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Sample records for a2 receptor antagonist

  1. 3D pharmacophore models for thromboxane A(2) receptor antagonists.

    PubMed

    Wei, Jing; Liu, Yixi; Wang, Songqing

    2009-10-01

    Thromboxane A(2) (TXA(2)) is an endogenous arachidonic acid derivative closely correlated to thrombosis and other cardiovascular diseases. The action of TXA(2) can be effectively inhibited with TXA(2) receptor antagonists (TXRAs). Previous studies have attempted to describe the interactions between the TXA(2) receptor and its ligands, but their conclusions are still controversial. In this study, ligand-based computational drug design is used as a new and effective way to investigate the structure-activity relationship of TXRAs. Three-dimensional pharmacophore models of TXRAs were built with HypoGenRefine and HipHop modules in CATALYST software. The optimal HypoGenRefine model was developed on the basis of 25 TXRAs. It consists of two hydrophobic groups, one aromatic ring, one hydrogen-bond acceptor and four excluded volumes. The optimal HipHop model contains two hydrophobic groups and two hydrogen-bond acceptors. These models describe the key structure-activity relationship of TXRAs, can predict their activities, and can thus be used to design novel antagonists. PMID:19263096

  2. 3D pharmacophore models for thromboxane A(2) receptor antagonists.

    PubMed

    Wei, Jing; Liu, Yixi; Wang, Songqing

    2009-10-01

    Thromboxane A(2) (TXA(2)) is an endogenous arachidonic acid derivative closely correlated to thrombosis and other cardiovascular diseases. The action of TXA(2) can be effectively inhibited with TXA(2) receptor antagonists (TXRAs). Previous studies have attempted to describe the interactions between the TXA(2) receptor and its ligands, but their conclusions are still controversial. In this study, ligand-based computational drug design is used as a new and effective way to investigate the structure-activity relationship of TXRAs. Three-dimensional pharmacophore models of TXRAs were built with HypoGenRefine and HipHop modules in CATALYST software. The optimal HypoGenRefine model was developed on the basis of 25 TXRAs. It consists of two hydrophobic groups, one aromatic ring, one hydrogen-bond acceptor and four excluded volumes. The optimal HipHop model contains two hydrophobic groups and two hydrogen-bond acceptors. These models describe the key structure-activity relationship of TXRAs, can predict their activities, and can thus be used to design novel antagonists.

  3. Lack of tolerance to motor stimulant effects of a selective adenosine A(2A) receptor antagonist.

    PubMed

    Halldner, L; Lozza, G; Lindström, K; Fredholm, B B

    2000-10-20

    It is well known that tolerance develops to the actions of caffeine, which acts as an antagonist on adenosine A(1) and A(2A) receptors. Since selective adenosine A(2A) antagonists have been proposed as adjuncts to 3,4-dihydroxyphenylalanine (L-DOPA) therapy in Parkinson's disease we wanted to examine if tolerance also develops to the selective A(2A) receptor antagonist 5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo-[4,3-e]-1,2, 4-triazolo [1,5-c]pyrimidine (SCH 58261). SCH 58261 (0.1 and 7.5 mg/kg) increased basal locomotion and the motor stimulation afforded by apomorphine. Neither effect was subject to tolerance following long-term treatment with the same doses given intraperitoneally twice daily. There were no adaptive changes in A(1) and A(2A) adenosine receptors or their corresponding messenger RNA or in dopamine D(1) or D(2) receptors. These results demonstrate that the tolerance that develops to caffeine is not secondary to its inhibition of adenosine A(2A) receptors. The results also offer hope that long-term treatment with an adenosine A(2A) receptor antagonist may be possible in man.

  4. 3D-pharmacophore models for selective A2A and A2B adenosine receptor antagonists.

    PubMed

    Wei, Jing; Wang, Songqing; Gao, Shaofen; Dai, Xuedong; Gao, Qingzhi

    2007-01-01

    Three-dimensional pharmacophore models were generated for A2A and A2B adenosine receptors (ARs) based on highly selective A2A and A2B antagonists using the Catalyst program. The best pharmacophore model for selective A2A antagonists (Hypo-A2A) was obtained through a careful validation process. Four features contained in Hypo-A2A (one ring aromatic feature (R), one positively ionizable feature (P), one hydrogen bond acceptor lipid feature (L), and one hydrophobic feature (H)) seem to be essential for antagonists in terms of binding activity and A2A AR selectivity. The best pharmacophore model for selective A2B antagonists (Hypo-A2B) was elaborated by modifying the Catalyst common features (HipHop) hypotheses generated from the selective A2B antagonists training set. Hypo-A2B also consists of four features: one ring aromatic feature (R), one hydrophobic aliphatic feature (Z), and two hydrogen bond acceptor lipid features (L). All features play an important role in A2B AR binding affinity and are essential for A2B selectivity. Both A2A and A2B pharmacophore models have been validated toward a wide set of test molecules containing structurally diverse selective antagonists of all AR subtypes. They are capable of identifying correspondingly high potent antagonists and differentiating antagonists between subtypes. The results of our study will act as a valuable tool for retrieving structurally diverse compounds with desired biological activities and designing novel selective adenosine receptor ligands. PMID:17330954

  5. 3D-pharmacophore models for selective A2A and A2B adenosine receptor antagonists.

    PubMed

    Wei, Jing; Wang, Songqing; Gao, Shaofen; Dai, Xuedong; Gao, Qingzhi

    2007-01-01

    Three-dimensional pharmacophore models were generated for A2A and A2B adenosine receptors (ARs) based on highly selective A2A and A2B antagonists using the Catalyst program. The best pharmacophore model for selective A2A antagonists (Hypo-A2A) was obtained through a careful validation process. Four features contained in Hypo-A2A (one ring aromatic feature (R), one positively ionizable feature (P), one hydrogen bond acceptor lipid feature (L), and one hydrophobic feature (H)) seem to be essential for antagonists in terms of binding activity and A2A AR selectivity. The best pharmacophore model for selective A2B antagonists (Hypo-A2B) was elaborated by modifying the Catalyst common features (HipHop) hypotheses generated from the selective A2B antagonists training set. Hypo-A2B also consists of four features: one ring aromatic feature (R), one hydrophobic aliphatic feature (Z), and two hydrogen bond acceptor lipid features (L). All features play an important role in A2B AR binding affinity and are essential for A2B selectivity. Both A2A and A2B pharmacophore models have been validated toward a wide set of test molecules containing structurally diverse selective antagonists of all AR subtypes. They are capable of identifying correspondingly high potent antagonists and differentiating antagonists between subtypes. The results of our study will act as a valuable tool for retrieving structurally diverse compounds with desired biological activities and designing novel selective adenosine receptor ligands.

  6. An efficient route to xanthine based A(2A) adenosine receptor antagonists and functional derivatives.

    PubMed

    Labeaume, Paul; Dong, Ma; Sitkovsky, Michail; Jones, Elizabeth V; Thomas, Rhiannon; Sadler, Sara; Kallmerten, Amy E; Jones, Graham B

    2010-09-21

    A one-pot route to 8-substituted xanthines has been developed from 5,6-diaminouracils and carboxaldehydes. Yields are good and the process applicable to a range of substrates including a family of A(2A) adenosine receptor antagonists. A new route to the KW-6002 family of antagonists is presented including a pro-drug variant, and application to related image contrast agents developed.

  7. Discovery of LAS101057: A Potent, Selective, and Orally Efficacious A2B Adenosine Receptor Antagonist

    PubMed Central

    2010-01-01

    The structure−activity relationships for a series of pyrazine-based A2B adenosine receptor antagonists are described. From this work, LAS101057 (17), a potent, selective, and orally efficacious A2B receptor antagonist, was identified as a clinical development candidate. LAS101057 inhibits agonist-induced IL-6 production in human fibroblasts and is active in an ovalbumin (OVA)-sensitized mouse model after oral administration, reducing airway hyperresponsiveness to methacholine, Th2 cytokine production, and OVA-specific IgE levels. PMID:24900298

  8. Discovery of Potent and Highly Selective A2B Adenosine Receptor Antagonist Chemotypes.

    PubMed

    El Maatougui, Abdelaziz; Azuaje, Jhonny; González-Gómez, Manuel; Miguez, Gabriel; Crespo, Abel; Carbajales, Carlos; Escalante, Luz; García-Mera, Xerardo; Gutiérrez-de-Terán, Hugo; Sotelo, Eddy

    2016-03-10

    Three novel families of A2B adenosine receptor antagonists were identified in the context of the structural exploration of the 3,4-dihydropyrimidin-2(1H)-one chemotype. The most appealing series contain imidazole, 1,2,4-triazole, or benzimidazole rings fused to the 2,3-positions of the parent diazinone core. The optimization process enabled identification of a highly potent (3.49 nM) A2B ligand that exhibits complete selectivity toward A1, A2A, and A3 receptors. The results of functional cAMP experiments confirmed the antagonistic behavior of representative ligands. The main SAR trends identified within the series were substantiated by a molecular modeling study based on a receptor-driven docking model constructed on the basis of the crystal structure of the human A2A receptor.

  9. Antagonists of the human A(2A) receptor. Part 6: Further optimization of pyrimidine-4-carboxamides.

    PubMed

    Gillespie, Roger J; Bamford, Samantha J; Clay, Alex; Gaur, Suneel; Haymes, Tim; Jackson, Philip S; Jordan, Allan M; Klenke, Burkhard; Leonardi, Stefania; Liu, Jeanette; Mansell, Howard L; Ng, Sean; Saadi, Mona; Simmonite, Heather; Stratton, Gemma C; Todd, Richard S; Williamson, Douglas S; Yule, Ian A

    2009-09-15

    Antagonists of the human A(2A) receptor have been reported to have potential therapeutic benefit in the alleviation of the symptoms associated with neurodegenerative movement disorders such as Parkinson's disease. As part of our efforts to discover potent and selective antagonists of this receptor, we herein describe the detailed optimization and structure-activity relationships of a series of pyrimidine-4-carboxamides. These optimized derivatives display desirable physiochemical and pharmacokinetic profiles, which have led to promising oral activity in clinically relevant models of Parkinson's disease.

  10. Therapeutic Opportunities for Caffeine and A2A Receptor Antagonists in Retinal Diseases.

    PubMed

    Boia, Raquel; Ambrósio, António Francisco; Santiago, Ana Raquel

    2016-01-01

    Caffeine, the major component of coffee, is the most consumed psychostimulant in the world. Caffeine is an adenosine analog and acts as a nonselective adenosine receptor antagonist. The majority of the effects of caffeine are mainly mediated by the blockade of adenosine receptors, and the proved neuroprotective effects of caffeine in brain disorders have been mimicked by the blockade of adenosine A2A receptor (A2AR). A growing body of evidence demonstrates that microglia-mediated neuroinflammation plays a key role in the pathophysiology of brain and retinal diseases. Moreover, the control of microglia reactivity by blocking A2AR has been proposed to be the mechanism underlying the observed protective effects of caffeine. Hence, it is conceivable that caffeine and A2AR antagonists offer therapeutic value for the treatment of retinal diseases, mainly those involving microglia-mediated neuroinflammation.

  11. Therapeutic Opportunities for Caffeine and A2A Receptor Antagonists in Retinal Diseases.

    PubMed

    Boia, Raquel; Ambrósio, António Francisco; Santiago, Ana Raquel

    2016-01-01

    Caffeine, the major component of coffee, is the most consumed psychostimulant in the world. Caffeine is an adenosine analog and acts as a nonselective adenosine receptor antagonist. The majority of the effects of caffeine are mainly mediated by the blockade of adenosine receptors, and the proved neuroprotective effects of caffeine in brain disorders have been mimicked by the blockade of adenosine A2A receptor (A2AR). A growing body of evidence demonstrates that microglia-mediated neuroinflammation plays a key role in the pathophysiology of brain and retinal diseases. Moreover, the control of microglia reactivity by blocking A2AR has been proposed to be the mechanism underlying the observed protective effects of caffeine. Hence, it is conceivable that caffeine and A2AR antagonists offer therapeutic value for the treatment of retinal diseases, mainly those involving microglia-mediated neuroinflammation. PMID:26959995

  12. Evidence for homogeneity of thromboxane A2 receptor using structurally different antagonists.

    PubMed

    Swayne, G T; Maguire, J; Dolan, J; Raval, P; Dane, G; Greener, M; Owen, D A

    1988-08-01

    Nine structurally dissimilar thromboxane antagonists (SQ 29548, ICI 185282, AH 23848, BM 13505 (Daltroban), BM 13177 (Sulotroban), SK&F 88046, L-636499, L-640035 and a Bayer compound SK&F 47821) were studied for activity as thromboxane A2 receptor antagonists. The assays used were inhibition of responses induced by the thromboxane mimetic, U46619, on human washed platelet aggregation, rabbit platelet aggregation, rabbit aortic strip contraction, anaesthetised guinea-pig bronchoconstriction, and a radio-labelled ligand (125I-PTA-OH) binding assay as a measure of affinity for the human platelet receptor. The results of the present study, with activities spanning at least four orders of magnitude along with statistically significant correlations (at least P less than 0.01), strongly suggests that between assays, antagonists and species a homogenous population of thromboxane A2 receptors exists. This finding is in contrast to those of a close series of 13-azapinane antagonists studied by other workers which have suggested receptor heterogeneity.

  13. Adenosine A2A Receptor Antagonists and Parkinson’s Disease

    PubMed Central

    2011-01-01

    This Review summarizes and updates the work on adenosine A2A receptor antagonists for Parkinson’s disease from 2006 to the present. There have been numerous publications, patent applications, and press releases within this time frame that highlight new medicinal chemistry approaches to this attractive and promising target to treat Parkinson’s disease. The Review is broken down by scaffold type and will discuss the efforts to optimize particular scaffolds for activity, pharmacokinetics, and other drug discovery parameters. The majority of approaches focus on preparing selective A2A antagonists, but a few approaches to dual A2A/A1 antagonists will also be highlighted. The in vivo profiles of compounds will be highlighted and discussed to compare activities across different chemical series. A clinical report and update will be given on compounds that have entered clinical trials. PMID:22860156

  14. 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

  15. Striatal pre- and postsynaptic profile of adenosine A(2A) receptor antagonists.

    PubMed

    Orru, Marco; Bakešová, Jana; Brugarolas, Marc; Quiroz, César; Beaumont, Vahri; Goldberg, Steven R; Lluís, Carme; Cortés, Antoni; Franco, Rafael; Casadó, Vicent; Canela, Enric I; Ferré, Sergi

    2011-01-11

    Striatal adenosine A(2A) receptors (A(2A)Rs) are highly expressed in medium spiny neurons (MSNs) of the indirect efferent pathway, where they heteromerize with dopamine D(2) receptors (D(2)Rs). A(2A)Rs are also localized presynaptically in cortico-striatal glutamatergic terminals contacting MSNs of the direct efferent pathway, where they heteromerize with adenosine A(1) receptors (A(1)Rs). It has been hypothesized that postsynaptic A(2A)R antagonists should be useful in Parkinson's disease, while presynaptic A(2A)R 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 A(2A)R 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 A(2A)R-D(2)R and A(1)R-A(2A)R heteromers to determine possible differences in the affinity of these compounds for different A(2A)R heteromers. Heteromerization played a key role in the presynaptic profile of SCH-442416, since it bound with much less affinity to A(2A)R when co-expressed with D(2)R than with A(1)R. KW-6002 showed the best relative affinity for A(2A)R co-expressed with D(2)R than co-expressed with A(1)R, 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

  16. 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

  17. 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

  18. PD 115,199: an antagonist ligand for adenosine A2 receptors

    SciTech Connect

    Bruns, R.F.; Fergus, J.H.; Badger, E.W.; Bristol, J.A.; Santay, L.A.; Hays, S.J.

    1986-03-05

    PD 115,199, N-(2-(dimethylamino)ethyl)-N-methyl-4-((2,3,6,-7-tetrahydro)-2,6-dioxo-1,3-dipropyl-1H-purin-8-yl)benzenesulfonamide, is an adenosine (ado) antagonist with high affinity at both the A1 and A2 subtypes of ado receptor, with an IC50 of 24 nM in (/sup 3/H)CHA binding to A1 receptors and 23 nM in (/sup 3/H)NECA binding to A2 receptors. (/sup 3/H)PD 115,199 (126 Ci/mmol) was prepared by reduction of the diallyl analog. In rat striatal membranes, dose-inhibition curves for the A1-selective ado antagonist PD 116,948 vs 0.5 nM (/sup 3/H)PD 115,199 were markedly biphasic, with 21% of specific binding representing A1 sites with an IC50 for PD 116,948 of 0.52 nM, and the remaining 79% representing apparent A2 sites with an IC50 for PD 116,948 of 163 nM. Subsequent experiments were done in the presence of 20 nM PD 116,948 to eliminate A1 binding. Under these conditions, about 80% of binding was specific. (/sup 3/H)PD 115,199 bound with high affinity (K/sub d/ 10 nM) to a limited number of sites (Bmax 120 pmol/g wet weight). Affinities of compounds in (/sup 3/H)PD 115,199 binding closely paralleled their affinities in (/sup 3/H)NECA binding. Ado antagonists were generally several fold more active vs (/sup 3/H)PD 115,199 than vs (/sup 3/H)NECA, whereas the reverse was the case for agonists. Binding was much higher in striatum than in other brain areas. These results indicate that (/sup 3/H)PD 115,199 binds to a high-affinity A2 receptor.

  19. Discovery and optimization of potent and selective functional antagonists of the human adenosine A2B receptor.

    PubMed

    Bedford, Simon T; Benwell, Karen R; Brooks, Teresa; Chen, Ijen; Comer, Mike; Dugdale, Sarah; Haymes, Tim; Jordan, Allan M; Kennett, Guy A; Knight, Anthony R; Klenke, Burkhard; LeStrat, Loic; Merrett, Angela; Misra, Anil; Lightowler, Sean; Padfield, Anthony; Poullennec, Karine; Reece, Mark; Simmonite, Heather; Wong, Melanie; Yule, Ian A

    2009-10-15

    We herein report the discovery of a novel class of antagonists of the human adenosine A2B receptor. This low molecular weight scaffold has been optimized to offer derivatives with potential utility for the alleviation of conditions associated with this receptor subtype, such as nociception, diabetes, asthma and COPD. Furthermore, preliminary pharmacokinetic analysis has revealed compounds with profiles suitable for either inhaled or systemic routes of administration.

  20. Application of lipid microspheres to prepare a thromboxane A2 receptor antagonist aerosol for inhalation.

    PubMed

    Takenaga, M; Nakagawa, T; Igarashi, R; Mizushima, Y

    1993-01-01

    The methyl ester of a new thromboxane A2 receptor antagonist, (+)S-145, i.e. (1R,2S,3S,4S)-(5Z)-7-(3-phenyl-sulfonyl-aminobicyclo[2,2,1]he pt-2-yl)heptenoic acid, was incorporated into lipid microspheres (lipo S-145-Me) and its pharmacological effect and tissue distribution were examined in guinea pigs following aerosol delivery. Bronchoconstrictive responses induced by intravenous injection of U46619 or the inhalation of ovalbumin were suppressed in a dose-dependent manner by aerosol inhalation of lipo S-145-Me, which was 3-10 times more potent that the unencapsulated calcium dihydrate of the original drug (S-1452). There was no significant difference in the airway tissue distribution of labelled lipo S-145-Me versus S-1452 after 2 or 5 min of inhalation, but the encapsulated drug showed marked accumulation in the lungs after 30 min of inhalation. The in vitro uptake of lipo [14C] S-145-Me by fresh human neutrophils and an eosinophil cell line was respectively 7 times and 3.5 times higher than that of [14C] S-1452. These results suggest that lipo S-145-Me has the potential to be used as an inhalational antiasthma agent, and that its effect may be partly attributable to a for inflammatory cells which are responsible for allergic airway inflammation.

  1. Brain-Penetrant Tetrahydronaphthalene Thromboxane A2-Prostanoid (TP) Receptor Antagonists as Prototype Therapeutics for Alzheimer’s Disease

    PubMed Central

    2012-01-01

    A hallmark pathological feature of the Alzheimer’s disease (AD) brain is the presence of senile plaques, which comprise amyloid β (Aβ) peptides that are derived from the amyloid precursor protein (APP). The plaque-containing AD brain is thought to be under oxidative stress, as evidenced by increased lipid oxidation products that include isoprostane-F2αIII (iPF2αIII). IPF2αIII can bind to and activate the thromboxane A2-prostanoid (TP) receptor, and TP receptor activation causes increased Aβ production through enhancement of APP mRNA stability. Moreover, TP receptor antagonists have been shown to block iPF2αIII-induced increases of Aβ secretion. Thus, the TP receptor may be a potential drug target for AD therapy. However, here we show that existing TP receptor antagonists have poor blood-brain barrier (BBB) permeability, likely due to the presence of a carboxylic acid moiety that is believed to be important for receptor interaction, but which may hamper passive diffusion across the BBB. We now report selected analogues of a known tetrahydronaphthalene TP receptor antagonist, wherein the carboxylic acid moiety has been replaced by heterocyclic bioisosteres. These heterocyclic analogues retained relatively high affinity for the mouse and human TP receptors, and, unlike the parent carboxylic acid compound, several examples freely diffused across the BBB into the brain upon administration to mice. These results reveal that brain-penetrant tetrahydronaphthalene TP receptor antagonists can be developed by substituting the carboxylic acid moiety with a suitable nonacidic bioisostere. Compounds of this type hold promise as potential lead structures to develop drug candidates for the treatment of AD. PMID:23173073

  2. Time-course of protection by the selective A2A receptor antagonist SCH58261 after transient focal cerebral ischemia.

    PubMed

    Melani, Alessia; Dettori, Ilaria; Corti, Francesca; Cellai, Lucrezia; Pedata, Felicita

    2015-08-01

    Evidence indicates that the adenosine A2A receptor subtype is of critical importance in stroke. In previous studies, in the model of permanent middle cerebral artery occlusion (pMCAo), the adenosine A2A receptor antagonist, SCH58261, administered soon after ischemia, proved protective against excessive glutamate outflow in the first 4 h after ischemia and against neurological deficit and tissue damage evaluated 24 h after pMCAo. In the present work, we investigated if neuroprotective effect of SCH58261 was maintained 7 days after transient MCAo (tMCAo). SCH58261 (0.01 mg/kg, i.p.), administered twice/day for 7 days, protected from neurological deficit 1 day after tMCAo, but no more after 5 and 7 days. Two days after tMCAo, SCH58261 did not reduce blood cell infiltration, evaluated as HIS-48 positive cells, into ischemic striatal and cortical tissue. Moreover, 7 days after tMCAo, SCH58261 has not protected ischemic areas from damage and has not ameliorated myelin organization into the ischemic striatum. Protection by the A2A receptor antagonist 24 h after ischemia is attributable to reduced excitotoxicity. Seven days after ischemia the early protective effect of the A2A receptor antagonist likely has been overwhelmed by a secondary damage due to blood cell infiltration and neuroinflammation.

  3. Leukotriene receptor antagonist therapy

    PubMed Central

    Dempsey, O

    2000-01-01

    Leukotriene receptor antagonists (LTRA) are a new class of drugs for asthma treatment, available in tablet form. Their unique mechanism of action results in a combination of both bronchodilator and anti-inflammatory effects. While their optimal place in asthma management is still under review, LTRA represent an important advance in asthma pharmacotherapy.


Keywords: leukotriene receptor antagonist; asthma; montelukast; zafirlukast PMID:11085767

  4. 1-, 3- and 8-substituted-9-deazaxanthines as potent and selective antagonists at the human A2B adenosine receptor.

    PubMed

    Stefanachi, Angela; Brea, Jose Manuel; Cadavid, Maria Isabel; Centeno, Nuria B; Esteve, Cristina; Loza, Maria Isabel; Martinez, Ana; Nieto, Rosa; Raviña, Enrique; Sanz, Ferran; Segarra, Victor; Sotelo, Eddy; Vidal, Bernat; Carotti, Angelo

    2008-03-15

    A large series of piperazin-, piperidin- and tetrahydroisoquinolinamides of 4-(1,3-dialkyl-9-deazaxanthin-8-yl)phenoxyacetic acid were prepared through conventional or multiple parallel syntheses and evaluated for their binding affinity at the recombinant human adenosine receptors, chiefly at the hA(2B) and hA(2A) receptor subtypes. Several ligands endowed with high binding affinity at hA(2B) receptors, excellent selectivity over hA(2A) and hA(3) and a significant, but lower, selectivity over hA(1) were identified. Among them, piperazinamide derivatives 23 and 52, and piperidinamide derivative 69 proved highly potent at hA(2B) (K(i)=11, 2 and 5.5 nM, respectively) and selective towards hA(2A) (hA(2A)/hA(2B) SI=912, 159 and 630, respectively), hA(3) (hA(3)/hA(2B) SI=>100, 3090 and >180, respectively) and hA(1) (hA(1)/hA(2B) SI=>100, 44 and 120, respectively), SI being the selectivity index. A number of selected ligands tested in functional assays in vitro showed very interesting antagonist activities and efficacies at both A(2A) and A(2B) receptor subtypes, with pA(2) values close to the corresponding pK(i)s. Structure-affinity and structure-selectivity relationships suggested that the binding potency at the hA(2B) receptor may be increased by lipophilic substituents at the N4-position of piperazinamides and that an ortho-methoxy substituent at the 8-phenyl ring and alkyl groups at N1 larger than the ones at N3, in the 9-deazaxanthine ring, may strongly enhance the hA(2A)/hA(2B) SI. PMID:18226909

  5. Vasopressin receptor antagonists.

    PubMed

    Palmer, Biff F

    2015-01-01

    Arginine vasopressin (AVP) is the principal hormone involved in regulating the tonicity of body fluids. Less appreciated is the role that AVP plays in a variety of other physiologic functions including glucose metabolism, cardiovascular homeostasis, bone metabolism, and cognitive behavior. AVP receptor antagonists are now available and currently approved to treat hyponatremia. There is a great deal of interest in exploring the potential benefits that these drugs may play in blocking AVP-mediated effects in other organ systems. The purpose of this report is to provide an update on the expanding role of AVP receptor antagonists and what disease states these drugs may eventually be used for.

  6. Vasopressin receptor antagonists.

    PubMed

    Palmer, Biff F

    2015-01-01

    Arginine vasopressin (AVP) is the principal hormone involved in regulating the tonicity of body fluids. Less appreciated is the role that AVP plays in a variety of other physiologic functions including glucose metabolism, cardiovascular homeostasis, bone metabolism, and cognitive behavior. AVP receptor antagonists are now available and currently approved to treat hyponatremia. There is a great deal of interest in exploring the potential benefits that these drugs may play in blocking AVP-mediated effects in other organ systems. The purpose of this report is to provide an update on the expanding role of AVP receptor antagonists and what disease states these drugs may eventually be used for. PMID:25604388

  7. [3H]SCH 58261, a selective adenosine A2A receptor antagonist, is a useful ligand in autoradiographic studies.

    PubMed

    Fredholm, B B; Lindström, K; Dionisotti, S; Ongini, E

    1998-03-01

    We have characterized the new potent and selective nonxanthine adenosine A2A receptor antagonist SCH 58261 as a new radioligand for receptor autoradiography. In autoradiographic studies using agonist radioligands for A2A receptors ([3H]CGS 21680) or A1 receptors (N6-[3H]cyclohexyladenosine), it was found that SCH 58261 is close to 800-fold selective for rat brain A2A versus A1 receptors (Ki values of 1.2 nM versus 0.8 microM). Moreover, receptor autoradiography showed that [3H]SCH 58261, in concentrations below 2 nM, binds only to the dopamine-rich regions of the rat brain, with a K(D) value of 1.4 (0.8-1.8) nM. The maximal number of binding sites was 310 fmol/mg of protein in the striatum. Below concentrations of 3 nM, the nonspecific binding was <15%. Three adenosine analogues displaced all specific binding of [3H] SCH 58261 with the following estimated Ki values (nM): 2-hex-1-ynyl-5'-N-ethylcarboxamidoadenosine, 3.9 (1.8-8.4); CGS 21680, 130 (42-405); N6-cyclohexyladenosine, 9,985 (3,169-31,462). The binding of low concentrations of SCH 58261 was not influenced by either GTP (100 microM) or Mg2+ (10 mM). The present results show that in its tritium-labeled form, SCH 58261 appears to be a good radioligand for autoradiographic studies, because it does not suffer from some of the problems encountered with the currently used agonist radioligand [3H]CGS 21680.

  8. Adenosine A2A receptor antagonists: blockade of adenosinergic effects and T regulatory cells

    PubMed Central

    Sitkovsky, M; Lukashev, D; Deaglio, S; Dwyer, K; Robson, S C; Ohta, A

    2008-01-01

    The intensity and duration of host responses are determined by protective mechanisms that control tissue injury by dampening down inflammation. Adenosine generation and consequent effects, mediated via A2A adenosine receptors (A2AR) on effector cells, play a critical role in the pathophysiological modulation of these responses in vivo. Adenosine is both released by hypoxic cells/tissues and is also generated from extracellular nucleotides by ecto-enzymes e.g. CD39 (ENTPD1) and CD73 that are expressed by the vasculature and immune cells, in particular by T regulatory cell. In general, these adenosinergic mechanisms minimize the extent of collateral damage to host tissues during the course of inflammatory reactions. However, induction of suppressive pathways might also cause escape of pathogens and permit dissemination. In addition, adenosinergic responses may inhibit immune responses while enhancing vascular angiogenic responses to malignant cells that promote tumor growth. Novel drugs that block A2AR-adenosinergic effects and/or adenosine generation have the potential to boost pathogen destruction and to selectively destroy malignant tissues. In the latter instance, future treatment modalities might include novel ‘anti-adenosinergic' approaches that augment immune clearance of malignant cells and block permissive angiogenesis. This review addresses several possible pharmacological modalities to block adenosinergic pathways and speculates on their future application together with impacts on human disease. PMID:18311159

  9. Novel Alexa Fluor-488 labeled antagonist of the A(2A) adenosine receptor: Application to a fluorescence polarization-based receptor binding assay.

    PubMed

    Kecskés, Miklós; Kumar, T Santhosh; Yoo, Lena; Gao, Zhan-Guo; Jacobson, Kenneth A

    2010-08-15

    Fluorescence polarization (FP) assay has many advantages over the traditional radioreceptor binding studies. We developed an A(2A) adenosine receptor (AR) FP assay using a newly synthesized fluorescent antagonist of the A(2A)AR (MRS5346), a pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amine derivative conjugated to the fluorescent dye Alexa Fluor-488. MRS5346 displayed a K(i) value of 111+/-16nM in radioligand binding using [(3)H]CGS21680 and membranes prepared from HEK293 cells stably expressing the human A(2A)AR. In a cyclic AMP functional assay, MRS5346 was shown to be an A(2A)AR antagonist. MRS5346 did not show any effect on A(1) and A(3) ARs in binding or the A(2B)AR in a cyclic AMP assay at 10microM. Its suitability as a fluorescent tracer was indicated in an initial observation of an FP signal following A(2A)AR binding. The FP signal was optimal with 20nM MRS5346 and 150microg protein/mL HEK293 membranes. The association and dissociation kinetic parameters were readily determined using this FP assay. The K(d) value of MRS5346 calculated from kinetic parameters was 16.5+/-4.7nM. In FP competition binding experiments using MRS5346 as a tracer, K(i) values of known AR agonists and antagonists consistently agreed with K(i) values from radioligand binding. Thus, this FP assay, which eliminates using radioisotopes, appears to be appropriate for both routine receptor binding and high-throughput screening with respect to speed of analysis, displaceable signal and precision. The approach used in the present study could be generally applicable to other GPCRs.

  10. Use of molecular modeling aided design to dial out hERG liability in adenosine A(2A) receptor antagonists.

    PubMed

    Deng, Qiaolin; Lim, Yeon-Hee; Anand, Rajan; Yu, Younong; Kim, Jae-hun; Zhou, Wei; Zheng, Junying; Tempest, Paul; Levorse, Dorothy; Zhang, Xiaoping; Greene, Scott; Mullins, Deborra; Culberson, Chris; Sherborne, Brad; Parker, Eric M; Stamford, Andrew; Ali, Amjad

    2015-08-01

    Molecular modeling was performed on a triazolo quinazoline lead compound to help develop a series of adenosine A2A receptor antagonists with improved hERG profile. Superposition of the lead compound onto MK-499, a benchmark hERG inhibitor, combined with pKa calculations and measurement, identified terminal fluorobenzene to be responsible for hERG activity. Docking of the lead compound into an A2A crystal structure suggested that this group is located at a flexible, spacious, and solvent-exposed opening of the binding pocket, making it possible to tolerate various functional groups. Transformation analysis (MMP, matched molecular pair) of in-house available experimental data on hERG provided suggestions for modifications in order to mitigate this liability. This led to the synthesis of a series of compounds with significantly reduced hERG activity. The strategy used in the modeling work can be applied to other medicinal chemistry programs to help improve hERG profile. PMID:26048804

  11. Discovery of 3,4-Dihydropyrimidin-2(1H)-ones As a Novel Class of Potent and Selective A2B Adenosine Receptor Antagonists.

    PubMed

    Crespo, Abel; El Maatougui, Abdelaziz; Biagini, Pierfrancesco; Azuaje, Jhonny; Coelho, Alberto; Brea, José; Loza, María Isabel; Cadavid, María Isabel; García-Mera, Xerardo; Gutiérrez-de-Terán, Hugo; Sotelo, Eddy

    2013-11-14

    We describe the discovery and optimization of 3,4-dihydropyrimidin-2(1H)-ones as a novel family of (nonxanthine) A2B receptor antagonists that exhibit an unusually high selectivity profile. The Biginelli-based hit optimization process enabled a thoughtful exploration of the structure-activity and structure-selectivity relationships for this chemotype, enabling the identification of ligands that combine structural simplicity with excellent hA2B AdoR affinity and remarkable selectivity profiles.

  12. Actions of adenosine A1 and A2 receptor antagonists on CFTR antibody-inhibited β-adrenergic mucin secretion response

    PubMed Central

    Pereira, M M C; Lloyd Mills, C; Dormer, R L; McPherson, M A

    1998-01-01

    The cystic fibrosis gene protein, the cystic fibrosis transmembrane conductance regulator (CFTR) acts as a chloride channel and is a key regulator of mucin secretion. The mechanism by which 3-isobutyl-1-methylxanthine (IBMX) corrects the defect in CFTR mediated β-adrenergic stimulation of mucin secretion has not been determined. The present study has investigated the actions of adenosine A1 and A2 receptor antagonists to determine whether ability to stimulate mucin secretion correlates with correction of CFTR antibody inhibited β-adrenergic response and whether excessive cyclic AMP rise is required.CFTR antibodies were introduced into living rat submandibular acini by hypotonic swelling. Following recovery, mucin secretion in response to isoproterenol was measured.The adenosine A1 receptor antagonist, 8 cyclopentyltheophylline (CPT) was a less potent stimulator of mucin secretion than was the A2 receptor antagonist dimethylpropargylxanthine (DMPX). A concentration of CPT close to the Ki for A1 receptor antagonism (10 nM) did not stimulate mucin secretion.DMPX, although a potent stimulator of mucin secretion, did not correct CFTR antibody inhibited mucin secretion.CPT corrected defective CFTR antibody inhibited mucin secretion at a high (1 mM) concentration, suggesting a mechanism other than adenosine receptor antagonism.DMPX potentiated the isoproterenol induced cyclic AMP rise, whereas CPT did not.Correction of the defective CFTR mucin secretion response did not correlate with ability to stimulate mucin secretion and did not require potentiation of β-adrenergic induced increases in cyclic AMP. This affords real promise for the development of a selective drug treatment for cystic fibrosis. PMID:9831904

  13. Antagonistic interaction between adenosine A2A receptors and Na+/K+-ATPase-α2 controlling glutamate uptake in astrocytes.

    PubMed

    Matos, Marco; Augusto, Elisabete; Agostinho, Paula; Cunha, Rodrigo A; Chen, Jiang-Fan

    2013-11-20

    Astrocytic glutamate transporter-1 (GLT-I) is critical to control the bulk of glutamate uptake and, thus, to regulate synaptic plasticity and excitotoxicity. GLT-I glutamate uptake is driven by the sodium gradient implemented by Na(+)/K(+)-ATPases (NKAs) and the α2 subunit of NKA (NKA-α2) is actually linked to GLT-I to regulate astrocytic glutamate transport. We recently found that adenosine A2A receptors (A2ARs), which control synaptic plasticity and neurodegeneration, regulate glutamate uptake through unknown mechanisms. Here we report that A2AR activation decreases NKA activity selectively in astrocytes to inhibit glutamate uptake. Furthermore, we found a physical association of A2ARs with NKA-α2s in astrocytes, as gauged by coimmunoprecipitation and in situ proximity ligation assays, in the cerebral cortex and striatum, two brain regions where A2ARs inhibit the astrocytic glutamate uptake. Moreover, the selective deletion of A2ARs in astrocytes (using Gfa2-A2AR-KO mice) leads to a concurrent increase of both astrocytic glutamate uptake and NKA-α2 levels and activity in the striatum and cortex. This coupling of astrocytic A2ARs to the regulation of glutamate transport through modulation of NKA-α2 activity provides a novel mechanism linking neuronal activity to ion homeostasis controlling glutamatergic activity, all of which are processes intricately associated with the etiology of several brain diseases.

  14. Adenosine A(2A) receptor antagonists are broad facilitators of antinicotinic neuromuscular blockade monitored either with 2 Hz train-of-four or 50 Hz tetanic stimuli.

    PubMed

    Pereira, Monalisa W; Correia-de-Sá, Paulo; Alves-Do-Prado, Wilson

    2012-10-01

    1. The 2 Hz train-of-four ratio (TOF(ratio)) is used to monitor the degree of patient curarization. Using a rat phrenic nerve-hemidiaphragm preparation, we showed that antinicotinic agents, such as hexamethonium, d-tubocurarine and pancuronium, but not cisatracurium, decreased contractions produced by physiological nerve activity patterns (50 Hz) more efficiently than those caused by 2 Hz trains. Uncertainty about the usefulness of the TOF(ratio) to control safe recovery from curarization prompted us to investigate the muscarinic and adenosine neuromodulation of tetanic (50 Hz) fade induced by antinicotinic agents at concentrations that cause a 25% reduction in the TOF(ratio) (TOF(fade)). 2. Tetanic fade caused by d-tubocurarine (1.1 μmol/L), pancuronium (3 μmol/L) and hexamethonium (5.47 mmol/L) was attenuated by blocking presynaptic inhibitory muscarinic M(2) and adenosine A(1) receptors with methoctramine (1 μmol/L) and 1,3-dipropyl-8-cyclopentylxanthine (2.5 nmol/L), respectively. These compounds enhanced rather than decreased tetanic fade induced by cisatracurium (2.2 μmol/L), but they consistently attenuated cisatracurium-induced TOF(fade). The effect of the M(1) receptor antagonist pirenzepine (10 nmol/L) on fade produced by antinicotinic agents at 50 Hz was opposite to that observed with TOF stimulation. Blockade of adenosine A(2A) receptors with ZM 241385 (10 nmol/L) attenuated TOF(fade) caused by all antinicotinic drugs tested, with the exception of the 'pure' presynaptic nicotinic antagonist hexamethonium. ZM 241385 was the only compound tested in this series that facilitated recovery from tetanic fade produced by cisatracurium. 3. The data suggest that distinct antinicotinic relaxants interfere with fine-tuning neuromuscular adaptations to motor nerve stimulation patterns via activation of presynaptic muscarinic and adenosine receptors. These results support the use of A(2A) receptor antagonists together with atropine to facilitate recovery from

  15. Binding of the Antagonist Caffeine to the Human Adenosine Receptor hA2AR in Nearly Physiological Conditions.

    PubMed

    Cao, Ruyin; Rossetti, Giulia; Bauer, Andreas; CarIoni, Paolo

    2015-01-01

    Lipid composition may significantly affect membrane proteins function, yet its impact on the protein structural determinants is not well understood. Here we present a comparative molecular dynamics (MD) study of the human adenosine receptor type 2A (hA(2A)R) in complex with caffeine--a system of high neuro-pharmacological relevance--within different membrane types. These are POPC, mixed POPC/POPE and cholesterol-rich membranes. 0.8-μs MD simulations unambiguously show that the helical folding of the amphipathic helix 8 depends on membrane contents. Most importantly, the distinct cholesterol binding into the cleft between helix 1 and 2 stabilizes a specific caffeine-binding pose against others visited during the simulation. Hence, cholesterol presence (~33%-50% in synaptic membrane in central nervous system), often neglected in X-ray determination of membrane proteins, affects the population of the ligand binding poses. We conclude that including a correct description of neuronal membranes may be very important for computer-aided design of ligands targeting hA(2A)R and possibly other GPCRs. PMID:25992797

  16. Effect of adenosine A(2A) receptor antagonists and L-DOPA on hydroxyl radical, glutamate and dopamine in the striatum of 6-OHDA-treated rats.

    PubMed

    Gołembiowska, Krystyna; Dziubina, Anna

    2012-02-01

    A(2A) adenosine receptor antagonists have been proposed as a new therapy of PD. Since oxidative stress plays an important role in the pathogenesis of PD, we studied the effect of the selective A(2A) adenosine receptor antagonists 8-(-3-chlorostyryl)caffeine (CSC) and 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385) on hydroxyl radical generation, and glutamate (GLU) and dopamine (DA) extracellular level using a microdialysis in the striatum of 6-OHDA-treated rats. CSC (1 mg/kg) and ZM 241385 (3 mg/kg) given repeatedly for 14 days decreased the production of hydroxyl radical and extracellular GLU level, both enhanced by prior 6-OHDA treatment in dialysates from the rat striatum. CSC and ZM 241385 did not affect DA and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA) extracellular levels in the striatum of 6-OHDA-treated rats. L-DOPA (6 mg/kg) given twice daily for two weeks in the presence of benserazide (3 mg/kg) decreased striatal hydroxyl radical and glutamate extracellular level in 6-OHDA-treated rats. At the same time, L-DOPA slightly but significantly increased the extracellular levels of DOPAC and HVA. A combined repeated administration of L-DOPA and CSC or ZM 241385 did not change the effect of L-DOPA on hydroxyl radical production and glutamate extracellular level in spite of an enhancement of extracellular DA level by CSC and elevation of extracellular level of DOPAC and HVA by ZM 241385. The data suggest that the 6-OHDA-induced damage of nigrostriatal DA-terminals is related to oxidative stress and excessive release of glutamate. Administration of L-DOPA in combination with CSC or ZM 241385, by restoring striatal DA-glutamate balance, suppressed 6-OHDA-induced overproduction of hydroxyl radical.

  17. Thromboxane A2 receptor antagonist SQ29548 reduces ischemic stroke-induced microglia/macrophages activation and enrichment, and ameliorates brain injury

    PubMed Central

    Yan, Aijuan; Zhang, Tingting; Yang, Xiao; Shao, Jiaxiang; Fu, Ningzhen; Shen, Fanxia; Fu, Yi; Xia, Weiliang

    2016-01-01

    Thromboxane A2 receptor (TXA2R) activation is thought to be involved in thrombosis/hemostasis and inflammation responses. We have previously shown that TXA2R antagonist SQ29548 attenuates BV2 microglia activation by suppression of ERK pathway, but its effect is not tested in vivo. The present study aims to explore the role of TXA2R on microglia/macrophages activation after ischemia/reperfusion brain injury in mice. Adult male ICR mice underwent 90-min transient middle cerebral artery occlusion (tMCAO). Immediately and 24 h after reperfusion, SQ29548 was administered twice to the ipsilateral ventricle (10 μl, 2.6 μmol/ml, per dose). Cerebral infarction volume, inflammatory cytokines release and microglia/macrophages activation were measured using the cresyl violet method, quantitative polymerase chain reaction (qPCR), and immunofluorescence double staining, respectively. Expression of TXA2R was significantly increased in the ipsilateral brain tissue after ischemia/reperfusion, which was also found to co-localize with activated microglia/macrophages in the infarct area. Administration of SQ29548 inhibited microglia/macrophages activation and enrichment, including both M1 and M2 phenotypes, and attenuated ischemia-induced IL-1ß, IL-6, and TNF-α up-regulation and iNOS release. TXA2R antagonist SQ29548 inhibited ischemia-induced inflammatory response and furthermore reduced microglia/macrophages activation and ischemic/reperfusion brain injury. PMID:27775054

  18. 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

  19. Antiplatelet therapy: thrombin receptor antagonists

    PubMed Central

    Tello-Montoliu, Antonio; Tomasello, Salvatore D; Ueno, Masafumi; Angiolillo, Dominick J

    2011-01-01

    Activated platelets stimulate thrombus formation in response to rupture of an atherosclerotic plaque or endothelial cell erosion, promoting atherothrombotic disease. Multiple pathways contribute to platelet activation. Aspirin, an irreversible inhibitor of thromboxane A2 synthesis, in combination with clopidogrel, an inhibitor of P2Y12 adenosine diphosphate platelet receptors, represent the current standard-of-care of antiplatelet therapy for patients with acute coronary syndrome and for those undergoing percutaneous coronary intervention. Although these agents have demonstrated significant clinical benefit, the increased risk of bleeding and the recurrence of thrombotic events represent substantial limitations. Thrombin is one of the most important platelet activators. The inhibition of protease-activated receptor 1 showed a good safety profile in preclinical studies. In fact, phase II studies with vorapaxar (SCH530348) and atopaxar (E5555) showed no increase of bleeding events in addition to the current standard-of-care of antiplatelet therapy. Although the results of phase III trials for both drugs are awaited, this family is a promising new addition to the current clinical practice for patients with atherothrombotic disease, not only as an alternative, but also as additional therapy. PMID:21906120

  20. High-affinity neuropeptide Y receptor antagonists.

    PubMed Central

    Daniels, A J; Matthews, J E; Slepetis, R J; Jansen, M; Viveros, O H; Tadepalli, A; Harrington, W; Heyer, D; Landavazo, A; Leban, J J

    1995-01-01

    Neuropeptide Y (NPY) is one of the most abundant peptide transmitters in the mammalian brain. In the periphery it is costored and coreleased with norepinephrine from sympathetic nerve terminals. However, the physiological functions of this peptide remain unclear because of the absence of specific high-affinity receptor antagonists. Three potent NPY receptor antagonists were synthesized and tested for their biological activity in in vitro, ex vivo, and in vivo functional assays. We describe here the effects of these antagonists inhibiting specific radiolabeled NPY binding at Y1 and Y2 receptors and antagonizing the effects of NPY in human erythroleukemia cell intracellular calcium mobilization perfusion pressure in the isolated rat kidney, and mean arterial blood pressure in anesthetized rats. PMID:7568074

  1. The neuromedin B receptor antagonist, BIM-23127, is a potent antagonist at human and rat urotensin-II receptors.

    PubMed

    Herold, Christopher L; Behm, David J; Buckley, Peter T; Foley, James J; Wixted, William E; Sarau, Henry M; Douglas, Stephen A

    2003-05-01

    The functional activity of the peptidic neuromedin B receptor antagonist BIM-23127 was investigated at recombinant and native urotensin-II receptors (UT receptors). Human urotensin-II (hU-II) promoted intracellular calcium mobilization in HEK293 cells expressing the human UT (hUT) or rat UT (rUT) receptors with pEC(50) values of 9.80+/-0.34 (n=6) and 9.06+/-0.32 (n=4), respectively. While BIM-23127 alone had no effect on calcium responses in either cell line, it was a potent and competitive antagonist at both hUT (pA(2)=7.54+/-0.14; n=3) and rUT (pA(2)=7.70+/-0.05; n=3) receptors. Furthermore, BIM-23127 reversed hU-II-induced contractile tone in the rat-isolated aorta with a pIC(50) of 6.66+/-0.04 (n=4). In conclusion, BIM- 23127 is the first hUT receptor antagonist identified to date and should not be considered as a selective neuromedin B receptor antagonist. PMID:12770925

  2. Lixivaptan: a novel vasopressin receptor antagonist.

    PubMed

    Ku, Elaine; Nobakht, Niloofar; Campese, Vito M

    2009-05-01

    Arginine vasopressin, also known as antidiuretic hormone, is a neuropeptide that functions in the maintenance of body water homeostasis. Inappropriate secretion of vasopressin has been implicated in the pathophysiology of multiple diseases, including polycystic kidney disease, syndrome of inappropriate antidiuretic hormone (SIADH) secretion, and the hyponatremia commonly associated with cirrhosis and congestive heart failure. Vasopressin receptor antagonists are novel agents that block the physiologic actions of vasopressin. Lixivaptan is a vasopressin receptor antagonist with high V2 receptor affinity and is now undergoing Phase III clinical trials. Studies so far have demonstrated that lixivaptan is efficacious in the correction of hyponatremia in SIADH, heart failure and liver cirrhosis with ascites, and few adverse effects have been noted. Thus, lixivaptan remains a promising therapeutic modality for the treatment of multiple diseases and prevention of the associated morbidity and mortality associated with hyponatremia.

  3. 3-(Fur-2-yl)-10-(2-phenylethyl)-[1,2,4]triazino[4,3-a]benzimidazol-4(10H)-one, a Novel Adenosine Receptor Antagonist with A2A-Mediated Neuroprotective Effects

    PubMed Central

    2011-01-01

    In this study, compound FTBI (3-(2-furyl)-10-(2-phenylethyl)[1,2,4]triazino[4,3-a]benzimidazol-4(10H)-one) was selected from a small library of triazinobenzimidazole derivatives as a potent A2A adenosine receptor (AR) antagonist and tested for its neuroprotective effects against two different kinds of dopaminergic neurotoxins, 1-methyl-4-phenylpyridinium (MPP+) and methamphetamine (METH), in rat PC12 and in human neuroblastoma SH-SY5Y cell lines. FTBI, in a concentration range corresponding to its affinity for A2A AR subtype, significantly increased the number of viable PC12 cells after their exposure to METH and, to a similar extent, to MPP+, as demonstrated in both trypan blue exclusion assay and in cytological staining. These neuroprotective effects were also observed with a classical A2A AR antagonist, ZM241385, and appeared to be completely counteracted by the AR agonist, NECA, supporting A2A ARs are directly involved in FTBI-mediated effects. Similarly, in human SH-SY5Y cells, FTBI was able to prevent cell toxicity induced by MPP+ and METH, showing that this A2A AR antagonist has a neuroprotective effect independently by the specific cell model. Altogether these results demonstrate that the A2A AR blockade mediates cell protection against neurotoxicity induced by dopaminergic neurotoxins in dopamine containing cells, supporting the potential use of A2A AR antagonists in dopaminergic degenerative diseases including Parkinson’s disease. PMID:22860174

  4. Adenosine receptor antagonists alter the stability of human epileptic GABAA receptors

    PubMed Central

    Roseti, Cristina; Martinello, Katiuscia; Fucile, Sergio; Piccari, Vanessa; Mascia, Addolorata; Di Gennaro, Giancarlo; Quarato, Pier Paolo; Manfredi, Mario; Esposito, Vincenzo; Cantore, Gianpaolo; Arcella, Antonella; Simonato, Michele; Fredholm, Bertil B.; Limatola, Cristina; Miledi, Ricardo; Eusebi, Fabrizio

    2008-01-01

    We examined how the endogenous anticonvulsant adenosine might influence γ-aminobutyric acid type A (GABAA) receptor stability and which adenosine receptors (ARs) were involved. Upon repetitive activation (GABA 500 μM), GABAA receptors, microtransplanted into Xenopus oocytes from neurosurgically resected epileptic human nervous tissues, exhibited an obvious GABAA-current (IGABA) run-down, which was consistently and significantly reduced by treatment with the nonselective adenosine receptor antagonist CGS15943 (100 nM) or with adenosine deaminase (ADA) (1 units/ml), that inactivates adenosine. It was also found that selective antagonists of A2B (MRS1706, 10 nM) or A3 (MRS1334, 30 nM) receptors reduced IGABA run-down, whereas treatment with the specific A1 receptor antagonist DPCPX (10 nM) was ineffective. The selective A2A receptor antagonist SCH58261 (10 nM) reduced or potentiated IGABA run-down in ≈40% and ≈20% of tested oocytes, respectively. The ADA-resistant, AR agonist 2-chloroadenosine (2-CA) (10 μM) potentiated IGABA run-down but only in ≈20% of tested oocytes. CGS15943 administration again decreased IGABA run-down in patch-clamped neurons from either human or rat neocortex slices. IGABA run-down in pyramidal neurons was equivalent in A1 receptor-deficient and wt neurons but much larger in neurons from A2A receptor-deficient mice, indicating that, in mouse cortex, GABAA-receptor stability is tonically influenced by A2A but not by A1 receptors. IGABA run-down from wt mice was not affected by 2-CA, suggesting maximal ARs activity by endogenous adenosine. Our findings strongly suggest that cortical A2–A3 receptors alter the stability of GABAA receptors, which could offer therapeutic opportunities. PMID:18809912

  5. Rational discovery of novel nuclear hormone receptor antagonists

    NASA Astrophysics Data System (ADS)

    Schapira, Matthieu; Raaka, Bruce M.; Samuels, Herbert H.; Abagyan, Ruben

    2000-02-01

    Nuclear hormone receptors (NRs) are potential targets for therapeutic approaches to many clinical conditions, including cancer, diabetes, and neurological diseases. The crystal structure of the ligand binding domain of agonist-bound NRs enables the design of compounds with agonist activity. However, with the exception of the human estrogen receptor-, the lack of antagonist-bound "inactive" receptor structures hinders the rational design of receptor antagonists. In this study, we present a strategy for designing such antagonists. We constructed a model of the inactive conformation of human retinoic acid receptor- by using information derived from antagonist-bound estrogen receptor-α and applied a computer-based virtual screening algorithm to identify retinoic acid receptor antagonists. Thus, the currently available crystal structures of NRs may be used for the rational design of antagonists, which could lead to the development of novel drugs for a variety of diseases.

  6. A novel adenosine A(1) and A(2A) receptor antagonist ASP5854 ameliorates motor impairment in MPTP-treated marmosets: comparison with existing anti-Parkinson's disease drugs.

    PubMed

    Mihara, Takuma; Iwashita, Akinori; Matsuoka, Nobuya

    2008-12-12

    Recent evidence indicates that adenosine A(2A) receptor antagonists hold therapeutic potential for the treatment of Parkinson's disease (PD). A study on the novel adenosine A(1) and A(2A) receptor dual antagonist 5-[5-amino-3-(4-fluorophenyl)pyrazin-2-yl]-1-isopropylpyridine-2(1H)-one (ASP5854) showed it to be effective in various rodents models of PD and cognition. In the present study, we further investigated the potential of ASP5854 as an anti-PD drug using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated common marmosets, which is a highly predictive model of clinical efficacy in PD, and compared its effect with those of existing anti-PD drugs. ASP5854 significantly and dose-dependently improved the total motor disability score for 7h at doses higher than 1mg/kg, and significantly increased total locomotor activity at doses higher than 0.1mg/kg without adverse effects. l-3,4-Dihydroxyphenylalanine+benserazide and bromocriptine also significantly improved the motor disability score and the hypolocomotion caused by MPTP treatment in a dose-dependent fashion. This amelioration was significant at 32+8 and 10-32 mg/kg, respectively, although bromocriptine induced severe emesis. Trihexiphenidyl also significantly improved the total motor disability score at doses of 10-32 mg/kg; however, while a significant increase in the total locomotor activity was observed at 10mg/kg, the drug induced ataxia-like behavior at 32 mg/kg. On the other hand, neither selegiline nor amantadine improved the total motor disability and hypolocomotion. These data substantiate the evidence that the novel adenosine antagonist ASP5854 exerts comparable anti-PD activity with existing anti-PD drugs, which indicates that ASP5854 might have potential to ameliorate motor deficits in PD.

  7. Mineralocorticoid receptor antagonists and endothelial function

    PubMed Central

    Maron, Bradley A.; Leopold, Jane A.

    2010-01-01

    Hyperaldosteronism has been associated with endothelial dysfunction and impaired vascular reactivity in patients with hypertension or congestive heart failure. The mineralocorticoid receptor (MR) antagonists spironolactone and eplerenone have been shown to reduce morbidity and mortality, in part, by ameliorating the adverse effects of aldosterone on vascular function. Although spironolactone and eplerenone are increasingly utilized in patients with cardiovascular disease, widespread clinical use is limited by the development of gynecomastia with spironolactone and hyperkalemia with both agents. This suggests that the development of newer agents with favorable side effect profiles is warranted. PMID:18729003

  8. H1 receptor antagonist treatment of chronic rhinitis.

    PubMed

    Simons, F E; Simons, K J

    1988-05-01

    In patients with chronic rhinitis, H1 receptor antagonists play an important role in relieving the symptoms of sneezing, itching, and rhinorrhea. New information about the pharmacokinetics and pharmacodynamics of first-generation H1 receptor antagonists such as chlorpheniramine has become available in the past few years. Comprehensive pharmacokinetic and pharmacodynamic studies of new relatively nonsedating H1 receptor antagonists such as terfenadine, astemizole, loratadine, and cetirizine are appearing. An understanding of the differences in pharmacokinetics and pharmacodynamics among H1 receptor antagonists is required for optimal use of these drugs.

  9. High affinity retinoic acid receptor antagonists: analogs of AGN 193109.

    PubMed

    Johnson, A T; Wang, L; Gillett, S J; Chandraratna, R A

    1999-02-22

    A series of high affinity retinoic acid receptor (RAR) antagonists were prepared based upon the known antagonist AGN 193109 (2). Introduction of various phenyl groups revealed a preference for substitution at the para-position relative to the meta-site. Antagonists with the highest affinities for the RARs possessed hydrophobic groups, however, the presence of polar functionality was also well tolerated.

  10. Aldosterone receptor antagonists: current perspectives and therapies

    PubMed Central

    Guichard, Jason L; Clark, Donald; Calhoun, David A; Ahmed, Mustafa I

    2013-01-01

    Aldosterone is a downstream effector of angiotensin II in the renin–angiotensin–aldosterone system and binds to the mineralocorticoid receptor. The classical view of aldosterone primarily acting at the level of the kidneys to regulate plasma potassium and intravascular volume status is being supplemented by evidence of new “off-target” effects of aldosterone in other organ systems. The genomic effects of aldosterone are well known, but there is also evidence for non-genomic effects and these recently identified effects of aldosterone have required a revision in the traditional view of aldosterone’s role in human health and disease. The aim of this article is to review the biological action of aldosterone and the mineralocorticoid receptor leading to subsequent physiologic and pathophysiologic effects involving the vasculature, central nervous system, heart, and kidneys. Furthermore, we outline current evidence evaluating the use of mineralocorticoid receptor antagonists in the treatment of primary aldosteronism, primary hypertension, resistant hypertension, obstructive sleep apnea, heart failure, and chronic kidney disease. PMID:23836977

  11. Functionalized Congeners of P2Y1 Receptor Antagonists:

    SciTech Connect

    de Castro, Sonia; Maruoka, Hiroshi; Hong, Kunlun; Kilbey, II, S Michael; Costanzi, Stefano; Hechler, Béatrice; Gachet, Christian; Harden, T. Kendall; Jacobson, Kenneth A.

    2010-01-01

    The P2Y{sub 1} receptor is a prothrombotic G protein-coupled receptor (GPCR) activated by ADP. Preference for the North (N) ring conformation of the ribose moiety of adenine nucleotide 3',5'-bisphosphate antagonists of the P2Y{sub 1} receptor was established by using a ring-constrained methanocarba (a bicyclo[3.1.0]hexane) ring as a ribose substitute. A series of covalently linkable N{sup 6}-methyl-(N)-methanocarba-2'-deoxyadenosine-3',5'-bisphosphates containing extended 2-alkynyl chains was designed, and binding affinity at the human (h) P2Y{sub 1} receptor determined. The chain of these functionalized congeners contained hydrophilic moieties, a reactive substituent, or biotin, linked via an amide. Variation of the chain length and position of an intermediate amide group revealed high affinity of carboxylic congener 8 (K{sub i} 23 nM) and extended amine congener 15 (K{sub i} 132 nM), both having a 2-(1-pentynoyl) group. A biotin conjugate 18 containing an extended {epsilon}-aminocaproyl spacer chain exhibited higher affinity than a shorter biotinylated analogue. Alternatively, click coupling of terminal alkynes of homologous 2-dialkynyl nucleotide derivatives to alkyl azido groups produced triazole derivatives that bound to the P2Y{sub 1} receptor following deprotection of the bisphosphate groups. The preservation of receptor affinity of the functionalized congeners was consistent with new P2Y{sub 1} receptor modeling and ligand docking. Attempted P2Y{sub 1} antagonist conjugation to PAMAM dendrimer carriers by amide formation or palladium-catalyzed reaction between an alkyne on the dendrimer and a 2-iodopurine-derivatized nucleotide was unsuccessful. A dialkynyl intermediate containing the chain length favored in receptor binding was conjugated to an azide-derivatized dendrimer, and the conjugate inhibited ADP-promoted human platelet aggregation. This is the first example of attaching a strategically functionalized P2Y receptor antagonist to a PAMAM dendrimer to

  12. Multiple Targeting Approaches on Histamine H3 Receptor Antagonists

    PubMed Central

    Khanfar, Mohammad A.; Affini, Anna; Lutsenko, Kiril; Nikolic, Katarina; Butini, Stefania; Stark, Holger

    2016-01-01

    With the very recent market approval of pitolisant (Wakix®), the interest in clinical applications of novel multifunctional histamine H3 receptor antagonists has clearly increased. Since histamine H3 receptor antagonists in clinical development have been tested for a variety of different indications, the combination of pharmacological properties in one molecule for improved pharmacological effects and reduced unwanted side-effects is rationally based on the increasing knowledge on the complex neurotransmitter regulations. The polypharmacological approaches on histamine H3 receptor antagonists on different G-protein coupled receptors, transporters, enzymes as well as on NO-signaling mechanism are described, supported with some lead structures. PMID:27303254

  13. Multiple Targeting Approaches on Histamine H3 Receptor Antagonists.

    PubMed

    Khanfar, Mohammad A; Affini, Anna; Lutsenko, Kiril; Nikolic, Katarina; Butini, Stefania; Stark, Holger

    2016-01-01

    With the very recent market approval of pitolisant (Wakix®), the interest in clinical applications of novel multifunctional histamine H3 receptor antagonists has clearly increased. Since histamine H3 receptor antagonists in clinical development have been tested for a variety of different indications, the combination of pharmacological properties in one molecule for improved pharmacological effects and reduced unwanted side-effects is rationally based on the increasing knowledge on the complex neurotransmitter regulations. The polypharmacological approaches on histamine H3 receptor antagonists on different G-protein coupled receptors, transporters, enzymes as well as on NO-signaling mechanism are described, supported with some lead structures. PMID:27303254

  14. The search for calcium receptor antagonists (calcilytics).

    PubMed

    Nemeth, E F

    2002-08-01

    The Ca(2+) receptor on the surface of parathyroid cells is the primary molecular entity regulating secretion of parathyroid hormone (PTH). Because of this, it is a particularly appealing target for new drugs intended to increase or decrease circulating levels of PTH. Calcilytic compounds are Ca(2+) receptor antagonists which increase the secretion of PTH. The first reported calcilytic compound was NPS 2143, an orally active molecule which elicits rapid, 3- to 4-fold increases in circulating levels of PTH. These rapid changes in plasma PTH levels are sufficient to increase bone turnover in ovariectomized, osteopenic rats. When administered together with an antiresorptive agent (estradiol), NPS 2143 causes an increase in trabecular bone volume and bone mineral density in osteopenic rats. The magnitude of these changes are far in excess of those caused by estradiol alone and are comparable with those achieved by daily administration of PTH or a peptide analog. These anabolic effects of NPS 2143 on bone are not associated with hyperplasia of the parathyroid glands. Calcilytic compounds can increase endogenous levels of circulating PTH to an extent that stimulates new bone formation. Such compounds could replace the use of exogenous PTH or its peptide fragments in treating osteoporosis. PMID:12200226

  15. β1-adrenergic receptor antagonists signal via PDE4 translocation.

    PubMed

    Richter, Wito; Mika, Delphine; Blanchard, Elise; Day, Peter; Conti, Marco

    2013-03-01

    It is generally assumed that antagonists of Gs-coupled receptors do not activate cAMP signalling, because they do not stimulate cAMP production via Gs-protein/adenylyl cyclase activation. Here, we report a new signalling pathway whereby antagonists of β1-adrenergic receptors (β1ARs) increase cAMP levels locally without stimulating cAMP production directly. Binding of antagonists causes dissociation of a preformed complex between β1ARs and Type-4 cyclic nucleotide phosphodiesterases (PDE4s). This reduces the local concentration of cAMP-hydrolytic activity, thereby increasing submembrane cAMP and PKA activity. Our study identifies receptor/PDE4 complex dissociation as a novel mechanism of antagonist action that contributes to the pharmacological properties of β1AR antagonists and might be shared by other receptor subtypes.

  16. Interaction between Antagonist of Cannabinoid Receptor and Antagonist of Adrenergic Receptor on Anxiety in Male Rat

    PubMed Central

    Komaki, Alireza; Abdollahzadeh, Fatemeh; Sarihi, Abdolrahman; Shahidi, Siamak; Salehi, Iraj

    2014-01-01

    Introduction Anxiety is among the most common and treatable mental disorders. Adrenergic and cannabinoid systems have an important role in the neurobiology of anxiety. The elevated plus-maze (EPM) has broadly been used to investigate anxiolytic and anxiogenic compounds. The present study investigated the effects of intraperitoneal (IP) injection of cannabinoid CB1 receptor antagonist (AM251) in the presence of alpha-1 adrenergic antagonist (Prazosin) on rat behavior in the EPM. Methods In this study, the data were obtained from male Wistar rat, which weighing 200- 250 g. Animal behavior in EPM were videotaped and saved in computer for 10 min after IP injection of saline, AM251 (0.3 mg/kg), Prazosin (0.3 mg/kg) and AM251 + Prazosin, subsequently scored for conventional indices of anxiety. During the test period, the number of open and closed arms entries, the percentage of entries into the open arms of the EPM, and the spent time in open and closed arms were recorded. Diazepam was considered as a positive control drug with anxiolytic effect (0.3, 0.6, 1.2 mg/kg). Results Diazepam increased the number of open arm entries and the percentage of spent time on the open arms. IP injection of AM251 before EPM trial decreased open arms exploration and open arm entry. Whereas, Prazosin increased open arms exploration and open arm entry. This study showed that both substances in simultaneous injection have conflicting effects on the responses of each of these two compounds in a single injection. Discussion Injection of CB1 receptor antagonist may have an anxiogenic profile in rat, whereas adrenergic antagonist has an anxiolytic effect. Further investigations are essential for better understanding of anxiolytic and anxiogenic properties and neurobiological mechanisms of action and probable interactions of the two systems. PMID:25337383

  17. Identification of a novel conformationally constrained glucagon receptor antagonist.

    PubMed

    Lee, Esther C Y; Tu, Meihua; Stevens, Benjamin D; Bian, Jianwei; Aspnes, Gary; Perreault, Christian; Sammons, Matthew F; Wright, Stephen W; Litchfield, John; Kalgutkar, Amit S; Sharma, Raman; Didiuk, Mary T; Ebner, David C; Filipski, Kevin J; Brown, Janice; Atkinson, Karen; Pfefferkorn, Jeffrey A; Guzman-Perez, Angel

    2014-02-01

    Identification of orally active, small molecule antagonists of the glucagon receptor represents a novel treatment paradigm for the management of type 2 diabetes mellitus. The present work discloses novel glucagon receptor antagonists, identified via conformational constraint of current existing literature antagonists. Optimization of lipophilic ligand efficiency (LLE or LipE) culminated in enantiomers (+)-trans-26 and (-)-trans-27 which exhibit good physicochemical and in vitro drug metabolism profiles. In vivo, significant pharmacokinetic differences were noted with the two enantiomers, which were primarily driven through differences in clearance rates. Enantioselective oxidation by cytochrome P450 was ruled out as a causative factor for pharmacokinetic differences.

  18. Approaches to the rational design of selective melanocortin receptor antagonists

    PubMed Central

    Hruby, Victor J; Cai, Minying; Nyberg, Joel; Muthu, Dhanasekaran

    2015-01-01

    Introduction When establishing the physiological roles of specific receptors in normal and disease states, it is critical to have selective antagonist ligands for each receptor in a receptor system with several subtypes. The melanocortin receptors have five subtypes referred to as the melanocortin 1 receptor, melanocortin 2 receptor, melanocortin 3 receptor, melanocortin 4 receptor and melanocortin 5 receptor, and they are of critical importance for many aspects of human health and disease. Areas covered This article reviews the current efforts to design selective antagonistic ligands for the five human melanocortin receptors summarizing the currently published orthosteric and allosteric antagonists for each of these receptors. Expert opinion Though there has been progress, there are still few drugs available that address the many significant biological activities and diseases that are associated with these receptors, which is possibly due to the lack of receptor selectivity that these designed ligands are currently showing. The authors believe that further studies into the antagonists’ 3D conformational and topographical properties in addition to future mutagenesis studies will provide greater insight into these ligands which could play a role in the treatment of various diseases in the future. PMID:22646078

  19. Antagonists of the kappa opioid receptor.

    PubMed

    Urbano, Mariangela; Guerrero, Miguel; Rosen, Hugh; Roberts, Edward

    2014-05-01

    The research community has increasingly focused on the development of OPRK antagonists as pharmacotherapies for the treatment of depression, anxiety, addictive disorders and other psychiatric conditions produced or exacerbated by stress. Short-acting OPRK antagonists have been recently developed as a potential improvement over long-acting prototypic ligands including nor-BNI and JDTic. Remarkably the short-acting LY2456302 is undergoing phase II clinical trials for the augmentation of the antidepressant therapy in treatment-resistant depression. This Letter reviews relevant chemical and pharmacological advances in the identification and development of OPRK antagonists.

  20. Discovery of cannabinoid-1 receptor antagonists by virtual screening.

    PubMed

    Lee, Gil Nam; Kim, Kwang Rok; Ahn, Sung-Hoon; Bae, Myung Ae; Kang, Nam Sook

    2010-09-01

    In this work, we tried to find a new scaffold for a CB1 receptor antagonist using virtual screening. We first analyzed structural features for the known cannabinoid-1 receptor antagonists and, then, we built pharmacophore models using the HipHop concept and carried out a docking study based on our homology CB1 receptor 3D structure. The most active compound, including thiazole-4-one moiety, showed an activity value of 125 nM IC(50), with a good PK profile. PMID:20667724

  1. Discovery of cannabinoid-1 receptor antagonists by virtual screening.

    PubMed

    Lee, Gil Nam; Kim, Kwang Rok; Ahn, Sung-Hoon; Bae, Myung Ae; Kang, Nam Sook

    2010-09-01

    In this work, we tried to find a new scaffold for a CB1 receptor antagonist using virtual screening. We first analyzed structural features for the known cannabinoid-1 receptor antagonists and, then, we built pharmacophore models using the HipHop concept and carried out a docking study based on our homology CB1 receptor 3D structure. The most active compound, including thiazole-4-one moiety, showed an activity value of 125 nM IC(50), with a good PK profile.

  2. Non-NMDA receptor antagonist-induced drinking in rat

    NASA Technical Reports Server (NTRS)

    Xu, Z.; Johnson, A. K.

    1998-01-01

    Glutamate has been implicated in the central control of mechanisms that maintain body fluid homeostasis. The present studies demonstrate that intracerebroventricular (i.c.v.) injections of the non-N-methyl-d-aspartate (NMDA) receptor antagonists 6, 7-dinitroquinoxaline-2,3-dione (DNQX) and 6-cyano-7-nitroquinoxaline-2,3 dione (CNQX) induce drinking in rats. The dipsogenic effect of i.c.v. DNQX was antagonized by the non-NMDA receptor agonist alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA). The water intake induced by DNQX was also blocked by pretreatment with a NMDA receptor antagonist, MK-801, but not by angiotensin type 1 (AT1) or acetylcholine muscarinic receptor antagonists (losartan and atropine). The results indicate that non-NMDA receptors may exert a tonic inhibitory effect within brain circuits that control dipsogenic activity and that functional integrity of NMDA receptors may be required for the non-NMDA receptor antagonists to induce water intake. Copyright 1998 Published by Elsevier Science B.V.

  3. Design and evaluation of xanthine based adenosine receptor antagonists: Potential hypoxia targeted immunotherapies

    PubMed Central

    Thomas, Rhiannon; Lee, Joslynn; Chevalier, Vincent; Sadler, Sara; Selesniemi, Kaisa; Hatfield, Stephen; Sitkovsky, Michail; Ondrechen, Mary Jo; Jones, Graham B.

    2015-01-01

    Molecular modeling techniques were applied to the design, synthesis and optimization of a new series of xanthine based adenosine A2A receptor antagonists. The optimized lead compound was converted to a PEG derivative and a functional in vitro bioassay used to confirm efficacy. Additionally, the PEGylated version showed enhanced aqueous solubility and was inert to photoisomerization, a known limitation of existing antagonists of this class. PMID:24126093

  4. Azogabazine; a photochromic antagonist of the GABAA receptor.

    PubMed

    Huckvale, Rosemary; Mortensen, Martin; Pryde, David; Smart, Trevor G; Baker, James R

    2016-07-12

    The design and synthesis of azogabazine is described, which represents a highly potent (IC50 = 23 nM) photoswitchable antagonist of the GABAA receptor. An azologization strategy is adopted, in which a benzyl phenyl ether in a high affinity gabazine analogue is replaced by an azobenzene, with resultant retention of antagonist potency. We show that cycling from blue to UV light, switching between trans and cis isomeric forms, leads to photochemically controlled antagonism of the GABA ion channel. PMID:27327397

  5. PAF receptor and "Cache-oreilles" effect. Simple PAF antagonists.

    PubMed

    Lamotte-Brasseur, J; Heymans, F; Dive, G; Lamouri, A; Batt, J P; Redeuilh, C; Hosford, D; Braquet, P; Godfroid, J J

    1991-12-01

    Nine simple and structurally flexible PAF antagonists were synthesized and their inhibitory effects on PAF induced platelet aggregation were measured. Compounds with PAF antagonistic activity exhibited a negative electrostatic potential generated by two trimethoxyphenyl groups (isocontour at -10 Kcal/mole) at various distances between the negative clouds. The optimal distance between the atoms generating the "cache-oreilles" system for exhibiting potent PAF antagonistic activity is estimated to be 11-13 A. In the flexible molecules studied, the dispersion of the electronic distribution is not necessarily favorable for anti-PAF activity. The data support the simple bipolarized model for the PAF receptor that has been proposed by the authors.

  6. 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

  7. Chimeric, mutant orexin receptors show key interactions between orexin receptors, peptides and antagonists.

    PubMed

    Tran, Da-Thao; Bonaventure, Pascal; Hack, Michael; Mirzadegan, Taraneh; Dvorak, Curt; Letavic, Michael; Carruthers, Nicholas; Lovenberg, Timothy; Sutton, Steven W

    2011-09-30

    Orexin receptor antagonists are being investigated as therapeutic agents for insomnia and addictive disorders. In this study the interactions between the orexin receptors (orexin 1 receptor and orexin 2 receptor), orexin peptides, and small molecule orexin antagonists were explored. To study these phenomena, a variety of mutant orexin receptors was made and tested using receptor binding and functional assays. Domains of the two orexin receptors were exchanged to show the critical ligand binding domains for orexin peptides and representative selective orexin receptor antagonists. Results from domain exchanges between the orexin receptors suggest that transmembrane domain 3 is crucially important for receptor interactions with small molecule antagonists. These data also suggest that the orexin peptides occupy a larger footprint, interacting with transmembrane domain 1, the amino terminus and transmembrane domain 5 as well as transmembrane domain 3. Transmembrane domain 3 has been shown to be an important part of the small molecule binding pocket common to rhodopsin and β2-adrenergic receptors. Additional orexin receptor 2 point mutations were made based on the common arrangement of receptor transmembrane domains shown in the G-protein coupled receptor crystal structure literature and the impact of orexin 2 receptor residue threonine 135 on the ligand selectivity of the 2 orexin receptors. These data support a model of the orexin receptor binding pocket in which transmembrane domains 3 and 5 are prominent contributors to ligand binding and functional activity. The data also illustrate key contact points for ligand interactions in the consensus small molecule pocket of these receptors.

  8. In silico binding characteristics between human histamine H1 receptor and antagonists.

    PubMed

    Wang, Xiaojian; Yang, Qian; Li, Minyong; Yin, Dali; You, Qidong

    2010-09-01

    It is widely acknowledged that the H(1) receptor antagonists have important therapeutic significance in the treatment of various allergic disorders, but little was known about the binding mode between the receptor and antagonists since the crystal structure of G-protein coupling receptors (GPCRs) were hard to obtain. In this paper, a theoretical three-dimensional model of human histamine H(1) receptor (HHR1) was developed on the basis of recently reported high resolution structures of human A(2A) adenosine receptor, human beta(2)-adrenoceptor and turkey beta(1)-adrenoceptor. Furthermore, three representative H(1) receptor antagonists were chosen for docking studies. Subsequently, a qualitative pharmacophore model was developed by Hiphop algorithm based on the docking conformations of these three antagonists. In this paper, active environment, certain key residues, and the corresponding pharmacophore features of H(1) receptor were identified by such combinations of receptor-based and ligand-based approaches, which would give sufficient guidance for the rational design of novel antihistamine agents. PMID:20179978

  9. In silico binding characteristics between human histamine H1 receptor and antagonists.

    PubMed

    Wang, Xiaojian; Yang, Qian; Li, Minyong; Yin, Dali; You, Qidong

    2010-09-01

    It is widely acknowledged that the H(1) receptor antagonists have important therapeutic significance in the treatment of various allergic disorders, but little was known about the binding mode between the receptor and antagonists since the crystal structure of G-protein coupling receptors (GPCRs) were hard to obtain. In this paper, a theoretical three-dimensional model of human histamine H(1) receptor (HHR1) was developed on the basis of recently reported high resolution structures of human A(2A) adenosine receptor, human beta(2)-adrenoceptor and turkey beta(1)-adrenoceptor. Furthermore, three representative H(1) receptor antagonists were chosen for docking studies. Subsequently, a qualitative pharmacophore model was developed by Hiphop algorithm based on the docking conformations of these three antagonists. In this paper, active environment, certain key residues, and the corresponding pharmacophore features of H(1) receptor were identified by such combinations of receptor-based and ligand-based approaches, which would give sufficient guidance for the rational design of novel antihistamine agents.

  10. Are CB1 Receptor Antagonists Nootropic or Cognitive Impairing Agents?

    PubMed Central

    Varvel, Stephen A.; Wise, Laura E.; Lichtman, Aron H.

    2010-01-01

    For more than a decade, a considerable amount of research has examined the effects of rimonabant (SR 141716) and other CB1 receptor antagonists in both in vivo and in vitro models of learning and memory. In addition to its utility in determining whether the effects of drugs are mediated though a CB1 receptor mechanism of action, these antagonists are useful in providing insight into the physiological function of the endogenous cannabinoid system. Several groups have reported that CB1 receptor antagonists enhance memory duration in a variety of spatial and operant paradigms, but not in all paradigms. Conversely, disruption of CB1 receptor signaling also impairs extinction learning in which the animal actively suppresses a learned response when reinforcement has been withheld. These extinction deficits occur in aversively motivated tasks, such as in fear conditioning or escape behavior in the Morris water maze task, but not in appetitively motivated tasks. Similarly, in electrophysiological models, CB1 receptor antagonists elicit a variety of effects, including enhancement of long-term potentiation (LTP), while disrupting long-term depression (LTD) and interfering with transient forms of plasticity, including depolarization-induced suppression of inhibition (DSI) and depolarization-induced suppression of excitation (DSE). The collective results of the in vivo and in vitro studies employing CB1 receptor antagonists, demonstrate that these receptors play integral roles in different components of cognitive processing. Functionally, pharmacological blockade of CB1 receptors may strengthen memory duration, but interferes with extinction of learned behaviors that are associated with traumatic or aversive memories. PMID:20539824

  11. Discovery of Tertiary Sulfonamides as Potent Liver X Receptor Antagonists

    SciTech Connect

    Zuercher, William J.; Buckholz†, Richard G.; Campobasso, Nino; Collins, Jon L.; Galardi, Cristin M.; Gampe, Robert T.; Hyatt, Stephen M.; Merrihew, Susan L.; Moore, John T.; Oplinger, Jeffrey A.; Reid, Paul R.; Spearing, Paul K.; Stanley, Thomas B.; Stewart, Eugene L.; Willson, Timothy M.

    2010-08-12

    Tertiary sulfonamides were identified in a HTS as dual liver X receptor (LXR, NR1H2, and NR1H3) ligands, and the binding affinity of the series was increased through iterative analogue synthesis. A ligand-bound cocrystal structure was determined which elucidated key interactions for high binding affinity. Further characterization of the tertiary sulfonamide series led to the identification of high affinity LXR antagonists. GSK2033 (17) is the first potent cell-active LXR antagonist described to date. 17 may be a useful chemical probe to explore the cell biology of this orphan nuclear receptor.

  12. Histamine 2 Receptor Antagonists and Proton Pump Inhibitors.

    PubMed

    Brinkworth, Megan D; Aouthmany, Mouhammad; Sheehan, Michael

    2016-01-01

    Within the last 50 years, the pharmacologic market for gastric disease has grown exponentially. Currently, medical management with histamine 2 receptor antagonist and proton pump inhibitors are the mainstay of therapy over surgical intervention. These are generally regarded as safe medications, but there are growing numbers of cases documenting adverse effects, especially those manifesting in the skin. Here we review the pharmacology, common clinical applications, and adverse reactions of both histamine 2 receptor antagonists and proton pump inhibitors with a particular focus on the potential for allergic reactions including allergic contact dermatitis. PMID:27172303

  13. Neuroprotection by NMDA receptor antagonists in a variety of neuropathologies.

    PubMed

    Palmer, G C

    2001-09-01

    Because of adverse reactions, early efforts to introduce high affinity competitive or use-dependent NMDA receptor antagonists into patients suffering from stroke, head trauma or epilepsy met with failure. Later it was discovered that both low affinity use-dependent NMDA receptor antagonists and compounds with selective affinity for the NR2B receptor subunit met the criteria for safe administration into patients. Furthermore, these low affinity antagonists exhibit significant mechanistic differences from their higher affinity counterparts. Success of the latter is attested to the ability of the following low affinity compounds to be marketed: 1) Cough suppressant-dextromethorphan (available for decades); 2) Parkinson's disease--amantadine, memantine and budipine; 3) Dementia--memantine; and 4) Epilepsy--felbamate. Moreover, Phase III clinical trials are ongoing with remacemide for epilepsy and Huntington's disease and head trauma for HU-211. A host of compounds are or were under evaluation for the possible treatment of stroke, head trauma, hyperalgesia and various neurodegenerative disorders. Despite the fact that other drugs with associated NMDA receptor mechanisms have reached clinical status, this review focuses only on those competitive and use-dependent NMDA receptor antagonists that reached clinical trails. The ensuing discussions link the in vivo pharmacological investigations that led to the success/mistakes/ failures for eventual testing of promising compounds in the clinic. PMID:11554551

  14. Novel alkoxy-oxazolyl-tetrahydropyridine muscarinic cholinergic receptor antagonists.

    PubMed

    Shannon, H E; Bymaster, F P; Hendrix, J C; Quimby, S J; Mitch, C H

    1995-01-01

    The purpose of the present studies was to compare a novel series of alkoxy-oxazolyl-tetrahydropyridines (A-OXTPs) as muscarinic receptor antagonists. The affinity of these compounds for muscarinic receptors was determined by inhibition of [3H]pirenzepine to M1 receptors in hippocampus, [3H]QNB to M2 receptors in brainstem, and [3H]oxotremorine-M to high affinity muscarinic agonist binding sites in cortex. All of the compounds had higher affinity for [3H]pirenzepine than for [3H]QNB or [3H]oxotremorine-M labeled receptors, consistent with an interpretation that they are relatively selective M1 receptor antagonists, although none were as selective as pirenzepine. In addition, dose-response curves were determined for antagonism of oxotremorine-induced salivation (mediated by M3 receptors) and tremor (mediated by non-M1 receptors) in mice. In general, the A-OXTPs were equipotent and equieffective in antagonizing both salivation and tremor, although there were modest differences for some compounds. Dose-response curves also were determined on behavior maintained under a spatial-alternation schedule of food presentation in rats as a measure of effects on working memory. The A-OXTPs produced dose-related decreases in percent correct responding at doses three- to ten-fold lower than those which decreased rates of responding. However, only one compound, MB-OXTP, produced effects on percent correct responding consistent with a selective effect on memory as opposed to non-memory variables. The present results provide evidence that these alkoxy-oxazolyl-tetrahydropyridines are a novel series of modestly M1-selective muscarinic receptor antagonists, and that one member of the series, MB-OXTP, appears to be more selective in its effects on memory than previously studies muscarinic antagonists. PMID:7753969

  15. Disubstituted piperidines as potent Orexin (hypocretin) receptor antagonists

    PubMed Central

    Jiang, Rong; Song, Xinyi; Bali, Purva; Smith, Anthony; Bayona, Claudia Ruiz; Lin, Li; Cameron, Michael D.; McDonald, Patricia H.; Kenny, Paul J.

    2012-01-01

    A series of orexin receptor antagonists was synthesized based on a substituted piperidine scaffold. Through traditional medicinal chemistry structure activity relationships (SAR), installation of various groups at the 3–6-positions of the piperidine led to modest enhancement in receptor selectivity. Compounds were profiled in vivo for plasma and brain levels in order to identify candidates suitable for efficacy in a model of drug addiction. PMID:22617492

  16. The comparative pharmacokinetics of H1-receptor antagonists.

    PubMed

    Simons, F E; Simons, K J; Chung, M; Yeh, J

    1987-12-01

    H1-receptor antagonists appear to be absorbed rapidly after oral administration, with peak serum concentrations being reached one to three hours after a dose. For most of these drugs, the absolute bioavailability is unknown because no intravenous formulations are available for comparative purposes. The serum elimination half-life values of these agents are variable: a few hours for terfenadine and triprolidine; about 9 hours for cetirizine, azatadine, and loratadine; from 20 to 25 hours for hydroxyzine, chlorpheniramine, and brompheniramine; and from 5 to 14 days for astemizole. Few pharmacokinetic studies of H1-receptor antagonists in children have been reported. However, it is known that chlorpheniramine, hydroxyzine, cetirizine, and terfenadine have shorter elimination half-life values in children than in adults. Regardless of the age of patients, for most of the H1-receptor antagonists the apparent volumes of distribution and total body clearances appear to be large (3.4 to 18.5 L/kg and 4.4 to 32.1 mL/min/kg, respectively). Cetirizine is an exception, with values of 0.8 L/kg and 0.5 mL/min/kg. Urinary excretion of unchanged antihistamine is higher after cetirizine (60% of dose) than any other H1 blocker. For H1-receptor antagonists with long half-life values, steady state may not be reached for several days (chlorpheniramine and brompheniramine) or several weeks (astemizole), and significant accumulation of drug occurs if the dosing interval is more frequent than every half-life. There is no evidence for the introduction of metabolism of H1-receptor antagonists, even after months of treatment.

  17. Extra-helical binding site of a glucagon receptor antagonist.

    PubMed

    Jazayeri, Ali; Doré, Andrew S; Lamb, Daniel; Krishnamurthy, Harini; Southall, Stacey M; Baig, Asma H; Bortolato, Andrea; Koglin, Markus; Robertson, Nathan J; Errey, James C; Andrews, Stephen P; Teobald, Iryna; Brown, Alastair J H; Cooke, Robert M; Weir, Malcolm; Marshall, Fiona H

    2016-05-12

    Glucagon is a 29-amino-acid peptide released from the α-cells of the islet of Langerhans, which has a key role in glucose homeostasis. Glucagon action is transduced by the class B G-protein-coupled glucagon receptor (GCGR), which is located on liver, kidney, intestinal smooth muscle, brain, adipose tissue, heart and pancreas cells, and this receptor has been considered an important drug target in the treatment of diabetes. Administration of recently identified small-molecule GCGR antagonists in patients with type 2 diabetes results in a substantial reduction of fasting and postprandial glucose concentrations. Although an X-ray structure of the transmembrane domain of the GCGR has previously been solved, the ligand (NNC0640) was not resolved. Here we report the 2.5 Å structure of human GCGR in complex with the antagonist MK-0893 (ref. 4), which is found to bind to an allosteric site outside the seven transmembrane (7TM) helical bundle in a position between TM6 and TM7 extending into the lipid bilayer. Mutagenesis of key residues identified in the X-ray structure confirms their role in the binding of MK-0893 to the receptor. The unexpected position of the binding site for MK-0893, which is structurally similar to other GCGR antagonists, suggests that glucagon activation of the receptor is prevented by restriction of the outward helical movement of TM6 required for G-protein coupling. Structural knowledge of class B receptors is limited, with only one other ligand-binding site defined--for the corticotropin-releasing hormone receptor 1 (CRF1R)--which was located deep within the 7TM bundle. We describe a completely novel allosteric binding site for class B receptors, providing an opportunity for structure-based drug design for this receptor class and furthering our understanding of the mechanisms of activation of these receptors. PMID:27111510

  18. Clinical pharmacokinetics and pharmacodynamics of the endothelin receptor antagonist macitentan.

    PubMed

    Sidharta, P N; Treiber, A; Dingemanse, J

    2015-05-01

    Pulmonary arterial hypertension (PAH) is a progressive disease of the lung vascular system, which leads to right-sided heart failure and ultimately death if untreated. Treatments to regulate the pulmonary vascular pressure target the prostacyclin, nitric oxide, and endothelin (ET) pathways. Macitentan, an oral, once-daily, dual ETA and ETB receptor antagonist with high affinity and sustained receptor binding is the first ET receptor antagonist to show significant reduction of the risk of morbidity and mortality in PAH patients in a large-scale phase III study with a long-term outcome. Here we present a review of the available clinical pharmacokinetic, pharmacodynamic, pharmacokinetic/pharmacodynamic relationship, and drug-drug interaction data of macitentan in healthy subjects, patients with PAH, and in special populations.

  19. Hyperglycemia of Diabetic Rats Decreased by a Glucagon Receptor Antagonist

    NASA Astrophysics Data System (ADS)

    Johnson, David G.; Ulichny Goebel, Camy; Hruby, Victor J.; Bregman, Marvin D.; Trivedi, Dev

    1982-02-01

    The glucagon analog [l-Nα-trinitrophenylhistidine, 12-homoarginine]-glucagon (THG) was examined for its ability to lower blood glucose concentrations in rats made diabetic with streptozotocin. In vitro, THG is a potent antagonist of glucagon activation of the hepatic adenylate cyclase assay system. Intravenous bolus injections of THG caused rapid decreases (20 to 35 percent) of short duration in blood glucose. Continuous infusion of low concentrations of the inhibitor led to larger sustained decreases in blood glucose (30 to 65 percent). These studies demonstrate that a glucagon receptor antagonist can substantially reduce blood glucose levels in diabetic animals without addition of exogenous insulin.

  20. μ Opioid receptor: novel antagonists and structural modeling

    NASA Astrophysics Data System (ADS)

    Kaserer, Teresa; Lantero, Aquilino; Schmidhammer, Helmut; Spetea, Mariana; Schuster, Daniela

    2016-02-01

    The μ opioid receptor (MOR) is a prominent member of the G protein-coupled receptor family and the molecular target of morphine and other opioid drugs. Despite the long tradition of MOR-targeting drugs, still little is known about the ligand-receptor interactions and structure-function relationships underlying the distinct biological effects upon receptor activation or inhibition. With the resolved crystal structure of the β-funaltrexamine-MOR complex, we aimed at the discovery of novel agonists and antagonists using virtual screening tools, i.e. docking, pharmacophore- and shape-based modeling. We suggest important molecular interactions, which active molecules share and distinguish agonists and antagonists. These results allowed for the generation of theoretically validated in silico workflows that were employed for prospective virtual screening. Out of 18 virtual hits evaluated in in vitro pharmacological assays, three displayed antagonist activity and the most active compound significantly inhibited morphine-induced antinociception. The new identified chemotypes hold promise for further development into neurochemical tools for studying the MOR or as potential therapeutic lead candidates.

  1. Pyrazolo Derivatives as Potent Adenosine Receptor Antagonists: An Overview on the Structure-Activity Relationships

    PubMed Central

    Cheong, Siew Lee; Venkatesan, Gopalakrishnan; Paira, Priyankar; Jothibasu, Ramasamy; Mandel, Alexander Laurence; Federico, Stephanie; Spalluto, Giampiero; Pastorin, Giorgia

    2011-01-01

    In the past few decades, medicinal chemistry research towards potent and selective antagonists of human adenosine receptors (namely, A1, A2A, A2B, and A3) has been evolving rapidly. These antagonists are deemed therapeutically beneficial in several pathological conditions including neurological and renal disorders, cancer, inflammation, and glaucoma. Up to this point, many classes of compounds have been successfully synthesized and identified as potent human adenosine receptor antagonists. In this paper, an overview of the structure-activity relationship (SAR) profiles of promising nonxanthine pyrazolo derivatives is reported and discussed. We have emphasized the SAR for some representative structures such as pyrazolo-[4,3-e]-1,2,4-triazolo-[1,5-c]pyrimidines; pyrazolo-[3,4-c] or -[4,3-c]quinolines; pyrazolo-[4,3-d]pyrimidinones; pyrazolo-[3,4-d]pyrimidines and pyrazolo-[1,5-a]pyridines. This overview not only clarifies the structural requirements deemed essential for affinity towards individual adenosine receptor subtypes, but it also sheds light on the rational design and optimization of existing structural templates to allow us to conceive new, more potent adenosine receptor antagonists. PMID:25954519

  2. 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

  3. Effects of H1 and H2 receptor antagonists on Tetrahymena.

    PubMed

    Csaba, G; László, V; Darvas, Z

    1978-01-01

    In Tetrahymena pyriformis the phagocytotic rate increases in response to histamine, but neither the H1 antagonist phenindamine nor the H2 antagonist metiamide stimulate phagocytosis. The H1 antagonist counteracts the effect of histamine, whereas the H2 antagonist does not. The histamine receptor of Tetrahymena is of H1-type, since it cannot distinguish between histamine and antagonists which are closely related to it chemically. It does, however, distinguish between histamine and the chemically unrelated H1 antagonist, phenindamine. The H2 antagonist does not interact with the receptor.

  4. Targeting a family B GPCR/RAMP receptor complex: CGRP receptor antagonists and migraine

    PubMed Central

    Moore, Eric L; Salvatore, Christopher A

    2012-01-01

    The clinical effectiveness of antagonizing the calcitonin gene-related peptide (CGRP) receptor for relief of migraine pain has been clearly demonstrated, but the road to the development of these small molecule antagonists has been daunting. The key hurdle that needed to be overcome was the CGRP receptor itself. The vast majority of the current antagonists recognize similar epitopes on the calcitonin receptor-like receptor (CLR) and receptor activity-modifying protein 1 (RAMP1). RAMP1 is a relatively small, single, transmembrane-spanning protein and along with the G-protein-coupled receptor CLR comprise a functional CGRP receptor. The tri-helical extracellular domain of RAMP1 plays a key role in the high affinity binding of CGRP receptor antagonists and drives their species-selective pharmacology. Over the years, a significant amount of mutagenesis data has been generated to identify specific amino acids or regions within CLR and RAMP1 that are critical to antagonist binding and has directed attention to the CLR/RAMP1 extracellular domain (ECD) complex. Recently, the crystal structure of the CGRP receptor ECD has been elucidated and not only reinforces the early mutagenesis data, but provides critical insight into the molecular mechanism of CGRP receptor antagonism. This review will highlight the drug design hurdles that must be overcome to meet the desired potency, selectivity and pharmacokinetic profile while retaining drug-like properties. Although the development of these antagonists has proved challenging, blocking the CGRP receptor may one day represent a new way to manage migraine and offer hope to migraine sufferers. LINKED ARTICLES This article is part of a themed section on Secretin Family (Class B) G Protein-Coupled Receptors. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.166.issue-1 PMID:21871019

  5. Inhibition of ionotropic neurotransmitter receptors by antagonists: strategy to estimate the association and the dissociation rate constant of antagonists with very strong affinity to the receptors.

    PubMed

    Aoshima, H; Inoue, Y; Hori, K

    1992-10-01

    Since binding of an agonist to an ionotropic neurotransmitter receptor causes not only channel opening, but also desensitization of the receptor, inhibition of the receptor by the antagonist sometimes becomes very complicated. The transient state kinetics of ligand association and dissociation, and desensitization of the receptor were considered on the basis of the minimal model proposed by Hess' group, and the following possibilities were proposed. 1) When an agonist is simultaneously applied to the receptor with an antagonist whose affinity to the receptor is extremely strong and different from that of the agonist, it is usually impossible to estimate the real inhibition constant exactly from the responses because desensitization of the receptor proceeds before the equilibrium of the ligand binding. Simultaneous addition of the antagonist with strong affinity to the receptor may apparently accelerate inactivation (desensitization) of the receptor. The association rate constant of the antagonist can be estimated by analyses of the rate of the inactivation in the presence and the absence of the antagonist. 2) A preincubated antagonist with a slow dissociation rate constant, i.e., a very effective inhibitor, may cause apparent noncompetitive inhibition of the receptor, since the receptor is desensitized by an agonist as soon as the antagonist dissociates from the receptor and the dissociation of the antagonist from the receptor becomes the rate-determining step. A nicotinic acetylcholine receptor (nAChR) was expressed in Xenopus oocytes by injecting mRNA prepared from Electrophorus electricus electroplax and used for the experiments on inhibition by an antagonist.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1337082

  6. Characterization of a novel non-steroidal glucocorticoid receptor antagonist

    SciTech Connect

    Li, Qun-Yi; Zhang, Meng; Hallis, Tina M.; DeRosier, Therese A.; Yue, Jian-Min; Ye, Yang; Mais, Dale E.; Wang, Ming-Wei

    2010-01-15

    Selective antagonists of the glucocorticoid receptor (GR) are desirable for the treatment of hypercortisolemia associated with Cushing's syndrome, psychic depression, obesity, diabetes, neurodegenerative diseases, and glaucoma. NC3327, a non-steroidal small molecule with potent binding affinity to GR (K{sub i} = 13.2 nM), was identified in a high-throughput screening effort. As a full GR antagonist, NC3327 greatly inhibits the dexamethasone (Dex) induction of marker genes involved in hepatic gluconeogenesis, but has a minimal effect on matrix metalloproteinase 9 (MMP-9), a GR responsive pro-inflammatory gene. Interestingly, the compound recruits neither coactivators nor corepressors to the GR complex but competes with glucocorticoids for the interaction between GR and a coactivator peptide. Moreover, NC3327 does not trigger GR nuclear translocation, but significantly blocks Dex-induced GR transportation to the nucleus, and thus appears to be a 'competitive' GR antagonist. Therefore, the non-steroidal compound, NC3327, may represent a new class of GR antagonists as potential therapeutics for a variety of cortisol-related endocrine disorders.

  7. NMDA receptor antagonists extend the sensitive period for imprinting.

    PubMed

    Parsons, C H; Rogers, L J

    2000-03-01

    Filial imprinting in the domestic chick occurs during a sensitive period of development. The exact timing of this period can vary according to the methods used to measure imprinting. Using our imprinting paradigm, we have shown that normal, dark-reared chicks lose the ability to imprint after the second day post-hatching. Further, we reported that chicks treated 10 h after hatching with a mixture of the noncompetitive NMDA receptor antagonist ketamine (55 mg/kg) and the alpha(2)-adrenergic receptor agonist xylazine (6 mg/kg) were able to imprint on day 8 after hatching, whereas controls treated with saline did not imprint. We now show that the effect of the ketamine-xylazine mixture can be mimicked by treating chicks with ketamine alone or with another noncompetitive NMDA receptor antagonist, MK-801 (5 mg/kg). Treating chicks with a single dose of ketamine (55 mg/kg) or with a single dose of xylazine (6 mg/kg) failed to produce the effect on the sensitive period. However, prolonging the action of ketamine by treating chicks with two doses of ketamine (at 10 and 12 h after hatching) did allow imprinting on day 8. In contrast, prolonging the action of xylazine had no effect on the sensitive period for imprinting. Chicks treated with MK-801 were also able to imprint on day 8. Thus, we have evidence that the NMDA receptor system is involved in the mechanisms that control the sensitive period for imprinting.

  8. NMDA receptor antagonists extend the sensitive period for imprinting.

    PubMed

    Parsons, C H; Rogers, L J

    2000-03-01

    Filial imprinting in the domestic chick occurs during a sensitive period of development. The exact timing of this period can vary according to the methods used to measure imprinting. Using our imprinting paradigm, we have shown that normal, dark-reared chicks lose the ability to imprint after the second day post-hatching. Further, we reported that chicks treated 10 h after hatching with a mixture of the noncompetitive NMDA receptor antagonist ketamine (55 mg/kg) and the alpha(2)-adrenergic receptor agonist xylazine (6 mg/kg) were able to imprint on day 8 after hatching, whereas controls treated with saline did not imprint. We now show that the effect of the ketamine-xylazine mixture can be mimicked by treating chicks with ketamine alone or with another noncompetitive NMDA receptor antagonist, MK-801 (5 mg/kg). Treating chicks with a single dose of ketamine (55 mg/kg) or with a single dose of xylazine (6 mg/kg) failed to produce the effect on the sensitive period. However, prolonging the action of ketamine by treating chicks with two doses of ketamine (at 10 and 12 h after hatching) did allow imprinting on day 8. In contrast, prolonging the action of xylazine had no effect on the sensitive period for imprinting. Chicks treated with MK-801 were also able to imprint on day 8. Thus, we have evidence that the NMDA receptor system is involved in the mechanisms that control the sensitive period for imprinting. PMID:10764906

  9. Mechanism of A2 adenosine receptor activation. I. Blockade of A2 adenosine receptors by photoaffinity labeling

    SciTech Connect

    Lohse, M.J.; Klotz, K.N.; Schwabe, U.

    1991-04-01

    It has previously been shown that covalent incorporation of the photoreactive adenosine derivative (R)-2-azido-N6-p-hydroxy-phenylisopropyladenosine ((R)-AHPIA) into the A1 adenosine receptor of intact fat cells leads to a persistent activation of this receptor, resulting in a reduction of cellular cAMP levels. In contrast, covalent incorporation of (R)-AHPIA into human platelet membranes, which contain only stimulatory A2 adenosine receptors, reduces adenylate cyclase stimulation via these receptors. This effect of (R)-AHPIA is specific for the A2 receptor and can be prevented by the adenosine receptor antagonist theophylline. Binding studies indicate that up to 90% of A2 receptors can be blocked by photoincorporation of (R)-AHPIA. However, the remaining 10-20% of A2 receptors are sufficient to mediate an adenylate cyclase stimulation of up to 50% of the control value. Similarly, the activation via these 10-20% of receptors occurs with a half-life that is only 2 times longer than that in control membranes. This indicates the presence of a receptor reserve, with respect to both the extent and the rate of adenylate cyclase stimulation. These observations require a modification of the models of receptor-adenylate cyclase coupling.

  10. Vasopressin receptor antagonists, heart failure, and polycystic kidney disease.

    PubMed

    Torres, Vicente E

    2015-01-01

    The synthesis of nonpeptide orally bioavailable vasopressin antagonists devoid of agonistic activity (vaptans) has made possible the selective blockade of vasopressin receptor subtypes for therapeutic purposes. Vaptans acting on the vasopressin V2 receptors (aquaretics) have attracted attention as a possible therapy for heart failure and polycystic kidney disease. Despite a solid rationale and encouraging preclinical testing, aquaretics have not improved clinical outcomes in randomized clinical trials for heart failure. Additional clinical trials with select population targets, more flexible dosing schedules, and possibly a different drug type or combination (balanced V1a/V2 receptor antagonism) may be warranted. Aquaretics are promising for the treatment of autosomal dominant polycystic kidney disease and have been approved in Japan for this indication. More studies are needed to better define their long-term safety and efficacy and optimize their utilization.

  11. Suvorexant: The first orexin receptor antagonist to treat insomnia

    PubMed Central

    Dubey, Ashok K.; Handu, Shailendra S.; Mediratta, Pramod K.

    2015-01-01

    Primary insomnia is mainly treated with drugs acting on benzodiazepine receptors and a few other classes of drugs used for different co-morbidities. A novel approach to treat insomnia has been introduced recently, with the approval of suvorexant, the first in a new class of orexin receptor antagonists. Orexin receptors in the brain have been found to play an important role in the regulation of various aspects of arousal and motivation. The drugs commonly used for insomnia therapy to date, have often been associated with adverse effects, such as, day-time somnolence, amnesia, confusion, and gait disturbance, apart from the risk of dependence on chronic use. Suvorexant has not shown these adverse effects because of its unique mechanism of action. It also appears to be suitable as a chronic therapy for insomnia, because of minimal physical dependence. The availability of this new drug as an effective and safe alternative is an important and welcome development in insomnia management. PMID:25969666

  12. Mineralocorticoid receptor antagonists: emerging roles in cardiovascular medicine

    PubMed Central

    Funder, John W

    2013-01-01

    Spironolactone was first developed over 50 years ago as a potent mineralocorticoid receptor (MR) antagonist with undesirable side effects; it was followed a decade ago by eplerenone, which is less potent but much more MR-specific. From a marginal role as a potassium-sparing diuretic, spironolactone was shown to be an extraordinarily effective adjunctive agent in the treatment of progressive heart failure, as was eplerenone in subsequent heart failure trials. Neither acts as an aldosterone antagonist in the heart as the cardiac MR are occupied by cortisol, which becomes an aldosterone mimic in conditions of tissue damage. The accepted term “MR antagonist”, (as opposed to “aldosterone antagonist” or, worse, “aldosterone blocker”), should be retained, despite the demonstration that they act not to deny agonist access but as inverse agonists. The prevalence of primary aldosteronism is now recognized as accounting for about 10% of hypertension, with recent evidence suggesting that this figure may be considerably higher: in over two thirds of cases of primary aldosteronism therapy including MR antagonists is standard of care. MR antagonists are safe and vasoprotective in uncomplicated essential hypertension, even in diabetics, and at low doses they also specifically lower blood pressure in patients with so-called resistant hypertension. Nowhere are more than 1% of patients with primary aldosteronism ever diagnosed and specifically treated. Given the higher risk profile in patients with primary aldosteronism than that of age, sex, and blood pressure matched essential hypertension, on public health grounds alone the guidelines for first-line treatment of all hypertension should mandate inclusion of a low-dose MR antagonist. PMID:24133375

  13. Carbobenzoxy amino acids: Structural requirements for cholecystokinin receptor antagonist activity

    SciTech Connect

    Maton, P.N.; Sutliff, V.E.; Jensen, R.T.; Gardner, J.D.

    1985-04-01

    The authors used dispersed acini prepared from guinea pig pancreas to examine 28 carbobenzoxy (CBZ) amino acids for their abilities to function as cholecystokinin receptor antagonists. All amino acid derivatives tested, except for CBZ-alanine, CBZ-glycine, and N alpha-CBZ- lysine, were able to inhibit the stimulation of amylase secretion caused by the C-terminal octapeptide of cholecystokinin. In general, there was a good correlation between the ability of a carbobenzoxy amino acid to inhibit stimulated amylase secretion and the ability of the amino acid derivative to inhibit binding of /sup 125/I-cholecystokinin. The inhibition of cholecystokinin-stimulated amylase secretion was competitive, fully reversible, and specific for those secretagogues that interact with the cholecystokinin receptor. The potencies with which the various carbobenzoxy amino acids inhibited the action of cholecystokinin varied 100-fold and CBZ-cystine was the most potent cholecystokinin receptor antagonist. This variation in potency was primarily but not exclusively a function of the hydrophobicity of the amino acid side chain.

  14. Safety profile of mineralocorticoid receptor antagonists: Spironolactone and eplerenone.

    PubMed

    Lainscak, Mitja; Pelliccia, Francesco; Rosano, Giuseppe; Vitale, Cristiana; Schiariti, Michele; Greco, Cesare; Speziale, Giuseppe; Gaudio, Carlo

    2015-12-01

    Spironolactone was first developed over 50 years ago as a potent mineralocorticoid receptor antagonist with undesirable side effects; it was followed a decade ago by eplerenone, which is less potent but much more mineralocorticoid receptor-specific. From a marginal role as a potassium-sparing diuretic, spironolactone has been shown to be an extraordinarily effective adjunctive agent in the treatment of progressive heart failure. Also, spironolactone is safe and protective in arterial hypertension, particularly in patients with so-called resistant hypertension. Eplerenone is the second oral aldosterone antagonist available for the treatment of arterial hypertension and heart failure. Treatment with eplerenone has been associated with decreased blood pressure and improved survival for patients with heart failure and reduced left ventricular ejection fraction. Due to the selectivity of eplerenone for the aldosterone receptor, severe adverse effects such as gynecomastia and vaginal bleeding seem to be less likely in patients who take eplerenone than in those who take spironolactone. The most common and potentially dangerous side effect of spironolactone--hyperkalemia--is also observed with eplerenone but the findings from clinical trials do not indicate more hyperkalemia induced drug withdrawals. Treatment with eplerenone should be initiated at a dosage of 25mg once daily and titrated to a target dosage of 50mg once daily preferably within 4 weeks. Serum potassium levels and renal function should be assessed prior to initiating eplerenone therapy, and periodic monitoring is recommended, especially in patients at high risk of developing hyperkalemia.

  15. [Growth hormone receptor antagonist in the treatment of acromegaly].

    PubMed

    Hubina, Erika; Tóth, Agnes; Kovács, Gábor László; Dénes, Judit; Kovács, László; Góth, Miklós

    2011-05-01

    Exploration of construction, function and interaction of human growth hormone and growth hormone receptor in details resulted in the innovation of the new growth hormone receptor antagonist, pegvisomant. Pegvisomant with different mechanism of action extended the tools of medical management of acromegaly. Importance of the novel treatment modality is high. In one hand the necessity of the strict control of growth hormone/insulin-like growth factor-I axis has been proven regarding the mortality of the disease. On the other hand, despite the use of all current modes of treatment (surgery, radiotherapy, dopamine agonists, somatostatin analogs), a significant cohort of patients with acromegaly remains inadequately controlled. Pegvisomant has been registered in 2004. Since 2006, it has been used in Hungary for the treatment of acromegaly in patients who have had an inadequate response to surgery and/or radiation therapy and/or other medical therapies, or for whom these therapies are not appropriate. Clinical use of pegvisomant in the treatment of acromegaly is effective, well tolerated, and safe, based on international Acrostudy database. In order to improve the efficacy of therapy clinical trials started with pegvisomant and somatostatin analog combination treatment. Evidence of several further effects of the growth hormone/insulin-like growth factor-I axis suggests other potential uses of growth hormone receptor antagonists. PMID:21498159

  16. Structure-based discovery of antagonists of nuclear receptor LRH-1.

    PubMed

    Benod, Cindy; Carlsson, Jens; Uthayaruban, Rubatharshini; Hwang, Peter; Irwin, John J; Doak, Allison K; Shoichet, Brian K; Sablin, Elena P; Fletterick, Robert J

    2013-07-01

    Liver receptor homolog 1 (nuclear receptor LRH-1, NR5A2) is an essential regulator of gene transcription, critical for maintenance of cell pluripotency in early development and imperative for the proper functions of the liver, pancreas, and intestines during the adult life. Although physiological hormones of LRH-1 have not yet been identified, crystallographic and biochemical studies demonstrated that LRH-1 could bind regulatory ligands and suggested phosphatidylinositols as potential hormone candidates for this receptor. No synthetic antagonists of LRH-1 are known to date. Here, we identify the first small molecule antagonists of LRH-1 activity. Our search for LRH-1 modulators was empowered by screening of 5.2 million commercially available compounds via molecular docking followed by verification of the top-ranked molecules using in vitro direct binding and transcriptional assays. Experimental evaluation of the predicted ligands identified two compounds that inhibit the transcriptional activity of LRH-1 and diminish the expression of the receptor's target genes. Among the affected transcriptional targets are co-repressor SHP (small heterodimer partner) as well as cyclin E1 (CCNE1) and G0S2 genes that are known to regulate cell growth and proliferation. Treatments of human pancreatic (AsPC-1), colon (HT29), and breast adenocarcinoma cells T47D and MDA-MB-468 with the LRH-1 antagonists resulted in the receptor-mediated inhibition of cancer cell proliferation. Our data suggest that specific antagonists of LRH-1 could be used as specific molecular probes for elucidating the roles of the receptor in different types of malignancies.

  17. Structure-based Discovery of Antagonists of Nuclear Receptor LRH-1*

    PubMed Central

    Benod, Cindy; Carlsson, Jens; Uthayaruban, Rubatharshini; Hwang, Peter; Irwin, John J.; Doak, Allison K.; Shoichet, Brian K.; Sablin, Elena P.; Fletterick, Robert J.

    2013-01-01

    Liver receptor homolog 1 (nuclear receptor LRH-1, NR5A2) is an essential regulator of gene transcription, critical for maintenance of cell pluripotency in early development and imperative for the proper functions of the liver, pancreas, and intestines during the adult life. Although physiological hormones of LRH-1 have not yet been identified, crystallographic and biochemical studies demonstrated that LRH-1 could bind regulatory ligands and suggested phosphatidylinositols as potential hormone candidates for this receptor. No synthetic antagonists of LRH-1 are known to date. Here, we identify the first small molecule antagonists of LRH-1 activity. Our search for LRH-1 modulators was empowered by screening of 5.2 million commercially available compounds via molecular docking followed by verification of the top-ranked molecules using in vitro direct binding and transcriptional assays. Experimental evaluation of the predicted ligands identified two compounds that inhibit the transcriptional activity of LRH-1 and diminish the expression of the receptor's target genes. Among the affected transcriptional targets are co-repressor SHP (small heterodimer partner) as well as cyclin E1 (CCNE1) and G0S2 genes that are known to regulate cell growth and proliferation. Treatments of human pancreatic (AsPC-1), colon (HT29), and breast adenocarcinoma cells T47D and MDA-MB-468 with the LRH-1 antagonists resulted in the receptor-mediated inhibition of cancer cell proliferation. Our data suggest that specific antagonists of LRH-1 could be used as specific molecular probes for elucidating the roles of the receptor in different types of malignancies. PMID:23667258

  18. Development of prolactin receptor antagonists with reduced pH-dependence of receptor binding.

    PubMed

    Hansen, Mathilde J Kaas; Olsen, Johan G; Bernichtein, Sophie; O'Shea, Charlotte; Sigurskjold, Bent W; Goffin, Vincent; Kragelund, Birthe B

    2011-01-01

    The cytokine hormone prolactin has a vast number of diverse functions. Unfortunately, it also exhibits tumor growth promoting properties, which makes the development of prolactin receptor antagonists a priority. Prolactin binds to its cognate receptor with much lower affinity at low pH than at physiological pH and since the extracellular environment around solid tumors often is acidic, it is desirable to develop antagonists that have improved binding affinity at low pH. The pK(a) value of a histidine side chain is ∼6.8 making histidine residues obvious candidates for examination. From evaluation of known molecular structures of human prolactin, of the prolactin receptor and of different complexes of the two, three histidine residues in the hormone-receptor binding site 1 were selected for mutational studies. We analyzed 10 variants by circular dichroism spectroscopy, affinity and thermodynamic characterization of receptor binding by isothermal titration calorimetry combined with in vitro bioactivity in living cells. Histidine residue 27 was recognized as a central hot spot for pH sensitivity and conservative substitutions at this site resulted in strong receptor binding at low pH. Pure antagonists were developed earlier and the histidine mutations were introduced within such background. The antagonistic properties were maintained and the high affinity at low pH conserved. The implications of these findings may open new areas of research in the field of prolactin cancer biology.

  19. Substituted Tetrahydroisoquinolines as Selective Antagonists for the Orexin 1 Receptor

    PubMed Central

    Perrey, David A.; German, Nadezhda A.; Gilmour, Brian P.; Li, Jun-Xu; Harris, Danni L.; Thomas, Brian F.; Zhang, Yanan

    2013-01-01

    Increasing evidence implicates the orexin 1 (OX1) receptor in reward processes, suggesting OX1 antagonism could be therapeutic in drug addiction. In a program to develop an OX1 selective antagonist, we designed and synthesized a series of substituted tetrahydroisoquinolines and determined their potency in OX1 and OX2 calcium mobilization assays. Structure-activity relationship (SAR) studies revealed limited steric tolerance and preference for electron deficiency at the 7-position. Pyridylmethyl groups were shown to be optimal for activity at the acetamide position. Computational studies resulted in a pharmacophore model and confirmed the SAR results. Compound 72 significantly attenuated the development of place preference for cocaine in rats. PMID:23941044

  20. Toxicological Differences Between NMDA Receptor Antagonists and Cholinesterase Inhibitors.

    PubMed

    Shi, Xiaodong; Lin, Xiaotian; Hu, Rui; Sun, Nan; Hao, Jingru; Gao, Can

    2016-08-01

    Cholinesterase inhibitors (ChEIs), represented by donepezil, rivastigmine, and galantamine, used to be the only approved class of drugs for the treatment of Alzheimer's disease. After the approval of memantine by the Food and Drug Administration (FDA), N-methyl-d-aspartic acid (NMDA) receptor antagonists have been recognized by authorities and broadly used in the treatment of Alzheimer's disease. Along with complementary mechanisms of action, NMDA antagonists and ChEIs differ not only in therapeutic effects but also in adverse reactions, which is an important consideration in clinical drug use. And the number of patients using NMDA antagonists and ChEIs concomitantly has increased, making the matter more complicated. Here we used the FDA Adverse Event Reporting System for statistical analysis , in order to compare the adverse events of memantine and ChEIs. In general, the clinical evidence confirmed the safety advantages of memantine over ChEIs, reiterating the precautions of clinical drug use and the future direction of antidementia drug development. PMID:26769920

  1. Pharmacology of JB-9315, a new selective histamine H2-receptor antagonist.

    PubMed

    Palacios, B; Montero, M J; Sevilla, M A; San Román, L

    1998-02-01

    1. The histamine H2-receptor antagonistic activity and antisecretory and antiulcer effects of JB-9315 were studied in comparison with the standard H2 blocker ranitidine. 2. In vitro, JB-9315 is a competitive antagonist of histamine H2 receptors in the isolated, spontaneously beating guinea-pig right atrium, with a pA2 value of 7.30 relative to a value of 7.36 for ranitidine. JB-9315 was specific for the histamine H2 receptor because, at high concentration, it did not affect histamine- or acetylcholine-induced contractions in guinea-pig isolated ileum or rat isolated duodenum, respectively. 3. JB-9315 dose dependently inhibited histamine-, pentagastrin- or carbachol-stimulated acid secretion and basal secretion in the perfused stomach preparation of the anesthetized rat. In the pylorus-ligated rat after intraperitoneal administration, total acid output over 4 h was inhibited by JB-9315 with an ID50 of 32.8 mg/kg, confirming its H2-receptor antagonist properties. 4. JB-9315 showed antiulcer activity against cold stress plus indomethacin-induced lesions with an ID50 of 6.8 mg/kg. 5. JB-9315, 50 and 100 mg/kg, inhibited macroscopic gastric hemorrhagic lesions induced by ethanol. In contrast, ranitidine (50 mg/kg) failed to reduce these lesions. 6. These results indicate that JB-9315 is a new antiulcer drug that exerts a cytoprotective effect in addition to its gastric antisecretory activity.

  2. Neurokinin-1 Receptor Antagonists in Preventing Postoperative Nausea and Vomiting

    PubMed Central

    Liu, Meng; Zhang, Hao; Du, Bo-Xiang; Xu, Feng-Ying; Zou, Zui; Sui, Bo; Shi, Xue-Yin

    2015-01-01

    Abstract Newly developed neurokinin-1 receptor (NK-1R) antagonists have been recently tried in the prevention of postoperative nausea and vomiting (PONV). This systematic review and meta-analysis was conducted to explore whether NK-1R antagonists were effective in preventing PONV. The PRISMA statement guidelines were followed. Randomized clinical trials (RCTs) that tested the preventive effects of NK-1R antagonists on PONV were identified by searching EMBASE, CINAHL, PubMed, and the Cochrane Library databases followed by screening. Data extraction was performed using a predefined form and trial quality was assessed using a modified Jadad scale. The primary outcome measure was the incidence of PONV. Meta-analysis was performed for studies using similar interventions. Network meta-analysis (NMA) was conducted to compare the anti-vomiting effects of placebo, ondansetron, and aprepitant at different doses. Fourteen RCTs were included. Meta-analysis found that 80 mg of aprepitant could reduce the incidences of nausea (3 RCTs with 224 patients, pooled risk ratio (RR) = 0.60, 95% confidence interval (CI) = 0.47 to 0.75), and vomiting (3 RCTs with 224 patients, pooled RR = 0.13, 95% CI = 0.04 to 0.37) compared with placebo. Neither 40 mg (3 RCTs with 1171 patients, RR = 0.47, 95% CI = 0.37 to 0.60) nor 125 mg (2 RCTs with 1058 patients, RR = 0.32, 95% CI = 0.13 to 0.78) of aprepitant showed superiority over 4 mg of ondansetron in preventing postoperative vomiting. NMA did not find a dose-dependent effect of aprepitant on preventing postoperative vomiting. Limited data suggested that NK-1R antagonists, especially aprepitant were effective in preventing PONV compared with placebo. More large-sampled high-quality RCTs are needed. PMID:25984662

  3. Interleukin-6 (IL-6) Receptor Antagonist Protects Against Rheumatoid Arthritis.

    PubMed

    Li, Songsong; Wu, Zhenzhou; Li, Ling; Liu, Xuehua

    2016-01-01

    BACKGROUND The aim of this study was to investigate the protective effect of interleukin-6 (IL-6) receptor antagonist tocilizumab (TCZ) on rheumatoid arthritis (RA) and its related mechanism. MATERIAL AND METHODS Thirty RA patients receiving long-term methotrexate therapy at moderate and severe active stages were selected and treated with TCZ 8 mg/kg/time iv gtt intravenously guttae every 4 weeks. Peripheral blood was extracted before and 24 weeks after TCZ treatment. Peripheral blood mononuclear cells (PBMC) were collected by density gradient centrifugation. Flow cytometry was used to detect the ratio of CD4 naïve T cells and CD4 memory T cells, Th17 cells, and Treg cells in PBMC. DAS28 score, CRP, RF, and CCP levels in patients were evaluated. RESULTS Compared with before treatment, IL-6 receptor antagonist TCZ significantly improved patients' condition, including DAS28 score, CRP, RF, and CCP levels (P<0.01). Furthermore, TCZ obviously upregulated CD4 naïve T cells proportion and decreased CD4 memory T cells ratio (P<0.01). TCZ also markedly reduced the proportion of Th17 cells and increased the proportion of Treg cells (P<0.01). CONCLUSIONS TCZ can treat RA patients through regulating the ratio of CD4 naïve T cells, CD4 memory T cells, Th17 cells, and Treg cells in PBMC. PMID:27322646

  4. Interleukin-6 (IL-6) Receptor Antagonist Protects Against Rheumatoid Arthritis

    PubMed Central

    Li, Songsong; Wu, Zhenzhou; Li, Ling; Liu, Xuehua

    2016-01-01

    Background The aim of this study was to investigate the protective effect of interleukin-6 (IL-6) receptor antagonist tocilizumab (TCZ) on rheumatoid arthritis (RA) and its related mechanism. Material/Methods Thirty RA patients receiving long-term methotrexate therapy at moderate and severe active stages were selected and treated with TCZ 8 mg/kg/time iv gtt intravenously guttae every 4 weeks. Peripheral blood was extracted before and 24 weeks after TCZ treatment. Peripheral blood mononuclear cells (PBMC) were collected by density gradient centrifugation. Flow cytometry was used to detect the ratio of CD4 naïve T cells and CD4 memory T cells, Th17 cells, and Treg cells in PBMC. DAS28 score, CRP, RF, and CCP levels in patients were evaluated. Results Compared with before treatment, IL-6 receptor antagonist TCZ significantly improved patients’ condition, including DAS28 score, CRP, RF, and CCP levels (P<0.01). Furthermore, TCZ obviously upregulated CD4 naïve T cells proportion and decreased CD4 memory T cells ratio (P<0.01). TCZ also markedly reduced the proportion of Th17 cells and increased the proportion of Treg cells (P<0.01). Conclusions TCZ can treat RA patients through regulating the ratio of CD4 naïve T cells, CD4 memory T cells, Th17 cells, and Treg cells in PBMC. PMID:27322646

  5. Evodiamine as a novel antagonist of aryl hydrocarbon receptor

    SciTech Connect

    Yu, Hui; Tu, Yongjiu; Zhang, Chun; Fan, Xia; Wang, Xi; Wang, Zhanli; Liang, Huaping

    2010-11-05

    Research highlights: {yields} Evodiamine interacted with the AhR. {yields} Evodiamine inhibited the specific binding of [{sup 3}H]-TCDD to the AhR. {yields} Evodiamine acts as an antagonist of the AhR. -- Abstract: Evodiamine, the major bioactive alkaloid isolated from Wu-Chu-Yu, has been shown to interact with a wide variety of proteins and modify their expression and activities. In this study, we investigated the interaction between evodiamine and the aryl hydrocarbon receptor (AhR). Molecular modeling results revealed that evodiamine directly interacted with the AhR. Cytosolic receptor binding assay also provided the evidence that evodiamine could interact with the AhR with the K{sub i} value of 28.4 {+-} 4.9 nM. In addition, we observed that evodiamine suppressed the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induced nuclear translocation of the AhR and the expression of CYP1A1 dose-dependently. These results suggested that evodiamine was able to bind to the AhR as ligand and exhibit antagonistic effects.

  6. Classification and virtual screening of androgen receptor antagonists.

    PubMed

    Li, Jiazhong; Gramatica, Paola

    2010-05-24

    Computational tools, such as quantitative structure-activity relationship (QSAR), are highly useful as screening support for prioritization of substances of very high concern (SVHC). From the practical point of view, QSAR models should be effective to pick out more active rather than inactive compounds, expressed as sensitivity in classification works. This research investigates the classification of a big data set of endocrine-disrupting chemicals (EDCs)-androgen receptor (AR) antagonists, mainly aiming to improve the external sensitivity and to screen for potential AR binders. The kNN, lazy IB1, and ADTree methods and the consensus approach were used to build different models, which improve the sensitivity on external chemicals from 57.1% (literature) to 76.4%. Additionally, the models' predictive abilities were further validated on a blind collected data set (sensitivity: 85.7%). Then the proposed classifiers were used: (i) to distinguish a set of AR binders into antagonists and agonists; (ii) to screen a combined estrogen receptor binder database to find out possible chemicals that can bind to both AR and ER; and (iii) to virtually screen our in-house environmental chemical database. The in silico screening results suggest: (i) that some compounds can affect the normal endocrine system through a complex mechanism binding both to ER and AR; (ii) new EDCs, which are nonER binders, but can in silico bind to AR, are recognized; and (iii) about 20% of compounds in a big data set of environmental chemicals are predicted as new AR antagonists. The priority should be given to them to experimentally test the binding activities with AR.

  7. AT(2) receptor stimulation enhances antihypertensive effect of AT(1) receptor antagonist in hypertensive rats.

    PubMed

    Barber, M N; Sampey, D B; Widdop, R E

    1999-11-01

    In the present study, we investigated the role of the angiotensin type 2 (AT(2)) receptor in the regulation of blood pressure in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). We tested the hypothesis that AT(2) receptor activation may contribute to the antihypertensive effects of angiotensin type 1 (AT(1)) receptor antagonists. Mean arterial pressure (MAP) and heart rate were measured over a 4-day protocol in various groups of rats that received the following drug combinations: the AT(1) receptor antagonist candesartan (0.01 or 0.1 mg/kg IV) alone, the AT(2) receptor agonist CGP42112 (1 microg/kg per minute) alone, and candesartan plus CGP42112. In both SHR and WKY, 4-hour infusions of saline and CGP42112 alone did not alter MAP. In WKY, both doses of candesartan alone caused small decreases in MAP, which were similar when combined with CGP42112. In SHR, candesartan (0.1 mg/kg) caused an immediate, marked decrease in MAP, which was unaffected when combined with CGP42112. By contrast, in separate SHR, a 10-fold lower dose of candesartan (0.01 mg/kg) caused a slower-onset depressor response, which was enhanced when combined with CGP42112. The involvement of AT(2) receptors was confirmed in another group of SHR, since this facilitation of the antihypertensive effect of candesartan by CGP42112 was abolished by the coinfusion of the AT(2) receptor antagonist PD123319 (50 microg/kg per minute) with the candesartan/CGP42112 combination. Collectively, these data suggest that in SHR, AT(2) receptor activation can facilitate the initial depressor response caused by an AT(1) receptor antagonist.

  8. Target hopping as a useful tool for the identification of novel EphA2 protein-protein antagonists.

    PubMed

    Tognolini, Massimiliano; Incerti, Matteo; Pala, Daniele; Russo, Simonetta; Castelli, Riccardo; Hassan-Mohamed, Iftiin; Giorgio, Carmine; Lodola, Alessio

    2014-01-01

    Lithocholic acid (LCA), a physiological ligand for the nuclear receptor FXR and the G-protein-coupled receptor TGR5, has been recently described as an antagonist of the EphA2 receptor, a key member of the ephrin signalling system involved in tumour growth. Given the ability of LCA to recognize FXR, TGR5, and EphA2 receptors, we hypothesized that the structural requirements for a small molecule to bind each of these receptors might be similar. We therefore selected a set of commercially available FXR or TGR5 ligands and tested them for their ability to inhibit EphA2 by targeting the EphA2-ephrin-A1 interface. Among the selected compounds, the stilbene carboxylic acid GW4064 was identified as an effective antagonist of EphA2, being able to block EphA2 activation in prostate carcinoma cells, in the micromolar range. This finding proposes the "target hopping" approach as a new effective strategy to discover new protein-protein interaction inhibitors.

  9. N-Benzylpiperidine Derivatives as α7 Nicotinic Receptor Antagonists.

    PubMed

    Criado, Manuel; Mulet, José; Sala, Francisco; Sala, Salvador; Colmena, Inés; Gandía, Luis; Bautista-Aguilera, Oscar M; Samadi, Abdelouahid; Chioua, Mourad; Marco-Contelles, José

    2016-08-17

    A series of multitarget directed propargylamines, as well as other differently susbstituted piperidines have been screened as potential modulators of neuronal nicotinic acetylcholine receptors (nAChRs). Most of them showed antagonist actions on α7 nAChRs. Especially, compounds 13, 26, and 38 displayed submicromolar IC50 values on homomeric α7 nAChRs, whereas they were less effective on heteromeric α3β4 and α4β2 nAChRs (up to 20-fold higher IC50 values in the case of 13). Antagonism was concentration dependent and noncompetitive, suggesting that these compounds behave as negative allosteric modulators of nAChRs. Upon the study of a series of less complex derivatives, the N-benzylpiperidine motif, common to these compounds, was found to be the main pharmacophoric group. Thus, 2-(1-benzylpiperidin-4-yl)-ethylamine (48) showed an inhibitory potency comparable to the one of the previous compounds and also a clear preference for α7 nAChRs. In a neuroblastoma cell line, representative compounds 13 and 48 also inhibited, in a concentration-dependent manner, cytosolic Ca(2+) signals mediated by nAChRs. Finally, compounds 38 and 13 inhibited 5-HT3A serotonin receptors whereas they had no effect on α1 glycine receptors. Given the multifactorial nature of many pathologies in which nAChRs are involved, these piperidine antagonists could have a therapeutic potential in cases where cholinergic activity has to be negatively modulated. PMID:27254782

  10. Purification and reconstitution of the calcium antagonist receptor of the voltage-sensitive calcium channel

    SciTech Connect

    Curtis, B.M.

    1986-01-01

    Treatment with digitonin solubilized the calcium antagonist receptor as a stable complex with (/sup 3/H)nitrendipine from rat brain membranes. The solubilized complex retains allosteric coupling to binding sites for diltiazem, verapamil, and inorganic calcium antagonist sites. The calcium antagonist receptor from cardiac sarcolemma and the transverse-tubule membrane of skeletal muscle is also efficiently solubilized with digitonin and the receptor in all three tissues is a large glycoprotein with a sedimentation coefficient of 20 S. The T-tubule calcium antagonist receptor complex was extensively purified by a combination of chromatography on WGA-Sepharose, ion exchange chromatography, and sedimentation on sucrose gradients to yield preparations estimated to be 41% homogeneous by specific activity and 63% homogeneous by SDS gel electrophoresis. Analysis of SDS gels detect three polypeptides termed ..cap alpha..(Mr 135,000), ..beta..(Mr 50,000), and ..gamma..(Mr 32,000) as noncovalently associated subunits of the calcium antagonist receptor. The ..cap alpha.. and ..gamma.. subunits are glycosylated polypeptides, and the molecular weight of the core polypeptides are 108,000 and 24,000 respectively. The calcium antagonist receptor was reconstituted into a phospholipid bilayer by adding CHAPS and exogeneous lipid to the purified receptor followed by rapid detergent removal. This procedure resulted in the incorporation of 45% of the calcium antagonist receptor into closed phospholipid vesicles. Data suggests that the ..cap alpha.., ..beta.., and ..gamma.. subunits of the T-tubule calcium antagonist receptor are sufficient to form a functional calcium channel.

  11. Phenylthiophenecarboxamide antagonists of the olfactory receptor co-receptor subunit from a mosquito.

    PubMed

    Chen, Sisi; Luetje, Charles W

    2013-01-01

    Insects detect environmental chemicals using chemosensory receptors, such as the ORs, a family of odorant-gated ion channels. Insect ORs are multimeric complexes of unknown stoichiometry, formed by a common subunit (the odorant receptor co-receptor subunit, Orco) and one of many variable subunits that confer odorant specificity. The recent discovery of Orco directed ligands, including both agonists and antagonists, suggests Orco as a promising target for chemical control of insects. In addition to competitively inhibiting OR activation by Orco agonists, several Orco antagonists have been shown to act through a non-competitive mechanism to inhibit OR activation by odorants. We previously identified a series of Orco antagonists, including N-(4-ethylphenyl)-2-thiophenecarboxamide (OX1a, previously referred to as OLC20). Here, we explore the chemical space around the OX1a structure to identify more potent Orco antagonists. Cqui\\Orco+Cqui\\Or21, an OR from Culex quinquefasciatus (the Southern House Mosquito) that responds to 3-methylindole (skatole) and is thought to mediate oviposition behavior, was expressed in Xenopus oocytes and receptor function assayed by two-electrode voltage clamp electrophysiology. 22 structural analogs of OX1a were screened for antagonism of OR activation by an Orco agonist. By varying the moieties decorating the phenyl and thiophene rings, and altering the distance between the rings, we were able to identify antagonists with improved potency. Detailed examination of three of these compounds (N-mesityl-2-thiophenecarboxamide, N-(4-methylbenzyl)-2-thiophenecarboxamide and N-(2-ethylphenyl)-3-(2-thienyl)-2-propenamide) demonstrated competitive inhibition of receptor activation by an Orco agonist and non-competitive inhibition of receptor activation by an odorant. The ability to inhibit OR activation by odorants may be a general property of this class of Orco antagonist, suggesting that odorant mediated behaviors can be manipulated through Orco

  12. Phenylthiophenecarboxamide Antagonists of the Olfactory Receptor Co-Receptor Subunit from a Mosquito

    PubMed Central

    Chen, Sisi; Luetje, Charles W.

    2013-01-01

    Insects detect environmental chemicals using chemosensory receptors, such as the ORs, a family of odorant-gated ion channels. Insect ORs are multimeric complexes of unknown stoichiometry, formed by a common subunit (the odorant receptor co-receptor subunit, Orco) and one of many variable subunits that confer odorant specificity. The recent discovery of Orco directed ligands, including both agonists and antagonists, suggests Orco as a promising target for chemical control of insects. In addition to competitively inhibiting OR activation by Orco agonists, several Orco antagonists have been shown to act through a non-competitive mechanism to inhibit OR activation by odorants. We previously identified a series of Orco antagonists, including N-(4-ethylphenyl)-2-thiophenecarboxamide (OX1a, previously referred to as OLC20). Here, we explore the chemical space around the OX1a structure to identify more potent Orco antagonists. Cqui\\Orco+Cqui\\Or21, an OR from Culex quinquefasciatus (the Southern House Mosquito) that responds to 3-methylindole (skatole) and is thought to mediate oviposition behavior, was expressed in Xenopus oocytes and receptor function assayed by two-electrode voltage clamp electrophysiology. 22 structural analogs of OX1a were screened for antagonism of OR activation by an Orco agonist. By varying the moieties decorating the phenyl and thiophene rings, and altering the distance between the rings, we were able to identify antagonists with improved potency. Detailed examination of three of these compounds (N-mesityl-2-thiophenecarboxamide, N-(4-methylbenzyl)-2-thiophenecarboxamide and N-(2-ethylphenyl)-3-(2-thienyl)-2-propenamide) demonstrated competitive inhibition of receptor activation by an Orco agonist and non-competitive inhibition of receptor activation by an odorant. The ability to inhibit OR activation by odorants may be a general property of this class of Orco antagonist, suggesting that odorant mediated behaviors can be manipulated through Orco

  13. Bovine pancreatic polypeptide as an antagonist of muscarinic cholinergic receptors

    SciTech Connect

    Pan, G.Z.; Lu, L.; Qian, J.; Xue, B.G.

    1987-03-01

    In dispersed acini from rat pancreas, it was found that bovine pancreatic polypeptide (BPP) and its C-fragment hexapeptide amide (PP-6), at concentrations of 0.1 and 30 ..mu..M, respectively, could significantly inhibit amylase secretion stimulated by carbachol, and this inhibition by BPP was dose dependent. /sup 45/Ca outflux induced by carbachol was also inhibited by BPP or PP-6, but they had no effect on cholecystokinin octapeptide- (CCK-8) or A23187-stimulated /sup 45/Ca outflux. BPP was also capable of displacing the specific binding of (/sup 3/H)-quinuclidinyl benzilate to its receptors, and it possessed a higher affinity (K/sub i/35nM) than carbachol (K/sub i/ 1.8 ..mu..M) in binding with M-receptors. It is concluded from this study that BPP acts as an antagonist of muscarinic cholinergic receptors in rat pancreatic acini. In addition, BPP inhibited the potentiation of amylase secretion caused by the combination of carbachol plus secretin or vasoactive intestinal peptide. This may be a possible explanation of the inhibitory effect of BPP on secretin-induced pancreatic enzyme secretion shown in vivo, since pancreatic enzyme secretion stimulated by secretin under experimental conditions may be the result of potentiation of enzyme release produced by the peptide in combination with a cholinergic stimulant.

  14. Orexin receptor antagonists as therapeutic agents for insomnia

    PubMed Central

    Equihua, Ana C.; De La Herrán-Arita, Alberto K.; Drucker-Colin, Rene

    2013-01-01

    Insomnia is a common clinical condition characterized by difficulty initiating or maintaining sleep, or non-restorative sleep with impairment of daytime functioning. Currently, treatment for insomnia involves a combination of cognitive behavioral therapy (CBTi) and pharmacological therapy. Among pharmacological interventions, the most evidence exists for benzodiazepine (BZD) receptor agonist drugs (GABAA receptor), although concerns persist regarding their safety and their limited efficacy. The use of these hypnotic medications must be carefully monitored for adverse effects. Orexin (hypocretin) neuropeptides have been shown to regulate transitions between wakefulness and sleep by promoting cholinergic/monoaminergic neural pathways. This has led to the development of a new class of pharmacological agents that antagonize the physiological effects of orexin. The development of these agents may lead to novel therapies for insomnia without the side effect profile of hypnotics (e.g., impaired cognition, disturbed arousal, and motor balance difficulties). However, antagonizing a system that regulates the sleep-wake cycle may create an entirely different side effect profile. In this review, we discuss the role of orexin and its receptors on the sleep-wake cycle and that of orexin antagonists in the treatment of insomnia. PMID:24416019

  15. NMDA receptor antagonist ketamine impairs feature integration in visual perception.

    PubMed

    Meuwese, Julia D I; van Loon, Anouk M; Scholte, H Steven; Lirk, Philipp B; Vulink, Nienke C C; Hollmann, Markus W; Lamme, Victor A F

    2013-01-01

    Recurrent interactions between neurons in the visual cortex are crucial for the integration of image elements into coherent objects, such as in figure-ground segregation of textured images. Blocking N-methyl-D-aspartate (NMDA) receptors in monkeys can abolish neural signals related to figure-ground segregation and feature integration. However, it is unknown whether this also affects perceptual integration itself. Therefore, we tested whether ketamine, a non-competitive NMDA receptor antagonist, reduces feature integration in humans. We administered a subanesthetic dose of ketamine to healthy subjects who performed a texture discrimination task in a placebo-controlled double blind within-subject design. We found that ketamine significantly impaired performance on the texture discrimination task compared to the placebo condition, while performance on a control fixation task was much less impaired. This effect is not merely due to task difficulty or a difference in sedation levels. We are the first to show a behavioral effect on feature integration by manipulating the NMDA receptor in humans. PMID:24223927

  16. NMDA Receptor Antagonist Ketamine Impairs Feature Integration in Visual Perception

    PubMed Central

    Meuwese, Julia D. I.; van Loon, Anouk M.; Scholte, H. Steven; Lirk, Philipp B.; Vulink, Nienke C. C.; Hollmann, Markus W.; Lamme, Victor A. F.

    2013-01-01

    Recurrent interactions between neurons in the visual cortex are crucial for the integration of image elements into coherent objects, such as in figure-ground segregation of textured images. Blocking N-methyl-D-aspartate (NMDA) receptors in monkeys can abolish neural signals related to figure-ground segregation and feature integration. However, it is unknown whether this also affects perceptual integration itself. Therefore, we tested whether ketamine, a non-competitive NMDA receptor antagonist, reduces feature integration in humans. We administered a subanesthetic dose of ketamine to healthy subjects who performed a texture discrimination task in a placebo-controlled double blind within-subject design. We found that ketamine significantly impaired performance on the texture discrimination task compared to the placebo condition, while performance on a control fixation task was much less impaired. This effect is not merely due to task difficulty or a difference in sedation levels. We are the first to show a behavioral effect on feature integration by manipulating the NMDA receptor in humans. PMID:24223927

  17. Preliminary investigations into triazole derived androgen receptor antagonists.

    PubMed

    Altimari, Jarrad M; Niranjan, Birunthi; Risbridger, Gail P; Schweiker, Stephanie S; Lohning, Anna E; Henderson, Luke C

    2014-05-01

    A range of 1,4-substituted-1,2,3-N-phenyltriazoles were synthesized and evaluated as non-steroidal androgen receptor (AR) antagonists. The motivation for this study was to replace the N-phenyl amide portion of small molecule antiandrogens with a 1,2,3-triazole and determine effects, if any, on biological activity. The synthetic methodology presented herein is robust, high yielding and extremely rapid. Using this methodology a series of 17 N-aryl triazoles were synthesized from commercially available starting materials in less than 3h. After preliminary biological screening at 20 and 40 μM, the most promising three compounds were found to display IC50 values of 40-50 μM against androgen dependent (LNCaP) cells and serve as a starting point for further structure-activity investigations. All compounds in this work were the focus of an in silico study to dock the compounds into the human androgen receptor ligand binding domain (hARLBD) and compare their predicted binding affinity with known antiandrogens. A comparison of receptor-ligand interactions for the wild type and T877A mutant AR revealed two novel polar interactions. One with Q738 of the wild type site and the second with the mutated A877 residue.

  18. Leukotriene receptor antagonists for the treatment of asthma.

    PubMed

    Kemp, J P

    2000-04-01

    Leukotriene receptor antagonists (LTRAs) are novel medications that provide symptom control in patients with persistent asthma. Current guidelines recommend the use of LTRAs as a treatment option for patients with mild-persistent asthma of at least 12 years of age. As illustrated by the results of controlled, multicenter clinical trials with zafirlukast and montelukast, as well as studies with pranlukast in Japan, LTRAs reduce daytime and night time asthma symptoms, improve pulmonary function, lower beta-adrenergic agonist use, and reduce asthma morbidity in patients with mild-intermittent to moderate-persistent asthma. Moreover, several recent clinical studies demonstrate that these agents are effective in preventing exercise-induced bronchoconstriction in children, and in improving disease control in symptomatic patients taking inhaled steroids. Based on clinical results to date, LTRAs appear to be safe and well tolerated in patients with mildto- moderate asthma. These agents represent an important addition to the drug armamentarium against asthma.

  19. Mineralocorticoid receptor antagonists-pharmacodynamics and pharmacokinetic differences.

    PubMed

    Yang, Jun; Young, Morag J

    2016-04-01

    Mineralocorticoid receptor antagonists (MRAs) are best known as potassium-sparing diuretics due to their blockade of aldosterone action in renal epithelial tissues. They are also beneficial for the treatment of heart failure, primarily due to effects in non-epithelial tissues. Currently there are only two steroidal MRAs that have been approved for use; spironolactone (and its active metabolite canrenone) and eplerenone. However, the search is on for novel generations of MRAs with increased potency and tissue selectivity. A number of novel non-steroidal compounds are in preclinical and early development, with one agent moving to phase III trials. The development of these agents and the mechanisms for their pharmacologic superiority compared to earlier generations of MRAs will be discussed in this review. PMID:26939027

  20. Implementation of a fluorescence-based screening assay identifies histamine H3 receptor antagonists clobenpropit and iodophenpropit as subunit-selective N-methyl-D-aspartate receptor antagonists.

    PubMed

    Hansen, Kasper B; Mullasseril, Praseeda; Dawit, Sara; Kurtkaya, Natalie L; Yuan, Hongjie; Vance, Katie M; Orr, Anna G; Kvist, Trine; Ogden, Kevin K; Le, Phuong; Vellano, Kimberly M; Lewis, Iestyn; Kurtkaya, Serdar; Du, Yuhong; Qui, Min; Murphy, T J; Snyder, James P; Bräuner-Osborne, Hans; Traynelis, Stephen F

    2010-06-01

    N-Methyl-D-aspartate (NMDA) receptors are ligand-gated ion channels that mediate a slow, Ca(2+)-permeable component of excitatory synaptic transmission in the central nervous system and play a pivotal role in synaptic plasticity, neuronal development, and several neurological diseases. We describe a fluorescence-based assay that measures NMDA receptor-mediated changes in intracellular calcium in a BHK-21 cell line stably expressing NMDA receptor NR2D with NR1 under the control of a tetracycline-inducible promoter (Tet-On). The assay selectively identifies allosteric modulators by using supramaximal concentrations of glutamate and glycine to minimize detection of competitive antagonists. The assay is validated by successfully identifying known noncompetitive, but not competitive NMDA receptor antagonists among 1800 screened compounds from two small focused libraries, including the commercially available library of pharmacologically active compounds. Hits from the primary screen are validated through a secondary screen that used two-electrode voltage-clamp recordings on recombinant NMDA receptors expressed in Xenopus laevis oocytes. This strategy identified several novel modulators of NMDA receptor function, including the histamine H3 receptor antagonists clobenpropit and iodophenpropit, as well as the vanilloid receptor transient receptor potential cation channel, subfamily V, member 1 (TRPV1) antagonist capsazepine. These compounds are noncompetitive antagonists and the histamine H3 receptor ligand showed submicromolar potency at NR1/NR2B NMDA receptors, which raises the possibility that compounds can be developed that act with high potency on both glutamate and histamine receptor systems simultaneously. Furthermore, it is possible that some actions attributed to histamine H3 receptor inhibition in vivo may also involve NMDA receptor antagonism.

  1. Implementation of a Fluorescence-Based Screening Assay Identifies Histamine H3 Receptor Antagonists Clobenpropit and Iodophenpropit as Subunit-Selective N-Methyl-d-Aspartate Receptor Antagonists

    PubMed Central

    Hansen, Kasper B.; Mullasseril, Praseeda; Dawit, Sara; Kurtkaya, Natalie L.; Yuan, Hongjie; Vance, Katie M.; Orr, Anna G.; Kvist, Trine; Ogden, Kevin K.; Le, Phuong; Vellano, Kimberly M.; Lewis, Iestyn; Kurtkaya, Serdar; Du, Yuhong; Qui, Min; Murphy, T. J.; Snyder, James P.; Bräuner-Osborne, Hans

    2010-01-01

    N-Methyl-d-aspartate (NMDA) receptors are ligand-gated ion channels that mediate a slow, Ca2+-permeable component of excitatory synaptic transmission in the central nervous system and play a pivotal role in synaptic plasticity, neuronal development, and several neurological diseases. We describe a fluorescence-based assay that measures NMDA receptor-mediated changes in intracellular calcium in a BHK-21 cell line stably expressing NMDA receptor NR2D with NR1 under the control of a tetracycline-inducible promoter (Tet-On). The assay selectively identifies allosteric modulators by using supramaximal concentrations of glutamate and glycine to minimize detection of competitive antagonists. The assay is validated by successfully identifying known noncompetitive, but not competitive NMDA receptor antagonists among 1800 screened compounds from two small focused libraries, including the commercially available library of pharmacologically active compounds. Hits from the primary screen are validated through a secondary screen that used two-electrode voltage-clamp recordings on recombinant NMDA receptors expressed in Xenopus laevis oocytes. This strategy identified several novel modulators of NMDA receptor function, including the histamine H3 receptor antagonists clobenpropit and iodophenpropit, as well as the vanilloid receptor transient receptor potential cation channel, subfamily V, member 1 (TRPV1) antagonist capsazepine. These compounds are noncompetitive antagonists and the histamine H3 receptor ligand showed submicromolar potency at NR1/NR2B NMDA receptors, which raises the possibility that compounds can be developed that act with high potency on both glutamate and histamine receptor systems simultaneously. Furthermore, it is possible that some actions attributed to histamine H3 receptor inhibition in vivo may also involve NMDA receptor antagonism. PMID:20197375

  2. Prostaglandins, H2-receptor antagonists and peptic ulcer disease.

    PubMed

    Bright-Asare, P; Habte, T; Yirgou, B; Benjamin, J

    1988-01-01

    Peptic ulcer develops when offensive factors overwhelm defensive processes in the gastroduodenal mucosa. Offensive factors include NSAIDs, hydrochloric acid-peptic activity, bile reflux, and some products of the lipoxygenase pathway such as leukotriene B4; whereas defensive processes are largely mediated by prostaglandins through poorly understood mechanisms uniformly termed cytoprotection. Cytoprotection, a physiological process working through the products of arachidonic acid metabolism, may result from the net effect of the protective actions of prostaglandins versus the damaging actions of leukotrienes. Some prostaglandins also have antisecretory effects. Therefore the peptic ulcer healing effects of prostaglandin analogues, all of which have significant antisecretory activity, may be more due to their antisecretory effects than primarily to their effects on mucosal defences. Certain drug-induced gastroduodenal lesions, e.g. NSAID-induced ulcers, which are often unresponsive to H2-receptor antagonists, have been healed and their recurrence prevented by the use of PGE1 and PGE2 analogues. All the prostaglandin analogues investigated to date in humans have the potential for inducing abortion, an important side effect which may limit their worldwide use. The optimal prostaglandin analogue for ulcer healing should not induce abortion and should be potently cytoprotective. The predominant damaging agent in the development of peptic ulcer disease is gastric hydrochloric acid. Thus, the worldwide established efficacy and safety of H2-receptor antagonists such as cimetidine, ranitidine, famotidine and most recently of roxatidine acetate suggest that these agents have become the standard by which other forms of anti-ulcer therapy should be judged. PMID:2905237

  3. /sup 125/I-labeled 8-phenylxanthine derivatives: antagonist radioligands for adenosine A1 receptors

    SciTech Connect

    Linden, J.; Patel, A.; Earl, C.Q.; Craig, R.H.; Daluge, S.M.

    1988-04-01

    A series of 8-phenylxanthine derivatives has been synthesized with oxyacetic acid on the para phenyl position to increase aqueous solubility and minimize nonspecific binding and iodinatable groups on the 1- or 3-position of the xanthine ring. The structure-activity relationship for binding of these compounds to A1 adenosine receptors of bovine and rat brain and A2 receptors of human platelets was examined. The addition of arylamine or photosensitive aryl azide groups to the 3-position of xanthine had little effect on A1 binding affinity with or without iodination, whereas substitutions at the 1-position caused greatly reduced A1 binding affinity. The addition of an aminobenzyl group to the 3-position of the xanthine had little effect on A2 binding affinity, but 3-aminophenethyl substitution decreased A2 binding affinity. Two acidic 3-(arylamino)-8-phenylxanthine derivatives were labeled with /sup 125/I and evaluated as A1 receptor radioligands. The new radioligands bound to A1 receptors with KD values of 1-1.25 nM. Specific binding represented over 80% of total binding. High concentrations of NaCl or other salts increased the binding affinity of acidic but not neutral antagonists, suggesting that interactions between ionized xanthines and receptors may be affected significantly by changes in ionic strength. On the basis of binding studies with these antagonists and isotope dilution with the agonist (/sup 125/I)N6-(4-amino-3-iodobenzyl)adenosine, multiple agonist affinity states of A1 receptors have been identified.

  4. Synthesis and pharmacological investigation of azaphthalazinone human histamine H(1) receptor antagonists.

    PubMed

    Procopiou, Panayiotis A; Browning, Christopher; Gore, Paul M; Lynn, Sean M; Richards, Stephen A; Slack, Robert J; Sollis, Steven L

    2012-10-15

    5-Aza, 6-aza, 7-aza and 8-aza-phthalazinone, and 5,8-diazaphthalazinone templates were synthesised by stereoselective routes starting from the appropriate pyridine/pyrazine dicarboxylic acids by activation with CDI, reaction with 4-chlorophenyl acetate ester enolate to give a β-ketoester, which was hydrolysed, and decarboxylated. The resulting ketone was condensed with hydrazine to form the azaphthalazinone core. The azaphthalazinone cores were alkylated with N-Boc-D-prolinol at N-2 by Mitsunobu reaction, de-protected, and then alkylated at the pyrrolidine nitrogen to provide the target H(1) receptor antagonists. All four mono-azaphthalazinone series had higher affinity (pK(i)) for the human H(1) receptor than azelastine, but were not as potent as the parent non-aza phthalazinone. The 5,8-diazaphthalazinone was equipotent with azelastine. The least potent series were the 7-azaphthalazinones, whereas the 5-azaphthalazinones were the most lipophilic. The more hydrophilic series were the 8-aza series. Replacement of the N-methyl substituent on the pyrrolidine with the n-butyl group caused an increase in potency (pA(2)) and a corresponding increase in lipophilicity. Introduction of a β-ether oxygen in the n-butyl analogues (2-methoxyethyl group) decreased the H(1) pA(2) slightly, and increased the selectivity against hERG. The duration of action in vitro was longer in the 6-azaphthalazinone series. The more potent and selective 6-azaphthalazinone core was used to append an H(3) receptor antagonist fragment, and to convert the series into the long acting single-ligand, dual H(1) H(3) receptor antagonist 44. The pharmacological profile of 44 was very similar to our intranasal clinical candidate 1. PMID:22985961

  5. 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.

  6. Vasopressin receptor antagonists and their role in clinical medicine

    PubMed Central

    Narayen, Girish; Mandal, Surya Narayan

    2012-01-01

    Hyponatremia is the most common electrolyte abnormality in hospitalized patients. Its treatment is based not only on extracellular fluid volume status of patients but also on its pathogenetic mechanisms. Conventional treatment of hyponatremia like fluid restriction, which is useful in euvolemic and hypervolemic hyponatremia, has very poor patient compliance over long term. Vasopressin receptor antagonists (Vaptans) are a new group of nonpeptide drugs which have been used in various clinical conditions with limited success. Whereas conivaptan is to be administered intravenously, the other vaptans like tolvaptan, lixivaptan, and satavaptan are effective as oral medication. They produce aquaresis by their action on vasopressin type 2 (V2R) receptors in the collecting duct and thus increase solute free water excretion. Vaptans are being used as an alternative to fluid restriction in euvolemic and hypervolemic hyponatremic patients. Efficacy of vaptans is now well accepted for management of correction of hyponatremia over a short period. However, its efficacy in improving the long-term morbidity and mortality in patients with chronic hyponatremia due to cirrhosis and heart failure is yet to be established. Vaptans have not become the mainstay treatment of hyponatremia yet. PMID:22470853

  7. CGRP Receptor Antagonists in the Treatment of Migraine

    PubMed Central

    Durham, Paul L.; Vause, Carrie V.

    2011-01-01

    Based on preclinical and clinical studies, the neuropeptide calcitonin gene-related peptide (CGRP) is proposed to play a central role in the underlying pathology of migraine. CGRP and its receptor are widely expressed in both the peripheral and central nervous system by multiple cell types involved in the regulation of inflammatory and nociceptive responses. Peripheral release of CGRP from trigeminal nerve fibers within the dura and from the cell body of trigeminal ganglion neurons is likely to contribute to peripheral sensitization of trigeminal nociceptors. Similarly, the release of CGRP within the trigeminal nucleus caudalis can facilitate activation of nociceptive second order neurons and glial cells. Thus, CGRP is involved in the development and maintenance of persistent pain, central sensitization, and allodynia, events characteristic of migraine pathology. In contrast, CGRP release within the brain is likely to function in an anti-nociceptive capacity. This review will focus on the development and clinical data on CGRP receptor antagonists as well as discussing their potential roles in migraine therapy via modulation of multiple cell types within the peripheral and central nervous systems. PMID:20433208

  8. KW-3902, a selective high affinity antagonist for adenosine A1 receptors.

    PubMed Central

    Nonaka, H.; Ichimura, M.; Takeda, M.; Kanda, T.; Shimada, J.; Suzuki, F.; Kase, H.

    1996-01-01

    1. We demonstrate that 8-(noradamantan-3-yl)-1,3-dipropylxanthine (KW-3902) is a very potent and selective adenosine A1 receptor antagonist, assessed by radioligand binding and cyclic AMP response in cells. 2. In rat forebrain adenosine A1 receptors labelled with [3H]-cyclohexyladenosine (CHA), KW-3902 had a Ki value of 0.19 nM, whereas it showed a Ki value of 170 nM in rat striatal A2A receptors labelled with [3H]-2-[p-(2-carboxyethyl)-phenethylamino]-5'-N-ethylcarboxamidoad enosine (CGS21680), indicating 890 fold A1 receptor selectivity versus the A2A receptor. KW-3902 at 10 microM showed no effect on recombinant rat A3 receptors expressed on CHO cells. 3. Saturation studies with [3H]-KW-3902 revealed that it bound with high affinity (Kd = 77 pM) and limited capacity (Bmax = 470 fmol mg-1 of protein) to a single class of recognition sites. A high positive correlation was observed between the pharmacological profile of adenosine ligands inhibiting the binding of [3H]-KW-3902 and that of [3H]-CHA. 4. KW-3902 showed potent A1 antagonism against the inhibition of forskolin-induced cyclic AMP accumulation in DDT1 MF-2 cells by the A1-selective agonist, cyclopentyladenosine with a dissociation constant (KB value) of 0.34 nM. KW-3902 antagonized 5'-N-ethylcarboxamidoadenosine-elicited cyclic AMP accumulation via A2B receptors with a KB value of 52 nM. 5. KW-3902 exhibited marked species-dependent differences in the binding affinities. The highest affinity was for the rat A1 receptor (ki = 0.19 nM) and these values for guinea-pig and dog A1 receptors were 1.3 and 10 nM, respectively. PMID:8732272

  9. Structure Based Prediction of Subtype-Selectivity for Adenosine Receptor Antagonists

    PubMed Central

    Katritch, Vsevolod; Kufareva, Irina; Abagyan, Ruben

    2010-01-01

    One of the major hurdles in the development of safe and effective drugs targeting G-protein coupled receptors (GPCRs) is finding ligands that are highly selective for a specific receptor subtype. Structural understanding of subtype-specific binding pocket variations and ligand-receptor interactions may greatly facilitate design of selective ligands. To gain insights into the structural basis of ligand subtype selectivity within the family of adenosine receptors (AR: A1, A2A, A2B, and A3) we generated 3D models of all four subtypes using the recently determined crystal structure of the AA2AR as a template, and employing the methodology of ligand-guided receptor optimization for refinement. This approach produced 3D conformational models of AR subtypes that effectively explain binding modes and subtype selectivity for a diverse set of known AR antagonists. Analysis of the subtype-specific ligand-receptor interactions allowed identification of the major determinants of ligand selectivity, which may facilitate discovery of more efficient drug candidates. PMID:20637786

  10. Inhibition of tryptase release from human colon mast cells by histamine receptor antagonists.

    PubMed

    He, Shao-Heng; Xie, Hua; Fu, Yi-Ling

    2005-03-01

    The main objective of this study was to investigate the ability of histamine receptor antagonists to modulate tryptase release from human colon mast cells induced by histamine. Enzymatically dispersed cells from human colon were challenged with histamine in the absence or presence of the histamine receptor antagonists, and the tryptase release was determined. It was found that histamine induced tryptase release from colon mast cells was inhibited by up to approximately 61.5% and 24% by the H1 histamine receptor antagonist terfenadine and the H2 histamine receptor antagonist cimetidine, respectively, when histamine and its antagonists were added to cells at the same time. The H3 histamine receptor antagonist clobenpropit had no effect on histamine induced tryptase release from colon mast cells at all concentrations tested. Preincubation of terfenadine, cimetidine or clobenpropit with cells for 20 minutes before challenging with histamine did not enhance the ability of these antihistamines to inhibit histamine induced tryptase release. Apart from terfenadine at 100 microg/ml, the antagonists themselves did not stimulate tryptase release from colon mast cells following both 15 minutes and 35 minutes incubation periods. It was concluded that H1 and H2 histamine receptor antagonists were able to inhibit histamine induced tryptase release from colon mast cells. This not only added some new data to our hypothesis of self-amplification mechanisms of mast cell degranulation, but also suggested that combining these two types of antihistamine drugs could be useful for the treatment of inflammatory bowel disease (IBD).

  11. Androgen receptor antagonists (antiandrogens): structure-activity relationships.

    PubMed

    Singh, S M; Gauthier, S; Labrie, F

    2000-02-01

    Prostate cancer, acne, seborrhea, hirsutism, and androgenic alopecia are well recognized to depend upon an excess or increased sensitivity to androgens or to be at least sensitive to androgens. It thus seems logical to use antiandrogens as therapeutic agents to prevent androgens from binding to the androgen receptor. The two predominant naturally occurring androgens are testosterone (T) and dihydrotestosterone (DHT). DHT is the more potent androgen in vivo and in vitro. All androgen-responsive genes are activated by androgen receptor (AR) bound to either T or DHT and it is believed that AR is more transcriptionally active when bound to DHT than T. The two classes of antiandrogens, presently available, are the steroidal derivatives, all of which possess mixed agonistic and antagonistic activities, and the pure non-steroidal antiandrogens of the class of flutamide and its derivatives. The intrinsic androgenic, estrogenic and glucocorticoid activities of steroidal derivatives have limited their use in the treatment of prostate cancer. The non-steroidal flutamide and its derivatives display pure antiandrogenic activity, without exerting agonistic or any other hormonal activity. Flutamide (89) and its derivatives, Casodex (108) and Anandron (114), are highly effective in the treatment of prostate cancer. The combination of flutamide and Anandron with castration has shown prolongation of life in prostate cancer. Furthermore, combined androgen blockade in association with radical prostatectomy or radiotherapy are very effective in the treatment of localized prostate cancer. Such an approach certainly raises the hope of a further improvement in prostate cancer therapy. However, all antiandrogens, developed so-far display moderate affinity for the androgen receptor, and thus moderate efficacy in vitro and in vivo. There is thus a need for next-generation antiandrogens, which could display an equal or even higher affinity for AR compared to the natural androgens, and at the

  12. Synthesis of Indole Derived Protease-Activated Receptor 4 Antagonists and Characterization in Human Platelets

    PubMed Central

    Young, Summer E.; Duvernay, Matthew T.; Schulte, Michael L.; Lindsley, Craig W.; Hamm, Heidi E.

    2013-01-01

    Protease activated receptor-4 (PAR4) is one of the thrombin receptors on human platelets and is a potential target for the management of thrombotic disorders. We sought to develop potent, selective, and novel PAR4 antagonists to test the role of PAR4 in thrombosis and hemostasis. Development of an expedient three-step synthetic route to access a novel series of indole-based PAR4 antagonists also necessitated the development of a platelet based high-throughput screening assay. Screening and subsequent structure activity relationship analysis yielded several selective PAR4 antagonists as well as possible new scaffolds for future antagonist development. PMID:23776495

  13. Combined effects of oestrogen receptor antagonists on in vitro vitellogenesis.

    PubMed

    Petersen, Karina; Tollefsen, Knut Erik

    2012-05-15

    Some environmental compounds are known to have anti-oestrogenic activity and their modes of action (MoA) are believed to include competitive inhibition of 17β-estradiol (E2) binding to the oestrogen receptor (ER) or interference with ER-dependent processes. The presence of multiple compounds having the same MoA may cause concern, as exposure to multiple compounds at concentrations below their threshold for effect can interact with cellular targets to cause effects in combination. The combined effect of mixtures can be assessed using prediction models such as concentration addition (CA) and independent action (IA). The objective of the present study was to determine if the CA and IA prediction models could accurately characterise the combined effects of mixtures of ER antagonists in rainbow trout (Oncorhynchus mykiss) hepatocytes using the ER-mediated production of the oestrogenic biomarker vitellogenin (Vtg) as a screening assay. Model anti-oestrogens (4-hydroxytamoxifen and ZM 189.154) and environmentally relevant compounds (PCBs and PAHs) were tested to ensure inclusion of compounds from different chemical classes and with different MoAs. All eleven tested compounds had the ability to reduce the in vitro E2-induced production of Vtg in a concentration-dependent manner. The potency of the tested compounds differed by four orders of magnitude based on the concentrations for 50% inhibition (IC(50)). The observed order of potency was 2,3,7,8-tetrachlorodibenzo-p-dioxin>4-hydroxytamoxifen>3,3',4,4',5-pentachlorobiphenyl>benzo(k)fluoranthene>3,3',4,4'-tetrachlorobiphenyl>β-naphthoflavone>ZM 189.154>indeno[1,2,3-cd]pyrene>benzo(b)fluoranthene>benzo(a)pyrene>benzo(a)anthracene. The CA and IA models were able to predict the combined effects of mixtures of ER antagonists with similar MoA. The mixtures of certain ER-antagonists with different and/or complex MoA caused deviations from both the CA and the IA model by causing higher anti-oestrogenic activity than predicted

  14. Discovery of the First α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptor Antagonist Dependent upon Transmembrane AMPA Receptor Regulatory Protein (TARP) γ-8.

    PubMed

    Gardinier, Kevin M; Gernert, Douglas L; Porter, Warren J; Reel, Jon K; Ornstein, Paul L; Spinazze, Patrick; Stevens, F Craig; Hahn, Patric; Hollinshead, Sean P; Mayhugh, Daniel; Schkeryantz, Jeff; Khilevich, Albert; De Frutos, Oscar; Gleason, Scott D; Kato, Akihiko S; Luffer-Atlas, Debra; Desai, Prashant V; Swanson, Steven; Burris, Kevin D; Ding, Chunjin; Heinz, Beverly A; Need, Anne B; Barth, Vanessa N; Stephenson, Gregory A; Diseroad, Benjamin A; Woods, Tim A; Yu, Hong; Bredt, David; Witkin, Jeffrey M

    2016-05-26

    Transmembrane AMPA receptor regulatory proteins (TARPs) are a family of scaffolding proteins that regulate AMPA receptor trafficking and function. TARP γ-8 is one member of this family and is highly expressed within the hippocampus relative to the cerebellum. A selective TARP γ-8-dependent AMPA receptor antagonist (TDAA) is an innovative approach to modulate AMPA receptors in specific brain regions to potentially increase the therapeutic index relative to known non-TARP-dependent AMPA antagonists. We describe here, for the first time, the discovery of a noncompetitive AMPA receptor antagonist that is dependent on the presence of TARP γ-8. Three major iteration cycles were employed to improve upon potency, CYP1A2-dependent challenges, and in vivo clearance. An optimized molecule, compound (-)-25 (LY3130481), was fully protective against pentylenetetrazole-induced convulsions in rats without the motor impairment associated with non-TARP-dependent AMPA receptor antagonists. Compound (-)-25 could be utilized to provide proof of concept for antiepileptic efficacy with reduced motor side effects in patients. PMID:27067148

  15. Modulation of glutamate transport and receptor binding by glutamate receptor antagonists in EAE rat brain.

    PubMed

    Sulkowski, Grzegorz; Dąbrowska-Bouta, Beata; Salińska, Elżbieta; Strużyńska, Lidia

    2014-01-01

    The etiology of multiple sclerosis (MS) is currently unknown. However, one potential mechanism involved in the disease may be excitotoxicity. The elevation of glutamate in cerebrospinal fluid, as well as changes in the expression of glutamate receptors (iGluRs and mGluRs) and excitatory amino acid transporters (EAATs), have been observed in the brains of MS patients and animals subjected to experimental autoimmune encephalomyelitis (EAE), which is the predominant animal model used to investigate the pathophysiology of MS. In the present paper, the effects of glutamatergic receptor antagonists, including amantadine, memantine, LY 367583, and MPEP, on glutamate transport, the expression of mRNA of glutamate transporters (EAATs), the kinetic parameters of ligand binding to N-methyl-D-aspartate (NMDA) receptors, and the morphology of nerve endings in EAE rat brains were investigated. The extracellular level of glutamate in the brain is primarily regulated by astrocytic glutamate transporter 1 (GLT-1) and glutamate-aspartate transporter (GLAST). Excess glutamate is taken up from the synaptic space and metabolized by astrocytes. Thus, the extracellular level of glutamate decreases, which protects neurons from excitotoxicity. Our investigations showed changes in the expression of EAAT mRNA, glutamate transport (uptake and release) by synaptosomal and glial plasmalemmal vesicle fractions, and ligand binding to NMDA receptors; these effects were partially reversed after the treatment of EAE rats with the NMDA antagonists amantadine and memantine. The antagonists of group I metabotropic glutamate receptors (mGluRs), including LY 367385 and MPEP, did not exert any effect on the examined parameters. These results suggest that disturbances in these mechanisms may play a role in the processes associated with glutamate excitotoxicity and the progressive brain damage in EAE.

  16. The kappa opioid receptor antagonist JDTic attenuates alcohol seeking and withdrawal anxiety.

    PubMed

    Schank, Jesse R; Goldstein, Andrea L; Rowe, Kelly E; King, Courtney E; Marusich, Julie A; Wiley, Jenny L; Carroll, F Ivy; Thorsell, Annika; Heilig, Markus

    2012-05-01

    The role of kappa-opioid receptors (KOR) in the regulation of alcohol-related behaviors is not completely understood. For example, alcohol consumption has been reported to increase following treatment with KOR antagonists in rats, but was decreased in mice with genetic deletion of KOR. Recent studies have further suggested that KOR antagonists may selectively decrease alcohol self-administration in rats following a history of dependence. We assessed the effects of the KOR antagonist JDTic on alcohol self-administration, reinstatement of alcohol seeking induced by alcohol-associated cues or stress, and acute alcohol withdrawal-induced anxiety ('hangover anxiety'). JDTic dose-dependently reversed hangover anxiety when given 48 hours prior to testing, a time interval corresponding to the previously demonstrated anxiolytic efficacy of this drug. In contrast, JDTic decreased alcohol self-administration and cue-induced reinstatement of alcohol seeking when administered 2 hours prior to testing, but not at longer pre-treatment times. For comparison, we determined that the prototypical KOR antagonist nor-binaltorphimine can suppress self-administration of alcohol at 2 hours pre-treatment time, mimicking our observations with JDTic. The effects of JDTic were behaviorally specific, as it had no effect on stress-induced reinstatement of alcohol seeking, self-administration of sucrose, or locomotor activity. Further, we demonstrate that at a 2 hours pre-treatment time JDTic antagonized the antinociceptive effects of the KOR agonist U50,488H but had no effect on morphine-induced behaviors. Our results provide additional evidence for the involvement of KOR in regulation of alcohol-related behaviors and provide support for KOR antagonists, including JDTic, to be evaluated as medications for alcoholism.

  17. Volunteer models for predicting antiemetic activity of 5-HT3-receptor antagonists.

    PubMed Central

    Minton, N A

    1994-01-01

    1. Selective 5-HT3-receptor antagonists are highly effective in preventing nausea and vomiting associated with chemotherapy, radiotherapy and surgery. Their pharmacological activity may be determined in vitro and in animal models of emesis. However, these methods may not give an accurate indication of the antiemetic dose range of 5-HT3-receptor antagonists in patients. Two volunteer models have been used to predict more accurately clinically effective antiemetic doses of 5-HT3-receptor antagonists. 2. The flare response to intradermal 5-HT is thought to be mediated by excitation of 5-HT3-receptors on cutaneous afferents, with release of substance P and subsequent vasodilation. Antagonism of the flare response appears to provide an indication of the effective antiemetic dose of 5-HT3-receptor antagonists but data on duration of action are conflicting. 3. Ipecacuanha-induced emesis is thought to be mediated through both peripheral and central 5-HT3-receptors. Antagonism of this response has demonstrated a close correlation with clinically effective antiemetic doses of the specific 5-HT3-receptor antagonist, ondansetron, and has the advantage of being more conceptually relevant than the flare model. 4. Further work, with newer 5-HT3-receptor antagonists, will clarify the role of these models as predictive of the use of these drugs in clinical practice. PMID:7917768

  18. Antagonist of prostaglandin E2 receptor 4 induces metabolic alterations in liver of mice.

    PubMed

    Li, Ning; Zhang, Limin; An, Yanpeng; Zhang, Lulu; Song, Yipeng; Wang, Yulan; Tang, Huiru

    2015-03-01

    Prostaglandin E2 receptor 4 (EP4) is one of the receptors for prostaglandin E2 and plays important roles in various biological functions. EP4 antagonists have been used as anti-inflammatory drugs. To investigate the effects of an EP4 antagonist (L-161982) on the endogenous metabolism in a holistic manner, we employed a mouse model, and obtained metabolic and transcriptomic profiles of multiple biological matrixes, including serum, liver, and urine of mice with and without EP4 antagonist (L-161982) exposure. We found that this EP4 antagonist caused significant changes in fatty acid metabolism, choline metabolism, and nucleotide metabolism. EP4 antagonist exposure also induced oxidative stress to mice. Our research is the first of its kind to report information on the alteration of metabolism associated with an EP4 antagonist. This information could further our understanding of current and new biological functions of EP4.

  19. Sulfur-Containing 1,3-Dialkylxanthine Derivatives as Selective Antagonists at A1-Adenosine Receptors

    PubMed Central

    Kiriasis, Leonidas; Barone, Suzanne; Bradbury, Barton J.; Kammula, Udai; Campagne, Jean Michel; Secunda, Sherrie; Daly, John W.; Neumeyer, John L.; Pfleiderer, Wolfgang

    2012-01-01

    Sulfur-containing analogues of 8-substituted xanthines were prepared in an effort to increase selectivity or potency as antagonists at adenosine receptors. Either cyclopentyl or various aryl substituents were utilized at the 8-position, because of the association of these groups with high potency at A1-adenosine receptors. Sulfur was incorporated on the purine ring at positions 2 and/or 6, in the 8-position substituent in the form of 2- or 3-thienyl groups, or via thienyl groups separated from an 8-aryl substituent through an amide-containing chain. The feasibility of using the thienyl group as a prosthetic group for selective iodination via its Hg2+ derivative was explored. Receptor selectivity was determined in binding assays using membrane homogenates from rat cortex [[3H]-N6-(phenylisopropyl) adenosine as radioligand] or striatum [[3H]-5′-(N-ethylcarbamoyl)adenosine as radioligand] for A1- and A2-adenosine receptors, respectively. Generally, 2-thio-8-cycloalkylxanthines were at least as A1 selective as the corresponding oxygen analogue. 2-Thio-8-aryl derivatives tended to be more potent at A2 receptors than the oxygen analogue. 8-[4-[(Carboxymethyl)oxy]phenyl]-1,3-dipropyl-2-thioxanthine ethyl ester was >740-fold A1 selective. PMID:2754711

  20. Bioactivation pathways of the cannabinoid receptor 1 antagonist rimonabant.

    PubMed

    Bergström, Moa Andresen; Isin, Emre M; Castagnoli, Neal; Milne, Claire E

    2011-10-01

    In the present work, the characterization of the biotransformation and bioactivation pathways of the cannabinoid receptor 1 antagonist rimonabant (Acomplia) is described. Rimonabant was approved in Europe in 2006 for the treatment of obesity but was withdrawn in 2008 because of a significant drug-related risk of serious psychiatric disorders. The aim of the present work is to characterize the biotransformation and potential bioactivation pathways of rimonabant in vitro in human and rat liver microsomes. The observation of a major iminium ion metabolite led us to perform reactive metabolite trapping, covalent binding to proteins, and time-dependent inhibition of cytochrome P450 3A4 studies. The major biotransformation pathways were oxidative dehydrogenation of the piperidinyl ring to an iminium ion, hydroxylation of the 3 position of the piperidinyl ring, and cleavage of the amide linkage. In coincubations with potassium cyanide, three cyanide adducts were detected. A high level of covalent binding of rimonabant in human liver microsomes was observed (920 pmol equivalents/mg protein). In coincubations with potassium cyanide and methoxylamine, the covalent binding was reduced by approximately 40 and 30%, respectively, whereas GSH had no significant effect on covalent binding levels. Rimonabant was also found to inhibit cytochrome P450 3A4 irreversibly in a time-dependent manner. In view of these findings, it is noteworthy that, to date, no toxicity findings related to the formation of reactive metabolites from rimonabant have been reported. PMID:21733882

  1. Mineralocorticoid Receptor Antagonists for Treatment of Hypertension and Heart Failure

    PubMed Central

    Sica, Domenic A.

    2015-01-01

    Spironolactone and eplerenone are both mineralocorticoid-receptor antagonists. These compounds block both the epithelial and nonepithelial actions of aldosterone, with the latter assuming increasing clinical relevance. Spironolactone and eplerenone both affect reductions in blood pressure either as mono- or add-on therapy; moreover, they each afford survival benefits in diverse circumstances of heart failure and the probability of renal protection in proteinuric chronic kidney disease. However, as use of mineralocorticoid-blocking agents has expanded, the hazards inherent in taking such drugs have become more apparent. Whereas the endocrine side effects of spironolactone are in most cases little more than a cosmetic annoyance, the potassium-sparing effects of both spironolactone and eplerenone can prove disastrous, even fatal, if sufficient degrees of hyperkalemia emerge. For most patients, however, the risk of developing hyperkalemia in and of itself should not discourage the sensible clinician from bringing these compounds into play. Hyperkalemia should always be considered a possibility in patients receiving either of these medications; therefore, anticipatory steps should be taken to minimize the likelihood of its occurrence if long-term therapy of these agents is being considered. PMID:27057293

  2. Iontophoresis of Endothelin Receptor Antagonists in Rats and Men

    PubMed Central

    Roustit, Matthieu; Blaise, Sophie; Arnaud, Claire; Hellmann, Marcin; Millet, Claire; Godin-Ribuot, Diane; Dufournet, Boris; Boutonnat, Jean; Ribuot, Christophe; Cracowski, Jean-Luc

    2012-01-01

    Introduction The treatment of scleroderma-related digital ulcers is challenging. The oral endothelin receptor antagonist (ERA) bosentan has been approved but it may induce liver toxicity. The objective of this study was to test whether ERAs bosentan and sitaxentan could be locally delivered using iontophoresis. Methods Cathodal and anodal iontophoresis of bosentan and sitaxentan were performed on anaesthetized rat hindquarters without and during endothelin-1 infusion. Skin blood flow was quantified using laser-Doppler imaging and cutaneous tolerability was assessed. Iontophoresis of sitaxentan (20 min, 20 or 100 µA) was subsequently performed on the forearm skin of healthy men (n = 5). Results In rats neither bosentan nor sitaxentan increased skin blood flux compared to NaCl. When simultaneously infusing endothelin-1, cathodal iontophoresis of sitaxentan increased skin blood flux compared to NaCl (AUC0–20 were 44032.2±12277 and 14957.5±23818.8 %BL.s, respectively; P = 0.01). In humans, sitaxentan did not significantly increase skin blood flux as compared to NaCl. Iontophoresis of ERAs was well tolerated both in animals and humans. Conclusions This study shows that cathodal iontophoresis of sitaxentan but not bosentan partially reverses endothelin-induced skin vasoconstriction in rats, suggesting that sitaxentan diffuses into the dermis. However, sitaxentan does not influence basal skin microvascular tone in rats or in humans. PMID:22808263

  3. Side Effects of Leukotriene Receptor Antagonists in Asthmatic Children

    PubMed Central

    Erdem, Semiha Bahceci; Nacaroglu, Hikmet Tekin; Unsal Karkiner, Canan Sule; Gunay, Ilker; Can, Demet

    2015-01-01

    Background: Leukotriene receptor antagonists (LTRAs) are drugs which have been widely used more than ten years. As the use of LTRAs increases, our knowledge with respect to their side effects increases as well. Objectives: The objective of our study was to evaluat the observed side effects of LTRAs used in patients with astma. Patients and Methods: 1024 patients treated only with LTRAs owing to asthma or early wheezing were included in the study for a five-year period. The observed side effects of LTRAs in these patients were retrospectively investigated. The side effects were divided into two parts as psychiatric and non-psychiatric. Results: Among the 1024 cases included in the study, 67.5% of the patients out of 41 with side effects were male, 32.5% were female and the average age was 6.5 years. The rate of patients with asthma was 63.41% and 36.58% of the patients had early wheezing. It was determined that sex, age and diagnosis (early wheezing or asthma) of the patients were ineffective in the emergence of side effects. The average period for the emergence of side effects was the first month. It was observed that hyperactivity was the most frequently observed psychiatric side effect and that abdominal pain was the non-psychiatric side effect. Conclusions: The side effects of LTRAs were common in children. Therefore, patients must be informed at the beginning of the treatment and they must be evaluated at certain intervals. PMID:26495098

  4. Meta-diamide insecticides acting on distinct sites of RDL GABA receptor from those for conventional noncompetitive antagonists.

    PubMed

    Nakao, Toshifumi; Banba, Shinich; Nomura, Michikazu; Hirase, Kangetsu

    2013-04-01

    The RDL GABA receptor is an attractive target of insecticides. Here we demonstrate that meta-diamides [3-benzamido-N-(4-(perfluoropropan-2-yl)phenyl)benzamides] are a distinct class of RDL GABA receptor antagonists showing high insecticidal activity against Spodoptera litura. We also suggest that the mode of action of the meta-diamides is distinct from that of conventional noncompetitive antagonists (NCAs), such as fipronil, picrotoxin, lindane, dieldrin, and α-endosulfan. Using a membrane potential assay, we examined the effects of the meta-diamide 3-benzamido-N-(2-bromo-4-(perfluoropropan-2-yl)-6-(trifluoromethyl)phenyl)-2-fluorobenzamide (meta-diamide 7) and NCAs on mutant Drosophila RDL GABA receptors expressed in Drosophila Mel-2 cells. NCAs had little or no inhibitory activity against at least one of the three mutant receptors (A2'S, A2'G, and A2'N), which were reported to confer resistance to NCAs. In contrast, meta-diamide 7 inhibited all three A2' mutant receptors, at levels comparable to its activity with the wild-type receptor. Furthermore, the A2'S·T6'V mutation almost abolished the inhibitory effects of all NCAs. However, meta-diamide 7 inhibited the A2'S・T6'S mutant receptor at the same level as its activity with the wild-type receptor. In contrast, a G336M mutation in the third transmembrane domain of the RDL GABA receptor abolished the inhibitory activities of meta-diamide 7, although the G336M mutation had little effect on the inhibitory activities of conventional NCAs. Molecular modeling studies also suggested that the binding site of meta-diamides was different from those of NCAs. Meta-diamide insecticides are expected to be prominent insecticides effective against A2' mutant RDL GABA receptors with a different mode of action.

  5. Identification of potent CNS-penetrant thiazolidinones as novel CGRP receptor antagonists.

    PubMed

    Joshi, Pramod; Anderson, Corey; Binch, Hayley; Hadida, Sabine; Yoo, Sanghee; Bergeron, Danielle; Decker, Caroline; terHaar, Ernst; Moore, Jonathan; Garcia-Guzman, Miguel; Termin, Andreas

    2014-02-01

    Calcitonin gene-related peptide (CGRP) has been implicated in acute migraine pathogenesis. In an effort to identify novel CGRP receptor antagonists for the treatment of migraine, we have discovered thiazolidinone 49, a potent (Ki=30 pM, IC50=1 nM), orally bioavailable, CNS-penetrant CGRP antagonist with good pharmacokinetic properties. PMID:24405707

  6. The NK1 receptor antagonist L822429 reduces heroin reinforcement.

    PubMed

    Barbier, Estelle; Vendruscolo, Leandro F; Schlosburg, Joel E; Edwards, Scott; Juergens, Nathan; Park, Paula E; Misra, Kaushik K; Cheng, Kejun; Rice, Kenner C; Schank, Jesse; Schulteis, Gery; Koob, George F; Heilig, Markus

    2013-05-01

    Genetic deletion of the neurokinin 1 receptor (NK1R) has been shown to decrease the reinforcing properties of opioids, but it is unknown whether pharmacological NK1R blockade has the same effect. Here, we examined the effect of L822429, a rat-specific NK1R antagonist, on the reinforcing properties of heroin in rats on short (1 h: ShA) or long (12 h: LgA) access to intravenous heroin self-administration. ShA produces heroin self-administration rates that are stable over time, whereas LgA leads to an escalation of heroin intake thought to model important dependence-related aspects of addiction. L822429 reduced heroin self-administration and the motivation to consume heroin, measured using a progressive-ratio schedule, in both ShA and LgA rats. L822429 also decreased anxiety-like behavior in both groups, measured on the elevated plus maze, but did not affect mechanical hypersensitivity observed in LgA rats. Expression of TacR1 (the gene encoding NK1R) was decreased in reward- and stress-related brain areas both in ShA and LgA rats compared with heroin-naïve rats, but did not differ between the two heroin-experienced groups. In contrast, passive exposure to heroin produced increases in TacR1 expression in the prefrontal cortex and nucleus accumbens. Taken together, these results show that pharmacological NK1R blockade attenuates heroin reinforcement. The observation that animals with ShA and LgA to heroin were similarly affected by L822429 indicates that the SP/NK1R system is not specifically involved in neuroadaptations that underlie escalation resulting from LgA self-administration. Instead, the NK1R antagonist appears to attenuate acute, positively reinforcing properties of heroin and may be useful as an adjunct to relapse prevention in detoxified opioid-dependent subjects.

  7. Anti-idiotypic antibody: A new strategy for the development of a growth hormone receptor antagonist.

    PubMed

    Lan, Hainan; Zheng, Xin; Khan, Muhammad Akram; Li, Steven

    2015-11-01

    In general, traditional growth hormone receptor antagonist can be divided into two major classes: growth hormone (GH) analogues and anti-growth hormone receptor (GHR) antibodies. Herein, we tried to explore a new class of growth hormone receptor (GHR) antagonist that may have potential advantages over the traditional antagonists. For this, we developed a monoclonal anti-idiotypic antibody growth hormone, termed CG-86. A series of experiments were conducted to characterize and evaluate this antibody, and the results from a competitive receptor-binding assay, Enzyme Linked Immunosorbent Assays (ELISA) and epitope mapping demonstrate that CG-86 behaved as a typical Ab2β. Next, we examined its antagonistic activity using in vitro cell models, and the results showed that CG-86 could effectively inhibit growth hormone receptor-mediated signalling and effectively inhibit growth hormone-induced Ba/F3-GHR638 proliferation. In summary, these studies show that an anti-idiotypic antibody (CG-86) has promise as a novel growth hormone receptor antagonist. Furthermore, the current findings also suggest that anti-idiotypic antibody may represent a novel strategy to produce a new class of growth hormone receptor antagonist, and this strategy may be applied with other cytokines or growth factors.

  8. Sphingosine-1-Phosphate Receptor-2 Antagonists: Therapeutic Potential and Potential Risks

    PubMed Central

    Blankenbach, Kira V.; Schwalm, Stephanie; Pfeilschifter, Josef; Meyer zu Heringdorf, Dagmar

    2016-01-01

    The sphingosine-1-phosphate (S1P) signaling system with its specific G-protein-coupled S1P receptors, the enzymes of S1P metabolism and the S1P transporters, offers a multitude of promising targets for drug development. Until today, drug development in this area has nearly exclusively focused on (functional) antagonists at the S1P1 receptor, which cause a unique phenotype of immunomodulation. Accordingly, the first-in class S1P1 receptor modulator, fingolimod, has been approved for the treatment of relapsing-remitting multiple sclerosis, and novel S1P1 receptor (functional) antagonists are being developed for autoimmune and inflammatory diseases such as psoriasis, inflammatory bowel disease, lupus erythematodes, or polymyositis. Besides the S1P1 receptor, also S1P2 and S1P3 are widely expressed and regulate many diverse functions throughout the body. The S1P2 receptor, in particular, often exerts cellular functions which are opposed to the functions of the S1P1 receptor. As a consequence, antagonists at the S1P2 receptor have the potential to be useful in a contrasting context and different areas of indication compared to S1P1 antagonists. The present review will focus on the therapeutic potential of S1P2 receptor antagonists and discuss their opportunities as well as their potential risks. Open questions and areas which require further investigations will be emphasized in particular. PMID:27445808

  9. Pharmacology of glutamate receptor antagonists in the kindling model of epilepsy.

    PubMed

    Löscher, W

    1998-04-01

    It is widely accepted that excitatory amino acid transmitters such as glutamate are involved in the initiation of seizures and their propagation. Most attention has been directed to synapses using NMDA receptors, but more recent evidence indicates potential roles for ionotropic non-NMDA (AMPA/kainate) and metabotropic glutamate receptors as well. Based on the role of glutamate in the development and expression of seizures, antagonism of glutamate receptors has long been thought to provide a rational strategy in the search for new, effective anticonvulsant drugs. Furthermore, because glutamate receptor antagonists, particularly those acting on NMDA receptors, protect effectively in the induction of kindling, it was suggested that they may have utility in epilepsy prophylaxis, for example, after head trauma. However, first clinical trials with competitive and uncompetitive NMDA receptor antagonists in patients with partial (focal) seizures, showed that these drugs lack convincing anticonvulsant activity but induce severe neurotoxic adverse effects in doses which were well tolerated in healthy volunteers. Interestingly, the only animal model which predicted the unfavorable clinical activity of competitive NMDA antagonists in patients with chronic epilepsy was the kindling model of temporal lobe epilepsy, indicating that this model should be used in the search for more effective and less toxic glutamate receptor antagonists. In this review, results from a large series of experiments on different categories of glutamate receptor antagonists in fully kindled rats are summarized and discussed. NMDA antagonists, irrespective whether they are competitive, high- or low-affinity uncompetitive, glycine site or polyamine site antagonists, do not counteract focal seizure activity and only weakly, if at all, attenuate propagation to secondarily generalized seizures in this model, indicating that once kindling is established, NMDA receptors are not critical for the expression of

  10. Attenuation of morphine antinociceptive tolerance by a CB1 receptor agonist and an NMDA receptor antagonist: interactive effects

    PubMed Central

    Fischer, Bradford D.; Ward, Sara J.; Henry, Fredrick E.; Dykstra, Linda A.

    2009-01-01

    CB1 cannabinoid (CB1) receptor agonists and N-Methyl-d-Aspartate (NMDA) receptor antagonists attenuate the development of morphine antinociceptive tolerance. The present study used dose-addition analysis to evaluate CB1/NMDA receptor interactions on this endpoint. Chronic morphine administration (5 days, 100 mg/kg, twice daily) resulted in a 2.8-fold rightward shift in the morphine dose-effect curve. Co-administration of either the CB1 receptor agonist CP-55940 (5-(1,1-Dimethylheptyl)-2-[5-hydroxy-2-(3-hydroxypropyl)cyclohexyl]phenol; 0.32-1.0 mg/kg) or the NMDA receptor antagonist (−)-6-phosphonomethyl-deca-hydroisoquinoline-3-carboxylic acid (LY235959; 1.0-3.2 mg/kg) with morphine dose-dependently attenuated morphine tolerance. The relative potency of each drug alone was quantified using a defined level of effect (one-quarter log shift in the morphine dose-effect curve), resulting in equieffective doses of 0.42 mg/kg and 1.1 mg/kg for CP-55940 and LY235959, respectively. Subsequent experiments assessed CP-55940/LY235959 interactions using a fixed-proportion design. Co-administration of CP-55940/LY235959 mixtures (1:1, 1:3.2, or 1:10 CP-55940/LY235959) with morphine dose-dependently attenuated morphine tolerance. Isobolographic and dose-addition analysis were used to statistically compare the experimentally determined potency for each mixture (zmix) with predicted additive potency (zadd). Mixtures of 1:1 and 1:3.2 CP-55940/LY235959 produced additive effects (zadd = zmix), while the mixture of 1:10 CP-55940/LY235959 produced a supra-additive effect (zadd > zmix). These results suggest that CP-55940 and LY235959 produce additive or supra-additive attenuation of morphine antinociceptive tolerance after repeated morphine administration, depending on their relative concentrations. PMID:19699755

  11. The influence of 5-HT2 and 5-HT4 receptor antagonists to modify drug induced disinhibitory effects in the mouse light/dark test

    PubMed Central

    Costall, Brenda; Naylor, Robert J

    1997-01-01

    The ability of 5-HT2 and 5-HT4 receptor antagonists to modify the disinhibitory profile of diazepam and other agents was investigated in male BKW mice in the light/dark test box. The 5-HT2A/2B/2C receptor antagonists ritanserin, MDL11939 and RP62203 and also methysergide, which failed to modify mouse behaviour when administered alone, caused dose-related enhancements (4 to 8 fold) in the potency of diazepam to disinhibit behavioural responding to the aversive situation of the test box. Ritanserin was shown to enhance the disinhibitory potency of other benzodiazepines, chlordiazepoxide (4 fold), temazepam (10 fold) and lorazepam (10 fold), the 5-HT1A receptor ligands, 8-OH-DPAT (25 fold), buspirone (100 fold) and lesopitron (500 fold), the 5-HT3 receptor antagonists, ondansetron (100 fold) R(+)-zacopride (100 fold) and S(−)-zacopride (greater than a 1000 fold), the substituted benzamides, sulpiride (10 fold) and tiapride (5 to 10 fold) and the cholecystokinin (CCK)A receptor antagonist, devazepide (100 fold). It also reduced the onset of action of disinhibition following treatment with the 5-HT synthesis inhibitor parachlorophenylalanine. Ritanserin failed to enhance the disinhibitory effects of the CCKB receptor antagonist CI-988, the angiotensin AT1 receptor antagonist losarten or the angiotensin converting enzyme inhibitor ceranapril. The 5-HT4 receptor antagonists SDZ205-557, GR113808 and SB204070 caused dose-related reductions in the disinhibitory effect of diazepam, returning values to those shown in vehicle treated controls. The antagonists failed to modify mouse behaviour when administered alone. GR113808 was also shown to cause a dose-related antagonism of the disinhibitory effects of chlordiazepoxide, lorazepam, 8-OH-DPAT, buspirone, lesopitron, ondansetron, R(+)-zacopride, sulpiride, tiapride, devazepide, CI-988, losarten, ceranapril and parachlorophenylalanine. It was concluded that in BKW mice (a) the failure of 5-HT2 and 5-HT4 receptor antagonists

  12. High-throughput screening of antagonists for the orphan G-protein coupled receptor GPR139

    PubMed Central

    Wang, Jia; Zhu, Lin-yun; Liu, Qing; Hentzer, Morten; Smith, Garrick Paul; Wang, Ming-wei

    2015-01-01

    Aim: To discover antagonists of the orphan G-protein coupled receptor GPR139 through high-throughput screening of a collection of diverse small molecules. Methods: Calcium mobilization assays were used to identify initial hits and for subsequent confirmation studies. Results: Five small molecule antagonists, representing 4 different scaffolds, were identified following high-throughput screening of 16 000 synthetic compounds. Conclusion: The findings provide important tools for further study of this orphan G-protein coupled receptor. PMID:26027661

  13. Dynamics of histamine H(3) receptor antagonists on brain histamine metabolism: do all histamine H(3) receptor antagonists act at a single site?

    PubMed

    Barnes, W; Boyd, D; Hough, L

    2001-11-16

    Thioperamide, the prototypical histamine H(3) receptor antagonist, acts at the brain histamine H(3) autoreceptor to promote the release and metabolism of neuronal histamine, resulting in higher brain levels of the metabolite tele-methylhistamine. However, unlike thioperamide, several new histamine H(3) receptor antagonists enter the central nervous system (CNS), block brain histamine H(3) receptors and increase histamine release without increasing brain tele-methylhistamine levels. Experiments were performed presently in an attempt to understand these results. Consistent with previous findings, thioperamide significantly increased the content and synthesis rate of tele-methylhistamine in mouse and rat brain. In contrast, the histamine H(3) receptor antagonists GT-2227 (4-(6-cyclohexylhex-cis-3-enyl)imidazole) and clobenpropit did not affect tele-methylhistamine synthesis rate in mouse whole brain. The histamine H(3) receptor ligand GT-2016 (5-cyclohexyl-1-(4-imidazol-4-ylpiperidyl)pentan-1-one) had no effect on tele-methylhistamine levels in any rat brain region and decreased tele-methylhistamine synthesis rates in the mouse whole brain. To examine the possibility that these histamine H(3) receptor antagonists might prevent the methylation of newly released histamine, they were co-administered with thioperamide to determine their effects on the thioperamide-induced stimulation of tele-methylhistamine synthesis. GT-2016 significantly reduced the thioperamide-induced activation of tele-methylhistamine synthesis in mouse whole brain and in several regions of rat brain. Although further clarification is needed, these results suggest that some histamine H(3) receptor antagonists may promote the release of neuronal histamine, but also act to reduce histamine methylation in vivo by an unknown mechanism.

  14. Discovery of 2-substituted benzoxazole carboxamides as 5-HT3 receptor antagonists.

    PubMed

    Yang, Zhicai; Fairfax, David J; Maeng, Jun-Ho; Masih, Liaqat; Usyatinsky, Alexander; Hassler, Carla; Isaacson, Soshanna; Fitzpatrick, Kevin; DeOrazio, Russell J; Chen, Jianqing; Harding, James P; Isherwood, Matthew; Dobritsa, Svetlana; Christensen, Kevin L; Wierschke, Jonathan D; Bliss, Brian I; Peterson, Lisa H; Beer, Cathy M; Cioffi, Christopher; Lynch, Michael; Rennells, W Martin; Richards, Justin J; Rust, Timothy; Khmelnitsky, Yuri L; Cohen, Marlene L; Manning, David D

    2010-11-15

    A new class of 2-substituted benzoxazole carboxamides are presented as potent functional 5-HT(3) receptor antagonists. The chemical series possesses nanomolar in vitro activity against human 5-HT(3)A receptors. A chemistry optimization program was conducted and identified 2-aminobenzoxazoles as orally active 5-HT(3) receptor antagonists with good metabolic stability. These novel analogues possess drug-like characteristics and have potential utility for the treatment of diseases attributable to improper 5-HT(3) receptor function, especially diarrhea predominant irritable bowel syndrome (IBS-D).

  15. Increased Orbitofrontal Brain Activation after Administration of a Selective Adenosine A2A Antagonist in Cocaine Dependent Subjects

    PubMed Central

    Moeller, F. Gerard; Steinberg, Joel L.; Lane, Scott D.; Kjome, Kimberly L.; Ma, Liangsuo; Ferre, Sergi; Schmitz, Joy M.; Green, Charles E.; Bandak, Stephen I.; Renshaw, Perry F.; Kramer, Larry A.; Narayana, Ponnada A.

    2012-01-01

    Background: Positron Emission Tomography imaging studies provide evidence of reduced dopamine function in cocaine dependent subjects in the striatum, which is correlated with prefrontal cortical glucose metabolism, particularly in the orbitofrontal cortex. However, whether enhancement of dopamine in the striatum in cocaine dependent subjects would be associated with changes in prefrontal cortical brain activation is unknown. One novel class of medications that enhance dopamine function via heteromer formation with dopamine receptors in the striatum is the selective adenosine A2A receptor antagonists. This study sought to determine the effects administration of the selective adenosine A2A receptor antagonist SYN115 on brain function in cocaine dependent subjects. Methodology/Principle Findings: Twelve cocaine dependent subjects underwent two fMRI scans (one after a dose of placebo and one after a dose of 100 mg of SYN115) while performing a working memory task with three levels of difficulty (3, 5, and 7 digits). fMRI results showed that for 7-digit working memory activation there was significantly greater activation from SYN115 compared to placebo in portions of left (L) lateral orbitofrontal cortex, L insula, and L superior and middle temporal pole. Conclusion/Significance: These findings are consistent with enhanced dopamine function in the striatum in cocaine dependent subjects via blockade of adenosine A2A receptors producing increased brain activation in the orbitofrontal cortex and other cortical regions. This suggests that at least some of the changes in brain activation in prefrontal cortical regions in cocaine dependent subjects may be related to altered striatal dopamine function, and that enhancement of dopamine function via adenosine A2A receptor blockade could be explored further for amelioration of neurobehavioral deficits associated with chronic cocaine use. PMID:22654774

  16. YM-50001: a novel, potent and selective dopamine D4 receptor antagonist.

    PubMed

    Hidaka, K; Tada, S; Matsumoto, M; Ohmori, J; Maeno, K; Yamaguchi, T

    1996-11-01

    We investigated some in vitro pharmacological properties of a novel human dopamine D2-like receptor antagonist, YM-50001 [(R)-5-chloro-4-cyclopropylacarbonylamino-2-methoxy-N-[1-(3-methox ybenzyl)- 3-pyrrolidinyl]benzamide monooxalate]. Receptor binding studies revealed that YM-50001 had a potent affinity for human D4 receptors (Ki = 5.62 nM). YM-50001 displayed weak or negligible affinity for other neurotransmitter receptors including human D2 and D3 receptors. YM-50001 shifted the dopamine response curve on each human D2-like receptor subtype-mediated low-Km GTPase activity to the right. YM-50001 also exhibited good D4 selectivity with respect to D2-like receptor antagonism in the functional assay. These results indicate that YM-50001 is a novel, potent and selective D4 receptor antagonist.

  17. Pharmacophore modeling of dual angiotensin II and endothelin A receptor antagonists.

    PubMed

    Xue, Wei-Zhe; Lü, Wei; Zhou, Zhi-Ming; Wang, Zhan-Li

    2009-09-01

    Three-dimensional pharmacophore models were generated for AT1 and ET(A) receptors based on highly selective AT1 and ET(A) antagonists using the program Catalyst/HipHop. Both the best pharmacophore model for selective AT1 antagonists (Hypo-AT(1)-7) and ETA antagonists (Hypo-ET(A)-1) were obtained through a careful validation process. All five features contained in Hypo-AT(1)-7 and Hypo-ET(A)-1 (hydrogen-bond acceptor (A), hydrophobic aliphatic (Z), negative ionizable (N), ring aromatic (R), and hydrophobic aromatic (Y)) seem to be essential for antagonists in terms of binding activity. Dual AT1 and ET(A) receptor antagonists (DARAs) can map to both Hypo-AT(1)-7 and Hypo-ET(A)-1, separately. Comparison of Hypo-AT(1)-7 and Hypo-ET(A)-1, not only AT1 and ET(A) antagonist pharmacophore models consist of essential features necessary for compounds to be highly active and selective toward their corresponding receptor, but also have something in common. The results in this study will act as a valuable tool for designing and researching structural relationship of novel dual AT1 and ET(A) receptor antagonists. PMID:20055175

  18. Pharmacophore modeling of dual angiotensin II and endothelin A receptor antagonists.

    PubMed

    Xue, Wei-Zhe; Lü, Wei; Zhou, Zhi-Ming; Wang, Zhan-Li

    2009-09-01

    Three-dimensional pharmacophore models were generated for AT1 and ET(A) receptors based on highly selective AT1 and ET(A) antagonists using the program Catalyst/HipHop. Both the best pharmacophore model for selective AT1 antagonists (Hypo-AT(1)-7) and ETA antagonists (Hypo-ET(A)-1) were obtained through a careful validation process. All five features contained in Hypo-AT(1)-7 and Hypo-ET(A)-1 (hydrogen-bond acceptor (A), hydrophobic aliphatic (Z), negative ionizable (N), ring aromatic (R), and hydrophobic aromatic (Y)) seem to be essential for antagonists in terms of binding activity. Dual AT1 and ET(A) receptor antagonists (DARAs) can map to both Hypo-AT(1)-7 and Hypo-ET(A)-1, separately. Comparison of Hypo-AT(1)-7 and Hypo-ET(A)-1, not only AT1 and ET(A) antagonist pharmacophore models consist of essential features necessary for compounds to be highly active and selective toward their corresponding receptor, but also have something in common. The results in this study will act as a valuable tool for designing and researching structural relationship of novel dual AT1 and ET(A) receptor antagonists.

  19. Competitive Agonists and Antagonists of Steroid Nuclear Receptors: Evolution of the Concept or Its Reversal.

    PubMed

    Smirnova, O V

    2015-10-01

    The mechanisms displaying pure and mixed steroid agonist/antagonist activity as well as principles underlying in vivo action of selective steroid receptor modulators dependent on tissue or cell type including interaction with various types of nuclear receptors are analyzed in this work. Mechanisms of in vitro action for mixed agonist/antagonist steroids are discussed depending on: specific features of their interaction with receptor hormone-binding pocket; steroid-dependent allosteric modulation of interaction between hormone-receptor complex and hormone response DNA elements; features of interacting hormone-receptor complex with protein transcriptional coregulators; level and tissue-specific composition of transcriptional coregulators. A novel understanding regarding context-selective modulators replacing the concept of steroid agonists and antagonists is discussed.

  20. 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

  1. Discovery of 1,2,4-Triazine Derivatives as Adenosine A2A Antagonists using Structure Based Drug Design

    PubMed Central

    2012-01-01

    Potent, ligand efficient, selective, and orally efficacious 1,2,4-triazine derivatives have been identified using structure based drug design approaches as antagonists of the adenosine A2A receptor. The X-ray crystal structures of compounds 4e and 4g bound to the GPCR illustrate that the molecules bind deeply inside the orthosteric binding cavity. In vivo pharmacokinetic and efficacy data for compound 4k are presented, demonstrating the potential of this series of compounds for the treatment of Parkinson’s disease. PMID:22220592

  2. Homology modelling of the human adenosine A2B receptor based on X-ray structures of bovine rhodopsin, the beta2-adrenergic receptor and the human adenosine A2A receptor.

    PubMed

    Sherbiny, Farag F; Schiedel, Anke C; Maass, Astrid; Müller, Christa E

    2009-11-01

    A three-dimensional model of the human adenosine A2B receptor was generated by means of homology modelling, using the crystal structures of bovine rhodopsin, the beta2-adrenergic receptor, and the human adenosine A2A receptor as templates. In order to compare the three resulting models, the binding modes of the adenosine A2B receptor antagonists theophylline, ZM241385, MRS1706, and PSB601 were investigated. The A2A-based model was much better able to stabilize the ligands in the binding site than the other models reflecting the high degree of similarity between A2A and A2B receptors: while the A2B receptor shares about 21% of the residues with rhodopsin, and 31% with the beta2-adrenergic receptor, it is 56% identical to the adenosine A2A receptor. The A2A-based model was used for further studies. The model included the transmembrane domains, the extracellular and the intracellular hydrophilic loops as well as the terminal domains. In order to validate the usefulness of this model, a docking analysis of several selective and nonselective agonists and antagonists was carried out including a study of binding affinities and selectivities of these ligands with respect to the adenosine A2A and A2B receptors. A common binding site is proposed for antagonists and agonists based on homology modelling combined with site-directed mutagenesis and a comparison between experimental and calculated affinity data. The new, validated A2B receptor model may serve as a basis for developing more potent and selective drugs.

  3. CGRP receptor antagonists and antibodies against CGRP and its receptor in migraine treatment

    PubMed Central

    Edvinsson, Lars

    2015-01-01

    Recently developed calcitonin gene-related peptide (CGRP) receptor antagonistic molecules have shown promising results in clinical trials for acute treatment of migraine attacks. Drugs from the gepant class of CGRP receptor antagonists are effective and do not cause vasoconstriction, one of the major limitations in the use of triptans. However their use had to be discontinued because of risk of liver toxicity after continuous exposure. As an alternative approach to block CGRP transmission, fully humanized monoclonal antibodies towards CGRP and the CGRP receptor have been developed for treatment of chronic migraine (attacks >15 days/month). Initial results from phase I and II clinical trials have revealed promising results with minimal side effects and significant relief from chronic migraine as compared with placebo. The effectiveness of these various molecules raises the question of where is the target site(s) for antimigraine action. The gepants are small molecules that can partially pass the blood–brain barrier (BBB) and therefore, might have effects in the CNS. However, antibodies are large molecules and have limited possibility to pass the BBB, thus effectively excluding them from having a major site of action within the CNS. It is suggested that the antimigraine site should reside in areas not limited by the BBB such as intra- and extracranial vessels, dural mast cells and the trigeminal system. In order to clarify this topic and surrounding questions, it is important to understand the localization of CGRP and the CGRP receptor components in these possible sites of migraine-related regions and their relation to the BBB. PMID:25731075

  4. 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

  5. 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

  6. 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

  7. Heterogeneity of binding of muscarinic receptor antagonists in rat brain homogenates

    SciTech Connect

    Lee, J.H.; el-Fakahany, E.E.

    1985-06-01

    The binding properties of (-)-(/sup 3/H)quinuclidinyl benzilate and (/sup 3/H) N-methylscopolamine to muscarinic acetylcholine receptors have been investigated in rat brain homogenates. The binding of both antagonists demonstrated high affinity and saturability. Analysis of the binding data resulted in linear Scatchard plots. However, (-)-(/sup 3/H)quinuclidinyl benzilate showed a significantly higher maximal binding capacity than that of (/sup 3/H)N-methylscopolamine. Displacement of both ligands with several muscarinic receptor antagonists resulted in competition curves in accordance with the law of mass-action for quinuclidinyl benzilate, atropine and scopolamine. A similar profile was found for the quaternary ammonium analogs of atropine and scopolamine when (/sup 3/H)N-methylscopolamine was used to label the receptors. However, when these hydrophilic antagonists were used to displace (-)-(/sup 3/H) quinuclidinyl benzilate binding, they showed interaction with high- and low-affinity binding sites. On the other hand, the nonclassical muscarinic receptor antagonist, pirenzepine, was able to displace both ligands from two binding sites. The present data are discussed in terms of the relationship of this anomalous heterogenity of binding of these hydrophilic muscarinic receptor antagonists and the proposed M1 and M2 receptor subtypes.

  8. Ligand Binding and Subtype Selectivity of the Human A2A Adenosine Receptor

    PubMed Central

    Jaakola, Veli-Pekka; Lane, J. Robert; Lin, Judy Y.; Katritch, Vsevolod; IJzerman, Adriaan P.; Stevens, Raymond C.

    2010-01-01

    The crystal structure of the human A2A adenosine receptor bound to the A2A receptor-specific antagonist, ZM241385, was recently determined at 2.6-Å resolution. Surprisingly, the antagonist binds in an extended conformation, perpendicular to the plane of the membrane, and indicates a number of interactions unidentified before in ZM241385 recognition. To further understand the selectivity of ZM241385 for the human A2A adenosine receptor, we examined the effect of mutating amino acid residues within the binding cavity likely to have key interactions and that have not been previously examined. Mutation of Phe-168 to Ala abolishes both agonist and antagonist binding as well as receptor activity, whereas mutation of this residue to Trp or Tyr had only moderate effects. The Met-177 → Ala mutation impeded antagonist but not agonist binding. Finally, the Leu-249 → Ala mutant showed neither agonist nor antagonist binding affinity. From our results and previously published mutagenesis data, we conclude that conserved residues Phe-168(5.29), Glu-169(5.30), Asn-253(6.55), and Leu-249(6.51) play a central role in coordinating the bicyclic core present in both agonists and antagonists. By combining the analysis of the mutagenesis data with a comparison of the sequences of different adenosine receptor subtypes from different species, we predict that the interactions that determine subtype selectivity reside in the more divergent “upper” region of the binding cavity while the “lower” part of the binding cavity is conserved across adenosine receptor subtypes. PMID:20147292

  9. Adenosine A2A receptors are necessary and sufficient to trigger memory impairment in adult mice

    PubMed Central

    Pagnussat, N; Almeida, A S; Marques, D M; Nunes, F; Chenet, G C; Botton, P H S; Mioranzza, S; Loss, C M; Cunha, R A; Porciúncula, L O

    2015-01-01

    Background and Purpose Caffeine (a non-selective adenosine receptor antagonist) prevents memory deficits in aging and Alzheimer’s disease, an effect mimicked by adenosine A2A receptor, but not A1 receptor, antagonists. Hence, we investigated the effects of adenosine receptor agonists and antagonists on memory performance and scopolamine-induced memory impairment in mice. Experimental Approach We determined whether A2A receptors are necessary for the emergence of memory impairments induced by scopolamine and whether A2A receptor activation triggers memory deficits in naïve mice, using three tests to assess short-term memory, namely the object recognition task, inhibitory avoidance and modified Y-maze. Key Results Scopolamine (1.0 mg·kg−1, i.p.) impaired short-term memory performance in all three tests and this scopolamine-induced amnesia was prevented by the A2A receptor antagonist (SCH 58261, 0.1–1.0 mg·kg−1, i.p.) and by the A1 receptor antagonist (DPCPX, 0.2–5.0 mg·kg−1, i.p.), except in the modified Y-maze where only SCH58261 was effective. Both antagonists were devoid of effects on memory or locomotion in naïve rats. Notably, the activation of A2A receptors with CGS 21680 (0.1–0.5 mg·kg−1, i.p.) before the training session was sufficient to trigger memory impairment in the three tests in naïve mice, and this effect was prevented by SCH 58261 (1.0 mg·kg−1, i.p.). Furthermore, i.c.v. administration of CGS 21680 (50 nmol) also impaired recognition memory in the object recognition task. Conclusions and Implications These results show that A2A receptors are necessary and sufficient to trigger memory impairment and further suggest that A1 receptors might also be selectively engaged to control the cholinergic-driven memory impairment. PMID:25939452

  10. An adenosine A(2A) antagonist injected in the NTS reverses thermal prolongation of the LCR in decerebrate piglets.

    PubMed

    Xia, Luxi; Bartlett, Donald; Leiter, J C

    2008-12-31

    Hyperthermia prolongs the laryngeal chemoreflex (LCR). Under normothermic conditions, adenosine antagonists shorten and adenosine A(2A) (Ad-A(2A)) agonists prolong the LCR. Therefore, we tested the hypothesis that SCH-58261, an Ad-A(2A) receptor antagonist, would prevent thermal prolongation of the LCR when injected unilaterally within the nucleus of the solitary tract (NTS). We studied decerebrate piglets aged 4-13 days. We elicited the LCR by injecting 0.1ml of water into the larynx and recorded integrated phrenic nerve activity. The laryngeal chemoreflex was prolonged when the body temperature of each piglet was raised approximately 2.5 degrees C, and SCH-58261 reversed the thermal prolongation of the LCR when injected into the NTS (n=13), but not when injected in the nucleus ambiguus (n=9). Injections of vehicle alone into the NTS did not alter the thermal prolongation of the LCR (n=9). We conclude that activation of adenosine receptors, perhaps located on GABAergic neurons in the NTS, contributes to thermal prolongation of the LCR.

  11. The impact of adenosine and A(2B) receptors on glucose homoeostasis.

    PubMed

    Rüsing, D; Müller, C E; Verspohl, E J

    2006-12-01

    Adenosine and adenosine receptor antagonists are involved in glucose homoeostasis. The participating receptors are not known, mainly due to a lack of specific agonists and antagonists, but are reasonable targets for anti-diabetic therapy. The stable, albeit nonselective, adenosine analogue NECA (5'-N-ethylcarboxamidoadenosine) (10 microM) reduced glucose-stimulated insulin release from INS-1 cells. This was mimicked by A(1)-(CHA), A(2A)-(CGS-21680) and A(3)-receptor agonists (Cl-IB-MECA). Two newly synthesized A(2B)-receptor antagonists, PSB-53 and PSB-1115, counteracted the inhibitory effect of NECA. These in-vitro effects were mirrored by in-vivo data with respect to CHA, CGS and Cl-IB-MECA. Distinct concentrations of either PSB-53 or PSB-1115 reversed the decrease in plasma insulin induced by NECA. This was not mimicked by a corresponding change in blood glucose. The effect of PSB-1115 was also obvious in diabetic GotoKakizaki rats: plasma insulin was increased whereas blood glucose was unchanged. During most experiments the effects on blood glucose were not impressive probably because of the physiologically necessary homoeostasis. The adenosine levels were not different in normal Wistar rats and in diabetic GotoKakzaki rats. Altogether the A(2B)-receptor antagonists showed an anti-diabetic potential mainly by increasing plasma insulin levels under conditions when the adenosine tonus was elevated in-vivo and increased insulin release in-vitro.

  12. In Silico Discovery of Androgen Receptor Antagonists with Activity in Castration Resistant Prostate Cancer

    PubMed Central

    Shen, Howard C.; Shanmugasundaram, Kumaran; Simon, Nicholas I.; Cai, Changmeng; Wang, Hongyun; Chen, Sen; Rigby, Alan C.

    2012-01-01

    Previously available androgen receptor (AR) antagonists (bicalutamide, flutamide, and nilutamide) have limited activity against AR in prostate cancers that relapse after castration [castration resistant prostate cancer (CRPC)]. However, recent AR competitive antagonists such as MDV3100, generated through chemical modifications to the current AR ligands, appear to have increased activity in CRPC and have novel mechanisms of action. Using pharmacophore models and a refined homology model of the antagonist-liganded AR ligand binding domain, we carried out in silico screens of small molecule libraries and report here on the identification of a series of structurally distinct nonsteroidal small molecule competitive AR antagonists. Despite their unique chemical architectures, compounds representing each of six chemotypes functioned in vitro as pure AR antagonists. Moreover, similarly to MDV3100 and in contrast to previous AR antagonists, these compounds all prevented AR binding to chromatin, consistent with each of the six chemotypes stabilizing a similar AR antagonist conformation. Additional studies with the lead chemotype (chemotype A) showed enhanced AR protein degradation, which was dependent on helix 12 in the AR ligand binding domain. Significantly, chemotype A compounds functioned as AR antagonists in vivo in normal male mice and suppressed AR activity and tumor cell proliferation in human CRPC xenografts. These data indicate that certain ligand-induced structural alterations in the AR ligand binding domain may both impair AR chromatin binding and enhance AR degradation and support continued efforts to develop AR antagonists with unique mechanisms of action and efficacy in CRPC. PMID:23023563

  13. Lead generation using pharmacophore mapping and three-dimensional database searching: application to muscarinic M(3) receptor antagonists.

    PubMed

    Marriott, D P; Dougall, I G; Meghani, P; Liu, Y J; Flower, D R

    1999-08-26

    By using a pharmacophore model, a geometrical representation of the features necessary for molecules to show a particular biological activity, it is possible to search databases containing the 3D structures of molecules and identify novel compounds which may possess this activity. We describe our experiences of establishing a working 3D database system and its use in rational drug design. By using muscarinic M(3) receptor antagonists as an example, we show that it is possible to identify potent novel lead compounds using this approach. Pharmacophore generation based on the structures of known M(3) receptor antagonists, 3D database searching, and medium-throughput screening were used to identify candidate compounds. Three compounds were chosen to define the pharmacophore: a lung-selective M(3) antagonist patented by Pfizer and two Astra compounds which show affinity at the M(3) receptor. From these, a pharmacophore model was generated, using the program DISCO, and this was used subsequently to search a UNITY 3D database of proprietary compounds; 172 compounds were found to fit the pharmacophore. These compounds were then screened, and 1-[2-(2-(diethylamino)ethoxy)phenyl]-2-phenylethanone (pA(2) 6.67) was identified as the best hit, with N-[2-(piperidin-1-ylmethyl)cycohexyl]-2-propoxybenz amide (pA(2) 4. 83) and phenylcarbamic acid 2-(morpholin-4-ylmethyl)cyclohexyl ester (pA(2) 5.54) demonstrating lower activity. As well as its potency, 1-[2-(2-(diethylamino)ethoxy)phenyl]-2-phenylethanone is a simple structure with limited similarity to existing M(3) receptor antagonists.

  14. A widely used retinoic acid receptor antagonist induces peroxisome proliferator-activated receptor-gamma activity.

    PubMed

    Schupp, Michael; Curtin, Joshua C; Kim, Roy J; Billin, Andrew N; Lazar, Mitchell A

    2007-05-01

    Nuclear receptors (NRs) are transcription factors whose activity is regulated by the binding of small lipophilic ligands, including hormones, vitamins, and metabolites. Pharmacological NR ligands serve as important therapeutic agents; for example, all-trans retinoic acid, an activating ligand for retinoic acid receptor alpha (RARalpha), is used to treat leukemia. Another RARalpha ligand, (E)-S,S-dioxide-4-(2-(7-(heptyloxy)-3,4-dihydro-4,4-dimethyl-2H-1-benzothiopyran-6-yl)-1-propenyl)-benzoic acid (Ro 41-5253), is a potent antagonist that has been a useful and purportedly specific probe of RARalpha function. Here, we report that Ro 41-5253 also activates the peroxisome proliferator-activated receptor gamma (PPARgamma), a master regulator of adipocyte differentiation and target of widely prescribed antidiabetic thiazolidinediones (TZDs). Ro 41-5253 enhanced differentiation of mouse and human preadipocytes and activated PPARgamma target genes in mature adipocytes. Like the TZDs, Ro 41-5253 also down-regulated PPARgamma protein expression in adipocytes. In addition, Ro 41-5253 activated the PPARgamma-ligand binding domain in transiently transfected HEK293T cells. These effects were not prevented by a potent RARalpha agonist or by depleting cells of RARalpha, indicating that PPARgamma activation was not related to RARalpha antagonism. Indeed, Ro 41-5253 was able to compete with TZD ligands for binding to PPARgamma, suggesting that Ro 41-5253 directly affects PPAR activity. These results vividly demonstrate that pharmacological NR ligands may have "off-target" effects on other NRs. Ro 41-5253 is a PPARgamma agonist as well as an RARalpha antagonist whose pleiotropic effects on NRs may signify a unique spectrum of biological responses.

  15. Using caffeine and other adenosine receptor antagonists and agonists as therapeutic tools against neurodegenerative diseases: a review.

    PubMed

    Rivera-Oliver, Marla; Díaz-Ríos, Manuel

    2014-04-17

    Caffeine is the most consumed pychostimulant in the world, and it is known to affect basic and fundamental human processes such as sleep, arousal, cognition and learning and memory. It works as a nonselective blocker of adenosine receptors (A1, A2a, A2b and A3) and has been related to the regulation of heart rate, the contraction/relaxation of cardiac and smooth muscles, and the neural signaling in the central nervous system (CNS). Since the late 1990s, studies using adenosine receptor antagonists, such as Caffeine, to block the A1 and A2a adenosine receptor subtypes have shown to reduce the physical, cellular and molecular damages caused by a spinal cord injury (SCI) or a stroke (cerebral infarction) and by other neurodegenerative diseases such as Parkinson's and Alzheimer's diseases. Interestingly, other studies using adenosine receptor agonists have also shown to provide a neuroprotective effect on various models of neurodegenerative diseases through the reduction of excitatory neurotransmitter release, apoptosis and inflammatory responses, among others. The seemingly paradoxical use of both adenosine receptor agonists and antagonists as neuroprotective agents has been attributed to differences in dosage levels, drug delivery method, extracellular concentration of excitatory neurotransmitters and stage of disease progression. We discuss and compare recent findings using both antagonists and agonists of adenosine receptors in animal models and patients that have suffered spinal cord injuries, brain strokes, and Parkinson's and Alzheimer's diseases. Additionally, we propose alternative interpretations on the seemingly paradoxical use of these drugs as potential pharmacological tools to treat these various types of neurodegenerative diseases.

  16. Using caffeine and other adenosine receptor antagonists and agonists as therapeutic tools against neurodegenerative diseases: a review.

    PubMed

    Rivera-Oliver, Marla; Díaz-Ríos, Manuel

    2014-04-17

    Caffeine is the most consumed pychostimulant in the world, and it is known to affect basic and fundamental human processes such as sleep, arousal, cognition and learning and memory. It works as a nonselective blocker of adenosine receptors (A1, A2a, A2b and A3) and has been related to the regulation of heart rate, the contraction/relaxation of cardiac and smooth muscles, and the neural signaling in the central nervous system (CNS). Since the late 1990s, studies using adenosine receptor antagonists, such as Caffeine, to block the A1 and A2a adenosine receptor subtypes have shown to reduce the physical, cellular and molecular damages caused by a spinal cord injury (SCI) or a stroke (cerebral infarction) and by other neurodegenerative diseases such as Parkinson's and Alzheimer's diseases. Interestingly, other studies using adenosine receptor agonists have also shown to provide a neuroprotective effect on various models of neurodegenerative diseases through the reduction of excitatory neurotransmitter release, apoptosis and inflammatory responses, among others. The seemingly paradoxical use of both adenosine receptor agonists and antagonists as neuroprotective agents has been attributed to differences in dosage levels, drug delivery method, extracellular concentration of excitatory neurotransmitters and stage of disease progression. We discuss and compare recent findings using both antagonists and agonists of adenosine receptors in animal models and patients that have suffered spinal cord injuries, brain strokes, and Parkinson's and Alzheimer's diseases. Additionally, we propose alternative interpretations on the seemingly paradoxical use of these drugs as potential pharmacological tools to treat these various types of neurodegenerative diseases. PMID:24530739

  17. Identification of Receptor Ligands and Receptor Subtypes Using Antagonists in a Capillary Electrophoresis Single-Cell Biosensor Separation System

    NASA Astrophysics Data System (ADS)

    Fishman, Harvey A.; Orwar, Owe; Scheller, Richard H.; Zare, Richard N.

    1995-08-01

    A capillary electrophoresis system with single-cell biosensors as a detector has been used to separate and identify ligands in complex biological samples. The power of this procedure was significantly increased by introducing antagonists that inhibited the cellular response from selected ligand-receptor interactions. The single-cell biosensor was based on the ligand-receptor binding and G-protein-mediated signal transduction pathways in PC12 and NG108-15 cell lines. Receptor activation was measured as increases in cytosolic free calcium ion concentration by using fluorescence microscopy with the intracellular calcium ion indicator fluo-3 acetoxymethyl ester. Specifically, a mixture of bradykinin (BK) and acetylcholine (ACh) was fractionated and the components were identified by inhibiting the cellular response with icatibant (HOE 140), a selective antagonist to the BK B_2 receptor subtype (B_2BK), and atropine, an antagonist to muscarinic ACh receptor subtypes. Structurally related forms of BK were also identified based on inhibiting B_2BK receptors. Applications of this technique include identification of endogenous BK in a lysate of human hepatocellular carcinoma cells (Hep G2) and screening for bioactivity of BK degradation products in human blood plasma. The data demonstrate that the use of antagonists with a single-cell biosensor separation system aids identification of separated components and receptor subtypes.

  18. A peripherally selective diphenyl purine antagonist of the CB1 receptor

    PubMed Central

    Fulp, Alan; Bortoff, Katherine; Zhang, Yanan; Mathews, James; Snyder, Rodney; Fennell, Tim; Marusich, Julie A.; Wiley, Jenny L.; Seltzman, Herbert; Maitra, Rangan

    2014-01-01

    Antagonists of the CB1 receptor can be useful in the treatment of several diseases including obesity, diabetes, and liver disease. However, to date, the only clinically approved CB1 receptor antagonist, rimonabant, was withdrawn due to adverse CNS related side effects such as depression and suicidal ideation. Since rimonabant’s withdrawal, several groups have begun pursuing peripherally selective CB1 antagonists. These compounds are expected to be devoid of undesirable CNS related effects but maintain efficacy through antagonism of peripherally expressed CB1 receptors within target tissues. Reported here are our latest results toward development of a peripherally selective analog of the diphenyl purine CB1 antagonist otenabant 1. Compound 9 (N-{1-[8-(2-Chlorophenyl)-9-(4-chlorophenyl)-9H-purin-6-yl]piperidin-4-yl}pentanamide) is a potent, orally absorbed antagonist of the CB1 receptor that is >50-fold selective for CB1 over CB2, highly selective for the periphery in a rodent model, and without efficacy in a series of in vivo assays designed to evaluate its ability to mitigate the central effects of Δ9-THC through the CB1 receptor. PMID:24041123

  19. Abscisic Acid Analogues That Act as Universal or Selective Antagonists of Phytohormone Receptors.

    PubMed

    Rajagopalan, Nandhakishore; Nelson, Ken M; Douglas, Amy F; Jheengut, Vishal; Alarcon, Idralyn Q; McKenna, Sean A; Surpin, Marci; Loewen, Michele C; Abrams, Suzanne R

    2016-09-13

    The plant hormone abscisic acid (ABA) plays many important roles in controlling plant development and physiology, from flowering to senescence. ABA is now known to exert its effects through a family of soluble ABA receptors, which in Arabidopsis thaliana has 13 members divided into three clades. Homologues of these receptors are present in other plants, also in relatively large numbers. Investigation of the roles of each homologue in mediating the diverse physiological roles of ABA is hampered by this genetic redundancy. We report herein the in vitro screening of a targeted ABA-like analogue library and identification of novel antagonist hits, including the analogue PBI686 that had been developed previously as a probe for identifying ABA-binding proteins. Further in vitro characterization of PBI686 and development of second-generation leads yielded both receptor-selective and universal antagonist hits. In planta assays in different species have demonstrated that these antagonist leads can overcome various ABA-induced physiological changes. While the general antagonists open up a hitherto unexplored avenue for controlling plant growth through inhibition of ABA-regulated physiological processes, the receptor-selective antagonist can be developed into chemical probes to explore the physiological roles of individual receptors.

  20. Abscisic Acid Analogues That Act as Universal or Selective Antagonists of Phytohormone Receptors.

    PubMed

    Rajagopalan, Nandhakishore; Nelson, Ken M; Douglas, Amy F; Jheengut, Vishal; Alarcon, Idralyn Q; McKenna, Sean A; Surpin, Marci; Loewen, Michele C; Abrams, Suzanne R

    2016-09-13

    The plant hormone abscisic acid (ABA) plays many important roles in controlling plant development and physiology, from flowering to senescence. ABA is now known to exert its effects through a family of soluble ABA receptors, which in Arabidopsis thaliana has 13 members divided into three clades. Homologues of these receptors are present in other plants, also in relatively large numbers. Investigation of the roles of each homologue in mediating the diverse physiological roles of ABA is hampered by this genetic redundancy. We report herein the in vitro screening of a targeted ABA-like analogue library and identification of novel antagonist hits, including the analogue PBI686 that had been developed previously as a probe for identifying ABA-binding proteins. Further in vitro characterization of PBI686 and development of second-generation leads yielded both receptor-selective and universal antagonist hits. In planta assays in different species have demonstrated that these antagonist leads can overcome various ABA-induced physiological changes. While the general antagonists open up a hitherto unexplored avenue for controlling plant growth through inhibition of ABA-regulated physiological processes, the receptor-selective antagonist can be developed into chemical probes to explore the physiological roles of individual receptors. PMID:27523384

  1. Pathophysiology of the cysteinyl leukotrienes and effects of leukotriene receptor antagonists in asthma.

    PubMed

    Bisgaard, H

    2001-01-01

    Cysteinyl leukotrienes, synthesized de novo from cell membrane phospholipids, are proinflammatory mediators that play an important role in the pathophysiology of asthma. These mediators are among the most potent of bronchoconstrictors and cause vasodilation, increased microvascular permeability, exudation of macromolecules and edema. The cysteinyl leukotrienes also have potent chemoattractant properties for eosinophils, causing an influx of eosinophils into the airway mucosa, which further fuels the inflammatory process. In addition, the cysteinyl leukotrienes are potent secretagogues and reduce ciliary motility, which may hinder mucociliary clearance. Asthmatic patients demonstrate increased production of cysteinyl leukotrienes during naturally occurring asthma and acute asthma attacks as well as after allergen and exercise challenge. The leukotriene receptor antagonists montelukast, zafirlukast and pranlukast inhibit bronchoconstriction in asthmatic patients undergoing allergen, exercise, cold air or aspirin challenge. They attenuate the hallmarks of asthmatic inflammation, including eosinophilia in the airway mucosa and peripheral blood. Moreover, exhaled nitric oxide concentrations, another correlate of airway inflammation, are decreased during montelukast treatment in children. Cysteinyl leukotriene synthesis is not blocked by corticosteroid therapy. This important observation suggests that the leukotriene receptor antagonists represent a novel therapeutic approach, one that may provide benefits that are additive with corticosteroid therapy. This supposition is supported by clinical observations that treatment with leukotriene receptor antagonists significantly improve asthma control when added to inhaled corticosteroid therapy. Moreover, the bronchodilator properties of the leukotriene receptor antagonists are additive with those of beta agonists. These data provide strong support for the use of leukotriene receptor antagonists for treating asthma. PMID

  2. Discovery of BMS-641988, a Novel Androgen Receptor Antagonist for the Treatment of Prostate Cancer

    PubMed Central

    2015-01-01

    BMS-641988 (23) is a novel, nonsteroidal androgen receptor antagonist designed for the treatment of prostate cancer. The compound has high binding affinity for the AR and acts as a functional antagonist in vitro. BMS-641988 is efficacious in multiple human prostate cancer xenograft models, including CWR22-BMSLD1 where it displays superior efficacy relative to bicalutamide. Based on its promising preclinical profile, BMS-641988 was selected for clinical development. PMID:26288692

  3. The efficacy of oral adenosine A(2A) antagonist istradefylline for the treatment of moderate to severe Parkinson's disease.

    PubMed

    Vorovenci, Ruxandra Julia; Antonini, Angelo

    2015-01-01

    The moderate and severe stages of Parkinson's disease (PD) are marked by motor and non-motor complications that still remain difficult to control with the currently available therapy. Adenosine A(2A) receptor antagonists target non-dopaminergic systems, and have emerged as promising add-on therapy in the management of PD, a little more than a decade ago. While the development of this new drug class was slower than initially expected, istradefylline was recently registered in Japan, because it provides reduction of the off-time, when given in association with levodopa. Effects on some non-motor features have also been suggested, and preliminary studies further suggest a potential neuroprotective effect. Associations of A(2A) receptor antagonists with dopaminergic agents, as well as enzyme blockers like catechol-O-methyltransferase (COMT) and monoamine oxidase-B (MAO-B) inhibitors, should provide even greater benefit in advanced PD patients, and, thus, a more individualized treatment approach would be at hand. PMID:26630457

  4. Medicinal Chemistry of the A3 Adenosine Receptor: Agonists, Antagonists, and Receptor Engineering

    PubMed Central

    Jacobson, Kenneth A.; Klutz, Athena M.; Tosh, Dilip K.; Ivanov, Andrei A.; Preti, Delia; Baraldi, Pier Giovanni

    2012-01-01

    A3 adenosine receptor (A3AR) ligands have been modified to optimize their interaction with the A3AR. Most of these modifications have been made to the N6 and C2 positions of adenine as well as the ribose moiety, and using a combination of these substitutions leads to the most efficacious, selective, and potent ligands. A3AR agonists such as IB-MECA and Cl-IB-MECA are now advancing into Phase II clinical trials for treatments targeting diseases such as cancer, arthritis, and psoriasis. Also, a wide number of compounds exerting high potency and selectivity in antagonizing the human (h)A3AR have been discovered. These molecules are generally characterized by a notable structural diversity, taking into account that aromatic nitrogen-containing monocyclic (thiazoles and thiadiazoles), bicyclic (isoquinoline, quinozalines, (aza)adenines), tricyclic systems (pyrazoloquinolines, triazoloquinoxalines, pyrazolotriazolopyrimidines, triazolopurines, tricyclic xanthines) and nucleoside derivatives have been identified as potent and selective A3AR antagonists. Probably due to the “enigmatic” physiological role of A3AR, whose activation may produce opposite effects (for example, concerning tissue protection in inflammatory and cancer cells) and may produce effects that are species dependent, only a few molecules have reached preclinical investigation. Indeed, the most advanced A3AR antagonists remain in preclinical testing. Among the antagonists described above, compound OT-7999 is expected to enter clinical trials for the treatment of glaucoma, while several thiazole derivatives are in development as antiallergic, antiasthmatic and/or antiinflammatory drugs. PMID:19639281

  5. Neurokinin-1 Receptor Antagonists as Antitumor Drugs in Gastrointestinal Cancer: A New Approach

    PubMed Central

    Muñoz, Miguel; Coveñas, Rafael

    2016-01-01

    Gastrointestinal (GI) cancer is the term for a group of cancers affecting the digestive system. After binding to the neurokinin-1 (NK-1) receptor, the undecapeptide substance P (SP) regulates GI cancer cell proliferation and migration for invasion and metastasis, and controls endothelial cell proliferation for angiogenesis. SP also exerts an antiapoptotic effect. Both SP and the NK-1 receptor are located in GI tumor cells, the NK-1 receptor being overexpressed. By contrast, after binding to the NK-1 receptor, NK-1 receptor antagonists elicit the inhibition (epidermal growth factor receptor inhibition) of the proliferation of GI cancer cells in a concentration-dependent manner, induce the death of GI cancer cells by apoptosis, counteract the Warburg effect, inhibit cancer cell migration (counteracting invasion and metastasis), and inhibit angiogenesis (vascular endothelial growth factor inhibition). NK-1 receptor antagonists are safe and well tolerated. Thus, the NK-1 receptor could be considered as a new target in GI cancer and NK-1 receptor antagonists (eg, aprepitant) could be a new promising approach for the treatment of GI cancer. PMID:27488320

  6. Competitive molecular docking approach for predicting estrogen receptor subtype α agonists and antagonists

    PubMed Central

    2014-01-01

    Background Endocrine disrupting chemicals (EDCs) are exogenous compounds that interfere with the endocrine system of vertebrates, often through direct or indirect interactions with nuclear receptor proteins. Estrogen receptors (ERs) are particularly important protein targets and many EDCs are ER binders, capable of altering normal homeostatic transcription and signaling pathways. An estrogenic xenobiotic can bind ER as either an agonist or antagonist to increase or inhibit transcription, respectively. The receptor conformations in the complexes of ER bound with agonists and antagonists are different and dependent on interactions with co-regulator proteins that vary across tissue type. Assessment of chemical endocrine disruption potential depends not only on binding affinity to ERs, but also on changes that may alter the receptor conformation and its ability to subsequently bind DNA response elements and initiate transcription. Using both agonist and antagonist conformations of the ERα, we developed an in silico approach that can be used to differentiate agonist versus antagonist status of potential binders. Methods The approach combined separate molecular docking models for ER agonist and antagonist conformations. The ability of this approach to differentiate agonists and antagonists was first evaluated using true agonists and antagonists extracted from the crystal structures available in the protein data bank (PDB), and then further validated using a larger set of ligands from the literature. The usefulness of the approach was demonstrated with enrichment analysis in data sets with a large number of decoy ligands. Results The performance of individual agonist and antagonist docking models was found comparable to similar models in the literature. When combined in a competitive docking approach, they provided the ability to discriminate agonists from antagonists with good accuracy, as well as the ability to efficiently select true agonists and antagonists from

  7. GABAA receptor partial agonists and antagonists: structure, binding mode, and pharmacology.

    PubMed

    Krall, Jacob; Balle, Thomas; Krogsgaard-Larsen, Niels; Sørensen, Troels E; Krogsgaard-Larsen, Povl; Kristiansen, Uffe; Frølund, Bente

    2015-01-01

    A high degree of structural heterogeneity of the GABAA receptors (GABAARs) has been revealed and is reflected in multiple receptor subtypes. The subunit composition of GABAAR subtypes is believed to determine their localization relative to the synapses and adapt their functional properties to the local temporal pattern of GABA impact, enabling phasic or tonic inhibition. Specific GABAAR antagonists are essential tools for physiological and pharmacological elucidation of the different type of GABAAR inhibition. However, distinct selectivity among the receptor subtypes (populations) has been shown for only a few orthosteric ligands. Still, these examples show that it is indeed possible to obtain orthosteric subtype selectivity and they serve as models for further development in the orthosteric GABAAR ligand area. This review presents the very few existing structural classes of orthosteric GABAAR antagonists and describes the development of potent antagonists from partial agonists originally derived from the potent GABAAR agonist muscimol. In this process, several heterocyclic aromatic systems have been used in combination with structural models in order to map the orthosteric binding site and to reveal structural details to be used for obtaining potency and subtype selectivity. The challenges connected to functional characterization of orthosteric GABAAR partial agonists and antagonists, especially with regard to GABAAR stoichiometry and alternative binding sites are discussed. GABAAR antagonists have been essential in defining the tonic current but both remaining issues concerning the GABAARs involved and the therapeutic possibilities of modulating tonic inhibition underline the need for GABAAR antagonists with improved selectivity.

  8. Discovery of potent adenosine A2a antagonists as potential anti-Parkinson disease agents. Non-linear QSAR analyses integrated with pharmacophore modeling.

    PubMed

    Khanfar, Mohammad A; Al-Qtaishat, Saja; Habash, Maha; Taha, Mutasem O

    2016-07-25

    Adenosine A2A receptor antagonists are of great interest in the treatment for Parkinson's disease. In this study, we combined extensive pharmacophore modeling and quantitative structure-activity relationship (QSAR) analysis to explore the structural requirements for potent Adenosine A2A antagonists. Genetic function algorithm (GFA) joined with k nearest neighbor (kNN) analyses were applied to build predictive QSAR models. Successful pharmacophores were complemented with exclusion spheres to improve their receiver operating characteristic curve (ROC) profiles. Best QSAR models and their associated pharmacophore hypotheses were validated by identification of several novel Adenosine A2A antagonist leads retrieved from the National Cancer Institute (NCI) structural database. The most potent hit illustrated IC50 value of 545.7 nM. PMID:27216633

  9. Quantitative insights towards the design of potent deazaxanthine antagonists of adenosine 2B receptors.

    PubMed

    Paz, Odailson Santos; Brito, Camila Carane Bitencourt; Castilho, Marcelo Santos

    2014-08-01

    Adenosine receptors have been considered as potential targets for drug development, but one of the main obstacles to this goal is to selectively inhibit one receptor subtype over the others. This subject is particularly crucial for adenosine A2b receptor antagonists (AdoRA2B). The structure–activity relationships of xanthine derivatives which are AdoRA2B have been comprehensively investigated, but the steric and electronic requirements of deazaxanthine AdoRA2B have not been described from a quantitative standpoint of view. Herein we report our efforts to shorten this knowledge gap through 2D-QSAR (HQSAR) and 3D-QSAR (CoMFA) approaches. The good statistical quality (HQSAR--r(2) = 0.85, q(2)(LOO) = 0.77; CoMFA – r(2) = 0.86, q(2) = 0.70) and predictive ability (r(2) = (pred1) = 0.78, r(2)(pred2) = 0.78 and r(2) = (pred1) = 0.70, r(2) = (pred2) = 0.70,respectively) of the models, along with the information provided by contribution and contour maps hints their usefulness to the design of more potent 9-deazaxanthine derivatives.

  10. A potential role of odorant receptor agonists and antagonists in the treatment of infertility and contraception.

    PubMed

    Spehr, Marc; Hatt, Hanns

    2005-04-01

    In 1992, the identification of odorant receptor expression in mammalian testicular tissue prepared the ground for an ongoing debate about a potential role for these chemoreceptors in significant sperm behaviors, in particular chemotaxis. The identification of hOR17-4, a human testicular odorant receptor that mediates sperm chemotaxis in various bioassays, revealed the first potential key player in this reproductively relevant scenario. Detailed knowledge of the receptor's molecular receptive field, the discovery of a potent receptor antagonist, as well as specific insight into the receptor-linked signaling cascade(s), could establish a basis for pioneering future applications in fertility treatment and/or contraception. PMID:15898342

  11. Fancy bioisosteres: novel paracyclophane derivatives as super-affinity dopamine D3 receptor antagonists.

    PubMed

    Schlotter, Karin; Boeckler, Frank; Hübner, Harald; Gmeiner, Peter

    2006-06-15

    The exploration of the chemical diversity space depends on the discovery of novel bioisosteric elements. As a continuation of our project on bilayered arene surrogates, we herein report on [2.2]paracyclophane-derived dopamine D3 receptor antagonists of type 4 and 6. For the most promising test compound 6a, bearing a 2-methoxyphenyl substituent, a stereocontrolled preparation was performed when the planar chirality of enantiomers (R)-6a (FAUC 418) and (S)-6a caused a considerable differentiation of D3 binding, which is indicated by K(i) values of 0.19 and 3.0 nM, respectively. Functional experiments showed D3 antagonist properties for the paracyclophane derivatives of type 6. To elucidate putative bioactive low-energy conformations, DFT-based studies including the calculation of diagnostic magnetic shielding properties were performed. An 89% increase in volume for the [2.2]paracyclophane moiety compared to that of the monolayered benzofurane of lead compound 3b indicates higher plasticity of GPCR binding regions than usually expected. PMID:16759104

  12. Roles of affinity and lipophilicity in the slow kinetics of prostanoid receptor antagonists on isolated smooth muscle preparations

    PubMed Central

    Jones, RL; Woodward, DF; Wang, JW; Clark, RL

    2011-01-01

    BACKGROUND AND PURPOSE The highly lipophilic acyl-sulphonamides L-798106 and L-826266 showed surprisingly slow antagonism of the prostanoid EP3 receptor system in guinea-pig aorta. Roles of affinity and lipophilicity in the onset kinetics of these and other prostanoid ligands were investigated. EXPERIMENTAL APPROACH Antagonist selectivity was assessed using a panel of human recombinant prostanoid receptor-fluorimetric imaging plate reader assays. Potencies/affinities and onset half-times of agonists and antagonists were obtained on guinea-pig-isolated aorta and vas deferens. n-Octanol-water partition coefficients were predicted. KEY RESULTS L-798106, L-826266 and the less lipophilic congener (DG)-3ap appear to behave as selective, competitive-reversible EP3 antagonists. For ligands of low to moderate lipophilicity, potency increments for EP3 and TP (thromboxane-like) agonism on guinea-pig aorta (above pEC50 of 8.0) were associated with progressively longer onset half-times; similar trends were found for TP and histamine H1 antagonism above a pA2 limit of 8.0. In contrast, L-798106 (EP3), L-826266 (EP3, TP) and the lipophilic H1 antagonists astemizole and terfenadine exhibited very slow onset rates despite their moderate affinities; (DG)-3ap (EP3) had a faster onset. Agonism and antagonism on the vas deferens EP3 system were overall much faster, although trends were similar. CONCLUSIONS AND IMPLICATIONS High affinity and high liphophilicity may contribute to the slow onsets of prostanoid ligands in some isolated smooth muscle preparations. Both relationships are explicable by tissue disposition under the limited diffusion model. EP3 antagonists used as research tools should have moderate lipophilicity. The influence of lipophilicity on the potential clinical use of EP3 antagonists is discussed. PMID:20973775

  13. Endothelin ETA receptor antagonist reverses naloxone-precipitated opioid withdrawal in mice.

    PubMed

    Bhalla, Shaifali; Pais, Gwendolyn; Tapia, Melissa; Gulati, Anil

    2015-11-01

    Long-term use of opioids for pain management results in rapid development of tolerance and dependence leading to severe withdrawal symptoms. We have previously demonstrated that endothelin-A (ETA) receptor antagonists potentiate opioid analgesia and eliminate analgesic tolerance. This study was designed to investigate the involvement of central ET mechanisms in opioid withdrawal. The effect of intracerebroventricular administration of ETA receptor antagonist BQ123 on morphine and oxycodone withdrawal was determined in male Swiss Webster mice. Opioid tolerance was induced and withdrawal was precipitated by the opioid antagonist naloxone. Expression of ETA and ETB receptors, nerve growth factor (NGF), and vascular endothelial growth factor was determined in the brain using Western blotting. BQ123 pretreatment reversed hypothermia and weight loss during withdrawal. BQ123 also reduced wet shakes, rearing behavior, and jumping behavior. No changes in expression of vascular endothelial growth factor, ETA receptors, and ETB receptors were observed during withdrawal. NGF expression was unaffected in morphine withdrawal but significantly decreased during oxycodone withdrawal. A decrease in NGF expression in oxycodone- but not in morphine-treated mice could be due to mechanistic differences in oxycodone and morphine. It is concluded that ETA receptor antagonists attenuate opioid-induced withdrawal symptoms.

  14. (D-Phe/sup 12/)bombesin analogues: a new class of bombesin receptor antagonists

    SciTech Connect

    Heinz-Erian, P.; Coy, D.H.; Tamura, M.; Jones, S.W.; Gardner, J.D.; Jensen, R.T.

    1987-03-01

    Previous attempts to develop analogues of bombesin that function as specific receptor antagonists have been unsuccessful. Alteration of the histidine in luteinizing hormone releasing factor has resulted in analogues that function as competitive antagonists. In the present study the authors have used a similar strategy and altered the histidine in bombesin. (D-Phe/sup 12/)bombesin, (D-Phe/sup 12/,Leu/sup 14/)bombesin, and (Try/sup 4/, D-)je/sup 12/) bombesin did not stimulate amylase release from guinea pig pancreatic acini when present alone, but each analog inhibited bombesin-stimulated secretion. For each analog, detectable inhibition occurred at 1 ..mu..M and half-maximal inhibition at 4 ..mu..M. Each analog inhibited amylase release by bombesin and other agonists that stimulate secretion by interacting with bombesin receptors. The analogues of bombesin did not alter stimulation by substance P or other agonists that interact with other receptors. The inhibition of the action of bombesin was competitive with Schild plots having slopes of 1.0. Each analog also inhibited binding of /sup 125/I-labeled (Try/sup 4/) bombesin but not /sup 125/I-labeled substance P. These results demonstrate that (D-Phe/sup 12/) analogues of bombesin function as bombesin receptor antagonists and are the only bombesin receptor antagonists that interact only with the bombesin receptor. Because of their specificity, these analogues may prove useful for defining the role of bombesin in various physiological or pathological processes.

  15. Agonist- and antagonist-induced up-regulation of surface 5-HT3A receptors

    PubMed Central

    Morton, Russell A; Baptista-Hon, Daniel T; Hales, Tim G; Lovinger, David M

    2015-01-01

    Background and Purpose The 5-HT3 receptor is a member of the pentameric ligand-gated ion channel family and is pharmacologically targeted to treat irritable bowel syndrome and nausea/emesis. Furthermore, many antidepressants elevate extracellular concentrations of 5-HT. This study investigates the functional consequences of exposure of recombinant 5-HT3A receptors to agonists and antagonists. Experimental Approach We used HEK cells stably expressing recombinant 5-HT3A receptors and the ND7/23 (mouse neuroblastoma/dorsal root ganglion hybrid) cell line, which expresses endogenous 5-HT3 receptors. Surface expression of recombinant 5-HT3A receptors, modified to contain the bungarotoxin (BTX) binding sequence, was quantified using fluorescence microscopy to image BTX-conjugated fluorophores. Whole cell voltage-clamp electrophysiology was used to measure the density of current mediated by 5-HT3A receptors. Key Results 5-HT3A receptors were up-regulated by the prolonged presence of agonists (5-HT and m-chlorophenylbiguanide) and antagonists (MDL-72222 and morphine). The up-regulation of 5-HT3A receptors by 5-HT and MDL-72222 was time- and concentration-dependent but was independent of newly translated receptors. The phenomenon was observed for recombinant rodent and human 5-HT3A receptors and for endogenous 5-HT3 receptors in neuronal ND7/23 cells. Conclusions and Implications Up-regulation of 5-HT3A receptors, following exposure to either agonists or antagonists suggests that this phenomenon may occur in response to different therapeutic agents. Medications that elevate 5-HT levels, such as the antidepressant inhibitors of 5-HT reuptake and antiemetic inhibitors of 5-HT3 receptor function, may both raise receptor expression. However, this will require further investigation in vivo. PMID:25989383

  16. A long-acting GH receptor antagonist through fusion to GH binding protein

    PubMed Central

    Wilkinson, Ian R.; Pradhananga, Sarbendra L.; Speak, Rowena; Artymiuk, Peter J.; Sayers, Jon R.; Ross, Richard J.

    2016-01-01

    Acromegaly is a human disease of growth hormone (GH) excess with considerable morbidity and increased mortality. Somatostatin analogues are first line medical treatment but the disease remains uncontrolled in up to 40% of patients. GH receptor (GHR) antagonist therapy is more effective but requires frequent high-dose injections. We have developed an alternative technology for generating a long acting potent GHR antagonist through translational fusion of a mutated GH linked to GH binding protein and tested three candidate molecules. All molecules had the amino acid change (G120R), creating a competitive GHR antagonist and we tested the hypothesis that an amino acid change in the GH binding domain (W104A) would increase biological activity. All were antagonists in bioassays. In rats all antagonists had terminal half-lives >20 hours. After subcutaneous administration in rabbits one variant displayed a terminal half-life of 40.5 hours. A single subcutaneous injection of the same variant in rabbits resulted in a 14% fall in IGF-I over 7 days. In conclusion: we provide proof of concept that a fusion of GHR antagonist to its binding protein generates a long acting GHR antagonist and we confirmed that introducing the W104A amino acid change in the GH binding domain enhances antagonist activity. PMID:27731358

  17. Orexin 1 receptor antagonists in compulsive behavior and anxiety: possible therapeutic use

    PubMed Central

    Merlo Pich, Emilio; Melotto, Sergio

    2014-01-01

    Fifteen years after the discovery of hypocretin/orexin a large body of evidence has been collected supporting its critical role in the modulation of several regulatory physiological functions. While reduced levels of hypocretin/orexin were initially associated with narcolepsy, increased levels have been linked in recent years to pathological states of hypervigilance and, in particular, to insomnia. The filing to FDA of the dual-activity orexin receptor antagonist (DORA) suvorexant for the indication of insomnia further corroborates the robustness of such evidences. However, as excessive vigilance is also typical of anxiety and panic episodes, as well as of abstinence and craving in substance misuse disorders. In this review we briefly discuss the evidence supporting the development of hypocretin/orexin receptor 1 (OX1) antagonists for these indications. Experiments using the OX1 antagonist SB-334867 and mutant mice have involved the OX1 receptor in mediating the compulsive reinstatement of drug seeking for ethanol, nicotine, cocaine, cannabinoids and morphine. More recently, data have been generated with the novel selective OX1 antagonists GSK1059865 and ACT-335827 on behavioral and cardiovascular response to stressors and panic-inducing agents in animals. Concluding, while waiting for pharmacologic data to become available in humans, risks and benefits for the development of an OX1 receptor antagonist for Binge Eating and Anxiety Disorders are discussed. PMID:24592206

  18. Corticosteroid receptor antagonists are amnestic for passive avoidance learning in day-old chicks.

    PubMed

    Sandi, C; Rose, S P

    1994-08-01

    Glucocorticoids can modulate behavioural processes and neural plasticity. They are released during learning situations and can trigger neural actions through binding to brain receptors. We hypothesized that a glucocorticoid action could play a critical role in the mechanisms involved in long-term memory formation. In order to test this hypothesis, chicks were trained on a passive avoidance learning task and given bilateral intracerebral injections of selective mineralocorticoid (RU-28318) or glucocorticoid (RU-38486) receptor antagonists. The results showed that both antagonists alter information processing when injected prior to the training session. Possible state-dependent effects were discharged. Further experiments evaluating possible effects of the antagonists on concomitant aspects of the learning situation (such as novelty reaction and pecking pattern) indicated that, as opposed to the glucocorticoid receptor antagonist, the mineralocorticoid antagonist altered the birds' reactivity to non-specific aspects of the training task. These results suggest that the two types of intracellular corticosteroid receptors could be mediating different aspects of the information processing and storage involved in avoidance learning. In addition, this study points out that passive avoidance learning in the chick could be a good model to investigate the biochemical mechanisms involved in corticosteroid actions on learning-induced neural plasticity.

  19. Targeted Opioid Receptor Antagonists in the Treatment of Alcohol Use Disorders

    PubMed Central

    Niciu, Mark J.

    2015-01-01

    In 1994, the US Food and Drug Administration approved the μ-opioid receptor antagonist naltrexone to treat alcohol dependence. However, treatments requiring daily administration, such as naltrexone, are inconsistently adhered to in substance abusing populations, and constant medication exposure can increase risk of adverse outcomes, e.g., hepatotoxicity. This has fostered a ‘targeted’ or ‘as needed’ approach to opioid receptor antagonist treatment, in which medications are used only in anticipation of or during high-risk situations, including times of intense cravings. Initial studies of the ability of targeted naltrexone to reduce drinking-related outcomes were conducted in problem drinkers and have been extended into larger, multi-site, placebo-controlled investigations with positive results. Another μ-opioid receptor antagonist, nalmefene, has been studied on an ‘as-needed’ basis to reduce heavy drinking in alcohol-dependent individuals. These studies include three large multi-site trials in Europe of up to 1 year in duration, and serve as the basis for the recent approval of nalmefene by the European Medicines Agency as an ‘as-needed’ adjunctive treatment for alcohol dependence. We review potential moderators of opioid receptor antagonist treatment response including subjective assessments, objective clinical measures and genetic variants. In sum, the targeted or ‘as-needed’ approach to treatment with opioid antagonists is an efficacious harmreduction strategy for problem drinking and alcohol dependence. PMID:23881605

  20. Mineralocorticoid Receptor Antagonists-A New Sprinkle of Salt and Youth.

    PubMed

    Stojadinovic, Olivera; Lindley, Linsey E; Jozic, Ivan; Tomic-Canic, Marjana

    2016-10-01

    Skin atrophy and impaired cutaneous wound healing are the recognized side effects of topical glucocorticoid (GC) therapy. Although GCs have high affinity for the glucocorticoid receptor, they also bind and activate the mineralocorticoid receptor. In light of this, one can speculate that some of the GC-mediated side effects can be remedied by blocking activation of the mineralocorticoid receptor. Indeed, according to Nguyen et al., local inhibition of the mineralocorticoid receptor via antagonists (spironolactone, canrenoate, and eplerenone) rescues GC-induced delayed epithelialization and accelerates wound closure in diabetic animals by targeting epithelial sodium channels and stimulating keratinocyte proliferation. These findings suggest that the use of mineralocorticoid receptor antagonists coupled with GC therapy may be beneficial in overcoming at least some of the GC-mediated side effects. PMID:27664711

  1. Aldosterone and aldosterone receptor antagonists in patients with chronic heart failure

    PubMed Central

    Nappi, Jean M; Sieg, Adam

    2011-01-01

    Aldosterone is a mineralocorticoid hormone synthesized by the adrenal glands that has several regulatory functions to help the body maintain normal volume status and electrolyte balance. Studies have shown significantly higher levels of aldosterone secretion in patients with congestive heart failure compared with normal patients. Elevated levels of aldosterone have been shown to elevate blood pressure, cause left ventricular hypertrophy, and promote cardiac fibrosis. An appreciation of the true role of aldosterone in patients with chronic heart failure did not become apparent until the publication of the Randomized Aldactone Evaluation Study. Until recently, the use of aldosterone receptor antagonists has been limited to patients with severe heart failure and patients with heart failure following myocardial infarction. The Eplerenone in Mild Patients Hospitalization and Survival Study in Heart Failure (EMPHASIS-HF) study added additional evidence to support the expanded use of aldosterone receptor antagonists in heart failure patients. The results of the EMPHASIS-HF trial showed that patients with mild-to-moderate (New York Heart Association Class II) heart failure had reductions in mortality and hospitalizations from the addition of eplerenone to optimal medical therapy. Evidence remains elusive about the exact mechanism by which aldosterone receptor antagonists improve heart failure morbidity and mortality. The benefits of aldosterone receptor antagonist use in heart failure must be weighed against the potential risk of complications, ie, hyperkalemia and, in the case of spironolactone, possible endocrine abnormalities, in particular gynecomastia. With appropriate monitoring, these risks can be minimized. We now have evidence that patients with mild-to-severe symptoms associated with systolic heart failure will benefit from the addition of an aldosterone receptor antagonist to the standard therapies of angiotensin-converting enzyme inhibitors and beta

  2. Modulation of radiation induced lipid peroxidation by phospholipase A 2 and calmodulin antagonists: Relevance to detoxification

    NASA Astrophysics Data System (ADS)

    Varshney, Rajeev; Kale, R. K.

    1995-04-01

    Ghost membranes prepared from erythrocytes of Swiss albino mice were irradiated with 0.9 Gy s -1. Lipid peroxidation initiated by ionizing radiation was enhanced by phospholipase A 2, and required both phospholipase A 2 and GSH-peroxidase for consecutive action to convert fatty acid peroxides into corresponding alcohols. The ability of phospholipase A 2 to enhance lipid peroxidation was increased in presence of Ca 2+. However, in combination, phospholipase A 2 and GSH-peroxidase were effective in inhibiting lipid peroxidation. These findings show that free fatty acid peroxides considerably increase the peroxidation. Calmodulin antagonists inhibit lipid peroxidation and decrease the radiation induced release of Ca 2+ from the membranes. Our results suggest the importance of Ca 2+ dependent phospholipase A 2 in detoxification of fatty acid peroxides in the membranes. It is quite possible that scavenging of free radicals by calmodulin antagonists lower the formation of hydroperoxides, resulting in the decrease in activity of phospholipase A 2. Alternatively, decrease in Ca 2+ release due to the calmodulin antagonists might have affected the activity of phospholipase A 2. Our observations might be of considerable significance in the understanding of post irradiation effect on biological membranes.

  3. Substituted pyrrolidin-2-ones: Centrally acting orexin receptor antagonists promoting sleep. Part 2.

    PubMed

    Sifferlen, Thierry; Boller, Amandine; Chardonneau, Audrey; Cottreel, Emmanuelle; Gatfield, John; Treiber, Alexander; Roch, Catherine; Jenck, Francois; Aissaoui, Hamed; Williams, Jodi T; Brotschi, Christine; Heidmann, Bibia; Siegrist, Romain; Boss, Christoph

    2015-05-01

    Starting from advanced pyrrolidin-2-one lead compounds, this novel series of small-molecule orexin receptor antagonists was further optimized by fine-tuning of the C-3 substitution at the γ-lactam ring. We discuss our design to align in vitro potency with metabolic stability and improved physicochemical/pharmacokinetic properties while avoiding P-glycoprotein-mediated efflux. These investigations led to the identification of the orally active 3-hydroxypyrrolidin-2-one 46, a potent and selective orexin-2 receptor antagonist, that achieved good brain exposure and promoted physiological sleep in rats.

  4. Potent Dmt-Tic pharmacophoric delta- and mu-opioid receptor antagonists.

    PubMed

    Li, Tingyou; Fujita, Yoshio; Shiotani, Kimitaka; Miyazaki, Anna; Tsuda, Yuko; Ambo, Akihiro; Sasaki, Yusuke; Jinsmaa, Yunden; Marczak, Ewa; Bryant, Sharon D; Salvadori, Severo; Lazarus, Lawrence H; Okada, Yoshio

    2005-12-15

    A series of dimeric Dmt-Tic (2',6'-dimethyl-L-tyrosyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid) analogues (8-14, 18-22) were covalently linked through diaminoalkane and symmetric or asymmetric 3,6-diaminoalkyl-2(1H)-pyrazinone moieties. All the compounds exhibited high affinity for both delta-opioid receptors [Ki(delta) = 0.06-1.53 nM] and mu-opioid receptors [Ki(mu) = 1.37-5.72 nM], resulting in moderate delta-receptor selectivity [Ki(mu)/Ki(delta) = 3-46]. Regardless of the type of linker between the Dmt-Tic pharmacophores, delta-opioid-mediated antagonism was extraordinarily high in all analogues (pA2 = 10.42-11.28), while in vitro agonism (MVD and GPI bioassays) was essentially absent (ca. 3 to >10 microM). While an unmodified N-terminus (9, 13, 18) revealed weak mu-opioid antagonism (pA2 = 6.78-6.99), N,N'-dimethylation (21, 22), which negatively impacts on mu-opioid-associated agonism (Balboni et al., Bioorg. Med. Chem. 2003, 11, 5435-5441), markedly enhanced mu-opioid antagonism (pA2 = 8.34 and 7.71 for 21 and 22, respectively) without affecting delta-opioid activity. These data are the first evidence that a single dimeric opioid ligand containing the Dmt-Tic pharmacophore exhibits highly potent delta- and mu-opioid antagonist activities.

  5. Palonosetron: a unique 5-HT3-receptor antagonist for the prevention of chemotherapy-induced emesis.

    PubMed

    Grunberg, Steven M; Koeller, James M

    2003-12-01

    Palonosetron (Aloxi) is a 5-HT(3)-receptor antagonist antiemetic indicated for the prevention of acute and delayed nausea and vomiting following moderately emetogenic chemotherapy and for acute nausea and vomiting following highly emetogenic chemotherapy. Although it is the fourth member of this class to enter the US market, palonosetron is distinguished by distinct pharmacological characteristics. It has a higher binding affinity for the 5-HT(3 )receptor and a terminal serum half-life at least four times greater than any other available agent of this class (approximately 40 h). The high affinity and long half-life may explain the persistence of antiemetic effect throughout the delayed emesis risk period. The indications for palonosetron are supported by one dose-ranging study and three large, randomised, Phase III studies that all demonstrated at least equivalent activity (and in some cases, superior activity) compared to other 5-HT(3)-receptor antagonists. In spite of the pharmacological differences, the side effect profile of palonosetron is comparable to that of other 5-HT(3)-receptor antagonists. Palonosetron may prove valuable in combination therapy for delayed emesis and may be an appropriate agent for clinical settings, such as multiple-day chemotherapy, where acute emesis is repeatedly induced. Palonosetron provides a convenience advantage if multiple-day 5-HT(3)-receptor antagonist therapy is anticipated and is a unique addition to the antiemetic armamentarium. PMID:14640928

  6. Orexin-1 and orexin-2 receptor antagonists reduce ethanol self-administration in high-drinking rodent models.

    PubMed

    Anderson, Rachel I; Becker, Howard C; Adams, Benjamin L; Jesudason, Cynthia D; Rorick-Kehn, Linda M

    2014-01-01

    To examine the role of orexin-1 and orexin-2 receptor activity on ethanol self-administration, compounds that differentially target orexin (OX) receptor subtypes were assessed in various self-administration paradigms using high-drinking rodent models. Effects of the OX1 antagonist SB334867, the OX2 antagonist LSN2424100, and the mixed OX1/2 antagonist almorexant (ACT-078573) on home cage ethanol consumption were tested in ethanol-preferring (P) rats using a 2-bottle choice procedure. In separate experiments, effects of SB334867, LSN2424100, and almorexant on operant ethanol self-administration were assessed in P rats maintained on a progressive ratio operant schedule of reinforcement. In a third series of experiments, SB334867, LSN2424100, and almorexant were administered to ethanol-preferring C57BL/6J mice to examine effects of OX receptor blockade on ethanol intake in a binge-like drinking (drinking-in-the-dark) model. In P rats with chronic home cage free-choice ethanol access, SB334867 and almorexant significantly reduced ethanol intake, but almorexant also reduced water intake, suggesting non-specific effects on consummatory behavior. In the progressive ratio operant experiments, LSN2424100 and almorexant reduced breakpoints and ethanol consumption in P rats, whereas the almorexant inactive enantiomer and SB334867 did not significantly affect the motivation to consume ethanol. As expected, vehicle-injected mice exhibited binge-like drinking patterns in the drinking-in-the-dark model. All three OX antagonists reduced both ethanol intake and resulting blood ethanol concentrations relative to vehicle-injected controls, but SB334867 and LSN2424100 also reduced sucrose consumption in a different cohort of mice, suggesting non-specific effects. Collectively, these results contribute to a growing body of evidence indicating that OX1 and OX2 receptor activity influences ethanol self-administration, although the effects may not be selective for ethanol consumption

  7. CJ-023,423, a novel, potent and selective prostaglandin EP4 receptor antagonist with antihyperalgesic properties.

    PubMed

    Nakao, Kazunari; Murase, Akio; Ohshiro, Hiroyuki; Okumura, Takako; Taniguchi, Kana; Murata, Yoko; Masuda, Masatoshi; Kato, Tomoki; Okumura, Yoshiyuki; Takada, Junji

    2007-08-01

    The prostaglandin (PG) EP(4) receptor subtype is expressed by peripheral sensory neurons. Although a potential role of EP(4) receptor in pain has been suggested, a limited number of selective ligands have made it difficult to explore the physiological functions of EP(4) or its potential as a new analgesic target. Here, we describe the in vitro and in vivo pharmacology of a novel EP(4) receptor antagonist, N-[({2-[4-(2-ethyl-4,6-dimethyl-1H-imidazo [4,5-c] pyridin-1-yl) phenyl]ethyl}amino) carbonyl]-4-methylbenzenesulfonamide (CJ-023,423). In vitro, CJ-023,423 inhibits [(3)H]PGE(2) binding to both human and rat EP(4) receptors with K(i) of 13 +/- 4 and 20 +/- 1 nM, respectively. CJ-023,423 is highly selective for the human EP(4) receptor over other human prostanoid receptor subtypes. It also inhibits PGE(2)-evoked elevation in intracellular cAMP at the human and rat EP(4) receptors with pA(2) of 8.3 +/- 0.03 and 8.2 +/- 0.2 nM, respectively. In vivo, oral administration of CJ-023,423 significantly reduces thermal hyperalgesia induced by intraplantar injection of PGE(2) (ED(50) = 12.8 mg/kg). CJ-023,423 is also effective in models of acute and chronic inflammatory pain. CJ-023,423 significantly reduces mechanical hyperalgesia in the carrageenan model. Furthermore, CJ-023,423 significantly reverses complete Freund's adjuvant-induced chronic inflammatory pain response. Taken together, the present data indicate that CJ-023,423, a highly potent and selective antagonist of both human and rat EP(4) receptors, produces antihyperalgesic effects in animal models of inflammatory pain. Thus, specific blockade of the EP(4) receptor signaling may represent a novel therapeutic approach for the treatment of inflammatory pain.

  8. Muscarinic preferential M(1) receptor antagonists enhance the discriminative-stimulus effects of cocaine in rats.

    PubMed

    Tanda, Gianluigi; Katz, Jonathan L

    2007-10-01

    Previous studies of benztropine analogues have found them to inhibit dopamine uptake like cocaine, but with less effectiveness than cocaine in producing behavioral effects related to drug abuse. Studies have assessed whether nonselective muscarinic antagonists decrease the effects of cocaine because many of the benztropine analogues are also muscarinic antagonists. As previous studies were conducted with nonselective muscarinic antagonists and the benztropine analogues show preferential affinity for the M(1) muscarinic receptor subtype, the present study examined interactions of cocaine and the preferential M(1) antagonists, telenzepine (TZP) and trihexyphenidyl (TXP) on subjective effects in rats trained to discriminate cocaine (10 mg/kg, i.p.) from saline injections. Cocaine dose-dependently increased the percentage of responses on the cocaine-appropriate lever, with full substitution at the training dose. In contrast neither TZP nor TXP produced more than 25% cocaine-appropriate responding at any dose. Both M(1) antagonists produced significant leftward shifts in the cocaine dose-effect curve, TZP at 3.0 and TXP at 0.3 and 1.0 mg/kg. The present results indicate that preferential antagonist actions at muscarinic M(1) receptors enhance rather than attenuate the discriminative-stimulus effects of cocaine, and thus those actions unlikely contribute to the reduced cocaine-like effects of BZT analogues.

  9. 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

  10. Discovery and development of orexin receptor antagonists as therapeutics for insomnia.

    PubMed

    Winrow, C J; Renger, J J

    2014-01-01

    Insomnia persistently affects the quality and quantity of sleep. Currently approved treatments for insomnia primarily target γ-aminobutyric acid-A (GABA-A) receptor signalling and include benzodiazepines and GABA-A receptor modulators. These drugs are used to address this sleep disorder, but have the potential for side effects such as tolerance and dependence, making them less attractive as maintenance therapy. Forward and reverse genetic approaches in animals have implicated orexin signalling (also referred to as hypocretin signalling) in the control of vigilance and sleep/wake states. Screening for orexin receptor antagonists using in vitro and in vivo methods in animals has identified compounds that block one or other of the orexin receptors (single or dual orexin receptor antagonists [SORAs and DORAs], respectively) in animals and humans. SORAs have primarily been used as probes to further elucidate the roles of the individual orexin receptors, while a number of DORAs have progressed to clinical development as pharmaceutical candidates for insomnia. The DORA almorexant demonstrated significant improvements in a number of clinically relevant sleep parameters in animal models and in patients with insomnia but its development was halted. SB-649868 and suvorexant have demonstrated efficacy and tolerability in Phase II and III trials respectively. Furthermore, suvorexant is currently under review by the Food and Drug Administration for the treatment of insomnia. Based on the publication of recent non-clinical and clinical data, orexin receptor antagonists potentially represent a targeted, effective and well-tolerated new class of medications for insomnia.

  11. Allosteric interactions of three muscarine antagonists at bovine tracheal smooth muscle and cardiac M2 receptors.

    PubMed

    Roffel, A F; Elzinga, C R; Meurs, H; Zaagsma, J

    1989-03-01

    The kinetics of [3H]dexetimide dissociation from muscarine receptors in bovine cardiac left ventricular and tracheal smooth muscle membranes were studied in the absence and presence of three muscarine antagonists. It was found that [3H]dexetimide dissociation from cardiac muscarine receptors was monophasic and very fast (half life less than 1 min) and was slowed by the cardioselective muscarine antagonists, gallamine, methoctramine and AF-DX 116, concentration dependently. [3H]Dexetimide dissociation from tracheal muscarine receptors was biphasic, with a fast phase (half-life less than 1 min) followed after 4-5 min by a slow phase (half-life = 38.5 min). The fast component, but not the slow component, was slowed by the muscarine antagonists with concentration dependencies very similar to those found in the heart. We conclude from these data that the major population of tracheal smooth muscle muscarine receptors resembles the cardiac M2 type not only with respect to equilibrium binding affinities but also with respect to the secondary, allosteric binding site on the muscarine receptor. The results also imply that the cardiac receptor subtype is much more sensitive to allosteric modulation than the glandular/smooth muscle receptor subtype. PMID:2714370

  12. Binding of antagonists of H1 and H2 histamine receptors to peripheral blood lymphocytes of atopic and healthy subjects.

    PubMed

    Zak-Nejmark, T; Małolepszy, J; Osos, M; Nadobna, G; Jutel, M

    1991-01-01

    The binding of the antagonists of histamine H1 and H2 receptors by peripheral blood lymphocytes from atopic and healthy subjects was investigated. We found that lymphocytes from atopic subjects showed statistically significant decrease in the binding of H2 receptor antagonist - ranitidine. In addition, lymphocytes from atopic and control subjects had similar capacity of binding of H1 receptor antagonist - promethazine. The ratio of the amount of H1 and H2 antagonists, bound to lymphocytes from atopic and healthy subjects, was calculated. The difference between the values in the group of atopic (2.55) and control subjects (1.55) was statistically significant. PMID:1841552

  13. Rational Design of Potent Antagonists to the Human Growth Hormone Receptor

    NASA Astrophysics Data System (ADS)

    Fuh, Germaine; Cunningham, Brian C.; Fukunaga, Rikiro; Nagata, Shigekazu; Goeddel, David V.; Wells, James A.

    1992-06-01

    A hybrid receptor was constructed that contained the extracellular binding domain of the human growth hormone (hGH) receptor linked to the transmembrane and intracellular domains of the murine granulocyte colony-stimulating factor receptor. Addition of hGH to a myeloid leukemia cell line (FDC-P1) that expressed the hybrid receptor caused proliferation of these cells. The mechanism for signal transduction of the hybrid receptor required dimerization because monoclonal antibodies to the hGH receptor were agonists whereas their monovalent fragments were not. Receptor dimerization occurs sequentially-a receptor binds to site 1 on hGH, and then a second receptor molecule binds to site 2 on hGH. On the basis of this sequential mechanism, which may occur in many other cytokine receptors, inactive hGH analogs were designed that were potent antagonists to hGH-induced cell proliferation. Such antagonists could be useful for treating clinical conditions of hGH excess, such as acromegaly.

  14. Scalable synthesis of a prostaglandin EP4 receptor antagonist.

    PubMed

    Gauvreau, Danny; Dolman, Sarah J; Hughes, Greg; O'Shea, Paul D; Davies, Ian W

    2010-06-18

    The evolution of scalable, economically viable synthetic approaches to the potent and selective prostaglandin EP4 antagonist 1 is presented. The chromatography-free synthesis of multikilogram quantities of 1 using a seven-step sequence (six in the longest linear sequence) is described. This approach has been further modified in an effort to identify a long-term manufacturing route. Our final synthesis involves no step requiring cryogenic (< -25 degrees C) conditions; comprises a total of four steps, only three of which are in the longest linear synthesis; and features the use of two consecutive iron-catalyzed Friedel-Crafts substitutions.

  15. Modeling the interactions between alpha(1)-adrenergic receptors and their antagonists.

    PubMed

    Du, Lupei; Li, Minyong

    2010-09-01

    As crucial members of the G-protein coupled receptor (GPCR) superfamily, alpha (1)-adrenergic receptors (alpha(1)-ARs) are recognized to intervene the actions of endogenous catecholamines such as norepinephrine and epinephrine. So far three distinct alpha(1)-AR subtypes, alpha(1A), alpha(1B) and alpha(1D), have been characterized by functional analysis, radio-ligand binding and molecular biology studies. The alpha(1)-ARs are of therapeutic interest because of their distinct and critical roles in many physiological processes, containing hypertension, benign prostatic hyperplasia, smooth muscle contraction, myocardial inotropy and chronotropy, and hepatic glucose metabolism. Accordingly, designing subtype-selective antagonists for each of the three alpha(1)-AR subtypes has been an enthusiastic region of medicinal research. Even though a large number of studies on GPCRs have been conducted, understanding of how known antagonists bind to alpha(1)-ARs still remains sketchy and has been a serious impediment to search for potent and subtype-selective alpha(1)-AR antagonists because of the lack of detailed experimental structural knowledge. This review deliberates the simulation of alpha(1)-ARs and their interactions with antagonists by using ligand-based (pharmacophore identification and QSAR modeling) and structure-based (comparative modeling and molecular docking) approaches. Combined with experimental data, these computational attempts could improve our understanding of the structural basis of antagonist binding and the molecular basis of receptor activation, thus offering a more reasonable approach in the design of drugs targeting alpha(1)-ARs.

  16. Slow receptor dissociation kinetics differentiate macitentan from other endothelin receptor antagonists in pulmonary arterial smooth muscle cells.

    PubMed

    Gatfield, John; Mueller Grandjean, Celia; Sasse, Thomas; Clozel, Martine; Nayler, Oliver

    2012-01-01

    Two endothelin receptor antagonists (ERAs), bosentan and ambrisentan, are currently approved for the treatment of pulmonary arterial hypertension (PAH), a devastating disease involving an activated endothelin system and aberrant contraction and proliferation of pulmonary arterial smooth muscle cells (PASMC). The novel ERA macitentan has recently concluded testing in a Phase III morbidity/mortality clinical trial in PAH patients. Since the association and dissociation rates of G protein-coupled receptor antagonists can influence their pharmacological activity in vivo, we used human PASMC to characterize inhibitory potency and receptor inhibition kinetics of macitentan, ambrisentan and bosentan using calcium release and inositol-1-phosphate (IP(1)) assays. In calcium release assays macitentan, ambrisentan and bosentan were highly potent ERAs with K(b) values of 0.14 nM, 0.12 nM and 1.1 nM, respectively. Macitentan, but not ambrisentan and bosentan, displayed slow apparent receptor association kinetics as evidenced by increased antagonistic potency upon prolongation of antagonist pre-incubation times. In compound washout experiments, macitentan displayed a significantly lower receptor dissociation rate and longer receptor occupancy half-life (ROt(1/2)) compared to bosentan and ambrisentan (ROt(1/2):17 minutes versus 70 seconds and 40 seconds, respectively). Because of its lower dissociation rate macitentan behaved as an insurmountable antagonist in calcium release and IP(1) assays, and unlike bosentan and ambrisentan it blocked endothelin receptor activation across a wide range of endothelin-1 (ET-1) concentrations. However, prolongation of the ET-1 stimulation time beyond ROt(1/2) rendered macitentan a surmountable antagonist, revealing its competitive binding mode. Bosentan and ambrisentan behaved as surmountable antagonists irrespective of the assay duration and they lacked inhibitory activity at high ET-1 concentrations. Thus, macitentan is a competitive ERA with

  17. (-) Arctigenin and (+) pinoresinol are antagonists of the human thyroid hormone receptor β.

    PubMed

    Ogungbe, Ifedayo Victor; Crouch, Rebecca A; Demeritte, Teresa

    2014-11-24

    Lignans are important biologically active dietary polyphenolic compounds. Consumption of foods that are rich in lignans is associated with positive health effects. Using modeling tools to probe the ligand-binding pockets of molecular receptors, we found that lignans have high docking affinity for the human thyroid hormone receptor β. Follow-up experimental results show that lignans (-) arctigenin and (+) pinoresinol are antagonists of the human thyroid hormone receptor β. The modeled complexes show key plausible interactions between the two ligands and important amino acid residues of the receptor. PMID:25383984

  18. Inhibition of Morphine Tolerance and Dependence by the NMDA Receptor Antagonist MK-801

    NASA Astrophysics Data System (ADS)

    Trujillo, Keith A.; Akil, Huda

    1991-01-01

    The N-methyl-D-aspartate (NMDA) subtype of the glutamate receptor is an important mediator of several forms of neural and behavioral plasticity. The present studies examined whether NMDA receptors might be involved in the development of opiate tolerance and dependence, two examples of behavioral plasticity. The noncompetitive NMDA receptor antagonist MK-801 attenuated the development of tolerance to the analgesic effect of morphine without affecting acute morphine analgesia. In addition, MK-801 attenuated the development of morphine dependence as assessed by naloxone-precipitated withdrawal. These results suggest that NMDA receptors may be important in the development of opiate tolerance and dependence.

  19. (-) Arctigenin and (+) pinoresinol are antagonists of the human thyroid hormone receptor β.

    PubMed

    Ogungbe, Ifedayo Victor; Crouch, Rebecca A; Demeritte, Teresa

    2014-11-24

    Lignans are important biologically active dietary polyphenolic compounds. Consumption of foods that are rich in lignans is associated with positive health effects. Using modeling tools to probe the ligand-binding pockets of molecular receptors, we found that lignans have high docking affinity for the human thyroid hormone receptor β. Follow-up experimental results show that lignans (-) arctigenin and (+) pinoresinol are antagonists of the human thyroid hormone receptor β. The modeled complexes show key plausible interactions between the two ligands and important amino acid residues of the receptor.

  20. Identification of Trisubstituted-pyrazol Carboxamide Analogs as Novel and Potent Antagonists of Farnesoid X Receptor

    PubMed Central

    Yu, Donna D.; Lin, Wenwei; Forman, Barry M.; Chen, Taosheng

    2014-01-01

    Farnesoid X receptor (FXR, NRIH4) plays a major role in the control of cholesterol metabolism. This suggests that antagonizing the transcriptional activity of FXR is a potential means to treat cholestasis and related metabolic disorders. Here we describe the synthesis, biological evaluation, and structure-activity relationship (SAR) studies of trisubstituted-pyrazol carboxamides as novel and potent FXR antagonists. One of these novel FXR antagonists, 4j has an IC50 of 7.5 nM in an FXR binding assay and 468.5 nM in a cell-based FXR antagonistic assay. Compound 4j has no detectable FXR agonistic activity or cytotoxicity. Notably, 4j is the most potent FXR antagonist identified to date; it has a promising in vitro profile and could serve as an excellent chemical tool to elucidate the biological function of FXR. PMID:24775917

  1. Growth hormone receptor antagonists: discovery and potential uses.

    PubMed

    Kopchick, J J; Okada, S

    2001-06-01

    Serum levels of growth hormone (GH) in the human body vary and can influence the levels of insulin-like growth factor I (IGF-1). Low levels of GH can result in a dwarf phenotype and have been positively correlated with an increased life expectancy. High levels of GH can lead to gigantism or a clinical syndrome termed acromegaly, and also have been implicated in diabetic eye and kidney damage. Additionally, it has been postulated that the GH-IGF-I system can be involved in several types of cancers. Overall, both elevated and suppressed circulating levels of GH can have pronounced physiological effects. More than a decade ago a new class of drug, a GH antagonist, was discovered. It is now being tested for its ability to combat the effects of high circulating levels of GH. In this review, we will discuss some of the detrimental actions of GH and how a GH antagonist may be used to combat these effects. PMID:11527080

  2. Small-molecule ghrelin receptor antagonists improve glucose tolerance, suppress appetite, and promote weight loss.

    PubMed

    Esler, William P; Rudolph, Joachim; Claus, Thomas H; Tang, Weifeng; Barucci, Nicole; Brown, Su-Ellen; Bullock, William; Daly, Michelle; Decarr, Lynn; Li, Yaxin; Milardo, Lucinda; Molstad, David; Zhu, Jian; Gardell, Stephen J; Livingston, James N; Sweet, Laurel J

    2007-11-01

    Ghrelin, through action on its receptor, GH secretagogue receptor type 1a (GHS-R1a), exerts a variety of metabolic functions including stimulation of appetite and weight gain and suppression of insulin secretion. In the present study, we examined the effects of novel small-molecule GHS-R1a antagonists on insulin secretion, glucose tolerance, and weight loss. Ghrelin dose-dependently suppressed insulin secretion from dispersed rat islets. This effect was fully blocked by a GHS-R1a antagonist. Consistent with this observation, a single oral dose of a GHS-R1a antagonist improved glucose homeostasis in an ip glucose tolerance test in rat. Improvement in glucose tolerance was attributed to increased insulin secretion. Daily oral administration of a GHS-R1a antagonist to diet-induced obese mice led to reduced food intake and weight loss (up to 15%) due to selective loss of fat mass. Pair-feeding experiments indicated that weight loss was largely a consequence of reduced food intake. The impact of a GHS-R1a antagonist on gastric emptying was also examined. Although the GHS-R1a antagonist modestly delayed gastric emptying at the highest dose tested (10 mg/kg), delayed gastric emptying does not appear to be a requirement for weight loss because lower doses produced weight loss without an effect on gastric emptying. Consistent with the hypothesis that ghrelin regulates feeding centrally, the anorexigenic effects of potent GHS-R1a antagonists in mice appeared to correspond with their brain exposure. These observations demonstrate that GHS-R1a antagonists have the potential to improve the diabetic condition by promoting glucose-dependent insulin secretion and promoting weight loss.

  3. Bradykinin as a pain mediator: receptors are localized to sensory neurons, and antagonists have analgesic actions

    SciTech Connect

    Steranka, L.R.; Manning, D.C.; DeHaas, C.J.; Ferkany, J.W.; Borosky, S.A.; Connor, J.R.; Vavrek, R.J.; Stewart, J.M.; Snyder, S.H.

    1988-05-01

    Autoradiographic studies localize (/sup 3/H)bradykinin receptor binding sites to the substantia gelatinosa, dorsal root, and a subset of small cells in both the dorsal root and trigeminal ganglia of the guinea pig. (/sup 3/H)Bradykinin labeling is also observed over myocardinal/coronary visceral afferent fibers. The localization of (/sup 3/H)bradykinin receptors to nociceptive pathways supports a role for bradykinin in pain mediation. Several bradkykinin antagonists block bradykinin-induced acute vascular pain in the rat. The bradykinin antagonists also relieve bradykinin- and urate-induced hyperalgesia in the rat paw. These results indicate that bradykinin is a physiologic mediator of pain and that bradykinin antagonists have analgesic activity in both acute and chronic pain models.

  4. Structure-based design of eugenol analogs as potential estrogen receptor antagonists.

    PubMed

    Anita, Yulia; Radifar, Muhammad; Kardono, Leonardus Bs; Hanafi, Muhammad; Istyastono, Enade P

    2012-01-01

    Eugenol is an essential oil mainly found in the buds and leaves of clove (Syzygium aromaticum (L.) Merrill and Perry), which has been reported to have activity on inhibition of cell proliferation and apoptosis induction in human MCF-7 breast cancer cells. This biological activity is correlated to its activity as an estrogen receptor antagonist. In this article, we present the construction and validation of structure-based virtual screening (SBVS) protocols to identify the potent estrogen receptor α (ER) antagonists. The selected protocol, which gave acceptable enrichment factors as a virtual screening protocol, subsequently used to virtually screen eugenol, its analogs and their dimers. Based on the virtual screening results, dimer eugenol of 4-[4-hydroxy-3-(prop-2-en-1- yl)phenyl]-2-(prop-2-en-1-yl)phenol is recommended to be developed further in order to discover novel and potent ER antagonists. PMID:23144548

  5. SAR studies of 1,5-diarylpyrazole-based CCK1 receptor antagonists.

    PubMed

    Gomez, Laurent; Hack, Michael D; McClure, Kelly; Sehon, Clark; Huang, Liming; Morton, Magda; Li, Lina; Barrett, Terrance D; Shankley, Nigel; Breitenbucher, J Guy

    2007-12-01

    A high throughput screening campaign revealed compound 1 as a potent antagonist of the human CCK(1) receptor. Here, we report the syntheses and SAR studies of 1,5-diarylpyrazole analogs with various structural modifications of the alkane side chain of the molecule. The difference in affinity between the two enantiomers for the CCK(1) receptor and the flexible nature of the linker led to the design of constrained analogs with increased potency.

  6. Molecular determinants of agonist and antagonist signaling through the IL-36 receptor.

    PubMed

    Günther, Sebastian; Sundberg, Eric J

    2014-07-15

    The IL-1 family consists of 11 cytokines that control a complex network of proinflammatory signals critical for regulating immune responses to infections. They also play a central role in numerous chronic inflammatory disorders. Accordingly, inhibiting the activities of these cytokines is an important therapeutic strategy for treating autoimmune diseases and lymphomas. Agonist cytokines in the IL-1 family activate signaling by binding their cognate receptor and then recruiting a receptor accessory protein. Conversely, antagonist cytokines bind their cognate receptor but prohibit recruitment of receptor accessory protein, which precludes functional signaling complexes. The IL-36 subfamily of cytokines is the most diverse, including three agonists and at least one antagonist, and is the least well-characterized group within this family. Signaling through the IL-36 receptor directly stimulates dendritic cells and primes naive CD4 T cells for Th1 responses. Appropriately balanced IL-36 signaling is a critical determinant of skin and lung health. IL-36 signaling has been presumed to function analogously to IL-1 signaling. In this study, we have defined molecular determinants of agonist and antagonist signaling through the IL-36 receptor. We present the crystal structure of IL-36γ, which, to our knowledge, is the first reported structure of an IL-36 agonist. Using this structure as a guide, we designed a comprehensive series of IL-36 agonist/antagonist chimeric proteins for which we measured binding to the IL-36 receptor/IL-1 receptor accessory protein complex and functional activation and inhibition of signaling. Our data reveal how the fine specificity of IL-36 signaling is distinct from that of IL-1.

  7. Angiotensin II receptor antagonists (AT1-blockers, ARBs, sartans): similarities and differences

    PubMed Central

    van Zwieten, P.A.

    2006-01-01

    A survey is presented of the registered non-peptidergic angiotensin II receptor antagonists (AT1 blockers, ARBs, sartans) and their general properties and similarities. Accordingly, their receptor profile, pharmacokinetic and therapeutic applications are discussed. In addition, attention is paid to the individual characteristics of the AT1 blockers now available. A few components of this category offer additional potentially beneficial properties, owing to their pharmacological or metabolic characteristics. Such additional properties are critically discussed for eprosartan, losartan, telmisartan and valsartan. PMID:25696573

  8. CHOLECYSTOKININ RECEPTOR ANTAGONIST HALTS PROGRESSION OF PANCREATIC CANCER PRECURSOR LESIONS AND FIBROSIS IN MICE

    PubMed Central

    Smith, Jill P.; Cooper, Timothy K.; McGovern, Christopher O.; Gilius, Evan L.; Zhong, Qing; Liao, Jiangang; Molinolo, Alfredo A.; Gutkind, J. Silvio; Matters, Gail L.

    2014-01-01

    Objectives Exogenous administration of cholecystokinin (CCK) induces hypertrophy and hyperplasia of the pancreas with an increase in DNA content. We hypothesized that endogenous CCK is involved with the malignant progression of pancreatic intraepithelial neoplasia (PanIN) lesions and the fibrosis associated with pancreatic cancer. Methods The presence of CCK receptors in early PanIN lesions was examined by immunohistochemistry in mouse and human pancreas. Pdx1-Cre/LSL-KrasG12D transgenic mice were randomized to receive either untreated drinking water or water supplemented with a CCK-receptor antagonist (proglumide, 0.1mg/ml). Pancreas from mice were removed and examined histologically for number and grade of PanINs after 1, 2 or 4 months of antagonist therapy. Results Both CCK-A and CCK-B receptors were identified in early stage PanINs from mouse and human pancreas. The grade of PanIN lesions was reversed and progression to advanced lesions arrested in mice treated with proglumide compared to controls (p=0.004). Furthermore, pancreatic fibrosis was significantly reduced in antagonist-treated animals compared to vehicle (pitalic>0.001). Conclusions These findings demonstrate that endogenous CCK is in part responsible for the development and progression of pancreatic cancer. Use of CCK-receptor antagonists may have a role in cancer prophylaxis in high risk subjects, and may reduce fibrosis in the microenvironment. PMID:25058882

  9. I. Effects of a Dopamine Receptor Antagonist on Fathead Minnow, Pimephales promelas ,Reproduction

    EPA Science Inventory

    This study used a 21 d fathead minnow (Pimephales promelas) reproduction assay to test the hypothesis that exposure to the dopamine 2 receptor (D2R) antagonist, haloperidol, would impair fish reproduction. Additionally, a 96 h experiment with fathead minnows and zebrafish (Danio ...

  10. Design, synthesis, and biological evaluation of 4-phenylpyrrole derivatives as novel androgen receptor antagonists.

    PubMed

    Yamamoto, Satoshi; Matsunaga, Nobuyuki; Hitaka, Takenori; Yamada, Masami; Hara, Takahito; Miyazaki, Junichi; Santou, Takashi; Kusaka, Masami; Yamaoka, Masuo; Kanzaki, Naoyuki; Furuya, Shuichi; Tasaka, Akihiro; Hamamura, Kazumasa; Ito, Mitsuhiro

    2012-01-01

    A series of 4-phenylpyrrole derivatives D were designed, synthesized, and evaluated for their potential as novel orally available androgen receptor antagonists therapeutically effective against castration-resistant prostate cancers. 4-Phenylpyrrole compound 1 exhibited androgen receptor (AR) antagonistic activity against T877A and W741C mutant-type ARs as well as wild-type AR. An arylmethyl group incorporated into compound 1 contributed to enhancement of antagonistic activity. Compound 4n, 1-{[6-chloro-5-(hydroxymethyl)pyridin-3-yl]methyl}-4-(4-cyanophenyl)-2,5-dimethyl-1H-pyrrole-3-carbonitrile exhibited inhibitory effects on tumor cell growth against the bicalutamide-resistant LNCaP-cxD2 cell line as well as the androgen receptor-dependent JDCaP cell line in a mouse xenograft model. These results demonstrate that this series of pyrrole compounds are novel androgen receptor antagonists with efficacy against prostate cancer cells, including castration-resistant prostate cancers such as bicalutamide-resistant prostate cancer.

  11. A Time-course Study with the Androgen Receptor Antagonist Flutamide in Fish

    EPA Science Inventory

    Flutamide, a drug registered to treat some types of prostate cancer in humans, has been used for many years as a model androgen receptor (AR) antagonist in studies aimed at characterizing disruption of the vertebrate hypothalamic-pituitary-gonadal (HPG) axis. Various studies hav...

  12. Orally active vasopressin V1a receptor antagonist, SRX251, selectively blocks aggressive behavior.

    PubMed

    Ferris, Craig F; Lu, Shi-Fang; Messenger, Tara; Guillon, Christophe D; Heindel, Ned; Miller, Marvin; Koppel, Gary; Robert Bruns, F; Simon, Neal G

    2006-02-01

    Arginine vasopressin functions as a neurochemical signal in the brain to affect social behavior. There is an expanding literature from animal and human studies showing that vasopressin, through the vasopressin 1A receptor (V1A), can stimulate aggressive behavior. Using a novel monocylic beta lactam platform, a series of orally active vasopressin V1a antagonists was developed with high affinity for the human receptor. SRX251 was chosen from this series of V1a antagonists to screen for effects on serenic activity in a resident-intruder model of offensive aggression. Resident, male Syrian golden hamsters were given oral doses of SRX251 or intraperitoneal Manning compound, a selective V1a receptor antagonist with reduced brain penetrance, at doses of 0.2 microg, 20 microg, 2 mg/kg or vehicle. When tested 90-120 min later, SRX251, but not Manning compound, caused a significant dose-dependent reduction in offensive aggression toward intruders as measured by latency to bite and number of bites. The reduction in aggression persisted for over 6 h and was no longer present 12 h post treatment. SRX251 did not alter the amount of time the resident investigated the intruder, olfactory communication, general motor activity, or sexual motivation. These data corroborate previous studies showing a role for vasopressin neurotransmission in aggression and suggest that V1a receptor antagonists may be used to treat interpersonal violence co-occurring with such illness as ADHD, autism, bipolar disorder, and substance abuse. PMID:16504276

  13. Structure of the human M2 muscarinic acetylcholine receptor bound to an antagonist

    SciTech Connect

    Haga, Kazuko; Kruse, Andrew C.; Asada, Hidetsugu; Yurugi-Kobayashi, Takami; Shiroishi, Mitsunori; Zhang, Cheng; Weis, William I.; Okada, Tetsuji; Kobilka, Brian K.; Haga, Tatsuya; Kobayashi, Takuya

    2012-03-15

    The parasympathetic branch of the autonomic nervous system regulates the activity of multiple organ systems. Muscarinic receptors are G-protein-coupled receptors that mediate the response to acetylcholine released from parasympathetic nerves. Their role in the unconscious regulation of organ and central nervous system function makes them potential therapeutic targets for a broad spectrum of diseases. The M2 muscarinic acetylcholine receptor (M2 receptor) is essential for the physiological control of cardiovascular function through activation of G-protein-coupled inwardly rectifying potassium channels, and is of particular interest because of its extensive pharmacological characterization with both orthosteric and allosteric ligands. Here we report the structure of the antagonist-bound human M2 receptor, the first human acetylcholine receptor to be characterized structurally, to our knowledge. The antagonist 3-quinuclidinyl-benzilate binds in the middle of a long aqueous channel extending approximately two-thirds through the membrane. The orthosteric binding pocket is formed by amino acids that are identical in all five muscarinic receptor subtypes, and shares structural homology with other functionally unrelated acetylcholine binding proteins from different species. A layer of tyrosine residues forms an aromatic cap restricting dissociation of the bound ligand. A binding site for allosteric ligands has been mapped to residues at the entrance to the binding pocket near this aromatic cap. The structure of the M2 receptor provides insights into the challenges of developing subtype-selective ligands for muscarinic receptors and their propensity for allosteric regulation.

  14. A1 and A2a receptors mediate inhibitory effects of adenosine on the motor activity of human colon.

    PubMed

    Fornai, M; Antonioli, L; Colucci, R; Ghisu, N; Buccianti, P; Marioni, A; Chiarugi, M; Tuccori, M; Blandizzi, C; Del Tacca, M

    2009-04-01

    Experimental evidence in animal models suggests that adenosine is involved in the regulation of digestive functions. This study examines the influence of adenosine on the contractile activity of human colon. Reverse transcription-polymerase chain reaction revealed A(1) and A(2a) receptor expression in colonic neuromuscular layers. Circular muscle preparations were connected to isotonic transducers to determine the effects of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; A(1) receptor antagonist), ZM 241385 (A(2a) receptor antagonist), CCPA (A(1) receptor agonist) and 2-[(p-2-carboxyethyl)-phenethylamino]-5'-N-ethyl-carboxamide-adenosine (CGS 21680; A(2a) receptor agonist) on motor responses evoked by electrical stimulation or carbachol. Electrically evoked contractions were enhanced by DPCPX and ZM 241385, and reduced by CCPA and CGS 21680. Similar effects were observed when colonic preparations were incubated with guanethidine (noradrenergic blocker), L-732,138, GR-159897 and SB-218795 (NK receptor antagonists). However, in the presence of guanethidine, NK receptor antagonists and N(omega)-propyl-L-arginine (NPA; neuronal nitric oxide synthase inhibitor), the effects of DPCPX and CCPA were still evident, while those of ZM 241385 and CGS 21680 no longer occurred. Carbachol-induced contractions were unaffected by A(2a) receptor ligands, but they were enhanced or reduced by DPCPX and CCPA, respectively. When colonic preparations were incubated with guanethidine, NK antagonists and atropine, electrically induced relaxations were partly reduced by ZM 241385 or NPA, but unaffected by DPCPX. Dipyridamole or application of exogenous adenosine reduced electrically and carbachol-evoked contractions, whereas adenosine deaminase enhanced such motor responses. In conclusion, adenosine exerts an inhibitory control on human colonic motility. A(1) receptors mediate direct modulating actions on smooth muscle, whereas A(2a) receptors operate through inhibitory nitrergic nerve pathways.

  15. Histamine H₄ Receptor Antagonists: A New Approach for Tinnitus Treatment?

    PubMed

    Hagenow, Jens; Stark, Holger

    2015-01-01

    Tinnitus, a disorder with disruptive sound perception in the head without an external source, affects around 15 % of the worldwide adult population. Since there is no approved drug for the treatment for this symptom, novel strategies need to be developed to provide relief for the patient. A patent from the small French start-up company Sensorion suggests the use of histamine H4 receptor (H4R) inhibitors as potential treatment. Since histamine and its receptor subtypes are strongly involved in neuronal and inflammatory processes in vestibular areas, targeting the H4R could be a novel way to gain a treatment for tinnitus. Although mRNA and protein levels of H4R have been demonstrated on isolated spiral ganglion neurons from mice, the methods of receptor detection as well as the species relevance of the data are under discussion and require considerable further verification, especially on a disease with a high medical need like tinnitus.

  16. Current perspectives on selective dopamine D3 receptor antagonists as pharmacotherapeutics for addictions and related disorders

    PubMed Central

    Heidbreder, Christian A.; Newman, Amy H.

    2011-01-01

    Repeated exposure to drugs of abuse produces long-term molecular and neurochemical changes that may explain the core features of addiction, such as the compulsive seeking and taking of the drug, as well as the risk of relapse. A growing number of new molecular and cellular targets of addictive drugs have been identified, and rapid advances are being made in relating those targets to specific behavioral phenotypes in animal models of addiction. In this context, the pattern of expression of the dopamine (DA) D3 receptor in the rodent and human brain and changes in this pattern in response to drugs of abuse have contributed primarily to direct research efforts toward the development of selective DA D3 receptor antagonists. Growing preclinical evidence indicates that these compounds may actually regulate the motivation to self-administer drugs and disrupt drug-associated cue-induced craving. This report will be divided into three parts. First, preclinical evidence in support of the efficacy of selective DA D3 receptor antagonists in animal models of drug addiction will be reviewed. The effects of mixed DA D2/D3 receptor antagonists will not be discussed here because most of these compounds have low selectivity at the D3 versus D2 receptor, and their efficacy profile is related primarily to functional antagonism at D2 receptors and possibly interactions with other neurotransmitter systems. Second, major advances in medicinal chemistry for the identification and optimization of selective DA D3 receptor antagonists and partial agonists will be analyzed. Third, translational research from preclinical efficacy studies to so-called proof-of-concept studies for drug addiction indications will be discussed. PMID:20201845

  17. TNF-α receptor antagonist attenuates isoflurane-induced cognitive impairment in aged rats

    PubMed Central

    YANG, NENGLI; LIANG, YAFENG; YANG, PEI; WANG, WEIJIAN; ZHANG, XUEZHENG; WANG, JUNLU

    2016-01-01

    Postoperative cognitive dysfunction (POCD), a common clinical in aged patients, is characterized by deficits in cognitive functions in patients following anesthesia and surgery. It has been demonstrated that isoflurane may lead to cognitive impairment in aged rats; however, effective clinical interventions for preventing this disorder are limited. Tumor necrosis factor (TNF)-α has been suggested to be involved in neuroinflammation as well as the development of POCD. Accordingly, the present study aimed to investigate whether TNF-α signaling is involved in the isoflurane-induced cognitive impairment in aged rats, and whether TNF-α receptor antagonist are able to attenuate isoflurane-induced cognitive impairment in aged rats. A population of 20-month-old rats were administered TNF-α receptor antagonist R-7050 or an equal volume of saline by intraperitoneal injection 12 h prior to exposure to isoflurane to model cognitive impairment following anesthesia in old patients. Then the rats were exposed to 1.3% isoflurane for 4 h. In the control group, rats showed impaired cognitive functions evaluated by Morris water maze assay after isoflurane exposure. Furthermore, isoflurane exposure induced marked upregulation of proinflammatory cytokines, including interleukin (IL)-1β, TNF-α, IL-6 and IL-8 in the hippocampus tissue. In the experimental group, intracisternal administration of TNF-α receptor antagonist R-7050 significantly attenuated isoflurane-induced cognitive impairment and upregulation of proinflammatory cytokines. Further investigation revealed that intracisternal administration of TNF-α receptor antagonist R-7050 notably suppressed isoflurane-induced activation of NF-κB and MAPK signaling. Collectively, the present results suggest that TNF-α receptor antagonist may serve as a potential agent for the prevention of anesthesia-induced cognitive decline in aged patients. PMID:27347079

  18. The 5-HT1A receptor agonist flesinoxan shares discriminative stimulus properties with some 5-HT2 receptor antagonists.

    PubMed

    Herremans, A H; van der Heyden, J A; van Drimmelen, M; Olivier, B

    1999-10-01

    Ten homing pigeons were trained to discriminate the selective 5-HT1A receptor agonist flesinoxan (0.25 mg/kg p.o.) from its vehicle in a fixed-ratio (FR) 30 two-key operant drug discrimination procedure. The 5-HT2 receptor antagonist mianserin (ED50 = 4.8 mg/kg) fully substituted for flesinoxan, whereas ketanserin, ritanserin, mesulergine, and SB200646A substituted only partially, suggesting an interaction between 5-HT1A and 5-HT2 receptors. However, the 5-HT2 receptor agonists [DOI (0.6 mg/kg), TFMPP (10 mg/kg), mCPP (4 mg/kg)] were unable to antagonize the flesinoxan cue. The 5-HT1A receptor antagonists DU125530 (0.5-13 mg/kg) and WAY100,635 (0.1-1 mg/kg) partially antagonized the generalization of mianserin to flesinoxan. Taken together, these results are in accordance with the hypothesis that 5-HT1A receptor activation exerts an inhibitory effect on activation of 5-HT2 receptors. These results are in broad agreement with existing theories on 5-HT1A and 5-HT2 receptor interaction. Furthermore, it is argued that the discriminative stimulus properties of a drug may undergo qualitative changes with prolonged training.

  19. Crystal structures of the A2A adenosine receptor and their use in medicinal chemistry.

    PubMed

    Jacobson, Kenneth A

    2013-12-20

    New insights into drug design are derived from the X-ray crystallographic structures of G protein-coupled receptors (GPCRs), and the adenosine receptors (ARs) are at the forefront of this effort. The 3D knowledge of receptor binding and activation promises to enable drug discovery for GPCRs in general, and specifically for the ARs. The predictability of modeling based on the X-ray structures of the A2AAR has been well demonstrated in the identification, design and modification of both known and novel AR agonists and antagonists. It is expected that structure-based design of drugs acting through ARs will provide new avenues to clinically useful agents.

  20. APORPHINOID ANTAGONISTS OF 5-HT2A RECEPTORS: FURTHER EVALUATION OF RING A SUBSTITUENTS AND THE SIZE OF RING C

    PubMed Central

    Ponnala, Shashikanth; Kapadia, Nirav; Navarro, Hernán A.; Harding, Wayne W.

    2014-01-01

    A series of ring A modified analogs of nantenine as well as structural variants in ring C were synthesized and evaluated for antagonist activity at 5-HT2A and α1A receptors. Halogenation improves 5-HT2A antagonist potency in molecules containing a C1 methoxyl/C2 methoxyl or C1 methoxyl/C2 hydroxyl moiety. Bromination or iodination (but not chlorination) with the latter moiety also significantly increased α1A antagonist potency. Homologation or contraction of ring C adversely affected antagonist activity at both receptors, implying that a six-membered ring C motif is beneficial for high antagonist potency at both receptors. Molecular docking studies suggest that the improved antagonist activity (by virtue of improved affinity) of C3 halogenated aporphines in this study, is attributable to favorable interactions with the C3 halogen and F339 and/or F340. PMID:24766771

  1. Biochemical and pharmacological profile of a potent and selective nonpeptide antagonist of the neurotensin receptor.

    PubMed Central

    Gully, D; Canton, M; Boigegrain, R; Jeanjean, F; Molimard, J C; Poncelet, M; Gueudet, C; Heaulme, M; Leyris, R; Brouard, A

    1993-01-01

    We describe the characteristics of SR 48692, a selective, nonpeptide antagonist of the neurotensin receptor. In vitro, this compound competitively inhibits 125I-labeled neurotensin binding to the high-affinity binding site present in brain tissue from various species with IC50 values of 0.99 +/- 0.14 nM (guinea pig), 4.0 +/- 0.4 nM (rat mesencephalic cells), 7.6 +/- 0.6 nM (COS-7 cells transfected with the cloned high-affinity rat brain receptor), 13.7 +/- 0.3 nM (newborn mouse brain), 17.8 +/- 0.9 nM (newborn human brain), 8.7 +/- 0.7 nM (adult human brain), and 30.3 +/- 1.5 nM (HT-29 cells). It also displaces 125I-labeled neurotensin from the low-affinity levocabastine-sensitive binding sites but at higher concentrations (34.8 +/- 8.3 nM for adult mouse brain and 82.0 +/- 7.4 nM for adult rat brain). In guinea pig striatal slices, SR 48692 blocks K(+)-evoked release of [3H]dopamine stimulated by neurotensin with a potency (IC50 = 0.46 +/- 0.02 nM) that correlates with its binding affinity. In a cell line derived from a human colon carcinoma (HT-29), SR 48692 competitively antagonizes neurotensin-induced intracellular Ca2+ mobilization with a pA2 (-log Kapp) values of 8.13 +/- 0.03, which is consistent with results obtained in binding studies. Moreover, SR 48692 is devoid of any intrinsic agonist activity. This compound is also active in vivo, since it reverses at low dose (80 micrograms/kg) the turning behavior induced by intrastriatal injection of neurotensin in mice with similar potency whatever the route of administration (i.p. or orally) and with a long duration of action (6 hr). Thus, being a potent and selective neurotensin receptor antagonist, SR 48692 may be considered as a powerful tool for investigating the role of neurotensin in physiological and pathological processes. Images PMID:8380498

  2. Inhibition of Ebola and Marburg Virus Entry by G Protein-Coupled Receptor Antagonists

    PubMed Central

    Cheng, Han; Lear-Rooney, Calli M.; Johansen, Lisa; Varhegyi, Elizabeth; Chen, Zheng W.; Olinger, Gene G.

    2015-01-01

    ABSTRACT Filoviruses, consisting of Ebola virus (EBOV) and Marburg virus (MARV), are among the most lethal infectious threats to mankind. Infections by these viruses can cause severe hemorrhagic fevers in humans and nonhuman primates with high mortality rates. Since there is currently no vaccine or antiviral therapy approved for humans, there is an urgent need to develop prophylactic and therapeutic options for use during filoviral outbreaks and bioterrorist attacks. One of the ideal targets against filoviral infection and diseases is at the entry step, which is mediated by the filoviral glycoprotein (GP). In this report, we screened a chemical library of small molecules and identified numerous inhibitors, which are known G protein-coupled receptor (GPCR) antagonists targeting different GPCRs, including histamine receptors, 5-HT (serotonin) receptors, muscarinic acetylcholine receptor, and adrenergic receptor. These inhibitors can effectively block replication of both infectious EBOV and MARV, indicating a broad antiviral activity of the GPCR antagonists. The time-of-addition experiment and microscopic studies suggest that GPCR antagonists block filoviral entry at a step following the initial attachment but prior to viral/cell membrane fusion. These results strongly suggest that GPCRs play a critical role in filoviral entry and GPCR antagonists can be developed as an effective anti-EBOV/MARV therapy. IMPORTANCE Infection of Ebola virus and Marburg virus can cause severe illness in humans with a high mortality rate, and currently there is no FDA-approved vaccine or therapeutic treatment available. The 2013-2015 epidemic in West Africa underscores a lack of our understanding in the infection and pathogenesis of these viruses and the urgency of drug discovery and development. In this study, we have identified numerous inhibitors that are known G protein-coupled receptor (GPCR) antagonists targeting different GPCRs. These inhibitors can effectively block replication of

  3. Central administration of GPR55 receptor agonist and antagonist modulates anxiety-related behaviors in rats.

    PubMed

    Rahimi, Abbasali; Hajizadeh Moghaddam, Akbar; Roohbakhsh, Ali

    2015-04-01

    G-protein-coupled receptor 55 (GPR55) has been proposed as an atypical cannabinoid receptor, which is activated by lysophosphatidylinositols and some synthetic or endogenous cannabinoid molecules. The exact role of GPR55 receptors in the central nervous system especially in anxiety needs to be evaluated. In this study, the effects of intracerebroventricular (i.c.v.) administration of agonist and antagonist of GPR55 receptor on anxiety-related behaviors in rats were investigated. Here, O-1602 (GPR55 agonist) at the doses of 0.2, 1, and 5 μg/rat increased %OAT and %OAE but not the locomotor activity, showing an anxiolytic response, whereas i.c.v. injection of ML193 (GPR55 antagonist) at the doses of 0.1 and 1 μg/rat increased anxiety-like behaviors while causing locomotor impairment. The antagonistic effect of ML193 on the anxiolytic-like effect of O-1602 was also evaluated. The results showed that ML193 decreased the anxiolytic-like effect of O-1602. Based on these results, it may be concluded that central GPR55 may have a role in modulation of anxiety-like behaviors in rats. Further experiments are needed to elucidate the exact role of these receptors in anxiety.

  4. Clobenpropit (VUF-9153), a new histamine H3 receptor antagonist, inhibits electrically induced convulsions in mice.

    PubMed

    Yokoyama, H; Onodera, K; Maeyama, K; Sakurai, E; Iinuma, K; Leurs, R; Timmerman, H; Watanabe, T

    1994-07-21

    The effect of clobenpropit (VUF-9153), a new histamine H3 receptor antagonist, on electrically induced convulsions was studied in mice. Clobenpropit significantly and dose dependently decreased the duration of each convulsive phase. Its anticonvulsant effects were prevented by pretreatment with (R)-alpha-methylhistamine and imetit (VUF-8325), histamine H3 receptor agonists. These findings suggest that the effect of clobenpropit on electrically induced convulsions is due to an increase in endogenous histamine release in the brain, which is consistent with biochemical results that clobenpropit increased brain histidine decarboxylase activity dose dependently. The anticonvulsive effect of clobenpropit was antagonized by mepyramine, a histamine H1 receptor antagonist, but not by zolantidine, a histamine H2 receptor antagonist, indicating that histamine released by the anticonvulsant effect of clobenpropit interacts with histamine H1 receptors of postsynaptic neurons. The present findings of the effect of clobenpropit on electrically induced convulsions are fully consistent with those of thioperamide as described previously (Yokoyama et al., 1993, Eur. J. Pharmacol. 234, 129), supporting the hypothesis that the central histaminergic neuron system is involved in the inhibition of seizures.

  5. Dopamine D3 Receptor Antagonists as Potential Therapeutics for the Treatment of Neurological Diseases

    PubMed Central

    Maramai, Samuele; Gemma, Sandra; Brogi, Simone; Campiani, Giuseppe; Butini, Stefania; Stark, Holger; Brindisi, Margherita

    2016-01-01

    D3 receptors represent a major focus of current drug design and development of therapeutics for dopamine-related pathological states. Their close homology with the D2 receptor subtype makes the development of D3 selective antagonists a challenging task. In this review, we explore the relevance and therapeutic utility of D3 antagonists or partial agonists endowed with multireceptor affinity profile in the field of central nervous system disorders such as schizophrenia and drug abuse. In fact, the peculiar distribution and low brain abundance of D3 receptors make them a valuable target for the development of drugs devoid of motor side effects classically elicited by D2 antagonists. Recent research efforts were devoted to the conception of chemical templates possibly endowed with a multi-target profile, especially with regards to other G-protein-coupled receptors (GPCRs). A comprehensive overview of the recent literature in the field is herein provided. In particular, the evolution of the chemical templates has been tracked, according to the growing advancements in both the structural information and the refinement of the key pharmacophoric elements. The receptor/multireceptor affinity and functional profiles for the examined compounds have been covered, together with their most significant pharmacological applications. PMID:27761108

  6. Mixed antagonistic effects of the ginkgolides at recombinant human ρ1 GABAC receptors

    PubMed Central

    Huang, Shelley H.; Lewis, Trevor M.; Lummis, Sarah C.R.; Thompson, Andrew J.; Chebib, Mary; Johnston, Graham A.R.; Duke, Rujee K.

    2012-01-01

    The diterpene lactones of Ginkgo biloba, ginkgolides A, B and C are antagonists at a range of Cys-loop receptors. This study examined the effects of the ginkgolides at recombinant human ρ1 GABAC receptors expressed in Xenopus oocytes using two-electrode voltage clamp. The ginkgolides were moderately potent antagonists with IC50s in the μM range. At 10 μM, 30 μM and 100 μM, the ginkgolides caused rightward shifts of GABA dose–response curves and reduced maximal GABA responses, characteristic of noncompetitive antagonists, while the potencies showed a clear dependence on GABA concentration, indicating apparent competitive antagonism. This suggests that the ginkgolides exert a mixed-type antagonism at the ρ1 GABAC receptors. The ginkgolides did not exhibit any obvious use-dependent inhibition. Fitting of the data to a number of kinetic schemes suggests an allosteric inhibition as a possible mechanism of action of the ginkgolides which accounts for their inhibition of the responses without channel block or use-dependent inhibition. Kinetic modelling predicts that the ginkgolides exhibit saturation of antagonism at high concentrations of GABA, but this was only partially observed for ginkgolide B. It also suggests that there may be different binding sites in the closed and open states of the receptor, with a higher affinity for the receptor in the closed state. PMID:22828636

  7. Effects of histamine H(1) receptor antagonists on depressive-like behavior in diabetic mice.

    PubMed

    Hirano, Shoko; Miyata, Shigeo; Onodera, Kenji; Kamei, Junzo

    2006-02-01

    We previously reported that streptozotocin-induced diabetic mice showed depressive-like behavior in the tail suspension test. It is well known that the central histaminergic system regulates many physiological functions including emotional behaviors. In this study, we examined the role of the central histaminergic system in the diabetes-induced depressive-like behavior in the mouse tail suspension test. The histamine contents in the hypothalamus were significantly higher in diabetic mice than in non-diabetic mice. The histamine H(1) receptor antagonist chlorpheniramine (1-10 mg/kg, s.c.) dose-dependently and significantly reduced the duration of immobility in both non-diabetic and diabetic mice. In contrast, the selective histamine H(1) receptor antagonists epinastine (0.03-0.3 microg/mouse, i.c.v.) and cetirizine (0.01-0.1 microg/mouse, i.c.v.) dose-dependently and significantly suppressed the duration of immobility in diabetic mice, but not in non-diabetic mice. Spontaneous locomotor activity was not affected by histamine H(1) receptor antagonists in either non-diabetic or diabetic mice. In addition, the number and affinity of histamine H(1) receptors in the frontal cortex were not affected by diabetes. In conclusion, we suggest that the altered neuronal system mediated by the activation of histamine H(1) receptors is involved, at least in part, in the depressive-like behavior seen in diabetic mice.

  8. The cannabinoid CB1 receptor antagonist AM251 does not modify methamphetamine reinstatement of responding.

    PubMed

    Boctor, Sherin Y; Martinez, Joe L; Koek, Wouter; France, Charles P

    2007-09-24

    Cannabinoid CB(1) receptor antagonists can decrease methamphetamine self-administration. This study examined whether the CB(1) receptor antagonist AM251 [N-(piperidin-1-yl)-5-(4-indophonyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide] modifies reinstatement in rats that previously self-administered methamphetamine. Rats (n=10) self-administered methamphetamine (0.1 mg/kg/infusion) under a fixed ratio 2 schedule. Non-contingent methamphetamine (0.01-1.78 mg/kg, i.v.) yielded responding for saline (reinstatement) that was similar to responding for self-administered methamphetamine. AM251 (0.032-0.32, i.v.) did not affect methamphetamine-induced reinstatement but significantly attenuated Delta(9)-tetrahydrocannabinol (2.0 mg/kg, i.p.)-induced hypothermia. These data fail to support a role for endogenous cannabinoids or cannabinoid CB(1) receptors in reinstatement and, therefore, relapse to stimulant abuse.

  9. Nicotine cue: lack of effect of the alpha 7 nicotinic receptor antagonist methyllycaconitine.

    PubMed

    Brioni, J D; Kim, D J; O'Neill, A B

    1996-04-22

    To assess the role of the alpha 7 neuronal nicotinic acetylcholine receptor in the discriminative stimulus properties of (-)-nicotine, this study investigated the ability of the alpha 7 receptor antagonist methyllycaconitine to modulate the nicotine cue. In rats trained to discriminate (-)-nicotine from saline, intraperitoneal injections of methyllycaconitine neither induced nor blocked the nicotine cue. Intracerebroventricular administration of methyllycaconitine, neither potentiated nor blocked the effect of (-)-nicotine. On the other hand, intracerebroventricular injections of mecamylamine blocked the nicotine cue. The available evidence indicate that the nicotinic acetylcholine receptors in the brain blocked by methyllycaconitine, those presumably containing alpha 7 subunits, do not participate in the expression of the discriminative stimulus properties of (-)-nicotine.

  10. 3-Carboxy-pyrazolinalanine as a new scaffold for developing potent and selective NMDA receptor antagonists.

    PubMed

    Tamborini, Lucia; Pinto, Andrea; Mastronardi, Federica; Iannuzzi, Maria C; Cullia, Gregorio; Nielsen, Birgitte; De Micheli, Carlo; Conti, Paola

    2013-10-01

    A synthetic method for the preparation of suitably protected 3-carboxy-Δ2-pyrazolin-5-yl-alanine was developed. This scaffold is amenable to further decoration at the N1 position and was used to generate novel NMDA receptor ligands. Although weaker than the previously reported N1-Ph derivatives, the new ligands retain the ability to selectively bind to NMDA receptor with micromolar to submicromolar affinity. Considering the relevance of the N-functionalization for the biological activity, the results presented in this communication are preliminary to a full SAR study of this novel class of NMDA receptor antagonists. PMID:23954238

  11. Identification of a New Morpholine Scaffold as a P2Y12 Receptor Antagonist.

    PubMed

    Ahn, Young Ha; Lee, Joo-Youn; Park, Hee Dong; Kim, Tae Hun; Park, Min Chul; Choi, Gildon; Kim, Sunghoon

    2016-01-01

    The P2Y12 receptor is critical for platelet activation and is an attractive drug target for the prevention of atherothrombotic events. Despite the proven antithrombotic efficacy of P2Y12 inhibitors, these thienopyridine scaffolds are prodrugs that lack important features of the ideal antithrombotic agent. For this reason, ticagrelor-a new chemical class of P2Y12 receptor antagonist-was developed, but it can cause shortness of breath and various types of bleeding. Moreover, ticagrelor is a cytochrome P450 3A4 substrate/inhibitor and, therefore, caution should be exercised when it is used concomitantly with strong CYP3A4 inducers/inhibitors. There is a need for novel P2Y12 receptor antagonist scaffolds that are reversible and have high efficacy without associated side effects. Here, we describe a novel antagonist containing a morpholine moiety that was identified by screening libraries of commercially available compounds. The molecule, Compound E, acted on P2Y12, but not P2Y1 and P2Y13, and exhibited pharmacological characteristics that were distinct from those of ticagrelor, acting instead on P2Y12 via an allosteric mechanism. These results provide a basis for the development/optimization of a new class of P2Y12 antagonists. PMID:27563870

  12. Functional assays to define agonists and antagonists of the sigma-2 receptor

    PubMed Central

    Zeng, Chenbo; Rothfuss, Justin M.; Zhang, Jun; Vangveravong, Suwanna; Chu, Wenhua; Li, Shihong; Tu, Zhude; Xu, Jinbin; Mach, Robert H.

    2014-01-01

    The sigma-2 receptor has been identified as a biomarker in proliferating tumors. Up to date there is no well-established functional assay for defining sigma-2 agonists and antagonists. Many sigma-2 ligands with diverse structures have been shown to induce cell death in a variety of cancer cells by triggering caspase-dependent and independent apoptosis. Therefore, in the current study, we used the cell viability assay and the caspase-3 activity assay to determine sigma-2 agonists and antagonists. Three classes of sigma-2 ligands developed in our laboratory were evaluated for their potency to induce cell death in two tumor cell lines, mouse breast cancer cell line EMT-6 and human melanoma cell line MDA-MB-435. The data showed that the EC50 values of the sigma-2 ligands using the cell viability assay ranged from 11.4 μM to >200 μM, which were comparable with the EC50 values obtained using the caspase-3 assay. Based on the cytotoxicity of a sigma-2 ligand relative to that of siramesine, a commonly accepted sigma-2 agonist, we have categorized our sigma-2 ligands into agonists, partial agonists, and antagonists. The establishment of functional assays for defining sigma-2 agonists and antagonists will facilitate functional characterization of sigma-2 receptor ligands and sigma-2 receptors. PMID:24333652

  13. Glutamate NMDA receptor antagonists rapidly reverse behavioral and synaptic deficits caused by chronic stress exposure

    PubMed Central

    Li, Nanxin; Liu, Rong-Jian; Dwyer, Jason M.; Banasr, Mounira; Lee, Boyoung; Son, Hyeon; Li, Xiao-Yuan; Aghajanian, George; Duman, Ronald S.

    2011-01-01

    Background Despite widely reported clinical and preclinical studies of rapid antidepressant actions of glutamate N-methyl-D-aspartic acid (NMDA) receptor antagonists, there has been very little work examining the effects of these drugs in stress models of depression that require chronic administration of antidepressants, or the molecular mechanisms that could account for the rapid responses. Methods We used a rat 21-day chronic unpredictable stress (CUS) model to test the rapid actions of NMDA receptor antagonists on depressant-like behavior, neurochemistry, and spine density and synaptic function of prefrontal cortex (PFC) neurons. Results The results demonstrate that acute treatment with the non-competitive NMDA channel blocker ketamine or the selective NR2B antagonist Ro 25-6981 rapidly ameliorates CUS-induced anhedonia and anxiogenic behaviors. We also find that CUS exposure decreases the expression levels of synaptic proteins and spine number and the frequency/amplitude of synaptic currents (EPSCs) in layer V pyramidal neurons in the PFC, and that these deficits are rapidly reversed by ketamine. Blockade of the mammalian target of rapamycin (mTOR) protein synthesis cascade abolishes both the behavioral and biochemical effects of ketamine. Conclusions The results indicate that the structural and functional deficits resulting from long-term stress exposure, which could contribute to the pathophysiology of depression, are rapidly reversed by NMDA receptor antagonists in an mTOR-dependent manner. PMID:21292242

  14. A(2B) receptors mediate antimitogenesis in vascular smooth muscle cells.

    PubMed

    Dubey, R K; Gillespie, D G; Shue, H; Jackson, E K

    2000-01-01

    Adenosine inhibits growth of vascular smooth muscle cells. The goals of this study were to determine which adenosine receptor subtype mediates the antimitogenic effects of adenosine and to investigate the signal transduction mechanisms involved. In rat aortic vascular smooth muscle cells, platelet-derived growth factor-BB (PDGF-BB) (25 ng/mL) stimulated DNA synthesis ([(3)H]thymidine incorporation), cellular proliferation (cell number), collagen synthesis ([(3)H]proline incorporation), total protein synthesis ([(3)H]leucine incorporation), and mitogen-activated protein (MAP) kinase activity. The adenosine receptor agonists 2-chloroadenosine and 5'-N-methylcarboxamidoadenosine, but not N(6)-cyclopentyladenosine or CGS21680, inhibited the growth effects of PDGF-BB, an agonist profile consistent with an A(2B) receptor-mediated effect. The adenosine receptor antagonists KF17837 and 1,3-dipropyl-8-p-sulfophenylxanthine, but not 8-cyclopentyl-1, 3-dipropylxanthine, blocked the growth-inhibitory effects of 2-chloroadenosine and 5'-N-methylcarboxamidoadenosine, an antagonist profile consistent with an A(2) receptor-mediated effect. Antisense, but not sense or scrambled, oligonucleotides to the A(2B) receptor stimulated basal and PDGF-induced DNA synthesis, cell proliferation, and MAP kinase activity. Moreover, the growth-inhibitory effects of 2-chloroadenosine, 5'-N-methylcarboxamidoadenosine, and erythro-9-(2-hydroxy-3-nonyl) adenine plus iodotubericidin (inhibitors of adenosine deaminase and adenosine kinase, respectively) were abolished by antisense, but not scrambled or sense, oligonucleotides to the A(2B) receptor. Our findings strongly support the hypothesis that adenosine causes inhibition of vascular smooth muscle cell growth by activating A(2B) receptors coupled to inhibition of MAP kinase activity. Pharmacological or molecular biological activation of A(2B) receptors may prevent vascular remodeling associated with hypertension, atherosclerosis, and restenosis

  15. Major Depressive Disorder and Kappa Opioid Receptor Antagonists

    PubMed Central

    Li, Wei; Sun, Huijiao; Chen, Hao; Yang, Xicheng; Xiao, Li; Liu, Renyu; Shao, Liming; Qiu, Zhuibai

    2016-01-01

    Major depressive disorder (MDD) is a common psychiatric disease worldwide. The clinical use of tricyclic antidepressants (TCAs), monoamine oxidase inhibitors (MAOIs) and selective serotonin reuptake inhibitors (SSRIs)/serotonin–norepinephrine reuptake inhibitor (SNRIs) for this condition have been widely accepted, but they were challenged by unacceptable side-effects, potential drug-drug interactions (DDIs) or slow onset/lack of efficacy. The endogenous opioid system is involved in stress and emotion regulatory processes and its role in MDD has been implicated. Although several KOR antagonists including JDTic and PF-04455242 were discontinued in early clinical trials, ALKS 5461 and CERC-501(LY-2456302) survived and entered into Phase-III and Phase-II trials, respectively. Considering the efficacy and safety of early off-label use of buprenorphine in the management of the treatment-resistant depression (TRD), it will be not surprising to predict the potential success of ALKS 5461 (a combination of buprenorphine and ALKS-33) in the near future. Moreover, CERC-501 will be expected to be available as monotherapy or adjuvant therapy with other first-line antidepressants in the treatment of TRD, if ongoing clinical trials continue to provide positive benefit-risk profiles. Emerging new researches might bring more drug candidates targeting the endogenous opioid system to clinical trials to address current challenges in MDD treatment in clinical practice. PMID:27213169

  16. Two novel and selective nonimidazole histamine H3 receptor antagonists A-304121 and A-317920: I. In vitro pharmacological effects.

    PubMed

    Esbenshade, Timothy A; Krueger, Kathleen M; Miller, Thomas R; Kang, Chae Hee; Denny, Lynne I; Witte, David G; Yao, Betty B; Fox, Gerard B; Faghih, Ramin; Bennani, Youssef L; Williams, Michael; Hancock, Arthur A

    2003-06-01

    Histamine H3 receptor (H3R) antagonists enhance neurotransmitter release and are being developed for the treatment of a variety of neurological and cognitive disorders. Many potent histamine H3R antagonists contain an imidazole moiety that limits receptor selectivity and the tolerability of this class of compounds. Here we present the in vitro pharmacological data for two novel piperazine amide ligands, A-304121 [4-(3-((2R)-2-aminopropanoyl-1-piperazinyl)propoxy)phenyl)cyclopropylmethanone] and A-317920 [N-((1R)-2-(4-(3-(4-(cyclopropylcarbonyl)phenoxy)propyl)-1-piperazinyl)-1-methyl-2-oxo-ethyl-)-2-furamide], and compare them with the imidazole H3R antagonists ciproxifan, clobenpropit, and thioperamide. Both A-304121 and A-317920 bind potently to recombinant full-length rat H3R(pKi values = 8.6 and 9.2, respectively) but have lower potencies for binding the full-length human H3R (pKi values = 6.1 and 7.0, respectively). A-304121 and A-317920 are potent antagonists at rat H3R in reversing R-alpha-methylhistamine [(R)-alpha-MeHA] inhibition of forskolin-stimulated cAMP formation (pKb values = 8.0 and 9.1) but weak antagonists at human H3Rs in cyclase (pKb values = 6.0 and 6.3) and calcium mobilization (pKb values = 6.0 and 7.3) assays in cells co-expressing Galphaqi5-protein. Both compounds potently antagonize native H3Rs by blocking histamine inhibition of potassium-evoked [3H]histamine release from rat brain cortical synaptosomes (pKb values = 8.6 and 9.3) and (R)-alpha-MeHA reversal of electric field-stimulated guinea pig ileum contractions (pA2 values = 7.1 and 8.3). A-304121 and A-317920 are also more efficacious inverse agonists in reversing basal guanosine 5'-O-(3-[35S]thio)triphosphate ([35S]GTP gamma S) binding at the human H3R (pEC50 values = 5.7 and 7.0) than are the imidazole antagonists. These novel and selective piperazine amides represent useful leads for the development of H3R antagonist therapeutic agents.

  17. An Update on Adenosine A2A-Dopamine D2 receptor interactions. Implications for the Function of G Protein-Coupled Receptors

    PubMed Central

    Ferré, S.; Quiroz, C.; Woods, A. S.; Cunha, R.; Popoli, P.; Ciruela, F.; Lluis, C.; Franco, R.; Azdad, K.; Schiffmann, S. N.

    2008-01-01

    Adenosine A2A-dopamine D2 receptor interactions play a very important role in striatal function. A2A-D2 receptor interactions provide an example of the capabilities of information processing by just two different G protein-coupled receptors. Thus, there is evidence for the coexistence of two reciprocal antagonistic interactions between A2A and D2 receptors in the same neurons, the GABAergic enkephalinergic nens. An antagonistic A2A-D2 intramembrane receptor interaction, which depends on A2A-D2 receptor heteromerization and Gq/11-PLC signaling, modulates neuronal excitability and neurotransmitter release. On the other hand, an antagonistic A2A-D2 receptor interaction at the adenylyl-cyclase level, which depends on Gs/olf- and Gi/o- type V adenylyl-cyclase signaling, modulates protein phosphorylation and gene expression. Finally, under conditions of upregulation of an activator of G protein signaling (AGS3), such as during chronic treatment with addictive drugs, a synergistic A2A-D2 receptor interaction can also be demonstrated. AGS3 facilitates a synergistic interaction between Gs/olf- and Gi/o- coupled receptors on the activation of types II/IV adenylyl cyclase, leading to a paradoxical increase in protein phosphorylation and gene expression upon co-activation of A2A and D2 receptors. The analysis of A2-D2 receptor interactions will have implications for the pathophysiology and treatment of basal ganglia disorders and drug addiction. PMID:18537670

  18. Serotonin 2C receptor antagonists induce fast-onset antidepressant effects.

    PubMed

    Opal, M D; Klenotich, S C; Morais, M; Bessa, J; Winkle, J; Doukas, D; Kay, L J; Sousa, N; Dulawa, S M

    2014-10-01

    Current antidepressants must be administered for several weeks to produce therapeutic effects. We show that selective serotonin 2C (5-HT2C) antagonists exert antidepressant actions with a faster-onset (5 days) than that of current antidepressants (14 days) in mice. Subchronic (5 days) treatment with 5-HT2C antagonists induced antidepressant behavioral effects in the chronic forced swim test (cFST), chronic mild stress (CMS) paradigm and olfactory bulbectomy paradigm. This treatment regimen also induced classical markers of antidepressant action: activation of cAMP response element-binding protein (CREB) and induction of brain-derived neurotrophic factor (BDNF) in the medial prefrontal cortex (mPFC). None of these effects were induced by subchronic treatment with citalopram, a prototypical selective serotonin reuptake inhibitor (SSRI). Local infusion of 5-HT2C antagonists into the ventral tegmental area was sufficient to induce BDNF in the mPFC, and dopamine D1 receptor antagonist treatment blocked the antidepressant behavioral effects of 5-HT2C antagonists. 5-HT2C antagonists also activated mammalian target of rapamycin (mTOR) and eukaryotic elongation factor 2 (eEF2) in the mPFC, effects recently linked to rapid antidepressant action. Furthermore, 5-HT2C antagonists reversed CMS-induced atrophy of mPFC pyramidal neurons. Subchronic SSRI treatment, which does not induce antidepressant behavioral effects, also activated mTOR and eEF2 and reversed CMS-induced neuronal atrophy, indicating that these effects are not sufficient for antidepressant onset. Our findings reveal that 5-HT2C antagonists are putative fast-onset antidepressants, which act through enhancement of mesocortical dopaminergic signaling. PMID:24166413

  19. Species differences in the effects of the κ-opioid receptor antagonist zyklophin.

    PubMed

    Sirohi, Sunil; Aldrich, Jane V; Walker, Brendan M

    2016-03-01

    We have shown that dysregulation of the dynorphin/kappa-opioid receptor (DYN/KOR) system contributes to escalated alcohol self-administration in alcohol dependence and that KOR antagonists with extended durations of action selectively reduce escalated alcohol consumption in alcohol-dependent animals. As KOR antagonism has gained widespread attention as a potential therapeutic target to treat alcoholism and multiple neuropsychiatric disorders, we tested the effect of zyklophin (a short-acting KOR antagonist) on escalated alcohol self-administration in rats made alcohol-dependent using intermittent alcohol vapor exposure. Following dependence induction, zyklophin was infused centrally prior to alcohol self-administration sessions and locomotor activity tests during acute withdrawal. Zyklophin did not impact alcohol self-administration or locomotor activity in either exposure condition. To investigate the neurobiological basis of this atypical effect for a KOR antagonist, we utilized a κ-, μ-, and δ-opioid receptor agonist-stimulated GTPyS coupling assay to examine the opioid receptor specificity of zyklophin in the rat brain and mouse brain. In rats, zyklophin did not affect U50488-, DAMGO-, or DADLE-stimulated GTPyS coupling, whereas the prototypical KOR antagonist nor-binaltorphimine (norBNI) attenuated U50488-induced stimulation in the rat brain tissue at concentrations that did not impact μ- and δ-receptor function. To reconcile the discrepancy between the present rat data and published mouse data, comparable GTPyS assays were conducted using mouse brain tissue; zyklophin effects were consistent with KOR antagonism in mice. Moreover, at higher concentrations, zyklophin exhibited agonist properties in rat and mouse brains. These results identify species differences in zyklophin efficacy that, given the rising interest in the development of short-duration KOR antagonists, should provide valuable information for therapeutic development efforts. PMID:26992699

  20. Discovery and development of orexin receptor antagonists as therapeutics for insomnia

    PubMed Central

    Winrow, CJ; Renger, JJ

    2014-01-01

    Insomnia persistently affects the quality and quantity of sleep. Currently approved treatments for insomnia primarily target γ-aminobutyric acid-A (GABA-A) receptor signalling and include benzodiazepines and GABA-A receptor modulators. These drugs are used to address this sleep disorder, but have the potential for side effects such as tolerance and dependence, making them less attractive as maintenance therapy. Forward and reverse genetic approaches in animals have implicated orexin signalling (also referred to as hypocretin signalling) in the control of vigilance and sleep/wake states. Screening for orexin receptor antagonists using in vitro and in vivo methods in animals has identified compounds that block one or other of the orexin receptors (single or dual orexin receptor antagonists [SORAs and DORAs], respectively) in animals and humans. SORAs have primarily been used as probes to further elucidate the roles of the individual orexin receptors, while a number of DORAs have progressed to clinical development as pharmaceutical candidates for insomnia. The DORA almorexant demonstrated significant improvements in a number of clinically relevant sleep parameters in animal models and in patients with insomnia but its development was halted. SB-649868 and suvorexant have demonstrated efficacy and tolerability in Phase II and III trials respectively. Furthermore, suvorexant is currently under review by the Food and Drug Administration for the treatment of insomnia. Based on the publication of recent non-clinical and clinical data, orexin receptor antagonists potentially represent a targeted, effective and well-tolerated new class of medications for insomnia. Linked ArticlesThis article is part of a themed section on Orexin Receptors. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-2 PMID:23731216

  1. In vitro characterisation of the duration of action of the histamine-1 receptor antagonist azelastine.

    PubMed

    Slack, Robert J; Hart, Adam D; Luttmann, Mark A; Clark, Kenneth L; Begg, Malcolm

    2011-11-30

    Azelastine is a selective antagonist at the human histamine-1 receptor and is used clinically in the treatment of allergic rhinitis. In this study we have investigated its duration of action in vitro in an effort to characterise the receptor and tissue components involved. Chinese hamster ovary cell membrane fragments were used to determine the kinetics of azelastine at the H₁ receptor in a radioligand binding assay. Further duration of action studies were completed in tissue preparations using guinea-pig trachea and human bronchus. In radioligand binding studies, azelastine reached steady state at the H₁ receptor after approximately 41 min and exhibited a significantly slower dissociation rate constant from the receptor than the first generation antihistamine, diphenhydramine. In washout studies completed in guinea-pig and human airway in vitro tissue preparations, azelastine continued to antagonise the effects of histamine at the H₁ receptor for at least 18 h post-washout of the antagonist. This outcome was reversed following removal of the epithelium from guinea-pig isolated tracheal strips. These studies indicate there is a tissue component contributing to azelastine's duration of action, in addition to its direct H₁ receptor binding, with evidence suggesting a role for the epithelial layer. PMID:21946109

  2. An overview of SR121463, a selective non-peptide vasopressin V(2) receptor antagonist.

    PubMed

    Serradeil-Le Gal, C

    2001-01-01

    SR121463 is a selective, orally active, non-peptide antagonist of vasopressin (AVP) V(2) receptors with powerful aquaretic properties in various animal species and humans. SR121463 belongs to a new class of drugs, called aquaretics, which are capable of inducing free-water excretion without affecting electrolyte balance. SR121463 displays high affinity for animal and human V(2) receptors and exhibits a remarkably selective V(2) receptor profile. SR121463 and [(3)H]SR121463 are used, therefore, as selective probes for characterization and labeling of V(2) receptors. In various functional studies in vitro, SR121463 behaves as a potent antagonist. It inhibits AVP-stimulated human renal adenylyl cyclase and dDAVP (1-desamino, 8-D arginine-vasopressin)-induced relaxation of rat aorta. SR121463 also behaves as an inverse agonist in cells expressing a constitutively activated human V(2) receptor mutant. In vitro, SR121463 rescued misfolded V(2) AVP receptor mutants by increasing cell surface expression and restoring V(2) function. In normally hydrated conscious rats, dogs and monkeys, SR121463, by either i.v. or p.o. administration, induced a dose-dependent aquaresis with no major changes in urinary Na+ and K+ excretion (unlike classical diuretics). In cirrhotic rats with ascites and impaired renal function, a 10-day treatment with SR121463 totally corrected hyponatremia and restored normal urine excretion. In a model of diabetic nephropathy in rats, SR121463 strongly reduced albumin excretion. SR121463 was also effective at extrarenal V(2) (or V(2)-like) receptors involved in vascular relaxation or clotting factor release in vitro and in vivo. In the rabbit model of ocular hypertension, SR121463 by either single or repeated instillation, decreased intraocular pressure. After acute and chronic administration to rats, dogs or healthy human volunteers, SR121463 was well absorbed and well tolerated. In all species studied the drug produced pronounced aquaresis without any

  3. Effects of Urotensin II Receptor Antagonist, GSK1440115, in Asthma

    PubMed Central

    Portnoy, Alison; Kumar, Sanjay; Behm, David J.; Mahar, Kelly M.; Noble, Robert B.; Throup, John P.; Russ, Steven F.

    2013-01-01

    Background: Urotensin II (U-II) is highly expressed in the human lung and has been implicated in regulating respiratory physiology in preclinical studies. Our objective was to test antagonism of the urotensin (UT) receptor by GSK1440115, a novel, competitive, and selective inhibitor of the UT receptor, as a therapeutic strategy for the treatment of asthma. Methods: Safety, tolerability, and pharmacokinetics (PK) of single doses of GSK1440115 (1–750 mg) were assessed in a Phase I, placebo controlled study in 70 healthy subjects. In a Phase Ib study, 12 asthmatic patients were randomized into a two-period, single-blind crossover study and treated with single doses of 750 mg GSK1440115 or placebo and given a methacholine challenge. Results: Administration of GSK1440115 was safe and well-tolerated in healthy subjects and asthmatic patients. In both studies, there was a high degree of variability in the observed PK following oral dosing with GSK1440115 at all doses. There was a marked food effect in healthy subjects at the 50 mg dose. In the presence of food at the 750 mg dose, the time to maximal concentration was between 2 and 6 h and the terminal half-life was short at approximately 2 h. All asthmatic patients maintained greater than the predicted concentration levels necessary to achieve predicted 96% receptor occupancy for ≥3 h (between 4 and 7 h post-dose). There were no apparent trends or relationships between the systemic plasma exposure of GSK1440115 and pharmacodynamic endpoints, PC20 after methacholine challenge and FEV1, in asthmatics. Conclusion: While GSK1440115 was safe and well-tolerated, it did not induce bronchodilation in asthmatics, or protect against methacholine-induced bronchospasm, suggesting that acute UT antagonism is not likely to provide benefit as an acute bronchodilator in this patient population. PMID:23641215

  4. 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

  5. mGlu5 receptor antagonists: a novel class of anxiolytics?

    PubMed

    Spooren, Will; Gasparini, Fabrizio

    2004-05-01

    In the early 1990s, a new family of receptors were cloned that were found to mediate the intracellular metabolic effects of glutamate via coupling to secondary messenger systems, that is, the metabotropic glutamate (mGlu) receptors. Eight such receptors (mGlu1 to mGlu8) have been cloned to date, and according to their amino acid sequence, pharmacology and second-messenger coupling, these receptors have been clustered into three groups (I-III). In contrast to the glutamate-gated ion channels (NMDA, AMPA and kainate receptors), which are responsible for fast excitatory transmission, mGlu receptors have been shown to play a modulatory role in the glutamatergic synaptic transmission either by modulating the ion channel activity or by influencing neurotransmitter release. Given the fact that the mGlu receptors are G-protein- coupled, they obviously constitute a new attractive group of "drugable" targets for the treatment of various CNS disorders. The recent discovery of small molecules that selectively bind to receptors of group I (mGlu1 and mGlu5) and group II (mGlu2 and mGlu3) allowed significant advances in our understanding of the roles of these receptors in brain physiology and pathophysiology. The identification of MPEP (2-methyl-6-(phenylethynyl)-pyridine), a highly selective and brain-penetrant mGlu5 receptor antagonist, allowed the exploration of the therapeutic potential of this class of compounds. Subsequent behavior studies revealed that--with the exception of benzodiazepines--mGlu5 receptor antagonists exhibit the widest and most robust anxiolytic activity in preclinical models seen to date. Upcoming clinical studies will soon indicate if the preclinical anxiolytic-like efficacy translates into anxiolytic activity in humans. PMID:15334174

  6. Molecular Basis of Ligand Dissociation from the Adenosine A2A Receptor.

    PubMed

    Guo, Dong; Pan, Albert C; Dror, Ron O; Mocking, Tamara; Liu, Rongfang; Heitman, Laura H; Shaw, David E; IJzerman, Adriaan P

    2016-05-01

    How drugs dissociate from their targets is largely unknown. We investigated the molecular basis of this process in the adenosine A2Areceptor (A2AR), a prototypical G protein-coupled receptor (GPCR). Through kinetic radioligand binding experiments, we characterized mutant receptors selected based on molecular dynamic simulations of the antagonist ZM241385 dissociating from the A2AR. We discovered mutations that dramatically altered the ligand's dissociation rate despite only marginally influencing its binding affinity, demonstrating that even receptor features with little contribution to affinity may prove critical to the dissociation process. Our results also suggest that ZM241385 follows a multistep dissociation pathway, consecutively interacting with distinct receptor regions, a mechanism that may also be common to many other GPCRs.

  7. Cannabinoid-1 receptor antagonists in type-2 diabetes.

    PubMed

    Scheen, André J

    2007-12-01

    Type-2 diabetes is closely related to abdominal obesity and is generally associated with other cardiometabolic risk factors, resulting in a risk of major cardiovascular disease. Several animal and human observations suggest that the endocannabinoid system is over-active in the presence of abdominal obesity and/or diabetes. Both central and peripheral endocannabinoid actions, via the activation of CB1 receptors, promote weight gain and associated metabolic changes. Rimonabant, the first selective CB(1) receptor blocker in clinical use, has been shown to reduce body weight, waist circumference, triglycerides, blood pressure, insulin resistance index and C-reactive protein levels, and to increase high-density lipoprotein (HDL) cholesterol and adiponectin concentrations in both non-diabetic and diabetic overweight/obese patients. In addition, a 0.5-0.7% reduction in HbA1c levels was observed in metformin- or sulphonylurea-treated patients with type-2 diabetes and in drug-naïve diabetic patients. Almost half of the metabolic changes, including HbA1c reduction, could not be explained by weight loss, suggesting that there are direct peripheral effects. Rimonabant was generally well-tolerated, and the safety profile was similar in diabetic and non-diabetic patients, with a higher incidence of depressed mood disorders, nausea and dizziness. In conclusion, the potential role of rimonabant in overweight/obese patients with type-2 diabetes and at high risk of cardiovascular disease deserves much consideration.

  8. GPCR Ligand Dendrimer (GLiDe) Conjugates: Adenosine Receptor Interactions of a Series of Multivalent Xanthine Antagonists

    PubMed Central

    Kecskés, Angela; Tosh, Dilip K.; Wei, Qiang; Gao, Zhan-Guo; Jacobson, Kenneth A.

    2011-01-01

    Previously, G protein–coupled receptor (GPCR) agonists were tethered from polyamidoamine (PAMAM) dendrimers to provide high receptor affinity and selectivity. Here we prepared GPCR Ligand Dendrimer (GLiDe) conjugates from a potent adenosine receptor (AR) antagonist; such agents are of interest for treating Parkinson’s disease, asthma, and other conditions. Xanthine amine congener (XAC) was appended with an alkyne group on an extended C8 substituent for coupling by Cu(I)-catalyzed click chemistry to azide-derivatized G4 (fourth-generation) PAMAM dendrimers to form triazoles. These conjugates also contained triazole-linked PEG groups (8 or 22 moieties per 64 terminal positions) for increasing water-solubility and optionally prosthetic groups for spectroscopic characterization and affinity labeling. Human AR binding affinity increased progressively with the degree of xanthine substitution to reach Ki values in the nM range. The order of affinity of each conjugate was hA2AAR > hA3AR > hA1AR, while the corresponding monomer was ranked hA2AAR > hA1AR ≥ hA3AR. The antagonist activity of the most potent conjugate 14 (34 xanthines per dendrimer) was examined at the Gi-coupled A1AR. Conjugate 14 at 100 nM right-shifted the AR agonist concentration-response curve in a cyclic AMP functional assay in a parallel manner, but at 10 nM (lower than its Ki value) it significantly suppressed the maximal agonist effect in calcium mobilization. This is the first systematic probing of a potent AR antagonist tethered on a dendrimer and its activity as a function of variable loading. PMID:21539392

  9. Metabolism studies of ifenprodil, a potent GluN2B receptor antagonist.

    PubMed

    Falck, Evamaria; Begrow, Frank; Verspohl, Eugen; Wünsch, Bernhard

    2014-01-01

    The NMDA receptor antagonist ifenprodil is an important lead structure for developing new GluN2B selective NMDA receptor antagonists. Ifenprodil itself has a high affinity to the GluN2B subunit but a poor selectivity for the NMDA receptor. This aspect and the fast biotransformation are the major drawbacks of ifenprodil. In order to optimize the development of new and more selective GluN2B (NMDA) receptor antagonists, the identification of the main metabolic pathways of ifenprodil is necessary. Herein the in vitro and in vivo phase I and phase II metabolites of ifenprodil were generated and analyzed via LC-MS(n) experiments. In vitro experiments were carried out with rat liver microsomes and various co-factors to generate phase I and phase II metabolites. The application of ifenprodil to a rat and the analysis of its urine led to the identification of diverse formed in vivo metabolites. The phenol represents the metabolically most labile structural element since glucuronide 7 and 8 appeared as main metabolites.

  10. Thioperamide, a histamine H3 receptor antagonist, increases GABA release from the rat hypothalamus.

    PubMed

    Yamamoto, Y; Mochizuki, T; Okakura-Mochizuki, K; Uno, A; Yamatodani, A

    1997-06-01

    Using a microdialysis method and a new high performance liquid chromatography (HPLC)-fluorometric method for the detection of gamma-aminobutyric acid (GABA), we investigated the effect of thioperamide, an H3 receptor antagonist, on the GABA content in the dialysate from the anterior hypothalamic area of rats anesthetized with urethane. The addition of thioperamide to the perfusion fluid increased the release of GABA and histamine. Depleting neuronal histamine with alpha-fluoromethylhistidine, a specific inhibitor of histidine decarboxylase, and the administration of immepip, an H3 agonist, had no effect on basal- and thioperamide-induced GABA release. In addition, an infusion of clobenpropit, the most specific H3 receptor antagonist available, did not alter the basal release of GABA. On the other hand, histamine release was decreased by immepip and increased by thioperamide and clobenpropit. Removing Ca2+ from the perfusion fluid did not alter the effect of thioperamide on the GABA release, whereas that on histamine release was abrogated. These results suggest that the effect of thioperamide on GABA release is not mediated by histamine H3 receptors and that thioperamide acts on the transporter to cause an efflux of GABA from neurons and/or glia. Thioperamide is a popular H3 receptor antagonist which has been used applied to many studies. However, results using this compound should be interpreted in consideration of its effects on GABA release.

  11. Structure based virtual screening of ligands to identify cysteinyl leukotriene receptor 1 antagonist.

    PubMed

    Bandaru, Srinivas; Marri, Vijaya Kumar; Kasera, Priyadarshani; Kovuri, Purnima; Girdhar, Amandeep; Mittal, Deepti Raj; Ikram, Sabeen; Gv, Ravi; Nayarisseri, Anuraj

    2014-01-01

    Montelukast and Zafirlukast are known leukotriene receptor antagonists prescribed in asthma treatment. However, these fall short as mono therapy and are frequently used in combination with inhaled glucocorticosteroids with or without long acting beta 2 agonists. Therefore, it is of interest to apply ligand and structure based virtual screening strategies to identify compounds akin to lead compounds Montelukast and Zafirlukast. Hence, compounds with structures having 95% similarity to these compounds were retrieved from NCBI׳s PubChem database. Compounds similar to lead were grouped and docked at the antagonist binding site of cysteinyl leukotriene receptor 1. This exercise identified compounds UNII 70RV86E50Q (Pub Cid 71587778) and Sure CN 9587085 (Pub Cid 19793614) with higher predicted binding compared to Montelukast and Zafirlukast. It is shown that the compound Sure CN 9587085 showed appreciable ligand receptor interaction compared to UNII 70RV86E50Q. Thus, the compound Sure CN 9587085 is selected as a potent antagonist to cysteinyl leukotriene receptor 1 for further consideration in vitro and in vivo validation. PMID:25489175

  12. Effect of Y-25130, a selective 5-hydroxytryptamine3 receptor antagonist, on gastric emptying in mice.

    PubMed

    Haga, K; Asano, K; Inaba, K; Morimoto, Y; Setoguchi, M

    1994-01-01

    The effect of Y-25130 on gastric emptying of nutrient test meals (solid chow) was examined in mice. In a dose range of 0.01-1 mg/kg, p.o., Y-25130 significantly accelerated gastric emptying of solid meals in a dose-dependent manner, at an ED30 of 0.021 mg/kg. Other 5-hydroxytryptamine3 receptor antagonists and prokinetic agents having 5-hydroxytryptamine3 receptor antagonistic properties accelerated the emptying of solid meals in the following rank order of potency: Y-25130 = granisetron > or = tropisetron > ondansetron > cisapride > metoclopramide. The acceleration of the gastric emptying showed a good correlation with the antagonistic potencies of these compounds on 5-hydroxytryptamine3 receptors, determined by the inhibition test of the von Bezold-Jarisch reflex in anesthetized rats (r2 = 0.99). Domperidone (1 and 10 mg/kg, p.o.) and trimebutine (10 and 100 mg/kg, p.o.) failed to increase the rate of emptying from the stomach. Cisplatin (30 mg/kg, i.p.), a chemotherapeutic agent, significantly delayed the gastric emptying of solid meals, and Y-25130 (0.1-1 mg/kg, p.o.) prevented such a delay in emptying in a dose-dependent manner. These results suggest that Y-25130 accelerates the gastric emptying in mice by antagonism of the 5-hydroxytryptamine3 receptor. PMID:7625886

  13. Design and Synthesis of Cannabinoid Receptor 1 Antagonists for Peripheral Selectivity

    PubMed Central

    Fulp, Alan; Bortoff, Katherine; Seltzman, Herbert; Zhang, Yanan; Mathews, James; Snyder, Rodney; Fennell, Tim; Maitra, Rangan

    2012-01-01

    Antagonists of cannabinoid receptor 1 (CB1) have potential for the treatment of several diseases such as obesity, liver disease and diabetes. Recently, development of several CB1 antagonists was halted due to adverse central nervous system (CNS) related side effects observed with rimonabant, the first clinically approved CB1 inverse agonist. However, recent studies indicate that regulation of peripherally expressed CB1 with CNS-sparing compounds is a viable strategy to treat several important disorders. Our efforts aimed at rationally designing peripherally restricted CB1 antagonists have resulted in compounds that have limited blood-brain barrier (BBB) permeability and CNS exposure in preclinical in vitro and in vivo models. Typically, compounds with high topological polar surface areas (TPSAs) do not cross the BBB passively. Compounds with TPSAs higher than rimonabant (rimonabant TPSA = 50) and excellent functional activity with limited CNS penetration were identified. These compounds will serve as templates for further optimization. PMID:22372835

  14. Discovery and SAR of 6-alkyl-2,4-diaminopyrimidines as histamine H₄ receptor antagonists.

    PubMed

    Savall, Brad M; Chavez, Frank; Tays, Kevin; Dunford, Paul J; Cowden, Jeffery M; Hack, Michael D; Wolin, Ronald L; Thurmond, Robin L; Edwards, James P

    2014-03-27

    This report discloses the discovery and SAR of a series of 6-alkyl-2-aminopyrimidine derived histamine H4 antagonists that led to the development of JNJ 39758979, which has been studied in phase II clinical trials in asthma and atopic dermatitis. Building on our SAR studies of saturated derivatives from the indole carboxamide series, typified by JNJ 7777120, and incorporating knowledge from the tricyclic pyrimidines led us to the 6-alkyl-2,4-diaminopyrimidine series. A focused medicinal chemistry effort delivered several 6-alkyl-2,4-diaminopyrimidines that behaved as antagonists at both the human and rodent H4 receptor. Further optimization led to a panel of antagonists that were profiled in animal models of inflammatory disease. On the basis of the preclinical profile and efficacy in several animal models, JNJ 39758979 was selected as a clinical candidate; however, further development was halted during phase II because of the observation of drug-induced agranulocytosis (DIAG) in two subjects.

  15. Novel Yeast-based Strategy Unveils Antagonist Binding Regions on the Nuclear Xenobiotic Receptor PXR*

    PubMed Central

    Li, Hao; Redinbo, Matthew R.; Venkatesh, Madhukumar; Ekins, Sean; Chaudhry, Anik; Bloch, Nicolin; Negassa, Abdissa; Mukherjee, Paromita; Kalpana, Ganjam; Mani, Sridhar

    2013-01-01

    The pregnane X receptor (PXR) is a master regulator of xenobiotic metabolism, and its activity is critical toward understanding the pathophysiology of several diseases, including inflammation, cancer, and steatosis. Previous studies have demonstrated that ketoconazole binds to ligand-activated PXR and antagonizes receptor control of gene expression. Structure-function as well as computational docking analysis suggested a putative binding region containing critical charge clamp residues Gln-272, and Phe-264 on the AF-2 surface of PXR. To define the antagonist binding surface(s) of PXR, we developed a novel assay to identify key amino acid residues on PXR based on a yeast two-hybrid screen that examined mutant forms of PXR. This screen identified multiple “gain-of-function” mutants that were “resistant” to the PXR antagonist effects of ketoconazole. We then compared our screen results identifying key PXR residues to those predicted by computational methods. Of 15 potential or putative binding residues based on docking, we identified three residues in the yeast screen that were then systematically verified to functionally interact with ketoconazole using mammalian assays. Among the residues confirmed by our study was Ser-208, which is on the opposite side of the protein from the AF-2 region critical for receptor regulation. The identification of new locations for antagonist binding on the surface or buried in PXR indicates novel aspects to the mechanism of receptor antagonism. These results significantly expand our understanding of antagonist binding sites on the surface of PXR and suggest new avenues to regulate this receptor for clinical applications. PMID:23525103

  16. The effect of intrahippocampal injections of ritanserin (5HT2A/2C antagonist) and granisetron (5HT3 antagonist) on learning as assessed in the spatial version of the water maze.

    PubMed

    Naghdi, Nasser; Harooni, Hooman E

    2005-02-28

    5HT(2A/2C) and 5HT(3) receptors have an important role in cognitive behavior specially in spatial learning and memory but the literature concerning the role of these receptors in hippocampus in cognition remains controversial. In the present study a 5HT(2A/2C) antagonist ritanserin (0, 2, 4, 8 microg/0.5 microl) and a 5HT(3) antagonist granisetron (0.0, 0.05, 0.25, 0.5 microg/0.5 microl) were injected bilaterally into the CA1 region of rat hippocampus, 20 min before each training session in Morris Water Maze (MWM) task. Compare with control group, ritanserin (4 microg/0.5 microl) significantly reduced the escape latency and traveled distance of swimming to platform, but granisetron (0.25 microg/0.5 microl) significantly increased those parameters. Both drugs had no effect on escape latency and traveled distance of a non-spatial visual discrimination task. These results suggest a differential role of 5HT(2A/2C) and 5HT(3) receptors during spatial learning that ritanserin improves rat performance in spatial discrimination task whereas granisetron impairs it.

  17. Opioid Receptor Antagonists in the Treatment of Alcoholism.

    PubMed

    Serecigni, Josep Guardia

    2015-09-29

    Objetivos: A partir de los recientes progresos en la farmacoterapia del alcoholismo, hemos efectuado una revisión sobre los fármacos antagonistas de los receptores opioides, que tienen aprobada la indicación para el tratamiento del alcoholismo, como son naltrexona y nalmefeno. Metodología: Hemos revisado más de 100 publicaciones sobre péptidos y receptores opioides, el efecto de los fármacos antagonistas de los receptores opioides sobre el consumo de alcohol, tanto en animales como en humanos, tanto en el laboratorio como para el tratamiento del alcoholismo. También se describen las características farmacológicas de naltrexona y de nalmefeno y su utilidad en la práctica clínica. Resultados: Múltiples evidencias han demostrado la eficacia de naltrexona y nalmefeno para reducir el consumo de alcohol, tanto en animales de laboratorio como también en personas estudiadas en situación de bar experimental, aunque debido al diferente perfil receptorial, nalmefeno ha sido relacionado con una mayor eficacia para la reducción del consumo de alcohol, en ratas que presentan dependencia del alcohol. Además, un gran número de ensayos clínicos controlados han demostrado la eficacia de naltrexona para la prevención de recaídas, en personas que presentan un trastorno por dependencia del alcohol. Ensayos clínicos controlados recientes han demostrado la eficacia de nalmefeno “a demanda” para reducir el consumo de alcohol, en personas que presentan un trastorno por dependencia del alcohol de baja gravedad. Conclusiones: Tanto naltrexona como nalmefeno han demostrado ser fármacos seguros, bien tolerados, de manejo sencillo, y eficaces para el tratamiento del trastorno por dependencia del alcohol, (actualmente llamado trastorno por consumo de alcohol). A partir de recientes ensayos clínicos controlados se ha comprobado que nalmefeno produce una reducción significativa del consumo de alcohol, lo cual supone un nuevo objetivo que amplía las posibilidades de

  18. In vitro and in vivo comparison of two non-peptide tachykinin NK3 receptor antagonists: Improvements in efficacy achieved through enhanced brain penetration or altered pharmacological characteristics.

    PubMed

    Dawson, Lee A; Langmead, Christopher J; Dada, Adeshola; Watson, Jeannette M; Wu, Zining; de la Flor, Raúl; Jones, Gareth A; Cluderay, Jane E; Southam, Eric; Murkitt, Graham S; Hill, Mark D; Jones, Declan N C; Davies, Ceri H; Hagan, Jim J; Smith, Paul W

    2010-02-10

    Clinical evaluation of tachykinin NK(3) receptor antagonists has provided support for the therapeutic utility of this target in schizophrenia. However, these studies have not been entirely conclusive, possibly because of the pharmacokinetic limitations of these molecules. In the search for tachykinin NK(3) receptor antagonists with improved properties, we have discovered GSK172981 and GSK256471. Both compounds demonstrated high affinity for recombinant human (pK(i) values 7.7 and 8.9, respectively) and native guinea pig (pK(i) values 7.8 and 8.4, respectively) tachykinin NK(3) receptors. In vitro functional evaluations revealed GSK172981 to be a competitive antagonist (pA(2)=7.2) at cloned human tachykinin NK(3) receptor whereas GSK256471 diminished the neurokinin B-induced E(max) response, indicative of non-surmountable antagonist pharmacology (pA(2)=9.2). GSK172981 also exhibited a competitive profile in antagonizing neurokinin B-stimulated neuronal activity recorded from the guinea pig medial habenula slices (apparent pK(B)=8.1), whilst GSK256471 abolished the agonist-induced response. Central nervous system penetration by GSK172981 and GSK256471 was indicated by dose-dependent ex vivo tachykinin NK(3) receptor occupancy in medial prefrontal cortex (ED(50) values of 0.8 and 0.9 mg/kg, i.p., respectively) and the dose-dependent attenuation of agonist-induced "wet dog shake" behaviours in guinea pigs. Finally, in vivo microdialysis studies demonstrated that acute GSK172981 (30 mg/kg, i.p.) and GSK256471 (1mg/kg, i.p.) attenuated haloperidol-induced increases in extracellular dopamine in the guinea pig nucleus accumbens. Taken together, these in vitro and in vivo characterisations of the tachykinin NK(3) receptor antagonists GSK172981 and GSK256471 support their potential utility in the treatment of schizophrenia.

  19. Positron tomography of a radiobrominated analog of SCH 23390: A selective dopamine D1 receptor antagonist

    SciTech Connect

    De Jesus, O.T.; Woolverton, W.L.; Van Moffaert, G.J.C.; Goldberg, L.I.; Dinerstein, R.J.; Yasillo, N.J.; Ortega, C.; Cooper, M.D.; Friedman, A.M.

    1985-05-01

    Alterations in the central dopaminergic system have been hypothesized to underlie several neuropsychiatric disorders. Dopamine (DA) receptors in the CNS have been classified into two classes based on whether linkage to the enzyme adenylate cyclase exists, the D1 receptors, or not, D2 receptors. To date, studies on cerebral DA system by positron tomography (PET) have utilized the butyrophenones which are predominantly D2 antagonists. We have prepared Br-75 or Br-76 labelled 8-bromo analog of SCH 23390, (BrSCH), a highly selective antagonist for DA D1 receptors and have measured its distribution in the intact monkey brain by PET and by postmortem section of the mouse brain. An anesthesized 8.5 kg male rhesus monkey was given, i.v., ca. 2 mCi BrSCH on two occasions and scanned with The University of Chicago PETT VI system. Results revealed that the drug localized specifically in the basal ganglia. In a similar experiment in the same monkey given Br-76-bromospiroperidol (BrSP), a predominantly D2 antagonist, high uptake in the basal ganglia was also observed but the time course for specific localization of BrSCH was much faster than that of BrSP. These results provide evidence the D1 receptors, like D2 receptors, are localized in the caudate nucleus (CN) although BrSCH, compared to BrSP, appear to localize more in the posterior aspect of the CN. In conclusion, BrSCH should be a useful imaging agent to study dopamine D1 receptors in the CNS.

  20. Cucurbitacins are insect steroid hormone antagonists acting at the ecdysteroid receptor.

    PubMed Central

    Dinan, L; Whiting, P; Girault, J P; Lafont, R; Dhadialla, T S; Cress, D E; Mugat, B; Antoniewski, C; Lepesant, J A

    1997-01-01

    Two triterpenoids, cucurbitacins B and D, have been isolated from seeds of Iberis umbellata (Cruciferae) and shown to be responsible for the antagonistic activity of a methanolic extract of this species in preventing the 20-hydroxyecdysone (20E)-induced morphological changes in the Drosophila melanogaster BII permanent cell line. With a 20E concentration of 50 nM, cucurbitacins B and D give 50% responses at 1.5 and 10 microM respectively. Both cucurbitacins are able to displace specifically bound radiolabelled 25-deoxy-20-hydroxyecdysone (ponasterone A) from a cell-free preparation of the BII cells containing ecdysteroid receptors. The Kd values for cucurbitacins B and D (5 and 50 microM respectively) are similar to the concentrations required to antagonize 20E activity with whole cells. Cucurbitacin B (cucB) prevents stimulation by 20E of an ecdysteroid-responsive reporter gene in a transfection assay. CucB also prevents the formation of the Drosophila ecdysteroid receptor/Ultraspiracle/20E complex with the hsp27 ecdysteroid response element as demonstrated by gel-shift assay. This is therefore the first definitive evidence for the existence of antagonists acting at the ecdysteroid receptor. Preliminary structure/activity studies indicate the importance of the Delta23-22-oxo functional grouping in the side chain for antagonistic activity. Hexanorcucurbitacin D, which lacks carbon atoms C-22 to C-27, is found to be a weak agonist rather than an antagonist. Moreover, the side chain analogue 5-methylhex-3-en-2-one possesses weak antagonistic activity. PMID:9581538

  1. Acute NK₁ receptor antagonist administration affects reward incentive anticipation processing in healthy volunteers.

    PubMed

    Saji, Kanako; Ikeda, Yumiko; Kim, Woochan; Shingai, Yoshitoshi; Tateno, Amane; Takahashi, Hidehiko; Okubo, Yoshiro; Fukayama, Haruhisa; Suzuki, Hidenori

    2013-08-01

    The primary brain structures of reward processing are mainly situated in the mid-brain dopamine system. The nucleus accumbens (NAc) receives dopaminergic projections from the ventral tegmental area and works as a key brain region for the positive incentive value of rewards. Because neurokinin-1 (NK₁) receptor, the cognate receptor for substance P (SP), is highly expressed in the NAc, we hypothesized that the SP/NK₁ receptor system might play a role in positive reward processing in the NAc in humans. Therefore, we conducted a functional MRI (fMRI) study to assess the effects of an NK₁ receptor antagonist on human reward processing through a monetary incentive delay task that is known to elicit robust activation in the NAc especially during gain anticipation. Eighteen healthy adults participated in two series of an fMRI study, taking either a placebo or the NK₁ receptor antagonist aprepitant. Behavioural measurements revealed that there was no significant difference in reaction time, hit rate, or self-reported effort for incentive cues between the placebo and aprepitant treatments. fMRI showed significant decrease in blood oxygenation-level-dependent signals in the NAc during gain anticipation with the aprepitant treatment compared to the placebo treatment. These results suggest that SP/NK₁ receptor system is involved in processing of positive incentive anticipation and plays a role in accentuating positive valence in association with the primary dopaminergic pathways in the reward circuit.

  2. X-ray structures define human P2X3 receptor gating cycle and antagonist action

    NASA Astrophysics Data System (ADS)

    Mansoor, Steven E.; Lü, Wei; Oosterheert, Wout; Shekhar, Mrinal; Tajkhorshid, Emad; Gouaux, Eric

    2016-10-01

    P2X receptors are trimeric, non-selective cation channels activated by ATP that have important roles in the cardiovascular, neuronal and immune systems. Despite their central function in human physiology and although they are potential targets of therapeutic agents, there are no structures of human P2X receptors. The mechanisms of receptor desensitization and ion permeation, principles of antagonism, and complete structures of the pore-forming transmembrane domains of these receptors remain unclear. Here we report X-ray crystal structures of the human P2X3 receptor in apo/resting, agonist-bound/open-pore, agonist-bound/closed-pore/desensitized and antagonist-bound/closed states. The open state structure harbours an intracellular motif we term the ‘cytoplasmic cap’, which stabilizes the open state of the ion channel pore and creates lateral, phospholipid-lined cytoplasmic fenestrations for water and ion egress. The competitive antagonists TNP-ATP and A-317491 stabilize the apo/resting state and reveal the interactions responsible for competitive inhibition. These structures illuminate the conformational rearrangements that underlie P2X receptor gating and provide a foundation for the development of new pharmacological agents.

  3. Synthesis, pharmacological evaluation and docking studies of pyrrole structure-based CB2 receptor antagonists.

    PubMed

    Ragusa, Giulio; Gómez-Cañas, María; Morales, Paula; Hurst, Dow P; Deligia, Francesco; Pazos, Ruth; Pinna, Gerard A; Fernández-Ruiz, Javier; Goya, Pilar; Reggio, Patricia H; Jagerovic, Nadine; García-Arencibia, Moisés; Murineddu, Gabriele

    2015-08-28

    During the last years, there has been a continuous interest in the development of cannabinoid receptor ligands that may serve as therapeutic agents and/or as experimental tools. This prompted us to design and synthesize analogues of the CB2 receptor antagonist N-fenchyl-5-(4-chloro-3-methyl-phenyl)-1-(4-methyl-benzyl)-1H-pyrazole-3-carboxamide (SR144528). The structural modifications involved the bioisosteric replacement of the pyrazole ring by a pyrrole ring and variations on the amine carbamoyl substituents. Two of these compounds, the fenchyl pyrrole analogue 6 and the myrtanyl derivative 10, showed high affinity (Ki in the low nM range) and selectivity for the CB2 receptor and both resulted to be antagonists/inverse agonists in [(35)S]-GTPγS binding analysis and in an in vitro CB2 receptor bioassay. Cannabinoid receptor binding data of the series allowed identifying steric constraints within the CB2 binding pocket using a study of Van der Waals' volume maps. Glide docking studies revealed that all docked compounds bind in the same region of the CB2 receptor inactive state model. PMID:26209834

  4. Effects of the nicotinic acetylcholine receptor antagonist mecamylamine on the discriminative stimulus effects of cocaine in male rhesus monkeys.

    PubMed

    Banks, Matthew L

    2014-06-01

    Preclinical drug discrimination procedures have been useful in understanding the pharmacological mechanisms of the subjective-like effects of abused drugs. Converging lines of evidence from neurochemical and behavioral studies implicate a potential role of nicotinic acetylcholine (nACh) receptors in the abuse-related effects of cocaine. The aim of the present study was to determine the effects of the nACh receptor antagonist mecamylamine on the discriminative stimulus effects of cocaine in nonhuman primates. The effects of mecamylamine on the cocaine-like discriminative stimulus effects of nicotine were also examined. Male rhesus monkeys (n = 5) were trained to discriminate 0.32 mg/kg, IM cocaine from saline in a 2-key, food-reinforced discrimination procedure. Initially, potency and time course of cocaine-like discriminative stimulus effects were determined for nicotine and mecamylamine alone. Test sessions were then conducted examining the effects of mecamylamine on cocaine or the cocaine-like discriminative stimulus effects of nicotine. Curiously, mecamylamine produced partial cocaine-like discriminative stimulus effects. Mecamylamine did not significantly alter the discriminative stimulus effects of cocaine up to doses that significantly decreased rates of operant responding. Mecamylamine and nicotine combinations were not different than saline. These results confirm previous nonhuman primate studies of partial substitution with nicotine and extend these findings with mecamylamine. Furthermore, these results extend previous results in rats suggesting cocaine may have nACh receptor antagonist properties. PMID:24548245

  5. [N-allyl-Dmt1]-endomorphins are micro-opioid receptor antagonists lacking inverse agonist properties.

    PubMed

    Marczak, Ewa D; Jinsmaa, Yunden; Li, Tingyou; Bryant, Sharon D; Tsuda, Yuko; Okada, Yoshio; Lazarus, Lawrence H

    2007-10-01

    [N-allyl-Dmt1]-endomorphin-1 and -2 ([N-allyl-Dmt1]-EM-1 and -2) are new selective micro-opioid receptor antagonists obtained by N-alkylation with an allyl group on the amino terminus of 2',6'-dimethyl-L-tyrosine (Dmt) derivatives. To further characterize properties of these compounds, their intrinsic activities were assessed by functional guanosine 5'-O-(3-[35S]thiotriphosphate) binding assays and forskolin-stimulated cyclic AMP accumulation in cell membranes obtained from vehicle, morphine, and ethanol-treated SK-N-SH cells and brain membranes isolated from naive and morphine-dependent mice; their mode of action was compared with naloxone or naltrexone, which both are standard nonspecific opioid-receptor antagonists. [N-allyl-Dmt1]-EM-1 and -2 were neutral antagonists under all of the experimental conditions examined, in contrast to naloxone and naltrexone, which behave as neutral antagonists only in membranes from vehicle-treated cells and mice but act as inverse agonists in membranes from morphine- and ethanol-treated cells as well as morphine-treated mice. Both endomorphin analogs inhibited the naloxone- and naltrexone-elicited withdrawal syndromes from acute morphine dependence in mice. This suggests their potential therapeutic application in the treatment of drug addiction and alcohol abuse without the adverse effects observed with inverse agonist alkaloid-derived compounds that produce severe withdrawal symptoms.

  6. A low-molecular-weight antagonist for the human thyrotropin receptor with therapeutic potential for hyperthyroidism.

    PubMed

    Neumann, Susanne; Kleinau, Gunnar; Costanzi, Stefano; Moore, Susanna; Jiang, Jian-kang; Raaka, Bruce M; Thomas, Craig J; Krause, Gerd; Gershengorn, Marvin C

    2008-12-01

    Low-molecular-weight (LMW) antagonists for TSH receptor (TSHR) may have therapeutic potential as orally active drugs to block stimulating antibodies (TsAbs) in Graves' hyperthyroidism. We describe an approach to identify LMW ligands for TSHR based on Org41841, a LMW partial agonist for the LH/choriogonadotropin receptor and TSHR. We used molecular modeling and functional experiments to guide the chemical modification of Org41841. We identified an antagonist (NIDDK/CEB-52) that selectively inhibits activation of TSHR by both TSH and TsAbs. Whereas initially characterized in cultured cells overexpressing TSHRs, the antagonist was also active under more physiologically relevant conditions in primary cultures of human thyrocytes expressing endogenous TSHRs in which it inhibited TSH- and TsAb-induced up-regulation of mRNA transcripts for thyroperoxidase. Our results establish this LMW compound as a lead for the development of higher potency antagonists and serve as proof of principle that LMW ligands that target TSHR could serve as drugs in patients with Graves' disease.

  7. The beneficial effects of a thromboxane receptor antagonist on spinal cord perfusion following experimental cord injury.

    PubMed

    Tempel, G E; Martin, H F

    1992-06-01

    The eicosanoids thromboxane A2 and prostacyclin have opposing actions causing vasoconstriction and vasodilation respectively. The ratio of these two eicosanoids is thus an important determinant of circulatory homeostasis. An increase in this ratio occurs in certain inflammatory conditions with dramatic consequences in organ perfusion. In spinal cord trauma, in addition to direct physical perturbation of the spinal cord, it is likely that further structural and functional loss occurs as a result of decreased tissue perfusion precipitated by an increase in the thromboxane/prostacyclin ratio. This study evaluated hemodynamics and organ perfusion, 3 h following 24 g-cm spinal cord trauma in the rat. The role of thromboxane was investigated with an inhibitor of thromboxane synthesis (Dazoxiben) and with a receptor antagonist (13-APT). Cardiac output and blood pressure were unaffected by Dazoxiben, 13-APT, or spinal cord trauma. Injury effected approximately a 40% decrease in spinal cord perfusion from 0.41 to 0.25 ml/min/g which was not improved by the thromboxane synthase inhibitor, Dazoxiben. 13-ATP completely abrogated the decline in spinal cord blood flow flowing injury. Perfusion of other selected organs demonstrated little change as a result of the spinal trauma. Brain flow remained constant at 0.78 ml/min/g brain. Coronary blood flow, however, declined from 3.2 to 2.0 ml/min/g heart tissue. The data suggest consideration of the importance of thromboxane in therapeutic attempts to reduce secondary injury arising in spinal cord trauma. PMID:1386102

  8. Activation of NTS A2a adenosine receptors differentially resets baroreflex control of renal vs. adrenal sympathetic nerve activity.

    PubMed

    Ichinose, Tomoko K; O'Leary, Donal S; Scislo, Tadeusz J

    2009-04-01

    The role of nucleus of solitary tract (NTS) A(2a) adenosine receptors in baroreflex mechanisms is controversial. Stimulation of these receptors releases glutamate within the NTS and elicits baroreflex-like decreases in mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA), whereas inhibition of these receptors attenuates HR baroreflex responses. In contrast, stimulation of NTS A(2a) adenosine receptors increases preganglionic adrenal sympathetic nerve activity (pre-ASNA), and the depressor and sympathoinhibitory responses are not markedly affected by sinoaortic denervation and blockade of NTS glutamatergic transmission. To elucidate the role of NTS A(2a) adenosine receptors in baroreflex function, we compared full baroreflex stimulus-response curves for HR, RSNA, and pre-ASNA (intravenous nitroprusside/phenylephrine) before and after bilateral NTS microinjections of selective adenosine A(2a) receptor agonist (CGS-21680; 2.0, 20 pmol/50 nl), selective A(2a) receptor antagonist (ZM-241385; 40 pmol/100 nl), and nonselective A(1) + A(2a) receptor antagonist (8-SPT; 1 nmol/100 nl) in urethane/alpha-chloralose anesthetized rats. Activation of A(2a) receptors decreased the range, upper plateau, and gain of baroreflex-response curves for RSNA, whereas these parameters all increased for pre-ASNA, consistent with direct effects of the agonist on regional sympathetic activity. However, no resetting of baroreflex-response curves along the MAP axis occurred despite the marked decreases in baseline MAP. The antagonists had no marked effects on baseline variables or baroreflex-response functions. We conclude that the activation of NTS A(2a) adenosine receptors differentially alters baroreflex control of HR, RSNA, and pre-ASNA mostly via non-baroreflex mechanism(s), and these receptors have virtually no tonic action on baroreflex control of these sympathetic outputs.

  9. Postprandial gastric, pancreatic, and biliary response to histamine H2-receptor antagonists active duodenal ulcer.

    PubMed

    Longstreth, G F; Go, V L; Malagelada, J R

    1977-01-01

    Histamine H2-receptor antagonists are potentially useful agents in duodenal ulcer and knowledge of their effect on postprandial digestive events will contribute to their clinical application. We studied the effect of 200- and 300-mg doses of cimetidine, an H2-receptor antagonist, taken with an ordinary meal, on gastric, pancreatic, and biliary function. Both doses significantly reduced acid output and its delivery into the duodenum. Gastric secretory volume and pepsin output were less affected. Acid inhibition was related to blood drug levels and was less than that previously found at night in nocturnal fasting studies. As the stomach emptied the food, the gastric pH rose. The fractional gastric emptying rate, pancreatic enzyme, and bile acid outputs were unaltered. Cimetidine taken orally with meals at these doses is a potent gastric antisecretory agent without affecting other postprandial gastric, pancreatic, or biliary functions.

  10. C-C chemokine receptor type 4 antagonist Compound 22 ameliorates experimental autoimmune encephalomyelitis.

    PubMed

    Moriguchi, Kota; Miyamoto, Katsuichi; Tanaka, Noriko; Ueno, Rino; Nakayama, Takashi; Yoshie, Osamu; Kusunoki, Susumu

    2016-02-15

    Chemokines and chemokine receptors play important roles in the immune response. We previously reported the pathogenic role of C-C chemokine receptor type 4 (CCR4) in experimental autoimmune encephalomyelitis (EAE). Here, we examined whether CCR4 antagonism modulates the disease course of EAE. Wild-type and CCR4-knockout mice were induced EAE and were administered Compound 22, an antagonist of CCR4. Compound 22 significantly ameliorated the severity of EAE in wild-type mice, but not in the CCR4-knockout mice. Compound 22 inhibited Th1 and Th17 polarization of antigen-induced T-cell responses. Therefore, CCR4 antagonists might be potential therapeutic agents for multiple sclerosis. PMID:26857495

  11. Biaryls as potent, tunable dual neurokinin 1 receptor antagonists and serotonin transporter inhibitors.

    PubMed

    Degnan, Andrew P; Tora, George O; Han, Ying; Rajamani, Ramkumar; Bertekap, Robert; Krause, Rudolph; Davis, Carl D; Hu, Joanna; Morgan, Daniel; Taylor, Sarah J; Krause, Kelly; Li, Yu-Wen; Mattson, Gail; Cunningham, Melissa A; Taber, Matthew T; Lodge, Nicholas J; Bronson, Joanne J; Gillman, Kevin W; Macor, John E

    2015-08-01

    Depression is a serious illness that affects millions of patients. Current treatments are associated with a number of undesirable side effects. Neurokinin 1 receptor (NK1R) antagonists have recently been shown to potentiate the antidepressant effects of serotonin-selective reuptake inhibitors (SSRIs) in a number of animal models. Herein we describe the optimization of a biaryl chemotype to provide a series of potent dual NK1R antagonists/serotonin transporter (SERT) inhibitors. Through the choice of appropriate substituents, the SERT/NK1R ratio could be tuned to afford a range of target selectivity profiles. This effort culminated in the identification of an analog that demonstrated oral bioavailability, favorable brain uptake, and efficacy in the gerbil foot tap model. Ex vivo occupancy studies with compound 58 demonstrated the ability to maintain NK1 receptor saturation (>88% occupancy) while titrating the desired level of SERT occupancy (11-84%) via dose selection. PMID:26048800

  12. The antiparkinsonian drugs budipine and biperiden are use-dependent (uncompetitive) NMDA receptor antagonists.

    PubMed

    Jackisch, R; Kruchen, A; Sauermann, W; Hertting, G; Feuerstein, T J

    1994-10-24

    N-Methyl-D-aspartate- (NMDA-) evoked [3H]acetylcholine release in rabbit caudate nucleus slices was inhibited by the antiparkinsonian drugs budipine (1-tert-butyl-4,4-diphenylpiperidine) and biperiden (1-bicyclo[2.2.1.]hept-5-en-2-yl-1-phenyl-3-piperidino propanol) yielding functional Ki values of 4.6 and 8.8 microM. In contrast to the competitive antagonist 2-amino-5-phosphonopentaonate, budipine and biperidene significantly reduced both the apparent KD and the Emax value of NMDA. Moreover, they displaced [3H]MK-801 specifically bound to membranes of the same tissue, although with low affinity (IC50: 38 and 92 microM). It is concluded that budipine and biperiden are use-dependent (uncompetitive) antagonists at the NMDA receptor, binding to the receptor-linked ion channel, but probably not to the MK-801 binding site. NMDA antagonism may contribute to the antiparkinsonian effects of budipine.

  13. P2Y12 Receptor Antagonists and Morphine: A Dangerous Liaison?

    PubMed

    Giannopoulos, Georgios; Deftereos, Spyridon; Kolokathis, Fotios; Xanthopoulou, Ioanna; Lekakis, John; Alexopoulos, Dimitrios

    2016-09-01

    P2Y12 receptor antagonists, concurrently administered with aspirin in what has come to be commonly called dual antiplatelet therapy, are a mainstay of treatment for patients with acute coronary syndromes. Morphine, on the contrary, is a commonly used drug in the acute phase of acute coronary syndromes to relieve pain-with the added potential benefit of attenuating acutely raised sympathetic tone. In current guidelines, though, morphine is recommended with decreasing strength of recommendation. One reason is that it raises concern regarding the potentially significant interaction with antiplatelet agents, leading to impaired inhibition of platelet activation. In any case, it is still considered a mandatory part of the inventory of available medications in prehospital acute myocardial infarction management. The goal of the present review is to present published evidence on morphine and its potential interactions with P2Y12 receptor antagonists, as well as on the central issue of whether such interactions may underlie clinically significant effects on patient outcomes.

  14. Optimizing control of acromegaly: integrating a growth hormone receptor antagonist into the treatment algorithm.

    PubMed

    Clemmons, David R; Chihara, Kazuo; Freda, Pamela U; Ho, Ken K Y; Klibanski, Anne; Melmed, Shlomo; Shalet, Stephen M; Strasburger, Christian J; Trainer, Peter J; Thorner, Michael O

    2003-10-01

    Acromegaly is associated with significant morbidities and a 2- to 3-fold increase in mortality because of the excessive metabolic action of GH and IGF-I, a marker of GH output. Reductions in morbidity correspond with decreases in IGF-I, and mortality is lowered following normalization of IGF-I or GH levels. Therefore, this has become an important end point. Current guidelines for the treatment of acromegaly have not considered recent advances in medical therapy, in particular, the place of pegvisomant, a GH receptor antagonist. Treatment goals include normalizing biochemical markers, controlling tumor mass, preserving pituitary function, and relieving signs and symptoms. Surgery reduces tumor volume and is considered first-line therapy. Radiation reduces tumor volume and GH and IGF-I levels, but the onset of action is slow and hypopituitarism typically develops. Therefore, pharmacotherapy is often used following surgery or as first-line therapy for nonresectable tumors. Dopamine agonists can be considered in patients exhibiting minimal disease or those with GH-prolactin-cosecreting tumors but will not achieve hormone normalization in most patients. Somatostatin analogs effectively suppress GH and IGF-I in most patients, but intolerance (e.g. diarrhea, cramping, gallstones) can occur. Pegvisomant, the newest therapeutic option, blocks GH action at peripheral receptors, normalizes IGF-I levels, reduces signs and symptoms, and corrects metabolic defects. Pegvisomant does not appear to affect tumor size and has few adverse effects. Pegvisomant is the most effective drug treatment for acromegaly in normalizing IGF-I and producing a clinical response; it is the preferred agent in patients resistant to or intolerant of somatostatin analogs.

  15. Discovery and characterization of a potent and selective EP4 receptor antagonist.

    PubMed

    Schiffler, Matthew A; Chandrasekhar, Srinivasan; Fisher, Matthew J; Harvey, Anita; Kuklish, Steven L; Wang, Xu-Shan; Warshawsky, Alan M; York, Jeremy S; Yu, Xiao-Peng

    2015-08-15

    EP4 is a prostaglandin E2 receptor that is a target for potential anti-nociceptive therapy. Described herein is a class of amphoteric EP4 antagonists which reverses PGE2-induced suppression of TNFα production in human whole blood. From this class, a potent and highly bioavailable compound (6) has been selected for potential clinical studies. EP4 binding and functional data, selectivity, and pharmacokinetic properties of this compound are included.

  16. A novel series of glucagon receptor antagonists with reduced molecular weight and lipophilicity.

    PubMed

    Filipski, Kevin J; Bian, Jianwei; Ebner, David C; Lee, Esther C Y; Li, Jian-Cheng; Sammons, Matthew F; Wright, Stephen W; Stevens, Benjamin D; Didiuk, Mary T; Tu, Meihua; Perreault, Christian; Brown, Janice; Atkinson, Karen; Tan, Beijing; Salatto, Christopher T; Litchfield, John; Pfefferkorn, Jeffrey A; Guzman-Perez, Angel

    2012-01-01

    A novel series of glucagon receptor antagonists has been discovered. These pyrazole ethers and aminopyrazoles have lower molecular weight and increased polarity such that the molecules fall into better drug-like property space. This work has culminated in compounds 44 and 50 that were shown to have good pharmacokinetic attributes in dog, in contrast to rats, in which clearance was high; and compound 49, which demonstrated a dose-dependent reduction in glucose excursion in a rat glucagon challenge experiment.

  17. Characterization of protoberberine analogs employed as novel human P2X{sub 7} receptor antagonists

    SciTech Connect

    Lee, Ga Eun; Lee, Won-Gil; Lee, Song-Yi; Lee, Cho-Rong; Park, Chul-Seung; Chang, Sunghoe; Park, Sung-Gyoo; Song, Mi-Ryoung; Kim, Yong-Chul

    2011-04-15

    The P2X{sub 7} receptor (P2X{sub 7}R), a member of the ATP-gated ion channel family, is regarded as a promising target for therapy of immune-related diseases including rheumatoid arthritis and chronic pain. A group of novel protoberberine analogs (compounds 3-5), discovered by screening of chemical libraries, was here investigated with respect to their function as P2X{sub 7}R antagonists. Compounds 3-5 non-competitively inhibited BzATP-induced ethidium ion influx into hP2X{sub 7}-expressing HEK293 cells, with IC{sub 50} values of 100-300 nM. This antagonistic action on the channel further confirmed that both BzATP-induced inward currents and Ca{sup 2+} influx were strongly inhibited by compounds 3-5 in patch-clamp and Ca{sup 2+} influx assays. The antagonists also effectively suppressed downstream signaling of P2X{sub 7} receptors including IL-1{beta} release and phosphorylation of ERK1/2 and p38 proteins in hP2X{sub 7}-expressing HEK293 cells or in differentiated human monocytes (THP-1 cells). Moreover, IL-2 secretion from CD3/CD28-stimulated Jurkat T cell was also dramatically inhibited by the antagonist. These results imply that novel protoberberine analogs may modulate P2X{sub 7} receptor-mediated immune responses by allosteric inhibition of the receptor. - Graphical abstract: Display Omitted

  18. In vitro availability studies of enoxacin in presence of H2 receptor antagonists.

    PubMed

    Arayne, M Saeed; Sultana, Najma; Haroon, Urooj; Hamza, Erum

    2007-07-01

    Enoxacin is a second-generation quinolone with increased antibacterial activity both in potency as well as in terms of broad spectrum against a wide range of clinically important pathogens over the first generation quinolones and produces its effect by inhibiting bacterial enzyme DNA gyrase. There are a number of drug interactions reported for enoxacin. On the other hand H2-receptor antagonists block gastric acid secretion and some cardiovascular effects of histamine. As the later drugs are used for a long-term therapy, they may be coadministered with other drugs. In present study in vitro release of enoxacin in presence of cimetidine, ranitidine and famotidine has been studied on a B.P. 2003 dissolution test apparatus and compared with the availability of enoxacin and H2-receptor antagonists alone. The interacting drugs were analyzed spectrophotometrically. These studies were carried out in simulated gastric juice, simulating empty stomach, simulated intestinal juice (pH 9) and buffers of pH 7.4 simulating blood pH at 37 degrees C. In order to support these interaction studies, the effect of H2-receptor antagonists on the antibacterial efficacy (MIC) of enoxacin was also studied by turbidity method and compared with parent drug against Staphylococcus aureus, Streptococcus pyogens, Streptococcus pneumoniae, Enterococcus, Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis and Bacillus subtilis. On the basis of these results, it is suggested that enoxacin should be coadministered with care along with H2-receptor antagonists especially in case of ranitidine, although chances of adverse reactions are rare but decrease in MIC of enoxacin may result in delayed effect or require prolonged use of the drug.

  19. Clinical pharmacokinetics and drug-drug interactions of endothelin receptor antagonists in pulmonary arterial hypertension.

    PubMed

    Venitz, Jürgen; Zack, Julia; Gillies, Hunter; Allard, Martine; Regnault, Jean; Dufton, Christopher

    2012-12-01

    The authors review the basic pharmacology and potential for adverse drug-drug interactions (DDIs) of bosentan and ambrisentan, the 2 endothelin receptor antagonists currently approved for pulmonary arterial hypertension (PAH) treatment. Bosentan, an endothelin (ET) receptor-type ET(A) and ET(B) antagonist, is metabolized to active metabolites by and an inducer of cytochrome P450 (CYP)2C9 and CYP3A. Ambrisentan, a selective ET(A) receptor antagonist, is metabolized primarily by uridine 5'diphosphate glucuronosyltransferases (UGTs) 1A9S, 2B7S, and 1A3S and, to a lesser extent, by CYP3A and CYP2C19. Drug interactions observed with bosentan DDI studies have demonstrated a potential for significant clinical implications during PAH management: bosentan is contraindicated with cyclosporine A and glyburide, and additional monitoring/dose adjustments are required when coadministered with hormonal contraceptives, simvastatin, lopinavir/ritonavir, and rifampicin. As bosentan carries a boxed warning regarding risks of liver injury and showed dose-dependant increases in serum aminotransferase abnormalities, drug interactions that increase bosentan exposure are of particular clinical concern. Ambrisentan DDI studies performed to date have shown only one clinically relevant DDI, an interaction with cyclosporine A that requires ambrisentan dose reduction. As the treatment of PAH moves toward multimodal combination therapy, scrutiny should be placed on ensuring that drug combinations achieve maximal clinical benefit while minimizing side effects.

  20. Dopamine D₄ Receptor Antagonists for the Treatment of Cocaine Use Disorders.

    PubMed

    Bergman, Jack; Rheingold, Curtis G

    2015-01-01

    The identification of effective medications for the management of cocaine use disorders remains an unmet public health challenge. In view of the prominent role of dopaminergic mechanisms in cocaine's abuse-related effects, research has focused on the development of subtype-selective dopamine D1-4 receptor antagonists. Here, we briefly recap the current status of this research effort, with a focus on several aspects of D4 research that may be pertinent to the consideration of D4 ligands in the development of candidate medications. Additionally, we present data from self administration studies in nonhuman primates showing that intravenous cocaine-maintained behavior is moderately, though non-significantly, decreased by doses of the D4-selective partial agonist Ro10-5824 and dramatically reduced by the D4- selective receptor antagonist NGD-94-1. The effects of these D4 ligands on cocaine self-administration were consistent among subjects and occurred in the absence of comparable effects on food-maintained responding. These data suggest that available D4 receptor antagonists should be investigated further as candidate medications for the management of cocaine use disorders. PMID:26022267

  1. Extended N-Arylsulfonylindoles as 5-HT₆ Receptor Antagonists: Design, Synthesis & Biological Evaluation.

    PubMed

    Vera, Gonzalo; Lagos, Carlos F; Almendras, Sebastián; Hebel, Dan; Flores, Francisco; Valle-Corvalán, Gissella; Pessoa-Mahana, C David; Mella-Raipán, Jaime; Montecinos, Rodrigo; Recabarren-Gajardo, Gonzalo

    2016-01-01

    Based on a known pharmacophore model for 5-HT₆ receptor antagonists, a series of novel extended derivatives of the N-arylsulfonyindole scaffold were designed and identified as a new class of 5-HT₆ receptor modulators. Eight of the compounds exhibited moderate to high binding affinities and displayed antagonist profile in 5-HT₆ receptor functional assays. Compounds 2-(4-(2-methoxyphenyl)piperazin-1-yl)-1-(1-tosyl-1H-indol-3-yl)ethanol (4b), 1-(1-(4-iodophenylsulfonyl)-1H-indol-3-yl)-2-(4-(2-methoxyphenyl)piperazin-1-yl)ethanol (4g) and 2-(4-(2-methoxyphenyl)piperazin-1-yl)-1-(1-(naphthalen-1-ylsulfonyl)-1H-indol-3-yl)ethanol (4j) showed the best binding affinity (4b pKi = 7.87; 4g pKi = 7.73; 4j pKi = 7.83). Additionally, compound 4j was identified as a highly potent antagonist (IC50 = 32 nM) in calcium mobilisation functional assay. PMID:27537868

  2. New insights into the stereochemical requirements of the bradykinin B2 receptor antagonists binding.

    PubMed

    Lupala, Cecylia S; Gomez-Gutierrez, Patricia; Perez, Juan J

    2016-01-01

    Bradykinin (BK) is a member of the kinin family, released in response to inflammation, trauma, burns, shock, allergy and some cardiovascular diseases, provoking vasodilatation and increased vascular permeability among other effects. Their actions are mediated through at least two G-protein coupled receptors, B1 a receptor up-regulated during inflammation episodes or tissue trauma and B2 that is constitutively expressed in a variety of cell types. The goal of the present work is to carry out a structure-activity study of BK B2 antagonism, taking into account the stereochemical features of diverse non-peptide antagonists and the way these features translate into ligand anchoring points to complementary regions of the receptor, through the analysis of the respective ligand-receptor complex. For this purpose an atomistic model of the BK B2 receptor was built by homology modeling and subsequently refined embedded in a lipid bilayer by means of a 600 ns molecular dynamics trajectory. The average structure from the last hundred nanoseconds of the molecular dynamics trajectory was energy minimized and used as model of the receptor for docking studies. For this purpose, a set of compounds with antagonistic profile, covering maximal diversity were selected from the literature. Specifically, the set of compounds include Fasitibant, FR173657, Anatibant, WIN64338, Bradyzide, CHEMBL442294, and JSM10292. Molecules were docked into the BK B2 receptor model and the corresponding complexes analyzed to understand ligand-receptor interactions. The outcome of this study is summarized in a 3D pharmacophore that explains the observed structure-activity results and provides insight into the design of novel molecules with antagonistic profile. To prove the validity of the pharmacophore hypothesized a virtual screening process was also carried out. The pharmacophore was used as query to identify new hits using diverse databases of molecules. The results of this study revealed a set of new

  3. Towards rational design of cannabinoid receptor 1 (CB1) antagonists for peripheral selectivity.

    PubMed

    Fulp, Alan; Bortoff, Katherine; Zhang, Yanan; Seltzman, Herbert; Snyder, Rodney; Maitra, Rangan

    2011-10-01

    CB1 receptor antagonists that are peripherally restricted were targeted. Compounds with permanent charge as well as compounds that have increased polar surface area were made and tested against CB1 for binding and activity. Sulfonamide and sulfamide with high polar surface area and good activity at CB1 were rationally designed and pharmacologically tested. Further optimization of these compounds and testing could lead to the development of a new class of therapeutics to treat disorders where the CB1 receptor system has been implicated. PMID:21875798

  4. Towards rational design of cannabinoid receptor 1 (CB1) antagonists for peripheral selectivity

    PubMed Central

    Fulp, Alan; Bortoff, Katherine; Zhang, Yanan; Seltzman, Herbert; Snyder, Rodney; Maitra, Rangan

    2011-01-01

    CB1 receptor antagonists that are peripherally restricted were targeted. Compounds with permanent charge as well as compounds that have increased polar surface area were made and tested against CB1 for binding and activity. Sulfonamide and sulfamide with high polar surface area and good activity at CB1 were rationally designed and pharmacologically tested. Further optimization of these compounds and testing could lead to the development of a new class of therapeutics to treat disorders where the CB1 receptor system has been implicated. PMID:21875798

  5. Evolution of physicochemical properties of melanin concentrating hormone receptor 1 (MCHr1) antagonists.

    PubMed

    Johansson, Anders

    2016-10-01

    One pharmacological principle for the treatment of obesity is blockade of the melanin concentrating hormone receptor 1 (MCHr1), which in rodents has been shown to be strongly associated with food intake and energy expenditure. However, discovery of safe and efficacious MCHr1 antagonists has proved to be complex. So far, six compounds have been progressed into clinical trials, but clinical validation of the concept is still lacking. An account of discovery of the three most recent clinical candidates targeting the MCHr1 receptor is given, with an emphasis on their physicochemical properties.

  6. Evolution of physicochemical properties of melanin concentrating hormone receptor 1 (MCHr1) antagonists.

    PubMed

    Johansson, Anders

    2016-10-01

    One pharmacological principle for the treatment of obesity is blockade of the melanin concentrating hormone receptor 1 (MCHr1), which in rodents has been shown to be strongly associated with food intake and energy expenditure. However, discovery of safe and efficacious MCHr1 antagonists has proved to be complex. So far, six compounds have been progressed into clinical trials, but clinical validation of the concept is still lacking. An account of discovery of the three most recent clinical candidates targeting the MCHr1 receptor is given, with an emphasis on their physicochemical properties. PMID:27595423

  7. New P2X3 receptor antagonists. Part 1: Discovery and optimization of tricyclic compounds.

    PubMed

    Szántó, Gábor; Makó, Attila; Bata, Imre; Farkas, Bence; Kolok, Sándor; Vastag, Mónika; Cselenyák, Attila

    2016-08-15

    Purinergic P2X3 receptors are trimeric ligand-gated ion channels whose antagonism is an appealing yet challenging and not fully validated drug development idea. With the aim of identification of an orally active, potent human P2X3 receptor antagonist compound that can penetrate the central nervous system, the compound collection of Gedeon Richter was screened. A hit series of tricyclic compounds was subjected to a rapid, two-step optimization process focusing on increasing potency, improving metabolic stability and CNS penetrability. Attempts resulted in compound 65, a potential tool compound for testing P2X3 inhibitory effects in vivo. PMID:27423478

  8. Novel dual endothelin receptor antagonist macitentan reverses severe pulmonary arterial hypertension in rats.

    PubMed

    Kunita-Takanezawa, Mutsumi; Abe, Kohtaro; Hirooka, Yoshitaka; Kuwabara, Yukimitsu; Hirano, Katsuya; Oka, Masahiko; Sunagawa, Kenji

    2014-11-01

    The efficacy of endothelin (ET) receptor antagonist bosentan in patients with severe pulmonary arterial hypertension (PAH) remains limited, partly because its higher doses for potential blockade of ET receptors have never been tested due to liver dysfunction. We hypothesized that rigorous blockade of ET receptors using the novel dual ET receptor antagonist macitentan would be effective in treating severe PAH without major side effects in a preclinical model appropriately representing the human disorder. In normal rats, 30 mg·kg·d of macitentan completely abolished big ET-1-induced increases in right ventricle (RV) systolic pressure. Adult male rats were injected with SU5416, a vascular endothelial growth factor blocker, and exposed to hypoxia for 3 weeks and then to normoxia for an additional 5 weeks (total 8 weeks). In intrapulmonary arterial rings isolated from rats with severe PAH, macitentan concentration dependently inhibited ET-1-induced contraction. Long-term treatment with macitentan (30 mg·kg·d, from week 3 to 8) reversed the high RV systolic pressure with preserved cardiac output. Development of RV hypertrophy, luminal occlusive lesions and medial wall thickening were also significantly improved without increasing serum levels of liver enzymes by macitentan. In conclusion, efficacious blockade of ET receptors with macitentan would reverse severe PAH without major adverse effects.

  9. Discovery of piperidine ethers as selective orexin receptor antagonists (SORAs) inspired by filorexant.

    PubMed

    Raheem, Izzat T; Breslin, Michael J; Bruno, Joseph; Cabalu, Tamara D; Cooke, Andrew; Cox, Christopher D; Cui, Donghui; Garson, Susan; Gotter, Anthony L; Fox, Steven V; Harrell, C Meacham; Kuduk, Scott D; Lemaire, Wei; Prueksaritanont, Thomayant; Renger, John J; Stump, Craig; Tannenbaum, Pamela L; Williams, Peter D; Winrow, Christopher J; Coleman, Paul J

    2015-02-01

    Highly selective orexin receptor antagonists (SORAs) of the orexin 2 receptor (OX2R) have become attractive targets both as potential therapeutics for insomnia as well as biological tools to help further elucidate the underlying pharmacology of the orexin signaling pathway. Herein, we describe the discovery of a novel piperidine ether 2-SORA class identified by systematic lead optimization beginning with filorexant, a dual orexin receptor antagonist (DORA) that recently completed Phase 2 clinical trials. Changes to the ether linkage and pendant heterocycle of filorexant were found to impart significant selectivity for OX2R, culminating in lead compound PE-6. PE-6 displays sub-nanomolar binding affinity and functional potency on OX2R while maintaining >1600-fold binding selectivity and >200-fold functional selectivity versus the orexin 1 receptor (OX1R). PE-6 bears a clean off-target profile, a good overall preclinical pharmacokinetic (PK) profile, and reduces wakefulness with increased NREM and REM sleep when evaluated in vivo in a rat sleep study. Importantly, subtle structural changes to the piperidine ether class impart dramatic changes in receptor selectivity. To this end, our laboratories have identified multiple piperidine ether 2-SORAs, 1-SORAs, and DORAs, providing access to a number of important biological tool compounds from a single structural class. PMID:25577040

  10. Possible Mechanisms for Functional Antagonistic Effect of Ferula assafoetida on Muscarinic Receptors in Tracheal Smooth Muscle

    PubMed Central

    Kiyanmehr, Majid; Boskabady, Mohammad Hossein; Khazdair, Mohammad Reza; Hashemzehi, Milad

    2016-01-01

    Background The contribution of histamine (H1) receptors inhibitory and/or β-adrenoceptors stimulatory mechanisms in the relaxant property of Ferula assa-foetida. (F. asafoetida) was examined in the present study. Methods We evaluated the effect of three concentrations of F. asafoetida extract (2.5, 5, and 10 mg/mL), a muscarinic receptors antagonist, and saline on methacholine concentration-response curve in tracheal smooth muscles incubated with β-adrenergic and histamine (H1) (group 1), and only β-adrenergic (group 2) receptors antagonists. Results EC50 values in the presence of atropine, extract (5 and 10 mg/mL) and maximum responses to methacholine due to the 10 mg/mL extract in both groups and 5 mg/mL extract in group 1 were higher than saline (P < 0.0001, P = 0.0477, and P = 0.0008 in group 1 and P < 0.0001, P = 0.0438, and P = 0.0107 in group 2 for atropine, 5 and 10 mg/mL extract, respectively). Values of concentration ratio minus one (CR-1), in the presence of extracts were lower than atropine in both groups (P = 0.0339 for high extract concentration in group 1 and P < 0.0001 for other extract concentrations in both groups). Conclusion Histamine (H1) receptor blockade affects muscarinic receptors inhibitory property of F. asafoetida in tracheal smooth muscle PMID:27540324

  11. Mineralocorticoid receptor antagonists, a class beyond spironolactone--Focus on the special pharmacologic properties of eplerenone.

    PubMed

    Seferovic, Petar M; Pelliccia, Francesco; Zivkovic, Ivana; Ristic, Arsen; Lalic, Nebojsa; Seferovic, Jelena; Simeunovic, Dejan; Milinkovic, Ivan; Rosano, Giuseppe

    2015-12-01

    The renin-angiotensin-aldosterone system can be blocked at specific levels by using different classes of pharmacologic agents, including angiotensin-converting-enzyme inhibitors, angiotensin II receptor blockers and mineralocorticoid receptor antagonists. Broad use of the latter, such as spironolactone, has been limited by significant incidence of gynecomastia and other sex-related adverse effects. These problems can be overcome with use of eplerenone, a selective mineralocorticoid receptor antagonist. Eplerenone has been specifically developed to bind selectively to the mineralocorticoid receptors in order to minimize binding to the progesterone and androgen receptors. In the last decade, multiple scientific evidences have been accumulated showing the efficacy and safety of the drug in multiple clinical conditions, including heart failure and arterial hypertension. Eplerenone is generally well tolerated, with the most frequent adverse event being hyperkalemia, with sexual adverse events (i.e. gynecomastia) being more uncommon, due to the selectivity of eplerenone. This review focuses on the pharmacodynamic and pharmacokinetic properties of eplerenone, thus providing the scientific basis to fully understand drug-to-drug interactions, in particular, and its efficacy and tolerability, in general. Noteworthy, the activity of eplerenone in special conditions and different patient populations is summarized.

  12. Clonidine potentiates the effects of 5-HT1A, 5-HT1B and 5-HT2A/2C antagonists and 8-OH-DPAT in the mouse forced swimming test.

    PubMed

    Redrobe, J P; Bourin, M

    1998-08-01

    The present study was undertaken to identify the receptor subtypes involved in clonidine's ability to enhance the effects of antidepressant drugs in the mouse forced swimming test. Clonidine (0.06 mg/kg, i.p.) significantly enhanced the antidepressant-like effects of subactive doses of the 5-HT1A receptor agonist, 8-OH-DPAT (1 mg/kg, i.p.; P<0.01); the 5-HT1A receptor antagonist, NAN 190 (0.5 mg/kg, i.p.; P<0.01); the 5-HT1A/1B autoreceptor antagonist, (+/-) pindolol (32 mg/kg, i.p.; P<0.01); the 5-HT2A/2C receptor antagonist, ritanserin (4 mg/kg, i.p.; P<0.01). Pretreatment with clonidine failed to increase mobility when administered in combination with the 5-HT1B receptor agonist, RU 24969 (1 mg/kg, i.p.) or the 5-HT2A receptor antagonist, ketanserin (8 mg/kg, i.p.). In conclusion, clonidine-induced anti-immobility effects are more likely mediated by 5-HT1A and 5-HT2C receptors, as well as alpha-2-adrenergic autoreceptors situated on noradrenergic neurones. The results of the present study also demonstrate that serotonergic receptor function can influence alpha-2-adrenoreceptor mediated responses in the mouse forced swimming test.

  13. Effects of A1 receptor agonist/antagonist on spontaneous seizures in pilocarpine-induced epileptic rats.

    PubMed

    Amorim, Beatriz Oliveira; Hamani, Clement; Ferreira, Elenn; Miranda, Maísa Ferreira; Fernandes, Maria José S; Rodrigues, Antonio M; de Almeida, Antônio-Carlos G; Covolan, Luciene

    2016-08-01

    Adenosine is an endogenous anticonvulsant that activates pre- and postsynaptic adenosine A1 receptors. A1 receptor agonists increase the latency for the development of seizures and status epilepticus following pilocarpine administration. Although hippocampal adenosine is increased in the chronic phase of the pilocarpine model, it is not known whether the modulation of A1 receptors may influence the frequency of spontaneous recurrent seizures (SRS). Here, we tested the hypothesis that the A1 receptor agonist RPia ([R]-N-phenylisopropyladenosine) and the A1 antagonist DPCPX (8-Cyclopentyl-1,3-dipropylxanthine) administered to chronic pilocarpine epileptic rats would respectively decrease and increase the frequency of SRS and hippocampal excitability. Four months after Pilo-induced SE, chronic epileptic rats were video-monitored for the recording of SRS before (basal) and after a 2-week treatment with RPia (25μg/kg) or DPCPX (50μg/kg). Following sacrifice, brain slices were studied with electrophysiology. We found that rats given RPia had a 93% nonsignificant reduction in the frequency of seizures compared with their own pretreatment baseline. In contrast, the administration of DPCPX resulted in an 87% significant increase in seizure rate. Nontreated epileptic rats had a similar frequency of seizures along the study. Corroborating our behavioral data, in vitro recordings showed that slices from animals previously given DPCPX had a shorter latency to develop epileptiform activity, longer and higher DC shifts, and higher spike amplitude compared with slices from nontreated Pilo controls. In contrast, smaller spike amplitude was recorded in slices from animals given RPia. In summary, the administration of A1 agonists reduced hippocampal excitability but not the frequency of spontaneous recurrent seizures in chronic epileptic rats, whereas A1 receptor antagonists increased both.

  14. Effects of A1 receptor agonist/antagonist on spontaneous seizures in pilocarpine-induced epileptic rats.

    PubMed

    Amorim, Beatriz Oliveira; Hamani, Clement; Ferreira, Elenn; Miranda, Maísa Ferreira; Fernandes, Maria José S; Rodrigues, Antonio M; de Almeida, Antônio-Carlos G; Covolan, Luciene

    2016-08-01

    Adenosine is an endogenous anticonvulsant that activates pre- and postsynaptic adenosine A1 receptors. A1 receptor agonists increase the latency for the development of seizures and status epilepticus following pilocarpine administration. Although hippocampal adenosine is increased in the chronic phase of the pilocarpine model, it is not known whether the modulation of A1 receptors may influence the frequency of spontaneous recurrent seizures (SRS). Here, we tested the hypothesis that the A1 receptor agonist RPia ([R]-N-phenylisopropyladenosine) and the A1 antagonist DPCPX (8-Cyclopentyl-1,3-dipropylxanthine) administered to chronic pilocarpine epileptic rats would respectively decrease and increase the frequency of SRS and hippocampal excitability. Four months after Pilo-induced SE, chronic epileptic rats were video-monitored for the recording of SRS before (basal) and after a 2-week treatment with RPia (25μg/kg) or DPCPX (50μg/kg). Following sacrifice, brain slices were studied with electrophysiology. We found that rats given RPia had a 93% nonsignificant reduction in the frequency of seizures compared with their own pretreatment baseline. In contrast, the administration of DPCPX resulted in an 87% significant increase in seizure rate. Nontreated epileptic rats had a similar frequency of seizures along the study. Corroborating our behavioral data, in vitro recordings showed that slices from animals previously given DPCPX had a shorter latency to develop epileptiform activity, longer and higher DC shifts, and higher spike amplitude compared with slices from nontreated Pilo controls. In contrast, smaller spike amplitude was recorded in slices from animals given RPia. In summary, the administration of A1 agonists reduced hippocampal excitability but not the frequency of spontaneous recurrent seizures in chronic epileptic rats, whereas A1 receptor antagonists increased both. PMID:27371881

  15. Adenosine receptor binding of the A1-selective antagonist (/sup 3/H)PD 116,948

    SciTech Connect

    Fergus, J.H.; Bruns, R.F.; Badger, E.W.; Bristol, J.A.; Hartman, J.D.; Santay, L.A.; Hays, S.J.; Huang, C.C.

    1986-03-05

    PD 116,948 (8-cyclopentyl-1,3-dipropylxanthine) is a potent adenosine (ado) antagonist which is highly selective for the A1 subtype of ado receptor, with an IC50 of 0.8 nM in (/sup 3/H)CHA binding to A1 receptors and 500 nM in (/sup 3/H)NECA binding to A2 receptors. (/sup 3/H)PD 116,948 (117 Ci/mmol) was prepared by reduction of the diallyl analog, and binding was performed at 25/sup 0/C in 2 ml of 50 mM Tris pH 7.7 for 60 min using membranes from 10 mg wet weight of rat whole brain, with 100 ..mu..M N/sup 6/-cyclopentylado used to define nonspecific binding. Under these conditions, (/sup 3/H)PD 116,948 bound to a single site with a K/sub d/ of 0.4 nM and a B/sub max/ of 46 pmol/g wet weight. Under optimal conditions, more than 99% of the binding of (/sup 3/H)PD 116,948 was specific. Affinities of ado agonists and antagonists versus 0.1 nM (/sup 3/H)PD 116,948 were highly consistent with binding to an A1 ado receptor. Substantial amounts of specific binding of (/sup 3/H)PD 116,948 were detected in testes and spleen, and smaller amounts were found in heart. (/sup 3/H)PD 116,948 should be a useful tool for labeling A1 receptors in the brain and other organs.

  16. Early Use of the NMDA Receptor Antagonist Ketamine in Refractory and Superrefractory Status Epilepticus

    PubMed Central

    Zeiler, F. A.

    2015-01-01

    Refractory status epilepticus (RSE) and superrefractory status epilepticus (SRSE) pose a difficult clinical challenge. Multiple cerebral receptor and transporter changes occur with prolonged status epilepticus leading to pharmacoresistance patterns unfavorable for conventional antiepileptics. In particular, n-methyl-d-aspartate (NMDA) receptor upregulation leads to glutamate mediated excitotoxicity. Targeting these NMDA receptors may provide a novel approach to otherwise refractory seizures. Ketamine has been utilized in RSE. Recent systematic review indicates 56.5% and 63.5% cessation in seizures in adults and pediatrics, respectively. No complications were described. We should consider earlier implementation of ketamine or other NMDA receptor antagonists, for RSE. Prospective study of early implementation of ketamine should shed light on the role of such medications in RSE. PMID:25649724

  17. Antitumor activity of neurokinin-1 receptor antagonists in MG-63 human osteosarcoma xenografts.

    PubMed

    Muñoz, Miguel; Berger, Michael; Rosso, Marisa; Gonzalez-Ortega, Ana; Carranza, Andrés; Coveñas, Rafael

    2014-01-01

    Osteosarcoma is a highly malignant bone tumor in children and adolescents. Aprepitant is a selective high‑affinity antagonist of the human neurokinin‑1 (NK‑1) receptor (NK1R) with robust antitumor activity. No data exist on the presence of NK1R in osteosarcoma and whether this tumor responds to NK1R antagonists. Here, we analyzed the expression of NK1R in the human osteosarcoma cell line MG-63 with western blot analysis and PCR and found significant expression both at the protein and mRNA levels. We further studied the growth inhibitory capacity of aprepitant and other NK1R antagonists on MG-63 in vitro using an MTS cytotoxicity assay and DAPI staining. All antagonists induced tumor growth inhibition and apoptosis. Synergism was observed for the combination of L-733,060 with common cytostatic drugs in MG-63, but not in non-malignant HEK293 cells. Pretreatment of HEK293 with L-733,060 prior to exposure to cytostatic drugs partially protected HEK293 cells from inhibition by these drugs. Furthermore, nanomolar concentrations of substance P (SP), the natural ligand of the NK1R, increased the growth rate of MG‑63 cells and micromolar concentrations of aprepitant inhibited SP-induced growth in a dose‑dependent manner. In vivo, a xenograft for MG-63 was created in nude mice and treated with peritumoral s.c. injections of fosaprepitant, which resulted in a significant reduction of tumor volume. Collectively, we demonstrated for the first time that the NK1R is expressed in human osteosarcoma cell line MG‑63 and that this receptor can be targeted with NK1R antagonists both in vitro as well as in vivo. PMID:24190675

  18. Serotonin (5-HT3) receptor antagonists for the reduction of symptoms of low anterior resection syndrome

    PubMed Central

    Itagaki, Ryohei; Koda, Keiji; Yamazaki, Masato; Shuto, Kiyohiko; Kosugi, Chihiro; Hirano, Atsushi; Arimitsu, Hidehito; Shiragami, Risa; Yoshimura, Yukino; Suzuki, Masato

    2014-01-01

    Purpose Serotonin (5-hydroxytryptamine [5-HT])3 receptor antagonists are effective for the treatment of diarrhea-predominant irritable bowel syndrome (IBS-D), in which exaggerated intestinal/colonic hypermotility is often observed. Recent studies have suggested that the motility disorder, especially spastic hypermotility, seen in the neorectum following sphincter-preserving operations for rectal cancer may be the basis of the postoperative defecatory malfunction seen in these patients. We investigated the efficacy of 5-HT3 receptor antagonists in patients suffering from severe low anterior resection syndrome. Patients and methods A total of 25 male patients with complaints of uncontrollable urgency or fecal incontinence following sphincter-preserving operations were enrolled in this study. Defecatory status, assessed on the basis of incontinence score (0–20), urgency grade (0–3), and number of toilet visits per day, was evaluated using a questionnaire before and 1 month after the administration of the 5-HT3 antagonist ramosetron. Results All the parameters assessed improved significantly after taking ramosetron for 1 month. The effect was more prominent in cases whose anastomotic line was lower, ie, inside the anal canal. Defecatory function was better in patients who commenced ramosetron therapy within 6 months postoperatively, as compared to those who were not prescribed ramosetron for more than 7 months postoperatively. Conclusion These results suggest that 5-HT3 antagonists are effective for the treatment of low anterior resection syndrome, as in diarrhea-predominant irritable bowel syndrome. The improvement in symptoms is not merely time dependent, but it is related to treatment with 5-HT3 antagonists. PMID:24648748

  19. Chemical function based pharmacophore generation of endothelin-A selective receptor antagonists.

    PubMed

    Funk, Oliver F; Kettmann, Viktor; Drimal, Jan; Langer, Thierry

    2004-05-20

    Both quantitative and qualitative chemical function based pharmacophore models of endothelin-A (ET(A)) selective receptor antagonists were generated by using the two algorithms HypoGen and HipHop, respectively, which are implemented in the Catalyst molecular modeling software. The input for HypoGen is a training set of 18 ET(A) antagonists exhibiting IC(50) values ranging between 0.19 nM and 67 microM. The best output hypothesis consists of five features: two hydrophobic (HY), one ring aromatic (RA), one hydrogen bond acceptor (HBA), and one negative ionizable (NI) function. The highest scoring Hip Hop model consists of six features: three hydrophobic (HY), one ring aromatic (RA), one hydrogen bond acceptor (HBA), and one negative ionizable (NI). It is the result of an input of three highly active, selective, and structurally diverse ET(A) antagonists. The predictive power of the quantitative model could be approved by using a test set of 30 compounds, whose activity values spread over 6 orders of magnitude. The two pharmacophores were tested according to their ability to extract known endothelin antagonists from the 3D molecular structure database of Derwent's World Drug Index. Thereby the main part of selective ET(A) antagonistic entries was detected by the two hypotheses. Furthermore, the pharmacophores were used to screen the Maybridge database. Six compounds were chosen from the output hit lists for in vitro testing of their ability to displace endothelin-1 from its receptor. Two of these are new potential lead compounds because they are structurally novel and exhibit satisfactory activity in the binding assay. PMID:15139753

  20. Chemical function based pharmacophore generation of endothelin-A selective receptor antagonists.

    PubMed

    Funk, Oliver F; Kettmann, Viktor; Drimal, Jan; Langer, Thierry

    2004-05-20

    Both quantitative and qualitative chemical function based pharmacophore models of endothelin-A (ET(A)) selective receptor antagonists were generated by using the two algorithms HypoGen and HipHop, respectively, which are implemented in the Catalyst molecular modeling software. The input for HypoGen is a training set of 18 ET(A) antagonists exhibiting IC(50) values ranging between 0.19 nM and 67 microM. The best output hypothesis consists of five features: two hydrophobic (HY), one ring aromatic (RA), one hydrogen bond acceptor (HBA), and one negative ionizable (NI) function. The highest scoring Hip Hop model consists of six features: three hydrophobic (HY), one ring aromatic (RA), one hydrogen bond acceptor (HBA), and one negative ionizable (NI). It is the result of an input of three highly active, selective, and structurally diverse ET(A) antagonists. The predictive power of the quantitative model could be approved by using a test set of 30 compounds, whose activity values spread over 6 orders of magnitude. The two pharmacophores were tested according to their ability to extract known endothelin antagonists from the 3D molecular structure database of Derwent's World Drug Index. Thereby the main part of selective ET(A) antagonistic entries was detected by the two hypotheses. Furthermore, the pharmacophores were used to screen the Maybridge database. Six compounds were chosen from the output hit lists for in vitro testing of their ability to displace endothelin-1 from its receptor. Two of these are new potential lead compounds because they are structurally novel and exhibit satisfactory activity in the binding assay.

  1. Monomeric gremlin is a novel vascular endothelial growth factor receptor-2 antagonist

    PubMed Central

    Grillo, Elisabetta; Ravelli, Cosetta; Corsini, Michela; Ballmer-Hofer, Kurt; Zammataro, Luca; Oreste, Pasqua; Zoppetti, Giorgio; Tobia, Chiara; Ronca, Roberto; Presta, Marco; Mitola, Stefania

    2016-01-01

    Angiogenesis plays a key role in various physiological and pathological conditions, including inflammation and tumor growth. The bone morphogenetic protein (BMP) antagonist gremlin has been identified as a novel pro-angiogenic factor. Gremlin promotes neovascular responses via a BMP-independent activation of the vascular endothelial growth factor (VEGF) receptor-2 (VEGFR2). BMP antagonists may act as covalent or non-covalent homodimers or in a monomeric form, while VEGFRs ligands are usually dimeric. However, the oligomeric state of gremlin and its role in modulating the biological activity of the protein remain to be elucidated. Here we show that gremlin is expressed in vitro and in vivo both as a monomer and as a covalently linked homodimer. Mutagenesis of amino acid residue Cys141 prevents gremlin dimerization leading to the formation of gremlinC141A monomers. GremlinC141A monomer retains a BMP antagonist activity similar to the wild-type dimer, but is devoid of a significant angiogenic capacity. Notably, we found that gremlinC141A mutant engages VEGFR2 in a non-productive manner, thus acting as receptor antagonist. Accordingly, both gremlinC141A and wild-type monomers inhibit angiogenesis driven by dimeric gremlin or VEGF-A165. Moreover, by acting as a VEGFR2 antagonist, gremlinC141A inhibits the angiogenic and tumorigenic potential of murine breast and prostate cancer cells in vivo. In conclusion, our data show that gremlin exists in multiple forms endowed with specific bioactivities and provide new insights into the molecular bases of gremlin dimerization. Furthermore, we propose gremlin monomer as a new inhibitor of VEGFR2 signalling during tumor growth. PMID:27174917

  2. Similarities and Distinctions in Actions of Surface-Directed and Classic Androgen Receptor Antagonists.

    PubMed

    Suh, Ji Ho; Chattopadhyay, Arundhati; Sieglaff, Douglas H; Storer Samaniego, Cheryl; Cox, Marc B; Webb, Paul

    2015-01-01

    The androgen receptor (AR) surface-directed antagonist MJC13 inhibits AR function and proliferation of prostate cancer (PC) cells. These effects are related to arrest of an AR/chaperone complex in the cytoplasm. Here, we compared MJC13 and classic AR antagonists such as flutamide and bicalutamide. Microarray analysis and confirmatory qRT-PCR reveals that MJC13 and flutamide inhibit dihydrotestosterone (DHT)-dependent genes in LNCaP PC cells. Both compounds are equally effective on a genome wide basis and as effective as second generation AR antagonists (MDV3100, ARN-509) at selected genes. MJC13 inhibits AR binding to the prostate specific antigen (PSA) promoter more strongly than flutamide, consistent with different mechanisms of action. Examination of efficacy of MJC13 in conditions that reflect aspects castrate resistant prostate cancer (CRPC) reveals that it inhibits flutamide activation of an AR mutant (ART877A) that emerges during flutamide withdrawal syndrome, but displays greatly restricted gene-specific activity in 22Rv1 cells that express a constitutively active truncated AR and is inactive against glucocorticoid receptor (GR), which can co-opt androgen-dependent signaling networks in CRPC. Importantly, MJC13 inhibits AR interactions with SRC2 and β-catenin in the nucleus and, unlike flutamide, strongly inhibits amplification of AR activity obtained with transfected SRC2 and β-catenin. MJC13 also inhibits DHT and β-catenin-enhanced cell division in LNCaP cells. Thus, a surface-directed antagonist can block AR activity in some conditions in which a classic antagonist fails and may display utility in particular forms of CRPC.

  3. Antidepressant-Like Effects of κ-Opioid Receptor Antagonists in Wistar Kyoto Rats

    PubMed Central

    Carr, Gregory V; Bangasser, Debra A; Bethea, Thelma; Young, Matthew; Valentino, Rita J; Lucki, Irwin

    2010-01-01

    The Wistar Kyoto (WKY) rat strain is a putative genetic model of comorbid depression and anxiety. Previous research showing increased κ-opioid receptor (KOR) gene expression in the brains of WKY rats, combined with studies implicating the KOR in animal models of depression and anxiety, suggests that alterations in the KOR system could have a role in the WKY behavioral phenotype. Here, the effects of KOR antagonists in the forced swim test (FST) were compared with the WKY and the Sprague–Dawley (SD) rat strains. As previously reported, WKY rats showed more immobility behavior than SD rats. The KOR antagonists selectively produced antidepressant-like effects in the WKY rats. By contrast, the antidepressant desipramine reduced immobility in both strains. Brain regions potentially underlying the strain-specific effects of KOR antagonists in the FST were identified using c-fos expression as a marker of neuronal activity. The KOR antagonist nor-binaltorphimine produced differential effects on the number of c-fos-positive profiles in the piriform cortex and nucleus accumbens shell between SD and WKY rats. The piriform cortex and nucleus accumbens also contained higher levels of KOR protein and dynorphin A peptide, respectively, in the WKY strain. In addition, local administration of nor-binaltorphimine directly into the piriform cortex produced antidepressant-like effects in WKY rats further implicating this region in the antidepressant-like response to KOR antagonists. These results support the use of the WKY rat as a model of affective disorders potentially involving KOR overactivity and provide more evidence that KOR antagonists could potentially be used as novel antidepressants. PMID:19924112

  4. Synthesis of 4-(aminoalkyl) substituted 1,3-dioxanes as potent NMDA and σ receptor antagonists.

    PubMed

    Utech, Tina; Köhler, Jens; Wünsch, Bernhard

    2011-06-01

    Elongation of the distance between the oxygen heterocycle and the basic amino moiety or ring expansion of the oxygen heterocycle of the NMDA receptor antagonists dexoxadrol and etoxadrol led to compounds with promising NMDA receptor affinity. Herein the combination of both structural features, i.e. elongation of the O-heterocycle--amine distance with a 1,3-dioxane ring is envisaged. The synthesis of aminoethyl-1,3-dioxanes 13, 22, 23 and 29 was performed by transacetalization of various acetals with pentane-1,3,5-triol, activation of the remaining free OH moiety with tosyl chloride and subsequent nucleophilic substitution. The corresponding 3-aminopropyl derivatives 33-35 were prepared by substitution of the tosylates with KCN and LiAlH4 reduction. The highest NMDA receptor affinity was found for 1,3-dioxanes with a phenyl and an ethyl residue at the acetalic position (23) followed by diphenyl (22) and monophenyl derivatives (13). Generally the NMDA affinity of primary amines is higher than the NMDA affinity of secondary and tertiary amines. Altogether the primary amine 23a (Ki=24 nM) represents the most promising NMDA receptor antagonist of this series exceeding the NMDA affinity of the mono-homologues (2-aminoethyl)-1,3-dioxolanes (3,4) and (aminomethyl)-1,3-dioxanes (5,6). Whereas the primary amine 23a turned out to be selective against σ1 and σ2 receptors the benzylamine 13d was identified as potent (Ki=19 nM) and selective σ1 antagonist, which showed extraordinarily high antiallodynic activity in the capsaicin assay. PMID:21444132

  5. Novel class of medications, orexin receptor antagonists, in the treatment of insomnia - critical appraisal of suvorexant.

    PubMed

    Norman, Jessica L; Anderson, Sarah L

    2016-01-01

    Insomnia, a highly prevalent disorder, can be detrimental to patients' overall health and worsen existing comorbidities. Patients may have acute episodes of insomnia related to a traumatic event, but more commonly insomnia occurs chronically. While proper sleep hygiene and behavioral therapy play important roles in the nonpharmacologic management of short-term and chronic insomnia, medications may also be required. Historically, insomnia has been treated with agents such as benzodiazepines, nonbenzodiazepine receptor agonists, and melatonin agonists. Dual orexin receptor antagonists represent a new class of medications for the treatment of insomnia, which block the binding of wakefulness-promoting neuropeptides orexin A and orexin B to their respective receptor sites. Suvorexant (Belsomra) is the first dual orexin receptor antagonist to be approved in the US and Japan and has demonstrated efficacy in decreasing time to sleep onset and increasing total sleep time. Its unique mechanism of action, data to support efficacy and safety over 12 months of use, and relative lack of withdrawal effects when discontinued may represent an alternative for patients with chronic insomnia who cannot tolerate or do not receive benefit from more traditional sleep agents. Suvorexant is effective and well tolerated, but precautions exist for certain patient populations, including females, obese patients, and those with respiratory disease. Suvorexant has only been studied vs placebo, and hence it is unknown how it directly compares with other medications approved by the US Food and Drug Administration for insomnia. Suvorexant is not likely to replace benzodiazepines or nonbenzodiazepine receptor antagonists as a first-line sleep agent but does represent a novel option for the treatment of patients with chronic insomnia. PMID:27471419

  6. Subtype selective NMDA receptor antagonists induce recovery of synapses lost following exposure to HIV-1 Tat

    PubMed Central

    Shin, AH; Kim, HJ; Thayer, SA

    2012-01-01

    BACKGROUND AND PURPOSE Neurocognitive disorders afflict approximately 20% of HIV-infected patients. HIV-1-infected cells in the brain shed viral proteins such as transactivator of transcription (Tat). Tat elicits cell death and synapse loss via processes initiated by NMDA receptor activation but mediated by separate downstream signalling pathways. Subunit selective NMDA receptor antagonists may differentially modulate survival relative to synaptic changes. EXPERIMENTAL APPROACH Tat-evoked cell death was quantified by measuring propidium iodide uptake into rat hippocampal neurons in culture. The effects of Tat on synaptic changes were measured using an imaging-based assay that quantified clusters of the scaffolding protein postsynaptic density 95 fused to green fluorescent protein. KEY RESULTS Dizocilpine, a non-competitive NMDA receptor antagonist, inhibited Tat-induced synapse loss, subsequent synapse recovery and Tat-induced cell death with comparable potencies. Memantine (10 µM) and ifenprodil (10 µM), which preferentially inhibit GluN2B-containing NMDA receptors, protected from Tat-induced cell death with no effect on synapse loss. Surprisingly, memantine and ifenprodil induced synapse recovery in the presence of Tat. In contrast, the GluN2A-prefering antagonist TCN201 prevented synapse loss and recovery with no effect on cell death. CONCLUSIONS AND IMPLICATIONS Synapse loss is a protective mechanism that enables the cell to cope with excess excitatory input. Thus, memantine and ifenprodil are promising neuroprotective drugs because they spare synaptic changes and promote survival. These GluN2B-preferring drugs induced recovery from Tat-evoked synapse loss, suggesting that synaptic pharmacology changed during the neurotoxic process. NMDA receptor subtypes differentially participate in the adaptation and death induced by excitotoxic insult. PMID:22142193

  7. A neutral CB1 receptor antagonist reduces weight gain in rat.

    PubMed

    Chambers, Adam P; Vemuri, V Kiran; Peng, Yan; Wood, Jodianne T; Olszewska, Teresa; Pittman, Quentin J; Makriyannis, Alexandros; Sharkey, Keith A

    2007-12-01

    Cannabinoid (CB)1 receptor inverse agonists inhibit food intake in animals and humans but also potentiate emesis. It is not clear whether these effects result from inverse agonist properties or from the blockade of endogenous cannabinoid signaling. Here, we examine the effect of a neutral CB1 antagonist, AM4113, on food intake, weight gain, and emesis. Neutral antagonist and binding properties were confirmed in HEK-293 cells transfected with human CB1 or CB2 receptors. AM4113 had no effect on forskolin-stimulated cAMP production at concentrations up to 630 nM. The Ki value of AM4113 (0.80 +/- 0.44 nM) in competitive binding assays with the CB1/2 agonist [3H]CP55,940 was 100-fold more selective for CB1 over CB2 receptors. We determined that AM4113 antagonized CB1 receptors in brain by blocking hypothermia induced by CP55,940. AM4113 (0-20 mg/kg) significantly reduced food intake and weight gain in rat. Compared with AM251, higher doses of AM4113 were needed to produce similar effects on food intake and body weight. Unlike AM251 (5 mg/kg), a highly anorectic dose of AM4113 (10 mg/kg) did not significantly potentiate vomiting induced by the emetic morphine-6-glucoronide. We show that a centrally active neutral CB1 receptor antagonist shares the appetite suppressant and weight loss effects of inverse agonists. If these compounds display similar properties in humans, they could be developed into a new class of antiobesity agents. PMID:17959701

  8. In vitro pharmacological characterization of vorapaxar, a novel platelet thrombin receptor antagonist.

    PubMed

    Hawes, Brian E; Zhai, Ying; Hesk, David; Wirth, Mark; Wei, Huijun; Chintala, Madhu; Seiffert, Dietmar

    2015-09-01

    Vorapaxar is a novel protease-activated receptor-1 (PAR1) antagonist recently approved for the reduction of thrombotic cardiovascular events in patients with a history of myocardial infarction or with peripheral arterial disease. The present study provides a comprehensive in vitro pharmacological characterization of vorapaxar interaction with the PAR1 receptor on human platelets. Similar studies were performed with a metabolite of vorapaxar (M20). Vorapaxar and M20 were competitive PAR1 antagonists that demonstrated concentration-dependent, saturable, specific, and slowly reversible binding to the receptor present on intact human platelets. The affinities of vorapaxar and M20 for the PAR1 receptor were in the low nanomolar range, as determined by saturation-, kinetic- and competitive binding studies. The calculated Kd and Ki values for vorapaxar increased in the presence of plasma, indicating a decrease in the free fraction available for binding to the PAR1 receptor on human platelets. Vorapaxar was also evaluated in functional assays using thrombin or a PAR1 agonist peptide (SFLLRN). Vorapaxar and M20 completely blocked thrombin-stimulated PAR1/β-arrestin association in recombinant cells and abolished thrombin-stimulated calcium influx in washed human platelets and vascular smooth muscle cells. Moreover, vorapaxar and M20 inhibited PAR1 agonist peptide-mediated platelet aggregation in human platelet rich plasma with a steep concentration response relationship. Vorapaxar exhibited high selectivity for inhibition of PAR1 over other platelet GPCRs. In conclusion, vorapaxar is a potent PAR1 antagonist exhibiting saturable, reversible, selective binding with slow off-rate kinetics and effectively inhibits thrombin's PAR1-mediated actions on human platelets. PMID:26022529

  9. Effect of prostanoid EP4 receptor antagonist, CJ-042,794, in rat models of pain and inflammation.

    PubMed

    Murase, Akio; Okumura, Takako; Sakakibara, Ayano; Tonai-Kachi, Hiroko; Nakao, Kazunari; Takada, Junji

    2008-02-01

    Recent study suggests that the proinflammatory and nociceptive effects of prostaglandin E(2) are mediated by prostanoid receptor subtype EP(4) and prostanoid EP(4) receptor may be a potential target for the treatment of inflammatory pain. Here we describe pharmacological characterization of a novel prostanoid EP(4) receptor antagonist, CJ-042,794 (4-{(1S)-1-[({5-chloro-2-[(4-fluorophenyl) oxy] phenyl} carbonyl) amino] ethyl} benzoic acid) in comparison with piroxicam (non-steroidal anti-inflammatory drug) or rofecoxib (cyclooxygenase-2 inhibitor). CJ-042,794 competitively antagonized cAMP accumulation with a pA(2) value of 8.7 in HEK293 cells overexpressing rat prostanoid EP(4) receptors. Orally administered CJ-042,794 dose-dependently inhibited carrageenan-induced mechanical hyperalgesia with an ED(50) value of 4.7 mg/kg (11 micromol/kg) and its maximal activity was somewhat less effective than that of 10 mg/kg piroxicam (30 micromol/kg p.o.). When CJ-042,794 and rofecoxib were administered to adjuvant-induced arthritis rats on Days 12-22 twice daily, both compounds reversed paw swelling to normal levels. These results suggest that a pharmacological blockade of the prostanoid EP(4) receptor may represent a new therapeutic strategy in signs and symptomatic relief of osteoarthritis and/or rheumatoid arthritis.

  10. Pharmacological characteristics of liriodenine, isolated from Fissistigma glaucescens, a novel muscarinic receptor antagonist in guinea-pigs.

    PubMed

    Lin, C H; Chang, G J; Su, M J; Wu, Y C; Teng, C M; Ko, F N

    1994-09-01

    1. The pharmacological activities of liriodenine, isolated from Fissistigma glaucescens, were determined in isolated trachea, ileum and cardiac tissues of guinea-pigs. 2. Liriodenine was found to be a muscarinic receptor antagonist in guinea-pig trachea as revealed by its competitive antagonism of carbachol (pA2 = 6.22 +/- 0.08)-induced smooth muscle contraction. It was slightly more potent than methoctramine (pA2 = 5.92 +/- 0.05), but was less potent than atropine (pA2 = 8.93 +/- 0.07), pirenzepine (pA2 = 7.02 +/- 0.09) and 4-diphenylacetoxy-N-methylpiperidine (4-DAMP, pA2 = 8.72 +/- 0.07). 3. Liriodenine was also a muscarinic antagonist in guinea-pig ileum (pA2 = 6.36 +/- 0.10) with a pA2 value that closely resembled that obtained in the trachea. 4. Liriodenine was 10 fold less potent in atrial preparations (left atria, pA2 = 5.24 +/- 0.04; right atria, pA2 = 5.35 +/- 0.09 and 5.28 +/- 0.07 for inotropic and chronotropic effects, respectively) than in smooth muscle preparations. 5. High concentration of liriodenine (300 microM) partially depressed the contractions induced by U-46619, histamine, prostaglandin F2 alpha, neurokinin A, leukotriene C4 and high K+ in the guinea-pig trachea. The inhibitions were characterized by a rightward shift in the concentration-response curves with suppression of their maximal contraction. 6. High concentration of liriodenine (300 microM) did not affect U-46619- or neurokinin A-induced tracheal contraction in the presence of nifedipine (1 microM) or in Ca(2+)-free (containing 0.2 mM EGTA) medium. 7. Neither cyclic AMP nor cyclic GMP content of guinea-pig trachealis was changed by liriodenine (30-300 microM). 8. It is concluded that liriodenine is a selective muscarinic receptor antagonist in isolated trachea, ileum and cardiac tissues of guinea-pigs. It is more potent in smooth muscle than in cardiac preparations. It also acts as a blocker of voltage-dependent Ca2+ channels at a high concentration (300 microM).

  11. Computational Discovery and Experimental Confirmation of TLR9 Receptor Antagonist Leads.

    PubMed

    Zatsepin, Maria; Mattes, Angela; Rupp, Steffen; Finkelmeier, Doris; Basu, Arijit; Burger-Kentischer, Anke; Goldblum, Amiram

    2016-09-26

    Toll-like receptors (TLR) are receptors of innate immunity that recognize pathogen associated molecular patterns. They play a critical role in many pathological states, in acute and chronic inflammatory processes. TLR9 is a promising target for drug discovery, since it has been implicated in several pathologies, including defense against viral infections and psoriasis. Immune-modulators are promising molecules for therapeutic intervention in these indications. TLR9 is located in the endosome and activated by dsDNA with CpG motives encountered in microbial DNA. Here we report on a combined approach to discover new TLR9 antagonists by computational chemistry and cell based assays. We used our in-house iterative stochastic elimination (ISE) algorithm to create models that distinguish between TLR9 antagonists ("actives") and other molecules ("inactives"), based on molecular physicochemical properties. Subsequent screening and scoring of a data set of 1.8 million commercially available molecules led to the purchasing of top scored molecules, which were tested in a new cell based system based on human pattern recognition receptors (PRRs) stably expressed in NIH3T3 fibroblasts. As described previously, this cell line shows a very low endogenous PRR-activity and contains a reporter gene which is selectively activated by the integrated human PRR enabling rapid screening of potential ligands. IC50 values of each of these top scored molecules were determined. Out of 60 molecules tested, 56 showed antagonistic activity. We discovered 21 new highly potential antagonists with IC50 values lower than 10 μM, with 5 of them having IC50 values under 1 μM. PMID:27537371

  12. Prostaglandin E receptor EP4 antagonist suppresses osteolysis due to bone metastasis of mouse malignant melanoma cells.

    PubMed

    Takita, Morichika; Inada, Masaki; Maruyama, Takayuki; Miyaura, Chisato

    2007-02-01

    We examined the effects of prostaglandin E (PGE) receptor subtype EP4 antagonist on bone metastasis of cancer to clarify PGE's role in bone metastasis. Metastatic regions were detected in femurs accompanying severe bone loss in mice injected with B16 malignant melanoma cells. Administration of EP4 antagonist restored the bone loss induced by B16 melanoma. Adding B16 cells induced osteoclast formation in the coculture of bone marrow cells and osteoblasts without any exogenous bone-resorbing factor, and EP4 antagonist completely suppressed the osteoclast formation induced by B16 cells. Therefore, EP4 antagonist is a possible candidate for the therapy of bone metastasis of cancer.

  13. Prospective therapeutic agents for obesity: molecular modification approaches of centrally and peripherally acting selective cannabinoid 1 receptor antagonists.

    PubMed

    Sharma, Mayank Kumar; Murumkar, Prashant R; Kanhed, Ashish M; Giridhar, Rajani; Yadav, Mange Ram

    2014-05-22

    Presently, obesity is one of the major health problems in the developed as well as developing countries due to lack of physical work and increasing sedentary life style. Endocannabinoid system (ECS) and especially cannabinoid 1 (CB1) receptor play a key role in energy homeostasis. Food intake and energy storage is enhanced due to the stimulation of ECS hence, inhibition of ECS by blocking CB1 receptors could be a promising approach in the treatment of obesity. Rimonabant, a diaryl pyrazole was the first potent and selective CB1 receptor antagonist that was introduced into the market in 2006 but was withdrawn in 2008 due to its psychiatric side effects. Researchers all over the world are interested to develop peripherally acting potent and selective CB1 receptor antagonists having a better pharmacokinetic profile and therapeutic index. In this development process, pyrazole ring of rimonabant has been replaced by different bioisosteric scaffolds like pyrrole, imidazole, triazole, pyrazoline, pyridine etc. Variations in substituents around the pyrazole ring have also been done. New strategies were also employed for minimizing the psychiatric side effects by making more polar and less lipophilic antagonists/inverse agonists along with neutral antagonists acting peripherally. It has been observed that some of the peripherally acting compounds do not show adverse effects and could be used as potential leads for the further design of selective CB1 receptor antagonists. Chemical modification strategies used for the development of selective CB1 receptor antagonists are discussed here in this review.

  14. 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

  15. Antagonist-induced micro-opioid receptor up-regulation decreases G-protein receptor kinase-2 and dynamin-2 abundance in mouse spinal cord.

    PubMed

    Patel, Minesh; Gomes, Benedict; Patel, Chintan; Yoburn, Byron C

    2002-06-20

    Chronic treatment with opioid receptor antagonists has been shown to increase the density of micro-, delta- and kappa-opioid receptors in cell culture and in the intact animal. Although opioid receptor antagonist-induced up-regulation is a robust phenomenon, the mechanisms responsible for the increase in receptor density remain unclear. In the present study, changes in a kinase and a GTPase that have been implicated in G-protein-coupled receptor regulation were examined following opioid receptor antagonist treatment. Mice were implanted s.c. with a naltrexone pellet or placebo pellet. On the eighth day following implantation, spinal cord was removed and G-protein receptor kinase-2 (GRK-2) and dynamin-2 abundance were determined using a quantitative immunoblot approach. Changes in micro-opioid receptor density were also determined. Naltrexone treatment produced a significant (145%) increase in micro-opioid receptor density. Naltrexone treatment was associated with a significant 36% decrease in GRK-2 and 30% decrease in dynamin-2 abundance in spinal cord. These data raise the possibility that opioid receptor antagonist-induced micro-opioid receptor up-regulation in the intact animal may be due to a reduction in constitutive internalization of opioid receptors.

  16. Nonpeptidic urotensin-II receptor antagonists I: in vitro pharmacological characterization of SB-706375.

    PubMed

    Douglas, Stephen A; Behm, David J; Aiyar, Nambi V; Naselsky, Diane; Disa, Jyoti; Brooks, David P; Ohlstein, Eliot H; Gleason, John G; Sarau, Henry M; Foley, James J; Buckley, Peter T; Schmidt, Dulcie B; Wixted, William E; Widdowson, Katherine; Riley, Graham; Jin, Jian; Gallagher, Timothy F; Schmidt, Stanley J; Ridgers, Lance; Christmann, Lisa T; Keenan, Richard M; Knight, Steven D; Dhanak, Dashyant

    2005-07-01

    1. SB-706375 potently inhibited [(125)I]hU-II binding to both mammalian recombinant and 'native' UT receptors (K(i) 4.7+/-1.5 to 20.7+/-3.6 nM at rodent, feline and primate recombinant UT receptors and K(i) 5.4+/-0.4 nM at the endogenous UT receptor in SJRH30 cells). 2. Prior exposure to SB-706375 (1 microM, 30 min) did not alter [(125)I]hU-II binding affinity or density in recombinant cells (K(D) 3.1+/-0.4 vs 5.8+/-0.9 nM and B(max) 3.1+/-1.0 vs 2.8+/-0.8 pmol mg(-1)) consistent with a reversible mode of action. 3. The novel, nonpeptidic radioligand [(3)H]SB-657510, a close analogue of SB-706375, bound to the monkey UT receptor (K(D) 2.6+/-0.4 nM, B(max) 0.86+/-0.12 pmol mg(-1)) in a manner that was inhibited by both U-II isopeptides and SB-706375 (K(i) 4.6+/-1.4 to 17.6+/-5.4 nM) consistent with the sulphonamides and native U-II ligands sharing a common UT receptor binding domain. 4. SB-706375 was a potent, competitive hU-II antagonist across species with pK(b) 7.29-8.00 in HEK293-UT receptor cells (inhibition of [Ca(2+)](i)-mobilization) and pK(b) 7.47 in rat isolated aorta (inhibition of contraction). SB-706375 also reversed tone established in the rat aorta by prior exposure to hU-II (K(app) approximately 20 nM). 5. SB-706375 was a selective U-II antagonist with >/=100-fold selectivity for the human UT receptor compared to 86 distinct receptors, ion channels, enzymes, transporters and nuclear hormones (K(i)/IC(50)>1 microM). Accordingly, the contractile responses induced in isolated aortae by KCl, phenylephrine, angiotensin II and endothelin-1 were unaltered by SB-706375 (1 microM). 6. In summary, SB-706375 is a high-affinity, surmountable, reversible and selective nonpeptide UT receptor antagonist with cross-species activity that will assist in delineating the pathophysiological actions of U-II in mammals.

  17. Devazepide, a nonpeptide antagonist of CCK receptors, induces apoptosis and inhibits Ewing tumor growth.

    PubMed

    Carrillo, Jaime; Agra, Noelia; Fernández, Noemí; Pestaña, Angel; Alonso, Javier

    2009-08-01

    The Ewing family of tumors is a group of highly malignant tumors that mainly arise in bone and most often affect children and young adults in the first two decades of life. Despite the use of multimodal therapy, the long-term disease-free survival rate of patients with Ewing tumors is still disappointingly low, making the discovery of innovative therapeutic strategies all the more necessary. We have recently shown that cholecystokinin (CCK), a neuroendocrine peptide, involved in many biological functions, including cell growth and proliferation, is a relevant target of the EWS/FLI1 oncoprotein characteristic of Ewing tumors. CCK silencing inhibits cell proliferation and tumor growth in vivo, suggesting that CCK acts as an autocrine growth factor for Ewing cells. Here, we analyzed the impact of two CCK receptor antagonists, devazepide (a CCK1-R antagonist) and L365 260 (a CCK2-R antagonist), on the growth of Ewing tumor cells. Devazepide (10 micromol/l) inhibited cell growth of four different Ewing tumor cells in vitro (range 85-88%), whereas the effect of the CCK2-R antagonist on cell growth was negligible. In a mouse tumor xenograft model, devazepide reduced tumor growth by 40%. Flow cytometry experiments showed that devazepide, but not L365 260, induced apoptosis of Ewing tumor cells. In summary, devazepide induces cell death of Ewing tumor cells, suggesting that it could represent a new therapeutic approach in the management of Ewing's tumor patients.

  18. Non-peptide angiotensin II receptor antagonists: chemical feature based pharmacophore identification.

    PubMed

    Krovat, Eva M; Langer, Thierry

    2003-02-27

    Chemical feature based pharmacophore models were elaborated for angiotensin II receptor subtype 1 (AT(1)) antagonists using both a quantitative and a qualitative approach (Catalyst HypoGen and HipHop algorithms, respectively). The training sets for quantitative model generation consisted of 25 selective AT(1) antagonists exhibiting IC(50) values ranging from 1.3 nM to 150 microM. Additionally, a qualitative pharmacophore hypothesis was derived from multiconformational structure models of the two highly active AT(1) antagonists 4u (IC(50) = 0.2 nM) and 3k (IC(50) = 0.7 nM). In the case of the quantitative model, the best pharmacophore hypothesis consisted of a five-features model (Hypo1: seven points, one hydrophobic aromatic, one hydrophobic aliphatic, a hydrogen bond acceptor, a negative ionizable function, and an aromatic plane function). The best qualitative model consisted of seven features (Hypo2: 11 points, two aromatic rings, two hydrogen bond acceptors, a negative ionizable function, and two hydrophobic functions). The obtained pharmacophore models were validated on a wide set of test molecules. They were shown to be able to identify a range of highly potent AT(1) antagonists, among those a number of recently launched drugs and some candidates presently undergoing clinical tests and/or development phases. The results of our study provide confidence for the utility of the selected chemical feature based pharmacophore models to retrieve structurally diverse compounds with desired biological activity by virtual screening. PMID:12593652

  19. 3D-pharmacophere models for CC chemokine receptor 1 antagonists.

    PubMed

    Liu, Yixi; Andre, Philippe; Wei, Jing; Zhao, Kang

    2009-07-01

    The CC Chemokine Receptor 1 (CCR1) is closely related to various chronic inflammatory diseases like rheumatoid arthritis and multiple sclerosis, and plays a crucial role in transplant rejection. Inhibiting its activity with CCR1 antagonists has been proved to be effective in preventing some diseases. A number of in vivo experiments have been carried out to shed light on the underlying mechanism of the interactions between the CCR1 and its ligands. However, their conclusions are still controversial. In this study, ligand-based computational drug design is applied as a new and effective way to study the structure-activity relationship of CCR1 antagonists. Three-dimensional pharmacophore models were generated for CCR1 antagonists, using both HypoGen and HipHop algorithms in Catalyst software. Two optimal pharmacophore models were defined through careful qualification processes. Both of them have four features: one hydrogen-bond acceptor, one positive ionable and two hydrophobic groups. Additional information was obtained through comparison between the two models. Our results can be valuable tools for the discovery and development of specific, highly potent CCR1 antagonists. For Supplement material, please see the online version of the article. PMID:19689388

  20. Non-peptide angiotensin II receptor antagonists: chemical feature based pharmacophore identification.

    PubMed

    Krovat, Eva M; Langer, Thierry

    2003-02-27

    Chemical feature based pharmacophore models were elaborated for angiotensin II receptor subtype 1 (AT(1)) antagonists using both a quantitative and a qualitative approach (Catalyst HypoGen and HipHop algorithms, respectively). The training sets for quantitative model generation consisted of 25 selective AT(1) antagonists exhibiting IC(50) values ranging from 1.3 nM to 150 microM. Additionally, a qualitative pharmacophore hypothesis was derived from multiconformational structure models of the two highly active AT(1) antagonists 4u (IC(50) = 0.2 nM) and 3k (IC(50) = 0.7 nM). In the case of the quantitative model, the best pharmacophore hypothesis consisted of a five-features model (Hypo1: seven points, one hydrophobic aromatic, one hydrophobic aliphatic, a hydrogen bond acceptor, a negative ionizable function, and an aromatic plane function). The best qualitative model consisted of seven features (Hypo2: 11 points, two aromatic rings, two hydrogen bond acceptors, a negative ionizable function, and two hydrophobic functions). The obtained pharmacophore models were validated on a wide set of test molecules. They were shown to be able to identify a range of highly potent AT(1) antagonists, among those a number of recently launched drugs and some candidates presently undergoing clinical tests and/or development phases. The results of our study provide confidence for the utility of the selected chemical feature based pharmacophore models to retrieve structurally diverse compounds with desired biological activity by virtual screening.

  1. 3D-pharmacophere models for CC chemokine receptor 1 antagonists.

    PubMed

    Liu, Yixi; Andre, Philippe; Wei, Jing; Zhao, Kang

    2009-07-01

    The CC Chemokine Receptor 1 (CCR1) is closely related to various chronic inflammatory diseases like rheumatoid arthritis and multiple sclerosis, and plays a crucial role in transplant rejection. Inhibiting its activity with CCR1 antagonists has been proved to be effective in preventing some diseases. A number of in vivo experiments have been carried out to shed light on the underlying mechanism of the interactions between the CCR1 and its ligands. However, their conclusions are still controversial. In this study, ligand-based computational drug design is applied as a new and effective way to study the structure-activity relationship of CCR1 antagonists. Three-dimensional pharmacophore models were generated for CCR1 antagonists, using both HypoGen and HipHop algorithms in Catalyst software. Two optimal pharmacophore models were defined through careful qualification processes. Both of them have four features: one hydrogen-bond acceptor, one positive ionable and two hydrophobic groups. Additional information was obtained through comparison between the two models. Our results can be valuable tools for the discovery and development of specific, highly potent CCR1 antagonists. For Supplement material, please see the online version of the article.

  2. Heterogeneous receptor binding of classical quaternary muscarinic antagonists. I. Bovine tissue distribution.

    PubMed

    Roffel, A F; Ensing, K; in 't Hout, W G; de Zeeuw, R A; Zaagsma, J

    1991-01-01

    In competition experiments with the tertiary radioligand [3H]dexetimide, classical quaternary muscarinic antagonists like ipratropium bromide and N-methylscopolamine bromide distinguished two muscarinic binding sites in bovine brain (total brain minus cerebellum) membranes, in contrast to their tertiary analogues, atropine and scopolamine, which recognized only one binding site. This binding behavior was found to be almost identical in bovine striatal membranes, both in terms of binding affinities and proportions of high (Q1) and low (Q2) affinity binding sites. Both in total brain and in striatal membranes, the Q1/Q2 binding heterogeneity was independent of pirenzepine binding heterogeneity (M1/M2). In peripheral tissues, the binding properties of quaternary muscarinic antagonists varied. Whereas tertiary as well as quaternary compounds showed only high affinity binding towards muscarinic receptors in bovine atrial and left ventricular membranes, heterogeneous binding behavior was observed with quaternary but not with tertiary antagonists in bovine tracheal smooth muscle membranes. The tissue distribution found in the present study suggests that bovine tracheal smooth muscle contraction studies might shed light on the functional significance of the anomalous binding behavior of quaternary muscarinic antagonists. PMID:1824191

  3. 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

  4. Pharmacological activity of (-)-discretamine, a novel vascular alpha-adrenoceptor and 5-hydroxytryptamine receptor antagonist, isolated from Fissistigma glaucescens.

    PubMed

    Ko, F N; Yu, S M; Su, M J; Wu, Y C; Teng, C M

    1993-10-01

    1. The pharmacological activity of (-)-discretamine, isolated from Fissistigma glaucescens, was determined in rat isolated thoracic aorta, cardiac tissues and ventricular myocytes and guinea-pig isolated trachea. 2. (-)-Discretamine was found to be an alpha 1-adrenoceptor blocking agent in rat thoracic aorta as revealed by its competitive antagonism of noradrenaline (pA2 = 7.20 +/- 0.10)- or phenylephrine (pA2 = 7.60 +/- 0.09)-induced vasoconstriction. It was as potent as phentolamine (pA2 = 7.51 +/- 0.10), but was more potent than yohimbine (pA2 = 6.18 +/- 0.06). Removal of endothelium significantly increased the antagonistic potency of (-)-discretamine on noradrenaline (pA2 = 7.52 +/- 0.09)- or phenylephrine (pA2 = 7.90 +/- 0.09)-induced vasoconstriction. 3. (-)-Discretamine was also an alpha 2-adrenoceptor blocking agent (pA2 = 6.30 +/- 0.15) and a 5-hydroxytryptamine antagonist (pA2 = 6.87 +/- 0.06), both in rat aorta denuded of endothelium. 4. (-)-Discretamine protected alpha-adrenoceptors from alkylation by the irreversible blocking agent, phenoxybenzamine. 5. [3H]-inositol monophosphate formation caused by noradrenaline (3 microM) in rat thoracic aorta was suppressed by (-)-discretamine (10 and 30 microM) and prazosin (3 microM). 6. A high concentration of (-)-discretamine (30 microM) did not affect the contraction induced by the thromboxane receptor agonist U-46619, prostaglandin F2 alpha (PGF2 alpha), angiotensin II, high K+ or endothelin in rat aorta denuded of endothelium. Neither cyclic AMP nor cyclic GMP content of rat thoracic aorta was changed by (-)-discretamine. 7. Contraction of guinea-pig trachea caused by histamine, leukotriene C4 or carbachol was not affected by (-)-discretamine (30 microM). (-)-Discretamine also did not block beta l- or beta2-adrenoceptor-mediated responses induced by isoprenaline in rat right atria and guinea-pig trachea.8. A voltage clamp study in rat ventricular single myocytes revealed that sodium inward current, slow

  5. 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

  6. Conversion of the interleukin 1 receptor antagonist into an agonist by site-specific mutagenesis.

    PubMed Central

    Ju, G; Labriola-Tompkins, E; Campen, C A; Benjamin, W R; Karas, J; Plocinski, J; Biondi, D; Kaffka, K L; Kilian, P L; Eisenberg, S P

    1991-01-01

    Interleukin 1 (IL-1) receptor antagonist (IL-1ra) is a naturally occurring protein that binds to the IL-1 receptor present on T cells, fibroblasts, and other cell types and acts to block IL-1-induced responses. IL-1ra is a pure antagonist and has no agonist activity in in vitro or in vivo systems. By site-specific mutagenesis, an analog of IL-1ra was created that contained a substitution of a single amino acid, Lys-145----Asp. This analog, IL-1ra K145D, exhibited partial agonist activity in the D10.G4.1 cell proliferation assay. The newly acquired agonist activity could not be neutralized by antisera to IL-1 alpha or IL-1 beta, but it could be blocked by a monoclonal antibody to the T-cell IL-1 receptor. The analog also showed agonist activity as assayed by increased prostaglandin E2 synthesis from CHO cells expressing recombinant mouse IL-1 receptor. These results with IL-1ra K145D demonstrate the importance of the region surrounding the corresponding Asp-145 residue in IL-1 beta for triggering the biological response to IL-1. Images PMID:1826365

  7. Discovery of a 7-arylaminobenzimidazole series as novel CRF1 receptor antagonists.

    PubMed

    Mochizuki, Michiyo; Kori, Masakuni; Kono, Mitsunori; Yano, Takahiko; Sako, Yuu; Tanaka, Maiko; Kanzaki, Naoyuki; Gyorkos, Albert C; Corrette, Christopher P; Aso, Kazuyoshi

    2016-10-01

    A promising lead compound 1 of a benzimidazole series has been identified as a corticotropin-releasing factor 1 (CRF1) receptor antagonist. In this study, we focused on replacement of a 7-alkylamino group of 1, predicted to occupy a large lipophilic pocket of a CRF1 receptor, with an aryl group. During the course of this examination, we established new synthetic approaches to 2,7-diarylaminobenzimidazoles. The novel synthesis of 7-arylaminobenzimidazoles culminated in the identification of compounds exhibiting inhibitory activities comparable to the alkyl analog 1. A representative compound, p-methoxyanilino analog 16g, showed potent CRF binding inhibitory activity against a human CRF1 receptor and human CRF1 receptor antagonistic activity (IC50=27nM, 56nM, respectively). This compound exhibited ex vivo (125)I-Tyr(0) ((125)I-CRF) binding inhibitory activity in mouse frontal cortex, olfactory bulb, and pituitary gland at 20mg/kg after oral administration. In this report, we discuss the structure-activity-relationship of these 7-arylamino-1H-benzimidazoles and their synthetic method. PMID:27567079

  8. Synthesis and evaluation of novel angiotensin II receptor 1 antagonists as anti-hypertension drugs.

    PubMed

    Bao, Xiaolu; Zhu, Weibo; Zhang, Ruijing; Wen, Caihong; Wang, Li; Yan, Yijia; Tang, Hesheng; Chen, Zhilong

    2016-05-01

    Three new angiotensin II receptor 1 antagonists, 1, 2 and 3 were designed, synthesized and evaluated. The AT1 receptor-binding assays in vitro showed that all the synthesized compounds had nanomolar affinity for the AT1 receptor. From which compound 3 was found to be the most potent ligands with an IC50 value of 2.67±0.23 nM. Biological evaluation in vivo revealed that all the compounds could cause significant decrease on MBP in a dose dependent manner in spontaneously hypertensive rats, and compound 3 especially showed an efficient and long-lasting effect in reducing blood pressure, whose maximal response lowered 41 mmHg of MBP at 10mg/kg and 62 mmHg at 15 mg/kg after oral administration, the significant anti-hypertensive effect lasted beyond 12 h, which is better than the reference compound losartan. The pharmacokinetic experiments showed that compound 3 could be absorbed efficiently and metabolized smoothly both in blood and in tissues in Wistar rats. The acute toxicity assay suggested that it has low toxicity with the LD50 value of 2974.35 mg/kg. These results demonstrate that compound 3 is a potent angiotensin AT1 receptor antagonist which could be considered as a novel anti-hypertension candidate and deserved for further investigation. PMID:27004954

  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. The urotensin II receptor antagonist, urantide, protects against atherosclerosis in rats

    PubMed Central

    ZHAO, JUAN; YU, QUAN-XIN; KONG, WEI; GAO, HAI-CHENG; SUN, BO; XIE, YA-QIN; REN, LI-QUN

    2013-01-01

    The aim of this study was to explore the use of urantide as an antagonist of the urotensin II (UII) receptor, G protein-coupled receptor 14 (GPR14), to protect against atherosclerosis (AS) in rats. The AS rat model was induced by an intraperitoneal injection of vitamin D3 (VD3) into rats fed with a high-fat diet for four weeks. Urantide was then injected into the rats. Immunohistochemical staining, serum biochemical assay, reverse transcription-polymerase chain reaction (RT-PCR) and western blotting were used to investigate the expression of UII and its receptor GPR14 in the AS rat model. Four weeks after induction, pathological changes typical of AS were observed in the AS rat model. In the plaques of the aortic tunica intima and tunica media, expression of UII and GPR14 was observed. The protein and gene expression levels of UII and GPR14 in the model group were significantly increased compared with those in the normal group (P<0.01). Urantide ameliorated the pathological changes of AS in the rat model and reduced the gene and protein expression levels of UII and GPR14 (P<0.05 or P<0.01). UII is associated with AS and the UII receptor GPR14-specific antagonist, urantide, demonstrates the ability to protect against AS. Thus, this study provides new insight and experimental theories for the clinical application of urantide to treat AS. PMID:23837070

  11. Characterization of mechanisms involved in presynaptic inhibition of sympathetic pressor effects induced by some 5-HT1 receptor antagonists.

    PubMed

    Fernández, M M; Calama, E; Morán, A; Martín, M L; San Román, L

    2000-01-01

    1. In a previous study, we showed that the presynaptic inhibitory action of 5-hydroxytryptamine receptor agonists on sympathetic pressor effects obtained in the pithed rats were mainly mediated by activation of 5-HT1A and 5-HT1D receptor subtypes. At the time, we observed that some 5-HT1 receptors antagonists - WAY 100,635 and NAN-190 (both 5-HT1A receptor antagonists), methiothepin (a 5-HT1,2,5,6,7 receptor antagonist) and spiperone (a 5-HT1,2 receptor antagonist) - reduced per se the pressor effects obtained by electrical stimulation. The aim of the present work was to investigate the mechanism participating in this inhibitory effect. 2. The inhibition induced by WAY 100,635 (1000 microg kg-1, i.v.) was blocked after i.v. treatment with idazoxan, an alpha2-adrenoceptor antagonist (300 and 1000 microg kg-1) and was not modified after i.v. treatment with propranolol, a beta-adrenoceptor antagonist (1000 microg kg-1) and sulpiride, a D2 receptor antagonist (1000 microg kg-1). The inhibition induced by spiperone (500 microg kg-1 i.v.) was significantly blocked by sulpiride (1000 microg kg-1) and was not modified by idazoxan or propranolol. 3. Sulpiride (1000 microg kg-1) partially blocked the inhibition induced by methiothepin (50 microg kg-1 i.v.). Only pretreatment with idazoxan (300 microg kg-1) modified the inhibition induced by NAN-190 (100 microg kg-1 i.v.), such inhibition increasing after intravenous administration of idazoxan. 4. All the antagonists used in our experiments failed to inhibit the pressor responses elicited by i.v. noradrenaline administration. 5. The above results suggest that the inhibitory effects of these 5-HT1 receptor antagonists are presynaptic in nature, but not related to the blockade of 5-HT1 receptors subtypes. The simultaneous activation or inhibition of other receptor systems could explain the inhibition produced by each 5-HT1 receptor antagonist studied.

  12. Adenosine A2a receptors form distinct oligomers in protein detergent complexes.

    PubMed

    Schonenbach, Nicole S; Rieth, Monica D; Han, Songi; O'Malley, Michelle A

    2016-09-01

    The human adenosine A2a receptor (A2aR) tunes its function by forming homo-oligomers and hetero-oligomers with other G protein-coupled receptors, but the biophysical characterization of these oligomeric species is limited. Here, we show that upon reconstitution into an optimized mixed micelle system, and purification via an antagonist affinity column, full-length A2aR exists as a distribution of oligomers. We isolated the dimer population from the other oligomers via size exclusion chromatography and showed that it is stable upon dilution, thus supporting the hypotheses that the A2aR dimer has a defined structure and function. This study presents a crucial enabling step to a detailed biophysical characterization of A2aR homodimers. PMID:27543907

  13. Piperazine-2,3-dicarboxylic acid Derivatives as Dual Antagonists of NMDA and GluK1-Containing Kainate Receptors

    PubMed Central

    Irvine, Mark W.; Costa, Blaise M.; Dlaboga, Daniel; Culley, Georgia; Hulse, Richard; Scholefield, Caroline L.; Atlason, Palmi; Fang, Guangyu; Eaves, Richard; Morley, Richard; Mayo-Martin, Maria B.; Amici, Mascia; Bortolotto, Zuner A.; Donaldson, Lucy; Collingridge, Graham L.; Molnár, Elek; Monaghan, Daniel T.; Jane, David E.

    2011-01-01

    Competitive N-methyl-D-aspartate receptor (NMDAR) antagonists bind to the GluN2 subunit, of which there are four types (GluN2A-D). We report that some N1-substituted derivatives of cis-piperazine-2,3-dicarboxylic acid display improved relative affinity for GluN2C and GluN2D versus GluN2A and GluN2B. These derivatives also display subtype-selectivity among the more distantly related kainate receptor family. Compounds 18i and (−)-4 were the most potent kainate receptor antagonists and 18i was selective for GluK1 versus GluK2, GluK3 and AMPA receptors. Modeling studies revealed structural features required for activity at GluK1 subunits and suggested that S674 was vital for antagonist activity. Consistent with this hypothesis, replacing the equivalent residue in GluK3 (alanine) with a serine imparts 18i antagonist activity. Antagonists with dual GluN2D and GluK1 antagonist activity may have beneficial effects in various neurological disorders. Consistent with this idea, antagonist 18i (30 mg/Kg i.p.) showed antinociceptive effects in an animal model of mild nerve injury. PMID:22111545

  14. [Effect of the 5-HT3 receptor antagonist granisetron on estramustine phosphate sodium (Estracyt)-induced emesis in ferrets].

    PubMed

    Higashioka, Masaya; Yamaguchi, Emi; Takatori, Shingo; Tanaka, Mitsushi; Kyoi, Takashi

    2010-07-01

    Estracyt(R) is an antimitotic drug used for the treatment of prostate cancer, and its most common adverse effects are nausea and vomiting. In this study, we investigated the effect of a 5-HT3 receptor antagonist, granisetron, on emesis induced in ferrets by estramustine phosphate sodium (EMP), the active ingredient of Estracyt. To clarify the mechanism of action of EMP-induced emesis, we also investigated the effect of EMP on the release of serotonin (5-HT) in the isolated rat ileum. EMP (3 mg/kg, per os) induced 75.3+/-10.2 retching episodes and 7.5+/-1.3 vomiting episodes during a 2-h observation period. The latency to the first emetic response was 58.0+/-13.5 min. Granisetron (0.1 mg/kg, per os) administered 1 h before the administration of EMP reduced the number of EMP-induced retching and vomiting episodes to 1.3+/-1.3 and 1.0+/-1.0, respectively, and prolonged the latency by a factor of almost two. EMP (10-5 and 10-4 M) increased 5-HT release from isolated rat ileum, and 10 -7 M granisetron almost completely inhibited the increase induced by 10-4 M EMP. These results suggest that EMP induces nausea and vomiting via 5-HT release from the ileum, and that 5-HT3 receptor antagonists may be useful to prevent gastrointestinal adverse effects that occur during treatment with Estracyt.

  15. Natural variants of cytotoxic epitopes are T-cell receptor antagonists for antiviral cytotoxic T cells

    NASA Astrophysics Data System (ADS)

    Bertoletti, Antonio; Sette, Alessandro; Chisari, Francis V.; Penna, Amalia; Levrero, Massimo; Carli, Marco De; Fiaccadori, Franco; Ferrari, Carlo

    1994-06-01

    IT has been suggested that mutations within immunodominant cytotoxic T-lymphocyte (CTL) epitopes may be exploited by viruses to evade protective immune responses critical for clearance1-4. Viral escape could originate from passive mechanisms, such as mutations within crucial CTL epitopes, either affecting major histocompatibility complex binding or T-cell antigen receptor (TCR) recognition. Additionally, it has recently been shown that substitutions of TCR contact sites can yield analogue peptides that can still interact with the T-cell receptor but be unable to deliver a full stimulatory signal, thus inducing anergy5 or acting as an antagonist for the TCR6-8. We report here that hepatitis B virus isolates derived from two chronically infected patients display variant epitopes that act as natural TCR antagonists with the capacity to inhibit the CTL response to the wild-type epitope. During natural infection, TCR antagonist mutations of CTL epitopes could contribute to the development of viral persistence, especially if the antiviral CTL response is monospecific or the epitope is strongly immunodominant.

  16. Microbiome-Derived Tryptophan Metabolites and Their Aryl Hydrocarbon Receptor-Dependent Agonist and Antagonist Activities

    PubMed Central

    Jin, Un-Ho; Lee, Syng-Ook; Sridharan, Gautham; Lee, Kyongbum; Davidson, Laurie A.; Jayaraman, Arul; Chapkin, Robert S.; Alaniz, Robert

    2014-01-01

    The tryptophan metabolites indole, indole-3-acetate, and tryptamine were identified in mouse cecal extracts and fecal pellets by mass spectrometry. The aryl hydrocarbon receptor (AHR) agonist and antagonist activities of these microbiota-derived compounds were investigated in CaCo-2 intestinal cells as a model for understanding their interactions with colonic tissue, which is highly aryl hydrocarbon (Ah)–responsive. Activation of Ah-responsive genes demonstrated that tryptamine and indole 3-acetate were AHR agonists, whereas indole was an AHR antagonist that inhibited TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin)–induced CYP1A1 expression. In contrast, the tryptophan metabolites exhibited minimal anti-inflammatory activities, whereas TCDD decreased phorbol ester-induced CXCR4 [chemokine (C-X-C motif) receptor 4] gene expression, and this response was AHR dependent. These results demonstrate that the tryptophan metabolites indole, tryptamine, and indole-3-acetate modulate AHR-mediated responses in CaCo-2 cells, and concentrations of indole that exhibit AHR antagonist activity (100–250 μM) are detected in the intestinal microbiome. PMID:24563545

  17. Stereochemistry of quinoxaline antagonist binding to a glutamate receptor investigated by Fourier transform infrared spectroscopy.

    PubMed

    Madden, D R; Thiran, S; Zimmermann, H; Romm, J; Jayaraman, V

    2001-10-12

    The stereochemistry of the interactions between quinoxaline antagonists and the ligand-binding domain of the glutamate receptor 4 (GluR4) have been investigated by probing their vibrational modes using Fourier transform infrared spectroscopy. In solution, the electron-withdrawing nitro groups of both compounds establish a resonance equilibrium that appears to stabilize the keto form of one of the cyclic amide carbonyl bonds. Changes in the 6,7-dinitro-2,3-dihydroxyquinoxaline vibrational spectra on binding to the glutamate receptor, interpreted within the framework of a published crystal structure, illuminate the stereochemistry of the interaction and suggest that the binding site imposes a more polarized electronic bonding configuration on this antagonist. Similar spectral changes are observed for 6-cyano-7-dinitro-2,3-dihydroxyquinoxaline, confirming that its interactions with the binding site are highly similar to those of 6,7-dinitro-2,3-dihydroxyquinoxaline and leading to a model of the 6-cyano-7-dinitro-2,3-dihydroxyquinoxaline-S1S2 complex, for which no crystal structure is available. Conformational changes within the GluR ligand binding domain were also monitored. Compared with the previously reported spectral changes seen on binding of the agonist glutamate, only a relatively small change is detected on antagonist binding. This correlation between the functional effects of different classes of ligand and the magnitude of the spectroscopic changes they induce suggests that the spectral data reflect physiologically relevant conformational processes.

  18. Long-acting muscarinic receptor antagonists for the treatment of chronic airway diseases

    PubMed Central

    Palot, Alain; Sofalvi, Tunde; Pahus, Laurie; Gouitaa, Marion; Tummino, Celine; Martinez, Stephanie; Charpin, Denis; Bourdin, Arnaud; Chanez, Pascal

    2014-01-01

    Acetylcholine (neuronal and non-neuronal origin) regulates bronchoconstriction, and mucus secretion. It has an inflammatory effect by inducing attraction, survival and cytokine release from inflammatory cells. Muscarinic receptors throughout the bronchial tree are mainly restricted to muscarinic M1, M2 and M3 receptors. Three long-acting muscarinic receptor antagonists (LAMAs) were approved for the treatment of chronic obstructive pulmonary disease (COPD) in Europe: once-daily tiotropium bromide; once-daily glycopyrronium bromide; and twice-daily aclidinium bromide. All have higher selectivity for M3 receptors than for M2 receptors, and dissociate more slowly from the M3 receptors than they do from the M2 receptors. Some LAMAs showed anti-inflammatory effects [inhibition of neutrophil chemotactic activity and migration of alveolar neutrophils, decrease of several cytokines in the bronchoalveolar lavage (BAL) including interleukin (IL)-6, tumor necrosis factor (TNF)-α and leukotriene (LT)B4] and antiremodeling effects (inhibition of mucus gland hypertrophy and decrease in MUC5AC-positive goblet cell number, decrease in MUC5AC overexpression). In the clinic, LAMAs showed a significant improvement of forced expiratory volume in 1 second (FEV1), quality of life, dyspnea and reduced the number of exacerbations in COPD and more recently in asthma. This review will focus on the three LAMAs approved in Europe in the treatment of chronic airway diseases. PMID:24587893

  19. Identification and optimization of anthranilic sulfonamides as novel, selective cholecystokinin-2 receptor antagonists.

    PubMed

    Allison, Brett D; Phuong, Victor K; McAtee, Laura C; Rosen, Mark; Morton, Magda; Prendergast, Clodagh; Barrett, Terry; Lagaud, Guy; Freedman, Jamie; Li, Lina; Wu, Xiaodong; Venkatesan, Hariharan; Pippel, Marna; Woods, Craig; Rizzolio, Michèle C; Hack, Michael; Hoey, Kenway; Deng, Xiaohu; King, Christopher; Shankley, Nigel P; Rabinowitz, Michael H

    2006-10-19

    A high throughput screening approach to the identification of selective cholecystokinin-2 receptor (CCK-2R) ligands resulted in the discovery of a novel series of antagonists, represented by 1-[2-[(2,1,3-benzothiadiazol-4-ylsulfonyl)amino]-5-chlorobenzoyl]-piperidine (1; CCK-2R, pK(I) = 6.4). Preliminary exploration of the structure-activity relationships around the anthranilic ring and the amide and sulfonamide moieties led to a nearly 50-fold improvement of receptor affinity and showed a greater than 1000-fold selectivity over the related cholecystokinin-1 receptor. Pharmacokinetic evaluation led to the identification of 4-[4-iodo-2-[(5-quinoxalinylsulfonyl)amino]benzoyl]-morpholine, 26d, a compound that demonstrates promising pharmacokinetic properties in the rat and dog with respect to plasma clearance and oral bioavailability and is a potent inhibitor in vivo of pentagastrin-stimulated acid secretion in the rat when dosed orally.

  20. Enhanced attenuation of nicotine discrimination in rats by combining nicotine-specific antibodies with a nicotinic receptor antagonist.

    PubMed

    LeSage, Mark G; Shelley, David; Pravetoni, Marco; Pentel, Paul R

    2012-07-01

    Tobacco addiction requires activation by nicotine of a variety of central nicotinic acetylcholine receptors (nAChRs). In animals, both nAChR antagonists and immunization against nicotine can reduce nAChR activation by nicotine and block a variety of addiction-relevant behaviors. However, clinical use of nAChR antagonists for smoking cessation is limited by dose-related side effects, and immunization does not reliably produce sufficient antibody levels in smokers to enhance smoking cessation rates. Combining these approaches may be one way of addressing the limitations of each while enhancing overall efficacy. This study examined the individual and combined effects of passive immunization with the monoclonal nicotine-specific antibody Nic311 and the nicotinic receptor antagonist mecamylamine (MEC) on nicotine's discriminative stimulus effects. Rats were trained to discriminate 0.4 mg/kg of nicotine from saline using a two-lever operant discrimination procedure. Antagonism of nicotine discrimination by Nic311 (160 mg/kg i.v.) and ascending doses of MEC (0.03, 0.1, 0.3, and 1.0 mg/kg s.c.) was assessed across four consecutive daily 2-min extinction test sessions using a 2×2 design. Nic311 alone produced a 24-48% reduction in % nicotine-lever responding (%NLR) across all four test sessions. MEC produced a dose-dependent decrease in %NLR, with no effect at the two lowest doses and 80-93% attenuation at the two highest doses. Nic311 combined with MEC significantly suppressed %NLR at every MEC dose (85-92% reduction across all four test sessions). Very low doses of MEC that were ineffective alone completely blocked nicotine discrimination when combined with Nic311. These data demonstrate that nicotine-specific antibodies and MEC can work synergistically to suppress the subjective effects of nicotine and suggest that low doses of MEC may significantly enhance the efficacy of immunotherapy.

  1. Pharmacological activity of (-)-discretamine, a novel vascular alpha-adrenoceptor and 5-hydroxytryptamine receptor antagonist, isolated from Fissistigma glaucescens.

    PubMed Central

    Ko, F. N.; Yu, S. M.; Su, M. J.; Wu, Y. C.; Teng, C. M.

    1993-01-01

    1. The pharmacological activity of (-)-discretamine, isolated from Fissistigma glaucescens, was determined in rat isolated thoracic aorta, cardiac tissues and ventricular myocytes and guinea-pig isolated trachea. 2. (-)-Discretamine was found to be an alpha 1-adrenoceptor blocking agent in rat thoracic aorta as revealed by its competitive antagonism of noradrenaline (pA2 = 7.20 +/- 0.10)- or phenylephrine (pA2 = 7.60 +/- 0.09)-induced vasoconstriction. It was as potent as phentolamine (pA2 = 7.51 +/- 0.10), but was more potent than yohimbine (pA2 = 6.18 +/- 0.06). Removal of endothelium significantly increased the antagonistic potency of (-)-discretamine on noradrenaline (pA2 = 7.52 +/- 0.09)- or phenylephrine (pA2 = 7.90 +/- 0.09)-induced vasoconstriction. 3. (-)-Discretamine was also an alpha 2-adrenoceptor blocking agent (pA2 = 6.30 +/- 0.15) and a 5-hydroxytryptamine antagonist (pA2 = 6.87 +/- 0.06), both in rat aorta denuded of endothelium. 4. (-)-Discretamine protected alpha-adrenoceptors from alkylation by the irreversible blocking agent, phenoxybenzamine. 5. [3H]-inositol monophosphate formation caused by noradrenaline (3 microM) in rat thoracic aorta was suppressed by (-)-discretamine (10 and 30 microM) and prazosin (3 microM). 6. A high concentration of (-)-discretamine (30 microM) did not affect the contraction induced by the thromboxane receptor agonist U-46619, prostaglandin F2 alpha (PGF2 alpha), angiotensin II, high K+ or endothelin in rat aorta denuded of endothelium. Neither cyclic AMP nor cyclic GMP content of rat thoracic aorta was changed by (-)-discretamine.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7902181

  2. PG01037, a novel dopamine D3 receptor antagonist, inhibits the effects of methamphetamine in rats.

    PubMed

    Higley, Amanda E; Spiller, Krista; Grundt, Peter; Newman, Amy Hauck; Kiefer, Stephen W; Xi, Zheng-Xiong; Gardner, Eliot L

    2011-02-01

    Our previous studies have shown that the selective dopamine D(3) receptor antagonists SB-277011A or NGB 2904 significantly attenuate cocaine self-administration under a progressive-ratio reinforcement schedule and cocaine-, methamphetamine- or nicotine-enhanced brain stimulation reward. However, the poor bioavailability of SB-277011A has limited its potential use in humans. In the present study, we investigated the effects of the novel D(3) receptor antagonist PG01037 on methamphetamine self-administration, methamphetamine-associated cue-induced reinstatement of drug seeking and methamphetamine-enhanced brain stimulation reward. Rats were allowed to intravenously self-administer methamphetamine under fixed-ratio 2 and progressive-ratio reinforcement conditions, and then the effects of PG01037 on methamphetamine self-administration and cue-induced reinstatement were assessed. Additional groups of rats were trained for intracranial electrical brain stimulation reward and the effects of PG01037 and methamphetamine on brain stimulation reward were assessed. Acute intraperitoneal administration of PG01037 (3, 10, 30 mg/kg) failed to alter methamphetamine or sucrose self-administration under fixed-ratio 2 reinforcement, but significantly lowered the break-point levels for methamphetamine or sucrose self-administration under progressive-ratio reinforcement. In addition, PG01037 significantly inhibited methamphetamine-associated cue-triggered reinstatement of drug-seeking behavior and methamphetamine-enhanced brain stimulation reward. These data suggest that the novel D(3) antagonist PG01037 significantly attenuates the rewarding effects as assessed by progressive-ratio self-administration and brain stimulation reward, and inhibits methamphetamine-associated cue-induced reinstatement of drug-seeking behavior These findings support the potential use of PG01037 or other selective D(3) antagonists in the treatment of methamphetamine addiction.

  3. The effects of sigma (σ1) receptor-selective ligands on muscarinic receptor antagonist-induced cognitive deficits in mice

    PubMed Central

    Malik, Maninder; Rangel-Barajas, Claudia; Sumien, Nathalie; Su, Chang; Singh, Meharvan; Chen, Zhenglan; Huang, Ren-Qi; Meunier, Johann; Maurice, Tangui; Mach, Robert H; Luedtke, Robert R

    2015-01-01

    Background and Purpose Cognitive deficits in patients with Alzheimer's disease, Parkinson's disease, traumatic brain injury and stroke often involve alterations in cholinergic signalling. Currently available therapeutic drugs provide only symptomatic relief. Therefore, novel therapeutic strategies are needed to retard and/or arrest the progressive loss of memory. Experimental Approach Scopolamine-induced memory impairment provides a rapid and reversible phenotypic screening paradigm for cognition enhancement drug discovery. Male C57BL/6J mice given scopolamine (1 mg·kg−1) were used to evaluate the ability of LS-1–137, a novel sigma (σ1) receptor-selective agonist, to improve the cognitive deficits associated with muscarinic antagonist administration. Key Results LS-1–137 is a high-affinity (Ki = 3.2 nM) σ1 receptor agonist that is 80-fold selective for σ1, compared with σ2 receptors. LS-1–137 binds with low affinity at D2-like (D2, D3 and D4) dopamine and muscarinic receptors. LS-1–137 was found to partially reverse the learning deficits associated with scopolamine administration using a water maze test and an active avoidance task. LS-1–137 treatment was also found to trigger the release of brain-derived neurotrophic factor from rat astrocytes. Conclusions and Implications The σ1 receptor-selective compound LS-1–137 may represent a novel candidate cognitive enhancer for the treatment of muscarinic receptor-dependent cognitive deficits. PMID:25573298

  4. LY341495 is a nanomolar potent and selective antagonist of group II metabotropic glutamate receptors.

    PubMed

    Kingston, A E; Ornstein, P L; Wright, R A; Johnson, B G; Mayne, N G; Burnett, J P; Belagaje, R; Wu, S; Schoepp, D D

    1998-01-01

    The in vitro pharmacology of a structurally novel compound, LY341495, was investigated at human recombinant metabotropic glutamate (mGlu) receptor subtypes expressed in non-neuronal (RGT, rat glutamate transporter) cells. LY341495 was a nanomolar potent antagonist of 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD)-induced inhibition of forskolin-stimulated cAMP formation at mGlu2 and mGlu3 receptors (respective IC50S of 0.021 and 0.014 microM). At group I mGlu receptor expressing cells, LY341495 was micromolar potent in antagonizing quisqualate-induced phosphoinositide (PI) hydrolysis, with IC50 values of 7.8 and 8.2 microM for mGlu1a and mGlu5a receptors, respectively. Among the human group III mGlu receptors, the most potent inhibition of L-2-amino-4-phosphonobutyric acid (L-AP4) responses was seen for LY341495 at mGlu8, with an IC50 of 0.17 microM. LY341495 was less potent at mGlu7 (IC50 = 0.99 microM) and least potent at mGlu4 (IC50 = 22 microM). Binding studies in rat brain membranes also demonstrated nanomolar potent group II mGlu receptor affinity for LY341495, with no appreciable displacement of ionotropic glutamate receptor ligand binding. Thus, LY341495 has a unique range of selectivity across the mGlu receptor subtypes with a potency order of mGlu3 > or = mGlu2 > mGlu8 > mGlu7 > mGlu1a = mGlu5a > mGlu4. In particular, LY341495 is the most potent antagonist yet reported at mGlu2, 3 and 8 receptors. Thus, it represents a novel pharmacological agent for elucidating the function of mGlu receptors in experimental systems. PMID:9680254

  5. The A2B adenosine receptor modulates pulmonary hypertension associated with interstitial lung disease

    PubMed Central

    Karmouty-Quintana, Harry; Zhong, Hongyan; Acero, Luis; Weng, Tingting; Melicoff, Ernestina; West, James D.; Hemnes, Anna; Grenz, Almut; Eltzschig, Holger K.; Blackwell, Timothy S.; Xia, Yang; Johnston, Richard A.; Zeng, Dewan; Belardinelli, Luiz; Blackburn, Michael R.

    2012-01-01

    Development of pulmonary hypertension is a common and deadly complication of interstitial lung disease. Little is known regarding the cellular and molecular mechanisms that lead to pulmonary hypertension in patients with interstitial lung disease, and effective treatment options are lacking. The purpose of this study was to examine the adenosine 2B receptor (A2BR) as a regulator of vascular remodeling and pulmonary hypertension secondary to pulmonary fibrosis. To accomplish this, cellular and molecular changes in vascular remodeling were monitored in mice exposed to bleomycin in conjunction with genetic removal of the A2BR or treatment with the A2BR antagonist GS-6201. Results demonstrated that GS-6201 treatment or genetic removal of the A2BR attenuated vascular remodeling and hypertension in our model. Furthermore, direct A2BR activation on vascular cells promoted interleukin-6 and endothelin-1 release. These studies identify a novel mechanism of disease progression to pulmonary hypertension and support the development of A2BR antagonists for the treatment of pulmonary hypertension secondary to interstitial lung disease.—Karmouty-Quintana, H., Zhong, H., Acero, L., Weng, T., Melicoff, E., West, J. D., Hemnes, A., Grenz, A., Eltzschig, H. K., Blackwell, T. S., Xia, Y., Johnston, R. A., Zeng, D., Belardinelli, L., Blackburn, M. R. The A2B adenosine receptor modulates pulmonary hypertension associated with interstitial lung disease. PMID:22415303

  6. Identification of androgen receptor antagonists: In vitro investigation and classification methodology for flavonoid.

    PubMed

    Wu, Yang; Doering, Jon A; Ma, Zhiyuan; Tang, Song; Liu, Hongling; Zhang, Xiaowei; Wang, Xiaoxiang; Yu, Hongxia

    2016-09-01

    A tremendous gap exists between the number of potential endocrine disrupting chemicals (EDCs) possibly in the environment and the limitation of traditional regulatory testing. In this study, the anti-androgenic potencies of 21 flavonoids were analyzed in vitro, and another 32 flavonoids from the literature were selected as additional chemicals. Molecular dynamic simulations were employed to obtain four different separation approaches based on the different behaviors of ligands and receptors during the process of interaction. Specifically, ligand-receptor complex which highlighted the discriminating features of ligand escape or retention via "mousetrap" mechanism, hydrogen bonds formed during simulation times, ligand stability and the stability of the helix-12 of the receptor were investigated. Together, a methodology was generated that 87.5% of flavonoids could be discriminated as active versus inactive antagonists, and over 90% inactive antagonists could be filtered out before QSAR study. This methodology could be used as a "proof of concept" to identify inactive anti-androgenic flavonoids, as well could be beneficial for rapid risk assessment and regulation of multiple new chemicals for androgenicity. PMID:27258897

  7. Selective small molecule angiotensin II type 2 receptor antagonists for neuropathic pain: preclinical and clinical studies.

    PubMed

    Smith, Maree T; Anand, Praveen; Rice, Andrew S C

    2016-02-01

    Neuropathic pain affects up to 10% of the general population, but drug treatments recommended for the treatment of neuropathic pain are associated with modest efficacy and/or produce dose-limiting side effects. Hence, neuropathic pain is an unmet medical need. In the past 2 decades, research on the pathobiology of neuropathic pain has revealed many novel pain targets for use in analgesic drug discovery programs. However, these efforts have been largely unsuccessful as molecules that showed promising pain relief in rodent models of neuropathic pain generally failed to produce analgesia in early phase clinical trials in patients with neuropathic pain. One notable exception is the angiotensin II type 2 (AT2) receptor that has clinical validity on the basis of a successful double-blind, randomized, placebo-controlled, clinical trial of EMA401, a highly selective, orally active, peripherally restricted AT2 receptor antagonist in patients with postherpetic neuralgia. In this study, we review research to date on target validation, efficacy, and mode of action of small molecule AT2 receptor antagonists in rodent models of peripheral neuropathic pain and in cultured human sensory neurons, the preclinical pharmacokinetics of these compounds, and the outcome of the above clinical trial.

  8. Skeletal effects of a gastrin receptor antagonist in H+/K+ATPase beta subunit KO mice.

    PubMed

    Aasarød, Kristin M; Ramezanzadehkoldeh, Masoud; Shabestari, Maziar; Mosti, Mats P; Stunes, Astrid K; Reseland, Janne E; Beisvag, Vidar; Eriksen, Erik Fink; Sandvik, Arne K; Erben, Reinhold G; Schüler, Christiane; Boyce, Malcolm; Skallerud, Bjørn H; Syversen, Unni; Fossmark, Reidar

    2016-08-01

    Epidemiological studies suggest an increased fracture risk in patients taking proton pump inhibitors (PPIs) for long term. The underlying mechanism, however, has been disputed. By binding to the gastric proton pump, PPIs inhibit gastric acid secretion. We have previously shown that proton pump (H(+)/K(+)ATPase beta subunit) KO mice exhibit reduced bone mineral density (BMD) and inferior bone strength compared with WT mice. Patients using PPIs as well as these KO mice exhibit gastric hypoacidity, and subsequently increased serum concentrations of the hormone gastrin. In this study, we wanted to examine whether inhibition of the gastrin/CCK2 receptor influences bone quality in these mice. KO and WT mice were given either the gastrin/CCK2 receptor antagonist netazepide dissolved in polyethylene glycol (PEG) or only PEG for 1year. We found significantly lower bone mineral content and BMD, as well as inferior bone microarchitecture in KO mice compared with WT. Biomechanical properties by three-point bending test also proved inferior in KO mice. KO mice receiving netazepide exhibited significantly higher cortical thickness, cortical area fraction, trabecular thickness and trabecular BMD by micro-CT compared with the control group. Three-point bending test also showed higher Young's modulus of elasticity in the netazepide KO group compared with control mice. In conclusion, we observed that the gastrin receptor antagonist netazepide slightly improved bone quality in this mouse model, suggesting that hypergastrinemia may contribute to deteriorated bone quality during acid inhibition. PMID:27325243

  9. Endothelin receptor antagonists: a new therapeutic option for improving the outcome after solid organ transplantation?

    PubMed

    Göttmann, Uwe; van der Woude, Fokko J; Braun, Claude

    2003-10-01

    Initially described as the most potent vasoconstrictor peptide, endothelin (ET) has also been shown to possess extraordinary immunomodulatory and proinflammatory properties. Because of this broad spectrum of biological activities, a possible role of the ET-system in solid organ transplantation has soon become a focus of research. Several studies demonstrated a pathogenetic involvement of ET in ischemia/reperfusion injury of heart, liver, kidney, and lung grafts. ET accumulates during cold storage of organs and can be detected in the effluent preservation solution. In addition ET is very, likely to play a pivotal role in the development of chronic rejection, which represents the major cause of late allograft loss. Increased expression of components of the ET-system has been described in areas of neointimal proliferation, a hallmark of chronic graft rejection. Both selective ET-A as well as non-selective ET-A/B receptor antagonists improved histomorphological and functional sequelae of chronic rejection. However these data have largely been derived from experimental animal transplantation, and ET receptor blockers have only recently been introduced in clinical medicine. A significant number of investigational drugs are now being tested in humans, with a main focus on cardiovascular diseases, such as congestive heart failure and pulmonary hypertension. First results have markedly dampened the initial enthusiastic vision of ET receptor blockers being organoprotective super-weapons. Thus the clinical potential of ET antagonists in general, and especially in solid-organ transplantation, is still to be defined.

  10. Antinociceptive activity of CP-101,606, an NMDA receptor NR2B subunit antagonist

    PubMed Central

    Taniguchi, Kana; Shinjo, Katsuhiro; Mizutani, Mayumi; Shimada, Kaoru; Ishikawa, Toshihisa; Menniti, Frank S; Nagahisa, Atsushi

    1997-01-01

    The analgesic activity of CP-101,606, an NR2B subunit-selective N-methyl-D-aspartate (NMDA) receptor antagonist, was examined in carrageenan-induced hyperalgesia, capsaicin- and 4β-phorbol-12-myristate-13-acetate (PMA)-induced nociceptive tests in the rat. CP-101,606 30 mg kg−1, s.c., at 0.5 and 2.5 h after carrageenan challenge suppressed mechanical hyperalgesia without any apparant alternations in motor coordination or behaviour in the rat. CP-101,606 also inhibited capsaicin- and PMA-induced nociceptive responses (licking behaviour) with ED50 values of 7.5 and 5.7 mg kg−1, s.c., respectively. These results suggest that inhibition of the NR2B subunit of the NMDA receptor is effective in vivo at modulating nociception and hyperalgesia responses without causing the behavioural side effects often observed with currently available NMDA receptor antagonists. PMID:9384494

  11. Action of adenosine receptor antagonists on the cardiovascular response to defence area stimulation in the rat.

    PubMed Central

    St Lambert, J H; Dawid-Milner, M S; Silva-Carvalho, L; Spyer, K M

    1994-01-01

    1. The action of adenosine in the mediation of the cardiovascular changes associated with the defence reaction has been investigated in the rat using two A1 receptor antagonists. 2. Cumulative doses of 1,3 dipropyl-cyclopentylxanthine (DPCPX) (0.3-3 mg kg-1) and ethanol (0.03-0.25 ml) and bolus doses of DPCPX (3 mg kg-1) and 8-sulphophenyltheophylline (8-SPT) (20 mg kg-1) were given into alpha-chloralose, paralysed and artificially ventilated rats. Recordings were made of arterial blood pressure and heart rate. 3. Ethanol, the vehicle for DPCPX, failed to modify the magnitude of the defence response; however, cumulative doses of DPCPX produced a dose-dependent decrease in the HDA (hypothalamic defence area)-evoked increase in arterial blood pressure, accompanied by a similar fall in the magnitude of the evoked heart rate response. 4. The evoked rise in arterial blood pressure was reduced significantly by intravenous injection of DPCPX (3 mg kg-1) but not 8-SPT (20 mg kg-1), a purely peripherally acting adenosine antagonist. 5. These results suggest that adenosine acting at A1 receptors located in the central nervous system, is involved in the HDA-evoked pressor response. Whilst the site of action of the A1 receptors is not known, possible locations are discussed. PMID:7812606

  12. Key features of candesartan cilexetil and a comparison with other angiotensin II receptor antagonists.

    PubMed

    Sever, P S

    1999-01-01

    Current research on angiotensin II AT1-receptor antagonists (AIIRAs) and selected studies presented at the recent symposium held in Amsterdam, The Netherlands, on 6 June 1998, titled 'Angiotensin II Receptor Antagonists are NOT all the Same' are reviewed. AIIRAs offer a number of potential advantages over alternative antihypertensive agents acting via the renin-angiotensin-aldosterone system. They combine blood pressure-lowering effects at least equivalent to those of angiotensin-converting enzyme (ACE) inhibitors, coupled with placebo-like tolerability. Candesartan cilexetil is a novel AIIRA that has demonstrated clinical efficacy superior to losartan, has a sustained duration of action over 24 hours (trough:peak ratio close to 100%) and is well tolerated in patients with essential hypertension. Candesartan cilexetil has a rapid onset of action (approximately 80% of total blood pressure reduction within the first 2 weeks) and dose-dependent effects on blood pressure, is comparable in efficacy to a number of classes of antihypertensives, and is effective in combination therapy (eg, with hydrochlorothiazide and amlodipine). This favourable profile may be due in part to the highly selective, tight binding to and slow dissociation of candesartan from the AT1 receptor. Preliminary studies suggest that candesartan cilexetil also protects end organs (kidney, heart, vasculature, and brain) beyond blood pressure control. PMID:10076915

  13. Receptor residence time trumps drug-likeness and oral bioavailability in determining efficacy of complement C5a antagonists

    NASA Astrophysics Data System (ADS)

    Seow, Vernon; Lim, Junxian; Cotterell, Adam J.; Yau, Mei-Kwan; Xu, Weijun; Lohman, Rink-Jan; Kok, W. Mei; Stoermer, Martin J.; Sweet, Matthew J.; Reid, Robert C.; Suen, Jacky Y.; Fairlie, David P.

    2016-04-01

    Drug discovery and translation are normally based on optimizing efficacy by increasing receptor affinity, functional potency, drug-likeness (rule-of-five compliance) and oral bioavailability. Here we demonstrate that residence time of a compound on its receptor has an overriding influence on efficacy, exemplified for antagonists of inflammatory protein complement C5a that activates immune cells and promotes disease. Three equipotent antagonists (3D53, W54011, JJ47) of inflammatory responses to C5a (3nM) were compared for drug-likeness, receptor affinity and antagonist potency in human macrophages, and anti-inflammatory efficacy in rats. Only the least drug-like antagonist (3D53) maintained potency in cells against higher C5a concentrations and had a much longer duration of action (t1/2 ~ 20 h) than W54011 or JJ47 (t1/2 ~ 1–3 h) in inhibiting macrophage responses. The unusually long residence time of 3D53 on its receptor was mechanistically probed by molecular dynamics simulations, which revealed long-lasting interactions that trap the antagonist within the receptor. Despite negligible oral bioavailability, 3D53 was much more orally efficacious than W54011 or JJ47 in preventing repeated agonist insults to induce rat paw oedema over 24 h. Thus, residence time on a receptor can trump drug-likeness in determining efficacy, even oral efficacy, of pharmacological agents.

  14. Novel nonimidazole histamine H3 receptor antagonists: 1-(4-(phenoxymethyl)benzyl)piperidines and related compounds.

    PubMed

    Mikó, Tibor; Ligneau, Xavier; Pertz, Heinz H; Ganellin, C Robin; Arrang, Jean-Michel; Schwartz, Jean-Charles; Schunack, Walter; Stark, Holger

    2003-04-10

    In an extension of very recently published studies on successful imidazole replacements in some series of histamine H(3) receptor antagonists, we report on a new class of lipophilic nonimidazole antagonist having an aliphatic tertiary amino moiety connected to a benzyl template substituted in the 4-position by a phenoxymethyl group. The structural modifications were performed with the intention to avoid possible negative side effects reported for other series of antagonists. The novel compounds combine different characteristics of recently developed histamine H(3) receptor antagonists. The compounds were screened for their affinity in a binding assay for the human histamine H(3) receptor stably expressed in CHO-K1 cells and tested for their in vivo potency in the central nervous system of mice after oral administration. Different substitution patterns on the phenoxy group were used to optimize in vitro and/or in vivo potency leading to some compounds with low nanomolar affinity and high oral in vivo potency. Modifications of the basic piperidino moiety were performed by ring expansion, contraction, and opening. Selected compounds exhibited selectivity in functional assays on isolated organs of guinea-pig for H(3) vs H(1) and H(2) receptors. Unexpectedly, some of the novel antagonists also showed a slight preference for the human histamine H(3) receptor compared to their affinities for the guinea-pig H(3) receptor.

  15. Receptor residence time trumps drug-likeness and oral bioavailability in determining efficacy of complement C5a antagonists

    PubMed Central

    Seow, Vernon; Lim, Junxian; Cotterell, Adam J.; Yau, Mei-Kwan; Xu, Weijun; Lohman, Rink-Jan; Kok, W. Mei; Stoermer, Martin J.; Sweet, Matthew J.; Reid, Robert C.; Suen, Jacky Y.; Fairlie, David P.

    2016-01-01

    Drug discovery and translation are normally based on optimizing efficacy by increasing receptor affinity, functional potency, drug-likeness (rule-of-five compliance) and oral bioavailability. Here we demonstrate that residence time of a compound on its receptor has an overriding influence on efficacy, exemplified for antagonists of inflammatory protein complement C5a that activates immune cells and promotes disease. Three equipotent antagonists (3D53, W54011, JJ47) of inflammatory responses to C5a (3nM) were compared for drug-likeness, receptor affinity and antagonist potency in human macrophages, and anti-inflammatory efficacy in rats. Only the least drug-like antagonist (3D53) maintained potency in cells against higher C5a concentrations and had a much longer duration of action (t1/2 ~ 20 h) than W54011 or JJ47 (t1/2 ~ 1–3 h) in inhibiting macrophage responses. The unusually long residence time of 3D53 on its receptor was mechanistically probed by molecular dynamics simulations, which revealed long-lasting interactions that trap the antagonist within the receptor. Despite negligible oral bioavailability, 3D53 was much more orally efficacious than W54011 or JJ47 in preventing repeated agonist insults to induce rat paw oedema over 24 h. Thus, residence time on a receptor can trump drug-likeness in determining efficacy, even oral efficacy, of pharmacological agents. PMID:27094554

  16. Antagonistic effects of extracts from Artemisia rupetris L. and Leontopodium leontopodioides to CC chemokine receptor 2b (CCR2b).

    PubMed

    Yu, Qin-Wei; Hu, Jie; Wang, Hao; Chen, Xin; Zhao, Fang; Gao, Peng; Yang, Qiu-Bin; Sun, Dan-Dan; Zhang, Lu-Yong; Yan, Ming

    2016-05-01

    The present study was designed to establish a suitable assay to explore CCR2b receptor antagonists from the natural products of Artemisia rupetris and Leontopodium leontopodioides. An aequorin assay was developed as a cell-based assay suitable for 384-well microplate and used for screening CCR2b receptor antagonists from natural products. Through establishing suitable conditions, the assay was shown to be suitable for screening of CCR2b receptor antagonists. Seven compounds were identified in preliminary screening. Five of them showed evident dose-response relationship in secondary screening. The structure-activity relationship study suggested that 7-position hydroxyl group of flavonoids was necessary, a polar group should be introduced on the 3-position, and the substituents on 2-position benzene ring of flavonoids have little influence on the potentency of the inhibition activity on CCR2b receptor. The ortho-position dihydroxyl structure in quinic acid compounds may be important. In conclusion, Compounds HR-1, 5, 7, and AR-20, 35 showed activity as antagonist of CCR2b receptor, which shed lights on the development of novel drugs as CCR2b receptor antagonists for preventing inflammation related diseases. PMID:27478099

  17. Sulforaphane is not an effective antagonist of the human Pregnane X-Receptor in vivo

    PubMed Central

    Poulton, Emma Jane; Levy, Lisa; Lampe, Johanna W.; Shen, Danny D.; Tracy, Julia; Shuhart, Margaret C.; Thummel, Kenneth E.; Eaton, David L.

    2012-01-01

    Sulforaphane (SFN), is an effective in vitro antagonist of ligand activation of the human pregnane and xenobiotic receptor (PXR). PXR mediated CYP3A4 up-regulation is implicated in adverse drug-drug interactions making identification of small molecule antagonists a desirable therapeutic goal. SFN is not an antagonist to mouse or rat PXR in vitro; thus, normal rodent species are not suitable as in vivo models for human response. To evaluate whether SFN can effectively antagonize ligand activation of human PXR in vivo, a three-armed, randomized, crossover trial was conducted with 24 healthy adults. The potent PXR ligand – rifampicin (300 mg/d) was given alone for 7 days in arm 1, or in daily combination with 450 µmoles SFN (Broccoli Sprout extract) in arm 2; SFN was given alone in arm 3. Midazolam as an in vivo phenotype marker of CYP3A was administered before and after each treatment arm. Rifampicin alone decreased midazolam AUC by 70%, indicative of the expected increase in CYP3A4 activity. Co-treatment with SFN did not reduce CYP3A4 induction. Treatment with SFN alone also did not affect CYP3A4 activity in the cohort as a whole, although in the subset with the highest basal CYP3A4 activity there was a statistically significant increase in midazolam AUC (i.e., decrease in CYP3A4 activity). A parallel study in humanized PXR mice yielded similar results. The parallel effects of SFN between humanized PXR mice and human subjects demonstrate the predictive value of humanized mouse models in situations where species differences in ligand-receptor interactions preclude the use of a native mouse model for studying human ligand-receptor pharmacology. PMID:23153560

  18. Pharmacological characterization of a novel centrally permeable P2X7 receptor antagonist: JNJ-47965567

    PubMed Central

    Bhattacharya, Anindya; Wang, Qi; Ao, Hong; Shoblock, James R; Lord, Brian; Aluisio, Leah; Fraser, Ian; Nepomuceno, Diane; Neff, Robert A; Welty, Natalie; Lovenberg, Timothy W; Bonaventure, Pascal; Wickenden, Alan D; Letavic, Michael A

    2013-01-01

    BACKGROUND AND PURPOSE An increasing body of evidence suggests that the purinergic receptor P2X, ligand-gated ion channel, 7 (P2X7) in the CNS may play a key role in neuropsychiatry, neurodegeneration and chronic pain. In this study, we characterized JNJ-47965567, a centrally permeable, high-affinity, selective P2X7 antagonist. EXPERIMENTAL APPROACH We have used a combination of in vitro assays (calcium flux, radioligand binding, electrophysiology, IL-1β release) in both recombinant and native systems. Target engagement of JNJ-47965567 was demonstrated by ex vivo receptor binding autoradiography and in vivo blockade of Bz-ATP induced IL-1β release in the rat brain. Finally, the efficacy of JNJ-47965567 was tested in standard models of depression, mania and neuropathic pain. KEY RESULTS JNJ-47965567 is potent high affinity (pKi 7.9 ± 0.07), selective human P2X7 antagonist, with no significant observed speciation. In native systems, the potency of the compound to attenuate IL-1β release was 6.7 ± 0.07 (human blood), 7.5 ± 0.07 (human monocytes) and 7.1 ± 0.1 (rat microglia). JNJ-47965567 exhibited target engagement in rat brain, with a brain EC50 of 78 ± 19 ng·mL−1 (P2X7 receptor autoradiography) and functional block of Bz-ATP induced IL-1β release. JNJ-47965567 (30 mg·kg−1) attenuated amphetamine-induced hyperactivity and exhibited modest, yet significant efficacy in the rat model of neuropathic pain. No efficacy was observed in forced swim test. Conclusion and Implications JNJ-47965567 is centrally permeable, high affinity P2X7 antagonist that can be used to probe the role of central P2X7 in rodent models of CNS pathophysiology. PMID:23889535

  19. The Dual Orexin Receptor Antagonist Almorexant Induces Sleep and Decreases Orexin-Induced Locomotion by Blocking Orexin 2 Receptors

    PubMed Central

    Mang, Géraldine M.; Dürst, Thomas; Bürki, Hugo; Imobersteg, Stefan; Abramowski, Dorothee; Schuepbach, Edi; Hoyer, Daniel; Fendt, Markus; Gee, Christine E.

    2012-01-01

    Study Objectives: Orexin peptides activate orexin 1 and orexin 2 receptors (OX1R and OX2R), regulate locomotion and sleep-wake. The dual OX1R/OX2R antagonist almorexant reduces activity and promotes sleep in multiple species, including man. The relative contributions of the two receptors in locomotion and sleep/wake regulation were investigated in mice. Design: Mice lacking orexin receptors were used to determine the contribution of OX1R and OX2R to orexin A-induced locomotion and to almorexant-induced sleep. Setting: N/A. Patients or Participants: C57BL/6J mice and OX1R+/+, OX1R-/-, OX2R+/+, OX2R-/- and OX1R-/-/OX2R-/- mice. Interventions: Intracerebroventricular orexin A; oral dosing of almorexant. Measurements and Results: Almorexant attenuated orexin A-induced locomotion. As in other species, almorexant dose-dependently increased rapid eye movement sleep (REM) and nonREM sleep in mice. Almorexant and orexin A were ineffective in OX1R-/-/OX2R-/- mice. Both orexin A-induced locomotion and sleep induction by almorexant were absent in OX2R-/- mice. Interestingly, almorexant did not induce cataplexy in wild-type mice under conditions where cataplexy was seen in mice lacking orexins and in OX1R-/-/OX2R-/- mice. Almorexant dissociates very slowly from OX2R as measured functionally and in radioligand binding. Under non equilibrium conditions in vitro, almorexant was a dual antagonist whereas at equilibrium, almorexant became OX2R selective. Conclusions: In vivo, almorexant specifically inhibits the actions of orexin A. The two known orexin receptors mediate sleep induction by almorexant and orexin A-induced locomotion. However, OX2R activation mediates locomotion induction by orexin A and antagonism of OX2R is sufficient to promote sleep in mice. Citation: Mang GM; Dürst T; Bürki H; Imobersteg S; Abramowski D; Schuepbach E; Hoyer D; Fendt M; Gee CE. The dual orexin receptor antagonist almorexant induces sleep and decreases orexin-induced locomotion by blocking orexin

  20. Pulmonary aerosol actions of LY188695 (KB2413), a new potent H1-receptor antagonist.

    PubMed

    Silbaugh, S A; Stengel, P W; Rinkema, L E

    1987-06-01

    The new potent H1 receptor antagonist, LY188695 (KB2413), was delivered to guinea pigs as a pulmonary aerosol and its ability to inhibit histamine-induced airway obstruction examined. Aerosol LY188695 was more effective than inhaled chlorpheniramine or clemastine in reducing the pulmonary gas trapping produced by histamine challenge. Lung antihistamine effects occurred within minutes of a brief, low concentration aerosol exposure and persisted for at least 1 hour. LY188695 aerosol treatment did not produce significant inhibition of methacholine-induced gas trapping. Although systemic antihistamine effects occurred 50 minutes after LY188695 inhalation, aerosol administration produced an enhanced local (i.e., lung) action compared to intravenous delivery.

  1. 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

  2. Lipopolysaccharide and Raf-1 kinase regulate secretory interleukin-1 receptor antagonist gene expression by mutually antagonistic mechanisms.

    PubMed Central

    Guthridge, C J; Eidlen, D; Arend, W P; Gutierrez-Hartmann, A; Smith, M F

    1997-01-01

    Lipopolysaccharide (LPS) treatment of monocytic cells has been shown to activate the Raf-1/mitogen-activated protein kinase (MAPK) signaling pathway and to increase secretory interleukin-1 receptor antagonist (sIL-1Ra) gene expression. The significance of the activation of the Raf-1/MAPK signaling pathway to LPS regulation of sIL-1Ra gene expression, however, has not been determined. This study addresses the role of the Raf-1/MAPK signaling pathway in regulation of sIL-1Ra gene expression by LPS. Cotransfection of the murine macrophage cell line RAW 264.7 with a 294-bp sIL-1Ra promoter/luciferase construct (pRA-294-luc) and a constitutively active Raf-1 kinase expression vector (pRSV-Raf-BXB) resulted in induction of sIL-1Ra promoter activity, indicating that Raf-1, like LPS, can regulate sIL-1Ra promoter activity. An in vitro MAPK analysis indicated that both LPS treatment and pRSV-Raf-BXB transfection of RAW 264.7 cells increases p42 MAPK activity. An in vitro Raf-1 kinase assay, however, failed to detect LPS-induced Raf-1 kinase activity in RAW 264.7 cells, suggesting that in RAW 264.7 cells, Raf-1 kinase is not an activating component of the LPS signaling pathway regulating MAPK activity or sIL-1Ra promoter activity. This observation was supported by results from transfection studies which demonstrated that expression of a dominant-inhibitory Raf-1 mutant in RAW 264.7 cells does not inhibit LPS-induced MAPK activity or sIL-1Ra promoter activity, indicating that LPS-induced sIL-1Ra promoter activation occurs independent of the Raf-1/MAPK signaling pathway. In additional studies, cotransfection of RAW 264.7 cells with pRA-294-luc and increasing amounts of pRSV-Raf-BXB caused a dose-dependent inhibition of LPS-induced sIL-1Ra promoter activity, indicating that the role of the Raf-1 pathway in the regulation of sIL-1Ra promoter activity by LPS is as an antagonizer. Interestingly, LPS treatment of RAW 264.7 cells, cotransfected with pRA-294-luc and p

  3. Lipopolysaccharide and Raf-1 kinase regulate secretory interleukin-1 receptor antagonist gene expression by mutually antagonistic mechanisms.

    PubMed

    Guthridge, C J; Eidlen, D; Arend, W P; Gutierrez-Hartmann, A; Smith, M F

    1997-03-01

    Lipopolysaccharide (LPS) treatment of monocytic cells has been shown to activate the Raf-1/mitogen-activated protein kinase (MAPK) signaling pathway and to increase secretory interleukin-1 receptor antagonist (sIL-1Ra) gene expression. The significance of the activation of the Raf-1/MAPK signaling pathway to LPS regulation of sIL-1Ra gene expression, however, has not been determined. This study addresses the role of the Raf-1/MAPK signaling pathway in regulation of sIL-1Ra gene expression by LPS. Cotransfection of the murine macrophage cell line RAW 264.7 with a 294-bp sIL-1Ra promoter/luciferase construct (pRA-294-luc) and a constitutively active Raf-1 kinase expression vector (pRSV-Raf-BXB) resulted in induction of sIL-1Ra promoter activity, indicating that Raf-1, like LPS, can regulate sIL-1Ra promoter activity. An in vitro MAPK analysis indicated that both LPS treatment and pRSV-Raf-BXB transfection of RAW 264.7 cells increases p42 MAPK activity. An in vitro Raf-1 kinase assay, however, failed to detect LPS-induced Raf-1 kinase activity in RAW 264.7 cells, suggesting that in RAW 264.7 cells, Raf-1 kinase is not an activating component of the LPS signaling pathway regulating MAPK activity or sIL-1Ra promoter activity. This observation was supported by results from transfection studies which demonstrated that expression of a dominant-inhibitory Raf-1 mutant in RAW 264.7 cells does not inhibit LPS-induced MAPK activity or sIL-1Ra promoter activity, indicating that LPS-induced sIL-1Ra promoter activation occurs independent of the Raf-1/MAPK signaling pathway. In additional studies, cotransfection of RAW 264.7 cells with pRA-294-luc and increasing amounts of pRSV-Raf-BXB caused a dose-dependent inhibition of LPS-induced sIL-1Ra promoter activity, indicating that the role of the Raf-1 pathway in the regulation of sIL-1Ra promoter activity by LPS is as an antagonizer. Interestingly, LPS treatment of RAW 264.7 cells, cotransfected with pRA-294-luc and p

  4. MEN 11420 (Nepadutant), a novel glycosylated bicyclic peptide tachykinin NK2 receptor antagonist

    PubMed Central

    Catalioto, R-M; Criscuoli, M; Cucchi, P; Giachetti, A; Giannotti, D; Giuliani, S; Lecci, A; Lippi, A; Patacchini, R; Quartara, L; Renzetti, A R; Tramontana, M; Arcamone, F; Maggi, C A

    1998-01-01

    The pharmacological profile was studied of MEN 11420, or cyclo{[Asn(β-D-GlcNAc)-Asp-Trp-Phe-Dap-Leu]cyclo(2β-5β)}, a glycosylated derivative of the potent, selective, conformationally-constrained tachykinin NK2 receptor antagonist MEN 10627 (cyclo(Met-Asp-Trp-Phe-Dap-Leu)cyclo(2β-5β)).MEN 11420 competitively bound with high affinity to the human NK2 receptor stably transfected in CHO cells, displacing radiolabelled [125I]-neurokinin A and [3H]-SR 48968 with Ki values of 2.5±0.7 nM (n=6) and 2.6±0.4 nM (n=3), respectively.MEN 11420 showed negligible binding affinity (pIC50<6) at 50 different receptors (including tachykinin NK1 and NK3 receptors) and ion channels.In the rabbit isolated pulmonary artery and rat urinary bladder MEN 11420 potently and competitively antagonized tachykinin NK2 receptor-mediated contractions (pKB=8.6±0.07, n=10, and 9.0±0.04, n=12; Schild plot slope=−1.06 (95% c.l.=−1.3; −0.8) and −1.17 (95% c.l.=−1.3; −1.0), respectively). MEN 11420 produced an insurmountable antagonism at NK2 receptors in the hamster trachea and mouse urinary bladder. However, in both preparations, the effect of MEN 11420 was reverted by washout and an apparent pKB of 10.2±0.14, n= 9, and 9.8±0.15, n=9, was calculated in the hamster trachea and mouse urinary bladder, respectively.MEN 11420 showed low affinity (pKB<6) at guinea-pig and rat tachykinin NK1 (guinea-pig ileum and rat urinary bladder) and NK3 (guinea-pig ileum and rat portal vein) receptors. On the whole, the affinities (potency and selectivity) showed by MEN 11420 for different tachykinin receptors, measured either in binding or in functional bioassays, were similar to those shown by the parent compound, MEN 10627.The in vivo antagonism of the contractions produced by [βAla8]neurokinin A(4–10) (1 nmol kg−1) was observed after intravenous (dose range: 1–10 nmol kg−1), intranasal (3–10 nmol kg−1), intrarectal (30–100

  5. Pharmacology of modality-specific transient receptor potential vanilloid-1 antagonists that do not alter body temperature.

    PubMed

    Reilly, Regina M; McDonald, Heath A; Puttfarcken, Pamela S; Joshi, Shailen K; Lewis, LaGeisha; Pai, Madhavi; Franklin, Pamela H; Segreti, Jason A; Neelands, Torben R; Han, Ping; Chen, Jun; Mantyh, Patrick W; Ghilardi, Joseph R; Turner, Teresa M; Voight, Eric A; Daanen, Jerome F; Schmidt, Robert G; Gomtsyan, Arthur; Kort, Michael E; Faltynek, Connie R; Kym, Philip R

    2012-08-01

    The transient receptor potential vanilloid-1 (TRPV1) channel is involved in the development and maintenance of pain and participates in the regulation of temperature. The channel is activated by diverse agents, including capsaicin, noxious heat (≥ 43°C), acidic pH (< 6), and endogenous lipids including N-arachidonoyl dopamine (NADA). Antagonists that block all modes of TRPV1 activation elicit hyperthermia. To identify efficacious TRPV1 antagonists that do not affect temperature antagonists representing multiple TRPV1 pharmacophores were evaluated at recombinant rat and human TRPV1 channels with Ca(2+) flux assays, and two classes of antagonists were identified based on their differential ability to inhibit acid activation. Although both classes of antagonists completely blocked capsaicin- and NADA-induced activation of TRPV1, select compounds only partially inhibited activation of the channel by protons. Electrophysiology and calcitonin gene-related peptide release studies confirmed the differential pharmacology of these antagonists at native TRPV1 channels in the rat. Comparison of the in vitro pharmacological properties of these TRPV1 antagonists with their in vivo effects on core body temperature confirms and expands earlier observations that acid-sparing TRPV1 antagonists do not significantly increase core body temperature. Although both classes of compounds elicit equivalent analgesia in a rat model of knee joint pain, the acid-sparing antagonist tested is not effective in a mouse model of bone cancer pain.

  6. Comparison of the β-Adrenergic Receptor Antagonists Landiolol and Esmolol: Receptor Selectivity, Partial Agonism, and Pharmacochaperoning Actions.

    PubMed

    Nasrollahi-Shirazi, Shahrooz; Sucic, Sonja; Yang, Qiong; Freissmuth, Michael; Nanoff, Christian

    2016-10-01

    Blockage of β1-adrenergic receptors is one of the most effective treatments in cardiovascular medicine. Esmolol was introduced some three decades ago as a short-acting β1-selective antagonist. Landiolol is a more recent addition. Here we compared the two compounds for their selectivity for β1-adrenergic receptors over β2-adrenergic receptors, partial agonistic activity, signaling bias, and pharmacochaperoning action by using human embryonic kidney (HEK)293 cell lines, which heterologously express each human receptor subtype. The affinity of landiolol for β1-adrenergic receptors and β2-adrenergic receptors was higher and lower than that of esmolol, respectively, resulting in an improved selectivity (216-fold versus 30-fold). The principal metabolite of landiolol (M1) was also β1-selective, but its affinity was very low. Both landiolol and esmolol caused a very modest rise in cAMP levels but a robust increase in the phosphorylation of extracellular signal regulated kinases 1 and 2, indicating that the two drugs exerted partial agonist activity with a signaling bias. If cells were incubated for ≥24 hours in the presence of ≥1 μM esmolol, the levels of β1-adrenergic-but not of β2-adrenergic-receptors increased. This effect was contingent on export of the β1-receptor from endoplasmic reticulum and was not seen in the presence of landiolol. On the basis of these observations, we conclude that landiolol offers the advantage of: 1) improved selectivity and 2) the absence of pharmacochaperoning activity, which sensitizes cells to rebound effects upon drug discontinuation. PMID:27451411

  7. Opioid agonist and antagonist treatment differentially regulates immunoreactive mu-opioid receptors and dynamin-2 in vivo.

    PubMed

    Yoburn, Byron C; Purohit, Vishal; Patel, Kaushal; Zhang, Qiuyu

    2004-09-13

    Opioid agonists and antagonists can regulate the density of mu-opioid receptors in whole animal and in cell culture. High intrinsic efficacy agonists (e.g., etorphine), but not lower intrinsic efficacy agonists (e.g., morphine), produce mu-opioid receptor down-regulation and can alter the abundance of mu-opioid receptor mRNA. Conversely, opioid antagonists substantially increase the density of mu-opioid receptors without changing its mRNA. Mu-opioid receptor up-regulation has been associated with decreases in the trafficking protein dynamin-2, whereas mu-opioid receptor down-regulation produces an increase in dynamin-2 abundance. To probe the differences between opioid agonist and antagonist-induced mu-opioid receptor regulation, the current study determined changes in mu-opioid receptor density using a combined radioligand binding ([3H] DAMGO) and quantitative Western blotting approach in mouse spinal cord. Furthermore, the differences between intermittent and continuous dosing protocols were evaluated. Continuous (7-8 days) s.c. infusions of naloxone (5 mg/kg/day) or naltrexone (15 mg s.c. implant pellet) increased mu-opioid receptor density in radioligand binding assays (approximately +80%) in mouse spinal cord and down-regulated dynamin-2 abundance (approximately -30%), but had no effect on the abundance of immunoreactive mu-opioid receptor. Continuous (7 days) s.c. infusion of etorphine (200 microg/kg/day) decreased immunoreactive mu-opioid receptor (approximately -35%) and [3H] DAMGO binding (approximately -30%), and concurrently increased dynamin-2 abundance (approximately +40%). Continuous (7 days) morphine infusion (40 mg/kg/day plus 25 mg s.c. implant pellet) had no effect on any outcome measure. Delivery of the same daily dose of etorphine or naloxone using intermittent (every 24 h for 7 days) s.c. administration had no effect on immunoreactive mu-opioid receptor, [3H] DAMGO binding or dynamin-2 abundance. These data indicate that mu-opioid receptor

  8. Communication over the Network of Binary Switches Regulates the Activation of A2A Adenosine Receptor

    PubMed Central

    Lee, Yoonji; Choi, Sun; Hyeon, Changbong

    2015-01-01

    Dynamics and functions of G-protein coupled receptors (GPCRs) are accurately regulated by the type of ligands that bind to the orthosteric or allosteric binding sites. To glean the structural and dynamical origin of ligand-dependent modulation of GPCR activity, we performed total ~ 5 μsec molecular dynamics simulations of A2A adenosine receptor (A2AAR) in its apo, antagonist-bound, and agonist-bound forms in an explicit water and membrane environment, and examined the corresponding dynamics and correlation between the 10 key structural motifs that serve as the allosteric hotspots in intramolecular signaling network. We dubbed these 10 structural motifs “binary switches” as they display molecular interactions that switch between two distinct states. By projecting the receptor dynamics on these binary switches that yield 210 microstates, we show that (i) the receptors in apo, antagonist-bound, and agonist-bound states explore vastly different conformational space; (ii) among the three receptor states the apo state explores the broadest range of microstates; (iii) in the presence of the agonist, the active conformation is maintained through coherent couplings among the binary switches; and (iv) to be most specific, our analysis shows that W246, located deep inside the binding cleft, can serve as both an agonist sensor and actuator of ensuing intramolecular signaling for the receptor activation. Finally, our analysis of multiple trajectories generated by inserting an agonist to the apo state underscores that the transition of the receptor from inactive to active form requires the disruption of ionic-lock in the DRY motif. PMID:25664580

  9. Synthesis of inositol phosphate-based competitive antagonists of inositol 1,4,5-trisphosphate receptors.

    PubMed

    Konieczny, Vera; Stefanakis, John G; Sitsanidis, Efstratios D; Ioannidou, Natalia-Anastasia T; Papadopoulos, Nikolaos V; Fylaktakidou, Konstantina C; Taylor, Colin W; Koumbis, Alexandros E

    2016-02-28

    Inositol 1,4,5-trisphosphate receptors (IP3Rs) are intracellular Ca(2+) channels that are widely expressed in animal cells, where they mediate the release of Ca(2+) from intracellular stores evoked by extracellular stimuli. A diverse array of synthetic agonists of IP3Rs has defined structure-activity relationships, but existing antagonists have severe limitations. We combined analyses of Ca(2+) release with equilibrium competition binding to IP3R to show that (1,3,4,6)IP4 is a full agonist of IP3R1 with lower affinity than (1,4,5)IP3. Systematic manipulation of this meso-compound via a versatile synthetic scheme provided a family of dimeric analogs of 2-O-butyryl-(1,3,4,6)IP4 and (1,3,4,5,6)IP5 that compete with (1,4,5)IP3 for binding to IP3R without evoking Ca(2+) release. These novel analogs are the first inositol phosphate-based competitive antagonists of IP3Rs with affinities comparable to that of the only commonly used competitive antagonist, heparin, the utility of which is limited by off-target effects.

  10. A representative retinoid X receptor antagonist UVI3003 induced teratogenesis in zebrafish embryos.

    PubMed

    Zheng, Liang; Xu, Ting; Li, Daoji; Zhou, Junliang

    2015-03-01

    Retinoid X receptor (RXR) interfering activity has been detected in different water resources. To study RXR disruptor-induced toxicological effects on vertebrates, embryos of zebrafish (Danio rerio) were exposed to a representative RXR antagonist UVI3003. Results showed that the teratogenic index (LC50 /EC50 ) of UVI3003 was as high as 5.4. UVI3003 induced multiple malformations of embryos, including deformed fins, reduced brains, small jaws, bent tails and edema in hearts, the degree of which became more severe with increasing exposure concentration. Although no significant difference was observed in the hatching rates between the exposure group and control, the whole body length was significantly reduced by 6.5% and 8.9% when exposed to 200 and 300 µg l(-1) of UVI3003, respectively. The heart rate also significantly decreased by 8.8-50.2% during exposure. Further experiments revealed that the pharyngula stage was the most sensitive development phase in terms of embryo response to UVI3003. The results demonstrated severe teratogenicity of RXR antagonist in zebrafish embryos and provided important data for ecotoxicological evaluation of RXR antagonists. PMID:25186191

  11. Quantitative toxicoproteomic analysis of zebrafish embryos exposed to a retinoid X receptor antagonist UVI3003.

    PubMed

    Zheng, Liang; Yu, Jianlan; Shi, Huahong; Xia, Liang; Xin, Qi; Zhang, Qiang; Zhao, Heng; Luo, Ji; Jin, Wenhai; Li, Daoji; Zhou, Junliang

    2015-09-01

    Retinoid X receptor (RXR) antagonists, including some environmental endocrine disruptors, have a teratogenic effect on vertebrate embryos. To investigate the toxicological mechanism on the protein expression level, a quantitative proteomic study was conducted to analyze the proteome alterations of zebrafish (Danio rerio) embryos exposed to gradient concentrations of a representative RXR antagonist UVI3003. Using isobaric Tags for Relative and Absolute Quantitation (iTRAQ) labeling coupled nano high-performance liquid chromatography-tandem mass spectrometry (nano HPLC-MS/MS), in total 6592 proteins were identified, among which 195 proteins were found to be differentially expressed by more than a two-fold change in exposed groups compared with the control. Gene ontology analysis showed that these differential proteins were mostly involved in anatomical structure development, biosynthetic process, ion binding and oxidoreductase activity. Moreover, the biological pathways of translation, lipoprotein metabolism, cell survival and gluconeogenesis were intensively inhibited after exposure. Some significantly downregulated proteins such as apolipoprotein A-I and vitellogenin and upregulated proteins such as calcium activated nucleotidase 1b, glutathione S-transferase and glucose 6-dehydrogenases showed a strong dose-dependent response. The results provided new insight into the molecular details of RXR antagonist-induced teratogenicity and added novel information of pathways and potential biomarkers for evaluation of RXR interfering activity. PMID:25581642

  12. The discovery of novel human androgen receptor antagonist chemotypes using a combined pharmacophore screening procedure.

    PubMed

    Voet, Arnout; Helsen, Christine; Zhang, Kam Y J; Claessens, Frank

    2013-04-01

    Unraveling the mechanisms involved in castration- and therapy-resistant prostate cancer has led to a renewed interest in androgen receptor (AR)-targeted therapeutics. Anti-androgens that block the activity of the AR therefore remain a valid therapeutic option. However, they must be more effective than, or display a distinct mechanism of action or binding mode from those of bicalutamide and hydroxyflutamide, which are currently in clinical use. For that reason, the second-generation anti-androgen MDV3100 was developed. MDV3100, however, shares its 4-cyano-3-(trifluoromethyl)phenyl group with bicalutamide and hydroxyflutamide required for binding to the AR. In this work, we used a combined strategy to find new antagonist structures distinct from the 4-cyano-3-(trifluoromethyl)phenyl group to avoid cross-resistance for these compounds and to find structures without agonist activity on mutant ARs (AR W741C and AR T877A). We found two novel chemotypes with AR-antagonistic activity (IC(50): 3-6 μM) by virtual screening and confirmed their biological activity in an androgen-responsive reporter assay. The design of our computational approach was validated by the observation of strongly decreased or absence of agonistic activity on the two mutant ARs. Further structural derivatization to optimize the potency of these compounds can render these chemotypes into very promising, alternative AR antagonists for prostate cancer therapy.

  13. In Hamsters the D1 Receptor Antagonist SCH 23390 Depresses Ventilation during Hypoxia

    PubMed Central

    Schlenker, Evelyn H.

    2008-01-01

    During exposure of animals to hypoxia, brain and blood dopamine levels increase stimulating dopaminergic receptors which influence the integrated ventilatory response to low oxygen. The purpose of the present study is to test the hypothesis, that in conscious hamsters, systemic antagonism of D1 receptors would depress their breathing in air and in response to hypoxic and hypercapnic challenges. Nine male hamsters were treated with saline or 0.25 mg/kg SCH-23390 (SCH), a D1 receptor antagonist that crosses the blood-brain barrier. Ventilation was determined using the barometric method and oxygen consumption and CO2 production were evaluated utilizing the flow-through method. During exposure to air, SCH decreased frequency of breathing. During exposure to hypoxia (10% oxygen in nitrogen), relative to saline, SCH-treated hamsters decreased minute ventilation by decreasing tidal volume and oxygen consumption but not CO2 production. During exposure to hypercapnia (5% CO2 in 95% O2) frequency of breathing was decreased with SCH, but there was no significant effect on minute ventilation. Relative to saline treatment body temperature was lower in SCH treated hamsters by 0.6 degrees Celsius. These results demonstrate that in hamsters D1 receptors can modulate control of ventilation in air and during hypoxia and hypercapnic exposures. Whether D1 receptors located centrally or on carotid bodies modulate these effects is not clear from this study. PMID:18036574

  14. (Phenylpiperazinyl-butyl)oxindoles as selective 5-HT7 receptor antagonists.

    PubMed

    Volk, Balázs; Barkóczy, József; Hegedus, Endre; Udvari, Szabolcs; Gacsályi, István; Mezei, Tibor; Pallagi, Katalin; Kompagne, Hajnalka; Lévay, György; Egyed, András; Hársing, László G; Spedding, Michael; Simig, Gyula

    2008-04-24

    A series of potent 5-hydroxytryptamine 7 (5-HT 7) ligands has been synthesized that contain a 1,3-dihydro-2 H-indol-2-one (oxindole) skeleton. The binding of these compounds to the 5-HT 7 and 5-HT 1A receptors was measured. Despite the structural similarity of these two serotonin receptor subtypes, several derivatives exhibited a high selectivity to the 5-HT 7 receptor. According to the structure-activity relationship observations, compounds unsubstituted at the oxindole nitrogen atom and containing a tetramethylene spacer between the oxindole skeleton and the basic nitrogen atom are the most potent ligands. Concerning the basic group, besides the moieties of the 4-phenylpiperazine type, halophenyl-1,2,3,6-tetrahydropyridines also proved to be 5-HT 7 receptor-ligands. Because of halogen substitution on the aromatic rings, good metabolic stability could be achieved. A representative of the family, 3-{4-[4-(4-chlorophenyl)-piperazin-1-yl]-butyl}-3-ethyl-6-fluoro-1,3-dihydro-2 H-indol-2-one ( 9e') exhibited selective 5-HT 7 antagonist activity ( K i = 0.79 nM). The in vivo pharmacological potencies of these 5-HT 7 receptor-ligands were estimated by the conflict drinking (Vogel) and the light-dark anxiolytic tests.

  15. Preclinical pharmacology and pharmacokinetics of AZD3783, a selective 5-hydroxytryptamine 1B receptor antagonist.

    PubMed

    Zhang, Minli; Zhou, Diansong; Wang, Yi; Maier, Donna L; Widzowski, Daniel V; Sobotka-Briner, Cynthia D; Brockel, Becky J; Potts, William M; Shenvi, Ashok B; Bernstein, Peter R; Pierson, M Edward

    2011-11-01

    The preclinical pharmacology and pharmacokinetic properties of (2R)-6-methoxy-8-(4-methylpiperazin-1-yl)-N-(4-morpholin-4-ylphenyl)chromane-2-carboxamide (AZD3783), a potent 5-hydroxytryptamine 1B (5-HT(1B)) receptor antagonist, were characterized as part of translational pharmacokinetic/pharmacodynamic hypothesis testing in human clinical trials. The affinity of AZD3783 to the 5-HT(1B) receptor was measured in vitro by using membrane preparations containing recombinant human or guinea pig 5-HT(1B) receptors and in native guinea pig brain tissue. In vivo antagonist potency of AZD3783 for the 5HT(1B) receptor was investigated by measuring the blockade of 5-HT(1B) agonist-induced guinea pig hypothermia. The anxiolytic-like potency was assessed using the suppression of separation-induced vocalization in guinea pig pups. The affinity of AZD3783 for human and guinea pig 5-HT(1B) receptor (K(i), 12.5 and 11.1 nM, respectively) was similar to unbound plasma EC(50) values for guinea pig receptor occupancy (11 nM) and reduction of agonist-induced hypothermia (18 nM) in guinea pig. Active doses of AZD3783 in the hypothermia assay were similar to doses that reduced separation-induced vocalization in guinea pig pups. AZD3783 demonstrated favorable pharmacokinetic properties. The predicted pharmacokinetic parameters (total plasma clearance, 6.5 ml/min/kg; steady-state volume of distribution, 6.4 l/kg) were within 2-fold of the values observed in healthy male volunteers after a single 20-mg oral dose. This investigation presents a direct link between AZD3783 in vitro affinity and in vivo receptor occupancy to preclinical disease model efficacy. Together with predicted human pharmacokinetic properties, we have provided a model for the quantitative translational pharmacology of AZD3783 that increases confidence in the optimal human receptor occupancy required for antidepressant and anxiolytic effects in patients.

  16. [Use of ondansetron, a 5-HT3 receptor antagonist, as a new type of antiemetic in pediatric oncology].

    PubMed

    Csáki, C; Ferencz, T; Koós, R; Schuler, D; Borsi, J

    1993-06-20

    The effectiveness of the new antiemetic drug, the 5-hydroxytryptamin (5-HT) receptor antagonist ondansetron was evaluated in paediatric cancer patients. 5-HT3 antagonists represent a new class of drugs effective in the control of chemo- and radiotherapy-induced emesis. Based on their selectivity 5-HT3 antagonist are free from extrapyramidal side effects, a major problem in children in the case of currently used dopamine receptor antagonists (e.g. metoclopramide). In this study ondansetron was tested as antiemetic in 33 children with malignant disease (132 chemotherapy cycles) treated with: 1. high-dose cisplatin (120 mg/m2), 2. intermediate-dose cisplatin (60 mg/m2) and 3. no cisplatin-containing, combined high-dose chemotherapy. Ondansetron was found to be safe and effective in the control of acute and delayed emesis in all treatment groups. Its effectiveness was superior to the currently used antiemetic drugs in the period of acute emesis.

  17. Antarlides: A New Type of Androgen Receptor (AR) Antagonist that Overcomes Resistance to AR-Targeted Therapy.

    PubMed

    Saito, Shun; Fujimaki, Takahiro; Panbangred, Watanalai; Igarashi, Yasuhiro; Imoto, Masaya

    2016-02-18

    Prostate cancer is treated with androgen receptor (AR) antagonists but most patients experience disease progression after long-term treatment with these compounds. Therefore, new AR antagonists are required for patient follow-up treatment. In the course of screening for a new AR antagonist, we isolated the novel compounds antarlides A-E (1-5) from Streptomyces sp. BB47. Antarlides are mutually isomeric with respect to the double bond and have a 22-membered-ring macrocyclic structure. The full stereostructure of 1 was established by chemical modifications, including methanolysis, the Trost method, acetonide formation, and the PGME method. 1-5 inhibited the binding of androgen to ARs in vitro. In addition, 2 inhibited the transcriptional activity of not only wild-type AR but also mutant ARs, which are seen in patients with acquired resistance to clinically used AR antagonists. Therefore, antarlides are a potent new generation of AR antagonists that overcome resistance.

  18. Suvorexant: efficacy and safety profile of a dual orexin receptor antagonist in treating insomnia.

    PubMed

    Owen, R T

    2016-01-01

    Suvorexant is a hypnotic representing the first-in-class of a new group of agents known as dual orexin receptor antagonists. They target cerebral orexin receptors which, when activated, contribute to arousal and wakefulness. Suvorexant was shown to decrease sleep onset times and increase sleep duration, whether assessed objectively by polysomnography or subjectively by sleep diaries in primary insomnia patients. Overall tolerability was good, with somnolence being the commonest adverse event (≤ 7% in 3-month studies). No strong signals for rebound or withdrawal were seen after 1-12 months of treatment and few adverse events suggestive of residual psychomotor or cognitive events have been recorded. Further studies are required in patients with insomnia comorbid with depression and head-to-head studies with established hypnotics such as zolpidem and eszopiclone. Studies augmenting the small number of patients evaluating the initial recommended dose (10 mg) would also be prudent. PMID:26937493

  19. Binding optimization through coordination chemistry: CXCR4 chemokine receptor antagonists from ultra rigid metal complexes

    PubMed Central

    Khan, Abid; Nicholson, Gary; Greenman, John; Madden, Leigh; McRobbie, Graeme; Pannecouque, Christophe; De Clercq, Erik; Ullom, Robert; Maples, Danny L.; Maples, Randall L.; Silversides, Jon D.; Hubin, Timothy J.; Archibald, Stephen J.

    2009-01-01

    A new copper(II) containing bis-macrocyclic CXCR4 chemokine receptor antagonist is shown to have improved binding properties to the receptor protein in comparison to the drug AMD3100 (Plerixafor, Mozobil™). The interaction of the metallodrug has been optimized by using ultra rigid chelator units that offer an equatorial site for coordination to the amino acid side chains of the protein. Binding competition assays with anti-CXCR4 antibodies show that the new compound stays bound longer and it has improved anti-HIV potency in vitro (EC50 = 4.3 nM). X-ray structural studies using acetate as a model for carboxylate amino acid side chains indicate the nature of the coordination interaction. PMID:19231846

  20. Structural model for gamma-aminobutyric acid receptor noncompetitive antagonist binding: widely diverse structures fit the same site.

    PubMed

    Chen, Ligong; Durkin, Kathleen A; Casida, John E

    2006-03-28

    Several major insecticides, including alpha-endosulfan, lindane, and fipronil, and the botanical picrotoxinin are noncompetitive antagonists (NCAs) for the GABA receptor. We showed earlier that human beta(3) homopentameric GABA(A) receptor recognizes all of the important GABAergic insecticides and reproduces the high insecticide sensitivity and structure-activity relationships of the native insect receptor. Despite large structural diversity, the NCAs are proposed to fit a single binding site in the chloride channel lumen lined by five transmembrane 2 segments. This hypothesis is examined with the beta(3) homopentamer by mutagenesis, pore structure studies, NCA binding, and molecular modeling. The 15 amino acids in the cytoplasmic half of the pore were mutated to cysteine, serine, or other residue for 22 mutants overall. Localization of A-1'C, A2'C, T6'C, and L9'C (index numbers for the transmembrane 2 region) in the channel lumen was established by disulfide cross-linking. Binding of two NCA radioligands [(3)H]1-(4-ethynylphenyl)-4-n-propyl-2,6,7-trioxabicyclo[2.2.2]octane and [(3)H] 3,3-bis-trifluoromethyl-bicyclo[2,2,1]heptane-2,2-dicarbonitrile was dramatically reduced with 8 of the 15 mutated positions, focusing attention on A2', T6', and L9' as proposed binding sites, consistent with earlier mutagenesis studies. The cytoplasmic half of the beta3 homopentamer pore was modeled as an alpha-helix. The six NCAs listed above plus t-butylbicyclophosphorothionate fit the 2' to 9' pore region forming hydrogen bonds with the T6' hydroxyl and hydrophobic interactions with A2', T6', and L9' alkyl substituents, thereby blocking the channel. Thus, widely diverse NCA structures fit the same GABA receptor beta subunit site with important implications for insecticide cross-resistance and selective toxicity between insects and mammals.

  1. [3H]-SCH 58261 labelling of functional A2A adenosine receptors in human neutrophil membranes

    PubMed Central

    Varani, Katia; Gessi, Stefania; Dionisotti, Silvio; Ongini, Ennio; Andrea Borea, Pier

    1998-01-01

    The present study describes the direct labelling of A2A adenosine receptors in human neutrophil membranes with the potent and selective antagonist radioligand, [3H]-5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4 triazolo[1,5-c]pyrimidine, ([3H]-SCH 58261). In addition, both receptor affinity and potency of a number of adenosine receptor agonists and antagonists were determined in binding, adenylyl cyclase and superoxide anion production assays.Saturation experiments revealed a single class of binding sites with Kd and Bmax values of 1.34 nM and 75 fmol mg−1 protein, respectively. Adenosine receptor ligands competed for the binding of 1 nM [3H]-SCH 58261 to human neutrophil membranes, with a rank order of potency consistent with that typically found for interactions with the A2A adenosine receptors. In the adenylyl cyclase and in the superoxide anion production assays the same compounds exhibited a rank order of potency identical to that observed in binding experiments.Thermodynamic data indicated that [3H]-SCH 58261 binding to human neutrophils is entropy and enthalpy-driven. This finding is in agreement with the thermodynamic behaviour of antagonists binding to rat striatal A2A adenosine receptors.It was concluded that in human neutrophil membranes, [3H]-SCH 58261 directly labels binding sites with pharmacological properties similar to those of A2A adenosine receptors of other tissues. The receptors labelled by [3H]-SCH 58261 mediated the effects of adenosine and adenosine receptor agonists to stimulate cyclic AMP accumulation and inhibition of superoxide anion production in human neutrophils. PMID:9605581

  2. Antinociceptive effects of MSVIII-19, a functional antagonist of the GluK1 kainate receptor.

    PubMed

    Qiu, Chang-Shen; Lash-Van Wyhe, Leanne; Sasaki, Makoto; Sakai, Ryuichi; Swanson, Geoffrey T; Gereau, Robert W

    2011-05-01

    The ionotropic glutamate receptor subunit, GluK1 (GluR5), is expressed in many regions of the nervous system related to sensory transmission. Recently, a selective ligand for the GluK1 receptor, MSVIII-19 (8,9-dideoxy-neodysiherbaine), was synthesized as a derivative of dysiherbaine, a toxin isolated from the marine sponge Lendenfeldia chondrodes. MSVIII-19 potently desensitizes GluK1 receptors without channel activation, rendering it useful as a functional antagonist. Given the high selectivity for GluK1 and the proposed role for this glutamate receptor in nociception, we sought to test the analgesic potential of MSVIII-19 in a series of models of inflammatory, neuropathic, and visceral pain in mice. MSVIII-19 delivered intrathecally dose-dependently reduced formalin-induced spontaneous behaviors and reduced thermal hypersensitivity 3 hours after formalin injection and 24 hours after complete Freund's adjuvant-induced inflammation, but had no effect on mechanical sensitivity in the same models. Intrathecal MSVIII-19 significantly reduced both thermal hyperalgesia and mechanical hypersensitivity in the chronic constriction injury model of neuropathic pain, but had no effect in the acetic acid model of visceral pain. Peripheral administration of MSVIII-19 had no analgesic efficacy in any of these models. Finally, intrathecal MSVIII-19 did not alter responses in Tail-flick tests or performance on the accelerating RotaRod. These data suggest that spinal administration of MSVIII-19 reverses hypersensitivity in several models of pain in mice, supporting the clinical potential of GluK1 antagonists for the management of pain. PMID:21324591

  3. Racial Differences in Resistance to P2Y12 Receptor Antagonists in Type 2 Diabetic Subjects

    PubMed Central

    Duvernay, Matthew T.; Holinstat, Michael; Colowick, Nancy E.; Hudson, Willie J.; Song, Yanna; Harrell, Frank E.

    2014-01-01

    Although resistance to the P2Y12 antagonist clopidogrel is linked to altered drug metabolism, some studies suggest that these pharmacokinetic abnormalities only partially account for drug resistance. To circumvent pharmacokinetic complications and target P2Y12 receptor function we applied the direct P2Y12 antagonist 2-methylthio-AMP (2-methylthioadenosine 5′-monophosphate triethylammonium salt) to purified platelets ex vivo. Platelets were purified from healthy and type 2 diabetes mellitus (T2DM) patients and stimulated with thrombin or the selective protease-activated receptor agonists, protease-activated receptor 1–activating peptide (PAR1-AP), or PAR4-AP. Platelet activation as measured by αIIbβ3 activation, and P-selectin expression was monitored in 141 subjects. Our results demonstrate that, compared with healthy subjects, platelets from diabetic patients are resistant to inhibition by 2-methylthio-AMP, demonstrating P2Y12 pharmacodynamic defects among diabetic patients. Inhibition of thrombin-mediated αIIbβ3 activation by 2-methylthio-AMP was lower in diabetic platelets versus healthy platelets. Subgroup analysis revealed a racial difference in the resistance to 2-methylthio-AMP. We found no resistance in platelets from diabetic African Americans; they were inhibited by 2-methylthio-AMP equally as well as platelets from healthy African Americans. In contrast, platelets from Caucasian patients with diabetes were resistant to P2Y12 antagonism compared with healthy Caucasians. Multivariable analysis demonstrated that other variables, such as obesity, age, or gender, could not account for the differential resistance to 2-methylthio-AMP among races. These results suggest that in addition to altered drug metabolism, P2Y12 receptor function itself is altered in the Caucasian diabetic population. The racial difference in platelet function in T2DM is a novel finding, which may lead to differences in treatment as well as new targets for antiplatelet therapy

  4. Pyrazole CCK(1) receptor antagonists. Part 1: Solution-phase library synthesis and determination of Free-Wilson additivity.

    PubMed

    McClure, Kelly; Hack, Michael; Huang, Liming; Sehon, Clark; Morton, Magda; Li, Lina; Barrett, Terrance D; Shankley, Nigel; Breitenbucher, J Guy

    2006-01-01

    High throughput screening revealed compound 1 as a potent antagonist of the CCK(1) receptor. Evaluation of the CCK(1) SAR in a series of these diarylpyrazole antagonists was conducted in a matrix synthesis format revealing additive (Free-Wilson) and non-additive SAR. This use of additive QSAR modeling in conjunction with combinatorial libraries represents a unique approach to the evaluation of SAR interactions between the variables of any combinatorial matrix.

  5. Antagonist of GH-releasing hormone receptors alleviates experimental ocular inflammation.

    PubMed

    Qin, Yong Jie; Chan, Sun On; Chong, Kelvin Kam Lung; Li, Benjamin Fuk Loi; Ng, Tsz Kin; Yip, Yolanda Wong Ying; Chen, Haoyu; Zhang, Mingzhi; Block, Norman L; Cheung, Herman S; Schally, Andrew V; Pang, Chi Pui

    2014-12-23

    Disruptions in immunity and occurrence of inflammation cause many eye diseases. The growth hormone-releasing hormone-growth hormone-insulin-like growth factor-1 (GHRH-GH-IGF1) axis exerts regulatory effects on the immune system. Its involvement in ocular inflammation remains to be investigated. Here we studied this signaling in endotoxin-induced uveitis (EIU) generated by LPS. The increase in GHRH receptor (GHRH-R) protein levels was parallel to the increase in mRNA levels of pituitary-specific transcription factor-1, GHRH-R splice variant 1, GHRH, and GH following LPS insult. Elevation of GHRH-R and GH receptor was localized on the epithelium of the iris and ciliary body, and GHRH-R was confined to the infiltrating macrophages and leukocytes in aqueous humor but not to those in stroma. Treatment with GHRH-R antagonist decreased LPS-stimulated surges of GH and IGF1 in aqueous humor and alleviated inflammation by reducing the infiltration of macrophages and leukocytes and the production of TNF-α, IL-1β, and monocyte chemotactic protein-1. Our results indicate that inflammation in the iris and ciliary body involves the activation of GHRH signaling, which affects the recruitment of immune cells and the production of proinflammatory mediators that contribute to EIU pathogenesis. Moreover, the results suggest that GHRH-R antagonists are potential therapeutic agents for the treatment of acute ocular inflammation. PMID:25489106

  6. Interleukin-1 receptor antagonist gene polymorphism and mortality in patients with severe sepsis.

    PubMed

    Arnalich, F; López-Maderuelo, D; Codoceo, R; Lopez, J; Solis-Garrido, L M; Capiscol, C; Fernandez-Capitán, C; Madero, R; Montiel, C

    2002-02-01

    This study aims to determine the influence of the polymorphism within the intron 2 of the interleukin-1 receptor antagonist gene (IL-1RN*) on the outcome of severe sepsis, and to assess its functional significance by correlating this polymorphism with the total production of interleukin-1 receptor antagonist (IL-1Ra) protein determined in stimulated peripheral blood mononuclear cells (PBMC). A group of 78 patients with severe sepsis (51 survivors and 27 nonsurvivors) was compared with a healthy control group of 130 blood donors, and 56 patients with uncomplicated pneumonia. We found a significant association between IL-1RN* polymorphism and survival. Thus, after adjusting for age and APACHE II score, multiple logistic regression analysis showed that patients homozygotes for the allele *2 had a 6.47-fold increased risk of death (95% CI 1.01--41.47, P = 0.04). Besides, compared with patients homozygous or heterozygous for the allele *1, IL-1RN*2 homozygotes produced significantly lower levels of IL-1Ra from their PBMC. Our results suggest that insufficient production of this cytokine might contribute, among other factors, to the higher mortality rate found in severe sepsis patients with the IL-1RN*2 homozygous genotype.

  7. Dopamine receptor antagonists impair place conditioning after acute stress in rats.

    PubMed

    Shen, Ying-Ling; Chen, Yao-Chu; Liao, Ruey-Ming

    2010-02-01

    An immediate and robust release of dopamine appears in the brain under an acute stressor, but the functional role of dopamine under stress remains elusive. We recently showed conditioned place preference (CPP) induced by the acute application of a stressor such as being placed on an elevated stand or immobilized in a restraint holder. This study tested whether dopamine is involved in such CPP. The selective dopamine D1 and D2 receptor antagonists, SCH23390 and raclopride, respectively, were injected before stressor manipulation. The doses of SCH23390 (0.025 and 0.05 mg/kg) and raclopride (0.05 and 0.1 mg/kg) used to test for stressor-induced CPP were verified to be ineffective on spontaneous locomotor activity. The results showed that both drugs attenuated the development of stressor-induced CPP. Such a CPP blocking effect by pretreatment of dopamine receptor antagonist was true for either kind of stressor manipulated. These findings indicate that an acute stressor can facilitate a follow-up place conditioning, and that dopamine is involved in the present type of CPP formation.

  8. Discriminating agonist and antagonist ligands of the nuclear receptors using 3D-pharmacophores.

    PubMed

    Lagarde, Nathalie; Delahaye, Solenne; Zagury, Jean-François; Montes, Matthieu

    2016-01-01

    Nuclear receptors (NRs) constitute an important class of therapeutic targets. We evaluated the performance of 3D structure-based and ligand-based pharmacophore models in predicting the pharmacological profile of NRs ligands using the NRLiSt BDB database. We could generate selective pharmacophores for agonist and antagonist ligands and we found that the best performances were obtained by combining the structure-based and the ligand-based approaches. The combination of pharmacophores that were generated allowed to cover most of the chemical space of the NRLiSt BDB datasets. By screening the whole NRLiSt BDB on our 3D pharmacophores, we demonstrated their selectivity towards their dedicated NRs ligands. The 3D pharmacophores herein presented can thus be used as a predictor of the pharmacological activity of NRs ligands.Graphical AbstractUsing a combination of structure-based and ligand-based pharmacophores, agonist and antagonist ligands of the Nuclear Receptors included in the NRLiSt BDB database could be separated.

  9. P2Y12 Receptor Antagonists and Morphine: A Dangerous Liaison?

    PubMed

    Giannopoulos, Georgios; Deftereos, Spyridon; Kolokathis, Fotios; Xanthopoulou, Ioanna; Lekakis, John; Alexopoulos, Dimitrios

    2016-09-01

    P2Y12 receptor antagonists, concurrently administered with aspirin in what has come to be commonly called dual antiplatelet therapy, are a mainstay of treatment for patients with acute coronary syndromes. Morphine, on the contrary, is a commonly used drug in the acute phase of acute coronary syndromes to relieve pain-with the added potential benefit of attenuating acutely raised sympathetic tone. In current guidelines, though, morphine is recommended with decreasing strength of recommendation. One reason is that it raises concern regarding the potentially significant interaction with antiplatelet agents, leading to impaired inhibition of platelet activation. In any case, it is still considered a mandatory part of the inventory of available medications in prehospital acute myocardial infarction management. The goal of the present review is to present published evidence on morphine and its potential interactions with P2Y12 receptor antagonists, as well as on the central issue of whether such interactions may underlie clinically significant effects on patient outcomes. PMID:27586412

  10. 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

  11. Reversal of trauma-induced amnesia in mice by a thrombin receptor antagonist.

    PubMed

    Itzekson, Zeev; Maggio, Nicola; Milman, Anat; Shavit, Efrat; Pick, Chaim G; Chapman, Joab

    2014-05-01

    Minimal traumatic brain injury (mTBI) is associated with the existence of retrograde amnesia and microscopic bleeds containing activated coagulation factors. In an mTBI model, we report that thrombin induces amnesia through its receptor protease-activated receptor 1 (PAR-1). Thrombin activity was significantly elevated (32 %, p < 0.05) 5 min following mTBI compared to controls. Amnesia was assessed by the novel object recognition test in mTBI animals and in animals injected intracerebroventricularly (ICV) with either thrombin or a PAR-1 agonist 1 h after the acquisition phase. Saline-injected controls had a preference index of over 0.3 while mTBI animals and those injected with thrombin or the PAR-1 agonist spent equal time with both objects indicating no recall of the object presented to them 24 h previously (p < 0.05). Co-injecting a PAR-1 antagonist (SCH79797) completely blocked the amnestic effects of mTBI, thrombin, and the PAR-1 agonist. Long-term potentiation, measured in hippocampal slices 24 h after mTBI, ICV thrombin or the PAR-1 agonist, was significantly impaired and this effect was completely reversed by the PAR-1 antagonist. The results support a crucial role for PAR-1 in the generation of amnesia following mTBI, revealing a novel therapeutic target for the cognitive effects of brain trauma.

  12. Brain Changes Associated with Thromboxane Receptor Antagonist, SQ 29,548, Treatment in a Mouse Model

    PubMed Central

    Rebel, Andrew A.; Urquhart, Siri A.; Puig, Kendra L.; Ghatak, Atreyi; Brose, Stephen A.; Golovko, Mikhail Y.; Combs, Colin K.

    2015-01-01

    The purpose of this study was to characterize behavioral and physiological effects of a selective thromboxane receptor (TP) antagonist, SQ 29,548, in the C57BL/6 mouse model. At six months of age, male mice were given either sham or drug intraperitoneal injections for three days at a dose of 2mg/kg each day. On the day after the final injection mice were subjected to behavioral testing paradigms before brain collection. Left hemisphere hippocampi were collected from all mice for protein analysis via western blot. Right brain hemispheres were fixed and imbedded in gelatin, and serially sectioned. The sections were immunostained using anti-c-Fos antibodies. Prostaglandin analysis was performed from remaining homogenized brain samples, minus the hippocampi. Injection of SQ 29,548 decreased selective brain prostaglandin levels compared to sham controls. This correlated with robust increases in limbic region c-Fos immunoreactivity in the SQ 29,548 injected mice. However, drug treated mice demonstrated no significant changes in relevant hippocampal protein levels compared to sham treatments, as determined by western blots. Surprisingly, injection of SQ 29,548 caused mixed changes in parameters of depression and anxiety-like behavior in the mice. In conclusion, the results indicate that administration of peripheral TP receptor antagonists alters brain levels of prostanoids and influences neuronal activity with only minimal alterations of behavior. Whether the drug affects neurons directly or through a secondary pathway involving endothelium or other tissues remains unclear. PMID:25703023

  13. GLP-1 receptor antagonist as a potential probe for pancreatic {beta}-cell imaging

    SciTech Connect

    Mukai, Eri; Toyoda, Kentaro; Kimura, Hiroyuki; Kawashima, Hidekazu; Fujimoto, Hiroyuki; Ueda, Masashi; Temma, Takashi; Hirao, Konomu; Nagakawa, Kenji; Saji, Hideo; Inagaki, Nobuya

    2009-11-20

    We examined exendin(9-39), an antagonist of glucagon-like peptide-1 (GLP-1) receptor (GLP-1R), as a potential probe for imaging of pancreatic {beta}-cells. To evaluate in vitro receptor specificity, binding assay was performed using dispersed mouse islet cells. Binding assay showed competitive inhibition of [{sup 125}I]BH-exendin(9-39) binding by non-radioactive exendin(9-39). To assess in vivo selectivity, the biodistribution was evaluated by intravenous administration of [{sup 125}I]BH-exendin(9-39) to mice. Radioactivity of harvested pancreas reached highest levels at 60 and 120 min among organs examined except lung. Pre-administration of excess non-radioactive exendin(9-39) remarkably and specifically blocked the radioactivity of pancreas. After [{sup 125}I]BH-exendin(9-39) injection into transgenic mice with pancreatic {beta}-cells expressing GFP, fluorescent and radioactive signals of sections of pancreas were evaluated with an image analyzer. Imaging analysis showed that the fluorescent GFP signals and the radioactive signals were correspondingly located. Thus, the GLP-1R antagonist exendin(9-39) may serve as a useful probe for pancreatic {beta}-cell imaging.

  14. Antagonist of GH-releasing hormone receptors alleviates experimental ocular inflammation

    PubMed Central

    Qin, Yong Jie; Chan, Sun On; Chong, Kelvin Kam Lung; Li, Benjamin Fuk Loi; Ng, Tsz Kin; Yip, Yolanda Wong Ying; Chen, Haoyu; Zhang, Mingzhi; Block, Norman L.; Cheung, Herman S.; Schally, Andrew V.; Pang, Chi Pui

    2014-01-01

    Disruptions in immunity and occurrence of inflammation cause many eye diseases. The growth hormone-releasing hormone–growth hormone–insulin-like growth factor-1 (GHRH–GH–IGF1) axis exerts regulatory effects on the immune system. Its involvement in ocular inflammation remains to be investigated. Here we studied this signaling in endotoxin-induced uveitis (EIU) generated by LPS. The increase in GHRH receptor (GHRH-R) protein levels was parallel to the increase in mRNA levels of pituitary-specific transcription factor-1, GHRH-R splice variant 1, GHRH, and GH following LPS insult. Elevation of GHRH-R and GH receptor was localized on the epithelium of the iris and ciliary body, and GHRH-R was confined to the infiltrating macrophages and leukocytes in aqueous humor but not to those in stroma. Treatment with GHRH-R antagonist decreased LPS-stimulated surges of GH and IGF1 in aqueous humor and alleviated inflammation by reducing the infiltration of macrophages and leukocytes and the production of TNF-α, IL-1β, and monocyte chemotactic protein-1. Our results indicate that inflammation in the iris and ciliary body involves the activation of GHRH signaling, which affects the recruitment of immune cells and the production of proinflammatory mediators that contribute to EIU pathogenesis. Moreover, the results suggest that GHRH-R antagonists are potential therapeutic agents for the treatment of acute ocular inflammation. PMID:25489106

  15. CCK1 receptor antagonist, dexloxiglumide: effects on human isolated gallbladder. Potential clinical applications.

    PubMed

    Maselli, M A; Mennuni, L

    2003-09-01

    Cholecystokinin is the main hormonal regulator of gallbladder motility. Dexloxiglumide, the active enantiomer of loxiglumide, interacts competitively with CCK1 receptors as determined in preclinical studies, such as specific radioligand binding assays or functional studies on isolated guinea pig gallbladder, where it inhibited smooth muscle cell contractions induced by cholecystokinin-octapeptide (CCK-8), the most prominent active forms of cholecystokinin. Dexloxiglumide has a potent antagonistic effect, of a competitive nature, on human gallbladder cholecystokinin type 1 receptors. In isolated human gallbladder, dexloxiglumide produced a concentration-dependent rightward shift of the cholecystokinin-octapeptide curve, without affecting its maximal response. Gallbladder motility was evaluated in clinical studies. Dexloxiglumide, orally administered to healthy volunteers at putative therapeutic doses, did not interfere with post-prandial gallbladder kinetics, despite an increase of fasting gallbladder volume. At present, dexloxiglumide is in an advanced stage of clinical research in gastroenterology. Overall, clinical observations suggest that dexloxiglumide may become an effective treatment in several gastrointestinal disorders. Moreover, the beneficial effects can be obtained without increasing the risk of gallstones formation, a potential hazard subsequent to the inhibition of gallbladder contractions and the resulting bile stasis. The potent and selective antagonist dexloxiglumide may offer a possible therapeutic tool for use not only in functional gastrointestinal disorders, such as irritable bowel syndrome, constipation, gastroesophageal reflux disease and functional dyspepsia, but also in other pathologies, such as biliary colics, pancreatic diseases and gastrointestinal tumors. PMID:16484960

  16. Interleukin-1 receptor antagonist gene polymorphism and mortality in patients with severe sepsis

    PubMed Central

    ARNALICH, F; LÓPEZ-MADERUELO, D; CODOCEO, R; LOPEZ, J; SOLIS-GARRIDO, L M; CAPISCOL, C; FERNANDEZ-CAPITÁN, C; MADERO, R; MONTIEL, C

    2002-01-01

    This study aims to determine the influence of the polymorphism within the intron 2 of the interleukin-1 receptor antagonist gene (IL-1RN*) on the outcome of severe sepsis, and to assess its functional significance by correlating this polymorphism with the total production of interleukin-1 receptor antagonist (IL-1Ra) protein determined in stimulated peripheral blood mononuclear cells (PBMC). A group of 78 patients with severe sepsis (51 survivors and 27 nonsurvivors) was compared with a healthy control group of 130 blood donors, and 56 patients with uncomplicated pneumonia. We found a significant association between IL-1RN* polymorphism and survival. Thus, after adjusting for age and APACHE II score, multiple logistic regression analysis showed that patients homozygotes for the allele *2 had a 6·47-fold increased risk of death (95% CI 1·01–41·47, P = 0·04). Besides, compared with patients homozygous or heterozygous for the allele *1, IL-1RN*2 homozygotes produced significantly lower levels of IL-1Ra from their PBMC. Our results suggest that insufficient production of this cytokine might contribute, among other factors, to the higher mortality rate found in severe sepsis patients with the IL-1RN*2 homozygous genotype. PMID:11876758

  17. 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.

  18. Discriminating agonist and antagonist ligands of the nuclear receptors using 3D-pharmacophores.

    PubMed

    Lagarde, Nathalie; Delahaye, Solenne; Zagury, Jean-François; Montes, Matthieu

    2016-01-01

    Nuclear receptors (NRs) constitute an important class of therapeutic targets. We evaluated the performance of 3D structure-based and ligand-based pharmacophore models in predicting the pharmacological profile of NRs ligands using the NRLiSt BDB database. We could generate selective pharmacophores for agonist and antagonist ligands and we found that the best performances were obtained by combining the structure-based and the ligand-based approaches. The combination of pharmacophores that were generated allowed to cover most of the chemical space of the NRLiSt BDB datasets. By screening the whole NRLiSt BDB on our 3D pharmacophores, we demonstrated their selectivity towards their dedicated NRs ligands. The 3D pharmacophores herein presented can thus be used as a predictor of the pharmacological activity of NRs ligands.Graphical AbstractUsing a combination of structure-based and ligand-based pharmacophores, agonist and antagonist ligands of the Nuclear Receptors included in the NRLiSt BDB database could be separated. PMID:27602059

  19. Two related forms of memory in the crab Chasmagnathus are differentially affected by NMDA receptor antagonists.

    PubMed

    Troncoso, Julieta; Maldonado, Héctor

    2002-05-01

    A visual danger stimulus (VDS) elicits an escape response in the crab Chasmagnathus that declines after a few iterative presentations. Long-lasting retention of such decrement, termed context-signal memory (CSM), is mediated by an association between danger stimulus and environmental cues, cycloheximide sensitive, correlated with PKA activity and NFkappa-B activation, positively modulated by angiotensins, and selectively regulated by a muscarinic-cholinergic mechanism. The present research was aimed at studying the possible involvement of NMDA-like receptors in CSM, given the role attributed to these receptors in vertebrate memory and their occurrence in invertebrates including crustaceans. Vertebrate antagonists (+/-)-2-amino-5-phosphonopentanoic acid (AP5) and (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801) were used. Memory retention impairment was shown with MK-801 10(-3) M (1 microg/g) injected immediately before training or after training, or delayed 1 or 4 h, but not 6 h, posttraining. An AP5 10(-3) M dose (0.6 microg/g) impairs retention when given before but not after training. Neither antagonist produced retrieval deficit. A memory process similar to CSM but nonassociative in nature and induced by massed training (termed signal memory, SM), proved entirely insensitive to AP5 or MK-801, confirming the view that distinct mechanisms subserve these different types of memory in the crab.

  20. Displacement of Cortisol From Human Heart by Acute Administration of a Mineralocorticoid Receptor Antagonist

    PubMed Central

    Iqbal, Javaid; Andrew, Ruth; Cruden, Nicholas L.; Kenyon, Christopher J.; Hughes, Katherine A.; Newby, David E.; Hadoke, Patrick W. F.; Walker, Brian R.

    2015-01-01

    Context Mineralocorticoid receptor (MR) antagonists have beneficial effects in patients with heart failure and myocardial infarction, often attributed to blocking aldosterone action in the myocardium. However, binding of aldosterone to MR requires local activity of the enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), which inactivates cortisol to cortisone and thereby prevents receptor occupancy by cortisol. In vivo activity of 11β-HSD2 and potential occupancy of MR by cortisol in human heart have not been quantified. Objective This study aimed to measure in vivo activity of 11β-HSD2 and to establish whether cortisol binds MR in human heart. Participants and Interventions Nine patients without heart failure undergoing diagnostic coronary angiography were infused to steady state with the stable isotope tracers 9,11,12,12-[2H]4-cortisol and 1,2-[2H]2-cortisone to quantify cortisol and cortisone production. Samples were obtained from the femoral artery and coronary sinus before and for 40 minutes after bolus iv administration of an MR antagonist, potassium canrenoate. Coronary sinus blood flow was measured by venography and Doppler flow wire. Results There was no detectable production of cortisol or cortisone across the myocardium. After potassium canrenoate administration, plasma aldosterone concentrations increased substantially but aldosterone was not detectably released from the myocardium. In contrast, plasma cortisol concentrations did not change in the systemic circulation but tissue-bound cortisol was released transiently from the myocardium after potassium canrenoate administration. Conclusions Human cardiac 11β-HSD2 activity appears too low to inactivate cortisol to cortisone. Cortisol is displaced acutely from the myocardium by MR antagonists and may contribute to adverse MR activation in human heart. PMID:24423282

  1. Evaluation of the abuse potential of AM281, a new synthetic cannabinoid CB1 receptor antagonist.

    PubMed

    Botanas, Chrislean Jun; de la Peña, June Bryan; Dela Pena, Irene Joy; Tampus, Reinholdgher; Kim, Hee Jin; Yoon, Seong Shoon; Seo, Joung-Wook; Jeong, Eun Ju; Cheong, Jae Hoon

    2015-11-01

    AM281 (1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-4-morpholinyl-1H-pyrazole-3-carboxamide) is a new synthetic cannabinoid CB1 receptor antagonist. Similar to other cannabinoid antagonists, AM281 has been suggested to have therapeutic indications. However, recent reports have suggested that cannabinoid CB1 receptor antagonists may share similar behavioral effects with other drugs of abuse such as cocaine and amphetamine. These reports cast doubts on the safety profile of AM281. Thus, in the present study we evaluated the abuse potential (rewarding and reinforcing effects) of AM281 through two of the most widely used animal models for assessing the abuse potential of drugs: the conditioned place preference (CPP) and self-administration (SA) tests. Experiments were performed in Sprague-Dawley rats in various dosages [CPP (0.1, 0.5 or 2.5mg/kg), SA (0.005, 0.025 or 0.1mg/kg/infusion)]. We also delved into the consequences of repeated drug exposure on the subsequent response to the drug. Thus, parallel experiments were carried out in rats pretreated with AM281 for 7 or 14 days. Our findings indicated that AM281, at any dose, did not induce CPP and SA in drug-naïve rats. Interestingly, significant CPP (0.5mg/kg of AM281), but not SA, was observed in 14 days pretreated rats. These observations suggest that AM281 per se has no or minimal rewarding and reinforcing properties, but alterations in neuronal functions and behavior due to repeated AM281 exposure may contribute in part to the abuse potential of this drug. In view of this finding, we advocate the careful use, monitoring, and dispensation of AM281.

  2. Dynamic Regulation of Quaternary Organization of the M1 Muscarinic Receptor by Subtype-selective Antagonist Drugs*

    PubMed Central

    Pediani, John D.; Ward, Richard J.; Godin, Antoine G.; Marsango, Sara

    2016-01-01

    Although rhodopsin-like G protein-coupled receptors can exist as both monomers and non-covalently associated dimers/oligomers, the steady-state proportion of each form and whether this is regulated by receptor ligands are unknown. Herein we address these topics for the M1 muscarinic acetylcholine receptor, a key molecular target for novel cognition enhancers, by using spatial intensity distribution analysis. This method can measure fluorescent particle concentration and assess oligomerization states of proteins within defined regions of living cells. Imaging and analysis of the basolateral surface of cells expressing some 50 molecules·μm−2 human muscarinic M1 receptor identified a ∼75:25 mixture of receptor monomers and dimers/oligomers. Both sustained and shorter term treatment with the selective M1 antagonist pirenzepine resulted in a large shift in the distribution of receptor species to favor the dimeric/oligomeric state. Although sustained treatment with pirenzepine also resulted in marked up-regulation of the receptor, simple mass action effects were not the basis for ligand-induced stabilization of receptor dimers/oligomers. The related antagonist telenzepine also produced stabilization and enrichment of the M1 receptor dimer population, but the receptor subtype non-selective antagonists atropine and N-methylscopolamine did not. In contrast, neither pirenzepine nor telenzepine altered the quaternary organization of the related M3 muscarinic receptor. These data provide unique insights into the selective capacity of receptor ligands to promote and/or stabilize receptor dimers/oligomers and demonstrate that the dynamics of ligand regulation of the quaternary organization of G protein-coupled receptors is markedly more complex than previously appreciated. This may have major implications for receptor function and behavior. PMID:27080256

  3. Dynamic Regulation of Quaternary Organization of the M1 Muscarinic Receptor by Subtype-selective Antagonist Drugs.

    PubMed

    Pediani, John D; Ward, Richard J; Godin, Antoine G; Marsango, Sara; Milligan, Graeme

    2016-06-17

    Although rhodopsin-like G protein-coupled receptors can exist as both monomers and non-covalently associated dimers/oligomers, the steady-state proportion of each form and whether this is regulated by receptor ligands are unknown. Herein we address these topics for the M1 muscarinic acetylcholine receptor, a key molecular target for novel cognition enhancers, by using spatial intensity distribution analysis. This method can measure fluorescent particle concentration and assess oligomerization states of proteins within defined regions of living cells. Imaging and analysis of the basolateral surface of cells expressing some 50 molecules·μm(-2) human muscarinic M1 receptor identified a ∼75:25 mixture of receptor monomers and dimers/oligomers. Both sustained and shorter term treatment with the selective M1 antagonist pirenzepine resulted in a large shift in the distribution of receptor species to favor the dimeric/oligomeric state. Although sustained treatment with pirenzepine also resulted in marked up-regulation of the receptor, simple mass action effects were not the basis for ligand-induced stabilization of receptor dimers/oligomers. The related antagonist telenzepine also produced stabilization and enrichment of the M1 receptor dimer population, but the receptor subtype non-selective antagonists atropine and N-methylscopolamine did not. In contrast, neither pirenzepine nor telenzepine altered the quaternary organization of the related M3 muscarinic receptor. These data provide unique insights into the selective capacity of receptor ligands to promote and/or stabilize receptor dimers/oligomers and demonstrate that the dynamics of ligand regulation of the quaternary organization of G protein-coupled receptors is markedly more complex than previously appreciated. This may have major implications for receptor function and behavior. PMID:27080256

  4. 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

  5. Potency enhancement of the κ-opioid receptor antagonist probe ML140 through sulfonamide constraint utilizing a tetrahydroisoquinoline motif

    PubMed Central

    Frankowski, Kevin J.; Slauson, Stephen R.; Lovell, Kimberly M.; Phillips, Angela M.; Streicher, John M.; Zhou, Lei; Whipple, David A.; Schoenen, Frank J.; Prisinzano, Thomas E.; Bohn, Laura M.; Aubé, Jeffrey

    2015-01-01

    Optimization of the sulfonamide-based kappa opioid receptor (KOR) antagonist probe molecule ML140 through constraint of the sulfonamide nitrogen within a tetrahydroisoquinoline moiety afforded a marked increase in potency. This strategy, when combined with additional structure-activity relationship exploration, has led to a compound only six-fold less potent than norBNI, a widely utilized KOR antagonist tool compound, but significantly more synthetically accessible. The new optimized probe is suitably potent for use as an in vivo tool to investigate the therapeutic potential of KOR antagonists. PMID:25593096

  6. Novel Benzamide-Based Histamine H3 Receptor Antagonists: The Identification of Two Candidates for Clinical Development

    PubMed Central

    2015-01-01

    The preclinical characterization of novel phenyl(piperazin-1-yl)methanones that are histamine H3 receptor antagonists is described. The compounds described are high affinity histamine H3 antagonists. Optimization of the physical properties of these histamine H3 antagonists led to the discovery of several promising lead compounds, and extensive preclinical profiling aided in the identification of compounds with optimal duration of action for wake promoting activity. This led to the discovery of two development candidates for Phase I and Phase II clinical trials. PMID:25893048

  7. Characterization of A2A adenosine receptors in human lymphocyte membranes by [3H]-SCH 58261 binding

    PubMed Central

    Varani, Katia; Gessi, Stefania; Dalpiaz, Alessandro; Ongini, Ennio; Andrea Borea, Pier

    1997-01-01

    The present study describes for the first time the characterization of the adenosine A2A receptor in human lymphocyte membranes with the new potent and selective antagonist radioligand, [3H]-5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo [4,3-e]-1,2,4 triazolo [1,5-c] pyrimidine, ([3H]-SCH 58261). In addition, both receptor affinity and potency of reference adenosine receptor agonists and antagonists were determined in binding and adenylyl cyclase studies. Saturation experiments revealed a single class of binding sites with Kd and Bmax values of 0.85 nM and 35 fmol mg−1 protein, respectively. A series of adenosine receptor ligands were found to compete for the binding of 0.8 nM [3H]-SCH 58261 to human lymphocyte membranes with a rank order of potency consistent with that typically found for interactions with the A2A-adenosine receptor. In the adenylyl cyclase assay the same compounds exhibited a rank order of potency similar to that observed in binding experiments. Thermodynamic data indicate that [3H]-SCH 58261 binding to human lymphocytes is entropy and enthalpy-driven, a finding in agreement with the thermodynamic behaviour of antagonists for rat striatal A2A-adenosine receptors. It is concluded that in human lymphocyte membranes [3H]-SCH 58261 directly labels binding sites showing the characteristic properties of the adenosine A2A-receptor. The presence of A2A-receptors in peripheral tissue such as human lymphocytes strongly suggests an important role for adenosine in modulating immune and inflammatory responses. PMID:9313951

  8. SB 242084, a selective and brain penetrant 5-HT2C receptor antagonist.

    PubMed

    Kennett, G A; Wood, M D; Bright, F; Trail, B; Riley, G; Holland, V; Avenell, K Y; Stean, T; Upton, N; Bromidge, S; Forbes, I T; Brown, A M; Middlemiss, D N; Blackburn, T P

    1997-01-01

    SB 242084 has a high affinity (pKi 9.0) for the cloned human 5-HT2C receptor and 100- and 158-fold selectivity over the closely related cloned human 5-HT2B and 5-HT2A subtypes respectively. SB 242084 had over 100-fold selectivity over a range of other 5-HT, dopamine and adrenergic receptors. In studies of 5-HT-stimulated phosphatidylinositol hydrolysis using SH-SY5Y cells stably expressing the cloned human 5-HT2C receptor, SB 242084 acted as an antagonist with a pKb of 9.3, which closely resembled its corresponding receptor binding affinity. SB 242084 potently inhibited m-chlorophenylpiperazine (mCPP, 7 mgkg i.p. 20 min pre-test)-induced hypolocomotion in rats, a model of in vivo central 5-HT2C receptor function, with an ID50 of 0.11 mg/kg i.p., and 2.0 mg/kg p.o. SB 242084 (0.1-1 mg/kg i.p.) exhibited an anxiolytic-like profile in the rat social interaction test, increasing time spent in social interaction, but having no effect on locomotion. SB 242084 (0.1-1 mg/kg i.p.) also markedly increased punished responding in a rat Geller-Seifter conflict test of anxiety, but had no consistent effect on unpunished responding. A large acute dose of SB 242084 (30 mg/kg p.o.) had no effect on seizure susceptibility in the rat maximal electroshock seizure threshold test. Also, while SB 242084 (2 and 6 mg/kg p.o. 1 hr pre-test) antagonized the hypophagic response to mCPP, neither acute nor subchronic administration of the drug, for 5 days at 2 or 6 mg/kg p.o. twice daily, affected food intake or weight gain. The results suggest that SB 242084 is the first reported selective potent and brain penetrant 5-HT2C receptor antagonist and has anxiolytic-like activity, but does not possess either proconvulsant or hyperphagic properties which are characteristic of mutant mice lacking the 5-HT2C receptor. PMID:9225286

  9. Effect of adenosine and adenosine receptor antagonist on Müller cell potassium channel in Rat chronic ocular hypertension models.

    PubMed

    Yang, Zijian; Huang, Ping; Liu, Xiaohong; Huang, Shouyue; Deng, Lianfu; Jin, Zhe; Xu, Shuo; Shen, Xi; Luo, Xunda; Zhong, Yisheng

    2015-01-01

    Müller cells are principal glial cells in rat retina and have attracted much attention in glaucoma studies. However, it is not clear whether adenosine and adenosine receptor (AR) antagonists play any roles in the regulation of potassium channels in Müller cells and subsequently in the promotion of glutamine synthetase (GS) and L-Glutamate/L-Aspartate Transporter (GLAST) functions. We found that chronic ocular hypertension (COH) in rat down-regulated Müller cells Kir2.1, Kir4.1, TASK-1, GS and GLAST expressions and attenuated the peak of inward potassium current. Retinal ganglion cells (RGC) count was lower in the COH rats than that in the sham operation animals. Intravitreal injection of selective A2A AR antagonist SCH442416 up-regulated Müller cell Kir4.1, TASK-1, GS and GLAST expressions and enhanced inward potassium currents compared with those in the COH rats with vehicle control. Meanwhile, the RGC count was higher following intravitreal injection of SCH442416 in the COH rats than that after vehicle injection. The fact that PKA inhibitor H-89 blocked these SCH442416 effects suggested that the PKA signaling pathway was involved in the observed ocular responses following the intravitreal SCH442416 injection. PMID:26063641

  10. Blockade of adenosine A2A receptors prevents protein phosphorylation in the striatum induced by cortical stimulation.

    PubMed

    Quiroz, César; Gomes, Catarina; Pak, Arlene C; Ribeiro, Joaquim A; Goldberg, Steven R; Hope, Bruce T; Ferré, Sergi

    2006-10-18

    Previous studies have shown that cortical stimulation selectively activates extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and immediate early gene expression in striatal GABAergic enkephalinergic neurons. In the present study, we demonstrate that blockade of adenosine A2A receptors with caffeine or a selective A2A receptor antagonist counteracts the striatal activation of cAMP-protein kinase A cascade (phosphorylation of the Ser845 residue of the glutamate receptor 1 subunit of the AMPA receptor) and mitogen-activated protein kinase (ERK1/2 phosphorylation) induced by the in vivo stimulation of corticostriatal afferents. The results indicate that A2A receptors strongly modulate the efficacy of glutamatergic synapses on striatal enkephalinergic neurons.

  11. Naturally-Occurring Glucosinolates, Glucoraphanin and Glucoerucin, are Antagonists to Aryl Hydrocarbon Receptor as Their Chemopreventive Potency.

    PubMed

    Abdull Razis, Ahmad Faizal; Noor, Noramaliza Mohd

    2015-01-01

    As a cytosolic transcription factor, the aryl hydrocarbon (Ah) receptor is involved in several patho- physiological events leading to immunosuppression and cancer; hence antagonists of the Ah receptor may possess chemoprevention properties. It is known to modulate carcinogen-metabolising enzymes, for instance the CYP1 family of cytochromes P450 and quinone reductase, both important in the biotransformation of many chemical carcinogens via regulating phase I and phase II enzyme systems. Utilising chemically-activated luciferase expression (CALUX) assay it was revealed that intact glucosinolates, glucoraphanin and glucoerucin, isolated from Brassica oleracea L. var. acephala sabellica and Eruca sativa ripe seeds, respectively, are such antagonists. Both glucosinolates were poor ligands for the Ah receptor; however, they effectively antagonised activation of the receptor by the avid ligand benzo[a]pyrene. Indeed, intact glucosinolate glucoraphanin was a more potent antagonist to the receptor than glucoerucin. It can be concluded that both glucosinolates effectively act as antagonists for the Ah receptor, and this may contribute to their established chemoprevention potency. PMID:26320454

  12. The metabotropic glutamate receptor subtype 5 antagonist fenobam is analgesic and has improved in vivo selectivity compared with the prototypical antagonist 2-methyl-6-(phenylethynyl)-pyridine.

    PubMed

    Montana, Michael C; Cavallone, Laura F; Stubbert, Kristi K; Stefanescu, Andrei D; Kharasch, Evan D; Gereau, Robert W

    2009-09-01

    Metabotropic glutamate receptor subtype 5 (mGlu5) has been demonstrated to play a role in the modulation of numerous nociceptive modalities. When administered via peripheral, intrathecal, or systemic routes, mGlu5 antagonists have analgesic properties in a variety of preclinical pain models. Despite a wealth of data supporting the use of mGlu5 antagonists to treat pain, studies have been limited to preclinical animal models due to a lack of mGlu5 antagonists that are approved for use in humans. It has been demonstrated previously that fenobam [N-(3-chlorophenyl)-N'-(4,5-dihydro-1-methyl-4-oxo-1H-imidazole-2-yl)urea], an anxiolytic shown to be safe and effective in human trials, is a selective and potent noncompetitive antagonist of mGlu5 (J Pharmacol Exp Ther 315:711-721, 2005). Here, we report a series of studies aimed at testing whether fenobam, similar to the prototypical mGlu5 antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP), has analgesic properties in mice. We show that fenobam reduces formalin-induced pain behaviors and relieves established inflammation-induced thermal hypersensitivity in mice. Similar results were seen with MPEP. Administration of fenobam resulted in an increase in locomotor activity in the open-field task but did not impair performance on the accelerating Rotarod. Analysis of brain and plasma fenobam levels indicated that fenobam is rapidly concentrated in brain after intraperitoneal administration in mice but is essentially cleared from circulation within 1 h after injection. Fenobam had no analgesic effect in mGlu5 knockout mice, whereas the prototypical antagonist MPEP retained significant analgesic efficacy in mGlu5 knockouts. These results demonstrate that fenobam is analgesic in mice and has an improved in vivo selectivity for mGlu5 over MPEP. PMID:19515968

  13. Senktide-induced gerbil foot tapping behaviour is blocked by selective tachykinin NK1 and NK3 receptor antagonists.

    PubMed

    Sundqvist, Monika; Kristensson, Elin; Adolfsson, Rebecka; Leffler, Agnes; Ahlstedt, Ingela; Engberg, Susanna; Drmota, Tomas; Sigfridsson, Kalle; Jussila, Rainer; de Verdier, Jennie; Novén, Anna; Johansson, Anders; Påhlman, Ingrid; von Mentzer, Bengt; Lindström, Erik

    2007-12-22

    Intracerebroventricular (i.c.v.) administration of tachykinin NK(1) receptor agonists induces tapping of the hind legs in gerbils, so-called gerbil foot tapping, which is thought to reflect a fear-related response. The aim of the present study was to examine how ligands selective for NK(1), NK(2) and NK(3) receptors affect the gerbil foot tap response. Agonists selective for NK receptor subtypes were administered i.c.v. and the gerbil foot tap response was monitored. The effect of systemically administered antagonists was also studied. The interaction of ligands with gerbil NK(1) receptors was evaluated using autoradiography on gerbil brain slices with [(3)H]-Sar,Met(O(2))-substance P or [(3)H]GR205171 as radioligand. The effects of ligands on NK(1) and NK(3) receptor-mediated increases in intracellular calcium in vitro were studied in Chinese hamster ovary cells expressing the cloned gerbil receptors. The selective NK(1) receptor agonist ASMSP and the selective NK(3) receptor agonist senktide induced dose-dependent increases in gerbil foot tapping with similar potency. The maximal effect of senktide was approximately 40% of the maximal response evoked by ASMSP. The effects of ASMSP and senktide were blocked by administration of the selective NK(1) receptor antagonist CP99,994 (10 micromol/kg s.c.). The effects of senktide, but not ASMSP, were blocked by administration of the selective NK(3) receptor antagonist SB223412 (50 micromol/kg i.p.). Senktide did not displace NK(1) receptor radioligand binding and was >1000-fold less potent than ASMSP at activating gerbil NK(1) receptors. The selective NK(3) receptor agonist senktide evokes fear-related gerbil foot tapping, an effect which probably involves indirect enhancement of NK(1) receptor signalling.

  14. Postsynaptic Adenosine A2A Receptors Modulate Intrinsic Excitability of Pyramidal Cells in the Rat Basolateral Amygdala

    PubMed Central

    Rau, Andrew R.; Ariwodola, Olusegun J.

    2015-01-01

    Background: The basolateral amygdala plays a critical role in the etiology of anxiety disorders and addiction. Pyramidal neurons, the primary output cells of this region, display increased firing following exposure to stressors, and it is thought that this increase in excitability contributes to stress responsivity and the expression of anxiety-like behaviors. However, much remains unknown about the underlying mechanisms that regulate the intrinsic excitability of basolateral amygdala pyramidal neurons. Methods: Ex vivo gramicidin perforated patch recordings were conducted in current clamp mode where hyper- and depolarizing current steps were applied to basolateral amygdala pyramidal neurons to assess the effects of adenosine A2A receptor modulation on intrinsic excitability. Results: Activation of adenosine A2A receptors with the selective A2A receptor agonist CGS-21680 significantly increased the firing rate of basolateral amygdala pyramidal neurons in rat amygdala brain slices, likely via inhibition of the slow afterhyperpolarization potential. Both of these A2A receptor-mediated effects were blocked by preapplication of a selective A2A receptor antagonist (ZM-241385) or by intra-pipette infusion of a protein kinase A inhibitor, suggesting a postsynaptic locus of A2A receptors on basolateral amygdala pyramidal neurons. Interestingly, bath application of the A2A receptor antagonist alone significantly attenuated basolateral amygdala pyramidal cell firing, consistent with a role for tonic adenosine in the regulation of the intrinsic excitability of these neurons. Conclusions: Collectively, these data suggest that adenosine, via activation of A2A receptors, may directly facilitate basolateral amygdala pyramidal cell output, providing a possible balance for the recently described inhibitory effects of adenosine A1 receptor activation on glutamatergic excitation of basolateral amygdala pyramidal cells. PMID:25716780

  15. Effect of 1-Substitution on Tetrahydroisoquinolines as Selective Antagonists for the Orexin-1 Receptor

    PubMed Central

    Perrey, David A.; German, Nadezhda A.; Decker, Ann M.; Thorn, David; Li, Jun-Xu; Gilmour, Brian P.; Thomas, Brian F.; Harris, Danni L.; Runyon, Scott P.; Zhang, Yanan

    2015-01-01

    Selective blockade of the Orexin-1 receptor has been suggested as a potential approach to drug addiction therapy because of its role in modulating the brain's reward system. We have recently reported a series of tetrahydroisoquinoline-based OX1 selective antagonists. Aimed at elucidating SAR requirements in other regions of the molecule and further enhancing OX1 potency and selectivity, we have designed and synthesized a series of analogs bearing a variety of substituents at the 1-position of the tetrahydroisoquinoline. The results show that an optimally substituted benzyl group is required for activity at the OX1 receptor. Several compounds with improved potency and/or selectivity have been identified. When combined with structural modifications that were previously found to improve selectivity, we have identified compound 73 (RTIOX-251) with an apparent dissociation constant (Ke) of 16.1 nM at the OX1 receptor and >620-fold selectivity over the OX2 receptor. In vivo, compound 73 was shown to block the development of locomotor sensitization to cocaine in rats. PMID:25643283

  16. Residues remote from the binding pocket control the antagonist selectivity towards the corticotropin-releasing factor receptor-1

    NASA Astrophysics Data System (ADS)

    Sun, Xianqiang; Cheng, Jianxin; Wang, Xu; Tang, Yun; Ågren, Hans; Tu, Yaoquan

    2015-01-01

    The corticotropin releasing factors receptor-1 and receptor-2 (CRF1R and CRF2R) are therapeutic targets for treating neurological diseases. Antagonists targeting CRF1R have been developed for the potential treatment of anxiety disorders and alcohol addiction. It has been found that antagonists targeting CRF1R always show high selectivity, although CRF1R and CRF2R share a very high rate of sequence identity. This has inspired us to study the origin of the selectivity of the antagonists. We have therefore built a homology model for CRF2R and carried out unbiased molecular dynamics and well-tempered metadynamics simulations for systems with the antagonist CP-376395 in CRF1R or CRF2R to address this issue. We found that the side chain of Tyr6.63 forms a hydrogen bond with the residue remote from the binding pocket, which allows Tyr6.63 to adopt different conformations in the two receptors and results in the presence or absence of a bottleneck controlling the antagonist binding to or dissociation from the receptors. The rotameric switch of the side chain of Tyr3566.63 allows the breaking down of the bottleneck and is a perquisite for the dissociation of CP-376395 from CRF1R.

  17. The duration of sleep promoting efficacy by dual orexin receptor antagonists is dependent upon receptor occupancy threshold

    PubMed Central

    2013-01-01

    Background Drugs targeting insomnia ideally promote sleep throughout the night, maintain normal sleep architecture, and are devoid of residual effects associated with morning sedation. These features of an ideal compound are not only dependent upon pharmacokinetics, receptor binding kinetics, potency and pharmacodynamic activity, but also upon a compound’s mechanism of action. Results Dual orexin receptor antagonists (DORAs) block the arousal-promoting activity of orexin peptides and, as demonstrated in the current work, exhibit an efficacy signal window dependent upon oscillating levels of endogenous orexin neuropeptide. Sleep efficacy of structurally diverse DORAs in rat and dog was achieved at plasma exposures corresponding to orexin 2 receptor (OX2R) occupancies in the range of 65 to 80%. In rats, the time course of OX2R occupancy was dependent upon receptor binding kinetics and was tightly correlated with the timing of active wake reduction. In rhesus monkeys, direct comparison of DORA-22 with GABA-A modulators at similar sleep-inducing doses revealed that diazepam produced next-day residual sleep and both diazepam and eszopiclone induced next-day cognitive deficits. In stark contrast, DORA-22 did not produce residual effects. Furthermore, DORA-22 evoked only minimal changes in quantitative electroencephalogram (qEEG) activity during the normal resting phase in contrast to GABA-A modulators which induced substantial qEEG changes. Conclusion The higher levels of receptor occupancy necessary for DORA efficacy require a plasma concentration profile sufficient to maintain sleep for the duration of the resting period. DORAs, with a half-life exceeding 8 h in humans, are expected to fulfill this requirement as exposures drop to sub-threshold receptor occupancy levels prior to the wake period, potentially avoiding next-day residual effects at therapeutic doses. PMID:23981345

  18. Sphingosine 1-phosphate receptor 2 antagonist JTE-013 increases the excitability of sensory neurons independently of the receptor

    PubMed Central

    Li, Chao; Chi, Xian Xuan; Xie, Wenrui; Strong, J. A.; Zhang, J.-M.

    2012-01-01

    Previously we demonstrated that sphingosine 1-phosphate receptor 1 (S1PR1) played a prominent, but not exclusive, role in enhancing the excitability of small-diameter sensory neurons, suggesting that other S1PRs can modulate neuronal excitability. To examine the potential role of S1PR2 in regulating neuronal excitability we used the established selective antagonist of S1PR2, JTE-013. Here we report that exposure to JTE-013 alone produced a significant increase in excitability in a time- and concentration-dependent manner in 70–80% of recorded neurons. Internal perfusion of sensory neurons with guanosine 5′-O-(2-thiodiphosphate) (GDP-β-S) via the recording pipette inhibited the sensitization produced by JTE-013 as well as prostaglandin E2. Pretreatment with pertussis toxin or the selective S1PR1 antagonist W146 blocked the sensitization produced by JTE-013. These results indicate that JTE-013 might act as an agonist at other G protein-coupled receptors. In neurons that were sensitized by JTE-013, single-cell RT-PCR studies demonstrated that these neurons did not express the mRNA for S1PR2. In behavioral studies, injection of JTE-013 into the rat's hindpaw produced a significant increase in the mechanical sensitivity in the ipsilateral, but not contralateral, paw. Injection of JTE-013 did not affect the withdrawal latency to thermal stimulation. Thus JTE-013 augments neuronal excitability independently of S1PR2 by unknown mechanisms that may involve activation of other G protein-coupled receptors such as S1PR1. Clearly, further studies are warranted to establish the causal nature of this increased sensitivity, and future studies of neuronal function using JTE-013 should be interpreted with caution. PMID:22673325

  19. The Administration of Levocabastine, a NTS2 Receptor Antagonist, Modifies Na(+), K(+)-ATPase Properties.

    PubMed

    Gutnisky, Alicia; López Ordieres, María Graciela; Rodríguez de Lores Arnaiz, Georgina

    2016-06-01

    Neurotensin behaves as a neuromodulator or as a neurotransmitter interacting with NTS1 and NTS2 receptors. Neurotensin in vitro inhibits synaptosomal membrane Na(+), K(+)-ATPase activity. This effect is prevented by administration of SR 48692 (antagonist for NTS1 receptor). The administration of levocabastine (antagonist for NTS2 receptor) does not prevent Na(+), K(+)-ATPase inhibition by neurotensin when the enzyme is assayed with ATP as substrate. Herein levocabastine effect on Na(+), K(+)-ATPase K(+) site was explored. For this purpose, levocabastine was administered to rats and K(+)-p-nitrophenylphosphatase (K(+)-p-NPPase) activity in synaptosomal membranes and [(3)H]-ouabain binding to cerebral cortex membranes were assayed in the absence (basal) and in the presence of neurotensin. Male Wistar rats were administered with levocabastine (50 μg/kg, i.p., 30 min) or the vehicle (saline solution). Synaptosomal membranes were obtained from cerebral cortex by differential and gradient centrifugation. The activity of K(+)-p-NPPase was determined in media laking or containing ATP plus NaCl. In such phosphorylating condition enzyme behaviour resembles that observed when ATP hydrolyses is recorded. In the absence of ATP plus NaCl, K(+)-p-NPPase activity was similar for levocabastine or vehicle injected (roughly 11 μmole hydrolyzed substrate per mg protein per hour). Such value remained unaltered by the presence of 3.5 × 10(-6) M neurotensin. In the phosphorylating medium, neurotensin decreased (32 %) the enzyme activity in membranes obtained from rats injected with the vehicle but failed to alter those obtained from rats injected with levocabastine. Levocabastine administration enhanced (50 %) basal [(3)H]-ouabain binding to cerebral cortex membranes but failed to modify neurotensin inhibitory effect on this ligand binding. It is concluded that NTS2 receptor blockade modifies the properties of neuronal Na(+), K(+)-ATPase and that neurotensin effect on Na(+), K

  20. Pharmacology of macitentan, an orally active tissue-targeting dual endothelin receptor antagonist.

    PubMed

    Iglarz, Marc; Binkert, Christoph; Morrison, Keith; Fischli, Walter; Gatfield, John; Treiber, Alexander; Weller, Thomas; Bolli, Martin H; Boss, Christoph; Buchmann, Stephan; Capeleto, Bruno; Hess, Patrick; Qiu, Changbin; Clozel, Martine

    2008-12-01

    Macitentan, also called Actelion-1 or ACT-064992 [N-[5-(4-bromophenyl)-6-(2-(5-bromopyrimidin-2-yloxy)ethoxy)-pyrimidin-4-yl]-N'-propylaminosulfonamide], is a new dual ET(A)/ET(B) endothelin (ET) receptor antagonist designed for tissue targeting. Selection of macitentan was based on inhibitory potency on both ET receptors and optimization of physicochemical properties to achieve high affinity for lipophilic milieu. In vivo, macitentan is metabolized into a major and pharmacologically active metabolite, ACT-132577. Macitentan and its metabolite antagonized the specific binding of ET-1 on membranes of cells overexpressing ET(A) and ET(B) receptors and blunted ET-1-induced calcium mobilization in various natural cell lines, with inhibitory constants within the nanomolar range. In functional assays, macitentan and ACT-132577 inhibited ET-1-induced contractions in isolated endothelium-denuded rat aorta (ET(A) receptors) and sarafotoxin S6c-induced contractions in isolated rat trachea (ET(B) receptors). In rats with pulmonary hypertension, macitentan prevented both the increase of pulmonary pressure and the right ventricle hypertrophy, and it markedly improved survival. In diabetic rats, chronic administration of macitentan decreased blood pressure and proteinuria and prevented end-organ damage (renal vascular hypertrophy and structural injury). In conclusion, macitentan, by its tissue-targeting properties and dual antagonism of ET receptors, protects against end-organ damage in diabetes and improves survival in pulmonary hypertensive rats. This profile makes macitentan a new agent to treat cardiovascular disorders associated with chronic tissue ET system activation.

  1. Salvianolic Acid A, as a Novel ETA Receptor Antagonist, Shows Inhibitory Effects on Tumor in Vitro.

    PubMed

    Zhang, Qiao; Wang, Shifeng; Yu, Yangyang; Sun, Shengnan; Zhang, Yuxin; Zhang, Yanling; Yang, Wei; Li, Shiyou; Qiao, Yanjiang

    2016-01-01

    Endothelin-1 (ET-1) autocrine and paracrine signaling modulate cell proliferation of tumor cells by activating its receptors, endothelin A receptor (ETAR) and endothelin B receptor (ETBR). Dysregulation of ETAR activation promotes tumor development and progression. The potential of ETAR antagonists and the dual-ETAR and ETBR antagonists as therapeutic approaches are under preclinical and clinical studies. Salvianolic acid A (Sal A) is a hydrophilic polyphenolic derivative isolated from Salvia miltiorrhiza Bunge (Danshen), which has been reported as an anti-cancer and cardio-protective herbal medicine. In this study, we demonstrate that Sal A inhibits ETAR activation induced by ET-1 in both recombinant and endogenous ETAR expression cell lines. The IC50 values were determined as 5.7 µM in the HEK293/ETAR cell line and 3.14 µM in HeLa cells, respectively. Furthermore, our results showed that Sal A suppressed cell proliferation and extended the doubling times of multiple cancer cells, including HeLa, DU145, H1975, and A549 cell lines. In addition, Sal A inhibited proliferation of DU145 cell lines stimulated by exogenous ET-1 treatment. Moreover, the cytotoxicity and cardio-toxicity of Sal A were assessed in human umbilical vein endothelial cells (HUVEC) and Human-induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs), which proved that Sal A demonstrates no cytotoxicity or cardiotoxicity. Collectively, our findings indicate that Sal A is a novel anti-cancer candidate through targeting ETAR. PMID:27490540

  2. Salvianolic Acid A, as a Novel ETA Receptor Antagonist, Shows Inhibitory Effects on Tumor in Vitro

    PubMed Central

    Zhang, Qiao; Wang, Shifeng; Yu, Yangyang; Sun, Shengnan; Zhang, Yuxin; Zhang, Yanling; Yang, Wei; Li, Shiyou; Qiao, Yanjiang

    2016-01-01

    Endothelin-1 (ET-1) autocrine and paracrine signaling modulate cell proliferation of tumor cells by activating its receptors, endothelin A receptor (ETAR) and endothelin B receptor (ETBR). Dysregulation of ETAR activation promotes tumor development and progression. The potential of ETAR antagonists and the dual-ETAR and ETBR antagonists as therapeutic approaches are under preclinical and clinical studies. Salvianolic acid A (Sal A) is a hydrophilic polyphenolic derivative isolated from Salvia miltiorrhiza Bunge (Danshen), which has been reported as an anti-cancer and cardio-protective herbal medicine. In this study, we demonstrate that Sal A inhibits ETAR activation induced by ET-1 in both recombinant and endogenous ETAR expression cell lines. The IC50 values were determined as 5.7 µM in the HEK293/ETAR cell line and 3.14 µM in HeLa cells, respectively. Furthermore, our results showed that Sal A suppressed cell proliferation and extended the doubling times of multiple cancer cells, including HeLa, DU145, H1975, and A549 cell lines. In addition, Sal A inhibited proliferation of DU145 cell lines stimulated by exogenous ET-1 treatment. Moreover, the cytotoxicity and cardio-toxicity of Sal A were assessed in human umbilical vein endothelial cells (HUVEC) and Human-induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs), which proved that Sal A demonstrates no cytotoxicity or cardiotoxicity. Collectively, our findings indicate that Sal A is a novel anti-cancer candidate through targeting ETAR. PMID:27490540

  3. Facilitation of memory storage by the acetylcholine M2 muscarinic receptor antagonist AF-DX 116.

    PubMed

    Baratti, C M; Opezzo, J W; Kopf, S R

    1993-07-01

    Post-training administration of the acetylcholine muscarinic M2 presynaptic receptor antagonist AF-DX 116 (0.1-10.0 mg/kg, ip), facilitated 48 h retention, in male Swiss mice, of a one-trial step-through inhibitory avoidance task. The dose-response curve was an inverted U. AF-DX 116 did not increase the retention latencies of mice that had not received a footshock during training. The influence of AF-DX 116 (1 mg/kg, ip) on retention was time-dependent, which suggests that the drug facilitated memory storage. The memory facilitation induced by AF-DX 116 (1 mg/kg, ip) was prevented by atropine (0.5 mg/kg, ip) administered after training, but 10 min prior to AF-DX 116 treatment. In contrast, neither methylatropine (0.5 mg/kg, ip), a peripherally acting muscarinic receptor blocker, nor mecamylamine (5 mg/kg, ip) or hexamethonium (5 mg/kg, ip), two cholinergic nicotinic receptor antagonists, prevented the effects of post-training AF-DX 116 on retention. Low subeffective doses of the central acting anticholinesterase physostigmine (35 micrograms/kg, ip), administered immediately after training, and AF-DX 116 (0.1 mg/kg, ip), given 10 min after training, acted synergistically to improve retention. The effects of AF-DX 116 (0.1 mg/kg, ip) were not influenced by the peripherally acting anticholinesterase neostigmine (35 micrograms/kg, ip). Considered together, these findings suggest that the activation of a muscarinic cholinergic presynaptic inhibitory mechanism, probably by increasing brain acetylcholine release, may modulate the activity of post-training processes involved in memory storage. PMID:8216161

  4. Selective and potent agonists and antagonists for investigating the role of mouse oxytocin receptors.

    PubMed

    Busnelli, Marta; Bulgheroni, Elisabetta; Manning, Maurice; Kleinau, Gunnar; Chini, Bice

    2013-08-01

    The neuropeptides oxytocin (OT) and vasopressin (AVP) have been shown to play a central role in social behaviors; as a consequence, they have been recognized as potential drugs to treat neurodevelopmental and psychiatric disorders characterized by impaired social interactions. However, despite the basic and preclinical relevance of mouse strains carrying genetic alterations in the OT/AVP systems to basic and preclinical translational neuroscience, the pharmacological profile of mouse OT/AVP receptor subtypes has not been fully characterized. To fill in this gap, we have characterized a number of OT and AVP agonists and antagonists at three murine OT/AVP receptors expressed in the nervous system as follows: the oxytocin (mOTR) and vasopressin V1a (mV1aR) and V1b (mV1bR) subtypes. These three receptors were transiently expressed in vitro for binding and intracellular signaling assays, and then a homology model of the mOTR structure was constructed to investigate how its molecular features compare with human and rat OTR orthologs. Our data indicate that the selectivity profile of the natural ligands, OT and AVP, is conserved in humans, rats, and mice. Furthermore, we found that the synthetic peptide [Thr(4)Gly(7)]OT (TGOT) is remarkably selective for the mOTR and, like the endogenous OT ligand, activates Gq and Gi and recruits β-arrestins. Finally, we report three antagonists that exhibit remarkably high affinities and selectivities at mOTRs. These highly selective pharmacological tools will contribute to the investigation of the specific physiologic and pathologic roles of mOTR for the development of selective OT-based therapeutics.

  5. Discovery and pharmacological characterization of a small-molecule antagonist at neuromedin U receptor NMUR2.

    PubMed

    Liu, Jay J; Payza, Kemal; Huang, Jian; Liu, Ruifeng; Chen, Tongming; Coupal, Martin; Laird, Jennifer M A; Cao, Chang-Qing; Butterworth, Joanne; Lapointe, Stéphanie; Bayrakdarian, Malken; Trivedi, Shephali; Bostwick, J Robert

    2009-07-01

    Neuromedin U (NMU), through its cognate receptor NMUR2 in the central nervous system, regulates several important physiological functions, including energy balance, stress response, and nociception. By random screening of our corporate compound collection with a ligand binding assay, we discovered (R)-5'-(phenylaminocarbonylamino)spiro[1-azabicyclo[2.2.2]octane-3,2'(3'H)-furo[2,3-b]pyridine] (R-PSOP), a highly potent and selective NMUR2 antagonist. R-PSOP is a nonpeptidic small-molecule with the chemical composition C(20)N(4)O(2)H(22). In competition binding experiments, this compound was found to bind to NMUR2 with high affinity; the K(i) values were determined to be 52 and 32 nM for the human and rat NMUR2, respectively. Moreover, in functional assays measuring phosphoinositide turnover or intracellular calcium mobilization, R-PSOP strongly inhibited the responses stimulated by peptide agonists NMU-25, NMU-23, and NMU-8 in human embryonic kidney 293 cells expressing NMUR2. From Schild analyses, the functional K(b) values for R-PSOP were determined to be 92 and 155 nM at human and rat NMUR2, respectively. Highly selective for NMUR2, R-PSOP exhibited low affinity to the other subtype of NMU receptor, NMUR1, with a K(i) value >10 microM. R-PSOP in vivo attenuated NMU-23-evoked nociceptive responses in a rat spinal reflex preparation. To our knowledge, this is the first antagonist ever reported for NMU receptors. This compound could serve as a valuable tool for further understanding the physiological and pathophysiological roles of NMU system, while providing a chemical starting point that may lead to development of new therapeutics for treatment of eating disorders, obesity, pain, and stress-related disorders. PMID:19369576