharma, Shyam S

    2005-01-01

    This study examined the effects of chronic administration of adenosine and CGS 21680 hydrochloride (adenosine A(2A) receptor agonist) on motor nerve conduction velocity (MNCV), nerve blood flow (NBF) and histology of sciatic nerve in animal model of diabetic neuropathy. Adenosinergic agents were administered for 2 weeks after 6 weeks of streptozotocin-induced (50 mg/kg i.p.) diabetes in male Sprague-Dawley rats. Significant reduction in sciatic MNCV and NBF were observed after 8 weeks in diabetic animals in comparison with control (non diabetic) rats. Adenosine (10 mg/kg, i.p.) significantly improved sciatic MNCV and NBF in diabetic rats. The protective effect of adenosine on MNCV and NBF was completely reversed by theophylline (50 mg/kg, i.p.), a non-selective adenosine receptor antagonist, suggesting that the adenosine effect was mediated via adenosinergic receptors. CGS 21680 (0.1 mg/kg, i.p.) significantly improved NBF; however, MNCV was not significantly improved in diabetic rats. At a dose of 1 mg/kg, neither MNCV nor NBF was improved by CGS 21680 in diabetic rats. ZM 241385 (adenosine A(2A) receptor antagonist) prevented the effect of CGS 21680 (0.1 mg/kg, i.p.). Histological changes observed in sciatic nerve were partially improved by the adenosinergic agents in diabetic rats. Results of the present study, suggest the potential of adenosinergic agents in the therapy of diabetic neuropathy. PMID:15829161

  12. Effects of adenosine A2a receptor agonist and antagonist on cerebellar nuclear factor-kB expression preceded by MDMA toxicity

    PubMed Central

    Kermanian, Fatemeh; Soleimani, Mansoureh; Pourheydar, Bagher; Samzadeh-Kermani, Alireza; Mohammadzadeh, Farzaneh; Mehdizadeh, Mehdi

    2014-01-01

    Background: Adenosine is an endogenous purine nucleoside that has a neuromodulatory role in the central nervous system. The amphetamine derivative (±)-3,4-methylenedioxymethamphetamine (MDMA or ecstasy) is a synthetic amphetamine analogue used recreationally to obtain an enhanced affiliated emotional response. MDMA is a potent monoaminergic neurotoxin with the potential of damage to brain neurons. The NF-kB family of proteins are ubiquitously expressed and are inducible transcription factors that regulate the expression of genes involved in disparate processes such as immunity and ingrowth, development and cell-death regulation. In this study we investigated the effects of the A2a adenosine receptor (A2a-R) agonist (CGS) and antagonist (SCH) on NF-kB expression after MDMA administration. Methods: Sixty three male Sprague–Dawley rats were injected to MDMA (10 and 20mg/kg) followed by intraperitoneal CGS (0.03 mg/kg) or SCH (0.03mg/kg) injection. The cerebellum were then removed forcresylviolet staining, western blot and RT- PCR analyses. MDMA significantly elevated NF-kB expression. Our results showed that MDMA increased the number of cerebellar dark neurons. Results: We observed that administration of CGS following MDMA, significantly elevated the NF-kB expression both at mRNA and protein levels. By contrast, administration of the A2a-R antagonist SCH resulted in a decrease in the NF-kB levels. Conclusion: These results indicated that, co-administration of A2a agonist (CGS) can protect against MDMA neurotoxic effects by increasing NF-kB expression levels; suggesting a potential application for protection against the neurotoxic effects observed in MDMA users. PMID:25678999

  13. Sickle cell vaso-occlusion causes activation of iNKT cells that is decreased by the adenosine A2A receptor agonist regadenoson

    PubMed Central

    Lin, Gene; Okam, Maureen M.; Majerus, Elaine; Keefer, Jeffrey; Onyekwere, Onyinye; Ross, Ainsley; Campigotto, Federico; Neuberg, Donna; Linden, Joel; Nathan, David G.

    2013-01-01

    Adenosine A2A receptor (A2AR) agonists reduce invariant natural killer T (iNKT) cell activation and decrease inflammation in sickle cell disease (SCD) mice. We conducted a phase 1 trial of the A2AR agonist regadenoson in adults with SCD. The target dose was 1.44 μg/kg/h. iNKT cell activation was evaluated using antibodies targeting the p65 subunit of nuclear factor-κB (phospho-NF-κB p65), interferon-γ (IFN-γ), and A2AR. Regadenoson was administered to 27 adults with SCD. We examined 21 patients at steady state and 6 during painful vaso-occlusive crises (pVOC). iNKT cell activation was also measured in 14 African-American controls. During pVOC, the fraction of iNKT cells demonstrating increased phospho-NF-κB p65 and A2AR expression was significantly higher compared with controls (P < .01) and steady-state patients (P < .05). IFN-γ expression was also significantly higher compared with controls (P = .02). After a 24-hour infusion of regadenoson during pVOC, phospho-NF-κB p65 activation in iNKT cells decreased compared to baseline by a median of 48% (P = .03) to levels similar to controls and steady-state SCD. No toxicities were identified. Infusional regadenoson administered to adults with SCD at 1.44 μg/kg/h during pVOC decreases activation of iNKT cells without toxicity. This trial was registered at www.clinicaltrials.gov as #NCT01085201. PMID:23377438

  14. Topical application of the adenosine A2A receptor agonist CGS-21680 prevents phorbol-induced epidermal hyperplasia and inflammation in mice.

    PubMed

    Arasa, Jorge; Martos, Patricio; Terencio, María Carmen; Valcuende-Cavero, Francisca; Montesinos, María Carmen

    2014-08-01

    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. PMID:24889129

  15. Design, synthesis, and biological evaluation of novel 2-((2-(4-(substituted)phenylpiperazin-1-yl)ethyl)amino)-5'-N-ethylcarboxamidoadenosines as potent and selective agonists of the A2A adenosine receptor.

    PubMed

    Preti, Delia; Baraldi, Pier Giovanni; Saponaro, Giulia; Romagnoli, Romeo; Aghazadeh Tabrizi, Mojgan; Baraldi, Stefania; Cosconati, Sandro; Bruno, Agostino; Novellino, Ettore; Vincenzi, Fabrizio; Ravani, Annalisa; Borea, Pier Andrea; Varani, Katia

    2015-04-01

    Stimulation of A2A adenosine receptors (AR) promotes anti-inflammatory responses in animal models of allergic rhinitis, asthma, chronic obstructive pulmonary disease, and rheumatic diseases. Herein we describe the results of a research program aimed at identifying potent and selective agonists of the A2AAR as potential anti-inflammatory agents. The recent crystallographic analysis of A2AAR agonists and antagonists in complex with the receptor provided key information on the structural determinants leading to receptor activation or blocking. In light of this, we designed a new series of 2-((4-aryl(alkyl)piperazin-1-yl)alkylamino)-5'-N-ethylcarboxamidoadenosines with high A2AAR affinity, activation potency and selectivity obtained by merging distinctive structural elements of known agonists and antagonists of the investigated target. Docking-based SAR optimization allowed us to identify compound 42 as one of the most potent and selective A2A agonist discovered so far (Ki hA2AAR = 4.8 nM, EC50 hA2AAR = 4.9 nM, Ki hA1AR > 10 000 nM, Ki hA3AR = 1487 nM, EC50 hA2BAR > 10 000 nM). PMID:25780876

  16. The adenosine A2A receptor antagonist, istradefylline enhances anti-parkinsonian activity induced by combined treatment with low doses of L-DOPA and dopamine agonists in MPTP-treated common marmosets.

    PubMed

    Uchida, Shin-ichi; Soshiroda, Kazuhiro; Okita, Eri; Kawai-Uchida, Mika; Mori, Akihisa; Jenner, Peter; Kanda, Tomoyuki

    2015-11-01

    The adenosine A2A receptor antagonist, istradefylline improves motor function in patients with advanced Parkinson's disease (PD) optimally treated with a combination of L-DOPA and a dopamine agonist without increasing the risk of troublesome dyskinesia. However, the effects of istradefylline on motor function when administered in combination with low dose of L-DOPA and dopamine agonists as occurs in early PD are unknown. We investigated whether istradefylline enhances the combined anti-parkinsonian effects of a suboptimal dose of L-DOPA and a threshold dose of either the non-ergot dopamine agonist, ropinirole or the ergot dopamine agonist, pergolide in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated common marmoset. Threshold doses of ropinirole (0.025-0.075 mg/kg p.o.) and pergolide (0.01 mg/kg p.o.) produced a weak anti-parkinsonian effect. Co-administration of a suboptimal dose of L-DOPA (2.5mg/kg p.o.) with threshold doses of the dopamine agonists enhanced their anti-parkinsonian effect that led to increased 'ON' time without dyskinesia appearing. Administering istradefylline (10mg/kg p.o.) with the threshold doses of dopamine agonists and the suboptimal dose of L-DOPA in a triple combination caused a further enhancement of the anti-parkinsonian response but dyskinesia was still absent. In early PD, dopamine agonists are often used as first-line monotherapy, but efficacy is usually lost within a few years, at which time L-DOPA is added but with the risk of dyskinesia appearance. These results show that istradefylline is effective in improving motor function in combination with low dose dopaminergic drug treatment without provoking dyskinesia. PMID:26415982

  17. Adenosine and the adenosine A2A receptor agonist, CGS21680, upregulate CD39 and CD73 expression through E2F-1 and CREB in regulatory T cells isolated from septic mice.

    PubMed

    Bao, Rui; Shui, Xianqi; Hou, Jiong; Li, Jinbao; Deng, Xiaoming; Zhu, Xiaoyan; Yang, Tao

    2016-09-01

    The number of regulatory T cells (Treg cells) and the expression of ectonucleoside triphosphate diphosphohydrolase 1 (ENTPD1; also known as CD39) and 5'-ectonucleotidase (NT5E; also known as CD73) on the Treg cell surface are increased during sepsis. In this study, to determine the factors leading to the high expression of CD39 and CD73, and the regulation of the CD39/CD73/adenosine pathway in Treg cells under septic conditions, we constructed a mouse model of sepsis and separated the Treg cells using a flow cytometer. The Treg cells isolated from the peritoneal lavage and splenocytes of the mice were treated with adenosine or the specific adenosine A2A receptor agonist, CGS21680, and were transfected with specific siRNA targeting E2F transcription factor 1 (E2F-1) or cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB), which are predicted transcription regulatory factors of CD39 or CD73. The regulatory relationships among these factors were then determined by western blot analysis and dual-luciferase reporter assay. In addition, changes in adenosine metabolism were measured in the treated cells. The results revealed that adenosine and CGS21680 significantly upregulated CD39 and CD73 expression (P<0.01). E2F-1 and CREB induced CD39 and CD73 expression, and were upregulated by adenosine and CGS21680. Adenosine triphosphate (ATP) hydrolysis and adenosine generation were inhibited by the knockdown of E2F-1 or CREB, and were accelerated in the presence of CGS21680. Based on these results, it can be inferred that adenosine, the adenosine A2A receptor agonist, E2F-1 and CREB are the possible factors contributing to the high expression of CD39 and CD73 on the Treg cell surface during sepsis. Adenosine and its A2A receptor agonist served as the signal transducer factors of the CD39/CD73/adenosine pathway, accelerating adenosine generation. Our study may benefit further research on adenosine metabolism for the treatment of sepsis

  18. Adenosine A2A Agonist Improves Lung Function During Ex-vivo Lung Perfusion

    PubMed Central

    Emaminia, Abbas; LaPar, Damien J.; Zhao, Yunge; Steidle, John F.; Harris, David A.; Linden, Joel; Kron, Irving L.; Lau, Christine L.

    2012-01-01

    Background Ex-vivo lung perfusion (EVLP) is a novel technique to assess, and potentially repair marginal lungs that may otherwise be rejected for transplantation. Adenosine has been shown to protect against lung ischemia-reperfusion injury through its A2A receptor. We hypothesized that combining EVLP with adenosine A2A receptor agonist treatment would enhance lung functional quality and increase donor lung usage. Methods Eight bilateral pig lungs were harvested and flushed with cold Perfadex. After 14 hours storage at 4°C, EVLP was performed for 5 hours on two explanted lung groups: 1) Control group lungs (n=4), were perfused with Steen Solution and Dimethyl sulfoxide (DMSO), and 2) treated group lungs (n=4) received 10μM CGS21680, a selective A2A receptor agonist, in a Steen Solution-primed circuit. Lung histology, tissue cytokines, gas analysis and pulmonary function were compared between groups. Results Treated lungs demonstrated significantly less edema as reflected by wet-dry weight ratio (6.6 vs. 5.2, p<0.03) and confirmed by histology. In addition, treated lung demonstrated significantly lower levels of interferon gamma (45.1 vs. 88.5, p<0.05). Other measured tissue cytokines (interleukin (IL) 1 beta, IL-6, and IL-8) were lower in treatment group, but values failed to reach statistical significance. Oxygenation index was improved in the treated group (1.5 vs. 2.3, p<0.01) as well as mean airway pressure (10.3 vs. 13 p<0.009). Conclusions EVLP is a novel and efficient way to assess and optimize lung function and oxygen exchange within donor lungs, and the use of adenosine A2A agonist potentiates its potential. EVLP with the concomitant administration of A2A agonist may enhance donor lung quality and could increase the donor lung pool for transplantation. PMID:22051279

  19. Piperidine derivatives as nonprostanoid IP receptor agonists.

    PubMed

    Hayashi, Ryoji; Sakagami, Hideki; Koiwa, Masakazu; Ito, Hiroaki; Miyamoto, Mitsuko; Isogaya, Masafumi

    2016-05-01

    The discovery of a new class of nonprostanoid prostaglandin I2 receptor (IP receptor) agonists is reported. Among them, the unique piperidine derivative 31b (2-((1-(2-(N-(4-tolyl)benzamido)ethyl)piperidin-4-yl)oxy)acetic acid) was a good IP receptor agonist and was 50-fold more selective for the human IP receptor than for other human prostanoid receptors. This compound showed good pharmacokinetic properties in dog. PMID:26996371

  20. Kappa Opioid Receptor Agonist and Brain Ischemia

    PubMed Central

    Chunhua, Chen; Chunhua, Xi; Megumi, Sugita; Renyu, Liu

    2014-01-01

    Opioid receptors, especially Kappa opioid receptor (KOR) play an important role in the pathophysiological process of cerebral ischemia reperfusion injury. Previously accepted KOR agonists activity has included anti-nociception, cardiovascular, anti-pruritic, diuretic, and antitussive effects, while compelling evidence from various ischemic animal models indicate that KOR agonist have neuroprotective effects through various mechanisms. In this review, we aimed to demonstrate the property of KOR agonist and its role in global and focal cerebral ischemia. Based on current preclinical research, the KOR agonists may be useful as a neuroprotective agent. The recent discovery of salvinorin A, highly selective non-opioid KOR agonist, offers a new tool to study the role of KOR in brain HI injury and the protective effects of KOR agonist. The unique pharmacological profile of salvinorin A along with the long history of human usage provides its high candidacy as a potential alternative medication for brain HI injury. PMID:25574482

  1. The discovery of a selective and potent A2a agonist with extended lung retention

    PubMed Central

    Åstrand, Annika B M; Lamm Bergström, Eva; Zhang, Hui; Börjesson, Lena; Söderdahl, Therese; Wingren, Cecilia; Jansson, Anne-Helene; Smailagic, Amir; Johansson, Camilla; Bladh, Håkan; Shamovsky, Igor; Tunek, Anders; Drmota, Tomas

    2015-01-01

    Although the anti-inflammatory role of the A2a receptor is well established, controversy remains with regard to the therapeutic value for A2a agonists in treatment of inflammatory lung diseases, also as a result of unwanted A2a-mediated cardiovascular effects. In this paper, we describe the discovery and characterization of a new, potent and selective A2a agonist (compound 2) with prolonged lung retention and limited systemic exposure following local administration. To support the lead optimization chemistry program with compound selection and profiling, multiple in vitro and in vivo assays were used, characterizing compound properties, pharmacodynamics (PD), and drug concentrations. Particularly, pharmacokinetic-PD modeling was applied to quantify the effects on the cardiovascular system, and an investigative toxicology study in rats was performed to explore potential myocardial toxicities. Compound 2, in comparison to a reference A2a agonist, UK-432,097, demonstrated higher solubility, lower lipophilicity, lower plasma protein binding, high rat lung retention (28% remaining after 24 h), and was efficacious in a lung inflammatory rat model following intratracheal dosing. Despite these properties, compound 2 did not provide a sufficient therapeutic index, that is, separation of local anti-inflammatory efficacy in the lung from systemic side effects in the cardiovascular system. The plasma concentration that resulted in induction of hypotension (half maximal effective concentration; EC50 0.5 nmol/L) correlated to the in vitro A2a potency (rIC50 0.6 nmol/L). Histopathological lesions in the heart were observed at a dose level which is threefold above the efficacious dose level in the inflammatory rat lung model. In conclusion, compound 2 is a highly potent and selective A2a agonist with significant lung retention after intratracheal administration. Despite its local anti-inflammatory efficacy in rat lung, small margins to the cardiovascular effects suggested

  2. Reengineering the Collision Coupling and Diffusion Mode of the A2A-adenosine Receptor

    PubMed Central

    Keuerleber, Simon; Thurner, Patrick; Gruber, Christian W.; Zezula, Jürgen; Freissmuth, Michael

    2012-01-01

    The A2A-adenosine receptor undergoes restricted collision coupling with its cognate G protein Gs and lacks a palmitoylation site at the end of helix 8 in its intracellular C terminus. We explored the hypothesis that there was a causal link between the absence of a palmitoyl moiety and restricted collision coupling by introducing a palmitoylation site. The resulting mutant A2A-R309C receptor underwent palmitoylation as verified by both mass spectrometry and metabolic labeling. In contrast to the wild type A2A receptor, the concentration-response curve for agonist-induced cAMP accumulation was shifted to the left with increasing expression levels of A2A-R309C receptor, an observation consistent with collision coupling. Single particle tracking of quantum dot-labeled receptors confirmed that wild type and mutant A2A receptor differed in diffusivity and diffusion mode; agonist activation resulted in a decline in mean square displacement of both receptors, but the drop was substantially more pronounced for the wild type receptor. In addition, in the agonist-bound state, the wild type receptor was frequently subject to confinement events (estimated radius 110 nm). These were rarely seen with the palmitoylated A2A-R309C receptor, the preferred diffusion mode of which was a random walk in both the basal and the agonist-activated state. Taken together, the observations link restricted collision coupling to diffusion limits imposed by the absence of a palmitoyl moiety in the C terminus of the A2A receptor. The experiments allowed for visualizing local confinement of an agonist-activated G protein-coupled receptor in an area consistent with the dimensions of a lipid raft. PMID:23071116

  3. Spinal adenosine A2a receptor activation elicits long-lasting phrenic motor facilitation.

    PubMed

    Golder, Francis J; Ranganathan, Lavanya; Satriotomo, Irawan; Hoffman, Michael; Lovett-Barr, Mary Rachael; Watters, Jyoti J; Baker-Herman, Tracy L; Mitchell, Gordon S

    2008-02-27

    Acute intermittent hypoxia elicits a form of spinal, brain-derived neurotrophic factor (BDNF)-dependent respiratory plasticity known as phrenic long-term facilitation. Ligands that activate G(s)-protein-coupled receptors, such as the adenosine 2a receptor, mimic the effects of neurotrophins in vitro by transactivating their high-affinity receptor tyrosine kinases, the Trk receptors. Thus, we hypothesized that A2a receptor agonists would elicit phrenic long-term facilitation by mimicking the effects of BDNF on TrkB receptors. Here we demonstrate that spinal A2a receptor agonists transactivate TrkB receptors in the rat cervical spinal cord near phrenic motoneurons, thus inducing long-lasting (hours) phrenic motor facilitation. A2a receptor activation increased phosphorylation and new synthesis of an immature TrkB protein, induced TrkB signaling through Akt, and strengthened synaptic pathways to phrenic motoneurons. RNA interference targeting TrkB mRNA demonstrated that new TrkB protein synthesis is necessary for A2a-induced phrenic motor facilitation. A2a receptor activation also increased breathing in unanesthetized rats, and improved breathing in rats with cervical spinal injuries. Thus, small, highly permeable drugs (such as adenosine receptor agonists) that transactivate TrkB receptors may provide an effective therapeutic strategy in the treatment of patients with ventilatory control disorders, such as obstructive sleep apnea, or respiratory insufficiency after spinal injury or during neurodegenerative diseases. PMID:18305238

  4. Striatal adenosine-cannabinoid receptor interactions in rats over-expressing adenosine A2A receptors.

    PubMed

    Chiodi, Valentina; Ferrante, Antonella; Ferraro, Luca; Potenza, Rosa Luisa; Armida, Monica; Beggiato, Sarah; Pèzzola, Antonella; Bader, Michael; Fuxe, Kjell; Popoli, Patrizia; Domenici, Maria Rosaria

    2016-03-01

    Adenosine A2A receptors (A2 A Rs) and cannabinoid CB1 receptors (CB1 Rs) are highly expressed in the striatum, where they functionally interact and form A2A /CB1 heteroreceptor complexes. We investigated the effects of CB1 R stimulation in a transgenic rat strain over-expressing A2 A Rs under the control of the neural-specific enolase promoter (NSEA2A rats) and in age-matched wild-type (WT) animals. The effects of the CB1 R agonist WIN 55,212-2 (WIN) were significantly lower in NSEA2A rats than in WT animals, as demonstrated by i) electrophysiological recordings of synaptic transmission in corticostriatal slices; ii) the measurement of glutamate outflow from striatal synaptosomes and iii) in vivo experiments on locomotor activity. Moreover, while the effects of WIN were modulated by both A2 A R agonist (CGS 21680) and antagonists (ZM 241385, KW-6002 and SCH-442416) in WT animals, the A2 A R antagonists failed to influence WIN-mediated effects in NSEA2A rats. The present results demonstrate that in rats with genetic neuronal over-expression of A2 A Rs, the effects mediated by CB1 R activation in the striatum are significantly reduced, suggesting a change in the stoichiometry of A2A and CB1 receptors and providing a strategy to dissect the involvement of A2 A R forming or not forming heteromers in the modulation of striatal functions. These findings add additional evidence for the existence of an interaction between striatal A2 A Rs and CB1 Rs, playing a fundamental role in the regulation of striatal functions. We studied A2A -CB1 receptor interaction in transgenic rats over-expressing adenosine A2A receptors under the control of the neuron-specific enolase promoter (NSEA2A ). In these rats, we demonstrated a reduced effect of the CB1 receptor agonist WIN 55,212-2 in the modulation of corticostriatal synaptic transmission and locomotor activity, while CB1 receptor expression level did not change with respect to WT rats. A reduction in the expression of A2A -CB1

  5. Contractile response of bovine lateral saphenous vein to ergovaline serotonin2A a2A- and a2C-adrenergic receptor agonists relative to time off endophyte-infected tall fescue

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Previous research has demonstrated differences in contractile responses to ergot alkaloids, serotonin (5HT), and adrenergic agonists by lateral saphenous veins collected from cattle that grazed either endophyte (Neotyphodium coenophialum)-infected or endophyte-free tall fescue (Lolium arundinaceum),...

  6. Adenosine A2A Receptors Modulate Acute Injury and Neuroinflammation in Brain Ischemia

    PubMed Central

    Pedata, Felicita; Pugliese, Anna Maria; Coppi, Elisabetta; Dettori, Ilaria; Maraula, Giovanna; Cellai, Lucrezia; Melani, Alessia

    2014-01-01

    The extracellular concentration of adenosine in the brain increases dramatically during ischemia. Adenosine A2A receptor is expressed in neurons and glial cells and in inflammatory cells (lymphocytes and granulocytes). Recently, adenosine A2A receptor emerged as a potential therapeutic attractive target in ischemia. Ischemia is a multifactorial pathology characterized by different events evolving in the time. After ischemia the early massive increase of extracellular glutamate is followed by activation of resident immune cells, that is, microglia, and production or activation of inflammation mediators. Proinflammatory cytokines, which upregulate cell adhesion molecules, exert an important role in promoting recruitment of leukocytes that in turn promote expansion of the inflammatory response in ischemic tissue. Protracted neuroinflammation is now recognized as the predominant mechanism of secondary brain injury progression. A2A receptors present on central cells and on blood cells account for important effects depending on the time-related evolution of the pathological condition. Evidence suggests that A2A receptor antagonists provide early protection via centrally mediated control of excessive excitotoxicity, while A2A receptor agonists provide protracted protection by controlling massive blood cell infiltration in the hours and days after ischemia. Focus on inflammatory responses provides for adenosine A2A receptor agonists a wide therapeutic time-window of hours and even days after stroke. PMID:25165414

  7. Melanocortin 1 Receptor Agonists Reduce Proteinuria

    PubMed Central

    Ebefors, Kerstin; Johansson, Martin E.; Stefánsson, Bergur; Granqvist, Anna; Arnadottir, Margret; Berg, Anna-Lena; Nyström, Jenny; Haraldsson, Börje

    2010-01-01

    Membranous nephropathy is one of the most common causes of nephrotic syndrome in adults. Recent reports suggest that treatment with adrenocorticotropic hormone (ACTH) reduces proteinuria, but the mechanism of action is unknown. Here, we identified gene expression of the melanocortin receptor MC1R in podocytes, glomerular endothelial cells, mesangial cells, and tubular epithelial cells. Podocytes expressed most MC1R protein, which colocalized with synaptopodin but not with an endothelial-specific lectin. We treated rats with passive Heymann nephritis (PHN) with MS05, a specific MC1R agonist, which significantly reduced proteinuria compared with untreated PHN rats (P < 0.01). Furthermore, treatment with MC1R agonists improved podocyte morphology and reduced oxidative stress. In summary, podocytes express MC1R, and MC1R agonism reduces proteinuria, improves glomerular morphology, and reduces oxidative stress in nephrotic rats with PHN. These data may explain the proteinuria-reducing effects of ACTH observed in patients with membranous nephropathy, and MC1R agonists may provide a new therapeutic option for these patients. PMID:20507942

  8. Nucleus tractus solitarii A(2a) adenosine receptors inhibit cardiopulmonary chemoreflex control of sympathetic outputs.

    PubMed

    Minic, Zeljka; O'Leary, Donal S; Scislo, Tadeusz J

    2014-02-01

    Previously we have shown that stimulation of inhibitory A1 adenosine receptors located in the nucleus tractus solitarii (NTS) attenuates cardiopulmonary chemoreflex (CCR) evoked inhibition of renal, adrenal and lumbar sympathetic nerve activity and reflex decreases in arterial pressure and heart rate. Activation of facilitatory A2a adenosine receptors, which dominate over A1 receptors in the NTS, contrastingly alters baseline activity of regional sympathetic outputs: it decreases renal, increases adrenal and does not change lumbar nerve activity. Considering that NTS A2a receptors may facilitate release of inhibitory transmitters we hypothesized that A2a receptors will act in concert with A1 receptors differentially inhibiting regional sympathetic CCR responses (adrenal>lumbar>renal). In urethane/chloralose anesthetized rats (n=38) we compared regional sympathetic responses evoked by stimulation of the CCR with right atrial injections of serotonin 5HT3 receptor agonist, phenylbiguanide, (1-8μg/kg) before and after selective stimulation, blockade or combined blockade and stimulation of NTS A2a adenosine receptors (microinjections into the NTS of CGS-21680 0.2-20pmol/50nl, ZM-241385 40pmol/100nl or ZM-241385+CGS-21680, respectively). We found that stimulation of A2a adenosine receptors uniformly inhibited the regional sympathetic and hemodynamic reflex responses and this effect was abolished by the selective blockade of NTS A2a receptors. This indicates that A2a receptor triggered inhibition of CCR responses and the contrasting shifts in baseline sympathetic activity are mediated via different mechanisms. These data implicate that stimulation of NTS A2a receptors triggers unknown inhibitory mechanism(s) which in turn inhibit transmission in the CCR pathway when adenosine is released into the NTS during severe hypotension. PMID:24216055

  9. Activation of the A2A adenosine G-protein-coupled receptor by conformational selection.

    PubMed

    Ye, Libin; Van Eps, Ned; Zimmer, Marco; Ernst, Oliver P; Prosser, R Scott

    2016-05-12

    Conformational selection and induced fit are two prevailing mechanisms to explain the molecular basis for ligand-based activation of receptors. G-protein-coupled receptors are the largest class of cell surface receptors and are important drug targets. A molecular understanding of their activation mechanism is critical for drug discovery and design. However, direct evidence that addresses how agonist binding leads to the formation of an active receptor state is scarce. Here we use (19)F nuclear magnetic resonance to quantify the conformational landscape occupied by the adenosine A2A receptor (A2AR), a prototypical class A G-protein-coupled receptor. We find an ensemble of four states in equilibrium: (1) two inactive states in millisecond exchange, consistent with a formed (state S1) and a broken (state S2) salt bridge (known as 'ionic lock') between transmembrane helices 3 and 6; and (2) two active states, S3 and S3', as identified by binding of a G-protein-derived peptide. In contrast to a recent study of the β2-adrenergic receptor, the present approach allowed identification of a second active state for A2AR. Addition of inverse agonist (ZM241385) increases the population of the inactive states, while full agonists (UK432097 or NECA) stabilize the active state, S3', in a manner consistent with conformational selection. In contrast, partial agonist (LUF5834) and an allosteric modulator (HMA) exclusively increase the population of the S3 state. Thus, partial agonism is achieved here by conformational selection of a distinct active state which we predict will have compromised coupling to the G protein. Direct observation of the conformational equilibria of ligand-dependent G-protein-coupled receptor and deduction of the underlying mechanisms of receptor activation will have wide-reaching implications for our understanding of the function of G-protein-coupled receptor in health and disease. PMID:27144352

  10. Agonists and antagonists for P2 receptors

    PubMed Central

    Jacobson, Kenneth A.; Costanzi, Stefano; Joshi, Bhalchandra V.; Besada, Pedro; Shin, Dae Hong; Ko, Hyojin; Ivanov, Andrei A.; Mamedova, Liaman

    2015-01-01

    Recent work has identified nucleotide agonists selective for P2Y1, P2Y2 and P2Y6 receptors and nucleotide antagonists selective for P2Y1, P2Y12 and P2X1 receptors. Selective non-nucleotide antagonists have been reported for P2Y1, P2Y2, P2Y6, P2Y12, P2Y13, P2X2/3/P2X3 and P2X7 receptors. For example, the dinucleotide INS 37217 (Up4dC) potently activates the P2Y2 receptor, and the non-nucleotide antagonist A-317491 is selective for P2X2/3/P2X3 receptors. Nucleotide analogues in which the ribose moiety is substituted by a variety of novel ring systems, including conformation-ally locked moieties, have been synthesized as ligands for P2Y receptors. The focus on conformational factors of the ribose-like moiety allows the inclusion of general modifications that lead to enhanced potency and selectivity. At P2Y1,2,4,11 receptors, there is a preference for the North conformation as indicated with (N)-methanocarba analogues. The P2Y1 antagonist MRS2500 inhibited ADP-induced human platelet aggregation with an IC50 of 0.95 nM. MRS2365, an (N)-methanocarba analogue of 2-MeSADP, displayed potency (EC50) of 0.4 nM at the P2Y1 receptor, with >10 000-fold selectivity in comparison to P2Y12 and P2Y13 receptors. At P2Y6 receptors there is a dramatic preference for the South conformation. Three-dimensional structures of P2Y receptors have been deduced from structure activity relationships (SAR), mutagenesis and modelling studies. Detailed three-dimensional structures of P2X receptors have not yet been proposed. PMID:16805423

  11. Role of extracellular cysteine residues in the adenosine A2A receptor.

    PubMed

    De Filippo, Elisabetta; Namasivayam, Vigneshwaran; Zappe, Lukas; El-Tayeb, Ali; Schiedel, Anke C; Müller, Christa E

    2016-06-01

    The G protein-coupled A2A 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 A2BAR subtype appears to require only disulfide bond III for proper function. In this study, each of the three disulfide bonds in the A2AAR 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 A2AAR is dynamic. This might add another level of G protein-coupled receptor (GPCR) modulation, in particular for the cysteine-rich A2A and A2BARs. PMID:26969588

  12. The human D2 dopamine receptor synergizes with the A2A adenosine receptor to stimulate adenylyl cyclase in PC12 cells.

    PubMed

    Kudlacek, Oliver; Just, Herwig; Korkhov, Vladimir M; Vartian, Nina; Klinger, Markus; Pankevych, Halyna; Yang, Qiong; Nanoff, Christian; Freissmuth, Michael; Boehm, Stefan

    2003-07-01

    The adenosine A(2A) receptor and the dopamine D(2) receptor are prototypically coupled to G(s) and G(i)/G(o), respectively. In striatal intermediate spiny neurons, these receptors are colocalized in dendritic spines and act as mutual antagonists. This antagonism has been proposed to occur at the level of the receptors or of receptor-G protein coupling. We tested this model in PC12 cells which endogenously express A(2A) receptors. The human D(2) receptor was introduced into PC12 cells by stable transfection. A(2A)-agonist-mediated inhibition of D(2) agonist binding was absent in PC12 cell membranes but present in HEK293 cells transfected as a control. However, in the resulting PC12 cell lines, the action of the D(2) agonist quinpirole depended on the expression level of the D(2) receptor: at low and high receptor levels, the A(2A)-agonist-induced elevation of cAMP was enhanced and inhibited, respectively. Forskolin-stimulated cAMP formation was invariably inhibited by quinpirole. The effects of quinpirole were abolished by pretreatment with pertussis toxin. A(2A)-receptor-mediated cAMP formation was inhibited by other G(i)/G(o)-coupled receptors that were either endogenously present (P(2y12)-like receptor for ADP) or stably expressed after transfection (A(1) adenosine, metabotropic glutamate receptor-7A). Similarly, voltage activated Ca(2+) channels were inhibited by the endogenous P(2Y) receptor and by the heterologously expressed A(1) receptor but not by the D(2) receptor. These data indicate functional segregation of signaling components. Our observations are thus compatible with the proposed model that D(2) and A(2A) receptors are closely associated, but they highlight the fact that this interaction can also support synergism. PMID:12784121

  13. Increased desensitization of dopamine D₂ receptor-mediated response in the ventral tegmental area in the absence of adenosine A(2A) receptors.

    PubMed

    Al-Hasani, R; Foster, J D; Metaxas, A; Ledent, C; Hourani, S M O; Kitchen, I; Chen, Y

    2011-09-01

    G-protein coupled receptors interact to provide additional regulatory mechanisms for neurotransmitter signaling. Adenosine A(2A) receptors are expressed at a high density in striatal neurons, where they closely interact with dopamine D₂ receptors and modulate effects of dopamine and responses to psychostimulants. A(2A) receptors are expressed at much lower densities in other forebrain neurons but play a more prominent yet opposing role to striatal receptors in response to psychostimulants in mice. It is, therefore, possible that A(2A) receptors expressed at low levels elsewhere in the brain may also regulate neurotransmitter systems and modulate neuronal functions. Dopamine D₂ receptors play an important role in autoinhibition of neuronal firing in dopamine neurons of the ventral tegmental area (VTA) and dopamine release in other brain areas. Here, we examined the effect of A(2A) receptor deletion on D₂ receptor-mediated inhibition of neuronal firing in dopamine neurons in the VTA. Spontaneous activity of dopamine neurons was recorded in midbrain slices, and concentration-dependent effects of the dopamine D₂ receptor agonist, quinpirole, was compared between wild-type and A(2A) knockout mice. The potency of quinpirole applied in single concentrations and the expression of D₂ receptors were not altered in the VTA of the knockout mice. However, quinpirole applied in stepwise escalating concentrations caused significantly reduced maximal inhibition in A(2A) knockout mice, indicating an enhanced agonist-induced desensitization of D₂ receptors in the absence of A(2A) receptors. The A(2A) receptor agonist, CGS21680, did not exert any effect on dopamine neuron firing or response to quinpirole, revealing a novel non-pharmacological interaction between adenosine A(2A) receptors and dopaminergic neurotransmission in midbrain dopamine neurons. Altered D₂ receptor desensitization may result in changes in dopamine neuron firing rate and pattern and dopamine

  14. Interactions between cannabinoid receptor agonists and mu opioid receptor agonists in rhesus monkeys discriminating fentanyl.

    PubMed

    Maguire, David R; France, Charles P

    2016-08-01

    Cannabinoid receptor agonists such as delta-9-tetrahydrocannabinol (Δ(9)-THC) enhance some (antinociceptive) but not other (positive reinforcing) effects of mu opioid receptor agonists, suggesting that cannabinoids might be combined with opioids to treat pain without increasing, and possibly decreasing, abuse. The degree to which cannabinoids enhance antinociceptive effects of opioids varies across drugs insofar as Δ(9)-THC and the synthetic cannabinoid receptor agonist CP55940 increase the potency of some mu opioid receptor agonists (e.g., fentanyl) more than others (e.g., nalbuphine). It is not known whether interactions between cannabinoids and opioids vary similarly for other (abuse-related) effects. This study examined whether Δ(9)-THC and CP55940 differentially impact the discriminative stimulus effects of fentanyl and nalbuphine in monkeys (n=4) discriminating 0.01mg/kg of fentanyl (s.c.) from saline. Fentanyl (0.00178-0.0178mg/kg) and nalbuphine (0.01-0.32mg/kg) dose-dependently increased drug-lever responding. Neither Δ(9)-THC (0.032-1.0mg/kg) nor CP55940 (0.0032-0.032mg/kg) enhanced the discriminative stimulus effects of fentanyl or nalbuphine; however, doses of Δ(9)-THC and CP55940 that shifted the nalbuphine dose-effect curve markedly to the right and/or down were less effective or ineffective in shifting the fentanyl dose-effect curve. The mu opioid receptor antagonist naltrexone (0.032mg/kg) attenuated the discriminative stimulus effects of fentanyl and nalbuphine similarly. These data indicate that the discriminative stimulus effects of nalbuphine are more sensitive to attenuation by cannabinoids than those of fentanyl. That the discriminative stimulus effects of some opioids are more susceptible to modification by drugs from other classes has implications for developing maximally effective therapeutic drug mixtures with reduced abuse liability. PMID:27184925

  15. Estrogen receptor beta agonists in neurobehavioral investigations.

    PubMed

    Choleris, Elena; Clipperton, Amy E; Phan, Anna; Kavaliers, Martin

    2008-07-01

    Neurobehavioral investigations into the functions of estrogen receptor (ER)alpha and ERbeta have utilized 'knockout' mice, phytoestrogens and, more recently, ER-specific agonists. Feeding, sexual, aggressive and social behavior, anxiety, depression, drug abuse, pain perception, and learning (and associated synaptic plasticity) are affected by ERalpha and ERbeta in a manner that is dependent upon the specific behavior studied, gender and developmental stage. Overall, ERalpha and ERbeta appear to function together to foster sociosexual behavior while inhibiting behaviors that, if occurring at the time of behavioral estrous, may compete with reproduction (eg, feeding). Recently developed pharmacological tools have limited selectivity and availability to the research community at large, as they are not commercially available. The development of highly selective, commercially available ERbeta-specific antagonists would greatly benefit preclinical and applied research. PMID:18600582

  16. Non-Benzodiazepine Receptor Agonists for Insomnia.

    PubMed

    Becker, Philip M; Somiah, Manya

    2015-03-01

    Because of proven efficacy, reduced side effects, and less concern about addiction, non-benzodiazepine receptor agonists (non-BzRA) have become the most commonly prescribed hypnotic agents to treat onset and maintenance insomnia. First-line treatment is cognitive-behavioral therapy. When pharmacologic treatment is indicated, non-BzRA are first-line agents for the short-term and long-term management of transient and chronic insomnia related to adjustment, psychophysiologic, primary, and secondary causation. In this article, the benefits and risks of non-BzRA are reviewed, and the selection of a hypnotic agent is defined, based on efficacy, pharmacologic profile, and adverse events. PMID:26055674

  17. Mechanisms of the adenosine A2A receptor-induced sensitization of esophageal C fibers.

    PubMed

    Brozmanova, M; Mazurova, L; Ru, F; Tatar, M; Hu, Y; Yu, S; Kollarik, M

    2016-02-01

    Clinical studies indicate that adenosine contributes to esophageal mechanical hypersensitivity in some patients with pain originating in the esophagus. We have previously reported that the esophageal vagal nodose C fibers express the adenosine A2A receptor. Here we addressed the hypothesis that stimulation of the adenosine A2A receptor induces mechanical sensitization of esophageal C fibers by a mechanism involving transient receptor potential A1 (TRPA1). Extracellular single fiber recordings of activity originating in C-fiber terminals were made in the ex vivo vagally innervated guinea pig esophagus. The adenosine A2A receptor-selective agonist CGS21680 induced robust, reversible sensitization of the response to esophageal distention (10-60 mmHg) in a concentration-dependent fashion (1-100 nM). At the half-maximally effective concentration (EC50: ≈3 nM), CGS21680 induced an approximately twofold increase in the mechanical response without causing an overt activation. This sensitization was abolished by the selective A2A antagonist SCH58261. The adenylyl cyclase activator forskolin mimicked while the nonselective protein kinase inhibitor H89 inhibited mechanical sensitization by CGS21680. CGS21680 did not enhance the response to the purinergic P2X receptor agonist α,β-methylene-ATP, indicating that CGS21680 does not nonspecifically sensitize to all stimuli. Mechanical sensitization by CGS21680 was abolished by pretreatment with two structurally different TRPA1 antagonists AP18 and HC030031. Single cell RT-PCR and whole cell patch-clamp studies in isolated esophagus-specific nodose neurons revealed the expression of TRPA1 in A2A-positive C-fiber neurons and demonstrated that CGS21682 potentiated TRPA1 currents evoked by allylisothiocyanate. We conclude that stimulation of the adenosine A2A receptor induces mechanical sensitization of nodose C fibers by a mechanism sensitive to TRPA1 antagonists indicating the involvement of TRPA1. PMID:26564719

  18. Adenosine receptor agonists attenuate and adenosine receptor antagonists exacerbate opiate withdrawal signs.

    PubMed

    Kaplan, G B; Sears, M T

    1996-01-01

    Previous studies have demonstrated a role for adenosine in mediating opiate effects. Adenosine receptors and their functions have been shown to be regulated by chronic opiate treatment. This study examines the role of adenosine receptors in the expression of opiate withdrawal behaviors. The effects of single doses of parenterally administered adenosine receptor subtype-selective agonists and antagonists on opiate withdrawal signs in morphine-dependent mice were measured. Mice received subcutaneous morphine pellet treatment for 72 h and then underwent naloxone-precipitated withdrawal after pretreatment with adenosinergic agents. Adenosine agonists attenuated different opiate withdrawal signs. The A1 agonist R-N6(phenylisopropyl)adenosine (0, 0.01, 0.02 mg/kg, IP) significantly reduced wet dog shakes and withdrawal diarrhea, while the A2a-selective agonist 2-p-(2-carboxethyl)phenylethylamino-5'-N-ethylcarboxamido adenosine or CGS 21680 (0, 0.01, 0.05 mg/kg, IP) significantly inhibited teeth chattering and forepaw treads. Adenosine receptor antagonists enhanced different opiate withdrawal signs. The adenosine A1 antagonist 1,3-dipropyl-8-cyclopentylxanthine (0, 1, 10 mg/kg, IP) significantly increased weight loss and the A2 antagonist, 3,7-dimethyl-1-propargylxanthine (0, 1 and 10 mg/kg, IP) enhanced wet dog shakes and withdrawal diarrhea. Treatment effects of adenosinergic agents were not due to nonspecific motor effects, as demonstrated by activity monitoring studies. These results support a role for adenosine receptors in the expression of opiate withdrawal and suggest the potential utility of adenosine agonists in its treatment. PMID:8741956

  19. Allosteric mechanisms within the adenosine A2A-dopamine D2 receptor heterotetramer.

    PubMed

    Ferré, Sergi; Bonaventura, Jordi; Tomasi, Dardo; Navarro, Gemma; Moreno, Estefanía; Cortés, Antonio; Lluís, Carme; Casadó, Vicent; Volkow, Nora D

    2016-05-01

    The structure constituted by a G protein coupled receptor (GPCR) homodimer and a G protein provides a main functional unit and oligomeric entities can be viewed as multiples of dimers. For GPCR heteromers, experimental evidence supports a tetrameric structure, comprised of two different homodimers, each able to signal with its preferred G protein. GPCR homomers and heteromers can act as the conduit of allosteric interactions between orthosteric ligands. The well-known agonist/agonist allosteric interaction in the adenosine A2A receptor (A2AR)-dopamine D2 receptor (D2R) heteromer, by which A2AR agonists decrease the affinity of D2R agonists, gave the first rationale for the use of A2AR antagonists in Parkinson's disease. We review new pharmacological findings that can be explained in the frame of a tetrameric structure of the A2AR-D2R heteromer: first, ligand-independent allosteric modulations by the D2R that result in changes of the binding properties of A2AR ligands; second, differential modulation of the intrinsic efficacy of D2R ligands for G protein-dependent and independent signaling; third, the canonical antagonistic Gs-Gi interaction within the frame of the heteromer; and fourth, the ability of A2AR antagonists, including caffeine, to also exert the same allosteric modulations of D2R ligands than A2AR agonists, while A2AR agonists and antagonists counteract each other's effects. These findings can have important clinical implications when evaluating the use of A2AR antagonists. They also call for the need of monitoring caffeine intake when evaluating the effect of D2R ligands, when used as therapeutic agents in neuropsychiatric disorders or as probes in imaging studies. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'. PMID:26051403

  20. The Role of The A2A Receptor in Cell Apoptosis Caused by MDMA

    PubMed Central

    Soleimani, Mansooreh; Katebi, Majid; Alizadeh, Akram; Mohammadzadeh, Farzaneh; Mehdizadeh, Mehdi

    2012-01-01

    Objective: Ecstasy, also known as 3, 4-methylenedioxymethamphetamine (MDMA), is a psychoactive recreational hallucinogenic substance and a major worldwide recreational drug. There are neurotoxic effects observed in laboratory animals and humans following MDMA use. MDMA causes apoptosis in neurons of the central nervous system (CNS). Withdrawal signs are attenuated by treatment with the adenosine receptor (A2A receptor). This study reports the effects of glutamyl cysteine synthetase (GCS), as an A2A receptor agonist, and succinylcholine (SCH), as an A2A receptor antagonist, on Sprague Dawley rats, both in the presence and absence of MDMA. Materials and Methods: In this experimental study, we used seven groups of Sprague Dawley rats (200-250 g each). Each group was treated with daily intraperitoneal (IP) injections for a period of one week, as follows: i. MDMA (10 mg/kg); ii. GCS (0.3 mg/kg); iii. SCH (0.3 mg/kg); iv. GCS + SCH (0.3 mg/kg each); v. MDMA (10 mg/kg) + GCS (0.3 mg/kg); vi. MDMA (10 mg/kg) + SCH (0.3 mg/kg); and vi. normal saline (1 cc/kg) as the sham group. Bax (apoptotic protein) and Bcl-2 (anti-apoptotic protein) expressions were evaluated by striatum using RT-PCR and Western blot analysis. Results: There was a significant increase in Bax protein expression in the MDMA+SCH group and a significant decrease in Bcl-2 protein expression in the MDMA+SCH group (p<0.05). Conclusion: A2A receptors have a role in the apoptotic effects of MDMA via the Bax and Bcl-2 pathways. An agonist of this receptor (GCS) decreases the cytotoxcity of MDMA, while the antagonist of this receptor (SCH) increases its cytotoxcity. PMID:23508639

  1. Role of adenosine A1 and A2A receptors in the alcohol withdrawal syndrome.

    PubMed

    Kaplan, G B; Bharmal, N H; Leite-Morris, K A; Adams, W R

    1999-10-01

    The role of adenosine receptor-mediated signaling was examined in the alcohol withdrawal syndrome. CD-1 mice received a liquid diet containing ethanol (6.7%, v/v) or a control liquid diet that were abruptly discontinued after 14 days of treatment. Mice consuming ethanol showed a progressive increase in signs of intoxication throughout the drinking period. Following abrupt discontinuation of ethanol diet, mice demonstrated reversible signs of handling-induced hyperexcitability that were maximal between 5-8 h. Withdrawing mice received treatment with adenosine receptor agonists at the onset of peak withdrawal (5.5 h) and withdrawal signs were blindly rated (during withdrawal hours 6 and 7). Adenosine A1-receptor agonist R-N6(phenylisopropyl)adenosine (0.15 and 0.3 mg/ kg) reduced withdrawal signs 0.5 and 1.5 h after drug administration in a dose-dependent fashion. Adenosine A2A-selective agonist 2-p-(2-carboxyethyl)phenylethyl-amino-5'-N-ethylcarboxamidoadenosine (0.3 mg/kg) reduced withdrawal signs at both time points. In ethanol-withdrawing mice, there were significant decreases in adenosine transporter sites in striatum without changes in cortex or cerebellum. In ethanol-withdrawing mice, there were no changes in adenosine A1 and A2A receptor concentrations in cortex, striatum, or cerebellum. There appears to be a role for adenosine A1 and A2A receptors in the treatment of the ethanol withdrawal syndrome. Published by Elsevier Science Inc. PMID:10548160

  2. Agonist pharmacology of two Drosophila GABA receptor splice variants.

    PubMed Central

    Hosie, A. M.; Sattelle, D. B.

    1996-01-01

    1. The Drosophila melanogaster gamma-aminobutyric acid (GABA) receptor subunits, RDLac and DRC 17-1-2, form functional homo-oligomeric receptors when heterologously expressed in Xenopus laevis oocytes. The subunits differ in only 17 amino acids, principally in regions of the N-terminal domain which determine agonist pharmacology in vertebrate ionotropic neurotransmitter receptors. A range of conformationally restricted GABA analogues were tested on the two homo-oligomers and their agonists pharmacology compared with that of insect and vertebrate iontropic GABA receptors. 2. The actions of GABA, isoguvacine and isonipecotic acid on RDLac and DRC 17-1-2 homo-oligomers were compared, by use of two-electrode voltage-clamp. All three compounds were full agonists of both receptors, but were 4-6 fold less potent agonists of DRC 17-1-2 homo-oligomers than of RDLac. However, the relative potencies of these agonists on each receptor were very similar. 3. A more complete agonist profile was established for RDLac homo-oligomers. The most potent agonists of these receptors were GABA, muscimol and trans-aminocrotonic acid (TACA), which were approximately equipotent. RDLac homo-oligomers were fully activated by a range of GABA analogues, with the order of potency: GABA > ZAPA ((Z)-3-[(aminoiminomethyl)thio]prop-2-enoic acid) > isoguvacine > imidazole-4-acetic acid > or = isonipecotic acid > or = cis-aminocrotonic acid (CACA) > beta-alanine. 3-Aminopropane sulphonic acid (3-APS), a partial agonist of RDLac homo-oligomers, was the weakest agonist tested and 100 fold less potent than GABA. 4. SR95531, an antagonist of vertebrate GABAA receptors, competitively inhibited the GABA responses of RDLac homo-oligomers, which have previously been found to insensitive to bicuculline. However, its potency (IC50 500 microM) was much reduced when compared to GABAA receptors. 5. The agonist pharmacology of Drosophila RDLac homo-oligomers exhibits aspects of the characteristic pharmacology of

  3. Preladenant, a selective A(2A) receptor antagonist, is active in primate models of movement disorders.

    PubMed

    Hodgson, Robert A; Bedard, Paul J; Varty, Geoffrey B; Kazdoba, Tatiana M; Di Paolo, Therese; Grzelak, Michael E; Pond, Annamarie J; Hadjtahar, Abdallah; Belanger, Nancy; Gregoire, Laurent; Dare, Aurelie; Neustadt, Bernard R; Stamford, Andrew W; Hunter, John C

    2010-10-01

    Parkinson's Disease (PD) and Extrapyramidal Syndrome (EPS) are movement disorders that result from degeneration of the dopaminergic input to the striatum and chronic inhibition of striatal dopamine D(2) receptors by antipsychotics, respectively. Adenosine A(2A) receptors are selectively localized in the basal ganglia, primarily in the striatopallidal ("indirect") pathway, where they appear to operate in concert with D(2) receptors and have been suggested to drive striatopallidal output balance. In cases of dopaminergic hypofunction, A(2A) receptor activation contributes to the overdrive of the indirect pathway. A(2A) receptor antagonists, therefore, have the potential to restore this inhibitor imbalance. Consequently, A(2A) receptor antagonists have therapeutic potential in diseases of dopaminergic hypofunction such as PD and EPS. Targeting the A(2A) receptor may also be a way to avoid the issues associated with direct dopamine agonists. Recently, preladenant was identified as a potent and highly selective A(2A) receptor antagonist, and has produced a significant improvement in motor function in rodent models of PD. Here we investigate the effects of preladenant in two primate movement disorder models. In MPTP-treated cynomolgus monkeys, preladenant (1 or 3 mg/kg; PO) improved motor ability and did not evoke any dopaminergic-mediated dyskinetic or motor complications. In Cebus apella monkeys with a history of chronic haloperidol treatment, preladenant (0.3-3.0 mg/kg; PO) delayed the onset of EPS symptoms evoked by an acute haloperidol challenge. Collectively, these data support the use of preladenant for the treatment of PD and antipsychotic-induced movement disorders. PMID:20655910

  4. Identification of A3 adenosine receptor agonists as novel non-narcotic analgesics.

    PubMed

    Janes, K; Symons-Liguori, A M; Jacobson, K A; Salvemini, D

    2016-04-01

    Chronic pain negatively impacts the quality of life in a variety of patient populations. The current therapeutic repertoire is inadequate in managing patient pain and warrants the development of new therapeutics. Adenosine and its four cognate receptors (A1 , A2A , A2B and A3 ) have important roles in physiological and pathophysiological states, including chronic pain. Preclinical and clinical studies have revealed that while adenosine and agonists of the A1 and A2A receptors have antinociceptive properties, their therapeutic utility is limited by adverse cardiovascular side effects. In contrast, our understanding of the A3 receptor is only in its infancy, but exciting preclinical observations of A3 receptor antinociception, which have been bolstered by clinical trials of A3 receptor agonists in other disease states, suggest pain relief without cardiovascular side effects and with sufficient tolerability. Our goal herein is to briefly discuss adenosine and its receptors in the context of pathological pain and to consider the current data regarding A3 receptor-mediated antinociception. We will highlight recent findings regarding the impact of the A3 receptor on pain pathways and examine the current state of selective A3 receptor agonists used for these studies. The adenosine-to-A3 receptor pathway represents an important endogenous system that can be targeted to provide safe, effective pain relief from chronic pain. PMID:26804983

  5. [Effects of GLP-1 receptor agonists on carbohydrate metabolism control].

    PubMed

    Fernández-García, José Carlos; Colomo, Natalia; Tinahones, Francisco José

    2014-01-01

    Glucagon-like peptide-1 (GLP-1) receptor agonists are a new group of drugs for the treatment of type 2 diabetes mellitus (DM2). In the present article, we review the available evidence on the efficacy of GLP-1 receptor agonists as glucose-lowering agents, their place in therapeutic algorithms, and the clinical factors associated with a favorable treatment response. Finally, we describe the clinical characteristics of patients who may benefit from these drugs. PMID:25326839

  6. [Effects of GLP-1 receptor agonists on carbohydrate metabolism control].

    PubMed

    Fernández-García, José Carlos; Colomo, Natalia; Tinahones, Francisco José

    2014-09-01

    Glucagon-like peptide-1 (GLP-1) receptor agonists are a new group of drugs for the treatment of type 2 diabetes mellitus (DM2). In the present article, we review the available evidence on the efficacy of GLP-1 receptor agonists as glucose-lowering agents, their place in therapeutic algorithms, and the clinical factors associated with a favorable treatment response. Finally, we describe the clinical characteristics of patients who may benefit from these drugs. PMID:25437461

  7. NTS adenosine A2a receptors inhibit the cardiopulmonary chemoreflex control of regional sympathetic outputs via a GABAergic mechanism.

    PubMed

    Minic, Zeljka; O'Leary, Donal S; Scislo, Tadeusz J

    2015-07-01

    Adenosine is a powerful central neuromodulator acting via opposing A1 (inhibitor) and A2a (activator) receptors. However, in the nucleus of the solitary tract (NTS), both adenosine receptor subtypes attenuate cardiopulmonary chemoreflex (CCR) sympathoinhibition of renal, adrenal, and lumbar sympathetic nerve activity and attenuate reflex decreases in arterial pressure and heart rate. Adenosine A1 receptors inhibit glutamatergic transmission in the CCR pathway, whereas adenosine A2a receptors most likely facilitate release of an unknown inhibitory neurotransmitter, which, in turn, inhibits the CCR. We hypothesized that adenosine A2a receptors inhibit the CCR via facilitation of GABA release in the NTS. In urethane-chloralose-anesthetized rats (n = 51), we compared regional sympathetic responses evoked by stimulation of the CCR with right atrial injections of the 5-HT3 receptor agonist phenylbiguanide (1-8 μg/kg) before and after selective stimulation of NTS adenosine A2a receptors [microinjections into the NTS of CGS-21680 (20 pmol/50 nl)] preceded by blockade of GABAA or GABAB receptors in the NTS [bicuculline (10 pmol/100 nl) or SCH-50911 (1 nmol/100 nl)]. Blockade of GABAA receptors virtually abolished adenosine A2a receptor-mediated inhibition of the CCR. GABAB receptors had much weaker but significant effects. These effects were similar for the different sympathetic outputs. We conclude that stimulation of NTS adenosine A2a receptors inhibits CCR-evoked hemodynamic and regional sympathetic reflex responses via a GABA-ergic mechanism. PMID:25910812

  8. Anti-nociception mediated by a κ opioid receptor agonist is blocked by a δ receptor agonist

    PubMed Central

    Taylor, A M W; Roberts, K W; Pradhan, A A; Akbari, H A; Walwyn, W; Lutfy, K; Carroll, F I; Cahill, C M; Evans, C J

    2015-01-01

    BACKGROUND AND PURPOSE The opioid receptor family comprises four structurally homologous but functionally distinct sub-groups, the μ (MOP), δ (DOP), κ (KOP) and nociceptin (NOP) receptors. As most opioid agonists are selective but not specific, a broad spectrum of behaviours due to activation of different opioid receptors is expected. In this study, we examine whether other opioid receptor systems influenced KOP-mediated antinociception. EXPERIMENTAL APPROACH We used a tail withdrawal assay in C57Bl/6 mice to assay the antinociceptive effect of systemically administered opioid agonists with varying selectivity at KOP receptors. Pharmacological and genetic approaches were used to analyse the interactions of the other opioid receptors in modulating KOP-mediated antinociception. KEY RESULTS Etorphine, a potent agonist at all four opioid receptors, was not anti-nociceptive in MOP knockout (KO) mice, although etorphine is an efficacious KOP receptor agonist and specific KOP receptor agonists remain analgesic in MOP KO mice. As KOP receptor agonists are aversive, we considered KOP-mediated antinociception might be a form of stress-induced analgesia that is blocked by the anxiolytic effects of DOP receptor agonists. In support of this hypothesis, pretreatment with the DOP antagonist, naltrindole (10 mg·kg−1), unmasked etorphine (3 mg·kg−1) antinociception in MOP KO mice. Further, in wild-type mice, KOP-mediated antinociception by systemic U50,488H (10 mg·kg−1) was blocked by pretreatment with the DOP agonist SNC80 (5 mg·kg−1) and diazepam (1 mg·kg−1). CONCLUSIONS AND IMPLICATIONS Systemic DOP receptor agonists blocked systemic KOP antinociception, and these results identify DOP receptor agonists as potential agents for reversing stress-driven addictive and depressive behaviours mediated through KOP receptor activation. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles

  9. [Adenosine A2A receptor as a drug target for treatment of sepsis].

    PubMed

    Sivak, K V; Vasin, A V; Egorov, V V; Tsevtkov, V B; Kuzmich, N N; Savina, V A; Kiselev, O I

    2016-01-01

    Sepsis is a generalized infection accompanied by response of the body that manifests in a clinical and laboratory syndrome, namely, in the systemic inflammatory response syndrome (SIRS) from the organism to the infection. Although sepsis is a widespread and life-threatening disease, the assortment of drugs for its treatment is mostly limited by antibiotics. Therefore, the search for new cellular targets for drug therapy of sepsis is an urgent task of modern medicine and pharmacology. One of the most promising targets is the adenosine A(2A) receptor (A(2A)AR). The activation of this receptor, which is mediated by extracellular adenosine, manifests in almost all types of immune cells (lymphocytes, monocytes, macrophages, and dendritic cells) and results in reducing the severity of inflammation and reperfusion injury in various tissues. The activation of adenosine A(2A) receptor inhibits the proliferation of T cells and production of proinflammatory cytokines, which contributes to the activation of the synthesis of anti-inflammatory cytokines, thereby suppressing the systemic response. For this reason, various selective A(2A)AR agonists and antagonists may be considered to be drug candidates for sepsis pharmacotherapy. Nevertheless, they remain only efficient ligands and objects of pre-clinical and clinical trials. This review examines the molecular mechanisms of inflammatory response in sepsis and the structure and functions of A(2A)AR and its role in the pathogenesis of sepsis, as well as examples of using agonists and antagonists of this receptor for the treatment of SIRS and sepsis. PMID:27239843

  10. The cardiovascular effects of peroxisome proliferator-activated receptor agonists.

    PubMed

    Friedland, Sayuri N; Leong, Aaron; Filion, Kristian B; Genest, Jacques; Lega, Iliana C; Mottillo, Salvatore; Poirier, Paul; Reoch, Jennifer; Eisenberg, Mark J

    2012-02-01

    Although peroxisome proliferator-activated receptor agonists are prescribed to improve cardiovascular risk factors, their cardiovascular safety is controversial. We therefore reviewed the literature to identify landmark randomized controlled trials evaluating the effect of peroxisome proliferator-activated receptor gamma agonists (pioglitazone and rosiglitazone), alpha agonists (fenofibrate and gemfibrozil), and pan agonists (bezafibrate, muraglitazar, ragaglitazar, tesaglitazar, and aleglitazar) on cardiovascular outcomes. Pioglitazone may modestly reduce cardiovascular events but also may increase the risk of bladder cancer. Rosiglitazone increases the risk of myocardial infarction and has been withdrawn in European and restricted in the United States. Fibrates improve cardiovascular outcomes only in select subgroups: fenofibrate in diabetic patients with metabolic syndrome, gemfibrozil in patients with dyslipidemia, and bezafibrate in patients with diabetes or metabolic syndrome. The cardiovascular safety of the new pan agonist aleglitazar, currently in phase II trials, remains to be determined. The heterogenous effects of peroxisome proliferator-activated receptor agonists to date highlight the importance of postmarketing surveillance. The critical question of why peroxisome proliferator-activated receptor agonists seem to improve cardiovascular risk factors without significantly improving cardiovascular outcomes requires further investigation. PMID:22269613

  11. Mechanisms of inverse agonist action at D2 dopamine receptors.

    PubMed

    Roberts, David J; Strange, Philip G

    2005-05-01

    Mechanisms of inverse agonist action at the D2(short) dopamine receptor have been examined. Discrimination of G-protein-coupled and -uncoupled forms of the receptor by inverse agonists was examined in competition ligand-binding studies versus the agonist [3H]NPA at a concentration labelling both G-protein-coupled and -uncoupled receptors. Competition of inverse agonists versus [3H]NPA gave data that were fitted best by a two-binding site model in the absence of GTP but by a one-binding site model in the presence of GTP. K(i) values were derived from the competition data for binding of the inverse agonists to G-protein-uncoupled and -coupled receptors. K(coupled) and K(uncoupled) were statistically different for the set of compounds tested (ANOVA) but the individual values were different in a post hoc test only for (+)-butaclamol. These observations were supported by simulations of these competition experiments according to the extended ternary complex model. Inverse agonist efficacy of the ligands was assessed from their ability to reduce agonist-independent [35S]GTP gamma S binding to varying degrees in concentration-response curves. Inverse agonism by (+)-butaclamol and spiperone occurred at higher potency when GDP was added to assays, whereas the potency of (-)-sulpiride was unaffected. These data show that some inverse agonists ((+)-butaclamol, spiperone) achieve inverse agonism by stabilising the uncoupled form of the receptor at the expense of the coupled form. For other compounds tested, we were unable to define the mechanism. PMID:15735658

  12. Mechanisms of agonist action at D2 dopamine receptors.

    PubMed

    Roberts, David J; Lin, Hong; Strange, Philip G

    2004-12-01

    In this study, we investigated the biochemical mechanisms of agonist action at the G protein-coupled D2 dopamine receptor expressed in Chinese hamster ovary cells. Stimulation of guanosine 5'-O-(3-[35S]thio)triphosphate ([35S]GTPgammaS) binding by full and partial agonists was determined at different concentrations of [35S]GTPgammaS (0.1 and 10 nM) and in the presence of different concentrations of GDP. At both concentrations of [35S]GTPgammaS, increasing GDP decreased the [35S]GTPgammaS binding observed with maximally stimulating concentrations of agonist, with partial agonists exhibiting greater sensitivity to the effects of GDP than full agonists. The relative efficacy of partial agonists was greater at the lower GDP concentrations. Concentration-response experiments were performed for a range of agonists at the two [35S]GTPgammaS concentrations and with different concentrations of GDP. At 0.1 nM [35S]GTPgammaS, the potency of both full and partial agonists was dependent on the GDP concentration in the assays. At 10 nM [35S]GTPgammaS, the potency of full agonists exhibited a greater dependence on the GDP concentration, whereas the potency of partial agonists was virtually independent of GDP. We concluded that at the lower [35S]GTPgammaS concentration, the rate-determining step in G protein activation is the binding of [35S]GTPgammaS to the G protein. At the higher [35S]GTPgammaS concentration, for full agonists, [35S]GTPgammaS binding remains the slowest step, whereas for partial agonists, another (GDP-independent) step, probably ternary complex breakdown, becomes rate-determining. PMID:15340043

  13. Therapeutic Potential of 5-HT6 Receptor Agonists.

    PubMed

    Karila, Delphine; Freret, Thomas; Bouet, Valentine; Boulouard, Michel; Dallemagne, Patrick; Rochais, Christophe

    2015-10-22

    Given its predominant expression in the central nervous system (CNS), 5-hydroxytryptamine (5-HT: serotonin) subtype 6 receptor (5-HT6R) has been considered as a valuable target for the development of CNS drugs with limited side effects. After 2 decades of intense research, numerous selective ligands have been developed to target this receptor; this holds potential interest for the treatment of neuropathological disorders. In fact, some agents (mainly antagonists) are currently undergoing clinical trial. More recently, a series of potent and selective agonists have been developed, and preclinical studies have been conducted that suggest the therapeutic interest of 5-HT6R agonists. This review details the medicinal chemistry of these agonists, highlights their activities, and discusses their potential for treating cognitive issues associated with Alzheimer's disease (AD), depression, or obesity. Surprisingly, some studies have shown that both 5-HT6R agonists and antagonists exert similar procognitive activities. This article summarizes the hypotheses that could explain this paradox. PMID:26099069

  14. Clinical/pharmacological aspect of adenosine A2A receptor antagonist for dyskinesia.

    PubMed

    Kanda, Tomoyuki; Uchida, Shin-ichi

    2014-01-01

    Dopamine replacement therapy using the dopamine precursor, l-3,4-dihydroxyphenylalanine (l-DOPA), with a peripheral dopa decarboxylase inhibitor is the most effective treatment currently available for the symptoms of Parkinson's disease (PD). However, the long-term use of dopaminergic therapies for PD is often limited by the development of motor response complications, such as dyskinesia. Adenosine A2A receptors are a promising nondopaminergic target for the treatment of PD. The treatment of motor response complications involves combinations of regular and controlled release L-DOPA, perhaps with the addition of a COMT inhibitor or the use of a longer-acting dopamine agonist. However, when dyskinesia is already established, the increase in dopaminergic load produced by the addition of a dopamine agonist can result in an increase in the severity and duration of dyskinesia. Currently, there are no well-tolerated antidyskinesia agents available. Amantadine, which may exert its effects through the inhibition of N-methyl-D-aspartate (NMDA) receptors, shows some effects on established dyskinesia. Dyskinesia has a negative impact on the quality of life of patients, sometimes being more disabling than PD itself. Although some patients prefer experiencing dyskinesia than being in the OFF state and unable to move, alternative, more effective therapies are still required for severe disabling dyskinesia to afford patients an improved quality of life while in the ON state. The mechanisms causing and maintaining the dyskinesia have not been clarified. The application of a nondopaminergic approach to modify the basal ganglial activity would be helpful to better understand and treat dyskinesia. The use of an adenosine A2A receptor may provide one such approach. In this literature review, we will summarize the current knowledge from both clinical and nonclinical studies on the effects of adenosine A2A receptor blockade on dyskinesia. PMID:25175964

  15. [PPAR receptors and insulin sensitivity: new agonists in development].

    PubMed

    Pégorier, J-P

    2005-04-01

    Thiazolidinediones (or glitazones) are synthetic PPARgamma (Peroxisome Proliferator-Activated Receptors gamma) ligands with well recognized effects on glucose and lipid metabolism. The clinical use of these PPARgamma agonists in type 2 diabetic patients leads to an improved glycemic control and an inhanced insulin sensitivity, and at least in animal models, to a protective effect on pancreatic beta-cell function. However, they can produce adverse effects, generally mild or moderate, but some of them (mainly peripheral edema and weight gain) may conduct to treatment cessation. Several pharmacological classes are currently in pre-clinical or clinical development, with the objective to retain the beneficial metabolic properties of PPARgamma agonists, either alone or in association with the PPARalpha agonists (fibrates) benefit on lipid profile, but devoid of the side-effects on weight gain and fluid retention. These new pharmacological classes: partial PPARgamma agonists, PPARgamma antagonists, dual PPARalpha/PPARgamma agonists, pan PPARalpha/beta(delta)/gamma agonists, RXR receptor agonists (rexinoids), are presented in this review. Main results from in vitro cell experiments and animal model studies are discussed, as well as the few published short-term studies in type 2 diabetic patients. PMID:15959400

  16. Principles of agonist recognition in Cys-loop receptors

    PubMed Central

    Lynagh, Timothy; Pless, Stephan A.

    2014-01-01

    Cys-loop receptors are ligand-gated ion channels that are activated by a structurally diverse array of neurotransmitters, including acetylcholine, serotonin, glycine, and GABA. After the term “chemoreceptor” emerged over 100 years ago, there was some wait until affinity labeling, molecular cloning, functional studies, and X-ray crystallography experiments identified the extracellular interface of adjacent subunits as the principal site of agonist binding. The question of how subtle differences at and around agonist-binding sites of different Cys-loop receptors can accommodate transmitters as chemically diverse as glycine and serotonin has been subject to intense research over the last three decades. This review outlines the functional diversity and current structural understanding of agonist-binding sites, including those of invertebrate Cys-loop receptors. Together, this provides a framework to understand the atomic determinants involved in how these valuable therapeutic targets recognize and bind their ligands. PMID:24795655

  17. Piperidine derivatives as nonprostanoid IP receptor agonists 2.

    PubMed

    Hayashi, Ryoji; Ito, Hiroaki; Ishigaki, Takeshi; Morita, Yasuhiro; Miyamoto, Mitsuko; Isogaya, Masafumi

    2016-06-15

    We searched for a strong and selective nonprostanoid IP agonist bearing piperidine and benzanilide moieties. Through optimization of substituents on the benzanilide moiety, the crucial part of the agonist, 43 (2-((1-(2-(N-(4-tolyl)benzo[d][1,3]dioxole-5-carboxamido)ethyl)piperidin-4-yl)oxy)acetic acid monohydrate monohydrochloride) was discovered and exhibited strong platelet aggregation inhibition (IC50=21nM) and 100-fold selectivity for IP receptor over other PG receptors. The systemic exposure level and bioavailability after oral administration of 43 were also good in dog. PMID:27133594

  18. Adenosine A2A Receptor Activation Prevents Wear Particle-Induced Osteolysis

    PubMed Central

    Mediero, Aránzazu; Frenkel, Sally R.; Wilder, Tuere; He, Wenjie; Mazumder, Amitabha; Cronstein, Bruce N.

    2012-01-01

    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 A2A receptors (A2AR) mediate potent anti-inflammatory effects in many tissues and prevent osteoclast differentiation. We tested the hypothesis that an A2AR agonist could reduce osteoclast-mediated bone resorption in a murine calvaria model of wear-particle–induced bone resorption. C57Bl/6 and A2A knockout (A2ARKO) mice received ultrahigh-molecular weight polyethylene particles (UHMWPE) and were treated daily with either saline or the A2AR 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 A2AKO mice, CGS21680 did not affect osteoclast-mediated bone resorption or inflammation. Levels of bone-resorption markers receptor activator of nuclear factor-kB (RANK), RANK ligand (RANKL), cathepsin K, CD163, and osteopontin were reduced following CGS21680 treatment, together with a reduction in osteoclasts. Secretion of interleukin 1β (IL-1β) and TNFα 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 A2AR agonist could enhance implant survival, delaying or eliminating the need for revision arthroplastic surgery. PMID:22623741

  19. 2-Triazole-Substituted Adenosines: A New Class of Selective A3 Adenosine Receptor Agonists, Partial Agonists, and Antagonists

    PubMed Central

    Cosyn, Liesbet; Palaniappan, Krishnan K.; Kim, Soo-Kyung; Duong, Heng T.; Gao, Zhan-Guo; Jacobson, Kenneth A.; Van Calenbergh, Serge

    2016-01-01

    “Click chemistry” was explored to synthesize two series of 2-(1,2,3-triazolyl)adenosine derivatives (1–14). Binding affinity at the human A1, A2A, and A3ARs (adenosine receptors) and relative efficacy at the A3AR were determined. Some triazol-1-yl analogues showed A3AR affinity in the low nanomolar range, a high ratio of A3/A2A selectivity, and a moderate-to-high A3/A1 ratio. The 1,2,3-triazol-4-yl regiomers typically showed decreased A3AR affinity. Sterically demanding groups at the adenine C2 position tended to reduce relative A3AR efficacy. Thus, several 5′-OH derivatives appeared to be selective A3AR antagonists, i.e., 10, with 260-fold binding selectivity in comparison to the A1AR and displaying a characteristic docking mode in an A3AR model. The corresponding 5′-ethyluronamide analogues generally showed increased A3AR affinity and behaved as full agonists, i.e., 17, with 910-fold A3/A1 selectivity. Thus, N6-substituted 2-(1,2,3-triazolyl)-adenosine analogues constitute a novel class of highly potent and selective nucleoside-based A3AR antagonists, partial agonists, and agonists. PMID:17149867

  20. Emerging strategies for exploiting cannabinoid receptor agonists as medicines.

    PubMed

    Pertwee, Roger G

    2009-02-01

    Medicines that activate cannabinoid CB(1) and CB(2) receptor are already in the clinic. These are Cesamet (nabilone), Marinol (dronabinol; Delta(9)-tetrahydrocannabinol) and Sativex (Delta(9)-tetrahydrocannabinol with cannabidiol). The first two of these medicines can be prescribed to reduce chemotherapy-induced nausea and vomiting. Marinol can also be prescribed to stimulate appetite, while Sativex is prescribed for the symptomatic relief of neuropathic pain in adults with multiple sclerosis and as an adjunctive analgesic treatment for adult patients with advanced cancer. One challenge now is to identify additional therapeutic targets for cannabinoid receptor agonists, and a number of potential clinical applications for such agonists are mentioned in this review. A second challenge is to develop strategies that will improve the efficacy and/or the benefit-to-risk ratio of a cannabinoid receptor agonist. This review focuses on five strategies that have the potential to meet either or both of these objectives. These are strategies that involve: (i) targeting cannabinoid receptors located outside the blood-brain barrier; (ii) targeting cannabinoid receptors expressed by a particular tissue; (iii) targeting up-regulated cannabinoid receptors; (iv) targeting cannabinoid CB(2) receptors; or (v) 'multi-targeting'. Preclinical data that justify additional research directed at evaluating the clinical importance of each of these strategies are also discussed. PMID:19226257

  1. Emerging strategies for exploiting cannabinoid receptor agonists as medicines

    PubMed Central

    Pertwee, Roger G

    2009-01-01

    Medicines that activate cannabinoid CB1 and CB2 receptor are already in the clinic. These are Cesamet® (nabilone), Marinol® (dronabinol; Δ9-tetrahydrocannabinol) and Sativex® (Δ9-tetrahydrocannabinol with cannabidiol). The first two of these medicines can be prescribed to reduce chemotherapy-induced nausea and vomiting. Marinol® can also be prescribed to stimulate appetite, while Sativex® is prescribed for the symptomatic relief of neuropathic pain in adults with multiple sclerosis and as an adjunctive analgesic treatment for adult patients with advanced cancer. One challenge now is to identify additional therapeutic targets for cannabinoid receptor agonists, and a number of potential clinical applications for such agonists are mentioned in this review. A second challenge is to develop strategies that will improve the efficacy and/or the benefit-to-risk ratio of a cannabinoid receptor agonist. This review focuses on five strategies that have the potential to meet either or both of these objectives. These are strategies that involve: (i) targeting cannabinoid receptors located outside the blood-brain barrier; (ii) targeting cannabinoid receptors expressed by a particular tissue; (iii) targeting up-regulated cannabinoid receptors; (iv) targeting cannabinoid CB2 receptors; or (v) ‘multi-targeting’. Preclinical data that justify additional research directed at evaluating the clinical importance of each of these strategies are also discussed. PMID:19226257

  2. Modulatory effect of the 5-HT1A agonist buspirone and the mixed non-hallucinogenic 5-HT1A/2A agonist ergotamine on psilocybin-induced psychedelic experience.

    PubMed

    Pokorny, Thomas; Preller, Katrin H; Kraehenmann, Rainer; Vollenweider, Franz X

    2016-04-01

    The mixed serotonin (5-HT) 1A/2A/2B/2C/6/7 receptor agonist psilocybin dose-dependently induces an altered state of consciousness (ASC) that is characterized by changes in sensory perception, mood, thought, and the sense of self. The psychological effects of psilocybin are primarily mediated by 5-HT2A receptor activation. However, accumulating evidence suggests that 5-HT1A or an interaction between 5-HT1A and 5-HT2A receptors may contribute to the overall effects of psilocybin. Therefore, we used a double-blind, counterbalanced, within-subject design to investigate the modulatory effects of the partial 5-HT1A agonist buspirone (20mg p.o.) and the non-hallucinogenic 5-HT2A/1A agonist ergotamine (3mg p.o.) on psilocybin-induced (170 µg/kg p.o.) psychological effects in two groups (n=19, n=17) of healthy human subjects. Psychological effects were assessed using the Altered State of Consciousness (5D-ASC) rating scale. Buspirone significantly reduced the 5D-ASC main scale score for Visionary Restructuralization (VR) (p<0.001), which was mostly driven by a reduction of the VR item cluster scores for elementary and complex visual hallucinations. Further, buspirone also reduced the main scale score for Oceanic Boundlessness (OB) including derealisation and depersonalisation phenomena at a trend level (p=0.062), whereas ergotamine did not show any effects on the psilocybin-induced 5D-ASC main scale scores. The present finding demonstrates that buspirone exerts inhibitory effects on psilocybin-induced effects, presumably via 5-HT1A receptor activation, an interaction between 5-HT1A and 5-HT2A receptors, or both. The data suggest that the modulation of 5-HT1A receptor activity may be a useful target in the treatment of visual hallucinations in different psychiatric and neurological diseases. PMID:26875114

  3. Physician perceptions of GLP-1 receptor agonists in the UK.

    PubMed

    Matza, Louis S; Curtis, Sarah E; Jordan, Jessica B; Adetunji, Omolara; Martin, Sherry A; Boye, Kristina S

    2016-05-01

    Objectives Glucagon-like peptide-1 (GLP-1) receptor agonists have been used to treat type 2 diabetes for almost a decade, and new treatments in this class have recently been introduced. The purpose of this study was to examine perceptions of GLP-1 receptor agonists among physicians who treat patients with type 2 diabetes in the UK. Methods A total of 670 physicians (226 diabetes specialists; 444 general practice [GP] physicians) completed a survey in 2014. Results Almost all physicians had prescribed GLP-1 receptor agonists (95.4% total sample; 99.1% specialists; 93.5% GP), most frequently to patients whose glucose levels are not adequately controlled with oral medications (85.9% of physicians) and obese/overweight patients (83.7%). Physicians' most common reasons for prescribing a GLP-1 receptor agonist were: associated with weight loss (65.8%), good efficacy (55.7%), less hypoglycemia risk than insulin (55.2%), not associated with weight gain (34.5%), and better efficacy than oral medications (32.7%). Factors that most commonly cause hesitation when prescribing this class were: not considered first line therapy according to guidelines (56.9%), injectable administration (44.6%), cost (36.7%), gastrointestinal side effects (33.4%), and risk of pancreatitis (26.7%). Almost all specialists (99.1%) believed they had sufficient knowledge to prescribe a GLP-1 receptor agonist, compared with 76.1% of GPs. Conclusions Results highlight the widespread use of GLP-1 receptor agonists for treatment of type 2 diabetes in the UK. However, almost a quarter of GPs reported that they do not have enough knowledge to prescribe GLP-1s, suggesting a need for increased dissemination of information to targeted groups of physicians. Study limitations were that the generalizability of the clinician sample is unknown; survey questions required clinicians to select answers from multiple response options rather than generating the responses themselves; and responses to this survey conducted

  4. Highly selective agonists for substance P receptor subtypes.

    PubMed Central

    Wormser, U; Laufer, R; Hart, Y; Chorev, M; Gilon, C; Selinger, Z

    1986-01-01

    The existence of a third tachykinin receptor (SP-N) in the mammalian nervous system was demonstrated by development of highly selective agonists. Systematic N-methylation of individual peptide bonds in the C-terminal hexapeptide of substance P gave rise to agonists which specifically act on different receptor subtypes. The most selective analog of this series, succinyl-[Asp6,Me-Phe8]SP6-11, elicits half-maximal contraction of the guinea pig ileum through the neuronal SP-N receptor at a concentration of 0.5 nM. At least 60,000-fold higher concentrations of this peptide are required to stimulate the other two tachykinin receptors (SP-P and SP-E). The action of selective SP-N agonists in the guinea pig ileum is antagonized by opioid peptides, suggesting a functional counteraction between opiate and SP-N receptors. These results indicate that the tachykinin receptors are distinct entities which may mediate different physiological functions. PMID:2431898

  5. Insect Nicotinic Receptor Agonists as Flea Adulticides in Small Animals

    PubMed Central

    Vo, Dai Tan; Hsu, Walter H.; Martin, Richard J.

    2013-01-01

    Fleas are significant ectoparasites of small animals. They can be a severe irritant to animals and serve as a vector for a number of infectious diseases. In this article, we discuss the pharmacological characteristics of four insect nicotinic acetylcholine receptor (nAChR) agonists used as fleacides in dogs and cats, which include three neonicotinoids (imidacloprid, nitenpyram, and dinotefuran) and spinosad. Insect nAChR agonists are one of the most important new classes of insecticides, which are used to control sucking insects both on plants and on companion animals. These new compounds provide a new approach for practitioners to safely and effectively eliminate fleas. PMID:20646191

  6. Ligand Binding Ensembles Determine Graded Agonist Efficacies at a G Protein-coupled Receptor.

    PubMed

    Bock, Andreas; Bermudez, Marcel; Krebs, Fabian; Matera, Carlo; Chirinda, Brian; Sydow, Dominique; Dallanoce, Clelia; Holzgrabe, Ulrike; De Amici, Marco; Lohse, Martin J; Wolber, Gerhard; Mohr, Klaus

    2016-07-29

    G protein-coupled receptors constitute the largest family of membrane receptors and modulate almost every physiological process in humans. Binding of agonists to G protein-coupled receptors induces a shift from inactive to active receptor conformations. Biophysical studies of the dynamic equilibrium of receptors suggest that a portion of receptors can remain in inactive states even in the presence of saturating concentrations of agonist and G protein mimetic. However, the molecular details of agonist-bound inactive receptors are poorly understood. Here we use the model of bitopic orthosteric/allosteric (i.e. dualsteric) agonists for muscarinic M2 receptors to demonstrate the existence and function of such inactive agonist·receptor complexes on a molecular level. Using all-atom molecular dynamics simulations, dynophores (i.e. a combination of static three-dimensional pharmacophores and molecular dynamics-based conformational sampling), ligand design, and receptor mutagenesis, we show that inactive agonist·receptor complexes can result from agonist binding to the allosteric vestibule alone, whereas the dualsteric binding mode produces active receptors. Each agonist forms a distinct ligand binding ensemble, and different agonist efficacies depend on the fraction of purely allosteric (i.e. inactive) versus dualsteric (i.e. active) binding modes. We propose that this concept may explain why agonist·receptor complexes can be inactive and that adopting multiple binding modes may be generalized also to small agonists where binding modes will be only subtly different and confined to only one binding site. PMID:27298318

  7. Saralasin and Sarile Are AT2 Receptor Agonists

    PubMed Central

    2014-01-01

    Saralasin and sarile, extensively studied over the past 40 years as angiotensin II (Ang II) receptor blockers, induce neurite outgrowth in a NG108-15 cell assay to a similar extent as the endogenous Ang II. In their undifferentiated state, these cells express mainly the AT2 receptor. The neurite outgrowth was inhibited by preincubation with the AT2 receptor selective antagonist PD 123,319, which suggests that the observed outgrowth was mediated by the AT2 receptor. Neither saralasin nor sarile reduced the neurite outgrowth induced by Ang II proving that the two octapeptides do not act as antagonists at the AT2 receptor and may be considered as AT2 receptor agonists. PMID:25313325

  8. Peptide agonists of the thrombopoietin receptor.

    PubMed

    Dower, W J; Cwirla, S E; Balasubramanian, P; Schatz, P J; Baccanari, D P; Barrett, R W

    1998-01-01

    We have screened a variety of L-amino acid peptide libraries against the extracellular domain of the human thrombopoietin (HuTPO) receptor, c-Mpl. A large number of peptide ligands were recovered and categorized into two families. Peptides from each family compete with the binding of HuTPO and with the binding of peptides from the other familiy. Representative peptides were synthesized and found to activate the full-length HuTPO receptor expressed in Ba/F3 cells to promote proliferation. These peptide families show no apparent homology to the primary sequence of TPO. We have focused our optimization efforts on one of the peptides, a linear 14-mer (IEGPTLRQWLAARA) with an IC50 of 2 nM in a competition binding assay and an EC50 of 400 nM in the proliferation assay. In order to enhance the potency of the compound, we constructed dimeric peptides by linking the carboxy-termini of the 14-mers to a lysine branch. These molecules exhibited slightly higher affinity (0.5 nM) and greatly increased potency (0.1 nM). The EC50 of the dimeric peptide was equivalent to that of the 332 aa form of baculovirus-expressed recombinant HuTPO. As previously shown for the erythropoietin-mimetic peptides, the TPO-mimetic peptides probably activate the TPO receptor by binding and inducing receptor dimerization. This supposition is supported by the observation that covalent dimerization of the peptide enhances its potency by 4,000-fold over that of the monomer. The peptide dimer is also active in stimulating in vitro proliferation of progenitors and maturation of megakaryocytes from human bone marrow, and in promoting an increase in platelet count when administered to normal mice. PMID:11012174

  9. Covalent agonists for studying G protein-coupled receptor activation

    PubMed Central

    Weichert, Dietmar; Kruse, Andrew C.; Manglik, Aashish; Hiller, Christine; Zhang, Cheng; Hübner, Harald; Kobilka, Brian K.; Gmeiner, Peter

    2014-01-01

    Structural studies on G protein-coupled receptors (GPCRs) provide important insights into the architecture and function of these important drug targets. However, the crystallization of GPCRs in active states is particularly challenging, requiring the formation of stable and conformationally homogeneous ligand-receptor complexes. Native hormones, neurotransmitters, and synthetic agonists that bind with low affinity are ineffective at stabilizing an active state for crystallogenesis. To promote structural studies on the pharmacologically highly relevant class of aminergic GPCRs, we here present the development of covalently binding molecular tools activating Gs-, Gi-, and Gq-coupled receptors. The covalent agonists are derived from the monoamine neurotransmitters noradrenaline, dopamine, serotonin, and histamine, and they were accessed using a general and versatile synthetic strategy. We demonstrate that the tool compounds presented herein display an efficient covalent binding mode and that the respective covalent ligand-receptor complexes activate G proteins comparable to the natural neurotransmitters. A crystal structure of the β2-adrenoreceptor in complex with a covalent noradrenaline analog and a conformationally selective antibody (nanobody) verified that these agonists can be used to facilitate crystallogenesis. PMID:25006259

  10. Octopaminergic agonists for the cockroach neuronal octopamine receptor

    PubMed Central

    Hirashima, Akinori; Morimoto, Masako; Kuwano, Eiichi; Eto, Morifusa

    2003-01-01

    The compounds 1-(2,6-diethylphenyl)imidazolidine-2-thione and 2-(2,6-diethylphenyl)imidazolidine showed the almost same activity as octopamine in stimulating adenylate cyclase of cockroach thoracic nervous system among 70 octopamine agonists, suggesting that only these compounds are full octopamine agonists and other compounds are partial octopamine agonists. The quantitative structure-activity relationship of a set of 22 octopamine agonists against receptor 2 in cockroach nervous tissue, was analyzed using receptor surface modeling. Three-dimensional energetics descriptors were calculated from receptor surface model/ligand interaction and these three-dimensional descriptors were used in quantitative structure-activity relationship analysis. A receptor surface model was generated using some subset of the most active structures and the results provided useful information in the characterization and differentiation of octopaminergic receptor. Abbreviation: AEA arylethanolamine AII 2-(arylimino)imidazolidine AIO 2-(arylimino)oxazolidine AIT 2-(arylimino)thiazolidine APAT 2-(α-phenylethylamino)-2-thiazoline BPAT 2-(β-phenylethylamino)-2-thiazoline CAO 2-(3-chlorobenzylamino)-2-oxazoline DCAO 2-(3,5-dichlorobenzylamino)-2-oxazoline DET5 2-(2,6-diethylphenylimino)-5-methylthiazolidine DET6 2-(2,6-diethylphenylimino)thiazine EGTA ethylene glycol bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid GFA genetic function approximation G/PLS genetic partial least squares IND 2-aminomethyl-2-indanol LAH lithium aluminum hydride MCSG maximum common subgroup MCT6 2-(2-methyl-4-chlorophenylimino)thiazine OA octopamine PLS partial least squares QSAR quantitative structure-activity relationship SBAT 2-(substituted benzylamino)-2-thiazoline SD the sum of squared deviations of the dependent variable values from their mean SPIT 3-(substituted phenyl)imidazolidine-2-thione THI 2-amino-1-(2-thiazoyl)ethanol TMS tetramethyl silane PMID:15841226

  11. Activation of endplate nicotinic acetylcholine receptors by agonists.

    PubMed

    Auerbach, Anthony

    2015-10-15

    The interaction of a small molecule made in one cell with a large receptor made in another is the signature event of cell signaling. Understanding the structure and energy changes associated with agonist activation is important for engineering drugs, receptors and synapses. The nicotinic acetylcholine receptor (AChR) is a ∼300kD ion channel that binds the neurotransmitter acetylcholine (ACh) and other cholinergic agonists to elicit electrical responses in the central and peripheral nervous systems. This mini-review is in two sections. First, general concepts of skeletal muscle AChR operation are discussed in terms of energy landscapes for conformational change. Second, adult vs. fetal AChRs are compared with regard to interaction energies between ACh and agonist-site side chains, measured by single-channel electrophysiology and molecular dynamics simulations. The five aromatic residues that form the core of each agonist binding site can be divided into two working groups, a triad (led by αY190) that behaves similarly at all sites and a coupled pair (led by γW55) that has a large influence on affinity only in fetal AChRs. Each endplate AChR has 5 homologous subunits, two of α(1) and one each of β, δ, and either γ (fetal) or ϵ (adult). These nicotinic AChRs have only 2 functional agonist binding sites located in the extracellular domain, at αδ and either αγ or αϵ subunit interfaces. The receptor undergoes a reversible, global isomerization between structures called C and O. The C shape does not conduct ions and has a relatively low affinity for ACh, whereas O conducts cations and has a higher affinity. When both agonist sites are empty (filled only with water) the probability of taking on the O conformation (PO) is low, <10(-6). When ACh molecules occupy the agonist sites the C→O opening rate constant and C↔O gating equilibrium constant increase dramatically. Following a pulse of ACh at the nerve-muscle synapse, the endplate current rises rapidly

  12. A Sphingosine 1-phosphate receptor 2 selective allosteric agonist

    PubMed Central

    Satsu, Hideo; Schaeffer, Marie-Therese; Guerrero, Miguel; Saldana, Adrian; Eberhart, Christina; Hodder, Peter; Cayanan, Charmagne; Schürer, Stephan; Bhhatarai, Barun; Roberts, Ed; Rosen, Hugh; Brown, Steven J.

    2013-01-01

    Molecular probe tool compounds for the Sphingosine 1-phosphate receptor 2 (S1PR2) are important for investigating the multiple biological processes in which the S1PR2 receptor has been implicated. Amongst these are NF-κB-mediated tumor cell survival and fibroblast chemotaxis to fibronectin. Here we report our efforts to identify selective chemical probes for S1PR2 and their characterization. We employed high throughput screening to identify two compounds which activate the S1PR2 receptor. SAR optimization led to compounds with high nanomolar potency. These compounds, XAX-162 and CYM-5520, are highly selective and do not activate other S1P receptors. Binding of CYM-5520 is not competitive with the antagonist JTE-013. Mutation of receptor residues responsible for binding to the zwitterionic headgroup of sphingosine 1-phosphate (S1P) abolishes S1P activation of the receptor, but not activation by CYM-5520. Competitive binding experiments with radiolabeled S1P demonstrate that CYM-5520 is an allosteric agonist and does not displace the native ligand. Computational modeling suggests that CYM-5520 binds lower in the orthosteric binding pocket, and that co-binding with S1P is energetically well tolerated. In summary, we have identified an allosteric S1PR2 selective agonist compound. PMID:23849205

  13. Improving the developability profile of pyrrolidine progesterone receptor partial agonists

    SciTech Connect

    Kallander, Lara S.; Washburn, David G.; Hoang, Tram H.; Frazee, James S.; Stoy, Patrick; Johnson, Latisha; Lu, Qing; Hammond, Marlys; Barton, Linda S.; Patterson, Jaclyn R.; Azzarano, Leonard M.; Nagilla, Rakesh; Madauss, Kevin P.; Williams, Shawn P.; Stewart, Eugene L.; Duraiswami, Chaya; Grygielko, Eugene T.; Xu, Xiaoping; Laping, Nicholas J.; Bray, Jeffrey D.; Thompson, Scott K.

    2010-09-17

    The previously reported pyrrolidine class of progesterone receptor partial agonists demonstrated excellent potency but suffered from serious liabilities including hERG blockade and high volume of distribution in the rat. The basic pyrrolidine amine was intentionally converted to a sulfonamide, carbamate, or amide to address these liabilities. The evaluation of the degree of partial agonism for these non-basic pyrrolidine derivatives and demonstration of their efficacy in an in vivo model of endometriosis is disclosed herein.

  14. Synthesis of fluorinated agonist of sphingosine-1-phosphate receptor 1.

    PubMed

    Aliouane, Lucie; Chao, Sovy; Brizuela, Leyre; Pfund, Emmanuel; Cuvillier, Olivier; Jean, Ludovic; Renard, Pierre-Yves; Lequeux, Thierry

    2014-09-01

    The bioactive metabolite sphingosine-1-phosphate (S1P), a product of sphingosine kinases (SphKs), mediates diverse biological processes such as cell differentiation, proliferation, survival and angiogenesis. A fluorinated analogue of S1P receptor agonist has been synthesized by utilizing a ring opening reaction of oxacycles by a lithiated difluoromethylphosphonate anion as the key reaction. In vitro activity of this S1P analogue is also reported. PMID:25047939

  15. Dopamine-deficient mice are hypersensitive to dopamine receptor agonists.

    PubMed

    Kim, D S; Szczypka, M S; Palmiter, R D

    2000-06-15

    Dopamine-deficient (DA-/-) mice were created by targeted inactivation of the tyrosine hydroxylase gene in dopaminergic neurons. The locomotor activity response of these mutants to dopamine D1 or D2 receptor agonists and l-3,4-dihydroxyphenylalanine (l-DOPA) was 3- to 13-fold greater than the response elicited from wild-type mice. The enhanced sensitivity of DA-/- mice to agonists was independent of changes in steady-state levels of dopamine receptors and the presynaptic dopamine transporter as measured by ligand binding. The acute behavioral response of DA-/- mice to a dopamine D1 receptor agonist was correlated with c-fos induction in the striatum, a brain nucleus that receives dense dopaminergic input. Chronic replacement of dopamine to DA-/- mice by repeated l-DOPA administration over 4 d relieved the hypersensitivity of DA-/- mutants in terms of induction of both locomotion and striatal c-fos expression. The results suggest that the chronic presence of dopaminergic neurotransmission is required to dampen the intracellular signaling response of striatal neurons. PMID:10844009

  16. Estrogen Receptor Agonists and Antagonists in the Yeast Estrogen Bioassay.

    PubMed

    Wang, Si; Bovee, Toine F H

    2016-01-01

    Cell-based bioassays can be used to predict the eventual biological activity of a substance on a living organism. In vitro reporter gene bioassays are based on recombinant vertebrate cell lines or yeast strains and especially the latter are easy-to-handle, cheap, and fast. Moreover, yeast cells do not express estrogen, androgen, progesterone or glucocorticoid receptors, and are thus powerful tools in the development of specific reporter gene systems that are devoid of crosstalk from other hormone pathways. This chapter describes our experience with an in-house developed RIKILT yeast estrogen bioassay for testing estrogen receptor agonists and antagonists, focusing on the applicability of the latter. PMID:26585147

  17. Glucagon-Like Peptide-1 Receptor Agonists: Beta-Cell Protection or Exhaustion?

    PubMed

    van Raalte, Daniël H; Verchere, C Bruce

    2016-07-01

    Glucagon-like peptide (GLP)-1 receptor agonists enhance insulin secretion and may improve pancreatic islet cell function. However, GLP-1 receptor (GLP-1R) agonist treatment may have more complex, and sometimes deleterious, effects on beta cells. We discuss the concepts of beta cell protection versus exhaustion for different GLP-1R agonists based on recent data. PMID:27160799

  18. Impact of Efficacy at the μ-Opioid Receptor on Antinociceptive Effects of Combinations of μ-Opioid Receptor Agonists and Cannabinoid Receptor Agonists

    PubMed Central

    Maguire, David R.

    2014-01-01

    Cannabinoid receptor agonists, such as Δ9-tetrahydrocannabinol (Δ9-THC), enhance the antinociceptive effects of μ-opioid receptor agonists, which suggests that combining cannabinoids with opioids would improve pain treatment. Combinations with lower efficacy agonists might be preferred and could avoid adverse effects associated with large doses; however, it is unclear whether interactions between opioids and cannabinoids vary across drugs with different efficacy. The antinociceptive effects of μ-opioid receptor agonists alone and in combination with cannabinoid receptor agonists were studied in rhesus monkeys (n = 4) using a warm water tail withdrawal procedure. Etorphine, fentanyl, morphine, buprenorphine, nalbuphine, Δ9-THC, and CP 55,940 (2-[(1R,2R,5R)-5-hydroxy-2-(3-hydroxypropyl) cyclohexyl]-5-(2-methyloctan-2-yl)phenol) each increased tail withdrawal latency. Pretreatment with doses of Δ9-THC (1.0 mg/kg) or CP 55,940 (0.032 mg/kg) that were ineffective alone shifted the fentanyl dose-effect curve leftward 20.6- and 52.9-fold, respectively, and the etorphine dose-effect curve leftward 12.4- and 19.6-fold, respectively. Δ9-THC and CP 55,940 shifted the morphine dose-effect curve leftward only 3.4- and 7.9-fold, respectively, and the buprenorphine curve only 5.4- and 4.1-fold, respectively. Neither Δ9-THC nor CP 55,940 significantly altered the effects of nalbuphine. Cannabinoid receptor agonists increase the antinociceptive potency of higher efficacy opioid receptor agonists more than lower efficacy agonists; however, because much smaller doses of each drug can be administered in combinations while achieving adequate pain relief and that other (e.g., abuse-related) effects of opioids do not appear to be enhanced by cannabinoids, these results provide additional support for combining opioids with cannabinoids to treat pain. PMID:25194020

  19. Adenosine (A)(2A)receptor modulation of nicotine-induced locomotor sensitization. A pharmacological and transgenic approach.

    PubMed

    Jastrzębska, Joanna; Nowak, Ewa; Smaga, Irena; Bystrowska, Beata; Frankowska, Małgorzata; Bader, Michael; Filip, Małgorzata; Fuxe, Kjell

    2014-06-01

    Preclinical evidence indicates an important role of adenosine (A)(2A) receptors in drug addiction while their therapeutic relevance is still a matter of debate. We examined the influence of the A(2A) receptor agonist CGS 21680 and the antagonist KW 6002 on nicotine sensitization and conditioned locomotor activity in adult (8-week old) male Sprague-Dawley rats (WT). Moreover, behavioral responses to nicotine were studied in rats overexpressing A(2A) receptors under the control of the neuronal specific enolase (NSE) promotor. Changes in the levels of dopamine, glutamate and γ-aminobutyric acid in wild type (WT) and NSEA(2A) rats were determined with using LC-MS. KW 6002 significantly enhanced expression of nicotine sensitization and conditioned locomotion, while CGS 21680 reduced all these effects in WT rats. A reduction of the expression of nicotine-evoked conditioned locomotor activity was also observed in the NSEA(2A) animals. The transgenic rats displayed a reduced basal tissue level of glutamate in the prefrontal cortex and hippocampus while dopamine basal levels in the nucleus accumbens were raised. Chronic nicotine treatment caused a significant reduction in the glutamate tissue level in the dorsal and ventral striatum, prefrontal cortex and cerebellum in wild type rats. In NSEA(2A) animals the same drug treatment instead produced a rise of glutamate levels in the hippocampus and dorsal striatum. Taken together, A(2A) receptor signaling in the rat brain can counteract locomotor sensitization and conditioned locomotion to nicotine which are related to nicotine reward-learning. It is suggested that treatment with A(2A) receptor agonists can help counteract the abuse actions of nicotine. PMID:24632528

  20. Cryptochinones from Cryptocarya chinensis act as farnesoid X receptor agonists.

    PubMed

    Lin, Hsiang-Ru; Chou, Tsung-Hsien; Huang, Din-Wen; Chen, Ih-Sheng

    2014-09-01

    Cryptochinones A-D are tetrahydroflavanones isolated from the leaves of Cryptocarya chinensis, an evergreen tree whose extracts are believed to have a variety of health benefits. The origin of their possible bioactivity is unclear. The farnesoid X receptor (FXR) is a member of nuclear receptor superfamily that has been widely targeted for developing treatments for chronic liver disease and for hyperglycemia. We studied whether cryptochinones A-D, which are structurally similar to known FXR ligands, may act at this target. Indeed, in mammalian one-hybrid and transient transfection reporter assays, cryptochinones A-D transactivated FXR to modulate promoter action including GAL4, SHP, CYP7A1, and PLTP promoters in dose-dependent manner, while they exhibited similar agonistic activity as chenodeoxycholic acid (CDCA), an endogenous FXR agonist. Through molecular modeling docking studies we evaluated their ability to bind to the FXR ligand binding pocket. Our results indicate that cryptochinones A-D can behave as FXR agonists. PMID:25127166

  1. Synthesis and structure-activity relationships of novel indazolyl glucocorticoid receptor partial agonists.

    PubMed

    Gilmore, John L; Sheppeck, James E; Wang, Jim; Dhar, T G Murali; Cavallaro, Cullen; Doweyko, Arthur M; Mckay, Lorraine; Cunningham, Mark D; Habte, Sium F; Nadler, Steven G; Dodd, John H; Somerville, John E; Barrish, Joel C

    2013-10-01

    SAR was used to further develop an indazole class of non-steroidal glucocorticoid receptor agonists aided by a GR LBD (ligand-binding domain)-agonist co-crystal structure described in the accompanying paper. Progress towards discovering a dissociated GR agonist guided by human in vitro assays biased the optimization of this compound series towards partial agonists that possessed excellent selectivity against other nuclear hormone receptors. PMID:23916594

  2. Interaction of a radiolabeled agonist with cardiac muscarinic cholinergic receptors

    SciTech Connect

    Harden, T.K.; Meeker, R.B.; Martin, M.W.

    1983-12-01

    The interaction of a radiolabeled muscarinic cholinergic receptor agonist, (methyl-/sup 3/H)oxotremorine acetate ((/sup 3/H)OXO), with a washed membrane preparation derived from rat heart, has been studied. In binding assays at 4 degrees C, the rate constants for association and dissociation of (/sup 3/H)OXO were 2 X 10(7) M-1 min-1 and 5 X 10(-3) min-1, respectively, Saturation binding isotherms indicated that binding was to a single population of sites with a Kd of approximately 300 pM. The density of (/sup 3/H)OXO binding sites (90-100 fmol/mg of protein) was approximately 75% of that determined for the radiolabeled receptor antagonist (/sup 3/H)quinuclidinyl benzilate. Both muscarinic receptor agonists and antagonists inhibited the binding of (/sup 3/H)OXO with high affinity and Hill slopes of approximately one. Guanine nucleotides completely inhibited the binding of (/sup 3/H)OXO. This effect was on the maximum binding (Bmax) of (/sup 3/H)OXO with no change occurring in the Kd; the order of potency for five nucleotides was guanosine 5'-O-(3-thio-triphosphate) greater than 5'-guanylylimidodiphosphate greater than GTP greater than or equal to guanosine/diphosphate greater than GMP. The (/sup 3/H)OXO-induced interaction of muscarinic receptors with a guanine nucleotide binding protein was stable to solubilization. That is, membrane receptors that were prelabeled with (/sup 3/H)OXO could be solubilized with digitonin, and the addition of guanine nucleotides to the soluble, (/sup 3/H)OXO-labeled complex resulted in dissociation of (/sup 3/H)OXO from the receptor. Pretreatment of membranes with relatively low concentrations of N-ethylmaleimide inhibited (/sup 3/H)OXO binding by 85% with no change in the Kd of (/sup 3/H)OXO, and with no effect on (/sup 3/H)quinuclidinyl benzilate binding.

  3. A2A adenosine receptor regulates the human blood brain barrier permeability

    PubMed Central

    Kim, Do-Geun; Bynoe, Margaret S.

    2015-01-01

    The blood brain barrier (BBB) symbolically represents the gateway to the central nervous system. It is a single layer of specialized endothelial cells that coats the central nervous system (CNS) vasculature and physically separates the brain environment from the blood constituents, to maintain the homeostasis of the CNS. However, this protective measure is a hindrance to the delivery of therapeutics to treat neurological diseases. Here, we show that activation of A2A adenosine receptor (AR) with an FDA-approved agonist potently permeabilizes an in vitro primary human brain endothelial barrier (hBBB) to the passage of chemotherapeutic drugs and T cells. T cell migration under AR signaling occurs primarily by paracellular transendothelial route. Permeabilization of the hBBB is rapid, time-dependent and reversible and is mediated by morphological changes in actin-cytoskeletal reorganization induced by RhoA signaling and a potent down-regulation of Claudin-5 and VE-Cadherin. Moreover, the kinetics of BBB permeability in mice closely overlaps with the permeability kinetics of the hBBB. These data suggest that activation of A2A AR is an endogenous mechanism that may be used for CNS drug delivery in human. PMID:25262373

  4. Hyperthermia induced by the dopamine D1 receptor agonist SK&F38393 in combination with the dopamine D2 receptor agonist talipexole in the rat.

    PubMed

    Nagashima, M; Yamada, K; Kimura, H; Matsumoto, S; Furukawa, T

    1992-12-01

    The present experiments were performed to investigate the effects of dopamine D1 receptor agonists given alone or in combination with dopamine D2 receptor agonists on body temperature in rats. The selective dopamine D1 receptor agonist, 1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol (SK&F38393), produced hyperthermia. However, the dopamine D2 receptor agonist, B-HT 920 (talipexole), and the newly synthesized dopamine D2 receptor agonist, (S)-2-amino-4,5,6,7-tetrahydro-6-propylamino-benzothiazole (SND 919), did not change the temperature. Interestingly, the SK&F38393-induced hyperthermia was enhanced by talipexole and SND 919. The drastic hyperthermia induced by combined administration of dopamine D1 and D2 receptor agonists was blocked by either the dopamine D1 receptor antagonist, SCH23390, or the dopamine D2 receptor antagonist, spiperone. On the other hand, treatment with prazosin, yohimbine, propranolol, scopolamine, or methysergide failed to affect the marked hyperthermia. The present results suggest that a functional link between dopamine D1 and D2 receptors may be synergistic in the regulation of body temperature and that concurrent stimulation of both dopamine D1 and D2 receptors thereby produces marked hyperthermia in the rat. PMID:1361996

  5. Antinociceptive properties of selective MT(2) melatonin receptor partial agonists.

    PubMed

    López-Canul, Martha; Comai, Stefano; Domínguez-López, Sergio; Granados-Soto, Vinicio; Gobbi, Gabriella

    2015-10-01

    Melatonin is a neurohormone involved in the regulation of both acute and chronic pain whose mechanism is still not completely understood. We have recently demonstrated that selective MT2 melatonin receptor partial agonists have antiallodynic properties in animal models of chronic neuropathic pain by modulating ON/OFF cells of the descending antinociceptive system. Here, we examined the antinociceptive properties of the selective MT2 melatonin receptor partial agonists N-{2-[(3-methoxyphenyl)phenylamino]ethyl}acetamide (UCM765) and N-{2-[(3-bromophenyl)-(4-fluorophenyl)amino]ethyl}acetamide (UCM924) in two animal models of acute and inflammatory pain: the hot-plate and formalin tests. UCM765 and UCM924 (5-40 mg/kg, s.c.) dose-dependently increased the temperature of the first hind paw lick in the hot-plate test, and decreased the total time spent licking the injected hind paw in the formalin test. Antinociceptive effects of UCM765 and UCM924 were maximal at the dose of 20mg/kg. At this dose, the effects of UCM765 and UCM924 were similar to those produced by 200 mg/kg acetaminophen in the hot-plate test, and by 3 mg/kg ketorolac or 150 mg/kg MLT in the formalin test. Notably, antinociceptive effects of the two MT2 partial agonists were blocked by the pre-treatment with the MT2 antagonist 4-phenyl-2-propionamidotetralin (4P-PDOT, 10 mg/kg) in both paradigms. These results demonstrate the antinociceptive properties of UCM765 and UCM924 in acute and inflammatory pain models and corroborate the concept that MT2 melatonin receptor may be a novel target for analgesic drug development. PMID:26162699

  6. Presynaptic adenosine A2A receptors dampen cannabinoid CB1 receptor-mediated inhibition of corticostriatal glutamatergic transmission

    PubMed Central

    Ferreira, S G; Gonçalves, F Q; Marques, J M; Tomé, Â R; Rodrigues, R J; Nunes-Correia, I; Ledent, C; Harkany, T; Venance, L; Cunha, R A; Köfalvi, A

    2015-01-01

    Background and Purpose Both cannabinoid CB1 and adenosine A2A receptors (CB1 receptors and A2A receptors) control synaptic transmission at corticostriatal synapses, with great therapeutic importance for neurological and psychiatric disorders. A postsynaptic CB1−A2A receptor interaction has already been elucidated, but the presynaptic A2A receptor-mediated control of presynaptic neuromodulation by CB1 receptors remains to be defined. Because the corticostriatal terminals provide the major input to the basal ganglia, understanding the interactive nature of converging neuromodulation on them will provide us with novel powerful tools to understand the physiology of corticostriatal synaptic transmission and interpret changes associated with pathological conditions. Experimental Approach Pharmacological manipulation of CB1 and A2A receptors was carried out in brain nerve terminals isolated from rats and mice, using flow synaptometry, immunoprecipitation, radioligand binding, ATP and glutamate release measurement. Whole-cell patch-clamp recordings were made in horizontal corticostriatal slices. Key Results Flow synaptometry showed that A2A receptors were extensively co-localized with CB1 receptor-immunopositive corticostriatal terminals and A2A receptors co-immunoprecipitated CB1 receptors in these purified terminals. A2A receptor activation decreased CB1 receptor radioligand binding and decreased the CB1 receptor-mediated inhibition of high-K+-evoked glutamate release in corticostriatal terminals. Accordingly, A2A receptor activation prevented CB1 receptor-mediated paired-pulse facilitation and attenuated the CB1 receptor-mediated inhibition of synaptic transmission in glutamatergic synapses of corticostriatal slices. Conclusions and Implications Activation of presynaptic A2A receptors dampened CB1 receptor-mediated inhibition of corticostriatal terminals. This constitutes a thus far unrecognized mechanism to modulate the potent CB1 receptor-mediated presynaptic

  7. Hypotensive effects of ghrelin receptor agonists mediated through a novel receptor

    PubMed Central

    Callaghan, Brid; Kosari, Samin; Pustovit, Ruslan V; Sartor, Daniela M; Ferens, Dorota; Ban, Kung; Baell, Jonathan; Nguyen, Trung V; Rivera, Leni R; Brock, James A; Furness, John B

    2014-01-01

    BACKGROUND AND PURPOSE Some agonists of ghrelin receptors cause rapid decreases in BP. The mechanisms by which they cause hypotension and the pharmacology of the receptors are unknown. EXPERIMENTAL APPROACH The effects of ligands of ghrelin receptors were investigated in rats in vivo, on isolated blood vessels and on cells transfected with the only molecularly defined ghrelin receptor, growth hormone secretagogue receptor 1a (GHSR1a). KEY RESULTS Three agonists of GHSR1a receptors, ulimorelin, capromorelin and CP464709, caused a rapid decrease in BP in the anaesthetized rat. The effect was not reduced by either of two GHSR1a antagonists, JMV2959 or YIL781, at doses that blocked effects on colorectal motility, in vivo. The rapid hypotension was not mimicked by ghrelin, unacylated ghrelin or the unacylated ghrelin receptor agonist, AZP531. The early hypotension preceded a decrease in sympathetic nerve activity. Early hypotension was not reduced by hexamethonium or by baroreceptor (sino-aortic) denervation. Ulimorelin also relaxed isolated segments of rat mesenteric artery, and, less potently, relaxed aorta segments. The vascular relaxation was not reduced by JMV2959 or YIL781. Ulimorelin, capromorelin and CP464709 activated GHSR1a in transfected HEK293 cells at nanomolar concentrations. JMV2959 and YIL781 both antagonized effects in these cells, with their pA2 values at the GHSR1a receptor being 6.55 and 7.84. CONCLUSIONS AND IMPLICATIONS Our results indicate a novel vascular receptor or receptors whose activation by ulimorelin, capromorelin and CP464709 lowered BP. This receptor is activated by low MW GHSR1a agonists, but is not activated by ghrelin. PMID:24670149

  8. Inflammatory Lung Injury After Cardiopulmonary Bypass is Attenuated by Adenosine A2A Receptor Activation

    PubMed Central

    Lisle, Turner C; Gazoni, Leo M; Fernandez, Lucas G; Sharma, Ashish K; Bellizzi, Andrew M; Schifflett, Grant D; Laubach, Victor E; Kron, Irving L

    2008-01-01

    Objectives Cardiopulmonary bypass has been shown to exert an inflammatory response within the lung, often resulting in postoperative pulmonary dysfunction. Several studies have shown that adenosine A2A receptor (A2AR) activation attenuates lung ischemia-reperfusion injury, however the effect of A2AR activation on cardiopulmonary bypass-induced lung injury has not been studied. We hypothesized that specific A2AR activation by ATL313 would attenuate inflammatory lung injury following cardiopulmonary bypass. Methods Adult male Sprague-Dawley rats were randomly divided into three groups: 1) SHAM group (underwent cannulation+heparinization only); 2) CONTROL group (underwent 90-minutes of normothermic cardiopulmonary bypass with normal whole-blood priming solution; 3) ATL group (underwent 90-minutes of normothermic cardiopulmonary bypass with ATL313 added to the normal priming solution). Results There was significantly less pulmonary edema and lung injury in the ATL group compared to the CONTROL group. The ATL group had significant reductions in bronchoalveolar lavage interleukin-1, interleukin-6, interferon-γ and myeloperoxidase levels compared to the CONTROL group. Similarly, lung tissue interleukin-6, tumor necrosis factor-α, and interferon-γ were significantly decreased in the ATL group compared to the CONTROL group. There was no significant difference between the SHAM and ATL groups in the amount of pulmonary edema, lung injury, or levels of pro-inflammatory cytokines. Conclusions The addition of a potent A2AR agonist to the normal priming solution prior to the initiation of CPB significantly protects the lung from the inflammatory effects of CPB and reduces the amount of lung injury. A2AR agonists could represent a new therapeutic strategy for reducing the potentially devastating consequences of the inflammatory response associated with CPB. Ultra-mini Abstract Pharmacologic activation of the adenosine A2A receptor during cardiopulmonary bypass resulted in

  9. Multi-Inhibitory Effects of A2A Adenosine Receptor Signaling on Neutrophil Adhesion Under Flow.

    PubMed

    Yago, Tadayuki; Tsukamoto, Hiroki; Liu, Zhenghui; Wang, Ying; Thompson, Linda F; McEver, Rodger P

    2015-10-15

    A2A adenosine receptor (A2AAR) signaling negatively regulates inflammatory responses in many disease models, but the detailed mechanisms remain unclear. We used the selective A2AAR agonist, ATL313, to examine how A2AAR signaling affects human and murine neutrophil adhesion under flow. Treating neutrophils with ATL313 inhibited selectin-induced, β2 integrin-dependent slow rolling and chemokine-induced, β2 integrin-dependent arrest on ICAM-1. ATL313 inhibited selectin-induced β2 integrin extension, which supports slow rolling, and chemokine-induced hybrid domain "swing-out," which supports arrest. Furthermore, ATL313 inhibited integrin outside-in signaling as revealed by reduced neutrophil superoxide production and spreading on immobilized anti-β2 integrin Ab. ATL313 suppressed selectin-triggered activation of Src family kinases (SFKs) and p38 MAPK, chemokine-triggered activation of Ras-related protein 1, and β2 integrin-triggered activation of SFKs and Vav cytoskeletal regulatory proteins. ATL313 activated protein kinase A and its substrate C-terminal Src kinase, an inhibitor of SFKs. Treating neutrophils with a protein kinase A inhibitor blocked the actions of ATL313. In vivo, ATL313-treated neutrophils rolled faster and arrested much less frequently in postcapillary venules of the murine cremaster muscle after TNF-α challenge. Furthermore, ATL313 markedly suppressed neutrophil migration into the peritoneum challenged with thioglycollate. ATL313 did not affect A2AAR-deficient neutrophils, confirming its specificity. Our findings provide new insights into the anti-inflammatory mechanisms of A2AAR signaling and the potential utility of A2AAR agonists in inflammatory diseases. PMID:26355151

  10. Newspapers and newspaper ink contain agonists for the ah receptor.

    PubMed

    Bohonowych, Jessica E S; Zhao, Bin; Timme-Laragy, Alicia; Jung, Dawoon; Di Giulio, Richard T; Denison, Michael S

    2008-04-01

    Ligand-dependent activation of the aryl hydrocarbon receptor (AhR) pathway leads to a diverse array of biological and toxicological effects. The best-studied ligands for the AhR include polycyclic and halogenated aromatic hydrocarbons, the most potent of which is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). However, as new AhR ligands are identified and characterized, their structural and physiochemical diversity continues to expand. Our identification of AhR agonists in crude extracts from diverse materials raises questions as to the magnitude and extent of human exposure to AhR ligands through normal daily activities. We have found that solvent extracts of newspapers from countries around the world stimulate the AhR signaling pathway. AhR agonist activity was observed for dimethyl sulfoxide (DMSO), ethanol, and water extracts of printed newspaper, unprinted virgin paper, and black printing ink, where activation of luciferase reporter gene expression was transient, suggesting that the AhR active chemical(s) was metabolically labile. DMSO and ethanol extracts also stimulated AhR transformation and DNA binding, and also competed with [(3)H]TCDD for binding to the AhR. In addition, DMSO extracts of printed newspaper induced cytochrome P450 1A associated 7-ethoxyresorufin-O-deethylase activity in zebrafish embryos in vivo. Although the responsible bioactive chemical(s) remain to be identified, our results demonstrate that newspapers and printing ink contain relatively potent metabolically labile agonists of the AhR. Given the large amount of recycling and reprocessing of newspapers throughout the world, release of these easily extractable AhR agonists into the environment should be examined and their potential effects on aquatic organisms assessed. PMID:18203687

  11. Therapeutic applications of TRAIL receptor agonists in cancer and beyond.

    PubMed

    Amarante-Mendes, Gustavo P; Griffith, Thomas S

    2015-11-01

    TRAIL/Apo-2L is a member of the TNF superfamily first described as an apoptosis-inducing cytokine in 1995. Similar to TNF and Fas ligand, TRAIL induces apoptosis in caspase-dependent manner following TRAIL death receptor trimerization. Because tumor cells were shown to be particularly sensitive to this cytokine while normal cells/tissues proved to be resistant along with being able to synthesize and release TRAIL, it was rapidly appreciated that TRAIL likely served as one of our major physiologic weapons against cancer. In line with this, a number of research laboratories and pharmaceutical companies have attempted to exploit the ability of TRAIL to kill cancer cells by developing recombinant forms of TRAIL or TRAIL receptor agonists (e.g., receptor-specific mAb) for therapeutic purposes. In this review article we will describe the biochemical pathways used by TRAIL to induce different cell death programs. We will also summarize the clinical trials related to this pathway and discuss possible novel uses of TRAIL-related therapies. In recent years, the physiological importance of TRAIL has expanded beyond being a tumoricidal molecule to one critical for a number of clinical settings - ranging from infectious disease and autoimmunity to cardiovascular anomalies. We will also highlight some of these conditions where modulation of the TRAIL/TRAIL receptor system may be targeted in the future. PMID:26343199

  12. Primary Macrophage Chemotaxis Induced by Cannabinoid Receptor 2 Agonists Occurs Independently of the CB2 Receptor

    PubMed Central

    Taylor, Lewis; Christou, Ivy; Kapellos, Theodore S.; Buchan, Alice; Brodermann, Maximillian H.; Gianella-Borradori, Matteo; Russell, Angela; Iqbal, Asif J.; Greaves, David R.

    2015-01-01

    Activation of CB2 has been demonstrated to induce directed immune cell migration. However, the ability of CB2 to act as a chemoattractant receptor in macrophages remains largely unexplored. Using a real-time chemotaxis assay and a panel of chemically diverse and widely used CB2 agonists, we set out to examine whether CB2 modulates primary murine macrophage chemotaxis. We report that of 12 agonists tested, only JWH133, HU308, L-759,656 and L-759,633 acted as macrophage chemoattractants. Surprisingly, neither pharmacological inhibition nor genetic ablation of CB2 had any effect on CB2 agonist-induced macrophage chemotaxis. As chemotaxis was pertussis toxin sensitive in both WT and CB2-/- macrophages, we concluded that a non-CB1/CB2, Gi/o-coupled GPCR must be responsible for CB2 agonist-induced macrophage migration. The obvious candidate receptors GPR18 and GPR55 could not mediate JWH133 or HU308-induced cytoskeletal rearrangement or JWH133-induced β-arrestin recruitment in cells transfected with either receptor, demonstrating that neither are the unidentified GPCR. Taken together our results conclusively demonstrate that CB2 is not a chemoattractant receptor for murine macrophages. Furthermore we show for the first time that JWH133, HU308, L-759,656 and L-759,633 have off-target effects of functional consequence in primary cells and we believe that our findings have wide ranging implications for the entire cannabinoid field. PMID:26033291

  13. Immobilized thrombin receptor agonist peptide accelerates wound healing in mice.

    PubMed

    Strukova, S M; Dugina, T N; Chistov, I V; Lange, M; Markvicheva, E A; Kuptsova, S; Zubov, V P; Glusa, E

    2001-10-01

    To accelerate the healing processes in wound repair, attempts have been repeatedly made to use growth factors including thrombin and its peptide fragments. Unfortunately, the employment of thrombin is limited because of its high liability and pro-inflammatory actions at high concentrations. Some cellular effects of thrombin in wound healing are mediated by the activation of protease activated receptor-1 (PAR-1). The thrombin receptor agonist peptide (TRAP:SFLLRN) activates this receptor and mimics the effects of thrombin, but TRAP is a relatively weak agonist. We speculated that the encapsulated peptide may be more effective for PAR-1 activation than nonimmobilized peptide and developed a novel method for TRAP encapsulation in hydrogel films based on natural and synthetic polymers. The effects of an encapsulated TRAP in composite poly(N-vinyl caprolactam)-calcium alginate (PVCL) hydrogel films were investigated in a mouse model of wound healing. On day 7 the wound sizes decreased by about 60% under TRAP-chitosan-containing PVCL films, as compared with control films without TRAP. In the case of TRAP-polylysine-containing films no significant decrease in wound sizes was found. The fibroblast/macrophage ratio increased under TRAP-containing films on day 3 and on day 7. The number of proliferating fibroblasts increased to 150% under TRAP-chitosan films on day 7 as compared with control films. The number of [3H]-thymidine labeled endothelial and epithelial cells in granulation tissues was also enhanced. Thus, the immobilized TRAP to PVCL-chitosan hydrogel films were found to promote wound healing following the stimulation of fibroblast and epithelial cell proliferation and neovascularization. Furthermore, TRAP was shown to inhibit the secretion of the inflammatory mediator PAF from stimulated rat peritoneal mast cells due to augmentation of NO release from the mast cells. The encapsulated TRAP is suggested to accelerate wound healing due to the anti-inflammatory effects

  14. Different serotonin receptor agonists have distinct effects on sound-evoked responses in inferior colliculus.

    PubMed

    Hurley, Laura M

    2006-11-01

    The neuromodulator serotonin has a complex set of effects on the auditory responses of neurons within the inferior colliculus (IC), a midbrain auditory nucleus that integrates a wide range of inputs from auditory and nonauditory sources. To determine whether activation of different types of serotonin receptors is a source of the variability in serotonergic effects, four selective agonists of serotonin receptors in the serotonin (5-HT) 1 and 5-HT2 families were iontophoretically applied to IC neurons, which were monitored for changes in their responses to auditory stimuli. Different agonists had different effects on neural responses. The 5-HT1A agonist had mixed facilitatory and depressive effects, whereas 5-HT1B and 5-HT2C agonists were both largely facilitatory. Different agonists changed threshold and frequency tuning in ways that reflected their effects on spike count. When pairs of agonists were applied sequentially to the same neurons, selective agonists sometimes affected neurons in ways that were similar to serotonin, but not to other selective agonists tested. Different agonists also differentially affected groups of neurons classified by the shapes of their frequency-tuning curves, with serotonin and the 5-HT1 receptors affecting proportionally more non-V-type neurons relative to the other agonists tested. In all, evidence suggests that the diversity of serotonin receptor subtypes in the IC is likely to account for at least some of the variability of the effects of serotonin and that receptor subtypes fulfill specialized roles in auditory processing. PMID:16870843

  15. Identification of Determinants Required for Agonistic and Inverse Agonistic Ligand Properties at the ADP Receptor P2Y12

    PubMed Central

    Schmidt, Philipp; Ritscher, Lars; Dong, Elizabeth N.; Hermsdorf, Thomas; Cöster, Maxi; Wittkopf, Doreen; Meiler, Jens

    2013-01-01

    The ADP receptor P2Y12 belongs to the superfamily of G protein–coupled receptors (GPCRs), and its activation triggers platelet aggregation. Therefore, potent antagonists, such as clopidogrel, are of high clinical relevance in prophylaxis and treatment of thromboembolic events. P2Y12 displays an elevated basal activity in vitro, and as such, inverse agonists may be therapeutically beneficial compared with antagonists. Only a few inverse agonists of P2Y12 have been described. To expand this limited chemical space and improve understanding of structural determinants of inverse agonist-receptor interaction, this study screened a purine compound library for lead structures using wild-type (WT) human P2Y12 and 28 constitutively active mutants. Results showed that ATP and ATP derivatives are agonists at P2Y12. The potency at P2Y12 was 2-(methylthio)-ADP > 2-(methylthio)-ATP > ADP > ATP. Determinants required for agonistic ligand activity were identified. Molecular docking studies revealed a binding pocket for the ATP derivatives that is bordered by transmembrane helices 3, 5, 6, and 7 in human P2Y12, with Y105, E188, R256, Y259, and K280 playing a particularly important role in ligand interaction. N-Methyl-anthraniloyl modification at the 3′-OH of the 2′-deoxyribose leads to ligands (mant-deoxy-ATP [dATP], mant-deoxy-ADP) with inverse agonist activity. Inverse agonist activity of mant-dATP was found at the WT human P2Y12 and half of the constitutive active P2Y12 mutants. This study showed that, in addition to ADP and ATP, other ATP derivatives are not only ligands of P2Y12 but also agonists. Modification of the ribose within ATP can result in inverse activity of ATP-derived ligands. PMID:23093496

  16. Induction of murine adenosine A(2A) receptor expression by LPS: analysis of the 5' upstream promoter.

    PubMed

    Elson, G; Eisenberg, M; Garg, C; Outram, S; Ferrante, C J; Hasko, G; Leibovich, S J

    2013-04-01

    Non-activated macrophages express low levels of A(2A)Rs and lipopolysaccharides (LPS) upregulates A(2A)R expression in an NF-κB-dependent manner. The murine A(2A)R gene is encoded by three exons, m1, m2 and m3. Exons m2 and m3 are conserved, while m1 encodes the 5' untranslated UTR. Three m1 variants have been defined, m1A, m1B and m1C, with m1C being farthest from the transcriptional start site. LPS upregulates A(2A)Rs in primary murine peritoneal and bone-marrow-derived macrophages and RAW264.7 cells by selectively splicing m1C to m2, through a promoter located upstream of m1C. We have cloned ∼1.6 kb upstream of m1C into pGL4.16(luc2CP/Hygro) promoterless vector. This construct in RAW 264.7 cells responds to LPS, and adenosine receptor agonists augmented LPS responsiveness. The NF-κB inhibitors BAY-11 and triptolide inhibited LPS-dependent induction. Deletion of a key proximal NF-κB site (402-417) abrogated LPS responsiveness, while deletion of distal NF-κB and C/EBPβ sites did not. Site-directed mutagenesis of CREB (309-320), STAT1 (526-531) and AP2 (566-569) sites had little effect on LPS and adenosine receptor agonist responsiveness; however, mutation of a second STAT1 site (582-588) abrogated this responsiveness. Further analysis of this promoter should provide valuable insights into regulation of A(2A)R expression in macrophages in response to inflammatory stimuli. PMID:23328845

  17. Proteasome involvement in agonist-induced down-regulation of mu and delta opioid receptors.

    PubMed

    Chaturvedi, K; Bandari, P; Chinen, N; Howells, R D

    2001-04-13

    This study investigated the mechanism of agonist-induced opioid receptor down-regulation. Incubation of HEK 293 cells expressing FLAG-tagged delta and mu receptors with agonists caused a time-dependent decrease in opioid receptor levels assayed by immunoblotting. Pulse-chase experiments using [(35)S]methionine metabolic labeling indicated that the turnover rate of delta receptors was accelerated 5-fold following agonist stimulation. Inactivation of functional G(i) and G(o) proteins by pertussis toxin-attenuated down-regulation of the mu opioid receptor, while down-regulation of the delta opioid receptor was unaffected. Pretreatment of cells with inhibitors of lysosomal proteases, calpain, and caspases had little effect on mu and delta opioid receptor down-regulation. In marked contrast, pretreatment with proteasome inhibitors attenuated agonist-induced mu and delta receptor down-regulation. In addition, incubation of cells with proteasome inhibitors in the absence of agonists increased steady-state mu and delta opioid receptor levels. Immunoprecipitation of mu and delta opioid receptors followed by immunoblotting with ubiquitin antibodies suggested that preincubation with proteasome inhibitors promoted accumulation of polyubiquitinated receptors. These data provide evidence that the ubiquitin/proteasome pathway plays a role in agonist-induced down-regulation and basal turnover of opioid receptors. PMID:11152677

  18. Antidiabetic Actions of an Estrogen Receptor β Selective Agonist

    PubMed Central

    Alonso-Magdalena, Paloma; Ropero, Ana B.; García-Arévalo, Marta; Soriano, Sergi; Quesada, Iván; Muhammed, Sarheed J.; Salehi, Albert; Gustafsson, Jan-Ake; Nadal, Ángel

    2013-01-01

    The estrogen receptor β (ERβ) is emerging as an important player in the physiology of the endocrine pancreas. We evaluated the role and antidiabetic actions of the ERβ selective agonist WAY200070 as an insulinotropic molecule. We demonstrate that WAY200070 enhances glucose-stimulated insulin secretion both in mouse and human islets. In vivo experiments showed that a single administration of WAY200070 leads to an increase in plasma insulin levels with a concomitant improved response to a glucose load. Two-week treatment administration increased glucose-induced insulin release and pancreatic β-cell mass and improved glucose and insulin sensitivity. In addition, streptozotocin-nicotinamide–induced diabetic mice treated with WAY200070 exhibited a significant improvement in plasma insulin levels and glucose tolerance as well as a regeneration of pancreatic β-cell mass. Studies performed in db/db mice demonstrated that this compound restored first-phase insulin secretion and enhanced pancreatic β-cell mass. We conclude that ERβ agonists should be considered as new targets for the treatment of diabetes. PMID:23349481

  19. Gene expression and function of adenosine A(2A) receptor in the rat carotid body.

    PubMed

    Kobayashi, S; Conforti, L; Millhorn, D E

    2000-08-01

    The present study was undertaken to determine whether rat carotid bodies express adenosine (Ado) A(2A) receptors and whether this receptor is involved in the cellular response to hypoxia. Our results demonstrate that rat carotid bodies express the A(2A) and A(2B) Ado receptor mRNAs but not the A(1) or A(3) receptor mRNAs as determined by reverse transcriptase-polymerase chain reaction. In situ hybridization confirmed the expression of the A(2A) receptor mRNA. Immunohistochemical studies further showed that the A(2A) receptor is expressed in the carotid body and that it is colocalized with tyrosine hydroxylase in type I cells. Whole cell voltage-clamp studies using isolated type I cells showed that Ado inhibited the voltage-dependent Ca(2+) currents and that this inhibition was abolished by the selective A(2A) receptor antagonist ZM-241385. Ca(2+) imaging studies using fura 2 revealed that exposure to severe hypoxia induced elevation of intracellular Ca(2+) concentration ([Ca(2+)](i)) in type I cells and that extracellularly applied Ado significantly attenuated the hypoxia-induced elevation of [Ca(2+)](i). Taken together, our findings indicate that A(2A) receptors are present in type I cells and that activation of A(2A) receptors modulates Ca(2+) accumulation during hypoxia. This mechanism may play a role in regulating intracellular Ca(2+) homeostasis and cellular excitability during hypoxia. PMID:10926550

  20. Recruitment of a Cytoplasmic Chaperone Relay by the A2A Adenosine Receptor*

    PubMed Central

    Bergmayr, Christian; Thurner, Patrick; Keuerleber, Simon; Kudlacek, Oliver; Nanoff, Christian; Freissmuth, Michael; Gruber, Christian W.

    2013-01-01

    The adenosine A2A receptor is a prototypical rhodopsin-like G protein-coupled receptor but has several unique structural features, in particular a long C terminus (of >120 residues) devoid of a palmitoylation site. It is known to interact with several accessory proteins other than those canonically involved in signaling. However, it is evident that many more proteins must interact with the A2A receptor, if the trafficking trajectory of the receptor is taken into account from its site of synthesis in the endoplasmic reticulum (ER) to its disposal by the lysosome. Affinity-tagged versions of the A2A receptor were expressed in HEK293 cells to identify interacting partners residing in the ER by a proteomics approach based on tandem affinity purification. The receptor-protein complexes were purified in quantities sufficient for analysis by mass spectrometry. We identified molecular chaperones (heat-shock proteins HSP90α and HSP70-1A) that interact with and retain partially folded A2A receptor prior to ER exit. Complex formation between the A2A receptor and HSP90α (but not HSP90β) and HSP70-1A was confirmed by co-affinity precipitation. HSP90 inhibitors also enhanced surface expression of the receptor in PC12 cells, which endogenously express the A2A receptor. Finally, proteins of the HSP relay machinery (e.g. HOP/HSC70-HSP90 organizing protein and P23/HSP90 co-chaperone) were recovered in complexes with the A2A receptor. These observations are consistent with the proposed chaperone/coat protein complex II exchange model. This posits that cytosolic HSP proteins are sequentially recruited to folding intermediates of the A2A receptor. Release of HSP90 is required prior to recruitment of coat protein complex II components. This prevents premature ER export of partially folded receptors. PMID:23965991

  1. Proopiomelanocortin Deficiency Treated with a Melanocortin-4 Receptor Agonist.

    PubMed

    Kühnen, Peter; Clément, Karine; Wiegand, Susanna; Blankenstein, Oliver; Gottesdiener, Keith; Martini, Lea L; Mai, Knut; Blume-Peytavi, Ulrike; Grüters, Annette; Krude, Heiko

    2016-07-21

    Patients with rare defects in the gene encoding proopiomelanocortin (POMC) have extreme early-onset obesity, hyperphagia, hypopigmentation, and hypocortisolism, resulting from the lack of the proopiomelanocortin-derived peptides melanocyte-stimulating hormone and corticotropin. In such patients, adrenal insufficiency must be treated with hydrocortisone early in life. No effective pharmacologic treatments have been available for the hyperphagia and obesity that characterize the condition. In this investigator-initiated, open-label study, two patients with proopiomelanocortin deficiency were treated with setmelanotide, a new melanocortin-4 receptor agonist. The patients had a sustainable reduction in hunger and substantial weight loss (51.0 kg after 42 weeks in Patient 1 and 20.5 kg after 12 weeks in Patient 2). PMID:27468060

  2. Use of Thrombopoietin Receptor Agonists in Childhood Immune Thrombocytopenia

    PubMed Central

    Garzon, Angelica Maria; Mitchell, William Beau

    2015-01-01

    Most children with immune thrombocytopenia (ITP) will have spontaneous remission regardless of therapy, while about 20% will go on to have chronic ITP. In those children with chronic ITP who need treatment, standard therapies for acute ITP may have adverse effects that complicate their long-term use. Thus, alternative treatment options are needed for children with chronic ITP. Thrombopoietin receptor agonists (TPO-RA) have been shown to be safe and efficacious in adults with ITP, and represent a new treatment option for children with chronic ITP. One TPO-RA, eltrombopag, is now approved for children. Clinical trials in children are ongoing and data are emerging on safety and efficacy. This review will focus on the physiology of TPO-RA, their clinical use in children, as well as the long-term safety issues that need to be considered when using these agents. PMID:26322297

  3. Antiinfective applications of toll-like receptor 9 agonists.

    PubMed

    Krieg, Arthur M

    2007-07-01

    The innate immune system detects pathogens by the presence of highly conserved pathogen-expressed molecules, which trigger host immune defenses. Toll-like receptor (TLR) 9 detects unmethylated CpG dinucleotides in bacterial or viral DNA, and can be stimulated for therapeutic applications with synthetic oligodeoxynucleotides containing immune stimulatory "CpG motifs." TLR9 activation induces both innate and adaptive immunity. The TLR9-induced innate immune activation can be applied in the prevention or treatment of infectious diseases, and the adaptive immune-enhancing effects can be harnessed for improving vaccines. This article highlights the current understanding of the mechanism of action of CpG oligodeoxynucleotides, and provides an overview of the preclinical data and early human clinical trial results, applying these TLR9 agonists in the field of infectious diseases. PMID:17607015

  4. Recent advances in the development of farnesoid X receptor agonists

    PubMed Central

    Carey, Elizabeth J.; Lindor, Keith D.

    2015-01-01

    Farnesoid X receptors (FXRs) are nuclear hormone receptors expressed in high amounts in body tissues that participate in bilirubin metabolism including the liver, intestines, and kidneys. Bile acids (BAs) are the natural ligands of the FXRs. FXRs regulate the expression of the gene encoding for cholesterol 7 alpha-hydroxylase, which is the rate-limiting enzyme in BA synthesis. In addition, FXRs play a critical role in carbohydrate and lipid metabolism and regulation of insulin sensitivity. FXRs also modulate live growth and regeneration during liver injury. Preclinical studies have shown that FXR activation protects against cholestasis-induced liver injury. Moreover, FXR activation protects against fatty liver injury in animal models of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), and improved hyperlipidemia, glucose intolerance, and insulin sensitivity. Obeticholic acid (OCA), a 6α-ethyl derivative of the natural human BA chenodeoxycholic acid (CDCA) is the first-in-class selective FXR agonist that is ~100-fold more potent than CDCA. Preliminary human clinical trials have shown that OCA is safe and effective. In a phase II clinical trial, administration of OCA was well-tolerated, increased insulin sensitivity and reduced markers of liver inflammation and fibrosis in patients with type II diabetes mellitus and NAFLD. In two clinical trials of OCA in patients with primary biliary cirrhosis (PBC), a progressive cholestatic liver disease, OCA significantly reduced serum alkaline phosphatase (ALP) levels, an important disease marker that correlates well with clinical outcomes of patients with PBC. Together, these studies suggest that FXR agonists could potentially be used as therapeutic tools in patients suffering from nonalcoholic fatty and cholestatic liver diseases. Larger and Longer-term studies are currently ongoing. PMID:25705637

  5. Recent advances in the development of farnesoid X receptor agonists.

    PubMed

    Ali, Ahmad H; Carey, Elizabeth J; Lindor, Keith D

    2015-01-01

    Farnesoid X receptors (FXRs) are nuclear hormone receptors expressed in high amounts in body tissues that participate in bilirubin metabolism including the liver, intestines, and kidneys. Bile acids (BAs) are the natural ligands of the FXRs. FXRs regulate the expression of the gene encoding for cholesterol 7 alpha-hydroxylase, which is the rate-limiting enzyme in BA synthesis. In addition, FXRs play a critical role in carbohydrate and lipid metabolism and regulation of insulin sensitivity. FXRs also modulate live growth and regeneration during liver injury. Preclinical studies have shown that FXR activation protects against cholestasis-induced liver injury. Moreover, FXR activation protects against fatty liver injury in animal models of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), and improved hyperlipidemia, glucose intolerance, and insulin sensitivity. Obeticholic acid (OCA), a 6α-ethyl derivative of the natural human BA chenodeoxycholic acid (CDCA) is the first-in-class selective FXR agonist that is ~100-fold more potent than CDCA. Preliminary human clinical trials have shown that OCA is safe and effective. In a phase II clinical trial, administration of OCA was well-tolerated, increased insulin sensitivity and reduced markers of liver inflammation and fibrosis in patients with type II diabetes mellitus and NAFLD. In two clinical trials of OCA in patients with primary biliary cirrhosis (PBC), a progressive cholestatic liver disease, OCA significantly reduced serum alkaline phosphatase (ALP) levels, an important disease marker that correlates well with clinical outcomes of patients with PBC. Together, these studies suggest that FXR agonists could potentially be used as therapeutic tools in patients suffering from nonalcoholic fatty and cholestatic liver diseases. Larger and Longer-term studies are currently ongoing. PMID:25705637

  6. The dopamine D1 receptor agonist SKF-82958 effectively increases eye blinking count in common marmosets.

    PubMed

    Kotani, Manato; Kiyoshi, Akihiko; Murai, Takeshi; Nakako, Tomokazu; Matsumoto, Kenji; Matsumoto, Atsushi; Ikejiri, Masaru; Ogi, Yuji; Ikeda, Kazuhito

    2016-03-01

    Eye blinking is a spontaneous behavior observed in all mammals, and has been used as a well-established clinical indicator for dopamine production in neuropsychiatric disorders, including Parkinson's disease and Tourette syndrome [1,2]. Pharmacological studies in humans and non-human primates have shown that dopamine agonists/antagonists increase/decrease eye blinking rate. Common marmosets (Callithrix jacchus) have recently attracted a great deal of attention as suitable experimental animals in the psychoneurological field due to their more developed prefrontal cortex than rodents, easy handling compare to other non-human primates, and requirement for small amounts of test drugs. In this study, we evaluated the effects of dopamine D1-4 receptors agonists on eye blinking in common marmosets. Our results show that the dopamine D1 receptor agonist SKF-82958 and the non-selective dopamine receptor agonist apomorphine significantly increased common marmosets eye blinking count, whereas the dopamine D2 agonist (+)-PHNO and the dopamine D3 receptor agonist (+)-PD-128907 produced somnolence in common marmosets resulting in a decrease in eye blinking count. The dopamine D4 receptor agonists PD-168077 and A-41297 had no effect on common marmosets' eye blinking count. Finally, the dopamine D1 receptor antagonist SCH 39166 completely blocked apomorphine-induced increase in eye blinking count. These results indicate that eye blinking in common marmosets may be a useful tool for in vivo screening of novel dopamine D1 receptor agonists as antipsychotics. PMID:26675887

  7. Adenosine A2a receptors and O2 sensing in development

    PubMed Central

    2011-01-01

    Reduced mitochondrial oxidative phosphorylation, via activation of adenylate kinase and the resulting exponential rise in the cellular AMP/ATP ratio, appears to be a critical factor underlying O2 sensing in many chemoreceptive tissues in mammals. The elevated AMP/ATP ratio, in turn, activates key enzymes that are involved in physiologic adjustments that tend to balance ATP supply and demand. An example is the conversion of AMP to adenosine via 5′-nucleotidase and the resulting activation of adenosine A2A receptors, which are involved in acute oxygen sensing by both carotid bodies and the brain. In fetal sheep, A2A receptors associated with carotid bodies trigger hypoxic cardiovascular chemoreflexes, while central A2A receptors mediate hypoxic inhibition of breathing and rapid eye movements. A2A receptors are also involved in hypoxic regulation of fetal endocrine systems, metabolism, and vascular tone. In developing lambs, A2A receptors play virtually no role in O2 sensing by the carotid bodies, but brain A2A receptors remain critically involved in the roll-off ventilatory response to hypoxia. In adult mammals, A2A receptors have been implicated in O2 sensing by carotid glomus cells, while central A2A receptors likely blunt hypoxic hyperventilation. In conclusion, A2A receptors are crucially involved in the transduction mechanisms of O2 sensing in fetal carotid bodies and brains. Postnatally, central A2A receptors remain key mediators of hypoxic respiratory depression, but they are less critical for O2 sensing in carotid chemoreceptors, particularly in developing lambs. PMID:21677265

  8. Application of the functionalized congener approach to dendrimer-based signaling agents acting through A(2A) adenosine receptors.

    PubMed

    Kim, Yoonkyung; Klutz, Athena M; Hechler, Béatrice; Gao, Zhan-Guo; Gachet, Christian; Jacobson, Kenneth A

    2009-03-01

    As a continued effort to develop multivalent ligands to enhance the pharmacological effects of monomeric drugs, DITC-APEC, a chemically reactive nucleoside A(2A) adenosine receptor (AR) agonist, was employed to derivatize the surface of third-generation (G3) polyamidoamine (PAMAM) dendrimers. The resulting conjugates carried multiple copies of the agonist attached through a thiourea linkage and differed in the number of attachments and in the presence of a fluorophore or additional surface modification. Computer modeling studies suggested that these DITC-APEC-loaded dendrimers extended the overall diameter of the previously reported PAMAM-CGS21680 dendrimer derivatives (Kim et al., Bioconjugate Chem 2008 19:406-411) by ca. 20 A, potentially increasing the conformational flexibility of the appended ligands to achieve optimal geometry for efficient binding at A(2A) ARs. Increased affinity and selectivity in binding in comparison to the CGS21680 conjugate were envisioned, due to the presence of an extended linker, i.e., a dithioureylenephenyl functionality. In vitro radioligand competition experiments showed effective binding of these PAMAM-DITC-APEC dendrimer conjugates at the human A(2A) and A(3) ARs with submicromolar K (i) values and selectivity in comparison to the human A(1) AR. Furthermore, these nucleoside-loaded dendrimers exhibited an A(2A) AR-mediated inhibitory effect on ADP-induced aggregation of human platelets. The present study demonstrates the potential of applying the functionalized congener concept to engineer dendrimer-based multivalent ligands for G protein-coupled receptors. PMID:18600474

  9. Recent improvements in the development of A2B adenosine receptor agonists

    PubMed Central

    Tabrizi, Mojgan Aghazadeh; Fruttarolo, Francesca; Romagnoli, Romeo; Preti, Delia

    2009-01-01

    Adenosine is known to exert most of its physiological functions by acting as local modulator at four receptor subtypes named A1, A2A, A2B and A3 (ARs). Principally as a result of the difficulty in identifying potent and selective agonists, the A2B AR is the least extensively characterised of the adenosine receptors family. Despite these limitations, growing understanding of the physiological meaning of this target indicates promising therapeutic perspectives for specific ligands. As A2B AR signalling seems to be associated with pre/postconditioning cardioprotective and anti-inflammatory mechanisms, selective agonists may represent a new therapeutic group for patients suffering from coronary artery disease. Herein we present an overview of the recent advancements in identifying potent and selective A2B AR agonists reported in scientific and patent literature. These compounds can be classified into adenosine-like and nonadenosine ligands. Nucleoside-based agonists are the result of modifying adenosine by substitution at the N6-, C2-positions of the purine heterocycle and/or at the 5′-position of the ribose moiety or combinations of these substitutions. Compounds 1-deoxy-1-{6-[N′-(furan-2-carbonyl)-hydrazino]-9H-purin-9-yl}-N-ethyl-β-D-ribofuranuronamide (19, hA1Ki = 1050 nM, hA2AKi = 1550 nM, hA2B EC50 = 82 nM, hA3Ki > 5 μM) and its 2-chloro analogue 23 (hA1Ki = 3500 nM, hA2AKi = 4950 nM, hA2B EC50 = 210 nM, hA3Ki > 5 μM) were confirmed to be potent and selective full agonists in a cyclic adenosine monophosphate (cAMP) functional assay in Chinese hamster ovary (CHO) cells expressing hA2B AR. Nonribose ligands are represented by conveniently substituted dicarbonitrilepyridines, among which 2-[6-amino-3,5-dicyano-4-[4-(cyclopropylmethoxy)phenyl]pyridin-2-ylsulfanyl]acetamide (BAY-60–6583, hA1, hA2A, hA3 EC50 > 10 μM; hA2B EC50 = 3 nM) is currently under preclinical-phase investigation for treating coronary

  10. Recent improvements in the development of A2B adenosine receptor agonists

    PubMed Central

    Tabrizi, Mojgan Aghazadeh; Fruttarolo, Francesca; Romagnoli, Romeo; Preti, Delia

    2008-01-01

    Adenosine is known to exert most of its physiological functions by acting as local modulator at four receptor subtypes named A1, A2A, A2B and A3 (ARs). Principally as a result of the difficulty in identifying potent and selective agonists, the A2B AR is the least extensively characterised of the adenosine receptors family. Despite these limitations, growing understanding of the physiological meaning of this target indicates promising therapeutic perspectives for specific ligands. As A2B AR signalling seems to be associated with pre/postconditioning cardioprotective and anti-inflammatory mechanisms, selective agonists may represent a new therapeutic group for patients suffering from coronary artery disease. Herein we present an overview of the recent advancements in identifying potent and selective A2B AR agonists reported in scientific and patent literature. These compounds can be classified into adenosine-like and nonadenosine ligands. Nucleoside-based agonists are the result of modifying adenosine by substitution at the N6-, C2-positions of the purine heterocycle and/or at the 5′-position of the ribose moiety or combinations of these substitutions. Compounds 1-deoxy-1-{6-[N′-(furan-2-carbonyl)-hydrazino]-9H-purin-9-yl}-N-ethyl-β-D-ribofuranuronamide (19, hA1Ki = 1050 nM, hA2AKi = 1550 nM, hA2B EC50 = 82 nM, hA3Ki > 5 μM) and its 2-chloro analogue 23 (hA1Ki = 3500 nM, hA2AKi = 4950 nM, hA2B EC50 = 210 nM, hA3Ki > 5 μM) were confirmed to be potent and selective full agonists in a cyclic adenosine monophosphate (cAMP) functional assay in Chinese hamster ovary (CHO) cells expressing hA2B AR. Nonribose ligands are represented by conveniently substituted dicarbonitrilepyridines, among which 2-[6-amino-3,5-dicyano-4-[4-(cyclopropylmethoxy)phenyl]pyridin-2-ylsulfanyl]acetamide (BAY-60–6583, hA1, hA2A, hA3 EC50 > 10 μM; hA2B EC50 = 3 nM) is currently under preclinical-phase investigation for treating coronary

  11. Liver X Receptor and Peroxisome Proliferator-Activated Receptor Agonist from Cornus alternifolia

    PubMed Central

    He, Yang-Qing; Ma, Guo-Yi; Peng, Jiang-nan; Ma, Zhan-Ying; Hamann, Mark T.

    2012-01-01

    Background Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear receptors superfamily and are transcription factors activated by specific ligands. Liver X receptors (LXR) belong to the nuclear hormone receptors and have been shown to play an important role in cholesterol homeostasis. From the previous screening of several medicinal plants for potential partial PPARγ agonists, the extracts of Cornus alternifolia were found to exhibit promising bioactivity. In this paper, we report the isolation and structural elucidation of four new compounds and their potential as ligands for PPAR. Methods The new compounds were extracted from the leaves of Cornus alternifolia and fractionated by high-performance liquid chromatography. Their structures were elucidated on the basis of spectroscopic evidence and analysis of their hydrolysis products. Results Three new iridoid glycosides including an iridolactone, alternosides A-C (1–3), a new megastigmane glycoside, cornalternoside (4) and 10 known compounds, were obtained from the leaves of Cornus alternifolia. Kaempferol-3-O-β-glucopyranoside (5) exhibited potent agonistic activities for PPARα, PPARγ and LXR with EC50 values of 0.62, 3.0 and 1.8 μ M, respectively. Conclusions We isolated four new and ten known compounds from Cornus alternifolia, and one known compound showed agonistic activities for PPARα, PPARγ and LXR. General significance Compound 1 is the first example of a naturally occurring iridoid glycoside containing a β-glucopyranoside moiety at C-6. PMID:22353334

  12. Dihydromorphine-peptide hybrids with delta receptor agonistic and mu receptor antagonistic actions

    SciTech Connect

    Smith, C.B.; Medzihradsky, F.; Woods, J.H.

    1986-03-05

    The actions of two morphine derivatives with short peptide side chains were evaluated upon the contraction of the isolated mouse vas deferens and upon displacement of /sup 3/H-etorphine from rat brain membranes. NIH-9833 (N-(6,14-endoetheno-7,8-dihydromorphine-7-alpha-carbonyl)-L-phenylalanyl-L-leucine ethyl ester HCl) was a potent agonist upon the vas deferens. Its EC50 for inhibition of the twitch was 1.2 +/- 0.1 nM. Both naltrexone (10/sup -7/ M) a relatively nonselective opioid antagonist, and ICI-174864 (10/sup -/' M) a highly selective delta receptor antagonist, blocked the actions of NIH-9833 which indicates that this drug is a delta receptor agonist. In contrast, NIH-9835 (N-(6,14-endoetheno-7,8-dihydromorphine-7-alpha-carbonyl)-L-glycyl-L-phenylalanyl-L-leucine ethyl ester HCl), which differs from NIH-9835 by the presence of a single amino acid residue, was devoid of opioid agonistic activity but was a potent antagonist of the inhibitory actions on the vas deferens of morphine and sufentanil. NIH-9833 and NIH-9835 were potent displacers of /sup 3/H-etorphine from rat cerebral membranes with EC50's of 0.58 nM and 1.7 nM, respectively. The observation that addition of a single glycyl group changes a dihydromorphine-peptide analog from a potent delta receptor agonist to an equally potent mu receptor antagonist suggests that the two receptor sites might be structurally quite similar.

  13. Classical and atypical agonists activate M1 muscarinic acetylcholine receptors through common mechanisms.

    PubMed

    Randáková, Alena; Dolejší, Eva; Rudajev, Vladimír; Zimčík, Pavel; Doležal, Vladimír; El-Fakahany, Esam E; Jakubík, Jan

    2015-07-01

    We mutated key amino acids of the human variant of the M1 muscarinic receptor that target ligand binding, receptor activation, and receptor-G protein interaction. We compared the effects of these mutations on the action of two atypical M1 functionally preferring agonists (N-desmethylclozapine and xanomeline) and two classical non-selective orthosteric agonists (carbachol and oxotremorine). Mutations of D105 in the orthosteric binding site and mutation of D99 located out of the orthosteric binding site decreased affinity of all tested agonists that was translated as a decrease in potency in accumulation of inositol phosphates and intracellular calcium mobilization. Mutation of D105 decreased the potency of the atypical agonist xanomeline more than that of the classical agonists carbachol and oxotremorine. Mutation of the residues involved in receptor activation (D71) and coupling to G-proteins (R123) completely abolished the functional responses to both classical and atypical agonists. Our data show that both classical and atypical agonists activate hM1 receptors by the same molecular switch that involves D71 in the second transmembrane helix. The principal difference among the studied agonists is rather in the way they interact with D105 in the orthosteric binding site. Furthermore, our data demonstrate a key role of D105 in xanomeline wash-resistant binding and persistent activation of hM1 by wash-resistant xanomeline. PMID:25882246

  14. Adenosine A2A receptor activation reduces recurrence and mortality from Clostridium difficile infection in mice following vancomycin treatment

    PubMed Central

    2012-01-01

    Background Activation of the A2A adenosine receptor (A2AAR) decreases production of inflammatory cytokines, prevents C. difficile toxin A-induced enteritis and, in combination with antibiotics, increases survival from sepsis in mice. We investigated whether A2AAR activation improves and A2AAR deletion worsens outcomes in a murine model of C. difficile (strain VPI10463) infection (CDI). Methods C57BL/6 mice were pretreated with an antibiotic cocktail prior to infection and then treated with vancomycin with or without an A2AAR agonist. A2AAR-/- and littermate wild-type (WT) mice were similarly infected, and IFNγ and TNFα were measured at peak of and recovery from infection. Results Infected, untreated mice rapidly lost weight, developed diarrhea, and had mortality rates of 50-60%. Infected mice treated with vancomycin had less weight loss and diarrhea during antibiotic treatment but mortality increased to near 100% after discontinuation of antibiotics. Infected mice treated with both vancomycin and an A2AAR agonist, either ATL370 or ATL1222, had minimal weight loss and better long-term survival than mice treated with vancomycin alone. A2AAR KO mice were more susceptible than WT mice to death from CDI. Increases in cecal IFNγ and blood TNFα were pronounced in the absence of A2AARs. Conclusion In a murine model of CDI, vancomycin treatment resulted in reduced weight loss and diarrhea during acute infection, but high recurrence and late-onset death, with overall mortality being worse than untreated infected controls. The administration of vancomycin plus an A2AAR agonist reduced inflammation and improved survival rates, suggesting a possible benefit of A2AAR agonists in the management of CDI to prevent recurrent disease. PMID:23217055

  15. Meclizine is an agonist ligand for mouse constitutive androstane receptor (CAR) and an inverse agonist for human CAR.

    PubMed

    Huang, Wendong; Zhang, Jun; Wei, Ping; Schrader, William T; Moore, David D

    2004-10-01

    The constitutive androstane receptor (CAR, NR1I3) is a key regulator of xenobiotic and endobiotic metabolism. The ligand-binding domains of murine (m) and human (h) CAR are divergent relative to other nuclear hormone receptors, resulting in species-specific differences in xenobiotic responses. Here we identify the widely used antiemetic meclizine (Antivert; Bonine) as both an agonist ligand for mCAR and an inverse agonist for hCAR. Meclizine increases mCAR transactivation in a dose-dependent manner. Like the mCAR agonist 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene, meclizine stimulates binding of steroid receptor coactivator 1 to the murine receptor in vitro. Meclizine administration to mice increases expression of CAR target genes in a CAR-dependent manner. In contrast, meclizine suppresses hCAR transactivation and inhibits the phenobarbital-induced expression of the CAR target genes, cytochrome p450 monooxygenase (CYP)2B10, CYP3A11, and CYP1A2, in primary hepatocytes derived from mice expressing hCAR, but not mCAR. The inhibitory effect of meclizine also suppresses acetaminophen-induced liver toxicity in humanized CAR mice. These results demonstrate that a single compound can induce opposite xenobiotic responses via orthologous receptors in rodents and humans. PMID:15272053

  16. GABAB Receptor-Positive Modulators: Enhancement of GABAB Receptor Agonist Effects In Vivo

    PubMed Central

    France, Charles P.; Cheng, Kejun; Rice, Kenner C.

    2010-01-01

    In vivo effects of GABAB receptor-positive modulators suggest that they have therapeutic potential for treating central nervous system disorders such as anxiety, depression, and drug abuse. Although these effects generally are thought to be mediated by positive modulation of GABAB receptors, such modulation has been examined primarily in vitro. The present study was aimed at further examining the in vivo positive modulatory properties of the GABAB receptor-positive modulators, 2,6-di-tert-butyl-4-(3-hydroxy-2,2-dimethylpropyl) phenol (CGP7930) and (R,S)-5,7-di-tert-butyl-3-hydroxy-3-trifluoromethyl-3H-benzofuran-2-one (rac-BHFF). Both compounds enhanced loss of righting induced by baclofen in mice. However, CGP7930 was less effective and rac-BHFF was less potent for enhancing loss of righting induced by γ-hydroxybutyrate (GHB), which, like baclofen, has GABAB receptor agonist properties. In contrast with baclofen- and GHB-induced loss of righting, the hypothermic effects of baclofen and GHB were not enhanced by rac-BHFF but were enhanced by CGP7930 only at doses that produced hypothermia when given alone. CGP7930-induced hypothermia was not attenuated by the GABAB receptor antagonist 3-aminopropyl(diethoxymethyl)phosphinic acid (CGP35348), at doses that blocked baclofen-induced hypothermia, and was not increased by the nitric-oxide synthase inhibitor Nω-nitro-l-arginine methyl ester, at doses that increased the hypothermic effects of baclofen and GHB. The results provide evidence that CGP7930 and rac-BHFF act in vivo as positive modulators at GABAB receptors mediating loss of righting, but not at GABAB receptors mediating hypothermia. Conceivably, CGP7930, but not rac-BHFF, acts as an allosteric agonist at these latter receptors. Taken together, the results provide further evidence of pharmacologically distinct GABAB receptor subtypes, possibly allowing for a more selective therapeutic interference with the GABAB system. PMID:20628000

  17. Discovery of potent and selective nonsteroidal indazolyl amide glucocorticoid receptor agonists.

    PubMed

    Sheppeck, James E; Gilmore, John L; Xiao, Hai-Yun; Dhar, T G Murali; Nirschl, David; Doweyko, Arthur M; Sack, Jack S; Corbett, Martin J; Malley, Mary F; Gougoutas, Jack Z; Mckay, Lorraine; Cunningham, Mark D; Habte, Sium F; Dodd, John H; Nadler, Steven G; Somerville, John E; Barrish, Joel C

    2013-10-01

    Modification of a phenolic lead structure based on lessons learned from increasing the potency of steroidal glucocorticoid agonists lead to the discovery of exceptionally potent, nonsteroidal, indazole GR agonists. SAR was developed to achieve good selectivity against other nuclear hormone receptors with the ultimate goal of achieving a dissociated GR agonist as measured by human in vitro assays. The specific interactions by which this class of compounds inhibits GR was elucidated by solving an X-ray co-crystal structure. PMID:23953070

  18. Sustained wash-resistant receptor activation responses of GPR119 agonists.

    PubMed

    Hothersall, J Daniel; Bussey, Charlotte E; Brown, Alastair J; Scott, James S; Dale, Ian; Rawlins, Philip

    2015-09-01

    G protein-coupled receptor 119 (GPR119) is involved in regulating metabolic homoeostasis, with GPR119 agonists targeted for the treatment of type-2 diabetes and obesity. Using the endogenous agonist oleoylethanolamide and a number of small molecule synthetic agonists we have investigated the temporal dynamics of receptor signalling. Using both a dynamic luminescence biosensor-based assay and an endpoint cAMP accumulation assay we show that agonist-driven desensitization is not a major regulatory mechanism for GPR119 despite robust activation responses, regardless of the agonist used. Temporal analysis of the cAMP responses demonstrated sustained signalling resistant to washout for some, but not all of the agonists tested. Further analysis indicated that the sustained effects of one synthetic agonist AR-231,453 were consistent with a role for slow dissociation kinetics. In contrast, the sustained responses to MBX-2982 and AZ1 appeared to involve membrane deposition. We also detect wash-resistant responses to AR-231,453 at the level of physiologically relevant responses in an endogenous expression system (GLP-1 secretion in GLUTag cells). In conclusion, our findings indicate that in a recombinant expression system GPR119 activation is sustained, with little evidence of pronounced receptor desensitization, and for some ligands persistent agonist responses continue despite removal of excess agonist. This provides novel understanding of the temporal responses profiles of potential drug candidates targetting GPR119, and highlights the importance of carefully examining the the mechanisms through which GPCRs generate sustained responses. PMID:26101059

  19. Selective activation of adenosine A2A receptors on immune cells by a CD73-dependent prodrug suppresses joint inflammation in experimental rheumatoid arthritis.

    PubMed

    Flögel, Ulrich; Burghoff, Sandra; van Lent, Peter L E M; Temme, Sebastian; Galbarz, Lisa; Ding, Zhaoping; El-Tayeb, Ali; Huels, Sandra; Bönner, Florian; Borg, Nadine; Jacoby, Christoph; Müller, Christa E; van den Berg, Wim B; Schrader, Jürgen

    2012-08-01

    Adenosine A(2A) receptor (A(2A)R) agonists are both highly effective anti-inflammatory agents and potent vasodilators. To separate these two activities, we have synthesized phosphorylated A(2A)R agonists (prodrugs) that require the presence of ecto-5'-nucleotidase (CD73) to become activated. In the model of collagen-induced arthritis, 2-(cyclohexylethylthio)adenosine 5'-monophosphate (chet-AMP), but not 2-(cyclohexylethylthio)adenosine (chet-adenosine), potently reduced inflammation as assessed by fluorine-19 ((19)F) magnetic resonance imaging and by histology. The prodrug effect was blunted by inhibition of CD73 and A(2A)R. The selectivity of drug action is due to profound up-regulation of CD73 and adenosine A(2A)R expression in neutrophils and inflammatory monocytes as found in recovered cells from the synovial fluid of arthritic mice. Plasma chet-adenosine was in the subnanomolar range when chet-AMP was applied, whereas concentrations required for vasodilation were about 100 times higher. Thus, chet-AMP is a potent immunosuppressant with negligible vasodilatory activity. These data suggest that phosphorylated A(2A)R agonists may serve as a promising new group of drugs for targeted immunotherapy of inflammation. PMID:22875828

  20. Cardiovascular Effects of Glucagon-Like Peptide-1 Receptor Agonists.

    PubMed

    Kang, Yu Mi; Jung, Chang Hee

    2016-06-01

    Glucagon-like peptide-1 (GLP-1) is a member of the proglucagon incretin family, and GLP-1 receptor agonists (RAs) have been introduced as a new class of antidiabetic medications in the past decade. The benefits of GLP-1 RAs are derived from their pleiotropic effects, which include glucose-dependent insulin secretion, suppressed glucagon secretion, and reduced appetite. Moreover, GLP-1 RAs also exert beneficial roles on multiple organ systems in which the GLP-1 receptors exist, including the cardiovascular system. Cardiovascular effects of GLP-1 RAs have been of great interest since the burden from cardiovascular diseases (CVD) has been unbearably increasing in a diabetic population worldwide, despite strict glycemic control and advanced therapeutic techniques to treat CVD. Preclinical studies have already demonstrated the beneficial effects of GLP-1 on myocardium and vascular endothelium, and many clinical studies evaluating changes in surrogate markers of CVD have suggested potential benefits from the use of GLP-1 RAs. Data from numerous clinical trials primarily evaluating the antihyperglycemic effects of multiple GLP-1 RAs have also revealed that changes in most CVD risk markers reported as secondary outcomes have been in favor of GLP-1 RAs treatment. However, to date, there is only one randomized clinical trial of GLP-1 RAs (the ELIXA study) evaluating major cardiovascular events as their primary outcomes, and in this study, a neutral cardiovascular effect of lixisenatide was observed in high-risk diabetic subjects. Therefore, the results of ongoing CVD outcome trials with the use of GLP-1 RAs should be awaited to elucidate the translation of benefits previously seen in CVD risk marker studies into large clinical trials with primary cardiovascular outcomes. PMID:27118277

  1. Cardiovascular Effects of Glucagon-Like Peptide-1 Receptor Agonists

    PubMed Central

    Kang, Yu Mi

    2016-01-01

    Glucagon-like peptide-1 (GLP-1) is a member of the proglucagon incretin family, and GLP-1 receptor agonists (RAs) have been introduced as a new class of antidiabetic medications in the past decade. The benefits of GLP-1 RAs are derived from their pleiotropic effects, which include glucose-dependent insulin secretion, suppressed glucagon secretion, and reduced appetite. Moreover, GLP-1 RAs also exert beneficial roles on multiple organ systems in which the GLP-1 receptors exist, including the cardiovascular system. Cardiovascular effects of GLP-1 RAs have been of great interest since the burden from cardiovascular diseases (CVD) has been unbearably increasing in a diabetic population worldwide, despite strict glycemic control and advanced therapeutic techniques to treat CVD. Preclinical studies have already demonstrated the beneficial effects of GLP-1 on myocardium and vascular endothelium, and many clinical studies evaluating changes in surrogate markers of CVD have suggested potential benefits from the use of GLP-1 RAs. Data from numerous clinical trials primarily evaluating the antihyperglycemic effects of multiple GLP-1 RAs have also revealed that changes in most CVD risk markers reported as secondary outcomes have been in favor of GLP-1 RAs treatment. However, to date, there is only one randomized clinical trial of GLP-1 RAs (the ELIXA study) evaluating major cardiovascular events as their primary outcomes, and in this study, a neutral cardiovascular effect of lixisenatide was observed in high-risk diabetic subjects. Therefore, the results of ongoing CVD outcome trials with the use of GLP-1 RAs should be awaited to elucidate the translation of benefits previously seen in CVD risk marker studies into large clinical trials with primary cardiovascular outcomes. PMID:27118277

  2. Desensitization of Functional µ-Opioid Receptors Increases Agonist Off-Rate

    PubMed Central

    2014-01-01

    Desensitization of µ-opioid receptors (MORs) develops over 5–15 minutes after the application of some, but not all, opioid agonists and lasts for tens of minutes after agonist removal. The decrease in function is receptor selective (homologous) and could result from 1) a reduction in receptor number or 2) a decrease in receptor coupling. The present investigation used photolysis of two caged opioid ligands to examine the kinetics of MOR-induced potassium conductance before and after MOR desensitization. Photolysis of a caged antagonist, carboxynitroveratryl-naloxone (caged naloxone), blocked the current induced by a series of agonists, and the time constant of decline was significantly decreased after desensitization. The increase in the rate of current decay was not observed after partial blockade of receptors with the irreversible antagonist, β-chlornaltrexamine (β-CNA). The time constant of current decay after desensitization was never more rapid than 1 second, suggesting an increased agonist off-rate rather than an increase in the rate of channel closure downstream of the receptor. The rate of G protein–coupled K+ channel (GIRK) current activation was examined using photolysis of a caged agonist, carboxynitrobenzyl-tyrosine-[Leu5]-enkephalin. After acute desensitization or partial irreversible block of MORs with β-CNA, there was an increase in the time it took to reach a peak current. The decrease in the rate of agonist-induced GIRK conductance was receptor selective and dependent on receptor number. The results indicate that opioid receptor desensitization reduced the number of functional receptor and that the remaining active receptors have a reduced agonist affinity. PMID:24748657

  3. Fluorescence characteristics of hydrophobic partial agonist probes of the cholecystokinin receptor.

    PubMed

    Harikumar, Kaleeckal G; Pinon, Delia I; Miller, Laurence J

    2006-04-01

    Fluorescence spectroscopic studies are powerful tools for the evaluation of receptor structure and the dynamic changes associated with receptor activation. Here, we have developed two chemically distinct fluorescent probes of the cholecystokinin (CCK) receptor by attaching acrylodan or a nitrobenzoxadiazole moiety to the amino terminus of a partial agonist CCK analogue. These two probes were able to bind to the CCK receptor specifically and with high affinity, and were able to elicit only submaximal intracellular calcium responses typical of partial agonists. The fluorescence characteristics of these probes were compared with those previously reported for structurally-related full agonist and antagonist probes. Like the previous probes, the partial agonist probes exhibited longer fluorescence lifetimes and increased anisotropy when bound to the receptor than when free in solution. The receptor-bound probes were not easily quenched by potassium iodide, suggesting that the fluorophores were protected from the extracellular aqueous milieu. The fluorescence characteristics of the partial agonist probes were quite similar to those of the analogous full agonist probes and quite distinct from the analogous antagonist probes. These data suggest that the partially activated conformational state of this receptor is more closely related to its fully active state than to its inactive state. PMID:16779661

  4. Identification of Ecdysone Hormone Receptor Agonists as a Therapeutic Approach for Treating Filarial Infections

    PubMed Central

    Mhashilkar, Amruta S.; Vankayala, Sai L.; Liu, Canhui; Kearns, Fiona; Mehrotra, Priyanka; Tzertzinis, George; Palli, Subba R.; Woodcock, H. Lee; Unnasch, Thomas R.

    2016-01-01

    Background A homologue of the ecdysone receptor has previously been identified in human filarial parasites. As the ecdysone receptor is not found in vertebrates, it and the regulatory pathways it controls represent attractive potential chemotherapeutic targets. Methodology/ Principal Findings Administration of 20-hydroxyecdysone to gerbils infected with B. malayi infective larvae disrupted their development to adult stage parasites. A stable mammalian cell line was created incorporating the B. malayi ecdysone receptor ligand-binding domain, its heterodimer partner and a secreted luciferase reporter in HEK293 cells. This was employed to screen a series of ecdysone agonist, identifying seven agonists active at sub-micromolar concentrations. A B. malayi ecdysone receptor ligand-binding domain was developed and used to study the ligand-receptor interactions of these agonists. An excellent correlation between the virtual screening results and the screening assay was observed. Based on both of these approaches, steroidal ecdysone agonists and the diacylhydrazine family of compounds were identified as a fruitful source of potential receptor agonists. In further confirmation of the modeling and screening results, Ponasterone A and Muristerone A, two compounds predicted to be strong ecdysone agonists stimulated expulsion of microfilaria and immature stages from adult parasites. Conclusions The studies validate the potential of the B. malayi ecdysone receptor as a drug target and provide a means to rapidly evaluate compounds for development of a new class of drugs against the human filarial parasites. PMID:27300294

  5. Synaptic mechanisms of adenosine A2A receptor-mediated hyperexcitability in the hippocampus.

    PubMed

    Rombo, Diogo M; Newton, Kathryn; Nissen, Wiebke; Badurek, Sylvia; Horn, Jacqueline M; Minichiello, Liliana; Jefferys, John G R; Sebastiao, Ana M; Lamsa, Karri P

    2015-05-01

    Adenosine inhibits excitatory neurons widely in the brain through adenosine A1 receptor, but activation of adenosine A2A receptor (A2A R) has an opposite effect promoting discharge in neuronal networks. In the hippocampus A2A R expression level is low, and the receptor's effect on identified neuronal circuits is unknown. Using optogenetic afferent stimulation and whole-cell recording from identified postsynaptic neurons we show that A2A R facilitates excitatory glutamatergic Schaffer collateral synapses to CA1 pyramidal cells, but not to GABAergic inhibitory interneurons. In addition, A2A R enhances GABAergic inhibitory transmission between CA1 area interneurons leading to disinhibition of pyramidal cells. Adenosine A2A R has no direct modulatory effect on GABAergic synapses to pyramidal cells. As a result adenosine A2A R activation alters the synaptic excitation - inhibition balance in the CA1 area resulting in increased pyramidal cell discharge to glutamatergic Schaffer collateral stimulation. In line with this, we show that A2A R promotes synchronous pyramidal cell firing in hyperexcitable conditions where extracellular potassium is elevated or following high-frequency electrical stimulation. Our results revealed selective synapse- and cell type specific adenosine A2A R effects in hippocampal CA1 area. The uncovered mechanisms help our understanding of A2A R's facilitatory effect on cortical network activity. PMID:25402014

  6. Combined sodium ion sensitivity in agonist binding and internalization of vasopressin V1b receptors.

    PubMed

    Koshimizu, Taka-Aki; Kashiwazaki, Aki; Taniguchi, Junichi

    2016-01-01

    Reducing Na(+) in the extracellular environment may lead to two beneficial effects for increasing agonist binding to cell surface G-protein coupled receptors (GPCRs): reduction of Na(+)-mediated binding block and reduce of receptor internalization. However, such combined effects have not been explored. We used Chinese Hamster Ovary cells expressing vasopressin V1b receptors as a model to explore Na(+) sensitivity in agonist binding and receptor internalization. Under basal conditions, a large fraction of V1b receptors is located intracellularly, and a small fraction is in the plasma membrane. Decreases in external Na(+) increased cell surface [(3)H]AVP binding and decreased receptor internalization. Substitution of Na(+) by Cs(+) or NH4(+) inhibited agonist binding. To suppress receptor internalization, the concentration of NaCl, but not of CsCl, had to be less than 50 mM, due to the high sensitivity of the internalization machinery to Na(+) over Cs(+). Iso-osmotic supplementation of glucose or NH4Cl maintained internalization of the V1b receptor, even in a low-NaCl environment. Moreover, iodide ions, which acted as a counter anion, inhibited V1b agonist binding. In summary, we found external ionic conditions that could increase the presence of high-affinity state receptors at the cell surface with minimum internalization during agonist stimulations. PMID:27138239

  7. Combined sodium ion sensitivity in agonist binding and internalization of vasopressin V1b receptors

    PubMed Central

    Koshimizu, Taka-aki; Kashiwazaki, Aki; Taniguchi, Junichi

    2016-01-01

    Reducing Na+ in the extracellular environment may lead to two beneficial effects for increasing agonist binding to cell surface G-protein coupled receptors (GPCRs): reduction of Na+-mediated binding block and reduce of receptor internalization. However, such combined effects have not been explored. We used Chinese Hamster Ovary cells expressing vasopressin V1b receptors as a model to explore Na+ sensitivity in agonist binding and receptor internalization. Under basal conditions, a large fraction of V1b receptors is located intracellularly, and a small fraction is in the plasma membrane. Decreases in external Na+ increased cell surface [3H]AVP binding and decreased receptor internalization. Substitution of Na+ by Cs+ or NH4+ inhibited agonist binding. To suppress receptor internalization, the concentration of NaCl, but not of CsCl, had to be less than 50 mM, due to the high sensitivity of the internalization machinery to Na+ over Cs+. Iso-osmotic supplementation of glucose or NH4Cl maintained internalization of the V1b receptor, even in a low-NaCl environment. Moreover, iodide ions, which acted as a counter anion, inhibited V1b agonist binding. In summary, we found external ionic conditions that could increase the presence of high-affinity state receptors at the cell surface with minimum internalization during agonist stimulations. PMID:27138239

  8. Potent achiral agonists of the ghrelin (growth hormone secretagogue) receptor. Part I: Lead identification.

    PubMed

    Heightman, Tom D; Scott, Jackie S; Longley, Mark; Bordas, Vincent; Dean, David K; Elliott, Richard; Hutley, Gail; Witherington, Jason; Abberley, Lee; Passingham, Barry; Berlanga, Manuela; de Los Frailes, Maite; Wise, Alan; Powney, Ben; Muir, Alison; McKay, Fiona; Butler, Sharon; Winborn, Kim; Gardner, Christopher; Darton, Jill; Campbell, Colin; Sanger, Gareth

    2007-12-01

    High throughput screening combined with efficient datamining and parallel synthesis led to the discovery of a novel series of indolines showing potent in vitro ghrelin receptor agonist activity and acceleration of gastric emptying in rats. PMID:17942309

  9. Aryl sulphonyl amides as potent agonists of the growth hormone secretagogue (ghrelin) receptor.

    PubMed

    Witherington, Jason; Abberley, Lee; Bellenie, Benjamin R; Boatman, Rio; Collis, Katharine; Dean, David K; Gaiba, Alessandra; King, N Paul; Shuker, Nicola; Steadman, Jon G A; Takle, Andrew K; Sanger, Gareth; Butler, Sharon; McKay, Fiona; Muir, Alison; Winborn, Kim; Ward, Robert W; Heightman, Tom D

    2009-02-01

    As part of an on-going lead optimisation effort, a cross screening exercise identified an aryl sulphonyl amide hit that was optimised to afford a highly potent series of ghrelin receptor agonists. PMID:19128969

  10. Trial Watch: Immunostimulation with Toll-like receptor agonists in cancer therapy

    PubMed Central

    Iribarren, Kristina; Bloy, Norma; Buqué, Aitziber; Cremer, Isabelle; Eggermont, Alexander; Fridman, Wolf Hervé; Fucikova, Jitka; Galon, Jérôme; Špíšek, Radek; Zitvogel, Laurence; Kroemer, Guido; Galluzzi, Lorenzo

    2016-01-01

    ABSTRACT Accumulating preclinical evidence indicates that Toll-like receptor (TLR) agonists efficiently boost tumor-targeting immune responses (re)initiated by most, if not all, paradigms of anticancer immunotherapy. Moreover, TLR agonists have been successfully employed to ameliorate the efficacy of various chemotherapeutics and targeted anticancer agents, at least in rodent tumor models. So far, only three TLR agonists have been approved by regulatory agencies for use in cancer patients. Moreover, over the past decade, the interest of scientists and clinicians in these immunostimulatory agents has been fluctuating. Here, we summarize recent advances in the preclinical and clinical development of TLR agonists for cancer therapy. PMID:27141345

  11. Rational design of orally-active, pyrrolidine-based progesterone receptor partial agonists

    SciTech Connect

    Thompson, Scott K.; Washburn, David G.; Frazee, James S.; Madauss, Kevin P.; Hoang, Tram H.; Lapinski, Leahann; Grygielko, Eugene T.; Glace, Lindsay E.; Trizna, Walter; Williams, Shawn P.; Duraiswami, Chaya; Bray, Jeffrey D.; Laping, Nicholas J.

    2010-09-03

    Using the X-ray crystal structure of an amide-based progesterone receptor (PR) partial agonist bound to the PR ligand binding domain, a novel PR partial agonist class containing a pyrrolidine ring was designed. Members of this class of N-alkylpyrrolidines demonstrate potent and highly selective partial agonism of the progesterone receptor, and one of these analogs was shown to be efficacious upon oral dosing in the OVX rat model of estrogen opposition.

  12. Differential effects of subtype-specific nicotinic acetylcholine receptor agonists on early and late hippocampal LTP.

    PubMed

    Kroker, Katja S; Rast, Georg; Rosenbrock, Holger

    2011-12-01

    Brain nicotinic acetylcholine receptors are involved in several neuropsychiatric disorders, e.g. Alzheimer's and Parkinson's diseases, Tourette's syndrome, schizophrenia, depression, autism, attention deficit hyperactivity disorder, and anxiety. Currently, approaches selectively targeting the activation of specific nicotinic acetylcholine receptors are in clinical development for treatment of memory impairment of Alzheimer's disease patients. These are α4β2 and α7 nicotinic acetylcholine receptor agonists which are believed to enhance cholinergic and glutamatergic neurotransmission, respectively. In order to gain a better insight into the mechanistic role of these two nicotinic acetylcholine receptors in learning and memory, we investigated the effects of the α4β2 nicotinic acetylcholine receptor agonist TC-1827 and the α7 nicotinic acetylcholine receptor partial agonist SSR180711 on hippocampal long-term potentiation (LTP), a widely accepted cellular experimental model of memory formation. Generally, LTP is distinguished in an early and a late form, the former being protein-synthesis independent and the latter being protein-synthesis dependent. TC-1827 was found to increase early LTP in a bell-shaped dose dependent manner, but did not affect late LTP. In contrast, the α7 nicotinic acetylcholine receptor partial agonist SSR180711 showed enhancing effects on both early and late LTP in a bell-shaped manner. Furthermore, SSR180711 not only increased early LTP, but also transformed it into late LTP, which was not observed with the α4β2 nicotinic acetylcholine receptor agonist. Therefore, based on these findings α7 nicotinic acetylcholine receptor (partial) agonists appear to exhibit stronger efficacy on memory improvement than α4β2 nicotinic acetylcholine receptor agonists. PMID:21968142

  13. Direct or indirect stimulation of adenosine A2A receptors enhances bone regeneration as well as bone morphogenetic protein-2

    PubMed Central

    Mediero, Aránzazu; Wilder, Tuere; Perez-Aso, Miguel; Cronstein, Bruce N.

    2015-01-01

    Promoting bone regeneration and repair of bone defects is a need that has not been well met to date. We have previously found that adenosine, acting via A2A receptors (A2AR) promotes wound healing and inhibits inflammatory osteolysis and hypothesized that A2AR might be a novel target to promote bone regeneration. Therefore, we determined whether direct A2AR stimulation or increasing endogenous adenosine concentrations via purine transport blockade with dipyridamole regulates bone formation. We determined whether coverage of a 3 mm trephine defect in a mouse skull with a collagen scaffold soaked in saline, bone morphogenetic protein-2 (BMP-2; 200 ng), 1 μM CGS21680 (A2AR agonist, EC50 = 160 nM), or 1 μM dipyridamole (EC50 = 32 nM) promoted bone regeneration. Microcomputed tomography examination demonstrated that CGS21680 and dipyridamole markedly enhanced bone regeneration as well as BMP-2 8 wk after surgery (60 ± 2%, 79 ± 2%, and 75 ± 1% bone regeneration, respectively, vs. 32 ± 2% in control, P < 0.001). Blockade by a selective A2AR antagonist (ZM241385, 1 μM) or deletion of A2AR abrogated the effect of CGS21680 and dipyridamole on bone regeneration. Both CGS21680 and dipyridamole treatment increased alkaline phosphatase-positive osteoblasts and diminished tartrate resistance acid phosphatase-positive osteoclasts in the defects. In vivo imaging with a fluorescent dye for new bone formation revealed a strong fluorescent signal in treated animals that was equivalent to BMP-2. In conclusion, stimulation of A2AR by specific agonists or by increasing endogenous adenosine levels stimulates new bone formation as well as BMP-2 and represents a novel approach to stimulating bone regeneration.—Mediero, A., Wilder, T., Perez-Aso, M., Cronstein, B. N. Direct or indirect stimulation of adenosine A2A receptors enhances bone regeneration as well as bone morphogenetic protein-2. PMID:25573752

  14. Positive cooperativity of acetylcholine and other agonists with allosteric ligands on muscarinic acetylcholine receptors.

    PubMed

    Jakubík, J; Bacáková, L; El-Fakahany, E E; Tucek, S

    1997-07-01

    It is well known that allosteric modulators of muscarinic acetylcholine receptors can both diminish and increase the affinity of receptors for their antagonists. We investigated whether the allosteric modulators can also increase the affinity of receptors for their agonists. Twelve agonists and five allosteric modulators were tested in experiments on membranes of CHO cells that had been stably transfected with genes for the M1-M4 receptor subtypes. Allosterically induced changes in the affinities for agonists were computed from changes in the ability of a fixed concentration of each agonist to compete with [3H]N-methylscopolamine for the binding to the receptors in the absence and the presence of varying concentrations of allosteric modulators. The effects of allosteric modulators varied greatly depending on the agonists and the subtypes of receptors. The affinity for acetylcholine was augmented by (-)-eburnamonine on the M2 and M4 receptors and by brucine on the M1 and M3 receptors. Brucine also enhanced the affinities for carbachol, bethanechol, furmethide, methylfurmethide, pilocarpine, 3-(3-pentylthio-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1- methylpyridine (pentylthio-TZTP), oxotremorine-M, and McN-A-343 on the M1, M3, and M4 receptors, for pentylthio-TZTP on the M2 receptors, and for arecoline on the M3 receptors. (-)-Eburnamonine enhanced the affinities for carbachol, bethanechol, furmethide, methylfurmethide, pentylthio-TZTP, pilocarpine, oxotremorine and oxotremorine-M on the M2 receptors and for pilocarpine on the M4 receptors. Vincamine, strychnine, and alcuronium displayed fewer positive allosteric interactions with the agonists, but each allosteric modulator displayed positive cooperativity with at least one agonist on at least one muscarinic receptor subtype. The highest degrees of positive cooperativity were observed between (-)-eburnamonine and pilocarpine and (-)-eburnamonine and oxotremorine-M on the M2 receptors (25- and 7-fold increases in

  15. CYP-epoxygenases contribute to A2A receptor-mediated aortic relaxation via sarcolemmal KATP channels.

    PubMed

    Ponnoth, Dovenia S; Nayeem, Mohammed A; Tilley, Stephen L; Ledent, Catherine; Jamal Mustafa, S

    2012-11-15

    Previously, we have shown that A(2A) adenosine receptor (A(2A)AR) mediates aortic relaxation via cytochrome P-450 (CYP)-epoxygenases. However, the signaling mechanism is not understood properly. We hypothesized that ATP-sensitive K(+) (K(ATP)) channels play an important role in A(2A)AR-mediated relaxation. Organ bath and Western blot experiments were done using isolated aorta from A(2A)KO and corresponding wild-type (WT) mice. Aortic rings from WT and A(2A) knockout (KO) mice were precontracted with submaximal dose of phenylephrine (PE, 10(-6) M), and concentration-response curves for pinacidil, cromakalim (nonselective K(ATP) openers), and diazoxide (mitochondrial K(ATP) opener) were obtained. Diazoxide did not have any relaxation effect on PE-precontracted tissues, whereas relaxation to pinacidil (48.09 ± 5.23% in WT vs. 25.41 ± 2.73% in A(2A)KO; P < 0.05) and cromakalim (51.19 ± 2.05% in WT vs. 38.50 ± 2.26% in A(2A)KO; P < 0.05) was higher in WT than A(2A)KO aorta. This suggested the involvement of sarcolemmal rather than mitochondrial K(ATP) channels. Endothelium removal, treatment with SCH 58651 (A(2A)AR antagonist; 10(-6) M), N(G)-nitro-l-arginine methyl ester (l-NAME, nitric oxide synthase inhibitor) and methylsulfonyl-propargyloxyphenylhexanamide (MS-PPOH, CYP-epoxygenases inhibitor; 10(-5) M) significantly reduced pinacidil-induced relaxation in WT compared with controls, whereas these treatments did not have any effect in A(2A)KO aorta. Glibenclamide (K(ATP) channel inhibitor, 10(-5) M) blocked 2-p-(2-carboxyethyl)phenethylamino-5'N-ethylcarboxamido adenosine hydrochloride (CGS 21680, A(2A)AR agonist)-induced relaxation in WT and changed 5'-N-ethylcarboxamide (NECA) (nonselective adenosine analog)-induced response to higher contraction in WT and A(2A)KO. 5-Hydroxydecanoate (5-HD, mitochondrial K(ATP) channel inhibitor, 10(-4) M) had no effect on CGS 21680-mediated response in WT aorta. Our data suggest that A(2A)AR-mediated vasorelaxation occurs

  16. Prolonging Survival of Corneal Transplantation by Selective Sphingosine-1-Phosphate Receptor 1 Agonist

    PubMed Central

    Gao, Min; Liu, Yong; Xiao, Yang; Han, Gencheng; Jia, Liang; Wang, Liqiang; Lei, Tian; Huang, Yifei

    2014-01-01

    Corneal transplantation is the most used therapy for eye disorders. Although the cornea is somewhat an immune privileged organ, immune rejection is still the major problem that reduces the success rate. Therefore, effective chemical drugs that regulate immunoreactions are needed to improve the outcome of corneal transplantations. Here, a sphingosine-1-phosphate receptor 1 (S1P1) selective agonist was systematically evaluated in mouse allogeneic corneal transplantation and compared with the commonly used immunosuppressive agents. Compared with CsA and the non-selective sphingosine 1-phosphate (S1P) receptor agonist FTY720, the S1P1 selective agonist can prolong the survival corneal transplantation for more than 30 days with a low immune response. More importantly, the optimal dose of the S1P1 selective agonist was much less than non-selective S1P receptor agonist FTY720, which would reduce the dose-dependent toxicity in drug application. Then we analyzed the mechanisms of the selected S1P1 selective agonist on the immunosuppression. The results shown that the S1P1 selective agonist could regulate the distribution of the immune cells with less CD4+ T cells and enhanced Treg cells in the allograft, moreover the expression of anti-inflammatory cytokines TGF-β1 and IL-10 unregulated which can reduce the immunoreactions. These findings suggest that S1P1 selective agonist may be a more appropriate immunosuppressive compound to effectively prolong mouse allogeneic corneal grafts survival. PMID:25216235

  17. Involvement of adenosine A2A receptors in depression and anxiety.

    PubMed

    Yamada, Koji; Kobayashi, Minoru; Kanda, Tomoyuki

    2014-01-01

    When administered to normal healthy patients, a nonselective adenosine A1/A2A antagonist, caffeine, tended to improve anxiety and depression at low doses and to exacerbate anxiety at high doses. Caffeine also appears to enhance anxiety-related symptoms in patients with panic disorder, and A2A receptor-deficient mice have been reported to exhibit higher anxiety-like behaviors, as well as a lower incidence of depression-like behaviors. Some selective A2A antagonists were reported to ameliorate anxiety-like behaviors in rodents, while others did not affect these behaviors. In addition, most A2A antagonists showed inhibitory effects on depression-like behaviors. The mechanisms underlying the relationship between A2A receptor antagonists and anxiety and depression remain unclear at the present time, although many studies have produced hypotheses. Given that a selective A2A receptor antagonist has recently become available for use in humans, research on the role of A2A receptors in the treatment of mental illness should progress in the near future. PMID:25175973

  18. Astrocytic adenosine receptor A2A and Gs-coupled signaling regulate memory

    PubMed Central

    Orr, Anna G.; Hsiao, Edward C.; Wang, Max M.; Ho, Kaitlyn; Kim, Daniel H.; Wang, Xin; Guo, Weikun; Kang, Jing; Yu, Gui-Qiu; Adame, Anthony; Devidze, Nino; Dubal, Dena B.; Masliah, Eliezer; Conklin, Bruce R.; Mucke, Lennart

    2014-01-01

    Astrocytes express a variety of G protein-coupled receptors and might influence cognitive functions, such as learning and memory. However, the roles of astrocytic Gs-coupled receptors in cognitive function are not known. We found that humans with Alzheimer’s disease (AD) had increased levels of the Gs-coupled adenosine receptor A2A in astrocytes. Conditional genetic removal of these receptors enhanced long-term memory in young and aging mice, and increased the levels of Arc/Arg3.1, an immediate-early gene required for long-term memory. Chemogenetic activation of astrocytic Gs-coupled signaling reduced long-term memory in mice without affecting learning. Similar to humans with AD, aging mice expressing human amyloid precursor protein (hAPP) showed increased levels of astrocytic A2A receptors. Conditional genetic removal of these receptors enhanced memory in aging hAPP mice. Together, these findings establish a regulatory role for astrocytic Gs-coupled receptors in memory and suggest that AD-linked increases in astrocytic A2A receptor levels contribute to memory loss. PMID:25622143

  19. A molecular characterization of the agonist binding site of a nematode cys-loop GABA receptor

    PubMed Central

    Kaji, Mark D; Kwaka, Ariel; Callanan, Micah K; Nusrat, Humza; Desaulniers, Jean-Paul; Forrester, Sean G

    2015-01-01

    Background and Purpose Cys-loop GABA receptors represent important targets for human chemotherapeutics and insecticides and are potential targets for novel anthelmintics (nematicides). However, compared with insect and mammalian receptors, little is known regarding the pharmacological characteristics of nematode Cys-loop GABA receptors. Here we have investigated the agonist binding site of the Cys-loop GABA receptor UNC-49 (Hco-UNC-49) from the parasitic nematode Haemonchus contortus. Experimental Approach We used two-electrode voltage-clamp electrophysiology to measure channel activation by classical GABA receptor agonists on Hco-UNC-49 expressed in Xenopus laevis oocytes, along with site-directed mutagenesis and in silico homology modelling. Key Results The sulphonated molecules P4S and taurine had no effect on Hco-UNC-49. Other classical Cys-loop GABAA receptor agonists tested on the Hco-UNC-49B/C heteromeric channel had a rank order efficacy of GABA > trans-4-aminocrotonic acid > isoguvacine > imidazole-4-acetic acid (IMA) > (R)-(−)-4-amino-3-hydroxybutyric acid [R(−)-GABOB] > (S)-(+)-4-amino-3-hydroxybutyric acid [S(+)-GABOB] > guanidinoacetic acid > isonipecotic acid > 5-aminovaleric acid (DAVA) (partial agonist) > β-alanine (partial agonist). In silico ligand docking revealed some variation in binding between agonists. Mutagenesis of a key serine residue in binding loop C to threonine had minimal effects on GABA and IMA but significantly increased the maximal response to DAVA and decreased twofold the EC50 for R(−)- and S(+)-GABOB. Conclusions and Implications The pharmacological profile of Hco-UNC-49 differed from that of vertebrate Cys-loop GABA receptors and insect resistance to dieldrin receptors, suggesting differences in the agonist binding pocket. These findings could be exploited to develop new drugs that specifically target GABA receptors of parasitic nematodes. PMID:25850584

  20. A novel fused 1,2,4-triazine aryl derivative as antioxidant and nonselective antagonist of adenosine A(2A) receptors in ethanol-activated liver stellate cells.

    PubMed

    Szuster-Ciesielska, Agnieszka; Sztanke, Krzysztof; Kandefer-Szerszeń, Martyna

    2012-01-01

    It has been detected that hepatic adenosine A(2A) receptors play an active role in the pathogenesis of hepatic fibrosis and suggest a novel therapeutic target in the treatment and prevention of hepatic cirrhosis. In this paper we examined if our new triazine derivative (IMT) can inhibit ethanol-induced activation of HSCs measured as increased α-SMA, collagen synthesis and enhanced oxidative stress in rat liver stellate cells. We also investigated its influence on cytokines (TGF-β, TNF-α) synthesis, MMP-2 and TIMP-1 production and ethanol-induced intracellular signal transduction. Moreover, with using of known adenosine A(2A) receptor agonist (CGS 21680), and antagonist (SCH 58261) we examined if this triazine derivative acts on adenosine receptors. We detected a strong antagonistic action of new triazine derivative (IMT) on ethanol-induced rat liver stellate cells activation, observed as a significant decrease in α-SMA, collagen synthesis, reactive oxygen species production, TGF-β, TNF-α, MMP-2 and TIMP-1 production as well as JNK, p38MAPK, NFκB, IκB, Smad3 phosphorylation. Moreover, IMT strongly inhibited activation of stellate cells by known selective agonist of adenosine A(2A) receptor (CGS 21680). When known A(2A) receptor antagonist (SCH 58261) was used together with IMT this effect was not spectacular. Additionally, only slight enhancement of inhibition was observed when cells were pretreated both IMT with SCH 58261, hence we suppose that IMT acts as nonselective antagonist of A(2A) receptors, and, besides its antioxidant activity, also by this way inhibited ethanol-induced stellate cell activation. PMID:22063920

  1. Involvement of histamine H4 and H1 receptors in scratching induced by histamine receptor agonists in Balb C mice.

    PubMed

    Bell, J K; McQueen, D S; Rees, J L

    2004-05-01

    The role of histamine H(1), H(2), H(3) and H(4) receptors in acute itch induced by histamine was investigated in female BalbC mice. Scratching was induced by intradermal injections of pruritogen into the back of the neck and "itch" assessed by quantifying the scratching evoked. Histamine (0.03-80 micromol), histamine-trifluoromethyl-toluidine (HTMT, H(1) agonist, 0.002-2 micromol), clobenpropit (H(4) agonist, H(3) antagonist, 0.002-0.6 micromol) and to a lesser extent imetit (H(3)/H(4) agonist, 0.03-3 micromol) all induced dose-dependent scratching. Dimaprit (H(2) agonist, 0.04-40 micromol) did not cause scratching. Mepyramine (H(1) antagonist, 20 mg kg(-1), i.p.) reduced scratching evoked by histamine and HTMT, but not that caused by H(3) or H(4) agonists. Thioperamide (H(3)/H(4) antagonist, 20 mg kg(-1), i.p.) reduced scratching induced by histamine, H(3) and H(4) agonists, but not that caused by HTMT. The non-sedating H(1) antagonist, terfenadine, also significantly reduced the scratching induced by the H(1) agonist, HTMT. Cimetidine (H(2) antagonist, 20 mg kg(-1), i.p.) did not affect histamine-induced scratching. These results indicate that activation of histamine H(4) receptors causes itch in mice, in addition to the previously recognised role for H(1) receptors in evoking itch. Histamine H(4) receptor antagonists therefore merit investigation as antipruritic agents. PMID:15066908

  2. Activation of the adenosine A2A receptor attenuates experimental autoimmune encephalomyelitis and is associated with increased intracellular calcium levels.

    PubMed

    Liu, Yumei; Zou, Haifeng; Zhao, Ping; Sun, Bo; Wang, Jinghua; Kong, Qingfei; Mu, Lili; Zhao, Sihan; Wang, Guangyou; Wang, Dandan; Zhang, Yao; Zhao, Jiaying; Yin, Pengqi; Liu, Lei; Zhao, Xiuli; Li, Hulun

    2016-08-25

    Multiple sclerosis (MS) is a common autoimmune disease that inevitably causes inflammatory nerve demyelination. However, an effective approach to prevent its course is still lacking and urgently needed. Recently, the adenosine A2A receptor (A2AR) has emerged as a novel inflammation regulator. Manipulation of A2AR activity may suppress the MS process and protect against nerve damage. To test this hypothesis, we treated murine experimental autoimmune encephalomyelitis (EAE), a model for MS, with the selective A2AR agonist, CGS21680 (CGS). We evaluated the effects of CGS on the pathological features of EAE progression, including CNS cellular infiltration, inflammatory cytokine expression, lymphocyte proliferation, and cell surface markers. Treatment with CGS significantly suppressed specific lymphocyte proliferation, reduced infiltration of CD4(+) T lymphocytes, and attenuated the expression of inflammatory cytokines, which in turn inhibited the EAE progression. For the first time, we demonstrate that CGS can increase the intracellular calcium concentration ([Ca(2+)]i) in murine lymphocytes, which may be the mechanism underlying the suppressive effects of CGS-induced A2AR activation on EAE progression. Our findings strongly suggest that A2AR is a potential therapeutic target for MS and provide insight into the mechanism of action of A2AR agonists, which may offer a therapeutic option for this disease. PMID:27217214

  3. Agonistic TAM-163 antibody targeting tyrosine kinase receptor-B

    PubMed Central

    Vugmeyster, Yulia; Rohde, Cynthia; Perreault, Mylene; Gimeno, Ruth E.; Singh, Pratap

    2013-01-01

    TAM-163, an agonist monoclonal antibody targeting tyrosine receptor kinase-B (TrkB), is currently being investigated as a potential body weight modulatory agent in humans. To support the selection of the dose range for the first-in-human (FIH) trial of TAM-163, we conducted a mechanistic analysis of the pharmacokinetic (PK) and pharmacodynamic (PD) data (e.g., body weight gain) obtained in lean cynomolgus and obese rhesus monkeys following single doses ranging from 0.3 to 60 mg/kg. A target-mediated drug disposition (TMDD) model was used to describe the observed nonlinear PK and Emax approach was used to describe the observed dose-dependent PD effect. The TMDD model development was supported by the experimental determination of the binding affinity constant (9.4 nM) and internalization rate of the drug-target complex (2.08 h−1). These mechanistic analyses enabled linking of exposure, target (TrkB) coverage, and pharmacological activity (e.g., PD) in monkeys, and indicated that ≥ 38% target coverage (time-average) was required to achieve significant body weight gain in monkeys. Based on the scaling of the TMDD model from monkeys to humans and assuming similar relationship between the target coverage and pharmacological activity between monkey and humans, subcutaneous (SC) doses of 1 and 15 mg/kg in humans were projected to be the minimally and the fully pharmacologically active doses, respectively. Based on the minimal anticipated biological effect level (MABEL) approach for starting dose selection, the dose of 0.05 mg/kg (3 mg for a 60 kg human) SC was recommended as the starting dose for FIH trials, because at this dose level < 10% target coverage was projected at Cmax (and all other time points). This study illustrates a rational mechanistic approach for the selection of FIH dose range for a therapeutic protein with a complex model of action. PMID:23529133

  4. Metabolic mapping of A3 adenosine receptor agonist MRS5980.

    PubMed

    Fang, Zhong-Ze; Tosh, Dilip K; Tanaka, Naoki; Wang, Haina; Krausz, Kristopher W; O'Connor, Robert; Jacobson, Kenneth A; Gonzalez, Frank J

    2015-09-15

    (1S,2R,3S,4R,5S)-4-(2-((5-Chlorothiophen-2-yl)ethynyl)-6-(methylamino)-9H-purin-9-yl)-2,3-dihydroxy-N-methylbicyclo[3.1.0]hexane-1-carboxamide (MRS5980) is an A3AR selective agonist containing multiple receptor affinity- and selectivity-enhancing modifications and a therapeutic candidate drug for many inflammatory diseases. Metabolism-related poor pharmacokinetic behavior and toxicities are a major reason for drug R&D failure. Metabolomics with UPLC-MS was employed to profile the metabolism of MRS5980 and MRS5980-induced disruption of endogenous compounds. Recombinant drug-metabolizing enzymes screening experiment were used to determine the enzymes involved in MRS5980 metabolism. Analysis of lipid metabolism-related genes was performed to investigate the reason for MRS5980-induced lipid metabolic disorders. Unsupervised principal components analysis separated the control and MRS5980 treatment groups in feces, urine, and liver samples, but not in bile and serum. The major ions mainly contributing to the separation of feces and urine were oxidized MRS5980, glutathione (GSH) conjugates and cysteine conjugate (degradation product of the GSH conjugates) of MRS5980. The major ions contributing to the group separation of liver samples were phosphatidylcholines. In vitro incubation experiments showed the involvement of CYP3A enzymes in the oxidative metabolism of MRS5980 and direct GSH reactivity of MRS5980. The electrophilic attack by MRS5980 is a minor pathway and did not alter GSH levels in liver or liver histology, and thus may be of minor clinical consequence. Gene expression analysis further showed decreased expression of PC biosynthetic genes choline kinase a and b, which further accelerated conversion of lysophosphatidylcholine to phosphatidylcholines through increasing the expression of lysophosphatidylcholine acyltransferase 3. These data will be useful to guide rational design of drugs targeting A3AR, considering efficacy, metabolic elimination, and

  5. Cocaine self-administration differentially affects allosteric A2A-D2 receptor-receptor interactions in the striatum. Relevance for cocaine use disorder.

    PubMed

    Pintsuk, Julia; Borroto-Escuela, Dasiel O; Pomierny, Bartosz; Wydra, Karolina; Zaniewska, Magdalena; Filip, Malgorzata; Fuxe, Kjell

    2016-05-01

    In the current study behavioral and biochemical experiments were performed to study changes in the allosteric A2AR-D2R interactions in the ventral and dorsal striatum after cocaine self-administration versus corresponding yoked saline control. By using ex vivo [(3)H]-raclopride/quinpirole competition experiments, the effects of the A2AR agonist CGS 21680 (100 nM) on the KiH and KiL values of the D2-like receptor (D2-likeR) were determined. One major result was a significant reduction in the D2-likeR agonist high affinity state observed with CGS 21680 after cocaine self-administration in the ventral striatum compared with the yoked saline group. The results therefore support the hypothesis that A2AR agonists can at least in part counteract the motivational actions of cocaine. This action is mediated via the D2-likeR by targeting the A2AR protomer of A2AR-D2-like R heteroreceptor complexes in the ventral striatum, which leads to the reduction of D2-likeR protomer recognition through the allosteric receptor-receptor interaction. In contrast, in the dorsal striatum the CGS 21680-induced antagonistic modulation in the D2-likeR agonist high affinity state was abolished after cocaine self-administration versus the yoked saline group probably due to a local dysfunction/disruption of the A2AR-D2-like R heteroreceptor complexes. Such a change in the dorsal striatum in cocaine self-administration can contribute to the development of either locomotor sensitization, habit-forming learning and/or the compulsive drug seeking by enhanced D2-likeR protomer signaling. Potential differences in the composition and stoichiometry of the A2AR-D2R heteroreceptor complexes, including differential recruitment of sigma 1 receptor, in the ventral and dorsal striatum may explain the differential regional changes observed in the A2A-D2-likeR interactions after cocaine self-administration. PMID:26987369

  6. Pentoxifylline inhibits pulmonary inflammation induced by infrarenal aorticcross-clamping dependent of adenosine receptor A2A

    PubMed Central

    Li, Hali; Tan, Gang; Tong, Liquan; Han, Peng; Zhang, Feng; Liu, Bing; Sun, Xueying

    2016-01-01

    Infrarenal aortic cross-clamping (IAC) is commonly used during infrarenal vascular operations. Prolonged IAC causes ischemia-reperfusion injury to local tissues, resulting in the release of inflammatory cytokines and acute lung injury (ALI). Pentoxifylline (PTX) is a clinically used drug for chronic occlusive arterial diseases and exerts protective effects against ALI induced by various factors in experimental models. In this study, we evaluated the protective effects of PTX in a rat model of IAC. Wistar rats underwent IAC for 2 h, followed by 4 h reperfusion. PTX alone, or in combination with ZM-241385 (an adenosine receptor A2A antagonist) or CGS-21680 (an A2A agonist), was pre-administered to rats 1 h prior to IAC, and the severity of lung injury and inflammation were examined. Administration of PTX significantly attenuated ALI induced by IAC, evidenced by reduced histological scores and wet lung contents, improved blood gas parameters, decreased cell counts and protein amounts in bronchoalveolar lavage fluids, and inhibition of MPO activity and ICAM-1 expression in lung tissues, and lower plasma levels of TNF-α, IL-6, IL-1β and soluble ICAM-1. ZM-241385 significantly abrogated, while CGS-21680 slightly enhanced, the effects of PTX in ameliorating ALI and inhibiting pulmonary inflammation. In exploration of the mechanisms, we found that PTX stimulated IL-10 production through the phosphorylation of STAT3, and A2A receptor participated in this regulation. The study indicates PTX plays a protective role in IAC-induced ALI in rats by inhibiting pulmonary inflammation through A2A signaling pathways. PMID:27347328

  7. A2A adenosine receptor modulates drug efflux transporter P-glycoprotein at the blood-brain barrier

    PubMed Central

    Kim, Do-Geun; Bynoe, Margaret S.

    2016-01-01

    The blood-brain barrier (BBB) protects the brain from toxic substances within the peripheral circulation. It maintains brain homeostasis and is a hurdle for drug delivery to the CNS to treat neurodegenerative diseases, including Alzheimer’s disease and brain tumors. The drug efflux transporter P-glycoprotein (P-gp) is highly expressed on brain endothelial cells and blocks the entry of most drugs delivered to the brain. Here, we show that activation of the A2A adenosine receptor (AR) with an FDA-approved A2A AR agonist (Lexiscan) rapidly and potently decreased P-gp expression and function in a time-dependent and reversible manner. We demonstrate that downmodulation of P-gp expression and function coincided with chemotherapeutic drug accumulation in brains of WT mice and in primary mouse and human brain endothelial cells, which serve as in vitro BBB models. Lexiscan also potently downregulated the expression of BCRP1, an efflux transporter that is highly expressed in the CNS vasculature and other tissues. Finally, we determined that multiple pathways, including MMP9 cleavage and ubiquitinylation, mediated P-gp downmodulation. Based on these data, we propose that A2A AR activation on BBB endothelial cells offers a therapeutic window that can be fine-tuned for drug delivery to the brain and has potential as a CNS drug-delivery technology. PMID:27043281

  8. Inhibition by adenosine A2A receptors of NMDA but not AMPA currents in rat neostriatal neurons

    PubMed Central

    Wirkner, Kerstin; Assmann, Heike; Köles, Laszlo; Gerevich, Zoltan; Franke, Heike; Nörenberg, Wolfgang; Boehm, Rudolf; Illes, Peter

    2000-01-01

    Whole-cell patch clamp experiments were used to investigate the transduction mechanism of adenosine A2A receptors in modulating N-methyl-D-aspartate (NMDA)-induced currents in rat striatal brain slices. The A2A receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5′-N-ethylcarboxamidoadenosine (CGS 21680) inhibited the NMDA, but not the (S)-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) current in a subset of striatal neurons. Lucifer yellow-filled pipettes in combination with immunostaining of A2A receptors were used to identify CGS 21680-sensitive cells as typical medium spiny striatal neurons. Dibutyryl cyclic AMP and the protein kinase A activator Sp-cyclic AMPs, but not the protein kinase A inhibitors Rp-cyclic AMPS or PKI(14–24)amide abolished the inhibitory effect of CGS 21680. The phospholipase C inhibitor U-73122, but not the inactive structural analogue U-73343 also interfered with CGS 21680. The activation of protein kinase C by phorbol 12-myristate 13-acetate or the blockade of this enzyme by staurosporine did not alter the effect of CGS 21680. Heparin, an antagonist of inositol 1,4,5-trisphosphate (InsP3) and a more efficient buffering of intracellular Ca2+ by BAPTA instead of EGTA in the pipette solution, abolished the CGS 21680-induced inhibition. The calmodulin antagonist W-7 and cytochalasin B which enhances actin depolymerization also prevented the effect of CGS 21680; the calmodulin kinase II inhibitors CaM kinase II(281–309) and KN-93 but not the inactive structural analogue KN-92 were also effective. The calcineurin inhibitor deltamethrin did not interfere with CGS 21680. It is suggested that the transduction mechanism of A2A receptors to inhibit NMDA receptor channels is the phospholipase C/InsP3/calmodulin and calmodulin kinase II pathway. The adenylate cyclase/protein kinase A and phospholipase C/protein kinase C pathways do not appear to be involved. PMID:10807662

  9. Dissociated sterol-based liver X receptor agonists as therapeutics for chronic inflammatory diseases.

    PubMed

    Yu, Shan; Li, Sijia; Henke, Adam; Muse, Evan D; Cheng, Bo; Welzel, Gustav; Chatterjee, Arnab K; Wang, Danling; Roland, Jason; Glass, Christopher K; Tremblay, Matthew

    2016-07-01

    Liver X receptor (LXR), a nuclear hormone receptor, is an essential regulator of immune responses. Activation of LXR-mediated transcription by synthetic agonists, such as T0901317 and GW3965, attenuates progression of inflammatory disease in animal models. However, the adverse effects of these conventional LXR agonists in elevating liver lipids have impeded exploitation of this intriguing mechanism for chronic therapy. Here, we explore the ability of a series of sterol-based LXR agonists to alleviate inflammatory conditions in mice without hepatotoxicity. We show that oral treatment with sterol-based LXR agonists in mice significantly reduces dextran sulfate sodium colitis-induced body weight loss, which is accompanied by reduced expression of inflammatory markers in the large intestine. The anti-inflammatory property of these agonists is recapitulated in vitro in mouse lamina propria mononuclear cells, human colonic epithelial cells, and human peripheral blood mononuclear cells. In addition, treatment with LXR agonists dramatically suppresses inflammatory cytokine expression in a model of traumatic brain injury. Importantly, in both disease models, the sterol-based agonists do not affect the liver, and the conventional agonist T0901317 results in significant liver lipid accumulation and injury. Overall, these results provide evidence for the development of sterol-based LXR agonists as novel therapeutics for chronic inflammatory diseases.-Yu, S., Li, S., Henke, A., Muse, E. D., Cheng, B., Welzel, G., Chatterjee, A. K., Wang, D., Roland, J., Glass, C. K., Tremblay, M. Dissociated sterol-based liver X receptor agonists as therapeutics for chronic inflammatory diseases. PMID:27025962

  10. Ascorbic acid enables reversible dopamine receptor /sup 3/H-agonist binding

    SciTech Connect

    Leff, S.; Sibley, D.R.; Hamblin, M.; Creese, I.

    1981-11-16

    The effects of ascorbic acid on dopaminergic /sup 3/H-agonist receptor binding were studied in membrane homogenates of bovine anterior pituitary and caudate, and rat striatum. In all tissues virtually no stereospecific binding (defined using 1uM (+)butaclamol) of the /sup 3/H-agonists N-propylnorapomorphine (NPA), apomorphine, or dopamine could be demonstrated in the absence of ascorbic acid. Although levels of total /sup 3/H-agonist binding were three to five times greater in the absence than in the presence of 0.1% ascorbic acid, the increased binding was entirely non-stereospecific. Greater amounts of dopamine-inhibitable /sup 3/H-NPA binding could be demonstrated in the absence of 0.1% ascorbic acid, but this measure of ''specific binding'' was demonstrated not to represent dopamine receptor binding since several other catecholamines and catechol were equipotent with dopamine and more potent than the dopamine agonist (+/-)amino-6,7-dihydroxy-1,2,3,4-tetrahydronapthalene (ADTN) in inhibiting this binding. High levels of dopamine-displaceable /sup 3/H-agonist binding were detected in fresh and boiled homogenates of cerebellum, an area of brain which receives no dopaminergic innervation, further demonstrating the non-specific nature of /sup 3/H-agonist binding in the absence of ascorbic acid. These studies emphasize that under typical assay conditions ascorbic acid is required in order to demonstrate reversible and specific /sup 3/H-agonist binding to dopamine receptors.

  11. GLP-1 Receptor Agonists: Nonglycemic Clinical Effects in Weight Loss and Beyond

    PubMed Central

    Ryan, Donna; Acosta, Andres

    2015-01-01

    Obective Glucagon-like peptide-1 (GLP-1) receptor agonists are indicated for treatment of type 2 diabetes since they mimic the actions of native GLP-1 on pancreatic islet cells, stimulating insulin release, while inhibiting glucagon release, in a glucose-dependent manner. The observation of weight loss has led to exploration of their potential as antiobesity agents, with liraglutide 3.0 mg day−1 approved for weight management in the US on December 23, 2014, and in the EU on March 23, 2015. This review examines the potential nonglycemic effects of GLP-1 receptor agonists. Methods A literature search was conducted to identify preclinical and clinical evidence on nonglycemic effects of GLP-1 receptor agonists. Results GLP-1 receptors are distributed widely in a number of tissues in humans, and their effects are not limited to the well-recognized effects on glycemia. Nonglycemic effects include weight loss, which is perhaps the most widely recognized nonglycemic effect. In addition, effects on the cardiovascular, neurologic, and renal systems and on taste perception may occur independently of weight loss. Conclusions GLP-1 receptor agonists may provide other nonglycemic clinical effects besides weight loss. Understanding these effects is important for prescribers in using GLP-1 receptor agonists for diabetic patients, but also if approved for chronic weight management. PMID:25959380

  12. Modulation of pre- and postsynaptic dopamine D2 receptor function by the selective kappa-opioid receptor agonist U69593.

    PubMed

    Acri, J B; Thompson, A C; Shippenberg, T

    2001-03-15

    The repeated administration of selective kappa-opioid receptor agonists prevents the locomotor activation produced by acute cocaine administration and the development of cocaine-induced behavioral sensitization. Previous studies have shown that dopamine (DA) D2 autoreceptors modulate the synthesis and release of DA in the striatum. Evidence that kappa agonist treatment downregulates DA D2 receptors in this same brain region has recently been obtained. Accordingly, the present studies were undertaken to examine the influence of repeated kappa-opioid receptor agonist administration on pre- and postsynaptic DA D2 receptor function in the dorsal striatum using pre- and postsynaptic receptor-selective doses of quinpirole. Rats were injected once daily with the selective kappa-opioid receptor agonist U69593 (0.16-0.32 mg/kg s.c.) or vehicle for 3 days. Microdialysis studies assessing basal and quinpirole-evoked (0.05 mg/kg s.c.) DA levels were conducted 2 days later. Basal and quinpirole-stimulated locomotor activity were assessed in a parallel group of animals. The no-net flux method of quantitative microdialysis revealed no effect of U69593 on basal DA dynamics, in that extracellular DA concentration and extraction fraction did not differ in control and U69593-treated animals. Acute administration of quinpirole significantly decreased striatal DA levels in control animals, but in animals treated with U69593, the inhibitory effects of quinpirole were significantly reduced. Quinpirole produced a dose-related increase in locomotor activity in control animals, and this effect was significantly attenuated in U69593-treated animals. These data reveal that prior repeated administration of a selective kappa-opioid receptor agonist attenuates quinpirole-induced alterations in DA neurotransmission and locomotor activity. These results suggest that both pre- and postsynaptic striatal DA D2 receptors may be downregulated following repeated kappa-opioid receptor agonist

  13. Site of action of a pentapeptide agonist at the glucagon-like peptide-1 receptor. Insight into a small molecule agonist-binding pocket

    PubMed Central

    Dong, Maoqing; Pinon, Delia I.; Miller, Laurence J.

    2011-01-01

    The development of small molecule agonists for class B G protein-coupled receptors (GPCRs) has been quite challenging. With proof-of-concept that exenatide, the parenterally administered peptide agonist of the glucagon-like peptide-1 (GLP1) receptor, is an effective treatment for patients with diabetes mellitus, the development of small molecule agonists could have substantial advantages. We previously reported a lead for small molecule GLP1 receptor agonist development representing the pentapeptide NRTFD. In this work, we have prepared an NRTFD derivative incorporating a photolabile benzoylphenylalanine and used it to define its site of action. This peptide probe was a full agonist with potency similar to NRTFD, which bound specifically and saturably to a single, distinct site within the GLP1 receptor. Peptide mapping using cyanogen bromide and endoproteinase Lys-C cleavage of labeled wild type and M397L mutant receptor constructs identified the site of covalent attachment of NRTFD within the third extracellular loop above the sixth transmembrane segment. This region is the same as that identified using an analogous photolabile probe based on secretin receptor sequences, and has been shown in mutagenesis studies to be important for natural agonist action of several members of this family. While these observations suggest that small molecule ligands can act at a site bordering the third extracellular loop to activate this class B GPCR, the relationship of this site to the site of action of the amino-terminal end of the natural agonist peptide is unclear. PMID:22079758

  14. Transgenic silkworms expressing human insulin receptors for evaluation of therapeutically active insulin receptor agonists.

    PubMed

    Matsumoto, Yasuhiko; Ishii, Masaki; Ishii, Kenichi; Miyaguchi, Wataru; Horie, Ryo; Inagaki, Yoshinori; Hamamoto, Hiroshi; Tatematsu, Ken-ichiro; Uchino, Keiro; Tamura, Toshiki; Sezutsu, Hideki; Sekimizu, Kazuhisa

    2014-12-12

    We established a transgenic silkworm strain expressing the human insulin receptor (hIR) using the GAL4/UAS system. Administration of human insulin to transgenic silkworms expressing hIR decreased hemolymph sugar levels and facilitated Akt phosphorylation in the fat body. The decrease in hemolymph sugar levels induced by injection of human insulin in the transgenic silkworms expressing hIR was blocked by co-injection of wortmannin, a phosphoinositide 3-kinase inhibitor. Administration of bovine insulin, an hIR ligand, also effectively decreased sugar levels in the transgenic silkworms. These findings indicate that functional hIRs that respond to human insulin were successfully induced in the transgenic silkworms. We propose that the humanized silkworm expressing hIR is useful for in vivo evaluation of the therapeutic activities of insulin receptor agonists. PMID:25449269

  15. Analysis of the agonist activity of fenoldopam (SKF 82526) at the vascular 5-HT2 receptor.

    PubMed Central

    Christie, M. I.; Harper, D.; Smith, G. W.

    1992-01-01

    1. The 5-HT2 receptor agonist activity of fenoldopam (SKF 82526) was characterized in the rabbit isolated aorta preparation. 2. Fenoldopam was an agonist at the vascular 5-HT2 receptor with lower affinity and efficacy than the naturally occurring agonist 5-hydroxytryptamine (5-HT). Fenoldopam had an affinity (pKA) of 5.84 +/- 0.04 and efficacy (tau) of 0.57 +/- 0.04, whereas 5-HT had a pKA of 6.65 +/- 0.12 and tau of 2.66 +/- 0.41. 3. The constrictor effects of fenoldopam and 5-HT were competitively antagonized by the 5-HT2 antagonist, ketanserin, with pKB values of 8.81 +/- 0.11 and 8.83 +/- 0.10 respectively. 4. Prior incubation with fenoldopam produced a concentration-related rightward shift of a subsequent 5-HT concentration-response curve. This inhibition was specific for 5-HT since constrictor responses to angiotensin II were unaffected. 5. This study indicates that the D1 receptor agonist, fenoldopam, acts as an agonist at the vascular 5-HT2 receptor, but with an affinity and efficacy less than that of the naturally occurring agonist, 5-HT. PMID:1361397

  16. Characterizing novel metabolic pathways of melatonin receptor agonist agomelatine using metabolomic approaches

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agomelatine (AGM), an analog of melatonin, is a potential agonist at melatonin receptors 1/2 and a selective antagonist at 5-hydroxytryptamine 2C receptors. AGM is widely used for the treatment of major depressive episodes in adults. However, multiple adverse effects associated with AGM have been re...

  17. Use of toll-like receptor agonists to reduce Salmonella colonization in neonatal swine

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Toll-like receptors (TLR) are members of a highly conserved group of receptors which recognize conserved molecular aspects of microbes. The purpose of these experiments were to ascertain the effects of the administration of the TLR 9 agonist, CpG, on the colonization of neonatal swine with Salmonel...

  18. Blockade of Cocaine or σ Receptor Agonist Self Administration by Subtype-Selective σ Receptor Antagonists.

    PubMed

    Katz, Jonathan L; Hiranita, Takato; Kopajtic, Theresa A; Rice, Kenner C; Mesangeau, Christophe; Narayanan, Sanju; Abdelazeem, Ahmed H; McCurdy, Christopher R

    2016-07-01

    The identification of sigma receptor (σR) subtypes has been based on radioligand binding and, despite progress with σ1R cellular function, less is known about σR subtype functions in vivo. Recent findings that cocaine self administration experience will trigger σR agonist self administration was used in this study to assess the in vivo receptor subtype specificity of the agonists (+)-pentazocine, PRE-084 [2-(4-morpholinethyl) 1-phenylcyclohexanecarboxylate hydrochloride], and 1,3-di-o-tolylguanidine (DTG) and several novel putative σR antagonists. Radioligand binding studies determined in vitro σR selectivity of the novel compounds, which were subsequently studied for self administration and antagonism of cocaine, (+)-pentazocine, PRE-084, or DTG self administration. Across the dose ranges studied, none of the novel compounds were self administered, nor did they alter cocaine self administration. All compounds blocked DTG self administration, with a subset also blocking (+)-pentazocine and PRE-084 self administration. The most selective of the compounds in binding σ1Rs blocked cocaine self administration when combined with a dopamine transport inhibitor, either methylphenidate or nomifensine. These drug combinations did not decrease rates of responding maintained by food reinforcement. In contrast, the most selective of the compounds in binding σ2Rs had no effect on cocaine self administration in combination with either dopamine transport inhibitor. Thus, these results identify subtype-specific in vivo antagonists, and the utility of σR agonist substitution for cocaine self administration as an assay capable of distinguishing σR subtype selectivity in vivo. These results further suggest that effectiveness of dual σR antagonism and dopamine transport inhibition in blocking cocaine self administration is specific for σ1Rs and further support this dual targeting approach to development of cocaine antagonists. PMID:27189970

  19. Blockade of Cocaine or σ Receptor Agonist Self Administration by Subtype-Selective σ Receptor Antagonists

    PubMed Central

    Hiranita, Takato; Kopajtic, Theresa A.; Rice, Kenner C.; Mesangeau, Christophe; Narayanan, Sanju; Abdelazeem, Ahmed H.; McCurdy, Christopher R.

    2016-01-01

    The identification of sigma receptor (σR) subtypes has been based on radioligand binding and, despite progress with σ1R cellular function, less is known about σR subtype functions in vivo. Recent findings that cocaine self administration experience will trigger σR agonist self administration was used in this study to assess the in vivo receptor subtype specificity of the agonists (+)-pentazocine, PRE-084 [2-(4-morpholinethyl) 1-phenylcyclohexanecarboxylate hydrochloride], and 1,3-di-o-tolylguanidine (DTG) and several novel putative σR antagonists. Radioligand binding studies determined in vitro σR selectivity of the novel compounds, which were subsequently studied for self administration and antagonism of cocaine, (+)-pentazocine, PRE-084, or DTG self administration. Across the dose ranges studied, none of the novel compounds were self administered, nor did they alter cocaine self administration. All compounds blocked DTG self administration, with a subset also blocking (+)-pentazocine and PRE-084 self administration. The most selective of the compounds in binding σ1Rs blocked cocaine self administration when combined with a dopamine transport inhibitor, either methylphenidate or nomifensine. These drug combinations did not decrease rates of responding maintained by food reinforcement. In contrast, the most selective of the compounds in binding σ2Rs had no effect on cocaine self administration in combination with either dopamine transport inhibitor. Thus, these results identify subtype-specific in vivo antagonists, and the utility of σR agonist substitution for cocaine self administration as an assay capable of distinguishing σR subtype selectivity in vivo. These results further suggest that effectiveness of dual σR antagonism and dopamine transport inhibition in blocking cocaine self administration is specific for σ1Rs and further support this dual targeting approach to development of cocaine antagonists. PMID:27189970

  20. γ-Hydroxybutyric acid (GHB) is not an agonist of extrasynaptic GABAA receptors.

    PubMed

    Connelly, William M; Errington, Adam C; Crunelli, Vincenzo

    2013-01-01

    γ-Hydroxybutyric acid (GHB) is an endogenous compound and a drug used clinically to treat the symptoms of narcolepsy. GHB is known to be an agonist of GABAB receptors with millimolar affinity, but also binds with much higher affinity to another site, known as the GHB receptor. While a body of evidence has shown that GHB does not bind to GABAA receptors widely, recent evidence has suggested that the GHB receptor is in fact on extrasynaptic α4β1δ GABAA receptors, where GHB acts as an agonist with an EC50 of 140 nM. We investigated three neuronal cell types that express a tonic GABAA receptor current mediated by extrasynaptic receptors: ventrobasal (VB) thalamic neurons, dentate gyrus granule cells and striatal medium spiny neurons. Using whole-cell voltage clamp in brain slices, we found no evidence that GHB (10 µM) induced any GABAA receptor mediated current in these cell types, nor that it modulated inhibitory synaptic currents. Furthermore, a high concentration of GHB (3 mM) was able to produce a GABAB receptor mediated current, but did not induce any other currents. These results suggest either that GHB is not a high affinity agonist at native α4β1δ receptors, or that these receptors do not exist in classical areas associated with extrasynaptic currents. PMID:24244421

  1. γ-Hydroxybutyric Acid (GHB) Is Not an Agonist of Extrasynaptic GABAA Receptors

    PubMed Central

    Connelly, William M.; Errington, Adam C.; Crunelli, Vincenzo

    2013-01-01

    γ-Hydroxybutyric acid (GHB) is an endogenous compound and a drug used clinically to treat the symptoms of narcolepsy. GHB is known to be an agonist of GABAB receptors with millimolar affinity, but also binds with much higher affinity to another site, known as the GHB receptor. While a body of evidence has shown that GHB does not bind to GABAA receptors widely, recent evidence has suggested that the GHB receptor is in fact on extrasynaptic α4β1δ GABAA receptors, where GHB acts as an agonist with an EC50 of 140 nM. We investigated three neuronal cell types that express a tonic GABAA receptor current mediated by extrasynaptic receptors: ventrobasal (VB) thalamic neurons, dentate gyrus granule cells and striatal medium spiny neurons. Using whole-cell voltage clamp in brain slices, we found no evidence that GHB (10 µM) induced any GABAA receptor mediated current in these cell types, nor that it modulated inhibitory synaptic currents. Furthermore, a high concentration of GHB (3 mM) was able to produce a GABAB receptor mediated current, but did not induce any other currents. These results suggest either that GHB is not a high affinity agonist at native α4β1δ receptors, or that these receptors do not exist in classical areas associated with extrasynaptic currents. PMID:24244421

  2. Structure-guided development of dual β2 adrenergic/dopamine D2 receptor agonists.

    PubMed

    Weichert, Dietmar; Stanek, Markus; Hübner, Harald; Gmeiner, Peter

    2016-06-15

    Aiming to discover dual-acting β2 adrenergic/dopamine D2 receptor ligands, a structure-guided approach for the evolution of GPCR agonists that address multiple targets was elaborated. Starting from GPCR crystal structures, we describe the design, synthesis and biological investigation of a defined set of compounds leading to the identification of the benzoxazinone (R)-3, which shows agonist properties at the adrenergic β2 receptor and substantial G protein-promoted activation at the D2 receptor. This directed approach yielded molecular probes with tuned dual activity. The congener desOH-3 devoid of the benzylic hydroxyl function was shown to be a β2 adrenergic antagonist/D2 receptor agonist with Ki values in the low nanomolar range. The compounds may serve as a promising starting point for the investigation and treatment of neurological disorders. PMID:27132867

  3. Solubilization and reconstitution of the D-1 dopamine receptor: potentiation of the agonist high-affinity state of the receptor

    SciTech Connect

    Sidhu, A.

    1988-11-29

    The D-1 dopamine receptor was extracted from rat striatal membranes with sodium cholate and NaCl in the presence of a specific agonist and phospholipids. The soluble receptor then was reconstituted into phospholipid vesicles by further addition of phospholipids prior to detergent removal. Of the total membrane receptors, up to 48% were extracted and 36% were reconstituted into phospholipid vesicles. Yields were greatly reduced if the agonist was omitted or replaced with an antagonist. The solubilized and reconstituted D-1 receptors retained the pharmacological properties of the membrane-bound receptors, including the ability to discriminate between active and inactive enantiomers of specific agonists and antagonists. In this regard, the affinity of the reconstituted receptors for the D-1 specific antagonist /sup 125/I SCH 23982 was similar to that of the membrane-bound receptors with a Kd of 1.5 nM. Both the soluble and reconstituted forms of the D-1 receptor exhibited two affinity states for the D-1 specific agonist SKandF R-38393. In contrast to the low proportion of the receptors that had a high affinity for the agonists in striatal membranes (less than 6%), there was a dramatic increase following solubilization (22%) and reconstitution (40%). Similar results were obtained by using dopamine; the proportion of high-affinity sites increased from 4% (membrane-bound) to 48% (reconstituted) of the total receptor population. These high-affinity sites were coupled to G proteins, as guanyl nucleotides completely abolished them. Addition of guanyl nucleotides prior to solubilization or to reconstitution, however, had no effect on the subsequent yield of the reconstituted receptors.

  4. Lepidozenolide from the liverwort Lepidozia fauriana acts as a farnesoid X receptor agonist.

    PubMed

    Lin, Hsiang-Ru

    2015-01-01

    Lepidozenolide is a sesquiterpenoid isolated from the liverwort Lepidozia fauriana and its possible bioactivity is unclear. The farnesoid X receptor (FXR) is a member of nuclear receptor superfamily that has been widely targeted for developing treatments for chronic liver disease and hyperglycemia. In this study, whether lepidozenolide may act as a FXR agonist was determined. Indeed, in mammalian one-hybrid and transient transfection reporter assays, lepidozenolide transactivated FXR to modulate promoter action including GAL4, CYP7A1, and PLTP promoters in a dose-dependent manner, while it exhibited slightly less agonistic activity than chenodeoxycholic acid, an endogenous FXR agonist. Through the molecular modeling docking studies lepidozenolide was shown to bind to FXR ligand binding pocket fairly well. All these results indicate that lepidozenolide acts as a FXR agonist. PMID:25315435

  5. PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR (PPAR) AGONISTS AS PROMISING NEW MEDICATIONS FOR DRUG ADDICTION: PRECLINICAL EVIDENCE

    PubMed Central

    Foll, Bernard Le; Ciano, Patricia Di; Panlilio, Leigh V.; Goldberg, Steven R.; Ciccocioppo, Roberto

    2013-01-01

    This review examines the growing literature on the role of peroxisome proliferator-activated receptors (PPARs) in addiction. There are two subtypes of PPAR receptors that have been studied in addiction: PPAR-α and PPAR-γ. The role of each PPAR subtype in common models of addictive behavior, mainly pre-clinical models, is summarized. In particular, studies are reviewed that investigated the effects of PPAR-α agonists on relapse, sensitization, conditioned place preference, withdrawal and drug intake, and effects of PPAR-γ agonists on relapse, withdrawal and drug intake. Finally, studies that investigated the effects of PPAR agonists on neural pathways of addiction are reviewed. Taken together this preclinical data indicates that PPAR agonists are promising new medications for drug addiction treatment. PMID:23614675

  6. Serotonin-2C Receptor Agonists Decrease Potassium-Stimulated GABA Release In the Nucleus Accumbens

    PubMed Central

    Kasper, James M; Booth, Raymond G; Peris, Joanna

    2014-01-01

    The serotonin 5-HT2C receptor has shown promise in vivo as a pharmacotherapeutic target for alcoholism. For example, recently, a novel 4-phenyl-2-N,N-dimethylaminotetralin (PAT) drug candidate, that demonstrates 5-HT2C receptor agonist activity together with 5-HT2A/2B receptor inverse agonist activity, was shown to reduce operant responding for ethanol after peripheral administration to rats. Previous studies have shown that the 5-HT2C receptor is found throughout the mesoaccumbens pathway and that 5-HT2C receptor agonism causes activation of ventral tegmental area (VTA) GABA neurons. It is unknown what effect 5-HT2C receptor modulation has on GABA release in the nucleus accumbens core (NAcc). To this end, microdialysis coupled to capillary electrophoresis with laser-induced fluorescence was used to quantify extracellular neurotransmitter concentrations in the NAcc under basal and after potassium stimulation conditions, in response to PAT analogs and other 5-HT2C receptor modulators administered by reverse dialysis to rats. 5-HT2C receptor agonists specifically attenuated stimulated GABA release in the NAcc while 5-HT2C antagonists or inverse agonists had no effect. Agents with activity at 5-HT2A receptors had no effect on GABA release. Thus, in contrast to results reported for the VTA, current results suggest 5-HT2C receptor agonists decrease stimulated GABA release in the NAcc, and provide a possible mechanism of action for 5HT2C-mediated negative modulation of ethanol self-administration. PMID:25382408

  7. Antinociceptive effects of imidazoline I2 receptor agonists in the formalin test in rats.

    PubMed

    Thorn, David A; Qiu, Yanyan; Jia, Shushan; Zhang, Yanan; Li, Jun-Xu

    2016-06-01

    The imidazoline I2 receptor is an emerging drug target for analgesics. This study extended previous studies by examining the antinociceptive effects of three I2 receptor agonists (2-BFI, BU224, and CR4056) in the formalin test. The receptor mechanisms and anatomical mediation of I2 receptor agonist-induced antinociception were also examined. Formalin-induced flinching responses (2%, 50 μl) were quantified after treatment with I2 receptor agonists alone or in combination with the I2 receptor antagonist idazoxan. Anatomical mediation was studied by locally administering 2-BFI into the plantar surface or into the right lateral ventricle through cannulae (intracerebroventricular). The locomotor activity was also examined after central (intracerebroventricular) administration of 2-BFI. 2-BFI (1-10 mg/kg, intraperitoneal) and BU224 (1-10 mg/kg, intraperitoneal) attenuated the spontaneous flinching response observed during 10 min (phase 1) and 20-60 min (phase 2) following formalin treatment, whereas CR4056 (1-32 mg/kg, intraperitoneal) decreased only phase 2 flinching response. The I2 receptor antagonist idazoxan attenuated the antinociceptive effects of 2-BFI and BU224 during phase 1, but not phase 2. Peripheral administration of 2-BFI (1-10 mg/kg, intraplantar) to the hind paw of rats had no antinociceptive effect. In contrast, centrally delivered 2-BFI (10-100 µg, intracerebroventricular) dose-dependently attenuated phase 1 and phase 2 flinching at doses that did not reduce the locomotor activity. Together, these data revealed the differential antinociceptive effects of I2 receptor agonists and the differential antagonism profiles by idazoxan, suggesting the involvement of different I2 receptor subtypes in reducing different phases of formalin-induced pain-like behaviors. In addition, the results also suggest the central mediation of I2 receptor agonist-induced antinociceptive actions. PMID:26599907

  8. NOP receptor mediates anti-analgesia induced by agonist-antagonist opioids.

    PubMed

    Gear, R W; Bogen, O; Ferrari, L F; Green, P G; Levine, J D

    2014-01-17

    Clinical studies have shown that agonist-antagonist opioid analgesics that produce their analgesic effect via action on the kappa-opioid receptor, produce a delayed-onset anti-analgesia in men but not women, an effect blocked by co-administration of a low dose of naloxone. We now report the same time-dependent anti-analgesia and its underlying mechanism in an animal model. Using the Randall-Selitto paw-withdrawal assay in male rats, we found that nalbuphine, pentazocine, and butorphanol each produced analgesia during the first hour followed by anti-analgesia starting at ∼90min after administration in males but not females, closely mimicking its clinical effects. As observed in humans, co-administration of nalbuphine with naloxone in a dose ratio of 12.5:1 blocked anti-analgesia but not analgesia. Administration of the highly selective kappa-opioid receptor agonist U69593 produced analgesia without subsequent anti-analgesia, and confirmed by the failure of the selective kappa antagonist nor-binaltorphimine to block nalbuphine-induced anti-analgesia, indicating that anti-analgesia is not mediated by kappa-opioid receptors. We therefore tested the role of other receptors in nalbuphine anti-analgesia. Nociceptin/orphanin FQ (NOP) and sigma-1 and sigma-2 receptors were chosen on the basis of their known anti-analgesic effects and receptor binding studies. The selective NOP receptor antagonists, JTC801, and J-113397, but not the sigma receptor antagonist, BD 1047, antagonized nalbuphine anti-analgesia. Furthermore, the NOP receptor agonist NNC 63-0532 produced anti-analgesia with the same delay in onset observed with the three agonist-antagonists, but without producing preceding analgesia and this anti-analgesia was also blocked by naloxone. These results strongly support the suggestion that clinically used agonist-antagonists act at the NOP receptor to produce anti-analgesia. PMID:24188792

  9. Kinetic determinants of agonist action at the recombinant human glycine receptor

    PubMed Central

    Lewis, Trevor M; Schofield, Peter R; McClellan, Annette M L

    2003-01-01

    The amino acids glycine, β-alanine and taurine are all endogenous agonists of the glycine receptor. In this study, a combination of rapid agonist application onto macropatches and steady-state single-channel recordings was used to compare the actions of glycine, β-alanine and taurine upon homomeric α1 human glycine receptors transiently expressed in human embryonic kidney (HEK 293) cells. The 10–90 % rise times determined from rapid application of 100 μm of each agonist were indistinguishable, indicating each agonist has a similar association rate. At saturating concentrations (30 mm) the rise time for glycine (0.26 ms) was 1.8-fold faster than that for β-alanine (0.47 ms) and 3.9-fold faster than that for taurine (1.01 ms), indicating clear differences in the maximum opening rate between agonists. The relaxation following rapid removal of agonist was fitted with a single exponential for β-alanine (3.0 ms) and taurine (2.2 ms), and two exponential components for glycine with a weighted mean time constant of 27.1 ms. This was consistent with differences in dissociation rates estimated from analysis of bursts, with taurine > β-alanine > glycine. Exponential fits to the open period distributions gave time constants that did not differ between agonists and the geometric distribution for the number of openings per burst indicated that all three agonists had a significant component of single-opening bursts. Based upon these data, we propose a kinetic scheme with three independent open states, where the opening rates are dependent upon the activating agonist, while the closing rates are an intrinsic characteristic of the receptor. PMID:12679369

  10. Rubimetide, humanin, and MMK1 exert anxiolytic-like activities via the formyl peptide receptor 2 in mice followed by the successive activation of DP1, A2A, and GABAA receptors.

    PubMed

    Zhao, Hui; Sonada, Soushi; Yoshikawa, Akihiro; Ohinata, Kousaku; Yoshikawa, Masaaki

    2016-09-01

    Rubimetide (Met-Arg-Trp), which had been isolated as an antihypertensive peptide from an enzymatic digest of spinach ribulose-bisphosphate carboxylase/oxygenase (Rubisco), showed anxiolytic-like activity prostaglandin (PG) D2-dependent manner in the elevated plus-maze test after administration at a dose of 0.1mg/kg (ip.) or 1mg/kg (p.o.) in male mice of ddY strain. In this study, we found that rubimetide has weak affinities for the FPR1 and FPR2, subtypes of formyl peptide receptor (FPR). The anxiolytic-like activity of rubimetide (0.1mg/kg, ip.) was blocked by WRW4, an antagonist of FPR2, but not by Boc-FLFLF, an antagonist of FPR1, suggesting that the anxiolytic-like activity was mediated by the FPR2. Humanin, an endogenous agonist peptide of the FPR2, exerted an anxiolytic-like activity after intracerebroventricular (icv) administration, which was also blocked by WRW4. MMK1, a synthetic agonist peptide of the FPR2, also exerted anxiolytic-like activity. Thus, FPR2 proved to mediate anxiolytic-like effect as the first example of central effect exerted by FPR agonists. As well as the anxiolytic-like activity of rubimetide, that of MMK1 was blocked by BW A868C, an antagonist of the DP1-receptor. Furthermore, anxiolytic-like activity of rubimetide was blocked by SCH58251 and bicuculline, antagonists for adenosine A2A and GABAA receptors, respectively. From these results, it is concluded that the anxiolytic-like activities of rubimetide and typical agonist peptides of the FPR2 were mediated successively by the PGD2-DP1 receptor, adenosine-A2A receptor, and GABA-GABAA receptor systems downstream of the FPR2. PMID:27475912

  11. Differentiation of agonist conformation and antagonist conformation in multiple opioid receptors.

    PubMed

    Ogawa, N; Yamawaki, Y; Kuroda, H; Nukina, I; Ofuji, T

    1981-12-11

    To differentiate the opiate (naloxone) receptor and the enkephalin receptor in rat brain, we solubilized the receptor molecules by detergent and determined the molecular weights by gel filtration. The receptor preparation was bound to [3H] naloxone or [3H] Met5-enkephalin, and was solubilized by Triton X-100. On gel chromatography with a Sepharose 6B column, the agonist and the antagonist conformation of opioid receptors eluted as molecules with the molecular weights of 240,000, and 120,000 and with Stokes' radii of 5.5 nm and 4.3 nm, respectively. Further, it was also disclosed that Na+ was bound to the antagonist conformation of opioid receptors but not to the agonist conformation. PMID:6275320

  12. Liver X receptor (LXR) partial agonists: biaryl pyrazoles and imidazoles displaying a preference for LXRβ.

    PubMed

    Kick, Ellen; Martin, Richard; Xie, Yinong; Flatt, Brenton; Schweiger, Edwin; Wang, Tie-Lin; Busch, Brett; Nyman, Michael; Gu, Xiao-Hui; Yan, Grace; Wagner, Brandee; Nanao, Max; Nguyen, Lam; Stout, Thomas; Plonowski, Artur; Schulman, Ira; Ostrowski, Jacek; Kirchgessner, Todd; Wexler, Ruth; Mohan, Raju

    2015-01-15

    A series of biaryl pyrazole and imidazole Liver X Receptor (LXR) partial agonists has been synthesized displaying LXRβ selectivity. The LXRβ selective partial agonist 18 was identified with potent induction of ATP binding transporters ABCA1 and ABCG1 in human whole blood (EC50=1.2μM, 55% efficacy). In mice 18 displayed peripheral induction of ABCA1 at 3 and 10mpk doses with no significant elevation of plasma or hepatic triglycerides at these doses, showing an improved profile compared to a full pan-agonist. PMID:25435151

  13. Alpha/sub 1/ receptor coupling events initiated by methoxy-substituted tolazoline partial agonists

    SciTech Connect

    Wick, P.; Keung, A.; Deth, R.

    1986-03-01

    A series of mono- and dimethyoxy substituted tolazoline derivatives, known to be partial agonists at the alpha/sub 1/ receptor, were compared with the ..cap alpha../sub 1/ selective full agonist phenylephrine (PE) on isolated strips of rabbit aorta Agonist activity was evaluated in contraction, /sup 45/Ca influx, /sup 45/Ca efflux, and /sup 32/P-Phospholipid labelling studies. Maximum contractile responses for the 2-, 3-, and 3, 5- methoxy substituted tolazoline derivatives (10/sup -5/M) were 53.8, 67.6 and 99.7% of the PE (10/sup -5/M) response respectively. These same partial agonists caused a stimulation of /sup 45/Ca influx to the extent of 64, 86, and 95% of the PE response respectively. In /sup 45/Ca efflux studies, (a measure of the intracellular Ca/sup +2/ release) the tolazolines caused: 30%, 63%, and 78% of the PE stimulated level. /sup 32/P-Phosphatidic acid (PA) labelling was measured as an index of PI turnover after ..cap alpha../sub 1/ receptor stimulation. Compared to PE, the 2-, 3-, and 3,5- methoxy substituted tolazoline derivatives caused 22, 46, and 72% PA labelling. The above values are all in reasonable accord with the rank order or agonist activity shown in maximum contractile responses. The results of this investigation suggest that partial agonists stimulate ..cap alpha.. receptor coupling events at a level which is quantitatively comparable to their potencies in causing contraction of arterial smooth muscle.

  14. Selective VIP Receptor Agonists Facilitate Immune Transformation for Dopaminergic Neuroprotection in MPTP-Intoxicated Mice

    PubMed Central

    Olson, Katherine E.; Kosloski-Bilek, Lisa M.; Anderson, Kristi M.; Diggs, Breha J.; Clark, Barbara E.; Gledhill, John M.; Shandler, Scott J.; Mosley, R. Lee

    2015-01-01

    Vasoactive intestinal peptide (VIP) mediates a broad range of biological responses by activating two related receptors, VIP receptor 1 and 2 (VIPR1 and VIPR2). Although the use of native VIP facilitates neuroprotection, clinical application of the hormone is limited due to VIP's rapid metabolism and inability to distinguish between VIPR1 and VIPR2 receptors. In addition, activation of both receptors by therapeutics may increase adverse secondary toxicities. Therefore, we developed metabolically stable and receptor-selective agonists for VIPR1 and VIPR2 to improve pharmacokinetic and pharmacodynamic therapeutic end points. Selective agonists were investigated for their abilities to protect mice against MPTP-induced neurodegeneration used to model Parkinson's disease (PD). Survival of tyrosine hydroxylase neurons in the substantia nigra was determined by stereological tests after MPTP intoxication in mice pretreated with either VIPR1 or VIPR2 agonist or after adoptive transfer of splenic cell populations from agonist-treated mice administered to MPTP-intoxicated animals. Treatment with VIPR2 agonist or splenocytes from agonist-treated mice resulted in increased neuronal sparing. Immunohistochemical tests showed that agonist-treated mice displayed reductions in microglial responses, with the most pronounced effects in VIPR2 agonist-treated, MPTP-intoxicated mice. In parallel studies, we observed reductions in proinflammatory cytokine release that included IL-17A, IL-6, and IFN-γ and increases in GM-CSF transcripts in CD4+ T cells recovered from VIPR2 agonist-treated animals. Moreover, a phenotypic shift of effector to regulatory T cells was observed. These results support the use of VIPR2-selective agonists as neuroprotective agents for PD treatment. SIGNIFICANCE STATEMENT Vasoactive intestinal peptide receptor 2 can elicit immune transformation in a model of Parkinson's disease (PD). Such immunomodulatory capabilities can lead to neuroprotection by attenuating

  15. Quantitative Measure of Receptor Agonist and Modulator Equi-Response and Equi-Occupancy Selectivity

    PubMed Central

    Zhang, Rumin; Kavana, Michael

    2016-01-01

    G protein-coupled receptors (GPCRs) are an important class of drug targets. Quantitative analysis by global curve fitting of properly designed dose-dependent GPCR agonism and allosterism data permits the determination of all affinity and efficacy parameters based on a general operational model. We report here a quantitative and panoramic measure of receptor agonist and modulator equi-response and equi-occupancy selectivity calculated from these parameters. The selectivity values help to differentiate not only one agonist or modulator from another, but on-target from off-target receptor or functional pathway as well. Furthermore, in conjunction with target site free drug concentrations and endogenous agonist tones, the allosterism parameters and selectivity values may be used to predict in vivo efficacy and safety margins. PMID:27116909

  16. Selexipag: An Oral and Selective IP Prostacyclin Receptor Agonist for the Treatment of Pulmonary Arterial Hypertension.

    PubMed

    Asaki, Tetsuo; Kuwano, Keiichi; Morrison, Keith; Gatfield, John; Hamamoto, Taisuke; Clozel, Martine

    2015-09-24

    Prostacyclin controls cardiovascular function via activation of the prostacyclin receptor. Decreased prostacyclin production occurs in several cardiovascular diseases. However, the clinical use of prostacyclin and its analogues is complicated by their chemical and metabolic instability. A medicinal chemistry program searched for novel nonprostanoid prostacyclin receptor agonists not subject to these limitations. A compound with a diphenylpyrazine structural core was synthesized. Metabolic stability and agonist potency were optimized through modification of the linear side chain. Compound 12b (MRE-269, ACT-333679) was identified as a potent and highly selective prostacyclin receptor agonist. Replacement of the terminal carboxyl group with an N-acylsulfonamide group yielded parent compound 26a (selexipag, NS-304, ACT-293987), which is orally active and provides sustained plasma exposure of 12b. Compound 26a was developed for the treatment of pulmonary arterial hypertension and shown to reduce the risk of the composite morbidity/mortality end point in a phase 3 event-driven clinical trial. PMID:26291199

  17. Influence of idazoxan on the dopamine D2 receptor agonist-induced behavioural effects in rats.

    PubMed

    Ferrari, F; Giuliani, D

    1993-11-30

    The behavioural effects in rats of the dopamine D2 receptor agonists, lisuride, B-HT 920 and SND 919, were variously influenced by pre-treatment with the selective alpha 2-adrenoceptor antagonist, idazoxan (2 mg/kg), depending on the nature of the effect in question and the doses of agonist employed. The influence of idazoxan on drug-induced stretching-yawning, penile erection, sedation, stereotyped behaviour, aggressiveness and mounting is described and tentatively interpreted in neurochemical terms, account being taken of the activity of respective alpha 2-adrenoceptor antagonist and dopamine receptor agonists used, at alpha 2-adrenoceptors and at different dopamine D2 receptor subtypes, pre- and postsynaptically located. PMID:7907024

  18. Group II Metabotropic Glutamate Receptor Agonist LY379268 Regulates AMPA Receptor Trafficking in Prefrontal Cortical Neurons

    PubMed Central

    Wang, Min-Juan; Li, Yan-Chun; Snyder, Melissa A.; Wang, Huaixing; Li, Feng; Gao, Wen-Jun

    2013-01-01

    Group II metabotropic glutamate receptor (mGluR) agonists have emerged as potential treatment drugs for schizophrenia and other neurological disorders, whereas the mechanisms involved remain elusive. Here we examined the effects of LY379268 (LY37) on the expression and trafficking of the α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor subunits GluA1 and GluA2 in prefrontal neurons. We show that LY37 significantly increased the surface and total expression of both GluA1 and GluA2 subunits in cultured prefrontal neurons and in vivo. This effect was mimicked by the selective mGluR2 agonist LY395756 and was blocked by mGluR2/3 antagonist LY341495. Moreover, we found that both GluA1 and GluA2 subunits were colocalized with PSD95 but not synapsin I, suggesting a postsynaptic localization. Consistently, treatment with LY37 significantly increased the amplitude, but not frequency, of miniature excitatory postsynaptic currents. Further, actinomycin-D blocked LY37's effects, suggesting a transcriptional regulation. In addition, application of glycogen synthase kinase-3beta (GSK-3β) inhibitor completely blocked LY37's effect on GluA2 surface expression, whereas GSK-3β inhibitor itself induced decreases in the surface and total protein levels of GluA1, but not GluA2 subunits. This suggests that GSK-3β differentially mediates GluA1 and GluA2 trafficking. Further, LY37 significantly increased the phosphorylation, but not total protein, of extracellular signal-regulated kinase 1/2 (ERK1/2). Neither ERK1/2 inhibitor PD98059 alone nor PD98059 combined with LY37 treatment induced changes in GluA1 or GluA2 surface expression or total protein levels. Our data thus suggest that mGluR2/3 agonist regulates postsynaptic AMPA receptors by affecting the synaptic trafficking of both GluA1 and GluA2 subunits and that the regulation is likely through ERK1/2 signaling in GluA1 and/or both ERK1/2 and GSK-3β signaling pathways in the GluA2 subunit. PMID:23593498

  19. Binding characteristics of gamma-hydroxybutyric acid as a weak but selective GABAB receptor agonist.

    PubMed

    Mathivet, P; Bernasconi, R; De Barry, J; Marescaux, C; Bittiger, H

    1997-02-19

    The aim of this study was to reexamine the concept that gamma-hydroxybutyric acid (GHB) is a weak but selective agonist at gamma-aminobutyric acidB (GABAB) receptors, using binding experiments with several radioligands. Ki values of GHB were similar (approximately equal to 100 microM) in three agonist radioligand assays for GABAB receptors, [3H]baclofen (beta-para-chlorophenyl-gamma-aminobutyric acid), [3H]CGP 27492 (3-aminopropyl-phosphinic acid) and [3H]GABA, in the presence of the GABAA receptor agonist isoguvacine with rat cortical, cerebellar and hippocampal membranes. In competition experiments between GHB and the GABAB receptor antagonist, [3H]CGP 54626 (3-N [1-{(S)-3,4-dichlorophenyl}-ethylamino]-2-(S)-hydroxypropyl cyclo-hexylmethyl phosphinic acid), the IC50 values were significantly increased with 300 microM of 5'-guanyl-imidodiphosphate (Gpp(NH)p), which suggested that guanine nucleotide binding proteins (G-proteins) modulate GHB binding on GABAB receptors. The inhibition by GHB of [3H]CGP 27492 binding in cortical membranes was not altered in the presence of 0.3 or 3 mM of the two GHB dehydrogenase inhibitors, valproate and ethosuximide. Thus, GHB is not reconverted into GABA by GHB dehydrogenase. Taken together, the results of this study demonstrated that GHB is an endogenous weak but selective agonist at GABAB receptors. PMID:9083788

  20. Agonist mediated conformational changes of solubilized calf forebrain muscarinic acetylcholine receptors.

    PubMed

    Vanderheyden, P; Andre, C; de Backer, J P; Vauquelin, G

    1984-10-01

    Muscarinic receptors in calf forebrain membranes can be identified by the specific binding of the radiolabelled antagonist [3H]dexetimide. These receptors (2.8 pM/mg protein) comprise two non-interconvertible subpopulations with respectively high and low agonist affinity but with the same antagonist affinity. For all the agonists tested the low affinity sites represent 85 +/- 5% of the total receptor population. 0.5% Digitonin solubilized extracts contain 0.8 pM muscarinic receptor/mg protein. In contrast with the membranes, these extracts contain only sites with low agonist affinity. The alkylating reagent N-ethylmaleimide causes an increase of the acetylcholine affinity for the low affinity sites in membranes as well as for the solubilized sites. This effect is time dependent until a maximal 3-fold increase in affinity is attained. The rate of N-ethylmaleimide action is enhanced by the concomitant presence of agonists. In contrast, N-ethylmaleimide does not affect antagonist binding. This suggests that agonists mediate a conformational change of both the membrane bound low affinity muscarinic sites and of the solubilized sites, resulting in their increased susceptibility towards NEM alkylation. PMID:6487351

  1. Identification of adiponectin receptor agonist utilizing a fluorescence polarization based high throughput assay.

    PubMed

    Sun, Yiyi; Zang, Zhihe; Zhong, Ling; Wu, Min; Su, Qing; Gao, Xiurong; Zan, Wang; Lin, Dong; Zhao, Yan; Zhang, Zhonglin

    2013-01-01

    Adiponectin, the adipose-derived hormone, plays an important role in the suppression of metabolic disorders that can result in type 2 diabetes, obesity, and atherosclerosis. It has been shown that up-regulation of adiponectin or adiponectin receptor has a number of therapeutic benefits. Given that it is hard to convert the full size adiponectin protein into a viable drug, adiponectin receptor agonists could be designed or identified using high-throughput screening. Here, we report on the development of a two-step screening process to identify adiponectin agonists. First step, we developed a high throughput screening assay based on fluorescence polarization to identify adiponectin ligands. The fluorescence polarization assay reported here could be adapted to screening against larger small molecular compound libraries. A natural product library containing 10,000 compounds was screened and 9 hits were selected for validation. These compounds have been taken for the second-step in vitro tests to confirm their agonistic activity. The most active adiponectin receptor 1 agonists are matairesinol, arctiin, (-)-arctigenin and gramine. The most active adiponectin receptor 2 agonists are parthenolide, taxifoliol, deoxyschizandrin, and syringin. These compounds may be useful drug candidates for hypoadiponectin related diseases. PMID:23691032

  2. Identification of Adiponectin Receptor Agonist Utilizing a Fluorescence Polarization Based High Throughput Assay

    PubMed Central

    Sun, Yiyi; Zang, Zhihe; Zhong, Ling; Wu, Min; Su, Qing; Gao, Xiurong; Zan, Wang; Lin, Dong; Zhao, Yan; Zhang, Zhonglin

    2013-01-01

    Adiponectin, the adipose-derived hormone, plays an important role in the suppression of metabolic disorders that can result in type 2 diabetes, obesity, and atherosclerosis. It has been shown that up-regulation of adiponectin or adiponectin receptor has a number of therapeutic benefits. Given that it is hard to convert the full size adiponectin protein into a viable drug, adiponectin receptor agonists could be designed or identified using high-throughput screening. Here, we report on the development of a two-step screening process to identify adiponectin agonists. First step, we developed a high throughput screening assay based on fluorescence polarization to identify adiponectin ligands. The fluorescence polarization assay reported here could be adapted to screening against larger small molecular compound libraries. A natural product library containing 10,000 compounds was screened and 9 hits were selected for validation. These compounds have been taken for the second-step in vitro tests to confirm their agonistic activity. The most active adiponectin receptor 1 agonists are matairesinol, arctiin, (-)-arctigenin and gramine. The most active adiponectin receptor 2 agonists are parthenolide, taxifoliol, deoxyschizandrin, and syringin. These compounds may be useful drug candidates for hypoadiponectin related diseases. PMID:23691032

  3. Discovery of Novel Potent and Selective Agonists at the Melanocortin-3 Receptor.

    PubMed

    Carotenuto, Alfonso; Merlino, Francesco; Cai, Minying; Brancaccio, Diego; Yousif, Ali Munaim; Novellino, Ettore; Hruby, Victor J; Grieco, Paolo

    2015-12-24

    The melanocortin receptors 3 and 4 control energy homeostasis, food-intake behavior, and correlated pathophysiological conditions. The melanocortin-4 receptor (MC4R) has been broadly investigated. In contrast, the knowledge related to physiological roles of the melanocortin-3 receptor (MC3R) is lacking because of the limited number of known MC3R selective ligands. Here, we report the design, synthesis, biological activity, conformational analysis, and docking with receptors of two potent and selective agonists at the human MC3 receptor. PMID:26599352

  4. Kaempferol is an estrogen-related receptor alpha and gamma inverse agonist.

    PubMed

    Wang, Junjian; Fang, Fang; Huang, Zhiyan; Wang, Yanfei; Wong, Chiwai

    2009-02-18

    Kaempferol is a dietary flavonoid that is thought to function as a selective estrogen receptor modulator. In this study, we established that kaempferol also functions as an inverse agonist for estrogen-related receptors alpha and gamma (ERRalpha and ERRgamma). We demonstrated that kaempferol binds to ERRalpha and ERRgamma and blocks their interaction with coactivator peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha). Kaempferol also suppressed the expressions of ERR-target genes pyruvate dehydrogenase kinase 2 and 4 (PDK2 and PDK4). This evidence suggests that kaempferol may exert some of its biological effect through both estrogen receptors and estrogen-related receptors. PMID:19171140

  5. Functional effects of the muscarinic receptor agonist, xanomeline, at 5-HT1 and 5-HT2 receptors

    PubMed Central

    Watson, J; Brough, S; Coldwell, M C; Gager, T; Ho, M; Hunter, A J; Jerman, J; Middlemiss, D N; Riley, G J; Brown, A M

    1998-01-01

    Xanomeline [3(3-hexyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine] has been reported to act as a functionally selective muscarinic partial agonist with potential use in the treatment of Alzheimer's disease. This study examined the functional activity of xanomeline at 5-HT1 and 5-HT2 receptors in native tissue and/or human cloned receptors.Xanomeline had affinity for muscarinic receptors in rat cortical membranes where the ratio of the displacement affinity of [3H]-Quinuclidinyl benzilate vs that of [3H]-Oxotremorine-M was 16, indicative of partial agonist activity. Radioligand binding studies on human cloned receptors confirmed that xanomeline had substantial affinity for M1, M2, M3, M4, M5 receptors and also for 5-HT1 and 5-HT2 receptor subtypes.Carbachol and xanomeline stimulated basal [35S]-GTPγS binding in rat cortical membranes with micromolar affinity. The response to carbachol was attenuated by himbacine and pirenzepine with pA2 of 8.2, 6.9 respectively consistent with the response being mediated, predominantly, via M2 and M4 receptors. Xanomeline-induced stimulation of [35S]-GTPγS binding was inhibited by himbacine with an apparent pKb of 6.3, was not attenuated by pirenzepine up to 3 μM and was inhibited by the selective 5-HT1A antagonist WAY100635 with an apparent pKb of 9.4. These data suggest the agonist effect of xanomeline in this tissue is, in part, via 5-HT1A receptors. Similar studies on human cloned receptors confirmed that xanomeline is an agonist at human cloned 5-HT1A and 5-HT1B receptors.In studies using the fluorescent cytoplasmic Ca2+ indicator FLUO-3AM, xanomeline induced an increase in cytoplasmic Ca2+ concentration in SH-SY5Y cells expressing recombinant human 5-HT2C receptors. Atropine antagonized this response, consistent with mediation via endogenously-expressed muscarinic receptors. In the presence of atropine, xanomeline antagonized 5-HT-induced cytoplasmic changes in Ca2+ concentration in cells expressing h5

  6. Activation of the adenosine A2A receptor exacerbates experimental autoimmune neuritis in Lewis rats in association with enhanced humoral immunity.

    PubMed

    Zhang, Min; Li, Xiao-Li; Li, Heng; Wang, Shan; Wang, Cong-Cong; Yue, Long-Tao; Xu, Hua; Zhang, Peng; Chen, Hui; Yang, Bing; Duan, Rui-Sheng

    2016-04-15

    Accumulated evidence demonstrated that Adenosine A2A receptor (A2AR) is involved in the inflammatory diseases. In the present study, we showed that a selective A2AR agonist, CGS21680, exacerbated experimental autoimmune neuritis in Lewis rats induced with bovine peripheral myelin. The exacerbation was accompanied with reduced CD4(+)Foxp3(+) T cells, increased CD4(+)CXCR5(+) T cells, B cells, dendritic cells and antigen-specific autoantibodies, which is possibly due to the inhibition of IL-2 induced by CGS21680. Combined with previous studies, our data indicate that the effects of A2AR stimulation in vivo are variable in different diseases. Caution should be taken in the use of A2AR agonists. PMID:27049573

  7. Extrinsic factors regulate partial agonist efficacy of strychnine-sensitive glycine receptors

    PubMed Central

    Farroni, Jeffrey S; McCool, Brian A

    2004-01-01

    Background Strychnine-sensitive glycine receptors in many adult forebrain regions consist of alpha2 + beta heteromeric channels. This subunit composition is distinct from the alpha1 + beta channels found throughout the adult spinal cord. Unfortunately, the pharmacology of forebrain alpha2beta receptors are poorly defined compared to 'neonatal' alpha2 homomeric channels or 'spinal' alpha1beta heteromers. In addition, the pharmacologic properties of native alpha2beta glycine receptors have been generally distinct from receptors produced by heterologous expression. To identify subtype-specific pharmacologic tools for the forebrain alpha2beta receptors, it is important to identify a heterologous expression system that closely resembles these native glycine-gated chloride channels. Results While exploring pharmacological properties of alpha2beta glycine receptors compared to alpha2-homomers, we found that distinct heterologous expression systems appeared to differentially influence partial agonist pharmacology. The β-amino acid taurine possessed 30–50% efficacy for alpha2-containing receptor isoforms when expressed in HEK 293 cells. However, taurine efficacy was dramatically reduced in L-cell fibroblasts. Similar results were obtained for β-alanine. The efficacy of these partial agonists was also strongly reduced by the beta subunit. There were no significant differences in apparent strychnine affinity values calculated from concentration-response data between expression systems or subunit combinations. Nor did relative levels of expression correlate with partial agonist efficacy when compared within or between several different expression systems. Finally, disruption of the tubulin cytoskeleton reduced the efficacy of partial agonists in a subunit-dependent, but system-independent, fashion. Conclusions Our results suggest that different heterologous expression systems can dramatically influence the agonist pharmacology of strychnine-sensitive glycine receptors. In

  8. Structural insights into Resveratrol’s antagonist and partial agonist actions on estrogen receptor alpha

    PubMed Central

    2013-01-01

    Background Resveratrol, a naturally occurring stilbene, has been categorized as a phytoestrogen due to its ability to compete with natural estrogens for binding to estrogen receptor alpha (ERα) and modulate the biological responses exerted by the receptor. Biological effects of resveratrol (RES) on estrogen receptor alpha (ERα) remain highly controversial, since both estrogenic and anti-estrogenic properties were observed. Results Here, we provide insight into the structural basis of the agonist/antagonist effects of RES on ERα ligand binding domain (LBD). Using atomistic simulation, we found that RES bound ERα monomer in antagonist conformation, where Helix 12 moves away from the ligand pocket and orients into the co-activator binding groove of LBD, is more stable than RES bound ERα in agonist conformation, where Helix 12 lays over the ligand binding pocket. Upon dimerization, the agonistic conformation of RES-ERα dimer becomes more stable compared to the corresponding monomer but still remains less stable compared to the corresponding dimer in antagonist conformation. Interestingly, while the binding pocket and the binding contacts of RES to ERα are similar to those of pure agonist diethylstilbestrol (DES), the binding energy is much less and the hydrogen bonding contacts also differ providing clues for the partial agonistic character of RES on ERα. Conclusions Our Molecular Dynamics simulation of RES-ERα structures with agonist and antagonist orientations of Helix 12 suggests RES action is more similar to Selective Estrogen Receptor Modulator (SERM) opening up the importance of cellular environment and active roles of co-regulator proteins in a given system. Our study reveals that potential co-activators must compete with the Helix 12 and displace it away from the activator binding groove to enhance the agonistic activity. PMID:24160181

  9. Agonist self-inhibition at the nicotinic acetylcholine receptor a nonspecific action

    SciTech Connect

    Forman, S.A.; Firestone, L.L.; Miller, K.W.

    1987-05-19

    Agonist concentration-response relationships at nicotinic postsynaptic receptors were established by measuring /sup 86/Rb/sup +/ efflux from acetylcholine receptor rich native Torpedo membrane vesicles under three different conditions: (1) integrated net ion efflux (in 10 s) from untreated vesicles, (2) integrated net efflux from vesicles in which most acetylcholine sites were irreversibly blocked with ..cap alpha..-bungarotoxin, and (3) initial rates of efflux (5-100 ms) from vesicles that were partially blocked with ..cap alpha..-bungarotoxin. Exposure to acetylcholine, carbamylcholine, suberyldicholine, phenyltrimethylammonium, or (-)-nicotine over 10/sup 8/-fold concentration ranges results in bell-shaped ion flux response curves due to stimulation of acetylcholine receptor channel opening at low concentrations and inhibition of channel function at 60-2000 times higher concentrations. Concentrations of agonists that inhibit their own maximum /sup 86/Rb/sup +/ efflux by 50% (K/sub B/ values) are 110, 211, 3.0, 39, and 8.9 mM, respectively, for the agonists listed above. For acetylcholine and carbamylcholine, K/sub B/ values determined from both 10-s and 15-ms efflux measurements are the same, indicating that the rate of agonist-induced desensitization increases to maximum at concentrations lower than those causing self-inhibition. For all partial and full agonists studied, Hill coefficients for self-inhibition are close to 1.0. Concentrations of agonists up to 8 times K/sub B/ did not change the order parameter reported by a spin-labeled fatty acid incorporated in Torpedo membranes. The authors conclude that agonist self-inhibition cannot be attributed to a general nonspecific membrane perturbation. Instead, these results are consistent with a saturable site of action either at the lipid-protein interface or on the acetylcholine receptor protein itself.

  10. Axonal elongation and dendritic branching is enhanced by adenosine A2A receptors activation in cerebral cortical neurons.

    PubMed

    Ribeiro, Filipa F; Neves-Tomé, Raquel; Assaife-Lopes, Natália; Santos, Telma E; Silva, Rui F M; Brites, Dora; Ribeiro, Joaquim A; Sousa, Mónica M; Sebastião, Ana M

    2016-06-01

    Axon growth and dendrite development are key processes for the establishment of a functional neuronal network. Adenosine, which is released by neurons and glia, is a known modulator of synaptic transmission but its influence over neuronal growth has been much less investigated. We now explored the action of adenosine A2A receptors (A2AR) upon neurite outgrowth, discriminating actions over the axon or dendrites, and the mechanisms involved. Morphometric analysis of primary cultures of cortical neurons from E18 Sprague-Dawley rats demonstrated that an A2AR agonist, CGS 21680, enhances axonal elongation and dendritic branching, being the former prevented by inhibitors of phosphoinositide 3-kinase, mitogen-activated protein kinase and phospholipase C, but not of protein kinase A. By testing the influence of a scavenger of BDNF (brain-derived neurotrophic factor) over the action of the A2AR agonist and the action of a selective A2AR antagonist over the action of BDNF, we could conclude that while the action of A2ARs upon dendritic branching is dependent on the presence of endogenous BDNF, the influence of A2ARs upon axonal elongation is independent of endogenous BDNF. In consonance with the action over axonal elongation, A2AR activation promoted a decrease in microtubule stability and an increase in microtubule growth speed in axonal growth cones. In conclusion, we disclose a facilitatory action of A2ARs upon axonal elongation and microtubule dynamics, providing new insights for A2ARs regulation of neuronal differentiation and axonal regeneration. PMID:26068054

  11. Selective Retinoic Acid Receptor γ Agonists Promote Repair of Injured Skeletal Muscle in Mouse.

    PubMed

    Di Rocco, Agnese; Uchibe, Kenta; Larmour, Colleen; Berger, Rebecca; Liu, Min; Barton, Elisabeth R; Iwamoto, Masahiro

    2015-09-01

    Retinoic acid signaling regulates several biological events, including myogenesis. We previously found that retinoic acid receptor γ (RARγ) agonist blocks heterotopic ossification, a pathological bone formation that mostly occurs in the skeletal muscle. Interestingly, RARγ agonist also weakened deterioration of muscle architecture adjacent to the heterotopic ossification lesion, suggesting that RARγ agonist may oppose skeletal muscle damage. To test this hypothesis, we generated a critical defect in the tibialis anterior muscle of 7-week-old mice with a cautery, treated them with RARγ agonist or vehicle corn oil, and examined the effects of RARγ agonist on muscle repair. The muscle defects were partially repaired with newly regenerating muscle cells, but also filled with adipose and fibrous scar tissue in both RARγ-treated and control groups. The fibrous or adipose area was smaller in RARγ agonist-treated mice than in the control. In addition, muscle repair was remarkably delayed in RARγ-null mice in both critical defect and cardiotoxin injury models. Furthermore, we found a rapid increase in retinoid signaling in lacerated muscle, as monitored by retinoid signaling reporter mice. Together, our results indicate that endogenous RARγ signaling is involved in muscle repair and that selective RARγ agonists may be beneficial to promote repair in various types of muscle injuries. PMID:26205250

  12. Agonist binding to the NMDA receptor drives movement of its cytoplasmic domain without ion flow.

    PubMed

    Dore, Kim; Aow, Jonathan; Malinow, Roberto

    2015-11-24

    The NMDA receptor (R) plays important roles in brain physiology and pathology as an ion channel. Here we examine the ion flow-independent coupling of agonist to the NMDAR cytoplasmic domain (cd). We measure FRET between fluorescently tagged cytoplasmic domains of GluN1 subunits of NMDARs expressed in neurons. Different neuronal compartments display varying levels of FRET, consistent with different NMDARcd conformations. Agonist binding drives a rapid and transient ion flow-independent reduction in FRET between GluN1 subunits within individual NMDARs. Intracellular infusion of an antibody targeting the GluN1 cytoplasmic domain blocks agonist-driven FRET changes in the absence of ion flow, supporting agonist-driven movement of the NMDARcd. These studies indicate that extracellular ligand binding to the NMDAR can transmit conformational information into the cell in the absence of ion flow. PMID:26553997

  13. Discovery of novel acetanilide derivatives as potent and selective beta3-adrenergic receptor agonists.

    PubMed

    Maruyama, Tatsuya; Onda, Kenichi; Hayakawa, Masahiko; Matsui, Tetsuo; Takasu, Toshiyuki; Ohta, Mitsuaki

    2009-06-01

    In the search for potent and selective human beta3-adrenergic receptor (AR) agonists as potential drugs for the treatment of obesity and noninsulin-dependent (type II) diabetes, a novel series of acetanilide-based analogues were prepared and their biological activities were evaluated at the human beta3-, beta2-, and beta1-ARs. Among these compounds, 2-pyridylacetanilide (2f), pyrimidin-2-ylacetanilide (2u), and pyrazin-2-ylacetanilide (2v) derivatives exhibited potent agonistic activity at the beta3-AR with functional selectivity over the beta1- and beta2-ARs. In particular, compound 2u was found to be the most potent and selective beta3-AR agonist with an EC(50) value of 0.11 microM and no agonistic activity for either the beta1- or beta2-AR. In addition, 2f, 2u, and 2v showed significant hypoglycemic activity in a rodent diabetic model. PMID:19232786

  14. The pharmacokinetics of Toll-like receptor agonists and the impact on the immune system.

    PubMed

    Engel, Abbi L; Holt, Gregory E; Lu, Hailing

    2011-03-01

    Toll-like receptor (TLR) ligation activates both the innate and adaptive immune systems, and plays an important role in antiviral and anti-tumor immunity. Therefore, a significant amount of effort has been devoted to exploit the therapeutic potential of TLR agonists. Depending on the therapeutic purpose, either as adjuvants to vaccine, chemotherapy or standalone therapy, TLR agonists have been administered via different routes. Both preclinical and clinical studies have suggested that the route of administration has significant effects on pharmacokinetics, and that understanding these effects is critical to the success of TLR agonist drug development. This article will summarize the pharmacokinetics of TLR agonists with different administration routes, with an emphasis on clinical studies of TLR ligands in oncologic applications. PMID:21643519

  15. The pharmacokinetics of Toll-like receptor agonists and the impact on the immune system

    PubMed Central

    Engel, Abbi L; Holt, Gregory E; Lu, Hailing

    2011-01-01

    Toll-like receptor (TLR) ligation activates both the innate and adaptive immune systems, and plays an important role in antiviral and anti-tumor immunity. Therefore, a significant amount of effort has been devoted to exploit the therapeutic potential of TLR agonists. Depending on the therapeutic purpose, either as adjuvants to vaccine, chemotherapy or standalone therapy, TLR agonists have been administered via different routes. Both preclinical and clinical studies have suggested that the route of administration has significant effects on pharmacokinetics, and that understanding these effects is critical to the success of TLR agonist drug development. This article will summarize the pharmacokinetics of TLR agonists with different administration routes, with an emphasis on clinical studies of TLR ligands in oncologic applications. PMID:21643519

  16. Agonist binding to the NMDA receptor drives movement of its cytoplasmic domain without ion flow

    PubMed Central

    Dore, Kim; Aow, Jonathan; Malinow, Roberto

    2015-01-01

    The NMDA receptor (R) plays important roles in brain physiology and pathology as an ion channel. Here we examine the ion flow-independent coupling of agonist to the NMDAR cytoplasmic domain (cd). We measure FRET between fluorescently tagged cytoplasmic domains of GluN1 subunits of NMDARs expressed in neurons. Different neuronal compartments display varying levels of FRET, consistent with different NMDARcd conformations. Agonist binding drives a rapid and transient ion flow-independent reduction in FRET between GluN1 subunits within individual NMDARs. Intracellular infusion of an antibody targeting the GluN1 cytoplasmic domain blocks agonist-driven FRET changes in the absence of ion flow, supporting agonist-driven movement of the NMDARcd. These studies indicate that extracellular ligand binding to the NMDAR can transmit conformational information into the cell in the absence of ion flow. PMID:26553997

  17. Antagonist but not agonist labeling of serotonin-1A receptors is decreased in major depressive disorder

    PubMed Central

    Stockmeier, Craig A.; Howley, Eimear; Shi, Xiaochun; Sobanska, Anna; Clarke, Gerard; Friedman, Lee; Rajkowska, Grazyna

    2009-01-01

    Serotonin-1A receptors may play a role in the pathophysiology of depression and suicide. In postmortem brain tissue, agonist binding to serotonin-1A receptors is reportedly increased or unchanged in depression or suicide, while neuroimaging studies report a decrease in antagonist binding to these receptors in subjects with depression. In this study, both agonist and antagonist radioligand binding to serotonin-1A receptors were examined in postmortem orbitofrontal cortex from subjects with major depressive disorder (MDD). Brain tissue was collected at autopsy from 11 subjects with MDD and 11 age- and gender-matched normal control subjects. Two depressed subjects had a recent psychoactive substance use disorder. Six subjects with MDD had a prescription for an antidepressant drug in the last month of life, and, of these six, postmortem bloods from only two subjects tested positive for an antidepressant drug. There was no significant difference between cohorts for age, postmortem interval or tissue pH. The receptor agonist [3H]8-OH-DPAT or the antagonist [3H]MPPF were used to autoradiographically label serotonin-1A receptors in frozen sections from cytoarchitectonically-defined left rostral orbitofrontal cortex (area 47). There was no significant difference between depressed and control subjects in agonist binding to serotonin-1A receptors. However, antagonist binding was significantly decreased in outer layers of orbitofrontal cortex in MDD. This observation in postmortem tissue confirms reports using an antagonist radioligand in living subjects with depression. Decreased antagonist binding to serotonin-1A receptors in outer layers of orbitofrontal cortex suggests diminished receptor signaling and may be linked to corresponding neuronal changes detected previously in these depressed subjects. PMID:19215942

  18. Characterization of methadone as a β-arrestin-biased μ-opioid receptor agonist

    PubMed Central

    Doi, Seira; Mori, Tomohisa; Uzawa, Naoki; Arima, Takamichi; Takahashi, Tomoyuki; Uchida, Masashi; Yawata, Ayaka; Narita, Michiko; Uezono, Yasuhito; Suzuki, Tsutomu

    2016-01-01

    Background Methadone is a unique µ-opioid receptor agonist. Although several researchers have insisted that the pharmacological effects of methadone are mediated through the blockade of NMDA receptor, the underlying mechanism by which methadone exerts its distinct pharmacological effects compared to those of other µ-opioid receptor agonists is still controversial. In the present study, we further investigated the pharmacological profile of methadone compared to those of fentanyl and morphine as measured mainly by the discriminative stimulus effect and in vitro assays for NMDA receptor binding, µ-opioid receptor-internalization, and µ-opioid receptor-mediated β-arrestin recruitment. Results We found that fentanyl substituted for the discriminative stimulus effects of methadone, whereas a relatively high dose of morphine was required to substitute for the discriminative stimulus effects of methadone in rats. Under these conditions, the non-competitive NMDA receptor antagonist MK-801 did not substitute for the discriminative stimulus effects of methadone. In association with its discriminative stimulus effect, methadone failed to displace the receptor binding of MK801 using mouse brain membrane. Methadone and fentanyl, but not morphine, induced potent µ-opioid receptor internalization accompanied by the strong recruitment of β-arrestin-2 in µ-opioid receptor-overexpressing cells. Conclusions These results suggest that methadone may, at least partly, produce its pharmacological effect as a β-arrestin-biased µ-opioid receptor agonist, similar to fentanyl, and NMDA receptor blockade is not the main contributor to the pharmacological profile of methadone. PMID:27317580

  19. History and perspectives of A2A adenosine receptor antagonists as potential therapeutic agents.

    PubMed

    Preti, Delia; Baraldi, Pier Giovanni; Moorman, Allan R; Borea, Pier Andrea; Varani, Katia

    2015-07-01

    Growing evidence emphasizes that the purine nucleoside adenosine plays an active role as a local regulator in different pathologies. Adenosine is a ubiquitous nucleoside involved in various physiological and pathological functions by stimulating A1 , A2A , A2B , and A3 adenosine receptors (ARs). At the present time, the role of A2A ARs is well known in physiological conditions and in a variety of pathologies, including inflammatory tissue damage and neurodegenerative disorders. In particular, the use of selective A2A antagonists has been reported to be potentially useful in the treatment of Parkinson's disease (PD). In this review, A2A AR signal transduction pathways, together with an analysis of the structure-activity relationships of A2A antagonists, and their corresponding pharmacological roles and therapeutic potential have been presented. The initial results from an emerging polypharmacological approach are also analyzed. This approach is based on the optimization of the affinity and/or functional activity of the examined compounds toward multiple targets, such as A1 /A2A ARs and monoamine oxidase-B (MAO-B), both closely implicated in the pathogenesis of PD. PMID:25821194

  20. Pharmacological and Therapeutic Effects of A3 Adenosine Receptor (A3AR) Agonists

    PubMed Central

    Fishman, Pnina; Bar-Yehuda, Sara; Liang, Bruce T.; Jacobson, Kenneth A.

    2011-01-01

    The Gi-coupled A3 adenosine receptor (A3AR) mediates anti-inflammatory, anticancer and anti-ischemic protective effects. The receptor is overexpressed in inflammatory and cancer cells, while low expression is found in normal cells, rendering the A3AR as a potential therapeutic target. Highly selective A3AR agonists have been synthesized and molecular recognition in the binding site has been characterized. The present review summarizes preclinical and clinical human studies demonstrating that A3AR agonists induce specific anti-inflammatory and anticancer effects via a molecular mechanism that entails modulation of the Wnt and the NF-κB signal transduction pathways. Currently, A3AR agonists are being developed for the treatment of inflammatory diseases including rheumatoid arthritis and psoriasis; ophthalmic diseases such as dry eye syndrome and glaucoma; liver diseases such as hepatocellular carcinoma and hepatitis. PMID:22033198

  1. Agonists with supraphysiological efficacy at the muscarinic M2 ACh receptor

    PubMed Central

    Schrage, R; Seemann, WK; Klöckner, J; Dallanoce, C; Racké, K; Kostenis, E; De Amici, M; Holzgrabe, U; Mohr, K

    2013-01-01

    Background and Purpose Artificial agonists may have higher efficacy for receptor activation than the physiological agonist. Until now, such ‘superagonism’ has rarely been reported for GPCRs. Iperoxo is an extremely potent muscarinic receptor agonist. We hypothesized that iperoxo is a ‘superagonist’. Experimental Approach Signalling of iperoxo and newly synthesized structural analogues was compared with that of ACh at label-free M2 muscarinic receptors applying whole cell dynamic mass redistribution, measurement of G-protein activation, evaluation of cell surface agonist binding and computation of operational efficacies. Key Results In CHO-hM2 cells, iperoxo significantly exceeds ACh in Gi/Gs signalling competence. In the orthosteric loss-of-function mutant M2-Y1043.33A, the maximum effect of iperoxo is hardly compromised in contrast to ACh. ‘Superagonism’ is preserved in the physiological cellular context of MRC-5 human lung fibroblasts. Structure–signalling relationships including iperoxo derivatives with either modified positively charged head group or altered tail suggest that ‘superagonism’ of iperoxo is mechanistically based on parallel activation of the receptor protein via two orthosteric interaction points. Conclusion and Implications Supraphysiological agonist efficacy at muscarinic M2 ACh receptors is demonstrated for the first time. In addition, a possible underlying molecular mechanism of GPCR ‘superagonism’ is provided. We suggest that iperoxo-like orthosteric GPCR activation is a new avenue towards a novel class of receptor activators. Linked Article This article is commented on by Langmead and Christopoulos, pp. 353–356 of this issue. To view this commentary visit http://dx.doi.org/10.1111/bph.12142 PMID:23062057

  2. Maxadilan, a PAC1 receptor agonist from sand flies

    PubMed Central

    Lerner, Ethan A.; Iuga, Aurel O.; Reddy, Vemuri B.

    2007-01-01

    In 1991, a potent 61 amino acid vasodilator peptide, named maxadilan, was isolated from the salivary glands of the sand fly. Subsequently, it was shown that this peptide specifically and potently activated the mammalian PAC1 receptor, one of the three receptors for PACAP. These studies and the link between maxadilan and leishmaniasis are discussed. PMID:17681401

  3. In vivo and in vitro evaluation of novel μ-opioid receptor agonist compounds.

    PubMed

    Nikaido, Yoshiaki; Kurosawa, Aya; Saikawa, Hitomi; Kuroiwa, Satoshi; Suzuki, Chiharu; Kuwabara, Nobuo; Hoshino, Hazime; Obata, Hideaki; Saito, Shigeru; Saito, Tamio; Osada, Hiroyuki; Kobayashi, Isao; Sezutsu, Hideki; Takeda, Shigeki

    2015-11-15

    Opioids are the most effective and widely used drugs for pain treatment. Morphine is an archetypal opioid and is an opioid receptor agonist. Unfortunately, the clinical usefulness of morphine is limited by adverse effects such as analgesic tolerance and addiction. Therefore, it is important to study the development of novel opioid agonists as part of pain control. The analgesic effects of opioids are mediated by three opioid receptors, namely opioid μ-, δ-, and κ-receptors. They belong to the G protein-coupled receptor superfamily and are coupled to Gi proteins. In the present study, we developed a ligand screening system to identify novel opioid μ-receptor agonists that measures [(35)S]GTPγS binding to cell membrane fractions prepared from the fat body of transgenic silkworms expressing μ-receptor-Gi1α fusion protein. We screened the RIKEN Natural Products Depository (NPDepo) chemical library, which contains 5848 compounds, and analogs of hit compounds. We successfully identified a novel, structurally unique compound, that we named GUM1, with agonist activity for the opioid μ-receptor (EC50 of 1.2 µM). The Plantar Test (Hargreaves' Method) demonstrated that subcutaneous injection of 3mg/kg of GUM1 into wild-type rats significantly extended latency time. This extension was also observed in a rat model of morphine tolerance and was inhibited by pre-treatment of naloxone. The unique molecular skeleton of GUM1 makes it an attractive molecule for further ligand-opioid receptor binding studies. PMID:26476280

  4. Differences in acute anorectic effects of long-acting GLP-1 receptor agonists in rats

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Long-acting glucagon-like peptide-1 receptor (GLP-1R) agonists have both glucose- and weight-lowering effects. The brain is poised to mediate both of these actions since GLP-1Rs are present in key areas known to control weight and glucose. Although some research has been performed on the effects of ...

  5. Differential Effects of Cannabinoid Receptor Agonist on Social Discrimination and Contextual Fear in Amygdala and Hippocampus

    ERIC Educational Resources Information Center

    Segev, Amir; Akirav, Irit

    2011-01-01

    We examined whether the cannabinoid receptor agonist WIN55,212-2 (WIN; 5 [mu]g/side) microinjected into the hippocampus or the amygdala would differentially affect memory processes in a neutral vs. an aversive task. In the aversive contextual fear task, WIN into the basolateral amygdala impaired fear acquisition/consolidation, but not retrieval.…

  6. Profound and rapid reduction in body temperature induced by the melanocortin receptor agonists

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The melanocortin receptor 4 (MC4R) plays a major role in body weight regulation and its agonist MTII has been widely used to study the role of MC4Rs in energy expenditure promotion and feeding reduction. Unexpectedly, we observed that intraperitoneal (i.p.) administration of MTII induced a rapid red...

  7. Discovery and characterization of novel small-molecule CXCR4 receptor agonists and antagonists

    PubMed Central

    Mishra, Rama K.; Shum, Andrew K.; Platanias, Leonidas C.; Miller, Richard J.; Schiltz, Gary E.

    2016-01-01

    The chemokine CXCL12 (SDF-1) and its cognate receptor CXCR4 are involved in a large number of physiological processes including HIV-1 infectivity, inflammation, tumorigenesis, stem cell migration, and autoimmune diseases. While previous efforts have identified a number of CXCR4 antagonists, there have been no small molecule agonists reported. Herein, we describe the identification of a novel series of CXCR4 modulators, including the first small molecules to display agonist behavior against this receptor, using a combination of structure- and ligand-based virtual screening. These agonists produce robust calcium mobilization in human melanoma cell lines which can be blocked by the CXCR4-selective antagonist AMD3100. We also demonstrate the ability of these new agonists to induce receptor internalization, ERK activation, and chemotaxis, all hallmarks of CXCR4 activation. Our results describe a new series of biologically relevant small molecules that will enable further study of the CXCR4 receptor and may contribute to the development of new therapeutics. PMID:27456816

  8. Possible differences in modes of agonist and antagonist binding at human 5-HT6 receptors.

    PubMed

    Pullagurla, Manik R; Westkaemper, Richard B; Glennon, Richard A

    2004-09-01

    A graphics model of the human 5-HT6 receptor was constructed and automated docking studies were performed. The model suggests that 5-HT6 antagonist arylsulfonyltryptamines might bind differently than that of the agonist serotonin. Furthermore, the model explains many of the empirical results from our previous structure-affinity studies. PMID:15357994

  9. Discovery and characterization of novel small-molecule CXCR4 receptor agonists and antagonists.

    PubMed

    Mishra, Rama K; Shum, Andrew K; Platanias, Leonidas C; Miller, Richard J; Schiltz, Gary E

    2016-01-01

    The chemokine CXCL12 (SDF-1) and its cognate receptor CXCR4 are involved in a large number of physiological processes including HIV-1 infectivity, inflammation, tumorigenesis, stem cell migration, and autoimmune diseases. While previous efforts have identified a number of CXCR4 antagonists, there have been no small molecule agonists reported. Herein, we describe the identification of a novel series of CXCR4 modulators, including the first small molecules to display agonist behavior against this receptor, using a combination of structure- and ligand-based virtual screening. These agonists produce robust calcium mobilization in human melanoma cell lines which can be blocked by the CXCR4-selective antagonist AMD3100. We also demonstrate the ability of these new agonists to induce receptor internalization, ERK activation, and chemotaxis, all hallmarks of CXCR4 activation. Our results describe a new series of biologically relevant small molecules that will enable further study of the CXCR4 receptor and may contribute to the development of new therapeutics. PMID:27456816

  10. Profiling of histamine H4 receptor agonists in native human monocytes

    PubMed Central

    Gschwandtner, M; Koether, B; Werfel, T; Stark, H; Gutzmer, R

    2013-01-01

    Background and Purpose Since the identification of the histamine H4 receptor, several ligands activating this receptor have been described and more compounds are in development. These ligands are well characterized in pharmacological assays, including radioligand competition binding studies, GTPγS and GTPase assays. In most cases, these experiments are performed in transfected cell lines, expressing unnaturally high levels of target receptors and G-protein signalling components. In this study we investigated the specific properties of H4 receptor ligands in native cells. Experimental Approach Histamine and five different H4 receptor agonists – 4-methylhistamine, UR-PI376, clobenpropit, VUF8430 and ST-1006 – were characterized in freshly isolated human monocytes. The ligands (10 nM–10 μM) were tested as inhibitors of IL-12p70 secretion from human monocytes and the effects of the H2 receptor antagonist ranitidine and the H4 receptor antagonist JNJ7777120 on their action was investigated. Key Results Histamine and all the tested agonists reduced IL-12p70 secretion into monocyte supernatants by 40–70%. The potencies varied with pEC50 values ranging from 5.7 to 6.9, depending on the agonist used. All potencies were lower than those determined in the original investigations of the compounds. Pretreatment of monocytes with H2 or H4 receptor antagonists showed that some H4 receptor ligands also had low activity at the H2 receptor. Conclusions and Implications Our study demonstrates discrepancies between the potencies obtained from assays in transfected cell lines and assays in native human cells, indicating the importance of evaluating H4 receptor ligands in native cells. Linked Articles This article is part of a themed issue on Histamine Pharmacology Update. To view the other articles in this issue visit http://dx.doi.org/10.1111/bph.2013.170.issue-1 PMID:23638754

  11. G-protein mediates voltage regulation of agonist binding to muscarinic receptors: effects on receptor-Na/sup +/ channel interaction

    SciTech Connect

    Cohen-Armon, M.; Garty, H.; Sokolovsky, M.

    1988-01-12

    The authors previous experiments in membranes prepared from rat heart and brain led them to suggest that the binding of agonist to the muscarinic receptors and to the Na/sup +/ channels is a coupled event mediated by guanine nucleotide binding protein(s) (G-protein(s)). These in vitro findings prompted us to employ synaptoneurosomes from brain stem tissue to examine (i) the binding properties of (/sup 3/H) acetylcholine at resting potential and under depolarization conditions in the absence and presence of pertussis toxin; (ii) the binding of (/sup 3/H)batrachotoxin to Na/sup +/ channel(s) in the presence of the muscarinic agonists; and (iii) muscarinically induced /sup 22/Na/sup +/ uptake in the presence and absence of tetrodotoxin, which blocks Na/sup +/ channels. The findings indicate that agonist binding to muscarinic receptors is voltage dependent, that this process is mediated by G-protein(s), and that muscarinic agonists induce opening of Na/sup +/channels. The latter process persists even after pertussis toxin treatment, indicating that it is not likely to be mediated by pertussis toxin sensitive G-protein(s). The system with its three interacting components-receptor, G-protein, and Na/sup +/ channel-is such that at resting potential the muscarinic receptor induces opening of Na/sup +/ channels; this property may provide a possible physiological mechanism for the depolarization stimulus necessary for autoexcitation or repetitive firing in heart or brain tissues.

  12. Behavioral and biochemical characterization of benzodiazepine receptor partial agonists in pigeons.

    PubMed

    Witkin, J M; Acri, J B; Wong, G; Gleeson, S; Barrett, J E

    1996-04-01

    The ability of benzodiazepine receptor partial agonists to exhibit full efficacy in preclinical anxiolytic tests, in conjunction with initial clinical results, has suggested the possibility of a reduced clinical side-effect profile compared to benzodiazepine receptor full agonists like diazepam. Because punished behavior of pigeons has been useful in detecting effects of novel anxiolytic drugs, effects of imidazobenzodiazepine and beta-carboline benzodiazepine receptor partial agonists and some related compounds were evaluated in this species. The abilities of these compounds to substitute for the discriminative stimulus effects of the full agonists midazolam also was determined. Intrinsic efficacy was assessed by the degree to which gamma-aminobutyric acid increased ligand potency to displace [(3)H]Ro15-1788 (flumazinil) from membranes of pigeon cerebrum, and ranged from full agonist-like efficacy (Ro 19-5470; 7-(3-cyclopropyl-1,2,4-oxodiazol-5-yl)-5,6-dihydro-5-methyl-4H- imidazo[1,5a]-thieno[3,2-f]diazin-4-one) to minimal gamma-aminobutyric acid potentiations close to that of the antagonist flumazenil (abecarnil and Ro 41-7812; 7-chloro-4,5-dihydro-3-(3-hydroxy-1-propynyl)-5-methyl-6H-imidazo[1,5-a] -[1,4 ]benzodiazepine-6-one). Punished responding was increased markedly by midazolam and by all partial agonists, except Ro 41-7812 and Ro 42-8773 (7-chloro-3-[3-(cyclopropylmethoxy)-1-propynyl]-4,5-dihyro-5 -methyl-6H-imidaz o[1,5-a][1,4]benzodiazepine-6-one), at doses that did not affect nonpunished responding. In contrast to the full substitution generally observed in mammals, all of the partial agonists produced incomplete substitution (40-70%) in the midazolam drug discrimination procedure in pigeons. A positive relationship was observed between the degree of substitution and intrinsic efficacy. The benzodiazepine antagonists, flumazenil and ZK 93,426 (ethyl-5-isopropoxy-4-methoxymethyl-beta-carboline-3-carboxylate), neither increased punished responding nor

  13. Mapping the agonist binding site of the nicotinic acetylcholine receptor. Orientation requirements for activation by covalent agonist.

    PubMed

    Sullivan, D A; Cohen, J B

    2000-04-28

    To characterize the structural requirements for ligand orientation compatible with activation of the Torpedo nicotinic acetylcholine receptor (nAChR), we used Cys mutagenesis in conjunction with sulfhydryl-reactive reagents to tether primary or quaternary amines at defined positions within the agonist binding site of nAChRs containing mutant alpha- or gamma-subunits expressed in Xenopus oocytes. 4-(N-Maleimido)benzyltrimethylammonium and 2-aminoethylmethanethiosulfonate acted as irreversible antagonists when tethered at alphaY93C, alphaY198C, or gammaE57C, as well as at alphaN94C (2-aminoethylmethanethiosulfonate only). [2-(Trimethylammonium)-ethyl]-methanethiosulfonate (MTSET), which attaches thiocholine to binding site Cys, also acted as an irreversible antagonist when tethered at alphaY93C, alphaN94C, or gammaE57C. However, MTSET modification of alphaY198C resulted in prolonged activation of the nAChR not reversible by washing but inhibitable by subsequent exposure to non-competitive antagonists. Modification of alphaY198C (or any of the other positions tested) by [(trimethylammonium)methyl]methanethiosulfonate resulted only in irreversible inhibition, while modification of alphaY198C by [3-(trimethylammonium)propyl]methanethiosulfonate resulted in irreversible activation of nAChR, but at lower efficacy than by MTSET. Thus changing the length of the tethering arm by less than 1 A in either direction markedly effects the ability of the covalent trimethylammonium to activate the nAChR, and agonist activation depends on a very selective orientation of the quaternary ammonium within the agonist binding site. PMID:10777557

  14. 2-(1-Hexyn-1-yl)adenosine-induced intraocular hypertension is mediated via K+ channel opening through adenosine A2A receptor in rabbits.

    PubMed

    Konno, Takashi; Uchibori, Takehiro; Nagai, Akihiko; Kogi, Kentaro; Nakahata, Norimichi

    2005-08-22

    The present study was performed to clarify the mechanism of change in intraocular pressure by 2-(1-hexyn-1-yl)adenosine (2-H-Ado), a selective adenosine A2 receptor agonist, in rabbits. 2-H-Ado (0.1%, 50 microl)-induced ocular hypertension (E(max): 7.7 mm Hg) was inhibited by an adenosine A2A receptor antagonist 1,3,7-trimethyl-8-(3-chlorostyryl)xanthine, ATP-sensitive K+ channel blocker glibenclamide or 5-hydroxydecanoic acid, but not by an adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine, an adenosine A2B receptor antagonist alloxazine or a cyclooxygenase inhibitor indomethacin. The outflow facility induced by 2-H-Ado seems to be independent of increase in intraocular pressure or ATP-sensitive K+ channel. In contrast, the recovery rate in intraocular pressure decreased by hypertonic saline was accelerated by 2-H-Ado, and this response was dependent on ATP-sensitive K+ channel. These results suggest that 2-H-Ado-induced ocular hypertension is mediated via K+ channel opening through adenosine A2A receptor, and this is probably due to aqueous formation, but independent of change in outflow facility or prostaglandin production. PMID:16023100

  15. 5-HT2 Receptor Regulation of Mitochondrial Genes: Unexpected Pharmacological Effects of Agonists and Antagonists.

    PubMed

    Harmon, Jennifer L; Wills, Lauren P; McOmish, Caitlin E; Demireva, Elena Y; Gingrich, Jay A; Beeson, Craig C; Schnellmann, Rick G

    2016-04-01

    In acute organ injuries, mitochondria are often dysfunctional, and recent research has revealed that recovery of mitochondrial and renal functions is accelerated by induction of mitochondrial biogenesis (MB). We previously reported that the nonselective 5-HT2 receptor agonist DOI [1-(4-iodo-2,5-dimethoxyphenyl)propan-2-amine] induced MB in renal proximal tubular cells (RPTCs). The goal of this study was to determine the role of 5-HT2 receptors in the regulation of mitochondrial genes and oxidative metabolism in the kidney. The 5-HT2C receptor agonist CP-809,101 [2-[(3-chlorophenyl)methoxy]-6-(1-piperazinyl)pyrazine] and antagonist SB-242,084 [6-chloro-2,3-dihydro-5-methyl-N-[6-[(2-methyl-3-pyridinyl)oxy]-3-pyridinyl]-1H-indole-1-carboxyamide dihydrochloride] were used to examine the induction of renal mitochondrial genes and oxidative metabolism in RPTCs and in mouse kidneys in the presence and absence of the 5-HT2C receptor. Unexpectedly, both CP-809,101 and SB-242,084 increased RPTC respiration and peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) mRNA expression in RPTCs at 1-10 nM. In addition, CP-809,101 and SB-242,084 increased mRNA expression of PGC-1α and the mitochondrial proteins NADH dehydrogenase subunit 1 and NADH dehydrogenase (ubiquinone) β subcomplex 8 in mice. These compounds increased mitochondrial genes in RPTCs in which the 5-HT2C receptor was downregulated with small interfering RNA and in the renal cortex of mice lacking the 5-HT2C receptor. By contrast, the ability of these compounds to increase PGC-1α mRNA and respiration was blocked in RPTCs treated with 5-HT2A receptor small interfering RNA or the 5-HT2A receptor antagonist eplivanserin. In addition, the 5-HT2A receptor agonist NBOH-2C-CN [4-[2-[[(2-hydroxyphenyl)methyl]amino]ethyl]-2,5-dimethoxybenzonitrile] increased RPTC respiration at 1-100 nM. These results suggest that agonism of the 5-HT2A receptor induces MB and that the classic 5-HT2C receptor agonist CP

  16. Systemic chemotherapy is modulated by platelet-activating factor-receptor agonists.

    PubMed

    Sahu, Ravi P; Ferracini, Matheus; Travers, Jeffrey B

    2015-01-01

    Chemotherapy is used to treat numerous cancers including melanoma. However, its effectiveness in clinical settings is often hampered by various mechanisms. Previous studies have demonstrated that prooxidative stressor-mediated generation of oxidized lipids with platelet-activating factor-receptor (PAF-R) agonistic activity induces systemic immunosuppression that augments the growth of experimental melanoma tumors. We have recently shown that treatment of murine B16F10 melanoma cells in vitro or tumors implanted into syngeneic mice and treated intratumorally with various chemotherapeutic agents generated PAF-R agonists in a process blocked by antioxidants. Notably, these intratumoral chemotherapy-generated PAF-R agonists augmented the growth of secondary (untreated) tumors in a PAF-R dependent manner. As both localized and systemic chemotherapies are used based on tumor localization/stage and metastases, the current studies were sought to determine effects of PAF-R agonists on systemic chemotherapy against experimental melanoma. Here, we show that systemic chemotherapy with etoposide (ETOP) attenuates the growth of melanoma tumors when given subsequent to the tumor cell implantation. Importantly, this ETOP-mediated suppression of melanoma tumor growth was blocked by exogenous administration of a PAF-R agonist, CPAF. These findings indicate that PAF-R agonists not only negatively affect the ability of localized chemotherapy but also compromise the efficacy of systemic chemotherapy against murine melanoma. PMID:25922565

  17. Antimitogenic effect of bitter taste receptor agonists on airway smooth muscle cells.

    PubMed

    Sharma, Pawan; Panebra, Alfredo; Pera, Tonio; Tiegs, Brian C; Hershfeld, Alena; Kenyon, Lawrence C; Deshpande, Deepak A

    2016-02-15

    Airway remodeling is a hallmark feature of asthma and chronic obstructive pulmonary disease. Clinical studies and animal models have demonstrated increased airway smooth muscle (ASM) mass, and ASM thickness is correlated with severity of the disease. Current medications control inflammation and reverse airway obstruction effectively but have limited effect on remodeling. Recently we identified the expression of bitter taste receptors (TAS2R) on ASM cells, and activation with known TAS2R agonists resulted in ASM relaxation and bronchodilation. These studies suggest that TAS2R can be used as new therapeutic targets in the treatment of obstructive lung diseases. To further establish their effectiveness, in this study we aimed to determine the effects of TAS2R agonists on ASM growth and promitogenic signaling. Pretreatment of healthy and asthmatic human ASM cells with TAS2R agonists resulted in a dose-dependent inhibition of ASM proliferation. The antimitogenic effect of TAS2R ligands was not dependent on activation of protein kinase A, protein kinase C, or high/intermediate-conductance calcium-activated K(+) channels. Immunoblot analyses revealed that TAS2R agonists inhibit growth factor-activated protein kinase B phosphorylation without affecting the availability of phosphatidylinositol 3,4,5-trisphosphate, suggesting TAS2R agonists block signaling downstream of phosphatidylinositol 3-kinase. Furthermore, the antimitogenic effect of TAS2R agonists involved inhibition of induced transcription factors (activator protein-1, signal transducer and activator of transcription-3, E2 factor, nuclear factor of activated T cells) and inhibition of expression of multiple cell cycle regulatory genes, suggesting a direct inhibition of cell cycle progression. Collectively, these findings establish the antimitogenic effect of TAS2R agonists and identify a novel class of receptors and signaling pathways that can be targeted to reduce or prevent airway remodeling as well as

  18. Comparative pharmacology of bombesin receptor subtype-3, nonpeptide agonist MK-5046, a universal peptide agonist, and peptide antagonist Bantag-1 for human bombesin receptors.

    PubMed

    Moreno, Paola; Mantey, Samuel A; Nuche-Berenguer, Bernardo; Reitman, Marc L; González, Nieves; Coy, David H; Jensen, Robert T

    2013-10-01

    Bombesin-receptor-subtype-3 (BRS-3) is an orphan G-protein-coupled receptor of the bombesin (Bn) family whose natural ligand is unknown and which does not bind any natural Bn-peptide with high affinity. It is present in the central nervous system, peripheral tissues, and tumors; however, its role in normal physiology/pathophysiology is largely unknown because of the lack of selective ligands. Recently, MK-5046 [(2S)-1,1,1-trifluoro-2-[4-(1H-pyrazol-1-yl)phenyl]-3-(4-{[1-(trifluoromethyl)cyclopropyl]methyl}-1H-imidazol-2-yl)propan-2-ol] and Bantag-1 [Boc-Phe-His-4-amino-5-cyclohexyl-2,4,5-trideoxypentonyl-Leu-(3-dimethylamino) benzylamide N-methylammonium trifluoroacetate], a nonpeptide agonist and a peptide antagonist, respectively, for BRS-3 have been described, but there have been limited studies on their pharmacology. We studied MK-5046 and Bantag-1 interactions with human Bn-receptors-human bombesin receptor subtype-3 (hBRS-3), gastrin-releasing peptide receptor (GRP-R), and neuromedin B receptor (NMB-R)-and compared them with the nonselective, peptide-agonist [d-Tyr6,βAla11,Phe13,Nle14]Bn-(6-14) (peptide #1). Receptor activation was detected by activation of phospholipase C (PLC), mitogen-activated protein kinase (MAPK), focal adhesion kinase (FAK), paxillin, and Akt. In hBRS-3 cells, the relative affinities were Bantag-1 (1.3 nM) > peptide #1 (2 nM) > MK-5046 (37-160 nM) > GRP, NMB (>10 μM), and the binding-dose-inhibition curves were broad (>4 logs), with Hill coefficients differing significantly from unity. Curve-fitting demonstrated high-affinity (MK-5046, Ki = 0.08 nM) and low-affinity (MK-5046, Ki = 11-29 nM) binding sites. For PLC activation in hBRS-3 cells, the relative potencies were MK-5046 (0.02 nM) > peptide #1 (6 nM) > GRP, NMB, Bantag-1 (>10 μM), and MK-5046 had a biphasic dose response, whereas peptide #1 was monophasic. Bantag-1 was a specific hBRS-3-antagonist. In hBRS-3 cells, MK-5046 was a full agonist for activation of MAPK, FAK, Akt

  19. Peroxisome Proliferator-Activated Receptor Agonist Treatment of Alcohol-Induced Hepatic Insulin Resistance

    PubMed Central

    de la Monte, Suzanne M.; Pang, Maoyin; Chaudhry, Rajeeve; Duan, Kevin; Longato, Lisa; Carter, Jade; Ouh, Jiyun; Wands, Jack R.

    2011-01-01

    Chronic ethanol exposure impairs insulin signaling in the liver. Peroxisome-proliferator activated receptor (PPAR) agonists function as insulin sensitizers and are used to treat type 2 diabetes mellitus. We examined the therapeutic effectiveness of PPAR agonists in reducing alcoholic hepatitis and hepatic insulin resistance in a model of chronic ethanol feeding. Adult male Long Evans rats were pair fed with isocaloric liquid diets containing 0% (control) or 37% ethanol (caloric content; 9.2% v/v) for 8 weeks. After 3 weeks on the diets, the rats were treated with vehicle, or a PPAR-α, PPAR-δ, or PPAR-γ agonist twice weekly by i.p. injection. Livers were harvested for histopathological, gene expression (RT-PCR), protein (Western and ELISA), and receptor binding studies. Ethanol-fed rats developed steatohepatitis with disordered hepatic chord architecture, increased hepatocellular apoptosis, reduced binding to the insulin, IGF-1, and IGF-2 receptors, and decreased expression of glyceraldehyde-3-phosphate dehydrogenase and aspartyl-(asparaginyl)-β-hydroxylase (mediates remodeling), which are regulated by insulin/IGF signaling. PPAR-α, PPAR-δ, or PPAR-γ agonist treatments reduced the severity of ethanol-mediated liver injury, including hepatic architectural disarray and steatosis. In addition, PPAR-δ and PPAR-γ agonists reduced insulin/IGF resistance and increased insulin/IGF-responsive gene expression. In conclusion, PPAR agonists may help reduce the severity of chronic ethanol-induced liver injury and insulin/IGF resistance, even in the context of continued high-level ethanol consumption. PMID:21426453

  20. Estrogen receptor agonists alleviate cardiac and renal oxidative injury in rats with renovascular hypertension.

    PubMed

    Özdemir Kumral, Zarife Nigâr; Kolgazi, Meltem; Üstünova, Savaş; Kasımay Çakır, Özgür; Çevik, Özge Dağdeviren; Şener, Göksel; Yeğen, Berrak Ç

    2016-01-01

    Although endogenous estrogen is known to offer cardiac and vascular protection, the involvement of estrogen receptors in mediating the protective effect of estrogen on hypertension-induced cardiovascular and renal injury is not fully explained. We aimed to investigate the effects of estrogen receptor (ER) agonists on oxidative injury, cardiovascular and renal functions of rats with renovascular hypertension (RVH). Female Sprague-Dawley rats were randomly divided as control and RVH groups, and RVH groups had either ovariectomy (OVX) or sham-OVX. Sham-OVX-RVH and OVX-RVH groups received either ERβ agonist diarylpropiolnitrile (1 mg/kg/day) or ERα agonist propyl pyrazole triol (1 mg/kg/day) for 6 weeks starting at the third week following the surgery. At the end of the 9(th) week, systolic blood pressures were recorded, cardiac functions were determined, and the contraction/relaxation responses of aortic rings were obtained. Serum creatinine levels, tissue malondialdehyde, glutathione, superoxide dismutase, catalase levels, and myeloperoxidase activity in heart and kidney samples were analyzed, and Na(+), K(+)-ATPase activity was measured in kidney samples. In both sham-OVX and OVX rats, both agonists reduced blood pressure and reversed the impaired contractile performance of the heart, while ERβ agonist improved renal functions in both the OVX and non-OVX rats. Both agonists reduced neutrophil infiltration, lipid peroxidation, and elevated antioxidant levels in the heart, but a more ERβ-mediated protective effect was observed in the kidney. Our data suggest that activation of ERβ might play a role in preserving the function of the stenotic kidney and delaying the progression of renal injury, while both receptors mediate similar cardioprotective effects. PMID:27399230

  1. A2A Adenosine Receptors Are Differentially Modulated by Pharmacological Treatments in Rheumatoid Arthritis Patients and Their Stimulation Ameliorates Adjuvant-Induced Arthritis in Rats

    PubMed Central

    Vincenzi, Fabrizio; Padovan, Melissa; Targa, Martina; Corciulo, Carmen; Giacuzzo, Sarah; Merighi, Stefania; Gessi, Stefania; Govoni, Marcello; Borea, Pier Andrea; Varani, Katia

    2013-01-01

    A2A 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 A2AARs in rheumatoid arthritis (RA) patients after different pharmacological treatments and to investigate the effect of A2AAR stimulation in a rat model of arthritis. We investigated A2AAR 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. A2AARs 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 A2AAR 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 A2AAR stimulation in lymphocytes from RA patients and in serum from arthritic rats was measured. In lymphocytes obtained from RA patients, the A2AAR 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 A2AAR 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 A2AAR agonists represent a physiological-like therapeutic alternative for RA treatment as suggested by the anti-inflammatory role of A2AARs in lymphocytes from RA patients. The effectiveness of A2AAR stimulation in a rat model of arthritis supported the role of A2AAR agonists as potential pharmacological treatment for RA. PMID:23326596

  2. Agonist-bound structure of the human P2Y12 receptor

    PubMed Central

    Zhang, Jin; Zhang, Kaihua; Gao, Zhan-Guo; Paoletta, Silvia; Zhang, Dandan; Han, Gye Won; Li, Tingting; Ma, Limin; Zhang, Wenru; Müller, Christa E.; Yang, Huaiyu; Jiang, Hualiang; Cherezov, Vadim; Katritch, Vsevolod; Jacobson, Kenneth A.; Stevens, Raymond C.; Wu, Beili; Zhao, Qiang

    2014-01-01

    The P2Y12 receptor (P2Y12R), one of eight members of the P2YR family expressed in humans, has been identified as one of the most prominent clinical drug targets for inhibition of platelet aggregation. Consequently, extensive mutagenesis and modeling studies of the P2Y12R have revealed many aspects of agonist/antagonist binding1-4. However, the details of agonist and antagonist recognition and function at the P2Y12R remain poorly understood at the molecular level. Here, we report the structures of the human P2Y12R in complex with a full agonist 2-methylthio-adenosine-5′-diphosphate (2MeSADP, a close analogue of endogenous agonist ADP) at 2.5 Å resolution, and the corresponding ATP derivative 2-methylthio-adenosine-5′-triphosphate (2MeSATP) at 3.1 Å resolution. Analysis of these structures, together with the structure of the P2Y12R with antagonist ethyl 6-(4-((benzylsulfonyl)carbamoyl)piperidin-1-yl)-5-cyano-2-methylnicotinate (AZD1283)5, reveals dramatic conformational changes between nucleotide and non-nucleotide ligand complexes in the extracellular regions, providing the first insight into a different ligand binding landscape in the δ-group of class A G protein-coupled receptors (GPCRs). Agonist and non-nucleotide antagonist adopt different orientations in the P2Y12R, with only partially overlapped binding pockets. The agonist-bound P2Y12R structure answers long-standing ambiguities surrounding P2Y12R-agonist recognition, and reveals interactions with several residues that had not been reported to be involved in agonist binding. As a first example of a GPCR where agonist access to the binding pocket requires large scale rearrangements in the highly malleable extracellular region, the structural studies therefore will provide invaluable insight into the pharmacology and mechanisms of action of agonists and different classes of antagonists for the P2Y12R and potentially for other closely related P2YRs. PMID:24784220

  3. Rational design of partial agonists for the muscarinic m1 acetylcholine receptor.

    PubMed

    Chen, Xinyu; Klöckner, Jessika; Holze, Janine; Zimmermann, Cornelia; Seemann, Wiebke K; Schrage, Ramona; Bock, Andreas; Mohr, Klaus; Tränkle, Christian; Holzgrabe, Ulrike; Decker, Michael

    2015-01-22

    Aiming to design partial agonists for a G-protein-coupled receptor based on dynamic ligand binding, we synthesized three different series of bipharmacophoric ligands composed of the orthosteric building blocks iperoxo and 1 linked to allosteric modulators (BQCA-derived compounds, BQCAd; TBPB-derived compound, TBPBd). Their interactions were studied with the human muscarinic acetylcholine M1-receptor (hM1) with respect to receptor binding and Gq-protein signaling. Results demonstrate that iperoxo/BQCAd (2, 3) and 1/BQCAd hybrids (4) act as M1 partial agonists, whereas 1/TBPBd hybrids (5) did not activate M1-receptors. Among the iperoxo/BQCAd-hybrids, spacer length in conjunction with the pattern of substitution tuned efficacy. Most interestingly, a model of dynamic ligand binding revealed that the spacer length of 2a and 3a controlled the probability of switch between the inactive purely allosteric and the active bitopic orthosteric/allosteric binding pose. In summary, dynamic ligand binding can be exploited in M1 receptors to design partial agonists with graded efficacy. PMID:25478907

  4. Agonistic aptamer to the insulin receptor leads to biased signaling and functional selectivity through allosteric modulation.

    PubMed

    Yunn, Na-Oh; Koh, Ara; Han, Seungmin; Lim, Jong Hun; Park, Sehoon; Lee, Jiyoun; Kim, Eui; Jang, Sung Key; Berggren, Per-Olof; Ryu, Sung Ho

    2015-09-18

    Due to their high affinity and specificity, aptamers have been widely used as effective inhibitors in clinical applications. However, the ability to activate protein function through aptamer-protein interaction has not been well-elucidated. To investigate their potential as target-specific agonists, we used SELEX to generate aptamers to the insulin receptor (IR) and identified an agonistic aptamer named IR-A48 that specifically binds to IR, but not to IGF-1 receptor. Despite its capacity to stimulate IR autophosphorylation, similar to insulin, we found that IR-A48 not only binds to an allosteric site distinct from the insulin binding site, but also preferentially induces Y1150 phosphorylation in the IR kinase domain. Moreover, Y1150-biased phosphorylation induced by IR-A48 selectively activates specific signaling pathways downstream of IR. In contrast to insulin-mediated activation of IR, IR-A48 binding has little effect on the MAPK pathway and proliferation of cancer cells. Instead, AKT S473 phosphorylation is highly stimulated by IR-A48, resulting in increased glucose uptake both in vitro and in vivo. Here, we present IR-A48 as a biased agonist able to selectively induce the metabolic activity of IR through allosteric binding. Furthermore, our study also suggests that aptamers can be a promising tool for developing artificial biased agonists to targeted receptors. PMID:26245346

  5. Potential antidepressant-like properties of the TC G-1008, a GPR39 (zinc receptor) agonist.

    PubMed

    Młyniec, Katarzyna; Starowicz, Gabriela; Gaweł, Magdalena; Frąckiewicz, Ewelina; Nowak, Gabriel

    2016-09-01

    Some forms of depression appear to be more related to the glutamatergic system. G-coupled protein receptor 39 (GPR39) is the metabotropic zinc receptor, which may be involved in the pathophysiology of depression and in the antidepressant response. Its deficiency abolishes the antidepressant response, which means that GPR39 is required to obtain a therapeutic effect in depression. This raises the possibility that agonists of the zinc receptor may have a role in antidepressant treatment. To explore this possibility we investigated animal behaviour in the forced swim test, the tail suspension test (to assess antidepressant-like properties), the light/dark test and the elevated plus maze test (to assess anxiolytic-like properties), following acute administration of a GPR39 agonist (TC G-1008). We found an antidepressant response (as measured by the forced swim test but not by the tail suspension test) in mice following the GPR39 agonist treatment. Additionally, we observed the opposite results in the light/dark box (decreased overall distance; increased time spent in the lit compartment; decreased time spent in the dark compartment; increased freezing time) and elevated plus maze (no significant changes), which may be a consequence of the sedative effect of TC G-1008. We also found hippocampal GPR39 and brain-derived neurotrophic factor (BDNF) up-regulation following administration of the GPR39 agonist, which may be undiscovered so far as a possible novel agent in the treatment of mood disorders. PMID:27235821

  6. Agonistic aptamer to the insulin receptor leads to biased signaling and functional selectivity through allosteric modulation

    PubMed Central

    Yunn, Na-Oh; Koh, Ara; Han, Seungmin; Lim, Jong Hun; Park, Sehoon; Lee, Jiyoun; Kim, Eui; Jang, Sung Key; Berggren, Per-Olof; Ryu, Sung Ho

    2015-01-01

    Due to their high affinity and specificity, aptamers have been widely used as effective inhibitors in clinical applications. However, the ability to activate protein function through aptamer-protein interaction has not been well-elucidated. To investigate their potential as target-specific agonists, we used SELEX to generate aptamers to the insulin receptor (IR) and identified an agonistic aptamer named IR-A48 that specifically binds to IR, but not to IGF-1 receptor. Despite its capacity to stimulate IR autophosphorylation, similar to insulin, we found that IR-A48 not only binds to an allosteric site distinct from the insulin binding site, but also preferentially induces Y1150 phosphorylation in the IR kinase domain. Moreover, Y1150-biased phosphorylation induced by IR-A48 selectively activates specific signaling pathways downstream of IR. In contrast to insulin-mediated activation of IR, IR-A48 binding has little effect on the MAPK pathway and proliferation of cancer cells. Instead, AKT S473 phosphorylation is highly stimulated by IR-A48, resulting in increased glucose uptake both in vitro and in vivo. Here, we present IR-A48 as a biased agonist able to selectively induce the metabolic activity of IR through allosteric binding. Furthermore, our study also suggests that aptamers can be a promising tool for developing artificial biased agonists to targeted receptors. PMID:26245346

  7. Dimethyl-diphenyl-propanamide derivatives as nonsteroidal dissociated glucocorticoid receptor agonists.

    PubMed

    Yang, Bingwei V; Weinstein, David S; Doweyko, Lidia M; Gong, Hua; Vaccaro, Wayne; Huynh, Tram; Xiao, Hai-Yun; Doweyko, Arthur M; McKay, Lorraine; Holloway, Deborah A; Somerville, John E; Habte, Sium; Cunningham, Mark; McMahon, Michele; Townsend, Robert; Shuster, David; Dodd, John H; Nadler, Steven G; Barrish, Joel C

    2010-12-01

    A series of 2,2-dimethyl-3,3-diphenyl-propanamides as novel glucocorticoid receptor modulators is reported. SAR exploration led to the identification of 4-hydroxyphenyl propanamide derivatives displaying good agonist activity in GR-mediated transrepression assays and reduced agonist activity in GR-mediated transactivation assays. Compounds 17 and 30 showed anti-inflammatory activity comparable to prednisolone in the rat carrageenan-induced paw edema model, with markedly decreased side effects with regard to increases in blood glucose and expression of hepatic tyrosine aminotransferase. A hypothetical binding mode accounting for the induction of the functional activity by a 4-hydroxyl group is proposed. PMID:21073190

  8. Motilin: towards a new understanding of the gastrointestinal neuropharmacology and therapeutic use of motilin receptor agonists

    PubMed Central

    Sanger, G J; Wang, Y; Hobson, A; Broad, J

    2013-01-01

    The gastrointestinal hormone motilin has been known about for >40 years, but after identification of its receptor and subsequent development of new tools and methods, a reappraisal of its actions is required. Firstly, it is important to note that motilin and ghrelin receptors are members of the same family (similar genomic organization, gastrointestinal distribution and abilities to stimulate gastrointestinal motility), yet each fails to recognize the ligand of the other; and whereas ghrelin and ghrelin receptors are widespread outside the gastrointestinal tract, motilin and its receptors are largely restricted to the gastrointestinal tract. Secondly, although some studies suggest motilin has activity in rodents, most do not, and receptor pseudogenes exist in rodents. Thirdly, motilin preferentially operates by facilitating enteric cholinergic activity rather than directly contracting the muscle, despite the relatively high expression of receptor immunoreactivity in muscle. This activity is ligand-dependent, with short-lasting actions of motilin contrasting with longer-lasting actions of the non-selective and selective motilin receptor agonists erythromycin and GSK962040. Finally, the use of erythromycin (also an antibiotic drug) to treat patients requiring acceleration of gastric emptying has led to concerns over safety and potential exacerbation of antibiotic resistance. Replacement motilin receptor agonists derived from erythromycin (motilides) have been unsuccessful. New, non-motilide, small molecule receptor agonists, designed to minimize self-desensitization, are now entering clinical trials for treating patients undergoing enteral feeding or with diabetic gastroparesis. Thus, for the translational pharmacologist, the study of motilin illustrates the need to avoid overreliance on artificial systems, on structural information and on animal studies. LINKED ARTICLES This article is part of a themed section on Neuropeptides. To view the other articles in this

  9. Physical origins of remarkable thermostabilization by an octuple mutation for the adenosine A2a receptor

    NASA Astrophysics Data System (ADS)

    Kajiwara, Yuta; Ogino, Takahiro; Yasuda, Satoshi; Takamuku, Yuuki; Murata, Takeshi; Kinoshita, Masahiro

    2016-07-01

    It was experimentally showed that the thermal stability of a membrane protein, the adenosine A2a receptor, was remarkably enhanced by an octuple mutation. Here we theoretically prove that the energy decrease arising from the formation of protein intramolecular hydrogen bonds and the solvent-entropy gain upon protein folding are made substantially larger by the mutation, leading to the remarkable enhancement. The solvent is formed by hydrocarbon groups constituting nonpolar chains of the lipid bilayer within a membrane. The mutation modifies geometric characteristics of the structure so that the solvent crowding can be reduced to a larger extent when the protein folds.

  10. Mass spectrometry-based ligand binding assays on adenosine A1 and A2A receptors.

    PubMed

    Massink, A; Holzheimer, M; Hölscher, A; Louvel, J; Guo, D; Spijksma, G; Hankemeier, T; IJzerman, A P

    2015-12-01

    Conventional methods to measure ligand-receptor binding parameters typically require radiolabeled ligands as probes. Despite the robustness of radioligand binding assays, they carry inherent disadvantages in terms of safety precautions, expensive synthesis, special lab requirements, and waste disposal. Mass spectrometry (MS) is a method that can selectively detect ligands without the need of a label. The sensitivity of MS equipment increases progressively, and currently, it is possible to detect low ligand quantities that are usually found in ligand binding assays. We developed a label-free MS ligand binding (MS binding) assay on the adenosine A(1) and A(2A) receptors (A(1)AR and A(2A)AR), which are well-characterized members of the class A G protein-coupled receptor (GPCR) family. Radioligand binding assays for both receptors are well established, and ample data is available to compare and evaluate the performance of an MS binding assay. 1,3-Dipropyl-8-cyclopentyl-xanthine (DPCPX) and 4-(2-((7-amino-2-(furan-2-yl)-[1,2,4]triazolo[1,5-a]-[1,3,5]triazin-5-yl)amino)ethyl)phenol (ZM-241,385) are high-affinity ligands selective for the A(1)AR and A(2A)AR, respectively. To proof the feasibility of MS binding on the A(1)AR and A(2A)AR, we first developed an MS detection method for unlabeled DPCPX and ZM-241,385. To serve as internal standards, both compounds were also deuterium-labeled. Subsequently, we investigated whether the two unlabeled compounds could substitute for their radiolabeled counterparts as marker ligands in binding experiments, including saturation, displacement, dissociation, and competition association assays. Furthermore, we investigated the accuracy of these assays if the use of internal standards was excluded. The results demonstrate the feasibility of the MS binding assay, even in the absence of a deuterium-labeled internal standard, and provide great promise for the further development of label-free assays based on MS for other GPCRs. PMID

  11. Ischaemic skeletal muscle hyperaemia in the anaesthetized cat: no contribution of A2A adenosine receptors.

    PubMed Central

    Poucher, S M

    1997-01-01

    1. The present study investigated the contribution of the A2A adenosine receptor subtype to the functional hyperaemia response evoked by muscle contraction in anaesthetized cats when muscle blood flow was limited. 2. Application of a stenosis reduced the hindlimb blood flow at rest from 9.67 +/- 1.80 to 5.53 +/- 0.91 ml min(-1) (kg body mass)(-1) and during muscle contraction from 36.80 +/- 2.55 to 11.11 +/- 1.19 ml min(-1) (kg body mass)(-1) (P < 0.001). The force produced by the extensor digitorum longus and tibialis anterior (EDL-TA) muscle groups was also reduced, from 9.66 +/- 0.56 to 4.10 +/- 0.4 N (kg muscle mass)(-1) (P < 0.01). 3. The selective A2A adenosine receptor antagonist ZM241385 (3 mg kg(-1), I.V.) had no effect upon the hindlimb vascular conductance or muscle contraction responses in the presence of the flow-limiting stenosis. 4. In contrast, in the absence of the flow restriction the vascular conductance response was reduced by 27.5 +/- 5.0% (P < 0.05), whilst the isometric force produced by the EDL-TA muscle group was unaffected (pre- vs. post-contraction, 5.8 +/- 0.8 vs. 4.6 +/- 1.0 N (kg muscle mass)(-1) contraction). Oxygen consumption by the contracting hindlimb muscles was maintained (1.71 +/- 0.25 vs. 1.69 +/- 0.26 ml min(-1) (kg body mass)(-1)) by an increase in the oxygen extraction (51.9 +/- 4.9 vs. 66.2 +/- 6.1%; P< 0.01). 5. These results confirm previous data showing that adenosine, acting at the A2A receptor subtype, can contribute up to 30% of the functional hyperaemia response in the hindlimb of anaesthetized cats under free flow conditions. However, when blood flow is limited by a stenosis, antagonism of the A2A adenosine receptor does not affect functional hyperaemia. Images Figure 1 PMID:9097944

  12. A photochromic agonist for μ-opioid receptors.

    PubMed

    Schönberger, Matthias; Trauner, Dirk

    2014-03-17

    Opioid receptors (ORs) are widely distributed in the brain, the spinal cord, and the digestive tract and play an important role in nociception. All known ORs are G-protein-coupled receptors (GPCRs) of family A. Another well-known member of this family, rhodopsin, is activated by light through the cis/trans isomerization of a covalently bound chromophore, retinal. We now show how an OR can be combined with a synthetic azobenzene photoswitch to gain light sensitivity. Our work extends the reach of photopharmacology and outlines a general strategy for converting Family A GPCRs, which account for the majority of drug targets, into photoreceptors. PMID:24519993

  13. Comparative Pharmacology of Bombesin Receptor Subtype-3, Nonpeptide Agonist MK-5046, a Universal Peptide Agonist, and Peptide Antagonist Bantag-1 for Human Bombesin Receptors

    PubMed Central

    Moreno, Paola; Mantey, Samuel A.; Nuche-Berenguer, Bernardo; Reitman, Marc L.; González, Nieves; Coy, David H.

    2013-01-01

    Bombesin-receptor-subtype-3 (BRS-3) is an orphan G-protein-coupled receptor of the bombesin (Bn) family whose natural ligand is unknown and which does not bind any natural Bn-peptide with high affinity. It is present in the central nervous system, peripheral tissues, and tumors; however, its role in normal physiology/pathophysiology is largely unknown because of the lack of selective ligands. Recently, MK-5046 [(2S)-1,1,1-trifluoro-2-[4-(1H-pyrazol-1-yl)phenyl]-3-(4-{[1-(trifluoromethyl)cyclopropyl]methyl}-1H-imidazol-2-yl)propan-2-ol] and Bantag-1 [Boc-Phe-His-4-amino-5-cyclohexyl-2,4,5-trideoxypentonyl-Leu-(3-dimethylamino) benzylamide N-methylammonium trifluoroacetate], a nonpeptide agonist and a peptide antagonist, respectively, for BRS-3 have been described, but there have been limited studies on their pharmacology. We studied MK-5046 and Bantag-1 interactions with human Bn-receptors—human bombesin receptor subtype-3 (hBRS-3), gastrin-releasing peptide receptor (GRP-R), and neuromedin B receptor (NMB-R)—and compared them with the nonselective, peptide-agonist [d-Tyr6,βAla11,Phe13,Nle14]Bn-(6–14) (peptide #1). Receptor activation was detected by activation of phospholipase C (PLC), mitogen-activated protein kinase (MAPK), focal adhesion kinase (FAK), paxillin, and Akt. In hBRS-3 cells, the relative affinities were Bantag-1 (1.3 nM) > peptide #1 (2 nM) > MK-5046 (37–160 nM) > GRP, NMB (>10 μM), and the binding-dose-inhibition curves were broad (>4 logs), with Hill coefficients differing significantly from unity. Curve-fitting demonstrated high-affinity (MK-5046, Ki = 0.08 nM) and low-affinity (MK-5046, Ki = 11–29 nM) binding sites. For PLC activation in hBRS-3 cells, the relative potencies were MK-5046 (0.02 nM) > peptide #1 (6 nM) > GRP, NMB, Bantag-1 (>10 μM), and MK-5046 had a biphasic dose response, whereas peptide #1 was monophasic. Bantag-1 was a specific hBRS-3-antagonist. In hBRS-3 cells, MK-5046 was a full agonist for activation of MAPK

  14. Key Modulatory Role of Presynaptic Adenosine A2A Receptors in Cortical Neurotransmission to the Striatal Direct Pathway

    PubMed Central

    Quiroz, César; Luján, Rafael; Uchigashima, Motokazu; Simoes, Ana Patrícia; Lerner, Talia N.; Borycz, Janusz; Kachroo, Anil; Canas, Paula M.; Orru, Marco; Schwarzschild, Michael A.; Rosin, Diane L.; Kreitzer, Anatol C.; Cunha, Rodrigo A.; Watanabe, Masahiko; Ferré, Sergi

    2010-01-01

    Basal ganglia processing results from a balanced activation of direct and indirect striatal efferent pathways, which are controlled by dopamine D1 and D2 receptors, respectively. Adenosine A2A receptors are considered novel anti-parkinsonian targets, based on their selective postsynaptic localization in the indirect pathway, where they modulate D2 receptor function. The present study provides evidence for the existence of an additional functionally significant segregation of A2A receptors at the presynaptic level. Using integrated anatomical, electrophysiological and biochemical approaches, we demonstrate that presynaptic A2A receptors are preferentially localized in cortical glutamatergic terminals that contact striatal neurons of the direct pathway, where they exert a selective modulation of cortico-striatal neurotransmission. Presynaptic striatal A2A receptors could provide a new target for the treatment of neuropsychiatric disorders. PMID:19936569

  15. Serotonin 2A receptor agonist binding in the human brain with [11C]Cimbi-36

    PubMed Central

    Ettrup, Anders; da Cunha-Bang, Sophie; McMahon, Brenda; Lehel, Szabolcs; Dyssegaard, Agnete; Skibsted, Anine W; Jørgensen, Louise M; Hansen, Martin; Baandrup, Anders O; Bache, Søren; Svarer, Claus; Kristensen, Jesper L; Gillings, Nic; Madsen, Jacob; Knudsen, Gitte M

    2014-01-01

    [11C]Cimbi-36 was recently developed as a selective serotonin 2A (5-HT2A) receptor agonist radioligand for positron emission tomography (PET) brain imaging. Such an agonist PET radioligand may provide a novel, and more functional, measure of the serotonergic system and agonist binding is more likely than antagonist binding to reflect 5-HT levels in vivo. Here, we show data from a first-in-human clinical trial with [11C]Cimbi-36. In 29 healthy volunteers, we found high brain uptake and distribution according to 5-HT2A receptors with [11C]Cimbi-36 PET. The two-tissue compartment model using arterial input measurements provided the most optimal quantification of cerebral [11C]Cimbi-36 binding. Reference tissue modeling was feasible as it induced a negative but predictable bias in [11C]Cimbi-36 PET outcome measures. In five subjects, pretreatment with the 5-HT2A receptor antagonist ketanserin before a second PET scan significantly decreased [11C]Cimbi-36 binding in all cortical regions with no effects in cerebellum. These results confirm that [11C]Cimbi-36 binding is selective for 5-HT2A receptors in the cerebral cortex and that cerebellum is an appropriate reference tissue for quantification of 5-HT2A receptors in the human brain. Thus, we here describe [11C]Cimbi-36 as the first agonist PET radioligand to successfully image and quantify 5-HT2A receptors in the human brain. PMID:24780897

  16. Agouti signalling protein is an inverse agonist to the wildtype and agonist to the melanic variant of the melanocortin-1 receptor in the grey squirrel (Sciurus carolinensis).

    PubMed

    McRobie, Helen R; King, Linda M; Fanutti, Cristina; Symmons, Martyn F; Coussons, Peter J

    2014-06-27

    The melanocortin-1 receptor (MC1R) is a key regulator of mammalian pigmentation. Melanism in the grey squirrel is associated with an eight amino acid deletion in the mutant melanocortin-1 receptor with 24 base pair deletion (MC1RΔ24) variant. We demonstrate that the MC1RΔ24 exhibits a higher basal activity than the wildtype MC1R (MC1R-wt). We demonstrate that agouti signalling protein (ASIP) is an inverse agonist to the MC1R-wt but is an agonist to the MC1RΔ24. We conclude that the deletion in the MC1RΔ24 leads to a receptor with a high basal activity which is further activated by ASIP. This is the first report of ASIP acting as an agonist to MC1R. PMID:24879893

  17. Time and space profiling of NMDA receptor co-agonist functions.

    PubMed

    Mothet, Jean-Pierre; Le Bail, Matildé; Billard, Jean-Marie

    2015-10-01

    The N-Methyl D-Aspartic acid (NMDA) receptors (NMDAR) are key tetrameric ionotropic glutamate receptors that transduce glutamatergic signals throughout the central nervous system (CNS) and spinal cord. Although NMDARs are diverse in their subunit composition, subcellular localization, and biophysical and pharmacological properties, their activation always requires the binding of a co-agonist that has long been thought to be glycine. However, intense research over the last decade has challenged this classical model by showing that another amino acid, d-serine, is the preferential co-agonist for a subset of synaptic NMDARs in many areas of the adult brain. Nowadays, a totally new picture of glutamatergic synapses at work is emerging where both glycine and d-serine are involved in a complex interplay to regulate NMDAR functions in the CNS following time and space constraints. The purpose of this review was to highlight the particular role of each co-agonist in modulating NMDAR-dependent activities in healthy and diseased brains. We have herein integrated our most advanced knowledge of how glycine and d-serine may orchestrate synapse dynamics and drive neuronal network activity in a time- and synapse-specific manner and how changes in synaptic availability of these amino acids may contribute to cognitive impairments such as those associated with healthy aging, epilepsy, and schizophrenia. The N-Methyl D-Aspartic acid (NMDA) subtype of glutamate receptors are central to many physiological functions and are linked to brain disorders. Their functions require glutamate and a co-agonist d-serine or glycine. After years of intense research and controversy on the identity of the amino acid that serves as the right co-agonist, we are just entering a new era of consensus where glycine and d-serine are teaming up to regulate the function of different subsets of NMDA receptors and at different synapses during different time windows of brain development. PMID:26088787

  18. Development of highly potent protease-activated receptor 2 agonists via synthetic lipid tethering

    PubMed Central

    Flynn, Andrea N.; Hoffman, Justin; Tillu, Dipti V.; Sherwood, Cara L.; Zhang, Zhenyu; Patek, Renata; Asiedu, Marina N. K.; Vagner, Josef; Price, Theodore J.; Boitano, Scott

    2013-01-01

    Protease-activated receptor-2 (PAR2) is a G-protein coupled receptor (GPCR) associated with a variety of pathologies. However, the therapeutic potential of PAR2 is limited by a lack of potent and specific ligands. Following proteolytic cleavage, PAR2 is activated through a tethered ligand. Hence, we reasoned that lipidation of peptidomimetic ligands could promote membrane targeting and thus significantly improve potency and constructed a series of synthetic tethered ligands (STLs). STLs contained a peptidomimetic PAR2 agonist (2-aminothiazol-4-yl-LIGRL-NH2) bound to a palmitoyl group (Pam) via polyethylene glycol (PEG) linkers. In a high-throughput physiological assay, these STL agonists displayed EC50 values as low as 1.47 nM, representing a ∼200 fold improvement over the untethered parent ligand. Similarly, these STL agonists were potent activators of signaling pathways associated with PAR2: EC50 for Ca2+ response as low as 3.95 nM; EC50 for MAPK response as low as 9.49 nM. Moreover, STLs demonstrated significant improvement in potency in vivo, evoking mechanical allodynia with an EC50 of 14.4 pmol. STLs failed to elicit responses in PAR2−/− cells at agonist concentrations of >300-fold their EC50 values. Our results demonstrate that the STL approach is a powerful tool for increasing ligand potency at PAR2 and represent opportunities for drug development at other protease activated receptors and across GPCRs.—Flynn, A. N., Hoffman, J., Tillu, D. V., Sherwood, C. L., Zhang, Z., Patek, R., Asiedu, M. N. K., Vagner, J., Price, T. J., Boitano, S. Development of highly potent protease-activated receptor 2 agonists via synthetic lipid tethering. PMID:23292071

  19. Differential Signaling of the Endogenous Agonists at the β2-Adrenergic Receptor*

    PubMed Central

    Reiner, Susanne; Ambrosio, Manuela; Hoffmann, Carsten; Lohse, Martin J.

    2010-01-01

    The concept of “functional selectivity” or “biased signaling” suggests that a ligand can have distinct efficacies with regard to different signaling pathways. We have investigated the question of whether biased signaling may be related to distinct agonist-induced conformational changes in receptors using the β2-adrenergic receptor (β2AR) and its two endogenous ligands epinephrine and norepinephrine as a model system. Agonist-induced conformational changes were determined in a fluorescently tagged β2AR FRET sensor. In this β2AR sensor, norepinephrine caused signals that amounted to only ≈50% of those induced by epinephrine and the standard “full” agonist isoproterenol. Furthermore, norepinephrine-induced changes in the β2AR FRET sensor were slower than those induced by epinephrine (rate constants, 47 versus 128 ms). A similar partial β2AR activation signal was revealed for the synthetic agonists fenoterol and terbutaline. However, norepinephrine was almost as efficient as epinephrine (and isoproterenol) in causing activation of Gs and adenylyl cyclase. In contrast, fenoterol was quite efficient in triggering β-arrestin2 recruitment to the cell surface and its interaction with β2AR, as well as internalization of the receptors, whereas norepinephrine caused partial and slow changes in these assays. We conclude that partial agonism of norepinephrine at the β2AR is related to the induction of a different active conformation and that this conformation is efficient in signaling to Gs and less efficient in signaling to β-arrestin2. These observations extend the concept of biased signaling to the endogenous agonists of the β2AR and link it to distinct conformational changes in the receptor. PMID:20837485

  20. Metabolic Syndrome Abolishes Glucagon-Like Peptide 1 Receptor Agonist Stimulation of SERCA in Coronary Smooth Muscle.

    PubMed

    Dineen, Stacey L; McKenney, Mikaela L; Bell, Lauren N; Fullenkamp, Allison M; Schultz, Kyle A; Alloosh, Mouhamad; Chalasani, Naga; Sturek, Michael

    2015-09-01

    Metabolic syndrome (MetS) doubles the risk of adverse cardiovascular events. Glucagon-like peptide 1 (GLP-1) receptor agonists induce weight loss, increase insulin secretion, and improve glucose tolerance. Studies in healthy animals suggest cardioprotective properties of GLP-1 receptor agonists, perhaps partially mediated by improved sarco-endoplasmic reticulum Ca(2+) ATPase (SERCA) activity. We examined the acute effect of GLP-1 receptor agonists on coronary smooth muscle cells (CSM) enzymatically isolated from lean, healthy Ossabaw miniature swine. Intracellular Ca(2+) handling was interrogated with fura-2. The GLP-1 receptor agonist exenatide activated SERCA but did not alter other Ca(2+) transporters. Further, we tested the hypothesis that chronic, in vivo treatment with GLP-1 receptor agonist AC3174 would attenuate coronary artery disease (CAD) in swine with MetS. MetS was induced in 20 swine by 6 months' feeding of a hypercaloric, atherogenic diet. Swine were then randomized (n = 10/group) into placebo or AC3174 treatment groups and continued the diet for an additional 6 months. AC3174 treatment attenuated weight gain, increased insulin secretion, and improved glucose tolerance. Intravascular ultrasound and histology showed no effect of AC3174 on CAD. MetS abolished SERCA activation by GLP-1 receptor agonists. We conclude that MetS confers vascular resistance to GLP-1 receptor agonists, partially through impaired cellular signaling steps involving SERCA. PMID:25845661

  1. Modulation of agonist binding to human dopamine receptor subtypes by L-prolyl-L-leucyl-glycinamide and a peptidomimetic analog.

    PubMed

    Verma, Vaneeta; Mann, Amandeep; Costain, Willard; Pontoriero, Giuseppe; Castellano, Jessica M; Skoblenick, Kevin; Gupta, Suresh K; Pristupa, Zdenek; Niznik, Hyman B; Johnson, Rodney L; Nair, Venugopalan D; Mishra, Ram K

    2005-12-01

    The present study was undertaken to investigate the role of the hypothalamic tripeptide L-prolyl-L-leucyl-glycinamide (PLG) and its conformationally constrained analog 3(R)-[(2(S)-pyrrolidinylcarbonyl)amino]-2-oxo-1-pyrrolidineacetamide (PAOPA) in modulating agonist binding to human dopamine (DA) receptor subtypes using human neuroblastoma SH-SY5Y cells stably transfected with respective cDNAs. Both PLG and PAOPA enhanced agonist [3H]N-propylnorapomorphine (NPA) and [3H]quinpirole binding in a dose-dependent manner to the DA D2L,D2S, and D4 receptors. However, agonist binding to the D1 and D3 receptors and antagonist binding to the D2L receptors by PLG were not significantly affected. Scatchard analysis of [3H]NPA binding to membranes in the presence of PLG revealed a significant increase in affinity of the agonist binding sites for the D2L, D2S, and D4 receptors. Analysis of agonist/antagonist competition curves revealed that PLG and PAOPA increased the population and affinity of the high-affinity form of the D2L receptor and attenuated guanosine 5'-(beta,gamma-imido)-triphosphate-induced inhibition of high-affinity agonist binding sites for the DA D2L receptor. Furthermore, direct NPA binding with D2L cell membranes pretreated with suramin, a compound that can uncouple receptor/G protein complexes, and incubated with and without DA showed that both PLG and PAOPA had only increased agonist binding in membranes pretreated with both suramin and DA, suggesting that PLG requires the D2L receptor/G protein complex to increase agonist binding. These results suggest that PLG possibly modulates DA D2S, D2L, and D4 receptors in an allosteric manner and that the coupling of D2 receptors to the G protein is essential for this modulation to occur. PMID:16126839

  2. Behavioral effects of a synthetic agonist selective for nociceptin/orphanin FQ peptide receptors in monkeys.

    PubMed

    Ko, Mei-Chuan; Woods, James H; Fantegrossi, William E; Galuska, Chad M; Wichmann, Jürgen; Prinssen, Eric P

    2009-08-01

    Behavioral effects of a nonpeptidic NOP (nociceptin/orphanin FQ Peptide) receptor agonist, Ro 64-6198, have not been studied in primate species. The aim of the study was to verify the receptor mechanism underlying the behavioral effects of Ro 64-6198 and to systematically compare behavioral effects of Ro 64-6198 with those of a mu-opioid receptor agonist, alfentanil, in monkeys. Both Ro 64-6198 (0.001-0.06 mg/kg, s.c.) and alfentanil (0.001-0.06 mg/kg, s.c.) produced antinociception against an acute noxious stimulus (50 degrees C water) and capsaicin-induced allodynia. An NOP receptor antagonist, J-113397 (0.01-0.1 mg/kg, s.c.), dose-dependently produced rightward shifts of the dose-response curve of Ro 64-6198-induced antinociception. The apparent pA(2) value of J-113397 was 8.0. Antagonist studies using J-113397 and naltrexone revealed that Ro 64-6198 produced NOP receptor-mediated antinociception independent of mu-opioid receptors. In addition, alfentanil dose-dependently produced respiratory depression and itch/scratching responses, but antinociceptive doses of Ro 64-6198 did not produce such effects. More important, Ro 64-6198 did not produce reinforcing effects comparable with those of alfentanil, cocaine, or methohexital under self-administration procedures in monkeys. These results provide the first functional evidence that the activation of NOP receptors produces antinociception without reinforcing effects in primates. Non-peptidic NOP receptor agonists may have therapeutic value as novel analgesics without abuse liability in humans. PMID:19279568

  3. Metabotropic glutamate receptor agonists potentiate a slow afterdepolarization in CNS neurons

    NASA Technical Reports Server (NTRS)

    Zheng, F.; Gallagher, J. P.

    1992-01-01

    We have previously reported that, in the rat dorsolateral septal nucleus (DLSN), metabotropic glutamate receptor (met-GluR) agonists evoked a slow depolarization accompanied by an increase in membrane conductance and burst firing. We have speculated that the burst firing elicited by met-GluR agonists may be due to activation or enhancement of a non-specific cation current, which exists in some DLSN neurons. Now we report that a slow afterdepolarization (sADP) mediated by a non-specific cation current was potentiated by both 1S,3R-ACPD and quisqualate. In addition, met-GluR agonists unmask a sADP in DLSN neurons which did not show a sADP under control conditions. Our data suggest that a non-specific cation current can be potentiated by activation of the met-GluR.

  4. Incorporation of Phosphonate into Benzonaphthyridine Toll-like Receptor 7 Agonists for Adsorption to Aluminum Hydroxide.

    PubMed

    Cortez, Alex; Li, Yongkai; Miller, Andrew T; Zhang, Xiaoyue; Yue, Kathy; Maginnis, Jillian; Hampton, Janice; Hall, De Shon; Shapiro, Michael; Nayak, Bishnu; D'Oro, Ugo; Li, Chun; Skibinski, David; Mbow, M Lamine; Singh, Manmohan; O'Hagan, Derek T; Cooke, Michael P; Valiante, Nicholas M; Wu, Tom Y-H

    2016-06-23

    Small molecule Toll-like receptor 7 (TLR7) agonists have been used as vaccine adjuvants by enhancing innate immune activation to afford better adaptive response. Localized TLR7 agonists without systemic exposure can afford good adjuvanticity, suggesting peripheral innate activation (non-antigen-specific) is not required for immune priming. To enhance colocalization of antigen and adjuvant, benzonaphthyridine (BZN) TLR7 agonists are chemically modified with phosphonates to allow adsorption onto aluminum hydroxide (alum), a formulation commonly used in vaccines for antigen stabilization and injection site deposition. The adsorption process is facilitated by enhancing aqueous solubility of BZN analogs to avoid physical mixture of two insoluble particulates. These BZN-phosphonates are highly adsorbed onto alum, which significantly reduced systemic exposure and increased local retention post injection. This report demonstrates a novel approach in vaccine adjuvant design using phosphonate modification to afford adsorption of small molecule immune potentiator (SMIP) onto alum, thereby enhancing co-delivery with antigen. PMID:27270029

  5. 2-Aminoalkyl nicotinamide derivatives as pure inverse agonists of the ghrelin receptor.

    PubMed

    Takahashi, Bitoku; Funami, Hideaki; Iwaki, Takehiko; Maruoka, Hiroshi; Nagahira, Asako; Koyama, Makoto; Kamiide, Yoshiyuki; Matsuo, Tsuyoshi; Muto, Tsuyoshi; Annoura, Hirokazu

    2015-07-01

    New inverse agonists of the ghrelin receptor (ghrelinR) were obtained through high-throughput screening and subsequent structural modification of 2-aminoalkyl nicotinamide derivatives. The key structural feature to improve in vitro activity was the introduction of a diazabicyclo ring at the 5-position of the pyridine ring. The final product showed potent inverse agonist activity and, despite its low brain permeability, reduced food intake in both normal and obese mice. These results implied that peripheral ghrelinR activity is important for appetite control and that a peripheral ghrelinR inverse agonist could be an anti-obesity drug with reduced risk of central nervous system (CNS)-related side effects. PMID:25981690

  6. Small-molecule nociceptin receptor agonist ameliorates mast cell activation and pain in sickle mice.

    PubMed

    Vang, Derek; Paul, Jinny A; Nguyen, Julia; Tran, Huy; Vincent, Lucile; Yasuda, Dennis; Zaveri, Nurulain T; Gupta, Kalpna

    2015-12-01

    Treatment of pain with morphine and its congeners in sickle cell anemia is suboptimal, warranting the need for analgesics devoid of side effects, addiction and tolerance liability. Small-molecule nociceptin opioid receptor ligands show analgesic efficacy in acute and chronic pain models. We show that AT-200, a high affinity nociceptin opioid receptor agonist with low efficacy at the mu opioid receptor, ameliorated chronic and hypoxia/reoxygenation-induced mechanical, thermal and deep tissue/musculoskeletal hyperalgesia in HbSS-BERK sickle mice. The antinociceptive effect of AT-200 was antagonized by SB-612111, a nociceptin opioid receptor antagonist, but not naloxone, a non-selective mu opioid receptor antagonist. Daily 7-day treatment with AT-200 did not develop tolerance and showed a sustained anti-nociceptive effect, which improved over time and led to reduced plasma serum amyloid protein, neuropeptides, inflammatory cytokines and mast cell activation in the periphery. These data suggest that AT-200 ameliorates pain in sickle mice via the nociceptin opioid receptor by reducing inflammation and mast cell activation without causing tolerance. Thus, nociceptin opioid receptor agonists are promising drugs for treating pain in sickle cell anemia. PMID:26294734

  7. Small-molecule nociceptin receptor agonist ameliorates mast cell activation and pain in sickle mice

    PubMed Central

    Vang, Derek; Paul, Jinny A.; Nguyen, Julia; Tran, Huy; Vincent, Lucile; Yasuda, Dennis; Zaveri, Nurulain T.; Gupta, Kalpna

    2015-01-01

    Treatment of pain with morphine and its congeners in sickle cell anemia is suboptimal, warranting the need for analgesics devoid of side effects, addiction and tolerance liability. Small-molecule nociceptin opioid receptor ligands show analgesic efficacy in acute and chronic pain models. We show that AT-200, a high affinity nociceptin opioid receptor agonist with low efficacy at the mu opioid receptor, ameliorated chronic and hypoxia/reoxygenation-induced mechanical, thermal and deep tissue/musculoskeletal hyperalgesia in HbSS-BERK sickle mice. The antinociceptive effect of AT-200 was antagonized by SB-612111, a nociceptin opioid receptor antagonist, but not naloxone, a non-selective mu opioid receptor antagonist. Daily 7-day treatment with AT-200 did not develop tolerance and showed a sustained anti-nociceptive effect, which improved over time and led to reduced plasma serum amyloid protein, neuropeptides, inflammatory cytokines and mast cell activation in the periphery. These data suggest that AT-200 ameliorates pain in sickle mice via the nociceptin opioid receptor by reducing inflammation and mast cell activation without causing tolerance. Thus, nociceptin opioid receptor agonists are promising drugs for treating pain in sickle cell anemia. PMID:26294734

  8. Targeting the endocannabinoid system with cannabinoid receptor agonists: pharmacological strategies and therapeutic possibilities.

    PubMed

    Pertwee, Roger G

    2012-12-01

    Human tissues express cannabinoid CB(1) and CB(2) receptors that can be activated by endogenously released 'endocannabinoids' or exogenously administered compounds in a manner that reduces the symptoms or opposes the underlying causes of several disorders in need of effective therapy. Three medicines that activate cannabinoid CB(1)/CB(2) receptors are now in the clinic: Cesamet (nabilone), Marinol (dronabinol; Δ(9)-tetrahydrocannabinol (Δ(9)-THC)) and Sativex (Δ(9)-THC with cannabidiol). These can be prescribed for the amelioration of chemotherapy-induced nausea and vomiting (Cesamet and Marinol), stimulation of appetite (Marinol) and symptomatic relief of cancer pain and/or management of neuropathic pain and spasticity in adults with multiple sclerosis (Sativex). This review mentions several possible additional therapeutic targets for cannabinoid receptor agonists. These include other kinds of pain, epilepsy, anxiety, depression, Parkinson's and Huntington's diseases, amyotrophic lateral sclerosis, stroke, cancer, drug dependence, glaucoma, autoimmune uveitis, osteoporosis, sepsis, and hepatic, renal, intestinal and cardiovascular disorders. It also describes potential strategies for improving the efficacy and/or benefit-to-risk ratio of these agonists in the clinic. These are strategies that involve (i) targeting cannabinoid receptors located outside the blood-brain barrier, (ii) targeting cannabinoid receptors expressed by a particular tissue, (iii) targeting upregulated cannabinoid receptors, (iv) selectively targeting cannabinoid CB(2) receptors, and/or (v) adjunctive 'multi-targeting'. PMID:23108552

  9. Endurance training in Wistar rats decreases receptor sensitivity to a serotonin agonist.

    PubMed

    Dwyer, D; Browning, J

    2000-11-01

    There is mounting evidence that increased brain serotonin during exercise is associated with the onset of CNS-mediated fatigue. Serotonin receptor sensitivity is likely to be an important determinant of this fatigue. Alterations in brain serotonin receptor sensitivity were examined in Wistar rats throughout 6 weeks of endurance training, running on a treadmill four times a week with two exercise tests per week to exhaustion. Receptor sensitivity was determined indirectly as the reduction in exercise time in response to a dose of a serotonin (1A) agonist, m-chlorophenylpiperazine (m-CPP). The two groups of controls were used to examine (i) the effect of the injection per se on exercise performance and (ii) changes in serotonin receptor sensitivity associated with maturation. In the test group, undrugged exercise performance significantly improved by 47% after 6 weeks of training (4518 +/- 729 to 6640 +/- 903 s, P=0.01). Drugged exercise performance also increased significantly from week 1 to week 6 (306 +/- 69-712 +/- 192 s, P = 0.04). Control group results indicated that the dose of m-CPP alone caused fatigue during exercise tests and that maturation was not responsible for any decrease in receptor sensitivity. Improved resistance to the fatiguing effects of the serotonin agonist suggests desensitization of central serotonin receptors, probably the 5-HT1A receptors. Endurance training appears to stimulate an adaptive response to the fatiguing effects of increased brain serotonin, which may enhance endurance exercise performance. PMID:11167306

  10. Targeting the endocannabinoid system with cannabinoid receptor agonists: pharmacological strategies and therapeutic possibilities

    PubMed Central

    Pertwee, Roger G.

    2012-01-01

    Human tissues express cannabinoid CB1 and CB2 receptors that can be activated by endogenously released ‘endocannabinoids’ or exogenously administered compounds in a manner that reduces the symptoms or opposes the underlying causes of several disorders in need of effective therapy. Three medicines that activate cannabinoid CB1/CB2 receptors are now in the clinic: Cesamet (nabilone), Marinol (dronabinol; Δ9-tetrahydrocannabinol (Δ9-THC)) and Sativex (Δ9-THC with cannabidiol). These can be prescribed for the amelioration of chemotherapy-induced nausea and vomiting (Cesamet and Marinol), stimulation of appetite (Marinol) and symptomatic relief of cancer pain and/or management of neuropathic pain and spasticity in adults with multiple sclerosis (Sativex). This review mentions several possible additional therapeutic targets for cannabinoid receptor agonists. These include other kinds of pain, epilepsy, anxiety, depression, Parkinson's and Huntington's diseases, amyotrophic lateral sclerosis, stroke, cancer, drug dependence, glaucoma, autoimmune uveitis, osteoporosis, sepsis, and hepatic, renal, intestinal and cardiovascular disorders. It also describes potential strategies for improving the efficacy and/or benefit-to-risk ratio of these agonists in the clinic. These are strategies that involve (i) targeting cannabinoid receptors located outside the blood-brain barrier, (ii) targeting cannabinoid receptors expressed by a particular tissue, (iii) targeting upregulated cannabinoid receptors, (iv) selectively targeting cannabinoid CB2 receptors, and/or (v) adjunctive ‘multi-targeting’. PMID:23108552

  11. Computational study of the binding modes of caffeine to the adenosine A2A receptor.

    PubMed

    Liu, Yuli; Burger, Steven K; Ayers, Paul W; Vöhringer-Martinez, Esteban

    2011-12-01

    Using the recently solved crystal structure of the human adenosine A(2A) receptor, we applied MM/PBSA to compare the binding modes of caffeine with those of the high-affinity selective antagonist ZM241385. MD simulations were performed in the environment of the lipid membrane bilayer. Four low-energy binding modes of caffeine-A(2A) were found, all of which had similar energies. Assuming an equal contribution of each binding mode of caffeine, the computed binding free energy difference between caffeine and ZM241385 is -2.4 kcal/mol, which compares favorably with the experimental value, -3.6 kcal/mol. The configurational entropy contribution of -0.9 kcal/mol from multiple binding modes of caffeine helps explain how a small molecule like caffeine can compete with a significantly larger molecule, ZM241385, which can form many more interactions with the receptor. We also performed residue-wise energy decomposition and found that Phe168, Leu249, and Ile274 contribute most significantly to the binding modes of caffeine and ZM241385. PMID:21970461

  12. A2A adenosine receptor deletion is protective in a mouse model of Tauopathy.

    PubMed

    Laurent, C; Burnouf, S; Ferry, B; Batalha, V L; Coelho, J E; Baqi, Y; Malik, E; Mariciniak, E; Parrot, S; Van der Jeugd, A; Faivre, E; Flaten, V; Ledent, C; D'Hooge, R; Sergeant, N; Hamdane, M; Humez, S; Müller, C E; Lopes, L V; Buée, L; Blum, D

    2016-01-01

    Consumption of caffeine, a non-selective adenosine A2A receptor (A2AR) antagonist, reduces the risk of developing Alzheimer's disease (AD) in humans and mitigates both amyloid and Tau burden in transgenic mouse models. However, the impact of selective A2AR blockade on the progressive development of AD-related lesions and associated memory impairments has not been investigated. In the present study, we removed the gene encoding A2AR from THY-Tau22 mice and analysed the subsequent effects on both pathological (Tau phosphorylation and aggregation, neuro-inflammation) and functional impairments (spatial learning and memory, hippocampal plasticity, neurotransmitter profile). We found that deleting A2ARs protect from Tau pathology-induced deficits in terms of spatial memory and hippocampal long-term depression. These effects were concomitant with a normalization of the hippocampal glutamate/gamma-amino butyric acid ratio, together with a global reduction in neuro-inflammatory markers and a decrease in Tau hyperphosphorylation. Additionally, oral therapy using a specific A2AR antagonist (MSX-3) significantly improved memory and reduced Tau hyperphosphorylation in THY-Tau22 mice. By showing that A2AR genetic or pharmacological blockade improves the pathological phenotype in a Tau transgenic mouse model, the present data highlight A2A receptors as important molecular targets to consider against AD and Tauopathies. PMID:25450226

  13. Bioassay directed identification of natural aryl hydrocarbon-receptor agonists in marmalade.

    PubMed

    van Ede, Karin; Li, An; Antunes-Fernandes, Elsa; Mulder, Patrick; Peijnenburg, Ad; Hoogenboom, Ron

    2008-06-01

    Citrus fruit and citrus fruit products, like grapefruit, lemon and marmalade were shown to contain aryl hydrocarbon receptor (AhR) agonists, as detected with the DR CALUX bioassay. This is of interest regarding the role of the Ah-receptor pathway in the adverse effects of dioxins, PCBs and other aromatic hydrocarbons. So far it is unclear which compounds in citrus fruit are responsible for the AhR-mediated activity and whether regular exposure to these compounds can cause effects comparable to, e.g. dioxins. The present study aimed at developing a method for identifying unknown Ah-receptor agonists in citrus products based on bioassay directed analysis, using marmalade as a first target. Following extraction with hexane and purification on an aluminium oxide-column, the extract was fractionated by HPLC using a C-18 semi-preparative column. Fractions were extracted, solvent-exchanged into dimethylsulfoxide and subsequently tested with DR CALUX. Extracts were shown to contain primarily coumarins, furocoumarins (FCs) and polymethoxyflavones (PMFs). Identification of fractions most active in the bioassay via LC/MS revealed that bergapten (an FC) is the most important Ah-receptor agonist in marmalade. The approach and method developed resulted in the successful identification of the bioactive component. However, potential pitfalls of the procedure will be discussed. PMID:18486664

  14. Melanocortin Receptor Agonists Facilitate Oxytocin-Dependent Partner Preference Formation in the Prairie Vole

    PubMed Central

    Modi, Meera E; Inoue, Kiyoshi; Barrett, Catherine E; Kittelberger, Kara A; Smith, Daniel G; Landgraf, Rainer; Young, Larry J

    2015-01-01

    The central melanocortin (MC) system has been widely studied for its effects on food intake and sexual behavior. However, the MC system, and more specifically the MC4 receptor (MC4R), also interacts with neurochemical systems that regulate socioemotional behaviors, including oxytocin (OT) and dopamine. In monogamous prairie voles, OT and dopamine interact to promote partner preference formation, a laboratory measure of an enduring social bond between mates. Here we investigated the effects of MC receptor activation on partner preference formation in prairie voles, as well as the interaction between the MC and OT systems during this process. Peripheral administration of the brain penetrant MC3/4R receptor peptide agonist, Melanotan II (MTII), and the highly selective, small-molecule MC4R agonist, Pf-446687, enhanced partner preference formation in the prairie vole, but not in the non-monogamous meadow vole. MTII-induced partner preferences were enduring, as they were present 1 week after drug manipulation. The prosocial effects of MCR agonists may be mediated, in part, through modulation of OT, as coadministration of an OT receptor antagonist prevented MTII-induced partner preferences. MTII also selectively activated hypothalamic OT neurons and potentiated central OT release. As OT has been shown to enhance some aspects of social cognition in humans, our data suggest that the MC4R may be a viable therapeutic target for enhancing social function in psychiatric disorders, including autism spectrum disorders and schizophrenia, potentially through activation of the OT system. PMID:25652247

  15. Melanocortin MC4 receptor agonists alleviate brain damage in abdominal compartment syndrome in the rat.

    PubMed

    Liu, Dong; Zhang, Hong-Guang; Zhao, Zi-Ai; Chang, Ming-Tao; Li, Yang; Yu, Jian; Zhang, Ye; Zhang, Lian-Yang

    2015-02-01

    Intra-abdominal hypertension (IAH) is accompanied by high morbidity and mortality in surgical departments and ICUs. However, its specific pathophysiology is unclear. IAH not only leads to intra-abdominal tissue damage but also causes dysfunction in distal organs, such as the brain. In this study, we explore the protective effects of melanocortin 4 receptor agonists in IAH-induced brain injury. The IAH rat models were induced by hemorrhagic shock/resuscitation (with the mean arterial pressure (MAP) maintained at 30 mm Hg for 90 min followed by the reinfusion of the withdrawn blood with lactated Ringer's solution). Then, air was injected into the peritoneal cavity of the rats to maintain an intra-abdominal pressure of 20 mm Hg for 4 h. The effects of the melanocortin 4 receptor agonist RO27-3225 in alleviating the rats' IAH brain injuries were observed, which indicated that RO27-3225 could reduce brain edema, the expressions of the IL-1β and TNF-α inflammatory cytokines, the blood-brain barrier's permeability and the aquaporin4 (AQP4) and matrix metalloproteinase 9 (MMP9) levels. Moreover, the nicotinic acetylcholine receptor antagonist chlorisondamine and the selective melanocortin 4 receptor antagonist HS024 can negate the protective effects of the RO27-3225. The MC4R agonist can effectively reduce the intracerebral proinflammatory cytokine gene expression and alleviate the brain injury caused by blood-brain barrier damage following IAH. PMID:25616531

  16. Melanocortin Receptor Agonists Facilitate Oxytocin-Dependent Partner Preference Formation in the Prairie Vole.

    PubMed

    Modi, Meera E; Inoue, Kiyoshi; Barrett, Catherine E; Kittelberger, Kara A; Smith, Daniel G; Landgraf, Rainer; Young, Larry J

    2015-07-01

    The central melanocortin (MC) system has been widely studied for its effects on food intake and sexual behavior. However, the MC system, and more specifically the MC4 receptor (MC4R), also interacts with neurochemical systems that regulate socioemotional behaviors, including oxytocin (OT) and dopamine. In monogamous prairie voles, OT and dopamine interact to promote partner preference formation, a laboratory measure of an enduring social bond between mates. Here we investigated the effects of MC receptor activation on partner preference formation in prairie voles, as well as the interaction between the MC and OT systems during this process. Peripheral administration of the brain penetrant MC3/4R receptor peptide agonist, Melanotan II (MTII), and the highly selective, small-molecule MC4R agonist, Pf-446687, enhanced partner preference formation in the prairie vole, but not in the non-monogamous meadow vole. MTII-induced partner preferences were enduring, as they were present 1 week after drug manipulation. The prosocial effects of MCR agonists may be mediated, in part, through modulation of OT, as coadministration of an OT receptor antagonist prevented MTII-induced partner preferences. MTII also selectively activated hypothalamic OT neurons and potentiated central OT release. As OT has been shown to enhance some aspects of social cognition in humans, our data suggest that the MC4R may be a viable therapeutic target for enhancing social function in psychiatric disorders, including autism spectrum disorders and schizophrenia, potentially through activation of the OT system. PMID:25652247

  17. Antitussive activity of sigma-1 receptor agonists in the guinea-pig

    PubMed Central

    Brown, Claire; Fezoui, Malika; Selig, William M; Schwartz, Carl E; Ellis, James L

    2003-01-01

    Current antitussive medications have limited efficacy and often contain the opiate-like agent dextromethorphan (DEX). The mechanism whereby DEX inhibits cough is ill defined. DEX displays affinity at both NMDA and sigma receptors, suggesting that the antitussive activity may involve central or peripheral activity at either of these receptors. This study examined and compared the antitussive activity of DEX and various putative sigma receptor agonists in the guinea-pig citric-acid cough model. Intraperitoneal (i.p.) administration of DEX (30 mg kg−1) and the sigma-1 agonists SKF-10,047 (1–5 mg kg−1), Pre-084 (5 mg kg−1), and carbetapentane (1–5 mg kg−1) inhibited citric-acid-induced cough in guinea-pigs. Intraperitoneal administration of a sigma-1 antagonist, BD 1047 (1–5 mg kg−1), reversed the inhibition of cough elicited by SKF-10,047. In addition, two structurally dissimilar sigma agonists SKF-10,047 (1 mg ml−1) and Pre-084 (1 mg ml−1) inhibited cough when administered by aerosol. Aerosolized BD 1047 (1 mg ml−1, 30 min) prevented the antitussive action of SKF-10,047 (5 mg kg−1) or DEX (30 mg kg−1) given by i.p. administration and, likewise, i.p. administration of BD 1047 (5 mg kg−1) prevented the antitussive action of SKF-10,047 given by aerosol (1 mg ml−1). These results therefore support the argument that antitussive effects of DEX may be mediated via sigma receptors, since both systemic and aerosol administration of sigma-1 receptor agonists inhibit citric-acid-induced cough in guinea-pigs. While significant systemic exposure is possible with aerosol administration, the very low doses administered (estimated <0.3 mg kg−1) suggest that there may be a peripheral component to the antitussive effect. PMID:14691051

  18. Therapeutic Potential of 5-HT2C Receptor Agonists for Addictive Disorders.

    PubMed

    Higgins, Guy A; Fletcher, Paul J

    2015-07-15

    The neurotransmitter 5-hydroxytryptamine (5-HT; serotonin) has long been associated with the control of a variety of motivated behaviors, including feeding. Much of the evidence linking 5-HT and feeding behavior was obtained from studies of the effects of the 5-HT releaser (dex)fenfluramine in laboratory animals and humans. Recently, the selective 5-HT2C receptor agonist lorcaserin received FDA approval for the treatment of obesity. This review examines evidence to support the use of selective 5-HT2C receptor agonists as treatments for conditions beyond obesity, including substance abuse (particularly nicotine, psychostimulant, and alcohol dependence), obsessive compulsive, and excessive gambling disorder. Following a brief survey of the early literature supporting a role for 5-HT in modulating food and drug reinforcement, we propose that intrinsic differences between SSRI and serotonin releasers may have underestimated the value of serotonin-based pharmacotherapeutics to treat clinical forms of addictive behavior beyond obesity. We then highlight the critical involvement of the 5-HT2C receptor in mediating the effect of (dex)fenfluramine on feeding and body weight gain and the evidence that 5-HT2C receptor agonists reduce measures of drug reward and impulsivity. A recent report of lorcaserin efficacy in a smoking cessation trial further strengthens the idea that 5-HT2C receptor agonists may have potential as a treatment for addiction. This review was prepared as a contribution to the proceedings of the 11th International Society for Serotonin Research Meeting held in Hermanus, South Africa, July 9-12, 2014. PMID:25870913

  19. Distinct Signaling Cascades Elicited by Different Formyl Peptide Receptor 2 (FPR2) Agonists

    PubMed Central

    Cattaneo, Fabio; Parisi, Melania; Ammendola, Rosario

    2013-01-01

    The formyl peptide receptor 2 (FPR2) is a remarkably versatile transmembrane protein belonging to the G-protein coupled receptor (GPCR) family. FPR2 is activated by an array of ligands, which include structurally unrelated lipids and peptide/proteins agonists, resulting in different intracellular responses in a ligand-specific fashion. In addition to the anti-inflammatory lipid, lipoxin A4, several other endogenous agonists also bind FPR2, including serum amyloid A, glucocorticoid-induced annexin 1, urokinase and its receptor, suggesting that the activation of FPR2 may result in potent pro- or anti-inflammatory responses. Other endogenous ligands, also present in biological samples, include resolvins, amyloidogenic proteins, such as beta amyloid (Aβ)-42 and prion protein (Prp)106–126, the neuroprotective peptide, humanin, antibacterial peptides, annexin 1-derived peptides, chemokine variants, the neuropeptides, vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating polypeptide (PACAP)-27, and mitochondrial peptides. Upon activation, intracellular domains of FPR2 mediate signaling to G-proteins, which trigger several agonist-dependent signal transduction pathways, including activation of phospholipase C (PLC), protein kinase C (PKC) isoforms, the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway, the mitogen-activated protein kinase (MAPK) pathway, p38MAPK, as well as the phosphorylation of cytosolic tyrosine kinases, tyrosine kinase receptor transactivation, phosphorylation and nuclear translocation of regulatory transcriptional factors, release of calcium and production of oxidants. FPR2 is an attractive therapeutic target, because of its involvement in a range of normal physiological processes and pathological diseases. Here, we review and discuss the most significant findings on the intracellular pathways and on the cross-communication between FPR2 and tyrosine kinase receptors triggered by different FPR2 agonists. PMID

  20. Functional potencies of dopamine agonists and antagonists at human dopamine D₂ and D₃ receptors.

    PubMed

    Tadori, Yoshihiro; Forbes, Robert A; McQuade, Robert D; Kikuchi, Tetsuro

    2011-09-01

    We measured the functional agonist potencies of dopamine agonists including antiparkinson drugs, and functional antagonist potencies of antipsychotics at human dopamine D(2) and D(3) receptors. In vitro pharmacological assessment included inhibition of forskolin-stimulated cAMP accumulation and the reversal of dopamine-induced inhibition in clonal Chinese hamster ovary cells expressing low and high densities of human dopamine D(2L) and D(2S) receptors (hD(2L)-Low, hD(2L)-High, hD(2S)-Low and hD(2S)-High, respectively) and human dopamine D(3) Ser-9 and D(3) Gly-9 receptors (hD(3)-Ser-9 and hD(3)-Gly-9, respectively). Cabergoline, bromocriptine, pergolide, (±)-7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT), talipexole, pramipexole, R-(+)-trans-3,4,4a,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano[4,3-b]-1,4-oxazin-9-olhydrochloride (PD128907) and ropinirole behaved as dopamine D(2) and D(3) receptor full agonists and showed higher potencies in hD(2L)-High and hD(2S)-High compared to hD(2L)-Low and hD(2S)-Low. In hD(3)-Ser-9 and hD(3)-Gly-9 compared to hD(2L)-Low and hD(2S)-Low, dopamine, ropinirole, PD128907, and pramipexole potencies were clearly higher; talipexole and 7-OH-DPAT showed slightly higher potencies; pergolide showed slightly lower potency; and, cabergoline and bromocriptine potencies were lower. Aripiprazole acted as an antagonist in hD(2L)-Low; a low intrinsic activity partial agonist in hD(2S)-Low; a moderate partial agonist in hD(3)-Ser-9 and hD(3)-Gly-9; a robust partial agonist in hD(2L)-High; and a full agonist in hD(2S)-High. Amisulpride, sulpiride and perphenazine behaved as preferential antagonists; and chlorpromazine and asenapine behaved as modest preferential antagonists; whereas fluphenazine, haloperidol, and blonanserin behaved as non-preferential antagonists in hD(2S)-Low and hD(2S)-High compared to hD(3)-Ser-9 and hD(3)-Gly-9. These findings may help to elucidate the basis of therapeutic benefit observed with these drugs, with

  1. Metabotropic glutamate receptor agonists modify the pyloric output of the crustacean stomatogastric ganglion.

    PubMed

    Pérez-Acevedo, Nivia L; Krenz, Wulf D

    2005-11-16

    We have studied the effects of groups I, II, and III metabotropic glutamate receptor (mGluR) agonists and antagonists on pyloric activity in the stomatogastric ganglion (STG) of the Caribbean spiny lobster Panulirus argus. We have found that agonists for all three groups of mGluRs modify the pyloric output. The group I agonist, l-quisqualic acid (l-QA), activated the pyloric central pattern generator (CPG). When the pyloric rhythm was partially suppressed by sucrose-block of input fibers in the stomatogastric nerve (stn), l-QA accelerated the rhythmic activity. In addition, the number of spike discharges was increased in pyloric motoneurons: pyloric (PY), and lateral pyloric (LP). In completely blocked preparations, a slow pyloric rhythm was initiated by l-QA. Groups II and III agonists exerted an inhibitory effect on pyloric activity. The group II agonist, (2S,1'S,2'S)-2-(Carboxycyclopropyl)glycine (L-CCG-I), decreased both the frequency of the pyloric rhythm and the number of spike discharges in the motoneurons: ventricular dilator (VD), PY, and LP. The effects of L-CCG-I were dose-dependent. The group III agonist, l-(+)-2-Amino-4-phosphonobutyric acid (l-AP4), slightly decreased the frequency of the pyloric rhythm and suppressed spike discharges in the VD neuron. All effects of mGluR agonists were reversible. The effect of l-QA was blocked by the broad spectrum mGluR antagonist (S)-Methyl-4-carboxyphenylglycine (MCPG). The inhibitory effect of L-CCG-I was prevented by MCPG and by the group II/III mGluR antagonist (RS)-alpha-Methyl-4-phosphonophenylglycine (MPPG), and was partially blocked by the group II mGluR antagonist (RS)-1-amino-5-phosphonoindan-1-carboxylic acid (APICA). The inhibitory effect of l-AP4 was blocked by MPPG and partially blocked by APICA. PMID:16256086

  2. Detection of glucocorticoid receptor agonists in effluents from sewage treatment plants in Japan.

    PubMed

    Suzuki, Go; Sato, Kentaro; Isobe, Tomohiko; Takigami, Hidetaka; Brouwer, Abraham; Nakayama, Kei

    2015-09-15

    Glucocorticoids (GCs) are widely used as anti-inflammatory drugs. Our previous study demonstrated that several GCs such as cortisol and dexamethasone (Dex) were frequently detected in effluents collected from Japanese sewage treatment plants (STPs) in 2012. In this study, we used the GC-Responsive Chemical-Activated LUciferase gene eXpression (GR-CALUX) assay to elucidate GC receptor (GR) agonistic activities of ten pure synthetic GCs and selected STP effluents in Japan for assessment of the risks associated with the presence of GR agonists. The tested GCs demonstrated dose-dependent agonistic effects in the GR-CALUX assay and their EC50 values were calculated for estimation of relative potencies (REPs) compared to Dex. The GR agonistic potency was in the rank of: clobetasol propionate > clobetasone butyrate > betamethasone 17-valerate > difluprednate > betamethasone 17,21-dipropionate > Dex > betamethasone > 6α-methylprednisolone > prednisolone > cortisol. The GR agonistic activity in STP effluents as measured in Dex-equivalent (Dex-EQ) activities ranged from < 3.0-78 ng L(-1) (median: 29 ng L(-1), n = 50). To evaluate the contribution of the target GCs, theoretical Dex-EQs were calculated by multiplying the concentrations of each GC by its respective REP. Our calculation of Dex-EQ contribution for individual GR agonists indicated that the well-known GCs cortisol and Dex should not be given priority for subsequent in vivo testing, monitoring and removal experiments, but rather the highly potent synthetic GCs clobetasol propionate and betamethasone 17-valerate (REP = 28 and 3.1) as well as other unidentified compounds are important GR agonists in STP effluents in Japan. PMID:25965047

  3. Dissociated nonsteroidal glucocorticoid receptor modulators; discovery of the agonist trigger in a tetrahydronaphthalene-benzoxazine series.

    PubMed

    Barker, Mike; Clackers, Margaret; Copley, Royston; Demaine, Derek A; Humphreys, Davina; Inglis, Graham G A; Johnston, Michael J; Jones, Haydn T; Haase, Michael V; House, David; Loiseau, Richard; Nisbet, Lesley; Pacquet, Francois; Skone, Philip A; Shanahan, Stephen E; Tape, Dan; Vinader, Victoria M; Washington, Melanie; Uings, Iain; Upton, Richard; McLay, Iain M; Macdonald, Simon J F

    2006-07-13

    The tetrahydronaphthalene-benzoxazine glucocorticoid receptor (GR) partial agonist 4b was optimized to produce potent full agonists of GR. Aromatic ring substitution of the tetrahydronaphthalene leads to weak GR antagonists. Discovery of an "agonist trigger" substituent on the saturated ring of the tetrahydronaphthalene leads to increased potency and efficacious GR agonism. These compounds are efficacy selective in an NFkB GR agonist assay (representing transrepression effects) over an MMTV GR agonist assay (representing transactivation effects). 52 and 60 have NFkB pIC(50) = 8.92 (105%) and 8.69 (92%) and MMTV pEC(50) = 8.20 (47%) and 7.75 (39%), respectively. The impact of the trigger substituent on agonism is modeled within GR and discussed. 36, 52, and 60 have anti-inflammatory activity in a mouse model of inflammation after topical dosing with 52 and 60, having an effect similar to that of dexamethasone. The original lead was discovered by a manual agreement docking method, and automation of this method is also described. PMID:16821781

  4. Modulation Effect of Peroxisome Proliferator-Activated Receptor Agonists on Lipid Droplet Proteins in Liver.

    PubMed

    Zhu, Yun-Xia; Zhang, Ming-Liang; Zhong, Yuan; Wang, Chen; Jia, Wei-Ping

    2016-01-01

    Peroxisome proliferator-activated receptor (PPAR) agonists are used for treating hyperglycemia and type 2 diabetes. However, the mechanism of action of these agonists is still under investigation. The lipid droplet-associated proteins FSP27/CIDEC and LSDP5, regulated directly by PPARγ and PPARα, are associated with hepatic steatosis and insulin sensitivity. Here, we evaluated the expression levels of FSP27/CIDEC and LSDP5 and the regulation of these proteins by consumption of a high-fat diet (HFD) or administration of PPAR agonists. Mice with diet-induced obesity were treated with the PPARγ or PPARα agonist, pioglitazone or fenofibrate, respectively. Liver tissues from db/db diabetic mice and human were also collected. Interestingly, FSP27/CIEDC was expressed in mouse and human livers and was upregulated in obese C57BL/6J mice. Fenofibrate treatment decreased hepatic triglyceride (TG) content and FSP27/CIDEC protein expression in mice fed an HFD diet. In mice, LSDP5 was not detected, even in the context of insulin resistance or treatment with PPAR agonists. However, LSDP5 was highly expressed in humans, with elevated expression observed in the fatty liver. We concluded that fenofibrate greatly decreased hepatic TG content and FSP27/CIDEC protein expression in mice fed an HFD, suggesting a potential regulatory role for fenofibrate in the amelioration of hepatic steatosis. PMID:26770990

  5. Natural product agonists of peroxisome proliferator-activated receptor gamma (PPARγ): a review

    PubMed Central

    Wang, Limei; Waltenberger, Birgit; Pferschy-Wenzig, Eva-Maria; Blunder, Martina; Liu, Xin; Malainer, Clemens; Blazevic, Tina; Schwaiger, Stefan; Rollinger, Judith M.; Heiss, Elke H.; Schuster, Daniela; Kopp, Brigitte; Bauer, Rudolf; Stuppner, Hermann; Dirsch, Verena M.; Atanasov, Atanas G.

    2014-01-01

    Agonists of the nuclear receptor PPARγ are therapeutically used to combat hyperglycaemia associated with the metabolic syndrome and type 2 diabetes. In spite of being effective in normalization of blood glucose levels, the currently used PPARγ agonists from the thiazolidinedione type have serious side effects, making the discovery of novel ligands highly relevant. Natural products have proven historically to be a promising pool of structures for drug discovery, and a significant research effort has recently been undertaken to explore the PPARγ-activating potential of a wide range of natural products originating from traditionally used medicinal plants or dietary sources. The majority of identified compounds are selective PPARγ modulators (SPPARMs), transactivating the expression of PPARγ-dependent reporter genes as partial agonists. Those natural PPARγ ligands have different binding modes to the receptor in comparison to the full thiazolidinedione agonists, and on some occasions activate in addition PPARα (e.g. genistein, biochanin A, sargaquinoic acid, sargahydroquinoic acid, resveratrol, amorphastilbol) or the PPARγ-dimer partner retinoid X receptor (RXR; e.g. the neolignans magnolol and honokiol). A number of in vivo studies suggest that some of the natural product activators of PPARγ (e.g. honokiol, amorfrutin 1, amorfrutin B, amorphastilbol) improve metabolic parameters in diabetic animal models, partly with reduced side effects in comparison to full thiazolidinedione agonists. The bioactivity pattern as well as the dietary use of several of the identified active compounds and plant extracts warrants future research regarding their therapeutic potential and the possibility to modulate PPARγ activation by dietary interventions or food supplements. PMID:25083916

  6. Computational Study and Modified Design of Selective Dopamine D3 Receptor Agonists.

    PubMed

    Duan, Xinli; Zhang, Xin; Xu, Binglin; Wang, Fang; Lei, Ming

    2016-07-01

    Dopamine D3 receptor (D3 R) is considered as a potential target for the treatment of nervous system disorders, such as Parkinson's disease. Current research interests primarily focus on the discovery and design of potent D3 agonists. In this work, we selected 40 D3 R agonists as the research system. Comparative molecular field analysis (CoMFA) of three-dimensional quantitative structure-activity relationship (3D-QSAR), structure-selectivity relationship (3D-QSSR), and molecular docking was performed on D3 receptor agonists to obtain the details at atomic level. The results indicated that both the CoMFA model (r(2) = 0.982, q(2) = 0.503, rpred2 = 0.893, SEE  = 0.057, F = 166.308) for structure-activity and (r(2) = 0.876, q(2) = 0.436, rpred2 = 0.828, F = 52.645) for structure-selectivity have good predictive capabilities. Furthermore, docking studies on three compounds binding to D3 receptor were performed to analyze the binding modes and interactions. The results elucidate that agonists formed hydrogen bond and hydrophobic interactions with key residues. Finally, we designed six molecules under the guidance of 3D-QSAR/QSSR models. The activity and selectivity of designed molecules have been improved, and ADMET properties demonstrate they have low probability of hepatotoxicity (<0.5). These results from 3D-QSAR/QSSR and docking studies have great significance for designing novel dopamine D3 selective agonists in the future. PMID:26851125

  7. Peroxisome proliferator-activated receptor-delta agonist ameliorated inflammasome activation in nonalcoholic fatty liver disease

    PubMed Central

    Lee, Hyun Jung; Yeon, Jong Eun; Ko, Eun Jung; Yoon, Eileen L; Suh, Sang Jun; Kang, Keunhee; Kim, Hae Rim; Kang, Seoung Hee; Yoo, Yang Jae; Je, Jihye; Lee, Beom Jae; Kim, Ji Hoon; Seo, Yeon Seok; Yim, Hyung Joon; Byun, Kwan Soo

    2015-01-01

    AIM: To evaluate the inflammasome activation and the effect of peroxisome proliferator-activated receptors (PPAR)-δ agonist treatment in nonalcoholic fatty liver disease (NAFLD) models. METHODS: Male C57BL/6J mice were classified according to control or high fat diet (HFD) with or without PPAR-δ agonist (GW) over period of 12 wk [control, HFD, HFD + lipopolysaccharide (LPS), HFD + LPS + GW group]. HepG2 cells were exposed to palmitic acid (PA) and/or LPS in the absence or presence of GW. RESULTS: HFD caused glucose intolerance and hepatic steatosis. In mice fed an HFD with LPS, caspase-1 and interleukin (IL)-1β in the liver were significantly increased. Treatment with GW ameliorated the steatosis and inhibited overexpression of pro-inflammatory cytokines. In HepG2 cells, PA and LPS treatment markedly increased mRNA of several nucleotide-binding and oligomerization domain-like receptor family members (NLRP3, NLRP6, and NLRP10), caspase-1 and IL-1β. PA and LPS also exaggerated reactive oxygen species production. All of the above effects of PA and LPS were reduced by GW. GW also enhanced the phosphorylation of AMPK-α. CONCLUSION: PPAR-δ agonist reduces fatty acid-induced inflammation and steatosis by suppressing inflammasome activation. Targeting the inflammasome by the PPAR-δ agonist may have therapeutic implication for NAFLD. PMID:26668503

  8. D-amino acid oxidase generates agonists of the aryl hydrocarbon receptor from D-tryptophan.

    PubMed

    Nguyen, Linh P; Hsu, Erin L; Chowdhury, Goutam; Dostalek, Miroslav; Guengerich, F Peter; Bradfield, Christopher A

    2009-12-01

    The aryl hydrocarbon receptor (AHR) is well-known for its role in mediating the toxic and adaptive responses to xenobiotic compounds. Recent studies also indicate that AHR ligands are endogenously produced and may be essential for normal development. Previously, we showed that the endogenous enzyme, aspartate aminotransferase (AST), generates the AHR proagonist, indole-3-pyruvic acid (I3P), by deamination of its substrate L-tryptophan. We hypothesized that other enzymatic pathways capable of producing I3P may generate AHR agonists in vivo. We now demonstrate that the enzyme d-amino acid oxidase (DAAO) catalyzes the production of AHR agonists through the enzymatic conversion of D-tryptophan to I3P. Moreover, we provide evidence that the nonenzymatic oxidation and condensation of I3P is a critical step in the generation of receptor agonists by DAAO and AST. Products of this process include two novel agonists, 1,3-di(1H-indol-3-yl)propan-2-one and 1-(1H-indol-3-yl)-3-(3H-indol-3-ylidene) propan-2-one [characterized in the accompanying paper, Chowdhury et al. ( 2009 ) Chem. Res. Toxicol. , DOI: 10.1021/tx9000418 ], both of which can potently activate the AHR at concentrations in the nanomolar range. These results show that endogenous AHR activity can be modulated by I3P production from amino acid precursors through multiple enzymatic pathways, including those catalyzed by DAAO and AST. PMID:19860415

  9. Preclinical evaluation of SMM-189, a cannabinoid receptor 2-specific inverse agonist

    PubMed Central

    Presley, Chaela; Abidi, Ammaar; Suryawanshi, Satyendra; Mustafa, Suni; Meibohm, Bernd; Moore, Bob M

    2015-01-01

    Cannabinoid receptor 2 agonists and inverse agonists are emerging as new therapeutic options for a spectrum of autoimmune-related disease. Of particular interest, is the ability of CB2 ligands to regulate microglia function in neurodegenerative diseases and traumatic brain injury. We have previously reported the receptor affinity of 3′,5′-dichloro-2,6-dihydroxy-biphenyl-4-yl)-phenyl-methanone (SMM-189) and the characterization of the beneficial effects of SMM-189 in the mouse model of mild traumatic brain injury. Herein, we report the further characterization of SMM-189 as a potent and selective CB2 inverse agonist, which acts as a noncompetitive inhibitor of CP 55,940. The ability of SMM-189 to regulate microglial activation, in terms of chemokine expression and cell morphology, has been determined. Finally, we have determined that SMM-189 possesses acceptable biopharmaceutical properties indicating that the triaryl class of CB2 inverse agonists are viable compounds for continued preclinical development for the treatment of neurodegenerative disorders and traumatic brain injury. PMID:26196013

  10. Role of ω-hydroxylase in adenosine-mediated aortic response through MAP kinase using A2A-receptor knockout mice.

    PubMed

    Ponnoth, Dovenia S; Nayeem, Mohammed A; Kunduri, Swati S; Tilley, Stephen L; Zeldin, Darryl C; Ledent, Catherine; Mustafa, S Jamal

    2012-02-15

    Previously, we have shown that A(2A) adenosine receptor (A(2A)AR) knockout mice (KO) have increased contraction to adenosine. The signaling mechanism(s) for A(2A)AR is still not fully understood. In this study, we hypothesize that, in the absence of A(2A)AR, ω-hydroxylase (Cyp4a) induces vasoconstriction through mitogen-activated protein kinase (MAPK) via upregulation of adenosine A(1) receptor (A(1)AR) and protein kinase C (PKC). Organ bath and Western blot experiments were done using isolated aorta from A(2A)KO and corresponding wild-type (WT) mice. Isolated aortic rings from WT and A(2A)KO mice were precontracted with submaximal dose of phenylephrine (10(-6) M), and concentration responses for selective A(1)AR, A(2A)AR agonists, angiotensin II and cytochrome P-450-epoxygenase, 20-hydroxyeicosatrienoic acid (20-HETE) PKC, PKC-α, and ERK1/2 inhibitors were obtained. 2-p-(2-Carboxyethyl)-phenethylamino-5'-N-ethylcarboxamidoadenosine hydrochloride (CGS-21680, A(2A)AR agonist) induced concentration-dependent relaxation in WT, which was blocked by methylsulfonyl-propargyloxyphenylhexanamide (cytochrome P-450-epoxygenase inhibitor; 10(-5) M) and also with removal of endothelium. A(1) agonist, 2-chloro-N(6)-cyclopentyladenosine (CCPA) produced higher contraction in A(2A)KO aorta than WT (49.2 ± 8.5 vs. 27 ± 5.9% at 10(-6) M, P < 0.05). 20-HETE produced higher contraction in A(2A)KO than WT (50.6 ± 8.8 vs. 21.1 ± 3.3% at 10(-7) M, P < 0.05). Contraction to CCPA in WT and A(2A)KO aorta was inhibited by PD-98059 (p42/p44 MAPK inhibitor; 10(-6) M), chelerythrine chloride (nonselective PKC blocker; 10(-6) M), Gö-6976 (selective PKC-α inhibitor; 10(-7) M), and HET0016 (20-HETE inhibitor; 10(-5) M). Also, contraction to 20-HETE in WT and A(2A)KO aorta was inhibited by PD-98059 and Gö-6976. Western blot analysis indicated the upregulation of A(1)AR, Cyp4a, PKC-α, and phosphorylated-ERK1/2 in A(2A)KO compared with WT (P < 0.05), while expression of Cyp2c29 was

  11. Thyroid receptor agonists for the treatment of androgenetic alopecia.

    PubMed

    Li, Jie Jack; Mitchell, Lorna H; Dow, Robert L

    2010-01-01

    A thyroid hormone receptor beta subtype-selective thyromimetic 5 was found to be efficacious in both mouse and monkey hair growth models after topical applications. It penetrates the skin according to the test in human cadaver skin mounted onto Franz diffusion chambers. The serum drug level of 5 is below the limit of quantification during tests in the bald stump-tailed macaques (Macaca arctoides). It is tested negative in the 3T3 neutral red uptake (NRU) phototoxicity test, indicating a low risk for causing photo-irritation. It is also rapidly metabolized according to the PK data, thus the systemic exposure is limited. PMID:19900809

  12. Selexipag: a selective prostacyclin receptor agonist that does not affect rat gastric function.

    PubMed

    Morrison, Keith; Ernst, Roland; Hess, Patrick; Studer, Rolf; Clozel, Martine

    2010-10-01

    Selexipag [2-{4-[(5,6-diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}-N-(methylsulfonyl)acetamide] is an orally available prostacyclin (PGI(2)) receptor (IP receptor) agonist that is chemically distinct from PGI(2) and is in clinical development for the treatment of pulmonary arterial hypertension. Selexipag is highly selective for the human IP receptor in vitro, whereas analogs of PGI(2) can activate prostanoid receptors other than the IP receptor. The goal of this study was to determine the impact of selectivity for the IP receptor on gastric function by measuring 1) contraction of rat gastric fundus ex vivo and 2) the rates of gastric emptying and intestinal transport in response to selexipag in comparison with other PGI(2) analogs. The rat gastric fundus expresses mRNA encoding multiple prostanoid receptors to different levels: prostaglandin E receptor 1 (EP(1)) > prostaglandin E receptor 3 (EP(3)), IP receptor > prostaglandin D(2) receptor 1, thromboxane receptor. Selexipag and metabolite {4-[(5,6-diphenylpyrazin-2-yl)(isopropyl)amino]butoxy}acetic acid (ACT-333679) did not contract gastric fundus at concentrations up to 10(-3) M. In contrast, the PGI(2) analogs iloprost and beraprost evoked concentration-dependent contraction of gastric fundus. Contraction to treprostinil was observed at high concentration (10(-4) M). Contraction to all PGI(2) analogs was mediated via activation of EP(3) receptors, although EP(1) receptors also contributed to the contraction of gastric fundus to iloprost and beraprost. Antagonism of IP receptors did not affect responses. Oral selexipag did not significantly alter gastric function in vivo, as measured by rates of stomach emptying and intestinal transport, whereas beraprost slowed gastrointestinal transport. The high functional selectivity of selexipag and ACT-333679 for the IP receptor precludes a stimulatory action on gastric smooth muscle and may help minimize gastric side effects such as nausea and vomiting. PMID:20660124

  13. Neuronal Ablation of p-Akt at Ser473 Leads to Altered 5-HT1A/2A Receptor Function

    PubMed Central

    Saunders, Christine; Siuta, Michael; Robertson, Sabrina D.; Davis, Adeola R.; Sauer, Jennifer; Matthies, Heinrich J.G.; Gresch, Paul J.; Airey, David; Lindsley, Craig W.; Schetz, John A.; Niswender, Kevin D.

    2014-01-01

    The serotonergic system regulates a wide range of behavior, including mood and impulsivity, and its dysregulation has been associated with mood disorders, autism spectrum disorder, and addiction. Diabetes is a risk factor for these conditions. Insulin resistance in the brain is specifically associated with susceptibility to psychostimulant abuse. Here, we examined whether phosphorylation of Akt, a key regulator of the insulin signaling pathway, controls serotonin (5-HT) signaling. To explore how impairment in Akt function regulates 5-HT homeostasis, we used a brain-specific rictor knockout (KO) mouse model of impaired neuronal phosphorylation of Akt at Ser473. Cortical 5-HT1A and 5-HT2A receptor binding was significantly elevated in rictor KO mice. Concomitant with this elevated receptor expression, the 5-HT1A receptor agonist 8-Hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) led to an increased hypothermic response in rictor KO mice. The increased cortical 5-HT1A receptor density was associated with higher 5-HT1A receptor levels on the cortical cell surface. In contrast, rictor KO mice displayed significantly reduced head-twitch response (HTR) to the 5-HT2A/C agonist 2,5-dimethoxy-4-iodoamphetamine (DOI), with evidence of impaired 5-HT2A/C receptor signaling. In vitro, pharmacological inhibition of Akt significantly increased 5-HT1A receptor expression and attenuated DOI-induced 5-HT2A receptor signaling, thereby lending credence to the observed in vivo cross-talk between neuronal Akt signaling and 5-HT receptor regulation. These data reveal that defective central Akt function alters 5-HT signaling as well as 5-HT-associated behaviors, demonstrating a novel role for Akt in maintaining neuronal 5-HT receptor function. PMID:24090638

  14. Self-administration of agonists selective for dopamine D2, D3, and D4 receptors by rhesus monkeys.

    PubMed

    Koffarnus, Mikhail N; Collins, Gregory T; Rice, Kenner C; Chen, Jianyong; Woods, James H; Winger, Gail

    2012-08-01

    Dopamine receptor mechanisms are believed to play a role in the reinforcing effects of cocaine and other drugs of abuse. The lack of receptor-selective agonists has made it difficult to determine the role of the individual dopamine receptors in mediating these reinforcing effects. In this study, rhesus monkeys with a history of intravenous cocaine self-administration were tested for the reinforcing effects of several D(3)-preferring agonists, a D(2)-preferring agonist, and a D(4) agonist. The D(2)-preferring agonist did not maintain responding in any monkeys, and the D(4) agonist was self-administered at low rates, just above those maintained by saline, in one monkey. The D(3)-preferring agonists were self-administered by approximately half of the animals, although at lower rates than cocaine. These results indicate that the apparent limited reinforcing effectiveness of D(2)-like agonists requires activity at D(3) receptors. Previous data from this laboratory and others also suggest that these drugs may not serve as reinforcers directly; the behavior may be maintained by response-contingent delivery of stimuli previously paired with cocaine. The ability of drug-related stimuli to maintain responding apparently differs among monkeys and other organisms, and may be related to individual differences in drug-taking behavior in humans. PMID:22785383

  15. Discovery of selective hexapeptide agonists to human neuromedin U receptors types 1 and 2.

    PubMed

    Takayama, Kentaro; Mori, Kenji; Taketa, Koji; Taguchi, Akihiro; Yakushiji, Fumika; Minamino, Naoto; Miyazato, Mikiya; Kangawa, Kenji; Hayashi, Yoshio

    2014-08-14

    Neuromedin U (NMU) are bioactive peptides with a common C-terminal heptapeptide sequence (FLFRPRN-amide, 1a) among mammals, which is responsible for receptor activation, namely NMU receptor types 1 (NMUR1) and 2 (NMUR2). Among the various physiological actions of NMU, the anorexigenic effect has recently attracted attention in drug discovery efforts for treating obesity. Although several structure-activity relationship (SAR) studies have been reported, receptor-selective small peptide agonists have yet to be disclosed. Herein a SAR study of 1a-derived peptide derivatives is described. We initially screened both human NMUR1- and NMUR2-selective peptides in calcium-mobilization assays with cells transiently expressing receptors. Then we performed a precise assay with a stable expression system of receptors and consequently discovered hexapeptides 8d and 6b possessing selective agonist activity toward each respective receptor. Hexapeptide 6b, which selectively activates NMUR2 without significant NMUR1 activation, should aid in the development of anorexigenic drugs as well as advance NMU-related endocrinological research. PMID:24999562

  16. Novel sigma (σ) receptor agonists produce antidepressant-like effects in mice

    PubMed Central

    Wang, Jiajia; Mack, Aisha L.; Coop, Andrew; Matsumoto, Rae R.

    2014-01-01

    Many antidepressant drugs interact with σ receptors and accumulating evidence suggests that these proteins mediate antidepressant-like effects in animals and humans. σ Receptors are localized in brain regions affected in depression, further strengthening the hypothesis that they represent logical drug development targets. In this study, two novel σ receptor agonists (UMB23, UMB82) were evaluated for antidepressant-like activity in mice. First, radioligand binding studies confirmed that the novel compounds had preferential affinity for σ receptors. Second, the forced swim test, a well established animal model for screening potential antidepressant drugs, showed that both compounds dose-dependently reduced immobility time. The σ receptor antagonist BD1047 attenuated the antidepressant-like effects of UMB23 and UMB82. Third, locomotor activity suggested that the effects of UMB23 and UMB82 in the forced swim test were not due to non-specific motor activating effects. Together, the data provide further evidence that σ receptor agonists represent a possible new class of antidepressant medication. PMID:17376658

  17. A Three-Site Mechanism for Agonist/Antagonist Selective Binding to Vasopressin Receptors.

    PubMed

    Saleh, Noureldin; Saladino, Giorgio; Gervasio, Francesco L; Haensele, Elke; Banting, Lee; Whitley, David C; Sopkova-de Oliveira Santos, Jana; Bureau, Ronan; Clark, Timothy

    2016-07-01

    Molecular-dynamics simulations with metadynamics enhanced sampling reveal three distinct binding sites for arginine vasopressin (AVP) within its V2 -receptor (V2 R). Two of these, the vestibule and intermediate sites, block (antagonize) the receptor, and the third is the orthosteric activation (agonist) site. The contacts found for the orthosteric site satisfy all the requirements deduced from mutagenesis experiments. Metadynamics simulations for V2 R and its V1a R-analog give an excellent correlation with experimental binding free energies by assuming that the most stable binding site in the simulations corresponds to the experimental binding free energy in each case. The resulting three-site mechanism separates agonists from antagonists and explains subtype selectivity. PMID:27184628

  18. Alpha-2 receptor agonists for the treatment of posttraumatic stress disorder

    PubMed Central

    Belkin, Molly R; Schwartz, Thomas L

    2015-01-01

    Clonidine and guanfacine are alpha-2 receptor agonists that decrease sympathetic outflow from the central nervous system. Posttraumatic stress disorder (PTSD) is an anxiety disorder that is theorized to be related to a hyperactive sympathetic nervous system. Currently, the only US Food and Drug Administration (FDA)-approved medications for PTSD are the selective serotonin reuptake inhibitors (SSRIs) sertraline and paroxetine. Sometimes use of the SSRIs may not lead to full remission and symptoms of hyperarousal often persist. This article specifically reviews the literature on alpha-2 receptor agonist use for the treatment of PTSD and concludes that while the evidence base is limited, these agents might be considered useful when SSRIs fail to treat symptoms of agitation and hyperarousal in patients with PTSD. PMID:26322115

  19. Alpha-2 receptor agonists for the treatment of posttraumatic stress disorder.

    PubMed

    Belkin, Molly R; Schwartz, Thomas L

    2015-01-01

    Clonidine and guanfacine are alpha-2 receptor agonists that decrease sympathetic outflow from the central nervous system. Posttraumatic stress disorder (PTSD) is an anxiety disorder that is theorized to be related to a hyperactive sympathetic nervous system. Currently, the only US Food and Drug Administration (FDA)-approved medications for PTSD are the selective serotonin reuptake inhibitors (SSRIs) sertraline and paroxetine. Sometimes use of the SSRIs may not lead to full remission and symptoms of hyperarousal often persist. This article specifically reviews the literature on alpha-2 receptor agonist use for the treatment of PTSD and concludes that while the evidence base is limited, these agents might be considered useful when SSRIs fail to treat symptoms of agitation and hyperarousal in patients with PTSD. PMID:26322115

  20. Peroxisome proliferator-activated receptors (PPARs) and PPAR agonists: the 'future' in dermatology therapeutics?

    PubMed

    Gupta, Mrinal; Mahajan, Vikram K; Mehta, Karaninder S; Chauhan, Pushpinder S; Rawat, Ritu

    2015-11-01

    Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors and comprise three different isoforms namely PPARα, PPARγ, and PPARβ/δ with PPARβ/δ being the predominant subtype in human keratinocytes. After binding with specific ligands, PPARs regulate gene expression, cell growth and differentiation, apoptosis, inflammatory responses, and tumorogenesis. PPARs also modulate a wide variety of skin functions including keratinocyte proliferation, epidermal barrier formation, wound healing, melanocyte proliferation, and sebum production. Recent studies have shown the importance of PPARs in the pathogenesis of many dermatological disorders. Clinical trials have suggested possible role of PPAR agonists in the management of various dermatoses ranging from acne vulgaris, psoriasis, hirsutism, and lipodystrophy to cutaneous malignancies including melanoma. This article is intended to be a primer for dermatologists in their understanding of clinical relevance of PPARs and PPAR agonists in dermatology therapeutics. PMID:25986745

  1. Immunoactive effects of cannabinoids: considerations for the therapeutic use of cannabinoid receptor agonists and antagonists.

    PubMed

    Greineisen, William E; Turner, Helen

    2010-05-01

    The active constituents of Cannabis sativa have been used for centuries as recreational drugs and medicinal agents. Today, marijuana is the most prevalent drug of abuse in the United States and, conversely, therapeutic use of marijuana constituents are gaining mainstream clinical and political acceptance. Given the documented contributions of endocannabinoid signaling to a range of physiological systems, including cognitive function, and the control of eating behaviors, it is unsurprising that cannabinoid receptor agonists and antagonists are showing significant clinical potential. In addition to the neuroactive effects of cannabinoids, an emerging body of data suggests that both endogenous and exogenous cannabinoids are potently immunoactive. The central premise of this review article is that the immunological effects of cannabinoids should be considered in the context of each prescribing decision. We present evidence that the immunological effects of cannabinoid receptor agonists and antagonists are highly relevant to the spectrum of disorders for which cannabinoid therapeutics are currently offered. PMID:20219697

  2. Ligand-based virtual screening identifies a family of selective cannabinoid receptor 2 agonists

    PubMed Central

    Gianella-Borradori, Matteo; Christou, Ivy; Bataille, Carole J.R.; Cross, Rebecca L.; Wynne, Graham M.; Greaves, David R.; Russell, Angela J.

    2015-01-01

    The cannabinoid receptor 2 (CB2R) has been linked with the regulation of inflammation, and selective receptor activation has been proposed as a target for the treatment of a range of inflammatory diseases such as atherosclerosis and arthritis. In order to identify selective CB2R agonists with appropriate physicochemical and ADME properties for future evaluation in vivo, we first performed a ligand-based virtual screen. Subsequent medicinal chemistry optimisation studies led to the identification of a new class of selective CB2R agonists. Several examples showed high levels of activity (EC50 < 200 nM) and binding affinity (Ki < 200 nM) for the CB2R, and no detectable activity at the CB1R. The most promising example, DIAS2, also showed favourable in vitro metabolic stability and absorption properties along with a clean selectivity profile when evaluated against a panel of GPCRs and kinases. PMID:25487422

  3. Therapeutic Effects of Melatonin Receptor Agonists on Sleep and Comorbid Disorders

    PubMed Central

    Laudon, Moshe; Frydman-Marom, Anat

    2014-01-01

    Several melatonin receptors agonists (ramelteon, prolonged-release melatonin, agomelatine and tasimelteon) have recently become available for the treatment of insomnia, depression and circadian rhythms sleep-wake disorders. The efficacy and safety profiles of these compounds in the treatment of the indicated disorders are reviewed. Accumulating evidence indicates that sleep-wake disorders and co-existing medical conditions are mutually exacerbating. This understanding has now been incorporated into the new Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5). Therefore, when evaluating the risk/benefit ratio of sleep drugs, it is pertinent to also evaluate their effects on wake and comorbid condition. Beneficial effects of melatonin receptor agonists on comorbid neurological, psychiatric, cardiovascular and metabolic symptomatology beyond sleep regulation are also described. The review underlines the beneficial value of enhancing physiological sleep in comorbid conditions. PMID:25207602

  4. Recent progress in the development of agonists and antagonists for melatonin receptors.

    PubMed

    Zlotos, D P

    2012-01-01

    The various physiological actions of the neurohormone melatonin are mediated mainly by two G-protein-coupled MT(1) and MT(2) receptors. The melatoninergic drugs on the market, ramelteon and agomelatine, as well as the most advanced drug candidates under clinical evaluation, tasimelteon and PD-6735, are high-affinity nonselective MT(1) and MT(2) agonists. However, exploring the exact physiological role of the MT(1) and MT(2) melatonin receptors requires subtype selective MT(1) and MT(2) ligands. This review covers novel melatoninergic agonists and antagonists published since 2010, focusing on high-affinity and subtype selective agents. Additionally, compounds not mentioned in the previous review articles and ligands selective for the MT(3) binding site are included. PMID:22680635

  5. The liver X receptor agonist T0901317 acts as androgen receptor antagonist in human prostate cancer cells

    SciTech Connect

    Chuu, Chih-pin; Chen, Rou-Yu; Hiipakka, Richard A.; Kokontis, John M.; Warner, Karen V.; Xiang, Jialing; Liao, Shutsung . E-mail: sliao@uchicago.edu

    2007-06-01

    T0901317 is a potent non-steroidal synthetic liver X receptor (LXR) agonist. T0901317 blocked androgenic stimulation of the proliferation of androgen-dependent LNCaP 104-S cells and androgenic suppression of the proliferation of androgen-independent LNCaP 104-R2 cells, inhibited the transcriptional activation of an androgen-dependent reporter gene by androgen, and suppressed gene and protein expression of prostate specific antigen (PSA), a target gene of androgen receptor (AR) without affecting gene and protein expression of AR. T0901317 also inhibited binding of a radiolabeled androgen to AR, but inhibition was much weaker compared to the effect of the antiandrogens, bicalutamide and hydroxyflutamide. The LXR agonist T0901317, therefore, acts as an antiandrogen in human prostate cancer cells.

  6. Effects of dopamine D2-like receptor agonists in mice trained to discriminate cocaine from saline: influence of feeding condition

    PubMed Central

    Collins, Gregory T.; Jackson, Jonathan A.; Koek, Wouter; France, Charles P.

    2014-01-01

    In rats, the discriminative stimulus effects of direct- and indirect-acting dopamine receptor agonists are mediated by multiple dopamine receptor subtypes and the relative contribution of dopamine D2 and D3 receptors to these effects varies as a function of feeding condition. In these studies, free-fed and food-restricted mice were trained to discriminate 10.0 mg/kg cocaine using a two-lever discrimination procedure in which responding was maintained by food. Both groups of mice acquired the discrimination; however, free-fed mice responded at lower rates than food-restricted mice. Dopamine D3 receptor agonists, pramipexole and quinpirole, increased cocaine-appropriate responding (>85%) in food-restricted, but not in free-fed mice. The dopamine D2 receptor agonist, sumanirole, and the nonselective dopamine receptor agonist, apomorphine, failed to increase cocaine-appropriate responding in either group. Free-fed mice were more sensitive than food-restricted mice to the rate-decreasing effects of dopamine receptor agonists and these effects could not be overcome by increasing the magnitude of reinforcement. Because feeding condition did not alter quinpirole-induced hypothermia, it is unlikely that differences in the discriminative stimulus or rate-decreasing effects of dopamine D2-like receptor agonists were due to differences in the pharmacokinetic properties of the drugs. Although these results suggest that the discriminative stimulus effects of cocaine are mediated by both dopamine D2 and D3 receptors in food-restricted mice, the increased sensitivity of free-fed mice to the rate-decreasing effects of dopamine D2-like receptor agonists limited conclusions about the impact of feeding conditions on the relative contribution of dopamine D2 and D3 receptors to the discriminative stimulus effects of cocaine. PMID:24561049

  7. Effects of cardiac-restricted overexpression of the A2A adenosine receptor on adriamycin-induced cardiotoxicity

    PubMed Central

    Hamad, Eman A.; Li, Xue; Song, Jianliang; Zhang, Xue-Qian; Myers, Valerie; Funakoshi, Hajime; Zhang, Jin; Wang, JuFang; Li, Jifen; Swope, David; Madonick, Ashley; Farber, John; Radice, Glenn L.; Cheung, Joseph Y.; Chan, Tung O.

    2010-01-01

    Activation of the A2A adenosine receptor (A2AR) has been shown to be cardioprotective. We hypothesized that A2AR overexpression could protect the heart from adriamycin-induced cardiomyopathy. Transgenic (TG) mice overexpressing the A2AR and wild-type mice (WT) were injected with adriamycin (5 mg·kg−1·wk−1 ip, 4 wk). All WT mice survived adriamycin treatment while A2AR TG mice suffered 100% mortality at 4 wk. Telemetry showed progressive prolongation of the QT interval, bradyarrhythmias, heart block, and sudden death in adriamycin-treated A2AR TG but not WT mice. Both WT and A2AR TG demonstrated similar decreases in heart function at 3 wk after treatment. Adriamycin significantly increased end-diastolic intracellular Ca2+ concentration in A2AR TG but not in WT myocytes (P < 0.05). Compared with WT myocytes, action potential duration increased dramatically in A2AR TG myoctyes (P < 0.05) after adriamycin treatment. Expression of connexin 43 was decreased in adriamycin treated A2AR TG but not WT mice. In sharp contrast, A2AR overexpression induced after the completion of adriamycin treatment resulted in no deaths and enhanced cardiac performance compared with WT adriamycin-treated mice. Our results indicate that the timing of A2AR activation is critical in terms of exacerbating or protecting adriamycin-induced cardiotoxicity. Our data have direct relevance on the clinical use of adenosine agonists or antagonists in the treatment of patients undergoing adriamycin therapy. PMID:20363887

  8. Disease Modification of Breast Cancer–Induced Bone Remodeling by Cannabinoid 2 Receptor Agonists

    PubMed Central

    Symons-Liguori, Ashley M; Largent-Milnes, Tally M; Havelin, Josh J; Ferland, Henry L; Chandramouli, Anupama; Owusu-Ankomah, Mabel; Nikolich-Zugich, Tijana; Bloom, Aaron P; Jimenez-Andrade, Juan Miguel; King, Tamara; Porreca, Frank; Nelson, Mark A; Mantyh, Patrick W; Vanderah, Todd W

    2015-01-01

    Most commonly originating from breast malignancies, metastatic bone cancer causes bone destruction and severe pain. Although novel chemotherapeutic agents have increased life expectancy, patients are experiencing higher incidences of fracture, pain, and drug-induced side effects; furthermore, recent findings suggest that patients are severely undertreated for their cancer pain. Strong analgesics, namely opiates, are first-line therapy in alleviating cancer-related pain despite the severe side effects, including enhanced bone destruction with sustained administration. Bone resorption is primarily treated with bisphosphonates, which are associated with highly undesirable side effects, including nephrotoxicity and osteonecrosis of the jaw. In contrast, cannabinoid receptor 2 (CB2) receptor-specific agonists have been shown to reduce bone loss and stimulate bone formation in a model of osteoporosis. CB2 agonists produce analgesia in both inflammatory and neuropathic pain models. Notably, mixed CB1/CB2 agonists also demonstrate a reduction in ErbB2-driven breast cancer progression. Here we demonstrate for the first time that CB2 agonists reduce breast cancer–induced bone pain, bone loss, and breast cancer proliferation via cytokine/chemokine suppression. Studies used the spontaneously-occurring murine mammary cell line (66.1) implanted into the femur intramedullary space; measurements of spontaneous pain, bone loss, and cancer proliferation were made. The systemic administration of a CB2 agonist, JWH015, for 7 days significantly attenuated bone remodeling, assuaged spontaneous pain, and decreased primary tumor burden. CB2-mediated effects in vivo were reversed by concurrent treatment with a CB2 antagonist/inverse agonist but not with a CB1 antagonist/inverse agonist. In vitro, JWH015 reduced cancer cell proliferation and inflammatory mediators that have been shown to promote pain, bone loss, and proliferation. Taken together, these results suggest CB2 agonists as a

  9. Agonist-independent, high constitutive activity of the human melanocortin 1 receptor.

    PubMed

    Sánchez-Más, Jesús; Hahmann, Christa; Gerritsen, Ineke; García-Borrón, José C; Jiménez-Cervantes, Celia

    2004-08-01

    The melanocortins (alpha-melanocyte-stimulating hormone and adrenocorticotropin) act on epidermal melanocytes to increase melanogenesis, the eumelanin/pheomelanin ratio and dendricity. These actions are mediated by the heptahelical melanocortin 1 receptor (MC1R), positively coupled to adenylyl cyclase. Gain-of-function mouse Mc1r alleles are associated with a dark, eumelanic coat. Conversely, loss-of-function variants, or overexpression of agouti, a natural melanocortin antagonist, yield yellow, pheomelanic furs. In humans, loss-of-function MC1R variants are associated with fair skin, poor tanning, propensity to freckle and increased skin cancer risk. Therefore, MC1R is a key regulator of mammalian pigmentation. Several observations such as induction of constitutive pigmentation in amelanotic mouse melanoma cells following expression of MC1R indicate that the receptor might display agonist-independent activity. We report a systematic and comparative study of MC1R and Mc1r constitutive activity. We show that expression of MC1R in heterologous systems leads to an agonist-independent increase in cyclic adenosine monophophate (cAMP). Basal signalling is a function of receptor expression and is two to fourfold higher for MC1R than for Mc1r. Moreover, it is observed in human melanoma cells over-expressing the MC1R. Constitutive signalling is abolished or reduced by point mutations of MC1R impairing the response to agonists, and is only doubled by the Lys94Glu mutation, mimicking the constitutively active mouse E(so-3J) allele. Stable or transient expression of wild-type MC1R, but not of loss-of-function mutants, potently stimulates forskolin activation of adenylyl cyclase, a common feature of constitutively active Gs-coupled receptors. Therefore, human MC1R displays a strong agonist-independent constitutive activity. PMID:15250941

  10. Novel heterocyclic scaffolds of GW4064 as farnesoid X receptor agonists.

    PubMed

    Smalley, Terrence L; Boggs, Sharon; Caravella, Justin A; Chen, Lihong; Creech, Katrina L; Deaton, David N; Kaldor, Istvan; Parks, Derek J

    2015-01-15

    The farnesoid X receptor (FXR) may play a crucial role in a number of metabolic diseases and, as such, could potentially serve as a target for the development of therapeutics as a treatment for those diseases. Previous work has described GW4064 as an FXR agonist with an interesting activity profile. This manuscript will describe the synthesis of novel analogs of GW4064 and the activity profile of those analogs. PMID:25499883

  11. Selective 5-HT2C receptor agonists: Design and synthesis of pyridazine-fused azepines.

    PubMed

    Green, Martin P; McMurray, Gordon; Storer, R Ian

    2016-08-15

    Heterocycle-fused azepines are discussed as potent 5-HT2C receptor agonists with excellent selectivity over 5-HT2B agonism. Synthesis and structure activity relationships are outlined for a series of bicyclic pyridazino[3,4-d]azepines. By comparison with earlier published work, in vitro assays predict a high probability for achieving CNS penetration for a potent and selective compound 15a, a pre-requisite to achieve in vivo efficacy. PMID:27381086

  12. Anti-Inflammatory Effects of β2-Receptor Agonists Salbutamol and Terbutaline Are Mediated by MKP-1

    PubMed Central

    Keränen, Tiina; Hömmö, Tuija; Hämäläinen, Mari; Moilanen, Eeva; Korhonen, Riku

    2016-01-01

    Mitogen-activated protein kinase phosphatase 1 (MKP-1) expression is induced by inflammatory factors, and it is an endogenous suppressor of inflammatory response. MKP-1 expression is increased by PDE4 inhibitor rolipram suggesting that it is regulated by cAMP-enhancing compounds. Therefore, we investigated the effect of β2-receptor agonists on MKP-1 expression and inflammatory response. We found that β2-receptor agonists salbutamol and terbutaline, as well as 8-Br-cAMP, increased MKP-1 expression. Salbutamol and terbutaline also inhibited p38 MAPK phosphorylation and TNF production in J774 mouse macrophages. Interestingly, salbutamol suppressed carrageenan-induced paw inflammation in wild-type mice, but the effect was attenuated in MKP-1(-/-) mice. In conclusion, these data show that β2-receptor agonists increase MKP-1 expression, which seems to mediate, at least partly, the observed anti-inflammatory effects of β2-receptor agonists. PMID:26849227

  13. Anti-Inflammatory Effects of β2-Receptor Agonists Salbutamol and Terbutaline Are Mediated by MKP-1.

    PubMed

    Keränen, Tiina; Hömmö, Tuija; Hämäläinen, Mari; Moilanen, Eeva; Korhonen, Riku

    2016-01-01

    Mitogen-activated protein kinase phosphatase 1 (MKP-1) expression is induced by inflammatory factors, and it is an endogenous suppressor of inflammatory response. MKP-1 expression is increased by PDE4 inhibitor rolipram suggesting that it is regulated by cAMP-enhancing compounds. Therefore, we investigated the effect of β2-receptor agonists on MKP-1 expression and inflammatory response. We found that β2-receptor agonists salbutamol and terbutaline, as well as 8-Br-cAMP, increased MKP-1 expression. Salbutamol and terbutaline also inhibited p38 MAPK phosphorylation and TNF production in J774 mouse macrophages. Interestingly, salbutamol suppressed carrageenan-induced paw inflammation in wild-type mice, but the effect was attenuated in MKP-1(-/-) mice. In conclusion, these data show that β2-receptor agonists increase MKP-1 expression, which seems to mediate, at least partly, the observed anti-inflammatory effects of β2-receptor agonists. PMID:26849227

  14. Driving under the influence of synthetic cannabinoid receptor agonist XLR-11.

    PubMed

    Lemos, Nikolas P

    2014-11-01

    The case of a 22-year-old male Caucasian driver is presented. He was involved in a traffic collision. At the roadside, he displayed blank stare and mellow speech with a barely audible voice. A DRE found low body temperature, rigid muscle tone, normal pulse, lack of horizontal and vertical gaze nystagmus, nonconvergence of the eyes, dilated pupil size, and normal Pupillary reaction to light. A standard toxicology DUID protocol was performed on the driver's whole blood including ELISA and GC-MS drug screens with negative results. Additional drug screening was undertaken for bath salts and synthetic cannabinoid receptor agonists by LC-MS/MS by a commercial laboratory and identified the synthetic cannabinoid receptor agonist XLR-11 in the driver's blood. XLR-11 was subsequently quantified at 1.34 ng/mL. This is the first documented case involving a driver operating a motor vehicle under the influence of the synthetic cannabinoid receptor agonist XLR-11. PMID:25088081

  15. A clinical review of GLP-1 receptor agonists: efficacy and safety in diabetes and beyond

    PubMed Central

    Prasad-Reddy, Lalita; Isaacs, Diana

    2015-01-01

    The prevalence of type 2 diabetes is increasing at an astounding rate. Many of the agents used to treat type 2 diabetes have undesirable adverse effects of hypoglycemia and weight gain. Glucagon-like peptide-1 (GLP-1) receptor agonists represent a unique approach to the treatment of diabetes, with benefits extending outside glucose control, including positive effects on weight, blood pressure, cholesterol levels, and beta-cell function. They mimic the effects of the incretin hormone GLP-1, which is released from the intestine in response to food intake. Their effects include increasing insulin secretion, decreasing glucagon release, increasing satiety, and slowing gastric emptying. There are currently four approved GLP-1 receptor agonists in the United States: exenatide, liraglutide, albiglutide, and dulaglutide. A fifth agent, lixisenatide, is available in Europe. There are important pharmacodynamic, pharmacokinetic, and clinical differences of each agent. The most common adverse effects seen with GLP-1 therapy include nausea, vomiting, and injection-site reactions. Other warnings and precautions include pancreatitis and thyroid cell carcinomas. GLP-1 receptor agonists are an innovative and effective option to improve blood glucose control, with other potential benefits of preserving beta-cell function, weight loss, and increasing insulin sensitivity. Once-weekly formulations may also improve patient adherence. Overall, these are effective agents for patients with type 2 diabetes, who are either uncontrolled on metformin or intolerant to metformin. PMID:26213556

  16. Selective Human Estrogen Receptor Partial Agonists (ShERPAs) for Tamoxifen-Resistant Breast Cancer.

    PubMed

    Xiong, Rui; Patel, Hitisha K; Gutgesell, Lauren M; Zhao, Jiong; Delgado-Rivera, Loruhama; Pham, Thao N D; Zhao, Huiping; Carlson, Kathryn; Martin, Teresa; Katzenellenbogen, John A; Moore, Terry W; Tonetti, Debra A; Thatcher, Gregory R J

    2016-01-14

    Almost 70% of breast cancers are estrogen receptor α (ERα) positive. Tamoxifen, a selective estrogen receptor modulator (SERM), represents the standard of care for many patients; however, 30-50% develop resistance, underlining the need for alternative therapeutics. Paradoxically, agonists at ERα such as estradiol (E2) have demonstrated clinical efficacy in patients with heavily treated breast cancer, although side effects in gynecological tissues are unacceptable. A drug that selectively mimics the actions of E2 in breast cancer therapy but minimizes estrogenic effects in other tissues is a novel, therapeutic alternative. We hypothesized that a selective human estrogen receptor partial agonist (ShERPA) at ERα would provide such an agent. Novel benzothiophene derivatives with nanomolar potency in breast cancer cell cultures were designed. Several showed partial agonist activity, with potency of 0.8-76 nM, mimicking E2 in inhibiting growth of tamoxifen-resistant breast cancer cell lines. Three ShERPAs were tested and validated in xenograft models of endocrine-independent and tamoxifen-resistant breast cancer, and in contrast to E2, ShERPAs did not cause significant uterine growth. PMID:26681208

  17. Discovery of a novel small molecule agonist scaffold for the APJ receptor.

    PubMed

    Narayanan, Sanju; Maitra, Rangan; Deschamps, Jeffery R; Bortoff, Katherine; Thomas, James B; Zhang, Yanyan; Warner, Keith; Vasukuttan, Vineetha; Decker, Ann; Runyon, Scott P

    2016-08-15

    The apelinergic system includes a series of endogenous peptides apelin, ELABELA/TODDLER and their 7-transmembrane G-protein coupled apelin receptor (APJ, AGTRL-1, APLNR). The APJ receptor is an attractive therapeutic target because of its involvement in cardiovascular diseases and potentially other disorders including liver fibrosis, obesity, diabetes, and neuroprotection. To date, pharmacological characterization of the APJ receptor has been limited due to the lack of small molecule functional agonists or antagonists. Through focused screening we identified a drug-like small molecule agonist hit 1 with a functional EC50 value of 21.5±5μM and binding affinity (Ki) of 5.2±0.5μM. Initial structure-activity studies afforded compound 22 having a 27-fold enhancement in potency and the first sub-micromolar full agonist with an EC50 value of 800±0.1nM and Ki of 1.3±0.3μM. Preliminary SAR, synthetic methodology, and in vitro pharmacological characterization indicate this scaffold will serve as a favorable starting point for further refinement of APJ potency and selectivity. PMID:27369451

  18. Oral serotonin receptor agonists: a review of their cost effectiveness in migraine.

    PubMed

    Lofland, Jennifer H; Nash, David B

    2005-01-01

    Migraine headache is a highly prevalent chronic, episodic condition. The direct and indirect costs of migraine headache have a tremendous economic impact in the US. Research has shown that serotonin (5HT(1B/D)) receptor agonists reduce healthcare costs, improve health-related QOL (HR-QOL), decrease migraine disability and keep patients effective in the workplace. The purpose of this manuscript is to examine the cost effectiveness of oral 5HT(1B/D) receptor agonists for the treatment of migraine headache. In general, 5HT(1B/D) receptor agonists are associated with increases in direct healthcare costs; however, they are also associated with reductions in the indirect costs associated with migraine headache. Therefore, it appears that the relatively high acquisition cost of these medications is offset and, as a class, these medications appear to be cost effective and demonstrate net benefits from the societal perspective. Based on meta-analyses in which data on eletriptan were not available, it appears that within the class, almotriptan and rizatriptan are the most cost effective. In a prospective study comparing eletriptan with sumatriptan, it appears that the former may be more cost effective than the latter. Additional investigations are needed to further explore the application of the friction-cost approach and QALYs to cost-effectiveness analyses of this class of medication. PMID:15836007

  19. N-terminal galanin-(1-16) fragment is an agonist at the hippocampal galanin receptor

    SciTech Connect

    Fisone, G.; Berthold, M.; Bedecs, K.; Unden, A.; Bartfai, T.; Bertorelli, R.; Consolo, S.; Crawley, J.; Martin, B.; Nilsson, S.; )

    1989-12-01

    The galanin N-terminal fragment (galanin-(1-16)) has been prepared by solid-phase synthesis and by enzymic cleavage of galanin by endoproteinase Asp-N. This peptide fragment displaced {sup 125}I-labeled galanin in receptor autoradiography experiments on rat forebrain and spinal cord and in equilibrium binding experiments from high-affinity binding sites in the ventral hippocampus with an IC50 of approximately 3 nM. In tissue slices of the same brain area, galanin-(1-16), similarly to galanin, inhibited the muscarinic agonist-stimulated breakdown of inositol phospholipids. Upon intracerebroventricular administration, galanin-(1-16) (10 micrograms/15 microliters) also inhibited the scopolamine (0.3 mg/kg, s.c.)-evoked release of acetylcholine, as studied in vivo by microdialysis. Substitution of (L-Trp2) for (D-Trp2) resulted in a 500-fold loss in affinity as compared with galanin-(1-16). It is concluded that, in the ventral hippocampus, the N-terminal galanin fragment (galanin-(1-16)) is recognized by the galanin receptors controlling acetylcholine release and muscarinic agonist-stimulated inositol phospholipid breakdown as a high-affinity agonist and that amino acid residue (Trp2) plays an important role in the receptor-ligand interactions.

  20. Rotigotine is a potent agonist at dopamine D1 receptors as well as at dopamine D2 and D3 receptors

    PubMed Central

    Wood, Martyn; Dubois, Vanessa; Scheller, Dieter; Gillard, Michel

    2015-01-01

    Background and Purpose Rotigotine acts as a dopamine receptor agonist with high affinity for the dopamine D2, D3, D4 and D5 receptors but with a low affinity for the dopamine D1 receptor. We have investigated this further in radioligand binding and functional studies and compared the profile of rotigotine with that of other drugs used in the treatment of Parkinson's disease (PD). Experimental Approach The binding of rotigotine to human dopamine D1, D2, D3, D4 and D5 receptors was determined in radioligand binding studies using [3H]rotigotine and compared with that of standard antagonist radioligands. Functional interactions of rotigotine with human dopamine receptors was also determined. Key Results [3H]rotigotine can be used as an agonist radioligand to label all dopamine receptor subtypes and this can be important to derive agonist affinity estimates. Rotigotine maintains this high affinity in functional studies at all dopamine receptors especially D1, D2 and D3 receptors and, to a lesser extent, D4 and D5 receptors. Rotigotine, like apomorphine but unlike ropinirole and pramipexole, was a potent agonist at all dopamine receptors. Conclusions and Implications Rotigotine is a high-potency agonist at human dopamine D1, D2 and D3 receptors with a lower potency at D4 and D5 receptors. These studies differentiate rotigotine from conventional dopamine D2 agonists, used in the treatment of PD, such as ropinirole and pramipexole which lack activity at the D1 and D5 receptors, but resembles that of apomorphine which has greater efficacy in PD than other dopamine agonists but has suboptimal pharmacokinetic properties. PMID:25339241

  1. Novel selective agonists and antagonists confirm neurokinin NK1 receptors in guinea-pig vas deferens.

    PubMed Central

    Hall, J. M.; Morton, I. K.

    1991-01-01

    1. This study investigated the recognition characteristics of neurokinin receptors mediating potentiation of the contractile response to field stimulation in the guinea-pig vas deferens. 2. A predominant NK1 receptor population is strongly suggested by the relative activities of the common naturally-occurring tachykinin agonists, which fall within less than one order of magnitude. This conclusion is supported by the relative activities of the synthetic NK1 selective agonists substance P methyl ester, [Glp6,L-Pro9]-SP(6-11) and delta-aminovaleryl-[L-Pro9,N-MeLeu10]- SP(7-11) (GR73632) which were 0.78, 9.3 and 120 as active as substance P, respectively. Furthermore, the NK2 selective agonist [Lys3, Gly8,-R-gamma-lactam-Leu9]-NKA(3-10) (GR64349) was active only at the highest concentrations tested (greater than 10 microM), and the NK3 selective agonist, succ-[Asp6,N-MePhe8]-SP(6-11) (senktide) was essentially inactive (10 nM-32 microM). 3. [D-Arg1,D-Pro2,D-Trp7,9,Leu11]-SP(1-11) antagonized responses to neurokinin A, neurokinin B, physalaemin, eledoisin, [Glp6,D-Pro9]-SP(6-11), GR73632 and GR64349 (apparent pKB s 5.6-6.2), but was less potent in antagonizing responses to substance P, substance P methyl ester and [Glp6,L-Pro9]-SP(6-11) (apparent pKB s less than or equal to 5.0-5.0). 4. In contrast, the recently developed NK1-selective receptor antagonist [D-Pro9[Spiro-gamma-lactam]Leu10,Trp11]-SP(1-11) (GR71251) did not produce agonist-dependent pKB estimates. Schild plot analysis indicated a competitive interaction with a single receptor population where the antagonist had an estimated overall pKB of 7.58 +/- 0.13 for the four agonists of differing subtype selectivity tested (GR73632, GR64349, substance P methyl ester and neurokinin B).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1707714

  2. Agonist-independent internalization of metabotropic glutamate receptor 1a is arrestin- and clathrin-dependent and is suppressed by receptor inverse agonists.

    PubMed

    Pula, Giordano; Mundell, Stuart J; Roberts, Peter J; Kelly, Eamonn

    2004-05-01

    Three group I mGluR antagonists CPCCOEt, LY367385 and BAY36-7620, were analyzed for their effect on cell surface expression of metabotropic glutamate receptor 1a and 1b. All three antagonists inhibited glutamate-induced internalization of mGluR1a and mGluR1b. However, when added alone, either LY367385 or BAY36-7620 increased the cell surface expression of mGluR1a but not mGluR1b. Both LY367385 and BAY36-7620 displayed inverse agonist activity as judged by their ability to inhibit basal inositol phosphate accumulation in cells expressing the constitutively active mGluR1a. Interestingly, mGluR1a but not mGluR1b was constitutively internalized in HEK293 cells and both LY367385 and BAY36-7620 inhibited the constitutive internalization of this splice variant. Furthermore, coexpression of dominant negative mutant constructs of arrestin-2 [arrestin-2-(319-418)] or Eps15 [Eps15(E Delta 95-295)] increased cell surface expression of mGluR1a and blocked constitutive receptor internalization. In the presence of these dominant negative mutants, incubation of cells with LY367385 and BAY36-7620 produced no further increase in cell surface expression of mGluR1a. Taken together, these results suggest that the constitutive activity of mGluR1a triggers the internalization of the receptor through an arrestin- and clathrin-dependent pathway, and that inverse agonists increase the cell surface expression of mGluR1a by promoting an inactive form of mGluR1a, which does not undergo constitutive internalization. PMID:15140199

  3. Recovery of brain biomarkers following peroxisome proliferator-activated receptor agonist neuroprotective treatment before ischemic stroke

    PubMed Central

    2014-01-01

    Background Lipid lowering agent such as agonists of peroxisome proliferator-activated receptors (PPAR) are suggested as neuroprotective agents and may protect from the sequelae of brain ischemic stroke. Although the demonstration is not clearly established in human, the underlying molecular mechanism may be of interest for future therapeutic purposes. To this end, we have used our well established rodent model of ischemia-reperfusion pre-treated or not with fenofibrate or atorvastatin and performed a differential proteomics analyses of the brain and analysed the protein markers which levels returned to “normal” following pre-treatments with PPARα agonists. Results In order to identify potential therapeutic targets positively modulated by pre-treatment with the PPARα agonists, two-dimensional gel electrophoresis proteome profiles between control, ischemia-reperfusion and pre-treated or not, were compared. The polypeptide which expression was altered following ischemia – reperfusion but whose levels remain unchanged after pre-treatment were characterized by mass spectrometry and further investigated by Western-blotting and immunohistochemistry. A series of 28 polypeptides were characterized among which the protein disulfide isomerase reduction – a protein instrumental to the unfolded protein response system - was shown to be reduced following PPARα agonists treatment while it was strongly increased in ischemia-reperfusion. Conclusions Pre-treatment with PPARα agonist or atorvastatin show potential neuroprotective effects by inhibiting the PDI overexpression in conjunction with the preservation of other neuronal markers, several of which are associated with the regulation of protein homeostasis, signal transduction and maintenance of synaptic plasticity. This proteomic study therefore suggests that neuroprotective effect of PPARα agonists supposes the preservation of the expression of several proteins essential for the maintenance of protein homeostasis

  4. Reduced striatal adenosine A2A receptor levels define a molecular subgroup in schizophrenia.

    PubMed

    Villar-Menéndez, Izaskun; Díaz-Sánchez, Sara; Blanch, Marta; Albasanz, José Luis; Pereira-Veiga, Thais; Monje, Alfonso; Planchat, Luis Maria; Ferrer, Isidre; Martín, Mairena; Barrachina, Marta

    2014-04-01

    Schizophrenia (SZ) is a mental disorder of unknown origin. Some scientific evidence seems to indicate that SZ is not a single disease entity, since there are patient groups with clear symptomatic, course and biomarker differences. SZ is characterized by a hyperdopaminergic state related to high dopamine D2 receptor activity. It has also been proposed that there is a hypoadenosynergic state. Adenosine is a nucleoside widely distributed in the organism with neuromodulative and neuroprotective activity in the central nervous system. In the brain, the most abundant adenosine receptors are A1R and A2AR. In the present report, we characterize the presence of both receptors in human postmortem putamens of patients suffering SZ with real time TaqMan PCR, western blotting and radioligand binding assay. We show that A1R levels remain unchanged with respect to age-matched controls, whereas nearly fifty percent of patients have reduced A2AR, at the transcriptional and translational levels. Moreover, we describe how DNA methylation plays a role in the pathological A2AR levels with the bisulfite-sequencing technique. In fact, an increase in 5-methylcytosine percentage in the 5' UTR region of ADORA2A was found in those SZ patients with reduced A2AR levels. Interestingly, there was a relationship between the A2A/β-actin ratio and motor disturbances as assessed with some items of the PANSS, AIMS and SAS scales. Therefore, there may be a subgroup of SZ patients with reduced striatal A2AR levels accompanied by an altered motor phenotype. PMID:24433848

  5. Identification of a Synthetic Agonist for the Orphan Nuclear Receptors RORα and RORγ, SR1078

    PubMed Central

    Wang, Yongjun; Kumar, Naresh; Nuhant, Philippe; Cameron, Michael D.; Istrate, Monica A.; Roush, William R.; Griffin, Patrick R.; Burris, Thomas P.

    2010-01-01

    The retinoic acid receptor-related receptors (RORs) are members of the nuclear receptor (NR) superfamily of transcription factors. Several NRs are still characterized as orphan receptors since ligands have not yet been identified for these proteins. Here, we describe the identification of a synthetic RORα/RORγ ligand, SR1078. SR1078 modulates the conformation of RORγ in a biochemical assay and activates RORα and RORγ driven transcription. Furthermore, SR1078 stimulates expression of endogenous ROR target genes in HepG2 cells that express both RORα and RORγ. Pharmacokinetic studies indicate that SR1078 displays reasonable exposure following injection into mice and consistent with SR1078 functioning as a RORα/RORγ agonist, expression of two ROR target genes, glucose-6-phosphatase and fibroblast growth factor 21, were stimulated in the liver. Thus, we have identified the first synthetic RORα/γ agonist and this compound can be utilized as a chemical tool to probe the function of these receptors both in vitro and in vivo. PMID:20735016

  6. Effect of GABA(B) receptor agonist SKF97541 on cortical and hippocampal epileptic afterdischarges.

    PubMed

    Fábera, P; Mareš, P

    2014-01-01

    Activation of GABA(B) receptors leads to longer inhibitory postsynaptic potentials than activation of GABA(A) receptors. Therefore GABA(B) receptors may be a target for anticonvulsant therapy. The present study examined possible effects of GABA(B) receptor agonist SKF97541 on cortical and hippocampal epileptic afterdischarges (ADs). Epileptic ADs elicited by electrical stimulation of sensorimotor cortex or dorsal hippocampus were studied in adult male Wistar rats. Stimulation series were applied 6 times with 10- or 20-min interval. Either interval was efficient for reliable elicitation of cortical ADs but stimulation at 10-min intervals did not reliably elicit hippocampal ADs, many stimulations were without effect. SKF97541 in dose 1 mg/kg significantly prolonged cortical ADs. Duration of hippocampal ADs was not significantly changed by either dose of SKF97541 in spite of a marked myorelaxant effect of the higher dose. Our present data demonstrated that neither cortical nor hippocampal ADs in adult rats were suppressed by GABA(B) receptor agonist SKF97541. Proconvulsant effect on cortical ADs indicates a different role in these two brain structures. In addition, duration of refractory period for electrically-induced ADs in these two structures in adult rats is different. PMID:24702499

  7. Characterization of agonist radioligand interactions with porcine atrial A1 adenosine receptors

    SciTech Connect

    Leid, M.; Schimerlik, M.I.; Murray, T.F.

    1988-09-01

    The agonist radioligand (-)-N6-(125I)-p-hydroxyphenylisopropyl-adenosine (( 125I)HPIA) was used to characterize adenosine recognition sites in porcine atrial membranes. (125I)HPIA showed saturable binding to an apparently homogeneous population of sites with a maximum binding capacity of 35 +/- 3 fmol/mg of protein and an equilibrium dissociation constant of 2.5 +/- 0.4 nM. Kinetic experiments were performed to address the molecular mechanism of (125I)HPIA binding in porcine atrial membranes. (125I)HPIA apparently interacts with the cardiac adenosine receptor in a simple bimolecular reaction. A kinetically derived (125I) HPIA dissociation constant (2.4 nM) was in good agreement with that parameter measured at equilibrium. Guanyl nucleotides negatively modulated (125I)HPIA binding by increasing its rate of dissociation. This finding is consonant with the formation of a ternary complex in porcine atrial membranes, consisting of ligand, receptor, and guanyl nucleotide-binding protein. Prototypic adenosine receptor agonists and antagonists inhibited specific binding in a manner consistent with the labeling of an A1 adenosine receptor. The results of these experiments suggest that the adenosine receptor present in porcine atrial membranes, as labeled by (125I)HPIA, is of the A1 subtype.

  8. High potency olfactory receptor agonists discovered by virtual high-throughput screening: molecular probes for receptor structure and olfactory function

    PubMed Central

    Triballeau, Nicolas; Van Name, Eric; Laslier, Guillaume; Cai, Diana; Paillard, Guillaume; Sorensen, Peter W.; Hoffmann, Rémy; Bertrand, Hugues-Olivier; Ngai, John; Acher, Francine C.

    2008-01-01

    The detection and discrimination of diverse chemical structures by the vertebrate olfactory system is accomplished by the recognition of odorous ligands by their cognate receptors. In the present study we used a computational high-throughput screening strategy to discover novel high affinity agonists of an olfactory G protein-coupled receptor tuned to recognize amino acid ligands. Functional testing of the top candidates validated several agonists with potencies higher than any of the receptor’s known natural ligands. Computational modeling revealed molecular interactions involved in ligand recognition by this receptor, and further highlighted interactions that have been conserved in evolutionarily divergent amino acid receptors. Significantly, the top compounds display robust activities as odorants in vivo, and include a natural product that may be used to signal the presence of bacteria in the aquatic environment. Our virtual screening approach should be applicable to the identification of new bioactive molecules for probing the structure of chemosensory receptors and the function of chemosensory systems in vivo. PMID:19081373

  9. Desensitization of human CRF2(a) receptor signaling governed by agonist potency and βarrestin2 recruitment.

    PubMed

    Hauger, Richard L; Olivares-Reyes, J Alberto; Braun, Sandra; Hernandez-Aranda, Judith; Hudson, Christine C; Gutknecht, Eric; Dautzenberg, Frank M; Oakley, Robert H

    2013-09-10

    The primary goal was to determine agonist-specific regulation of CRF2(a) receptor function. Exposure of human retinoblastoma Y79 cells to selective (UCN2, UCN3 or stresscopins) and non-selective (UCN1 or sauvagine) agonists prominently desensitized CRF2(a) receptors in a rapid, concentration-dependent manner. A considerably slower rate and smaller magnitude of desensitization developed in response to the weak agonist CRF. CRF1 receptor desensitization stimulated by CRF, cortagine or stressin1-A had no effect on CRF2(a) receptor cyclic AMP signaling. Conversely, desensitization of CRF2(a) receptors by UCN2 or UCN3 did not cross-desensitize Gs-coupled CRF1 receptor signaling. In transfected HEK293 cells, activation of CRF2(a) receptors by UCN2, UCN3 or CRF resulted in receptor phosphorylation and internalization proportional to agonist potency. Neither protein kinase A nor casein kinases mediated CRF2(a) receptor phosphorylation or desensitization. Exposure of HEK293 or U2OS cells to UCN2 or UCN3 (100nM) produced strong βarrestin2 translocation and colocalization with membrane CRF2(a) receptors while CRF (1μM) generated only weak βarrestin2 recruitment. βarrestin2 did not internalize with the receptor, however, indicating that transient CRF2(a) receptor-arrestin complexes dissociate at or near the cell membrane. Since deletion of the βarrestin2 gene upregulated Gs-coupled CRF2(a) receptor signaling in MEF cells, a βarrestin2 mechanism restrains Gs-coupled CRF2(a) receptor signaling activated by urocortins. We further conclude that the rate and extent of homologous CRF2(a) receptor desensitization are governed by agonist-specific mechanisms affecting GRK phosphorylation, βarrestin2 recruitment, and internalization thereby producing unique signal transduction profiles that differentially affect the stress response. PMID:23820308

  10. Stimulation of adenosine A2A receptors reduces intracellular cholesterol accumulation and rescues mitochondrial abnormalities in human neural cell models of Niemann-Pick C1.

    PubMed

    Ferrante, A; De Nuccio, C; Pepponi, R; Visentin, S; Martire, A; Bernardo, A; Minghetti, L; Popoli, P

    2016-04-01

    Niemann Pick C 1 (NPC1) disease is an incurable, devastating lysosomal-lipid storage disorder characterized by hepatosplenomegaly, progressive neurological impairment and early death. Current treatments are very limited and the research of new therapeutic targets is thus mandatory. We recently showed that the stimulation of adenosine A2A receptors (A2ARs) rescues the abnormal phenotype of fibroblasts from NPC1 patients suggesting that A2AR agonists could represent a therapeutic option for this disease. However, since all NPC1 patients develop severe neurological symptoms which can be ascribed to the complex pathology occurring in both neurons and oligodendrocytes, in the present paper we tested the effects of the A2AR agonist CGS21680 in human neuronal and oligodendroglial NPC1 cell lines (i.e. neuroblastoma SH-SY5Y and oligodendroglial MO3.13 transiently transfected with NPC1 small interfering RNA). The down-regulation of the NPC1 protein effectively resulted in intracellular cholesterol accumulation and altered mitochondrial membrane potential. Both effects were significantly attenuated by CGS21680 (500 nM). The protective effects of CGS were prevented by the selective A2AR antagonist ZM241385 (500 nM). The involvement of calcium modulation was demonstrated by the ability of Bapta-AM (5-7 μM) in reverting the effect of CGS. The A2A-dependent activity was prevented by the PKA-inhibitor KT5720, thus showing the involvement of the cAMP/PKA signaling. These findings provide a clear in vitro proof of concept that A2AR agonists are promising potential drugs for NPC disease. PMID:26631535

  11. Chronic treatment with estrogen receptor agonists restores acquisition of a spatial learning task in young ovariectomized rats

    PubMed Central

    Hammond, R.; Mauk, R.; Ninaci, D.; Nelson, D.; Gibbs, RB

    2009-01-01

    Previous work has shown that continuous estradiol replacement in young ovariectomized rats enhances acquisition of a delayed matching-to-position (DMP) T-maze task over that of ovariectomized controls. The mechanism by which estradiol confers this benefit has not been fully elucidated. This study examined the role of selective estrogen receptor agonists of ERα, ERβ, and GPR30 in the enhancement of spatial learning on a DMP task by comparing continuous estradiol replacement with continuous administration of PPT (an agonist of ERα), DPN (an agonist of ERβ), or G-1 (an agonist of GPR30) relative to gonadally intact and ovariectomized vehicle-treated controls. It was found that ovariectomy impaired acquisition on this task, whereas all ER selective agonists restored the rate of acquisition to that of gonadally intact controls. These data suggest that estradiol can work through any of several estrogen receptors to enhance the rate of acquisition on this task. PMID:19560466

  12. Binding characteristics of [3H]14-methoxymetopon, a high affinity mu-opioid receptor agonist.

    PubMed

    Spetea, Mariana; Tóth, Fanni; Schütz, Johannes; Otvös, Ferenc; Tóth, Géza; Benyhe, Sandor; Borsodi, Anna; Schmidhammer, Helmut

    2003-07-01

    The highly potent micro -opioid receptor agonist 14-methoxymetopon (4,5alpha-epoxy-3-hydroxy-14beta-methoxy-5beta,17-dimethylmorphinan-6-one) was prepared in tritium labelled form by a catalytic dehalogenation method resulting in a specific radioactivity of 15.9 Ci/mmol. Opioid binding characteristics of [3H]14-methoxymetopon were determined using radioligand binding assay in rat brain membranes. [3H]14-Methoxymetopon specifically labelled a single class of opioid sites with affinity in low subnanomolar range (Ki = 0.43 nm) and maximal number of binding sites of 314 fmol/mg protein. Binding of [3H]14-methoxymetopon was inhibited by ligands selective for the micro -opioid receptor with high potency, while selective kappa-opioids and delta-opioids were weaker inhibitors. 14-Methoxymetopon increased guanosine-5'-O-(3-[35S]thio)-triphosphate ([35S]GTPgammaS) binding with an EC50 of 70.9 nm, thus, providing evidence for the agonist character of this ligand. The increase of [35S]GTPgammaS binding was inhibited by naloxone and selective micro -opioid antagonists, indicating a micro -opioid receptor-mediated action. [3H]14-Methoxymetopon is one of the few nonpeptide mu-opioid receptor agonists available in radiolabelled form up to now. Due to its high affinity and selectivity, high stability and extremely low nonspecific binding (<10%), this radioligand would be an important and useful tool in probing mu-opioid receptor mechanisms, as well as to promote a further understanding of the opioid system at the cellular and molecular level. PMID:12887410

  13. Ractopamine, a livestock feed additive, is a full agonist at trace amine-associated receptor 1.

    PubMed

    Liu, Xuehong; Grandy, David K; Janowsky, Aaron

    2014-07-01

    Ractopamine (RAC) is fed to an estimated 80% of all beef, swine, and turkey raised in the United States. It promotes muscle mass development, limits fat deposition, and reduces feed consumption. However, it has several undesirable behavioral side effects in livestock, especially pigs, including restlessness, agitation, excessive oral-facial movements, and aggressive behavior. Numerous in vitro and in vivo studies suggest RAC's physiological actions begin with its stimulation of β1- and β2-adrenergic receptor-mediated signaling in skeletal muscle and adipose tissue; however, the molecular pharmacology of RAC's psychoactive effects is poorly understood. Using human cystic fibrosis transmembrane conductance regulator (hCFTR) chloride channels as a sensor for intracellular cAMP, we found that RAC and p-tyramine (TYR) produced concentration-dependent increases in chloride conductance in oocytes coexpressing hCFTR and mouse trace amine-associated receptor 1 (mTAAR1), which was completely reversed by the trace amine-associated receptor 1 (TAAR1)-selective antagonist EPPTB [N-(3-ethoxyphenyl)-4-pyrrolidin-1-yl-3-trifluoromethylbenzamide]. Oocytes coexpressing hCFTR and the human β2-adrenergic receptor showed no response to RAC or TYR. These studies demonstrate that, contrary to expectations, RAC is not an agonist of the human β2-adrenergic receptor but rather a full agonist for mTAAR1. Since TAAR1-mediated signaling can influence cardiovascular tone and behavior in several animal models, our finding that RAC is a full mTAAR1 agonist supports the idea that this novel mechanism of action influences the physiology and behavior of pigs and other species. These findings should stimulate future studies to characterize the pharmacological, physiological, and behavioral actions of RAC in humans and other species exposed to this drug. PMID:24799633

  14. Agonist ligand discrimination by the two orexin receptors depends on the expression system.

    PubMed

    Putula, Jaana; Turunen, Pauli M; Jäntti, Maria H; Ekholm, Marie E; Kukkonen, Jyrki P

    2011-04-20

    Despite the recent successes in producing orexin receptor subtype-selective antagonists, these are not commonly available, and therefore, agonist ligands are regularly used to ascribe cell and tissue responses to OX(1) or OX(2) receptors. In the current study, we have compared the native "subtype-selective" agonist, orexin-B, and its reputedly enhanced synthetic variant, Ala(11), d-Leu(15)-orexin-B, in two different recombinant cell lines. Ca2+ elevation was used as readout, and the two "selective" ligands were compared to the subtype-non-selective orexin-A, as is customary with these ligands. In transiently transfected HEK-293 cells, orexin-B showed 9-fold selectivity for the OX(2) receptor and Ala(11), d-Leu(15)-orexin-B 23-fold selectivity, when the potency ratios of ligands were compared between OX(1) and OX(2). In stable CHO-K1 cells, the corresponding values were only 2.6- and 14-fold, respectively. In addition to being low, the selectivity of the ligands was also variable, as indicated by the comparison of the two cell lines. For instance, the relative potency of Ala(11), d-Leu(15)-orexin-B at OX(2) in CHO cells was only 2.3-fold higher than its relative potency at OX(1) in HEK-293 cells; this indicates that Ala(11), d-Leu(15)-orexin-B does not show high enough selectivity for OX(2) to be useful for determination of receptor subtype expression. Comparison of the potencies of orexin-A and -B with respect to a number of published responses in OX(1)-expressing CHO cells, demonstrates that these show great variation: i.e., orexin-A is 1.6-18-fold more potent than orexin-B, depending on the response assessed. These data together suggest that orexin receptor ligands show signal trafficking, which makes agonist-based pharmacology unreliable. PMID:21362456

  15. Agonist action of taurine on glycine receptors in rat supraoptic magnocellular neurones: possible role in osmoregulation.

    PubMed

    Hussy, N; Deleuze, C; Pantaloni, A; Desarménien, M G; Moos, F

    1997-08-01

    1. To evaluate the implication of taurine in the physiology of supraoptic neurones, we (i) investigated the agonist properties of taurine on glycine and GABAA receptors of supraoptic magnocellular neurones acutely dissociated from adult rats, using whole-cell voltage clamp, (ii) studied the effects of taurine and strychnine in vivo by extracellular recordings of supraoptic vasopressin neurones in anaesthetized rats, and (iii) measured the osmolarity-dependent release of endogenous taurine from isolated supraoptic nuclei by HPLC. 2. GABA, glycine and taurine evoked rapidly activating currents that all reversed close to the equilibrium potential for Cl-, indicating activation of Cl(-)-selective channels. Glycine-activated currents were reversibly blocked by strychnine (IC50 of 35 nM with 100 microM glycine), but were unaffected by the GABAA antagonist gabazine (1-3 microM). GABA-activated currents were reversibly antagonized by 3 microM gabazine, but not by strychnine (up to 1 microM). 3. Responses to 1 mM taurine were blocked by strychnine but not by gabazine and showed no additivity with glycine-induced currents, indicating selective activation of glycine receptors. Responses to 10 mM taurine were partially antagonized by gabazine, the residual current being blocked by strychnine. Thus, taurine is also a weak agonist of GABAA receptors. 4. In the presence of gabazine, taurine activated glycine receptors with an EC50 of 406 microM. Taurine activated at most 70% of maximal glycine currents, suggesting that it is a partial agonist of glycine receptors. 5. In vivo, locally applied strychnine (300 nM) increased and taurine (1 mM) decreased the basal electrical activity of vasopressin neurones in normally hydrated rats. The effect of strychnine was markedly more pronounced in water-loaded rats. 6. Taurine, which is concentrated in supraoptic glial cells, could be released from isolated supraoptic nuclei upon hyposmotic stimulation. Decreases in osmolarity of 15 and 30

  16. Tachykinin NK(3) receptor agonists induced microvascular leakage hypersensitivity in the guinea-pig airways.

    PubMed

    Daoui, S; Ahnaou, A; Naline, E; Emonds-Alt, X; Lagente, V; Advenier, C

    2001-12-21

    Microvascular leakage hypersensitivity is a main component of neurogenic inflammation and of tachykinin effects. The aim of this study was to examine the ability of neurokinin B and of the tachykinin NK(3) receptor agonists, [MePhe(7)]neurokinin B or senktide, to potentiate when given by aerosol the microvascular leakage induced by histamine in guinea-pig airways and to compare their effects to those of tachykinin NK(1) (substance P, [Sar(9),Met(O(2))(11)]substance P) or tachykinin NK(2) (neurokinin A, [betaAla(8)]neurokinin A (4-10)) receptor agonists. Guinea-pigs were pretreated successively for 10 min with aerolized salbutamol and phosphoramidon; 15 min later, they were exposed for 30 min to an aerosolized solution of tachykinin receptor agonists; 24 h later, the animals were anaesthetized and vascular permeability was quantified by extravasation of Evans blue dye. Neurokinin B, [MePhe(7)]neurokinin B and senktide (3 x 10(-6)-3 x 10(-5)M) induced a potentiation of the effects of histamine on the vascular permeability in the trachea and main bronchi. Compared to other tachykinin NK(1) and NK(2) receptor agonists, the order of potency was: senktide>neurokinin B=[Sar(9),Met(O(2))(11)]substance P=[betaAla(8)]neurokinin A (4-10)=[MePhe(7)]neurokinin B>neurokinin A>substance P. The potentiation by [MePhe(7)]neurokinin B of histamine-induced microvascular leakage was abolished by the tachykinin NK(1) receptor antagonist SR140333 ([(S)1-(2-[3-(3,4-dichlorophenyl)-1-(3-iso-propoxyphenylacetyl)piperidin-3-yl]etyl)-4-phenyl-1-azoniabicyclo[2.2.2]octane, chloride]) or the tachykinin NK(3) receptor antagonists SR 142801 ([(R)-(N)-(1-(3-(l-benzoyl-3-(3,4-dichlorophenyl)piperidin-3-yl) propyl)-4-phenylpiperidin-4-yl)-N-methylacetamide]) and SB 223412 ([(S)-(-)-N-(alpha-ethylbenzyl)-3-hydroxy-2-phenylquinoline-4-carboxamide]). In conclusion, these results suggest that tachykinin NK(3) receptors might be involved in the potentiation of histamine-induced increase in microvascular

  17. Muscarinic receptor agonists stimulate matrix metalloproteinase 1-dependent invasion of human colon cancer cells.

    PubMed

    Raufman, Jean-Pierre; Cheng, Kunrong; Saxena, Neeraj; Chahdi, Ahmed; Belo, Angelica; Khurana, Sandeep; Xie, Guofeng

    2011-11-18

    Mammalian matrix metalloproteinases (MMPs) which degrade extracellular matrix facilitate colon cancer cell invasion into the bloodstream and extra-colonic tissues; in particular, MMP1 expression correlates strongly with advanced colon cancer stage, hematogenous metastasis and poor prognosis. Likewise, muscarinic receptor signaling plays an important role in colon cancer; muscarinic receptors are over-expressed in colon cancer compared to normal colon epithelial cells. Muscarinic receptor activation stimulates proliferation, migration and invasion of human colon cancer cells. In mouse intestinal neoplasia models genetic ablation of muscarinic receptors attenuates carcinogenesis. In the present work, we sought to link these observations by showing that MMP1 expression and activation plays a mechanistic role in muscarinic receptor agonist-induced colon cancer cell invasion. We show that acetylcholine, which robustly increases MMP1 expression, stimulates invasion of HT29 and H508 human colon cancer cells into human umbilical vein endothelial cell monolayers - this was abolished by pre-incubation with atropine, a non-selective muscarinic receptor inhibitor, and by pre-incubation with anti-MMP1 neutralizing antibody. Similar results were obtained using a Matrigel chamber assay and deoxycholyltaurine (DCT), an amidated dihydroxy bile acid associated with colon neoplasia in animal models and humans, and previously shown to interact functionally with muscarinic receptors. DCT treatment of human colon cancer cells resulted in time-dependent, 10-fold increased MMP1 expression, and DCT-induced cell invasion was also blocked by pre-treatment with anti-MMP1 antibody. This study contributes to understanding mechanisms underlying muscarinic receptor agonist-induced promotion of colon cancer and, more importantly, indicates that blocking MMP1 expression and activation has therapeutic promise to stop or retard colon cancer invasion and dissemination. PMID:22027145

  18. Design, synthesis, pharmacological characterization of a fluorescent agonist of the P2Y₁₄ receptor.

    PubMed

    Kiselev, Evgeny; Balasubramanian, Ramachandran; Uliassi, Elisa; Brown, Kyle A; Trujillo, Kevin; Katritch, Vsevolod; Hammes, Eva; Stevens, Raymond C; Harden, T Kendall; Jacobson, Kenneth A

    2015-11-01

    The P2Y14R is a G(i/o)-coupled receptor of the P2Y family of purinergic receptors that is activated by extracellular UDP and UDP-glucose (UDPG). In an earlier report we described a P2Y14R fluorescent probe, MRS4174, based on the potent and selective antagonist PPTN, a naphthoic acid derivative. Here, we report the design, preparation, and activity of an agonist-based fluorescent probe MRS4183 (11) and a shorter P2Y14R agonist congener, which contain a UDP-glucuronic acid pharmacophore and BODIPY fluorophores conjugated through diaminoalkyl linkers. The design relied on both docking in a P2Y14R homology model and established structure activity relationship (SAR) of nucleotide analogs. 11 retained P2Y14R potency with EC50 value of 0.96 nM (inhibition of adenylyl cyclase), compared to parent UDPG (EC50 47 nM) and served as a tracer for microscopy and flow cytometry, displaying minimal nonspecific binding. Binding saturation analysis gave an apparent binding constant for 11 in whole cells of 21.4±1.1 nM, with a t1/2 of association at 50 nM 11 of 23.9 min. Known P2Y14R agonists and PPTN inhibited cell binding of 11 with the expected rank order of potency. The success in the identification of a new P2Y14R fluorescent agonist with low nonspecific binding illustrates the advantages of rational design based on recently determined GPCR X-ray structures. Such conjugates will be useful tools in expanding the SAR of this receptor, which still lacks chemical diversity in its collective ligands. PMID:26303895

  19. Collybolide is a novel biased agonist of κ-opioid receptors with potent antipruritic activity.

    PubMed

    Gupta, Achla; Gomes, Ivone; Bobeck, Erin N; Fakira, Amanda K; Massaro, Nicholas P; Sharma, Indrajeet; Cavé, Adrien; Hamm, Heidi E; Parello, Joseph; Devi, Lakshmi A

    2016-05-24

    Among the opioid receptors, the κ-opioid receptor (κOR) has been gaining considerable attention as a potential therapeutic target for the treatment of complex CNS disorders including depression, visceral pain, and cocaine addiction. With an interest in discovering novel ligands targeting κOR, we searched natural products for unusual scaffolds and identified collybolide (Colly), a nonnitrogenous sesquiterpene from the mushroom Collybia maculata. This compound has a furyl-δ-lactone core similar to that of Salvinorin A (Sal A), another natural product from the plant Salvia divinorum Characterization of the molecular pharmacological properties reveals that Colly, like Sal A, is a highly potent and selective κOR agonist. However, the two compounds differ in certain signaling and behavioral properties. Colly exhibits 10- to 50-fold higher potency in activating the mitogen-activated protein kinase pathway compared with Sal A. Taken with the fact that the two compounds are equipotent for inhibiting adenylyl cyclase activity, these results suggest that Colly behaves as a biased agonist of κOR. Behavioral studies also support the biased agonistic activity of Colly in that it exhibits ∼10-fold higher potency in blocking non-histamine-mediated itch compared with Sal A, and this difference is not seen in pain attenuation by these two compounds. These results represent a rare example of functional selectivity by two natural products that act on the same receptor. The biased agonistic activity, along with an easily modifiable structure compared with Sal A, makes Colly an ideal candidate for the development of novel therapeutics targeting κOR with reduced side effects. PMID:27162327

  20. Nigramide J is a novel potent inverse agonist of the human constitutive androstane receptor.

    PubMed

    Kanno, Yuichiro; Tanuma, Nobuaki; Yatsu, Tomofumi; Li, Wei; Koike, Kazuo; Inouye, Yoshio

    2014-02-01

    The constitutive androstane receptor (CAR, NR1I3) is very important for drug development and for understanding pharmacokinetic drug-drug interactions. We screened by mammalian one hybrid assay among natural compounds to discover novel ligands of human constitutive androstane receptor (hCAR). hCAR transcriptional activity was measured by luciferase assay and mRNA levels of CYP2B6 and CYP3A4 in HepTR-hCAR cells and human primary hepatocytes were measured by real-time RT-PCR. Nigramide J (NJ) whose efficacy is comparable to those of hitherto known inverse agonists such as clotrimazole, PK11195, and ethinylestradiol. NJ is a naturally occurring cyclohexane-type amide alkaloid that was isolated from the roots of Piper nigrum. The suppressive effect of NJ on the CAR-dependent transcriptional activity was found to be species specific, in the descending order of hCAR, rat CAR, and mouse CAR. The unliganded hCAR-dependent transactivation of reporter and endogenous genes was suppressed by NJ at concentrations higher than 5 μmol/L. The ligand-binding cavity of hCAR was shared by NJ and CITCO, because they were competitive in the binding to hCAR. NJ interfered with the interaction of hCAR with coactivator SRC-1, but not with its interaction with the corepressor NCoR1. Furthermore, NJ is agonist of human pregnane X receptor (hPXR). NJ is a dual ligand of hCAR and hPXR, being an agonist of hPXR and an inverse agonist of hCAR. PMID:25505573

  1. Structure-activity relationships of vanilloid receptor agonists for arteriolar TRPV1

    PubMed Central

    Czikora, Á; Lizanecz, E; Bakó, P; Rutkai, I; Ruzsnavszky, F; Magyar, J; Pórszász, R; Kark, T; Facskó, A; Papp, Z; Édes, I; Tóth, A

    2012-01-01

    BACKGROUND AND PURPOSE The transient receptor potential vanilloid 1 (TRPV1) plays a role in the activation of sensory neurons by various painful stimuli and is a therapeutic target. However, functional TRPV1 that affect microvascular diameter are also expressed in peripheral arteries and we attempted to characterize this receptor. EXPERIMENTAL APPROACH Sensory TRPV1 activation was measured in rats by use of an eye wiping assay. Arteriolar TRPV1-mediated smooth muscle specific responses (arteriolar diameter, changes in intracellular Ca2+) were determined in isolated, pressurized skeletal muscle arterioles obtained from the rat and wild-type or TRPV1−/− mice and in canine isolated smooth muscle cells. The vascular pharmacology of the TRPV1 agonists (potency, efficacy, kinetics of action and receptor desensitization) was determined in rat isolated skeletal muscle arteries. KEY RESULTS Capsaicin evoked a constrictor response in isolated arteries similar to that mediated by noradrenaline, this was absent in arteries from TRPV1 knockout mice and competitively inhibited by TRPV1 antagonist AMG9810. Capsaicin increased intracellular Ca2+ in the arteriolar wall and in isolated smooth muscle cells. The TRPV1 agonists evoked similar vascular constrictions (MSK-195 and JYL-79) or were without effect (resiniferatoxin and JYL-273), although all increased the number of responses (sensory activation) in the eye wiping assay. Maximal doses of all agonists induced complete desensitization (tachyphylaxis) of arteriolar TRPV1 (with the exception of capsaicin). Responses to the partial agonist JYL-1511 suggested 10% TRPV1 activation is sufficient to evoke vascular tachyphylaxis without sensory activation. CONCLUSIONS AND IMPLICATIONS Arteriolar TRPV1 have different pharmacological properties from those located on sensory neurons in the rat. PMID:21883148

  2. Toll-like receptor 7 agonists: chemical feature based pharmacophore identification and molecular docking studies.

    PubMed

    Yu, Hui; Jin, Hongwei; Sun, Lidan; Zhang, Liangren; Sun, Gang; Wang, Zhanli; Yu, Yongchun

    2013-01-01

    Chemical feature based pharmacophore models were generated for Toll-like receptors 7 (TLR7) agonists using HypoGen algorithm, which is implemented in the Discovery Studio software. Several methods tools used in validation of pharmacophore model were presented. The first hypothesis Hypo1 was considered to be the best pharmacophore model, which consists of four features: one hydrogen bond acceptor, one hydrogen bond donor, and two hydrophobic features. In addition, homology modeling and molecular docking studies were employed to probe the intermolecular interactions between TLR7 and its agonists. The results further confirmed the reliability of the pharmacophore model. The obtained pharmacophore model (Hypo1) was then employed as a query to screen the Traditional Chinese Medicine Database (TCMD) for other potential lead compounds. One hit was identified as a potent TLR7 agonist, which has antiviral activity against hepatitis virus in vitro. Therefore, our current work provides confidence for the utility of the selected chemical feature based pharmacophore model to design novel TLR7 agonists with desired biological activity. PMID:23526932

  3. Identification of a novel partial agonist of liver X receptor α (LXRα) via screening.

    PubMed

    Li, Ni; Wang, Xiao; Zhang, Jing; Liu, Chang; Li, Yongzhen; Feng, Tingting; Xu, Yanni; Si, Shuyi

    2014-12-01

    Liver X receptor α (LXRα) plays an important role in the cholesterol metabolism process, and LXRα activation can reduce atherosclerosis. In the present study, using an LXRα-GAL4 luciferase reporter screening, we discovered IMB-170, a structural analog of quinazolinone, which showed potent LXRα agonistic activity. IMB-170 significantly activated LXRα, with an EC50 value of 0.27μM. Interestingly, IMB-170 not only increased the expression of ATP-binding cassette transporter A1 (ABCA1) and G1 (ABCG1), which are related to the reverse cholesterol transport (RCT) process, but also influenced the expression levels of other genes involved in the cholesterol metabolism pathway in many cell lines. Moreover, IMB-170 significantly reduced cellular lipid accumulation and increased cholesterol efflux from RAW264.7 and THP-1 macrophages. Interestingly, compared with TO901317, IMB-170 only slightly increased protein expression levels of lipogenesis-related genes in HepG2 cells, indicating that IMB-170 may have a lower lipogenesis side effect in vivo. These results suggest that IMB-170 showed the selective agonistic activity for LXRα. Moreover, compared with full LXR-agonists, IMB-170 possesses a differential ability to recruit coregulators. This suggests that IMB-170 has distinct interactions with the active sites in the LXRα ligand-binding domain. In summary, IMB-170 is a novel partial LXRα agonist without the classical lipogenesis side effects, which could be used as a potential anti-atherosclerotic leading compound in the future. PMID:25450668

  4. Therapeutic potential of vanilloid receptor TRPV1 agonists and antagonists as analgesics: Recent advances and setbacks.

    PubMed

    Wong, Gilbert Y; Gavva, Narender R

    2009-04-01

    The vanilloid receptor TRPV1 is a homotetrameric, non-selective cation channel abundantly expressed in the nociceptors (c-fibers). TRPV1 is considered as a highly validated pain target because, i) its agonists such as capsaicin cause desensitization of TRPV1 channels that relieves pain behaviors in preclinical species, and ii) its antagonists relieve pain behaviors in rodent models of inflammation, osteoarthritis, and cancer. Hence, both agonists and antagonists of TRPV1 are being evaluated as potential analgesics in clinical trials. Clinical trial results of TRPV1 agonists such as resiniferatoxin in interstitial cystitis, NGX 4010 in post-herpetic neuralgia, and 4975 (Adlea) in osteoarthritis, bunionectomy, and Morton's neuroma have been reported. Similarly, clinical trial results of TRPV1 antagonists such as SB-705498 and AMG 517 have also been published recently. Overall, some molecules (e.g., capsaicin) demonstrated potential analgesia in certain conditions (postsurgical pain, postherpetic neuralgia, pain in diabetic neuropathy, osteoarthritis, bunionectomy, and Morton's neuroma), whereas others fell out of the clinic due to on-target liabilities or failed to demonstrate efficacy. This review summarizes recent advances and setbacks of TRPV1 agonists and antagonists in the clinic and predicts future directions. PMID:19150372

  5. Divergent teratogenicity of agonists of retinoid X receptors in embryos of zebrafish (Danio rerio).

    PubMed

    Shi, Huahong; Zhu, Pan; Sun, Zhi; Yang, Bo; Zheng, Liang

    2012-07-01

    Zebrafish (Danio rerio) embryos were comparably exposed to seven known agonists of retinoid X receptors (RXRs) including two endogenous compounds (9-cis-retinoic acid and docosahexaenoic acid), four man-made selective ligands (LGD1069, SR11237, fluorobexarotene and CD3254), and a biocide (triphenyltin). The dominant phenotypes of malformation were sharp mouths and small caudal fins in 1 mg/L SR11237-treated group after 5 days exposure. 9-cis-retinoic acid and LGD1069 induced multiple malformations including small eyes, bent notochords, reduced brain, enlarged proctodaems, absence of fins, short tails and edema after 5 days exposure. Fluorobexarotene and CD3254 induced similar phenotypes of malformations after 5 days exposure at low concentration (20 μg/L) to those after the 1st d exposure at high concentrations (50 and 100 μg/L). Triphenlytin induced multiple malformations including deformed eyes, bent notochords, bent tails, and edema in hearts after 5 days exposure at concentrations of 1-10 μg Sn/L. In contrast, no discernible malformations were observed in triphenlytin-treated groups after each separate day exposure. These agonists not only showed different ability of teratogenicity but also induced different phenotypes of malformation in zebrafish embryos. In addition, the sensitive stages of zebrafish embryos were different in response to these agonists. Therefore, our results suggest that the agonists of RXRs had divergent teratogenicity in zebrafish embryos. PMID:22526925

  6. Novel Zn2+ Modulated GPR39 Receptor Agonists Do Not Drive Acute Insulin Secretion in Rodents

    PubMed Central

    Yasuda, Shin-ichiro; Tsuchida, Takuma; Oguma, Takahiro; Marley, Anna; Wennberg-Huldt, Charlotte; Hovdal, Daniel; Fukuda, Hajime; Yoneyama, Yukimi; Sasaki, Kazuyo; Johansson, Anders; Lundqvist, Sara; Brengdahl, Johan; Isaacs, Richard J.; Brown, Daniel; Geschwindner, Stefan; Benthem, Lambertus; Priest, Claire; Turnbull, Andrew

    2015-01-01

    Type 2 diabetes (T2D) occurs when there is insufficient insulin release to control blood glucose, due to insulin resistance and impaired β-cell function. The GPR39 receptor is expressed in metabolic tissues including pancreatic β-cells and has been proposed as a T2D target. Specifically, GPR39 agonists might improve β-cell function leading to more adequate and sustained insulin release and glucose control. The present study aimed to test the hypothesis that GPR39 agonism would improve glucose stimulated insulin secretion in vivo. A high throughput screen, followed by a medicinal chemistry program, identified three novel potent Zn2+ modulated GPR39 agonists. These agonists were evaluated in acute rodent glucose tolerance tests. The results showed a lack of glucose lowering and insulinotropic effects not only in lean mice, but also in diet-induced obese (DIO) mice and Zucker fatty rats. It is concluded that Zn2+ modulated GPR39 agonists do not acutely stimulate insulin release in rodents. PMID:26720709

  7. Melanocortin 1 receptor agonist protects podocytes through catalase and RhoA activation.

    PubMed

    Elvin, Johannes; Buvall, Lisa; Lindskog Jonsson, Annika; Granqvist, Anna; Lassén, Emelie; Bergwall, Lovisa; Nyström, Jenny; Haraldsson, Börje

    2016-05-01

    Drugs containing adrenocorticotropic hormone have been used as therapy for patients with nephrotic syndrome. We have previously shown that adrenocorticotropic hormone and a selective agonist for the melanocortin 1 receptor (MC1R) exert beneficial actions in experimental membranous nephropathy with reduced proteinuria, reduced oxidative stress, and improved glomerular morphology and function. Our hypothesis is that MC1R activation in podocytes elicits beneficial effects by promoting stress fibers and maintaining podocyte viability. To test the hypothesis, we cultured podocytes and used highly specific agonists for MC1R. Podocytes were subjected to the nephrotic-inducing agent puromycin aminonucleoside, and downstream effects of MC1R activation on podocyte survival, antioxidant defense, and cytoskeleton dynamics were studied. To increase the response and enhance intracellular signals, podocytes were transduced to overexpress MC1R. We showed that puromycin promotes MC1R expression in podocytes and that activation of MC1R promotes an increase of catalase activity and reduces oxidative stress, which results in the dephosphorylation of p190RhoGAP and formation of stress fibers through RhoA. In addition, MC1R agonists protect against apoptosis. Together, these mechanisms protect the podocyte against puromycin. Our findings strongly support the hypothesis that selective MC1R-activating agonists protect podocytes and may therefore be useful to treat patients with nephrotic syndromes commonly considered as podocytopathies. PMID:26887829

  8. Incretin-like effects of small molecule trace amine-associated receptor 1 agonists

    PubMed Central

    Raab, Susanne; Wang, Haiyan; Uhles, Sabine; Cole, Nadine; Alvarez-Sanchez, Ruben; Künnecke, Basil; Ullmer, Christoph; Matile, Hugues; Bedoucha, Marc; Norcross, Roger D.; Ottaway-Parker, Nickki; Perez-Tilve, Diego; Conde Knape, Karin; Tschöp, Matthias H.; Hoener, Marius C.; Sewing, Sabine

    2015-01-01

    Objective Type 2 diabetes and obesity are emerging pandemics in the 21st century creating worldwide urgency for the development of novel and safe therapies. We investigated trace amine-associated receptor 1 (TAAR1) as a novel target contributing to the control of glucose homeostasis and body weight. Methods We investigated the peripheral human tissue distribution of TAAR1 by immunohistochemistry and tested the effect of a small molecule TAAR1 agonist on insulin secretion in vitro using INS1E cells and human islets and on glucose tolerance in C57Bl6, and db/db mice. Body weight effects were investigated in obese DIO mice. Results TAAR1 activation by a selective small molecule agonist increased glucose-dependent insulin secretion in INS1E cells and human islets and elevated plasma PYY and GLP-1 levels in mice. In diabetic db/db mice, the TAAR1 agonist normalized glucose excursion during an oral glucose tolerance test. Sub-chronic treatment of diet-induced obese (DIO) mice with the TAAR1 agonist resulted in reduced food intake and body weight. Furthermore insulin sensitivity was improved and plasma triglyceride levels and liver triglyceride content were lower than in controls. Conclusions We have identified TAAR1 as a novel integrator of metabolic control, which acts on gastrointestinal and pancreatic islet hormone secretion. Thus TAAR1 qualifies as a novel and promising target for the treatment of type 2 diabetes and obesity. PMID:26844206

  9. Novel S1P1 receptor agonists - Part 4: Alkylaminomethyl substituted aryl head groups.

    PubMed

    Lescop, Cyrille; Müller, Claus; Mathys, Boris; Birker, Magdalena; de Kanter, Ruben; Kohl, Christopher; Hess, Patrick; Nayler, Oliver; Rey, Markus; Sieber, Patrick; Steiner, Beat; Weller, Thomas; Bolli, Martin H

    2016-06-30

    In a previous communication we reported on the discovery of alkylamino pyridine derivatives (e.g. 1) as a new class of potent, selective and efficacious S1P1 receptor (S1PR1) agonists. However, more detailed profiling revealed that this compound class is phototoxic in vitro. Here we describe a new class of potent S1PR1 agonists wherein the exocyclic nitrogen was moved away from the pyridine ring (e.g. 11c). Further structural modifications led to the identification of novel alkylaminomethyl substituted phenyl and thienyl derivatives as potent S1PR1 agonists. These new alkylaminomethyl aryl compounds showed no phototoxic potential. Based on their in vivo efficacy and ability to penetrate the brain, the 5-alkyl-aminomethyl thiophenes appeared to be the most interesting class. Potent and selective S1PR1 agonist 20e, for instance, maximally reduced the blood lymphocyte count (LC) for 24 h after oral administration of 10 mg/kg to rat and its brain concentrations reached >500 ng/g over 24 h. PMID:27061986

  10. A Robotic BG1Luc Reporter Assay to Detect Estrogen Receptor Agonists

    PubMed Central

    Stoner, Matthew A.; Yang, Chun Z.; Bittner, George D.

    2014-01-01

    Endocrine disrupting chemicals with estrogenic activity (EA) have been associated with various adverse health effects. US agencies (ICCVAM/NICEATM) tasked to assess in vitro transcription activation assays to detect estrogenic receptor (ER) agonists for EA have recently validated a BG1Luc assay in manual format, but prefer robotic formats. We have developed a robotic BG1Luc EA assay to detect EA that demonstrated 100% concordance with ICCVAM meta-analyses and ICCVAM BG1Luc results in manual format for 27 ICCVAM test substances, i.e. no false negatives or false positives. This robotic assay also consistently assessed other, more problematic ICCVAM test substances such as clomiphene citrate, L-thyroxin, and tamoxifen. Agonist responses using this robotic BG1Luc assay were consistently inhibited by the ER antagonist ICI 182,780, confirming that agonist responses were due to binding to ERs rather than to a non-specific agonist response. This robotic assay also detected EA in complex mixtures of substances such as extracts of personal care products, plastic resins or plastic consumer products. This robotic BG1Luc assay had at least as high accuracy and greater sensitivity and repeatability when compared to its manual version or to the other ICCVAM/OECD validated assays for EA (manual BG1Luc and CERI). PMID:24747293

  11. Development of Functionally Selective, Small Molecule Agonists at Kappa Opioid Receptors*

    PubMed Central

    Zhou, Lei; Lovell, Kimberly M.; Frankowski, Kevin J.; Slauson, Stephen R.; Phillips, Angela M.; Streicher, John M.; Stahl, Edward; Schmid, Cullen L.; Hodder, Peter; Madoux, Franck; Cameron, Michael D.; Prisinzano, Thomas E.; Aubé, Jeffrey; Bohn, Laura M.

    2013-01-01

    The kappa opioid receptor (KOR) is widely expressed in the CNS and can serve as a means to modulate pain perception, stress responses, and affective reward states. Therefore, the KOR has become a prominent drug discovery target toward treating pain, depression, and drug addiction. Agonists at KOR can promote G protein coupling and βarrestin2 recruitment as well as multiple downstream signaling pathways, including ERK1/2 MAPK activation. It has been suggested that the physiological effects of KOR activation result from different signaling cascades, with analgesia being G protein-mediated and dysphoria being mediated through βarrestin2 recruitment. Dysphoria associated with KOR activation limits the therapeutic potential in the use of KOR agonists as analgesics; therefore, it may be beneficial to develop KOR agonists that are biased toward G protein coupling and away from βarrestin2 recruitment. Here, we describe two classes of biased KOR agonists that potently activate G protein coupling but weakly recruit βarrestin2. These potent and functionally selective small molecule compounds may prove to be useful tools for refining the therapeutic potential of KOR-directed signaling in vivo. PMID:24187130

  12. Quantitative Phosphoproteomics Unravels Biased Phosphorylation of Serotonin 2A Receptor at Ser280 by Hallucinogenic versus Nonhallucinogenic Agonists*

    PubMed Central

    Karaki, Samah; Becamel, Carine; Murat, Samy; Mannoury la Cour, Clotilde; Millan, Mark J.; Prézeau, Laurent; Bockaert, Joël; Marin, Philippe; Vandermoere, Franck

    2014-01-01

    The serotonin 5-HT2A receptor is a primary target of psychedelic hallucinogens such as lysergic acid diethylamine, mescaline, and psilocybin, which reproduce some of the core symptoms of schizophrenia. An incompletely resolved paradox is that only some 5-HT2A receptor agonists exhibit hallucinogenic activity, whereas structurally related agonists with comparable affinity and activity lack such a psychoactive activity. Using a strategy combining stable isotope labeling by amino acids in cell culture with enrichment in phosphorylated peptides by means of hydrophilic interaction liquid chromatography followed by immobilized metal affinity chromatography, we compared the phosphoproteome in HEK-293 cells transiently expressing the 5-HT2A receptor and exposed to either vehicle or the synthetic hallucinogen 1-[2,5-dimethoxy-4-iodophenyl]-2-aminopropane (DOI) or the nonhallucinogenic 5-HT2A agonist lisuride. Among the 5995 identified phosphorylated peptides, 16 sites were differentially phosphorylated upon exposure of cells to DOI versus lisuride. These include a serine (Ser280) located in the third intracellular loop of the 5-HT2A receptor, a region important for its desensitization. The specific phosphorylation of Ser280 by hallucinogens was further validated by quantitative mass spectrometry analysis of immunopurified receptor digests and by Western blotting using a phosphosite specific antibody. The administration of DOI, but not of lisuride, to mice, enhanced the phosphorylation of 5-HT2A receptors at Ser280 in the prefrontal cortex. Moreover, hallucinogens induced a less pronounced desensitization of receptor-operated signaling in HEK-293 cells and neurons than did nonhallucinogenic agonists. The mutation of Ser280 to aspartic acid (to mimic phosphorylation) reduced receptor desensitization by nonhallucinogenic agonists, whereas its mutation to alanine increased the ability of hallucinogens to desensitize the receptor. This study reveals a biased phosphorylation of

  13. Quantitative phosphoproteomics unravels biased phosphorylation of serotonin 2A receptor at Ser280 by hallucinogenic versus nonhallucinogenic agonists.

    PubMed

    Karaki, Samah; Becamel, Carine; Murat, Samy; Mannoury la Cour, Clotilde; Millan, Mark J; Prézeau, Laurent; Bockaert, Joël; Marin, Philippe; Vandermoere, Franck

    2014-05-01

    The serotonin 5-HT(2A) receptor is a primary target of psychedelic hallucinogens such as lysergic acid diethylamine, mescaline, and psilocybin, which reproduce some of the core symptoms of schizophrenia. An incompletely resolved paradox is that only some 5-HT(2A) receptor agonists exhibit hallucinogenic activity, whereas structurally related agonists with comparable affinity and activity lack such a psychoactive activity. Using a strategy combining stable isotope labeling by amino acids in cell culture with enrichment in phosphorylated peptides by means of hydrophilic interaction liquid chromatography followed by immobilized metal affinity chromatography, we compared the phosphoproteome in HEK-293 cells transiently expressing the 5-HT(2A) receptor and exposed to either vehicle or the synthetic hallucinogen 1-[2,5-dimethoxy-4-iodophenyl]-2-aminopropane (DOI) or the nonhallucinogenic 5-HT(2A) agonist lisuride. Among the 5995 identified phosphorylated peptides, 16 sites were differentially phosphorylated upon exposure of cells to DOI versus lisuride. These include a serine (Ser(280)) located in the third intracellular loop of the 5-HT(2A) receptor, a region important for its desensitization. The specific phosphorylation of Ser(280) by hallucinogens was further validated by quantitative mass spectrometry analysis of immunopurified receptor digests and by Western blotting using a phosphosite specific antibody. The administration of DOI, but not of lisuride, to mice, enhanced the phosphorylation of 5-HT(2A) receptors at Ser(280) in the prefrontal cortex. Moreover, hallucinogens induced a less pronounced desensitization of receptor-operated signaling in HEK-293 cells and neurons than did nonhallucinogenic agonists. The mutation of Ser(280) to aspartic acid (to mimic phosphorylation) reduced receptor desensitization by nonhallucinogenic agonists, whereas its mutation to alanine increased the ability of hallucinogens to desensitize the receptor. This study reveals a biased

  14. The CB2 cannabinoid receptor-selective agonist O-3223 reduces pain and inflammation without apparent cannabinoid behavioral effects.

    PubMed

    Kinsey, Steven G; Mahadevan, Anu; Zhao, Bingjun; Sun, Hang; Naidu, Pattipati S; Razdan, Raj K; Selley, Dana E; Imad Damaj, M; Lichtman, Aron H

    2011-01-01

    Although Δ(9)-tetrahydrocannabinol (THC) and other mixed CB(1)/CB(2) receptor agonists are well established to elicit antinociceptive effects, their psychomimetic actions and potential for abuse have dampened enthusiasm for their therapeutic development. Conversely, CB(2) receptor-selective agonists have been shown to reduce pain and inflammation, without eliciting apparent cannabinoid behavioral effects. In the present study, we developed a novel ethyl sulfonamide THC analog, O-3223, and compared its pharmacological effects to those of the potent, mixed CB(1)/CB(2) receptor agonist, CP55,940, in a battery of preclinical pain models. Competitive cannabinoid receptor binding experiments revealed that O-3223 was approximately 80-fold more selective for CB(2) than CB(1) receptors. Additionally, O-3223 behaved as a full CB(2) receptor agonist in [(35)S]GTPγS binding. O-3223 reduced nociceptive behavior in both phases of the formalin test, reduced thermal hyperalgesia in the chronic constriction injury of the sciatic nerve (CCI) model, and reduced edema and thermal hyperalgesia elicited by intraplantar injection of LPS. These effects were blocked by pretreatment with the CB(2) receptor-selective antagonist SR144528, but not by the CB(1) receptor antagonist, rimonabant. Unlike CP55,940, O-3223 did not elicit acute antinociceptive effects in the hot-plate test, hypothermia, or motor disturbances, as assessed in the rotarod test. These data indicate that the CB(2) receptor-selective agonist, O-3223, reduces inflammatory and neuropathic nociception, without affecting basal nociception or eliciting overt behavioral effects. Moreover, this compound can serve as a template to develop new CB(2) receptor agonists with increased receptor selectivity and increased potency in treating inflammatory and neuropathic pain. PMID:20849866

  15. Muscarinic receptor agonists stimulate matrix metalloproteinase 1-dependent invasion of human colon cancer cells

    SciTech Connect

    Raufman, Jean-Pierre; Cheng, Kunrong; Saxena, Neeraj; Chahdi, Ahmed; Belo, Angelica; Khurana, Sandeep; Xie, Guofeng

    2011-11-18

    Highlights: Black-Right-Pointing-Pointer Muscarinic receptor agonists stimulated robust human colon cancer cell invasion. Black-Right-Pointing-Pointer Anti-matrix metalloproteinase1 antibody pre-treatment blocks cell invasion. Black-Right-Pointing-Pointer Bile acids stimulate MMP1 expression, cell migration and MMP1-dependent invasion. -- Abstract: Mammalian matrix metalloproteinases (MMPs) which degrade extracellular matrix facilitate colon cancer cell invasion into the bloodstream and extra-colonic tissues; in particular, MMP1 expression correlates strongly with advanced colon cancer stage, hematogenous metastasis and poor prognosis. Likewise, muscarinic receptor signaling plays an important role in colon cancer; muscarinic receptors are over-expressed in colon cancer compared to normal colon epithelial cells. Muscarinic receptor activation stimulates proliferation, migration and invasion of human colon cancer cells. In mouse intestinal neoplasia models genetic ablation of muscarinic receptors attenuates carcinogenesis. In the present work, we sought to link these observations by showing that MMP1 expression and activation plays a mechanistic role in muscarinic receptor agonist-induced colon cancer cell invasion. We show that acetylcholine, which robustly increases MMP1 expression, stimulates invasion of HT29 and H508 human colon cancer cells into human umbilical vein endothelial cell monolayers - this was abolished by pre-incubation with atropine, a non-selective muscarinic receptor inhibitor, and by pre-incubation with anti-MMP1 neutralizing antibody. Similar results were obtained using a Matrigel chamber assay and deoxycholyltaurine (DCT), an amidated dihydroxy bile acid associated with colon neoplasia in animal models and humans, and previously shown to interact functionally with muscarinic receptors. DCT treatment of human colon cancer cells resulted in time-dependent, 10-fold increased MMP1 expression, and DCT-induced cell invasion was also blocked by pre

  16. Identification of Darmstoff analogs as selective agonists and antagonists of lysophosphatidic acid receptors.

    PubMed

    Gududuru, Veeresa; Zeng, Kui; Tsukahara, Ryoko; Makarova, Natalia; Fujiwara, Yuko; Pigg, Kathryn R; Baker, Daniel L; Tigyi, Gabor; Miller, Duane D

    2006-01-15

    Darmstoff describes a family of gut smooth muscle-stimulating acetal phosphatidic acids initially isolated and characterized from the bath fluid of stimulated gut over 50 years ago. Despite similar structural and biological profiles, Darmstoff analogs have not previously been examined as potential LPA mimetics. Here, we report a facile method for the synthesis of potassium salts of Darmstoff analogs. To understand the effect of stereochemistry on lysophosphatidic acid mimetic activity, synthesis of optically pure stereoisomers of selected Darmstoff analogs was achieved starting with chiral methyl glycerates. Each Darmstoff analog was evaluated for subtype-specific LPA receptor agonist/antagonist activity, PPARgamma activation, and autotaxin inhibition. From this study we identified compound 12 as a pan-antagonist and several pan-agonists for the LPA(1-3) receptors. Introduction of an aromatic ring in the lipid chain such as analog 22 produced a subtype-specific LPA(3) agonist with an EC(50) of 692 nM. Interestingly, regardless of their LPA(1/2/3) ligand properties all of the Darmstoff analogs tested activated PPARgamma. However, these compounds are weak inhibitors of autotaxin. The results indicate that Darmstoff analogs constitute a novel class of lysophosphatidic acid mimetics. PMID:16290140

  17. A Novel Role of Serotonin Receptor 2B Agonist as an Anti-Melanogenesis Agent

    PubMed Central

    Oh, Eun Ju; Park, Jong Il; Lee, Ji Eun; Myung, Cheol Hwan; Kim, Su Yeon; Chang, Sung Eun; Hwang, Jae Sung

    2016-01-01

    BW723C86, a serotonin receptor 2B agonist, has been investigated as a potential therapeutic for various conditions such as anxiety, hyperphagia and hypertension. However, the functional role of BW723C86 against melanogenesis remains unclear. In this study, we investigate the effect of serotonin receptor 2B (5-HTR2B) agonist on melanogenesis and elucidate the mechanism involved. BW723C86 reduced melanin synthesis and intracellular tyrosinase activity in melan-A cells and normal human melanocytes. The expression of melanogenesis-related proteins (tyrosinase, TRP-1 and TRP-2) and microphthalmia-associated transcription factor (MITF) in melan-A cells decreased after BW723C86 treatment. The promoter activity of MITF was also reduced by BW723C86 treatment. The reduced level of MITF was associated with inhibition of protein kinase A (PKA) and cAMP response element-binding protein (CREB) activation by BW723C86 treatment. These results suggest that the serotonin agonist BW723C86 could be a potential therapeutic agent for skin hyperpigmentation disorders. PMID:27077852

  18. The Discovery of Indole Full Agonists of the Neurotensin Receptor 1 (NTSR1)

    PubMed Central

    Di Fruscia, Paolo; He, Yuanjun; Koenig, Marcel; Tabrizifard, Sahba; Nieto, Ainhoa; McDonald, Patricia H.; Kamenecka, Theodore M.

    2014-01-01

    Neurotensin (NT) is an endogenous tridecapeptide found in the central nervous system (CNS) and in peripheral tissues. Neurotensin exerts a wide range of physiological effects and it has been found to play a critical role in a number of human diseases, such as schizophrenia, Parkinson’s disease and drug addiction. The discovery of small-molecule non-peptide neurotensin receptor (NTSR) modulators would represent an important breakthrough as such compounds could be used as pharmacological tools, to further decipher the cellular functions of neurotensin, and potentially as therapeutic agents to treat human disease. Herein, we report the identification of non-peptide low-micromolar neurotensin receptor 1 (NTSR1) full agonists, discovered through structural optimization of the known NTSR1 partial agonist 1. In vitro cellular screenings, based on an intracellular Ca2+ mobilization assay, revealed our best hit molecule 8 (SR-12062) to have an EC50 of 2 μM at NTSR1 with full agonist behaviour (Emax = 100%), showing a higher efficacy and ~ 90-fold potency improvement compared to parent compound 1 (EC50 = 178 μM; Emax = 17%). PMID:24997685

  19. A Novel Role of Serotonin Receptor 2B Agonist as an Anti-Melanogenesis Agent.

    PubMed

    Oh, Eun Ju; Park, Jong Il; Lee, Ji Eun; Myung, Cheol Hwan; Kim, Su Yeon; Chang, Sung Eun; Hwang, Jae Sung

    2016-01-01

    BW723C86, a serotonin receptor 2B agonist, has been investigated as a potential therapeutic for various conditions such as anxiety, hyperphagia and hypertension. However, the functional role of BW723C86 against melanogenesis remains unclear. In this study, we investigate the effect of serotonin receptor 2B (5-HTR2B) agonist on melanogenesis and elucidate the mechanism involved. BW723C86 reduced melanin synthesis and intracellular tyrosinase activity in melan-A cells and normal human melanocytes. The expression of melanogenesis-related proteins (tyrosinase, TRP-1 and TRP-2) and microphthalmia-associated transcription factor (MITF) in melan-A cells decreased after BW723C86 treatment. The promoter activity of MITF was also reduced by BW723C86 treatment. The reduced level of MITF was associated with inhibition of protein kinase A (PKA) and cAMP response element-binding protein (CREB) activation by BW723C86 treatment. These results suggest that the serotonin agonist BW723C86 could be a potential therapeutic agent for skin hyperpigmentation disorders. PMID:27077852

  20. β2-Adrenergic receptor agonists activate CFTR in intestinal organoids and subjects with cystic fibrosis.

    PubMed

    Vijftigschild, Lodewijk A W; Berkers, Gitte; Dekkers, Johanna F; Zomer-van Ommen, Domenique D; Matthes, Elizabeth; Kruisselbrink, Evelien; Vonk, Annelotte; Hensen, Chantal E; Heida-Michel, Sabine; Geerdink, Margot; Janssens, Hettie M; van de Graaf, Eduard A; Bronsveld, Inez; de Winter-de Groot, Karin M; Majoor, Christof J; Heijerman, Harry G M; de Jonge, Hugo R; Hanrahan, John W; van der Ent, Cornelis K; Beekman, Jeffrey M

    2016-09-01

    We hypothesized that people with cystic fibrosis (CF) who express CFTR (cystic fibrosis transmembrane conductance regulator) gene mutations associated with residual function may benefit from G-protein coupled receptor (GPCR)-targeting drugs that can activate and enhance CFTR function.We used intestinal organoids to screen a GPCR-modulating compound library and identified β2-adrenergic receptor agonists as the most potent inducers of CFTR function.β2-Agonist-induced organoid swelling correlated with the CFTR genotype, and could be induced in homozygous CFTR-F508del organoids and highly differentiated primary CF airway epithelial cells after rescue of CFTR trafficking by small molecules. The in vivo response to treatment with an oral or inhaled β2-agonist (salbutamol) in CF patients with residual CFTR function was evaluated in a pilot study. 10 subjects with a R117H or A455E mutation were included and showed changes in the nasal potential difference measurement after treatment with oral salbutamol, including a significant improvement of the baseline potential difference of the nasal mucosa (+6.35 mV, p<0.05), suggesting that this treatment might be effective in vivo Furthermore, plasma that was collected after oral salbutamol treatment induced CFTR activation when administered ex vivo to organoids.This proof-of-concept study suggests that organoids can be used to identify drugs that activate CFTR function in vivo and to select route of administration. PMID:27471203

  1. Peroxisome proliferator-activated receptor gamma agonists as insulin sensitizers: from the discovery to recent progress.

    PubMed

    Cho, Nobuo; Momose, Yu

    2008-01-01

    An epidemic of metabolic diseases including type 2 diabetes and obesity is undermining the health of people living in industrialized societies. There is an urgent need to develop innovative therapeutics. The peroxisome proliferator-activated receptor gamma (PPARgamma) is one of the ligand-activated transcription factors in the nuclear hormone receptor superfamily and a pivotal regulator of glucose and lipid homeostasis. The discovery of PPARgamma as a target of multimodal insulin sensitizers, represented by thiazolidinediones (TZDs), has attracted remarkable scientific interest and had a great impact on the pharmaceutical industry. With the clinical success of the PPARgamma agonists, pioglitazone (Actos) and rosiglitazone (Avandia), development of novel and potent insulin-sensitizing agents with diverse clinical profiles has been accelerated. Currently, a number of PPARgamma agonists from different chemical classes and with varying pharmacological profiles are being developed. Despite quite a few obstacles to the development of PPAR-related drugs, PPARgamma-targeted agents still hold promise. There are new concepts and encouraging evidence emerging that suggest this class can yield improved anti-diabetic agents. This review covers the discovery of TZDs, provides an overview of PPARgamma including the significance of PPARgamma as a drug target, describes the current status of a wide variety of novel PPARgamma ligands including PPAR dual and pan agonists and selective PPARgamma modulators (SPPARgammaMs), and highlights new approaches for identifying agents targeting PPARgamma in the treatment of type 2 diabetes. PMID:19075761

  2. Novel S1P(1) receptor agonists--part 3: from thiophenes to pyridines.

    PubMed

    Bolli, Martin H; Abele, Stefan; Birker, Magdalena; Bravo, Roberto; Bur, Daniel; de Kanter, Ruben; Kohl, Christopher; Grimont, Julien; Hess, Patrick; Lescop, Cyrille; Mathys, Boris; Müller, Claus; Nayler, Oliver; Rey, Markus; Scherz, Michael; Schmidt, Gunther; Seifert, Jürgen; Steiner, Beat; Velker, Jörg; Weller, Thomas

    2014-01-01

    In preceding communications we summarized our medicinal chemistry efforts leading to the identification of potent, selective, and orally active S1P1 agonists such as the thiophene derivative 1. As a continuation of these efforts, we replaced the thiophene in 1 by a 2-, 3-, or 4-pyridine and obtained less lipophilic, potent, and selective S1P1 agonists (e.g., 2) efficiently reducing blood lymphocyte count in the rat. Structural features influencing the compounds' receptor affinity profile and pharmacokinetics are discussed. In addition, the ability to penetrate brain tissue has been studied for several compounds. As a typical example for these pyridine based S1P1 agonists, compound 53 showed EC50 values of 0.6 and 352 nM for the S1P1 and S1P3 receptor, respectively, displayed favorable PK properties, and penetrated well into brain tissue. In the rat, compound 53 maximally reduced the blood lymphocyte count for at least 24 h after oral dosing of 3 mg/kg. PMID:24367923

  3. Monoclonal antibodies to purified muscarinic receptor display agonist-like activity.

    PubMed Central

    Leiber, D; Harbon, S; Guillet, J G; André, C; Strosberg, A D

    1984-01-01

    Monoclonal antibody M-35, which immunoprecipitates native calf brain acetylcholine muscarinic receptor, mimics agonist stimulation of the intact guinea pig myometrium: the antibody, just like carbamoylcholine hydrochloride, causes a rise in intracellular cyclic GMP content, an inhibition of cyclic AMP accumulation due to prostacyclin, and induces uterine contractions. Another antibody, M-23, which reacts with the denatured muscarinic receptor, is devoid of agonist-like activity at the cyclic nucleotide level but is still able to induce contractions of both rat and guinea pig myometrium. The cyclic nucleotide changes caused by both carbamoylcholine and antibody M-35 are inhibited by atropine; this antagonist, which blocks carbamoylcholine-mediated contractions, fails however, to prevent contractions induced by antibodies M-35 and M-23. These results suggest that the information necessary to transmit muscarinic signals is entirely contained in the receptor and that ligands only act to trigger the biological response. The data also imply that the muscarinic receptors of the myometrium are coupled to multiple effector systems. PMID:6087318

  4. Dopamine D3 receptor-preferring agonists induce neurotrophic effects on mesencephalic dopamine neurons.

    PubMed

    Du, Fang; Li, Rui; Huang, Yuangui; Li, Xuping; Le, Weidong

    2005-11-01

    Anti-parkinsonian agents, pramipexole (PPX) and ropinirole (ROP), have been reported to possess neuroprotective properties, both in vitro and in vivo. The mechanisms underlying neuroprotection afforded by the D3-preferring receptor agonists remain poorly understood. The present study demonstrates that incubation of primary mesencephalic cultures with PPX and ROP or the conditioned medium from PPX- or ROP-treated primary cultures induced a marked increase in the number of dopamine (DA) neurons in the cultures. Similar effects can be observed after incubating with the conditioned medium derived from PPX- and ROP-treated substantia nigra astroglia. Meanwhile, PPX and ROP can protect the primary cells from insult of 1-methyl-4-phenylpyridinium (MPP+), the active metabolite of the neurotoxin 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP). Furthermore, the neurotrophic effects of PPX and ROP on mesencephalic dopamine neurons could be significantly blocked by D3 receptor antagonist, but not by D2 receptor antagonist. Moreover, we found that the levels of glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) in the conditioned medium of mesencephalic cultures treated with PPX and ROP were significantly increased. Blocking GDNF and BDNF with the neutralizing antibodies, the neurotrophic effects of PPX and ROP were greatly diminished. These results suggest that D3 dopamine receptor-preferring agonists, PPX and ROP, exert neurotrophic effects on cultured DA neurons by modulating the production of endogenous GDNF and BDNF, which may participate in their neuroprotection. PMID:16307585

  5. Estrogen receptor (ER) agonists and androgen receptor (AR) antagonists in effluents from Norwegian North Sea oil production platforms.

    PubMed

    Tollefsen, Knut-Erik; Harman, Christopher; Smith, Andy; Thomas, Kevin V

    2007-03-01

    The in vitro estrogen receptor (ER) agonist and androgen receptor (AR) antagonist potencies of offshore produced water effluents collected from the Norwegian Sector were determined using recombinant yeast estrogen and androgen screens. Solid phase extraction (SPE) concentrates of the effluents showed E2 agonist activities similar to those previously reported for the United Kingdom (UK) Continental Shelf (<0.1-4 ng E2 L(-1)). No activity was detected in the filtered oil droplets suggesting that produced water ER activity is primarily associated with the dissolved phase. Targeted analysis for methyl- to nonyl-substituted alkylphenol isomers show the occurrence of known ER agonists in the analysed samples. For the first time, AR antagonists were detected in both the dissolved and oil associated phase at concentrations of between 20 and 8000 microg of flutamide equivalents L(-1). The identity of the AR antagonists is unknown, however this represents a significant input into the marine environment of unknown compounds that exert a known biological effect. It is recommended that further analysis using techniques such as bioassay-directed analysis is performed to identify the compounds/groups of compounds that are responsible in order to improve the assessment of the risk posed by produced water discharges to the marine environment. PMID:17258235

  6. Chemokine receptor CXCR3 agonist prevents human T-cell migration in a humanized model of arthritic inflammation.

    PubMed

    O'Boyle, Graeme; Fox, Christopher R J; Walden, Hannah R; Willet, Joseph D P; Mavin, Emily R; Hine, Dominic W; Palmer, Jeremy M; Barker, Catriona E; Lamb, Christopher A; Ali, Simi; Kirby, John A

    2012-03-20

    The recruitment of T lymphocytes during diseases such as rheumatoid arthritis is regulated by stimulation of the chemokine receptors expressed by these cells. This study was designed to assess the potential of a CXCR3-specific small-molecule agonist to inhibit the migration of activated human T cells toward multiple chemokines. Further experiments defined the molecular mechanism for this anti-inflammatory activity. Analysis in vitro demonstrated agonist induced internalization of both CXCR3 and other chemokine receptors coexpressed by CXCR3(+) T cells. Unlike chemokine receptor-specific antagonists, the CXCR3 agonist inhibited migration of activated T cells toward the chemokine mixture in synovial fluid from patients with active rheumatoid arthritis. A humanized mouse air-pouch model showed that intravenous treatment with the CXCR3 agonist prevented inflammatory migration of activated human T cells toward this synovial fluid. A potential mechanism for this action was defined by demonstration that the CXCR3 agonist induces receptor cross-phosphorylation within CXCR3-CCR5 heterodimers on the surface of activated T cells. This study shows that generalized chemokine receptor desensitization can be induced by specific stimulation of a single chemokine receptor on the surface of activated human T cells. A humanized mouse model was used to demonstrate that this receptor desensitization inhibits the inflammatory response that is normally produced by the chemokines present in synovial fluid from patients with active rheumatoid arthritis. PMID:22392992

  7. MDA7: a novel selective agonist for CB2 receptors that prevents allodynia in rat neuropathic pain models

    PubMed Central

    Naguib, M; Diaz, P; Xu, J J; Astruc-Diaz, F; Craig, S; Vivas-Mejia, P; Brown, D L

    2008-01-01

    Background and purpose: There is growing interest in using cannabinoid type 2 (CB2) receptor agonists for the treatment of neuropathic pain. In this report, we describe the pharmacological characteristics of MDA7 (1-[(3-benzyl-3-methyl-2,3-dihydro-1-benzofuran-6-yl)carbonyl]piperidine), a novel CB2 receptor agonist. Experimental approach: We characterized the pharmacological profile of MDA7 by using radioligand-binding assays and in vitro functional assays at human cannabinoid type 1 (CB1) and CB2 receptors. In vitro functional assays were performed at rat CB1 and CB2 receptors. The effects of MDA7 in reversing neuropathic pain were assessed in spinal nerve ligation and paclitaxel-induced neuropathy models in rats. Key results: MDA7 exhibited selectivity and agonist affinity at human and rat CB2 receptors. MDA7 treatment attenuated tactile allodynia produced by spinal nerve ligation or by paclitaxel in a dose-related manner. These effects were selectively antagonized by a CB2 receptor antagonist but not by CB1 or opioid receptor antagonists. MDA7 did not affect rat locomotor activity. Conclusion and implications: MDA7, a novel selective CB2 agonist, was effective in suppressing neuropathic nociception in two rat models without affecting locomotor behaviour. These results confirm the potential for CB2 agonists in the treatment of neuropathic pain. PMID:18846037

  8. Different agonist- and antagonist-induced conformational changes in retinoic acid receptors analyzed by protease mapping.

    PubMed Central

    Keidel, S; LeMotte, P; Apfel, C

    1994-01-01

    The pleiotropic effects of retinoic acid on cell differentiation and proliferation are mediated by two subfamilies of nuclear receptors, the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs). Recently the synthetic retinoid Ro 41-5253 was identified as a selective RAR alpha antagonist. As demonstrated by gel retardation assays, Ro 41-5253 and two related new RAR alpha antagonists do not influence RAR alpha/RXR alpha heterodimerization and DNA binding. In a limited trypsin digestion assay, complexation of RAR alpha with retinoic acid or several other agonistic retinoids altered the degradation of the receptor such that a 30-kDa proteolytic fragment became resistant to proteolysis. This suggests a ligand-induced conformational change, which may be necessary for the interaction of the DNA-bound RAR alpha/RXR alpha heterodimer with other transcription factors. Our results demonstrate that antagonists compete with agonists for binding to RAR alpha and may induce a different structural alteration, suggested by the tryptic resistance of a shorter 25-kDa protein fragment in the digestion assay. This RAR alpha conformation seems to allow RAR alpha/RXR alpha binding to DNA but not the subsequent transactivation of target genes. Protease mapping with C-terminally truncated receptors revealed that the proposed conformational changes mainly occur in the DE regions of RAR alpha. Complexation of RAR beta, RAR gamma, and RXR alpha, as well as the vitamin D3 receptor, with their natural ligands resulted in a similar resistance of fragments to proteolytic digestion. This could mean that ligand-induced conformational changes are a general feature in the hormonal activation of vitamin D3 and retinoid receptors. Images PMID:8264595

  9. A Cannabinoid Receptor Agonist N-Arachidonoyl Dopamine Inhibits Adipocyte Differentiation in Human Mesenchymal Stem Cells

    PubMed Central

    Ahn, Seyeon; Yi, Sodam; Seo, Won Jong; Lee, Myeong Jung; Song, Young Keun; Baek, Seung Yong; Yu, Jinha; Hong, Soo Hyun; Lee, Jinyoung; Shin, Dong Wook; Jeong, Lak Shin; Noh, Minsoo

    2015-01-01

    Endocannabinoids can affect multiple cellular targets, such as cannabinoid (CB) receptors, transient receptor potential cation channel, subfamily V, member 1 (TRPV1) and peroxisome proliferator-activated receptor γ (PPARγ). The stimuli to induce adipocyte differentiation in hBM-MSCs increase the gene transcription of the CB1 receptor, TRPV1 and PPARγ. In this study, the effects of three endocannabinoids, N-arachidonoyl ethanolamine (AEA), N-arachidonoyl dopamine (NADA) and 2-arachidonoyl glycerol (2-AG), on adipogenesis in hBM-MSCs were evaluated. The adipocyte differentiation was promoted by AEA whereas inhibited by NADA. No change was observed by the treatment of non-cytotoxic concentrations of 2-AG. The difference between AEA and NADA in the regulation of adipogenesis is associated with their effects on PPARγ transactivation. AEA can directly activate PPARγ. The effect of AEA on PPARγ in hBM-MSCs may prevail over that on the CB1 receptor mediated signal transduction, giving rise to the AEA-induced promotion of adipogenesis. In contrast, NADA had no effect on the PPARγ activity in the PPARγ transactivation assay. The inhibitory effect of NADA on adipogenesis in hBM-MSCs was reversed not by capsazepine, a TRPV1 antagonist, but by rimonabant, a CB1 antagonist/inverse agonist. Rimonabant by itself promoted adipogenesis in hBM-MSCs, which may be interpreted as the result of the inverse agonism of the CB1 receptor. This result suggests that the constantly active CB1 receptor may contribute to suppress the adipocyte differentiation of hBM-MSCs. Therefore, the selective CB1 agonists that are unable to affect cellular PPARγ activity inhibit adipogenesis in hBM-MSCs. PMID:25995819

  10. Hyperactivation of D1 and A2A receptors contributes to cognitive dysfunction in Huntington's disease.

    PubMed

    Tyebji, Shiraz; Saavedra, Ana; Canas, Paula M; Pliassova, Anna; Delgado-García, José M; Alberch, Jordi; Cunha, Rodrigo A; Gruart, Agnès; Pérez-Navarro, Esther

    2015-02-01

    Stimulation of dopamine D1 receptor (D1R) and adenosine A2A receptor (A2AR) increases cAMP-dependent protein kinase (PKA) activity in the brain. In Huntington's disease, by essentially unknown mechanisms, PKA activity is increased in the hippocampus of mouse models and patients and contributes to hippocampal-dependent cognitive impairment in R6 mice. Here, we show for the first time that D1R and A2AR density and functional efficiency are increased in hippocampal nerve terminals from R6/1 mice, which accounts for increased cAMP levels and PKA signaling. In contrast, PKA signaling was not altered in the hippocampus of Hdh(Q7/Q111) mice, a full-length HD model. In line with these findings, chronic (but not acute) combined treatment with D1R plus A2AR antagonists (SCH23390 and SCH58261, respectively) normalizes PKA activity in the hippocampus, facilitates long-term potentiation in behaving R6/1 mice, and ameliorates cognitive dysfunction. By contrast, chronic treatment with either D1R or A2AR antagonist alone does not modify PKA activity or improve cognitive dysfunction in R6/1 mice. Hyperactivation of both D1R and A2AR occurs in HD striatum and chronic treatment with D1R plus A2AR antagonists normalizes striatal PKA activity but it does not affect motor dysfunction in R6/1 mice. In conclusion, we show that parallel alterations in dopaminergic and adenosinergic signaling in the hippocampus contribute to increase PKA activity, which in turn selectively participates in hippocampal-dependent learning and memory deficits in HD. In addition, our results point to the chronic inhibition of both D1R and A2AR as a novel therapeutic strategy to manage early cognitive impairment in this neurodegenerative disease. PMID:25449908

  11. Role of extracellular domain dimerization in agonist-induced activation of natriuretic peptide receptor A.

    PubMed

    Parat, Marie; McNicoll, Normand; Wilkes, Brian; Fournier, Alain; De Léan, André

    2008-02-01

    Natriuretic peptide receptor (NPR) A is composed of an extracellular domain (ECD) with a ligand binding site, a single transmembrane region, a kinase homology domain, and a guanylyl cyclase domain. The natural agonists atrial and brain natriuretic peptides (ANP, BNP) bind and activate NPRA, leading to cyclic GMP production, which is responsible for their role in cardiovascular homeostasis. Previous studies suggested that stabilization of a dimeric form of NPRA by agonist is essential for receptor activation. However, ligand specificity and sequential steps of this dimerization process have not been investigated. We used radioligand binding, fluorescence resonance energy transfer homoquenching, and molecular modeling to characterize the interaction of human NPRA-ECD with ANP, BNP, the superagonist (Arg(10),Leu(12),Ser(17),Leu(18))-rANP-(1-28), the minimized analog mini-ANP and the antagonist (Arg(6),beta-cyclohexyl-Ala(8),d-Tic(16),Arg(17),Cys(18))-rANP-(6-18)-amide (A71915). ANP binds to preformed ECD dimers and spontaneous dimerization is the rate-limiting step of the ligand binding process. All the studied peptides, including A71915 antagonist, induce a dose-dependent fluorescence homoquenching, specific to dimerization, with potencies highly correlated with their binding affinities. A71915 induced more quenching than other peptides, suggesting stabilization by the antagonist of ECD dimer in a distinct inactive conformation. In summary, these results indicate that the ligand-induced dimerization process of NPRA is different from that for cytokine receptor model. Agonists or antagonists bind to preformed dimeric ECD, leading to dimer stabilization in an active or inactive conformation, respectively. Furthermore, the highly sensitive fluorescence assay designed to assess dimerization could serve as a powerful tool for further detailing the kinetic steps involved in natriuretic peptide receptor binding and activation. PMID:17965196

  12. Estradiol and Estrogen Receptor Agonists Oppose Oncogenic Actions of Leptin in HepG2 Cells.

    PubMed

    Shen, Minqian; Shi, Haifei

    2016-01-01

    Obesity is a significant risk factor for certain cancers, including hepatocellular carcinoma (HCC). Leptin, a hormone secreted by white adipose tissue, precipitates HCC development. Epidemiology data show that men have a much higher incidence of HCC than women, suggesting that estrogens and its receptors may inhibit HCC development and progression. Whether estrogens antagonize oncogenic action of leptin is uncertain. To investigate potential inhibitory effects of estrogens on leptin-induced HCC development, HCC cell line HepG2 cells were treated with leptin in combination with 17 β-estradiol (E2), estrogen receptor-α (ER-α) selective agonist PPT, ER-β selective agonist DPN, or G protein-coupled ER (GPER) selective agonist G-1. Cell number, proliferation, and apoptosis were determined, and leptin- and estrogen-related intracellular signaling pathways were analyzed. HepG2 cells expressed a low level of ER-β mRNA, and leptin treatment increased ER-β expression. E2 suppressed leptin-induced HepG2 cell proliferation and promoted cell apoptosis in a dose-dependent manner. Additionally E2 reversed leptin-induced STAT3 and leptin-suppressed SOCS3, which was mainly achieved by activation of ER-β. E2 also enhanced ERK via activating ER-α and GPER and activated p38/MAPK via activating ER-β. To conclude, E2 and its receptors antagonize the oncogenic actions of leptin in HepG2 cells by inhibiting cell proliferation and stimulating cell apoptosis, which was associated with reversing leptin-induced changes in SOCS3/STAT3 and increasing p38/MAPK by activating ER-β, and increasing ERK by activating ER-α and GPER. Identifying roles of different estrogen receptors would provide comprehensive understanding of estrogenic mechanisms in HCC development and shed light on potential treatment for HCC patients. PMID:26982332

  13. Ractopamine, a Livestock Feed Additive, Is a Full Agonist at Trace Amine–Associated Receptor 1

    PubMed Central

    Grandy, David K.; Janowsky, Aaron

    2014-01-01

    Ractopamine (RAC) is fed to an estimated 80% of all beef, swine, and turkey raised in the United States. It promotes muscle mass development, limits fat deposition, and reduces feed consumption. However, it has several undesirable behavioral side effects in livestock, especially pigs, including restlessness, agitation, excessive oral-facial movements, and aggressive behavior. Numerous in vitro and in vivo studies suggest RAC’s physiological actions begin with its stimulation of β1- and β2-adrenergic receptor–mediated signaling in skeletal muscle and adipose tissue; however, the molecular pharmacology of RAC’s psychoactive effects is poorly understood. Using human cystic fibrosis transmembrane conductance regulator (hCFTR) chloride channels as a sensor for intracellular cAMP, we found that RAC and p-tyramine (TYR) produced concentration-dependent increases in chloride conductance in oocytes coexpressing hCFTR and mouse trace amine–associated receptor 1 (mTAAR1), which was completely reversed by the trace amine–associated receptor 1 (TAAR1)–selective antagonist EPPTB [N-(3-ethoxyphenyl)-4-pyrrolidin-1-yl-3-trifluoromethylbenzamide]. Oocytes coexpressing hCFTR and the human β2-adrenergic receptor showed no response to RAC or TYR. These studies demonstrate that, contrary to expectations, RAC is not an agonist of the human β2-adrenergic receptor but rather a full agonist for mTAAR1. Since TAAR1-mediated signaling can influence cardiovascular tone and behavior in several animal models, our finding that RAC is a full mTAAR1 agonist supports the idea that this novel mechanism of action influences the physiology and behavior of pigs and other species. These findings should stimulate future studies to characterize the pharmacological, physiological, and behavioral actions of RAC in humans and other species exposed to this drug. PMID:24799633

  14. Estradiol and Estrogen Receptor Agonists Oppose Oncogenic Actions of Leptin in HepG2 Cells

    PubMed Central

    Shen, Minqian; Shi, Haifei

    2016-01-01

    Obesity is a significant risk factor for certain cancers, including hepatocellular carcinoma (HCC). Leptin, a hormone secreted by white adipose tissue, precipitates HCC development. Epidemiology data show that men have a much higher incidence of HCC than women, suggesting that estrogens and its receptors may inhibit HCC development and progression. Whether estrogens antagonize oncogenic action of leptin is uncertain. To investigate potential inhibitory effects of estrogens on leptin-induced HCC development, HCC cell line HepG2 cells were treated with leptin in combination with 17 β-estradiol (E2), estrogen receptor-α (ER-α) selective agonist PPT, ER-β selective agonist DPN, or G protein-coupled ER (GPER) selective agonist G-1. Cell number, proliferation, and apoptosis were determined, and leptin- and estrogen-related intracellular signaling pathways were analyzed. HepG2 cells expressed a low level of ER-β mRNA, and leptin treatment increased ER-β expression. E2 suppressed leptin-induced HepG2 cell proliferation and promoted cell apoptosis in a dose-dependent manner. Additionally E2 reversed leptin-induced STAT3 and leptin-suppressed SOCS3, which was mainly achieved by activation of ER-β. E2 also enhanced ERK via activating ER-α and GPER and activated p38/MAPK via activating ER-β. To conclude, E2 and its receptors antagonize the oncogenic actions of leptin in HepG2 cells by inhibiting cell proliferation and stimulating cell apoptosis, which was associated with reversing leptin-induced changes in SOCS3/STAT3 and increasing p38/MAPK by activating ER-β, and increasing ERK by activating ER-α and GPER. Identifying roles of different estrogen receptors would provide comprehensive understanding of estrogenic mechanisms in HCC development and shed light on potential treatment for HCC patients. PMID:26982332

  15. Endomorphin-2: a biased agonist at the μ-opioid receptor.

    PubMed

    Rivero, Guadalupe; Llorente, Javier; McPherson, Jamie; Cooke, Alex; Mundell, Stuart J; McArdle, Craig A; Rosethorne, Elizabeth M; Charlton, Steven J; Krasel, Cornelius; Bailey, Christopher P; Henderson, Graeme; Kelly, Eamonn

    2012-08-01

    Previously we correlated the efficacy for G protein activation with that for arrestin recruitment for a number of agonists at the μ-opioid receptor (MOPr) stably expressed in HEK293 cells. We suggested that the endomorphins (endomorphin-1 and -2) might be biased toward arrestin recruitment. In the present study, we investigated this phenomenon in more detail for endomorphin-2, using endogenous MOPr in rat brain as well as MOPr stably expressed in HEK293 cells. For MOPr in neurons in brainstem locus ceruleus slices, the peptide agonists [d-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) and endomorphin-2 activated inwardly rectifying K(+) current in a concentration-dependent manner. Analysis of these responses with the operational model of pharmacological agonism confirmed that endomorphin-2 had a much lower operational efficacy for G protein-mediated responses than did DAMGO at native MOPr in mature neurons. However, endomorphin-2 induced faster desensitization of the K(+) current than did DAMGO. In addition, in HEK293 cells stably expressing MOPr, the ability of endomorphin-2 to induce phosphorylation of Ser375 in the COOH terminus of the receptor, to induce association of arrestin with the receptor, and to induce cell surface loss of receptors was much more efficient than would be predicted from its efficacy for G protein-mediated signaling. Together, these results indicate that endomorphin-2 is an arrestin-biased agonist at MOPr and the reason for this is likely to be the ability of endomorphin-2 to induce greater phosphorylation of MOPr than would be expected from its ability to activate MOPr and to induce activation of G proteins. PMID:22553358

  16. Endomorphin-2: A Biased Agonist at the μ-Opioid Receptor

    PubMed Central

    Rivero, Guadalupe; Llorente, Javier; McPherson, Jamie; Cooke, Alex; Mundell, Stuart J.; McArdle, Craig A.; Rosethorne, Elizabeth M.; Charlton, Steven J.; Krasel, Cornelius; Bailey, Christopher P.; Henderson, Graeme

    2012-01-01

    Previously we correlated the efficacy for G protein activation with that for arrestin recruitment for a number of agonists at the μ-opioid receptor (MOPr) stably expressed in HEK293 cells. We suggested that the endomorphins (endomorphin-1 and -2) might be biased toward arrestin recruitment. In the present study, we investigated this phenomenon in more detail for endomorphin-2, using endogenous MOPr in rat brain as well as MOPr stably expressed in HEK293 cells. For MOPr in neurons in brainstem locus ceruleus slices, the peptide agonists [d-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO) and endomorphin-2 activated inwardly rectifying K+ current in a concentration-dependent manner. Analysis of these responses with the operational model of pharmacological agonism confirmed that endomorphin-2 had a much lower operational efficacy for G protein-mediated responses than did DAMGO at native MOPr in mature neurons. However, endomorphin-2 induced faster desensitization of the K+ current than did DAMGO. In addition, in HEK293 cells stably expressing MOPr, the ability of endomorphin-2 to induce phosphorylation of Ser375 in the COOH terminus of the receptor, to induce association of arrestin with the receptor, and to induce cell surface loss of receptors was much more efficient than would be predicted from its efficacy for G protein-mediated signaling. Together, these results indicate that endomorphin-2 is an arrestin-biased agonist at MOPr and the reason for this is likely to be the ability of endomorphin-2 to induce greater phosphorylation of MOPr than would be expected from its ability to activate MOPr and to induce activation of G proteins. PMID:22553358

  17. Influence of the dopamine receptor agonists fenoldopam and quinpirole in the rat superior mesenteric vascular bed.

    PubMed Central

    Dupont, A. G.; Lefebvre, R. A.; Vanderniepen, P.

    1987-01-01

    The effect of local administration of the dopamine 2 (DA2)-receptor agonist quinpirole and of the DA1-receptor agonist fenoldopam was studied in the in situ, constant flow autoperfused, superior mesenteric vascular bed of the rat. Local infusion of quinpirole (30 micrograms kg-1 min-1 for 5 min) had no effect on baseline perfusion pressure; it reduced the pressor responses to electrical stimulation (4 Hz, 1 ms, supramaximal voltage) of the periarterial sympathetic nerves to 45.6 +/- 2.1% of its original value but did not modify similar pressor responses produced by locally administered noradrenaline. The inhibitory effect of quinpirole was antagonized by the selective DA2-receptor antagonist domperidone (10 micrograms kg-1) but not by the selective DA1-receptor antagonist SCH 23390 (50 micrograms kg-1). Local infusion of fenoldopam (30 micrograms kg-1 min-1 for 5 min) reduced baseline perfusion pressure to 89.9 +/- 1.9%, increased the pressor response to electrical stimulation (4 Hz, 1 ms, supramaximal voltage) of the periarterial nerves to 134.7 +/- 14.0%, but reduced the pressor response to locally administered noradrenaline to 37.2 +/- 8.2%. Similar pressor responses induced by the selective alpha 1-adrenoceptor agonist phenylephrine were also reduced by fenoldopam (to 38.4 +/- 6.4%), but responses to locally administered angiotensin II were not modified. Pretreatment with SCH 23390 (50 micrograms kg-1) antagonized the effect of fenoldopam on baseline perfusion pressure, but had no influence on the effect of fenoldopam on responses to electrical stimulation or to noradrenaline. Pretreatment with the selective alpha 2-adrenoceptor antagonist rauwolscine (100 micrograms kg-1) had no effect on the reduction in baseline perfusion pressure induced by fenoldopam nor on its inhibitory effect on the response to noradrenaline, but it antagonized the stimulatory effect of fenoldopam on the response to electrical stimulation.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2886174

  18. The adenosine 2A receptor agonist GW328267C improves lung function after acute lung injury in rats.

    PubMed

    Folkesson, Hans G; Kuzenko, Stephanie R; Lipson, David A; Matthay, Michael A; Simmons, Mark A

    2012-08-01

    There is a significant unmet need for treatments of patients with acute lung injury (ALI) and/or acute respiratory distress syndrome (ARDS). The primary mechanism that leads to resolution of alveolar and pulmonary edema is active vectorial Na(+) and Cl(-) transport across the alveolar epithelium. Several studies have suggested a role for adenosine receptors in regulating this fluid transport in the lung. Furthermore, these studies point to the A(2A) subtype of adenosine receptor (A(2A)R) as playing a role to enhance fluid transport, suggesting that activation of the A(2A)R may enhance alveolar fluid clearance (AFC). The current studies test the potential therapeutic value of the A(2A)R agonist GW328267C to accelerate resolution of alveolar edema and ALI/ARDS in rats. GW328267C, at concentrations of 10(-5) M to 10(-3) M, instilled into the airspaces, increased AFC in control animals. GW328267C did not increase AFC beyond that produced by maximal β-adrenergic stimulation. The effect of GW328267C was inhibited by amiloride but was not affected by cystic fibrosis transmembrane conductance regulator inhibition. The drug was tested in three models of ALI, HCl instillation 1 h, LPS instillation 16 h, and live Escherichia coli instillation 2 h before GW328267C instillation. After either type of injury, GW328267C (10(-4) M) decreased pulmonary edema formation and restored AFC, measured 1 h after GW328267C instillation. These findings show that GW328267C has beneficial effects in experimental models of ALI and may be a useful agent for treating patients with ALI or prophylactically to prevent ALI. PMID:22659881

  19. Design, synthesis and biological activity of flavonoid derivatives as selective agonists for neuromedin U 2 receptor.

    PubMed

    Ma, Ming-Liang; Li, Ming; Gou, Jiao-Jiao; Ruan, Tian-Yu; Jin, Hai-Shan; Zhang, Ling-Hong; Wu, Liang-Chun; Li, Xiao-Yan; Hu, Ying-He; Wen, Ke; Zhao, Zheng

    2014-11-01

    Central neuromedin U 2 receptor (NMU2R) plays important roles in the regulation of food intake and body weight. Identification of NMU2R agonists may lead to the development of pharmaceutical agents to treat obesity. Based on the structure of rutin, a typical flavonoid and one of the NMU2R agonists we previously identified from an in-house made natural product library, 30 flavonoid derivatives have been synthesized and screened on a cell-based reporter gene assay. A number of compounds were found to be selective and highly potent to NMU2R. For example, the EC50 value of compound NRA 4 is very close to that of NMU, the endogenous peptide ligand of NMU2R. Structure-activity relationship analysis revealed that a 3-hydroxyl group in ring C and a 2'-fluoride group in ring B were essential for this class of compounds to be active against NMU2R. PMID:25262941

  20. A peroxisome proliferator-activated receptor-gamma agonist and other constituents from Chromolaena odorata.

    PubMed

    Dat, Nguyen Tien; Lee, Kyeong; Hong, Young-Soo; Kim, Young Ho; Minh, Chau Van; Lee, Jung Joon

    2009-06-01

    Peroxisome proliferator-activated receptors (PPARs) are key regulators of lipid and glucose metabolism and have become important therapeutic targets for various diseases. The phytochemical investigation of the chloroform-soluble extract of Chromolaena odorata led to the isolation of a PPAR-gamma agonist, (9 S,13 R)-12-oxo-phytodienoic acid (1), together with 12 other compounds. The structures of chromomoric acid G (2), a new dehydrogenated derivative of 1, and chromolanone (3) were elucidated based on spectroscopic methods. Compound 1 showed a significant effect on PPAR-gamma activation in comparison with rosiglitazone. However, compound 2 was inactive, suggesting that the dehydrogenation of the prostaglandin-like structure in 1 abrogates its PPAR-gamma agonistic activity. PMID:19242902

  1. The Effect of Glutamate Receptor Agonists on Mouse Retinal Astrocyte [Ca2+]i

    PubMed Central

    Blandford, Stephanie N.

    2016-01-01

    Calcium-imaging techniques were used to determine if mouse retinal astrocytes in situ respond to agonists of ionotropic (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, AMPA; N-methyl-D-aspartate, NMDA) and metabotropic (S-3,5-dihydroxyphenylglycine, DHPG; trans-1-amino-1,3-cyclopentanedicarboxylic acid, ACPD) glutamate receptors. In most cases we found no evidence that retinal astrocyte intracellular calcium ion concentration ([Ca2+]i) increased in response to these glutamate agonists. The one exception was AMPA that increased [Ca2+]i in some, but not all, mouse retinal astrocytes in situ. However, AMPA did not increase [Ca2+]i in mouse retinal astrocytes in vitro, suggesting that the effect of AMPA in situ may be indirect. PMID:27413752

  2. Prospects for Creation of Cardioprotective and Antiarrhythmic Drugs Based on Opioid Receptor Agonists.

    PubMed

    Maslov, Leonid N; Khaliulin, Igor; Oeltgen, Peter R; Naryzhnaya, Natalia V; Pei, Jian-Ming; Brown, Stephen A; Lishmanov, Yury B; Downey, James M

    2016-09-01

    It has now been demonstrated that the μ, δ1 , δ2 , and κ1 opioid receptor (OR) agonists represent the most promising group of opioids for the creation of drugs enhancing cardiac tolerance to the detrimental effects of ischemia/reperfusion (I/R). Opioids are able to prevent necrosis and apoptosis of cardiomyocytes during I/R and improve cardiac contractility in the reperfusion period. The OR agonists exert an infarct-reducing effect with prophylactic administration and prevent reperfusion-induced cardiomyocyte death when ischemic injury of heart has already occurred; that is, opioids can mimic preconditioning and postconditioning phenomena. Furthermore, opioids are also effective in preventing ischemia-induced arrhythmias. PMID:27197922

  3. CPG-7909 (PF-3512676, ProMune): toll-like receptor-9 agonist in cancer therapy.

    PubMed

    Murad, Yanal M; Clay, Timothy M; Lyerly, H Kim; Morse, Michael A

    2007-08-01

    Stimulation of toll-like receptor (TLR)9 activates human plasmacytoid dendritic cells and B cells, and induces potent innate immune responses in preclinical tumor models and in patients. CpG oligodeoxynucleotides (ODNs) are TLR9 agonists that show promising results as vaccine adjuvants and in the treatment of cancers, infections, asthma and allergy. PF-3512676 (ProMune) was developed as a TLR9 agonist for the treatment of cancer as monotherapy and as an adjuvant in combination with chemo- and immunotherapy. Phase I and II trials have tested this drug in several hematopoietic and solid tumors. Pfizer has initiated Phase III trials to test PF-3512676 in combination with standard chemotherapy for non-small-cell lung cancer. PMID:17696823

  4. Regulation of specific target genes and biological responses by estrogen receptor subtype agonists

    PubMed Central

    Leitman, Dale C.; Paruthiyil, Sreenivasan; Vivar, Omar I.; Saunier, Elise F.; Herber, Candice B.; Cohen, Isaac; Tagliaferri, Mary; Speed, Terence P.

    2010-01-01

    Estrogenic effects are mediated through two estrogen receptor (ER) subtypes, ERα and ERβ. Estrogens are the most commonly prescribed drugs to treat menopausal conditions, but by non-selectively triggering both ERα and ERβ pathways in different tissues they can cause serious adverse effects. The different sizes of the binding pockets and sequences of their activation function domains indicate that ERα and ERβ should have different specificities for ligands and biological responses that can be exploited for designing safer and more selective estrogens. ERα and ERβ regulate different genes by binding to different regulatory elements and recruiting different transcription and chromatin remodeling factors that are expressed in a cell-specific manner. ERα- and ERβ-selective agonists have been identified that demonstrate that the two ERs produce distinct biological effects. ERα and ERβ agonists are promising new approach for treating specific conditions associated with menopause. PMID:20951642

  5. Behavioural effects of the dopamine D3 receptor agonist 7-OH-DPAT in rats.

    PubMed

    Ferrari, F; Giuliani, D

    1995-01-01

    The putative selective dopamine (DA) D3 receptor agonist, 7-OH-DPAT (25-4000 micrograms kg-1), enhanced stretching-yawning and penile erection in male rats, besides respectively increasing and decreasing sedation at low (25-200 micrograms kg-1) and high (1600 and 4000 micrograms kg-1) doses and inducing stereotypy from 800 micrograms kg-1 upwards. The DA D2 antagonist, (-) eticlopride (10 and 20 micrograms kg-1), antagonized stretching-yawning and penile erection induced by a low dose of 7-OH-DPAT (50 micrograms kg-1) but not those produced by high doses (1600 and 4000 micrograms kg-1), when stereotyped behaviour, on the other hand, was potently inhibited. Comparative experiments performed with the DA agonist SND 919 gave similar results. PMID:8668649

  6. Striatal Pre- and Postsynaptic Profile of Adenosine A2A Receptor Antagonists

    PubMed Central

    Quiroz, César; Beaumont, Vahri; Goldberg, Steven R.; Lluís, Carme; Cortés, Antoni; Franco, Rafael; Casadó, Vicent; Canela, Enric I.; Ferré, Sergi

    2011-01-01

    Striatal adenosine A2A receptors (A2ARs) are highly expressed in medium spiny neurons (MSNs) of the indirect efferent pathway, where they heteromerize with dopamine D2 receptors (D2Rs). A2ARs are also localized presynaptically in cortico-striatal glutamatergic terminals contacting MSNs of the direct efferent pathway, where they heteromerize with adenosine A1 receptors (A1Rs). It has been hypothesized that postsynaptic A2AR antagonists should be useful in Parkinson's disease, while presynaptic A2AR antagonists could be beneficial in dyskinetic disorders, such as Huntington's disease, obsessive-compulsive disorders and drug addiction. The aim or this work was to determine whether selective A2AR antagonists may be subdivided according to a preferential pre- versus postsynaptic mechanism of action. The potency at blocking the motor output and striatal glutamate release induced by cortical electrical stimulation and the potency at inducing locomotor activation were used as in vivo measures of pre- and postsynaptic activities, respectively. SCH-442416 and KW-6002 showed a significant preferential pre- and postsynaptic profile, respectively, while the other tested compounds (MSX-2, SCH-420814, ZM-241385 and SCH-58261) showed no clear preference. Radioligand-binding experiments were performed in cells expressing A2AR-D2R and A1R-A2AR heteromers to determine possible differences in the affinity of these compounds for different A2AR heteromers. Heteromerization played a key role in the presynaptic profile of SCH-442416, since it bound with much less affinity to A2AR when co-expressed with D2R than with A1R. KW-6002 showed the best relative affinity for A2AR co-expressed with D2R than co-expressed with A1R, which can at least partially explain the postsynaptic profile of this compound. Also, the in vitro pharmacological profile of MSX-2, SCH-420814, ZM-241385 and SCH-58261 was is in accordance with their mixed pre- and postsynaptic profile. On the basis of their preferential

  7. Past, present and future of A2A adenosine receptor antagonists in the therapy of Parkinson’s disease

    PubMed Central

    Armentero, Marie Therese; Pinna, Annalisa; Ferré, Sergi; Lanciego, José Luis; Müller, Christa E.; Franco, Rafael

    2011-01-01

    Several selective antagonists for adenosine A2A receptors (A2AR) are currently under evaluation in clinical trials (phases I to III) to treat Parkinson’s disease, and they will probably soon reach the market. The usefulness of these antagonists has been deduced from studies demonstrating functional interactions between dopamine D2 and adenosine A2A receptors in the basal ganglia. At present it is believed that A2AR antagonists can be used in combination with the dopamine precursor L-DOPA to minimize the motor symptoms of Parkinson’s patients. However, a considerable body of data indicates that in addition to ameliorating motor symptoms, adenosine A2AR antagonists may also prevent neurodegeneration. Despite these promising indications, one further issue must be considered in order to develop fully optimized anti-parkinsonian drug therapy, namely the existence of receptor (hetero)dimers/oligomers of G protein-coupled receptors, a topic currently the focus of intense debate within the scientific community. Dopamine D2 receptors (D2Rs) expressed in the striatum are known to form heteromers with A2A adenosine receptors. Thus, the development of heteromer-specific A2A receptor antagonists represents a promising strategy for the identification of more selective and safer drugs. PMID:21810444

  8. An Accessory Agonist Binding Site Promotes Activation of α4β2* Nicotinic Acetylcholine Receptors*

    PubMed Central

    Wang, Jingyi; Kuryatov, Alexander; Sriram, Aarati; Jin, Zhuang; Kamenecka, Theodore M.; Kenny, Paul J.; Lindstrom, Jon

    2015-01-01

    Neuronal nicotinic acetylcholine receptors containing α4, β2, and sometimes other subunits (α4β2* nAChRs) regulate addictive and other behavioral effects of nicotine. These nAChRs exist in several stoichiometries, typically with two high affinity acetylcholine (ACh) binding sites at the interface of α4 and β2 subunits and a fifth accessory subunit. A third low affinity ACh binding site is formed when this accessory subunit is α4 but not if it is β2. Agonists selective for the accessory ACh site, such as 3-[3-(3-pyridyl)-1,2,4-oxadiazol-5-yl]benzonitrile (NS9283), cannot alone activate a nAChR but can facilitate more efficient activation in combination with agonists at the canonical α4β2 sites. We therefore suggest categorizing agonists according to their site selectivity. NS9283 binds to the accessory ACh binding site; thus it is termed an accessory site-selective agonist. We expressed (α4β2)2 concatamers in Xenopus oocytes with free accessory subunits to obtain defined nAChR stoichiometries and α4/accessory subunit interfaces. We show that α2, α3, α4, and α6 accessory subunits can form binding sites for ACh and NS9283 at interfaces with α4 subunits, but β2 and β4 accessory subunits cannot. To permit selective blockage of the accessory site, α4 threonine 126 located on the minus side of α4 that contributes to the accessory site, but not the α4β2 sites, was mutated to cysteine. Alkylation of this cysteine with a thioreactive reagent blocked activity of ACh and NS9283 at the accessory site. Accessory agonist binding sites are promising drug targets. PMID:25869137

  9. Fine-tuning somatostatin receptor signalling by agonist-selective phosphorylation and dephosphorylation: IUPHAR Review 5

    PubMed Central

    Schulz, Stefan; Lehmann, Andreas; Kliewer, Andrea; Nagel, Falko

    2014-01-01

    The biological actions of somatostatin are mediated by a family of five GPCRs, named sst1 to sst5. Somatostatin receptors exhibit equally high-binding affinities to their natural ligand somatostatin-14 and largely overlapping distributions. The overexpression of somatostatin receptors in human tumours is the molecular basis for diagnostic and therapeutic application of the stable somatostatin analogues octreotide, lanreotide and pasireotide. The efficiency of somatostatin receptor signalling is tightly regulated and ultimately limited by the coordinated phosphorylation and dephosphorylation of intracellular carboxyl-terminal serine and threonine residues. Here, we review and discuss recent progress in the generation and application of phosphosite-specific antibodies for human sst2 and sst5 receptors. These phosphosite-specific antibodies are unique tools to monitor the spatial and temporal dynamics of receptors phosphorylation and dephosphorylation. Using a combined approach of phosphosite-specific antibodies and siRNA knock-down screening, relevant kinases and phosphatases were identified. Emerging evidence suggests distinct mechanisms of agonist-selective fine-tuning for individual somatostatin receptors. The recently uncovered differences in phosphorylation and dephosphorylation of these receptors may hence be of physiological significance in mediating responses to acute, persistent or repeated stimuli in a variety of target tissues. PMID:24328848

  10. Trialkyltin Rexinoid-X Receptor Agonists Selectively Potentiate Thyroid Hormone Induced Programs of Xenopus laevis Metamorphosis.

    PubMed

    Mengeling, Brenda J; Murk, Albertinka J; Furlow, J David

    2016-07-01

    The trialkyltins tributyltin (TBT) and triphenyltin (TPT) can function as rexinoid-X receptor (RXR) agonists. We recently showed that RXR agonists can alter thyroid hormone (TH) signaling in a mammalian pituitary TH-responsive reporter cell line, GH3.TRE-Luc. The prevalence of TBT and TPT in the environment prompted us to test whether they could also affect TH signaling. Both trialkyltins induced the integrated luciferase reporter alone and potentiated TH activation at low doses. Trimethyltin, which is not an RXR agonist, did not. We turned to a simple, robust, and specific in vivo model system of TH action: metamorphosis of Xenopus laevis, the African clawed frog. Using a precocious metamorphosis assay, we found that 1nM TBT and TPT, but not trimethyltin, greatly potentiated the effect of TH treatment on resorption phenotypes of the tail, which is lost at metamorphosis, and in the head, which undergoes extensive remodeling including gill loss. Consistent with these responses, TH-induced caspase-3 activation in the tail was enhanced by cotreatment with TBT. Induction of a transgenic reporter gene and endogenous collagenase 3 (mmp13) and fibroblast-activating protein-α (fap) genes were not induced by TBT alone, but TH induction was significantly potentiated by TBT. However, induction of other TH receptor target genes such as TRβ and deiodinase 3 by TH were not affected by TBT cotreatment. These data indicate that trialkyltins that can function as RXR agonists can selectively potentiate gene expression and resultant morphological programs directed by TH signaling in vivo. PMID:27167774

  11. Identification and optimization of small-molecule agonists of the human relaxin hormone receptor RXFP1.

    PubMed

    Xiao, Jingbo; Huang, Zaohua; Chen, Catherine Z; Agoulnik, Irina U; Southall, Noel; Hu, Xin; Jones, Raisa E; Ferrer, Marc; Zheng, Wei; Agoulnik, Alexander I; Marugan, Juan J

    2013-01-01

    The anti-fibrotic, vasodilatory and pro-angiogenic therapeutic properties of recombinant relaxin peptide hormone have been investigated in several diseases, and recent clinical trial data has shown benefit in treating acute heart failure. However, the remodelling capacity of these peptide hormones is difficult to study in chronic settings because of their short half-life and the need for intravenous administration. Here we present the first small-molecule series of human relaxin/insulin-like family peptide receptor 1 agonists. These molecules display similar efficacy as the natural hormone in several functional assays. Mutagenesis studies indicate that the small molecules activate relaxin receptor through an allosteric site. These compounds have excellent physical and in vivo pharmacokinetic properties to support further investigation of relaxin biology and animal efficacy studies of the therapeutic benefits of relaxin/insulin-like family peptide receptor 1 activation. PMID:23764525

  12. Revealing a steroid receptor ligand as a unique PPAR[gamma] agonist

    SciTech Connect

    Lin, Shengchen; Han, Ying; Shi, Yuzhe; Rong, Hui; Zheng, Songyang; Jin, Shikan; Lin, Shu-Yong; Lin, Sheng-Cai; Li, Yong

    2012-06-28

    Peroxisome proliferator-activated receptor gamma (PPAR{gamma}) regulates metabolic homeostasis and is a molecular target for anti-diabetic drugs. We report here the identification of a steroid receptor ligand, RU-486, as an unexpected PPAR{gamma} agonist, thereby uncovering a novel signaling route for this steroid drug. Similar to rosiglitazone, RU-486 modulates the expression of key PPAR{gamma} target genes and promotes adipocyte differentiation, but with a lower adipogenic activity. Structural and functional studies of receptor-ligand interactions reveal the molecular basis for a unique binding mode for RU-486 in the PPAR{gamma} ligand-binding pocket with distinctive properties and epitopes, providing the molecular mechanisms for the discrimination of RU-486 from thiazolidinediones (TZDs) drugs. Our findings together indicate that steroid compounds may represent an alternative approach for designing non-TZD PPAR{gamma} ligands in the treatment of insulin resistance.

  13. Adenosine A2A receptor deficiency alleviates blast-induced cognitive dysfunction

    PubMed Central

    Ning, Ya-Lei; Yang, Nan; Chen, Xing; Xiong, Ren-Ping; Zhang, Xiu-Zhu; Li, Ping; Zhao, Yan; Chen, Xing-Yun; Liu, Ping; Peng, Yan; Wang, Zheng-Guo; Chen, Jiang-Fan; Zhou, Yuan-Guo

    2013-01-01

    Traumatic brain injury (TBI), particularly explosive blast-induced TBI (bTBI), has become the most prevalent injury among military personnel. The disruption of cognitive function is one of the most serious consequences of bTBI because its long-lasting effects prevent survivors fulfilling their active duty and resuming normal civilian life. However, the mechanisms are poorly understood and there is no treatment available. This study investigated the effects of adenosine A2A receptor (A2AR) on bTBI-induced cognitive deficit, and explored the underlying mechanisms. After being subjected to moderate whole-body blast injury, mice lacking the A2AR (A2AR knockout (KO)) showed less severity and shorter duration of impaired spatial reference memory and working memory than wild-type mice did. In addition, bTBI-induced cortical and hippocampal lesions, as well as proinflammatory cytokine expression, glutamate release, edema, cell loss, and gliosis in both early and prolonged phases of the injury, were significantly attenuated in A2AR KO mice. The results suggest that early injury and chronic neuropathological damages are important mechanisms of bTBI-induced cognitive impairment, and that the impairment can be attenuated by preventing A2AR activation. These findings suggest that A2AR antagonism is a potential therapeutic strategy for mild-to-moderate bTBI and consequent cognitive impairment. PMID:23921902

  14. Interactions of dopamine agonists with brain D1 receptors labeled by /sup 3/H-antagonists. Evidence for the presence of high and low affinity agonist-binding states

    SciTech Connect

    Leff, S.E.; Hamblin, M.W.; Creese, I.

    1985-02-01

    The interactions of dopaminergic agonists and antagonists with /sup 3/H-antagonist labeled D1 dopamine receptors of rat striatum have been characterized. (/sup 3/H)Flupentixol has been found to selectively label D1 dopamine receptors when its binding to D2 dopamine receptors is blocked by the inclusion of D2 selective concentrations of unlabeled spiroperidol or domperidone. Antagonist//sup 3/H-antagonist competition curves are of uniformly steep slope (nH . 1.0) suggesting the presence of a single D1 dopamine receptor. Agonist//sup 3/H-antagonist competition curves are extremely shallow (nH less than or equal to 0.5) for agonists of high relative efficacy, suggesting the presence of heterogeneous populations of agonist-binding states of the D1 dopamine receptor. Computer-modeling techniques were used to estimate affinities and relative site densities for these heterogeneous binding states. This analysis indicates that the ratio of agonist affinities for low and high affinity agonist-binding states is correlated with agonist relative efficacies in activating adenylate cyclase in membrane homogenates. Under the assay conditions employed, the addition of saturating concentrations of guanine nucleotides reduced, but did not abolish, the relative density of high affinity agonist-binding sites. These binding data can, at least in part, be explained by postulating two states of the D1 dopamine receptor, inducible by agonists but not by antagonists and modulated by guanine nucleotides.

  15. A1-, A2A- and A3-subtype adenosine receptors modulate intraocular pressure in the mouse

    PubMed Central

    Avila, Marcel Y; Stone, Richard A; Civan, Mortimer M

    2001-01-01

    Despite the potential importance of the mouse in studying the pharmacology of aqueous dynamics, measurement of intraocular pressure (IOP) in its very small eye has been problematic. Utilizing a novel servo-null electrophysiologic approach recently applied to the mouse, we have identified a diversity of adenosine-receptor mechanisms in modulating IOP in this species. We report the first evidence that A3 receptors increase IOP in any species, and verify in the mouse reports with larger mammals that A1 receptors lower and A2A receptors increase IOP. PMID:11564641

  16. Detection of retinoic acid receptor agonistic activity and identification of causative compounds in municipal wastewater treatment plants in Japan.

    PubMed

    Sawada, Kazuko; Inoue, Daisuke; Wada, Yuichiro; Sei, Kazunari; Nakanishi, Tsuyoshi; Ike, Michihiko

    2012-02-01

    Retinoic acid (RA) receptor (RAR) agonists are potential toxicants that can cause teratogenesis in vertebrates. To determine the occurrence of RAR agonists in municipal wastewater treatment plants (WWTPs), we examined the RARα agonistic activities of influent and effluent samples from several municipal WWTPs in Osaka, Japan, using a yeast two-hybrid assay. Significant RARα agonistic activity was detected in all the influent samples investigated, suggesting that municipal wastewater consistently contains RAR agonists. Fractionations using high-performance liquid chromatography, directed by the bioassay, found several bioactive peaks from influent samples. The RAR agonists, all-trans RA (atRA), 13-cis RA (13cRA), 4-oxo-atRA, and 4-oxo-13cRA, possibly arising from human urine, were identified by liquid chromatography ion trap time-of-flight mass spectrometry. Quantification of the identified compounds in municipal WWTPs confirmed that they were responsible for the majority of RARα agonistic activity in WWTP influents, and also revealed they were readily removed from wastewater by activated sludge treatment. Simultaneous measurement of the RARα agonistic activity revealed that although total activity typically declined concomitant with the reduction of the four identified compounds, it remained high after the decline of RAs and 4-oxo-RAs in one WWTP, suggesting the occurrence of unidentified RAR agonists during the activated sludge treatment. PMID:22095885

  17. β-Arrestin-Selective G Protein-Coupled Receptor Agonists Engender Unique Biological Efficacy in Vivo

    PubMed Central

    Gesty-Palmer, Diane; Yuan, Ling; Martin, Bronwen; Wood, William H.; Lee, Mi-Hye; Janech, Michael G.; Tsoi, Lam C.; Zheng, W. Jim; Maudsley, Stuart

    2013-01-01

    Biased G protein-coupled receptor agonists are orthosteric ligands that possess pathway-selective efficacy, activating or inhibiting only a subset of the signaling repertoire of their cognate receptors. In vitro, d-Trp12,Tyr34-bPTH(7–34) [bPTH(7–34)], a biased agonist for the type 1 PTH receptor, antagonizes receptor-G protein coupling but activates arrestin-dependent signaling. In vivo, both bPTH(7–34) and the conventional agonist hPTH(1–34) stimulate anabolic bone formation. To understand how two PTH receptor ligands with markedly different in vitro efficacy could elicit similar in vivo responses, we analyzed transcriptional profiles from calvarial bone of mice treated for 8 wk with vehicle, bPTH(7–34) or hPTH(1–34). Treatment of wild-type mice with bPTH(7–34) primarily affected pathways that promote expansion of the osteoblast pool, notably cell cycle regulation, cell survival, and migration. These responses were absent in β-arrestin2-null mice, identifying them as downstream targets of β-arrestin2-mediated signaling. In contrast, hPTH(1–34) primarily affected pathways classically associated with enhanced bone formation, including collagen synthesis and matrix mineralization. hPTH(1–34) actions were less dependent on β-arrestin2, as might be expected of a ligand capable of G protein activation. In vitro, bPTH(7–34) slowed the rate of preosteoblast proliferation, enhanced osteoblast survival when exposed to an apoptotic stimulus, and stimulated cell migration in wild-type, but not β-arrestin2-null, calvarial osteoblasts. These results suggest that bPTH(7–34) and hPTH(1–34) affect bone mass in vivo through predominantly separate genomic mechanisms created by largely distinct receptor-signaling networks and demonstrate that functional selectivity can be exploited to change the quality of G protein-coupled receptor efficacy. PMID:23315939

  18. The pain receptor TRPV1 displays agonist-dependent activation stoichiometry.

    PubMed

    Hazan, Adina; Kumar, Rakesh; Matzner, Henry; Priel, Avi

    2015-01-01

    The receptor channel TRPV1 (Transient Receptor Potential Vanilloid 1) is expressed by primary afferent sensory neurons of the pain pathway, where it functions as a sensor of noxious heat and various chemicals, including eicosanoids, capsaicin, protons and peptide toxins. Comprised of four identical subunits that organize into a non-selective cationic permeable channel, this receptor has a variety of binding sites responsible for detecting their respective agonists. Although its physiological role as a chemosensor has been described in detail, the stoichiometry of TRPV1 activation by its different ligands remains unknown. Here, we combined the use of concatemeric constructs harboring mutated binding sites with patch-clamp recordings in order to determine the stoichiometry for TRPV1 activation through the vanilloid binding site and the outer-pore domain by capsaicin and protons, respectively. We show that, while a single capsaicin-bound subunit was sufficient to achieve a maximal open-channel lifetime, all four proton-binding sites were required. Thus, our results demonstrate a distinct stoichiometry of TRPV1 activation through two of its different agonist-binding domains. PMID:26194846

  19. Structural Determinants for the Binding of Morphinan Agonists to the μ-Opioid Receptor.

    PubMed

    Cong, Xiaojing; Campomanes, Pablo; Kless, Achim; Schapitz, Inga; Wagener, Markus; Koch, Thomas; Carloni, Paolo

    2015-01-01

    Atomistic descriptions of the μ-opioid receptor (μOR) noncovalently binding with two of its prototypical morphinan agonists, morphine (MOP) and hydromorphone (HMP), are investigated using molecular dynamics (MD) simulations. Subtle differences between the binding modes and hydration properties of MOP and HMP emerge from the calculations. Alchemical free energy perturbation calculations show qualitative agreement with in vitro experiments performed in this work: indeed, the binding free energy difference between MOP and HMP computed by forward and backward alchemical transformation is 1.2±1.1 and 0.8±0.8 kcal/mol, respectively, to be compared with 0.4±0.3 kcal/mol from experiment. Comparison with an MD simulation of μOR covalently bound with the antagonist β-funaltrexamine hints to agonist-induced conformational changes associated with an early event of the receptor's activation: a shift of the transmembrane helix 6 relative to the transmembrane helix 3 and a consequent loss of the key R165-T279 interhelical hydrogen bond. This finding is consistent with a previous proposal suggesting that the R165-T279 hydrogen bond between these two helices indicates an inactive receptor conformation. PMID:26280453

  20. A metabotropic glutamate receptor agonist does not mediate neuronal degeneration in cortical culture.

    PubMed

    Koh, J Y; Palmer, E; Lin, A; Cotman, C W

    1991-10-11

    In light of the evidence that calcium plays a critical role in excitotoxic neuronal death, it has been speculated that the metabotropic glutamate receptor may also contribute to excitotoxic damage through the mobilization of Ca2+ from intracellular stores. In the present study we examined this possibility by studying the neurotoxicity of trans-1-amino-cyclopentyl-1,3-dicarboxylate (trans-ACPD), a selective agonist of the metabotropic glutamate receptor. Exposure of cortical neurons to 100 microM trans-ACPD substantially increased phosphoinositide hydrolysis and intraneuronal free calcium in the presence of CPP and CNQX. Despite the presence of functional metabotropic receptors on cultured neurons, however, exposure of cultures to as high as 1 mM trans-ACPD for 24 h failed to produce any morphological or chemical signs of neuronal damage. Furthermore, trans-ACPD did not potentiate submaximal neurotoxicity produced by other non-N-methyl-D-aspartate (NMDA) agonists, kainate and D,L-alpha-amino-3-hydroxy-5-methyl-4-isoxazole-4-propionic acid (AMPA). PMID:1666330

  1. The protease-activated receptor-2 agonist induces gastric mucus secretion and mucosal cytoprotection

    PubMed Central

    Kawabata, Atsufumi; Kinoshita, Mitsuhiro; Nishikawa, Hiroyuki; Kuroda, Ryotaro; Nishida, Minoru; Araki, Hiromasa; Arizono, Naoki; Oda, Yasuo; Kakehi, Kazuaki

    2001-01-01

    Protease-activated receptor-2 (PAR-2), a receptor activated by trypsin/tryptase, modulates smooth muscle tone and exocrine secretion in the salivary glands and pancreas. Given that PAR-2 is expressed throughout the gastrointestinal tract, we investigated effects of PAR-2 agonists on mucus secretion and gastric mucosal injury in the rat. PAR-2–activating peptides triggered secretion of mucus in the stomach, but not in the duodenum. This mucus secretion was abolished by pretreatment with capsaicin, which stimulates and ablates specific sensory neurons, but it was resistant to cyclo-oxygenase inhibition. In contrast, capsaicin treatment failed to block PAR-2–mediated secretion from the salivary glands. Intravenous calcitonin gene–related peptide (CGRP) and neurokinin A markedly elicited gastric mucus secretion, as did substance P to a lesser extent. Specific antagonists of the CGRP1 and NK2, but not the NK1, receptors inhibited PAR-2–mediated mucus secretion. Pretreatment with the PAR-2 agonist strongly prevented gastric injury caused by HCl-ethanol or indomethacin. Thus, PAR-2 activation triggers the cytoprotective secretion of gastric mucus by stimulating the release of CGRP and tachykinins from sensory neurons. In contrast, the PAR-2–mediated salivary exocrine secretion appears to be independent of capsaicin-sensitive sensory neurons. PMID:11390426

  2. The pain receptor TRPV1 displays agonist-dependent activation stoichiometry

    PubMed Central

    Hazan, Adina; Kumar, Rakesh; Matzner, Henry; Priel, Avi

    2015-01-01

    The receptor channel TRPV1 (Transient Receptor Potential Vanilloid 1) is expressed by primary afferent sensory neurons of the pain pathway, where it functions as a sensor of noxious heat and various chemicals, including eicosanoids, capsaicin, protons and peptide toxins. Comprised of four identical subunits that organize into a non-selective cationic permeable channel, this receptor has a variety of binding sites responsible for detecting their respective agonists. Although its physiological role as a chemosensor has been described in detail, the stoichiometry of TRPV1 activation by its different ligands remains unknown. Here, we combined the use of concatemeric constructs harboring mutated binding sites with patch-clamp recordings in order to determine the stoichiometry for TRPV1 activation through the vanilloid binding site and the outer-pore domain by capsaicin and protons, respectively. We show that, while a single capsaicin-bound subunit was sufficient to achieve a maximal open-channel lifetime, all four proton-binding sites were required. Thus, our results demonstrate a distinct stoichiometry of TRPV1 activation through two of its different agonist-binding domains. PMID:26194846

  3. Development of a Single-Chain Peptide Agonist of the Relaxin-3 Receptor Using Hydrocarbon Stapling.

    PubMed

    Hojo, Keiko; Hossain, Mohammed Akhter; Tailhades, Julien; Shabanpoor, Fazel; Wong, Lilian L L; Ong-Pålsson, Emma E K; Kastman, Hanna E; Ma, Sherie; Gundlach, Andrew L; Rosengren, K Johan; Wade, John D; Bathgate, Ross A D

    2016-08-25

    Structure-activity studies of the insulin superfamily member, relaxin-3, have shown that its G protein-coupled receptor (RXFP3) binding site is contained within its central B-chain α-helix and this helical structure is essential for receptor activation. We sought to develop a single B-chain mimetic that retained agonist activity. This was achieved by use of solid phase peptide synthesis together with on-resin ruthenium-catalyzed ring closure metathesis of a pair of judiciously placed i,i+4 α-methyl, α-alkenyl amino acids. The resulting hydrocarbon stapled peptide was shown by solution NMR spectroscopy to mimic the native helical conformation of relaxin-3 and to possess potent RXFP3 receptor binding and activation. Alternative stapling procedures were unsuccessful, highlighting the critical need to carefully consider both the peptide sequence and stapling methodology for optimal outcomes. Our result is the first successful minimization of an insulin-like peptide to a single-chain α-helical peptide agonist which will facilitate study of the function of relaxin-3. PMID:27464307

  4. Effects of the neurotensin NTS1 receptor agonist PD149163 on visual signal detection in rats

    PubMed Central

    Hillhouse, Todd M.; Prus, Adam J.

    2013-01-01

    Antipsychotic drugs provide limited efficacy for cognitive impairment in schizophrenia. Recent studies have found that the neurotensin NTS1 receptor agonist and putative atypical antipsychotic drug PD149163 reverses deficits in sensory-gating and novel object recognition, suggesting that this compound may have the potential to improve cognitive functioning in schizophrenia. The present study sought to extend these investigations by evaluating the effects of PD149163 on sustained attention using a visual signal detection operant task in rats. PD149163, the atypical antipsychotic drug clozapine, and the dopamine D2/3 receptor antagonist raclopride all significantly decreased percent “hit” accuracy, while none of these compounds altered “correct rejections” (compared to vehicle control). Clozapine and raclopride significantly increased response latency, while high doses of PD149163 and raclopride significantly increased trial omissions. Nicotine, which was tested as a positive control, significantly improved overall performance in this task and did not affect response latency or trial omissions. The present findings suggest that neurotensin NTS1 receptor agonists, like antipsychotic drugs, may inhibit sustained attention in this task despite having different pharmacological mechanisms of action. PMID:24076181

  5. [Extrapancreatic effects of GLP-1 receptor agonists: an open window towards new treatment goals in type 2 diabetes].

    PubMed

    Salvador, Javier; Andrada, Patricia

    2014-09-01

    The wide ubiquity of GLP-1 receptors in the body has stimulated the search for different extrapancreatic actions of GLP-1 and its receptor agonists. Thus, severe cardioprotective effects directed on myocardial ischaemia and dysfunction as well as diverse antiaterogenic actions have been reported. Also, native and GLP-1 receptor agonists have demonstrated significant beneficial effects on liver steatosis and fibrosis and on neuronal protection in experimental models of Alzheimer, and Parkinson's disease as well as on cerebral ischaemia. Recent evidences suggest that these drugs may also be useful for prevention and treatment of diabetic retinopathy, nephropathy and peripheral neuropathy. Good results have also been reported in psoriasis. Despite we still need confirmation that these promising effects can be applied to clinical practice, they offer new interesting perspectives for treatment of type 2 diabetes associated complications and give to GLP-1 receptor agonists an even more integral position in diabetes therapy. PMID:25437463

  6. Selectivity optimization of substituted 1,2,3-triazoles as α7 nicotinic acetylcholine receptor agonists.

    PubMed

    Arunrungvichian, Kuntarat; Fokin, Valery V; Vajragupta, Opa; Taylor, Palmer

    2015-08-19

    Three series of substituted anti-1,2,3-triazoles (IND, PPRD, and QND), synthesized by cycloaddition from azide and alkyne building blocks, were designed to enhance selectivity and potency profiles of a lead α7 nicotinic acetylcholine receptor (α7-nAChR) agonist, TTIn-1. Designed compounds were synthesized and screened for affinity by a radioligand binding assay. Their functional characterization as agonists and antagonists was performed by fluorescence resonance energy transfer assay using cell lines expressing transfected cDNAs, α7-nAChRs, α4β2-nAChRs, and 5HT3A receptors, and a fluorescence cell reporter. In the IND series, a tropane ring of TTIn-1, substituted at N1, was replaced by mono- and bicyclic amines to vary length and conformational flexibility of a carbon linker between nitrogen atom and N1 of the triazole. Compounds with a two-carbon atom linker optimized binding with Kd's at the submicromolar level. Further modification at the hydrophobic indole of TTIn-1 was made in PPRD and QND series by fixing the amine center with the highest affinity building blocks in the IND series. Compounds from IND and PPRD series are selective as agonists for the α7-nAChRs over α4β2-nAChRs and 5HT3A receptors. Lead compounds in the three series have EC50's between 28 and 260 nM. Based on the EC50, affinity, and selectivity determined from the binding and cellular responses, two of the leads have been advanced to behavioral studies described in the companion article (DOI: 10.1021/acschemneuro.5b00059). PMID:25932897

  7. Neuroprotective actions of GR89696, a highly potent and selective kappa-opioid receptor agonist.

    PubMed Central

    Birch, P. J.; Rogers, H.; Hayes, A. G.; Hayward, N. J.; Tyers, M. B.; Scopes, D. I.; Naylor, A.; Judd, D. B.

    1991-01-01

    1. The effect of a novel, highly potent and selective kappa-opioid receptor agonist, GR89696, has been evaluated in two animal models of cerebral ischaemia: transient bilateral carotid artery occlusion in the Mongolian gerbil and permanent, unilateral middle cerebral artery occlusion in the mouse. 2. In the Mongolian gerbil model, administration of GR89696 (3 to 30 micrograms kg-1, s.c.), immediately before and at 4 h after insult, produced a dose-dependent reduction in the hippocampal CA1 neuronal cell loss resulting from a 7-min bilateral carotid occlusion. Similar effects were obtained with two other kappa-agonists, GR86014 (1 mgkg-1, s.c.) and GR91272 (1 mgkg-1, s.c.). The neuroprotective effect of GR89696 was completely blocked by prior administration of the opioid receptor antagonist, naltrexone, at 10 mgkg-1, s.c. Repeated post-treatment with GR89696 (100 micrograms kg-1, s.c.) or GR44821 (10 mgkg-1, s.c.) was also effective in protecting completely the hippocampal CA1 neurones from ischaemia-induced neurodegeneration. 3. In the permanent, unilateral middle cerebral artery occlusion model in the mouse, repeated administration of GR89696 at 300 micrograms kg-1, s.c. produced a 50% reduction in cerebrocortical infarct volume. In these experiments GR89696 was dosed 5 min, 4, 8, 12, 16, 20 and 24 h after occlusion on the first day and then three times daily for the next three days. GR89696 (300 micrograms kg-1) also produced a significant 35% reduction in infarct volume in this model when the initiation of dosing was delayed for 6 h after the insult. 4. The results indicate that the potent kappa-opioid receptor agonist, GR89696, is neuroprotective in both global and focal cerebral ischaemia models and suggest that, with this class of compound, there may be a considerable time window for pharmacological intervention. PMID:1657267

  8. Pharmacological characterization of a selective agonist for Bombesin Receptor Subtype - 3

    PubMed Central

    Zhang, Li; Nothacker, Hans-Peter; Wang, Zhiwei; Bohn, Laura M; Civelli, Olivier

    2009-01-01

    Bombesin receptor subtype-3 (BRS-3) is an orphan G protein-coupled receptor in the bombesin receptor family that still awaits identification of its natural ligand. BRS-3 deficient mice develop a mild late-onset obesity with metabolic defects, implicating BRS-3 plays a role in feeding and metabolism. We describe here the pharmacological characterization of a synthetic compound, 16a, which serves as a potent agonist for BRS-3. This compound is selective for BRS-3 as it does not activate neuromedin B or gastrin-releasing peptide receptors, two most closely related bombesin receptors, as well as a series of other GPCRs. We assessed the receptor trafficking of BRS-3 and found that compound 16a promoted β-arrestin translocation to the cell membrane. Neither central nor peripheral administration of compound 16a affects locomotor activity in mice. Therefore compound 16a is a potential tool to study the function of the BRS-3 system in vitro and possibly in vivo. PMID:19580790

  9. Design, Synthesis, and Evaluation of Tetrasubstituted Pyridines as Potent 5-HT2C Receptor Agonists

    PubMed Central

    2015-01-01

    A series of pyrido[3,4-d]azepines that are potent and selective 5-HT2C receptor agonists is disclosed. Compound 7 (PF-04781340) is identified as a suitable lead owing to good 5-HT2C potency, selectivity over 5-HT2B agonism, and in vitro ADME properties commensurate with an orally available and CNS penetrant profile. The synthesis of a novel bicyclic tetrasubstituted pyridine core template is outlined, including rationale to account for the unexpected formation of aminopyridine 13 resulting from an ammonia cascade cyclization. PMID:25815155

  10. Muscarinic receptors in rat nasal mucosa are predominantly of the low affinity agonist type.

    PubMed

    Rodrigues de Miranda, J F; Scheres, H M; Salden, H J; Beld, A J; Klaassen, A B; Kuijpers, W

    1985-07-31

    Specific [3H]l-quinuclidinyl benzilate binding to rat nasal mucosa homogenates occurs to a homogeneous class of binding sites with Kd = 60 +/- 2 10(-12) M and Bmax = 8.1 +/- 2 pmol/g tissue. Binding is stereoselectively inhibited by benzetimide enantiomers. Pirenzepine inhibits [3H]l-quinuclidinyl benzilate binding with low affinity (Ki = 5.0 10(-7) M), classifying the binding sites as muscarinic M2-receptors. Methylfurtrethonium and methacholine inhibit [3H]l-quinuclidinyl benzilate binding following an almost sigmoid curve at high concentrations pointing to the presence of mainly low affinity agonist binding sites. PMID:3840092

  11. Discovery of acylurea isosteres of 2-acylaminothiadiazole in the azaxanthene series of glucocorticoid receptor agonists.

    PubMed

    Gong, Hua; Yang, Michael; Xiao, Zili; Doweyko, Arthur M; Cunningham, Mark; Wang, Jinhong; Habte, Sium; Holloway, Deborah; Burke, Christine; Shuster, David; Gao, Ling; Carman, Julie; Somerville, John E; Nadler, Steven G; Salter-Cid, Luisa; Barrish, Joel C; Weinstein, David S

    2014-08-01

    Acylureas and acyclic imides are found to be excellent isosteres for 2-acylamino-1,3,4-thiadiazole in the azaxanthene-based series of glucocorticoid receptor (GR) agonists. The results reported herein show that primary acylureas maintain high affinity and selectivity for GR while providing improved CYP450 inhibition and pharmacokinetic profile over 2-acylamino-1,3,4-thiadiazoles. General methods for synthesis of a variety of acylureas and acyclic imides from a carboxylic acid were utilized and are described. PMID:24980053

  12. A Cluster Headache Responsive to Ramelteon, a Selective Melatonin MT1/MT2 Receptor Agonist.

    PubMed

    Imai, Noboru

    2016-01-01

    Patients with cluster headaches occasionally fail to respond to conventional preventive treatments. We herein report a case of a patient with a cluster headache in which the symptoms were refractory to conventional preventive treatments except for high-dose glucocorticoids. The headache attacks occurred daily while sleeping, thus the patient suffered from insomnia. Ramelteon, a selective melatonin receptor agonist and a member of a new class of insomnia therapies, completely suppressed the attacks during sleep and provided rapid relief from insomnia. This is the first English case report to describe the efficacy of ramelteon as a preventive treatment for cluster headaches. PMID:27580554

  13. (1R, 3S)-(−)-Trans-PAT: A novel full-efficacy serotonin 5-HT2C receptor agonist with 5-HT2A and 5-HT2B receptor inverse agonist/antagonist activity

    PubMed Central

    Booth, Raymond G.; Fang, Lijuan; Huang, Yingsu; Wilczynski, Andrzej; Sivendran, Sashikala

    2009-01-01

    The serotonin 5-HT2A, 5-HT2B, and 5-HT2C G protein-coupled receptors signal primarily through Gαq to activate phospholipase C (PLC) and formation of inositol phosphates (IP) and diacylglycerol. The human 5-HT2C receptor, expressed exclusively in the central nervous system, is involved in several physiological and psychological processes. Development of 5-HT2C agonists that do not also activate 5-HT2A or 5-HT2B receptors is challenging because transmembrane domain identity is about 75% among 5-HT2 subtypes. This paper reports 5-HT2 receptor affinity and function of (1R,3S)-(−)-trans-1-phenyl-3-dimethylamino-1,2,3,4-tetrahydronaphthalene (PAT), a small molecule that produces anorexia and weight-loss after peripheral administration to mice. (−)-Trans-PAT is a stereoselective full-efficacy agonist at human 5-HT2C receptors, plus, it is a 5-HT2A/5-HT2B inverse agonist and competitive antagonist. The Ki of (−)-trans-PAT at 5-HT2A, 5-HT2B, and 5-HT2C receptors is 410, 1200, and 37 nM, respectively. Functional studies measured activation of PLC/[3H]-IP formation in clonal cells expressing human 5-HT2 receptors. At 5-HT2C receptors, (−)-trans-PAT is an agonist (EC50 = 20 nM) comparable to serotonin in potency and efficacy. At 5-HT2A and 5-HT2B receptors, (−)-trans-PAT is an inverse agonist (IC50 = 490 and 1,000 nM, respectively) and competitive antagonist (KB = 460 and 1400 nM, respectively) of serotonin. Experimental results are interpreted in light of molecular modeling studies indicating the (−)-trans-PAT protonated amine can form an ionic bond with D3.32 of 5-HT2A and 5-HT2C receptors, but, not with 5-HT2B receptors. In addition to probing 5-HT2 receptor structure and function, (−)-trans-PAT is a novel lead regarding 5-HT2C agonist/5-HT2A inverse agonist drug development for obesity and neuropsychiatric disorders. PMID:19397907

  14. Agonists of the tissue-protective erythropoietin receptor in the treatment of Parkinson's disease.

    PubMed

    Punnonen, Juha; Miller, James L; Collier, Timothy J; Spencer, Jeffrey R

    2015-01-01

    Parkinson's disease (PD) is a neurodegenerative disease affecting more than a million people in the USA alone. While there are effective symptomatic treatments for PD, there is an urgent need for new therapies that slow or halt the progressive death of dopaminergic neurons. Significant progress has been made in understanding the pathophysiology of PD, which has substantially facilitated the discovery efforts to identify novel drugs. The tissue-protective erythropoietin (EPO) receptor, EPOR/CD131, has emerged as one promising target for disease-modifying therapies. Recombinant human EPO (rhEPO), several variants of EPO, EPO-mimetic peptides, cell-based therapies using cells incubated with or expressing EPO, gene therapy vectors encoding EPO, and small molecule EPO mimetic compounds all show potential as therapeutic candidates. Agonists of the EPOR/CD131 receptor demonstrate potent anti-apoptotic, antioxidant, and anti-inflammatory effects and protect neurons, including dopaminergic neurons, from diverse insults in vitro and in vivo. When delivered directly to the striatum, rhEPO protects dopaminergic neurons in animal models of PD. Early-stage clinical trials testing systemic rhEPO have provided encouraging results, while additional controlled studies are required to fully assess the potential of the treatment. Poor CNS availability of proteins and challenges related to invasive delivery limit delivery of EPO protein. Several variants of EPO and small molecule agonists of the EPO receptors are making progress in preclinical studies and may offer solutions to these challenges. While EPO was initially discovered as the primary modulator of erythropoiesis, the discovery and characterization of the tissue-protective EPOR/CD131 receptor offer an opportunity to selectively target the neuroprotective receptor as an approach to identify disease-modifying treatments for PD. PMID:25832721

  15. N-Methyl scan of somatostatin octapeptide agonists produces interesting effects on receptor subtype specificity.

    PubMed

    Rajeswaran, W G; Hocart, S J; Murphy, W A; Taylor, J E; Coy, D H

    2001-04-26

    The search for synthetic analogues of somatostatin which exhibit selective affinities for the five receptor subtypes is of considerable basic and therapeutic interest and has generated a large number of potent agonist analogues with a wide spectrum of binding profiles. In the past, conformational restriction of side chain groups and the peptide backbone has yielded the most interesting results. Under the latter category and as part of the present study, we were interested in the potential effects of N-methylation of peptide bond NH groups on binding affinity since this approach had not been systematically examined with these peptides. This was aided by new chemistries for introducing an N-Me group during regular solid-phase peptide synthesis using Boc protection. A number of interesting effects were noted on relative binding affinities of the two series of agonist sequences chosen, DPhe(5)(or Tyr(5))-c[Cys(6)-Phe(7)-DTrp(8)-Lys(9)-Thr(10)-Cys(11)]Thr(12)-NH(2) (SRIF numbering), at the five known human somatostatin receptors transfected into and stably expressed by CHO cells. N-Methylation of residues 7 (Phe), 10 (Thr), 11 (Cys), and 12 (Thr) largely destroyed affinities for all five receptors. N-Methylation of DTrp in the DPhe series gave an analogue with extraordinarily high affinity for the type 5 receptor for which it was also quite selective. N-Methylation of Lys in both series resulted in retention of type 2 affinity despite this residue constituting the "active center" of somatostatin peptides. N-Methylation of either the N-terminal Tyr residue or of Cys(6) in the Tyr series resulted in analogues with extraordinarily high affinity for the type 3 receptor, also with a degree of specificity. N-Methylation of the peptide bond constrains the conformational space of the amino acid and eliminates the possibility of donor hydrogen bond formation from the amide linkage. The beta-bend conformation of the agonists around DTrp-Lys is stabilized by a transannular

  16. Evidence for Noncanonical Neurotransmitter Activation: Norepinephrine as a Dopamine D2-Like Receptor Agonist.

    PubMed

    Sánchez-Soto, Marta; Bonifazi, Alessandro; Cai, Ning Sheng; Ellenberger, Michael P; Newman, Amy Hauck; Ferré, Sergi; Yano, Hideaki

    2016-04-01

    The Gαi/o-coupled dopamine D2-like receptor family comprises three subtypes: the D2 receptor (D2R), with short and long isoform variants (D2SR and D2LR), D3 receptor (D3R), and D4 receptor (D4R), with several polymorphic variants. The common overlap of norepinephrine innervation and D2-like receptor expression patterns prompts the question of a possible noncanonical action by norepinephrine. In fact, previous studies have suggested that norepinephrine can functionally interact with D4R. To our knowledge, significant interactions between norepinephrine and D2R or D3R receptors have not been demonstrated. By using radioligand binding and bioluminescent resonance energy transfer (BRET) assays in transfected cells, the present study attempted a careful comparison between dopamine and norepinephrine in their possible activation of all D2-like receptors, including the two D2R isoforms and the most common D4R polymorphic variants. Functional BRET assays included activation of G proteins with all Gαi/o subunits, adenylyl cyclase inhibition, and β arrestin recruitment. Norepinephrine acted as a potent agonist for all D2-like receptor subtypes, with the general rank order of potency of D3R > D4R ≥ D2SR ≥ D2L. However, for both dopamine and norepinephrine, differences depended on the Gαi/o protein subunit involved. The most striking differences were observed with Gαi2, where the rank order of potencies for both dopamine and norepinephrine were D4R > D2SR = D2LR > D3R. Furthermore the results do not support the existence of differences in the ability of dopamine and norepinephrine to activate different human D4R variants. The potency of norepinephrine for adrenergic α2A receptor was only about 20-fold higher compared with D3R and D4R across the three functional assays. PMID:26843180

  17. Evidence for Noncanonical Neurotransmitter Activation: Norepinephrine as a Dopamine D2-Like Receptor Agonist

    PubMed Central

    Sánchez-Soto, Marta; Bonifazi, Alessandro; Cai, Ning Sheng; Ellenberger, Michael P.; Newman, Amy Hauck

    2016-01-01

    The Gαi/o-coupled dopamine D2-like receptor family comprises three subtypes: the D2 receptor (D2R), with short and long isoform variants (D2SR and D2LR), D3 receptor (D3R), and D4 receptor (D4R), with several polymorphic variants. The common overlap of norepinephrine innervation and D2-like receptor expression patterns prompts the question of a possible noncanonical action by norepinephrine. In fact, previous studies have suggested that norepinephrine can functionally interact with D4R. To our knowledge, significant interactions between norepinephrine and D2R or D3R receptors have not been demonstrated. By using radioligand binding and bioluminescent resonance energy transfer (BRET) assays in transfected cells, the present study attempted a careful comparison between dopamine and norepinephrine in their possible activation of all D2-like receptors, including the two D2R isoforms and the most common D4R polymorphic variants. Functional BRET assays included activation of G proteins with all Gαi/o subunits, adenylyl cyclase inhibition, and β arrestin recruitment. Norepinephrine acted as a potent agonist for all D2-like receptor subtypes, with the general rank order of potency of D3R > D4R ≥ D2SR ≥ D2L. However, for both dopamine and norepinephrine, differences depended on the Gαi/o protein subunit involved. The most striking differences were observed with Gαi2, where the rank order of potencies for both dopamine and norepinephrine were D4R > D2SR = D2LR >> D3R. Furthermore the results do not support the existence of differences in the ability of dopamine and norepinephrine to activate different human D4R variants. The potency of norepinephrine for adrenergic α2A receptor was only about 20-fold higher compared with D3R and D4R across the three functional assays. PMID:26843180

  18. Effects of repeated treatment with the dopamine D2/D3 receptor partial agonist aripiprazole on striatal D2/D3 receptor availability in monkeys

    PubMed Central

    Czoty, Paul W.; Gage, H. Donald; Garg, Pradeep K.; Garg, Sudha; Nader, Michael A.

    2013-01-01

    Rationale Chronic treatment with dopamine (DA) receptor agonists and antagonists can differentially affect measures of DA D2/D3 receptor number and function, but the effects of chronic treatment with a partial D2/D3 receptor agonist are not clear. Objective We used a within-subjects design in male cynomolgus monkeys to determine the effects of repeated (17-day) treatment with the D2/D3 receptor partial agonist aripiprazole (ARI; 0.03 mg/kg and 0.1 mg/kg i.m.) on food-reinforced behavior (n=5) and on D2/D3 receptor availability as measured with positron emission tomography (PET; n=9). Methods Five monkeys responded under a fixed-ratio 50 schedule of food reinforcement and D2/D3 receptor availability was measured before and four days after ARI treatment using PET and the D2/D3 receptor-selective radioligand [18F]fluoroclebopride (FCP). Four additional monkeys were studied using [11C]raclopride and treated sequentially with each dose of ARI for 17 days. Results ARI decreased food-maintained responding with minimal evidence of tolerance. Repeated ARI administration increased FCP and raclopride distribution volume ratios (DVRs) in the caudate nucleus and putamen in most monkeys, but decreases were observed in monkeys with the highest baseline DVRs. Conclusions The results indicate that repeated treatment with a low efficacy DA receptor partial agonist produces effects on brain D2/D3 receptor availability that are qualitatively different from those of both high-efficacy receptor agonists and antagonists, and suggest that the observed individual differences in response to ARI treatment may reflect its partial agonist activity. PMID:24077804

  19. Development of flavonoid-based inverse agonists of the key signaling receptor US28 of human cytomegalovirus.

    PubMed

    Kralj, Ana; Nguyen, Mai-Thao; Tschammer, Nuska; Ocampo, Nicolette; Gesiotto, Quinto; Heinrich, Markus R; Phanstiel, Otto

    2013-06-27

    A series of 31 chalcone- and flavonoid-based derivatives were synthesized in good overall yields and screened for their inverse agonist activity on the US28 receptor of human cytomegalovirus (HCMV). With one exception (e.g., 2-(5-bromo-2-methoxyphenyl)-3-hydroxy-4H-chromen-4-one), halogen-substituted flavonoids were typically more potent inverse agonists than their related hydro derivatives. While toxicity could be used to partially explain the inverse agonist activity of some members of the series, 5-(benzyloxy)-2-(5-bromo-2-methoxyphenyl)-4H-chromen-4-one (11b) acted on the US28 receptor as a nontoxic, inverse agonist. The full inverse agonism (efficacy, -89%) and potency (EC50 = 3.5 μM) observed with flavonoid 11b is especially important as it provides both a new tool to study US28 signaling and a potential platform for the future development of HCMV-targeting drugs. PMID:23768434

  20. Adenosine A2A receptor plays an important role in radiation-induced dermal injury.

    PubMed

    Perez-Aso, Miguel; Mediero, Aránzazu; Low, Yee Cheng; Levine, Jamie; Cronstein, Bruce N

    2016-01-01

    Ionizing radiation is a common therapeutic modality and following irradiation dermal changes, including fibrosis and atrophy, may lead to permanent changes. We have previously demonstrated that occupancy of A2A receptor (A2AR) stimulates collagen production, so we determined whether blockade or deletion of A2AR could prevent radiation-induced fibrosis. After targeted irradiation (40 Gy) of the skin of wild-type (WT) or A2AR knockout (A2ARKO) mice, the A2AR antagonist ZM241385 was applied daily for 28 d. In irradiated WT mice treated with the A2AR antagonist, there was a marked reduction in collagen content and skin thickness, and ZM241385 treatment reduced the number of myofibroblasts and angiogenesis. After irradiation, there is an increase in loosely packed collagen fibrils, which is significantly diminished by ZM241385. Irradiation also induced an increase in epidermal thickness, prevented by ZM241385, by increasing the number of proliferating keratinocytes. Similarly, in A2ARKO mice, the changes in collagen alignment, skin thickness, myofibroblast content, angiogenesis, and epidermal hyperplasia were markedly reduced following irradiation. Radiation-induced changes in the dermis and epidermis were accompanied by an infiltrate of T cells, which was prevented in both ZM241385-treated and A2ARKO mice. Radiation therapy is administered to a significant number of patients with cancer, and radiation reactions may limit this therapeutic modality. Our findings suggest that topical application of an A2AR antagonist prevents radiation dermatitis and may be useful in the prevention or amelioration of radiation changes in the skin. PMID:26415936

  1. Activation of Human Brown Adipose Tissue by a β3-Adrenergic Receptor Agonist

    PubMed Central

    Cypess, Aaron M.; Weiner, Lauren S.; Roberts-Toler, Carla; Elía, Elisa Franquet; Kessler, Skyler H.; Kahn, Peter A.; English, Jeffrey; Chatman, Kelly; Trauger, Sunia A.; Doria, Alessandro; Kolodny, Gerald M.

    2015-01-01

    SUMMARY Increasing energy expenditure through activation of endogenous brown adipose tissue (BAT) is a potential approach to treat obesity and diabetes. The class of β3-adrenergic receptor (AR) agonists stimulates rodent BAT, but this activity has never been demonstrated in humans. Here we determined the ability of 200 mg oral mirabegron (Myrbetriq, Astellas Pharma, Inc.), a β3-AR agonist currently approved to treat overactive bladder, to stimulate BAT as compared to placebo. Mirabegron led to higher BAT metabolic activity as measured via 18F-fluorodeoxyglucose (18F-FDG) using positron emission tomography (PET) combined with computed tomography (CT) in all twelve healthy male subjects (p = 0.001), and it increased resting metabolic rate (RMR) by 203 ± 40 kcal/day (+13%; p = 0.001). BAT metabolic activity was also a significant predictor of the changes in RMR (p = 0.006). Therefore, a β3-AR agonist can stimulate human BAT thermogenesis and may be a promising treatment for metabolic disease. PMID:25565203

  2. E17110 promotes reverse cholesterol transport with liver X receptor β agonist activity in vitro.

    PubMed

    Li, Ni; Wang, Xiao; Liu, Peng; Lu, Duo; Jiang, Wei; Xu, Yanni; Si, Shuyi

    2016-05-01

    Liver X receptor (LXR) plays an important role in reverse cholesterol transport (RCT), and activation of LXR could reduce atherosclerosis. In the present study we used a cell-based screening method to identify new potential LXRβ agonists. A novel benzofuran-2-carboxylate derivative was identified with LXRβ agonist activity: E17110 showed a significant activation effect on LXRβ with an EC50 value of 0.72 μmol/L. E17110 also increased the expression of ATP-binding cassette transporter A1 (ABCA1) and G1 (ABCG1) in RAW264.7 macrophages. Moreover, E17110 significantly reduced cellular lipid accumulation and promoted cholesterol efflux in RAW264.7 macrophages. Interestingly, we found that the key amino acids in the LXRβ ligand-binding domain had distinct interactions with E17110 as compared to TO901317. These results suggest that E17110 was identified as a novel compound with LXRβ agonist activity in vitro via screening, and could be developed as a potential anti-atherosclerotic lead compound. PMID:27175330

  3. Orally Active Adenosine A1 Receptor Agonists with Antinociceptive Effects in Mice

    PubMed Central

    Korboukh, Ilia; Hull-Ryde, Emily A.; Rittiner, Joseph E.; Randhawa, Amarjit S.; Coleman, Jennifer; Fitzpatrick, Brendan J.; Setola, Vincent; Janzen, William P.; Frye, Stephen V.; Zylka, Mark J.; Jin, Jian

    2012-01-01

    Adenosine A1 receptor (A1AR) agonists have antinociceptive effects in multiple preclinical models of acute and chronic pain. Although numerous A1AR agonists have been developed, clinical applications of these agents have been hampered by their cardiovascular side effects. Herein we report a series of novel A1AR agonists, some of which are structurally related to adenosine 5′-monophosphate (5′-AMP), a naturally occurring nucleotide that itself activates A1AR. These novel compounds potently activate A1AR in several orthogonal in vitro assays and are subtype selective for A1AR over A2AAR, A2BAR, and A3AR. Among them, UNC32A (3a) is orally active and has dose-dependent antinociceptive effects in wild-type mice. The antinociceptive effects of 3a were completely abolished in A1AR knockout mice, revealing a strict dependence on A1AR for activity. The apparent lack of cardiovascular side effects when administered orally and high affinity (Ki of 36 nM for the human A1AR) make this compound potentially suitable as a therapeutic. PMID:22738238

  4. Structure-Activity Relationships in Toll-like Receptor 2-Agonists Leading to Simplified Monoacyl Lipopeptides

    PubMed Central

    Agnihotri, Geetanjali; Crall, Breanna M.; Lewis, Tyler C.; Day, Timothy P.; Balakrishna, Rajalakshmi; Warshakoon, Hemamali J.; Malladi, Subbalakshmi S.; David, Sunil A.

    2011-01-01

    Toll-like receptor 2-agonistic lipopeptides typified by S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-R-cysteinyl-S-serine (PAM2CS) compounds are potential vaccine adjuvants. In continuation of previously reported structure-activity relationships on this chemotype, we have determined that at least one acyl group of optimal length (C16) and an appropriately orientated ester carbonyl group is essential for TLR2-agonistic activity. The spacing between one of the palmitoyl ester carbonyl and the thioether is crucial to allow for an important H-bond, which observed in the crystal structure of the lipopeptide:TLR2 complex; consequently, activity is lost in homologated compounds. Penicillamine-derived analogues are also inactive, likely due to unfavorable steric interactions with the carbonyl of Ser 12 in TLR2. The thioether in this chemotype can be replaced with a selenoether. Importantly, the thioglycerol motif can be dispensed with altogether, and can be replaced with a thioethanol bridge. These results have led to a structurally simpler, synthetically more accessible, and water-soluble analogue possessing strong TLR2-agonistic activities in human blood. PMID:22007676

  5. E17110 promotes reverse cholesterol transport with liver X receptor β agonist activity in vitro

    PubMed Central

    Li, Ni; Wang, Xiao; Liu, Peng; Lu, Duo; Jiang, Wei; Xu, Yanni; Si, Shuyi

    2016-01-01

    Liver X receptor (LXR) plays an important role in reverse cholesterol transport (RCT), and activation of LXR could reduce atherosclerosis. In the present study we used a cell-based screening method to identify new potential LXRβ agonists. A novel benzofuran-2-carboxylate derivative was identified with LXRβ agonist activity: E17110 showed a significant activation effect on LXRβ with an EC50 value of 0.72 μmol/L. E17110 also increased the expression of ATP-binding cassette transporter A1 (ABCA1) and G1 (ABCG1) in RAW264.7 macrophages. Moreover, E17110 significantly reduced cellular lipid accumulation and promoted cholesterol efflux in RAW264.7 macrophages. Interestingly, we found that the key amino acids in the LXRβ ligand-binding domain had distinct interactions with E17110 as compared to TO901317. These results suggest that E17110 was identified as a novel compound with LXRβ agonist activity in vitro via screening, and could be developed as a potential anti-atherosclerotic lead compound. PMID:27175330

  6. Selective Estrogen Receptor β Agonist LY500307 as a Novel Therapeutic Agent for Glioblastoma

    PubMed Central

    Sareddy, Gangadhara R.; Li, Xiaonan; Liu, Jinyou; Viswanadhapalli, Suryavathi; Garcia, Lauren; Gruslova, Aleksandra; Cavazos, David; Garcia, Mike; Strom, Anders M.; Gustafsson, Jan-Ake; Tekmal, Rajeshwar Rao; Brenner, Andrew; Vadlamudi, Ratna K.

    2016-01-01

    Glioblastomas (GBM), deadly brain tumors, have greater incidence in males than females. Epidemiological evidence supports a tumor suppressive role of estrogen; however, estrogen as a potential therapy for GBM is limited due to safety concerns. Since GBM express ERβ, a second receptor for estrogen, targeting ERβ with a selective agonist may be a potential novel GBM therapy. In the present study, we examined the therapeutic effect of the selective synthetic ERβ agonist LY500307 using in vitro and in vivo GBM models. Treatment with LY500307 significantly reduced the proliferation of GBM cells with no activity on normal astrocytes in vitro. ERβ agonists promoted apoptosis of GBM cells, and mechanistic studies using RNA sequencing revealed that LY500307 modulated several pathways related to apoptosis, cell cycle, and DNA damage response. Further, LY500307 sensitized GBM cells to several FDA-approved chemotherapeutic drugs including cisplatin, lomustine and temozolomide. LY500307 treatment significantly reduced the in vivo tumor growth and promoted apoptosis of GBM tumors in an orthotopic model and improved the overall survival of tumor-bearing mice in the GL26 syngeneic glioma model. Our results demonstrate that LY500307 has potential as a therapeutic agent for GBM. PMID:27126081

  7. Polybrominated diphenyl ethers and arylhydrocarbon receptor agonists: Different toxicity and target gene expression.

    PubMed

    Wahl, M; Guenther, R; Yang, L; Bergman, A; Straehle, U; Strack, S; Weiss, C

    2010-10-01

    Polybrominated diphenyl ethers (PBDEs) accumulate in the environment and in humans. PBDEs are developmental neurotoxicants, disturb the endocrine system and induce tumors in rodents. However, underlying mechanisms of PBDE toxicity are still insufficiently understood. Some reports demonstrated activation but also inhibition of the aryl hydrocarbon receptor (AhR) by PBDEs based on expression of its target gene cyp1A1. In the present study, we used different PBDE congeners (BDE47, 99, 153 and 209) and analyzed their effects on AhR signaling in various cell lines and zebrafish embryos. Furthermore, we performed microarray experiments in rat hepatoma cells to compare changes in gene expression induced by either BDE47 or the AhR agonist 2,3,7,8-tetrabromo-dibenzofuran (TBDF). PBDEs did not activate but rather inhibited AhR signaling and specifically induced malformations in zebrafish embryos, which differ from those provoked by AhR agonists. Furthermore, BDE47 and TBDF differentially regulated global gene expression in hepatoma cells. Hence, PBDEs and AhR agonists trigger different toxicity and target gene expression. Several novel target genes of BDE47 and TBDF were identified and verified by RT-PCR. TBDF induced expression of the transcriptional regulators Sim2 and RevErbbeta whereas BDE47 specifically deregulated expression of two subunits of the cytochrome c oxidase complex, cox6a2 and cox4i2, which might be linked to its toxicity. PMID:20566336

  8. Agonist properties of N,N-dimethyltryptamine at serotonin 5-HT2A and 5-HT2C receptors.

    PubMed

    Smith, R L; Canton, H; Barrett, R J; Sanders-Bush, E

    1998-11-01

    Extensive behavioral and biochemical evidence suggests an agonist role at the 5-HT2A receptor, and perhaps the 5-HT2C receptor, in the mechanism of action of hallucinogenic drugs. However the published in vitro pharmacological properties of N,N-dimethyltryptamine (DMT), an hallucinogenic tryptamine analog, are not consistent with this hypothesis. We, therefore, undertook an extensive investigation into the properties of DMT at 5-HT2A and 5-HT2C receptors. In fibroblasts transfected with the 5-HT2A receptor or the 5-HT2C receptor, DMT activated the major intracellular signaling pathway (phosphoinositide hydrolysis) to an extent comparable to that produced by serotonin. Because drug efficacy changes with receptor density and cellular microenvironment, we also examined the properties of DMT in native preparations using a behavioral and biochemical approach. Rats were trained to discriminate an antagonist ketanserin from an agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) in a two-lever choice paradigm. Pharmacological studies showed that responding on the DOI and ketanserin lever reflected agonist and antagonist activity at 5-HT2A receptors, and hence, was a suitable model for evaluating the in vivo functional properties of DMT. Like other 5-HT2A receptor agonists, DMT substituted fully for DOI. Intact choroid plexus was used to evaluate the agonist properties at endogenous 5-HT2C receptors; DMT was a partial agonist at 5-HT2C receptors in this native preparation. Thus, we conclude that DMT behaves as an agonist at both 5-HT2A and 5-HT2A receptors. One difference was evident in that the 5-HT2C, but not the 5-HT2A, receptor showed a profound desensitization to DMT over time. This difference is interesting in light of the recent report that the hallucinogenic activity of DMT does not tolerate in humans and suggests the 5-HT2C receptor plays a less prominent role in the action of DMT. PMID:9768567

  9. γ-Aminobutyric acid type A (GABA(A)) receptor subtype inverse agonists as therapeutic agents in cognition.

    PubMed

    Gabriella, Guerrini; Giovanna, Ciciani

    2010-01-01

    The gabaergic system has been identified as a relevant regulator of cognitive and emotional processing. In fact, the discovery that negative allosteric regulators (or inverse agonists) at GABA(A) (γ-aminobutyric acid) α5 subtype receptors improve learning and memory tasks, has further validated this concept. The localization of these extrasynaptic subtype receptors, mainly in the hippocampus, has suggested that they play a key role in the three stages of memory: acquisition, consolidation, and retrieval. The "α5 inverse agonist" binds to an allosteric site at GABA(A) receptor, provoking a reduction of chlorine current, but to elicit this effect, the necessary condition is the binding of agonist neurotransmitter (γ-amino butyric acid) at its orthosteric site. In this case, the GABA(A) receptor is not a "constitutively active receptor" and, however, the presence of spontaneous opening channels for native GABA(A) receptors is rare. Here, we present various classes of nonselective and α5 selective GABA(A) receptor ligands, and the in vitro and in vivo tests to elucidate their affinity and activity. The study of the GABA(A) α5 inverse agonists is one of the important tools, although not the only one, for the development of clinical strategies for treatment of Alzheimer disease and mild cognitive impairment. PMID:21050918

  10. Mapping the effects of three dopamine agonists with different dyskinetogenic potential and receptor selectivity using pharmacological functional magnetic resonance imaging.

    PubMed

    Delfino, Marina; Kalisch, Raffael; Czisch, Michael; Larramendy, Celia; Ricatti, Jimena; Taravini, Irene R E; Trenkwalder, Claudia; Murer, Mario Gustavo; Auer, Dorothee P; Gershanik, Oscar S

    2007-09-01

    The mechanisms underlying dopamine agonist-induced dyskinesia in Parkinson's disease remain poorly understood. Similar to patients, rats with severe nigrostriatal degeneration induced by 6-hydroxydopamine are more likely to show dyskinesia during chronic treatment with unselective dopamine receptor agonists than with D2 agonists, suggesting that D1 receptor stimulation alone or in conjunction with D2 receptor stimulation increases the chances of experiencing dyskinesia. As a first step towards disclosing drug-induced brain activation in dyskinesia, we examined the effects of dopamine agonists on behavior and blood oxygenation level-dependent (BOLD) signal in the striatum and motor cortex of rats with unilateral nigrostriatal lesions. Rats were rendered dyskinetic before pharmacologic functional magnetic resonance imaging by means of a repeated treatment regime with dopamine agonists. The unselective agonist apomorphine and the selective D1/D5 agonist SKF-81297 induced strong forelimb dyskinesia (FD) and axial dystonia and increased BOLD signal in the denervated striatum. Besides, SKF-81297 produced a significant but smaller BOLD increase in the intact striatum and a symmetric bilateral increase in the motor cortex. The D2 family agonist quinpirole, which induced mild dyskinesia on chronic treatment, did not produce BOLD changes in the striatum or motor cortex. Further evidence to support an association between BOLD changes and dyskinesia comes from a direct correlation between scores of FD and magnitude of drug-induced BOLD increases in the denervated striatum and motor cortex. Our results suggest that striatal and cortical activation induced by stimulation of D1/D5 receptors has a primary role in the induction of peak dose dyskinesia in parkinsonism. PMID:17287822

  11. Molecular Recognition of Agonist and Antagonist for Peroxisome Proliferator-Activated Receptor-α Studied by Molecular Dynamics Simulations

    PubMed Central

    Liu, Mengyuan; Wang, Lushan; Zhao, Xian; Sun, Xun

    2014-01-01

    Peroxisome proliferator activated receptor-α (PPAR-α) is a ligand-activated transcription factor which plays important roles in lipid and glucose metabolism. The aim of this work is to find residues which selectively recognize PPAR-α agonists and antagonists. To achieve this aim, PPAR-α/13M and PPAR-α/471 complexes were subjected to perform molecular dynamics simulations. This research suggests that several key residues only participate in agonist recognition, while some other key residues only contribute to antagonist recognition. It is hoped that such work is useful for medicinal chemists to design novel PPAR-α agonists and antagonists. PMID:24837836

  12. Discovery of a potent and selective free fatty acid receptor 1 agonist with low lipophilicity and high oral bioavailability.

    PubMed

    Christiansen, Elisabeth; Due-Hansen, Maria E; Urban, Christian; Grundmann, Manuel; Schmidt, Johannes; Hansen, Steffen V F; Hudson, Brian D; Zaibi, Mohamed; Markussen, Stine B; Hagesaether, Ellen; Milligan, Graeme; Cawthorne, Michael A; Kostenis, Evi; Kassack, Matthias U; Ulven, Trond

    2013-02-14

    The free fatty acid receptor 1 (FFA1, also known as GPR40) mediates enhancement of glucose-stimulated insulin secretion and is emerging as a new target for the treatment of type 2 diabetes. Several FFA1 agonists are known, but the majority of these suffer from high lipophilicity. We have previously reported the FFA1 agonist 3 (TUG-424). We here describe the continued structure-activity exploration and optimization of this compound series, leading to the discovery of the more potent agonist 40, a compound with low lipophilicity, excellent in vitro metabolic stability and permeability, complete oral bioavailability, and appreciable efficacy on glucose tolerance in mice. PMID:23294321

  13. Activation of Protease Activated Receptor 2 by Exogenous Agonist Exacerbates Early Radiation Injury in Rat Intestine

    SciTech Connect

    Wang Junru; Boerma, Marjan; Kulkarni, Ashwini; Hollenberg, Morley D.; Hauer-Jensen, Martin

    2010-07-15

    Purpose: Protease-activated receptor-2 (PAR{sub 2}) is highly expressed throughout the gut and regulates the inflammatory, mitogenic, fibroproliferative, and nociceptive responses to injury. PAR{sub 2} is strikingly upregulated and exhibits increased activation in response to intestinal irradiation. We examined the mechanistic significance of radiation enteropathy development by assessing the effect of exogenous PAR{sub 2} activation. Methods and Materials: Rat small bowel was exposed to localized single-dose radiation (16.5 Gy). The PAR{sub 2} agonist (2-furoyl-LIGRLO-NH{sub 2}) or vehicle was injected intraperitoneally daily for 3 days before irradiation (before), for 7 days after irradiation (after), or both 3 days before and 7 days after irradiation (before-after). Early and delayed radiation enteropathy was assessed at 2 and 26 weeks after irradiation using quantitative histologic examination, morphometry, and immunohistochemical analysis. Results: The PAR{sub 2} agonist did not elicit changes in the unirradiated (shielded) intestine. In contrast, in the irradiated intestine procured 2 weeks after irradiation, administration of the PAR{sub 2} agonist was associated with more severe mucosal injury and increased intestinal wall thickness in all three treatment groups (p <.05) compared with the vehicle-treated controls. The PAR{sub 2} agonist also exacerbated the radiation injury score, serosal thickening, and mucosal inflammation (p <.05) in the before and before-after groups. The short-term exogenous activation of PAR{sub 2} did not affect radiation-induced intestinal injury at 26 weeks. Conclusion: The results of the present study support a role for PAR{sub 2} activation in the pathogenesis of early radiation-induced intestinal injury. Pharmacologic PAR{sub 2} antagonists might have the potential to reduce the intestinal side effects of radiotherapy and/or as countermeasures in radiologic accidents or terrorism scenarios.

  14. Prediction of selective estrogen receptor beta agonist using open data and machine learning approach

    PubMed Central

    Niu, Ai-qin; Xie, Liang-jun; Wang, Hui; Zhu, Bing; Wang, Sheng-qi

    2016-01-01

    Background Estrogen receptors (ERs) are nuclear transcription factors that are involved in the regulation of many complex physiological processes in humans. ERs have been validated as important drug targets for the treatment of various diseases, including breast cancer, ovarian cancer, osteoporosis, and cardiovascular disease. ERs have two subtypes, ER-α and ER-β. Emerging data suggest that the development of subtype-selective ligands that specifically target ER-β could be a more optimal approach to elicit beneficial estrogen-like activities and reduce side effects. Methods Herein, we focused on ER-β and developed its in silico quantitative structure-activity relationship models using machine learning (ML) methods. Results The chemical structures and ER-β bioactivity data were extracted from public chemogenomics databases. Four types of popular fingerprint generation methods including MACCS fingerprint, PubChem fingerprint, 2D atom pairs, and Chemistry Development Kit extended fingerprint were used as descriptors. Four ML methods including Naïve Bayesian classifier, k-nearest neighbor, random forest, and support vector machine were used to train the models. The range of classification accuracies was 77.10% to 88.34%, and the range of area under the ROC (receiver operating characteristic) curve values was 0.8151 to 0.9475, evaluated by the 5-fold cross-validation. Comparison analysis suggests that both the random forest and the support vector machine are superior for the classification of selective ER-β agonists. Chemistry Development Kit extended fingerprints and MACCS fingerprint performed better in structural representation between active and inactive agonists. Conclusion These results demonstrate that combining the fingerprint and ML approaches leads to robust ER-β agonist prediction models, which are potentially applicable to the identification of selective ER-β agonists. PMID:27486309

  15. Deletion of striatal adenosine A(2A) receptor spares latent inhibition and prepulse inhibition but impairs active avoidance learning.

    PubMed

    Singer, Philipp; Wei, Catherine J; Chen, Jiang-Fan; Boison, Detlev; Yee, Benjamin K

    2013-04-01

    Following early clinical leads, the adenosine A(2A)R receptor (A(2A)R) has continued to attract attention as a potential novel target for treating schizophrenia, especially against the negative and cognitive symptoms of the disease because of A(2A)R's unique modulatory action over glutamatergic in addition to dopaminergic signaling. Through (i) the antagonistic interaction with the dopamine D(2) receptor, and (ii) the regulation of glutamate release and N-methyl-d-aspartate receptor function, striatal A(2A)R is ideally positioned to fine-tune the dopamine-glutamate balance, the disturbance of which is implicated in the pathophysiology of schizophrenia. However, the precise function of striatal A(2A)Rs in the regulation of schizophrenia-relevant behavior is poorly understood. Here, we tested the impact of conditional striatum-specific A(2A)R knockout (st-A(2A)R-KO) on latent inhibition (LI) and prepulse inhibition (PPI) - behavior that is tightly regulated by striatal dopamine and glutamate. These are two common cross-species translational tests for the assessment of selective attention and sensorimotor gating deficits reported in schizophrenia patients; and enhanced performance in these tests is associated with antipsychotic drug action. We found that neither LI nor PPI was significantly affected in st-A(2A)R-KO mice, although a deficit in active avoidance learning was identified in these animals. The latter phenotype, however, was not replicated in another form of aversive conditioning - namely, conditioned taste aversion. Hence, the present study shows that neither learned inattention (as measured by LI) nor sensory gating (as indexed by PPI) requires the integrity of striatal A(2A)Rs - a finding that may undermine the hypothesized importance of A(2A)R in the genesis and/or treatment of schizophrenia. PMID:23276608

  16. Inverse agonist and pharmacochaperone properties of MK-0524 on the prostanoid DP1 receptor.

    PubMed

    Labrecque, Pascale; Roy, Sébastien J; Fréchette, Louis; Iorio-Morin, Christian; Gallant, Maxime A; Parent, Jean-Luc

    2013-01-01

    Prostaglandin D₂ (PGD₂) acts through two G protein-coupled receptors (GPCRs), the prostanoid DP receptor and CRTH2 also known as DP1 and DP2, respectively. Several previously characterized GPCR antagonists are now classified as inverse agonists and a number of GPCR ligands are known to display pharmacochaperone activity towards a given receptor. Here, we demonstrate that a DP1 specific antagonist, MK-0524 (also known as laropiprant), decreased basal levels of intracellular cAMP produced by DP1, a Gα(s)-coupled receptor, in HEK293 cells. This reduction in cAMP levels was not altered by pertussis toxin treatment, indicating that MK-0524 did not induce coupling of DP1 to Gα(i/o) proteins and that this ligand is a DP1 inverse agonist. Basal ERK1/2 activation by DP1 was not modulated by MK-0524. Interestingly, treatment of HEK293 cells expressing Flag-tagged DP1 with MK-0524 promoted DP1 cell surface expression time-dependently to reach a maximum increase of 50% compared to control after 24 h. In contrast, PGD₂ induced the internalization of 75% of cell surface DP1 after the same time of stimulation. The increase in DP1 cell surface targeting by MK-0524 was inhibited by Brefeldin A, an inhibitor of transport from the endoplasmic reticulum-Golgi to the plasma membrane. Confocal microscopy confirmed that a large population of DP1 remained trapped intracellularly and co-localized with calnexin, an endoplasmic reticulum marker. Redistribution of DP1 from intracellular compartments to the plasma membrane was observed following treatment with MK-0524 for 24 h. Furthermore, MK-0524 promoted the interaction between DP1 and the ANKRD13C protein, which we showed previously to display chaperone-like effects towards the receptor. We thus report that MK-0524 is an inverse agonist and a pharmacochaperone of DP1. Our findings may have important implications during therapeutic treatments with MK-0524 and for the development of new molecules targeting DP1. PMID:23762421

  17. Adlea (ALGRX-4975), an injectable capsaicin (TRPV1 receptor agonist) formulation for longlasting pain relief.

    PubMed

    Remadevi, Radhika; Szallisi, Arpad

    2008-02-01

    Anesiva Inc is developing Adlea (ALRGX-4975) - an injectable preparation of capsaicin, a TRPV1 (transient receptor potential vanilloid subfamily 1) receptor agonist - for the potential management of pain associated with osteoarthritis, tendonitiand postsurgical conditions, as well as for neuropathic pain occurring secondary to nerve injury. Adlea functions by desensitizing those neurons that conduct a long-lasting, throbbing form of pain. In phase II clinical trials, a single injection of Adlea significantly reduced pain levels in patients following total knee arthroplasty (TKA) or bunionectomy, and reduced pain in patients with osteoarthritis (OA) or Morton's neuroma. Phase II trials are ongoing to test Adlea in patients who are undergoing total hip arthroplasty or arthroscopic shoulder surgery and in patients with knee OA. Phase III clinical trials for the compound have been slated to begin in 2008 in patients following TKA or bunionectomy. Adlea appears to exhibit promise as a new medication in the treatment of conditions of chronic neuropathic pain. PMID:18240098

  18. Identification and optimization of small-molecule agonists of the human relaxin hormone receptor RXFP1

    PubMed Central

    Xiao, Jingbo; Huang, Zaohua; Chen, Catherine Z.; Agoulnik, Irina U.; Southall, Noel; Hu, Xin; Jones, Raisa E.; Ferrer, Marc; Zheng, Wei; Agoulnik, Alexander I.; Marugan, Juan J.

    2016-01-01

    The anti-fibrotic, vasodilatory, and pro-angiogenic therapeutic properties of recombinant relaxin peptide hormone have been investigated in several diseases and recent clinical trial data has shown benefit in treating acute heart failure. However, the remodeling capacity of these peptide hormones is difficult to study in chronic settings due to their short half-life and the need for intravenous administration. Here we present the first small-molecule series of human relaxin receptor 1 (RXFP1) agonists. These molecules display similar efficacy as the natural hormone in several functional assays. Mutagenesis studies indicate that the small molecules activate relaxin receptor through an allosteric site. These compounds have excellent physical and in vivo pharmacokinetic properties to support further investigation of relaxin biology and animal efficacy studies of the therapeutic benefits of RXFP1 activation. PMID:23764525

  19. Serotonin 5-ht2c receptor agonists: potential for the treatment of obesity.

    PubMed

    Miller, Keith J

    2005-10-01

    Obesity continues to be a burgeoning health problem worldwide. Before their removal from the market, fenfluramine and the more active enantiomer dexfenfluramine were considered to be among the most effective of weight loss agents. Much of the weight loss produced by fenfluramine was attributed to the direct activation of serotonin 5-HT(2C) receptors in the central nervous system via the desmethyl-metabolite of fenfluramine, norfenfluramine. Norfenfluramine, however, is non-selective, activating additional serotonin receptors, such as 5-HT(2A) and 5-HT(2B), which likely mediated the heart valve hypertrophy seen in many patients. Development of highly selective 5-HT(2C) agonists may recapitulate the clinical anti-obesity properties observed with fenfluramine while avoiding the significant cardiovascular and pulmonary side effects. PMID:16249524

  20. IFN-alpha/beta-dependent cross-priming induced by specific toll-like receptor agonists.

    PubMed

    Durand, Vanessa; Wong, Simon Y C; Tough, David F; Le Bon, Agnes

    2006-04-12

    Toll-like receptors (TLR) are pattern recognition receptors that have been identified as crucial in the initiation of innate immune responses against pathogens. They are thought to be involved in shaping appropriate adaptive immune responses, although their precise contribution has not yet been fully characterised. Our aim was to investigate in vivo the effect of different TLR stimuli on cellular immune responses. We examined the ability of a range of TLR stimuli to induce CD8+ T cell responses against a model soluble protein antigen, ovalbumin (OVA). We found that TLR 3, TLR 4, and TLR 9 agonists induced functional cross-priming, and that this process was dependent on IFN-alpha/beta signalling pathway. PMID:16823911

  1. Membrane omega-3 fatty acids modulate the oligomerisation kinetics of adenosine A2A and dopamine D2 receptors

    PubMed Central

    Guixà-González, Ramon; Javanainen, Matti; Gómez-Soler, Maricel; Cordobilla, Begoña; Domingo, Joan Carles; Sanz, Ferran; Pastor, Manuel; Ciruela, Francisco; Martinez-Seara, Hector; Selent, Jana

    2016-01-01

    Membrane levels of docosahexaenoic acid (DHA), an essential omega-3 polyunsaturated fatty acid (ω-3 PUFA), are decreased in common neuropsychiatric disorders. DHA modulates key cell membrane properties like fluidity, thereby affecting the behaviour of transmembrane proteins like G protein-coupled receptors (GPCRs). These receptors, which have special relevance for major neuropsychiatric disorders have recently been shown to form dimers or higher order oligomers, and evidence suggests that DHA levels affect GPCR function by modulating oligomerisation. In this study, we assessed the effect of membrane DHA content on the formation of a class of protein complexes with particular relevance for brain disease: adenosine A2A and dopamine D2 receptor oligomers. Using extensive multiscale computer modelling, we find a marked propensity of DHA for interaction with both A2A and D2 receptors, which leads to an increased rate of receptor oligomerisation. Bioluminescence resonance energy transfer (BRET) experiments performed on living cells suggest that this DHA effect on the oligomerisation of A2A and D2 receptors is purely kinetic. This work reveals for the first time that membrane ω-3 PUFAs play a key role in GPCR oligomerisation kinetics, which may have important implications for neuropsychiatric conditions like schizophrenia or Parkinson’s disease. PMID:26796668

  2. Membrane omega-3 fatty acids modulate the oligomerisation kinetics of adenosine A2A and dopamine D2 receptors

    NASA Astrophysics Data System (ADS)

    Guixà-González, Ramon; Javanainen, Matti; Gómez-Soler, Maricel; Cordobilla, Begoña; Domingo, Joan Carles; Sanz, Ferran; Pastor, Manuel; Ciruela, Francisco; Martinez-Seara, Hector; Selent, Jana

    2016-01-01

    Membrane levels of docosahexaenoic acid (DHA), an essential omega-3 polyunsaturated fatty acid (ω-3 PUFA), are decreased in common neuropsychiatric disorders. DHA modulates key cell membrane properties like fluidity, thereby affecting the behaviour of transmembrane proteins like G protein-coupled receptors (GPCRs). These receptors, which have special relevance for major neuropsychiatric disorders have recently been shown to form dimers or higher order oligomers, and evidence suggests that DHA levels affect GPCR function by modulating oligomerisation. In this study, we assessed the effect of membrane DHA content on the formation of a class of protein complexes with particular relevance for brain disease: adenosine A2A and dopamine D2 receptor oligomers. Using extensive multiscale computer modelling, we find a marked propensity of DHA for interaction with both A2A and D2 receptors, which leads to an increased rate of receptor oligomerisation. Bioluminescence resonance energy transfer (BRET) experiments performed on living cells suggest that this DHA effect on the oligomerisation of A2A and D2 receptors is purely kinetic. This work reveals for the first time that membrane ω-3 PUFAs play a key role in GPCR oligomerisation kinetics, which may have important implications for neuropsychiatric conditions like schizophrenia or Parkinson’s disease.

  3. Effects of Trace Amine-associated Receptor 1 Agonists on the Expression, Reconsolidation, and Extinction of Cocaine Reward Memory

    PubMed Central

    Liu, Jian-Feng; Thorn, David A; Zhang, Yanan

    2016-01-01

    Background: As a modulator of dopaminergic system, trace amine-associated receptor 1 has been shown to play a critical role in regulating the rewarding properties of additive drugs. It has been demonstrated that activation of trace amine-associated receptor 1 decreased the abuse-related behaviors of cocaine in rats. However, the role of trace amine-associated receptor 1 in specific stages of cocaine reward memory is still unclear. Methods: Here, using a cocaine-induced conditioned place preference model, we tested the effects of a selective trace amine-associated receptor 1 agonist RO5166017 on the expression, reconsolidation, and extinction of cocaine reward memory. Results: We found that RO5166017 inhibited the expression but not retention of cocaine-induced conditioned place preference. RO5166017 had no effect on the reconsolidation of cocaine reward memory. Pretreatment with RO5166017 before extinction hindered the formation of extinction long-term memory. RO5166017 did not affect the movement during the conditioned place preference test, indicating the inhibitory effect of RO5166017 on the expression of cocaine-induced conditioned place preference was not caused by locomotion inhibition. Using a cocaine i.v. self-administration model, we found that the combined trace amine-associated receptor 1 partial agonist RO5263397 with extinction had no effect on the following cue- and drug-induced reinstatement of cocaine-seeking behavior. Repeated administration of the trace amine-associated receptor 1 agonist during extinction showed a continually inhibitory effect on the expression of cocaine reward memory both in cocaine-induced conditioned place preference and cocaine self-administration models. Conclusions: Taken together, these results indicate that activation of trace amine-associated receptor 1 specifically inhibited the expression of cocaine reward memory. The inhibitory effect of trace amine-associated receptor 1 agonists on cocaine reward memory suggests

  4. The long-acting β2-adrenoceptor agonist, indacaterol, enhances glucocorticoid receptor-mediated transcription in human airway epithelial cells in a gene- and agonist-dependent manner

    PubMed Central

    Joshi, T; Johnson, M; Newton, R; Giembycz, M A

    2015-01-01

    Background and Purpose Inhaled glucocorticoid (ICS)/long-acting β2-adrenoceptor agonist (LABA) combination therapy is a recommended treatment option for patients with moderate/severe asthma in whom adequate control cannot be achieved by an ICS alone. Previously, we discovered that LABAs can augment dexamethasone-inducible gene expression and proposed that this effect may explain how these two drugs interact to deliver superior clinical benefit. Herein, we extended that observation by analysing, pharmacodynamically, the effect of the LABA, indacaterol, on glucocorticoid receptor (GR)-mediated gene transcription induced by seven ligands with intrinsic activity values that span the spectrum of full agonism to antagonism. Experimental Approach BEAS-2B human airway epithelial cells stably transfected with a 2× glucocorticoid response element luciferase reporter were used to model gene transcription together with an analysis of several glucocorticoid-inducible genes. Key Results Indacaterol augmented glucocorticoid-induced reporter activation in a manner that was positively related to the intrinsic activity of the GR agonist. This effect was demonstrated by an increase in response maxima without a change in GR agonist affinity or efficacy. Indacaterol also enhanced glucocorticoid-inducible gene expression. However, the magnitude of this effect was dependent on both the GR agonist and the gene of interest. Conclusions and Implications These data suggest that indacaterol activates a molecular rheostat, which increases the transcriptional competency of GR in an agonist- and gene-dependent manner without apparently changing the relationship between fractional GR occupancy and response. These findings provide a platform to rationally design ICS/LABA combination therapy that is based on the generation of agonist-dependent gene expression profiles in target and off-target tissues. PMID:25598440

  5. Targeting Incretins in Type 2 Diabetes: Role of GLP-1 Receptor Agonists and DPP-4 Inhibitors

    PubMed Central

    Pratley, Richard E.; Gilbert, Matthew

    2008-01-01

    Until recently, the pathogenesis of type 2 diabetes mellitus (T2DM) has been conceptualized in terms of the predominant defects in insulin secretion and insulin action. It is now recognized that abnormalities in other hormones also contribute to the development of hyperglycemia. For example, the incretin effect, mediated by glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP), is attenuated in T2DM. Intravenous administration of GLP-1 ameliorates hyperglycemia in patients with T2DM, but an extremely short half-life limits its utility as a therapeutic agent. Strategies to leverage the beneficial effects of GLP-1 include GLP-1 receptor agonists or analogs or dipeptidyl peptidase-4 (DPP-4) inhibitors—agents that act by slowing the inactivation of endogenous GLP-1 and GIP. The GLP-1 agonist exenatide has been shown to improve HbA1c and decrease body weight. However, exenatide is limited by its relatively short pharmacologic half-life, various gastrointestinal (GI) side effects, and the development of antibodies. Studies of a long-acting exenatide formulation suggest that it has improved efficacy and also promotes weight loss. Another prospect is liraglutide, a once-daily human GLP-1 analog. In phase 2 studies, liraglutide lowered HbA1c by up to 1.7% and weight by approximately 3 kg, with apparently fewer GI side effects than exenatide. DPP-4 inhibitors such as sitagliptin and vildagliptin result in clinically significant reductions in HbA1c, and are weight neutral with few GI side effects. This review will provide an overview of current and emerging agents that augment the incretin system with a focus on the role of GLP-1 receptor agonists and DPP-4 inhibitors. PMID:18795210

  6. Effect of dopamine D4 receptor agonists on sleep architecture in rats.

    PubMed

    Nakazawa, Shunsuke; Nakamichi, Keiko; Imai, Hideaki; Ichihara, Junji

    2015-12-01

    Dopamine plays a key role in the regulation of sleep-wake states, as revealed by the observation that dopamine-releasing agents such as methylphenidate have wake-promoting effects. However, the precise mechanisms for the wake-promoting effect produced by the enhancement of dopamine transmission are not fully understood. Although dopamine D1, D2, and D3 receptors are known to have differential effects on sleep architecture, the role of D4 receptors (D4Rs), and particularly the influence of D4R activation on the sleep-wake state, has not been studied so far. In this study, we investigated for the first time the effects of two structurally different D4R agonists, Ro 10-5824 and A-412997, on the sleep-wake states in rats. We found that both D4R agonists generally increased waking duration, and conversely, reduced non-rapid eye movement (NREM) sleep duration in rats. The onset of NREM sleep was also generally delayed. However, only the A-412997 agonist (but not the Ro 10-5824) influenced rapid eye movement sleep onset and duration. Furthermore, these effects were accompanied with an enhancement of EEG spectral power in the theta and the gamma bands. Our results suggest the involvement of dopamine D4R in the regulation of sleep-wake states. The activation of the D4R could enhance the arousal states as revealed by the behavioral and electrophysiological patterns in this study. Dopamine D4R may contribute to the arousal effects of dopamine-releasing agents such as methylphenidate. PMID:25985889

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