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Sample records for a1 receptor agonist

  1. AMP is an adenosine A1 receptor agonist.

    PubMed

    Rittiner, Joseph E; Korboukh, Ilia; Hull-Ryde, Emily A; Jin, Jian; Janzen, William P; Frye, Stephen V; Zylka, Mark J

    2012-02-17

    Numerous receptors for ATP, ADP, and adenosine exist; however, it is currently unknown whether a receptor for the related nucleotide adenosine 5'-monophosphate (AMP) exists. Using a novel cell-based assay to visualize adenosine receptor activation in real time, we found that AMP and a non-hydrolyzable AMP analog (deoxyadenosine 5'-monophosphonate, ACP) directly activated the adenosine A(1) receptor (A(1)R). In contrast, AMP only activated the adenosine A(2B) receptor (A(2B)R) after hydrolysis to adenosine by ecto-5'-nucleotidase (NT5E, CD73) or prostatic acid phosphatase (PAP, ACPP). Adenosine and AMP were equipotent human A(1)R agonists in our real-time assay and in a cAMP accumulation assay. ACP also depressed cAMP levels in mouse cortical neurons through activation of endogenous A(1)R. Non-selective purinergic receptor antagonists (pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid and suramin) did not block adenosine- or AMP-evoked activation. Moreover, mutation of His-251 in the human A(1)R ligand binding pocket reduced AMP potency without affecting adenosine potency. In contrast, mutation of a different binding pocket residue (His-278) eliminated responses to AMP and to adenosine. Taken together, our study indicates that the physiologically relevant nucleotide AMP is a full agonist of A(1)R. In addition, our study suggests that some of the physiological effects of AMP may be direct, and not indirect through ectonucleotidases that hydrolyze this nucleotide to adenosine.

  2. AMP Is an Adenosine A1 Receptor Agonist*

    PubMed Central

    Rittiner, Joseph E.; Korboukh, Ilia; Hull-Ryde, Emily A.; Jin, Jian; Janzen, William P.; Frye, Stephen V.; Zylka, Mark J.

    2012-01-01

    Numerous receptors for ATP, ADP, and adenosine exist; however, it is currently unknown whether a receptor for the related nucleotide adenosine 5′-monophosphate (AMP) exists. Using a novel cell-based assay to visualize adenosine receptor activation in real time, we found that AMP and a non-hydrolyzable AMP analog (deoxyadenosine 5′-monophosphonate, ACP) directly activated the adenosine A1 receptor (A1R). In contrast, AMP only activated the adenosine A2B receptor (A2BR) after hydrolysis to adenosine by ecto-5′-nucleotidase (NT5E, CD73) or prostatic acid phosphatase (PAP, ACPP). Adenosine and AMP were equipotent human A1R agonists in our real-time assay and in a cAMP accumulation assay. ACP also depressed cAMP levels in mouse cortical neurons through activation of endogenous A1R. Non-selective purinergic receptor antagonists (pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid and suramin) did not block adenosine- or AMP-evoked activation. Moreover, mutation of His-251 in the human A1R ligand binding pocket reduced AMP potency without affecting adenosine potency. In contrast, mutation of a different binding pocket residue (His-278) eliminated responses to AMP and to adenosine. Taken together, our study indicates that the physiologically relevant nucleotide AMP is a full agonist of A1R. In addition, our study suggests that some of the physiological effects of AMP may be direct, and not indirect through ectonucleotidases that hydrolyze this nucleotide to adenosine. PMID:22215671

  3. GLP-1 Receptor Agonists

    MedlinePlus

    ... Additional Resources Mayo Clinic FDA What are GLP-1 receptor agonist medicines? GLP-1 receptor agonist medicines, ... diabetes medicines. What are the benefits of GLP-1 receptor agonist medicines? They help keep your blood ...

  4. Sex Differences in the Neurotoxic Effects of Adenosine A1 Receptor Antagonism During Ethanol Withdrawal: Reversal With an A1 Receptor Agonist or an NMDA Receptor Antagonist

    PubMed Central

    Butler, Tracy R.; Smith, Katherine J.; Self, Rachel L.; Braden, Brittany B.; Prendergast, Mark A.

    2009-01-01

    Background Neuronal adaptations that occur during chronic ethanol (EtOH) exposure have been observed to sensitize the brain to excitotoxic insult during withdrawal. The adenosine receptor system warrants further examination in this regard, as recent evidence has implicated adenosine receptor involvement in the behavioral effects of both EtOH exposure and withdrawal. Methods The current studies examined effects of adenosine A1 receptor manipulation on neuronal injury in EtOH-naïve and EtOH-withdrawn male and female rat hippocampal slice cultures. EtOH-naïve and EtOH pretreated (43.1 to 26.9 mM from days 5 to 15 DIV) cultures were exposed to the A1 receptor agonist 2-Chloro-N6-cyclopentyladenosine (CCPA; 10 nM), the A1 receptor antagonist 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX;10 nM), or the N-methyl-D-aspartate (NMDA) receptor antagonist D,L,-2-amino-5-phosphovalerate (APV; 20 μM) at 15 days in vitro (DIV). Cytotoxicity was measured in the primary neuronal layers of the dentate gyrus, CA3 and CA1 hippocampal regions by quantification of propidium iodide (PI) fluorescence after 24 hours. Immunohistochemical analysis of A1 receptor abundance was conducted in EtOH-naïve and EtOH pretreated slice cultures at 15 DIV. Results Twenty-four hour exposure to DPCPX in EtOH-naïve slice cultures did not produced neurotoxicity in any region of slice cultures. Though withdrawal from 10 day EtOH exposure produced no toxicity in either male or female slice cultures, exposure to DPCPX during 24 hours of EtOH withdrawal produced a marked increase in PI uptake in all hippocampal culture subregions in female cultures (to ~160% of control values). A significant effect for sex was observed in the CA1 region such that toxicity in females cultures exposed to the A1 antagonist during withdrawal was greater than that observed in male cultures. These effects of DPCPX in EtOH withdrawn female and male slices were prevented by co-exposure to either the A1 agonist CCPA or the NMDA

  5. Hypothermia in mouse is caused by adenosine A1 and A3 receptor agonists and AMP via three distinct mechanisms.

    PubMed

    Carlin, Jesse Lea; Jain, Shalini; Gizewski, Elizabeth; Wan, Tina C; Tosh, Dilip K; Xiao, Cuiying; Auchampach, John A; Jacobson, Kenneth A; Gavrilova, Oksana; Reitman, Marc L

    2017-03-01

    Small mammals have the ability to enter torpor, a hypothermic, hypometabolic state, allowing impressive energy conservation. Administration of adenosine or adenosine 5'-monophosphate (AMP) can trigger a hypothermic, torpor-like state. We investigated the mechanisms for hypothermia using telemetric monitoring of body temperature in wild type and receptor knock out (Adora1 -/- , Adora3 -/- ) mice. Confirming prior data, stimulation of the A 3 adenosine receptor (AR) induced hypothermia via peripheral mast cell degranulation, histamine release, and activation of central histamine H 1 receptors. In contrast, A 1 AR agonists and AMP both acted centrally to cause hypothermia. Commonly used, selective A 1 AR agonists, including N 6 -cyclopentyladenosine (CPA), N 6 -cyclohexyladenosine (CHA), and MRS5474, caused hypothermia via both A 1 AR and A 3 AR when given intraperitoneally. Intracerebroventricular dosing, low peripheral doses of Cl-ENBA [(±)-5'-chloro-5'-deoxy-N 6 -endo-norbornyladenosine], or using Adora3 -/- mice allowed selective stimulation of A 1 AR. AMP-stimulated hypothermia can occur independently of A 1 AR, A 3 AR, and mast cells. A 1 AR and A 3 AR agonists and AMP cause regulated hypothermia that was characterized by a drop in total energy expenditure, physical inactivity, and preference for cooler environmental temperatures, indicating a reduced body temperature set point. Neither A 1 AR nor A 3 AR was required for fasting-induced torpor. A 1 AR and A 3 AR agonists and AMP trigger regulated hypothermia via three distinct mechanisms. Published by Elsevier Ltd.

  6. Structure-Based Design, Synthesis, and In Vivo Antinociceptive Effects of Selective A1Adenosine Receptor Agonists.

    PubMed

    Petrelli, Riccardo; Scortichini, Mirko; Belardo, Carmela; Boccella, Serena; Luongo, Livio; Capone, Fabio; Kachler, Sonja; Vita, Patrizia; Del Bello, Fabio; Maione, Sabatino; Lavecchia, Antonio; Klotz, Karl-Norbert; Cappellacci, Loredana

    2018-01-11

    Our previous work discovered that combining the appropriate 5'- and N 6 -substitution in adenosine derivatives leads to the highly selective human A 1 adenosine receptor (hA 1 AR) agonists or highly potent dual hA 1 AR agonists and hA 3 AR antagonists. In order to explore novel dual adenosine receptor ligands, a series of N 6 -substituted-5'-pyrazolyl-adenosine and 2-chloro-adenosine derivatives were synthesized and assayed in vitro at all ARs. The N 6 -(±)-endo-norbornyl derivative 12 was the most potent and selective at A 1 AR and effective as an analgesic in formalin test in mice, but none of the 5'-pyrazolyl series compounds showed a dual behavior at hA 1 and hA 3 AR. Molecular modeling studies rationalized the structure-activity relationships and the selectivity profiles of the new series of A 1 AR agonists. Interestingly, an unexpected inverted binding mode of the N 6 -tetrahydrofuranyl derivative 14 was hypothesized to explain its low affinity at A 1 AR.

  7. 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. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. A partial agonist of the A(1)-adenosine receptor selectively slows AV conduction in guinea pig hearts.

    PubMed

    Wu, L; Belardinelli, L; Zablocki, J A; Palle, V; Shryock, J C

    2001-01-01

    The use of full agonists of the A(1)-adenosine receptor (A(1)-ADOR) as antiarrhythmic agents is limited by their actions to cause high-grade atrioventricular (AV) block, profound bradycardia, atrial fibrillation, and vasodilation. It may be possible to avoid these undesired actions by use of partial agonists. We determined the effects of CVT-2759, a potential partial agonist of A(1)-ADORs, on guinea pig hearts. CVT-2759 (0.1-100 microM) increased the S-H interval of the isolated heart from 45 +/- 1 to 60 +/- 3 ms (P < 0. 01) with a half-maximal effect at 3.1 microM. CVT-2759 did not cause second-degree AV block. CVT-2759 significantly attenuated the actions of the full agonists N(6)-cyclopentyladenosine and adenosine. CVT-2759 caused a moderate slowing of atrial rate by 10 microM. In contrast, CVT-2759 was a full agonist to decrease cAMP content of rat adipocytes and Fischer rat thyroid line 5 cells. Results of radioligand binding assays indicated that CVT-2759 stabilized a high-affinity, G protein-coupled state of the A(1)-ADOR in membranes prepared from rat adipocytes but not in membranes prepared from the guinea pig brain. The results suggest that a weak A(1)-ADOR agonist, such as CVT-2759, may be useful to slow AV nodal conduction and thereby ventricular rate without causing AV block, bradycardia, atrial arrhythmias, or vasodilation.

  9. 5'-Carbamoyl derivatives of 2'-C-methyl-purine nucleosides as selective A1 adenosine receptor agonists: affinity, efficacy, and selectivity for A1 receptor from different species.

    PubMed

    Cappellacci, Loredana; Franchetti, Palmarisa; Vita, Patrizia; Petrelli, Riccardo; Lavecchia, Antonio; Costa, Barbara; Spinetti, Francesca; Martini, Claudia; Klotz, Karl-Norbert; Grifantini, Mario

    2008-01-01

    A series of 5'-carbamoyl and 5'-thionocarbamoyl derivatives of 2'-C-methyl analogues of the A(1) adenosine receptor (A(1)AR) full agonists N(6)-cyclopentyladenosine (CPA), 2-chloro-N(6)-cyclopentyladenosine (CCPA), N(6)-[3-(R)-tetrahydrofuranyl]adenosine (tecadenoson), and 2-chloro analogue (2-Cl-tecadenoson) was synthesized and evaluated for their affinity for adenosine receptor subtypes from bovine, porcine, and human species. In the N(6)-cyclopentylamino series, the 5'-substituted derivatives showed a reduced affinity at the bovine A(1)AR compared to the parent compounds; however, the selectivity for A(1) versus A(2A) receptor was retained or increased. The corresponding N(6)-3-(R)-tetrahydrofuranylamino analogues displayed a very low affinity toward the bovine A(1)AR. The 5'-methylthionocarbamoyl derivative of 2'-Me-CCPA showed the best affinity at porcine A(1)AR with a K(i) value of 13 nM. At human AR subtypes tecadenoson derivatives showed 2.3- to 5-fold lower affinity at A(1)AR and very low affinity at the other subtypes (A(2A), A(2B), and A(3)) compared to the corresponding N(6)-cyclopentyl analogues. The 5'-carbamoyl and 5'-thionocarbamoyl derivatives of 2'-Me-CCPA 3, 4, 7 and tecadenoson derivative 12 were found to be partial A(1) agonists at the porcine receptor. Docking studies explained the lower affinity of N(6)-3-(R)-tetrahydrofuranyl-substituted compounds at bovine A(1)AR compared to that of N(6)-cyclopentyl analogues, showing that the oxygen of the tetrahydrofuranyl ring establishes unfavorable electrostatic interactions with the CO oxygen of Asn254. The low binding affinity of the 2'-C-methyl-N(6)-3-(R)-tetrahydrofuranyl adenosine analogues at human A(1)AR may be ascribed to the presence of unfavorable interactions between the hydrophilic tetrahydrofuranyl ring and the surrounding hydrophobic residues Leu250 (TM6) and Ile274 (TM7).

  10. Differential effects of the adenosine A1 receptor agonist adenosine amine congener on renal, femoral and carotid vascular conductance in preterm fetal sheep.

    PubMed

    Booth, Lindsea C; Tummers, Leonie; Jensen, Ellen C; Barrett, Carolyn J; Malpas, Simon C; Gunn, Alistair J; Bennet, Laura

    2008-11-01

    1. Adenosine A(1) receptor activation is critical for endogenous neuroprotection from hypoxia-ischaemia, raising the possibility that treatment with A(1) receptor agonists may be an effective physiological protection strategy for vulnerable preterm infants. However, the A(1) receptor can mediate unwanted systemic effects, including vasoconstriction of the afferent glomerular arteriole. There is limited information on whether this occurs at doses that improve cerebral perfusion in the immature brain. 2. Therefore, in the present study, we examined whether infusion of the selective A(1) receptor agonist adenosine amine congener (ADAC) is associated with reduced renal perfusion in chronically instrumented preterm (0.7 gestation) fetal sheep. In the present study, ADAC was given in successive doses of 2.5, 5.0 and 15.0 microg, 45 min apart. 3. Treatment with ADAC was associated with a marked reduction in renal vascular conductance (and blood flow), whereas carotid conductance was increased and there was no significant effect on femoral conductance. In contrast with the stable effects of increasing ADAC dose on vascular conductance, there was a significant dose-related fall in fetal heart rate and blood pressure. 4. In conclusion, these short-term data support the concern that A(1) receptor agonist infusion can selectively impair renal perfusion, even at low doses.

  11. Thrombopoietin-receptor agonists.

    PubMed

    Basciano, Paul A; Bussel, James B

    2012-09-01

    Thrombopoietin-receptor agonists (TPO-RAs) have been approved for use in immune thrombocytopenia (ITP) after showing safety and efficacy. There is increasing interest to expand the role of TPO-RAs, both in ITP as well as in other thrombocytopenic disorders. In ITP, more studies are providing evidence of TPO-RA efficacy and safety, as well as their applicability to various patient groups, including children. Use of TPO-RAs in hepatitis C has shown early success in allowing treatments in patients who would otherwise be excluded due to thrombocytopenia. Use in congenital thrombocytopenias has also shown early success. The use of TPO-RAs in myelodysplastic syndrome (MDS) is questionable after reports of increasing blasts and leukemic transformation, whereas in other chemotherapy-induced thrombocytopenias (C-ITs) reports are few. Bone marrow fibrosis remains an area of active study, although the data to date suggest this is seen in a small minority of patients, and is reversible and of questionable clinical relevance. Thrombotic complications are also an area of concern and need further close follow-up. The use of TPO-RAs continues to grow as more evidence of safety and efficacy is found. More studies are needed to determine their utility in other diseases as well as to better characterize adverse events observed to date.

  12. Adenosine receptor agonists modulate visceral hyperalgesia in the rat.

    PubMed

    Sohn, Chong-Il; Park, Hyo Jin; Gebhart, G F

    2008-06-01

    Adenosine is an endogenous modulator of nociception. Its role in visceral nociception, particularly in visceral hyperalgesia, has not been studied. The aim of this study was to determine the effects of adenosine receptor agonists in a model of visceral hyperalgesia. The visceromotor response (VMR) in rats to colorectal distension (CRD; 80 mmHg, 20 seconds) was quantified by electromyographic recordings from the abdominal musculature. Three hours after the intracolonic administration of zymosan (25 mg/mL, 1 mL), VMRs to CRD were measured before and after either subcutaneous or intrathecal administration of an adenosine receptor agonist. Subcutaneous injection of 5'-N-ethylcarboxyamidoadenosine (NECA; an A1 and A2 receptor agonist), R(-)-N6-(2-phenylisopropyl)-adenosine (R-PIA; a selective A1 receptor agonist), or CGS-21680 hydrochloride (a selective A2a receptor agonist) dose-dependently (10-100 mg/kg) attenuated the VMR to CRD, although hindlimb weakness occurred at the higher doses tested. Intrathecal administration of NECA or R-PIA dose-dependently (0.1-1.0 microg/kg) decreased the VMR, whereas CGS-21680 hydrochloride was ineffective over the same concentration range. Higher intrathecal doses of the A1/A2 receptor agonist NECA produced motor weakness. Adenosine receptor agonists are antihyperalgesic, but also produce motor weakness at high doses. However, activation of the spinal A1 receptor significantly attenuates the VMR to CRD without producing motor weakness.

  13. Piperidine derivatives as nonprostanoid IP receptor agonists.

    PubMed

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

    2016-05-01

    The discovery of a new class of nonprostanoid prostaglandin I2 receptor (IP receptor) agonists is reported. Among them, the unique piperidine derivative 31b (2-((1-(2-(N-(4-tolyl)benzamido)ethyl)piperidin-4-yl)oxy)acetic acid) was a good IP receptor agonist and was 50-fold more selective for the human IP receptor than for other human prostanoid receptors. This compound showed good pharmacokinetic properties in dog. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Safety and Tolerability of Neladenoson Bialanate, a Novel Oral Partial Adenosine A1 Receptor Agonist, in Patients With Chronic Heart Failure.

    PubMed

    Voors, Adriaan Alexander; Düngen, Hans-Dirk; Senni, Michele; Nodari, Savina; Agostoni, Piergiuseppe; Ponikowski, Piotr; Bax, Jeroen J; Butler, Javed; Kim, Raymond J; Dorhout, Bernard; Dinh, Wilfried; Gheorghiade, Mihai

    2017-04-01

    We studied safety and tolerability of neladenoson bialanate, a novel oral selective partial adenosine A1 receptor agonist that maintains the cardioprotective effects of adenosine without the undesired side effects of a full agonist, in 2 pilot studies in patients with heart failure with reduced ejection fraction (HFrEF). The β-blocker interaction study was a single-blind, placebo-controlled study on the effects of a 30-mg single dose of neladenoson bialanate on atrioventricular (AV) conduction in 11 patients with HFrEF treated with β-blockers. The PARSiFAL pilot study was a double-blind, placebo-controlled study on the effects of a 7-day treatment with 10 or 20 mg neladenoson bialanate or placebo in 31 patients with HFrEF on β-blocker therapy. In the β-blocker interaction study with 11 HFrEF patients, no second- or third-degree AV block was detected on 48-hour Holter monitoring. In the 31 HFrEF patients included in the PARSiFAL pilot study, no second- or third-degree AV blocks were observed during 24-hour Holter monitoring, and no effects were seen on heart rate and blood pressure. Median absolute changes in LVEF, measured by cardiac magnetic resonance, were 1.9% (interquartile range -1.1 to 4.3), 0.3% (-1.4 to 2.7), and 2.2% (0.4 to 4.5), in the placebo, 10-mg, and 20-mg groups, respectively. Treatment of HFrEF patients with the novel partial adenosine A1 agonist neladenoson bialanate appeared to be safe in 2 small pilot studies, and no atrioventricular conduction disorders or neurological side effects were observed. No significant early changes in cardiac function were detected. © 2016, The American College of Clinical Pharmacology.

  15. The antinociceptive effect of 2-chloro-2'-C-methyl-N6-cyclopentyladenosine (2'-Me-CCPA), a highly selective adenosine A1 receptor agonist, in the rat.

    PubMed

    Maione, S; de Novellis, V; Cappellacci, L; Palazzo, E; Vita, D; Luongo, L; Stella, L; Franchetti, P; Marabese, I; Rossi, F; Grifantini, M

    2007-10-01

    This study was undertaken in order to investigate the effect of 2-chloro-2'-C-methyl-N(6)-cyclopentyladenosine (2'-Me-CCPA), a potent and highly selective adenosine A(1) receptor agonist, on nociceptive responses and on the ongoing or tail flick-related changes of rostral ventromedial medulla (RVM) ON- and OFF-cell activities. Systemic administrations of 2'-Me-CCPA (2.5-5 mg/kg, i.p.) reduced the nociceptive response in the plantar and formalin tests, in a way prevented by DPCPX (3 mg/kg, i.p.), a selective A(1) receptor antagonist. Similarly, intra-periaqueductal grey (PAG) 2'-Me-CCPA (0.5-1-2 nmol/rat) reduced pain behaviour in the plantar and formalin tests, in a way inhibited by DPCPX (0.5 nmol/rat). Moreover, when administered systemically (2.5-5 mg/kg, i.p.) or intra-PAG (0.5-1 nmol/rat) 2'-Me-CCPA increased the tail flick latencies, delayed the tail flick-related onset of the ON-cell burst and decreased the duration of the OFF-cell pause in a dose dependent manner. Furthermore, it decreased RVM ON-cell and increased OFF-cell ongoing activities. The in vivo electrophysiological effects were all prevented by DPCPX (0.5 nmol/rat). This study confirms the role of adenosine A(1) receptors in modulating pain and suggests a critical involvement of these receptors within PAG-RVM descending pathway for the processing of pain.

  16. Adverse Effects of GLP-1 Receptor Agonists

    PubMed Central

    Filippatos, Theodosios D.; Panagiotopoulou, Thalia V.; Elisaf, Moses S.

    2014-01-01

    Glucagon-like peptide-1 (GLP-1) receptor agonists are a class of injective anti-diabetic drugs that improve glycemic control and many other atherosclerosis-related parameters in patients with type 2 diabetes (T2D). However, the use of this relatively new class of drugs may be associated with certain adverse effects. Concerns have been expressed regarding the effects of these drugs on pancreatic and thyroid tissue, since animal studies and analyses of drug databases indicate an association of GLP-1 receptor agonists with pancreatitis, pancreatic cancer, and thyroid cancer. However, several meta-analyses failed to confirm a cause-effect relation between GLP-1 receptor agonists and the development of these adverse effects. One benefit of GLP-1 receptor agonists is that they do not cause hypoglycemia when combined with metformin or thiazolidinediones, but the dose of concomitant sulphonylurea or insulin may have to be decreased to reduce the risk of hypoglycemic episodes. On the other hand, several case reports have linked the use of these drugs, mainly exenatide, with the occurrence of acute kidney injury, primarily through hemodynamic derangement due to nausea, vomiting, and diarrhea. The most common symptoms associated with the use of GLP-1 receptor agonists are gastrointestinal symptoms, mainly nausea. Other common adverse effects include injection site reactions, headache, and nasopharyngitis, but these effects do not usually result in discontinuation of the drug. Current evidence shows that GLP-1 receptor agonists have no negative effects on the cardiovascular risk of patients with T2D. Thus, GLP-1 receptor agonists appear to have a favorable safety profile, but ongoing trials will further assess their cardiovascular effects. The aim of this review is to analyze critically the available data regarding adverse events of GLP-1 receptor agonists in different anatomic systems published in Pubmed and Scopus. Whenever possible, certain differences between GLP-1

  17. Adverse Effects of GLP-1 Receptor Agonists.

    PubMed

    Filippatos, Theodosios D; Panagiotopoulou, Thalia V; Elisaf, Moses S

    2014-01-01

    Glucagon-like peptide-1 (GLP-1) receptor agonists are a class of injective anti-diabetic drugs that improve glycemic control and many other atherosclerosis-related parameters in patients with type 2 diabetes (T2D). However, the use of this relatively new class of drugs may be associated with certain adverse effects. Concerns have been expressed regarding the effects of these drugs on pancreatic and thyroid tissue, since animal studies and analyses of drug databases indicate an association of GLP-1 receptor agonists with pancreatitis, pancreatic cancer, and thyroid cancer. However, several meta-analyses failed to confirm a cause-effect relation between GLP-1 receptor agonists and the development of these adverse effects. One benefit of GLP-1 receptor agonists is that they do not cause hypoglycemia when combined with metformin or thiazolidinediones, but the dose of concomitant sulphonylurea or insulin may have to be decreased to reduce the risk of hypoglycemic episodes. On the other hand, several case reports have linked the use of these drugs, mainly exenatide, with the occurrence of acute kidney injury, primarily through hemodynamic derangement due to nausea, vomiting, and diarrhea. The most common symptoms associated with the use of GLP-1 receptor agonists are gastrointestinal symptoms, mainly nausea. Other common adverse effects include injection site reactions, headache, and nasopharyngitis, but these effects do not usually result in discontinuation of the drug. Current evidence shows that GLP-1 receptor agonists have no negative effects on the cardiovascular risk of patients with T2D. Thus, GLP-1 receptor agonists appear to have a favorable safety profile, but ongoing trials will further assess their cardiovascular effects. The aim of this review is to analyze critically the available data regarding adverse events of GLP-1 receptor agonists in different anatomic systems published in Pubmed and Scopus. Whenever possible, certain differences between GLP-1

  18. Small Molecule Agonists of the Orphan Nuclear Receptors Steroidogenic Factor-1 (SF-1, NR5A1) and Liver Receptor Homologue-1 (LRH-1, NR5A2)

    PubMed Central

    Whitby, Richard J.; Stec, Jozef; Blind, Raymond D.; Dixon, Sally; Leesnitzer, Lisa M.; Orband-Miller, Lisa A.; Williams, Shawn P.; Willson, Timothy M.; Xu, Robert; Zuercher, William J.; Cai, Fang; Ingraham, Holly A.

    2014-01-01

    The crystal structure of LRH-1 ligand binding domain bound to our previously reported agonist 3-(E-oct-4-en-4-yl)-1-phenylamino-2-phenyl-cis-bicyclo[3.3.0]oct-2-ene 5 is described. Two new classes of agonists in which the bridgehead anilino group from our first series was replaced with an alkoxy or 1-ethenyl group were designed, synthesized, and tested for activity in a peptide recruitment assay. Both new classes gave very active compounds, particularly against SF-1. Structure-activity studies led to excellent dual-LRH-1/SF-1 agonists (e.g., RJW100) as well as compounds selective for LRH-1 (RJW101) and SF-1 (RJW102 and RJW103). The series based on 1-ethenyl substitution was acid stable, overcoming a significant drawback of our original bridgehead anilino-substituted series. Initial studies on the regulation of gene expression in human cell lines showed excellent, reproducible activity at endogenous target genes. PMID:21391689

  19. 5'-C-Ethyl-tetrazolyl-N(6)-substituted adenosine and 2-chloro-adenosine derivatives as highly potent dual acting A1 adenosine receptor agonists and A3 adenosine receptor antagonists.

    PubMed

    Petrelli, Riccardo; Torquati, Ilaria; Kachler, Sonja; Luongo, Livio; Maione, Sabatino; Franchetti, Palmarisa; Grifantini, Mario; Novellino, Ettore; Lavecchia, Antonio; Klotz, Karl-Norbert; Cappellacci, Loredana

    2015-03-12

    A series of N(6)-substituted-5'-C-(2-ethyl-2H-tetrazol-5-yl)-adenosine and 2-chloro-adenosine derivatives was synthesized as novel, highly potent dual acting hA1AR agonists and hA3AR antagonists, potentially useful in the treatment of glaucoma and other diseases. The best affinity and selectivity profiles were achieved by N(6)-substitution with a 2-fluoro-4-chloro-phenyl- or a methyl- group. Through an in silico receptor-driven approach, the molecular bases of the hA1- and hA3AR recognition and activation of this series of 5'-C-ethyl-tetrazolyl derivatives were explained.

  20. New thrombopoietin receptor agonists for platelet disorders.

    PubMed

    Homeida, S; Ebdon, C; Batty, P; Jackson, B; Kolade, S; Bateman, C; Peng, Y Y; Stasi, R

    2012-04-01

    Since thrombopoietin (TPO) was cloned in 1994, TPO receptor (TPO-R) agonists have been developed which have shown significant clinical activity in various conditions characterized by thrombocytopenia. First-generation TPO-R agonists were recombinant forms of human TPO. The clinical development of these molecules was discontinued after one of them, pegylated recombinant human megakaryocyte growth and development factor, was associated with the development of neutralizing autoantibodies cross-reacting with endogenous TPO. Second-generation TPO-R agonists are now available, which present no sequence homology to endogenous TPO. Two of these new agents, romiplostim and eltrombopag, have been granted marketing authorization for use in patients with primary immune thrombocytopenia unresponsive to conventional treatments. Clinical trials with TPO-R agonists are also ongoing in other thrombocytopenias, such as hepatitis C virus-related thrombocytopenia and the myelodysplastic syndromes. Copyright 2012 Prous Science, S.A.U. or its licensors. All rights reserved.

  1. 5'-Chloro-5'-deoxy-(±)-ENBA, a potent and selective adenosine A(1) receptor agonist, alleviates neuropathic pain in mice through functional glial and microglial changes without affecting motor or cardiovascular functions.

    PubMed

    Luongo, Livio; Petrelli, Riccardo; Gatta, Luisa; Giordano, Catia; Guida, Francesca; Vita, Patrizia; Franchetti, Palmarisa; Grifantini, Mario; de Novellis, Vito; Cappellacci, Loredana; Maione, Sabatino

    2012-11-22

    This study was undertaken in order to investigate the effect of chronic treatment with 5′-chloro-5′-deoxy-(±)-ENBA, a potent and highly selective agonist of human adenosine A(1) receptor, on thermal hyperalgesia and mechanical allodynia in a mouse model of neuropathic pain, the Spared Nerve Injury (SNI) of the sciatic nerve. Chronic systemic administration of 5′-chloro-5′-deoxy-(±)-ENBA (0.5 mg/kg, i.p.) reduced both mechanical allodynia and thermal hyperalgesia 3 and 7 days post-SNI, in a way prevented by DPCPX (3 mg/kg, i.p.), a selective A(1) adenosine receptor antagonist, without exerting any significant change on the motor coordination or arterial blood pressure. In addition, a single intraperitoneal injection of 5′-chloro-5′-deoxy-(±)-ENBA (0.5 mg/kg, i.p.) 7 days post-SNI also reduced both symptoms for at least two hours. SNI was associated with spinal changes in microglial activation ipsilaterally to the nerve injury. Activated, hypertrophic microglia were significantly reduced by 5′-chloro-5′-deoxy-(±)-ENBA chronic treatment. Our results demonstrated an involvement of adenosine A(1) receptor in the amplified nociceptive thresholds and in spinal glial and microglial changes occurred in neuropathic pain, without affecting motor coordination or blood pressure. Our data suggest a possible use of adenosine A(1) receptor agonist in neuropathic pain symptoms.

  2. Albiglutide: a unique GLP-1 receptor agonist.

    PubMed

    Rendell, Marc S

    2016-12-01

    Albiglutide is a long acting GLP-1 receptor agonist (GLP-1 RA) administered by weekly injection. Area covered: The pharmacokinetic and pharmacodynamic properties of albiglutide and its clinical effects are discussed. The review encompassed a search of PubMed and a thorough analysis of the European Union and US Food and Drug Administration approval documents. Expert opinion: Albiglutide has a chemical structure quite distinct from that of other marketed GLP-1 RAs. The agent has less gastrointestinal side effects than other comparable GLP-1 RAs and is safe in patients with renal failure. As a sole treatment for diabetes and used with other hypoglycemic agents, it achieves a lowering of HbA1c of up to 1%, less than several competitor GLP-1 RAs. The benefit on weight reduction is minimal compared to other GLP-1 RAs. There exists concern about an imbalance of pancreatitis cases in the approval program as well as injection site reactions which led to discontinuance of therapy in up to 2% of participants. A large long term study now underway will determine if albiglutide, with its lower level of GI intolerance, has a place in the treatment of patients with increased risk of cardiovascular events.

  3. Combining a GLP-1 receptor agonist and basal insulin: study evidence and practical considerations.

    PubMed

    Carris, Nicholas W; Taylor, James R; Gums, John G

    2014-12-01

    Most patients with diabetes mellitus require multiple medications to achieve glycemic goals. Considering this and the increasing incidence of type 2 diabetes worldwide, the need for effective combination therapy is pressing. Basal insulin and glucagon-like peptide 1 (GLP-1) receptor agonists are frequently used to treat type 2 diabetes. Though both classes of medication are exclusively injectable, which may cause initial hesitation from providers, evidence for their combined use is substantial. This review summarizes the theoretical benefit, supporting evidence, and implementation of a combined basal insulin-GLP-1 receptor agonist regimen. Basal insulin added to a GLP-1 receptor agonist reduces hemoglobin A1c (HbA1c) without weight gain or significantly increased hypoglycemia. A GLP-1 receptor agonist added to basal insulin reduces HbA1c and body weight. Compared with the addition of meal-time insulin to basal insulin, a GLP-1 receptor agonist produces similar or greater reduction in HbA1c, weight loss instead of weight gain, and less hypoglycemia. Gastrointestinal adverse events are common with GLP-1 receptor agonists, especially during initiation and titration. However, combination with basal insulin is not expected to augment expected adverse events that come with using a GLP-1 receptor agonist. Basal insulin can be added to a GLP-1 receptor agonist with a slow titration to target goal fasting plasma glucose. In patients starting a GLP-1 receptor agonist, the dose of basal insulin should be decreased by 20 % in patients with an HbA1c ≤8 %. The evidence from 15 randomized prospective studies supports the combined use of a GLP-1 receptor agonist with basal insulin in a broad range of patients with uncontrolled type 2 diabetes.

  4. N6-Cycloalkyl- and N6-bicycloalkyl-C5'(C2')-modified adenosine derivatives as high-affinity and selective agonists at the human A1 adenosine receptor with antinociceptive effects in mice.

    PubMed

    Franchetti, Palmarisa; Cappellacci, Loredana; Vita, Patrizia; Petrelli, Riccardo; Lavecchia, Antonio; Kachler, Sonja; Klotz, Karl-Norbert; Marabese, Ida; Luongo, Livio; Maione, Sabatino; Grifantini, Mario

    2009-04-23

    To further investigate new potent and selective human A(1) adenosine receptor agonists, we have synthesized a series of 5'-chloro-5'-deoxy- and 5'-(2-fluorophenylthio)-5'-deoxy-N(6)-cycloalkyl(bicycloalkyl)-substituted adenosine and 2'-C-methyladenosine derivatives. These compounds were evaluated for affinity and efficacy at human A(1), A(2A), A(2B), and A(3) adenosine receptors. In the series of N(6)-cyclopentyl- and N(6)-(endo-norborn-2-yl)adenosine derivatives, 5'-chloro-5'-deoxy-CPA (1) and 5'-chloro-5'-deoxy-(+/-)-ENBA (3) displayed the highest affinity in the subnanomolar range and relevant selectivity for hA(1) vs the other human receptor subtypes. The higher affinity and selectivity of 5'-chloro-5'-deoxyribonucleoside derivatives 1 and 3 for hA(1) AR vs hA(3) AR compared to that of the parent 5'-hydroxy compounds CPA and (+/-)-ENBA was rationalized by a molecular modeling analysis. 5'-Chloro-5'-deoxy-(+/-)-ENBA, evaluated for analgesic activity in the formalin test in mice, was found to inhibit the first or the second phases of the nocifensive response induced by intrapaw injection of formalin at doses ranging between 1 and 2 mg/kg i.p.

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

    PubMed Central

    Maguire, David R.; France, Charles P.

    2016-01-01

    Cannabinoid receptor agonists such as delta-9-tetrahydrocannabinol (Δ9-THC) enhance some (antinociceptive) but not other (positive reinforcing) effects of mu opioid receptor agonists, suggesting that cannabinoids might be combined with opioids to treat pain without increasing, and possibly decreasing, abuse. The degree to which cannabinoids enhance antinociceptive effects of opioids varies across drugs insofar as Δ9-THC and the synthetic cannabinoid receptor agonist CP55940 increase the potency of some mu opioid receptor agonists (e.g., fentanyl) more than others (e.g., nalbuphine). It is not known whether interactions between cannabinoids and opioids vary similarly for other (abuse-related) effects. This study examined whether Δ9-THC and CP55940 differentially impact the discriminative stimulus effects of fentanyl and nalbuphine in monkeys (n=4) discriminating 0.01 mg/kg of fentanyl (s.c.) from saline. Fentanyl (0.00178–0.0178 mg/kg) and nalbuphine (0.01–0.32 mg/kg) dose-dependently increased drug-lever responding. Neither Δ9-THC (0.032–1.0 mg/kg) nor CP55940 (0.0032–0.032 mg/kg) enhanced the discriminative stimulus effects of fentanyl or nalbuphine; however, doses of Δ9-THC and CP55940 that shifted the nalbuphine dose-effect curve markedly to the right and/or down were less effective or ineffective in shifting the fentanyl dose-effect curve. The mu opioid receptor antagonist naltrexone (0.032 mg/kg) attenuated the discriminative stimulus effects of fentanyl and nalbuphine similarly. These data indicate that the discriminative stimulus effects of nalbuphine are more sensitive to attenuation by cannabinoids than those of fentanyl. That the discriminative stimulus effects of some opioids are more susceptible to modification by drugs from other classes has implications for developing maximally effective therapeutic drug mixtures with reduced abuse liability. PMID:27184925

  6. Discovery of G Protein-Biased EP2 Receptor Agonists.

    PubMed

    Ogawa, Seiji; Watanabe, Toshihide; Sugimoto, Isamu; Moriyuki, Kazumi; Goto, Yoshikazu; Yamane, Shinsaku; Watanabe, Akio; Tsuboi, Kazuma; Kinoshita, Atsushi; Kigoshi, Hideo; Tani, Kousuke; Maruyama, Toru

    2016-03-10

    To identify G protein-biased and highly subtype-selective EP2 receptor agonists, a series of bicyclic prostaglandin analogues were designed and synthesized. Structural hybridization of EP2/4 dual agonist 5 and prostacyclin analogue 6, followed by simplification of the ω chain enabled us to discover novel EP2 agonists with a unique prostacyclin-like scaffold. Further optimization of the ω chain was performed to improve EP2 agonist activity and subtype selectivity. Phenoxy derivative 18a showed potent agonist activity and excellent subtype selectivity. Furthermore, a series of compounds were identified as G protein-biased EP2 receptor agonists. These are the first examples of biased ligands of prostanoid receptors.

  7. Nicotine receptor partial agonists for smoking cessation.

    PubMed

    Cahill, Kate; Stead, Lindsay F; Lancaster, Tim

    2011-02-16

    Nicotine receptor partial agonists may help people to stop smoking by a combination of maintaining moderate levels of dopamine to counteract withdrawal symptoms (acting as an agonist) and reducing smoking satisfaction (acting as an antagonist). Varenicline was developed as a nicotine receptor partial agonist from cytisine, a drug widely used in central and eastern Europe for smoking cessation. The first trial reports of varenicline were released in 2006, and further trials have now been published or are currently underway. The primary objective of this review is to assess the efficacy and tolerability of nicotine receptor partial agonists, including varenicline and cytisine, for smoking cessation. We searched the Cochrane Tobacco Addiction Group's specialised register for trials, using the terms ('varenicline' or 'cytisine' or 'Tabex' or 'nicotine receptor partial agonist') and 'smoking' in the title or abstract, or as keywords. We also searched MEDLINE, EMBASE, PsycINFO and CINAHL using MeSH terms and free text, and we contacted authors of trial reports for additional information where necessary. The latest search was in September 2010. We included randomized controlled trials which compared the treatment drug with placebo. We also included comparisons with bupropion and nicotine patches where available. We excluded trials which did not report a minimum follow-up period of six months from start of treatment. We extracted data on the type of participants, the dose and duration of treatment, the outcome measures, the randomization procedure, concealment of allocation, and completeness of follow up.The main outcome measured was abstinence from smoking after at least six months from the beginning of treatment. We used the most rigorous definition of abstinence, and preferred biochemically validated rates where they were reported. Where appropriate we performed meta-analysis to produce a risk ratio, using the Mantel-Haenszel fixed-effect model. We found 11 trials of

  8. Nicotine receptor partial agonists for smoking cessation.

    PubMed

    Cahill, Kate; Stead, Lindsay F; Lancaster, Tim

    2010-12-08

    Nicotine receptor partial agonists may help people to stop smoking by a combination of maintaining moderate levels of dopamine to counteract withdrawal symptoms (acting as an agonist) and reducing smoking satisfaction (acting as an antagonist). Varenicline was developed as a nicotine receptor partial agonist from cytisine, a drug widely used in central and eastern Europe for smoking cessation. The first trial reports of varenicline were released in 2006, and further trials have now been published or are currently underway. The primary objective of this review is to assess the efficacy and tolerability of nicotine receptor partial agonists, including varenicline and cytisine, for smoking cessation. We searched the Cochrane Tobacco Addiction Group's specialised register for trials, using the terms ('varenicline' or 'cytisine' or 'Tabex' or 'nicotine receptor partial agonist') and 'smoking' in the title or abstract, or as keywords. We also searched MEDLINE, EMBASE, PsycINFO and CINAHL using MeSH terms and free text, and we contacted authors of trial reports for additional information where necessary. The latest search was in September 2010. We included randomized controlled trials which compared the treatment drug with placebo. We also included comparisons with bupropion and nicotine patches where available. We excluded trials which did not report a minimum follow-up period of six months from start of treatment. We extracted data on the type of participants, the dose and duration of treatment, the outcome measures, the randomization procedure, concealment of allocation, and completeness of follow up.The main outcome measured was abstinence from smoking after at least six months from the beginning of treatment. We used the most rigorous definition of abstinence, and preferred biochemically validated rates where they were reported. Where appropriate we performed meta-analysis to produce a risk ratio, using the Mantel-Haenszel fixed-effect model. We found 11 trials of

  9. The 5-HT1A/1B-receptor agonist eltoprazine increases both catecholamine release in the prefrontal cortex and dopamine release in the nucleus accumbens and decreases motivation for reward and "waiting" impulsivity, but increases "stopping" impulsivity.

    PubMed

    Korte, S Mechiel; Prins, Jolanda; Van den Bergh, Filip S; Oosting, Ronald S; Dupree, Rudy; Korte-Bouws, Gerdien A H; Westphal, Koen G C; Olivier, Berend; Denys, Damiaan A; Garland, Alexis; Güntürkün, Onur

    2017-01-05

    The 5-HT 1A/1B -receptor agonist eltoprazine has a behavioral drug signature that resembles that of a variety of psychostimulant drugs, despite the differences in receptor binding profile. These psychostimulants are effective in treating impulsivity disorders, most likely because they increase norepinephrine (NE) and dopamine (DA) levels in the prefrontal cortex. Both amphetamine and methylphenidate, however, also increase dopamine levels in the nucleus accumbens (NAc), which has a significant role in motivation, pleasure, and reward. How eltoprazine affects monoamine release in the medial prefrontal cortex (mPFC), the orbitofrontal cortex (OFC), and the NAc is unknown. It is also unknown whether eltoprazine affects different forms of impulsivity and brain reward mechanisms. Therefore, in the present study, we investigate the effects of eltoprazine in rats in the following sequence: 1) the activity of the monoaminergic systems using in vivo microdialysis, 2) motivation for reward measured using the intracranial self-stimulation (ICSS) procedure, and finally, 3) "waiting" impulsivity in the delay-aversion task, and the "stopping" impulsivity in the stop-signal task. The microdialysis studies clearly showed that eltoprazine increased DA and NE release in both the mPFC and OFC, but only increased DA concentration in the NAc. In contrast, eltoprazine decreased 5-HT release in the mPFC and NAc (undetectable in the OFC). Remarkably, eltoprazine decreased impulsive choice, but increased impulsive action. Furthermore, brain stimulation was less rewarding following eltoprazine treatment. These results further support the long-standing hypothesis that "waiting" and "stopping" impulsivity are regulated by distinct neural circuits, because 5-HT 1A/1B -receptor activation decreases impulsive choice, but increases impulsive action. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Population pharmacokinetics and pharmacodynamics of peptidic erythropoiesis receptor agonist (ERA) in healthy volunteers.

    PubMed

    Woo, Sukyung; Krzyzanski, Wojciech; Duliege, Anne-Marie; Stead, Richard B; Jusko, William J

    2008-01-01

    Peptidic erythropoiesis receptor agonist is a synthetic, PEGylated peptide that can promote red blood cell production upon binding to the erythropoietin receptor. The objective of this study was to characterize the pharmacokinetics and erythropoietic effects of peptidic erythropoiesis receptor agonist in healthy volunteers. Plasma concentrations of peptidic erythropoiesis receptor agonist and pharmacodynamic responses were obtained after single intravenous injections at doses of 0.025, 0.05, and 0.1 mg/kg. Population pharmacokinetic/pharmacodynamic modeling was performed using NONMEM. Peptidic erythropoiesis receptor agonist exhibited nonlinear pharmacokinetics described by a 1-compartment model with parallel elimination by Michaelis-Menten and linear processes. A catenary, life span-based, indirect response model reflecting bone marrow erythroid and blood cells reflected the pharmacodynamics of peptidic erythropoiesis receptor agonist. A modest tolerance and rebound phenomenon in reticulocytes was modeled with negative feedback regulation related to hemoglobin. This pharmacokinetic/pharmacodynamic model well characterized the prolonged disposition, intrinsic pharmacologic parameters, and typical hematological system properties following single doses of peptidic erythropoiesis receptor agonist in normal subjects.

  11. Nicotine receptor partial agonists for smoking cessation.

    PubMed

    Cahill, Kate; Stead, Lindsay F; Lancaster, Tim

    2012-04-18

    Nicotine receptor partial agonists may help people to stop smoking by a combination of maintaining moderate levels of dopamine to counteract withdrawal symptoms (acting as an agonist) and reducing smoking satisfaction (acting as an antagonist). The primary objective of this review is to assess the efficacy and tolerability of nicotine receptor partial agonists, including cytisine, dianicline and varenicline for smoking cessation. We searched the Cochrane Tobacco Addiction Group's specialised register for trials, using the terms ('cytisine' or 'Tabex' or 'dianicline' or 'varenicline' or 'nicotine receptor partial agonist') in the title or abstract, or as keywords. The register is compiled from searches of MEDLINE, EMBASE, PsycINFO and Web of Science using MeSH terms and free text to identify controlled trials of interventions for smoking cessation and prevention. We contacted authors of trial reports for additional information where necessary. The latest update of the specialised register was in December 2011. We also searched online clinical trials registers. We included randomized controlled trials which compared the treatment drug with placebo. We also included comparisons with bupropion and nicotine patches where available. We excluded trials which did not report a minimum follow-up period of six months from start of treatment. We extracted data on the type of participants, the dose and duration of treatment, the outcome measures, the randomization procedure, concealment of allocation, and completeness of follow-up.The main outcome measured was abstinence from smoking at longest follow-up. We used the most rigorous definition of abstinence, and preferred biochemically validated rates where they were reported. Where appropriate we pooled risk ratios (RRs), using the Mantel-Haenszel fixed-effect model. Two recent cytisine trials (937 people) found that more participants taking cytisine stopped smoking compared with placebo at longest follow-up, with a pooled RR of

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

    PubMed

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

    2014-01-01

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

  13. Safety and tolerability of TRAIL receptor agonists in cancer treatment.

    PubMed

    Fulda, Simone

    2015-05-01

    Targeting the death receptor pathway of apoptosis represents a promising approach for the development of novel cancer therapeutics, since death receptors on the cell surface are directly linked to the apoptotic machinery. The tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptor/ligand system is of particular interest among the death receptor superfamily for therapeutic targeting in cancer, since TRAIL has been reported to preferentially induce apoptosis in cancer cells, while sparing non-malignant cells. Evaluation of TRAIL receptor agonists in clinical trials has revealed that they are, in principle, well-tolerated but exert limited efficacy in unselective patient populations. Currently, the challenge resides in the development of rational TRAIL-based combination therapies with potent TRAIL receptor agonists in order to exploit the potential of death receptor targeting for cancer therapy.

  14. PPAR δ agonist GW0742 interacts weakly with multiple nuclear receptors including the vitamin D receptor

    PubMed Central

    Nandhikonda, Premchendar; Yasgar, Adam; Baranowski, Athena M.; Sidhu, Preetpal S.; McCallum, Megan M.; Pawlak, Alan J.; Teske, Kelly; Feleke, Belaynesh; Yuan, Nina Y.; Kevin, Chinedum; Bikle, Daniel D.; Ayers, Steven D.; Webb, Paul; Rai, Ganesha; Simeonov, Anton; Jadhav, Ajit; Maloney, David; Arnold, Leggy A.

    2013-01-01

    A high throughput screening campaign was conducted to identify small molecules with the ability to inhibit the interaction between the vitamin D receptor (VDR) and steroid receptor coactivator 2. These inhibitors represent novel molecular probes to modulate gene regulation mediated by VDR. The peroxisome proliferator-activated receptor δ (PPARδ) agonist GW0742 was among the identified VDR-coactivator inhibitors and has been characterized herein as a pan nuclear receptor antagonist at concentrations higher than 12.1 µM. The highest antagonist activity for GW0742 was found for VDR and the androgen receptor (AR). Surprisingly, GW0742 behaved as PPAR agonist/antagonist activating transcription at lower concentration and inhibiting this effect at higher concentrations. A unique spectroscopic property of GW0742 was identified as well. In the presence of rhodamine-derived molecules, GW0742+ increased fluorescence intensity and fluorescence polarization at an excitation wavelength of 595 nm and emission wavelength of 615 nm in a dose dependent manner. The GW0742-inhibited NR-coactivator binding resulted in a reduced expression of five different NR target genes in LNCaP cells in the presence of agonist. Especially VDR target genes CYP24A1, IGFBP-3 and TRPV6 were negatively regulated by GW0742. GW0742 is the first VDR ligand inhibitor lacking the secosteroid structure of VDR ligand antagonists. Nevertheless, the VDR-meditated downstream process of cell differentiation was antagonized by GW0742 in HL-60 cells that were pretreated with the endogenous VDR agonist 1,25-dihydroxyvitamin D3. PMID:23713684

  15. The pharmacology and clinical application of thrombopoietin receptor agonists.

    PubMed

    Li, Caizheng; Zheng, Li

    2014-12-01

    The discovery and application of thrombopoietin (TPO) and thrombopoietin receptor (TPOR) agonists have changed the clinical treatment of thrombocytopenia. These compounds exert favorable clinical effects without the adverse events caused by traditional treatments (e.g., corticosteroids, immunoglobulins, monoclonal antibodies and splenectomy). This review provides a synopsis of new agents that boost platelet production, especially the TPOR agonists, and highlights their pharmacological characteristics and clinical applications.

  16. Studies Toward the Pharmacophore of Salvinorin A, a Potent Kappa Opioid Receptor Agonist

    PubMed Central

    Munro, Thomas A.; Rizzacasa, Mark A.; Roth, Bryan L.; Toth, Beth A.; Yan, Feng

    2009-01-01

    Salvinorin A (1), from the sage Salvia divinorum, is a potent and selective kappa opioid receptor (KOR) agonist. We screened other salvinorins and derivatives for binding affinity and functional activity at opioid receptors. Our results suggest that the methyl ester and furan ring are required for activity, but that the lactone and ketone functionalities are not. Other salvinorins showed negligible binding affinity at the KOR. None of the compounds bound to mu or delta opioid receptors. PMID:15658846

  17. Estrogen receptor agonists for attenuation of neuroinflammation and neurodegeneration

    PubMed Central

    Chakrabarti, Mrinmay; Haque, Azizul; Banik, Naren L.; Nagarkatti, Prakash; Nagarkatti, Mitzi; Ray, Swapan K.

    2014-01-01

    Recent results from laboratory investigations and clinical trials indicate important roles for estrogen receptor (ER) agonists in protecting the central nervous system (CNS) from noxious consequences of neuroinflammation and neurodegeneration. Neurodegenerative processes in several CNS disorders including spinal cord injury (SCI), multiple sclerosis (MS), Parkinson's disease (PD), and Alzheimer's disease (AD) are associated with activation of microglia and astrocytes, which drive the resident neuroinflammatory response. During neurodegenerative processes, activated microglia and astrocytes cause deleterious effects on surrounding neurons. The inhibitory activity of ER agonists on microglia activation might be a beneficial therapeutic option for delaying the onset or progression of neurodegenerative injuries and diseases. Recent studies suggest that ER agonists can provide neuroprotection by modulation of cell survival mechanisms, synaptic reorganization, regenerative responses to axonal injury, and neurogenesis process. The anti-inflammatory and neuroprotective actions of ER agonists are mediated mainly via two ERs known as ERα and ERβ. Although some studies have suggested that ER agonists may be deleterious to some neuronal populations, the potential clinical benefits of ER agonists for augmenting cognitive function may triumph over the associated side effects. Also, understanding the modulatory activities of ER agonists on inflammatory pathways will possibly lead to the development of selective anti-inflammatory molecules with neuroprotective roles in different CNS disorders such as SCI, MS, PD, and AD in humans. Future studies should be concentrated on finding the most plausible molecular pathways for enhancing protective functions of ER agonists in treating neuroinflammatory and neurodegenerative injuries and diseases in the CNS. PMID:25245209

  18. Unique Interaction Pattern for a Functionally Biased Ghrelin Receptor Agonist*

    PubMed Central

    Sivertsen, Bjørn; Lang, Manja; Frimurer, Thomas M.; Holliday, Nicholas D.; Bach, Anders; Els, Sylvia; Engelstoft, Maja S.; Petersen, Pia S.; Madsen, Andreas N.; Schwartz, Thue W.; Beck-Sickinger, Annette G.; Holst, Birgitte

    2011-01-01

    Based on the conformationally constrained d-Trp-Phe-d-Trp (wFw) core of the prototype inverse agonist [d-Arg1,d-Phe5,d-Trp7,9,Leu11]substance P, a series of novel, small, peptide-mimetic agonists for the ghrelin receptor were generated. By using various simple, ring-constrained spacers connecting the d-Trp-Phe-d-Trp motif with the important C-terminal carboxyamide group, 40 nm agonism potency was obtained and also in one case (wFw-Isn-NH2, where Isn is isonipecotic acid) ∼80% efficacy. However, in contrast to all previously reported ghrelin receptor agonists, the piperidine-constrained wFw-Isn-NH2 was found to be a functionally biased agonist. Thus, wFw-Isn-NH2 mediated potent and efficacious signaling through the Gαq and ERK1/2 signaling pathways, but in contrast to all previous ghrelin receptor agonists it did not signal through the serum response element, conceivably the Gα12/13 pathway. The recognition pattern of wFw-Isn-NH2 with the ghrelin receptor also differed significantly from that of all previously characterized unbiased agonists. Most importantly, wFw-Isn-NH2 was not dependent on GluIII:09 (Glu3.33), which otherwise is an obligatory TM III anchor point residue for ghrelin agonists. Molecular modeling and docking experiments indicated that wFw-Isn-NH2 binds in the classical agonist binding site between the extracellular segments of TMs III, VI, and VII, interacting closely with the aromatic cluster between TMs VI and VII, but that it does so in an opposite orientation as compared with, for example, the wFw peptide agonists. It is concluded that the novel peptide-mimetic ligand wFw-Isn-NH2 is a biased ghrelin receptor agonist and that the selective signaling pattern presumably is due to its unique receptor recognition pattern lacking interaction with key residues especially in TM III. PMID:21402696

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

    PubMed

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

    2014-09-01

    Glucagon-like peptide-1 (GLP-1) receptor agonists are a new group of drugs for the treatment of type 2 diabetes mellitus (DM2). In the present article, we review the available evidence on the efficacy of GLP-1 receptor agonists as glucose-lowering agents, their place in therapeutic algorithms, and the clinical factors associated with a favorable treatment response. Finally, we describe the clinical characteristics of patients who may benefit from these drugs. Copyright © 2014 Elsevier España, S.L.U. All rights reserved.

  20. Identification of A3 adenosine receptor agonists as novel non‐narcotic analgesics

    PubMed Central

    Janes, K; Symons‐Liguori, AM; Jacobson, K A

    2016-01-01

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

  1. Adenosine A(2A) receptor dynamics studied with the novel fluorescent agonist Alexa488-APEC.

    PubMed

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

    2008-08-20

    G protein-coupled receptors, such as the adenosine A(2A) receptor, are dynamic proteins, which undergo agonist-dependent redistribution from the cell surface to intracellular membranous compartments, such as endosomes. In order to study the kinetics of adenosine A(2A) receptor redistribution in living cells, we synthesized a novel fluorescent agonist, Alexa488-APEC. Alexa488-APEC binds to adenosine A(2A) (K(i)=149+/-27 nM) as well as A(3) receptors (K(i)=240+/-160 nM) but not to adenosine A(1) receptors. Further, we characterized the dose-dependent increase in Alexa488-APEC-induced cAMP production as well as cAMP response element binding (CREB) protein phosphorylation, verifying the ligand's functionality at adenosine A(2A) but not A(2B) receptors. In live-cell imaging studies, Alexa488-APEC-induced adenosine A(2A) receptor internalization, which was blocked by the competitive reversible antagonist ZM 241385 and hyperosmolaric sucrose. Further, internalized adenosine A(2A) receptors co-localized with clathrin and Rab5, indicating that agonist stimulation promotes adenosine A(2A) receptor uptake through a clathrin-dependent mechanism to Rab5-positive endosomes. The basic characterization of Alexa488-APEC described here showed that it provides a useful tool for tracing adenosine A(2A) receptors in vitro.

  2. Emerging strategies for exploiting cannabinoid receptor agonists as medicines

    PubMed Central

    Pertwee, Roger G

    2009-01-01

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

  3. 2'-C-Methyl analogues of selective adenosine receptor agonists: synthesis and binding studies.

    PubMed

    Franchetti, P; Cappellacci, L; Marchetti, S; Trincavelli, L; Martini, C; Mazzoni, M R; Lucacchini, A; Grifantini, M

    1998-05-07

    2'-C-Methyl analogues of selective adenosine receptor agonists such as (R)-PIA, CPA, CCPA, NECA, and IB-MECA were synthesized in order to further investigate the subdomain that binds the ribose moiety. Binding affinities of these new compounds at A1 and A2A receptors in bovine brain membranes and at A3 in rat testis membranes were determined and compared. It was found that the 2'-C-methyl modification resulted in a decrease of the affinity, particularly at A2A and A3 receptors. When such modification was combined with N6-substitutions with groups which induce high potency and selectivity at A1 receptors, the high affinity was retained and the selectivity was increased. Thus, 2-chloro-2'-C-methyl-N6-cyclopentyladenosine (2'-Me-CCPA), which displayed a Ki value of 1.8 nM at A1 receptors, was selective for A1 vs A2A and A3 receptors by 2166- and 2777-fold, respectively, resulting in one of the most potent and A1-selective agonists so far known. In functional assay, this compound inhibited forskolin-stimulated adenylyl cyclase activity with an IC50 value of 13.1 nM, acting as a full agonist.

  4. Pharmacological Studies of NOP Receptor Agonists as Novel Analgesics

    DTIC Science & Technology

    2009-05-01

    found in hot-chili peppers that evokes pain sensation by activating at the TRPV1 . TRPV1 and the up-regulation of its expression have been strongly...via nociceptin/orphanin FQ receptors. Br J Pharmacol 137:1355-1361. Knotkova H, Pappagallo M, Szallasi A (2008) Capsaicin ( TRPV1 Agonist) therapy...Szallasi A, Cortright DN, Blum CA, Eid SR (2007). The vanilloid receptor TRPV1 : 10 years from channel cloning to antagonist proof of concept. Nat Rev Drug

  5. Facile syntheses of functionalized toll-like receptor 7 agonists

    PubMed Central

    Akinbobuyi, Babatope; Byrd, Matthew R.; Chang, Charles A.; Nguyen, Mysa; Seifert, Zacharie J.; Flamar, Anne-Laure; Zurawski, Gerard; Upchurch, Katherine C.; Oh, SangKon; Dempsey, Stephen H.; Enke, Thomas J.; Le, John; Winstead, Hunter J.; Boquín, José R.; Kane, Robert R.

    2014-01-01

    Protein conjugates of toll-like receptor 7 agonists have been shown to elicit powerful immune responses. In order to facilitate our studies in this area our group has developed efficient syntheses for a number of functionalized derivatives that retain immune stimulatory activity. PMID:25601818

  6. Do agonists promote rapid internalization of beta-adrenergic receptors?

    PubMed Central

    Mahan, L C; Motulsky, H J; Insel, P A

    1985-01-01

    We used elution of radioligands at low pH to quantitate intracellular beta-adrenergic receptors on intact S49 lymphoma cells. We validated this method with respect to cell viability, beta-adrenergic receptor integrity, and transferrin receptors on these cells. On control cells, about 15% of the radiolabeled beta-adrenergic antagonists [3H]dihydroalprenolol and [125I]iodocyanopindolol specifically bound at 37 degrees C could not be eluted at low pH; these binding sites appear to be intracellular receptors that are inaccessible to the surface-restricted antagonist [3H]CGP-12177 [tritiated (+/-)-4-(3-t-butylamino-2-hydroxypropoxy)benzimidazole-2-one hydrochloride]. Incubation of cells with the agonist isoproterenol at 37 degrees C for 15 min did not change the number of [3H]dihydroalprenolol binding sites but reduced [3H]CGP-12177 binding sites by 50% or more. However, all specifically bound [3H]CGP-12177 and [3H]dihydroalprenolol were eluted by acid. In addition, the number of acid-elution-resistant [125I]iodocyanopindolol binding sites was not increased in cells coincubated with 1 microM isoproterenol and [125I]iodocyanopindolol for 15 min at 37 degrees C, even though those sites show a loss in apparent affinity for isoproterenol of about 2 orders of magnitude, a loss previously attributed to internalization. We conclude that the early phase of agonist-mediated desensitization of beta-adrenergic receptors in S49 cells does not coincide with the movement of receptors to intracellular sites; instead, agonist-modified receptors remain in association with the plasma membrane and are accessible to the extracellular environment. These "redistributed" receptors together with "cell-surface" and "intracellular" receptors represent three classes of beta-adrenergic receptors that can be selectively identified in intact target cells. PMID:2864689

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  9. Progesterone receptor isoforms, agonists and antagonists differentially reprogram estrogen signaling.

    PubMed

    Singhal, Hari; Greene, Marianne E; Zarnke, Allison L; Laine, Muriel; Al Abosy, Rose; Chang, Ya-Fang; Dembo, Anna G; Schoenfelt, Kelly; Vadhi, Raga; Qiu, Xintao; Rao, Prakash; Santhamma, Bindu; Nair, Hareesh B; Nickisch, Klaus J; Long, Henry W; Becker, Lev; Brown, Myles; Greene, Geoffrey L

    2018-01-12

    Major roadblocks to developing effective progesterone receptor (PR)-targeted therapies in breast cancer include the lack of highly-specific PR modulators, a poor understanding of the pro- or anti-tumorigenic networks for PR isoforms and ligands, and an incomplete understanding of the cross talk between PR and estrogen receptor (ER) signaling. Through genomic analyses of xenografts treated with various clinically-relevant ER and PR-targeting drugs, we describe how the activation or inhibition of PR differentially reprograms estrogen signaling, resulting in the segregation of transcriptomes into separate PR agonist and antagonist-mediated groups. These findings address an ongoing controversy regarding the clinical utility of PR agonists and antagonists, alone or in combination with tamoxifen, for breast cancer management. Additionally, the two PR isoforms PRA and PRB, bind distinct but overlapping genomic sites and interact with different sets of co-regulators to differentially modulate estrogen signaling to be either pro- or anti-tumorigenic. Of the two isoforms, PRA inhibited gene expression and ER chromatin binding significantly more than PRB. Differential gene expression was observed in PRA and PRB-rich patient tumors and PRA-rich gene signatures had poorer survival outcomes. In support of antiprogestin responsiveness of PRA-rich tumors, gene signatures associated with PR antagonists, but not PR agonists, predicted better survival outcomes. The better patient survival associated with PR antagonists versus PR agonists treatments was further reflected in the higher in vivo anti-tumor activity of therapies that combine tamoxifen with PR antagonists and modulators. This study suggests that distinguishing common effects observed due to concomitant interaction of another receptor with its ligand (agonist or antagonist), from unique isoform and ligand-specific effects will inform the development of biomarkers for patient selection and translation of PR

  10. Progesterone receptor isoforms, agonists and antagonists differentially reprogram estrogen signaling

    PubMed Central

    Singhal, Hari; Greene, Marianne E.; Zarnke, Allison L.; Laine, Muriel; Al Abosy, Rose; Chang, Ya-Fang; Dembo, Anna G.; Schoenfelt, Kelly; Vadhi, Raga; Qiu, Xintao; Rao, Prakash; Santhamma, Bindu; Nair, Hareesh B.; Nickisch, Klaus J.; Long, Henry W.; Becker, Lev; Brown, Myles; Greene, Geoffrey L.

    2018-01-01

    Major roadblocks to developing effective progesterone receptor (PR)-targeted therapies in breast cancer include the lack of highly-specific PR modulators, a poor understanding of the pro- or anti-tumorigenic networks for PR isoforms and ligands, and an incomplete understanding of the cross talk between PR and estrogen receptor (ER) signaling. Through genomic analyses of xenografts treated with various clinically-relevant ER and PR-targeting drugs, we describe how the activation or inhibition of PR differentially reprograms estrogen signaling, resulting in the segregation of transcriptomes into separate PR agonist and antagonist-mediated groups. These findings address an ongoing controversy regarding the clinical utility of PR agonists and antagonists, alone or in combination with tamoxifen, for breast cancer management. Additionally, the two PR isoforms PRA and PRB, bind distinct but overlapping genomic sites and interact with different sets of co-regulators to differentially modulate estrogen signaling to be either pro- or anti-tumorigenic. Of the two isoforms, PRA inhibited gene expression and ER chromatin binding significantly more than PRB. Differential gene expression was observed in PRA and PRB-rich patient tumors and PRA-rich gene signatures had poorer survival outcomes. In support of antiprogestin responsiveness of PRA-rich tumors, gene signatures associated with PR antagonists, but not PR agonists, predicted better survival outcomes. The better patient survival associated with PR antagonists versus PR agonists treatments was further reflected in the higher in vivo anti-tumor activity of therapies that combine tamoxifen with PR antagonists and modulators. This study suggests that distinguishing common effects observed due to concomitant interaction of another receptor with its ligand (agonist or antagonist), from unique isoform and ligand-specific effects will inform the development of biomarkers for patient selection and translation of PR

  11. Receptors and Channels Targeted by Synthetic Cannabinoid Receptor Agonists and Antagonists

    PubMed Central

    Pertwee, R.G.

    2010-01-01

    It is widely accepted that non-endogenous compounds that target CB1 and/or CB2 receptors possess therapeutic potential for the clinical management of an ever growing number of disorders. Just a few of these disorders are already treated with Δ9-tetrahydrocannabinol or nabilone, both CB1/CB2 receptor agonists, and there is now considerable interest in expanding the clinical applications of such agonists and also in exploiting CB2-selective agonists, peripherally restricted CB1/CB2 receptor agonists and CB1/CB2 antagonists and inverse agonists as medicines. Already, numerous cannabinoid receptor ligands have been developed and their interactions with CB1 and CB2 receptors well characterized. This review describes what is currently known about the ability of such compounds to bind to, activate, inhibit or block non-CB1, non-CB2 G protein-coupled receptors such as GPR55, transmitter gated channels, ion channels and nuclear receptors in an orthosteric or allosteric manner. It begins with a brief description of how each of these ligands interacts with CB1 and/or CB2 receptors. PMID:20166927

  12. Anthranilic acid replacements in a niacin receptor agonist.

    PubMed

    Schmidt, Darby; Smenton, Abigail; Raghavan, Subharekha; Shen, Hong; Ding, Fa-Xiang; Carballo-Jane, Ester; Luell, Silvi; Ciecko, Tanya; Holt, Tom G; Wolff, Michael; Taggart, Andrew; Wilsie, Larissa; Krsmanovic, Mihajlo; Ren, Ning; Blom, Daniel; Cheng, Kang; McCann, Peggy E; Waters, M Gerard; Tata, James; Colletti, Steven

    2010-06-01

    Niacin is an effective drug for raising HDL cholesterol. However, niacin must be taken in large doses and significant side effects are often observed, including facial flushing, loss of glucose tolerance, and liver toxicity. An anthranilic acid was identified as an agonist of the niacin receptor. In order to improve efficacy and provide structural diversity, replacements for the anthranilic acid were investigated and several compounds with improved properties were identified. Copyright 2010 Elsevier Ltd. All rights reserved.

  13. Pharmacological Studies of NOP Receptor Agonists as Novel Analgesics

    DTIC Science & Technology

    2010-05-01

    irritant found in hot-chili peppers that evokes pain sensation by activating at the TRPV1 . TRPV1 and the up-regulation of its expression have been 5...Capsaicin ( TRPV1 Agonist) therapy for pain relief: farewell or revival? Clin J Pain 24: 142-154. Ko MC, Butelman ER, Traynor JR, Woods JH (1998a...involvement of spinal NK1 receptors. Br J Pharmacol 127:1712-1718. Szallasi A, Cortright DN, Blum CA, Eid SR (2007). The vanilloid receptor TRPV1 : 10

  14. Therapeutic significance of estrogen receptor β agonists in gliomas.

    PubMed

    Sareddy, Gangadhara R; Nair, Binoj C; Gonugunta, Vijay K; Zhang, Quan-guang; Brenner, Andrew; Brann, Darrell W; Tekmal, Rajeshwar Rao; Vadlamudi, Ratna K

    2012-05-01

    Gliomas are the most common and devastating central nervous system neoplasms. A gender bias exists in their development: females are at lower risk than males, implicating estrogen-mediated protective effects. Estrogen functions are mediated by two estrogen receptor (ER) subtypes: ERα, which functions as tumor promoter, and ERβ, which functions as tumor suppressor. We examined the potential use of ERβ agonists as a novel therapeutic to curb the growth of gliomas. Western analysis of six glioma model cells showed detectable expression of ERβ with little or no ERα. Treatment of glioma cells with ERβ agonists resulted in significant decrease in proliferation. Immunohistochemical analysis of tumor tissues revealed that ERβ expression is downregulated in high-grade gliomas. We found that ERβ agonists promote both expression and tumor-suppressive functions of ERβ in glioma cells. Liquiritigenin, a plant-derived ERβ agonist significantly reduced in vivo tumor growth in a xenograft model. Compared with control mice, animals treated with liquiritigenin had greater than 50% reduction in tumor volume and size. Immunohistochemical analysis of tumors revealed a significant increase in the nuclear ERβ expression with a concomitant decrease in cell proliferation in the liquiritigenin-treated group. Our results suggest that ERβ signaling has a tumor-suppressive function in gliomas. Because ERβ agonists are currently in clinical trials and are well tolerated with fewer side effects, identification of an ERβ agonist as a therapeutic agent can be readily extended to clinical use with current chemotherapies, providing an additional tool for enhancing survival in glioma patients. ©2012 AACR

  15. Additive antinociceptive effects of mixtures of the κ-opioid receptor agonist spiradoline and the cannabinoid receptor agonist CP55940 in rats.

    PubMed

    Maguire, David R; France, Charles P

    2016-02-01

    Pain is a significant clinical problem, and there is a need for pharmacotherapies that are more effective with fewer adverse effects than currently available medications. Cannabinoid receptor agonists enhance the antinociceptive effects of μ-opioid receptor agonists; it is unclear whether they impact the effects of agonists acting at other opioid receptors. κ-Opioid receptor agonists have antinociceptive effects, but their clinical use is precluded by adverse effects; however, their therapeutic potential might be realized if antinociceptive effects could be selectively enhanced. In this study, the antinociceptive effects of the cannabinoid receptor agonist CP55940 and the κ-opioid receptor agonist spiradoline, alone and in combination, were studied in rats (n=7) using a warm water tail-withdrawal procedure. When administered alone, CP55940 (0.032-1.0 mg/kg) and spiradoline (1.0-32.0 mg/kg) increased tail-withdrawal latency, and mixtures of CP55940 and spiradoline (ratios of 1 : 3, 1 : 1, and 3 : 1) produced additive effects. It remains to be determined whether this additive interaction between a κ-opioid receptor agonist and a cannabinoid receptor agonist is selective for antinociception and whether it can be generalized to other drugs.

  16. Benzodiazepine agonist and inverse agonist actions on GABAA receptor-operated chloride channels. I. Acute effects of ethanol

    SciTech Connect

    Buck, K.J.; Harris, R.A.

    1990-05-01

    Acute exposure to ethanol was found to enhance the ability of a benzodiazepine (BZ) inverse agonist, methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM), to reduce muscimol-activated 36Cl- uptake by membranes isolated from mouse cerebral cortex. Pretreatment in vivo with a hypnotic dose of ethanol (but not a subhypnotic dose), or exposure to a corresponding concentration in vitro, was effective. This increase in sensitivity of gamma-aminobutyric acid receptor-operated chloride channels to the actions of DMCM was due to an increase in both the potency and efficacy of DMCM. Sensitization to DMCM was reversible and was not observed 24 hr after a single injection of ethanol. Pretreatmentmore » with ethanol (10, 50 and 100 mM) in vitro produced sensitization to DMCM in a concentration-dependent manner, similar to that produced by in vivo exposure; this increase in sensitivity did not develop if the membranes were pretreated with ethanol at 0 degrees C. Similarly, in vitro exposure to pentobarbital (200 microM) or flunitrazepam (1 microM) enhanced the actions of the inverse agonist Ro15-4513 (ethyl-8-azido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo(1,5a)(1,4)BZ-3- carboxylate). Acute ethanol exposure did not alter low-affinity gamma-aminobutyric acidA receptor binding or muscimol action, or the ability of a BZ agonist, flunitrazepam, to augment muscimol-activated chloride flux. Ethanol exposure did not alter (3H)flumazenil (Ro15-1788) binding to central BZ receptors, its displacement by DMCM or allosteric modulation of DMCM binding by muscimol (muscimol-shift).« less

  17. Agonist Binding to Chemosensory Receptors: A Systematic Bioinformatics Analysis

    PubMed Central

    Fierro, Fabrizio; Suku, Eda; Alfonso-Prieto, Mercedes; Giorgetti, Alejandro; Cichon, Sven; Carloni, Paolo

    2017-01-01

    Human G-protein coupled receptors (hGPCRs) constitute a large and highly pharmaceutically relevant membrane receptor superfamily. About half of the hGPCRs' family members are chemosensory receptors, involved in bitter taste and olfaction, along with a variety of other physiological processes. Hence these receptors constitute promising targets for pharmaceutical intervention. Molecular modeling has been so far the most important tool to get insights on agonist binding and receptor activation. Here we investigate both aspects by bioinformatics-based predictions across all bitter taste and odorant receptors for which site-directed mutagenesis data are available. First, we observe that state-of-the-art homology modeling combined with previously used docking procedures turned out to reproduce only a limited fraction of ligand/receptor interactions inferred by experiments. This is most probably caused by the low sequence identity with available structural templates, which limits the accuracy of the protein model and in particular of the side-chains' orientations. Methods which transcend the limited sampling of the conformational space of docking may improve the predictions. As an example corroborating this, we review here multi-scale simulations from our lab and show that, for the three complexes studied so far, they significantly enhance the predictive power of the computational approach. Second, our bioinformatics analysis provides support to previous claims that several residues, including those at positions 1.50, 2.50, and 7.52, are involved in receptor activation. PMID:28932739

  18. The biology of thrombopoietin and thrombopoietin receptor agonists.

    PubMed

    Kuter, David J

    2013-07-01

    Thrombopoietin (TPO) is the major physiological regulator of platelet production. TPO binds the TPO receptor, activates JAK and STAT pathways, thus stimulating megakaryocyte growth and platelet production. There is no "sensor" of the platelet count; rather TPO is produced in the liver at a constant rate and cleared by TPO receptors on platelets. TPO levels are inversely proportional to the rate of platelet production. Early recombinant TPO molecules were potent stimulators of platelet production and increased platelets in patients with immune thrombocytopenia, chemotherapy-induced thrombocytopenia, myelodysplastic syndromes and platelet apheresis donors. Neutralizing antibodies formed against one recombinant protein and ended their development. A second generation of TPO receptor agonists, romiplostim and eltrombopag, has been developed. Romiplostim is an IgG heavy chain into which four TPO agonist peptides have been inserted. Eltrombopag is an oral small molecule. These activate the TPO receptor by different mechanisms to increase megakaryocyte growth and platelet production. After administration of either to healthy volunteers, there is a delay of 5 days before the platelet count rises and subsequently reaches a peak after 12-14 days. Both have been highly effective in treating ITP and hepatitis C thrombocytopenia. Studies in a wide variety of other thrombocytopenic conditions are underway.

  19. Behavioral Characterization of κ Opioid Receptor Agonist Spiradoline and Cannabinoid Receptor Agonist CP55940 Mixtures in Rats.

    PubMed

    Minervini, Vanessa; Dahal, Sujata; France, Charles P

    2017-02-01

    Pain is a significant clinical problem, and there is a need for more effective treatments with reduced adverse effects that currently limit the use of μ opioid receptor agonists. Synthetic κ opioid receptor agonists have no abuse liability and well-documented antinociceptive effects; however, adverse effects (diuresis, dysphoria) preclude their use in the clinic. Combining κ opioids with nonopioid drugs (cannabinoid receptor agonists) allows for smaller doses of each drug to produce antinociception. This study tested whether a potentially useful effect of the κ opioid receptor agonist 2-(3,4-dichlorophenyl)-N-methyl-N-[(5R,7S,8S)-7-pyrrolidin-1-yl-1-oxaspiro[4.5]decan-8-yl] (spiradoline; antinociception) is selectively enhanced by the cannabinoid receptor agonist 2-[(1R,2R,5R)-5-hydroxy-2-(3-hydroxypropyl) cyclohexyl]-5-(2-methyloctan-2-yl)phenol (CP55940). Cumulative dose-response functions were determined in eight male Sprague-Dawley rats for spiradoline (0.032-32.0 mg/kg, i.p.) and CP55940 (0.0032-1.0 mg/kg, i.p.) for antinociception, hypothermia, food-maintained responding, and diuresis. Alone, each drug dose dependently increased tail withdrawal latencies from 50°C water, decreased body temperature by ∼4°C, and eliminated food-maintained responding. Spiradoline, but not CP55940, significantly increased urine output at doses that eliminated responding. Smaller doses of spiradoline and CP55940 in mixtures (3:1, 1:1, and 1:3 spiradoline:CP55940) had effects comparable to those observed with larger doses of either drug administered alone: the interaction was additive for antinociception and additive or greater than additive for hypothermia and food-maintained responding. Collectively, these data fail to provide support for the use of these mixtures for treating acute pain; however, κ opioid/cannabinoid mixtures might be useful for treating pain under other conditions (e.g., chronic pain), but only if the adverse effects of both drugs are not enhanced in

  20. Effects of adenosine receptor agonists on efferent renal nerve activity in anesthetized rats.

    PubMed

    Genovesi, S; Pieruzzi, F; Camisasca, P; Ragonesi, G; Protasoni, G; Golin, R; Zanchetti, A; Stella, A

    2000-02-01

    The aim of this study was to investigate the effects of A1 and A2 adenosine-receptor activation on the sympathetic nervous system. The effects on efferent renal nerve activity of selective A1 (CCPA; 2-chloro-N-6-cyclopentyladenosine) and A2 (2HE-NECA; 2-hexynyl-5'-N-ethylcarboxamidoadenosine) adenosine-receptor agonists were studied in anesthetized rats either with intact baroreflexes (intact rats) or with bilateral sinoaortic denervation and vagotomy (denervated rats). After a control period of 5 min, A1 or A2 agonist or vehicle were intravenously infused for 8 min in separate groups of intact or denervated rats, in which arterial pressure and heart rate were continuously recorded. CCPA (5.0 microg/kg/min) and 2HE-NECA (0.7 microg/kg/min) were selected to obtain comparable blood pressure changes over the period of observation. Arterial pressure significantly and equally decreased during the A1 (-41 +/- 8%), and A2 (-35 +/- 5%) agonist administration. Heart rate significantly decreased during A1 agonist infusion, but it did not change during A2 agonist administration. Bilateral sinoaortic denervation and vagotomy did not modify the hemodynamic responses to both drugs. The A1 and A2 administration caused a large and significant increase in efferent renal nerve activity (+66 +/- 22% and +76 +/- 15%, respectively), and this effect was entirely abolished in denervated rats. A linear relation with a significant negative slope between changes in arterial pressure and changes in neural discharge was observed for each treatment. The comparison of the regression slopes showed that the reflex increase of efferent sympathetic activity caused by the administration of both agonists was significantly smaller than the increment induced by equipotent hypotensive dose of sodium nitroprusside (10 microg/kg). These data show that the selective activation of A1 and A2 receptors elicits a reflex increase in efferent renal nerve activity. This neural activation is smaller as compared

  1. A Rationally Designed Agonist Defines Subfamily IIIA Abscisic Acid Receptors As Critical Targets for Manipulating Transpiration.

    PubMed

    Vaidya, Aditya S; Peterson, Francis C; Yarmolinsky, Dmitry; Merilo, Ebe; Verstraeten, Inge; Park, Sang-Youl; Elzinga, Dezi; Kaundal, Amita; Helander, Jonathan; Lozano-Juste, Jorge; Otani, Masato; Wu, Kevin; Jensen, Davin R; Kollist, Hannes; Volkman, Brian F; Cutler, Sean R

    2017-11-17

    Increasing drought and diminishing freshwater supplies have stimulated interest in developing small molecules that can be used to control transpiration. Receptors for the plant hormone abscisic acid (ABA) have emerged as key targets for this application, because ABA controls the apertures of stomata, which in turn regulate transpiration. Here, we describe the rational design of cyanabactin, an ABA receptor agonist that preferentially activates Pyrabactin Resistance 1 (PYR1) with low nanomolar potency. A 1.63 Å X-ray crystallographic structure of cyanabactin in complex with PYR1 illustrates that cyanabactin's arylnitrile mimics ABA's cyclohexenone oxygen and engages the tryptophan lock, a key component required to stabilize activated receptors. Further, its sulfonamide and 4-methylbenzyl substructures mimic ABA's carboxylate and C6 methyl groups, respectively. Isothermal titration calorimetry measurements show that cyanabactin's compact structure provides ready access to high ligand efficiency on a relatively simple scaffold. Cyanabactin treatments reduce Arabidopsis whole-plant stomatal conductance and activate multiple ABA responses, demonstrating that its in vitro potency translates to ABA-like activity in vivo. Genetic analyses show that the effects of cyanabactin, and the previously identified agonist quinabactin, can be abolished by the genetic removal of PYR1 and PYL1, which form subclade A within the dimeric subfamily III receptors. Thus, cyanabactin is a potent and selective agonist with a wide spectrum of ABA-like activities that defines subfamily IIIA receptors as key target sites for manipulating transpiration.

  2. Trace Amine-Associated Receptor 1 Agonists as Narcolepsy Therapeutics.

    PubMed

    Black, Sarah W; Schwartz, Michael D; Chen, Tsui-Ming; Hoener, Marius C; Kilduff, Thomas S

    2017-11-01

    Narcolepsy, a disorder of rapid eye movement (REM) sleep, is characterized by excessive daytime sleepiness and cataplexy, a loss of muscle tone triggered by emotional stimulation. Current narcolepsy pharmacotherapeutics include controlled substances with abuse potential or drugs with undesirable side effects. As partial agonists at trace amine-associated receptor 1 (TAAR1) promote wakefulness in mice and rats, we evaluated whether TAAR1 agonism had beneficial effects in two mouse models of narcolepsy. In the first experiment, male homozygous B6-Taar1 tm1(NLSLacZ)Blt (Taar1 knockout) and wild-type mice were surgically implanted to record electroencephalogram, electromyogram, locomotor activity, and body temperature, and the efficacy of the TAAR1 agonist, RO5256390, on sleep/wake and physiological parameters was determined. In the second experiment, the effects of the TAAR1 full agonist RO5256390 and partial agonist RO5263397 on sleep/wake, locomotor activity, body temperature, and cataplexy were assessed in two mouse narcolepsy models. RO5256390 profoundly reduced rapid eye movement sleep in wild-type mice; these effects were eliminated in Taar1 knockout mice. The TAAR1 partial agonist RO5263397 also promoted wakefulness and suppressed nonrapid eye movement sleep. Both compounds reduced body temperature in the two narcolepsy models at the highest doses tested. Both TAAR1 compounds also mitigated cataplexy, the pathognomonic symptom of this disorder, in the narcolepsy models. The therapeutic benefit was mediated through a reduction in number of cataplexy episodes and time spent in cataplexy. These results suggest TAAR1 agonism as a new therapeutic pathway for treatment of this orphan disease. The common underlying mechanism may be the suppression of rapid eye movement sleep. Copyright © 2016 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

  3. Exploring the binding energy profiles of full agonists, partial agonists, and antagonists of the α7 nicotinic acetylcholine receptor.

    PubMed

    Tabassum, Nargis; Ma, Qianyun; Wu, Guanzhao; Jiang, Tao; Yu, Rilei

    2017-09-01

    Nicotinic acetylcholine receptors (nAChRs) belong to the Cys-loop receptor family and are important drug targets for the treatment of neurological diseases. However, the precise determinants of the binding efficacies of ligands for these receptors are unclear. Therefore, in this study, the binding energy profiles of various ligands (full agonists, partial agonists, and antagonists) were quantified by docking those ligands with structural ensembles of the α7 nAChR exhibiting different degrees of C-loop closure. This approximate treatment of interactions suggested that full agonists, partial agonists, and antagonists of the α7 nAChR possess distinctive binding energy profiles. Results from docking revealed that ligand binding efficacy may be related to the capacity of the ligand to stabilize conformational states with a closed C loop.

  4. Cebranopadol: novel dual opioid/NOP receptor agonist analgesic.

    PubMed

    Raffa, R B; Burdge, G; Gambrah, J; Kinecki, H E; Lin, F; Lu, B; Nguyen, J T; Phan, V; Ruan, A; Sesay, M A; Watkins, T N

    2017-02-01

    Chronic pain presents a difficult clinical challenge because of the limited efficacy, the limiting adverse-effect profile or the abuse potential of current analgesic options. Cebranopadol is a novel new agent in clinical trials that combines dual agonist action at opioid and nociceptin/orphanin FQ peptide (NOP) receptors. It is the first truly unique, centrally acting analgesic in several years. We here review the basic and clinical pharmacology of cebranopadol. Published literature and Internet sources were searched to identify information related to the basic science (pharmacology and medicinal chemistry) and development (clinical trial) information on the mechanism of dual opioid and NOP receptor pharmacologic action in general, and for cebranopadol in particular. The identified sources were reviewed and the information synthesized. The preclinical testing of cebranopadol has characterized it as a dual opioid and NOP receptor agonist that displays antinociceptive and antihyperalgesic action in a variety of acute and chronic pain models in animals. Unlike most current traditional opioids, it is generally more potent against neuropathic than nociceptive pain. Several phase 2 clinical trials have been completed. Despite the medical need, a truly novel centrally acting analgesic has not been developed in many years. Cebranopadol represents a truly novel mechanistic approach. Its actual place in pain pharmacotherapy awaits the results of phase 3 clinical trials. © 2016 John Wiley & Sons Ltd.

  5. GLP-1 receptor agonist-induced polyarthritis: a case report.

    PubMed

    Ambrosio, Maria Luisa; Monami, Matteo; Sati, Lavinia; Marchionni, Niccolò; Di Bari, Mauro; Mannucci, Edoardo

    2014-08-01

    Occasional cases of bilateral, symmetrical, seronegative polyarthritis have been reported in patients treated with dipeptidyl peptidase-4 inhibitors (Crickx et al. in Rheumatol Int, 2013). We report here a similar case observed during treatment with a GLP-1 receptor agonist. A 42-year-old man with type 2 diabetes treated with metformin 1,500 mg/day and liraglutide 1.8 mg/day. After 6 months from the beginning of treatment, the patient complained of bilateral arthralgia (hands, feet, ankles, knees, and hips). Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and leukocytes were increased. Rheumatoid factor, anticyclic citrullinated protein antibody, antinuclear antibodies, anti-Borrelia, and burgdorferi antibodies were all negative, and myoglobin and calcitonin were normal. Liraglutide was withdrawn, and the symptoms completely disappeared within 1 week, with normalization of ESR, CRP, fibrinogen, and leukocytes. Previously described cases of polyarthritis associated with DPP4 inhibitors had been attributed to a direct effect of the drugs on inflammatory cells expressing the enzyme. The present case, occurred during treatment with a GLP-1 receptor agonists, suggests a possibly different mechanism, mediated by GLP-1 receptor stimulation, which deserved further investigation.

  6. Fluorescent agonists for the Torpedo nicotinic acetylcholine receptor.

    PubMed

    Krieger, Florian; Mourot, Alexandre; Araoz, Romulo; Kotzyba-Hibert, Florence; Molgó, Jordi; Bamberg, Ernst; Goeldner, Maurice

    2008-05-05

    We have synthesized a series of fluorescent acylcholine derivatives carrying different linkers that vary in length and structure and connect the acylcholine unit to the environment-sensitive fluorophores 7-(diethylamino)coumarin-3-carbonyl (DEAC) or N-(7-nitrobenz-2-oxa-1,3-diazol-yl) (NBD). The pharmacological properties of the fluorescent analogues were investigated on heterologously expressed nicotinic acetylcholine receptor (nAChR) from Torpedo californica and on oocytes transplanted with nAChR-rich Torpedo marmorata membranes. Agonist action strongly depends on the length and the structure of the linker. One particular analogue, DEAC-Gly-C6-choline, showed partial agonist behavior with about half of the maximum response of acetylcholine, which is at least 20 times higher than those observed with previously described fluorescent dansyl- and NBD-acylcholine analogues. Binding of DEAC-Gly-C6-choline to Torpedo nAChR induces a strong enhancement of fluorescence intensity. Association and displacement kinetic experiments revealed dissociation constants of 0.5 nM for the alphadelta-binding site and 15.0 nM for the alphagamma-binding site. Both the pharmacological and the spectroscopic properties of this agonist show great promise for characterizing the allosteric mechanism behind the function of the Torpedo nAChR, as well as for drug-screening studies.

  7. Synthesis, biological evaluation, and molecular modeling of ribose-modified adenosine analogues as adenosine receptor agonists.

    PubMed

    Cappellacci, Loredana; Franchetti, Palmarisa; Pasqualini, Michela; Petrelli, Riccardo; Vita, Patrizia; Lavecchia, Antonio; Novellino, Ettore; Costa, Barbara; Martini, Claudia; Klotz, Karl-Norbert; Grifantini, Mario

    2005-03-10

    A number of 3'-C-methyl analogues of selective adenosine receptor agonists such as CPA, CHA, CCPA, 2'-Me-CCPA, NECA, and IB-MECA was synthesized to further investigate the subdomain of the receptor that binds the ribose moiety of the ligands. Affinity data at A(1), A(2A), and A(3) receptors in bovine brain membranes showed that the 3'-C-modification in adenosine resulted in a decrease of the affinity at all three receptor subtypes. When this modification was combined with N(6)-substitution with groups that induce high potency and selectivity at A(1) receptor, the affinity and selectivity were increased. However, all 3'-C-methyl derivatives proved to be very less active than the corresponding 2'-C-methyl analogues. The most active compound was found to be 3'-Me-CPA which displayed a K(i) value of 0.35 microM at A(1) receptor and a selectivity for A(1) vs A(2A) and A(3) receptors higher than 28-fold. 2'-Me-CCPA was confirmed to be the most selective, high affinity agonist so far known also at human A(1) receptor with a K(i) value of 3.3 nM and 2903- and 341-fold selective vs human A(2A) and A(3) receptors, respectively. In functional assay, 3'-Me-CPA, 3'-Me-CCPA, and 2-Cl-3'-Me-IB-MECA inhibited forskolin-stimulated adenylyl cyclase activity with IC(50) values ranging from 0.3 to 4.9 microM, acting as full agonists. A rhodopsin-based model of the bovine A(1)AR was built to rationalize the higher affinity and selectivity of 2'-C-methyl derivatives of N(6)-substituted-adenosine compared to that of 3'-C-methyl analogues. In the docking exploration, it was found that 2'-Me-CCPA was able to form a number of interactions with several polar residues in the transmembrane helices TM-3, TM-6, and TM-7 of bA(1)AR which were not preserved in the molecular dynamics simulation of 3'-Me-CCPA/bA(1)AR complex.

  8. Newspapers and Newspaper Ink Contain Agonists for the Ah Receptor

    PubMed Central

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

    2010-01-01

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

  9. [Safety and tolerability of GLP-1 receptor agonists].

    PubMed

    Soldevila, Berta; Puig-Domingo, Manel

    2014-09-01

    Glucagon-like peptide-1 receptor agonists (GLP-1ra) are a new group of drugs with a glucose-lowering action due to their incretin effect. The GLP-1 receptor is expressed in various human tissues, which could be related to the pleiotropic effects of human GLP-1, as well as to the adverse effects described in patients treated with GLP-1ra. The risk of hypoglycaemia is low, which is one of the main considerations in the safety of this family of compounds and is also important to patients with diabetes. The most frequent adverse effect is nausea, which usually occurs at the start of treatment and is transient in 20-60% of affected patients. This article also reviews the information available on antibody formation, the potential effect on the thyroid gland, and the controversial association between this group of drugs with pancreatitis and cancer. Copyright © 2014 Elsevier España, S.L.U. All rights reserved.

  10. [Safety and tolerability of GLP-1 receptor agonists].

    PubMed

    Soldevila, Berta; Puig-Domingo, Manel

    2014-01-01

    Glucagon-like peptide-1 receptor agonists (GLP-1ra) are a new group of drugs with a glucose-lowering action due to their incretin effect. The GLP-1 receptor is expressed in various human tissues, which could be related to the pleiotropic effects of human GLP-1, as well as to the adverse effects described in patients treated with GLP-1ra. The risk of hypoglycaemia is low, which is one of the main considerations in the safety of this family of compounds and is also important to patients with diabetes. The most frequent adverse effect is nausea, which usually occurs at the start of treatment and is transient in 20-60% of affected patients. This article also reviews the information available on antibody formation, the potential effect on the thyroid gland, and the controversial association between this group of drugs with pancreatitis and cancer.

  11. Regional- and agonist-dependent facilitation of human neurogastrointestinal functions by motilin receptor agonists

    PubMed Central

    Broad, J; Mukherjee, S; Samadi, M; Martin, JE; Dukes, GE; Sanger, GJ

    2012-01-01

    BACKGROUND AND PURPOSE Delayed gastric emptying is poorly managed. Motilin agonists are potential treatments but inadequate understanding into how enteric nerve functions are stimulated compromises drug/dose selection. Resolution is hampered by extreme species dependency so methods were developed to study human gastrointestinal neuromuscular activities and the neurobiology of motilin. EXPERIMENTAL APPROACH Protocols to study neuromuscular activities were developed for different regions of human stomach and intestine (71 patients) using circular muscle preparations and electrical field stimulation (EFS) of intrinsic nerves. Other tissues were fixed for immunohistochemistry. KEY RESULTS EFS evoked contractions and/or relaxations via cholinergic and nitrergic neurons, with additional tachykinergic activity in colon; these were consistent after 154 min (longer if stored overnight). Motilin 1–300 nM and the selective motilin agonist GSK962040 0.1–30 µM acted pre-junctionally to strongly facilitate cholinergic contractions of the antrum (Emax≍ 1000% for motilin), with smaller increases in fundus, duodenum and ileum; high concentrations increased baseline muscle tension in fundus and small intestine. There were minimal effects in the colon. In the antrum, cholinergic facilitation by motilin faded irregularly, even with peptidase inhibitors, whereas facilitation by GSK962040 was long lasting. Motilin receptor immunoreactivity was identified in muscle and myenteric plexus predominantly in the upper gut, co-expressed with choline acetyltransferase in neurons. CONCLUSIONS AND IMPLICATIONS Motilin and GSK962040 strongly facilitated cholinergic activity in the antrum, with lower activity in fundus and small intestine only. Facilitation by motilin was short lived, consistent with participation in migrating motor complexes. Long-lasting facilitation by GSK962040 suggests different receptor interactions and potential for clinical evaluation. LINKED ARTICLE This article is

  12. Urolinin: The First Linear Peptidic Urotensin-II Receptor Agonist.

    PubMed

    Bandholtz, Sebastian; Erdmann, Sarah; von Hacht, Jan Lennart; Exner, Samantha; Krause, Gerd; Kleinau, Gunnar; Grötzinger, Carsten

    2016-11-23

    This study investigated the role of individual U-II amino acid positions and side chain characteristics important for U-IIR activation. A complete permutation library of 209 U-II variants was studied in an activity screen that contained single substitution variants of each position with one of the other 19 proteinogenic amino acids. Receptor activation was measured using a cell-based high-throughput fluorescence calcium mobilization assay. We generated the first complete U-II substitution map for U-II receptor activation, resulting in a detailed view into the structural features required for receptor activation, accompanied by complementary information from receptor modeling and ligand docking studies. On the basis of the systematic SAR study of U-II, we created 33 further short and linear U-II variants from eight to three amino acids in length, including d- and other non-natural amino acids. We identified the first high-potency linear U-II analogues. Urolinin, a linear U-II agonist (nWWK-Tyr(3-NO 2 )-Abu), shows low nanomolar potency as well as improved metabolic stability.

  13. New, potent, and selective peptidic oxytocin receptor agonists.

    PubMed

    Wiśniewski, Kazimierz; Alagarsamy, Sudarkodi; Galyean, Robert; Tariga, Hiroe; Thompson, Dorain; Ly, Brian; Wiśniewska, Halina; Qi, Steve; Croston, Glenn; Laporte, Regent; Rivière, Pierre J-M; Schteingart, Claudio D

    2014-06-26

    Mothers of preterm babies frequently have difficulty establishing or maintaining lactation, thought to be due to interference with the milk ejection reflex. Administration of exogenous oxytocin can produce alveolar contraction and adequate breast emptying resulting in establishment of successful lactation. The natural hormone oxytocin is not receptor-selective and may cause hyponatremia via V2 receptor mediated antidiuresis. We have designed a series of potent oxytocin analogues containing N-alkylglycines in position 7 with excellent selectivity versus the related V1a, V1b, and V2 vasopressin receptors and short half-life: agonists 31 ([2-ThiMeGly(7)]dOT), 47 (carba-6-[Phe(2),BuGly(7)]dOT), 55 (carba-6-[3-MeBzlGly(7)]dOT), and 57 (carba-1-[4-FBzlGly(7)]dOT) have EC50 values at hOTR < 0.1 nM, selectivity ratios versus related human vasopressin receptors of >2000, IC50 at hV1aR > 500 nM, and total clearance in rats in the range of 60-80 mL min(-1) kg(-1). Compound 57 (FE 202767) is currently in clinical development for the treatment of preterm mothers requiring lactation support.

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

    PubMed Central

    Amarante-Mendes, Gustavo P.; Griffith, Thomas S.

    2016-01-01

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

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

    PubMed

    Amarante-Mendes, Gustavo P; Griffith, Thomas S

    2015-11-01

    TRAIL/Apo-2L is a member of the TNF superfamily first described as an apoptosis-inducing cytokine in 1995. Similar to TNF and Fas ligand, TRAIL induces apoptosis in caspase-dependent manner following TRAIL death receptor trimerization. Because tumor cells were shown to be particularly sensitive to this cytokine while normal cells/tissues proved to be resistant along with being able to synthesize and release TRAIL, it was rapidly appreciated that TRAIL likely served as one of our major physiologic weapons against cancer. In line with this, a number of research laboratories and pharmaceutical companies have attempted to exploit the ability of TRAIL to kill cancer cells by developing recombinant forms of TRAIL or TRAIL receptor agonists (e.g., receptor-specific mAb) for therapeutic purposes. In this review article we will describe the biochemical pathways used by TRAIL to induce different cell death programs. We will also summarize the clinical trials related to this pathway and discuss possible novel uses of TRAIL-related therapies. In recent years, the physiological importance of TRAIL has expanded beyond being a tumoricidal molecule to one critical for a number of clinical settings - ranging from infectious disease and autoimmunity to cardiovascular anomalies. We will also highlight some of these conditions where modulation of the TRAIL/TRAIL receptor system may be targeted in the future. Copyright © 2015 Elsevier Inc. All rights reserved.

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

    PubMed

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

    2001-10-01

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

  17. Fast Modulation of μ-Opioid Receptor (MOR) Recycling Is Mediated by Receptor Agonists*

    PubMed Central

    Roman-Vendrell, Cristina; Yu, Y. Joy; Yudowski, Guillermo Ariel

    2012-01-01

    The μ-opioid receptor (MOR) is a member of the G protein-coupled receptor family and the main target of endogenous opioid neuropeptides and morphine. Upon activation by ligands, MORs are rapidly internalized via clathrin-coated pits in heterologous cells and dissociated striatal neurons. After initial endocytosis, resensitized receptors recycle back to the cell surface by vesicular delivery for subsequent cycles of activation. MOR trafficking has been linked to opioid tolerance after acute exposure to agonist, but it is also involved in the resensitization process. Several studies describe the regulation and mechanism of MOR endocytosis, but little is known about the recycling of resensitized receptors to the cell surface. To study this process, we induced internalization of MOR with [d-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin (DAMGO) and morphine and imaged in real time single vesicles recycling receptors to the cell surface. We determined single vesicle recycling kinetics and the number of receptors contained in them. Then we demonstrated that rapid vesicular delivery of recycling MORs to the cell surface was mediated by the actin-microtubule cytoskeleton. Recycling was also dependent on Rab4, Rab11, and the Ca2+-sensitive motor protein myosin Vb. Finally, we showed that recycling is acutely modulated by the presence of agonists and the levels of cAMP. Our work identifies a novel trafficking mechanism that increases the number of cell surface MORs during acute agonist exposure, effectively reducing the development of opioid tolerance. PMID:22378794

  18. Quantum chemical study of agonist-receptor vibrational interactions for activation of the glutamate receptor.

    PubMed

    Kubo, M; Odai, K; Sugimoto, T; Ito, E

    2001-06-01

    To understand the mechanism of activation of a receptor by its agonist, the excitation and relaxation processes of the vibrational states of the receptor should be examined. As a first approach to this problem, we calculated the normal vibrational modes of agonists (glutamate and kainate) and an antagonist (6-cyano-7-nitroquinoxaline-2,3-dione: CNQX) of the glutamate receptor, and then investigated the vibrational interactions between kainate and the binding site of glutamate receptor subunit GluR2 by use of a semiempirical molecular orbital method (MOPAC2000-PM3). We found that two local vibrational modes of kainate, which were also observed in glutamate but not in CNQX, interacted through hydrogen bonds with the vibrational modes of GluR2: (i) the bending vibration of the amine group of kainate, interacting with the stretching vibration of the carboxyl group of Glu705 of GluR2, and (ii) the symmetric stretching vibration of the carboxyl group of kainate, interacting with the bending vibration of the guanidinium group of Arg485. We also found collective modes with low frequency at the binding site of GluR2 in the kainate-bound state. The vibrational energy supplied by an agonist may flow from the high-frequency local modes to the low-frequency collective modes in a receptor, resulting in receptor activation.

  19. Prediction of response to GLP-1 receptor agonist therapy in Japanese patients with type 2 diabetes.

    PubMed

    Imai, Kenjiro; Tsujimoto, Tetsuro; Goto, Atsushi; Goto, Maki; Kishimoto, Miyako; Yamamoto-Honda, Ritsuko; Noto, Hiroshi; Kajio, Hiroshi; Noda, Mitsuhiko

    2014-01-01

    Glucagon-like peptide-1 (GLP-1) receptor agonists can maintain good glycemic control in some diabetic. Here we compared the clinical characteristics and parameters reflecting glucose metabolism at the time of the initiation of GLP-1 receptor agonist therapy between patients who responded well to therapy and those who did not. The records of 43 patients with type 2 diabetes who started receiving GLP-1 receptor agonist therapy during hospitalization were retrospectively reviewed. Glucagon stimulation tests were performed, and patients were started on liraglutide or exenatide therapy. Preprandial blood glucose levels were measured on days 2 and 3 of GLP-1 receptor agonist therapy. We used the Cox proportional hazard model to compare clinical parameters between responders (HbA1c level <8% at more than 3 months after the initiation of treatment) and non-responders (HbA1c level ≥8% at more than 3 months after the initiation of treatment or a switch to insulin therapy at any time). Twenty-six of the 43 patients were classified as non-responders. At baseline, mean HbA1c levels were 9.9% among responders and 9.7% among non-responders. Compared with treatment with only diet or metformin, the hazard ratio [HR] for non-response was 5.3 (95% confidence interval [CI]: 1.16-24.6, P = 0.03) for insulin therapy and 5.0 (95% CI: 1.13-22.16, P = 0.03) for sulfonylurea therapy. Compared with the lowest tertile, the HRs for non-response in the highest tertile were 3.1 (95% CI: 1.04-8.97, P = 0.04) for the mean preprandial blood glucose level on days 2 and 3 and 3.4 (95% CI: 1.05-11.01, P = 0.04) for the body mass index. The response was not significantly associated with the duration of diabetes or the glucagon stimulation test results. A receiver operating curve analysis showed that the mean preprandial blood glucose level had the highest area under the curve value (=0.72) for the prediction of non-responders. In patients with poorly controlled diabetes, the response to GLP-1

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

    PubMed

    van Raalte, Daniël H; Verchere, C Bruce

    2016-07-01

    Glucagon-like peptide (GLP)-1 receptor agonists enhance insulin secretion and may improve pancreatic islet cell function. However, GLP-1 receptor (GLP-1R) agonist treatment may have more complex, and sometimes deleterious, effects on beta cells. We discuss the concepts of beta cell protection versus exhaustion for different GLP-1R agonists based on recent data. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. α7 nicotinic receptor agonist reactivates neurogenesis in adult brain.

    PubMed

    Narla, Sridhar; Klejbor, Ilona; Birkaya, Barbara; Lee, Yu-Wei; Morys, Janusz; Stachowiak, Ewa K; Terranova, Christopher; Bencherif, Merouane; Stachowiak, Michal K

    2013-10-15

    Reactivation of neurogenesis by endogenous Neural Stem/Progenitor Cells (NS/PC) in the adult brain or spinal cord holds the key for treatment of CNS injuries as well as neurodegenerative disorders, which are major healthcare issues for the world's aging population. Recent studies show that targeting the α7 nicotinic acetylcholine receptors (α7nAChR) with a specific TC-7020 agonist inhibits proliferation and stimulates neuronal differentiation of NS/PC in subventricular zone (SVZ) in the adult mouse brain. TC-7020-induced neuronogenesis is observed in different brain regions, including: (1) βIII Tubulin-expressing cortical neurons, (2) calretinin expressing hippocampal neurons and (3) cells in substantia nigra (SN) expressing predopaminergic Nurr1+phenotype. Reactivation of developmental integrative nuclear FGFR1 signaling (INFS), via gene transfection reinstates neurogenesis in the adult brain by promoting neuronal differentiation of brain NS/PC. TC-7020 neuronogenic effect is associated with a robust accumulation of endogenous FGFR1 in the nuclei of differentiating cells. Furthermore, direct in vitro stimulation of neural stem/progenitor cells with α7nAChR agonist activates INFS and neuronal-like differentiation and activation of neuronal genes. The α7nAChR upregulation of early neuronal βIII-Tubulin gene involves neurogenic FGFR1-Nur signaling and direct FGFR1 interaction with the gene promoter. The reactivation of developmental INFS and neurogenesis in adult brain by the α7nAChR agonist may offer new strategy to treat brain injuries, neurodegenerative and neurodevelopmental diseases. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. Toll-Like Receptor 9 Agonists for Cancer Therapy.

    PubMed

    Melisi, Davide; Frizziero, Melissa; Tamburrino, Anna; Zanotto, Marco; Carbone, Carmine; Piro, Geny; Tortora, Giampaolo

    2014-08-04

    The immune system has acquired increasing importance as a key player in cancer maintenance and growth. Thus, modulating anti-tumor immune mediators has become an attractive strategy for cancer treatment. Toll-like receptors (TLRs) have gradually emerged as potential targets of newer immunotherapies. TLR-9 is preferentially expressed on endosome membranes of B-cells and plasmacytoid dendritic cells (pDC) and is known for its ability to stimulate specific immune reactions through the activation of inflammation-like innate responses. Several synthetic CpG oligonucleotides (ODNs) have been developed as TLR-9 agonists with the aim of enhancing cancer immune surveillance. In many preclinical models, CpG ODNs were found to suppress tumor growth and proliferation both in monotherapy and in addition to chemotherapies or target therapies. TLR-9 agonists have been also tested in several clinical trials in patients with solid tumors. These agents showed good tolerability and usually met activity endpoints in early phase trials. However, they have not yet been demonstrated to significantly impact survival, neither as single agent treatments, nor in combination with chemotherapies or cancer vaccines. Further investigations in larger prospective studies are required.

  3. Toll-Like Receptor 9 Agonists for Cancer Therapy

    PubMed Central

    Melisi, Davide; Frizziero, Melissa; Tamburrino, Anna; Zanotto, Marco; Carbone, Carmine; Piro, Geny; Tortora, Giampaolo

    2014-01-01

    The immune system has acquired increasing importance as a key player in cancer maintenance and growth. Thus, modulating anti-tumor immune mediators has become an attractive strategy for cancer treatment. Toll-like receptors (TLRs) have gradually emerged as potential targets of newer immunotherapies. TLR-9 is preferentially expressed on endosome membranes of B-cells and plasmacytoid dendritic cells (pDC) and is known for its ability to stimulate specific immune reactions through the activation of inflammation-like innate responses. Several synthetic CpG oligonucleotides (ODNs) have been developed as TLR-9 agonists with the aim of enhancing cancer immune surveillance. In many preclinical models, CpG ODNs were found to suppress tumor growth and proliferation both in monotherapy and in addition to chemotherapies or target therapies. TLR-9 agonists have been also tested in several clinical trials in patients with solid tumors. These agents showed good tolerability and usually met activity endpoints in early phase trials. However, they have not yet been demonstrated to significantly impact survival, neither as single agent treatments, nor in combination with chemotherapies or cancer vaccines. Further investigations in larger prospective studies are required. PMID:28548068

  4. Benzodiazepine agonist and inverse agonist actions on GABAA receptor-operated chloride channels. II. Chronic effects of ethanol

    SciTech Connect

    Buck, K.J.; Harris, R.A.

    1990-05-01

    Mice were made tolerant to and dependent on ethanol by administration of a liquid diet. Gamma-aminobutyric acid (GABA) receptor-dependent uptake of 36Cl- by mouse cortical microsacs was used to study the actions of benzodiazepine (BZ) agonists and inverse agonists. Chronic exposure to ethanol attenuated the ability of a BZ agonist, flunitrazepam, to augment muscimol-stimulated uptake of 36Cl- and enhanced the actions of BZ inverse agonists, Ro15-4513 (ethyl-8-azido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo(1,4)-benzodiazepine - 3-carboxylate) and DMCM (methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate), to inhibit GABAA receptor-operated chloride channels. Augmentation of chloride flux by pentobarbital was not reduced by chronic ethanol exposure. Attenuation of flunitrazepam efficacy was transient and returned tomore » control levels within 6 to 24 hr after withdrawal from ethanol, but increased sensitivity to Ro15-4513 was observed as long as 8 days after withdrawal. Chronic exposure to ethanol did not alter (3H)SR 95531 (2-(3'-carbethoxy-2'propyl)-3-amino-6-p-methoxyphenylpyridazinium bromide) binding to low-affinity GABAA receptors or muscimol stimulation of chloride flux; and did not alter (3H)Ro15-4513 or (3H)flunitrazepam binding to central BZ receptors or allosteric modulation of this binding by muscimol (i.e., muscimol-shift). These results suggest that chronic exposure to ethanol reduces coupling between BZ agonist sites and the chloride channel, and may be responsible for the development of cross-tolerance between ethanol and BZ agonists. In contrast, coupling between BZ inverse agonist sites and the chloride channel is increased.« less

  5. Association Between Benzodiazepine Receptor Agonists and Snoring Among Women in the Nurses' Health Study.

    PubMed

    Lin, Brian M; Hu, Frank B; Curhan, Gary C

    2017-02-01

    Snoring is highly prevalent among adults. The use of benzodiazepine receptor agonists is also common, with higher prevalence of use with more advanced age. Benzodiazepine receptor agonists cause muscle relaxation, which may affect muscle tone and airway dynamics and thereby increase snoring. Previous studies examining the association between use of benzodiazepine receptor agonists and snoring were underpowered to detect clinically meaningful differences or did not report the magnitude of association. To investigate the association between use of benzodiazepine receptor agonists and snoring in women. Women aged 62 to 86 years provided information on snoring and covariates of interest in the 2008 survey of the Nurses' Health Study, a cross-sectional cohort study of female registered nurses in the United States. Potential effect modification of the association between use of benzodiazepine receptor agonists and snoring by age, body mass index, waist circumference, smoking, alcohol consumption, and physical activity was explored. Logistic regression was used to adjust for potential confounders. Data analysis was conducted from November 2015 to March 2016. Self-reported habitual snoring, defined as a few nights a week or more. Of 52 504 participants (mean [SD] age, 72.4 [6.7] years), 14 831 (28.2%) reported habitual snoring. There was a slightly higher prevalence of benzodiazepine receptor agonist use among habitual snorers (11.4%) compared with nonhabitual snorers (10.6%) (absolute difference, 0.8%; 95% CI, 0.2%-1.4%). After multivariable adjustment, use of benzodiazepine receptor agonists was not associated with snoring (odds ratio, 1.01; 95% CI, 0.95-1.07) compared with women who did not use benzodiazepine receptor agonists. Although there was no significant interaction with smoking, there were higher odds of snoring with use of benzodiazepine receptor agonists among current smokers (odds ratio, 1.34; 95% CI, 1.04-1.73). Use of benzodiazepine receptor agonists is

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

    PubMed Central

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

    2012-01-01

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

  7. 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),more » 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.« less

  8. The mu-opioid receptor agonist morphine, but not agonists at delta- or kappa-opioid receptors, induces peripheral antinociception mediated by cannabinoid receptors.

    PubMed

    da Fonseca Pacheco, D; Klein, A; de Castro Perez, A; da Fonseca Pacheco, C M; de Francischi, J N; Duarte, I D G

    2008-07-01

    Although participation of opioids in antinociception induced by cannabinoids has been documented, there is little information regarding the participation of cannabinoids in the antinociceptive mechanisms of opioids. The aim of the present study was to determine whether endocannabinoids could be involved in peripheral antinociception induced by activation of mu-, delta- and kappa-opioid receptors. Nociceptive thresholds to mechanical stimulation of rat paws treated with intraplantar prostaglandin E2 (PGE2, 2 microg) to induce hyperalgesia were measured 3 h after injection using an algesimetric apparatus. Opioid agonists morphine (200 microg), (+)-4-[(alphaR)-alpha-((2S,5R)-4-Allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC80) (80 microg), bremazocine (50 microg); cannabinoid receptor antagonists N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251) (20-80 microg), 6-iodo-2-methyl-1-[2-(4-morpholinyl)ethyl]-1H-indol-3-yl(4-methoxyphenyl) methanone (AM630) (12.5-100 microg); and an inhibitor of methyl arachidonyl fluorophosphonate (MAFP) (1-4 microg) were also injected in the paw. The CB1-selective cannabinoid receptor antagonist AM251 completely reversed the peripheral antinociception induced by morphine in a dose-dependent manner. In contrast, the CB2-selective cannabinoid receptor antagonist AM630 elicited partial antagonism of this effect. In addition, the administration of the fatty acid amide hydrolase inhibitor, MAFP, enhanced the antinociception induced by morphine. The cannabinoid receptor antagonists AM251 and AM630 did not modify the antinociceptive effect of SNC80 or bremazocine. The antagonists alone did not cause any hyperalgesic or antinociceptive effect. Our results provide evidence for the involvement of endocannabinoids, in the peripheral antinociception induced by the mu-opioid receptor agonist morphine. The release of cannabinoids appears not to be involved in the

  9. Activation of single heteromeric GABAA receptor ion channels by full and partial agonists

    PubMed Central

    Mortensen, Martin; Kristiansen, Uffe; Ebert, Bjarke; Frølund, Bente; Krogsgaard-Larsen, Povl; Smart, Trevor G

    2004-01-01

    The linkage between agonist binding and the activation of a GABAA receptor ion channel is yet to be resolved. This aspect was examined on human recombinant α1β2γ2S GABAA receptors expressed in human embryonic kidney cells using the following series of receptor agonists: GABA, isoguvacine, 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP), isonipecotic acid, piperidine-4-sulphonic acid (P4S), imidazole-4-acetic acid (IAA), 5-(4-piperidyl)-3-isothiazolol (thio-4-PIOL) and 5-(4-piperidyl)-3-isoxazolol (4-PIOL). Whole-cell concentration–response curves enabled the agonists to be categorized into four classes based upon their maximum responses. Single channel analyses revealed that the channel conductance of 25–27 pS was unaffected by the agonists. However, two open states were resolved from the open period distributions with mean open times reduced 5-fold by the weakest partial agonists. Using saturating agonist concentrations, estimates of the channel shutting rate, α, ranged from 200 to 600 s−1. The shut period distributions were described by three or four components and for the weakest partial agonists, the interburst shut periods increased whilst the mean burst durations and longest burst lengths were reduced relative to the full agonists. From the burst analyses, the opening rates for channel activation, β, and the total dissociation rates, k−1, for the agonists leaving the receptor were estimated. The agonist efficacies were larger for the full agonists (E ∼7−9) compared to the weak partial agonists (∼0.4–0.6). Overall, changes in agonist efficacy largely determined the different agonist profiles with contributions from the agonist affinities and the degree of receptor desensitization. From this we conclude that GABAA receptor activation does not occur in a switch-like manner since the agonist recognition sites are flexible, accommodating diverse agonist structures which differentially influence the opening and shutting rates of the ion

  10. Metformin sensitizes triple-negative breast cancer to proapoptotic TRAIL receptor agonists by suppressing XIAP expression.

    PubMed

    Strekalova, Elena; Malin, Dmitry; Rajanala, Harisha; Cryns, Vincent L

    2017-06-01

    Despite robust antitumor activity in diverse preclinical models, TNF-related apoptosis-inducing ligand (TRAIL) receptor agonists have not demonstrated efficacy in clinical trials, underscoring the need to identify agents that enhance their activity. We postulated that the metabolic stress induced by the diabetes drug metformin would sensitize breast cancer cells to TRAIL receptor agonists. Human triple (estrogen receptor, progesterone receptor, and HER2)-negative breast cancer (TNBC) cell lines were treated with TRAIL receptor agonists (monoclonal antibodies or TRAIL peptide), metformin, or the combination. The effects on cell survival, caspase activation, and expression of TRAIL receptors and the antiapoptotic protein XIAP were determined. In addition, XIAP was silenced by RNAi in TNBC cells and the effects on sensitivity to TRAIL were determined. The antitumor effects of metformin, TRAIL, or the combination were evaluated in an orthotopic model of metastatic TNBC. Metformin sensitized diverse TNBC cells to TRAIL receptor agonists. Metformin selectively enhanced the sensitivity of transformed breast epithelial cells to TRAIL receptor agonist-induced caspase activation and apoptosis with little effect on untransformed breast epithelial cells. These effects of metformin were accompanied by robust reductions in the protein levels of XIAP, a negative regulator of TRAIL-induced apoptosis. Silencing XIAP in TNBC cells mimicked the TRAIL-sensitizing effects of metformin. Metformin also enhanced the antitumor effects of TRAIL in a metastatic murine TNBC model. Our findings indicate that metformin enhances the activity of TRAIL receptor agonists, thereby supporting the rationale for additional translational studies combining these agents.

  11. Molecular mechanisms of glucocorticoid action and selective glucocorticoid receptor agonists.

    PubMed

    Stahn, Cindy; Löwenberg, Mark; Hommes, Daniel W; Buttgereit, Frank

    2007-09-15

    Glucocorticoids (GC) are the most common used anti-inflammatory and immunosuppressive drugs in the treatment of rheumatic and other inflammatory diseases. Their therapeutic effects are considered to be mediated by four different mechanisms of action: the classical genomic mechanism of action caused by the cytosolic glucocorticoid receptor (cGCR); secondary non-genomic effects which are also initiated by the cGCR; membrane-bound glucocorticoid receptor (mGCR)-mediated non-genomic effects; non-specific, non-genomic effects caused by interactions with cellular membranes. The classical, genomic mechanism of GC-action can be divided into two processes: "transrepression", which is responsible for a large number of desirable anti-inflammatory and immunomodulating effects, and "transactivation" which is associated with frequently occurring side effects as well as with some immunosuppressive activities [Ehrchen, J., Steinmuller, L., Barczyk, K., Tenbrock, K., Nacken, W., Eisenacher, M., Nordhues, U., Sorg, C., Sunderkotter, C., Roth, J., 2007. Glucocorticoids induce differentiation of a specifically activated, anti-inflammatory subtype of human monocytes. Blood 109, 1265-1274]. Great efforts have been made to diminish glucocorticoid-induced adverse effects, but the improvement of conventional glucocorticoids has almost reached its limits. As a consequence, new variations of the conventional "good old drugs" are being tested and nitro-steroids and long circulating liposomal glucocorticoids indeed show promising results. Nevertheless, crux of the matter should be the design of qualitatively new drugs, such as selective glucocorticoid receptor agonists (SEGRAs). These innovative steroidal or non-steroidal molecules induce transrepression, while transactivation processes are less affected. First reports on two different GCR ligands, A276575 and ZK216348, show promising results. Here, we review the above-mentioned mechanisms of glucocorticoid action and give particular attention

  12. Dopamine D1 and adenosine A1 receptors form functionally interacting heteromeric complexes

    PubMed Central

    Ginés, Silvia; Hillion, Joëlle; Torvinen, Maria; Le Crom, Stèphane; Casadó, Vicent; Canela, Enric I.; Rondin, Sofia; Lew, Jow Y.; Watson, Stanley; Zoli, Michele; Agnati, Luigi Francesco; Vernier, Philippe; Lluis, Carmen; Ferré, Sergi; Fuxe, Kjell; Franco, Rafael

    2000-01-01

    The possible molecular basis for the previously described antagonistic interactions between adenosine A1 receptors (A1R) and dopamine D1 receptors (D1R) in the brain have been studied in mouse fibroblast Ltk− cells cotransfected with human A1R and D1R cDNAs or with human A1R and dopamine D2 receptor (long-form) (D2R) cDNAs and in cortical neurons in culture. A1R and D1R, but not A1R and D2R, were found to coimmunoprecipitate in cotransfected fibroblasts. This selective A1R/D1R heteromerization disappeared after pretreatment with the D1R agonist, but not after combined pretreatment with D1R and A1R agonists. A high degree of A1R and D1R colocalization, demonstrated in double immunofluorescence experiments with confocal laser microscopy, was found in both cotransfected fibroblast cells and cortical neurons in culture. On the other hand, a low degree of A1R and D2R colocalization was observed in cotransfected fibroblasts. Pretreatment with the A1R agonist caused coclustering (coaggregation) of A1R and D1R, which was blocked by combined pretreatment with the D1R and A1R agonists in both fibroblast cells and in cortical neurons in culture. Combined pretreatment with D1R and A1R agonists, but not with either one alone, substantially reduced the D1R agonist-induced accumulation of cAMP. The A1R/D1R heteromerization may be one molecular basis for the demonstrated antagonistic modulation of A1R of D1R receptor signaling in the brain. The persistence of A1R/D1R heteromerization seems to be essential for the blockade of A1R agonist-induced A1R/D1R coclustering and for the desensitization of the D1R agonist-induced cAMP accumulation seen on combined pretreatment with D1R and A1R agonists, which indicates a potential role of A1R/D1R heteromers also in desensitization mechanisms and receptor trafficking. PMID:10890919

  13. Interactions of histamine H1-receptor agonists and antagonists with the human histamine H4-receptor.

    PubMed

    Deml, Karl-Friedrich; Beermann, Silke; Neumann, Detlef; Strasser, Andrea; Seifert, Roland

    2009-11-01

    The human histamine H(4)-receptor (hH(4)R) possesses high constitutive activity and, like the human H(1)-receptor (hH(1)R), is involved in the pathogenesis of type-I allergic reactions. The study aims were to explore the value of dual H(1)/H(4)R antagonists as antiallergy drugs and to address the question of whether H(1)R ligands bind to hH(4)R. In an acute murine asthma model, the H(1)R antagonist mepyramine and the H(4)R antagonist 1-[(5-chloro-1H-indol-2-yl)carbonyl]-4-methyl-piperazine (JNJ 7777120) exhibited synergistic inhibitory effects on eosinophil accumulation in the bronchoalveolar lavage fluid. At the hH(4)R expressed in Sf9 insect cells, 18 H(1)R antagonists and 22 H(1)R agonists showed lower affinity to hH(4)R than to hH(1)R as assessed in competition binding experiments. For a small number of H(1)R antagonists, hH(4)R partial agonism was observed in the steady-state GTPase assay. Most compounds were neutral antagonists or inverse agonists. Twelve phenylhistamine-type hH(1)R partial agonists were also hH(4)R partial agonists. Four histaprodifen-type hH(1)R partial agonists were hH(4)R inverse agonists. Dimeric histaprodifen was a more efficacious hH(4)R inverse agonist than the reference compound thioperamide. Suprahistaprodifen was the only histaprodifen acting as hH(4)R partial agonist. Suprahistaprodifen was docked into the binding pocket of inactive and active hH(4)R models in two different orientations, predominantly stabilizing the active state of hH(4)R. Collectively, the synergistic effects of H(1)R and H(4)R antagonists in an acute asthma model and the overlapping interaction of structurally diverse H(1)R ligands with hH(1)R and hH(4)R indicate that the development of dual H(1)R/H(4)R antagonists is a worthwhile and technically feasible goal for the treatment of type-I allergic reactions.

  14. Effects of adenosine receptor agonist on the rocuroniuminduced neuromuscular block and sugammadex-induced recovery.

    PubMed

    Kim, Yong Beom; Lee, Sangseok; Choi, Hey Ran; In, Junyong; Chang, Young Jin; Kim, Ha Jung; Ro, Young Jin; Yang, Hong-Seuk

    2018-04-25

    Several types of receptors are found at neuromuscular presynaptic membranes. Presynaptic inhibitory A1 and facilitatory A2A receptors mediate different modulatory functions on acetylcholine release. This study investigated whether adenosine A1 receptor agonist contributes to the first twitch tension (T1) of train-of-four (TOF) stimulation depression and TOF fade during rocuronium-induced neuromuscular blockade, and sugammadex-induced recovery. Phrenic nerve-diaphragm tissues were obtained from 30 adult Sprague-Dawley rats. Each tissue specimen was randomly allocated to either control group or 2-chloroadenosine (CADO, 10 μM) group. One hour of reaction time was allowed before initiating main experimental data collection. Loading and boost doses of rocuronium were sequentially administered until > 95% depression of the T1 was achieved. After confirming that there was no T1 twitch tension response, 15 min of resting time was allowed, after which sugammadex was administered. Recovery profiles (T1, TOF ratio [TOFR], and recovery index) were collected for 1 h and compared between groups. There were statistically significant differences on amount of rocuronium (actually used during experiment), TOFR changes during concentration-response of rocuronium (P = 0.04), and recovery profiles (P < 0.01) of CADO group comparing with the control group. However, at the initial phase of this experiment, dose-response of rocuronium in each group demonstrated no statistically significant differences (P = 0.12). The adenosine A1 receptor agonist (CADO) influenced the TOFR and the recovery profile. After activating adenosine receptor, sugammadex-induced recovery from rocuronium-induced neuromuscular block was delayed.

  15. A series of Fas receptor agonist antibodies that demonstrate an inverse correlation between affinity and potency

    PubMed Central

    Chodorge, M; Züger, S; Stirnimann, C; Briand, C; Jermutus, L; Grütter, M G; Minter, R R

    2012-01-01

    Receptor agonism remains poorly understood at the molecular and mechanistic level. In this study, we identified a fully human anti-Fas antibody that could efficiently trigger apoptosis and therefore function as a potent agonist. Protein engineering and crystallography were used to mechanistically understand the agonistic activity of the antibody. The crystal structure of the complex was determined at 1.9 Å resolution and provided insights into epitope recognition and comparisons with the natural ligand FasL (Fas ligand). When we affinity-matured the agonist antibody, we observed that, surprisingly, the higher-affinity antibodies demonstrated a significant reduction, rather than an increase, in agonist activity at the Fas receptor. We propose and experimentally demonstrate a model to explain this non-intuitive impact of affinity on agonist antibody signalling and explore the implications for the discovery of therapeutic agonists in general. PMID:22261618

  16. 5-HT1F receptor agonists inhibit neurogenic dural inflammation in guinea pigs.

    PubMed

    Johnson, K W; Schaus, J M; Durkin, M M; Audia, J E; Kaldor, S W; Flaugh, M E; Adham, N; Zgombick, J M; Cohen, M L; Branchek, T A; Phebus, L A

    1997-07-07

    The serotonin (5-HT) receptor subtype mediating inhibition of neurogenic dural inflammation in guinea pigs was investigated using a series of serotonin agonists with differing affinities for the 5-HT1B, 5-HT1D and 5-HT1F receptors. When agonist potencies for inhibiting neurogenic inflammation were compared with affinities for these receptor subtypes, a significant positive correlation was seen only with the 5-HT1F receptor. The potency of agonists in inhibiting adenylate cyclase in cells transfected with human 5-HT1F receptor was also highly correlated with their potency in the animal model of migraine. In situ hybridization demonstrated 5-HT1F receptor mRNA in guinea pig trigeminal ganglion neurons. These data suggest that the 5-HT1F receptor is a rational target for migraine therapeutics.

  17. Selective Estrogen Receptor Modulators: Cannabinoid Receptor Inverse Agonists with Differential CB1 and CB2 Selectivity.

    PubMed

    Franks, Lirit N; Ford, Benjamin M; Prather, Paul L

    2016-01-01

    Selective estrogen receptor modulators (SERMs) are used to treat estrogen receptor (ER)-positive breast cancer and osteoporosis. Interestingly, tamoxifen and newer classes of SERMs also exhibit cytotoxic effects in cancers devoid of ERs, indicating a non-estrogenic mechanism of action. Indicative of a potential ER-independent target, reports demonstrate that tamoxifen binds to cannabinoid receptors (CBRs) with affinity in the low μM range and acts as an inverse agonist. To identify cannabinoids with improved pharmacological properties relative to tamoxifen, and further investigate the use of different SERM scaffolds for future cannabinoid drug development, this study characterized the affinity and activity of SERMs in newer structural classes at CBRs. Fourteen SERMs from five structurally distinct classes were screened for binding to human CBRs. Compounds from four of five SERM classes examined bound to CBRs. Subsequent studies fully characterized CBR affinity and activity of one compound from each class. Ospemifine (a triphenylethylene) selectively bound to CB1Rs, while bazedoxifine (an indole) bound to CB2Rs with highest affinity. Nafoxidine (a tetrahydronaphthalene) and raloxifene (RAL; a benzothiaphene) bound to CB1 and CB2Rs non-selectively. All four compounds acted as inverse agonists at CB1 and CB2Rs, reducing basal G-protein activity with IC 50 values in the nM to low μM range. Ospemifine, bazedoxifene and RAL also acted as inverse agonists to elevate basal intracellular cAMP levels in intact CHO-hCB2 cells. The four SERMs examined also acted as CB1 and CB2R antagonists in the cAMP assay, producing rightward shifts in the concentration-effect curve of the CBR agonist CP-55,940. In conclusion, newer classes of SERMs exhibit improved pharmacological characteristics (e.g., in CBR affinity and selectivity) relative to initial studies with tamoxifen, and thus suggest that different SERM scaffolds may be useful for development of safe and selective drugs acting

  18. Structural Probing and Molecular Modeling of the A3 Adenosine Receptor: A Focus on Agonist Binding

    PubMed Central

    Ciancetta, Antonella; Jacobson, Kenneth A.

    2017-01-01

    Adenosine is an endogenous modulator exerting its functions through the activation of four adenosine receptor (AR) subtypes, termed A1, A2A, A2B and A3, which belong to the G protein-coupled receptor (GPCR) superfamily. The human A3AR (hA3AR) subtype is implicated in several cytoprotective functions. Therefore, hA3AR modulators, and in particular agonists, are sought for their potential application as anti-inflammatory, anticancer, and cardioprotective agents. Structure-based molecular modeling techniques have been applied over the years to rationalize the structure-activity relationships (SARs) of newly emerged A3AR ligands, guide the subsequent lead optimization, and interpret site-directed mutagenesis (SDM) data from a molecular perspective. In this review, we showcase selected modeling-based and guided strategies that were applied to elucidate the binding of agonists to the A3AR and discuss the challenges associated with an accurate prediction of the receptor extracellular vestibule through homology modeling from the available X-ray templates. PMID:28287473

  19. Agonists and partial agonists of rhodopsin: retinal polyene methylation affects receptor activation.

    PubMed

    Vogel, Reiner; Lüdeke, Steffen; Siebert, Friedrich; Sakmar, Thomas P; Hirshfeld, Amiram; Sheves, Mordechai

    2006-02-14

    Using Fourier transform infrared (FTIR) difference spectroscopy, we have studied the impact of sites and extent of methylation of the retinal polyene with respect to position and thermodynamic parameters of the conformational equilibrium between the Meta I and Meta II photoproducts of rhodopsin. Deletion of methyl groups to form 9-demethyl and 13-demethyl analogues, as well as addition of a methyl group at C10 or C12, shifted the Meta I/Meta II equilibrium toward Meta I, such that the retinal analogues behaved like partial agonists. This equilibrium shift resulted from an apparent reduction of the entropy gain of the transition of up to 65%, which was only partially offset by a concomitant reduction of the enthalpy increase. The analogues produced Meta II photoproducts with relatively small alterations, while their Meta I states were significantly altered, which accounted for the aberrant transitions to Meta II. Addition of a methyl group at C14 influenced the thermodynamic parameters but had little impact on the position of the Meta I/Meta II equilibrium. Neutralization of the residue 134 in the E134Q opsin mutant increased the Meta II content of the 13-demethyl analogue, but not of the 9-demethyl analogue, indicating a severe impairment of the allosteric coupling between the conserved cytoplasmic ERY motif involved in proton uptake and the Schiff base/Glu 113 microdomain in the 9-demethyl analogue. The 9-methyl group appears therefore essential for the correct positioning of retinal to link protonation of the cytoplasmic motif with protonation of Glu 113 during receptor activation.

  20. Synthesis and SAR of amino acid-derived heterocyclic progesterone receptor full and partial agonists.

    PubMed

    Hammond, Marlys; Patterson, Jaclyn R; Manns, Sharada; Hoang, Tram H; Washburn, David G; Trizna, Walter; Glace, Lindsay; Grygielko, Eugene T; Nagilla, Rakesh; Nord, Melanie; Fries, Harvey E; Minick, Douglas J; Laping, Nicholas J; Bray, Jeffrey D; Thompson, Scott K

    2009-05-15

    Two classes of amino acid-derived heterocyclic progesterone receptor ligands were developed to address the metabolic issues posed by the dimethyl amide functionality of the lead compound (1). The tetrazole-derived ligands behaved as potent partial agonists, while the 1,2,4-triazole ligands behaved as potent full agonists.

  1. Regulation of adiponectin receptor 1 in human hepatocytes by agonists of nuclear receptors

    SciTech Connect

    Neumeier, Markus; Weigert, Johanna; Schaeffler, Andreas

    2005-09-02

    The adiponectin receptors AdipoR1 and AdipoR2 have been identified to mediate the insulin-sensitizing effects of adiponectin. Although AdipoR2 was suggested to be the main receptor for this adipokine in hepatocytes, AdipoR1 protein is highly abundant in primary human hepatocytes and hepatocytic cell lines. Nuclear receptors are main regulators of lipid metabolism and activation of peroxisome proliferator-activated receptor {alpha} and {gamma}, retinoid X receptor (RXR), and liver X receptor (LXR) by specific ligands may influence AdipoR1 abundance. AdipoR1 protein is neither altered by RXR or LXR agonists nor by pioglitazone. In contrast, fenofibric acid reduces AdipoR1 whereas hepatotoxic troglitazone upregulates AdipoR1more » protein in HepG2 cells. Taken together this work shows for the first time that AdipoR1 protein is expressed in human hepatocytes but that it is not a direct target gene of nuclear receptors. Elevated AdipoR1 induced by hepatotoxic troglitazone may indicate a role of this receptor in adiponectin-mediated beneficial effects in liver damage.« less

  2. Hydrogen/Deuterium Exchange Reveals Distinct Agonist/Partial Agonist Receptor Dynamics within the intact Vitamin D Receptor/Retinoid X Receptor Heterodimer

    PubMed Central

    Zhang, Jun; Chalmers, Michael J.; Stayrook, Keith R.; Burris, Lorri L.; Garcia-Ordonez, Ruben D.; Pascal, Bruce D.; Burris, Thomas P.; Dodge, Jeffery A.; Griffin, Patrick R.

    2010-01-01

    Summary Regulation of nuclear receptor (NR) activity is driven by alterations in the conformational dynamics of the receptor upon ligand binding. Previously we demonstrated that hydrogen/deuterium exchange (HDX) can be applied to determine novel mechanism of action of PPARγ ligands and in predicting tissue specificity of selective estrogen receptor modulators. Here we applied HDX to probe the conformational dynamics of the ligand binding domain (LBD) of the vitamin D receptor (VDR) upon binding its natural ligand 1α,25-dihydroxyvitamin D3 (1,25D3), and two analogs, alfacalcidol and ED-71. Comparison of HDX profiles from ligands in complex with the LBD with full-length receptor bound to its cognate receptor retinoid X receptor (RXR) revealed unique receptor dynamics that could not be inferred from static crystal structures. These results demonstrate that ligands modulate the dynamics of the heterodimer interface as well as providing insight into the role of AF-2 dynamics in the action of VDR partial agonists. PMID:20947021

  3. Hydrogen/deuterium exchange reveals distinct agonist/partial agonist receptor dynamics within vitamin D receptor/retinoid X receptor heterodimer.

    PubMed

    Zhang, Jun; Chalmers, Michael J; Stayrook, Keith R; Burris, Lorri L; Garcia-Ordonez, Ruben D; Pascal, Bruce D; Burris, Thomas P; Dodge, Jeffery A; Griffin, Patrick R

    2010-10-13

    Regulation of nuclear receptor (NR) activity is driven by alterations in the conformational dynamics of the receptor upon ligand binding. Previously, we demonstrated that hydrogen/deuterium exchange (HDX) can be applied to determine novel mechanism of action of PPARγ ligands and in predicting tissue specificity of selective estrogen receptor modulators. Here, we applied HDX to probe the conformational dynamics of the ligand binding domain (LBD) of the vitamin D receptor (VDR) upon binding its natural ligand 1α,25-dihydroxyvitamin D3 (1,25D3), and two analogs, alfacalcidol and ED-71. Comparison of HDX profiles from ligands in complex with the LBD with full-length receptor bound to its cognate receptor retinoid X receptor (RXR) revealed unique receptor dynamics that could not be inferred from static crystal structures. These results demonstrate that ligands modulate the dynamics of the heterodimer interface as well as provide insight into the role of AF-2 dynamics in the action of VDR partial agonists. Copyright © 2010 Elsevier Ltd. All rights reserved.

  4. Selective Allosteric Enhancement of Agonist Binding and Function at Human A3 Adenosine Receptors by a Series of Imidazoquinoline Derivatives

    PubMed Central

    Gao, Zhan-Guo; Kim, Seong Gon; Soltysiak, Kelly A.; Melman, Neli; Ijzerman, Adriaan P.; Jacobson, Kenneth A.

    2014-01-01

    We have identified a series of 1H-imidazo-[4,5-c]quinolines as selective allosteric enhancers of human A3 adenosine receptors. Several of these compounds potentiated both the potency and maximal efficacy of agonist-induced responses and selectively decreased the dissociation of the agonist N6-(4-amino-3-[125I]iodobenzyl)-5′-N-methylcarboxamidoadenosine from human A3 adenosine receptors. There was no effect on the dissociation of the antagonist [3H]8-ethyl-4-methyl-2-phenyl-(8R)-4,5,7,8-tetrahydro-1H-imidazo[2.1-i]purin-5-one (PSB-11) from the A3 receptors, as well as [3H]N6-[(R)-phenylisopropy-l]adenosine from rat brain A1 receptors and [3H]2-[p-(2-carboxyethyl)phenyl-ethylamino]-5′-N-ethylcarboxamidoad-enosine from rat striatal A2A receptors, suggesting the selective enhancement of agonist binding at A3 receptors. The analogs were tested as antagonists of competitive binding at human A3 receptors, and Ki values ranging from 120 nM to 101 μM were observed; as for many allosteric modulators of G protein-coupled receptors, an orthosteric effect was also present. The most promising leads from the present set of analogs seem to be the 2-cyclopentyl-1H-imidazo[4,5-c]quinoline derivatives, of which the 4-phenylamino analog DU124183 had the most favorable degree of allosteric modulation versus receptor antagonism. The inhibition of forskolin-stimulated cyclic AMP accumulation in intact cells that express human A3 receptors was employed as a functional index of A3 receptor activation. The enhancer DU124183 caused a marked leftward shift of the concentration-response curve of the A3 receptor agonists in the presence of antagonist and, surprisingly, a potentiation of the maximum agonist efficacy by approximately 30%. Thus, we have identified a novel structural lead for developing allosteric enhancers of A3 adenosine receptors; such enhancers may be useful for treating brain ischemia and other hypoxic conditions. PMID:12065758

  5. The discovery of biaryl carboxamides as novel small molecule agonists of the motilin receptor.

    PubMed

    Westaway, Susan M; Brown, Samantha L; Conway, Elizabeth; Heightman, Tom D; Johnson, Christopher N; Lapsley, Kate; Macdonald, Gregor J; MacPherson, David T; Mitchell, Darren J; Myatt, James W; Seal, Jon T; Stanway, Steven J; Stemp, Geoffrey; Thompson, Mervyn; Celestini, Paolo; Colombo, Andrea; Consonni, Alessandra; Gagliardi, Stefania; Riccaboni, Mauro; Ronzoni, Silvano; Briggs, Michael A; Matthews, Kim L; Stevens, Alexander J; Bolton, Victoria J; Boyfield, Izzy; Jarvie, Emma M; Stratton, Sharon C; Sanger, Gareth J

    2008-12-15

    Optimisation of urea (5), identified from high throughput screening and subsequent array chemistry, has resulted in the identification of pyridine carboxamide (33) which is a potent motilin receptor agonist possessing favourable physicochemical and ADME profiles. Compound (33) has demonstrated prokinetic-like activity both in vitro and in vivo in the rabbit and therefore represents a promising novel small molecule motilin receptor agonist for further evaluation as a gastroprokinetic agent.

  6. Liver X Receptor Agonist GW3965 Regulates Synaptic Function upon Amyloid Beta Exposure in Hippocampal Neurons.

    PubMed

    Báez-Becerra, C; Filipello, F; Sandoval-Hernández, A; Arboleda, H; Arboleda, G

    2018-04-01

    Alzheimer's disease (AD) is a devastating neurodegenerative disease characterized by beta-amyloid (Aβ) accumulation and neurofibrillary tangles formation in the brain which are associated to synaptic deficits and dementia. Liver X receptor (LXR) agonists have been demonstrated to revert of pathologic and cognitive defects in murine models of AD through the regulation of Apolipoprotein E, ATP-Binding Cassette A1 (ABCA1), by dampening neuroinflammation and also by reducing the levels of amyloid-β (Aβ) accumulation in the brain. However, the role of LXR with regard to the regulation of synaptic function remains relatively understudied. In the present paper, we analyzed the in-vitro effect of the LXR agonist GW3965 on synaptic function upon exposure of primary hippocampal cultures to oligomeric amyloid-β (oAβ(1-42)). We showed that oAβ(1-42) exposure significantly decreased the density of mature (mushroom shaped) dendritic spines density and synaptic contacts number. oAβ(1-42) also modulates the expression of pre- (VGlut1, SYT1, SV2A) and post-synaptic (SHANK2, NMDA) proteins, it decreases the expression of PINK1, and increases ROCKII, and activates of caspase-3; these changes were prevented by the pre-treating neuronal cultures with GW3965. These results show further support the role of the LXR agonist GW3965 in synaptic physiology and highlight its potential as an alternative pharmacological strategy for AD.

  7. The Therapeutic Potential of Nociceptin/Orphanin FQ Receptor Agonists as Analgesics without Abuse Liability

    PubMed Central

    2012-01-01

    Although mu opioid (MOP) receptor agonists are the most commonly used analgesics for the treatment of moderate to severe pain in the clinic, the side effects of MOP agonists such as abuse liability limit their value as a medication. Research to identify novel analgesics without adverse effects is pivotal to advance the health care of humans. The nociceptin/orphanin FQ peptide (NOP) receptor, the fourth opioid receptor subtype, mediates distinctive actions in nonhuman primates which suggests the possibility that activity at this receptor may result in strong analgesia in the absence of virtually all of the side effects associated with MOP agonists. The present review highlights the recent progress of pharmacological studies of NOP-related ligands in primates. Selective NOP agonists, either peptidic or nonpeptidic, produce full analgesia in various assays in primates, when delivered systemically or intrathecally. Yet small molecule NOP agonists do not serve as reinforcers, indicating a lack of abuse liability. Given that NOP agonists have low abuse liability and that coactivation of NOP and MOP receptors produces synergistic antinociception, it is worth developing bifunctional NOP/MOP ligands. The outcomes of these studies and recent developments provide new perspectives to establish a translational bridge for understanding the biobehavioral functions of NOP receptors in primates and for facilitating the development of NOP-related ligands as a new generation of analgesics without abuse liability in humans. PMID:23421672

  8. The atypical dopamine D1 receptor agonist SKF 83959 induces striatal Fos expression in rats.

    PubMed

    Wirtshafter, David; Osborn, Catherine V

    2005-12-28

    The effects of dopamine D1 receptor agonists are often presumed to result from an activation of adenylyl cyclase, but dopamine D1 receptors may also be linked to other signal transduction cascades and the relative importance of these various pathways is currently unclear. SKF 83959 is an agonist at dopamine D1 receptors linked to phospholipase C, but has been reported to be an antagonist at receptors linked to adenylyl cyclase. The current report demonstrates that SKF 83959 induces pronounced, nonpatchy, expression of the immediate-early gene product Fos in the striatum of intact rats which can be converted to a patchy pattern by pretreatment with the dopamine D2-like receptor agonist quinpirole. In rats with unilateral 6-hydroxydopamine lesions SKF 83959 induces strong behavioral rotation and a greatly potentiated Fos response. All of the responses to SKF 83959, in both intact and dopamine-depleted animals, can be blocked by pretreatment with the dopamine D1 receptor antagonist SCH-23390. In intact subjects, SKF 83959 induced Fos expression less potently than the standard dopamine D1 receptor agonist SKF 82958, but the two drugs were approximately equipotent in deinnervated animals. These results demonstrate for the first time that possession of full efficacy at dopamine D1 receptors linked to adenylyl cyclase is not a necessary requirement for the induction of striatal Fos expression in intact animals and suggest that alternative signal transduction pathways may play a role in dopamine agonist induced Fos expression, especially in dopamine-depleted subjects.

  9. Being mindful of seven-transmembrane receptor 'guests' when assessing agonist selectivity.

    PubMed

    Kenakin, Terry

    2010-07-01

    The time-honored approach of quantifying agonist selectivity through measurement of agonist affinity with binding and efficacy through potency ratios in model assays for prediction of effect in therapeutic systems can fall short of providing useful answers for functionally selective agonists. Agonists are now known to have pluridimensional efficacies that are associated with selected signalling pathways coupled to the receptor. This necessitates specifically tailored assay formats to measure pre-determined efficacies of ligands to characterize agonist selectivity fully. If such assays can access signalling that directly emanates from the interaction of the agonist-bound receptor and a cytosolic signalling protein, then the Black/Leff operational model can be used to specifically quantify 'transduction ratios' (tau/K(A)) that fully characterize selective activation of signalling pathways by a given agonist. As whole-cell processing of pleiotropic signalling cascades imposes cell-specific phenotypic agonist profiles, ultimately the assessment of agonist selectivity is most reliably done in the therapeutically relevant primary cell system.

  10. Naltrindole derivatives with fluorinated ethyl substituents on the 17-nitrogen as δ opioid receptor inverse agonists.

    PubMed

    Nemoto, Toru; Iihara, Yusuke; Hirayama, Shigeto; Iwai, Takashi; Higashi, Eika; Fujii, Hideaki; Nagase, Hiroshi

    2015-08-01

    We synthesized derivatives of the δ opioid receptor (DOR) antagonists naltrindole (NTI) and compound 1 that were modified with small alkyl or fluorinated ethyl substituents on the 17-nitrogen. Although the derivatives showed decreased binding affinities for the opioid receptors, their selectivities for the DOR were higher than the parent compounds NTI and compound 1. Surprisingly, 17-fluoroethyl NTI derivatives exerted DOR inverse agonistic activities. The DOR inverse agonism of compounds 4c-e was less efficacious but significant, as compared with a standard DOR inverse agonist ICI-174864. On the other hand, compound 1 and its derivatives with small alkyl or monofluoroethyl substituents were partial agonists, but the derivatives having di- or trifluoroethyl group showed neither agonistic nor inverse agonistic activities. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Optimization of Adenosine 5′-Carboxamide Derivatives as Adenosine Receptor Agonists Using Structure-Based Ligand Design and Fragment Screening

    PubMed Central

    Tosh, Dilip K.; Phan, Khai; Gao, Zhan-Guo; Gakh, Andrei A.; Xu, Fei; Deflorian, Francesca; Abagyan, Ruben; Stevens, Raymond C.; Jacobson, Kenneth A.; Katritch, Vsevolod

    2012-01-01

    Structures of G protein-coupled receptors (GPCRs) have a proven utility in the discovery of new antagonists and inverse agonists modulating signaling of this important family of clinical targets. Applicability of active-state GPCR structures to virtual screening and rational optimization of agonists, however, remains to be assessed. In this study of adenosine 5′ derivatives, we evaluated the performance of an agonist-bound A2A adenosine receptor (AR) structure in retrieval of known agonists and then employed the structure to screen for new fragments optimally fitting the corresponding subpocket. Biochemical and functional assays demonstrate high affinity of new derivatives that include polar heterocycles. The binding models also explain modest selectivity gain for some substituents toward the closely related A1AR subtype and the modified agonist efficacy of some of these ligands. The study suggests further applicability of in silico fragment screening to rational lead optimization in GPCRs. PMID:22486652

  12. Discovery of Peripheral κ-Opioid Receptor Agonists as Novel Analgesics.

    PubMed

    Suzuki, Shinya; Sugawara, Yuji; Inada, Hideaki; Tsuji, Riichiro; Inoue, Atsushi; Tanimura, Ryuji; Shimozono, Rieko; Konno, Mitsuhiro; Ohyama, Tomofumi; Higashi, Eriko; Sakai, Chizuka; Kawai, Koji

    2017-01-01

    κ-Opioid receptor agonists with high selectivity over the μ-opioid receptor and peripheral selectivity are attractive targets in the development of drugs for pain. We have previously attempted to create novel analgesics with peripheral selective κ-opioid receptor agonist on the basis of TRK-820. In this study, we elucidated the biological properties of 17-hydroxy-cyclopropylmethyl and 10α-hydroxy derivatives. These compounds were found to have better κ-opioid receptor selectivity and peripheral selectivity than TRK-820.

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

    PubMed

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

    2016-03-01

    Eye blinking is a spontaneous behavior observed in all mammals, and has been used as a well-established clinical indicator for dopamine production in neuropsychiatric disorders, including Parkinson's disease and Tourette syndrome [1,2]. Pharmacological studies in humans and non-human primates have shown that dopamine agonists/antagonists increase/decrease eye blinking rate. Common marmosets (Callithrix jacchus) have recently attracted a great deal of attention as suitable experimental animals in the psychoneurological field due to their more developed prefrontal cortex than rodents, easy handling compare to other non-human primates, and requirement for small amounts of test drugs. In this study, we evaluated the effects of dopamine D1-4 receptors agonists on eye blinking in common marmosets. Our results show that the dopamine D1 receptor agonist SKF-82958 and the non-selective dopamine receptor agonist apomorphine significantly increased common marmosets eye blinking count, whereas the dopamine D2 agonist (+)-PHNO and the dopamine D3 receptor agonist (+)-PD-128907 produced somnolence in common marmosets resulting in a decrease in eye blinking count. The dopamine D4 receptor agonists PD-168077 and A-41297 had no effect on common marmosets' eye blinking count. Finally, the dopamine D1 receptor antagonist SCH 39166 completely blocked apomorphine-induced increase in eye blinking count. These results indicate that eye blinking in common marmosets may be a useful tool for in vivo screening of novel dopamine D1 receptor agonists as antipsychotics. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. Effects of dopamine D1 receptor full agonists in rats trained to discriminate SKF 38393.

    PubMed

    Gleason, S D; Witkin, J M

    2004-02-01

    Although the dopaminergic pharmacology of the D1 receptor full agonists, dinapsoline, dihydrexidine and the prodrug ABT-431 have been studied, no information is available on the ability of these agonists to substitute for the D1 agonist SKF 38393 in rats trained to discriminate this compound from vehicle. The present study was designed to characterize the potential D1 discriminative stimulus effects of these compounds. The selective dopamine D1-receptor agonists dihydrexidine [(+/-)-trans-10,11-dihydroxy-5,6,6a,7,8,12b-hexahydrobenzo[a] phenanthridine hydrochloride], ABT-431 [(-)-trans-9,10-diacetyloxy-2-propyl-4,5,5a,6,7,11b-hexahydro-3-thia-5-azacyclopent-1-ena[c]phenanthrene hydrochloride], the diacetyl prodrug derivative of A-86929, and dinapsoline [9-dihydroxy-2,3,7,11b-tetrahydro-1H-naph[1,2,3-de]isoquinoline] were studied in rats trained to discriminate racemic SKF 38393 [(+/-)-1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol], a selective D1 receptor partial agonist from vehicle. All of the agonists substituted fully for the discriminative stimulus effects of SKF 38393. The rank order of potency for substitution was ABT-431 > dinapsoline > dihydrexidine > SKF 38393. The D1 receptor antagonist, SCH 23390, blocked the discriminative stimulus effects of SKF 38393. The D3/D2-receptor agonist PD 128,907 [S(+)-(4aR,10bR)-3,4,4a,10b-tetrahydro-4-propyl-2H,5H-[1]-benzopyrano[4,3-b]-1,4-oxazin-9-ol] did not substitute up to doses that produced profound rate-suppressant effects. Thus, consistent with their D1 receptor pharmacology, the full D1-receptor agonists substituted completely for the discriminative stimulus of SKF 38393.

  15. Computational structure-activity relationship analysis of small-molecule agonists for human formyl peptide receptors.

    PubMed

    Khlebnikov, Andrei I; Schepetkin, Igor A; Quinn, Mark T

    2010-11-01

    N-formyl peptide receptors (FPRs) are important in host defense. Because of the potential for FPRs as therapeutic targets, recent efforts have focused on identification of non-peptide agonists for two FPR subtypes, FPR1 and FPR2. Given that a number of specific small-molecule agonists have recently been identified, we hypothesized that computational structure-activity relationship (SAR) analysis of these molecules could provide new information regarding molecular features required for activity. We used a training set of 71 compounds, including 10 FPR1-specific agonists, 36 FPR2-specific agonists, and 25 non-active analogs. A sequence of (1) one-way analysis of variance selection, (2) cluster analysis, (3) linear discriminant analysis, and (4) classification tree analysis led to the derivation of SAR rules with high (95.8%) accuracy for correct classification of compounds. These SAR rules revealed key features distinguishing FPR1 versus FPR2 agonists. To verify predictive ability, we evaluated a test set of 17 additional FPR agonists, and found that the majority of these agonists (>94%) were classified correctly as agonists. This study represents the first successful application of classification tree methodology based on atom pairs to SAR analysis of FPR agonists. Importantly, these SAR rules represent a relatively simple classification approach for virtual screening of FPR1/FPR2 agonists. Copyright © 2010 Elsevier Masson SAS. All rights reserved.

  16. Roles of agonist-binding sites in nicotinic acetylcholine receptor function.

    PubMed

    Dunn, S M; Raftery, M A

    2000-12-20

    Under equilibrium conditions, the nicotinic acetylcholine receptor from Torpedo electroplax carries two high affinity-binding sites for agonists. It is generally assumed that these are the only agonist sites on the receptor and that their occupancy results in rapid channel activation followed by slower conformational transitions that lead to the high affinity equilibrium state. These slow transitions are thought to reflect the physiological process of desensitization. Here we show that preequilibration of the high affinity sites with saturating concentrations of carbamylcholine does not diminish the ion flux response to subsequent exposure to higher (activating) concentrations of this agonist. This finding has profound implications with respect to receptor function: (1) occupancy of the high affinity sites per se does not desensitize the receptor and (2) these sites cannot be directly involved in receptor activation. It is thus necessary to invoke the presence of additional binding sites in channel opening. Copyright 2000 Academic Press.

  17. Crystal structure of the GLP-1 receptor bound to a peptide agonist.

    PubMed

    Jazayeri, Ali; Rappas, Mathieu; Brown, Alastair J H; Kean, James; Errey, James C; Robertson, Nathan J; Fiez-Vandal, Cédric; Andrews, Stephen P; Congreve, Miles; Bortolato, Andrea; Mason, Jonathan S; Baig, Asma H; Teobald, Iryna; Doré, Andrew S; Weir, Malcolm; Cooke, Robert M; Marshall, Fiona H

    2017-06-08

    Glucagon-like peptide 1 (GLP-1) regulates glucose homeostasis through the control of insulin release from the pancreas. GLP-1 peptide agonists are efficacious drugs for the treatment of diabetes. To gain insight into the molecular mechanism of action of GLP-1 peptides, here we report the crystal structure of the full-length GLP-1 receptor bound to a truncated peptide agonist. The peptide agonist retains an α-helical conformation as it sits deep within the receptor-binding pocket. The arrangement of the transmembrane helices reveals hallmarks of an active conformation similar to that observed in class A receptors. Guided by this structural information, we design peptide agonists with potent in vivo activity in a mouse model of diabetes.

  18. 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

  19. Interactions between μ-opioid receptor agonists and cannabinoid receptor agonists in rhesus monkeys: antinociception, drug discrimination, and drug self-administration.

    PubMed

    Maguire, David R; Yang, Wenjuan; France, Charles P

    2013-06-01

    Cannabinoid receptor agonists enhance the antinociceptive effects of μ-opioid receptor agonists, which suggests that combinations of these drugs might enhance therapeutic effectiveness (e.g., analgesia). However, it is not clear whether combinations of these drugs also enhance abuse or dependence liability. This experiment examined whether combinations of cannabinoids and opioids that enhance antinociception also increase abuse-related effects by studying the effects of the cannabinoid receptor agonists 2-[(1R,2R,5R)-5-hydroxy-2-(3-hydroxypropyl)cyclohexyl]-5-(2-methyloctan-2-yl)phenol (CP 55,940) and (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone mesylate (WIN 55,212) on the antinociceptive, discriminative stimulus, and positive reinforcing effects of μ-opioid receptor agonists in rhesus monkeys. In one group of monkeys (n = 3), morphine (0.1-5.6 mg/kg s.c.), CP 55,940 (0.0032-0.032 mg/kg s.c.), and WIN 55,212 (0.1-1.0 mg/kg s.c.) dose-dependently increased tail withdrawal latency from 50°C water, and pretreatment with small, otherwise ineffective, doses of CP 55,940 and WIN 55,212 shifted the morphine dose-effect curve to the left. In monkeys (n = 3) discriminating 3.2 mg/kg morphine, CP 55,940 (0.01-0.032 mg/kg s.c.) and WIN 55,212 (0.1-1.78 mg/kg s.c.) attenuated the discriminative stimulus effects of morphine, shifting the dose-effect curve to the right. In monkeys (n = 4) self-administering heroin (0.32-32.0 µg/kg/infusion i.v.), CP 55,940 (0.001-0.032 mg/kg s.c.), and WIN 55,212 (0.1-1.0 mg/kg s.c.) shifted the heroin dose-effect curve rightward and downward. Cannabinoid receptor agonists CP 55,940 and WIN 55,212 enhanced the antinociceptive effects but not the discriminative stimulus or positive reinforcing effects of μ-opioid receptor agonists in rhesus monkeys, supporting the view that combining cannabinoid and opioid receptor agonists might result in enhanced treatment

  20. Biperiden enhances L-DOPA methyl ester and dopamine D(l) receptor agonist SKF-82958 but antagonizes D(2)/D(3) receptor agonist rotigotine antihemiparkinsonian actions.

    PubMed

    Domino, Edward F; Ni, Lisong

    2008-12-03

    The effects of biperiden (0, 100, and 320 microg/kg), a selective muscarinic M(1)/M(4) receptor cholinergic antagonist, were studied alone and in combination with those of L-DOPA methyl ester (16.7 mg/kg), a selective dopamine D(1) receptor agonist SKF-82958 (74.8 microg/kg), or a selective D(2)/D(3) receptor agonist rotigotine (32 microg/kg) on circling behavior in MPTP induced hemiparkinsonian monkeys. The doses selected were given i.m. in approximately equieffective doses to produce contraversive circling. Biperiden alone with 5% dextrose vehicle produced a slight increase in contraversive circling in a dose related manner. When combined with L-DOPA methyl ester, it enhanced contraversive circling and decreased ipsiversive circling. When biperiden was combined with SKF-82958, contraversive circling also was enhanced and ipsiversive circling decreased. Exactly the opposite was observed with the combination of biperiden and rotigotine. The results indicate a dramatic difference in effects of a prototypic muscarinic M(1)/M(4) receptor cholinergic antagonist in combination with prototypic full dopamine D(1) or D(2)/D(3) receptor agonists. Biperiden interactions with L-DOPA methyl ester were more predominantly D(l) than D(2)/D(3) receptor-like in this animal model of hemiparkinsonism.

  1. Therapeutic significance of estrogen receptor β agonists in gliomas

    PubMed Central

    Sareddy, Gangadhara R; Nair, Binoj C.; Gonugunta, Vijay K.; Zhang, Quan-guang; Brenner, Andrew; Brann, Darrell W.; Tekmal, Rajeshwar Rao; Vadlamudi, Ratna K.

    2013-01-01

    Gliomas are the most common and devastating central nervous system neoplasms. A gender bias exists in their development: females are at lower risk than males, implicating estrogen-mediated protective effects. Estrogen functions are mediated by two ER subtypes: ERα, that functions as tumor promoter and ERβ that function as tumor suppressor. We examined the potential use of ERβ agonists as a novel therapeutic to curb the growth of gliomas. Western analysis of six glioma model cells showed detectable expression of ERβ with little or no ERα. Treatment of glioma cells with ERβ agonists resulted in significant decrease in proliferation. IHC analysis of tumor tissues revealed that ERβ expression is down regulated in high-grade gliomas. We found that ERβ agonists promote both expression and tumor suppressive functions of ERβ in glioma cells. Liquiritigenin, a plant-derived ERβ agonist significantly reduced in vivo tumor growth in a xenograft model. Compared to control mice, animals treated with liquiritigenin had greater than 50% reduction in tumor volume and size. IHC analysis of tumors revealed a significant increase in the nuclear ERβ expression with a concomitant decrease in cell proliferation in the liquiritigenin-treated group. Our results suggest that ERβ signaling has a tumor suppressive function in gliomas. Since ERβ agonists are currently in clinical trials and are well tolerated with fewer side effects, identification of an ERβ agonist as a therapeutic agent can be readily extended to clinical use with current chemotherapies, providing an additional tool for enhancing survival in glioma patients. PMID:22442308

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

    PubMed

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

    2016-07-01

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

  3. Selective Estrogen Receptor Modulators: Cannabinoid Receptor Inverse Agonists with Differential CB1 and CB2 Selectivity

    PubMed Central

    Franks, Lirit N.; Ford, Benjamin M.; Prather, Paul L.

    2016-01-01

    Selective estrogen receptor modulators (SERMs) are used to treat estrogen receptor (ER)-positive breast cancer and osteoporosis. Interestingly, tamoxifen and newer classes of SERMs also exhibit cytotoxic effects in cancers devoid of ERs, indicating a non-estrogenic mechanism of action. Indicative of a potential ER-independent target, reports demonstrate that tamoxifen binds to cannabinoid receptors (CBRs) with affinity in the low μM range and acts as an inverse agonist. To identify cannabinoids with improved pharmacological properties relative to tamoxifen, and further investigate the use of different SERM scaffolds for future cannabinoid drug development, this study characterized the affinity and activity of SERMs in newer structural classes at CBRs. Fourteen SERMs from five structurally distinct classes were screened for binding to human CBRs. Compounds from four of five SERM classes examined bound to CBRs. Subsequent studies fully characterized CBR affinity and activity of one compound from each class. Ospemifine (a triphenylethylene) selectively bound to CB1Rs, while bazedoxifine (an indole) bound to CB2Rs with highest affinity. Nafoxidine (a tetrahydronaphthalene) and raloxifene (RAL; a benzothiaphene) bound to CB1 and CB2Rs non-selectively. All four compounds acted as inverse agonists at CB1 and CB2Rs, reducing basal G-protein activity with IC50 values in the nM to low μM range. Ospemifine, bazedoxifene and RAL also acted as inverse agonists to elevate basal intracellular cAMP levels in intact CHO-hCB2 cells. The four SERMs examined also acted as CB1 and CB2R antagonists in the cAMP assay, producing rightward shifts in the concentration-effect curve of the CBR agonist CP-55,940. In conclusion, newer classes of SERMs exhibit improved pharmacological characteristics (e.g., in CBR affinity and selectivity) relative to initial studies with tamoxifen, and thus suggest that different SERM scaffolds may be useful for development of safe and selective drugs acting

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

    PubMed

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

    2013-05-01

    Artificial agonists may have higher efficacy for receptor activation than the physiological agonist. Until now, such 'superagonism' has rarely been reported for GPCRs. Iperoxo is an extremely potent muscarinic receptor agonist. We hypothesized that iperoxo is a 'superagonist'. Signalling of iperoxo and newly synthesized structural analogues was compared with that of ACh at label-free M2 muscarinic receptors applying whole cell dynamic mass redistribution, measurement of G-protein activation, evaluation of cell surface agonist binding and computation of operational efficacies. In CHO-hM2 cells, iperoxo significantly exceeds ACh in Gi /Gs signalling competence. In the orthosteric loss-of-function mutant M2 -Y104(3.33) A, the maximum effect of iperoxo is hardly compromised in contrast to ACh. 'Superagonism' is preserved in the physiological cellular context of MRC-5 human lung fibroblasts. Structure-signalling relationships including iperoxo derivatives with either modified positively charged head group or altered tail suggest that 'superagonism' of iperoxo is mechanistically based on parallel activation of the receptor protein via two orthosteric interaction points. Supraphysiological agonist efficacy at muscarinic M2 ACh receptors is demonstrated for the first time. In addition, a possible underlying molecular mechanism of GPCR 'superagonism' is provided. We suggest that iperoxo-like orthosteric GPCR activation is a new avenue towards a novel class of receptor activators. © 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.

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

    PubMed Central

    Ryan, Donna; Acosta, Andres

    2015-01-01

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

  6. Impact of isotype-selective estrogen receptor agonists on ovarian function

    PubMed Central

    Hegele-Hartung, Christa; Siebel, Philip; Peters, Olaf; Kosemund, Dirk; Müller, Gerd; Hillisch, Alexander; Walter, Alexander; Kraetzschmar, Jörn; Fritzemeier, Karl-Heinrich

    2004-01-01

    Other isotype-selective estrogen receptor (ER) agonists, the selective ERα agonist 3,17-dihydroxy-19-nor-17α-pregna-1,3,5 (10)triene-21,16α-lactone and the selective ERβ agonist 8-vinylestra-1,3,5 (10)-triene-3,17β-diol, were used in hypophysectomized rats, gonadotropin-releasing hormone antagonist-treated mice, as well as intact rats to elucidate the effects of isotype-selective estrogens on the physiology of folliculogenesis and ovulation. In hypophysectomized rats and gonadotropin-releasing hormone antagonist-treated mice, the ERβ agonist caused stimulation of early folliculogenesis, a decrease in follicular atresia, induction of ovarian gene expression, and stimulation of late follicular growth, accompanied by an increase in the number of ovulated oocytes similar to 17β-estradiol (E2). In contrast, the ERα agonist had little or no effect on these parameters, implying that direct estrogen effects on ovarian follicular development are mediated by ERβ. In intact rats, E2 and the ERα agonist dose-dependently inhibited ovulation, in contrast to the ERβ agonist. On the other hand, the ERβ agonist did not stimulate uterine weight in intact rats, in contrast to E2 and the ERα agonist. This finding is in line with the assumption that estrogen mediated ovulation inhibition and stimulation of uterine growth are mediated by ERα but not by ERβ PMID:15037755

  7. Agonist signalling properties of radiotracers used for imaging of dopamine D2/3 receptors.

    PubMed

    van Wieringen, Jan-Peter; Michel, Martin C; Janssen, Henk M; Janssen, Anton G; Elsinga, Philip H; Booij, Jan

    2014-01-01

    Dopamine D2/3 receptor (D2/3R) agonist radiopharmaceuticals are considered superior to antagonists to detect dopamine release, e.g. induced by amphetamines. Agonists bind preferentially to the high-affinity state of the dopamine D2R, which has been proposed as the reason why agonists are more sensitive to detect dopamine release than antagonist radiopharmaceuticals, but this theory has been challenged. Interestingly, not all agonists similarly activate the classic cyclic adenosine mono phosphate (cAMP) and the ?-arrestin-2 pathway, some stimulate preferentially one of these pathways; a phenomenon called biased agonism. Because these pathways can be affected separately by pathologies or drugs (including dopamine releasers), it is important to know how agonist radiotracers act on these pathways. Therefore, we characterized the intracellular signalling of the well-known D2/3R agonist radiopharmaceuticals NPA and PHNO and of several novel D2/3R agonists. cAMP accumulation and ?-arrestin-2 recruitment were measured on cells expressing human D2R. All tested agonists showed (almost) full agonism in both pathways. The tested D2/3R agonist radiopharmaceuticals did not exhibit biased agonism in vitro. Consequently, it is likely that drugs (including psychostimulants like amphetamines) and/or pathologies that influence the cAMP and/or the ?-arrestin-2 pathway may influence the binding of these radiopharmaceuticals.

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

    USDA-ARS?s Scientific Manuscript database

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

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

    PubMed

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

    2013-01-01

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

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2016-06-15

    Aiming to discover dual-acting β2 adrenergic/dopamine D2 receptor ligands, a structure-guided approach for the evolution of GPCR agonists that address multiple targets was elaborated. Starting from GPCR crystal structures, we describe the design, synthesis and biological investigation of a defined set of compounds leading to the identification of the benzoxazinone (R)-3, which shows agonist properties at the adrenergic β2 receptor and substantial G protein-promoted activation at the D2 receptor. This directed approach yielded molecular probes with tuned dual activity. The congener desOH-3 devoid of the benzylic hydroxyl function was shown to be a β2 adrenergic antagonist/D2 receptor agonist with Ki values in the low nanomolar range. The compounds may serve as a promising starting point for the investigation and treatment of neurological disorders. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. The dopamine D(1) receptor agonist SKF-82958 serves as a discriminative stimulus in the rat.

    PubMed

    Haile, C N; Carey, G; Varty, G B; Coffin, V L

    2000-01-28

    We examined the discriminative stimulus effects of the high-efficacy dopamine D(1) receptor agonist (+/-)6-chloro-7, 8-dihydroxy-3-ally1-phenyl-2,3,4,5-tetrahydro-1H-3benzazepine++ + hydrobromide (SKF-82958) in rats trained to discriminate SKF-82958 (0.03 mg/kg) from vehicle in a two-lever food-reinforced drug discrimination task. SKF-82958 produced dose-related increases in responding to the SKF-82958 appropriate lever with full substitution occurring at the training dose. Pretreatment with the dopamine D(1)/D(5) receptor antagonist (-)-trans-6,7,7a,8,9, 13b-hexahydro-3-chloro-2hydroxy-N-methyl-5H-benzo-[d]naphtho -¿2, 1-b¿azepine (SCH-39166) (0.01 mg/kg) attenuated the discriminative stimulus effects of SKF-82958. Pretreatment with the dopamine D(2) receptor antagonist raclopride (0.03 mg/kg) had no effect. The high-efficacy dopamine D(1) receptor agonist R(+)6chloro-7, 8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrobromide (SKF-81297) fully substituted for SKF-82958, whereas the low-efficacy dopamine D(1) receptor agonist (+/-)1-phenyl-2,3,4, 5-tetrahydro-(1H)-3-benzazepine-7,8-diol hydrochloride (SKF-38393) produced only partial substitution. The dopamine D(2) receptor agonist trans-(+/-)-4,4a,5,6,7,8,8a, 9-octahydro-5-propyl-1H-propyl-1H-pyrazolo[3,4-g]quinoline dihydrochloride (quinpirole) and the indirect dopamine agonist cocaine did not substitute fully for the SKF-82958 discriminative stimulus cue. These results demonstrate that the high-efficacy dopamine D(1) receptor agonist SKF-82958 can serve as an effective discriminative stimulus in the rat, and that these effects are mediated by a dopamine D(1)-like receptor mechanism.

  13. Synergistic and additive interactions of the cannabinoid agonist CP55,940 with μ opioid receptor and α2-adrenoceptor agonists in acute pain models in mice

    PubMed Central

    Tham, Shao M; Angus, James A; Tudor, Elizabeth M; Wright, Christine E

    2004-01-01

    Cannabinoid receptor agonists elicit analgesic effects in acute and chronic pain states via spinal and supraspinal pathways. We investigated whether the combination of a cannabinoid agonist with other classes of antinociceptive drugs exerted supra-additive (synergistic) or additive effects in acute pain models in mice. The interactions between the cannabinoid agonist CP55,940, α2-adrenoceptor agonist dexmedetomidine and μ-opioid receptor agonist morphine were evaluated by isobolographic analysis of antinociception in hot plate (55°C) and tail flick assays in conscious male Swiss mice. Drug interactions were examined by administering fixed-ratio combinations of agonists (s.c.) in 1 : 1, 3 : 1 and 1 : 3 ratios of their respective ED50 fractions. CP55,940, dexmedetomidine and morphine all caused dose-dependent antinociception. In the hot plate and tail flick assays, ED50 values (mg kg−1) were CP55,940 1.13 and 0.51, dexmedetomidine 0.066 and 0.023, and morphine 29.4 and 11.3, respectively. Synergistic interactions existed between CP55,940 and dexmedetomidine in the hot plate assay, and CP55,940 and morphine in both assays. Additive interactions were found for CP55,940 and dexmedetomidine in the tail flick assay, and dexmedetomidine and morphine in both assays. Thus, an α2-adrenoceptor agonist or μ opioid receptor agonist when combined with a cannabinoid receptor agonist showed significant synergy in antinociception in the hot plate test. However, for the tail flick nociceptive response to heat, only cannabinoid and μ opioid receptor antinociceptive synergy was demonstrated. If these results translate to humans, then prudent selection of dose and receptor-specific agonists may allow an improved therapeutic separation from unwanted side effects. PMID:15778704

  14. Inverse agonistic activity of antihistamines and suppression of histamine H1 receptor gene expression.

    PubMed

    Mizuguchi, Hiroyuki; Ono, Shohei; Hattori, Masashi; Fukui, Hiroyuki

    2012-01-01

    Histamine H(1) receptor (H1R) expression influences the severity of allergy symptoms. We examined the effect of inverse agonists on H1R gene expression. Two inverse agonists (carebastine and mepyramine), but not the neutral antagonist oxatomide, decreased inositol phosphate accumulation. The inverse agonists also decreased H1R gene expression and down-regulated H1R mRNA below basal expression, while basal H1R mRNA expression was maintained after oxatomide treatment. These results suggest that inverse agonists more potently alleviate allergy symptoms by not only inhibiting stimulus-induced up-regulation of H1R gene expression but also by suppressing basal histamine signaling through their inverse agonistic activity.

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

    PubMed Central

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

    2013-01-01

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

  16. Antiallodynic effects of intrathecally administered 5-HT(2C) receptor agonists in rats with nerve injury.

    PubMed

    Obata, Hideaki; Saito, Shigeru; Sakurazawa, Shinobu; Sasaki, Masayuki; Usui, Tadashi; Goto, Fumio

    2004-03-01

    Intrathecal administration of serotonin type 2 (5-HT(2)) receptor agonists, alpha-methyl-5-hydroxytryptamine maleate (alpha-m-5-HT) or (+/-)-1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane hydrochloride (DOI), produces antiallodynic effects in a rat model of neuropathic pain. In the present study, we examined the antiallodynic effects of intrathecally administered agents which are selective for 5-HT(2C) receptors. Allodynia was produced by tight ligation of the left L5 and L6 spinal nerves, and was measured by applying von Frey filaments to the left hindpaw. Administration of the 5-HT(2C) receptor agonist, 6-chloro-2-(1-piperazinyl)-pyrazine (MK212; 3-100 microg), 1-(m-chlorophenyl)-piperazine (mCPP; 30-300 microg), or 1-(m-trifluoromethylphenyl)-piperazine (TFMPP; 30-300 microg), produced antiallodynic effects in a dose-dependent manner with no associated motor weakness. The ED(50) values of MK212, mCPP, and TFMPP were 39.2, 119.9, and 191.9 microg, respectively. Intrathecal pretreatment with the selective 5-HT(2C) receptor antagonist RS-102221 (30 microg) diminished the effects of the highest doses of 5-HT(2C) receptor agonists. The preferential 5-HT(2A) receptor antagonist ketanserin (30 microg) did not reverse the effects. In contrast to 5-HT(2C) receptor agonists, the antiallodynic effects of intrathecally administered alpha-m-5-HT (30 microg) and DOI (100 microg) were reversed by ketanserin, but not by RS-102221. These results indicate that 5-HT(2C) receptors have a role in spinal inhibition of neuropathic pain, and the effects produced by intrathecal administration of 5-HT(2C) receptor agonists are mediated by a mechanism different from that of alpha-m-5-HT or DOI, which seem to produce their effects through 5-HT(2A) receptors.

  17. Effects of glucagon-like peptide-1 receptor agonists on renal function.

    PubMed

    Filippatos, Theodosios D; Elisaf, Moses S

    2013-10-15

    Glucagon-like peptide-1 (GLP-1) receptor agonists result in greater improvements in glycemic control than placebo and promote weight loss with minimal hypoglycemia in patients with type 2 diabetes mellitus. A number of case reports show an association of GLP-1 receptor agonists, mainly exenatide, with the development of acute kidney injury. The present review aims to present the available data regarding the effects of GLP-1 receptor agonists on renal function, their use in subjects with chronic renal failure and their possible association with acute kidney injury. Based on the current evidence, exenatide is eliminated by renal mechanisms and should not be given in patients with severe renal impairment or end stage renal disease. Liraglutide is not eliminated by renal or hepatic mechanisms, but it should be used with caution since there are only limited data in patients with renal or hepatic impairment. There is evidence from animal studies that GLP-1 receptor agonists exert protective role in diabetic nephropathy with mechanisms that seem to be independent of their glucose-lowering effect. Additionally, there is evidence that GLP-1 receptor agonists influence water and electrolyte balance. These effects may represent new ways to improve or even prevent diabetic nephropathy.

  18. Efficacy of Full µ-Opioid Receptor Agonists is not Impaired by Concomitant Buprenorphine or Mixed Opioid Agonists/Antagonists - Preclinical and Clinical Evidence.

    PubMed

    van Niel, J C G; Schneider, J; Tzschentke, T M

    2016-11-01

    Buprenorphine and the mixed agonists/antagonists nalbuphine and pentazocine, formerly classified as µ-opioid (MOP) receptor antagonists, have more recently been shown to be partial to full agonists of the human MOP receptor. These receptors do not necessarily have to be maximally activated for a full physiological response. Partial agonists can also sufficiently stimulate signaling processes leading to a full analgesic response, as shown by the effectiveness of buprenorphine, nalbuphine and pentazocine in animal pain models and in clinical settings where these drugs induce analgesia with full efficacy without a ceiling effect. Submaximal doses of MOP receptor analgesics combined with submaximal doses of buprenorphine, pentazocine, or nalbuphine result in additive to over-additive antinociceptive effects in animal experiments. Only when doses are given that exceed the therapeutic dose range may the antinociceptive effect be reduced to the effect of either opioid alone. The analgesic effects of pentazocine and nalbuphine combined with morphine are reported to be additive or over-additive in various clinical pain conditions. Buprenorphine, which clinically behaves as a full MOP receptor agonist for pain relief, can be combined with full opioid agonists without precipitating withdrawal. Thus, the overall evidence on the analgesic effects of buprenorphine, pentazocine or nalbuphine combined with opioid analgesics under various clinical pain conditions contradicts the consensus that these compounds diminish MOP receptor analgesia when co-administered with a full MOP receptor agonist. © Georg Thieme Verlag KG Stuttgart · New York.

  19. Treatment potential of the GLP-1 receptor agonists in type 2 diabetes mellitus: a review.

    PubMed

    Østergaard, L; Frandsen, Christian S; Madsbad, S

    2016-01-01

    Over the last decade, the discovery of glucagon-like peptide 1 receptor agonists (GLP-1 RAs) has increased the treatment options for patients with type 2 diabetes mellitus (T2DM). GLP-1 RAs mimic the effects of native GLP-1, which increases insulin secretion, inhibits glucagon secretion, increases satiety and slows gastric emptying. This review evaluates the phase III trials for all approved GLP-1 RAs and reports that all GLP-1 RAs decrease HbA1c, fasting plasma glucose, and lead to a reduction in body weight in the majority of trials. The most common adverse events are nausea and other gastrointestinal discomfort, while hypoglycaemia is rarely reported when GLP-1 RAs not are combined with sulfonylurea or insulin. Treatment options in the near future will include co-formulations of basal insulin and a GLP-1 RA.

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

    PubMed Central

    Zhang, Rumin; Kavana, Michael

    2016-01-01

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

  1. Novel Aryl Hydrocarbon Receptor Agonist Suppresses Migration and Invasion of Breast Cancer Cells

    PubMed Central

    Mohafez, Omar; Hairul-Islam, Villianur Ibrahim; Alzahrani, Abdullah; Bani Ismail, Mohammad; Thirugnanasambantham, Krishnaraj

    2016-01-01

    Background Despite the remarkable progress to fight against breast cancer, metastasis remains the dominant cause of treatment failure and recurrence. Therefore, control of invasiveness potential of breast cancer cells is crucial. Accumulating evidences suggest Aryl hydrocarbon receptor (Ahr), a helix-loop-helix transcription factor, as a promising target to control migration and invasion in breast cancer cells. Thus, an Ahr-based exploration was performed to identify a new Ahr agonist with inhibitory potentials on cancer cell motility. Methods For prediction of potential interactions between Ahr and candidate molecules, bioinformatics analysis was carried out. The interaction of the selected ligand with Ahr and its effects on migration and invasion were examined in vitro using the MDA-MB-231 and T47D cell lines. The silencing RNAs were transfected into cells by electroporation. Expressions of microRNAs (miRNAs) and coding genes were quantified by real-time PCR, and the protein levels were detected by western blot. Results The in silico and in vitro results identified Flavipin as a novel Ahr agonist. It induces formation of Ahr/Ahr nuclear translocator (Arnt) heterodimer to promote the expression of cytochrome P450 family 1 subfamily A member 1 (Cyp1a1). Migration and invasion of MDA-MB-231 and T47D cells were inhibited with Flavipin treatment in an Ahr-dependent fashion. Interestingly, Flavipin suppressed the pro-metastatic factor SRY-related HMG-box4 (Sox4) by inducing miR-212/132 cluster. Moreover, Flavipin inhibited growth and adhesion of both cell lines by suppressing gene expressions of B-cell lymphoma 2 (Bcl2) and integrinα4 (ITGA4). Conclusion Taken together, the results introduce Flavipin as a novel Ahr agonist, and provide first evidences on its inhibitory effects on cancer cell motility, suggesting Flavipin as a candidate to control cell invasiveness in breast cancer patients. PMID:27907195

  2. Novel Aryl Hydrocarbon Receptor Agonist Suppresses Migration and Invasion of Breast Cancer Cells.

    PubMed

    Hanieh, Hamza; Mohafez, Omar; Hairul-Islam, Villianur Ibrahim; Alzahrani, Abdullah; Bani Ismail, Mohammad; Thirugnanasambantham, Krishnaraj

    2016-01-01

    Despite the remarkable progress to fight against breast cancer, metastasis remains the dominant cause of treatment failure and recurrence. Therefore, control of invasiveness potential of breast cancer cells is crucial. Accumulating evidences suggest Aryl hydrocarbon receptor (Ahr), a helix-loop-helix transcription factor, as a promising target to control migration and invasion in breast cancer cells. Thus, an Ahr-based exploration was performed to identify a new Ahr agonist with inhibitory potentials on cancer cell motility. For prediction of potential interactions between Ahr and candidate molecules, bioinformatics analysis was carried out. The interaction of the selected ligand with Ahr and its effects on migration and invasion were examined in vitro using the MDA-MB-231 and T47D cell lines. The silencing RNAs were transfected into cells by electroporation. Expressions of microRNAs (miRNAs) and coding genes were quantified by real-time PCR, and the protein levels were detected by western blot. The in silico and in vitro results identified Flavipin as a novel Ahr agonist. It induces formation of Ahr/Ahr nuclear translocator (Arnt) heterodimer to promote the expression of cytochrome P450 family 1 subfamily A member 1 (Cyp1a1). Migration and invasion of MDA-MB-231 and T47D cells were inhibited with Flavipin treatment in an Ahr-dependent fashion. Interestingly, Flavipin suppressed the pro-metastatic factor SRY-related HMG-box4 (Sox4) by inducing miR-212/132 cluster. Moreover, Flavipin inhibited growth and adhesion of both cell lines by suppressing gene expressions of B-cell lymphoma 2 (Bcl2) and integrinα4 (ITGA4). Taken together, the results introduce Flavipin as a novel Ahr agonist, and provide first evidences on its inhibitory effects on cancer cell motility, suggesting Flavipin as a candidate to control cell invasiveness in breast cancer patients.

  3. Nociceptin/Orphanin FQ Receptor Activation Attenuates Antinociception Induced by Mixed Nociceptin/Orphanin FQ/μ-Opioid Receptor Agonists

    PubMed Central

    Khroyan, Taline V.; Polgar, Willma E.; Jiang, Faming; Zaveri, Nurulain T.

    2009-01-01

    Activation of brain nociceptin/orphanin FQ (NOP) receptors leads to attenuation of μ-opioid receptor (MOP receptor)-mediated antinociception. Buprenorphine, a high-affinity partial MOP receptor agonist also binds to NOP receptors with 80 nM affinity. The buprenorphine-induced inverted U-shaped dose-response curve for antinociception may be due to NOP receptor activation, given that, in the presence of the NOP receptor antagonist, 1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one (J113397), or in NOP receptor knockout mice, buprenorphine has a steeper dose-response curve and acts as a full agonist. To further explore the involvement of the direct activation of NOP receptors by buprenorphine and other compounds that activate both NOP and MOP receptors, the antinociceptive effects of 1-(1-(2,3,3α,4,5,6-hexahydro-1H-phenalen-1-yl)piperidin-4-yl)-indolin-2-one. (SR16435), 3-ethyl-1-(1-(4-isopropylcyclohexyl)piperidin-4-yl)-indolin-2-one (SR16507), buprenorphine, pentazocine, and morphine, compounds with varying levels of MOP and NOP receptor affinity and efficacy, were assessed in mice using the tail-flick assay. The ability of the selective NOP receptor antagonist (−)-cis-1-methyl-7-[[4-(2,6-dichlorophenyl)piperidin-1-yl]methyl]-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol (SB-612111) to potentiate antinociception induced by the above compounds was examined to investigate whether activation of NOP receptors leads to attenuation of MOP receptor-mediated antinociception. SB-612111 potentiated antinociception induced by buprenorphine and the other mixed NOP/MOP receptor agonists SR16435 and SR16507. However, SB-612111 had no effect on pentazocine or morphine antinociception, two compounds with no NOP receptor-binding affinity. These results further support the hypothesis that activation of NOP receptors can lead to attenuation of MOP receptor-mediated antinociception elicited by mixed NOP/MOP receptor compounds such as

  4. 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. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. C-nucleoside analogues of furanfurin as ligands to A1 adenosine receptors.

    PubMed

    Franchetti, P; Cappellacci, L; Marchetti, S; Martini, C; Costa, B; Varani, K; Borea, P A; Grifantini, M

    2000-09-01

    Furanfurin (2-beta-D-ribofuranosylfuran-4-carboxamide) derivatives and analogues were synthesized and their affinity for adenosine receptors was determined. The agonistic behavior of furanfurin against A1 receptors is preserved only when the furan ring is substituted with isosteric pentatomic ring systems such as oxazole, thiazole or thiophene, and the carboxamide group is unsubstituted. Replacement of the hydrogen atoms of the carboxamide group with alkyl, cycloalkyl or arylalkyl groups generates compounds endowed with moderate antagonistic activity.

  6. Regulation of ventilation and oxygen consumption by delta- and mu-opioid receptor agonists.

    PubMed

    Schaeffer, J I; Haddad, G G

    1985-09-01

    To study the effect of endorphins on metabolic rate and on the relationship between O2 consumption (VO2) and ventilation, we administered enkephalin analogues (relatively selective delta-receptor agonists) and a morphiceptin analogue (a highly selective mu-receptor agonist) intracisternally in nine unanesthetized chronically instrumented adult dogs. Both delta- and mu-agonists decreased VO2 by 40-60%. delta-Agonists induced a dose-dependent decrease in mean instantaneous minute ventilation (VT/TT) associated with periodic breathing. The decrease in VT/TT started and resolved prior to the decrease and returned to baseline of VO2, respectively. In contrast, the mu-agonists induced an increase in VT/TT associated with rapid shallow breathing. Arterial PCO2 increased and arterial PO2 decreased after both delta- and mu-agonists. Low doses of intracisternal naloxone (0.002-2.0 micrograms/kg) reversed the opioid effect on VT/TT but not on VO2; higher doses of naloxone (5-25 micrograms/kg) reversed both. Naloxone administered alone had no effect on VT/TT or VO2. These data suggest that 1) both delta- and mu-agonists induce alveolar hypoventilation despite a decrease in VO2, 2) this hypoventilation results from a decrease in VT/TT after delta-agonists but an increase in dead space ventilation after mu-agonists, and 3) endorphins do not modulate ventilation and metabolic rate tonically, but we speculate that they may do so in response to stressful stimulation.

  7. Reports of pathological gambling, hypersexuality, and compulsive shopping associated with dopamine receptor agonist drugs.

    PubMed

    Moore, Thomas J; Glenmullen, Joseph; Mattison, Donald R

    2014-12-01

    Severe impulse control disorders involving pathological gambling, hypersexuality, and compulsive shopping have been reported in association with the use of dopamine receptor agonist drugs in case series and retrospective patient surveys. These agents are used to treat Parkinson disease, restless leg syndrome, and hyperprolactinemia. To analyze serious adverse drug event reports about these impulse control disorders received by the US Food and Drug Administration (FDA) and to assess the relationship of these case reports with the 6 FDA-approved dopamine receptor agonist drugs. We conducted a retrospective disproportionality analysis based on the 2.7 million serious domestic and foreign adverse drug event reports from 2003 to 2012 extracted from the FDA Adverse Event Reporting System. Cases were selected if they contained any of 10 preferred terms in the Medical Dictionary for Regulatory Activities (MedDRA) that described the abnormal behaviors. We used the proportional reporting ratio (PRR) to compare the proportion of target events to all serious events for the study drugs with a similar proportion for all other drugs. We identified 1580 events indicating impulse control disorders from the United States and 21 other countries:710 fordopamine receptor agonist drugs and 870 for other drugs. The dopamine receptor agonist drugs had a strong signal associated with these impulse control disorders (n = 710; PRR = 277.6, P < .001). The association was strongest for the dopamine agonists pramipexole (n = 410; PRR = 455.9, P < .001) and ropinirole (n = 188; PRR = 152.5, P < .001), with preferential affinity for the dopamine D3 receptor. A signal was also seen for aripiprazole, an antipsychotic classified as a partial agonist of the D3 receptor (n = 37; PRR = 8.6, P < .001). Our findings confirm and extend the evidence that dopamine receptor agonist drugs are associated with these specific impulse control disorders. At present

  8. Effect of Light and Melatonin and other Melatonin Receptor Agonists on Human Circadian Physiology

    PubMed Central

    Emens, Jonathan S.

    2015-01-01

    Synopsis Circadian (body clock) timing has a profound influence on mental health, physical health, and health behaviors. This review focuses on how light, melatonin and other melatonin receptor agonist drugs can be used to shift circadian timing in patients with misaligned circadian rhythms. A brief overview of the human circadian system is provided, followed by a discussion of patient characteristics and safety considerations that can influence the treatment of choice. The important features of light treatment, light avoidance, exogenous melatonin and other melatonin receptor agonists are reviewed, along with some of the practical aspects of light and melatonin treatment. PMID:26568121

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

    PubMed Central

    Farroni, Jeffrey S; McCool, Brian A

    2004-01-01

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

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

    SciTech Connect

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

    1987-05-19

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

  11. Agonist activation of α7 nicotinic acetylcholine receptors via an allosteric transmembrane site

    PubMed Central

    Gill, JasKiran K.; Savolainen, Mari; Young, Gareth T.; Zwart, Ruud; Sher, Emanuele; Millar, Neil S.

    2011-01-01

    Conventional nicotinic acetylcholine receptor (nAChR) agonists, such as acetylcholine, act at an extracellular “orthosteric” binding site located at the interface between two adjacent subunits. Here, we present evidence of potent activation of α7 nAChRs via an allosteric transmembrane site. Previous studies have identified a series of nAChR-positive allosteric modulators (PAMs) that lack agonist activity but are able to potentiate responses to orthosteric agonists, such as acetylcholine. It has been shown, for example, that TQS acts as a conventional α7 nAChR PAM. In contrast, we have found that a compound with close chemical similarity to TQS (4BP-TQS) is a potent allosteric agonist of α7 nAChRs. Whereas the α7 nAChR antagonist metyllycaconitine acts competitively with conventional nicotinic agonists, metyllycaconitine is a noncompetitive antagonist of 4BP-TQS. Mutation of an amino acid (M253L), located in a transmembrane cavity that has been proposed as being the binding site for PAMs, completely blocks agonist activation by 4BP-TQS. In contrast, this mutation had no significant effect on agonist activation by acetylcholine. Conversely, mutation of an amino acid located within the known orthosteric binding site (W148F) has a profound effect on agonist potency of acetylcholine (resulting in a shift of ∼200-fold in the acetylcholine dose-response curve), but had little effect on the agonist dose-response curve for 4BP-TQS. Computer docking studies with an α7 homology model provides evidence that both TQS and 4BP-TQS bind within an intrasubunit transmembrane cavity. Taken together, these findings provide evidence that agonist activation of nAChRs can occur via an allosteric transmembrane site. PMID:21436053

  12. Bile acid receptor agonist GW4064 regulates PPARγ coactivator-1α expression through estrogen receptor-related receptor α.

    PubMed

    Dwivedi, Shailendra Kumar Dhar; Singh, Nidhi; Kumari, Rashmi; Mishra, Jay Sharan; Tripathi, Sarita; Banerjee, Priyam; Shah, Priyanka; Kukshal, Vandana; Tyagi, Abdul Malik; Gaikwad, Anil Nilkanth; Chaturvedi, Rajnish Kumar; Mishra, Durga Prasad; Trivedi, Arun Kumar; Sanyal, Somali; Chattopadhyay, Naibedya; Ramachandran, Ravishankar; Siddiqi, Mohammad Imran; Bandyopadhyay, Arun; Arora, Ashish; Lundåsen, Thomas; Anakk, Sayee Priyadarshini; Moore, David D; Sanyal, Sabyasachi

    2011-06-01

    Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) is induced in energy-starved conditions and is a key regulator of energy homeostasis. This makes PGC-1α an attractive therapeutic target for metabolic syndrome and diabetes. In our effort to identify new regulators of PGC-1α expression, we found that GW4064, a widely used synthetic agonist for the nuclear bile acid receptor [farnesoid X receptor (FXR)] strongly enhances PGC-1α promoter reporter activity, mRNA, and protein expression. This induction in PGC-1α concomitantly enhances mitochondrial mass and expression of several PGC-1α target genes involved in mitochondrial function. Using FXR-rich or FXR-nonexpressing cell lines and tissues, we found that this effect of GW4064 is not mediated directly by FXR but occurs via activation of estrogen receptor-related receptor α (ERRα). Cell-based, biochemical and biophysical assays indicate GW4064 as an agonist of ERR proteins. Interestingly, FXR disruption alters GW4064 induction of PGC-1α mRNA in a tissue-dependent manner. Using FXR-null [FXR knockout (FXRKO)] mice, we determined that GW4064 induction of PGC-1α expression is not affected in oxidative soleus muscles of FXRKO mice but is compromised in the FXRKO liver. Mechanistic studies to explain these differences revealed that FXR physically interacts with ERR and protects them from repression by the atypical corepressor, small heterodimer partner in liver. Together, this interplay between ERRα-FXR-PGC-1α and small heterodimer partner offers new insights into the biological functions of ERRα and FXR, thus providing a knowledge base for therapeutics in energy balance-related pathophysiology.

  13. Effects of cannabinoid and vanilloid receptor agonists and their interaction on learning and memory in rats.

    PubMed

    Shiri, Mariam; Komaki, Alireza; Oryan, Shahrbanoo; Taheri, Masoumeh; Komaki, Hamidreza; Etaee, Farshid

    2017-04-01

    Despite previous findings on the effects of cannabinoid and vanilloid systems on learning and memory, the effects of the combined stimulation of these 2 systems on learning and memory have not been studied. Therefore, in this study, we tested the interactive effects of cannabinoid and vanilloid systems on learning and memory in rats by using passive avoidance learning (PAL) tests. Forty male Wistar rats were divided into the following 4 groups: (1) control (DMSO+saline), (2) WIN55,212-2, (3) capsaicin, and (4) WIN55,212-2 + capsaicin. On test day, capsaicin, a vanilloid receptor type 1 (TRPV1) agonist, or WIN55,212-2, a cannabinoid receptor (CB 1 /CB 2 ) agonist, or both substances were injected intraperitoneally. Compared to the control group, the group treated with capsaicin (TRPV1 agonist) had better scores in the PAL acquisition and retention test, whereas treatment with WIN55,212-2 (CB 1 /CB 2 agonist) decreased the test scores. Capsaicin partly reduced the effects of WIN55,212-2 on PAL and memory. We conclude that the acute administration of a TRPV1 agonist improves the rats' cognitive performance in PAL tasks and that a vanilloid-related mechanism may underlie the agonistic effect of WIN55,212-2 on learning and memory.

  14. Design and synthesis of small molecule agonists of EphA2 receptor.

    PubMed

    Petty, Aaron; Idippily, Nethrie; Bobba, Viharika; Geldenhuys, Werner J; Zhong, Bo; Su, Bin; Wang, Bingcheng

    2018-01-01

    Ligand-independent activation of EphA2 receptor kinase promotes cancer metastasis and invasion. Activating EphA2 receptor tyrosine kinase with small molecule agonist is a novel strategy to treat EphA2 overexpressing cancer. In this study, we performed a lead optimization of a small molecule Doxazosin that was identified as an EphA2 receptor agonist. 33 new analogs were developed and evaluated; a structure-activity relationship was summarized based on the EphA2 activation of these derivatives. Two new derivative compounds 24 and 27 showed much improved activity compared to Doxazosin. Compound 24 possesses a bulky amide moiety, and compound 27 has a dimeric structure that is very different to the parental compound. Compound 27 with a twelve-carbon linker of the dimer activated the kinase and induced receptor internalization and cell death with the best potency. Another dimer with a six-carbon linker has significantly reduced potency compared to the dimer with a longer linker, suggesting that the length of the linker is critical for the activity of the dimeric agonist. To explore the receptor binding characteristics of the new molecules, we applied a docking study to examine how the small molecule binds to the EphA2 receptor. The results reveal that compounds 24 and 27 form more hydrogen bonds to EphA2 than Doxazosin, suggesting that they may have higher binding affinity to the receptor. Published by Elsevier Masson SAS.

  15. Differential agonist sensitivity of glycine receptor α2 subunit splice variants

    PubMed Central

    Miller, Paul S; Harvey, Robert J; Smart, Trevor G

    2004-01-01

    The glycine receptor (GlyR) α2A and α2B splice variants differ by a dual, adjacent amino acid substitution from α2AV58,T59 to α2BI58,A59 in the N-terminal extracellular domain. Comparing the effects of the GlyR agonists, glycine, β-alanine and taurine, on the GlyR α2 isoforms, revealed a significant increase in potency for all three agonists at the α2B variant. The sensitivities of the splice variants to the competitive antagonist, strychnine, and to the biphasic modulator Zn2+, were comparable. In contrast, the allosteric inhibitor picrotoxin was more potent on GlyR α2A compared to GlyR α2B receptors. Coexpression of α2A or α2B subunits with the GlyR β subunit revealed that the higher agonist potencies observed with the α2B homomer were retained for the α2Bβ heteromer. The identical sensitivity to strychnine combined with a reduction in the maximum current induced by the partial agonist taurine at the GlyR α2A homomer, suggested that the changed sensitivity to agonists is in accordance with a modulation of agonist efficacy rather than agonist affinity. An effect on agonist efficacy was also supported by using a structural model of the GlyR, localising the region of splice variation to the proposed docking region between GlyR loop 2 and the TM2-3 loop, an area associated with channel activation. The existence of a spasmodic mouse phenotype linked to a GlyR α1A52S mutation, the equivalent position to the source of the α2 splice variation, raises the possibility that the GlyR α2 splice variants may be responsible for distinct roles in neuronal function. PMID:15302677

  16. N-desmethylclozapine, an allosteric agonist at muscarinic 1 receptor, potentiates N-methyl-d-aspartate receptor activity

    PubMed Central

    Sur, Cyrille; Mallorga, Pierre J.; Wittmann, Marion; Jacobson, Marlene A.; Pascarella, Danette; Williams, Jacinta B.; Brandish, Philip E.; Pettibone, Douglas J.; Scolnick, Edward M.; Conn, P. Jeffrey

    2003-01-01

    The molecular and neuronal substrates conferring on clozapine its unique and superior efficacy in the treatment of schizophrenia remain elusive. The interaction of clozapine with many G protein-coupled receptors is well documented but less is known about its biologically active metabolite, N-desmethylclozapine. Recent clinical and preclinical evidences of the antipsychotic activity of the muscarinic agonist xanomeline prompted us to investigate the effects of N-desmethylclozapine on cloned human M1-M5 muscarinic receptors. N-desmethylclozapine preferentially bound to M1 muscarinic receptors with an IC50 of 55 nM and was a more potent partial agonist (EC50, 115 nM and 50% of acetylcholine response) at this receptor than clozapine. Furthermore, pharmacological and site-directed mutagenesis studies suggested that N-desmethylclozapine preferentially activated M1 receptors by interacting with a site that does not fully overlap with the acetylcholine orthosteric site. As hypofunction of N-methyl-d-aspartate (NMDA) receptor-driven neuronal ensembles has been implicated in psychotic disorders, the neuronal activity of N-desmethylclozapine was electrophysiologically investigated in hippocampal rat brain slices. N-desmethylclozapine was shown to dose-dependently potentiate NMDA receptor currents in CA1 pyramidal cells by 53% at 100 nM, an effect largely mediated by activation of muscarinic receptors. Altogether, our observations provide direct evidence that the brain penetrant metabolite N-desmethylclozapine is a potent, allosteric agonist at human M1 receptors and is able to potentiate hippocampal NMDA receptor currents through M1 receptor activation. These observations raise the possibility that N-desmethylclozapine contributes to clozapine's clinical activity in schizophrenics through modulation of both muscarinic and glutamatergic neurotransmission. PMID:14595031

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

    SciTech Connect

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

    1988-01-12

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

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

    PubMed

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

    2015-11-15

    Opioids are the most effective and widely used drugs for pain treatment. Morphine is an archetypal opioid and is an opioid receptor agonist. Unfortunately, the clinical usefulness of morphine is limited by adverse effects such as analgesic tolerance and addiction. Therefore, it is important to study the development of novel opioid agonists as part of pain control. The analgesic effects of opioids are mediated by three opioid receptors, namely opioid μ-, δ-, and κ-receptors. They belong to the G protein-coupled receptor superfamily and are coupled to Gi proteins. In the present study, we developed a ligand screening system to identify novel opioid μ-receptor agonists that measures [(35)S]GTPγS binding to cell membrane fractions prepared from the fat body of transgenic silkworms expressing μ-receptor-Gi1α fusion protein. We screened the RIKEN Natural Products Depository (NPDepo) chemical library, which contains 5848 compounds, and analogs of hit compounds. We successfully identified a novel, structurally unique compound, that we named GUM1, with agonist activity for the opioid μ-receptor (EC50 of 1.2 µM). The Plantar Test (Hargreaves' Method) demonstrated that subcutaneous injection of 3mg/kg of GUM1 into wild-type rats significantly extended latency time. This extension was also observed in a rat model of morphine tolerance and was inhibited by pre-treatment of naloxone. The unique molecular skeleton of GUM1 makes it an attractive molecule for further ligand-opioid receptor binding studies. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Sigma-1 Receptor Agonists Directly Inhibit NaV1.2/1.4 Channels

    PubMed Central

    Gao, Xiao-Fei; Yao, Jin-Jing; He, Yan-Lin; Hu, Changlong; Mei, Yan-Ai

    2012-01-01

    (+)-SKF 10047 (N-allyl-normetazocine) is a prototypic and specific sigma-1 receptor agonist that has been used extensively to study the function of sigma-1 receptors. (+)-SKF 10047 inhibits K+, Na+ and Ca2+ channels via sigma-1 receptor activation. We found that (+)-SKF 10047 inhibited NaV1.2 and NaV1.4 channels independently of sigma-1 receptor activation. (+)-SKF 10047 equally inhibited NaV1.2/1.4 channel currents in HEK293T cells with abundant sigma-1 receptor expression and in COS-7 cells, which barely express sigma-1 receptors. The sigma-1 receptor antagonists BD 1063,BD 1047 and NE-100 did not block the inhibitory effects of (+)-SKF-10047. Blocking of the PKA, PKC and G-protein pathways did not affect (+)-SKF 10047 inhibition of NaV1.2 channel currents. The sigma-1 receptor agonists Dextromethorphan (DM) and1,3-di-o-tolyl-guanidine (DTG) also inhibited NaV1.2 currents through a sigma-1 receptor-independent pathway. The (+)-SKF 10047 inhibition of NaV1.2 currents was use- and frequency-dependent. Point mutations demonstrated the importance of Phe1764 and Tyr1771 in the IV-segment 6 domain of the NaV1.2 channel and Phe1579 in the NaV1.4 channel for (+)-SKF 10047 inhibition. In conclusion, our results suggest that sigma-1 receptor agonists directly inhibit NaV1.2/1.4 channels and that these interactions should be given special attention for future sigma-1 receptor function studies. PMID:23139844

  20. CB-Receptor Agonist HU-210 Mimics the Postconditioning Phenomenon of Isolated Heart.

    PubMed

    Gorbunov, A S; Maslov, L N; Tsibulnikov, S Yu; Khaliulin, I G; Tsepokina, A V; Khutornaya, M V; Kutikhin, A G

    2016-11-01

    CB receptor agonist HU-210 exhibits an infarction-limiting effect during in vitro reperfusion of the heart after focal ischemia. This effect is paralleled by a decrease in left-ventricular developed pressure and double product. In addition, HU-210 reduces end-diastolic pressure during the reperfusion period, which indirectly attests to reduced Ca 2+ overload of cardiomyocytes.

  1. [Cardiovascular effects of GLP-1 receptor agonist treatment: focus on liraglutide].

    PubMed

    Haluzík, Martin; Trachta, Pavel; Mráz, Miloš

    2015-01-01

    Cardiovascular risk reduction is the major aim of type 2 diabetes mellitus treatment. The effects of various antidiabetics on the cardiovascular complications are currently under careful scrutiny. Incretin-based therapy that utilizes the effects of glucagon-like peptide 1 (GLP-1) or stimulation of its receptor by GLP-1 receptor agonists represents one of the most promising approaches from the potential cardiovascular risk reduction point of view. Experimental studies have shown that the GLP-1 and GLP-1 agonists treatment improves endothelial function, decrease blood pressure and protects myocardium during experimentally-induced ischemia. Clinical studies with GLP-1 receptor agonists consistently show that, in addition to good antidiabetic efficacy, its long-term administration decreases blood pressure, body weight and improves circulating lipid levels while slightly increasing heart rate. In this paper, we focus on the cardiovascular effects of GLP-1 receptor agonist liraglutide. Preliminary analyses of cardiovascular complications in phase III trials with liraglutide indicate its good cardiovascular safety. A possibility of cardioprotective effects of liraglutide remains still open and is currently studied within a prospective cardiovascular trial LEADER.

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

    USDA-ARS?s Scientific Manuscript database

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

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

    ERIC Educational Resources Information Center

    Segev, Amir; Akirav, Irit

    2011-01-01

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

  4. Dopamine D1 receptor-agonist interactions: A mutagenesis and homology modeling study.

    PubMed

    Mente, Scot; Guilmette, Edward; Salafia, Michelle; Gray, David

    2015-01-01

    The dopamine D1 receptor is a G protein-coupled receptor that regulates intracellular signaling via agonist activation. Although the number of solved GPCR X-ray structures has been steadily increasing, still no structure of the D1 receptor exists. We have used site-directed mutagenesis of 12 orthosteric vicinity residues of possible importance to G protein-coupled activation to examine the function of prototypical orthosteric D1 agonists and partial agonists. We find that residues from four different regions of the D1 receptor make significant contributions to agonist function. All compounds studied, which are catechol-amines, are found to interact with the previously identified residues: the conserved D103(3.32), as well as the trans-membrane V serine residues. Additional key interactions are found for trans-membrane VI residues F288(6.51), F289(6.52) and N292(6.55), as well as the extra-cellular loop residue L190(ECL2). Molecular dynamics simulations of a D1 homology model have been used to help put the ligand-residue interactions into context. Finally, we considered the rescaling of fold-shift data as a method to account for the change in the size of the mutated side-chain and found that this rescaling helps to relate the calculated ligand-residue energies with observed experimental fold-shifts. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Anticonvulsant effect of cannabinoid receptor agonists in models of seizures in developing rats.

    PubMed

    Huizenga, Megan N; Wicker, Evan; Beck, Veronica C; Forcelli, Patrick A

    2017-09-01

    Although drugs targeting the cannabinoid system (e.g., CB1 receptor agonists) display anticonvulsant efficacy in adult animal models of seizures/epilepsy, they remain unexplored in developing animal models. However, cannabinoid system functions emerge early in development, providing a rationale for targeting this system in neonates. We examined the therapeutic potential of drugs targeting the cannabinoid system in three seizure models in developing rats. Postnatal day (P) 10, Sprague-Dawley rat pups were challenged with the chemoconvulsant methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM) or pentylenetetrazole (PTZ), after treatment with either CB1/2 mixed agonist (WIN 55,212-2), CB1 agonist (arachidonyl-2'-chloroethylamide [ACEA]), CB2 agonist (HU-308), CB1 antagonist (AM-251), CB2 antagonist (AM-630), fatty acid amide hydrolase inhibitor (URB-597), or G protein-coupled receptor 55 agonist (O-1602). P20 Sprague-Dawley pups were challenged with DMCM after treatment with WIN, ACEA, or URB. Finally, after pretreatment with WIN, P10 Sprague-Dawley rats were challenged against acute hypoxia-induced seizures. The mixed CB1/2 agonist and the CB1-specific agonist, but no other drugs, displayed anticonvulsant effects against clonic seizures in the DMCM model. By contrast, both CB1 and CB2 antagonism increased seizure severity. Similarly, we found that the CB1/2 agonist displayed antiseizure efficacy against acute hypoxia-induced seizures (automatisms, clonic and tonic-clonic seizures) and tonic-clonic seizures evoked by PTZ. Anticonvulsant effects were seen in P10 animals but not P20 animals. Early life seizures represent a significant cause of morbidity, with 30-40% of infants and children with epilepsy failing to achieve seizure remission with current pharmacotherapy. Identification of new therapies for neonatal/infantile epilepsy syndromes is thus of high priority. These data indicate that the anticonvulsant action of the CB system is specific to CB1

  6. Flavone and isoflavone phytoestrogens are agonists of estrogen-related receptors.

    PubMed

    Suetsugi, Masatomo; Su, Leila; Karlsberg, Kimberly; Yuan, Yate-Ching; Chen, Shiuan

    2003-11-01

    While estrogen-related receptors (ERRalpha, ERRbeta, and ERRgamma) share a high amino acid sequence homology with estrogen receptors (ERs), estrogens are not ligands of ERRs. Structure-function studies from this and other laboratories have revealed that ERRs have small ligand-binding pockets and have provided evidence to show that these receptors can activate gene transcription in a constitutive manner. To address the question as to whether there is any agonist for ERRs, our laboratory recently performed virtual ligand screening on ERRalpha that predicted flavone and isoflavone phytoestrogens to be ligands of this receptor. Our mammalian cell transfection and mammalian two-hybrid experiments revealed that three isoflavones (genistein, daidzein, and biochanin A) and one flavone (6,3',4'-trihydroxyflavone) behaved as agonists of ERRs. These phytoestrogens induced the activity of ERRalpha at concentrations that are comparable to those for the activation of ERalpha and ERbeta. In this study, we also used the results of ERRalpha ligand-binding site mutant, F232A, to verify our ERRalpha hypothetical computer model. Our recent ERR research has determined for the first time that flavone and isoflavone phytoestrogens are agonists of ERRs. In addition, our studies have demonstrated that an approach that combines structure-based virtual screening and receptor functional assays can identify novel ligands of orphan nuclear receptors.

  7. Identification of Benzothiazole Derivatives and Polycyclic Aromatic Hydrocarbons as Aryl Hydrocarbon Receptor Agonists Present in Tire Extracts

    PubMed Central

    He, Guochun; Zhao, Bin; Denison, Michael S.

    2012-01-01

    Leachate from rubber tire material contains a complex mixture of chemicals previously shown to produce toxic and biological effects in aquatic organisms. While the ability of these leachates to induce Ah receptor (AhR)-dependent cytochrome P4501A1 expression in fish indicated the presence of AhR active chemicals, the responsible chemical(s) and their direct interaction with the AhR signaling pathway were not examined. Using a combination of AhR-based bioassays, we have demonstrated the ability of tire extract to stimulate both AhR DNA binding and AhR-dependent gene expression and confirmed that the responsible chemical(s) was metabolically labile. The application of CALUX (Chemical-Activated LUciferase gene eXpression) cell bioassay-driven toxicant identification evaluation not only revealed that tire extract contained a variety of known AhR-active polycyclic aromatic hydrocarbons, but also identified 2-methylthiobenzothiazole and 2-mercaptobenzothiazole as AhR agonists. Analysis of a structurally diverse series of benzothiazoles identified many that could directly stimulate AhR DNA binding and transiently activate the AhR signaling pathway and identified benzothiazoles as a new class of AhR agonists. In addition to these compounds, the relatively high AhR agonist activity of a large number of fractions strongly suggests that tire extract contains a large number of physiochemically diverse AhR agonists whose identities and toxicological/biological significances are unknown. PMID:21590714

  8. 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

  9. Agonist-selective endocytosis of mu opioid receptor by neurons in vivo.

    PubMed Central

    Sternini, C; Spann, M; Anton, B; Keith, D E; Bunnett, N W; von Zastrow, M; Evans, C; Brecha, N C

    1996-01-01

    Opiate alkaloids are potent analgesics that exert multiple pharmacological effects in the nervous system by activating G protein-coupled receptors. Receptor internalization upon stimulation may be important for desensitization and resensitization, which affect cellular responsiveness to ligands. Here, we investigated the agonist-induced internalization of the mu opioid receptor (MOR) in vivo by using the guinea pig ileum as a model system and immunohistochemistry with an affinity-purified antibody to the C terminus of rat MOR. Antibody specificity was confirmed by the positive staining of human embryonic kidney 293 cells transfected with epitope-tagged MOR cDNA, by the lack of staining of cells transfected with the delta or kappa receptor cDNA, and by the abolition of staining when the MOR antibody was preadsorbed with the MOR peptide fragment. Abundant MOR immunoreactivity (MOR-IR) was localized to the cell body, dendrites, and axonal processes of myenteric neurons. Immunostaining was primarily confined to the plasma membrane of cell bodies and processes. Within 15 min of an intraperitoneal injection of the opiate agonist etorphine, intense MOR-IR was present in vesicle-like structures, which were identified as endosomes by confocal microscopy. At 30 min, MOR-IR was throughout the cytoplasm and in perinuclear vesicles. MOR-IR was still internalized at 120 min. Agonist-induced endocytosis was completely inhibited by the opiate antagonist naloxone. Interestingly, morphine, a high-affinity MOR agonist, did not cause detectable internalization, but it partially inhibited the etorphine-induced MOR endocytosis. These results demonstrate the occurrence of agonist-selective MOR endocytosis in neurons naturally expressing this receptor in vivo and suggest the existence of different mechanisms regulating cellular responsiveness to ligands. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:8799185

  10. Estrogen or estrogen receptor agonist inhibits lipopolysaccharide induced microglial activation and death.

    PubMed

    Smith, Joshua A; Das, Arabinda; Butler, Jonathan T; Ray, Swapan K; Banik, Naren L

    2011-09-01

    Inflammation is an important pathogenic mechanism in many neurodegenerative disorders. Activated microglia play a pivotal role in releasing pro-inflammatory factors including interleukin-1 (IL-1), tumor necrosis factor-α (TNF-α), and cyclooxygenase-2 (COX-2) for inducing inflammation. While microglia mediated inflammation is essential in maintaining CNS homeostasis, chronic inflammation results in activation of proteases for cell death. Here, we examined the effect of PPT (estrogen receptor α agonist), DPN (estrogen receptor β agonist), and estrogen on rat primary microglia following exposure to lipopolysaccharide (LPS). Exposure of microglia to LPS (200 ng/ml) for 24 h induced cell death. After LPS toxicity for 15 min, microglia were treated with 25 nM PPT, 25 nM DPN, or 100 nM estrogen that prevented cell death by attenuating the release of IL-1α, IL-1β, TNF-α, and COX-2. Treatment of cells with 100 nM fulvestrant (estrogen receptor antagonist) prior to addition of PPT, DPN, or estrogen significantly decreased their ability to prevent cell death, indicating involvement of estrogen receptor (ER) in providing PPT, DPN, or estrogen mediated cytoprotection. Reverse transcriptase polymerase chain reaction (RT-PCR) analyses showed alterations in mRNA expression of Bax, Bcl-2, calpain, and calpastatin during apoptosis. We also examined mRNA expression of ERβ and ERα following exposure of microglia to LPS and subsequent treatment with PPT, DPN, or estrogen. We found that estrogen or estrogen receptor agonists upregulated expression of ERs. Overall, results indicate that estrogen receptor agonist or estrogen uses a receptor mediated pathway to protect microglia from LPS toxicity.

  11. Evaluation of the Selective Glucocorticoid Receptor Agonist Compound A for Ototoxic Effects

    PubMed Central

    Honeder, Clemens; Engleder, Elisabeth; Schöpper, Hanna; Krause, Markus; Landegger, Lukas David; Plasenzotti, Roberto; Gabor, Franz; Gstoettner, Wolfgang; Arnoldner, Christoph

    2016-01-01

    Objective To evaluate the selective glucocorticoid receptor agonist (SEGRA) compound A, a potential novel therapeutic for inner ear disorders, for ototoxic effects. Study Design Laboratory animal study Methods Experimental guinea pigs were grouped as follows: 1 & 2) systemic application of compound A (1.5 mg/kg and 4.5 mg/kg; n=6/group); 3 & 4) intratympanic application of compound A (1 mM and 10 mM; n=6/group). Contralateral ears in topically treated animals served as controls. Hearing thresholds were determined by ABR before and directly after the application of compound A, as well as on days three, seven, 14, 21 and 28. At the end of the experiments temporal bones were harvested for histological evaluation. Results Systemic administration of compound A (1.5 mg/kg & 4.5 mg/kg) did not cause hearing threshold shifts, whereas the intratympanic injection (1 mM & 10 mM) resulted in a hearing loss. Histological analysis of the middle and inner ears after topical compound A application showed alterations in the tympanic membranes, the auditory ossicles and the round window membranes, whilst spiral ganglion cells and hair cells were not affected. Conclusion SEGRAs like compound A could provide novel therapeutic options with reduced metabolic side-effects for the treatment of inner ear disorders. Whereas intratympanic application of compound A resulted in hearing loss, the systemic application of compound A merits evaluation for otoprotective effects in trauma models. PMID:25382757

  12. Bio-analytical and chemical characterisation of offshore produced water effluents for estrogen receptor (ER) agonists.

    PubMed

    Thomas, Kevin V; Balaam, Jan; Hurst, Mark R; Thain, John E

    2004-07-01

    The in vitro estrogen receptor (ER) agonist potency and C1 to C9 alkyl substituted phenol content of offshore produced water effluents collected from the UK sector of the North Sea were determined using a combination of bio-analytical and chemical analysis techniques. An in vitro reporter gene assay was used to determine ER agonist potency, whilst gas chromatography coupled to mass spectrometry (GC-MS) was used to quantify the concentration of alkylphenols. The in vitro ER agonist potency was highly variable and ranged from less than the limit of detection (theoretically 0.03 ng 17beta-estradiol (E2) l(-1)) to 91 ng E2 l(-1). C1 to C5 alkylphenol concentrations were also highly variable ranging from 5 to 1600 microg l(-1) with a median concentration of 206 microg l(-1). These data reflect the highly variable composition of produced water discharges from different fields. The observed poor correlation of the alkylphenol isomer content and ER agonist activity suggests that other compounds present in the produced water discharges may be responsible for the ER agonist activity observed. It is recommended that further work be performed to characterise the full range of ER agonists present in offshore produced water discharges.

  13. Human pregnane X receptor antagonists and agonists define molecular requirements for different binding sites.

    PubMed

    Ekins, Sean; Chang, Cheng; Mani, Sridhar; Krasowski, Matthew D; Reschly, Erica J; Iyer, Manisha; Kholodovych, Vladyslav; Ai, Ni; Welsh, William J; Sinz, Michael; Swaan, Peter W; Patel, Rachana; Bachmann, Kenneth

    2007-09-01

    The pregnane X receptor (PXR) is an important transcriptional regulator of the expression of xenobiotic metabolism and transporter genes. The receptor is promiscuous, binding many structural classes of molecules that act as agonists at the ligand-binding domain, triggering up-regulation of genes, increasing the metabolism and excretion of therapeutic agents, and causing drug-drug interactions. It has been suggested that human PXR antagonists represent a means to counteract such interactions. Several azoles have been hypothesized to bind the activation function-2 (AF-2) surface on the exterior of PXR when agonists are concurrently bound in the ligand-binding domain. In the present study, we have derived novel computational models for PXR agonists using different series of imidazoles, steroids, and a set of diverse molecules with experimental PXR agonist binding data. We have additionally defined a novel pharmacophore for the steroidal agonist site. All agonist pharmacophores showed that hydrophobic features are predominant. In contrast, a qualitative comparison with the corresponding PXR antagonist pharmacophore models using azoles and biphenyls showed that they are smaller and hydrophobic with increased emphasis on hydrogen bonding features. Azole antagonists were docked into a proposed hydrophobic binding pocket on the outer surface at the AF-2 site and fitted comfortably, making interactions with key amino acids involved in charge clamping. Combining computational and experimental data for different classes of molecules provided strong evidence for agonists and antagonists binding distinct regions on PXR. These observations bear significant implications for future discovery of molecules that are more selective and potent antagonists.

  14. Therapeutic utility of natural estrogen receptor beta agonists on ovarian cancer

    PubMed Central

    Liu, Jinyou; Viswanadhapalli, Suryavathi; Garcia, Lauren; Zhou, Mei; Nair, Binoj C.; Kost, Edward; Tekmal, Rajeshwar Rao; Li, Rong; Rao, Manjeet K.; Curiel, Tyler; Vadlamudi, Ratna K.; Sareddy, Gangadhara R.

    2017-01-01

    Ovarian cancer is the deadliest of all gynecologic cancers. Despite success with initial chemotherapy, the majority of patients relapse with an incurable disease. Development of chemotherapy resistance is a major factor for poor long-term survival in ovarian cancer. The biological effects of estrogens are mediated by estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ). Emerging evidence suggests that ovarian cancer cells express ERβ that functions as a tumor suppressor; however, the clinical utility of ERβ agonists in ovarian cancer remains elusive. We tested the utility of two natural ERβ agonists liquiritigenin (Liq), which is isolated from Glycyrrhiza uralensis and S-equol, which is isolated from soy isoflavone daidzein, for treating ovarian cancer. Both natural ERβ ligands had significant growth inhibition in cell viability and survival assays, reduced migration and invasion, and promoted apoptosis. Further, ERβ agonists showed tumor suppressive functions in therapy-resistant ovarian cancer model cells and sensitized ovarian cancer cells to cisplatin and paclitaxel treatment. Global RNA-Seq analysis revealed that ERβ agonists modulate several tumor suppressive pathways, including downregulation of the NF-κB pathway. Immunoprecipitation assays revealed that ERβ interacts with p65 subunit of NF-κB and ERβ overexpression reduced the expression of NF-κB target genes. In xenograft assays, ERβ agonists reduced tumor growth and promoted apoptosis. Collectively, our findings demonstrated that natural ERβ agonists have the potential to significantly inhibit ovarian cancer cell growth by anti-inflammatory and pro-apoptotic actions, and natural ERβ agonists represent novel therapeutic agents for the management of ovarian cancer. PMID:28654894

  15. Therapeutic utility of natural estrogen receptor beta agonists on ovarian cancer.

    PubMed

    Liu, Jinyou; Viswanadhapalli, Suryavathi; Garcia, Lauren; Zhou, Mei; Nair, Binoj C; Kost, Edward; Rao Tekmal, Rajeshwar; Li, Rong; Rao, Manjeet K; Curiel, Tyler; Vadlamudi, Ratna K; Sareddy, Gangadhara R

    2017-07-25

    Ovarian cancer is the deadliest of all gynecologic cancers. Despite success with initial chemotherapy, the majority of patients relapse with an incurable disease. Development of chemotherapy resistance is a major factor for poor long-term survival in ovarian cancer. The biological effects of estrogens are mediated by estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ). Emerging evidence suggests that ovarian cancer cells express ERβ that functions as a tumor suppressor; however, the clinical utility of ERβ agonists in ovarian cancer remains elusive. We tested the utility of two natural ERβ agonists liquiritigenin (Liq), which is isolated from Glycyrrhiza uralensis and S-equol, which is isolated from soy isoflavone daidzein, for treating ovarian cancer. Both natural ERβ ligands had significant growth inhibition in cell viability and survival assays, reduced migration and invasion, and promoted apoptosis. Further, ERβ agonists showed tumor suppressive functions in therapy-resistant ovarian cancer model cells and sensitized ovarian cancer cells to cisplatin and paclitaxel treatment. Global RNA-Seq analysis revealed that ERβ agonists modulate several tumor suppressive pathways, including downregulation of the NF-κB pathway. Immunoprecipitation assays revealed that ERβ interacts with p65 subunit of NF-κB and ERβ overexpression reduced the expression of NF-κB target genes. In xenograft assays, ERβ agonists reduced tumor growth and promoted apoptosis. Collectively, our findings demonstrated that natural ERβ agonists have the potential to significantly inhibit ovarian cancer cell growth by anti-inflammatory and pro-apoptotic actions, and natural ERβ agonists represent novel therapeutic agents for the management of ovarian cancer.

  16. PPAR agonists: I. Role of receptor subunits in alcohol consumption in male and female mice

    PubMed Central

    Blednov, Yuri A.; Black, Mendy; Benavidez, Jillian M.; Stamatakis, Eleni E.; Harris, R. Adron

    2015-01-01

    Background Several peroxisome proliferator-activated receptor (PPAR) agonists reduce voluntary alcohol consumption in rodent models, and evidence suggests that PPARα and γ subunits play an important role in this effect. To define the subunit dependence of this action, we tested selective PPARα and α/γ agonists and antagonists in addition to null mutant mice lacking PPARα. Methods The effects of fenofibrate (PPARα agonist) and tesaglitazar (PPARα/γ agonist) on continuous and intermittent two-bottle choice drinking tests were examined in male and female wild-type mice and in male mice lacking PPARα. We compared the ability of MK886 (PPARα antagonist) and GW9662 (PPARγ antagonist) to inhibit the effects of fenofibrate and tesaglitazar in wild-type mice. The estrogen receptor antagonist, tamoxifen, can inhibit PPARγ-dependent transcription and was also studied in male and female mice. Results Fenofibrate and tesaglitazar reduced ethanol consumption and preference in wild-type mice, but these effects were not observed in mice lacking PPARα. MK886 inhibited the action of fenofibrate, but not tesaglitazer, while GW9662 did not inhibit either agonist. The PPAR agonists were more effective in male mice compared to females, and drinking in the continuous two-bottle choice test was more sensitive to fenofibrate and tesaglitazar compared to drinking in the intermittent access test. Tamoxifen also reduced ethanol consumption in male mice and this action was inhibited by GW9662, but not MK886, suggesting that it acts by activation of PPARγ. Conclusions Our study using selective PPAR agonists, antagonists, and null mutant mice indicates a key role for PPARα in mediating reduced ethanol consumption by fenofibrate and tesaglitazar. PMID:26857685

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

    PubMed

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

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

  18. Feeding responses to mu-, delta- and kappa-opioid receptor agonists in the meat-type chick.

    PubMed

    Bungo, Takashi; Kawamura, Kazuya; Izumi, Tomofumi; Dodo, Koh-Ichi; Ueda, Hiroshi

    2004-08-01

    The present study was designed to examine the effect of specific opioid agonists on feeding behavior in neonatal chicks. The food intake of broiler chicks was significantly decreased by intracerebroventricular injection of DAMGO and beta-casomorphin, micro-opioid receptor agonists, at 30-min postinjection. In contrast, both delta-opioid receptor agonists (DADLE and DPDPE) stimulated the food intake of the chick. Similar to the delta-opioid receptor agonists, food intake was elevated by the kappa-opioid receptor agonist (U-50488H and U-62066) in a dose-dependent manner. These results suggest that the endogenous opioid peptides have an important role for feeding behavior in the central nervous system of chicks. Copyright 2004 Elsevier Inc.

  19. Pharmacology and selectivity of various natural and synthetic Bombesin related peptide agonists for human and rat bombesin receptors differs

    PubMed Central

    Uehara, Hirotsugu; González, Nieves; Sancho, Veronica; Mantey, Samuel A.; Nuche-Berenguer, Bernardo; Pradhan, Tapas; Coy, David H.; Jensen, Robert T.

    2011-01-01

    The mammalian bombesin (Bn)-receptor family[gastrin-releasing peptide-receptor(GRPR-receptor), neuromedin B-receptor(NMB-receptor)], their natural ligands,GRP/NMB, as well as the related orphan-receptor,BRS-3, are widely-distributed, and frequently overexpressed by tumors. There is increased interest in agonists for this receptor family to explore their roles in physiological/pathophysiological processes, and for receptor-imaging/cytotoxicity in tumors. However, there is minimal data on human pharmacology of Bn-receptor agonists and most results are based on nonhuman receptor studies, particular rodent-receptors, which with other receptors frequently differ from human-receptors. To address this issue we compared hNMB/GRP-receptor affinities and potencies/efficacies of cell-activation(assessing phospholipase C activity) for 24 putative Bn-agonists(12-natural,12-synthetic) in four different cells with these receptors, containing native-receptors or receptors expressed at physiological densities, and compared the results to native rat-GRP-receptor-containing cells-(AR42J–cells) or rat-NMB-receptor cells(C6-glioblastoma cells). There were close correlations(r=0.92–99,p<0.0001) between their affinities/potencies for the two hGRP- or hNMB-receptor cells. Twelve analogues had high affinities(≤ 1 nM) for hGRP-receptor with 15 selective for it(greatest=GRP,NMC), 8 had high affinity/potencies for hNMB-receptors and 4 were selective for it. Only synthetic Bn-analogues containing β−alanine11 had high affinity for hBRS-3, but t also had high affinities/potencies for all GRP-/hNMB-receptor cells. There was no correlation between affinities for human-GRP-receptors and rat-GRP-receptors(r=0.131,p=0.54), but hNMB-receptor results correlated with rat-NMB-receptor(r=0.71, p<0.0001). These results elucidate the human- and rat-GRP-receptor pharmacophore for agonists differ markedly,whereas they do not for NMB-receptors, therefore potential GRP-receptor agonists for human

  20. Effects of acute cocaine or dopamine receptor agonists on AMPA receptor distribution in the rat nucleus accumbens

    PubMed Central

    Ferrario, Carrie R.; Li, Xuan; Wolf, Marina E.

    2010-01-01

    Changes in AMPA receptor (AMPAR) surface expression in the rodent nucleus accumbens (NAc) are produced by cocaine exposure and implicated in addiction-related behaviors. The direction of change depends on the animal’s prior drug history. However, little is known about the effect of a single exposure to cocaine on AMPAR distribution in the NAc of untreated rats. This is essential information for interpreting the literature on AMPAR trafficking after repeated cocaine exposure. In the present study, we used a protein crosslinking assay to determine the effect of a single cocaine injection on surface and intracellular AMPAR subunit levels in the rat NAc. We found increased AMPAR surface expression in the NAc 24 h, but not 30 min or 2 h, after cocaine injection. A major effect of cocaine is to increase extracellular dopamine (DA) levels, leading to DA receptor activation. Therefore, we also evaluated the effects of directly acting DA receptor agonists. In contrast to the effects of cocaine, AMPAR surface expression was significantly decreased 24 h after injection of the D2-class agonist quinpirole, whereas no significant effects were produced by the D1-class agonist SKF 81297 or the mixed DA agonist apomorphine. Our results show that the effects of a single cocaine exposure in drug- and injection-naïve rats are distinct from those previously reported after repeated cocaine administration. They further suggest that cocaine exerts these effects by influencing neuronal circuits rather than simply stimulating NAc DA transmission. PMID:20506566

  1. Modulation of gastrointestinal function by MuDelta, a mixed µ opioid receptor agonist/ µ opioid receptor antagonist

    PubMed Central

    Wade, PR; Palmer, JM; McKenney, S; Kenigs, V; Chevalier, K; Moore, BA; Mabus, JR; Saunders, PR; Wallace, NH; Schneider, CR; Kimball, ES; Breslin, HJ; He, W; Hornby, PJ

    2012-01-01

    BACKGROUND & PURPOSE Loperamide is a selective µ opioid receptor agonist acting locally in the gastrointestinal (GI) tract as an effective anti-diarrhoeal but can cause constipation. We tested whether modulating µ opioid receptor agonism with δ opioid receptor antagonism, by combining reference compounds or using a novel compound (‘MuDelta’), could normalize GI motility without constipation. EXPERIMENTAL APPROACH MuDelta was characterized in vitro as a potent µ opioid receptor agonist and high-affinity δ opioid receptor antagonist. Reference compounds, MuDelta and loperamide were assessed in the following ex vivo and in vivo experiments: guinea pig intestinal smooth muscle contractility, mouse intestinal epithelial ion transport and upper GI tract transit, entire GI transit or faecal output in novel environment stressed mice, or four weeks after intracolonic mustard oil (post-inflammatory). Colonic δ opioid receptor immunoreactivity was quantified. KEY RESULTS δ Opioid receptor antagonism opposed µ opioid receptor agonist inhibition of intestinal contractility and motility. MuDelta reduced intestinal contractility and inhibited neurogenically-mediated secretion. Very low plasma levels of MuDelta were detected after oral administration. Stress up-regulated δ opioid receptor expression in colonic epithelial cells. In stressed mice, MuDelta normalized GI transit and faecal output to control levels over a wide dose range, whereas loperamide had a narrow dose range. MuDelta and loperamide reduced upper GI transit in the post-inflammatory model. CONCLUSIONS AND IMPLICATIONS MuDelta normalizes, but does not prevent, perturbed GI transit over a wide dose-range in mice. These data support the subsequent assessment of MuDelta in a clinical phase II trial in patients with diarrhoea-predominant irritable bowel syndrome. PMID:22671931

  2. Kinetics of agonist-induced intrinsic fluorescence changes in the Torpedo acetylcholine receptor.

    PubMed

    Kawai, Hideki; Raftery, Michael A

    2010-05-01

    The nicotinic acetylcholine receptor from Torpedo electric organs is a ligand-gated ion channel that undergoes conformational transitions for activation and/or desensitization. Earlier work suggested that intrinsic fluorescence changes of the receptor monitors kinetic transitions toward the high-affinity, desensitized state. Here, using highly purified membrane preparations to minimize contaminating fluorescence, we examined kinetic mechanisms of the receptor as monitored by its intrinsic fluorescence. Fluorescence changes were specific to the receptor as they were blocked by alpha-bungarotoxin and were induced by agonists, but not by the antagonist hexamethonium. Acetylcholine, carbamylcholine and suberyldicholine showed only one kinetic phase with relatively fast rates (t(1/2) = 0.2-1.2 s). Effective dissociation constants were at least an order of magnitude higher than the high affinity, equilibrium binding constants for these agonists. A semirigid agonist isoarecolone-methiodide, whose activation constant was approximately 3-fold lower than acetylcholine, induced an additional slow phase (t(1/2) = 4.5-9 s) with apparent rates that increased and then decreased in a concentration dependent manner, revealing a branched mechanism for conformational transitions. We propose that the intrinsic fluorescence changes of the receptor describe a process(es) toward a fast desensitization state prior to the formation of the high affinity state.

  3. Kinetics of agonist-induced intrinsic fluorescence changes in the Torpedo acetylcholine receptor

    PubMed Central

    Kawai, Hideki; Raftery, Michael A.

    2010-01-01

    The nicotinic acetylcholine receptor from Torpedo electric organs is a ligand-gated ion channel that undergoes conformational transitions for activation and/or desensitization. Earlier work suggested that intrinsic fluorescence changes of the receptor monitors kinetic transitions toward the high-affinity, desensitized state. Here, using highly purified membrane preparations to minimize contaminating fluorescence, we examined kinetic mechanisms of the receptor as monitored by its intrinsic fluorescence. Fluorescence changes were specific to the receptor as they were blocked by α-bungarotoxin and were induced by agonists, but not by the antagonist hexamethonium. Acetylcholine, carbamylcholine and suberyldicholine showed only one kinetic phase with relatively fast rates (t1/2 = 0.2–1.2 s). Effective dissociation constants were at least an order of magnitude higher than the high affinity, equilibrium binding constants for these agonists. A semirigid agonist isoarecolone-methiodide, whose activation constant was ∼3-fold lower than acetylcholine, induced an additional slow phase (t1/2 = 4.5–9 s) with apparent rates that increased and then decreased in a concentration dependent manner, revealing a branched mechanism for conformational transitions. We propose that the intrinsic fluorescence changes of the receptor describe a process(es) toward a fast desensitization state prior to the formation of the high affinity state. PMID:20123701

  4. A Novel Non-Peptidic Agonist of the Ghrelin Receptor with Orexigenic Activity In vivo

    NASA Astrophysics Data System (ADS)

    Pastor-Cavada, Elena; Pardo, Leticia M.; Kandil, Dalia; Torres-Fuentes, Cristina; Clarke, Sarah L.; Shaban, Hamdy; McGlacken, Gerard P.; Schellekens, Harriet

    2016-11-01

    Loss of appetite in the medically ill and ageing populations is a major health problem and a significant symptom in cachexia syndromes, which is the loss of muscle and fat mass. Ghrelin is a gut-derived hormone which can stimulate appetite. Herein we describe a novel, simple, non-peptidic, 2-pyridone which acts as a selective agonist for the ghrelin receptor (GHS-R1a). The small 2-pyridone demonstrated clear agonistic activity in both transfected human cells and mouse hypothalamic cells with endogenous GHS-R1a receptor expression. In vivo tests with the hit compound showed significant increased food intake following peripheral administration, which highlights the potent orexigenic effect of this novel GHS-R1a receptor ligand.

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

    PubMed Central

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

    2015-01-01

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

  6. Identification of potent, selective, CNS-targeted inverse agonists of the ghrelin receptor.

    PubMed

    McClure, Kim F; Jackson, Margaret; Cameron, Kimberly O; Kung, Daniel W; Perry, David A; Orr, Suvi T M; Zhang, Yingxin; Kohrt, Jeffrey; Tu, Meihua; Gao, Hua; Fernando, Dilinie; Jones, Ryan; Erasga, Noe; Wang, Guoqiang; Polivkova, Jana; Jiao, Wenhua; Swartz, Roger; Ueno, Hirokazu; Bhattacharya, Samit K; Stock, Ingrid A; Varma, Sam; Bagdasarian, Victoria; Perez, Sylvie; Kelly-Sullivan, Dawn; Wang, Ruduan; Kong, Jimmy; Cornelius, Peter; Michael, Laura; Lee, Eunsun; Janssen, Ann; Steyn, Stefanus J; Lapham, Kimberly; Goosen, Theunis

    2013-10-01

    The optimization for selectivity and central receptor occupancy for a series of spirocyclic azetidine-piperidine inverse agonists of the ghrelin receptor is described. Decreased mAChR muscarinic M2 binding was achieved by use of a chiral indane in place of a substituted benzylic group. Compounds with desirable balance of human in vitro clearance and ex vivo central receptor occupancy were discovered by incorporation of heterocycles. Specifically, heteroaryl rings with nitrogen(s) vicinal to the indane linkage provided the most attractive overall properties. Copyright © 2013 Elsevier Ltd. All rights reserved.

  7. Molecular interactions of nonpeptide agonists and antagonists with the melanocortin-4 receptor.

    PubMed

    Fleck, Beth A; Chen, Chen; Yang, Weidong; Huntley, Rajesh; Markison, Stacy; Nickolls, Sarah A; Foster, Alan C; Hoare, Sam R J

    2005-11-08

    The melanocortin-4 (MC4) receptor is a potential therapeutic target for obesity and cachexia, for which nonpeptide agonists and antagonists are being developed, respectively. The aim of this study was to identify molecular interactions between the MC4 receptor and nonpeptide ligands, and to compare the mechanism of binding between agonist and antagonist ligands. Nonpeptide ligand interaction was affected by mutations that reduce peptide ligand binding (D122A, D126A, S190A, M200A, F261A, and F284A), confirming overlapping binding determinants for peptide and nonpeptide ligands. The common halogenated phenyl group of nonpeptide ligands was a determinant of F261A and F284A mutations' affinity-reducing effect, implying this group interacts with the aromatic side chains of these residues. All affected compounds contain this group, the mutations reduced binding of 2,4-dichloro-substituted compounds more than 4-chloro-substituted-compounds, and F284A mutation eliminated the affinity-enhancing effect of 2-chloro-substitution. F261A and F284A mutations reduced the affinity of antagonists more than agonists, suggesting that the stronger ligand interaction with these residues, the lower the ligand efficacy. Supporting this hypothesis, F261A mutation increased the efficacy of nonpeptide antagonist and partial agonist ligands. D122A and D126A mutations reduced nonpeptide ligand interaction. Removing the ligands' derivatized amide group eliminated the effect of the mutations. Interaction of agonists, which bear a common amine within this group, was strongly reduced by D126A mutation (550-3300-fold), suggesting an electrostatic interaction between the amine and the acidic group of D126. These postulated interactions with aromatic and acidic regions of the MC4 receptor are consistent with a molecular model of the receptor. Furthermore, the strength of interaction with the aromatic pocket, and potentially the acidic pocket, controls the signaling efficacy of the ligand.

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

    PubMed Central

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

    2013-01-01

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

  9. Selective Orthosteric Free Fatty Acid Receptor 2 (FFA2) Agonists

    PubMed Central

    Schmidt, Johannes; Smith, Nicola J.; Christiansen, Elisabeth; Tikhonova, Irina G.; Grundmann, Manuel; Hudson, Brian D.; Ward, Richard J.; Drewke, Christel; Milligan, Graeme; Kostenis, Evi; Ulven, Trond

    2011-01-01

    Free fatty acid receptor 2 (FFA2; GPR43) is a G protein-coupled seven-transmembrane receptor for short-chain fatty acids (SCFAs) that is implicated in inflammatory and metabolic disorders. The SCFA propionate has close to optimal ligand efficiency for FFA2 and can hence be considered as highly potent given its size. Propionate, however, does not discriminate between FFA2 and the closely related receptor FFA3 (GPR41). To identify FFA2-selective ligands and understand the molecular basis for FFA2 selectivity, a targeted library of small carboxylic acids was examined using holistic, label-free dynamic mass redistribution technology for primary screening and the receptor-proximal G protein [35S]guanosine 5′-(3-O-thio)triphosphate activation, inositol phosphate, and cAMP accumulation assays for hit confirmation. Structure-activity relationship analysis allowed formulation of a general rule to predict selectivity for small carboxylic acids at the orthosteric binding site where ligands with substituted sp3-hybridized α-carbons preferentially activate FFA3, whereas ligands with sp2- or sp-hybridized α-carbons prefer FFA2. The orthosteric binding mode was verified by site-directed mutagenesis: replacement of orthosteric site arginine residues by alanine in FFA2 prevented ligand binding, and molecular modeling predicted the detailed mode of binding. Based on this, selective mutation of three residues to their non-conserved counterparts in FFA3 was sufficient to transfer FFA3 selectivity to FFA2. Thus, selective activation of FFA2 via the orthosteric site is achievable with rather small ligands, a finding with significant implications for the rational design of therapeutic compounds selectively targeting the SCFA receptors. PMID:21220428

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

    PubMed

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

    2014-06-27

    The melanocortin-1 receptor (MC1R) is a key regulator of mammalian pigmentation. Melanism in the grey squirrel is associated with an eight amino acid deletion in the mutant melanocortin-1 receptor with 24 base pair deletion (MC1RΔ24) variant. We demonstrate that the MC1RΔ24 exhibits a higher basal activity than the wildtype MC1R (MC1R-wt). We demonstrate that agouti signalling protein (ASIP) is an inverse agonist to the MC1R-wt but is an agonist to the MC1RΔ24. We conclude that the deletion in the MC1RΔ24 leads to a receptor with a high basal activity which is further activated by ASIP. This is the first report of ASIP acting as an agonist to MC1R. Copyright © 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  11. Aged rat myocardium exhibits normal adenosine receptor-mediated bradycardia and coronary vasodilation but increased adenosine agonist-mediated cardioprotection.

    PubMed

    Kristo, Gentian; Yoshimura, Yukihiro; Keith, Byron J; Mentzer, Robert M; Lasley, Robert D

    2005-11-01

    The purpose of this study was to determine whether aged myocardium exhibits decreased responsiveness to adenosine A1 and A(2a) receptor activation. Studies were conducted in adult (4-6 months) and aged (24-26 months) Fischer 344 x Brown Norway hybrid (F344 x BN) rats. Effects of the adenosine A1/A(2a) agonist AMP579 were measured in isolated hearts and in rats submitted to in vivo regional myocardial ischemia. Aged isolated hearts exhibited lower spontaneous heart rates and higher coronary resistance, as well as normal A1- and A(2a)-mediated responses. There was no difference in control infarct size between adult and aged rats; however, AMP579 treatment resulted in a 50% greater infarct size reduction in aged rats (18 +/- 4% of risk area) compared to adult rats (37 +/- 3%). These findings suggest that adenosine A1 and A(2a) receptor-mediated effects are not diminished in normal aged myocardium, and that aged hearts exhibit increased adenosine agonist-induced infarct reduction.

  12. Biochemical, electrophysiological and neurohormonal studies with B-20991, a selective 5-HT1A receptor agonist.

    PubMed

    Caicoya, A G; Beneytez, M E; Delgado, M; Manzanares, J; López-Rodríguez, M L; Benhamu, B; Morcillo, M J; Pozo, M A; Rubia, F J; Fuentes, J A

    2001-05-01

    Different receptor subtypes mediate the effects produced by serotonin (5-HT) in mammals. Besides their proved anxiolytic action, agonists of the 5-HT1A receptor subtype show prospects as antidepressants or neuroprotective agents in case of ischemia. In order to better define the pharmacological profile and determine the selectivity for the 5-HT receptor type, the properties of the new 5-HT1A receptor agonist 2[[4-(o-methoxyphenyl)piperazin-1-yl]-methyl]-1.3-dioxoperhydroimidazo[1.5-a]pyridine (B-20991), an arylpiperazine derivative, have now been further studied. B-20991 was found to antagonize the forskolin-induced increase of cAMP synthesis in a HeLa cell line transfected with the human 5-HT1A in a process sensitive to the selective blocker N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinyl-cyclohexanecarboxamide maleate (WAY 100635). Additionally, B-20991 showed a dose-dependent inhibition of the spontaneous on-going activity of serotonin (5-HT) neurons in the dorsal raphe nucleus in rats, an effect that was reversed by treatment with WAY 100635. This, together with the fact that the hypothermia induced by B-20991 in mice was also antagonized by WAY 100635, suggests that the new compound acts upon somatodendritic 5-HT1A receptors. Additional activation of 5-HT1A postsynaptic receptors was indicated by the increase of corticosterone plasma levels induced by B-20991 in the rat. These results demonstrate that B-20991 is a selective 5-HT1A receptor agonist acting both pre- and postsynaptically, which represents an useful pharmacological tool to study 5-HT1A-receptor-mediated effects. Copyright 2001 S. Karger AG, Basel

  13. Cannabidiol is a partial agonist at dopamine D2High receptors, predicting its antipsychotic clinical dose

    PubMed Central

    Seeman, P

    2016-01-01

    Although all current antipsychotics act by interfering with the action of dopamine at dopamine D2 receptors, two recent reports showed that 800 to 1000 mg of cannabidiol per day alleviated the signs and symptoms of schizophrenia, although cannabidiol is not known to act on dopamine receptors. Because these recent clinical findings may indicate an important exception to the general rule that all antipsychotics interfere with dopamine at dopamine D2 receptors, the present study examined whether cannabidiol acted directly on D2 receptors, using tritiated domperidone to label rat brain striatal D2 receptors. It was found that cannabidiol inhibited the binding of radio-domperidone with dissociation constants of 11 nm at dopamine D2High receptors and 2800 nm at dopamine D2Low receptors, in the same biphasic manner as a dopamine partial agonist antipsychotic drug such as aripiprazole. The clinical doses of cannabidiol are sufficient to occupy the functional D2High sites. it is concluded that the dopamine partial agonist action of cannabidiol may account for its clinical antipsychotic effects. PMID:27754480

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

    PubMed

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

    2015-12-01

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

  15. Peroxisome Proliferator-Activated Receptor Agonists: Do They Increase Cardiovascular Risk?

    PubMed Central

    Aljada, Ahmad; Shah, Kshitij Ashwin; Mousa, Shaker A.

    2009-01-01

    Cardiovascular disease is a major cause of morbidity and mortality among people with type 2 diabetes mellitus. The peroxisome proliferator-activated receptor (PPAR) agonists have a significant role on glucose and fat metabolism. Thiazolidinediones (TZDs) are predominantly PPARγ agonists, and their primary benefit appears to be the prevention of diabetic complications by improving glycemic control and lipid profile. Recently, the cardiovascular safety of rosiglitazone was brought to center stage following meta analyses and the interim analysis of the RECORD trial. Current evidence points to rosiglitazone having a greater risk of myocardial ischemic events than placebo, metformin, or sulfonylureas. This review article discusses the mechanism of action of PPAR agonists and correlates it with clinical and laboratory outcomes in the published literature. In addition, this review article attempts to discuss some of the molecular mechanisms regarding the association between TZDs therapy and the nontraditional cardiovascular risks. PMID:19696948

  16. 2-Aminoalkyl nicotinamide derivatives as pure inverse agonists of the ghrelin receptor.

    PubMed

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

    2015-07-01

    New inverse agonists of the ghrelin receptor (ghrelinR) were obtained through high-throughput screening and subsequent structural modification of 2-aminoalkyl nicotinamide derivatives. The key structural feature to improve in vitro activity was the introduction of a diazabicyclo ring at the 5-position of the pyridine ring. The final product showed potent inverse agonist activity and, despite its low brain permeability, reduced food intake in both normal and obese mice. These results implied that peripheral ghrelinR activity is important for appetite control and that a peripheral ghrelinR inverse agonist could be an anti-obesity drug with reduced risk of central nervous system (CNS)-related side effects. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

    NASA Technical Reports Server (NTRS)

    Zheng, F.; Gallagher, J. P.

    1992-01-01

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

  18. Molecular dissection of tropisetron, an alpha7 nicotinic acetylcholine receptor-selective partial agonist.

    PubMed

    Papke, Roger L; Schiff, Hillary C; Jack, Brian A; Horenstein, Nicole A

    2005-04-22

    The alpha7 nicotinic acetylcholine receptor (nAChR)-selective partial agonist tropisetron is a conjugate of an indole and a tropane group. We tested compounds structurally related to either the indole or tropane domains of tropisetron on oocytes expressing human alpha7. alpha4beta2, or alpha3beta4 nAChR or rat 5HT(3A) receptors. The simple compounds tropane and tropinone had alpha7-selective agonist activity comparable to that of tropisetron. Tropinone was more efficacious than tropisetron but 100-fold less potent. Some tropane compounds had antagonist activity on alpha3beta4 nAChR but no effect on alpha4beta2 nAChR. Some tropanes also affected the responses of 5HT3 receptors to serotonin. Tropisetron was more potent at inhibiting alpha3beta4 receptors (IC(50)=1.8+/-0.6) than was tropane or tropinone, suggesting that the presence of the indole group has a large impact on the potency of tropisetron, both as an alpha7 agonist and as an alpha3beta4 antagonist. The further reduced structures of dimethyl piperidinium and 1-methylpyrrolidine also had agonist activity on alpha7 receptors, suggesting that the minimal activating pharmacophore of these compounds, as with tetramethylammonium, may simply be the charged nitrogen, while additional structure elements impact subtype selectivity, potency, and efficacy. It has previously been reported that 5-hydroxyindole (5HI) can potentiate alpha7 receptor responses to acetylcholine (ACh). However, the site where 5HI binds to the receptor is not known. We tested the hypothesis that the tropisetron binding site might overlap the 5HI site and thereby produce a block of 5HI potentiation. Our results indicate that the indole portion of tropisetron is not likely to be binding to the same site where 5HI binds to potentiate alpha7 receptor responses since 5HI can greatly potentiate responses of tropisetron, tropinone, and other partial agonists such as 4OH-GTS-21.

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

    PubMed

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

    2015-07-01

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

  20. Development of CINPA1 analogs as novel and potent inverse agonists of constitutive androstane receptor.

    PubMed

    Lin, Wenwei; Yang, Lei; Chai, Sergio C; Lu, Yan; Chen, Taosheng

    2016-01-27

    Constitutive androstane receptor (CAR, NR1I3) and pregnane X receptor (PXR, NR1I2) are master regulators of endobiotic and xenobiotic metabolism and disposition. Because CAR is constitutively active in certain cellular contexts, inhibiting CAR might reduce drug-induced hepatotoxicity and resensitize drug-resistant cancer cells to chemotherapeutic drugs. We recently reported a novel CAR inhibitor/inverse agonist CINPA1 (11). Here, we have obtained or designed 54 analogs of CINPA1 and used a time-resolved fluorescence resonance energy transfer (TR-FRET) assay to evaluate their CAR inhibition potency. Many of the 54 analogs showed CAR inverse agonistic activities higher than those of CINPA1, which has an IC50 value of 687 nM. Among them, 72 has an IC50 value of 11.7 nM, which is about 59-fold more potent than CINPA1 and over 10-fold more potent than clotrimazole (an IC50 value of 126.9 nM), the most potent CAR inverse agonist in a biochemical assay previously reported by others. Docking studies provide a molecular explanation of the structure-activity relationship (SAR) observed experimentally. To our knowledge, this effort is the first chemistry endeavor in designing and identifying potent CAR inverse agonists based on a novel chemical scaffold, leading to 72 as the most potent CAR inverse agonist so far. The 54 chemicals presented are novel and unique tools for characterizing CAR's function, and the SAR information gained from these 54 analogs could guide future efforts to develop improved CAR inverse agonists. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  1. Estrogen receptor β selective agonists reduce invasiveness of triple-negative breast cancer cells.

    PubMed

    Hinsche, Oliver; Girgert, Rainer; Emons, Günter; Gründker, Carsten

    2015-02-01

    Metastasis to bone is a frequent problem of advanced breast cancer. Particularly breast cancers, which do not express estrogen receptor α (ERα) and progesterone receptor (PR) and which have no overexpression of human epidermal growth factor receptor 2 (HER2), so-called triple-negative breast cancers (TNBCs), are considered as very aggressive and have a poor prognosis. Recently we have shown that breast cancer cell invasion was dramatically increased when co-cultured with MG63 osteoblast-like cells. Using this model we have now analyzed whether estrogen receptor β (ERβ) plays a role in TNBC cell invasion in vitro. ERα and ERβ protein expression was analyzed using western blot analysis. Invasion was quantified by assessment of TNBC cell migration rate through an artificial basement membrane in a modified Boyden chamber during co-culture with MG63 osteoblast-like cells. The effects of ERβ agonist treatment on CXC motif chemokine receptor 4 (CXCR4) protein expression during co-culture with MG64 cells was quantified using western blot analysis. Proliferation was measured using alamarBlue assay. TNBC cell lines HCC1806 and HCC1937 showed no ERα but high ERβ protein expression. Cell invasion of HCC1806 and HCC1937 TNBC cells was significantly increased when co-cultured with MG63 osteoblast-like cells. Treatment with ERβ selective estrogen agonists liquiritigenin and ERB-041 reduced the ability to invade a reconstituted basement membrane and to migrate in response to the cellular stimulus. During co-culture CXCR4 protein expression of TNBC cell lines HCC1806 and HCC1937 was significantly increased. Treatment with liquiritigenin resulted in a significant decrease of CXCR4 protein expression. Both ERβ agonists showed no effect on TNBC cell proliferation. Our findings suggest that ERβ plays a major role in TNBC invasion. Bone-directed invasion can be inhibited by ERβ agonists.

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

    PubMed

    Higgins, Guy A; Fletcher, Paul J

    2015-07-15

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

  3. Dulaglutide: the newest GLP-1 receptor agonist for the management of type 2 diabetes.

    PubMed

    Thompson, Angela M; Trujillo, Jennifer M

    2015-03-01

    To review the pharmacology, pharmacokinetics, safety, and efficacy of the glucagon-like peptide-1 receptor agonist (GLP-1 RA), dulaglutide, in the treatment of type 2 diabetes mellitus (T2D). A PubMed search was completed to identify publications from 1947 to October 2014 using the search terms dulaglutide and LY2189265. References were reviewed to identify additional resources. Articles were included if they evaluated the pharmacology, pharmacokinetics, safety, or efficacy of dulaglutide. Dulaglutide reduces both glycosylated hemoglobin (A1C) and weight by stimulating insulin secretion and suppressing glucagon in a glucose-dependent manner, delaying gastric emptying, and promoting satiety. Dulaglutide consists of 2 GLP-1 analogues that have been modified to make it a long-acting, once-weekly agent. Dulaglutide has been studied as monotherapy and in combination with metformin, glimepiride, pioglitazone, and insulin lispro. It has demonstrated superior A1C reduction compared with placebo, metformin, insulin glargine, sitagliptin, and twice-daily exenatide. It demonstrated noninferiority in A1C reduction to liraglutide. Dulaglutide changed A1C by -0.78% to -1.51%, and it changed weight by -0.35 kg to -3.03 kg. The most common adverse effects in clinical studies were nausea, vomiting, and diarrhea. Dulaglutide is the fifth GLP-1 RA approved for T2D in the United States. It is an attractive option because it is dosed once-weekly, provides A1C lowering similar to liraglutide, weight reduction similar to exenatide, and has an adverse effect profile similar to exenatide and liraglutide. © The Author(s) 2015.

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

    PubMed

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

    2015-09-15

    Glucocorticoids (GCs) are widely used as anti-inflammatory drugs. Our previous study demonstrated that several GCs such as cortisol and dexamethasone (Dex) were frequently detected in effluents collected from Japanese sewage treatment plants (STPs) in 2012. In this study, we used the GC-Responsive Chemical-Activated LUciferase gene eXpression (GR-CALUX) assay to elucidate GC receptor (GR) agonistic activities of ten pure synthetic GCs and selected STP effluents in Japan for assessment of the risks associated with the presence of GR agonists. The tested GCs demonstrated dose-dependent agonistic effects in the GR-CALUX assay and their EC50 values were calculated for estimation of relative potencies (REPs) compared to Dex. The GR agonistic potency was in the rank of: clobetasol propionate > clobetasone butyrate > betamethasone 17-valerate > difluprednate > betamethasone 17,21-dipropionate > Dex > betamethasone > 6α-methylprednisolone > prednisolone > cortisol. The GR agonistic activity in STP effluents as measured in Dex-equivalent (Dex-EQ) activities ranged from < 3.0-78 ng L(-1) (median: 29 ng L(-1), n = 50). To evaluate the contribution of the target GCs, theoretical Dex-EQs were calculated by multiplying the concentrations of each GC by its respective REP. Our calculation of Dex-EQ contribution for individual GR agonists indicated that the well-known GCs cortisol and Dex should not be given priority for subsequent in vivo testing, monitoring and removal experiments, but rather the highly potent synthetic GCs clobetasol propionate and betamethasone 17-valerate (REP = 28 and 3.1) as well as other unidentified compounds are important GR agonists in STP effluents in Japan. Copyright © 2015 Elsevier B.V. All rights reserved.

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

    PubMed

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

    2014-11-01

    Agonists of the nuclear receptor PPARγ are therapeutically used to combat hyperglycaemia associated with the metabolic syndrome and type 2 diabetes. In spite of being effective in normalization of blood glucose levels, the currently used PPARγ agonists from the thiazolidinedione type have serious side effects, making the discovery of novel ligands highly relevant. Natural products have proven historically to be a promising pool of structures for drug discovery, and a significant research effort has recently been undertaken to explore the PPARγ-activating potential of a wide range of natural products originating from traditionally used medicinal plants or dietary sources. The majority of identified compounds are selective PPARγ modulators (SPPARMs), transactivating the expression of PPARγ-dependent reporter genes as partial agonists. Those natural PPARγ ligands have different binding modes to the receptor in comparison to the full thiazolidinedione agonists, and on some occasions activate in addition PPARα (e.g. genistein, biochanin A, sargaquinoic acid, sargahydroquinoic acid, resveratrol, amorphastilbol) or the PPARγ-dimer partner retinoid X receptor (RXR; e.g. the neolignans magnolol and honokiol). A number of in vivo studies suggest that some of the natural product activators of PPARγ (e.g. honokiol, amorfrutin 1, amorfrutin B, amorphastilbol) improve metabolic parameters in diabetic animal models, partly with reduced side effects in comparison to full thiazolidinedione agonists. The bioactivity pattern as well as the dietary use of several of the identified active compounds and plant extracts warrants future research regarding their therapeutic potential and the possibility to modulate PPARγ activation by dietary interventions or food supplements. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  6. N(G)-acylated aminothiazolylpropylguanidines as potent and selective histamine H(2) receptor agonists.

    PubMed

    Kraus, Anja; Ghorai, Prasanta; Birnkammer, Tobias; Schnell, David; Elz, Sigurd; Seifert, Roland; Dove, Stefan; Bernhardt, Günther; Buschauer, Armin

    2009-02-01

    The bioisosteric replacement of the guanidino group in arpromidine-like histamine H(2) receptor (H(2)R) agonists by an acylguanidine moiety is a useful approach to obtain potent H(2)R agonists with improved oral bioavailability and blood-brain barrier penetration. Unfortunately, the selectivity of such N(G)-acylated imidazolylpropylguanidines for the H(2)R is poor, in particular versus histamine H(3) (H(3)R) and H(4) receptors (H(4)R). This drawback appears to depend on the "privileged" imidazolylpropylguanidine structure. The 2-amino-4-methylthiazol-5-yl moiety is a bioisostere of the imidazole ring in the moderately potent H(2)R-selective histamine analogue amthamine. This approach was successfully applied to acylguanidine-type H(2)R agonists. The aminothiazoles are nearly equipotent to the corresponding imidazoles as H(2)R agonists. Compared with histamine, the potency is increased up to 40-fold on the guinea pig right atrium, and up to 125- and 280-fold in GTPase assays with human and guinea pig H(2)R-G(salphaS) fusion proteins expressed in Sf9 insect cells, respectively. Docking studies on H(2)R models support the hypothesis that 2-aminothiazolyl and imidazolyl derivatives interact with H(2)Rs as bioisosteres. In contrast to the imidazoles, the aminothiazoles are devoid of agonistic or relevant antagonistic effects on H(1), H(3), and H(4) receptors. Moreover, unlike amthamine, the 4-methyl group does not significantly contribute to the H(2)R agonism of N(G)-acylated 2-amino-4-methylthiazol-5-ylpropylguanidines.

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

    PubMed

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

    2015-07-07

    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.

  8. 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

  9. Effects of aging on antagonist and agonist interactions with. beta. -adrenergic receptors on human leukocyte membranes

    SciTech Connect

    Zahniser, N.R.; Parker, D.C.; Bier-Laning, C.M.

    1986-03-01

    Alterations in properties and/or coupling of ..beta..-adrenergic receptors might explain the diminished responsiveness to ..beta..-receptor agonists observed in aged humans. Polymorphonuclear (PMN) and mononuclear (MN) leukocytes were isolated on Percoll gradients from young or old healthy volunteers (25-34 and 60-76 yrs). Saturation isotherms of /sup 125/I-pindolol binding to PMN and MN membranes were generated. The affinities did not differ between the two age groups or cell types (52-61 pM). The number of receptors differed only on MN membranes (PMN young: 37 +/- 5.7, old: 44 +/- 6.7; MN young: 55 +/- 7.1, old: 122 +/- 23 fmol/mg protein; N =more » 6-8); however, this apparent increase became a decrease if the data were expressed in fmol/million cells (MN young: 0.82 +/- 0.12; old: 0.57 +/- 0.10) suggesting alterations in protein content or cell types rather than receptors in aged MN's. Agonist affinities, determined from isoproterenol competition curves in the absence and presence of GTP, were not different between the two age groups or cell types. In agreement with most previous reports, no change with aging in the properties of antagonist binding to ..beta..-adrenergic receptors on MN's was detected. However, in contrast with an earlier report, no changes in agonist binding or coupling of the receptor in MN's from the elderly were found. These observations were extended to PMN's and suggest that changes in ..beta..-adrenergic receptors may not underlie age-related decreases in isoproterenol responsiveness.« less

  10. Intersubunit Bridge Formation Governs Agonist Efficacy at Nicotinic Acetylcholine α4β2 Receptors

    PubMed Central

    Rohde, Line Aagot Hede; Ahring, Philip Kiær; Jensen, Marianne Lerbech; Nielsen, Elsebet Østergaard; Peters, Dan; Helgstrand, Charlotte; Krintel, Christian; Harpsøe, Kasper; Gajhede, Michael; Kastrup, Jette Sandholm; Balle, Thomas

    2012-01-01

    The α4β2 subtype of the nicotinic acetylcholine receptor has been pursued as a drug target for treatment of psychiatric and neurodegenerative disorders and smoking cessation aids for decades. Still, a thorough understanding of structure-function relationships of α4β2 agonists is lacking. Using binding experiments, electrophysiology and x-ray crystallography we have investigated a consecutive series of five prototypical pyridine-containing agonists derived from 1-(pyridin-3-yl)-1,4-diazepane. A correlation between binding affinities at α4β2 and the acetylcholine-binding protein from Lymnaea stagnalis (Ls-AChBP) confirms Ls-AChBP as structural surrogate for α4β2 receptors. Crystal structures of five agonists with efficacies at α4β2 from 21–76% were determined in complex with Ls-AChBP. No variation in closure of loop C is observed despite large efficacy variations. Instead, the efficacy of a compound appears tightly coupled to its ability to form a strong intersubunit bridge linking the primary and complementary binding interfaces. For the tested agonists, a specific halogen bond was observed to play a large role in establishing such strong intersubunit anchoring. PMID:22170047

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

    Laudon, Moshe; Frydman-Marom, Anat

    2014-01-01

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

  13. Glucagon-like peptide-1 (GLP-1) receptor agonists, obesity and psoriasis: diabetes meets dermatology.

    PubMed

    Drucker, D J; Rosen, C F

    2011-11-01

    Type 2 diabetes mellitus is characterised by beta cell failure, which frequently develops in the setting of insulin resistance. Inflammation contributes to the pathophysiology of type 2 diabetes by impairing insulin action in peripheral tissues and via reduction of beta cell function. Inflammation may also play an important role in the development of complications that arise in patients with type 2 diabetes. Hence, the anti-inflammatory actions of commonly used glucose-lowering drugs may contribute, indirectly, to their mechanisms of action and therapeutic benefit. Herein we highlight the anti-inflammatory actions of glucagon-like peptide-1 (GLP-1), which exerts direct and indirect actions on immune function. The observations that GLP-1 receptor agonists exert anti-inflammatory actions in preclinical studies, taken together with case reports linking improvements in psoriasis with GLP-1 receptor agonist therapy, illustrates the emerging clinical implications of non-classical anti-inflammatory actions of incretin-based therapeutics.

  14. μ-Opioid Receptors: Correlation of Agonist Efficacy for Signalling with Ability to Activate InternalizationS⃞

    PubMed Central

    McPherson, Jamie; Rivero, Guadalupe; Baptist, Myma; Llorente, Javier; Al-Sabah, Suleiman; Krasel, Cornelius; Dewey, William L.; Bailey, Chris P.; Rosethorne, Elizabeth M.; Charlton, Steven J.; Henderson, Graeme

    2010-01-01

    We have compared the ability of a number of μ-opioid receptor (MOPr) ligands to activate G proteins with their abilities to induce MOPr phosphorylation, to promote association of arrestin-3 and to cause MOPr internalization. For a model of G protein-coupled receptor (GPCR) activation where all agonists stabilize a single active conformation of the receptor, a close correlation between signaling outputs might be expected. Our results show that overall there is a very good correlation between efficacy for G protein activation and arrestin-3 recruitment, whereas a few agonists, in particular endomorphins 1 and 2, display apparent bias toward arrestin recruitment. The agonist-induced phosphorylation of MOPr at Ser375, considered a key step in MOPr regulation, and agonist-induced internalization of MOPr were each found to correlate well with arrestin-3 recruitment. These data indicate that for the majority of MOPr agonists the ability to induce receptor phosphorylation, arrestin-3 recruitment, and internalization can be predicted from their ability as agonists to activate G proteins. For the prototypic MOPr agonist morphine, its relatively weak ability to induce MOPr internalization can be explained by its low agonist efficacy. PMID:20647394

  15. Albiglutide: a new GLP-1 receptor agonist for the treatment of type 2 diabetes.

    PubMed

    Trujillo, Jennifer M; Nuffer, Wesley

    2014-11-01

    To review the pharmacology, pharmacokinetics, safety, and efficacy of albiglutide, a glucagon-like peptide-1 receptor agonist (GLP-1 RA) in type 2 diabetes (T2D). A MEDLINE search (1950-June 2014) was conducted using the keyword albiglutide. References were reviewed to identify additional sources. Articles evaluating pharmacokinetics, pharmacodynamics, safety, or efficacy of albiglutide were included. Albiglutide is a long-acting GLP-1 RA that lowers glycosylated hemoglobin (A1C) and reduces weight by stimulating glucose-dependent insulin secretion, suppressing glucagon secretion, delaying gastric emptying, and promoting satiety. Albiglutide has a long half-life as a result of resistance to degradation by dipeptidyl peptidase-4 and fusion to albumin, thus allowing once-weekly dosing. Albiglutide has been studied as monotherapy and add-on therapy to metformin, sulfonylureas, thiazolidinediones, insulin glargine, and varying combinations of these agents. Clinical studies have shown albiglutide to be superior to placebo, sitagliptin, and glimepiride and noninferior to insulin glargine and insulin lispro at reducing A1C in T2D patients, with A1C changes from baseline ranging from -0.55% to -0.9%. Noninferiority was not achieved when compared to liraglutide and pioglitazone. Weight changes ranged from +0.28 to -1.21 kg. The most common side effects are upper-respiratory-tract infections, diarrhea, nausea, and injection-site reactions. Albiglutide is the fourth GLP-1 RA approved in the United States. Advantages include once-weekly dosing and fewer gastrointestinal side effects compared with liraglutide, but it is less effective at reducing A1C and weight compared to liraglutide. It has not been compared head to head with other GLP-1 RAs. © The Author(s) 2014.

  16. The pharmacology of imepitoin: the first partial benzodiazepine receptor agonist developed for the treatment of epilepsy.

    PubMed

    Rundfeldt, Chris; Löscher, Wolfgang

    2014-01-01

    Although benzodiazepines (BZDs) offer a wide spectrum of antiepileptic activity against diverse types of epileptic seizures, their use in the treatment of epilepsy is limited because of adverse effects, loss of efficacy (tolerance), and development of physical and psychological dependence. BZDs act as positive allosteric modulators of the inhibitory neurotransmitter GABA by binding to the BZD recognition site ("BZD receptor") of the GABAA receptor. Traditional BZDs such as diazepam or clonazepam act as full agonists at this site, so that one strategy to resolve the disadvantages of these compounds would be the development of partial agonists with lower intrinsic efficacy at the BZD site of the GABAA receptor. Several BZD site partial or subtype selective compounds, including bretazenil, abecarnil, or alpidem, have been developed as anxioselective anxiolytic drugs, but epilepsy was not a target indication for such compounds. More recently, the imidazolone derivatives imepitoin (ELB138) and ELB139 were shown to act as low-affinity partial agonists at the BZD site of the GABAA receptor, and imepitoin was developed for the treatment of epilepsy. Imepitoin displayed a broad spectrum of anticonvulsant activity in diverse seizure and epilepsy models at tolerable doses, and, as expected from its mechanism of action, lacked tolerance and abuse liability in rodent and primate models. The more favorable pharmacokinetic profile of imepitoin in dogs versus humans led to the decision to develop imepitoin for the treatment of canine epilepsy. Based on randomized controlled trials that demonstrated antiepileptic efficacy and high tolerability and safety in epileptic dogs, the drug was recently approved for this indication in Europe. Hopefully, the favorable profile of imepitoin for the treatment of epilepsy in dogs will reactivate the interest in partial BZD site agonists as new treatments for human epilepsy.

  17. The impact of improved glycaemic control with GLP-1 receptor agonist therapy on diabetic retinopathy.

    PubMed

    Varadhan, Lakshminarayanan; Humphreys, Tracy; Walker, Adrian B; Varughese, George I

    2014-03-01

    Rapid improvement in glycaemic control with GLP-1 receptor agonist (RA) therapy has been reported to be associated with significant progression of diabetic retinopathy. This deterioration is transient, and continuing GLP-1 RA treatment is associated with reversal of this phenomenon. Pre-existent maculopathy, higher grade of retinopathy and longer duration of diabetes may be risk factors for persistent deterioration. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  18. Rotigotine is a potent agonist at dopamine D1 receptors as well as at dopamine D2 and D3 receptors

    PubMed Central

    Wood, Martyn; Dubois, Vanessa; Scheller, Dieter; Gillard, Michel

    2015-01-01

    Background and Purpose Rotigotine acts as a dopamine receptor agonist with high affinity for the dopamine D2, D3, D4 and D5 receptors but with a low affinity for the dopamine D1 receptor. We have investigated this further in radioligand binding and functional studies and compared the profile of rotigotine with that of other drugs used in the treatment of Parkinson's disease (PD). Experimental Approach The binding of rotigotine to human dopamine D1, D2, D3, D4 and D5 receptors was determined in radioligand binding studies using [3H]rotigotine and compared with that of standard antagonist radioligands. Functional interactions of rotigotine with human dopamine receptors was also determined. Key Results [3H]rotigotine can be used as an agonist radioligand to label all dopamine receptor subtypes and this can be important to derive agonist affinity estimates. Rotigotine maintains this high affinity in functional studies at all dopamine receptors especially D1, D2 and D3 receptors and, to a lesser extent, D4 and D5 receptors. Rotigotine, like apomorphine but unlike ropinirole and pramipexole, was a potent agonist at all dopamine receptors. Conclusions and Implications Rotigotine is a high-potency agonist at human dopamine D1, D2 and D3 receptors with a lower potency at D4 and D5 receptors. These studies differentiate rotigotine from conventional dopamine D2 agonists, used in the treatment of PD, such as ropinirole and pramipexole which lack activity at the D1 and D5 receptors, but resembles that of apomorphine which has greater efficacy in PD than other dopamine agonists but has suboptimal pharmacokinetic properties. PMID:25339241

  19. Hydroxylated 2-Ethylhexyl tetrabromobenzoate isomers in house dust and their agonistic potencies with several nuclear receptors.

    PubMed

    Peng, Hui; Sun, Jianxian; Saunders, David M V; Codling, Garry; Wiseman, Steve; Jones, Paul D; Giesy, John P

    2017-08-01

    In the current study, by combining ultra-high resolution (UHR) MS 1 spectra, MS 2 spectra, and derivatization, three hydroxylated isomers of 2-ethylhexyl tetrabromobenzoate (OH-TBB) were identified in Firemaster ® 550 and BZ-54 technical products. Also, a new LC-UHRMS method, using atmospheric pressure chemical ionization (APCI), was developed for simultaneous analysis of OH-TBB, TBB, hydroxylated bis(2-ethylhexyl)-tetrabromophthalate (OH-TBPH) and TBPH in 23 samples of dust collected from houses in Saskatoon, SK, Canada. OH-TBBs were detected in 91% of samples, with a geometric mean concentration of 0.21 ng/g, which was slightly less than those of OH-TBPH (0.35 ng/g). TBB was detected in 100% of samples of dust with a geometric mean concentration of 992 ng/g. Significant (p < 0.001) log-linear relationships between concentrations of OH-TBBs, TBB, or OH-TBPHs and TBPH in dust support the hypothesis of a common source of these compounds. OH-TBBs were found to be strong agonists of peroxisome proliferator-activated receptor gamma (PPARγ) and weaker agonists of the estrogen receptor (ER), but no agonistic potencies was observed with the androgen receptor (AR). Occurrence of OH-TBBs in technical products and house dust, together with their relatively strong PPARγ potencies, indicated their potential risk to health of humans. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. The safety and tolerability of GLP-1 receptor agonists in the treatment of type-2 diabetes.

    PubMed

    Russell-Jones, D

    2010-09-01

    Established therapies for type-2 diabetes effectively reduce blood glucose, but are often associated with adverse effects that pose risks to patient's health or diminish adherence to treatment. Weight gain, hypoglycaemia and gastrointestinal symptoms are commonly reported and some agents may not be safe for use in patients with renal impairment or elevated cardiovascular risk. New treatments based on the action of the endogenous human hormone glucagon-like peptide-1 (GLP-1), including exenatide and liraglutide, are available. These therapies provide a novel pharmacological approach to glycaemic control via multiple mechanisms of action, and accordingly exhibit different safety and tolerability profiles than conventional treatments. GLP-1 receptor agonists stimulate insulin release only in the presence of elevated blood glucose and are therefore associated with a fairly low risk of hypoglycaemia. Gastrointestinal symptoms are common but transient, and there appears to be little potential for interaction with other drugs. GLP-1 receptor agonists are associated with weight loss rather than weight gain. As protein-based therapies, these agents have the potential to induce antibody formation, but the impact on efficacy and safety is minor. GLP-1 receptor agonists thus offer a new and potentially useful option for clinicians concerned about some of the common adverse effects of type-2 diabetes therapies.

  1. Crystal structures of agonist-bound human cannabinoid receptor CB1

    PubMed Central

    Hua, Tian; Vemuri, Kiran; Nikas, Spyros P.; Laprairie, Robert B.; Wu, Yiran; Qu, Lu; Pu, Mengchen; Korde, Anisha; Jiang, Shan; Ho, Jo-Hao; Han, Gye Won; Ding, Kang; Li, Xuanxuan; Liu, Haiguang; Hanson, Michael A.; Zhao, Suwen; Bohn, Laura M.; Makriyannis, Alexandros; Stevens, Raymond C.; Liu, Zhi-Jie

    2018-01-01

    The cannabinoid receptor 1 (CB1) is the principal target of the psychoactive constituent of marijuana, the partial agonist Δ9-tetrahydrocannabinol (Δ9-THC)1. Here we report two agonist-bound crystal structures of human CB1 in complex with a tetrahydrocannabinol (AM11542) and a hexahydrocannabinol (AM841) at 2.80 Å and 2.95 Å resolution, respectively. The two CB1–agonist complexes reveal important conformational changes in the overall structure, relative to the antagonist-bound state2, including a 53% reduction in the volume of the ligand-binding pocket and an increase in the surface area of the G-protein-binding region. In addition, a ‘twin toggle switch’ of Phe2003.36 and Trp3566.48 (superscripts denote Ballesteros–Weinstein numbering3) is experimentally observed and appears to be essential for receptor activation. The structures reveal important insights into the activation mechanism of CB1 and provide a molecular basis for predicting the binding modes of Δ9-THC, and endogenous and synthetic cannabinoids. The plasticity of the binding pocket of CB1 seems to be a common feature among certain class A G-protein-coupled receptors. These findings should inspire the design of chemically diverse ligands with distinct pharmacological properties. PMID:28678776

  2. Emerging new therapies for the treatment of type 2 diabetes mellitus: glucagon-like peptide-1 receptor agonists.

    PubMed

    Lindamood, Christopher A; Taylor, James R

    2015-03-01

    The goal of this article was to review the safety, efficacy, and potential for utilization of the newly approved once-weekly glucagon-like peptide-1 (GLP-1) receptor agonists in the treatment of type 2 diabetes. Published articles for Phase III trials were found by performing a MEDLINE search using the search terms exenatide, exenatide once weekly, DURATION, albiglutide, and HARMONY as key terms. Search results were restricted by using filters to include clinical trials in humans. A search of relevant diabetes journals (including Diabetes Care and Diabetologia) was also performed to find abstracts for studies that did not have complete published articles at the time of this review. Exenatide once weekly reduced glycosylated hemoglobin (HbA1c) by -1.0% to -2.0% when used as monotherapy and add-on therapy; it also provided significant weight loss ranging from 2 to 4 kg and maintained a relatively low risk of hypoglycemia. Albiglutide was able to reduce glycosylated hemoglobin levels between -0.5% and -0.84% when used as monotherapy and in combination with other antidiabetic medications. The newest once-weekly GLP-1 receptor agonist, dulaglutide, reduced glycosylated hemoglobin levels between -0.78% and -1.51% and demonstrated noninferiority to once-daily liraglutide. The GLP-1 receptor agonists have proven efficacy in the treatment of type 2 diabetes and may provide patients with additional nonglycemic benefits, including significant weight loss and decreased systolic blood pressure. The newer once-weekly formulations are more convenient than the BID and once-daily medications, which could improve adherence and may be more attractive to providers and patients. Copyright © 2015 Elsevier HS Journals, Inc. All rights reserved.

  3. In silico screening for agonists and blockers of the β(2) adrenergic receptor: implications of inactive and activated state structures.

    PubMed

    Costanzi, Stefano; Vilar, Santiago

    2012-02-15

    Ten crystal structures of the β(2) adrenergic receptor have been published, reflecting different signaling states. Here, through controlled-docking experiments, we examined the implications of using inactive or activated structures on the in silico screening for agonists and blockers of the receptor. Specifically, we targeted the crystal structures solved in complex with carazolol (2RH1), the neutral antagonist alprenalol, the irreversible agonist FAUC50 (3PDS), and the full agonist BI-167017 (3P0G). Our results indicate that activated structures favor agonists over blockers, whereas inactive structures favor blockers over agonists. This tendency is more marked for activated than for inactive structures. Additionally, agonists tend to receive more favorable docking scores when docked at activated rather than inactive structures, while blockers do the opposite. Hence, the difference between the docking scores attained with an activated and an inactive structure is an excellent means for the classification of ligands into agonists and blockers as we determined through receiver operating characteristic curves and linear discriminant analysis. With respect to virtual screening, all structures prioritized well agonists and blockers over nonbinders. However, inactive structures worked better for blockers and activated structures worked better for agonists, respectively. Notably, the combination of individual docking experiments through receptor ensemble docking resulted in an excellent performance in the retrieval of both agonists and blockers. Finally, we demonstrated that the induced-fit docking of agonists is a viable way of modifying an inactive crystal structure and bias it toward the in silico recognition of agonists rather than blockers. Copyright © 2011 Wiley Periodicals, Inc.

  4. Differential role of protein kinase C in desensitization of muscarinic receptor induced by phorbol esters and receptor agonists

    SciTech Connect

    Lai, Wi Sheung.

    1989-01-01

    PKC, a phorbol ester receptor, copurified with specific binding sites of ({sup 3}H)phorbol-12,13,-dibutyrate (({sup 3}H)PDBu). The specific binding of ({sup 3}H)PDBu to intact cells was saturable to a single class of binding sites. The PKC and phorbol ester receptors in N1E-115 cells can be down regulated by prolonged phorbol ester incubation. Phorbol 12-myristate 13-acetate (PMA) suppressed muscarinic receptor-mediated cyclic GMP response in a time-dependent and a concentration-dependent fashion and the suppressive effect of PMA could be attenuated by a protein kinase inhibitor, H-7, as well as by down-regulation of the PKC through long-term incubation with PDBu. Exposure of the cellsmore » to the muscarinic agonist carbamylcholine also desensitized subsequent CBC-mediated cyclic GMP response. However, pretreatment with carbamylcholine did not desensitize histamine-induced cyclic GMP formation while treatment with PMA suppressed this histamine-mediated response. Preincubation of the cells with CBC, but not with phorbol ester, resulted in down-regulation of muscarinic receptors. The loss of muscarinic receptors induced by agonist even occurred when the phosphoinositide hydrolysis response was suppressed.« less

  5. 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. © 2015 Société Française de Pharmacologie et de Thérapeutique.

  6. Decreased agonist affinity and chloride conductance of mutant glycine receptors associated with human hereditary hyperekplexia.

    PubMed Central

    Langosch, D; Laube, B; Rundström, N; Schmieden, V; Bormann, J; Betz, H

    1994-01-01

    Hereditary hyperekplexia is a dominant neurological disorder associated with point mutations at the channel-forming segment M2 of the glycine receptor alpha 1 subunit. Voltage-clamp recordings from the heterologously expressed mutants (alpha 1R271L or alpha 1R271Q) revealed 146- to 183-fold decreased potencies of glycine to activate the chloride channel, and significantly reduced maximal whole-cell currents as compared with wild-type receptors. In contrast, the ability of the competitive antagonist strychnine to block glycine-induced currents was similar in all cases. Radioligand binding assays showed a 90- to 1365-fold reduction in the ability of glycine to displace [3H]strychnine from its binding site on the mutant receptors. Paralleling the reductions in whole-cell current, the elementary main-state conductances of the mutants (alpha 1R271L, 64 pS; alpha 1R271Q, 14 pS) were lower than that of the wild-type receptor (86 pS). The decreased agonist affinities and chloride conductances of the mutants are likely to cause neural hyperexcitability of affected patients by impairing glycinergic inhibition. In addition, our data reveal that structural modifications of the ion-channel region can affect agonist binding to the glycine receptor. PMID:7925268

  7. Therapeutic potential of α7 nicotinic receptor agonists to regulate neuroinflammation in neurodegenerative diseases

    PubMed Central

    Foucault-Fruchard, Laura; Antier, Daniel

    2017-01-01

    Neurodegenerative diseases, such as Alzheimer's, Parkinson's and Huntington's diseases, are all characterized by a component of innate immunity called neuroinflammation. Neuronal loss and neuroinflammation are two phenomena closely linked. Hence, the neuroinflammation is a relevant target for the management of the neurodegenerative diseases given that, to date, there is no treatment to stop neuronal loss. Several studies have investigated the potential effects of activators of alpha 7 nicotinic acetylcholine receptors in animal models of neurodegenerative diseases. These receptors are widely distributed in the central nervous system. After activation, they seem to mediate the cholinergic anti-inflammatory pathway in the brain. This anti-inflammatory pathway, first described in periphery, regulates activation of microglial cells considered as the resident macrophage population of the central nervous system. In this article, we shortly review the agonists of the alpha 7 nicotinic acetylcholine receptors that have been evaluated in vivo and we focused on the selective positive allosteric modulators of these receptors. These compounds represent a key element to enhance receptor activity only in the presence of the endogenous agonist. PMID:29089979

  8. Site specificity of agonist-induced opening and desensitization of the Torpedo californica nicotinic acetylcholine receptor.

    PubMed

    Andreeva, Iraida E; Nirthanan, Selvanayagam; Cohen, Jonathan B; Pedersen, Steen E

    2006-01-10

    Agonist-binding kinetics to the nicotinic acetylcholine receptor (AChR) from Torpedo californica were measured using sequential-mixing stopped-flow fluorescence methods to determine the contribution of each individual site to agonist-induced opening and desensitization. Timed dansyl-C6-choline (DC6C) binding followed by its dissociation upon mixing with high, competing agonist concentrations revealed four kinetic components: an initial, fast fluorescence decay, followed by a transient increase, and then two characteristic decays that reflect dissociation from the desensitized agonist sites. The transient increase resulted from DC6C binding to the open-channel based on its prevention by proadifen, a noncompetitive antagonist. Further characterization of DC6C channel binding by the inhibition of [3H]phencyclidine binding and by equilibrium measurements of DC6C fluorescence yielded KD values of 2-4 microM for the desensitized AChR and approximately 600 microM for the closed state. At this site, DC6C displayed a strongly blue-shifted emission spectrum, higher intrinsic fluorescence, and weaker energy transfer from tryptophans than when bound to either agonist site. The initial, fast fluorescence decay was assigned to DC6C dissociation from the alphadelta site of the AChR in its closed conformation, on the basis of inhibition with the site-selective antagonists d-tubocurarine and alpha-conotoxin MI. Fast decay amplitude data indicated an apparent affinity of 0.9 microM for the closed-state alphadelta site; the closed-state alphagamma-site affinity is inferred to be near 100 microM. These values and the known affinities for the desensitized conformation show that the alphagamma site drives AChR desensitization to a approximately 40-fold greater extent than the alphadelta site, undergoes energetically larger conformational changes, and is the primary determinant of agonist potency.

  9. Effect of estrogen receptor β agonists on proliferation and gene expression of ovarian cancer cells.

    PubMed

    Schüler-Toprak, Susanne; Moehle, Christoph; Skrzypczak, Maciej; Ortmann, Olaf; Treeck, Oliver

    2017-05-08

    Estrogen receptor (ER) β has been suggested to affect ovarian carcinogenesis. We examined the effects of four ERβ agonists on proliferation and gene expression of two ovarian cancer cell lines. OVCAR-3 and OAW-42 ovarian cancer cells were treated with the ERβ agonists ERB-041, WAY200070, Liquiritigenin and 3β-Adiol and cell growth was measured by means of the Cell Titer Blue Assay (Promega). ERβ expression was knocked down by transfection with specific siRNA. Additionally, transcriptome analyses were performed by means of Affymetrix GeneChip arrays. To confirm the results of DNA microarray analysis, Western blot experiments were performed. All ERβ agonists tested significantly decreased proliferation of OVCAR-3 and OAW-42 cells at a concentration of 10 nM. Maximum antiproliferative effects were induced by flavonoid Liquiritigenin, which inhibited growth of OVCAR-3 cells by 31.2% after 5 days of treatment, and ERB-041 suppressing proliferation of the same cell line by 29.1%. In OAW-42 cells, maximum effects were observed after treatment with the ERβ agonist WAY200070, inhibiting cell growth by 26.8%, whereas ERB-041 decreased proliferation by 24.4%. In turn, knockdown of ERβ with specific siRNA increased cell growth of OAW-42 cells about 1.9-fold. Transcriptome analyses revealed a set of genes regulated by ERβ agonists including ND6, LCN1 and PTCH2, providing possible molecular mechanisms underlying the observed antiproliferative effects. In conclusion, the observed growth-inhibitory effects of all ERβ agonists on ovarian cancer cell lines in vitro encourage further studies to test their possible use in the clinical setting.

  10. The sigma receptor agonist SA4503 both attenuates and enhances the effects of methamphetamine

    PubMed Central

    Rodvelt, Kelli R.; Oelrichs, Clark E.; Blount, Lucas R.; Fan, Kuo-Hsien; Lever, Susan Z.; Lever, John R.; Miller, Dennis K.

    2011-01-01

    Background Methamphetamine’s behavioral effects have been attributed to its interaction with monoamine transporters; however, methamphetamine also has affinity for sigma receptors. Method The present study investigated the effect of the sigma receptor agonist SA 4503 and the sigma receptor antagonists BD-1047 and BD-1063 on methamphetamine-evoked [3H] dopamine release from preloaded rat striatal slices. The effect of SA 4503 on methamphetamine-induced hyperactivity and on the discriminative stimulus properties of methamphetamine also was determined. Results SA 4503 attenuated methamphetamine-evoked [3H]dopamine release in a concentration-dependent manner. BD-1047 and BD-1063 did not affect release. SA 4503 dose-dependently potentiated and attenuated methamphetamine-induced hyperactivity. SA 4503 pretreatment augmented the stimulus properties of methamphetamine. Conclusions Our findings indicate that SA 4503 both enhances and inhibits methamphetamine’s effects and that sigma receptors are involved in the neurochemical, locomotor stimulatory and discriminative stimulus properties of methamphetamine. PMID:21277708

  11. Nigramide J is a novel potent inverse agonist of the human constitutive androstane receptor

    PubMed Central

    Kanno, Yuichiro; Tanuma, Nobuaki; Yatsu, Tomofumi; Li, Wei; Koike, Kazuo; Inouye, Yoshio

    2014-01-01

    The constitutive androstane receptor (CAR, NR1I3) is very important for drug development and for understanding pharmacokinetic drug–drug interactions. We screened by mammalian one hybrid assay among natural compounds to discover novel ligands of human constitutive androstane receptor (hCAR). hCAR transcriptional activity was measured by luciferase assay and mRNA levels of CYP2B6 and CYP3A4 in HepTR-hCAR cells and human primary hepatocytes were measured by real-time RT-PCR. Nigramide J (NJ) whose efficacy is comparable to those of hitherto known inverse agonists such as clotrimazole, PK11195, and ethinylestradiol. NJ is a naturally occurring cyclohexane-type amide alkaloid that was isolated from the roots of Piper nigrum. The suppressive effect of NJ on the CAR-dependent transcriptional activity was found to be species specific, in the descending order of hCAR, rat CAR, and mouse CAR. The unliganded hCAR-dependent transactivation of reporter and endogenous genes was suppressed by NJ at concentrations higher than 5 μmol/L. The ligand-binding cavity of hCAR was shared by NJ and CITCO, because they were competitive in the binding to hCAR. NJ interfered with the interaction of hCAR with coactivator SRC-1, but not with its interaction with the corepressor NCoR1. Furthermore, NJ is agonist of human pregnane X receptor (hPXR). NJ is a dual ligand of hCAR and hPXR, being an agonist of hPXR and an inverse agonist of hCAR. PMID:25505573

  12. Working memory span capacity improved by a D2 but not D1 receptor family agonist

    PubMed Central

    Tarantino, Isadore S; Sharp, Richard F; Geyer, Mark A; Meves, Jessica M; Young, Jared W

    2011-01-01

    Patients with schizophrenia exhibit poor working memory (WM). Although several subcomponents of WM can be measured, evidence suggests the primary subcomponent affected in schizophrenia is span capacity (WMC). Indeed, the NIMH-funded MATRICS initiative recommended assaying the WMC when assessing the efficacy of a putative therapeutic for FDA approval. Although dopamine D1 receptor agonists improve delay-dependent memory in animals, evidence for improvements in WMC due to dopamine D1 receptor activation is limited. In contrast, the dopamine D2-family agonist bromocriptine improves WMC in humans. The radial arm maze (RAM) can be used to assess WMC, although complications due to ceiling effects or strategy confounds have limited its use. We describe a 12-arm RAM protocol designed to assess whether the dopamine D1-family agonist SKF 38393 (0, 1, 3, and 10 mg/kg) or bromocriptine (0, 1, 3, and 10 mg/kg) could improve WMC in C57BL/6N mice (n=12) in cross-over designs. WMC increased and strategy usage decreased with training. The dopamine D1 agonist SKF 38393 had no effect on WMC or long-term memory. Bromocriptine decreased WMC errors, without affecting long-term memory, consistent with human studies. These data confirm that WMC can be measured in mice and reveal drug effects that are consistent with reported effects in humans. Future research is warranted to identify the subtype of the D2-family of receptors responsible for the observed improvement in WMC. Finally, this RAM procedure may prove useful in developing animal models of deficient WMC to further assess putative treatments for the cognitive deficits in schizophrenia. PMID:21232557

  13. Working memory span capacity improved by a D2 but not D1 receptor family agonist.

    PubMed

    Tarantino, Isadore S; Sharp, Richard F; Geyer, Mark A; Meves, Jessica M; Young, Jared W

    2011-06-01

    Patients with schizophrenia exhibit poor working memory (WM). Although several subcomponents of WM can be measured, evidence suggests the primary subcomponent affected in schizophrenia is span capacity (WMC). Indeed, the NIMH-funded MATRICS initiative recommended assaying the WMC when assessing the efficacy of a putative therapeutic for FDA approval. Although dopamine D1 receptor agonists improve delay-dependent memory in animals, evidence for improvements in WMC due to dopamine D1 receptor activation is limited. In contrast, the dopamine D2-family agonist bromocriptine improves WMC in humans. The radial arm maze (RAM) can be used to assess WMC, although complications due to ceiling effects or strategy confounds have limited its use. We describe a 12-arm RAM protocol designed to assess whether the dopamine D1-family agonist SKF 38393 (0, 1, 3, and 10 mg/kg) or bromocriptine (0, 1, 3, and 10 mg/kg) could improve WMC in C57BL/6N mice (n=12) in cross-over designs. WMC increased and strategy usage decreased with training. The dopamine D1 agonist SKF 38393 had no effect on WMC or long-term memory. Bromocriptine decreased WMC errors, without affecting long-term memory, consistent with human studies. These data confirm that WMC can be measured in mice and reveal drug effects that are consistent with reported effects in humans. Future research is warranted to identify the subtype of the D2-family of receptors responsible for the observed improvement in WMC. Finally, this RAM procedure may prove useful in developing animal models of deficient WMC to further assess putative treatments for the cognitive deficits in schizophrenia. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Collybolide is a novel biased agonist of κ-opioid receptors with potent antipruritic activity

    PubMed Central

    Gupta, Achla; Gomes, Ivone; Bobeck, Erin N.; Fakira, Amanda K.; Massaro, Nicholas P.; Sharma, Indrajeet; Cavé, Adrien; Hamm, Heidi E.; Parello, Joseph

    2016-01-01

    Among the opioid receptors, the κ-opioid receptor (κOR) has been gaining considerable attention as a potential therapeutic target for the treatment of complex CNS disorders including depression, visceral pain, and cocaine addiction. With an interest in discovering novel ligands targeting κOR, we searched natural products for unusual scaffolds and identified collybolide (Colly), a nonnitrogenous sesquiterpene from the mushroom Collybia maculata. This compound has a furyl-δ-lactone core similar to that of Salvinorin A (Sal A), another natural product from the plant Salvia divinorum. Characterization of the molecular pharmacological properties reveals that Colly, like Sal A, is a highly potent and selective κOR agonist. However, the two compounds differ in certain signaling and behavioral properties. Colly exhibits 10- to 50-fold higher potency in activating the mitogen-activated protein kinase pathway compared with Sal A. Taken with the fact that the two compounds are equipotent for inhibiting adenylyl cyclase activity, these results suggest that Colly behaves as a biased agonist of κOR. Behavioral studies also support the biased agonistic activity of Colly in that it exhibits ∼10-fold higher potency in blocking non–histamine-mediated itch compared with Sal A, and this difference is not seen in pain attenuation by these two compounds. These results represent a rare example of functional selectivity by two natural products that act on the same receptor. The biased agonistic activity, along with an easily modifiable structure compared with Sal A, makes Colly an ideal candidate for the development of novel therapeutics targeting κOR with reduced side effects. PMID:27162327

  15. Collybolide is a novel biased agonist of κ-opioid receptors with potent antipruritic activity.

    PubMed

    Gupta, Achla; Gomes, Ivone; Bobeck, Erin N; Fakira, Amanda K; Massaro, Nicholas P; Sharma, Indrajeet; Cavé, Adrien; Hamm, Heidi E; Parello, Joseph; Devi, Lakshmi A

    2016-05-24

    Among the opioid receptors, the κ-opioid receptor (κOR) has been gaining considerable attention as a potential therapeutic target for the treatment of complex CNS disorders including depression, visceral pain, and cocaine addiction. With an interest in discovering novel ligands targeting κOR, we searched natural products for unusual scaffolds and identified collybolide (Colly), a nonnitrogenous sesquiterpene from the mushroom Collybia maculata. This compound has a furyl-δ-lactone core similar to that of Salvinorin A (Sal A), another natural product from the plant Salvia divinorum Characterization of the molecular pharmacological properties reveals that Colly, like Sal A, is a highly potent and selective κOR agonist. However, the two compounds differ in certain signaling and behavioral properties. Colly exhibits 10- to 50-fold higher potency in activating the mitogen-activated protein kinase pathway compared with Sal A. Taken with the fact that the two compounds are equipotent for inhibiting adenylyl cyclase activity, these results suggest that Colly behaves as a biased agonist of κOR. Behavioral studies also support the biased agonistic activity of Colly in that it exhibits ∼10-fold higher potency in blocking non-histamine-mediated itch compared with Sal A, and this difference is not seen in pain attenuation by these two compounds. These results represent a rare example of functional selectivity by two natural products that act on the same receptor. The biased agonistic activity, along with an easily modifiable structure compared with Sal A, makes Colly an ideal candidate for the development of novel therapeutics targeting κOR with reduced side effects.

  16. A robotic BG1Luc reporter assay to detect estrogen receptor agonists.

    PubMed

    Stoner, Matthew A; Yang, Chun Z; Bittner, George D

    2014-08-01

    Endocrine disrupting chemicals with estrogenic activity (EA) have been associated with various adverse health effects. US agencies (ICCVAM/NICEATM) tasked to assess in vitro transcription activation assays to detect estrogenic receptor (ER) agonists for EA have recently validated a BG1Luc assay in manual format, but prefer robotic formats. We have developed a robotic BG1Luc EA assay to detect EA that demonstrated 100% concordance with ICCVAM meta-analyses and ICCVAM BG1Luc results in manual format for 27 ICCVAM test substances, i.e. no false negatives or false positives. This robotic assay also consistently assessed other, more problematic ICCVAM test substances such as clomiphene citrate, L-thyroxin, and tamoxifen. Agonist responses using this robotic BG1Luc assay were consistently inhibited by the ER antagonist ICI 182,780, confirming that agonist responses were due to binding to ERs rather than to a non-specific agonist response. This robotic assay also detected EA in complex mixtures of substances such as extracts of personal care products, plastic resins or plastic consumer products. This robotic BG1Luc assay had at least as high accuracy and greater sensitivity and repeatability when compared to its manual version or to the other ICCVAM/OECD validated assays for EA (manual BG1Luc and CERI). Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Incretin-like effects of small molecule trace amine-associated receptor 1 agonists.

    PubMed

    Raab, Susanne; Wang, Haiyan; Uhles, Sabine; Cole, Nadine; Alvarez-Sanchez, Ruben; Künnecke, Basil; Ullmer, Christoph; Matile, Hugues; Bedoucha, Marc; Norcross, Roger D; Ottaway-Parker, Nickki; Perez-Tilve, Diego; Conde Knape, Karin; Tschöp, Matthias H; Hoener, Marius C; Sewing, Sabine

    2016-01-01

    Type 2 diabetes and obesity are emerging pandemics in the 21st century creating worldwide urgency for the development of novel and safe therapies. We investigated trace amine-associated receptor 1 (TAAR1) as a novel target contributing to the control of glucose homeostasis and body weight. We investigated the peripheral human tissue distribution of TAAR1 by immunohistochemistry and tested the effect of a small molecule TAAR1 agonist on insulin secretion in vitro using INS1E cells and human islets and on glucose tolerance in C57Bl6, and db/db mice. Body weight effects were investigated in obese DIO mice. TAAR1 activation by a selective small molecule agonist increased glucose-dependent insulin secretion in INS1E cells and human islets and elevated plasma PYY and GLP-1 levels in mice. In diabetic db/db mice, the TAAR1 agonist normalized glucose excursion during an oral glucose tolerance test. Sub-chronic treatment of diet-induced obese (DIO) mice with the TAAR1 agonist resulted in reduced food intake and body weight. Furthermore insulin sensitivity was improved and plasma triglyceride levels and liver triglyceride content were lower than in controls. We have identified TAAR1 as a novel integrator of metabolic control, which acts on gastrointestinal and pancreatic islet hormone secretion. Thus TAAR1 qualifies as a novel and promising target for the treatment of type 2 diabetes and obesity.

  18. Recent advances in histamine H3 receptor antagonists/inverse agonists.

    PubMed

    Łazewska, Dorota; Kieć-Kononowicz, Katarzyna

    2010-09-01

    Histamine H(3) receptor (H(3)R) antagonists/inverse agonists can be therapeutically useful in the treatment of various CNS, metabolic syndrome and allergic disorders, and constitute an attractive target in the search for new drugs. However, several drug candidates have been rejected because of unwanted effects. There is, therefore, a strong need to develop new H(3)R ligands. A review was conducted of recent advances in the search for H(3)R antagonists/inverse agonists as reflected by patent applications/patents over the last 3 years. A total of around 100 patent applications/patents along with selected peer-reviewed publications are surveyed. These involve antagonists/inverse agonists of H(3)R, which the authors have divided into five groups. The above-mentioned compounds were evaluated for their potential utility in the treatment of narcolepsy, attention deficit hyperactivity disorder, epilepsy, Alzheimer's disease, schizophrenia, obesity and neuropathic pain. Several H(3)R antagonists/inverse agonists appear to be promising drug candidates, including at least 15 compounds undergoing evaluation in clinical development. Especially interesting is pitolisant, which is progressing through to Phase III clinical trials.

  19. Ingestion of transient receptor potential channel agonists attenuates exercise-induced muscle cramps.

    PubMed

    Craighead, Daniel H; Shank, Sean W; Gottschall, Jinger S; Passe, Dennis H; Murray, Bob; Alexander, Lacy M; Kenney, W Larry

    2017-09-01

    Exercise-associated muscle cramping (EAMC) is a poorly understood problem that is neuromuscular in origin. Ingestion of transient receptor potential (TRP) channel agonists has been efficacious in attenuating electrically induced muscle cramps. This study examines the effect of TRP agonist ingestion on voluntarily induced EAMC and motor function. Study 1: Thirty-nine participants completed 2 trials after ingesting TRP agonist-containing active treatment (A), or vehicle (V) control. Cramping in the triceps surae muscle was induced via voluntary isometric contraction. Study 2: After ingesting A or V, 31 participants performed kinematic and psychomotor tests of manual dexterity. A increased precramp contraction duration (A, 36.9 ± 4.1 s; V, 27.8 ± 3.1 s), decreased cramp EMG area under the curve (A, 37.3 ± 7.7 %EMG max ·s; V, 77.2 ± 17.7 %EMG max ·s), increased contraction force to produce the cramp (A, 13.8 ± 1.8 kg; V, 9.9 ± 1.6 kg), and decreased postcramp soreness (A, 4.1 ± 0.3 arbitrary units (a.u.); V, 4.7 ± 0.3 a.u.). Kinematic and psychomotor tests were not affected. TRP agonist ingestion attenuated EAMC characteristics without affecting motor function. Muscle Nerve 56: 379-385, 2017. © 2017 Wiley Periodicals, Inc.

  20. Prostaglandin E receptor subtype EP4 agonist serves better to protect cochlea than prostaglandin E1.

    PubMed

    Hori, Ryusuke; Nakagawa, Takayuki; Yamamoto, Norio; Hamaguchi, Kiyomi; Ito, Juichi

    2013-12-01

    The present study aimed to examine whether an E-prostanoid receptor 4 (EP4) agonist has superior protective effects to those of prostaglandin E1 (PGE1) in a guinea pig model of noise trauma. Drugs were locally applied on the round window membrane of guinea pig cochleae, followed by exposure of the test animals to intense noise. Protective effects mediated by an EP4 agonist were compared with those mediated by PGE1. Auditory function was monitored by measurements of the auditory brainstem response (ABR), and histological damage was assessed by immunohistochemical analysis of cochlear specimens. Animals treated with an EP4 agonist exhibited significantly better hearing recovery than those pretreated with PGE1. Histologically, the numbers of remaining outer hair cells in cochleae treated with the EP4 agonist were significantly higher than in those treated with PGE1. The selective activation of EP4 has a stronger protective effect on cochleae against noise trauma than does the broad activation of EPs by PGE1. Copyright © 2013. Published by Elsevier Ireland Ltd.

  1. Incretin-like effects of small molecule trace amine-associated receptor 1 agonists

    PubMed Central

    Raab, Susanne; Wang, Haiyan; Uhles, Sabine; Cole, Nadine; Alvarez-Sanchez, Ruben; Künnecke, Basil; Ullmer, Christoph; Matile, Hugues; Bedoucha, Marc; Norcross, Roger D.; Ottaway-Parker, Nickki; Perez-Tilve, Diego; Conde Knape, Karin; Tschöp, Matthias H.; Hoener, Marius C.; Sewing, Sabine

    2015-01-01

    Objective Type 2 diabetes and obesity are emerging pandemics in the 21st century creating worldwide urgency for the development of novel and safe therapies. We investigated trace amine-associated receptor 1 (TAAR1) as a novel target contributing to the control of glucose homeostasis and body weight. Methods We investigated the peripheral human tissue distribution of TAAR1 by immunohistochemistry and tested the effect of a small molecule TAAR1 agonist on insulin secretion in vitro using INS1E cells and human islets and on glucose tolerance in C57Bl6, and db/db mice. Body weight effects were investigated in obese DIO mice. Results TAAR1 activation by a selective small molecule agonist increased glucose-dependent insulin secretion in INS1E cells and human islets and elevated plasma PYY and GLP-1 levels in mice. In diabetic db/db mice, the TAAR1 agonist normalized glucose excursion during an oral glucose tolerance test. Sub-chronic treatment of diet-induced obese (DIO) mice with the TAAR1 agonist resulted in reduced food intake and body weight. Furthermore insulin sensitivity was improved and plasma triglyceride levels and liver triglyceride content were lower than in controls. Conclusions We have identified TAAR1 as a novel integrator of metabolic control, which acts on gastrointestinal and pancreatic islet hormone secretion. Thus TAAR1 qualifies as a novel and promising target for the treatment of type 2 diabetes and obesity. PMID:26844206

  2. Novel Zn2+ Modulated GPR39 Receptor Agonists Do Not Drive Acute Insulin Secretion in Rodents

    PubMed Central

    Yasuda, Shin-ichiro; Tsuchida, Takuma; Oguma, Takahiro; Marley, Anna; Wennberg-Huldt, Charlotte; Hovdal, Daniel; Fukuda, Hajime; Yoneyama, Yukimi; Sasaki, Kazuyo; Johansson, Anders; Lundqvist, Sara; Brengdahl, Johan; Isaacs, Richard J.; Brown, Daniel; Geschwindner, Stefan; Benthem, Lambertus; Priest, Claire; Turnbull, Andrew

    2015-01-01

    Type 2 diabetes (T2D) occurs when there is insufficient insulin release to control blood glucose, due to insulin resistance and impaired β-cell function. The GPR39 receptor is expressed in metabolic tissues including pancreatic β-cells and has been proposed as a T2D target. Specifically, GPR39 agonists might improve β-cell function leading to more adequate and sustained insulin release and glucose control. The present study aimed to test the hypothesis that GPR39 agonism would improve glucose stimulated insulin secretion in vivo. A high throughput screen, followed by a medicinal chemistry program, identified three novel potent Zn2+ modulated GPR39 agonists. These agonists were evaluated in acute rodent glucose tolerance tests. The results showed a lack of glucose lowering and insulinotropic effects not only in lean mice, but also in diet-induced obese (DIO) mice and Zucker fatty rats. It is concluded that Zn2+ modulated GPR39 agonists do not acutely stimulate insulin release in rodents. PMID:26720709

  3. Muscarinic receptor agonists stimulate matrix metalloproteinase 1-dependent invasion of human colon cancer cells

    SciTech Connect

    Raufman, Jean-Pierre, E-mail: jraufman@medicine.umaryland.edu; Cheng, Kunrong; Saxena, Neeraj

    2011-11-18

    Highlights: Black-Right-Pointing-Pointer Muscarinic receptor agonists stimulated robust human colon cancer cell invasion. Black-Right-Pointing-Pointer Anti-matrix metalloproteinase1 antibody pre-treatment blocks cell invasion. Black-Right-Pointing-Pointer Bile acids stimulate MMP1 expression, cell migration and MMP1-dependent invasion. -- Abstract: Mammalian matrix metalloproteinases (MMPs) which degrade extracellular matrix facilitate colon cancer cell invasion into the bloodstream and extra-colonic tissues; in particular, MMP1 expression correlates strongly with advanced colon cancer stage, hematogenous metastasis and poor prognosis. Likewise, muscarinic receptor signaling plays an important role in colon cancer; muscarinic receptors are over-expressed in colon cancer compared to normal colon epithelial cells. Muscarinic receptor activation stimulates proliferation, migration and invasionmore » of human colon cancer cells. In mouse intestinal neoplasia models genetic ablation of muscarinic receptors attenuates carcinogenesis. In the present work, we sought to link these observations by showing that MMP1 expression and activation plays a mechanistic role in muscarinic receptor agonist-induced colon cancer cell invasion. We show that acetylcholine, which robustly increases MMP1 expression, stimulates invasion of HT29 and H508 human colon cancer cells into human umbilical vein endothelial cell monolayers - this was abolished by pre-incubation with atropine, a non-selective muscarinic receptor inhibitor, and by pre-incubation with anti-MMP1 neutralizing antibody. Similar results were obtained using a Matrigel chamber assay and deoxycholyltaurine (DCT), an amidated dihydroxy bile acid associated with colon neoplasia in animal models and humans, and previously shown to interact functionally with muscarinic receptors. DCT treatment of human colon cancer cells resulted in time-dependent, 10-fold increased MMP1 expression, and DCT-induced cell invasion was also blocked

  4. Structure-Based Screening of Uncharted Chemical Space for Atypical Adenosine Receptor Agonists.

    PubMed

    Rodríguez, David; Chakraborty, Saibal; Warnick, Eugene; Crane, Steven; Gao, Zhan-Guo; O'Connor, Robert; Jacobson, Kenneth A; Carlsson, Jens

    2016-10-21

    Small molecule screening libraries cover only a small fraction of the astronomical number of possible drug-like compounds, limiting the success of ligand discovery efforts. Computational screening of virtual libraries representing unexplored chemical space could potentially bridge this gap. Drug development for adenosine receptors (ARs) as targets for inflammation and cardiovascular diseases has been hampered by the paucity of agonist scaffolds. To identify novel AR agonists, a virtual library of synthetically tractable nucleosides with alternative bases was generated and structure-based virtual screening guided selection of compounds for synthesis. Pharmacological assays were carried out at three AR subtypes for 13 ribosides. Nine compounds displayed significant activity at the ARs, and several of these represented atypical agonist scaffolds. The discovered ligands also provided insights into receptor activation and revealed unknown interactions of endogenous and clinical compounds with the ARs. The results demonstrate that virtual compound databases provide access to bioactive matter from regions of chemical space that are sparsely populated in commercial libraries, an approach transferrable to numerous drug targets.

  5. Ligand-binding domain of an α7-nicotinic receptor chimera and its complex with agonist.

    PubMed

    Li, Shu-Xing; Huang, Sun; Bren, Nina; Noridomi, Kaori; Dellisanti, Cosma D; Sine, Steven M; Chen, Lin

    2011-09-11

    The α(7) acetylcholine receptor (AChR) mediates pre- and postsynaptic neurotransmission in the central nervous system and is a potential therapeutic target in neurodegenerative, neuropsychiatric and inflammatory disorders. We determined the crystal structure of the extracellular domain of a receptor chimera constructed from the human α(7) AChR and Lymnaea stagnalis acetylcholine binding protein (AChBP), which shares 64% sequence identity and 71% similarity with native α(7). We also determined the structure with bound epibatidine, a potent AChR agonist. Comparison of the structures revealed molecular rearrangements and interactions that mediate agonist recognition and early steps in signal transduction in α(7) AChRs. The structures further revealed a ring of negative charge within the central vestibule, poised to contribute to cation selectivity. Structure-guided mutational studies disclosed distinctive contributions to agonist recognition and signal transduction in α(7) AChRs. The structures provide a realistic template for structure-aided drug design and for defining structure-function relationships of α(7) AChRs. © 2011 Nature America, Inc. All rights reserved.

  6. Development of spiroguanidine-derived α7 neuronal nicotinic receptor partial agonists.

    PubMed

    Hill, Matthew D; Fang, Haiquan; Digavalli, Sivarao V; Healy, Francine L; Gallagher, Lizbeth; Post-Munson, Debra; Chen, Ping; Natale, Joanne; Benitex, Yulia; Morgan, Daniel; Lodge, Nicholas; Bristow, Linda; Macor, John E; Olson, Richard E

    2017-02-01

    We describe the synthesis of quinuclidine-containing spiroguanidines and their utility as α7 neuronal nicotinic acetylcholine receptor (nAChR) partial agonists. The convergent synthetic route developed for this study allowed for rapid SAR investigation and provided access to a structurally diverse set of analogs. A potent and selective α7 nAChR partial agonist, N-(6-methyl-1,3-benzoxazol-2-yl)-3',5'-dihydro-4-azaspiro[bicyclo[2.2.2]octane-2,4'-imidazole]-2'-amine (BMS-910731, 16), was identified. This compound induced immediate early genes c-fos and Arc in a preclinical rodent model of α7 nAChR-derived cellular activation and plasticity. Importantly, the ability to incorporate selectivity for the α7 nACh receptor over the 5-HT 3A receptor in this series suggested a significant difference in steric requirements between the two receptors. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. The electrophysiological effects of the serotonin 1A receptor agonist buspirone in emotional face processing.

    PubMed

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

    2015-04-01

    Emotional face processing is critically modulated by the serotonergic system, and serotonin (5-HT) receptor agonists impair emotional face processing. However, the specific contribution of the 5-HT1A receptor remains poorly understood. Here we investigated the spatiotemporal brain mechanisms underpinning the modulation of emotional face processing induced by buspirone, a partial 5-HT1A receptor agonist. In a psychophysical discrimination of emotional faces task, we observed that the discrimination fearful versus neutral faces were reduced, but not happy versus neutral faces. Electrical neuroimaging analyses were applied to visual evoked potentials elicited by emotional face images, after placebo and buspirone administration. Buspirone modulated response strength (i.e., global field power) in the interval 230-248ms after stimulus onset. Distributed source estimation over this time interval revealed that buspirone decreased the neural activity in the right dorsolateral prefrontal cortex that was evoked by fearful faces. These results indicate temporal and valence-specific effects of buspirone on the neuronal correlates of emotional face processing. Furthermore, the reduced neural activity in the dorsolateral prefrontal cortex in response to fearful faces suggests a reduced attention to fearful faces. Collectively, these findings provide new insights into the role of 5-HT1A receptors in emotional face processing and have implications for affective disorders that are characterized by an increased attention to negative stimuli. Copyright © 2015 Elsevier B.V. and ECNP. All rights reserved.

  8. Profound and Rapid Reduction in Body Temperature Induced by the Melanocortin Receptor Agonists

    PubMed Central

    Xu, Yuanzhong; Kim, Eun Ran; Fan, Shengjie; Xia, Yan; Xu, Yong; Huang, Cheng; Tong, Qingchun

    2014-01-01

    The melanocortin receptor 4 (MC4R) plays a major role in body weight regulation and its agonist MTII has been widely used to study the role of MC4Rs in energy expenditure promotion and feeding reduction. Unexpectedly, we observed that intraperitoneal (i.p.) administration of MTII induced a rapid reduction in both body temperature and energy expenditure, which was independent of its effect on feeding and followed by a prolonged increase in energy expenditure. The rapid reduction was at least partly mediated by brain neurons since intracerebroventricular (icv) administration of alpha melanocyte-stimulating hormone, an endogenous melanocortin receptor agonist, produced a similar response. In addition, the body temperature-lowering effect of MTII was independent of the presence of MC4Rs, but in a similar fashion to the previously shown effect on body temperature by 5′AMP. Moreover, β-adrenergic receptors (β-ARs) were required for the recovery from low body temperature induced by MTII and further pharmacological studies showed that the MTII’s effect on body temperature may be partially mediated by the vasopressin V1a receptors. Collectively, our results reveal a previously unappreciated role for the melanocortin pathway in rapidly lowering body temperature. PMID:25065745

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

    PubMed

    Xu, Yuanzhong; Kim, Eun Ran; Fan, Shengjie; Xia, Yan; Xu, Yong; Huang, Cheng; Tong, Qingchun

    2014-08-22

    The melanocortin receptor 4 (MC4R) plays a major role in body weight regulation and its agonist MTII has been widely used to study the role of MC4Rs in energy expenditure promotion and feeding reduction. Unexpectedly, we observed that intraperitoneal (i.p.) administration of MTII induced a rapid reduction in both body temperature and energy expenditure, which was independent of its effect on feeding and followed by a prolonged increase in energy expenditure. The rapid reduction was at least partly mediated by brain neurons since intracerebroventricular (icv) administration of alpha melanocyte-stimulating hormone, an endogenous melanocortin receptor agonist, produced a similar response. In addition, the body temperature-lowering effect of MTII was independent of the presence of MC4Rs, but in a similar fashion to the previously shown effect on body temperature by 5'AMP. Moreover, β-adrenergic receptors (β-ARs) were required for the recovery from low body temperature induced by MTII and further pharmacological studies showed that the MTII's effect on body temperature may be partially mediated by the vasopressin V1a receptors. Collectively, our results reveal a previously unappreciated role for the melanocortin pathway in rapidly lowering body temperature. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. Blockade of alcohol's amnestic activity in humans by an alpha5 subtype benzodiazepine receptor inverse agonist.

    PubMed

    Nutt, David J; Besson, Marie; Wilson, Susan J; Dawson, Gerard R; Lingford-Hughes, Anne R

    2007-12-01

    Alcohol produces many subjective and objective effects in man including pleasure, sedation, anxiolysis, plus impaired eye movements and memory. In human volunteers we have used a newly available GABA-A/benzodiazepine receptor inverse agonist that is selective for the alpha5 subtype (a5IA) to evaluate the role of this subtype in mediating these effects of alcohol on the brain. After pre-treatment with a5IA, we found almost complete blockade of the marked impairment caused by alcohol (mean breath concentration 150mg/100ml) of word list learning and partial but non-significant reversal of subjective sedation without effects on other measures such as intoxication, liking, and slowing of eye movements. This action was not due to alterations in alcohol kinetics and so provides the first proof of concept that selectively decreasing GABA-A receptor function at a specific receptor subtype can offset some actions of alcohol in humans. It also supports growing evidence for a key role of the alpha5 subtype in memory. Inverse agonists at other GABA-A receptor subtypes may prove able to reverse other actions of alcohol, and so offer a new approach to understanding the actions of alcohol in the human brain and in the treatment of alcohol related disorders in humans.

  11. Effect of NMDA, a Specific Agonist to NMDA Receptor Complex, on Rat Hippocampus.

    PubMed

    Motin, V G; Yasnetsov, V V

    2015-10-01

    Removal of Mg2+ ions from perfusion medium provoked epileptiform activity in CA1 field of surviving rat hippocampal slices manifested in generation of extra population spikes. MK-801 (100 μM), a specific non-competitive antagonist to NMDA-receptor complex, prevented this effect. NMDA (20 μM), the specific agonist to this complex, produced no significant effect on the orthodromic population spikes, but when applied at concentrations of 30 or 40 μM, it inhibited them partially (by 21-28%) or almost completely (by 98-99%), correspondingly. Thus, depending on concentration, NMDA can inhibit the synaptic transmission in Schaffer collaterals-hippocampal CA1 pyramidal neurons axis without triggering the epileptiform activity. D-AP5 (50 μM), a competitive antagonist to NMDA-receptor complex, completely prevented the inhibitory effect of NMDA (40 μM). While MK-801 (100 μM) almost completely prevented the inhibitory effect of NMDA, it did not eliminate it when applied after the agonist. Thus, MK-801 can prevent the inhibitory action of NMDA on synaptic transmission in Schaffer collaterals-hippocampal CA1 pyramidal neurons axis via blocking the channel of NMDA-receptor complex, while NMDA exerts its effect only via activation of NMDA receptors.

  12. Design and Synthesis of Selective Estrogen Receptor beta Agonists and Their Pharmacology

    NASA Astrophysics Data System (ADS)

    Perera, K. L. Iresha Sampathi

    Estrogens (17beta-estradiol, E2) have garnered considerable attention in influencing cognitive process in relation to phases of the menstrual cycle, aging and menopausal symptoms. However, hormone replacement therapy can have deleterious effects leading to breast and endometrial cancer, predominantly mediated by estrogen receptor-alpha (ERalpha) the major isoform present in the mammary gland and uterus. Further evidence supports a dominant role of estrogen receptor-beta (ERbeta) for improved cognitive effects such as enhanced hippocampal signaling and memory consolidation via estrogen activated signaling cascades. Creation of the ERbeta selective ligands is challenging due to high structural similarity of both receptors. Thus far, several ERbeta selective agonists have been developed, however, none of these have made it to clinical use due to their lower selectivity or considerable side effects. The research in this dissertation involved the design of non-steroidal ERbeta selective agonists for hippocampal memory consolidation. The step-wise process to achieve the ultimate goal of this research includes: (1) design and synthesis of (4-hydroxyphenyl)cyclohexyl or cycloheptyl derivatives, (2) in vitro biological evaluation of synthesized compounds to identify highly potent and selective candidates, and (3) in vivo biological evaluation of selected candidates for hippocampal memory consolidation. Several (4-hydroxyphenyl)cyclohexyl or cycloheptyl derivatives were synthesized having structural alterations on both aromatic and cyclohexyl/heptyl ring scaffolds. ERbeta agonist potency was initially evaluated in TR-FRET ERbeta ligand binding assay and compounds having high potency were re-evaluated in functional cell based assays for potency and ERbeta vs. ERalpha selectivity. Two compounds from each series, ISP 163-PK4 and ISP 358-2 were identified as most selective ERbeta agonists. Both compounds revealed high metabolic stability, solubility and no cross reactivity

  13. Significant Correlation between TLR2 Agonist Activity and TNF-α Induction in J774.A1 Macrophage Cells by Different Medicinal Mushroom Products.

    PubMed

    Coy, Catherine; Standish, Leanna J; Bender, Geoff; Lu, Hailing

    2015-01-01

    In the US market, there is a variety of mushroom preparations available, even within the same species of mushroom. Nonetheless, little is known about whether species or the various extraction methods affect biological activity and potency of the immune modulatory activity of mushroom extracts. After discovering that protein-bound polysaccharide-K, a hot water extract from Trametes versicolor, was a potent Toll-like receptor (TLR)-2 agonist that stimulates both innate and adaptive immunity, this study was initiated to evaluate whether other medicinal mushroom products also have TLR2 agonist activity and immune-enhancing potential as measured by the induction of tumor necrosis factor (TNF)-α in J774.A1 murine macrophage cells. Furthermore, the products were divided by extraction method and species to determine whether these factors affect their immunomodulatory activity. The results showed that the majority (75%) of mushroom products tested had TLR2 agonist activity and that there was a significant correlation between TLR2 agonist activity and TNF-α induction potential in the mushroom products analyzed. In addition, the data demonstrated that hot water mushroom extracts are more potent than ground mushroom products in activating TLR2 and inducing TNF-α. These data provide evidence that extraction methods may affect the biological activity of mushroom products; thus, further studies are warranted to investigate the structural differences between various mushroom products.

  14. Endomorphin-2: A Biased Agonist at the μ-Opioid Receptor

    PubMed Central

    Rivero, Guadalupe; Llorente, Javier; McPherson, Jamie; Cooke, Alex; Mundell, Stuart J.; McArdle, Craig A.; Rosethorne, Elizabeth M.; Charlton, Steven J.; Krasel, Cornelius; Bailey, Christopher P.; Henderson, Graeme

    2012-01-01

    Previously we correlated the efficacy for G protein activation with that for arrestin recruitment for a number of agonists at the μ-opioid receptor (MOPr) stably expressed in HEK293 cells. We suggested that the endomorphins (endomorphin-1 and -2) might be biased toward arrestin recruitment. In the present study, we investigated this phenomenon in more detail for endomorphin-2, using endogenous MOPr in rat brain as well as MOPr stably expressed in HEK293 cells. For MOPr in neurons in brainstem locus ceruleus slices, the peptide agonists [d-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO) and endomorphin-2 activated inwardly rectifying K+ current in a concentration-dependent manner. Analysis of these responses with the operational model of pharmacological agonism confirmed that endomorphin-2 had a much lower operational efficacy for G protein-mediated responses than did DAMGO at native MOPr in mature neurons. However, endomorphin-2 induced faster desensitization of the K+ current than did DAMGO. In addition, in HEK293 cells stably expressing MOPr, the ability of endomorphin-2 to induce phosphorylation of Ser375 in the COOH terminus of the receptor, to induce association of arrestin with the receptor, and to induce cell surface loss of receptors was much more efficient than would be predicted from its efficacy for G protein-mediated signaling. Together, these results indicate that endomorphin-2 is an arrestin-biased agonist at MOPr and the reason for this is likely to be the ability of endomorphin-2 to induce greater phosphorylation of MOPr than would be expected from its ability to activate MOPr and to induce activation of G proteins. PMID:22553358

  15. Ractopamine, a Livestock Feed Additive, Is a Full Agonist at Trace Amine–Associated Receptor 1

    PubMed Central

    Grandy, David K.; Janowsky, Aaron

    2014-01-01

    Ractopamine (RAC) is fed to an estimated 80% of all beef, swine, and turkey raised in the United States. It promotes muscle mass development, limits fat deposition, and reduces feed consumption. However, it has several undesirable behavioral side effects in livestock, especially pigs, including restlessness, agitation, excessive oral-facial movements, and aggressive behavior. Numerous in vitro and in vivo studies suggest RAC’s physiological actions begin with its stimulation of β1- and β2-adrenergic receptor–mediated signaling in skeletal muscle and adipose tissue; however, the molecular pharmacology of RAC’s psychoactive effects is poorly understood. Using human cystic fibrosis transmembrane conductance regulator (hCFTR) chloride channels as a sensor for intracellular cAMP, we found that RAC and p-tyramine (TYR) produced concentration-dependent increases in chloride conductance in oocytes coexpressing hCFTR and mouse trace amine–associated receptor 1 (mTAAR1), which was completely reversed by the trace amine–associated receptor 1 (TAAR1)–selective antagonist EPPTB [N-(3-ethoxyphenyl)-4-pyrrolidin-1-yl-3-trifluoromethylbenzamide]. Oocytes coexpressing hCFTR and the human β2-adrenergic receptor showed no response to RAC or TYR. These studies demonstrate that, contrary to expectations, RAC is not an agonist of the human β2-adrenergic receptor but rather a full agonist for mTAAR1. Since TAAR1-mediated signaling can influence cardiovascular tone and behavior in several animal models, our finding that RAC is a full mTAAR1 agonist supports the idea that this novel mechanism of action influences the physiology and behavior of pigs and other species. These findings should stimulate future studies to characterize the pharmacological, physiological, and behavioral actions of RAC in humans and other species exposed to this drug. PMID:24799633

  16. Potent complement C3a receptor agonists derived from oxazole amino acids: Structure-activity relationships.

    PubMed

    Singh, Ranee; Reed, Anthony N; Chu, Peifei; Scully, Conor C G; Yau, Mei-Kwan; Suen, Jacky Y; Durek, Thomas; Reid, Robert C; Fairlie, David P

    2015-12-01

    Potent ligands for the human complement C3a receptor (C3aR) were developed from the almost inactive tripeptide Leu-Ala-Arg corresponding to the three C-terminal residues of the endogenous peptide agonist C3a. The analogous Leu-Ser-Arg was modified by condensing the serine side chain with the leucine carbonyl with elimination of water to form leucine-oxazole-arginine. Subsequent elaboration with a variety of N-terminal amide capping groups produced agonists as potent as human C3a itself in stimulating Ca(2+) release from human macrophages. Structure-activity relationships are discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Transcriptomic and phenotypic profiling in developing zebrafish exposed to thyroid hormone receptor agonists

    SciTech Connect

    Haggard, Derik E.; Noyes, Pamela D.; Waters, Katrina M.

    2018-04-01

    There is a need to develop novel, high-throughput screening and prioritization methods to identify chemicals with adverse estrogen, androgen, and thyroid activity to protect human health and the environment and is of interest to the Endocrine Disruptor Screening Program. The current aim is to explore the utility of zebrafish as a testing paradigm to classify endocrine activity using phenotypically anchored transcriptome profiling. Transcriptome analysis was conducted on embryos exposed to 25 estrogen-, androgen-, or thyroid-active chemicals at a concentration that elicited adverse malformations or mortality at 120 hours post-fertilization in 80% of the animals exposed. Analysis of the top 1000more » significant differentially expressed transcripts across all treatments identified a unique transcriptional and phenotypic profile for thyroid hormone receptor agonists, which can be used as a biomarker screen for potential thyroid hormone agonists.« less

  18. Allosteric agonists of the calcium receptor (CaR): fluorine and SF5 analogues of cinacalcet.

    PubMed

    Chia, Poh Wai; Brennan, Sarah C; Slawin, Alexandra M Z; Riccardi, Daniela; O'Hagan, David

    2012-10-21

    Three selectively fluorinated cinacalcet analogues are prepared and their activity as calcium-sensing receptor (CaR) agonists is assessed. Individual (2R,1'R)-2 and (2S,1'R)-3 fluorocinacalcet diastereoisomers were prepared using the MacMillan asymmetric fluorination reaction. Assays with the recombinant human CaR revealed that both diastereoisomers have a similar potency to each other although slightly lower (75-80%) than that of cinacalcet 1. The SF(5)-cinacalcet analogue 4 was prepared from meta-pentafluorosulfanyl benzyl alcohol and has ~75% agonist activity relative to cinacalcet 1 indicating that the SF(5) group can replace the CF(3) group and retain significant bioactivity.

  19. Prospects for Creation of Cardioprotective and Antiarrhythmic Drugs Based on Opioid Receptor Agonists

    PubMed Central

    Maslov, Leonid N; Oeltgen, Peter R.; Naryzhnaya, Natalia V.; Pei, Jian‐Ming; Brown, Stephen A.; Lishmanov, Yury B.; Downey, James M.

    2016-01-01

    Abstract It has now been demonstrated that the μ, δ1, δ2, and κ1 opioid receptor (OR) agonists represent the most promising group of opioids for the creation of drugs enhancing cardiac tolerance to the detrimental effects of ischemia/reperfusion (I/R). Opioids are able to prevent necrosis and apoptosis of cardiomyocytes during I/R and improve cardiac contractility in the reperfusion period. The OR agonists exert an infarct‐reducing effect with prophylactic administration and prevent reperfusion‐induced cardiomyocyte death when ischemic injury of heart has already occurred; that is, opioids can mimic preconditioning and postconditioning phenomena. Furthermore, opioids are also effective in preventing ischemia‐induced arrhythmias. PMID:27197922

  20. The in vitro pharmacological profile of TD-5108, a selective 5-HT(4) receptor agonist with high intrinsic activity.

    PubMed

    Smith, J A M; Beattie, D T; Marquess, D; Shaw, J P; Vickery, R G; Humphrey, P P A

    2008-07-01

    The in vitro pharmacological profile of TD-5108, a novel, selective 5-HT(4) receptor agonist, was compared to that of clinically efficacious gastroprokinetic 5-HT(4) receptor agonists. TD-5108 produced an elevation of cyclic adenosine monophosphate in human embryonic kidney 293 cells expressing the human recombinant 5-HT(4(c)) (h5-HT(4(c))) receptor (pEC(50) = 8.3) and 5-HT(4) receptor-mediated relaxation of the rat esophagus (pEC(50) = 7.9) and contraction of the guinea pig colon (pEC(50) = 7.9). In all in vitro assays, TD-5108 was a high intrinsic activity agonist, unlike tegaserod, mosapride, and cisapride which, in the majority of test systems, had lower intrinsic activity. TD-5108 had high affinity (pK (i) = 7.7) and selectivity (> or =25-fold) for h5-HT(4(c)) receptors over other biogenic amine receptors. TD-5108 was >500-fold selective over other 5-HT receptors (including h5-HT(2B) and h5-HT(3A)) and, at 3 microM, had no effect on human ether-à-go-go-related gene K+ channels. In conclusion, TD-5108 is a selective 5-HT(4) receptor agonist in vitro. The high intrinsic activity and preferential binding of TD-5108 to 5-HT4 over other 5-HT receptors may result in an improved clinical profile for the treatment of gastrointestinal disorders of reduced motility.

  1. Agonist-regulated cleavage of the extracellular domain of parathyroid hormone receptor type 1.

    PubMed

    Klenk, Christoph; Schulz, Stefan; Calebiro, Davide; Lohse, Martin J

    2010-03-19

    The receptor for parathyroid hormone (PTHR) is a main regulator of calcium homeostasis and bone maintenance. As a member of class B of G protein-coupled receptors, it harbors a large extracellular domain, which is required for ligand binding. Here, we demonstrate that the PTHR extracellular domain is cleaved by a protease belonging to the family of extracellular metalloproteinases. We show that the cleavage takes place in a region of the extracellular domain that belongs to an unstructured loop connecting the ligand-binding parts and that the N-terminal 10-kDa fragment is connected to the receptor core by a disulfide bond. Cleaved receptor revealed reduced protein stability compared with noncleaved receptor, suggesting degradation of the whole receptor. In the presence of the agonistic peptides PTH(1-34), PTH(1-14), or PTH(1-31), the processing of the PTHR extracellular domain was inhibited, and receptor protein levels were stabilized. A processed form of the PTHR was also detected in human kidney. These findings suggest a new model of PTHR processing and regulation of its stability.

  2. Enhanced immunostimulatory activity of in silico discovered agonists of Toll-like receptor 2 (TLR2).

    PubMed

    Murgueitio, M S; Ebner, S; Hörtnagl, P; Rakers, C; Bruckner, R; Henneke, P; Wolber, G; Santos-Sierra, S

    2017-11-01

    Emergent therapies in anticancer vaccination use Toll-like receptors (TLRs) agonists as dendritic cell (DC) vaccine adjuvants. DCs from the patient are isolated, stimulated with TLR agonists and tumor antigens ex vivo and then infused back into the patient. Although some TLR ligands have been tested in clinical trials, novel TLR agonists with improved immunomodulatory properties are essential to optimize treatment success. We report on the discovery of small-molecule TLR2 agonists, with favorable properties as synthetic adjuvants. We performed a shape- and featured-based similarity virtual screening against a commercially available compound library. The selected virtual hits were experimentally tested in TLR2-reporter cells and their activity in phagocytes and DCs was characterized. A binding model of the compounds to TLR2 (docking studies) was proposed. Through a virtual screening approach against a library of three million compounds four virtual hits (AG1, AG2, AG3, AG4) were found to synergistically augment the NF-kB activation induced by the lipopeptide ligand Pam 3 CSK 4 in luciferase reporter assays using HEK293-TLR2 cells. Biacore experiments indicated that AG1-AG4 are ago-allosteric modulators of TLR2 and AG2 bound TLR2 with high affinity (K D 0.8μM). The compounds induced TNF-α production in human peripheral blood mononuclear cells (PBMCs) and they activated DCs as indicated by IL-12 production and upregulation of CD83/CD86. Following a combined in silico/in vitro approach we have discovered TLR2-agonists (AG1-AG4) that activate human and mouse immune cells. We introduce four novel TLR2 ago-allosteric modulators that stimulate myeloid cell activity and constitute promising candidates as synthetic adjuvants. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. An Accessory Agonist Binding Site Promotes Activation of α4β2* Nicotinic Acetylcholine Receptors*

    PubMed Central

    Wang, Jingyi; Kuryatov, Alexander; Sriram, Aarati; Jin, Zhuang; Kamenecka, Theodore M.; Kenny, Paul J.; Lindstrom, Jon

    2015-01-01

    Neuronal nicotinic acetylcholine receptors containing α4, β2, and sometimes other subunits (α4β2* nAChRs) regulate addictive and other behavioral effects of nicotine. These nAChRs exist in several stoichiometries, typically with two high affinity acetylcholine (ACh) binding sites at the interface of α4 and β2 subunits and a fifth accessory subunit. A third low affinity ACh binding site is formed when this accessory subunit is α4 but not if it is β2. Agonists selective for the accessory ACh site, such as 3-[3-(3-pyridyl)-1,2,4-oxadiazol-5-yl]benzonitrile (NS9283), cannot alone activate a nAChR but can facilitate more efficient activation in combination with agonists at the canonical α4β2 sites. We therefore suggest categorizing agonists according to their site selectivity. NS9283 binds to the accessory ACh binding site; thus it is termed an accessory site-selective agonist. We expressed (α4β2)2 concatamers in Xenopus oocytes with free accessory subunits to obtain defined nAChR stoichiometries and α4/accessory subunit interfaces. We show that α2, α3, α4, and α6 accessory subunits can form binding sites for ACh and NS9283 at interfaces with α4 subunits, but β2 and β4 accessory subunits cannot. To permit selective blockage of the accessory site, α4 threonine 126 located on the minus side of α4 that contributes to the accessory site, but not the α4β2 sites, was mutated to cysteine. Alkylation of this cysteine with a thioreactive reagent blocked activity of ACh and NS9283 at the accessory site. Accessory agonist binding sites are promising drug targets. PMID:25869137

  4. An Accessory Agonist Binding Site Promotes Activation of α4β2* Nicotinic Acetylcholine Receptors.

    PubMed

    Wang, Jingyi; Kuryatov, Alexander; Sriram, Aarati; Jin, Zhuang; Kamenecka, Theodore M; Kenny, Paul J; Lindstrom, Jon

    2015-05-29

    Neuronal nicotinic acetylcholine receptors containing α4, β2, and sometimes other subunits (α4β2* nAChRs) regulate addictive and other behavioral effects of nicotine. These nAChRs exist in several stoichiometries, typically with two high affinity acetylcholine (ACh) binding sites at the interface of α4 and β2 subunits and a fifth accessory subunit. A third low affinity ACh binding site is formed when this accessory subunit is α4 but not if it is β2. Agonists selective for the accessory ACh site, such as 3-[3-(3-pyridyl)-1,2,4-oxadiazol-5-yl]benzonitrile (NS9283), cannot alone activate a nAChR but can facilitate more efficient activation in combination with agonists at the canonical α4β2 sites. We therefore suggest categorizing agonists according to their site selectivity. NS9283 binds to the accessory ACh binding site; thus it is termed an accessory site-selective agonist. We expressed (α4β2)2 concatamers in Xenopus oocytes with free accessory subunits to obtain defined nAChR stoichiometries and α4/accessory subunit interfaces. We show that α2, α3, α4, and α6 accessory subunits can form binding sites for ACh and NS9283 at interfaces with α4 subunits, but β2 and β4 accessory subunits cannot. To permit selective blockage of the accessory site, α4 threonine 126 located on the minus side of α4 that contributes to the accessory site, but not the α4β2 sites, was mutated to cysteine. Alkylation of this cysteine with a thioreactive reagent blocked activity of ACh and NS9283 at the accessory site. Accessory agonist binding sites are promising drug targets. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  5. Revealing a steroid receptor ligand as a unique PPAR[gamma] agonist

    SciTech Connect

    Lin, Shengchen; Han, Ying; Shi, Yuzhe

    2012-06-28

    Peroxisome proliferator-activated receptor gamma (PPAR{gamma}) regulates metabolic homeostasis and is a molecular target for anti-diabetic drugs. We report here the identification of a steroid receptor ligand, RU-486, as an unexpected PPAR{gamma} agonist, thereby uncovering a novel signaling route for this steroid drug. Similar to rosiglitazone, RU-486 modulates the expression of key PPAR{gamma} target genes and promotes adipocyte differentiation, but with a lower adipogenic activity. Structural and functional studies of receptor-ligand interactions reveal the molecular basis for a unique binding mode for RU-486 in the PPAR{gamma} ligand-binding pocket with distinctive properties and epitopes, providing the molecular mechanisms for the discrimination ofmore » RU-486 from thiazolidinediones (TZDs) drugs. Our findings together indicate that steroid compounds may represent an alternative approach for designing non-TZD PPAR{gamma} ligands in the treatment of insulin resistance.« less

  6. Adrenergic Receptor Agonists' Modulation of Dopaminergic and Non-dopaminergic Neurons in the Ventral Tegmental Area.

    PubMed

    Pradel, Kamil; Blasiak, Tomasz; Solecki, Wojciech B

    2018-04-01

    The ventral tegmental area (VTA) neuronal population consists of dopaminergic (DAergic) and non-DAergic neurons (mainly GABAergic), the activity of which is intertwined with VTA behavioral functions. Both DAergic and GABAergic neurons in the VTA have been shown to express adrenergic receptors (ARs) and respond to AR stimulation. The aim of the present study was to demonstrate the effects of selective AR agonists on DAergic and non-DAergic neuronal activity in the central and lateral parts of the VTA using in vivo electrophysiological recording combined with microiontophoretic drug application in anaesthetized rats. Administration of phenylephrine, a selective α 1 -AR agonist, while having an inhibitory effect on putative DAergic neurons (11% decrease in firing rate), induced a clear excitatory effect (59% increase in firing rate) on putative non-DAergic neurons. In contrast, application of clonidine, a selective α 2 -AR agonist, or isoprenaline, a selective β-adrenergic receptor agonist, did not change the firing rate of either DAergic or non-DAergic neurons but influenced the firing pattern of non-DAergic cells only. Our results suggest that noradrenaline modulates activity of VTA neurons in vivo primarily via α 1 , but also via β- and α 2 -AR to a lesser extent. Furthermore, we show that α 1 -AR activation has contrasting effects on putative DAergic and non-DAergic neurons. We hypothesize that the phenylephrine-induced inhibition of putative DAergic neurons results from activation of GABAergic terminals present at the site of drug application. Such a mechanism is further supported by the observed α 1 -AR-induced excitation of putative GABAergic VTA neurons. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

  7. Predicted Structures of Agonist and Antagonist Bound Complexes of Adenosine A3 Receptor

    PubMed Central

    Kim, Soo-Kyung; Riley, Lindsay; Abrol, Ravinder; Jacobson, Kenneth A.; Goddard, William A.

    2011-01-01

    We used the GEnSeMBLE Monte Carlo method to predict ensemble of the 20 best packings (helix rotations and tilts) based on the neutral total energy (E) from a vast number (10 trillion) of potential packings for each of the 4 subtypes of the adenosine G protein-coupled receptors (GPCRs), which are involved in many cytoprotective functions. We then used the DarwinDock Monte Carlo methods to predict the binding pose for the human A3 adenosine receptor (hAA3R) for subtype selective agonists and antagonists. We find that all four A3 agonists stabilize the 15th lowest conformation of apo-hAA3R while also binding strongly to the 1st and 3rd. In contrast the four A3 antagonists stabilize the 2nd or 3rd lowest conformation. These results show that different ligands can stabilize different GPCR conformations, which will likely affect function, complicating the design of functionally unique ligands. Interestingly all agonists lead to a trans χ1 angle for W6.48 that experiments on other GPCRs associate with G-protein activation while all 20 apo-AA3R conformations have a W6.48 gauche+ χ1 angle associated experimentally with inactive GPCRs for other systems. Thus docking calculations have identified critical ligand-GPCR structures involved with activation. We find that the predicted binding site for selective agonist Cl-IB-MECA to the predicted structure of hAA3R shows favorable interactions to three subtype variable residues, I2536.58, V169EL2, and Q167EL2, while the predicted structure for hAA2AR shows weakened to the corresponding amino acids: T2566.58, E169EL2, and L167EL2, explaining the observed subtype selectivity. PMID:21488099

  8. Exposure to D2-like dopamine receptor agonists inhibits swimming in Daphnia magna.

    PubMed

    Barrozo, Enrico R; Fowler, David A; Beckman, Matthew L

    2015-10-01

    Daphnia are freshwater crustaceans that have been used for decades in ecotoxicology research. Despite the important role that Daphnia have played in environmental toxicology studies, very little is known about the neurobiology of Daphnia. Although many studies have investigated the swimming movements of these "water fleas", few studies have examined the underlying neurochemical basis for these movements. To characterize the locomotor effect of drugs in Daphnia, a two-dimensional video imaging tool was developed and animal tracking was performed with freely available software, CTRAX. Due to the central role that dopamine plays in the movement of animals, we sought to determine the role of dopamine receptor signaling in Daphnia movement by characterizing the effect of ten drugs that are agonists or antagonists of dopamine receptors. At 1, 2, and 6h of treatment with a 10μM drug, several dopamine receptor agonists with documented effects on the D2-like class of receptors decreased the movement. Further, we determined behavioral inhibition values (IC50) at 1h of treatment for (1R,3S)-1-(aminomethyl)-3-phenyl-3,4-dihydro-1H-isochromene-5,6-diol (A68930) to be 1.4μM and for bromocriptine to be 6.6μM. This study describes a new method to study Daphnia swimming and establishes this organism as a useful model for studies of dopaminergic signaling. Specifically, this study shows that a dopamine receptor signaling pathway, mediated by putative D2-like receptors, is involved in the control of Daphnia swimming behavior. Due to its ease of use and its rich motor program we propose that Daphnia should be considered for future studies of dopamine neuron toxicity and protection. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Unsaturated free fatty acids increase benzodiazepine receptor agonist binding depending on the subunit composition of the GABAA receptor complex.

    PubMed

    Witt, M R; Westh-Hansen, S E; Rasmussen, P B; Hastrup, S; Nielsen, M

    1996-11-01

    It has been shown previously that unsaturated free fatty acids (FFAs) strongly enhance the binding of agonist benzodiazepine receptor ligands and GABAA receptor ligands in the CNS in vitro. To investigate the selectivity of this effect, recombinant human GABAA/benzodiazepine receptor complexes formed by different subunit compositions (alpha x beta y gamma 2, x = 1, 2, 3, and 5; y = 1, 2, and 3) were expressed using the baculovirus-transfected Sf9 insect cell system. At 10(-4) M, unsaturated FFAs, particularly arachidonic (20:4) and docosahexaenoic (22:6) acids, strongly stimulated (> 200% of control values) the binding of [3H]flunitrazepam ([3H]FNM) to the alpha 3 beta 2 gamma 2 receptor combination in whole cell preparations. No effect or small increases in levels of unsaturated FFAs on [3H]FNM binding to alpha 1 beta x gamma 2 and alpha 2 beta x gamma 2 receptor combinations were observed, and weak effects (130% of control values) were detected using the alpha 5 beta 2 gamma 2 receptor combination. The saturated FFAs, stearic and palmitic acids, were without effect on [3H]FNM binding to any combination of receptor complexes. The hydroxylated unsaturated FFAs, ricinoleic and ricinelaidic acids, were shown to decrease the binding of [3H]FNM only if an alpha 1 beta 2 gamma 2 receptor combination was used. Given the heterogeneity of the GABAA/ benzodiazepine receptor subunit distribution in the CNS, the effects of FFAs on the benzodiazepine receptor can be assumed to vary at both cellular and regional levels.

  10. Hyodeoxycholic acid derivatives as liver X receptor α and G-protein-coupled bile acid receptor agonists

    NASA Astrophysics Data System (ADS)

    de Marino, Simona; Carino, Adriana; Masullo, Dario; Finamore, Claudia; Marchianò, Silvia; Cipriani, Sabrina; di Leva, Francesco Saverio; Catalanotti, Bruno; Novellino, Ettore; Limongelli, Vittorio; Fiorucci, Stefano; Zampella, Angela

    2017-02-01

    Bile acids are extensively investigated for their potential in the treatment of human disorders. The liver X receptors (LXRs), activated by oxysterols and by a secondary bile acid named hyodeoxycholic acid (HDCA), have been found essential in the regulation of lipid homeostasis in mammals. Unfortunately, LXRα activates lipogenic enzymes causing accumulation of lipid in the liver. In addition to LXRs, HDCA has been also shown to function as ligand for GPBAR1, a G protein coupled receptor for secondary bile acids whose activation represents a promising approach to liver steatosis. In the present study, we report a library of HDCA derivatives endowed with modulatory activity on the two receptors. The lead optimization of HDCA moiety was rationally driven by the structural information on the binding site of the two targets and results from pharmacological characterization allowed the identification of hyodeoxycholane derivatives with selective agonistic activity toward LXRα and GPBAR1 and notably to the identification of the first example of potent dual LXRα/GPBAR1 agonists. The new chemical entities might hold utility in the treatment of dyslipidemic disorders.

  11. Comparison of the discriminative-stimulus effects of SKF 38393 with those of other dopamine receptor agonists.

    PubMed

    Desai, R I; Terry, P; Katz, J L

    2003-05-01

    The dopamine D(1)-like receptor agonists have traditionally been defined molecularly by their efficacy in stimulating adenylyl cyclase. However, evidence correlating the effectiveness of these drugs in behavioral assays and their effectiveness biochemically has not been forthcoming. The present study compared the discriminative-stimulus effects of the D(1)-like partial agonist SKF 38393 with several other D(1)-like agonists, an indirect agonist, cocaine, and a D(2)-like agonist, quinpirole. Rats were trained under a fixed-ratio 30-response schedule to discriminate SKF 38393 (5.6 mg/kg) from vehicle. Under this schedule, 30 consecutive responses on one of two keys were reinforced with food presentation after a pre-session injection of 5.6 mg/kg SKF 38393, and 30 consecutive responses on the alternative key were reinforced after saline injection. When daily performances were stable, substitution patterns for several compounds were assessed during test sessions in which 30 consecutive responses on either key were reinforced. Quinpirole and cocaine each produced saline-appropriate responding. In contrast, the D(1)-like agonists, SKF 75670 and SKF 77434, fully substituted for SKF 38393. Curiously, SKF 82958, which is considered a full agonist based on adenylyl cyclase assays, was less effective in substituting for SKF 38393 (maximum drug-appropriate responding 66%) than was the partial agonist SKF 75670. The present results suggest that second messenger effects other than stimulation of adenylyl cyclase may play an important role in the behavioral effects of dopamine D(1)-like agonists.

  12. Structural Probing and Molecular Modeling of the A₃ Adenosine Receptor: A Focus on Agonist Binding.

    PubMed

    Ciancetta, Antonella; Jacobson, Kenneth A

    2017-03-11

    Adenosine is an endogenous modulator exerting its functions through the activation of four adenosine receptor (AR) subtypes, termed A₁, A 2A , A 2B and A₃, which belong to the G protein-coupled receptor (GPCR) superfamily. The human A₃AR (hA₃AR) subtype is implicated in several cytoprotective functions. Therefore, hA₃AR modulators, and in particular agonists, are sought for their potential application as anti-inflammatory, anticancer, and cardioprotective agents. Structure-based molecular modeling techniques have been applied over the years to rationalize the structure-activity relationships (SARs) of newly emerged A₃AR ligands, guide the subsequent lead optimization, and interpret site-directed mutagenesis (SDM) data from a molecular perspective. In this review, we showcase selected modeling-based and guided strategies that were applied to elucidate the binding of agonists to the A₃AR and discuss the challenges associated with an accurate prediction of the receptor extracellular vestibule through homology modeling from the available X-ray templates.

  13. Design of glucagon-like Peptide-1 receptor agonist for diabetes mellitus from traditional chinese medicine.

    PubMed

    Tang, Hsin-Chieh; Chen, Calvin Yu-Chian

    2014-01-01

    Glucagon-like peptide-1 (GLP-1) is a promising target for diabetes mellitus (DM) therapy and reduces the occurrence of diabetes due to obesity. However, GLP-1 will be hydrolyzed soon by the enzyme dipeptidyl peptidase-4 (DPP-4). We tried to design small molecular drugs for GLP-1 receptor agonist from the world's largest traditional Chinese medicine (TCM) Database@Taiwan. According to docking results of virtual screening, we selected 2 TCM compounds, wenyujinoside and 28-deglucosylchikusetsusaponin IV, for further molecular dynamics (MD) simulation. GLP-1 was assigned as the control compound. Based on the results of root mean square deviation (RMSD), solvent accessible surface (SAS), mean square deviation (MSD), Gyrate, total energy, root mean square fluctuation (RMSF), matrices of smallest distance of residues, database of secondary structure assignment (DSSP), cluster analysis, and distance of H-bond, we concluded that all the 3 compounds could bind and activate GLP-1 receptor by computational simulation. Wenyujinoside and 28-deglucosylchikusetsusaponin IV were the TCM compounds that could be GLP-1 receptor agonists.

  14. Design of Glucagon-Like Peptide-1 Receptor Agonist for Diabetes Mellitus from Traditional Chinese Medicine

    PubMed Central

    Tang, Hsin-Chieh; Chen, Calvin Yu-Chian

    2014-01-01

    Glucagon-like peptide-1 (GLP-1) is a promising target for diabetes mellitus (DM) therapy and reduces the occurrence of diabetes due to obesity. However, GLP-1 will be hydrolyzed soon by the enzyme dipeptidyl peptidase-4 (DPP-4). We tried to design small molecular drugs for GLP-1 receptor agonist from the world's largest traditional Chinese medicine (TCM) Database@Taiwan. According to docking results of virtual screening, we selected 2 TCM compounds, wenyujinoside and 28-deglucosylchikusetsusaponin IV, for further molecular dynamics (MD) simulation. GLP-1 was assigned as the control compound. Based on the results of root mean square deviation (RMSD), solvent accessible surface (SAS), mean square deviation (MSD), Gyrate, total energy, root mean square fluctuation (RMSF), matrices of smallest distance of residues, database of secondary structure assignment (DSSP), cluster analysis, and distance of H-bond, we concluded that all the 3 compounds could bind and activate GLP-1 receptor by computational simulation. Wenyujinoside and 28-deglucosylchikusetsusaponin IV were the TCM compounds that could be GLP-1 receptor agonists. PMID:24891870

  15. Positive Allosteric Modulators Differentially Affect Full versus Partial Agonist Activation of the Glycine Receptor

    PubMed Central

    Kirson, Dean; Todorovic, Jelena

    2012-01-01

    Taurine acts as a partial agonist at the glycine receptor (GlyR) in some brain regions such as the hippocampus, striatum, and nucleus accumbens. Ethanol, volatile anesthetics, and inhaled drugs of abuse are all known positive allosteric modulators of GlyRs, but their effects on taurine-activated GlyRs remain poorly understood, especially their effects on the high concentrations of taurine likely to be found after synaptic release. Two-electrode voltage-clamp electrophysiology in Xenopus laevis oocytes was used to compare the enhancing effects of ethanol, anesthetics, and inhalants on human homomeric α1-GlyR activated by saturating concentrations of glycine versus taurine. Allosteric modulators had negligible effects on glycine-activated GlyR while potentiating taurine-activated currents. In addition, inhaled anesthetics markedly enhanced desensitization rates of taurine- but not glycine-activated receptors. Our findings suggest that ethanol, volatile anesthetics, and inhalants differentially affect the time courses of synaptic events at GlyR, depending on whether the receptor is activated by a full or partial agonist. PMID:22473615

  16. Synthetic C5a receptor agonists. Pharmacology, metabolism and in vivo cardiovascular and hematologic effects.

    PubMed

    Drapeau, G; Brochu, S; Godin, D; Levesque, L; Rioux, F; Marceau, F

    1993-03-24

    Recent investigations have produced novel compounds that act on the receptor for anaphylatoxin C5a. These products are C-terminal analogues of C5a, some of which are modified extensively. We have measured the receptor affinities of such analogues in a binding assay on human neutrophils (PMNs). We have also characterized their pharmacological profiles in vitro on the isolated rabbit portal vein and pulmonary artery, on superoxide release by PMNs as well as in vivo in the anesthetized rabbit (acute hypotensive and neutropenic effects). The metabolic resistance of these analogues was also evaluated in the presence of different peptidases. One of these compounds, MePhe-Lys-Pro-D-Cha-Phe-D-Arg, behaved as an antagonist on the release of superoxide by neutrophils while exerting agonist activity in all other assays. Its partial agonist status was documented in a receptor down-regulation experiment on PMNs where its activity was compared with those of recombinant C5a and of protamine which behaves as a competitive antagonist on these cells. Degradation studies indicated that the discrepancy between the affinity of certain analogues in vitro and their potency in vivo was probably linked to their metabolic stability.

  17. Intracellular activation of vasopressin V2 receptor mutants in nephrogenic diabetes insipidus by nonpeptide agonists.

    PubMed

    Robben, Joris H; Kortenoeven, Marleen L A; Sze, Mozes; Yae, Chris; Milligan, Graeme; Oorschot, Viola M; Klumperman, Judith; Knoers, Nine V A M; Deen, Peter M T

    2009-07-21

    Binding of the peptide hormone vasopressin to its type-2 receptor (V2R) in kidney triggers a cAMP-mediated translocation of Aquaporin-2 water channels to the apical membrane, resulting in water reabsorption and thereby preventing dehydration. Mutations in the V2R gene lead to Nephrogenic Diabetes Insipidus (NDI), a disorder in which this process is disturbed, because the encoded, often intrinsically functional mutant V2 receptors are misfolded and retained in the endoplasmic reticulum (ER). Since plasma membrane expression is thought to be essential for V2R activation, cell permeable V2R antagonists have been used to induce maturation and rescue cell surface expression of V2R mutants, after which they need to be displaced by vasopressin for activation. Here, however, we show that 3 novel nonpeptide V2R agonists, but not vasopressin, activate NDI-causing V2R mutants at their intracellular location, without changing their maturation and at a sufficient level to induce the translocation of aquaporin-2 to the apical membrane. Moreover, in contrast to plasma membrane V2R, degradation of intracellular V2R mutants is not increased by their activation. Our data reveal that G protein-coupled receptors (GPCRs) normally active at the plasma membrane can be activated intracellularly and that intracellular activation does not induce their degradation; the data also indicate that nonpeptide agonists constitute highly promising therapeutics for diseases caused by misfolded GPCRs in general, and NDI in particular.

  18. Interactive effects of morphine and dopamine receptor agonists on spatial recognition memory in mice.

    PubMed

    Chen, Yanmei; Fu, Yu; An, Yingjie; Cao, Jun; Wang, Jianhong; Zhang, Jichuan

    2018-04-01

    Both opiates and dopamine play important roles in learning and memory. Although synergistic action between these two neurotransmitters has been found, their functional roles remain unclear. Here, low dose morphine (2.5 mg/kg) and low dose dopamine receptor agonists (apomorphine 0.05 mg/kg; SKF38393 0.01 mg/kg; bromocriptine 0.05 mg/kg), which have no effects on spatial recognition memory, were injected intraperitoneally into mice 30 minutes before a memory test in a two-trial recognition Y-maze. The Y-maze is based on the innate tendency of rodents to explore novel environments and is therefore suitable for exploring the effects of morphine on learning and memory. Our results showed that both D1-like and D2-like dopamine receptor agonists dose-dependently impaired the retrieval of spatial recognition memory in the Y-maze, and co-administration of memory ineffective doses of apomorphine (0.05 mg/kg), SKF38393 (0.01 mg/kg), or bromocriptine (0.05 mg/kg) and of morphine (2.5 mg/kg) resulted in impaired spatial recognition memory retrieval in mice. These findings suggest the existence of interactions between morphine and dopamine receptor agonists in memory processing and that activation of the dopamine system might contribute to morphine-induced impairment of memory, which could provide insight into human addiction. © 2017 John Wiley & Sons Australia, Ltd.

  19. Agonist and antagonist binding to rat brain muscarinic receptors: influence of aging

    SciTech Connect

    Gurwitz, D.; Egozi, Y.; Henis, Y.I.

    1987-03-01

    The objective of the present study was to determine the binding properties of muscarinic receptors in six brain regions in mature and old rats of both sexes by employing direct binding of (/sup 3/H)-antagonist as well as of the labeled natural neurotransmitter, (/sup 3/H)-acetylcholine (( /sup 3/H)-AcCh). In addition, age-related factors were evaluated in the modulation processes involved in agonist binding. The results indicate that as the rat ages the density of the muscarinic receptors is altered differently in the various brain regions: it is decreased in the cerebral cortex, hippocampus, striatum and olfactory bulb of both male and femalemore » rats, but is increased (58%) in the brain stem of senescent males while no significant change is observed for females. The use of the highly sensitive technique measuring direct binding of (/sup 3/H)-AcCh facilitated the separate detection of age-related changes in the two classes (high- and low-affinity) of muscarinic agonist binding sites. In old female rats the density of high-affinity (/sup 3/H)-AcCh binding sites was preserved in all tissues studied, indicating that the decreases in muscarinic receptor density observed with (/sup 3/H)-antagonist represent a loss of low-affinity agonist binding sites. In contrast, (/sup 3/H)-AcCh binding is decreased in the hypothalamus and increased in the brain stem of old male rats. These data imply sexual dimorphism of the aging process in central cholinergic mechanisms.« less

  20. Selectivity optimization of substituted 1,2,3-triazoles as α7 nicotinic acetylcholine receptor agonists.

    PubMed

    Arunrungvichian, Kuntarat; Fokin, Valery V; Vajragupta, Opa; Taylor, Palmer

    2015-08-19

    Three series of substituted anti-1,2,3-triazoles (IND, PPRD, and QND), synthesized by cycloaddition from azide and alkyne building blocks, were designed to enhance selectivity and potency profiles of a lead α7 nicotinic acetylcholine receptor (α7-nAChR) agonist, TTIn-1. Designed compounds were synthesized and screened for affinity by a radioligand binding assay. Their functional characterization as agonists and antagonists was performed by fluorescence resonance energy transfer assay using cell lines expressing transfected cDNAs, α7-nAChRs, α4β2-nAChRs, and 5HT3A receptors, and a fluorescence cell reporter. In the IND series, a tropane ring of TTIn-1, substituted at N1, was replaced by mono- and bicyclic amines to vary length and conformational flexibility of a carbon linker between nitrogen atom and N1 of the triazole. Compounds with a two-carbon atom linker optimized binding with Kd's at the submicromolar level. Further modification at the hydrophobic indole of TTIn-1 was made in PPRD and QND series by fixing the amine center with the highest affinity building blocks in the IND series. Compounds from IND and PPRD series are selective as agonists for the α7-nAChRs over α4β2-nAChRs and 5HT3A receptors. Lead compounds in the three series have EC50's between 28 and 260 nM. Based on the EC50, affinity, and selectivity determined from the binding and cellular responses, two of the leads have been advanced to behavioral studies described in the companion article (DOI: 10.1021/acschemneuro.5b00059).

  1. Isolation and chemical modification of clerodane diterpenoids from Salvia species as potential agonists at the kappa-opioid receptor.

    PubMed

    Li, Yiqiang; Husbands, Stephen M; Mahon, Mary F; Traynor, John R; Rowan, Michael G

    2007-07-01

    The clerodane diterpenoid salvinorin A (1), the main active component of the psychotropic herb Salvia divinorum, has been reported to be a potent agonist at the kappa-opioid receptor. Computer modeling suggested that splendidin (2) from S. splendens, as well as related compounds, might possess similar activities. In the present study, this hypothesis was tested by determination of the binding properties of a series of structural congeners, compounds 2-8, at the mu-, delta-, and kappa-opioid receptors. However, none of these compounds showed significant binding to any of the opioid-receptor subtypes, thus disproving the above hypothesis. The novel compounds 7 and 8 were obtained semi-synthetically by selective modification of salvifarin (5), isolated from Salvia farinacea, upon epoxide-ring opening with AcOH in the presence of indium(III) triflate. Also, the X-ray crystal structure of salvifaricin (6; Fig.), obtained from S. farinacea, was determined for the first time and used, in combination with in-depth NMR experiments, to elucidate the absolute configurations of the new products. Our experiments demonstrate that the relatively well-accessible diterpenoid 6 could be used as starting material for future studies into the structure-activity relationship at the kappa-opioid receptor.

  2. [Extrapancreatic effects of GLP-1 receptor agonists: an open window towards new treatment goals in type 2 diabetes].

    PubMed

    Salvador, Javier; Andrada, Patricia

    2014-01-01

    The wide ubiquity of GLP-1 receptors in the body has stimulated the search for different extrapancreatic actions of GLP-1 and its receptor agonists. Thus, severe cardioprotective effects directed on myocardial ischaemia and dysfunction as well as diverse antiaterogenic actions have been reported. Also, native and GLP-1 receptor agonists have demonstrated significant beneficial effects on liver steatosis and fibrosis and on neuronal protection in experimental models of Alzheimer, and Parkinson's disease as well as on cerebral ischaemia. Recent evidences suggest that these drugs may also be useful for prevention and treatment of diabetic retinopathy, nephropathy and peripheral neuropathy. Good results have also been reported in psoriasis. Despite we still need confirmation that these promising effects can be applied to clinical practice, they offer new interesting perspectives for treatment of type 2 diabetes associated complications and give to GLP-1 receptor agonists an even more integral position in diabetes therapy.

  3. Picosecond dynamics of the glutamate receptor in response to agonist-induced vibrational excitation.

    PubMed

    Kubo, Minoru; Shiomitsu, Eiji; Odai, Kei; Sugimoto, Tohru; Suzuki, Hideo; Ito, Etsuro

    2004-02-01

    Conformational changes of proteins are dominated by the excitation and relaxation processes of their vibrational states. To elucidate the mechanism of receptor activation, the conformation dynamics of receptors must be analyzed in response to agonist-induced vibrational excitation. In this study, we chose the bending vibrational mode of the guanidinium group of Arg485 of the glutamate receptor subunit GluR2 based on our previous studies, and we investigated picosecond dynamics of the glutamate receptor caused by the vibrational excitation of Arg485 via molecular dynamics simulations. The vibrational excitation energy in Arg485 in the ligand-binding site initially flowed into Lys730, and then into the J-helix at the subunit interface of the ligand-binding domain. Consequently, the atomic displacement in the subunit interface around an intersubunit hydrogen bond was evoked in about 3 ps. This atomic displacement may perturb the subunit packing of the receptor, triggering receptor activation. Copyright 2003 Wiley-Liss, Inc.

  4. Design and Synthesis of Potent Bivalent Peptide Agonists Targeting the EphA2 Receptor

    PubMed Central

    2013-01-01

    Designing potent and selective peptides and small molecules that target Eph receptor tyrosine kinases remains a challenge, and new strategies are needed for developing novel and potent ligands for these receptors. In this study, we performed a structure–activity relationship study of a previously identified 12 amino acid-long peptide, SWL, by alanine scanning to identify residues important for receptor binding. To further enhance and optimize the receptor binding affinity of the SWL peptide, we applied the concept of bivalent ligand design to synthesize several SWL-derived dimeric peptides as novel ligands capable of binding simultaneously to two EphA2 receptor molecules. The dimeric peptides possess higher receptor binding affinity than the original monomeric SWL peptide, consistent with bivalent binding. The most potent dimeric peptide, a SWL dimer with a six-carbon linker, has about 13-fold increased potency as compared to SWL. Furthermore, similar to SWL, the dimeric peptide is an agonist and can promote EphA2 tyrosine phosphorylation (activation) in cultured cells. PMID:24167659

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

    PubMed

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

    2016-08-15

    Heterocycle-fused azepines are discussed as potent 5-HT2C receptor agonists with excellent selectivity over 5-HT2B agonism. Synthesis and structure activity relationships are outlined for a series of bicyclic pyridazino[3,4-d]azepines. By comparison with earlier published work, in vitro assays predict a high probability for achieving CNS penetration for a potent and selective compound 15a, a pre-requisite to achieve in vivo efficacy. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Kinetics of activation of phospholipase C by P2Y purinergic receptor agonists and guanine nucleotides.

    PubMed

    Boyer, J L; Downes, C P; Harden, T K

    1989-01-15

    Membranes prepared from [3H]inositol-labeled turkey erythrocytes express a phospholipase C that is markedly stimulated by stable analogs of GTP (Harden, T. K., Stephens, L., Hawkins, P. T., and Downes, C. P. (1987) J. Biol. Chem. 262, 9057-9061). We now report that P2-purinergic receptor-mediated regulation of the enzyme occurs in the membrane preparation. The order of potency of a series of ATP and ADP analogs for stimulation of inositol phosphate formation, i.e. 2-methylthioadenosine 5'-triphosphate (2MeSATP) greater than adenosine 5'-O-(2-thiodiphosphate) greater than adenosine 5'-O-(3-thiotriphosphate) greater than ATP greater than 5'-adenylyl imidodiphosphate approximately ADP greater than alpha, beta-methyleneadenosine 5'-triphosphate greater than beta, gamma-methyleneadenosine 5'-triphosphate, was consistent with that for the P2Y-purinergic receptor subtype. Agonist-stimulated effects were completely dependent on the presence of guanine nucleotide. Activation of phospholipase C by guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) occurred with a considerable time lag. The rate of activation followed first order kinetics and was markedly increased by increasing concentrations of a P2Y receptor agonist; in contrast, the rate of activation at a fixed agonist concentration was independent of guanine nucleotide concentration. Addition of guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) prior to addition of agonist and GTP, 5'-guanylyl imidodiphosphate (Gpp(NH)p), or GTP gamma S blocked in a concentration-dependent manner the stimulatory effect of guanine nucleotide. GDP beta S, added subsequent to preactivation of membranes with 2MeSATP and GTP gamma S or Gpp(NH)p had only small inhibitory effects on the rate of inositol phosphate production observed over the subsequent 10 min. In contrast, addition of GDP beta S to GTP-preactivated membranes resulted in a rapid return of enzyme activity to the basal state within 60 s. Taken together, the data are consistent with

  7. Group II metabotropic glutamate receptor agonists and positive allosteric modulators as novel treatments for schizophrenia.

    PubMed

    Fell, Matthew J; McKinzie, David L; Monn, James A; Svensson, Kjell A

    2012-03-01

    Schizophrenia is a devastating chronic psychotic disorder characterized by positive, negative, and cognitive symptoms. Although the positive symptoms are relatively well controlled by current monoamine-based treatments for schizophrenia, these agents provide only modest efficacy against the negative and cognitive symptoms of the disease. Furthermore serious adverse events have been reported during treatment with antipsychotic drugs. Therefore, novel treatment strategies are needed that provide improved efficacy across the multiple symptom domains of schizophrenia and have improved tolerability/safety profiles. Glutamate is the primary excitatory neurotransmitter in the mammalian central nervous system (CNS) and plays an important role in physiological and pathological processes of the CNS. Group II metabotropic glutamate receptors (mGlu receptors), in particular, have been shown to modulate glutamatergic activity in brain synapses thought to be involved in the pathophysiology of schizophrenia. In recent years a number of selective mGlu2/3 receptor agonists and mGlu2 positive allosteric modulators have been disclosed with demonstrated efficacy in multiple animal models for schizophrenia. Consistent with predictions from pre-clinical animal studies, LY2140023 monohydrate, an mGlu2/3 receptor agonist prodrug, recently demonstrated evidence for antipsychotic activity in phase II proof of concept study. Although additional efficacy and safety studies are needed to understand the therapeutic potential of LY2140023, emerging preclinical and clinical data suggest that activation of group II mGlu receptors is a mechanistically novel and promising approach for the treatment of schizophrenia. Copyright © 2011 Elsevier Ltd. All rights reserved.

  8. The Protective Role of PAC1-Receptor Agonist Maxadilan in BCCAO-Induced Retinal Degeneration.

    PubMed

    Vaczy, A; Reglodi, D; Somoskeoy, T; Kovacs, K; Lokos, E; Szabo, E; Tamas, A; Atlasz, T

    2016-10-01

    A number of studies have proven that pituitary adenylate cyclase activating polypeptide (PACAP) is protective in neurodegenerative diseases. Permanent bilateral common carotid artery occlusion (BCCAO) causes severe degeneration in the rat retina. In our previous studies, protective effects were observed with PACAP1-38, PACAP1-27, and VIP but not with their related peptides, glucagon, or secretin in BCCAO. All three PACAP receptors (PAC1, VPAC1, VPAC2) appear in the retina. Molecular and immunohistochemical analysis demonstrated that the retinoprotective effects are most probably mainly mediated by the PAC1 receptor. The aim of the present study was to investigate the retinoprotective effects of a selective PAC1-receptor agonist maxadilan in BCCAO-induced retinopathy. Wistar rats were used in the experiment. After performing BCCAO, the right eye was treated with intravitreal maxadilan (0.1 or 1 μM), while the left eye was injected with vehicle. Sham-operated rats received the same treatment. Two weeks after the operation, retinas were processed for standard morphometric and molecular analysis. Intravitreal injection of 0.1 or 1 μM maxadilan caused significant protection in the thickness of most retinal layers and the number of cells in the GCL compared to the BCCAO-operated eyes. In addition, 1 μM maxadilan application was more effective than 0.1 μM maxadilan treatment in the ONL, INL, IPL, and the entire retina (OLM-ILM). Maxadilan treatment significantly decreased cytokine expression (CINC-1, IL-1α, and L-selectin) in ischemia. In summary, our histological and molecular analysis showed that maxadilan, a selective PAC1 receptor agonist, has a protective role in BCCAO-induced retinal degeneration, further supporting the role of PAC1 receptor conveying the retinoprotective effects of PACAP.

  9. Agonists of the tissue-protective erythropoietin receptor in the treatment of Parkinson's disease.

    PubMed

    Punnonen, Juha; Miller, James L; Collier, Timothy J; Spencer, Jeffrey R

    2015-01-01

    Parkinson's disease (PD) is a neurodegenerative disease affecting more than a million people in the USA alone. While there are effective symptomatic treatments for PD, there is an urgent need for new therapies that slow or halt the progressive death of dopaminergic neurons. Significant progress has been made in understanding the pathophysiology of PD, which has substantially facilitated the discovery efforts to identify novel drugs. The tissue-protective erythropoietin (EPO) receptor, EPOR/CD131, has emerged as one promising target for disease-modifying therapies. Recombinant human EPO (rhEPO), several variants of EPO, EPO-mimetic peptides, cell-based therapies using cells incubated with or expressing EPO, gene therapy vectors encoding EPO, and small molecule EPO mimetic compounds all show potential as therapeutic candidates. Agonists of the EPOR/CD131 receptor demonstrate potent anti-apoptotic, antioxidant, and anti-inflammatory effects and protect neurons, including dopaminergic neurons, from diverse insults in vitro and in vivo. When delivered directly to the striatum, rhEPO protects dopaminergic neurons in animal models of PD. Early-stage clinical trials testing systemic rhEPO have provided encouraging results, while additional controlled studies are required to fully assess the potential of the treatment. Poor CNS availability of proteins and challenges related to invasive delivery limit delivery of EPO protein. Several variants of EPO and small molecule agonists of the EPO receptors are making progress in preclinical studies and may offer solutions to these challenges. While EPO was initially discovered as the primary modulator of erythropoiesis, the discovery and characterization of the tissue-protective EPOR/CD131 receptor offer an opportunity to selectively target the neuroprotective receptor as an approach to identify disease-modifying treatments for PD.

  10. Effects of full D1 dopamine receptor agonists on firing rates in the globus pallidus and substantia nigra pars compacta in vivo: tests for D1 receptor selectivity and comparisons to the partial agonist SKF 38393.

    PubMed

    Ruskin, D N; Rawji, S S; Walters, J R

    1998-07-01

    Many studies have used the D1 agonist SKF 38393 to characterize D1 receptor influences on firing rates in basal ganglia nuclei in vivo. However, SKF 38393 is a partial agonist and so may not be ideal for delineating D1 receptor effects. This study characterizes the effects of four full D1 agonists, SKF 82958 (chloro-APB), SKF 81297 (6-chloro-PB), dihydrexidine and A-77636, on the firing rates of midbrain dopamine and globus pallidus neurons. Recordings were done in fully anesthetized or paralyzed, locally anesthetized rats, and drugs were given systemically intravenously. Dihydrexidine, SKF 81297 and A-77636 were free of rate effects on midbrain dopamine neurons (up to 10.2 mg/kg) and also did not antagonize the inhibitory effects of quinpirole. In contrast, SKF 82958 strongly inhibited dopamine cells through activation of D2 autoreceptors (ED50 = 0.70 mg/kg). Of these drugs, SKF 82958 also was the only one to increase pallidal unit firing rates when given alone (at 5.0 but not 1.0 mg/kg); the other compounds appeared to be selective for postsynaptic D1 receptors. The results suggest that SKF 82958 may be more properly classified as a mixed D1/D2 agonist. In addition, all four agonists strongly potentiated the pallidal response to quinpirole, demonstrating a D1 receptor potentiation of D2 receptor effects. The results support the role of D1 receptors in the midbrain and globus pallidus as previously characterized with SKF 38393. The similar actions of partial and full D1 agonists in these systems support evidence for a D1 receptor reserve and possibly an effector system other than adenylate cyclase.

  11. (1R, 3S)-(−)-Trans-PAT: A novel full-efficacy serotonin 5-HT2C receptor agonist with 5-HT2A and 5-HT2B receptor inverse agonist/antagonist activity

    PubMed Central

    Booth, Raymond G.; Fang, Lijuan; Huang, Yingsu; Wilczynski, Andrzej; Sivendran, Sashikala

    2009-01-01

    The serotonin 5-HT2A, 5-HT2B, and 5-HT2C G protein-coupled receptors signal primarily through Gαq to activate phospholipase C (PLC) and formation of inositol phosphates (IP) and diacylglycerol. The human 5-HT2C receptor, expressed exclusively in the central nervous system, is involved in several physiological and psychological processes. Development of 5-HT2C agonists that do not also activate 5-HT2A or 5-HT2B receptors is challenging because transmembrane domain identity is about 75% among 5-HT2 subtypes. This paper reports 5-HT2 receptor affinity and function of (1R,3S)-(−)-trans-1-phenyl-3-dimethylamino-1,2,3,4-tetrahydronaphthalene (PAT), a small molecule that produces anorexia and weight-loss after peripheral administration to mice. (−)-Trans-PAT is a stereoselective full-efficacy agonist at human 5-HT2C receptors, plus, it is a 5-HT2A/5-HT2B inverse agonist and competitive antagonist. The Ki of (−)-trans-PAT at 5-HT2A, 5-HT2B, and 5-HT2C receptors is 410, 1200, and 37 nM, respectively. Functional studies measured activation of PLC/[3H]-IP formation in clonal cells expressing human 5-HT2 receptors. At 5-HT2C receptors, (−)-trans-PAT is an agonist (EC50 = 20 nM) comparable to serotonin in potency and efficacy. At 5-HT2A and 5-HT2B receptors, (−)-trans-PAT is an inverse agonist (IC50 = 490 and 1,000 nM, respectively) and competitive antagonist (KB = 460 and 1400 nM, respectively) of serotonin. Experimental results are interpreted in light of molecular modeling studies indicating the (−)-trans-PAT protonated amine can form an ionic bond with D3.32 of 5-HT2A and 5-HT2C receptors, but, not with 5-HT2B receptors. In addition to probing 5-HT2 receptor structure and function, (−)-trans-PAT is a novel lead regarding 5-HT2C agonist/5-HT2A inverse agonist drug development for obesity and neuropsychiatric disorders. PMID:19397907

  12. Albiglutide: A once-weekly glucagon-like peptide-1 receptor agonist for type 2 diabetes mellitus.

    PubMed

    Davis, Portia N; Ndefo, Uche Anadu; Oliver, Ashley; Payton, Enryka

    2015-07-01

    The pharmacology, pharmacokinetics, efficacy, safety, dosage and administration, and place in therapy of the glucagon-like peptide-1 (GLP-1) receptor agonist albiglutide are reviewed. Albiglutide (Tanzeum, GlaxoSmithKline) is an injectable GLP-1 agonist approved in 2014 for use as an adjunct to diet modification and exercise to improve glycemic control in adults with type 2 diabetes. Albiglutide augments glucose-dependent insulin secretion and slows gastric emptying; it has an elimination half-life of approximately five days, allowing for once-weekly administration. Clinical trials demonstrated mean absolute reductions in glycosylated hemoglobin (HbA1c) values of 0.78-1.55% after 16 weeks of adjunctive therapy with albiglutide. Specific recommendations on albiglutide use have been issued by the American Association of Clinical Endocrinologists (AACE) and the American Diabetes Association (ADA). Studies show that the potential for hypoglycemic episodes with albiglutide use is low. In clinical trials, the most frequently reported adverse events were nausea and diarrhea. The use of albiglutide is contraindicated in patients with a history of pancreatitis and patients with a personal or family history of thyroid cancer. Albiglutide has been shown to be effective for the management of type 2 diabetes in adults and is recommended (by ADA) as second-line therapy when used in combination with metformin and (by AACE) as first-line monotherapy in patients with an HbA1c concentration of ≤7.5% at treatment initiation. In clinical trials, albiglutide was generally well tolerated by patients, with adverse effects comparable to those seen with other GLP-1 agonists. Copyright © 2015 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

  13. Structure-Activity Relationships in Toll-like Receptor 2-Agonists Leading to Simplified Monoacyl Lipopeptides

    PubMed Central

    Agnihotri, Geetanjali; Crall, Breanna M.; Lewis, Tyler C.; Day, Timothy P.; Balakrishna, Rajalakshmi; Warshakoon, Hemamali J.; Malladi, Subbalakshmi S.; David, Sunil A.

    2011-01-01

    Toll-like receptor 2-agonistic lipopeptides typified by S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-R-cysteinyl-S-serine (PAM2CS) compounds are potential vaccine adjuvants. In continuation of previously reported structure-activity relationships on this chemotype, we have determined that at least one acyl group of optimal length (C16) and an appropriately orientated ester carbonyl group is essential for TLR2-agonistic activity. The spacing between one of the palmitoyl ester carbonyl and the thioether is crucial to allow for an important H-bond, which observed in the crystal structure of the lipopeptide:TLR2 complex; consequently, activity is lost in homologated compounds. Penicillamine-derived analogues are also inactive, likely due to unfavorable steric interactions with the carbonyl of Ser 12 in TLR2. The thioether in this chemotype can be replaced with a selenoether. Importantly, the thioglycerol motif can be dispensed with altogether, and can be replaced with a thioethanol bridge. These results have led to a structurally simpler, synthetically more accessible, and water-soluble analogue possessing strong TLR2-agonistic activities in human blood. PMID:22007676

  14. Nanoparticles containing a liver X receptor agonist inhibit inflammation and atherosclerosis.

    PubMed

    Zhang, Xue-Qing; Even-Or, Orli; Xu, Xiaoyang; van Rosmalen, Mariska; Lim, Lucas; Gadde, Suresh; Farokhzad, Omid C; Fisher, Edward A

    2015-01-28

    Liver X receptor (LXR) signaling pathways regulate lipid metabolism and inflammation, which has generated widespread interest in developing synthetic LXR agonists as potential therapeutics for the management of atherosclerosis. In this study, it is demonstrated that nanoparticles (NPs) containing the synthetic LXR agonist GW3965 (NP-LXR) exert anti-inflammatory effects and inhibit the development of atherosclerosis without causing hepatic steatosis. These NPs are engineered through self-assembly of a biodegradable diblock poly(lactide-co-glycolide)-b-poly(ethylene glycol) (PLGA-b-PEG) copolymer. NP-LXR is significantly more effective than free GW3965 at inducing LXR-target gene expression and suppressing inflammatory factors in macrophages in vitro and in vivo. Additionally, the NPs elicit negligible lipogenic gene stimulation in the liver. Using the Ldlr (-/-) mouse model of atherosclerosis, abundant colocalization of fluorescently labeled NPs within plaque macrophages following systemic administration is seen. Notably, six intravenous injections of NP-LXR over 2 weeks markedly reduce the CD68-positive cell (macrophage) content of plaques (by 50%) without increasing total cholesterol or triglycerides in the liver and plasma. Together, these findings identify GW3965-encapsulated PLGA-b-PEG NPs as a promising nanotherapeutic approach to combat atherosclerosis, providing the benefits of LXR agonists without their adverse effects on hepatic and plasma lipid metabolism. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Molecular and therapeutic characterization of anti-ectodysplasin A receptor (EDAR) agonist monoclonal antibodies.

    PubMed

    Kowalczyk, Christine; Dunkel, Nathalie; Willen, Laure; Casal, Margret L; Mauldin, Elizabeth A; Gaide, Olivier; Tardivel, Aubry; Badic, Giovanna; Etter, Anne-Lise; Favre, Manuel; Jefferson, Douglas M; Headon, Denis J; Demotz, Stéphane; Schneider, Pascal

    2011-09-02

    The TNF family ligand ectodysplasin A (EDA) and its receptor EDAR are required for proper development of skin appendages such as hair, teeth, and eccrine sweat glands. Loss of function mutations in the Eda gene cause X-linked hypohidrotic ectodermal dysplasia (XLHED), a condition that can be ameliorated in mice and dogs by timely administration of recombinant EDA. In this study, several agonist anti-EDAR monoclonal antibodies were generated that cross-react with the extracellular domains of human, dog, rat, mouse, and chicken EDAR. Their half-life in adult mice was about 11 days. They induced tail hair and sweat gland formation when administered to newborn EDA-deficient Tabby mice, with an EC(50) of 0.1 to 0.7 mg/kg. Divalency was necessary and sufficient for this therapeutic activity. Only some antibodies were also agonists in an in vitro surrogate activity assay based on the activation of the apoptotic Fas pathway. Activity in this assay correlated with small dissociation constants. When administered in utero in mice or at birth in dogs, agonist antibodies reverted several ectodermal dysplasia features, including tooth morphology. These antibodies are therefore predicted to efficiently trigger EDAR signaling in many vertebrate species and will be particularly suited for long term treatments.

  16. Molecular and Therapeutic Characterization of Anti-ectodysplasin A Receptor (EDAR) Agonist Monoclonal Antibodies*

    PubMed Central

    Kowalczyk, Christine; Dunkel, Nathalie; Willen, Laure; Casal, Margret L.; Mauldin, Elizabeth A.; Gaide, Olivier; Tardivel, Aubry; Badic, Giovanna; Etter, Anne-Lise; Favre, Manuel; Jefferson, Douglas M.; Headon, Denis J.; Demotz, Stéphane; Schneider, Pascal

    2011-01-01

    The TNF family ligand ectodysplasin A (EDA) and its receptor EDAR are required for proper development of skin appendages such as hair, teeth, and eccrine sweat glands. Loss of function mutations in the Eda gene cause X-linked hypohidrotic ectodermal dysplasia (XLHED), a condition that can be ameliorated in mice and dogs by timely administration of recombinant EDA. In this study, several agonist anti-EDAR monoclonal antibodies were generated that cross-react with the extracellular domains of human, dog, rat, mouse, and chicken EDAR. Their half-life in adult mice was about 11 days. They induced tail hair and sweat gland formation when administered to newborn EDA-deficient Tabby mice, with an EC50 of 0.1 to 0.7 mg/kg. Divalency was necessary and sufficient for this therapeutic activity. Only some antibodies were also agonists in an in vitro surrogate activity assay based on the activation of the apoptotic Fas pathway. Activity in this assay correlated with small dissociation constants. When administered in utero in mice or at birth in dogs, agonist antibodies reverted several ectodermal dysplasia features, including tooth morphology. These antibodies are therefore predicted to efficiently trigger EDAR signaling in many vertebrate species and will be particularly suited for long term treatments. PMID:21730053

  17. Efficacy and safety of insulin-GLP-1 receptor agonists combination in type 2 diabetes mellitus: a systematic review.

    PubMed

    Cimmaruta, D; Maiorino, M I; Scavone, C; Sportiello, L; Rossi, F; Giugliano, D; Esposito, K; Capuano, A

    2016-12-01

    Attaining optimal glycemic targets in patients with type 2 diabetes is often hard and compromised by the shortcomings of the several treatments. Areas covered: When glycemic levels are not adequately controlled, an association of GLP-1 receptor agonists and insulin therapy can be adopted. In order to assess the benefit/risk profile of this combination therapy, a literature search of randomized clinical trials was performed.Eighteen trials matched the inclusion criteria. In 10 studies, GLP-1 receptor agonists were added on to an existing regimen, whereas insulin added to an existing GLP-1 receptor agonists regimen occurred in 2 studies. Six studies compared GLP-1 receptor agonists with short acting insulin as a treatment strategy to intensify basal insulin therapy. Expert opinion: Clinical trials herein reviewed demonstrated the safety and the efficacy of combining GLP-1 receptor agonists with basal insulin, with most studies showing equal or slightly superior efficacy, as compared with the addition of prandial insulin, associated with weight loss and less hypoglycemia.

  18. Thrombopoietin receptor agonists in refractory immune thrombocytopenia: differential responses to eltrombopag and romiplostim: a case report and possible explanations.

    PubMed

    Aoki, T; Harada, Y; Matsubara, E; Suzuki, T; Oyama, T; Kasai, M; Uchida, T; Ogura, M

    2012-12-01

    Although new thrombopoietin (TPO) receptor agonist drugs, such as romiplostim and eltrombopag, are highly effective and well tolerated for patients with immune thrombocytopenia (ITP) refractory to first-line treatments such as prednisolone, the cross-resistance of these two TPO receptor agonists is still unknown. An 84-year-old Japanese female patient with steroid-refractory ITP received eltrombopag with a gradually increasing dose schedule from 12.5 to 25 mg/day, 37.5 mg/day and finally 50 mg/day. As no increase in platelet count was observed even at the maximum dose of 50 mg/day, and eltrombopag-related grade 3 elevation of aspartate aminotransferase was observed, another TPO receptor agonist, romiplostim, was administered at 1 μg/kg/week subcutaneously. A rapid increase in platelet count was observed 1 week after the first injection. The dose of romiplostim was escalated to 4 μg/kg according to the platelet count and a complete response was achieved 7 weeks after the first injection without any adverse events. The successful treatment of ITP refractory to eltrombopag with romiplostim strongly suggests that the absence of cross-resistance between these two approved TPO receptor agonists and possible differences in mechanism of action. Further study of the mechanisms of action of TPO receptor agonists is called for along with further exploration of the potential of romiplostim in refractory ITP. © 2012 Blackwell Publishing Ltd.

  19. Peroxisome proliferator-activated receptoragonists attenuate biofilm formation by Pseudomonas aeruginosa.

    PubMed

    Bedi, Brahmchetna; Maurice, Nicholas M; Ciavatta, Vincent T; Lynn, K Sabrina; Yuan, Zhihong; Molina, Samuel A; Joo, Myungsoo; Tyor, William R; Goldberg, Joanna B; Koval, Michael; Hart, C Michael; Sadikot, Ruxana T

    2017-08-01

    Pseudomonas aeruginosa is a significant contributor to recalcitrant multidrug-resistant infections, especially in immunocompromised and hospitalized patients. The pathogenic profile of P. aeruginosa is related to its ability to secrete a variety of virulence factors and to promote biofilm formation. Quorum sensing (QS) is a mechanism wherein P. aeruginosa secretes small diffusible molecules, specifically acyl homo serine lactones, such as N-(3-oxo-dodecanoyl)- l -homoserine lactone (3O-C12-HSL), that promote biofilm formation and virulence via interbacterial communication. Strategies that strengthen the host's ability to inhibit bacterial virulence would enhance host defenses and improve the treatment of resistant infections. We have recently shown that peroxisome proliferator-activated receptor γ (PPARγ) agonists are potent immunostimulators that play a pivotal role in host response to virulent P. aeruginosa Here, we show that QS genes in P. aeruginosa (strain PAO1) and 3O-C12-HSL attenuate PPARγ expression in bronchial epithelial cells. PAO1 and 3O-C12-HSL induce barrier derangements in bronchial epithelial cells by lowering the expression of junctional proteins, such as zonula occludens-1, occludin, and claudin-4. Expression of these proteins was restored in cells that were treated with pioglitazone, a PPARγ agonist, before infection with PAO1 and 3O-C12-HSL. Barrier function and bacterial permeation studies that have been performed in primary human epithelial cells showed that PPARγ agonists are able to restore barrier integrity and function that are disrupted by PAO1 and 3O-C12-HSL. Mechanistically, we show that these effects are dependent on the induction of paraoxonase-2, a QS hydrolyzing enzyme, that mitigates the effects of QS molecules. Importantly, our data show that pioglitazone, a PPARγ agonist, significantly inhibits biofilm formation on epithelial cells by a mechanism that is mediated via paraoxonase-2. These findings elucidate a novel role

  20. Modulation of G protein-coupled adenosine receptors by strategically functionalized agonists and antagonists immobilized on gold nanoparticles.

    PubMed

    Jayasekara, P Suresh; Phan, Khai; Tosh, Dilip K; Kumar, T Santhosh; Moss, Steven M; Zhang, Guofeng; Barchi, Joseph J; Gao, Zhan-Guo; Jacobson, Kenneth A

    2013-06-01

    Gold nanoparticles (AuNPs) allow the tuning of pharmacokinetic and pharmacodynamic properties by active or passive targeting of drugs for cancer and other diseases. We have functionalized gold nanoparticles by tethering specific ligands, agonists and antagonists, of adenosine receptors (ARs) to the gold surface as models for cell surface interactions with G protein-coupled receptors (GPCRs). The AuNP conjugates with chain-extended AR ligands alone (PEGylated nucleosides and nonnucleosides, anchored to the Au via thioctic acid) were found to be insoluble in water due to hydrophobic entities in the ligand. Therefore, we added a second, biologically inactive pendant moiety to increase the water solubility, consisting of a PEGylated chain terminating in a carboxylic or phosphate group. The purity and stability of the immobilized biologically active ligand were examined by ultrafiltration and HPLC. Pharmacological receptor binding studies on these GPCR ligand-derivatized AuNPs (2-5 nm in diameter), performed using membranes of mammalian cells stably expressing human A1, A2A, and A3ARs, showed that the desired selectivity was retained with K(i) values (nanomolar) of A3AR agonist 21b and A2AAR antagonists 24 and 26a of 14 (A3), 34 (A2A), and 69 (A2A), respectively. The corresponding monomers displayed K i values of 37, 61, and 1,420 nM, respectively. In conclusion, we have synthesized stable, water-soluble AuNP derivatives of tethered A3 and A2AAR ligands that retain the biological properties of their monomeric ligands and are intended for therapeutic and imaging applications. This is the first prototypical application to gold carriers of small molecule (nonpeptide) GPCR ligands, which are under investigation for treatment of cancer and inflammatory diseases.

  1. Amyloid-β Pathology and APOE Genotype Modulate Retinoid X Receptor Agonist Activity in Vivo*

    PubMed Central

    Tai, Leon M.; Koster, Kevin P.; Luo, Jia; Lee, Sue H.; Wang, Yue-ting; Collins, Nicole C.; Ben Aissa, Manel; Thatcher, Gregory R. J.; LaDu, Mary Jo

    2014-01-01

    Previous data demonstrate that bexarotene (Bex), retinoid X receptor (RXR) agonist, reduces soluble and insoluble amyloid-β (Aβ) in Alzheimer disease (AD)-transgenic mice either by increasing the levels of mouse apolipoprotein E (apoE) or increasing ABCA1/ABCG1-induced apoE lipoprotein association/lipidation. However, although the mechanism of action of RXR agonists remains unclear, a major concern for their use is human (h)-APOE4, the greatest AD genetic risk factor. If APOE4 imparts a toxic gain-of-function, then increasing apoE4 may increase soluble Aβ, likely the proximal AD neurotoxin. If the APOE4 loss-of-function is lipidation of apoE4, then induction of ABCA1/ABCG1 may be beneficial. In novel EFAD-Tg mice (overexpressing h-Aβ42 with h-APOE), levels of soluble Aβ (Aβ42 and oligomeric Aβ) are highest in E4FAD hippocampus (HP) > E3FAD-HP > E4FAD cortex (CX) > E3FAD-CX, whereas levels of lipoprotein-associated/lipidated apoE have the opposite pattern (6 months). In E4FAD-HP, short-term RXR agonist treatment (Bex or LG100268; 5.75–6 months) increased ABCA1, apoE4 lipoprotein-association/lipidation, and apoE4/Aβ complex, decreased soluble Aβ, and increased PSD95. In addition, hydrogel delivery, which mimics low sustained release, was equally effective as gavage for Bex and LG100268. RXR agonists induced no beneficial effects in the E4FAD-HP in a prevention protocol (5–6 months) and actually increased soluble Aβ levels in E3FAD-CX and E4FAD-CX with the short-term protocol, possibly the result of systemic hepatomegaly. Thus, RXR agonists address the loss-of-function associated with APOE4 and exacerbated by Aβ pathology, i.e. low levels of apoE4 lipoprotein association/lipidation. Further studies are vital to address whether RXR agonists are an APOE4-specific AD therapeutic and the systemic side effects that limit translational application. PMID:25217640

  2. Characterizing the Dynamic Response of the Estrogen Receptor to Agonists and Antagonists by Multifrequency Electron Spin Resonance Spin-Labeling

    DTIC Science & Technology

    2008-05-01

    the Estrogen Receptor to Agonists and Antagonists by Multifrequency Electron Spin Resonance Spin-Labeling PRINCIPAL...Agonists and Antagonists by Multifrequency Electron Spin Resonance Spin-Labeling 5b. GRANT NUMBER W81XWH-06-1-0551 5c. PROGRAM ELEMENT NUMBER 6...antiestrogens using electron spin labeling. The first two technical aims for this reporting period involved completing preparation of site-directed spin

  3. Differential vasoactive effects of oestrogen, oestrogen receptor agonists and selective oestrogen receptor modulators in rat middle cerebral artery.

    PubMed

    Patkar, S; Farr, T D; Cooper, E; Dowell, F J; Carswell, H V O

    2011-09-01

    Cerebrovascular disorders are less common in pre-menopausal than post-menopausal women and in females than males. This protection may be due, in part at least, to direct effects of oestrogens on blood vessels. Oestrogen's vasodilatory mechanisms have been reported to be via the endothelium, vascular smooth muscle and extracellular matrix, depending on the vascular bed studied. Herein we investigated the vasoactive effects of oestrogen, oestrogen receptor (ER) and GPR30 agonists and selective ER modulators (SERMs) in the rat middle cerebral artery(MCA), an artery affected in focal ischaemia. MCAs isolated from male Sprague Dawley rats were mounted on a wire myograph. Concentration response curves were constructed to 17β-oestradiol, ERα agonist-PPT, ERβ agonist-DPN, GPR30 agonist-G1 and novel SERMs (LY362321 and LY2120310) in pre-constricted vessels, in the presence and absence of endothelium, blocking agents for nitric oxide synthase (L-NAME), classic ER antagonist (ICI182,780) or plasma membrane specific ERα (ERα-36) antibody. 17β-oestradiol induced rapid vasorelaxation of the MCA which was not affected by endothelium removal, L-NAME or ICI182,780. Vasorelaxation was mimicked by PPT, DPN and G1 but not by the SERMs. Using ERα-36 antibody, effects of oestrogen were partially blocked. PPT had a greater vasorelaxation, while DPN and G1 had a lesser effect than 17β-oestradiol. These findings indicate that activation of plasma membrane bound ERα, β and GPR30 elicits rapid, endothelial-nitric oxide-independent relaxation of the rat MCA. Copyright © 2011 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

  4. Pharmacochaperoning of the A1 adenosine receptor is contingent on the endoplasmic reticulum.

    PubMed

    Málaga-Diéguez, Laura; Yang, Qiong; Bauer, Jan; Pankevych, Halyna; Freissmuth, Michael; Nanoff, Christian

    2010-06-01

    Exchanging each of the conserved aromatic residues of the NPxxY(x)(5,6)F sequence (at the boundary of helices 7 and 8) generated variants of the A(1) adenosine receptor that were retained within the cell. The mutations disconnected a link between alpha-helix 7 and cytosolic helix 8, likely destabilizing the structure of the proximal carboxyl terminus. The mutant receptors were rescued by incubation of cells with a pharmacochaperone, a membrane-permeable ligand that homosterically binds to the receptor; pharmacochaperoning restored the density of functional receptors at the plasma membrane. The following observations support the assumption that retention and the site of pharmacochaperone action were within bounds of the endoplasmic reticulum (ER): 1) the retained receptor colocalized with an ER marker; 2) pharmacochaperoning initiated receptor transfer to Golgi stacks; and 3) the inhibitor of glycoprotein synthesis tunicamycin suppressed receptor chaperoning. Our data are consistent with the hypothesis that pharmacochaperoning stabilizes the structure of late folding intermediates and lifts a block on maturation, allowing the receptors to exit from the ER. We suggest that the ER-associated 40-kDa heat shock protein family member D(1) receptor interacting protein 78 (DRiP78; M(r), approximately 78,000) represents a model executor of quality control. Overexpressed DRiP78 interacted physically with the A(1) receptor, inhibited export to the plasma membrane, and in this action was selective for the mutants relative to the wild-type receptor. Both agonist and antagonist were effective chaperone ligands. Thus, occupancy of the binding pocket corrected the mutation-induced disorder, indicating a mutual impingement of the transmembrane domain and the proximal carboxyl terminus in establishing the stable receptor fold.

  5. [Effect of G protein in the dual regulation of opioid receptor agonist on the delayed rectified potassium channels].

    PubMed

    Ye, Cai-ying; Li, Qing-xia; Yu, Xiao-li; Qi, Jing-jing; Li, Juan; Zhang, De-chang

    2003-06-01

    To observe the role of G protein in the dual regulation of opioid receptor agonist on the delayed rectified potassium channels. Using whole-cell patch-clamp techniques applied to NG108-15 cells, investigate the effect of opioid receptor agonist on the delayed rectified potassium channels by administration of Guanosine-5'-0'-2-thiociphosphate (GDP beta S), Pertusis Toxin (PTX), Tetroacetic acid nueleoside diphosphate kinase (NDPK) and Adenosine-3' 5' cyclic monophosphate cAMP in the pipette solution. (1) GDP beta S could block the changes induced by both high and low concentration of (D-Pen2.5)-enkephalin (DPDPE) (P < 0.05). (2) PTX could inhibit the excitative regulation on K+ channel by high concentration of DPDPE (P < 0.05). But CTX had no effect on K+ channel caused by DPDPE. (3) UDP could block the excitative effect of K+ channel by high concentration of NDPK, while have no changes on the inhibitory effect caused by low concentration of opioid agonists. (4) cAMP took part in the regulation in high concentration of agonist administration (P < 0.05), while no changes for low concentration of agonists. Dual changes were observed on delayed rectifier potassium channel by agonist treatment on NG108-15 cells. The excitative effect was Gi/o coupled in high concentration of agonist incubation, related to cAMP. While the inhibitory effect was possibly induced by G protein beta gamma subunit directly.

  6. Structure-Activity Relationships of the Sustained Effects of Adenosine A2A Receptor Agonists Driven by Slow Dissociation Kinetics

    PubMed Central

    Hothersall, J. Daniel; Guo, Dong; Sarda, Sunil; Sheppard, Robert J.; Chen, Hongming; Keur, Wesley; Waring, Michael J.; IJzerman, Adriaan P.; Hill, Stephen J.; Dale, Ian L.

    2017-01-01

    The duration of action of adenosine A2A receptor (A2A) agonists is critical for their clinical efficacy, and we sought to better understand how this can be optimized. The in vitro temporal response profiles of a panel of A2A agonists were studied using cAMP assays in recombinantly (CHO) and endogenously (SH-SY5Y) expressing cells. Some agonists (e.g., 3cd; UK-432,097) but not others (e.g., 3ac; CGS-21680) demonstrated sustained wash-resistant agonism, where residual receptor activation continued after washout. The ability of an antagonist to reverse pre-established agonist responses was used as a surrogate read-out for agonist dissociation kinetics, and together with radioligand binding studies suggested a role for slow off-rate in driving sustained effects. One compound, 3ch, showed particularly marked sustained effects, with a reversal t1/2 > 6 hours and close to maximal effects that remained for at least 5 hours after washing. Based on the structure-activity relationship of these compounds, we suggest that lipophilic N6 and bulky C2 substituents can promote stable and long-lived binding events leading to sustained agonist responses, although a high compound logD is not necessary. This provides new insight into the binding interactions of these ligands and we anticipate that this information could facilitate the rational design of novel long-acting A2A agonists with improved clinical efficacy. PMID:27803241

  7. Anti-radiation damage effect of polyethylenimine as a toll-like receptor 5 targeted agonist

    PubMed Central

    Hu, Zhiqiang; Xing, Yaling; Qian, Yuanyu; Chen, Xiaojuan; Tu, Jian; Ren, Lening; Wang, Kai; Chen, Zhongbin

    2013-01-01

    A number of agents are now available for use in protecting against ionizing radiation. These radiation-protective agents, however, have many adverse effects. Efforts have been made to develop new radiation-protective agents for medical application. Here, we investigated whether a compound, polyethylenimine (PEI), which activates Toll-like receptor 5 (TLR5)-mediated NF-kB signaling pathways, could have an anti-radiation effect on a mouse model. First, a cell-based screening model for an agonist of TLR5-mediated NF-kB pathway was established and then validated by activation of TLR5-mediated NF-kB luciferase reporter activity with a known TLR5 agonist, flagellin. We found that PEI induced dose-dependent activation of the TLR5-mediated NF-kB pathway, indicating that PEI is indeed a TLR5 agonist. Furthermore, the anti-radiation effect of polyethylenimine was assessed using a γ-ray total body irradiation (TBI) mouse model. Compared with the irradiation control, both survival time and survival rate were significantly improved in mice that received either a low dose of polyethylenimine (P= 0.019) or a high dose of polyethylenimine (P< 0.001). We also observed a positive correlation between animal body weight and survival time in mice that received a low dose of polyethylenimine, a high dose of polyethylenimine and amifostine, over a period of 30 days, r= 0.42 (P< 0.02), 0.72 (P< 0.0001) and 0.95 (P< 0.0001), respectively, while a negative correlation between animal body weight and survival time was observed in the irradiation control (r= –0.89; P< 0.0001). These results indicate that polyethylenimine is a new TLR5 agonist with potential application in offering protection for patients receiving radiotherapy or in radiation-related accidents. PMID:23104900

  8. Activation of protease activated receptor 2 by exogenous agonist exacerbates early radiation injury in rat intestine.

    PubMed

    Wang, Junru; Boerma, Marjan; Kulkarni, Ashwini; Hollenberg, Morley D; Hauer-Jensen, Martin

    2010-07-15

    Protease-activated receptor-2 (PAR(2)) is highly expressed throughout the gut and regulates the inflammatory, mitogenic, fibroproliferative, and nociceptive responses to injury. PAR(2) is strikingly upregulated and exhibits increased activation in response to intestinal irradiation. We examined the mechanistic significance of radiation enteropathy development by assessing the effect of exogenous PAR(2) activation. Rat small bowel was exposed to localized single-dose radiation (16.5 Gy). The PAR(2) agonist (2-furoyl-LIGRLO-NH(2)) or vehicle was injected intraperitoneally daily for 3 days before irradiation (before), for 7 days after irradiation (after), or both 3 days before and 7 days after irradiation (before-after). Early and delayed radiation enteropathy was assessed at 2 and 26 weeks after irradiation using quantitative histologic examination, morphometry, and immunohistochemical analysis. The PAR(2) agonist did not elicit changes in the unirradiated (shielded) intestine. In contrast, in the irradiated intestine procured 2 weeks after irradiation, administration of the PAR(2) agonist was associated with more severe mucosal injury and increased intestinal wall thickness in all three treatment groups (p <.05) compared with the vehicle-treated controls. The PAR(2) agonist also exacerbated the radiation injury score, serosal thickening, and mucosal inflammation (p <.05) in the before and before-after groups. The short-term exogenous activation of PAR(2) did not affect radiation-induced intestinal injury at 26 weeks. The results of the present study support a role for PAR(2) activation in the pathogenesis of early radiation-induced intestinal injury. Pharmacologic PAR(2) antagonists might have the potential to reduce the intestinal side effects of radiotherapy and/or as countermeasures in radiologic accidents or terrorism scenarios. Published by Elsevier Inc.

  9. Activation of Protease Activated Receptor 2 by Exogenous Agonist Exacerbates Early Radiation Injury in Rat Intestine

    SciTech Connect

    Wang Junru; Boerma, Marjan; Kulkarni, Ashwini

    2010-07-15

    Purpose: Protease-activated receptor-2 (PAR{sub 2}) is highly expressed throughout the gut and regulates the inflammatory, mitogenic, fibroproliferative, and nociceptive responses to injury. PAR{sub 2} is strikingly upregulated and exhibits increased activation in response to intestinal irradiation. We examined the mechanistic significance of radiation enteropathy development by assessing the effect of exogenous PAR{sub 2} activation. Methods and Materials: Rat small bowel was exposed to localized single-dose radiation (16.5 Gy). The PAR{sub 2} agonist (2-furoyl-LIGRLO-NH{sub 2}) or vehicle was injected intraperitoneally daily for 3 days before irradiation (before), for 7 days after irradiation (after), or both 3 days before and 7 daysmore » after irradiation (before-after). Early and delayed radiation enteropathy was assessed at 2 and 26 weeks after irradiation using quantitative histologic examination, morphometry, and immunohistochemical analysis. Results: The PAR{sub 2} agonist did not elicit changes in the unirradiated (shielded) intestine. In contrast, in the irradiated intestine procured 2 weeks after irradiation, administration of the PAR{sub 2} agonist was associated with more severe mucosal injury and increased intestinal wall thickness in all three treatment groups (p <.05) compared with the vehicle-treated controls. The PAR{sub 2} agonist also exacerbated the radiation injury score, serosal thickening, and mucosal inflammation (p <.05) in the before and before-after groups. The short-term exogenous activation of PAR{sub 2} did not affect radiation-induced intestinal injury at 26 weeks. Conclusion: The results of the present study support a role for PAR{sub 2} activation in the pathogenesis of early radiation-induced intestinal injury. Pharmacologic PAR{sub 2} antagonists might have the potential to reduce the intestinal side effects of radiotherapy and/or as countermeasures in radiologic accidents or terrorism scenarios.« less

  10. Prediction of selective estrogen receptor beta agonist using open data and machine learning approach.

    PubMed

    Niu, Ai-Qin; Xie, Liang-Jun; Wang, Hui; Zhu, Bing; Wang, Sheng-Qi

    2016-01-01

    Estrogen receptors (ERs) are nuclear transcription factors that are involved in the regulation of many complex physiological processes in humans. ERs have been validated as important drug targets for the treatment of various diseases, including breast cancer, ovarian cancer, osteoporosis, and cardiovascular disease. ERs have two subtypes, ER-α and ER-β. Emerging data suggest that the development of subtype-selective ligands that specifically target ER-β could be a more optimal approach to elicit beneficial estrogen-like activities and reduce side effects. Herein, we focused on ER-β and developed its in silico quantitative structure-activity relationship models using machine learning (ML) methods. The chemical structures and ER-β bioactivity data were extracted from public chemogenomics databases. Four types of popular fingerprint generation methods including MACCS fingerprint, PubChem fingerprint, 2D atom pairs, and Chemistry Development Kit extended fingerprint were used as descriptors. Four ML methods including Naïve Bayesian classifier, k-nearest neighbor, random forest, and support vector machine were used to train the models. The range of classification accuracies was 77.10% to 88.34%, and the range of area under the ROC (receiver operating characteristic) curve values was 0.8151 to 0.9475, evaluated by the 5-fold cross-validation. Comparison analysis suggests that both the random forest and the support vector machine are superior for the classification of selective ER-β agonists. Chemistry Development Kit extended fingerprints and MACCS fingerprint performed better in structural representation between active and inactive agonists. These results demonstrate that combining the fingerprint and ML approaches leads to robust ER-β agonist prediction models, which are potentially applicable to the identification of selective ER-β agonists.

  11. SGLT2 inhibitors or GLP-1 receptor agonists as second-line therapy in type 2 diabetes: patient selection and perspectives.

    PubMed

    Gurgle, Holly E; White, Karen; McAdam-Marx, Carrie

    2016-01-01

    Controversy exists regarding the selection of second-line therapy for patients with type 2 diabetes mellitus (T2DM) who are unable to achieve glycemic control with metformin therapy alone. Newer pharmacologic treatments for T2DM include glucagon-like peptide-1 receptor agonists and sodium-glucose cotransporter 2 inhibitors. Both the classes of medication are efficacious, exhibit positive effects on weight, and are associated with minimal risk of hypoglycemia. The purpose of this review is to compare the clinical trial and real-world effectiveness data of glucagon-like peptide-1 receptor agonists versus sodium-glucose cotransporter 2 inhibitors related to A1c reduction, weight loss, cost-effectiveness, cardiovascular outcomes, and safety in patients with T2DM. This review summarizes comparative evidence for providers who are determining which of the two classes may be the most appropriate for a specific patient.

  12. Antinociceptive effects of novel melatonin receptor agonists in mouse models of abdominal pain.

    PubMed

    Chen, Chunqiu; Fichna, Jakub; Laudon, Moshe; Storr, Martin

    2014-02-07

    To characterize the antinociceptive action of the novel melatonin receptor (MT) agonists, Neu-P11 and Neu-P12 in animal models of visceral pain. Visceral pain was induced by intracolonic (ic) application of mustard oil or capsaicin solution or by intraperitoneal (ip) administration of acetic acid. Neu-P11, Neu-P12, or melatonin were given ip or orally and their effects on pain-induced behavioral responses were evaluated. To identify the receptors involved, the non-selective MT1/MT2 receptor antagonist luzindole, the MT2 receptor antagonist 4-P-PDOT, or the μ-opioid receptor antagonist naloxone were injected ip or intracerebroventricularly (icv) prior to the induction of pain. Orally and ip administered melatonin, Neu-P11, and Neu-P12 reduced pain responses in a dose-dependent manner. Neu-P12 was more effective and displayed longer duration of action compared to melatonin. The antinociceptive effects of Neu-P11 or Neu-P12 were antagonized by ip or icv. administered naloxone. Intracerebroventricularly, but not ip administration of luzindole or 4-P-PDOT blocked the antinociceptive actions of Neu-P11 or Neu-P12. Neu-P12 produced the most potent and long-lasting antinociceptive effect. Further development of Neu-P12 for future treatment of abdominal pain seems promising.

  13. Diminished natriuretic response to dopamine D1 receptor agonist, SKF-38393 in obese Zucker rats.

    PubMed

    Marwaha, Aditi; Lokhandwala, Mustafa F

    2003-11-01

    Dopamine causes natriuresis and diuresis via activation of D1 receptors located on the renal proximal tubules and subsequent inhibition of the sodium transporters, Na-H exchanger and Na+/K+ ATPase. We have reported that dopamine fails to inhibit the activities of these two transporters in the obese Zucker rats (OZR). The present study was designed to examine the functional consequence of this phenomenon by determining the natriuretic and diuretic response to D1 receptor activation in lean Zucker rats (LZR) and OZR. In 11-12 week-old OZR and LZR, natriuretic and diuretic responses to intravenously administered D1 receptor agonist, SKF 38393 (3 microg/kg/min for 30 min) were measured under Inactin anesthesia. Plasma insulin and glucose levels were significantly higher in the obese rats as compared to the lean rats. Intravenous infusion of SKF 38393 caused significant increases in urine flow, urinary sodium excretion (U(Na)V), fractional excretion of sodium (FE(Na)), and glomerular filtration rate (GFR) in the lean rats. However, the natriuretic and diuretic response to SKF 38393 was markedly blunted in OZR. Infusion of SKF 38393 did not cause significant changes in the mean blood pressure and heart rate in either of the two groups. We suggest that the diminished natriuretic response to D1 receptor activation in OZR is the consequence of the previously reported defect in the D1 receptor-G-protein coupling and the failure of dopamine to inhibit the sodium transporters in these animals.

  14. Dendrite-selective redistribution of the chemokine receptor CXCR4 following agonist stimulation.

    PubMed

    Baudouin, Stéphane J; Pujol, Fabien; Nicot, Arnaud; Kitabgi, Patrick; Boudin, Hélène

    2006-10-01

    The chemokine SDF-1 is a secreted protein that plays a critical role in several aspects of neuron development through interaction with its unique receptor CXCR4. A key mechanism that controls neuron responsiveness to extracellular signals during neuronal growth is receptor endocytosis. Since we previously reported that SDF-1 regulates axon development without affecting the other neurites, we asked whether this could correlate with a compartment-selective trafficking of CXCR4. We thus studied CXCR4 behavior upon SDF-1 exposure in rat hippocampus slices and in transfected neuron cultures. A massive agonist-induced redistribution of CXCR4 in endosomes was observed in dendrites whereas no modification was evidenced in axons. Our data suggest that CXCR4 trafficking may play a role in mediating selective effects of SDF-1 on distinct neuronal membrane subdomains.

  15. Benzoxazinones as Human Peroxisome Proliferator Activated Receptor Gamma (PPARγ) Agonists: A Docking Study Using Glide.

    PubMed

    Das, N; Dhanawat, M; Shrivastava, S K

    2011-03-01

    The purpose of the present study is to undertake a docking study of some benzoxazinone derivatives on human peroxisome proliferator activated receptor co-crystallized with an alpha-aryloxyphenylacetic acid agonist using Glide 4.5. The QikProp program was used to obtain the absorption, distribution, metabolism and excretion properties of the analogues. The intermolecular hydrogen bonding interaction of the best-fit ligands were found to be associated with Tyr473, Ser289, Hie 449, Hip 323, Ser 342 and Gly 284 amino acid residue at the receptor active site. Among all the observed interaction with similar binding pattern, the presence of methyl carboxypentyl side chain (Lig. No. 21) showed additional interaction with Ser 342 and the affinity was increased by carboxyl oxygen (as hydrogen bond acceptor) with a best Glide score of -14.54 as compared to the co-crystallized aryloxyphenyl acetic acid which achieved a glide score of -12.50.

  16. Benzoxazinones as Human Peroxisome Proliferator Activated Receptor Gamma (PPARγ) Agonists: A Docking Study Using Glide

    PubMed Central

    Das, N.; Dhanawat, M.; Shrivastava, S. K.

    2011-01-01

    The purpose of the present study is to undertake a docking study of some benzoxazinone derivatives on human peroxisome proliferator activated receptor co-crystallized with an alpha-aryloxyphenylacetic acid agonist using Glide 4.5. The QikProp program was used to obtain the absorption, distribution, metabolism and excretion properties of the analogues. The intermolecular hydrogen bonding interaction of the best-fit ligands were found to be associated with Tyr473, Ser289, Hie 449, Hip 323, Ser 342 and Gly 284 amino acid residue at the receptor active site. Among all the observed interaction with similar binding pattern, the presence of methyl carboxypentyl side chain (Lig. No. 21) showed additional interaction with Ser 342 and the affinity was increased by carboxyl oxygen (as hydrogen bond acceptor) with a best Glide score of -14.54 as compared to the co-crystallized aryloxyphenyl acetic acid which achieved a glide score of -12.50. PMID:22303058

  17. Pharmacology of the inhibitory glycine receptor: agonist and antagonist actions of amino acids and piperidine carboxylic acid compounds.

    PubMed

    Schmieden, V; Betz, H

    1995-11-01

    To define structure-activity relations for ligands binding to the inhibitory glycine receptor (GlyR), the agonistic and antagonistic properties of alpha- and beta-amino acids were analyzed at the recombinant human alpha 1 GlyR expressed in Xenopus oocytes. The agonistic activity of alpha-amino acids exhibited a marked stereoselectivity and was highly susceptible to substitutions at the C alpha-atom. In contrast, alpha-amino acid antagonism was not enantiomer dependent and was influenced little by C alpha-atom substitutions. The beta-amino acids taurine, beta-aminobutyric acid (beta-ABA), and beta-aminoisobutyric acid (beta-AIBA) are partial agonists at the GlyR. Low concentrations of these compounds competitively inhibited glycine responses, whereas higher concentrations elicited a significant membrane current. Nipecotic acid, which contains a trans-beta-amino acid configuration, behaved as purely competitive GlyR antagonist. Our data are consistent with the existence of a common binding site for all amino acid agonists and antagonists, at which the functional consequences of binding depend on the particular conformation a given ligand adopts within the binding pocket. In the case of beta-amino acids, the trans conformation appears to mediate antagonistic receptor binding, and the cis conformation appears to mediate agonistic receptor binding. This led us to propose that the partial agonist activity of a given beta-amino acid is determined by the relative mole fractions of the respective cis/trans conformers.

  18. On the role of subtype selective adenosine receptor agonists during proliferation and osteogenic differentiation of human primary bone marrow stromal cells.

    PubMed

    Costa, M Adelina; Barbosa, A; Neto, E; Sá-e-Sousa, A; Freitas, R; Neves, J M; Magalhães-Cardoso, T; Ferreirinha, F; Correia-de-Sá, P

    2011-05-01

    Purines are important modulators of bone cell biology. ATP is metabolized into adenosine by human primary osteoblast cells (HPOC); due to very low activity of adenosine deaminase, the nucleoside is the end product of the ecto-nucleotidase cascade. We, therefore, investigated the expression and function of adenosine receptor subtypes (A(1) , A(2A) , A(2B) , and A(3) ) during proliferation and osteogenic differentiation of HPOC. Adenosine A(1) (CPA), A(2A) (CGS21680C), A(2B) (NECA), and A(3) (2-Cl-IB-MECA) receptor agonists concentration-dependently increased HPOC proliferation. Agonist-induced HPOC proliferation was prevented by their selective antagonists, DPCPX, SCH442416, PSB603, and MRS1191. CPA and NECA facilitated osteogenic differentiation measured by increases in alkaline phosphatase (ALP) activity. This contrasts with the effect of CGS21680C which delayed HPOC differentiation; 2-Cl-IB-MECA was devoid of effect. Blockade of the A(2B) receptor with PSB603 prevented osteogenic differentiation by NECA. In the presence of the A(1) antagonist, DPCPX, CPA reduced ALP activity at 21 and 28 days in culture. At the same time points, blockade of A(2A) receptors with SCH442416 transformed the inhibitory effect of CGS21680C into facilitation. Inhibition of adenosine uptake with dipyridamole caused a net increase in osteogenic differentiation. The presence of all subtypes of adenosine receptors on HPOC was confirmed by immunocytochemistry. Data show that adenosine is an important regulator of osteogenic cell differentiation through the activation of subtype-specific receptors. The most abundant A(2B) receptor seems to have a consistent role in cell differentiation, which may be balanced through the relative strengths of A(1) or A(2A) receptors determining whether osteoblasts are driven into proliferation or differentiation. Copyright © 2010 Wiley-Liss, Inc.

  19. Effect of dopamine D4 receptor agonists on sleep architecture in rats.

    PubMed

    Nakazawa, Shunsuke; Nakamichi, Keiko; Imai, Hideaki; Ichihara, Junji

    2015-12-03

    Dopamine plays a key role in the regulation of sleep-wake states, as revealed by the observation that dopamine-releasing agents such as methylphenidate have wake-promoting effects. However, the precise mechanisms for the wake-promoting effect produced by the enhancement of dopamine transmission are not fully understood. Although dopamine D1, D2, and D3 receptors are known to have differential effects on sleep architecture, the role of D4 receptors (D4Rs), and particularly the influence of D4R activation on the sleep-wake state, has not been studied so far. In this study, we investigated for the first time the effects of two structurally different D4R agonists, Ro 10-5824 and A-412997, on the sleep-wake states in rats. We found that both D4R agonists generally increased waking duration, and conversely, reduced non-rapid eye movement (NREM) sleep duration in rats. The onset of NREM sleep was also generally delayed. However, only the A-412997 agonist (but not the Ro 10-5824) influenced rapid eye movement sleep onset and duration. Furthermore, these effects were accompanied with an enhancement of EEG spectral power in the theta and the gamma bands. Our results suggest the involvement of dopamine D4R in the regulation of sleep-wake states. The activation of the D4R could enhance the arousal states as revealed by the behavioral and electrophysiological patterns in this study. Dopamine D4R may contribute to the arousal effects of dopamine-releasing agents such as methylphenidate. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. Transdermal rotigotine: a clinically innovative dopamine-receptor agonist for the management of Parkinson's disease.

    PubMed

    Chen, Jack J; Swope, David M; Dashtipour, Khashayar; Lyons, Kelly E

    2009-12-01

    Rotigotine is a highly lipophilic dopamine-receptor agonist and the first transdermally delivered agent to demonstrate efficacy and safety as monotherapy in early Parkinson's disease and to reduce "off" hours in levodopa-treated patients with advanced Parkinson's disease. The rotigotine pharmacophore is nonergolinic and demonstrates high affinity for dopamine D(2) and D(3) receptors. With once-daily application, the patch matrix provides continuous, nonfluctuating plasma drug levels at steady state, resulting in continuous and steady plasma and brain levels and striatal dopamine-receptor stimulation. In early Parkinson's disease, doses of rotigotine up to 8 mg/24 hours demonstrate comparable efficacy to ropinirole (at doses up to 12 mg/day); in advanced Parkinson's disease, doses of rotigotine up to 16 mg/24 hours demonstrate comparable efficacy and tolerability to pramipexole (at doses up to 4.5 mg/day). In the registration trials for early and advanced Parkinson's disease, the adverse effects most commonly observed with rotigotine were minor application site reactions, dizziness, nausea, and somnolence. Doses of transdermal rotigotine can be titrated to a maintenance dose within 2-3 weeks, and the once-daily regimen minimizes complexity of therapy. The transdermal delivery system is also an advantage when nonoral administration is desired, and the 24-hour, continuous, nonfluctuating drug levels can improve early morning and nocturnal symptoms of Parkinson's disease. Thus, transdermally delivered rotigotine is a clinically innovative and useful addition to the dopamine-receptor agonist class. This review summarizes the key pharmacologic and clinical data for rotigotine and provides a focused clinical context for its use in early-to-advanced Parkinson's disease, as well as a brief summary for its role in restless legs syndrome.

  1. Synergistic Inhibitory Effect of Rosuvastatin and Angiotensin II Type 2 Receptor Agonist on Vascular Remodeling.

    PubMed

    Bai, Hui-Yu; Mogi, Masaki; Nakaoka, Hirotomo; Kan-No, Harumi; Tsukuda, Kana; Wang, Xiao-Li; Shan, Bao-Shuai; Kukida, Masayoshi; Yamauchi, Toshifumi; Higaki, Akinori; Min, Li-Juan; Iwanami, Jun; Horiuchi, Masatsugu

    2016-08-01

    We investigated the possibility that coadministration of rosuvastatin and compound 21 (C21), a selective angiotensin II type 2 (AT2) receptor agonist, could exert synergistic preventive effects on vascular injury. Vascular injury was induced by polyethylene cuff placement on the femoral artery in 9-week-old male C57BL/6J mice. Mice were treated with rosuvastatin and/or with C21 after cuff placement. Neointima formation was determined 14 days after the operation and cell proliferation, and superoxide anion production and expression of inflammatory cytokines were examined 7 days after cuff placement. Neointima formation was significantly attenuated by the treatment of rosuvastatin (5 mg kg(-1) day(-1)) or C21 (10 μg kg(-1) day(-1)), associated with the decreases in proliferating cell nuclear antigen (PCNA) labeling index, oxidative stress, and the expression of inflammatory markers. Treatment with a noneffective dose of rosuvastatin (0.5 mg kg(-1) day(-1)) plus a low dose of C21 (1 μg kg(-1) day(-1)) inhibited the PCNA labeling index, superoxide anion production, mRNA expressions of NAD(P)H subunits, and mRNA and protein expressions of inflammatory markers associated with marked inhibition of neointima formation. Angiotensin II type 1 (AT1) receptor mRNA expression did not differ the groups. By contrast, AT2 receptor mRNA expression was increased by administration of C21 at the dose of 10 μg kg(-1) day(-1) but not by C21 at the dose of 1 μg kg(-1) day(-1) or rosuvastatin. The combination of rosuvastatin and AT2 receptor agonist exerted synergistic preventive effects on vascular remodeling associated with the decreases in cell proliferation, oxidative stress, and inflammatory reaction. That could be a powerful approach to vascular disease prevention. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

  2. CB1 Cannabinoid Receptor Agonist Prevents NGF-Induced Sensitization of TRPV1 in Sensory Neurons

    PubMed Central

    McDowell, Thomas S.; Wang, Zun-yi; Singh, Ruchira; Bjorling, Dale

    2013-01-01

    The transient receptor potential vanilloid type 1 channel (TRPV1) and nerve growth factor (NGF) are important mediators of inflammatory pain. NGF released during inflammation sensitizes TRPV1 in afferent nerve endings of peripheral nociceptors, increasing pain sensation. Cannabinoids, by activating CB1 G protein-coupled receptors, produce analgesia in a variety of pain models, though the exact mechanisms are not known. We tested the hypothesis that activation of the CB1 receptor by cannabinoids attenuates NGF-induced TRPV1 sensitization. TRPV1-mediated currents were measured in acutely isolated primary sensory neurons with the whole-cell patch clamp technique using capsaicin (100 nM) as the agonist. After the first capsaicin application, during which the baseline current was measured, cells were exposed to NGF (100 ng/mL), and the capsaicin application was repeated after 5 minutes. NGF sensitized TRPV1 in 31.0 % of cells (13 of 42), with a mean (± SE) increase in the capsaicin-induced current of 262 ± 47 % over the baseline current. When the cannabinoid agonist ACEA (arachidonoyl-2’-chloroethylamide; 10 nM) was given before NGF, only 10.8 % of cells (4 of 37) were sensitized (p < 0.05). Neither this rate, nor the magnitude of the sensitization (198 ± 63 % of baseline) were different from that seen in cells not treated with NGF (3 of 25 cells sensitized (12.0 %), 253 ± 70 % of baseline). Pretreatment with the CB1 antagonist AM-251 (100 nM) prevented the effect of ACEA on NGF-induced sensitization. These results support the hypothesis that cannabinoids, acting through CB1 receptors, may produce analgesia in part by preventing NGF-induced sensitization of TRPV1 in afferent nociceptor nerve endings. PMID:23850608

  3. The acute anorexic effect of liraglutide, a GLP-1 receptor agonist, does not require functional leptin receptor, serotonin, and hypothalamic POMC and CART activities in mice.

    PubMed

    Nonogaki, Katsunori; Kaji, Takao

    2016-10-01

    The acute anorexic effect of liraglutide, a GLP-1 receptor agonist, did not require functional leptin receptor, serotonin, and hypothalamic proopiomelanocortin and cocaine amphetamine regulated transcript activities in mice, although decrease in functional hypothalamic orexin activity might be involved in the acute anorexic effect of liraglutide. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  4. Muscarinic and Nicotinic Acetylcholine Receptor Agonists and Allosteric Modulators for the Treatment of Schizophrenia

    PubMed Central

    Jones, Carrie K; Byun, Nellie; Bubser, Michael

    2012-01-01

    Muscarinic and nicotinic acetylcholine (ACh) receptors (mAChRs and nAChRs) are emerging as important targets for the development of novel treatments for the symptoms associated with schizophrenia. Preclinical and early proof-of-concept clinical studies have provided strong evidence that activators of specific mAChR (M1 and M4) and nAChR (α7 and α2β4) subtypes are effective in animal models of antipsychotic-like activity and/or cognitive enhancement, and in the treatment of positive and cognitive symptoms in patients with schizophrenia. While early attempts to develop selective mAChR and nAChR agonists provided important preliminary findings, these compounds have ultimately failed in clinical development due to a lack of true subtype selectivity and subsequent dose-limiting adverse effects. In recent years, there have been major advances in the discovery of highly selective activators for the different mAChR and nAChR subtypes with suitable properties for optimization as potential candidates for clinical trials. One novel strategy has been to identify ligands that activate a specific receptor subtype through actions at sites that are distinct from the highly conserved ACh-binding site, termed allosteric sites. These allosteric activators, both allosteric agonists and positive allosteric modulators, of mAChR and nAChR subtypes demonstrate unique mechanisms of action and high selectivity in vivo, and may provide innovative treatment strategies for schizophrenia. PMID:21956443

  5. Antibodies against the melanocortin-4 receptor act as inverse agonists in vitro and in vivo.

    PubMed

    Peter, Jean-Christophe; Nicholson, Janet R; Heydet, Déborah; Lecourt, Anne-Catherine; Hoebeke, Johan; Hofbauer, Karl G

    2007-06-01

    Functionally active antibodies (Abs) against central G-protein-coupled receptors have not yet been reported. We selected the hypothalamic melanocortin-4 receptor (MC4-R) as a target because of its crucial role in the regulation of energy homeostasis. A 15 amino acid sequence of the N-terminal (NT) domain was used as an antigen. This peptide showed functional activity in surface plasmon resonance experiments and in studies on HEK-293 cells overexpressing the human MC4-R (hMC4-R). Rats immunized against the NT peptide produced specific antibodies, which were purified and characterized in vitro. In HEK-293 cells, rat anti-NT Abs showed specific immunofluorescence labeling of hMC4-R. They reduced the production of cAMP under basal conditions and after stimulation with a synthetic MC4-R agonist. Rats immunized against the NT peptide developed a phenotype consistent with MC4-R blockade, that is, increased food intake and body weight, increased liver and fat pad weight, and elevated plasma triglycerides. In a separate experiment in rats, an increase in food intake could be produced after injection of purified Abs into the third ventricle. Similar results were obtained in rats injected with anti-NT Abs raised in rabbits. Our data show for the first time that active immunization of rats against the NT sequence of the MC4-R results in specific Abs, which appear to stimulate food intake by acting as inverse agonists in the hypothalamus.

  6. Cardiovascular effects of glucagon-like peptide 1 (GLP-1) receptor agonists.

    PubMed

    Saraiva, Francisco Kerr; Sposito, Andrei C

    2014-10-22

    Patients with type 2 diabetes have a several-fold increased risk of developing cardiovascular disease when compared with nondiabetic controls. Myocardial infarction and stroke are responsible for 75% of all death in patients with diabetes, who present a 2-4× increased incidence of death from coronary artery disease. Patients with diabetes are considered for cardiovascular disease secondary prevention because their risk level is similar to that reported in patients without diabetes who have already suffered a myocardial infarction. More recently, with a better risk factors control, mainly in intensive LDL cholesterol targets with statins, a significant decrease in acute cardiovascular events was observed in population with diabetes. Together with other major risk factors, type 2 diabetes must be considered as an important cause of cardiovascular disease.Glucagon like peptide-1 receptor agonists represent a novel class of anti-hyperglycemic agents that have a cardiac-friendly profile, preserve neuronal cells and inhibit neuronal degeneration, an anti-inflammatory effect in liver protecting it against steatosis, increase insulin sensitivity, promote weight loss, and increase satiety or anorexia.This review is intended to rationally compile the multifactorial cardiovascular effects of glucagon-like peptide-1 receptor agonists available for the treatment of patients with type 2 diabetes.

  7. AVE 0991, a non-peptide Mas-receptor agonist, facilitates penile erection.

    PubMed

    da Costa Gonçalves, Andrey C; Fraga-Silva, Rodrigo A; Leite, Romulo; Santos, Robson A S

    2013-03-01

    The renin-angiotensin system plays a crucial role in erectile function. It has been shown that elevated levels of angiotensin II contribute to the development of erectile dysfunction both in humans and in aminals. On the contrary, the heptapeptide angiotensin-(1-7) appears to mediate penile erection by activation of the Mas receptor. Recently, we have shown that the erectile function of Mas gene-deleted mice was substantially reduced, which was associated with a marked increase in fibrous tissue in the corpus cavernosum. We have hypothesized that the synthetic non-peptide Mas agonist, AVE 0991, would potentiate penile erectile function. We showed that intracavernosal injection of AVE 0991 potentiated the erectile response of anaesthetized Wistar rats, measured as the ratio between corpus cavernosum pressure and mean arterial pressure, upon electrical stimulation of the major pelvic ganglion. The facilitatory effect of AVE 0991 on erectile function was dose dependent and completely blunted by the nitric oxide synthesis inhibitor, l-NAME. Importantly, concomitant intracavernosal infusion of the specific Mas receptor blocker, A-779, abolished the effect of AVE 0991. We demonstrated that AVE 0991 potentiates the penile erectile response through Mas in an NO-dependent manner. Importantly, these results suggest that Mas agonists, such as AVE 0991, might have significant therapeutic benefits for the treatment of erectile dysfunction.

  8. Novel Retinoic Acid Receptor Alpha Agonists for Treatment of Kidney Disease

    PubMed Central

    Liu, Ruijie; Li, Zhengzhe; Chen, Yibang; Evans, Todd; Chuang, Peter; Das, Bhaskar; He, John Cijiang

    2011-01-01

    Development of pharmacologic agents that protect podocytes from injury is a critical strategy for the treatment of kidney glomerular diseases. Retinoic acid reduces proteinuria and glomerulosclerosis in multiple animal models of kidney diseases. However, clinical studies are limited because of significant side effects of retinoic acid. Animal studies suggest that all trans retinoic acid (ATRA) attenuates proteinuria by protecting podocytes from injury. The physiological actions of ATRA are mediated by binding to all three isoforms of the nuclear retinoic acid receptors (RARs): RARα, RARβ, and RARγ. We have previously shown that ATRA exerts its renal protective effects mainly through the agonism of RARα. Here, we designed and synthesized a novel boron-containing derivative of the RARα-specific agonist Am580. This new derivative, BD4, binds to RARα receptor specifically and is predicted to have less toxicity based on its structure. We confirmed experimentally that BD4 binds to RARα with a higher affinity and exhibits less cellular toxicity than Am580 and ATRA. BD4 induces the expression of podocyte differentiation markers (synaptopodin, nephrin, and WT-1) in cultured podocytes. Finally, we confirmed that BD4 reduces proteinuria and improves kidney injury in HIV-1 transgenic mice, a model for HIV-associated nephropathy (HIVAN). Mice treated with BD4 did not develop any obvious toxicity or side effect. Our data suggest that BD4 is a novel RARα agonist, which could be used as a potential therapy for patients with kidney disease such as HIVAN. PMID:22125642

  9. Docking and molecular dynamics simulations of peroxisome proliferator activated receptors interacting with pan agonist sodelglitazar.

    PubMed

    Liu, Xu-Yuan; Wang, Run-Ling; Xu, Wei-Ren; Tang, Li-Da; Wang, Shu-Qing; Chou, Kuo-Chen

    2011-10-01

    PPAR (peroxisome proliferator-activated receptor) pan agonists play a critical role in treating metabolic diseases, especially the Type-2 diabetes mellitus (T2DM). GlaxoSmithKline's sodelglitazar (GW677954) is one of the potent PPAR pan agonists, which is currently being investigated in Phase II clinical trials for the treatment of T2DM and its complications. The present study was aimed at investigation into the effect of sodelglitazar at the binding pockets of PPARs. The Schrodinger Suite program (2009) was used for the molecular docking, while the GROMACS program used for the molecular dynamics (MD) simulations. The results thus obtained showed that sodelglitazar being docked well in the active site of PPARs. It was revealed by the MD simulations that the structures of the receptors remained quite stable during the simulations and that the important AF-2 helix showed less flexibility after binding with sodelglitazar. Also, it was observed that sodelglitazar could periodically form hydrogen bonds with the AF-2 helix of PPARs to stabilize the AF-2 helix in an active conformation. Our findings have confirmed that GlaxoSmithKline's sodelglitazar can activate the PPARs, which is quite consistent with the previous biological studies.

  10. Thrombopoietin-receptor agonists for children with immune thrombocytopenia: a systematic review.

    PubMed

    Zhang, Jiaxing; Liang, Yi; Ai, Yuan; Xie, Juan; Li, Youping; Zheng, Wenyi

    2017-10-01

    We conducted a systematic review to assess the efficacy and safety of Thrombopoietin-receptor agonists (TPOras) for pediatric immune thrombocytopenia (ITP). We searched PubMed, Embase and Cochrane Library from their earliest records to January 2017. Randomized controlled trials (RCTs) were included. Primary outcomes were durable response and clinically significant bleeding. Secondary outcomes were overall response, overall bleeding events, the use of rescue medication and adverse events (AEs). Five randomized RCTs (261participants) were included. Compared with placebo group, the proportion of patients achieving durable platelet response was significantly higher in Eltrombopag (P = 0.0004) or Romiplostim (P = 0.002) group, so was the overall response in Eltrombopag [RR = 2.64, 95% CI (1.58, 4.44)] or Romiplostim [RR = 5.05, 95% CI (2.21, 11.53)] group. Both clinically significant bleeding (P = 0.04) and total bleeding (P = 0.01) in Eltrombopag group were significantly less frequent than those in placebo group, while no significant difference between Romiplostim and placebo group. The proportion of patients receiving rescue medication, the incidence of overall AEs and serious AEs between TPO-receptor agonists and placebo group were not significantly different. TPOras might improve both durable and overall platelet response in pediatric ITP, compared with placebo.

  11. Comparing the effects of endogenous and synthetic cannabinoid receptor agonists on survival of gastric cancer cells.

    PubMed

    Ortega, A; García-Hernández, V M; Ruiz-García, E; Meneses-García, A; Herrera-Gómez, A; Aguilar-Ponce, J L; Montes-Servín, E; Prospero-García, O; Del Angel, S A

    2016-11-15

    Anti-neoplastic activity induced by cannabinoids has been extensively documented for a number of cancer cell types; however, this topic has been explored in gastric cancer cells only in a limited number of approaches. Thus, the need of integrative and comparative studies still persists. In this study we tested and compared the effects of three different cannabinoid receptor agonists-anandamide (AEA), (R)-(+)-methanandamide (Meth-AEA) and CP 55,940 (CP)- on gastric cancer cell morphology, viability and death events in order to provide new insights to the use of these agents for therapeutic purposes. The three agents tested exhibited similar concentration-dependent effects in the induction of changes in cell morphology and cell loss, as well as in the decrease of cell viability and DNA laddering in the human gastric adenocarcinoma cell line (AGS). Differences among the cannabinoids tested were mostly observed in the density of cells found in early and late apoptosis and necrosis, favoring AEA and CP as the more effective inducers of apoptotic mechanisms, and Meth-AEA as a more effective inducer of necrosis through transient and rapid apoptosis. Through a comparative approach, our results support and confirm the therapeutic potential that cannabinoid receptor agonists exert in gastric cancer cells and open possibilities to use cannabinoids as part of a new gastric cancer therapy. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. Effects of glucagon-like peptide-1 receptor agonists on body weight: a meta-analysis.

    PubMed

    Monami, Matteo; Dicembrini, Ilaria; Marchionni, Niccolò; Rotella, Carlo M; Mannucci, Edoardo

    2012-01-01

    Glucagon-Like Peptide-1 receptor agonists (GLP-1RAs), approved as glucose-lowering drugs for the treatment of type 2 diabetes, have also been shown to reduce body weight. An extensive Medline, Cochrane database, and Embase search for "exenatide," "liraglutide," "albiglutide," "semaglutide," and "lixisenatide" was performed, collecting all randomized clinical trials on humans up to December 15, 2011, with a duration of at least 24 weeks, comparing GLP-1 receptor agonists with either placebo or active drugs. Twenty two (7,859 patients) and 7 (2,416 patients) trials with available results on body weight at 6 and 12 months, respectively, were included. When compared with placebo, GLP-1RAs determine a reduction of BMI at 6 months of -1.0 [-1.3; -0.6] kg/m(2). Considering the average BMI at baseline (32.4 kg/m(2)) these data means a weight reduction of about 3% at 6 months. This result could seem modest from a clinical standpoint; however, it could be affected by many factors contributing to an underestimation of the effect of GLP-1RA on body weight, such as non adequate doses, inclusion criteria, efficacy of GLP-1RA on reducing glycosuria, and association to non-pharmacological interventions not specifically aimed to weight reduction.

  13. Discovery of AZD3199, An Inhaled Ultralong Acting β2 Receptor Agonist with Rapid Onset of Action

    PubMed Central

    2014-01-01

    A series of dibasic des-hydroxy β2 receptor agonists has been prepared and evaluated for potential as inhaled ultralong acting bronchodilators. Determination of activities at the human β-adrenoreceptors demonstrated a series of highly potent and selective β2 receptor agonists that were progressed to further study in a guinea pig histamine-induced bronchoconstriction model. Following further assessment by onset studies in guinea pig tracheal rings and human bronchial rings contracted with methacholine (guinea pigs) or carbachol (humans), duration of action studies in guinea pigs after intratracheal (i.t.) administration and further selectivity and safety profiling AZD3199 was shown to have an excellent over all profile and was progressed into clinical evaluation as a new ultralong acting inhaled β2 receptor agonist with rapid onset of action. PMID:24900851

  14. Optically Pure, Structural, and Fluorescent Analogues of a Dimeric Y4 Receptor Agonist Derived by an Olefin Metathesis Approach.

    PubMed

    Liu, Mengjie; Mountford, Simon J; Richardson, Rachel R; Groenen, Marleen; Holliday, Nicholas D; Thompson, Philip E

    2016-07-14

    The dimeric peptide 1 (BVD-74D, as a diastereomeric mixture) is a potent and selective neuropeptide Y Y4 receptor agonist. It represents a valuable candidate in developing traceable ligands for pharmacological studies of Y4 receptors and as a lead compound for antiobesity drugs. Its optically pure stereoisomers along with analogues and fluorescently labeled variants were prepared by exploiting alkene metathesis reactions. The (2R,7R)-diaminosuberoyl containing peptide, (R,R)-1, had markedly higher affinity and agonist efficacy than its (S,S)-counterpart. Furthermore, the sulfo-Cy5 labeled (R,R)-14 retained high agonist potency as a novel fluorescent ligand for imaging Y4 receptors.

  15. The melanocortin MC1 receptor agonist BMS-470539 inhibits leucocyte trafficking in the inflamed vasculature

    PubMed Central

    Leoni, G; Voisin, M-B; Carlson, K; Getting, SJ; Nourshargh, S; Perretti, M

    2010-01-01

    Background and purpose: Over three decades of research evaluating the biology of melanocortin (MC) hormones and synthetic peptides, activation of the MC type 1 (MC1) receptor has been identified as a viable target for the development of novel anti-inflammatory therapeutic agents. Here, we have tested a recently described selective agonist of MC1 receptors, BMS-470539, on leucocyte/post-capillary venule interactions in murine microvascular beds. Experimental approach: Intravital microscopy of two murine microcirculations were utilized, applying two distinct modes of promoting inflammation. The specificity of the effects of BMS-470539 was assessed using mice bearing mutant inactive MC1 receptors (the recessive yellow e/e colony). Key results: BMS-470539, given before an ischaemia–reperfusion protocol, inhibited cell adhesion and emigration with no effect on cell rolling, as assessed 90 min into the reperfusion phase. These properties were paralleled by inhibition of tissue expression of both CXCL1 and CCL2. Confocal investigations of inflamed post-capillary venules revealed immunostaining for MC1 receptors on adherent and emigrated leucocytes. Congruently, the anti-inflammatory properties of BMS-470539 were lost in mesenteries of mice bearing the inactive mutant MC1 receptors. Therapeutic administration of BMS-470539 stopped cell emigration, but did not affect cell adhesion in the cremasteric microcirculation inflamed by superfusion with platelet-activating factor. Conclusions and implications: Activation of MC1 receptors inhibited leucocyte adhesion and emigration. Development of new chemical entities directed at MC1 receptors could be a viable approach in the development of novel anti-inflammatory therapeutic agents with potential application to post-ischaemic conditions. PMID:20331604

  16. Opioid Peptidomimetics: Leads for the Design of Bioavailable Mixed Efficacy Mu Opioid Receptor (MOR) Agonist/Delta Opioid Receptor (DOR) Antagonist Ligands

    PubMed Central

    Mosberg, Henry I.; Yeomans, Larisa; Harland, Aubrie A.; Bender, Aaron M.; Sobczyk-Kojiro, Katarzyna; Anand, Jessica P.; Clark, Mary J.; Jutkiewicz, Emily M.; Traynor, John R.

    2013-01-01

    We have previously described opioid peptidomimetic, 1, employing a tetrahydroquinoline scaffold and modeled on a series of cyclic tetrapeptide opioid agonists. We have recently described modifications to these peptides that confer a mu opioid receptor (MOR) agonist, delta opioid receptor (DOR) antagonist profile, which has been shown to reduce the development of tolerance to the analgesic actions of MOR agonists. Several such bifunctional ligands have been reported, but none has been demonstrated to cross the blood brain barrier. Here we describe the transfer of structural features that evoked MOR agonist/DOR antagonist behavior in the cyclic peptides to the tetrahydroquinoline scaffold and show that the resulting peptidomimetics maintain the desired pharmacological profile. Further, the 4R diastereomer of 1 was fully efficacious and approximately equipotent to morphine in the mouse warm water tail withdrawal assay following intraperitoneal administration and thus a promising lead for the development of opioid analgesics with reduced tolerance. PMID:23419026

  17. Agonist-induced internalisation of the glucagon-like peptide-1 receptor is mediated by the Gαq pathway.

    PubMed

    Thompson, Aiysha; Kanamarlapudi, Venkateswarlu

    2015-01-01

    The glucagon-like peptide-1 receptor (GLP-1R) is a G-protein-coupled receptor (GPCR) and an important target in the treatment of type 2 diabetes mellitus (T2DM). Upon stimulation with agonist, the GLP-1R signals through both Gαs and Gαq coupled pathways to stimulate insulin secretion. The agonist-induced GLP-1R internalisation has recently been shown to be important for insulin secretion. However, the molecular mechanisms underlying GLP-1R internalisation remain unknown. The aim of this study was to determine the role of GLP-1R downstream signalling pathways in its internalisation. Agonist-induced human GLP-1R (hGLP-1R) internalisation and activity were examined using a number of techniques including immunoblotting, ELISA, immunofluorescence and luciferase assays to determine cAMP production, intracellular Ca(2+) accumulation and ERK phosphorylation. Agonist-induced hGLP-1R internalisation is dependent on caveolin-1 and dynamin. Inhibition of the Gαq pathway but not the Gαs pathway affected hGLP-1R internalisation. Consistent with this, hGLP-1R mutant T149M and small-molecule agonists (compound 2 and compound B), which activate only the Gαs pathway, failed to induce internalisation of the receptor. Chemical inhibitors of the Gαq pathway, PKC and ERK phosphorylation significantly reduced agonist-induced hGLP-1R internalisation. These inhibitors also suppressed agonist-induced ERK1/2 phosphorylation demonstrating that the phosphorylated ERK acts downstream of the Gαq pathway in the hGLP-1R internalisation. In summary, agonist-induced hGLP-1R internalisation is mediated by the Gαq pathway. The internalised hGLP-1R stimulates insulin secretion from pancreatic β-cells, indicating the importance of GLP-1 internalisation for insulin secretion. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. The A1 adenosine receptor as a new player in microglia physiology.

    PubMed

    Luongo, L; Guida, F; Imperatore, R; Napolitano, F; Gatta, L; Cristino, L; Giordano, C; Siniscalco, D; Di Marzo, V; Bellini, G; Petrelli, R; Cappellacci, L; Usiello, A; de Novellis, V; Rossi, F; Maione, S

    2014-01-01

    The purinergic system is highly involved in the regulation of microglial physiological processes. In addition to the accepted roles for the P2 X4,7 and P2 Y12 receptors activated by adenosine triphosphate (ATP) and adenosine diphosphate, respectively, recent evidence suggests a role for the adenosine A2A receptor in microglial cytoskeletal rearrangements. However, the expression and function of adenosine A1 receptor (A1AR) in microglia is still unclear. Several reports have demonstrated possible expression of A1AR in microglia, but a new study has refuted such evidence. In this study, we investigated the presence and function of A1AR in microglia using biomolecular techniques, live microscopy, live calcium imaging, and in vivo electrophysiological approaches. The aim of this study was to clarify the expression of A1AR in microglia and to highlight its possible roles. We found that microglia express A1AR and that it is highly upregulated upon ATP treatment. Moreover, we observed that selective stimulation of A1AR inhibits the morphological activation of microglia, possibly by suppressing the Ca(2+) influx induced by ATP treatment. Finally, we recorded the spontaneous and evoked activity of spinal nociceptive-specific neuron before and after application of resting or ATP-treated microglia, with or without preincubation with a selective A1AR agonist. We found that the microglial cells, pretreated with the A1AR agonist, exhibit lower capability to facilitate the nociceptive neurons, as compared with the cells treated with ATP alone. Copyright © 2013 Wiley Periodicals, Inc.

  19. Positron emission tomography imaging of dopamine D2 receptors using a highly selective radiolabeled D2 receptor partial agonist

    PubMed Central

    Xu, Jinbin; Vangveravong, Suwanna; Li, Shihong; Fan, Jinda; Jones, Lynne A.; Cui, Jinquan; Wang, Ruike; Tu, Zhude; Chu, Wenhua; Perlmutter, Joel S.; Mach, Robert H.

    2013-01-01

    A series of microPET imaging studies were conducted in anesthetized rhesus monkeys using the dopamine D2-selective partial agonist, [11C]SV-III-130. There was a high uptake in regions of brain known to express a high density of D2 receptors under baseline conditions. Rapid displacement in the caudate and putamen, but not in the cerebellum, was observed after injection of the dopamine D2/3 receptor nonselective ligand S(−)-eticlopride at a low dosage (0.025 mg/kg/i.v.); no obvious displacement in the caudate, putamen and cerebellum was observed after the treatment with a dopamine D3 receptor selective ligand WC-34 (0.1 mg/kg/i.v.). Pretreatment with lorazepam (1 mg/kg, i.v. 30 min) to reduce endogenous dopamine prior to tracer injection resulted in unchanged binding potential (BP) values, a measure of D2 receptor binding in vivo, in the caudate and putamen. D-amphetamine challenge studies indicate that there is a significant displacement of [11C]SV-III-130 by d-amphetamine-induced increases in synaptic dopamine levels. PMID:23333701

  20. The non-biphenyl-tetrazole AT1 receptor blocker eprosartan is a unique and robust inverse agonist of the active state of AT1 receptor.

    PubMed

    Takezako, Takanobu; Unal, Hamiyet; Karnik, Sadashiva S; Node, Koichi

    2018-03-23

    Diseases such as hypertension and renal-allograft rejection are accompanied by chronic agonist-independent signaling by the angiotensin II (Ang II) type 1 receptor (AT1R). The current treatment paradigm for these diseases embraces the preferred use of inverse agonist AT1R blockers (ARBs). However, variability in the inverse agonist activities of common biphenyl-tetrazole ARBs for the active state of AT1R often leads to treatment failure. Therefore, characterization of robust inverse agonist ARBs for the active state of AT1R is necessary. To identify the robust inverse agonist for active state of AT1R and its molecular mechanism, we performed site-directed mutagenesis, competition binding assay, inositol phosphate production assay and molecular modeling for both ground state wild-type AT1R (WT-AT1R) and active state N111G-AT1R. Although candesartan and telmisartan exhibited weaker inverse agonist activity for N111G-AT1 compared to WT-AT1, only eprosartan exhibited robust inverse agonist activity for both N111G-AT1 and WT-AT1. Specific ligand-receptor contacts for candesartan and telmisartan are altered in the active state N111G-AT1R compare to in the ground state WT-AT1R, suggesting a potential basis for their attenuated inverse agonist activity for the active state of AT1R. In contrast, interactions between eprosartan and N111G-AT1R were not significantly altered, and the inverse agonist activity of eprosartan was robust. These findings suggest that eprosartan may be a better therapeutic option than other ARBs, and that comparative studies investigating eprosartan and other ARBs for the treatment of diseases caused by chronic agonist-independent AT1R activation are warranted. This article is protected by copyright. All rights reserved.

  1. Characterization of dual agonists for kinin B1 and B2 receptors and their biased activation of B2 receptors

    PubMed Central

    Zhang, Xianming; Lowry, Jessica L.; Brovkovych, Viktor; Skidgel, Randal A.

    2012-01-01

    Kinin B1 and B2 receptors (kB1R and kB2R) play important roles in many physiological and pathological processes. In some cases, kB1R or kB2R activation can have overlapping or complementary beneficial effects, thus an activator of both receptors might be advantageous. We found that replacement of the C-terminal Arg in the natural kB2R activators bradykinin (BK) or kallidin (KD) with Lys (K9-BK or K10-KD) resulted in agonists that effectively stimulate the downstream signaling of both the kB1R and kB2R as measured by increased inositol turnover, intracellular calcium, ERK1/2 phosphorylation, arachidonic acid release and NO production. However, K9-BK and K10-KD displayed some characteristics of biased agonism for kB2Rs as indicated by the rapid kinetics of ERK1/2 phosphorylation induced by K9-BK or K10-KD compared with the prolonged response mediated by BK or KD. In contrast, kinetics of ERK phosphorylation stimulated by K10-KD activation of the kB1R was as same as that induced by known kB1R agonist des-Arg10-KD. Furthermore, the endocytosis of kB2Rs mediated by K9-BK and K10-KD was remarkably less than that induced by BK and KD respectively. K10-KD stimulated kB1R and kB2R-dependent calcium responses and ERK1/2 phosphorylation in bovine endothelial cells. In cytokine-treated human endothelial cells, K10-KD stimulated ERK1/2 phosphorylation and a transient peak of NO production that was primarily kB2R-dependent. K10-KD also stimulated prolonged NO production that was both kB1R and kB2R-dependent. These data provide the first examples of dual agonists of kB1R and kB2R, and a biased agonist of kB2R and may provide useful clues for developing dual modulators of kB1Rs and kB2Rs for potential therapeutic use. PMID:22522052

  2. Overview of Glucagon-Like Peptide-1 Receptor Agonists for the Treatment of Patients with Type 2 Diabetes.

    PubMed

    Tran, Kelvin Lingjet; Park, Young In; Pandya, Shalin; Muliyil, Navin John; Jensen, Brandon David; Huynh, Kovin; Nguyen, Quang T

    2017-06-01

    It is estimated that 29.1 million people or 9.3% of the US population have diabetes, which contributes to considerable medical and financial burden. Type 2 diabetes mellitus is characterized by insulin resistance and insulin secretion impairment leading to hyperglycemia. The presence of insulin resistance is strongly correlated with obesity. This article reviews the available glucagon-like peptide-1 (GLP-1) receptor agonists and their role in the management of patients with diabetes, to help guide the selection of the most suitable agent for the individualized treatment of patients with type 2 diabetes. This article reviews the evidence from phase 3 clinical trials for each of the 5 GLP-1 receptor agonists by comparing them against one another and with other existing therapies, including metformin, dipeptidyl peptidase-4 (DPP-4) inhibitors, and sulfonylureas. Incretin-based therapies have emerged as attractive agents for the treatment of type 2 diabetes. They target the GLP-1 hormone, which is partly responsible for insulin release and for attenuating hyperglycemia during meals (ie, the incretin effect). The 2 classes of incretin-based therapy currently available are GLP-1 receptor agonists and DPP-4 inhibitors, which prevent the breakdown of GLP-1. Both classes are attractive options, given their glucose-lowering effects without the adverse effects of hypoglycemia and weight gain. The different mechanisms of action of these therapies result in generally greater efficacy with GLP-1 receptor agonists, albeit at the expense of slightly increased gastrointestinal symptoms. These agents exert their effects by improving glucose-dependent insulin release, suppressing glucagon release, suppressing hepatic glucose output, and decreasing the rate of gastric emptying, thereby reducing appetite. Currently, 5 GLP-1 receptor agonists are available, including exenatide, liraglutide, albiglutide, dulaglutide, and lixisenatide; semaglutide may soon become available as the newest

  3. Biology and therapeutic potential of cannabinoid CB2 receptor inverse agonists

    PubMed Central

    Lunn, C A; Reich, E-P; Fine, J S; Lavey, B; Kozlowski, J A; Hipkin, R W; Lundell, D J; Bober, L

    2007-01-01

    Evidence has emerged suggesting a role for the cannabinoid CB2 receptor in immune cell motility. This provides a rationale for a novel and generalized immunoregulatory role for cannabinoid CB2 receptor-specific compounds. In support of this possibility, we will review the biology of a class of cannabinoid CB2 receptor—specific inverse agonist, the triaryl bis-sulfones. We will show that one candidate, Sch.414319, is potent and selective for the cannabinoid CB2 receptor, based on profiling studies using biochemical assays for 45 enzymes and 80 G-protein coupled receptors and ion channels. We will describe initial mechanistic studies using this optimized triaryl bis-sulfone, showing that the compound exerts a broad effect on cellular protein phosphorylations in human monocytes. This profile includes the down regulation of a required phosphorylation of the monocyte-specific actin bundling protein L-plastin. We suggest that this observation may provide a mechanism for the observed activity of Sch.414319 in vivo. Our continued analysis of the in vivo efficacy of this compound in diverse disease models shows that Sch.414319 is a potent modulator of immune cell mobility in vivo, can modulate bone damage in antigen-induced mono-articular arthritis in the rat, and is uniquely potent at blocking experimental autoimmune encephalomyelitis in the rat. PMID:17906679

  4. Chimeric peptide EP45 as a dual agonist at GLP-1 and NPY2R receptors.

    PubMed

    Chepurny, Oleg G; Bonaccorso, Ron L; Leech, Colin A; Wöllert, Torsten; Langford, George M; Schwede, Frank; Roth, Christian L; Doyle, Robert P; Holz, George G

    2018-02-28

    We report the design and target validation of chimeric peptide EP45, a novel 45 amino acid monomeric dual agonist peptide that contains amino acid sequence motifs present within the blood glucose-lowering agent exendin-4 (Ex-4) and the appetite-suppressing agent PYY(3-36). In a new high-throughput FRET assay that provides real-time kinetic information concerning levels of cAMP in living cells, EP45 recapitulates the action of Ex-4 to stimulate cAMP production via the glucagon-like peptide-1 receptor (GLP-1R), while also recapitulating the action of PYY(3-36) to inhibit cAMP production via the neuropeptide Y 2 receptor (NPY2R). EP45 fails to activate glucagon or GIP receptors, whereas for cells that co-express NPY2R and adenosine A 2B receptors, EP45 acts in an NPY2R-mediated manner to suppress stimulatory effects of adenosine on cAMP production. Collectively, such findings are remarkable in that they suggest a new strategy in which the co-existing metabolic disorders of type 2 diabetes and obesity will be treatable using a single peptide such as EP45 that lowers levels of blood glucose by virtue of its GLP-1R-mediated effect, while simultaneously suppressing appetite by virtue of its NPY2R-mediated effect.

  5. Disruption of a putative intersubunit electrostatic bond enhances agonist efficacy at the human α1 glycine receptor.

    PubMed

    Welsh, Brian T; Todorovic, Jelena; Kirson, Dean; Allen, Hunter M; Bayly, Michelle D; Mihic, S John

    2017-02-15

    Partial agonists have lower efficacies than compounds considered 'full agonists', eliciting submaximal responses even at saturating concentrations. Taurine is a partial agonist at the glycine receptor (GlyR), a member of the cys-loop ligand-gated ion channel superfamily. The molecular mechanisms responsible for agonism are not fully understood but evidence suggests that efficacy at these receptors is determined by conformational changes that occur early in the process of receptor activation. We previously identified a residue located near the human α1 glycine binding site (aspartate-97; D97) that, when mutated to arginine (D97R), results in GlyR channels opening spontaneously with a high open probability, mimicking the effects of saturating glycine concentrations on wildtype GlyR. This D97 residue is hypothesized to form an electrostatic interaction with arginine-119 on an adjacent subunit, stabilizing the channel in a shut state. Here we demonstrate that the disruption of this putative bond increases the efficacy of partial agonists including taurine, as well as two other β-amino acid partial agonists, β-aminobutyric acid (β-ABA) and β-aminoisobutyric acid (β-AIBA). Even the subtle charge-conserving mutation of D97 to glutamate (D97E) markedly affects partial agonist efficacy. Mutation to the neutral alanine residue in the D97A mutant mimics the effects seen with D97R, indicating that charge repulsion does not significantly affect these findings. Our findings suggest that the determination of efficacy following ligand binding to the glycine receptor may involve the disruption of an intersubunit electrostatic interaction occurring near the agonist binding site. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Serotonin receptor agonists in the acute treatment of migraine: a review on their therapeutic potential

    PubMed Central

    Negro, Andrea; Koverech, Angela; Martelletti, Paolo

    2018-01-01

    Migraine is an important socioeconomic burden and is ranked the sixth cause of years of life lost because of disability in the general population and the third cause of years of life lost in people younger than 50 years. The cornerstone of pharmacological treatment is represented by the acute therapy. The serotonin (5-hydroxytryptamine [5-HT]) receptor subtype 1B/1D agonists, called triptans, are nowadays the first-line acute therapy for patients who experience moderate-to-severe migraine attacks. Unfortunately, a high percentage of patients are not satisfied with this acute treatment, either for lack of response or side effects. Moreover, their mechanism of action based on vasoconstriction makes them unsuitable for patients with previous cardio- and cerebrovascular diseases and for those with uncontrolled hypertension. Since the introduction of triptans, no other acute drug class has passed all developmental stages. The research for a new drug lacking vasoconstrictive effects led to the development of lasmiditan, a highly selective 5-HT1F receptor agonist with minimized interactions with other 5-HT receptor subtypes. Lasmiditan is considered to be the first member of a new drug category, the neurally acting anti-migraine agent (NAAMA). Phase II and III trials had shown superiority compared to placebo and absence of typical triptan-associated adverse events (AEs). Most of the AEs were related to the central nervous system, depending on the high permeability through the blood–brain barrier and mild to moderate severity. The results of ongoing long-term Phase III trials will determine whether lasmiditan will become available in the market, and then active triptan comparator studies will assess patients’ preference. Future studies could then explore the safety during pregnancy and breastfeeding or the risk that overuse of lasmiditan leads to medication overuse headache. PMID:29563831

  7. Serotonin receptor agonists in the acute treatment of migraine: a review on their therapeutic potential.

    PubMed

    Negro, Andrea; Koverech, Angela; Martelletti, Paolo

    2018-01-01

    Migraine is an important socioeconomic burden and is ranked the sixth cause of years of life lost because of disability in the general population and the third cause of years of life lost in people younger than 50 years. The cornerstone of pharmacological treatment is represented by the acute therapy. The serotonin (5-hydroxytryptamine [5-HT]) receptor subtype 1 B /1 D agonists, called triptans, are nowadays the first-line acute therapy for patients who experience moderate-to-severe migraine attacks. Unfortunately, a high percentage of patients are not satisfied with this acute treatment, either for lack of response or side effects. Moreover, their mechanism of action based on vasoconstriction makes them unsuitable for patients with previous cardio- and cerebrovascular diseases and for those with uncontrolled hypertension. Since the introduction of triptans, no other acute drug class has passed all developmental stages. The research for a new drug lacking vasoconstrictive effects led to the development of lasmiditan, a highly selective 5-HT1 F receptor agonist with minimized interactions with other 5-HT receptor subtypes. Lasmiditan is considered to be the first member of a new drug category, the neurally acting anti-migraine agent (NAAMA). Phase II and III trials had shown superiority compared to placebo and absence of typical triptan-associated adverse events (AEs). Most of the AEs were related to the central nervous system, depending on the high permeability through the blood-brain barrier and mild to moderate severity. The results of ongoing long-term Phase III trials will determine whether lasmiditan will become available in the market, and then active triptan comparator studies will assess patients' preference. Future studies could then explore the safety during pregnancy and breastfeeding or the risk that overuse of lasmiditan leads to medication overuse headache.

  8. Effect of buspirone, a 5-HT1A receptor agonist, on esophageal motility in healthy volunteers.

    PubMed

    Di Stefano, M; Papathanasopoulos, A; Blondeau, K; Vos, R; Boecxstaens, V; Farré, R; Rommel, N; Tack, J

    2012-07-01

    There are limited data concerning the effects of 5-HT(1A) receptor activation on esophageal motility. Sumatriptan, a 5-HT(1A) receptor agonist, was recently reported to enhance esophageal peristalsis after intravenous administration. Buspirone, an orally available 5-HT(1A) receptor agonist, was shown to modulate gastroduodenal motor function. Our aim was to evaluate the effect of buspirone on esophageal motility of healthy volunteers. On two separate visits, 20 healthy volunteers aged 21-29 years (nine women) underwent esophageal manometry before and 10, 30, and 60 minutes after the administration of buspirone 20-mg or placebo capsule, according to a double-blind crossover design. At each time point, we compared buspirone and placebo effects on: resting pressure of the lower esophageal sphincter (LES); residual pressure and duration of LES relaxation; amplitude, duration, and onset velocity of esophageal body contractions, during 10 swallows of 5 mL of water. Significant analysis of variance differences (P < 0.05) are presented as mean ± standard deviation. Buspirone significantly increased mean distal esophageal wave amplitude (151 vs. 87 mmHg, P < 0.05) and duration (6.1 vs. 4.2 seconds, P < 0.05). Similarly, buspirone significantly increased mean LES resting pressure (26 vs. 21 mmHg, P < 0.05) and mean residual LES pressure (7.9 vs. 2 mmHg, P < 0.05), whereas reduced mean LES relaxation duration (7.2 vs. 8.0 seconds, P < 0.05) and mean distal onset velocity (7.6 vs. 14.7 cm/second, P < 0.05). Buspirone enhances esophageal peristalsis and LES function in healthy volunteers. Further study is warranted on the effects of buspirone on esophageal function and symptoms in patients with ineffective esophageal motility. © 2011 Copyright the Authors. Journal compilation © 2011, Wiley Periodicals, Inc. and the International Society for Diseases of the Esophagus.

  9. GLP-1 Receptor Agonists and Type 1 Diabetes - Where Do We Stand?

    PubMed

    Popovic, Djordje S; Stokic, Edita; Popovic, Stevan L

    2015-01-01

    Type 1 diabetes (T1DM) is a disease characterized by autoimmune mediated destruction of the insulin producing beta cells of endocrine pancreas. Beside insulin deficiency, T1DM is also characterized by abnormal suppression of glucagon secretion in response to hyperglycemia. All these abnormalities are likely to leave patients dependent upon exogenous insulin administration for survival. GLP-1 is a hormone secreted by L-cells of distal small intestine and colon. GLP-1 exerts its effects through the interaction with GLP-1 receptor expressed in the pancreatic islets, lung, hypothalamus, stomach, heart and kidney. It belongs to the group of incretin peptides and it stimulates insulin and inhibits glucagon secretion. Actions of GLP-1 also include delaying of gastric emptying, reduction of appetite and induction of satiety. On the other hand, evidences mainly collected from animal models, have indicated the role of GLP-1 in increasing beta cell proliferation and differentiation and in decreasing the rate of beta cell apoptosis. GLP-1 receptor agonists are approved for the treatment of type 2 diabetes where they have established very important position. However, they are still not approved for use in T1DM, although they could have beneficial effects in both new onset and longstanding T1DM patients, mainly as an adjunctive therapy to insulin in order to improve glycemic control and body weight management in longstanding disease or to reduce insulin requirements or even to delay the absolute dependence upon insulin administration in new onset T1DM. Randomized, long-term, placebo controlled clinical trials are warranted before the official implementation of GLP-1 receptor agonists in the treatment of T1DM.

  10. Suppression of the cough reflex by α2-adrenergic receptor agonists in the rabbit

    PubMed Central

    Cinelli, Elenia; Bongianni, Fulvia; Pantaleo, Tito; Mutolo, Donatella

    2013-01-01

    The α2-adrenergic receptor agonist clonidine has been shown to inhibit citric acid-induced cough responses in guinea pigs when administered by aerosol, but not orally. In contrast, oral or inhaled clonidine had no effect on capsaicin-induced cough and reflex bronchoconstriction in humans. In addition, intravenous administration of clonidine has been shown to depress fentanyl-induced cough in humans. We investigated the effects of the α2-adrenergic receptor agonists, clonidine and tizanidine, on cough responses induced by mechanical and chemical (citric acid) stimulation of the tracheobronchial tree. Drugs were microinjected (30–50 nL) into the caudal nucleus tractus solitarii (cNTS) and the caudal ventral respiratory group (cVRG) as well as administered intravenously in pentobarbital sodium-anesthetized, spontaneously breathing rabbits. Bilateral microinjections of clonidine into the cNTS or the cVRG reduced cough responses at 0.5 mmol/L and abolished the cough reflex at 5 mmol/L. Bilateral microinjections of 0.5 mmol/L tizanidine into the cNTS completely suppressed cough responses, whereas bilateral microinjections of 5 mmol/L into the cVRG only caused mild reductions in them. Depressant effects on the cough reflex of clonidine and tizanidine were completely reverted by microinjections of 10 mmol/L yohimbine. Intravenous administration of clonidine (80–120 μg/kg) or tizanidine (150–300 μg/kg) strongly reduced or completely suppressed cough responses. These effects were reverted by intravenous administration of yohimbine (300 μg/kg). The results demonstrate that activation of α2-adrenergic receptors in the rabbit exerts potent inhibitory effects on the central mechanism generating the cough motor pattern with a clear action at the level of the cNTS and the cVRG. PMID:24400133

  11. Circannual rhythm in body temperature, torpor, and sensitivity to A₁ adenosine receptor agonist in arctic ground squirrels.

    PubMed

    Olson, Jasmine M; Jinka, Tulasi R; Larson, Lindy K; Danielson, Jeffrey J; Moore, Jeanette T; Carpluck, Joanna; Drew, Kelly L

    2013-06-01

    A₁ adenosine receptor (A₁AR) activation within the central nervous system induces torpor, but in obligate hibernators such as the arctic ground squirrel (AGS; Urocitellus parryii), A₁AR stimulation induces torpor only during the hibernation season, suggesting a seasonal increase in sensitivity to A₁AR signaling. The purpose of this research was to investigate the relationship between body temperature (Tb) and sensitivity to an adenosine A1 receptor agonist in AGS. We tested the hypothesis that increased sensitivity in A₁AR signaling would lead to lower Tb in euthermic animals during the hibernation season when compared with the summer season. We further predicted that if a decrease in euthermic Tb reflects increased sensitivity to A₁AR activation, then it should likewise predict spontaneous torpor. We used subcutaneous IPTT-300 transponders to monitor Tb in AGS housed under constant ambient conditions (12:12 L:D, 18 °C) for up to 16 months. These animals displayed an obvious rhythm in euthermic Tb that cycled with a period of approximately 8 months. Synchrony in the Tb rhythm within the group was lost after several months of constant L:D conditions; however, individual rhythms in Tb continued to show clear sine wave-like waxing and waning. AGS displayed spontaneous torpor only during troughs in euthermic Tb. To assess sensitivity to A₁AR activation, AGS were administered the A₁AR agonist N(6)-cyclohexyladenosine (CHA, 0.1 mg/kg, ip), and subcutaneous Tb was monitored. AGS administered CHA during a seasonal minimum in euthermic Tb showed a greater drug-induced decrease in Tb (1.6 ± 0.3 °C) than did AGS administered CHA during a peak in euthermic Tb (0.4 ± 0.3 °C). These results provide evidence for a circannual rhythm in Tb that is associated with increased sensitivity to A₁AR signaling and correlates with the onset of torpor.

  12. Dopamine Agonist-Induced Yawning in Rats: A Dopamine D3 Receptor-Mediated Behavior

    PubMed Central

    Collins, Gregory T.; Witkin, Jeffrey M.; Newman, Amy H.; Svensson, Kjell A.; Grundt, Peter; Cao, Jianjing; Woods, James H.

    2005-01-01

    A specific role for the dopamine D3 receptor in behavior has yet to be elucidated. We now report that dopamine D2/D3 agonists elicit dose-dependent yawning behavior in rats, resulting in an inverted U-shaped dose-response curve. A series of experiments was directed toward the hypothesis that the induction of yawning is a D3 receptor-mediated effect, whereas the inhibition of the yawning observed at higher doses is due to competing D2 receptor activity. We compared several dopaminergic agonists with a range of in vitro D3 selectivity, including PD-128,907 [(S)-(+)-(4aR, 10bR)-3,4,4a,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano-[4,3-b]-1,4-oxazin-9-ol HCl], PD-128,908 [(R)-(−)-(4aS,10bS)-3,4,4a,10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano-[4,3-b]-1,4-oxazin-9-ol HCl], quinelorane [(5aR-trans)-5,5a,6,7,8, 9,9a,10-octahydro-6-propylpyrido[2,3-g]quinazolin-2-amine dihydrochloride], pramipexole (N′ -propyl-4,5,6,7-tetrahydrobenzothiazole-2,6-diamine), 7-OH-DPAT [(±)-7-hydroxy-2-dipropylaminotetralin HBr], quinpirole [trans-(−)-(4aR)-4,4a,5,6,7,8, 8a,9-octahydro-5-propyl-1H-pyrazolo[3,4-g]quinoline HCl], bromocriptine [(+)-2-bromo-12′-hydroxy-2′-(1-methylethyl)-5′-(2-methylpropyl) ergotaman-3′,6′-18-trione methanesulfonate], and apomorphine [(R)-(−)-5,6,6a,7-tetrahydro-6-methyl-4H-dibenzo-[de,g]quinoline-10,11-diol HCl] with respect to their ability to induce yawning in rats. A series of D2/D3 antagonists differing in selectivity for D3 over D2 receptors were evaluated for their ability to alter the effects of the dopamine agonists. The antagonists L-741,626 (3-[4-(4-chlorophenyl)-4-hydroxypiperidin-l-yl]methyl-1 H-indole), haloperidol (4-[4-(4-chlorophenyl)-4-hydroxy-1-piperidinyl]-1-(4-fluorophenyl)-1-butanone HCl), nafadotride (N-[(1-butyl-2-pyrrolidinyl)methyl]-4-cyano-1-methoxy-2-naphthalenecarboxamide), U99194 (2,3-dihydro-5,6-dimethoxy-N,N-dipropyl-1H-inden-2-amine maleate), SB-277011A (trans-N-[4-[2-(6-cyano-1,2,3,4-tetrahydroisoquinolin-2-yl

  13. Treatment with oestrogen-receptor agonists or oxytocin in conjunction with exercise protects against myocardial infarction in ovariectomized rats.

    PubMed

    Bulut, Erman Caner; Abueid, Leyla; Ercan, Feriha; Süleymanoğlu, Selami; Ağırbaşlı, Mehmet; Yeğen, Berrak Ç

    2016-05-01

    What is the central question of this study? Could the activation of oxytocin or oestrogen receptors be protective against myocardial injury after ovariectomy? If so, would exercising have an additional ameliorating effect? What is the main finding and its importance? The results revealed that when accompanied by exercise, both oestrogen receptor agonists and oxytocin improved cardiac dysfunction, inhibited the generation of pro-inflammatory cytokines and reduced myocardial injury in ovariectomized female rats, suggesting a new approach for protecting postmenopausal women against ischaemia-induced myocardial injury. To investigate the putative protective effects of oxytocin or oestrogen receptor agonists against myocardial injury of ovariectomized sedentary or exercised rats, female Sprague-Dawley rats assigned to sham-operated control and ovariectomized (OVX) groups were kept sedentary or undertook swimming exercise for 4 weeks and were treated with saline, an oestrogen receptor (ER) β (DPN) or ERα agonist (PPT) or oxytocin. Ovariectomy increased weight gain and anxiety in sedentary rats, whereas exercise prevented weight gain. When accompanied by exercise, both ER agonists and oxytocin inhibited weight gain and anxiety; oxytocin, in the absence or presence of exercise, increased the left ventricular diastolic dimensions and ejection fraction, whereas ER agonists also increased left ventricular diameter when given to exercised rats. Upon the induction of myocardial ischaemia-reperfusion in the OVX rats, plasma creatine kinase-(muscle-brain) was depressed by PPT and oxytocin, whereas DPN, PPT and OT reduced plasminogen activator inhibitor-1 concentrations. The increased tumour necrosis factor-α concentration in OVX rats was also suppressed by exercise or DPN, PPT or oxytocin treatments, whereas the interleukin-6 concentration was diminished by all the treatments when given in conjunction with exercise. Disorganization of cardiac muscle fibres was reduced in all

  14. Neuronal A1 receptors mediate increase in extracellular kynurenic acid after local intrastriatal adenosine infusion.

    PubMed

    Wu, Hui-Qiu; Fuxe, Kjell; Schwarcz, Robert

    2004-08-01

    The naturally occurring purine nucleoside adenosine has pronounced anticonvulsant and neuroprotective properties and plays a neuromodulatory role in the CNS. Kynurenic acid (KYNA) is an astrocyte-derived, endogenous neuroinhibitory compound, which shares several of adenosine's properties. In a first attempt to examine possible interactions between these two biologically active molecules, adenosine was focally applied into the striatum of freely moving rats by reverse microdialysis, and changes in extracellular KYNA were monitored over time. A 2-h infusion of adenosine increased KYNA levels in a dose-dependent manner, with 10 mm of adenosine causing a twofold elevation within 1 h. This effect was reversible and was effectively blocked by coinfusion of the specific A1 adenosine receptor antagonist 8-cyclopentyltheophylline (100 microm). In contrast, coinfusion of adenosine with MSX-3 (100 microm), an A2A receptor antagonist, did not affect the adenosine-induced increase in KYNA levels. Local striatal perfusion with the A1 receptor agonist N6-cyclopentyladenosine (100 microm) mimicked the effect of adenosine, whereas perfusion with the A2A receptor agonist CGS-21680 (100 microm) was ineffective. Finally, we tested the effect of adenosine (10 mm) on extracellular KYNA in striata that had been injected with quinolinate (60 nmol/1 microL) 7 days earlier. In this neuron-depleted tissue, perfusion with adenosine failed to affect extracellular KYNA levels. These data demonstrate that adenosine is capable of raising extracellular KYNA in the rat striatum by interacting with postsynaptic neuronal A1 receptors. This mechanism may result in a synergism between the neurobiological effects of adenosine and KYNA.

  15. A unified model of the GABA(A) receptor comprising agonist and benzodiazepine binding sites.

    PubMed

    Bergmann, Rikke; Kongsbak, Kristine; Sørensen, Pernille Louise; Sander, Tommy; Balle, Thomas

    2013-01-01

    We present a full-length α(1)β(2)γ(2) GABA receptor model optimized for agonists and benzodiazepine (BZD) allosteric modulators. We propose binding hypotheses for the agonists GABA, muscimol and THIP and for the allosteric modulator diazepam (DZP). The receptor model is primarily based on the glutamate-gated chloride channel (GluCl) from C. elegans and includes additional structural information from the prokaryotic ligand-gated ion channel ELIC in a few regions. Available mutational data of the binding sites are well explained by the model and the proposed ligand binding poses. We suggest a GABA binding mode similar to the binding mode of glutamate in the GluCl X-ray structure. Key interactions are predicted with residues α(1)R66, β(2)T202, α(1)T129, β(2)E155, β(2)Y205 and the backbone of β(2)S156. Muscimol is predicted to bind similarly, however, with minor differences rationalized with quantum mechanical energy calculations. Muscimol key interactions are predicted to be α(1)R66, β(2)T202, α(1)T129, β(2)E155, β(2)Y205 and β(2)F200. Furthermore, we argue that a water molecule could mediate further interactions between muscimol and the backbone of β(2)S156 and β(2)Y157. DZP is predicted to bind with interactions comparable to those of the agonists in the orthosteric site. The carbonyl group of DZP is predicted to interact with two threonines α(1)T206 and γ(2)T142, similar to the acidic moiety of GABA. The chlorine atom of DZP is placed near the important α(1)H101 and the N-methyl group near α(1)Y159, α(1)T206, and α(1)Y209. We present a binding mode of DZP in which the pending phenyl moiety of DZP is buried in the binding pocket and thus shielded from solvent exposure. Our full length GABA(A) receptor is made available as Model S1.

  16. Activation of Cyclic AMP Synthesis by Full and Partial Beta-Adrenergic Receptor Agonists in Chicken Skeletal Muscle Cells

    NASA Technical Reports Server (NTRS)

    Young, R. B.; Bridge, K. Y.

    2003-01-01

    Several beta-adrenergic receptor (bAR) agonists are known to cause hypertrophy of skeletal muscle tissue. Accordingly, five bAR agonists encompassing a range in activity from strong to weak were evaluated for their ability to stimulate CAMP accumulation in embryonic chicken skeletal muscle cells in culture. Two strong agonists (epinephrine and isoproterenol), one moderate agonist (albuterol), and two weak agonists known to cause hypertrophy in animals (clenbuterol and cimaterol) were studied. Dose response curves were determined over six orders of magnitude in concentration for each agonist, and values were determined for their maximum stimulation of CAMP synthesis rate (Bmax) and the agonist concentration at which 50% stimulation of CAMP synthesis (EC50) occurred. Bmax values decreased in the following order: isoproterenol, epinephrine, albuterol, cimaterol, clenbuterol. Cimaterol and clenbuterol at their Bmax concentrations were approximately 15-fold weaker than isoproterenol in stimulating the rate of CAMP synthesis. When cimaterol and clenbuterol were added to culture media at concentrations known to cause significant muscle hypertrophy in animals, there was no detectable effect on stimulation of CAMP synthesis. Finally, these same levels of cimaterol and clenbuterol did not antagonize the stimulation of CAMP by either epinephrine or isoproterenol.

  17. Activation of Cyclic AMP Synthesis by Full and Partial Beta-Adrenergic Receptor Agonists in Chicken Skeletal Muscle Cells

    NASA Technical Reports Server (NTRS)

    Young, R. B.; Bridge, K. Y.; Cureri, Peter A. (Technical Monitor)

    2002-01-01

    Several beta-adrenergic receptor (bAR) agonists are known to cause hypertrophy of skeletal muscle tissue. Accordingly, five bAR agonists encompassing a range in activity from strong to weak were evaluated for their ability to stimulate cAMP accumulation in embryonic chicken skeletal muscle cells in culture. Two strong agonists (epinephrine and isoproterenol), one moderate agonist (albuterol), and two weak agonists known to cause hypertrophy in animals (clenbuterol and cimaterol) were studied. Dose response curves were determined over six orders of magnitude in concentration for each agonist, and values were determined for their maximum stimulation of cAMP synthesis rate (Bmax) and the agonist concentration at which 50% stimulation of cAMP synthesis (EC50) occurred. Bmax values decreased in the following order: isoproterenol, epinephrine, albuterol, cimaterol, clenbuterol. Cimaterol and clenbuterol at their Bmax concentrations were approximately 15-fold weaker than isoproterenol in stimulating the rate of cAMP synthesis. When cimaterol and clenbuterol were added to culture media at concentrations known to cause significant muscle hypertrophy in animals, there was no detectable effect on stimulation of cAMP synthesis. Finally, these same levels of cimaterol and clenbuterol did not antagonize the stimulation of cAMP by either epinephrine or isoproterenol.

  18. Red Clover Aryl Hydrocarbon Receptor (AhR) and Estrogen Receptor (ER) Agonists Enhance Genotoxic Estrogen Metabolism

    PubMed Central

    2017-01-01

    Many women consider botanical dietary supplements (BDSs) as safe alternatives to hormone therapy for menopausal symptoms. However, the effect of BDSs on breast cancer risk is largely unknown. In the estrogen chemical carcinogenesis pathway, P450 1B1 metabolizes estrogens to 4-hydroxylated catechols, which are oxidized to genotoxic quinones that initiate and promote breast cancer. In contrast, P450 1A1 catalyzed 2-hydroxylation represents a detoxification pathway. The current study evaluated the effects of red clover, a popular BDS used for women’s health, and its isoflavones, biochanin A (BA), formononetin (FN), genistein (GN), and daidzein (DZ), on estrogen metabolism. The methoxy estrogen metabolites (2-MeOE1, 4-MeOE1) were measured by LC-MS/MS, and CYP1A1 and CYP1B1 gene expression was analyzed by qPCR. Nonmalignant ER-negative breast epithelial cells (MCF-10A) and ER-positive breast cancer cells (MCF-7) were derived from normal breast epithelial tissue and ER+ breast cancer tissue. Red clover extract (RCE, 10 μg/mL) and isoflavones had no effect on estrogen metabolism in MCF-10A cells. However, in MCF-7 cells, RCE treatments downregulated CYP1A1 expression and enhanced genotoxic metabolism (4-MeOE1/CYP1B1 > 2-MeOE1/CYP1A1). Experiments with the isoflavones showed that the AhR agonists (BA, FN) preferentially induced CYP1B1 expression as well as 4-MeOE1. In contrast, the ER agonists (GN, DZ) downregulated CYP1A1 expression likely through an epigenetic mechanism. Finally, the ER antagonist ICI 182,780 potentiated isoflavone-induced XRE-luciferase reporter activity and reversed GN and DZ induced downregulation of CYP1A1 expression. Overall, these studies show that red clover and its isoflavones have differential effects on estrogen metabolism in “normal” vs breast cancer cells. In breast cancer cells, the AhR agonists stimulate genotoxic metabolism, and the ER agonists downregulate the detoxification pathway. These data may suggest that especially breast

  19. The case for cannabinoid CB1 receptors as a target for bronchodilator therapy for β-agonist resistant asthma.

    PubMed

    Ashton, John; Hancox, Robert J

    2017-06-15

    Although b2-receceptor agonists are powerful bronchodilators and are at the forefront of asthma symptom relief, patients who use them frequently develop partial resistance to them. This can be a particularly serious problem during severe attacks, where high dose b2-agonist treatment is the front line therapy. Alternative bronchodilators are urgently needed. In this article we review the evidence for the bronchodilator effects of the cannabinoid CB1 receptor tetrahydrocannabinol (THC) and suggest that the mechanism of action for these effects are sufficiently independent of the mechanisms of standard bronchodilators to warrant clinical investigation. Specifically, clinical trials testing the bronchodilator effects of THC in b2 agonist resistant asthmatic patients would show whether THC could fill the role of rescue bronchodilator in cases of b2 agonist resistance. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  20. The novel μ-opioid receptor agonist PZM21 depresses respiration and induces tolerance to antinociception.

    PubMed

    Hill, Rob; Disney, Alex; Conibear, Alex; Sutcliffe, Katy; Dewey, William; Husbands, Stephen; Bailey, Chris; Kelly, Eamonn; Henderson, Graeme

    2018-03-26

    PZM21 is a novel μ-opioid receptor (MOPr) ligand that has been reported to induce minimal arrestin recruitment and be devoid of the respiratory depressant effects characteristic of classical μ-opioid ligands such as morphine. We have re-examined the signalling profile of PZM21 and its ability to depress respiration. G protein (G i ) activation and arrestin-3 translocation were measured in vitro in MOPr expressing HEK 293 cells using BRET assays. Respiration (rate and tidal volume) was measured in awake, freely moving mice by whole body plethysmography and antinociception was measured in the hot plate test. PZM21 (10 -9 - 3 x 10 -5 M) produced concentration-dependent G i activation and arrestin-3 translocation. Comparison with responses evoked by morphine and D-Ala 2 , N-MePhe 4 , Gly-ol-enkephalin (DAMGO) revealed that PZM21 was a low efficacy agonist in both signalling assays. PZM21 (10 - 80 mg.kg -1 ) depressed respiration in a dose-dependent manner. The respiratory depression was due to a decrease in the rate of breathing not a decrease in tidal volume. On repeated daily administration of PZM21 (twice daily doses of 40 mg.kg -1 ) complete tolerance developed to the antinociceptive effect of PZM21 over 3 days but no tolerance developed to its respiratory depressant effect. These data demonstrate that PZM21 is a low efficacy MOPr agonist for both G protein and arrestin signalling. Contrary to a previous report, PZM21 depresses respiration in a manner similar to morphine, the classical opioid agonist. This article is protected by copyright. All rights reserved.

  1. Estrogen receptor β agonists affect growth and gene expression of human breast cancer cell lines.

    PubMed

    Lattrich, Claus; Stegerer, Anette; Häring, Julia; Schüler, Susanne; Ortmann, Olaf; Treeck, Oliver

    2013-02-01

    Expression of estrogen receptor β (ERβ) has been described to reduce growth of cancer cell lines derived from hormone-dependent tumors, like breast cancer. In this study we tested to what extent two ERβ agonists, androgen derivative 3β-Adiol and flavonoid Liquiritigenin, would affect growth and gene expression of different ERβ-positive human breast cancer cell lines. Under standard cell culture conditions, we observed 3β-Adiol to inhibit growth of MCF-7 cells in a dose-dependent manner, whereas growth of BT-474 and MCF-10A cells was suppressed by the maximum concentration (100 nM) only. When treated in serum-free medium, all cell lines except of MDA-MB-231 were responsive to 1 nM 3β-Adiol, and ZR75-1 cells exhibited a dose-dependent antiproliferative response. Providing putative mechanisms underlying the observed growth-inhibitory effect, expression of Ki-67 or cyclins A2 and B1 was downregulated after 3β-Adiol treatment in all responsive lines. In contrast, treatment with lower doses of Liquiritigenin did not affect growth. In MCF-7 cells, the highest dose of this flavonoid exerted proliferative effects accompanied by increased expression of cyclin B1, PR and PS2, indicating unspecific activation of ERα. In conclusion, the ERβ agonists tested exerted distinct concentration-dependent and cell line-specific effects on growth and gene expression. The observed inhibitory effects of 3β-Adiol on breast cancer cell growth encourage further studies on the potential of this and other ERβ agonists as targeted drugs for breast cancer therapy. Copyright © 2012 Elsevier Inc. All rights reserved.

  2. Involvement of β-arrestin-2 and clathrin in agonist-mediated internalization of the human cannabinoid CB2 receptor.

    PubMed

    Chen, Xiaopan; Zheng, Congxia; Qian, Jing; Sutton, Steven W; Wang, Zhen; Lv, Jianxin; Liu, Changlu; Zhou, Naiming

    2014-01-01

    The CB2 cannabinoid receptor is a promising therapeutic target for the treatment of inflammatory diseases, neuropathic pain, liver diseases, cancer and cardiovascular diseases. Obtaining detailed information on the internalization and trafficking of the human CB2 receptor in response to agonist will have a significant impact on drug discovery. Visualization and quantitative detection of EGFP-tagged CB2 receptor showed that, upon WIN55,212-2 stimulation, the CB2 receptor was rapidly internalized in a dose- and time-dependent manner from the cell membrane into the cytoplasm. Pretreatment with hypertonic sucrose, MDC clathrin inhibitor, or siRNA-mediated knock-down of clathrin heavy chain led to significant inhibition of agonist-induced CB2 internalization. Using the RNA interference method, we showed that knockdown of β-arrestin2 expression significantly impaired receptor internalisation. Further investigation demonstrated that the internalized CB2 receptors were co-localized with the early endosome probe and were recycled to the cell surface after the removal of agonist, but treatment with specific cell-permeable proteasome inhibitor MG132 a inhibited the recycling of internalized CB2 receptor, suggesting that the proteasome-mediated degradation pathway may be involved in CB2 internalization. Moreover, the single residue Ser(352) and residue cluster S(335)S(336)T(338)T(340) at the C-terminal tail are shown to be essential for receptor phosphorylation and β-arrestin2 association. These data provide new insights into the mechanisms regulating agonist-mediated internalization and trafficking of the human CB2 receptor.

  3. Novel Small Molecule Glucagon-Like Peptide-1 Receptor Agonist Stimulates Insulin Secretion in Rodents and From Human Islets

    PubMed Central

    Sloop, Kyle W.; Willard, Francis S.; Brenner, Martin B.; Ficorilli, James; Valasek, Kathleen; Showalter, Aaron D.; Farb, Thomas B.; Cao, Julia X.C.; Cox, Amy L.; Michael, M. Dodson; Gutierrez Sanfeliciano, Sonia Maria; Tebbe, Mark J.; Coghlan, Michael J.

    2010-01-01

    OBJECTIVE The clinical effectiveness of parenterally-administered glucagon-like peptide-1 (GLP-1) mimetics to improve glucose control in patients suffering from type 2 diabetes strongly supports discovery pursuits aimed at identifying and developing orally active, small molecule GLP-1 receptor agonists. The purpose of these studies was to identify and characterize novel nonpeptide agonists of the GLP-1 receptor. RESEARCH DESIGN AND METHODS Screening using cells expressing the GLP-1 receptor and insulin secretion assays with rodent and human islets were used to identify novel molecules. The intravenous glucose tolerance test (IVGTT) and hyperglycemic clamp characterized the insulinotropic effects of compounds in vivo. RESULTS Novel low molecular weight pyrimidine-based compounds that activate the GLP-1 receptor and stimulate glucose-dependent insulin secretion are described. These molecules induce GLP-1 receptor-mediated cAMP signaling in HEK293 cells expressing the GLP-1 receptor and increase insulin secretion from rodent islets in a dose-dependent manner. The compounds activate GLP-1 receptor signaling, both alone or in an additive fashion when combined with the endogenous GLP-1 peptide; however, these agonists do not compete with radiolabeled GLP-1 in receptor-binding assays. In vivo studies using the IVGTT and the hyperglycemic clamp in Sprague Dawley rats demonstrate increased insulin secretion in compound-treated animals. Further, perifusion assays with human islets isolated from a donor with type 2 diabetes show near-normalization of insulin secretion upon compound treatment. CONCLUSIONS These studies characterize the insulinotropic effects of an early-stage, small molecule GLP-1 receptor agonist and provide compelling evidence to support pharmaceutical optimization. PMID:20823098

  4. (+)Lysergic acid diethylamide, but not its nonhallucinogenic congeners, is a potent serotonin 5HT1C receptor agonist

    SciTech Connect

    Burris, K.D.; Breeding, M.; Sanders-Bush, E.

    1991-09-01

    Activation of central serotonin 5HT2 receptors is believed to be the primary mechanism whereby lysergic acid diethylamide (LSD) and other hallucinogens induce psychoactive effects. This hypothesis is based on extensive radioligand binding and electrophysiological and behavioral studies in laboratory animals. However, the pharmacological profiles of 5HT2 and 5HT1C receptors are similar, making it difficult to distinguish between effects due to activation of one or the other receptor. For this reason, it was of interest to investigate the interaction of LSD with 5HT1C receptors. Agonist-stimulated phosphoinositide hydrolysis in rat choroid plexus was used as a direct measure of 5HT1C receptor activation.more » (+)LSD potently stimulated phosphoinositide hydrolysis in intact choroid plexus and in cultures of choroid plexus epithelial cells, with EC50 values of 9 and 26 nM, respectively. The effect of (+)LSD in both systems was blocked by 5HT receptor antagonists with an order of activity consistent with interaction at 5HT1C receptors. Neither (+)-2-bromo-LSD nor lisuride, two nonhallucinogenic congeners of LSD, were able to stimulate 5HT1C receptors in cultured cells or intact choroid plexus. In contrast, lisuride, like (+)LSD, is a partial agonist at 5HT2 receptors in cerebral cortex slices and in NIH 3T3 cells transfected with 5HT2 receptor cDNA. The present finding that (+)LSD, but not its nonhallucinogenic congeners, is a 5HT1C receptor agonist suggests a possible role for these receptors in mediating the psychoactive effects of LSD.« less

  5. Procaine rapidly inactivates acetylcholine receptors from Torpedo and competes with agonist for inhibition sites

    SciTech Connect

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

    1989-02-21

    The relationship between the high-affinity procaine channel inhibition site and the agonist self-inhibition site on acetylcholine receptors (AChRs) from Torpedo electroplaque was investigated by using rapid {sup 86}Rb{sup +} quenched-flux assays at 4 {degree}C in native AChR-rich vesicles on which 50-60% of ACh activation sites were blocked with {alpha}-bungarotoxin ({alpha}-BTX). In the presence of channel-activating acetylcholine (ACh) concentrations alone, AChR undergoes one phase of inactivation in under a second. Addition of procaine produces two-phase inactivation similar to that seen with self-inhibiting ACh concentrations rapid inactivation complete in 30-75 ms is followed by fast desensitization at the same k{sub d} observedmore » without procaine. The dependence of k{sub r} on (procaine) is consistent with a bimolecular association between procaine and its AChR site. Inhibition of AChR function by mixtures of procaine plus self-inhibiting concentrations of ACh or suberyldicholine was studied by reducing the level of {alpha}-BTX block in vesicles. The data support a mechanism where procaine binds preferentially to the open-channel AChR state, since no procaine-induced inactivation is observed without agonist and k{sub r}'s dependence on (ACh) in channel-activating range closely parallels that of {sup 86}Rb{sup +} flux response to ACh.« less

  6. Proton pump inhibitor Lansoprazole is a nuclear Liver X Receptor agonist

    PubMed Central

    Cronican, Andrea A.; Fitz, Nicholas F.; Pham, Tam; Fogg, Allison; Kifer, Brionna; Koldamova, Radosveta; Lefterov, Iliya

    2010-01-01

    The liver X receptors (LXRα and LXRβ) are transcription factors that control the expression of genes primarily involved in cholesterol metabolism. In brain, in addition to normal neuronal function, cholesterol metabolism is important for APP proteolytic cleavage, secretase activities, Aβ aggregation and clearance. Particularly significant in this respect is the LXR mediated transcriptional control of APOE, which is the only proven risk factor for late onset Alzheimer’s disease. Using a transactivation reporter assay for screening pharmacologically active compounds and off patent drugs we identified the Proton Pump Inhibitor Lansoprazole as an LXR agonist. In secondary screens and counter-screening assays, it was confirmed that Lansoprazole directly activates LXR, increases the expression of LXR target genes in brain-derived human cell lines, and increases Abca1 and Apo-E protein levels in primary astrocytes derived from wild type but not LXRα/β double knockout mice. Other PPIs activate LXR as well, but the efficiency of activation depends on their structural similarities to Lansoprazole. The identification of widely used, drug with LXR agonist-like activity opens the possibility for systematic preclinical testing in at least two diseases – Alzheimer’s disease and atherosclerosis. PMID:20060385

  7. Affinity and kinetics study of anthranilic acids as HCA2 receptor agonists.

    PubMed

    van Veldhoven, Jacobus P D; Liu, Rongfang; Thee, Stephanie A; Wouters, Yessica; Verhoork, Sanne J M; Mooiman, Christiaan; Louvel, Julien; IJzerman, Adriaan P

    2015-07-15

    Structure-affinity relationship (SAR) and structure-kinetics relationship (SKR) studies were combined to investigate a series of biphenyl anthranilic acid agonists for the HCA2 receptor. In total, 27 compounds were synthesized and twelve of them showed higher affinity than nicotinic acid. Two compounds, 6g (IC50=75nM) and 6z (IC50=108nM) showed a longer residence time profile compared to nicotinic acid, exemplified by their kinetic rate index (KRI) values of 1.31 and 1.23, respectively. The SAR study resulted in the novel 2-F, 4-OH derivative (6x) with an IC50 value of 23nM as the highest affinity HCA2 agonist of the biphenyl series, although it showed a similar residence time as nicotinic acid. The SAR and SKR data suggest that an early compound selection based on binding kinetics is a promising addition to the lead optimization process. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Optimization of histone deacetylase inhibitor activity in non-secosteroidal vitamin D-receptor agonist hybrids.

    PubMed

    Kaldre, Dainis; Wang, Tian-Tian; Fischer, Joshua; White, John H; Gleason, James L

    2015-08-01

    The combination of (1α,25)-dihydroxyvitamin D3 (1,25D) and histone deacetylase inhibitor (HDACi) trichostatin A is highly antiproliferative in numerous cancer cell lines. We have previously prepared novel non-secosteroidal hybrid molecules which simultaneously act as both vitamin D receptor (VDR) agonists and HDACi. These molecules function as cytostatic and cytotoxic agents in 1,25D-resistant SCC4 squamous carcinoma cells. Here we have extended the scope of the hybrids by making several modifications to the diarylpentane core and to the aliphatic spacer unit to develop molecules with increased potency towards HDACs while maintaining VDR agonist activity. Notably, hybrid DK-366 (33a), a direct analog of first-generation hybrids but lacking a methyl group on one aryl ring possesses low micromolar potency for HDAC3 and HDAC6 and is a highly effective antiproliferative agent in SCC4 cells. Chain extended hybrids such as DK-367 (33c) possess even greater HDAC potency and are also highly antiproliferative. These results show that we can optimize HDACi potency in hybrid molecules without sacrificing VDR agonism. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Design, synthesis and biological activity of flavonoid derivatives as selective agonists for neuromedin U 2 receptor.

    PubMed

    Ma, Ming-Liang; Li, Ming; Gou, Jiao-Jiao; Ruan, Tian-Yu; Jin, Hai-Shan; Zhang, Ling-Hong; Wu, Liang-Chun; Li, Xiao-Yan; Hu, Ying-He; Wen, Ke; Zhao, Zheng

    2014-11-01

    Central neuromedin U 2 receptor (NMU2R) plays important roles in the regulation of food intake and body weight. Identification of NMU2R agonists may lead to the development of pharmaceutical agents to treat obesity. Based on the structure of rutin, a typical flavonoid and one of the NMU2R agonists we previously identified from an in-house made natural product library, 30 flavonoid derivatives have been synthesized and screened on a cell-based reporter gene assay. A number of compounds were found to be selective and highly potent to NMU2R. For example, the EC50 value of compound NRA 4 is very close to that of NMU, the endogenous peptide ligand of NMU2R. Structure-activity relationship analysis revealed that a 3-hydroxyl group in ring C and a 2'-fluoride group in ring B were essential for this class of compounds to be active against NMU2R. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Sofinicline: a novel nicotinic acetylcholine receptor agonist in the treatment of attention-deficit/hyperactivity disorder.

    PubMed

    Fleisher, Carl; McGough, James

    2014-08-01

    Psychostimulants are first-line treatments for attention-deficit/hyperactivity disorder (ADHD), but their tolerability profiles and individual response variability fuel a continuing search for alternative medications. The observation that nicotinic agents improve cognition has led pharmaceutical companies to explore the potential utility of agonists of the nicotinic acetylcholine receptor (nAChR) system for ADHD treatments. This article reviews Phase I and Phase II trials of sofinicline (ABT-894), an agonist of the nAChR α4β2 subtype, as a potential non-stimulant treatment for ADHD. This includes one Phase II trial that compared sofinicline with atomoxetine, a noradrenergic reuptake inhibitor currently approved as a non-stimulant ADHD treatment. This article also reviews the chemistry, pharmacodynamics and pharmacokinetics of sofinicline. Sofinicline appears to be well tolerated and showing efficacy similar to that of atomoxetine. Although the number of patients studied to date is small, further evaluation of sofinicline in Phase II, and possibly Phase III, trials appears to be warranted. Additional studies are needed to explore the efficacy and tolerability of sofinicline with respect to: i) optimal dosing; ii) its use in combination with other medications for ADHD; and iii) its use in children and adolescents, who more commonly experience adverse effects when taking psychostimulant medications.

  11. GLP-1 receptor agonist ameliorates obesity-induced chronic kidney injury via restoring renal metabolism homeostasis.

    PubMed

    Wang, Chengshi; Li, Ling; Liu, Shuyun; Liao, Guangneng; Li, Lan; Chen, Younan; Cheng, Jingqiu; Lu, Yanrong; Liu, Jingping

    2018-01-01

    Increasing evidence indicates that obesity is highly associated with chronic kidney disease (CKD). GLP-1 receptor (GLP-1R) agonist has shown benefits on kidney diseases, but its direct role on kidney metabolism in obesity is still not clear. This study aims to investigate the protection and metabolic modulation role of liraglutide (Lira) on kidney of obesity. Rats were induced obese by high-fat diet (HFD), and renal function and metabolism changes were evaluated by metabolomic, biological and histological methods. HFD rats exhibited systemic metabolic disorders such as obesity, hyperlipidemia and impaired glucose tolerance, as well as renal histological and function damages, while Lira significantly ameliorated these adverse effects in HFD rats. Metabolomic data showed that Lira directly reduced renal lipids including fatty acid residues, cholesterol, phospholipids and triglycerides, and improved mitochondria metabolites such as succinate, citrate, taurine, fumarate and nicotinamide adenine dinucleotide (NAD+) in the kidney of HFD rats. Furthermore, we revealed that Lira inhibited renal lipid accumulation by coordinating lipogenic and lipolytic signals, and partly rescued renal mitochondria function via Sirt1/AMPK/PGC1α pathways in HFD rats. This study suggested that Lira alleviated HFD-induced kidney injury at least partly via directly restoring renal metabolism, thus GLP-1R agonist is a promising therapy for obesity-associated CKD.

  12. Nonpeptide orexin type-2 receptor agonist ameliorates narcolepsy-cataplexy symptoms in mouse models.

    PubMed

    Irukayama-Tomobe, Yoko; Ogawa, Yasuhiro; Tominaga, Hiromu; Ishikawa, Yukiko; Hosokawa, Naoto; Ambai, Shinobu; Kawabe, Yuki; Uchida, Shuntaro; Nakajima, Ryo; Saitoh, Tsuyoshi; Kanda, Takeshi; Vogt, Kaspar; Sakurai, Takeshi; Nagase, Hiroshi; Yanagisawa, Masashi

    2017-05-30

    Narcolepsy-cataplexy is a debilitating disorder of sleep/wakefulness caused by a loss of orexin-producing neurons in the lateroposterior hypothalamus. Genetic or pharmacologic orexin replacement ameliorates symptoms in mouse models of narcolepsy-cataplexy. We have recently discovered a potent, nonpeptide OX2R-selective agonist, YNT-185. This study validates the pharmacological activity of this compound in OX2R-transfected cells and in OX2R-expressing neurons in brain slice preparations. Intraperitoneal, and intracerebroventricular, administration of YNT-185 suppressed cataplexy-like episodes in orexin knockout and orexin neuron-ablated mice, but not in orexin receptor-deficient mice. Peripherally administered YNT-185 also promotes wakefulness without affecting body temperature in wild-type mice. Further, there was no immediate rebound sleep after YNT-185 administration in active phase in wild-type and orexin-deficient mice. No desensitization was observed after repeated administration of YNT-185 with respect to the suppression of cataplexy-like episodes. These results provide a proof-of-concept for a mechanistic therapy of narcolepsy-cataplexy by OX2R agonists.

  13. Discovery of Selective Cannabinoid CB2Receptor Agonists by High-Throughput Screening.

    PubMed

    Ogawa, Lisa M; Burford, Neil T; Liao, Yu-Hsien; Scott, Caitlin E; Hine, Ashley M; Dowling, Craig; Chin, Jefferson; Power, Mike; Hunnicutt, Edward J; Emerick, Victoria L; Banks, Martyn; Zhang, Litao; Gerritz, Samuel W; Alt, Andrew; Kendall, Debra A

    2018-04-01

    The endocannabinoid system (ECS) plays a diverse role in human physiology ranging from the regulation of mood and appetite to immune modulation and the response to pain. Drug development that targets the cannabinoid receptors (CB 1 and CB 2 ) has been explored; however, success in the clinic has been limited by the psychoactive side effects associated with modulation of the neuronally expressed CB 1 that are enriched in the CNS. CB 2 , however, are expressed in peripheral tissues, primarily in immune cells, and thus development of CB 2 -selective drugs holds the potential to modulate pain among other indications without eliciting anxiety and other undesirable side effects associated with CB 1 activation. As part of a collaborative effort among industry and academic laboratories, we performed a high-throughput screen designed to discover selective agonists or positive allosteric modulators (PAMs) of CB 2 . Although no CB 2 PAMs were identified, 167 CB 2 agonists were discovered here, and further characterization of four select compounds revealed two with high selectivity for CB 2 versus CB 1 . These results broaden drug discovery efforts aimed at the ECS and may lead to the development of novel therapies for immune modulation and pain management with improved side effect profiles.

  14. Effects of thrombopoietin receptor agonists on procoagulant state in patients with immune thrombocytopenia.

    PubMed

    Alvarez Román, M T; Fernández Bello, I; Arias-Salgado, E G; Rivas Pollmar, M I; Jiménez Yuste, V; Martín Salces, M; Butta, N V

    2014-07-03

    Thrombopoietin receptor agonists (TPO-RA) have recently been introduced for the treatment of immune thrombocytopenia (ITP), an anti-platelet-antibodies autoimmune disease. The observation of a low frequency of bleeding episodes despite their thrombocytopenia suggests the existence of a compensatory mechanism. This study aimed to evaluate the effect of TPO-RA treatment on platelet function and on the procoagulant state in ITP patients before (ITP-bR) and after responding (ITP-aR) to treatment. Plasma- and microparticle (MP)-associated procoagulant capacity from ITP patients was similar before and after responding to the TPO-RA regimen but higher than the healthy control values. High MP-associated procoagulant activity did not seem to be due to increased platelet activation, since platelet stimulation by agonists was reduced in ITP-bR and ITP-aR patients. It could be related to increased platelet apoptosis, evaluated in terms of surface phosphatidylserine (PS), observed in both ITP groups. In summary, TPO-RA treatment increased platelet count but did not ameliorate their function and did not change plasma- and MP-associated procoagulant state of ITP patient responders to this therapy.

  15. Techniques for studying inverse agonist activity of antidepressants at recombinant nonedited 5-HT(₂C-INI) receptor and native neuronal 5-HT(₂C) receptors.

    PubMed

    Seimandi, Mathieu; Bockaert, Joël; Marin, Philippe

    2010-01-01

    Serotonin (5-HT)(₂C) receptors play a major role in the regulation of mood, and alteration of their functional status has been implicated in the etiology of affect disorders. Correspondingly, they represent an important target for various antidepressant categories, including tricyclics, tetracyclics, mCPP derivatives, specific serotonin reuptake inhibitors, and agomelatine, which exhibit medium to high affinities for 5-HT(₂C) receptors and behave as antagonists. Antidepressant effects of 5-HT(₂C) antagonists have been attributed to a disinhibition of mesocorticolimbic dopaminergic pathways, which exert a beneficial influence upon mood and cognitive functions altered in depression. However, recent experimental evidence revealed a prominent role of constitutive activity in the tonic inhibitory control of dopaminergic transmission exerted by 5-HT(₂C) receptors in specific brain areas such as the nucleus accumbens. Accordingly, alteration in the constitutive activity of 5-HT(₂C) receptors might participate in the induction of depressed states and drugs with inverse agonist properties should themselves be effective antidepressant agents and, possibly, more active than neutral antagonists. This highlights the relevance of systematically evaluating inverse agonist versus neutral antagonist activities of antidepressants acting at 5-HT(₂C) receptors. Here, we provide a detailed description of a palette of cellular assays exploiting constitutive activity of 5-HT(₂C) receptor expressed in heterologous cells (such as HEK-293 cells) toward Gq-operated signaling or their constitutive association with β-arrestins to evaluate inverse agonist activity of antidepressants. We also describe an approach allowing discrimination between inverse agonist and neutral antagonist activities of antidepressants at native constitutively active receptors expressed in cultured cortical neurons, based on previous findings indicating that prolonged treatments with inverse agonists

  16. ACTIVATION AND INTERNALIZATION OF THE μ-OPIOID RECEPTOR BY THE NEWLY DISCOVERED ENDOGENOUS AGONISTS, ENDOMORPHIN-1 AND ENDOMORPHIN-2

    PubMed Central

    McCONALOGUE, K.; GRADY, E. F.; MINNIS, J.; BALESTRA, B.; TONINI, M.; BRECHA, N. C.; BUNNETT, N. W.; STERNINI, C.

    2015-01-01

    The multiple effects of opiate alkaloids, important therapeutic drugs used for pain control, are mediated by the neuronal μ-opioid receptor. Among the side effects of these drugs is a profound impairment of gastrointestinal transit. Endomorphins are opioid peptides recently isolated from the nervous system, which have high affinity and selectivity for μ-opioid receptors. Since the μ-opioid receptor undergoes ligand-induced receptor endocytosis in an agonist-dependent manner, we compared the ability of endomorphin-1, endomorphin-2 and the μ-opioid receptor peptide agonist, [D-Ala2,MePhe4,Gly-ol5]-enkephalin (DAMGO), to induce receptor endocytosis in cells transfected with epitope-tagged μ-opioid receptor complementary DNA, and in myenteric neurons of the guinea-pig ileum, which naturally express this receptor. Immunohistochemistry with antibodies to the FLAG epitope or to the native receptor showed that the μ-opioid receptor was mainly located at the plasma membrane of unstimulated cells. Endomorphins and DAMGO induced μ-opioid receptor endocytosis into early endosomes, a process that was inhibited by naloxone. Quantification of surface receptors by flow cytometry indicated that endomorphins’ and DAMGO stimulated endocytosis with similar time-course and potency. They inhibited with similar potency electrically induced cholinergic contractions in the longitudinal muscle–myenteric plexus preparation through an action antagonized by naloxone. The apparent affinity estimate of naloxone (pA2 ~ 8.4) is consistent with antagonism at the μ-opioid receptor in myenteric neurons. These results indicate that endomorphins directly activate the μ-opioid receptor in neurons, thus supporting the hypothesis that they are ligands mediating opioid actions in the nervous system. Endomorphin-induced μ-opioid receptor activation can be visualized by receptor endocytosis. PMID:10218804

  17. Discriminative Stimulus Effects of the GABAB Receptor-Positive Modulator rac-BHFF: Comparison with GABAB Receptor Agonists and Drugs of Abuse

    PubMed Central

    Cheng, Kejun; Rice, Kenner C.

    2013-01-01

    GABAB receptor-positive modulators are thought to have advantages as potential medications for anxiety, depression, and drug addiction. They may have fewer side effects than GABAB receptor agonists, because selective enhancement of activated receptors could have effects different from nonselective activation of all receptors. To examine this, pigeons were trained to discriminate the GABAB receptor-positive modulator (R,S)-5,7-di-tert-butyl-3-hydroxy-3-trifluoromethyl-3H-benzofuran-2-one (rac-BHFF) from its vehicle. The discriminative stimulus effects of rac-BHFF were not mimicked by the GABAB receptor agonists baclofen and γ-hydroxybutyrate (GHB), not by diazepam, and not by alcohol, cocaine, and nicotine, whose self-administration has been reported to be attenuated by GABAB receptor-positive modulators. The discriminative stimulus effects of rac-BHFF were not antagonized by the GABAB receptor antagonist 3-aminopropyl (diethoxymethyl)phosphinic acid (CGP35348) but were attenuated by the less efficacious GABAB receptor-positive modulator 2,6-di-tert-butyl-4-(3-hydroxy-2,2-dimethylpropyl)phenol (CGP7930), suggesting the possibility that rac-BHFF produces its discriminative stimulus effects by directly activating GABAB2 subunits of GABAB receptors. At a dose 10-fold lower than the training dose, rac-BHFF enhanced the discriminative stimulus effects of baclofen, but not of GHB. This study provides evidence that the effects of GABAB receptor-positive modulators are not identical to those of GABAB receptor agonists. In addition, the results suggest that positive modulation of GABAB receptors does not produce discriminative stimulus effects similar to those of benzodiazepines, alcohol, cocaine, and nicotine. Finally, the finding that rac-BHFF enhanced effects of baclofen but not of GHB is consistent with converging evidence that the populations of GABAB receptors mediating the effects of baclofen and GHB are not identical. PMID:23275067

  18. In Vivo Protection against Strychnine Toxicity in Mice by the Glycine Receptor Agonist Ivermectin

    PubMed Central

    Radwan, Rasha

    2014-01-01

    The inhibitory glycine receptor, a ligand-gated ion channel that mediates fast synaptic inhibition in mammalian spinal cord and brainstem, is potently and selectively inhibited by the alkaloid strychnine. The anthelminthic and anticonvulsant ivermectin is a strychnine-independent agonist of spinal glycine receptors. Here we show that ivermectin is an effective antidote of strychnine toxicity in vivo and determine time course and extent of ivermectin protection. Mice received doses of 1 mg/kg and 5 mg/kg ivermectin orally or intraperitoneally, followed by an intraperitoneal strychnine challenge (2 mg/kg). Ivermectin, through both routes of application, protected mice against strychnine toxicity. Maximum protection was observed 14 hours after ivermectin administration. Combining intraperitoneal and oral dosage of ivermectin further improved protection, resulting in survival rates of up to 80% of animals and a significant delay of strychnine effects in up to 100% of tested animals. Strychnine action developed within minutes, much faster than ivermectin, which acted on a time scale of hours. The data agree with a two-compartment distribution of ivermectin, with fat deposits acting as storage compartment. The data demonstrate that toxic effects of strychnine in mice can be prevented if a basal level of glycinergic signalling is maintained through receptor activation by ivermectin. PMID:25317421

  19. In vivo protection against strychnine toxicity in mice by the glycine receptor agonist ivermectin.

    PubMed

    Maher, Ahmed; Radwan, Rasha; Breitinger, Hans-Georg

    2014-01-01

    The inhibitory glycine receptor, a ligand-gated ion channel that mediates fast synaptic inhibition in mammalian spinal cord and brainstem, is potently and selectively inhibited by the alkaloid strychnine. The anthelminthic and anticonvulsant ivermectin is a strychnine-independent agonist of spinal glycine receptors. Here we show that ivermectin is an effective antidote of strychnine toxicity in vivo and determine time course and extent of ivermectin protection. Mice received doses of 1 mg/kg and 5 mg/kg ivermectin orally or intraperitoneally, followed by an intraperitoneal strychnine challenge (2 mg/kg). Ivermectin, through both routes of application, protected mice against strychnine toxicity. Maximum protection was observed 14 hours after ivermectin administration. Combining intraperitoneal and oral dosage of ivermectin further improved protection, resulting in survival rates of up to 80% of animals and a significant delay of strychnine effects in up to 100% of tested animals. Strychnine action developed within minutes, much faster than ivermectin, which acted on a time scale of hours. The data agree with a two-compartment distribution of ivermectin, with fat deposits acting as storage compartment. The data demonstrate that toxic effects of strychnine in mice can be prevented if a basal level of glycinergic signalling is maintained through receptor activation by ivermectin.

  20. Specific mutations in the estrogen receptor change the properties of antiestrogens to full agonists.

    PubMed Central

    Mahfoudi, A; Roulet, E; Dauvois, S; Parker, M G; Wahli, W

    1995-01-01

    The estrogen receptor (ER) stimulates transcription of target genes by means of its two transcriptional activation domains, AF-1 in the N-terminal part of the receptor and AF-2 in its ligand-binding domain. AF-2 activity is dependent upon a putative amphipathic alpha-helix between residues 538 and 552 in the mouse ER. Point mutagenesis of conserved hydrophobic residues within this region reduces estrogen-dependent transcriptional activation without affecting hormone and DNA binding significantly. Here we show that these mutations dramatically alter the pharmacology of estrogen antagonists. Both tamoxifen and ICI 164,384 behave as strong agonists in HeLa cells expressing the ER mutants. In contrast to the wild-type ER, the mutant receptors maintain nuclear localization and DNA-binding activity after ICI 164,384 treatment. Structural alterations in AF-2 caused by gene mutations such as those described herein or by estrogen-independent signaling pathways may account for the insensitivity of some breast cancers to tamoxifen treatment. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:7753783

  1. Modeling and simulation studies of human β3 adrenergic receptor and its interactions with agonists.

    PubMed

    Sahi, Shakti; Tewatia, Parul; Malik, Balwant K

    2012-12-01

    β3 adrenergic receptor (β3AR) is known to mediate various pharmacological and physiological effects such as thermogenesis in brown adipocytes, lipolysis in white adipocytes, glucose homeostasis and intestinal smooth muscle relaxation. Several efforts have been made in this field to understand their function and regulation in different human tissues and they have emerged as potential attractive targets in drug discovery for the treatment of diabetes, depression, obesity etc. Although the crystal structures of Bovine Rhodopsin and β2 adrenergic receptor have been resolved, to date there is no three dimensional structural information on β3AR. Our aim in this study was to model 3D structure of β3AR by various molecular modeling and simulation techniques. In this paper, we describe a refined predicted model of β3AR using different algorithms for structure prediction. The structural refinement and minimization of the generated 3D model of β3AR were done by Schrodinger suite 9.1. Docking studies of β3AR model with the known agonists enabled us to identify specific residues, viz, Asp 117, Ser 208, Ser 209, Ser 212, Arg 315, Asn 332, within the β3AR binding pocket, which might play an important role in ligand binding. Receptor ligand interaction studies clearly indicated that these five residues showed strong hydrogen bonding interactions with the ligands. The results have been correlated with the experimental data available. The predicted ligand binding interactions and the simulation studies validate the methods used to predict the 3D-structure.

  2. Agonist Ligands Mediate the Transcriptional Response of Nuclear Receptor Heterodimers through Distinct Stoichiometric Assemblies with Coactivators*

    PubMed Central

    Pavlin, Mark Remec; Brunzelle, Joseph S.; Fernandez, Elias J.

    2014-01-01

    The constitutive androstane (CAR) and retinoid X receptors (RXR) are ligand-mediated transcription factors of the nuclear receptor protein superfamily. Functional CAR:RXR heterodimers recruit coactivator proteins, such as the steroid receptor coactivator-1 (SRC1). Here, we show that agonist ligands can potentiate transactivation through both coactivator binding sites on CAR:RXR, which distinctly bind two SRC1 molecules. We also observe that SRC1 transitions from a structurally plastic to a compact form upon binding CAR:RXR. Using small angle x-ray scattering (SAXS) we show that the CAR(tcp):RXR(9c)·SRC1 complex can encompass two SRC1 molecules compared with the CAR(tcp):RXR·SRC1, which binds only a single SRC1. Moreover, sedimentation coefficients and molecular weights determined by analytical ultracentrifugation confirm the SAXS model. Cell-based transcription assays show that disrupting the SRC1 binding site on RXR alters the transactivation by CAR:RXR. These data suggest a broader role for RXR within heterodimers, whereas offering multiple strategies for the assembly of the transcription complex. PMID:25053412

  3. Release and interconversion of P2 receptor agonists by human osteoblast-like cells.

    PubMed

    Buckley, K A; Golding, S L; Rice, J M; Dillon, J P; Gallagher, J A

    2003-08-01

    Nucleotides, acting as agonists at P2 receptors, are important extracellular signaling molecules in many tissues. In bone they affect both bone-forming osteoblast and bone-resorbing osteoclast cell activity. The presence of nucleotides in the extracellular microenvironment is largely determined by their release from cells and metabolism by ecto-enzymes, both of which have scarcely been studied in bone. We have investigated adenosine 5'-triphosphate (ATP) release from SaOS-2 osteoblastic cells and the activities of cell surface ecto-enzymes on ATP metabolism. ATP, but not LDH, was detected in SaOS-2 cell conditioned medium, suggesting these cells were actively releasing ATP. Introduction of ADP resulted in increased ATP concentrations in the medium, which was found not to be receptor mediated. Nucleotide inhibition and substrate specificity studies revealed an ecto-nucleoside diphosphokinase (ecto-NDPK) was responsible for the ADP-->ATP conversion; PCR and immunocytochemistry confirmed its presence. Analysis of ATP metabolism over time demonstrated overall ATP degradation was increased by inhibiting ecto-NDPK activity; confirming that the combined action of multiple osteoblast-expressed ecto-enzymes affected extracellular nucleotide concentration. The data establish the coexistence of ATP-consuming, and for the first time, ATP-generating activities on the osteoblast cell surface, the discovery of which has significant implications for studies involving P2 receptor subtypes in bone.

  4. Discovery of agonists of cannabinoid receptor 1 with restricted central nervous system penetration aimed for treatment of gastroesophageal reflux disease.

    PubMed

    Plowright, Alleyn T; Nilsson, Karolina; Antonsson, Madeleine; Amin, Kosrat; Broddefalk, Johan; Jensen, Jörgen; Lehmann, Anders; Jin, Shujuan; St-Onge, Stephane; Tomaszewski, Mirosław J; Tremblay, Maxime; Walpole, Christopher; Wei, Zhongyong; Yang, Hua; Ulander, Johan

    2013-01-10

    Agonists of the cannabinoid receptor 1 (CB1) have been suggested as possible treatments for a range of medical disorders including gastroesophageal reflux disease (GERD). While centrally acting cannabinoid agonists are known to produce psychotropic effects, it has been suggested that the CB1 receptors in the periphery could play a significant role in reducing reflux. A moderately potent and highly lipophilic series of 2-aminobenzamides was identified through focused screening of GPCR libraries. Development of this series focused on improving potency and efficacy at the CB1 receptor, reducing lipophilicity and limiting the central nervous system (CNS) exposure while maintaining good oral absorption. Improvement of the series led to compounds having excellent potency at the CB1 receptor and high levels of agonism, good physical and pharmacokinetic properties, and low penetration into the CNS. A range of compounds demonstrated a dose-dependent inhibition of transient lower esophageal sphincter relaxations in a dog model.

  5. S-Nitrosoglutathione and glutathione act as NMDA receptor agonists in cultured hippocampal neurons.

    PubMed

    Chin, Ting-yu; Chueh, Sheau-huei; Tao, Pao-luh

    2006-07-01

    To characterize the effect of combined pre- and postnatal morphine exposure on N-methyl-D-aspartate receptor (NMDA) receptor signaling in hippocampal neurons of the offspring of morphine-addicted female rats. Cultured hippocampal neurons and synaptosomes were prepared from neonatal and 2-week-old offspring, respectively, of control or morphine-addicted female rats. The increase in the cytosolic Ca2+ concentration ([Ca2+]i) of cultured cells was measured using Fura-2, and glutamate release from synaptosomes was measured enzymatically. Both glutamate and NMDA caused a dose-dependent increase in the [Ca2+]i. The nitric oxide (NO) donor, S-nitrosoglutathione (GSNO), but not 3-morpholinosydnonimine, sodium nitroprusside, and S-nitroso-N-acetylpenicillamine, also induced a [Ca2+]i increase. GSNO and glutathione caused a dose-dependent increase in the [Ca2+]i with respective EC50 values of 56 and 414 micromol/L. Both effects were inhibited by Mg2+ or an NMDA receptor antagonist and were unaffected by the presence of a glutamate scavenger. The other glutathione derivatives, oxidized glutathione, S-methylglutathione, S-ethylglutathione, S-propylglutathione, and S-butylglutathione, the dipeptides, Glu-Cys and Cys-Gly, and the antioxidants, dithiothreitol and mercaptoethanol, failed to induce a [Ca2+]i increase. In addition, glutathione caused a dose-dependent increase in glutamate release from synaptosomes. The maximal responses and the EC50 values for the glutamate-, NMDA-, GSNO-, and glutathione-induced [Ca2+]i increases and the glutathione-induced glutamate release were indistinguishable in the neurons of the offspring from control and morphine-addicted female rats. GSNO and glutathione act as NMDA receptor agonists and, in contrast to hippocampal brain slice, combined pre- and postnatal morphine exposure does not modulate NMDA receptor signaling in the cultured hippocampal neurons.

  6. Evaluation of the effects of specific opioid receptor agonists in a rodent model of spinal cord injury.

    PubMed

    Aceves, M; Mathai, B B; Hook, M A

    2016-10-01

    The current study aimed to evaluate the contribution(s) of specific opioid receptor systems to the analgesic and detrimental effects of morphine, observed after spinal cord injury in prior studies. We used specific opioid receptor agonists to assess the effects of μ- (DAMGO), δ- (DPDPE) and κ- (GR89696) opioid receptor activation on locomotor (Basso, Beattie and Bresnahan scale, tapered beam and ladder tests) and sensory (girdle, tactile and tail-flick tests) recovery in a rodent contusion model (T12). We also tested the contribution of non-classic opioid binding using [+]- morphine. First, a dose-response curve for analgesic efficacy was generated for each opioid agonist. Baseline locomotor and sensory reactivity was assessed 24 h after injury. Subjects were then treated with an intrathecal dose of a specific agonist and re-tested after 30 min. To evaluate the effects on recovery, subjects were treated with a single dose of an agonist and both locomotor and sensory function were monitored for 21 days. All agonists for the classic opioid receptors, but not the [+]- morphine enantiomer, produced antinociception at a concentration equivalent to a dose of morphine previously shown to produce strong analgesic effects (0.32 μmol). DAMGO and [+]- morphine did not affect long-term recovery. GR89696, however, significantly undermined the recovery of locomotor function at all doses tested. On the basis of these data, we hypothesize that the analgesic efficacy of morphine is primarily mediated by binding to the classic μ-opioid receptor. Conversely, the adverse effects of morphine may be linked to activation of the κ-opioid receptor. Ultimately, elucidating the molecular mechanisms underlying the effects of morphine is imperative to develop safe and effective pharmacological interventions in a clinical setting. USA. Grant DA31197 to MA Hook and the NIDA Drug Supply Program.

  7. [The beta2-adrenergic receptor agonists in the treatment of chronic obstructive pulmonary disease].

    PubMed

    Chorostowska-Wynimko, Joanna

    2005-01-01

    Chronic obstructive pulmonary disease (COPD) is considered one of the most common chronic diseases in the world. It is characterized by the progressive reduction of the respiratory parameters, relatively low effectiveness of recommended treatment as well as serious prognosis especially in the group of patients with advanced disease. The beta2-adrenergic receptor agonists are first-line therapeutics in the treatment of COPD patients. Due to their diverse pharmacokinetic characteristic beta2-mimetics are recommended both for regular or "rescue" treatment to prevent or to restrain dyspnea symptoms. This paper evaluates main differences between the mechanism of action and pharmacokinetic profile of the key beta2-mimetics, discusses consequences of those diversities for their the clinical application and potential side effects.

  8. AVE 0991-angiotensin-(1-7) receptor agonist, inhibits atherogenesis in apoE-knockout mice.

    PubMed

    Toton-Zuranska, J; Gajda, M; Pyka-Fosciak, G; Kus, K; Pawlowska, M; Niepsuj, A; Wolkow, P; Olszanecki, R; Jawien, J; Korbut, R

    2010-04-01

    Recent evidence shows that the renin-angiotensin system is a crucial player in atherosclerotic processes. It was also proved that Ang II promotes atherogenesis. Angiotensin-(1-7) [Ang-(1-7)] opposites Ang II action. Therefore, we would like to find out whether Ang-(1-7) receptor agonist: AVE 0991, could ameliorate atherosclerosis progression in an experimental model of atherosclerosis: apolipoprotein E (apoE) - knockout mice. AVE 0991 inhibited atherogenesis, measured both by "en face" method (7.63+/-1.6% vs. 14.6+/-2.1%) and "cross-section" method (47 235+/-7 546 microm(2) vs. 91 416+/-8 357 microm(2)). This is the first report showing the effect of AVE 0991 on atherogenesis in gene-targeted mice.

  9. Lignans from the Fruits of Melia toosendan and Their Agonistic Activities on Melatonin Receptor MT1.

    PubMed

    Wang, Hao; Geng, Chang-An; Xu, Hong-Bo; Huang, Xiao-Yan; Ma, Yun-Bao; Yang, Cai-Yan; Zhang, Xue-Mei; Chen, Ji-Jun

    2015-07-01

    Investigation on the fruits of Melia toosendan afforded seven new lignans (1-7), along with seventeen known compounds (8-24). The structures of the new compounds, involving four neo-lignans (1-4), two sesquilignans (5-6), and a nor-lignan (7), were elucidated based on extensive spectroscopic analyses (high-resolution electrospray ionization mass spectra, ultraviolet, infrared, one-dimensional and two-dimensional nuclear magnetic resonance). Compound 24 exhibited activity on melatonin receptor type 1 with an agonistic rate of 57.77% at 1.02 mM according to the assay on HEK293 cell lines in vitro. Georg Thieme Verlag KG Stuttgart · New York.

  10. [Treatment strategy for elderly diabetic patient with insulin or GLP-1 receptor agonist].

    PubMed

    Ando, Yasuyo

    2013-11-01

    It has been established that diabetes is an independent risk factor for microvascular and macrovascular complications, and many studies indicate that diabetic subjects are at greater risk of dementia, depression and fracture. Risk reductions for microvascular, macrovascular and death were observed by intensive therapy using insulin or oral diabetic agents. But a history of hypoglycemia was increased myocardial infarction, mortality, dementia and fracture. So it is important that optimum glycemic control has to be achieved without hypoglycemia. Treatment with a long-acting basal insulin analogue or glucagon-like peptide-1(GLP-1) receptor agonist, provide effective glycemic control without serious hypoglycemia in elderly patients. Self-monitoring of blood glucose might be effective in improving glycemic control in elderly patients, and it is useful for the diagnosis of hypoglycemia.

  11. Improvement in Aqueous Solubility of Retinoic Acid Receptor (RAR) Agonists by Bending the Molecular Structure.

    PubMed

    Hiramatsu, Michiaki; Ichikawa, Yuki; Tomoshige, Shusuke; Makishima, Makoto; Muranaka, Atsuya; Uchiyama, Masanobu; Yamaguchi, Takao; Hashimoto, Yuichi; Ishikawa, Minoru

    2016-08-05

    Aqueous solubility is a key requirement for many functional molecules, e. g., drug candidates. Decrease of the partition coefficient (log P) by chemical modification, i.e., introduction of hydrophilic group(s) into molecules, is a classical strategy for improving aqueous solubility. We have been investigating alternative strategies for improving the aqueous solubility of pharmaceutical compounds by disrupting intermolecular interactions. Here, we show that introducing a bend into the molecular structure of retinoic acid receptor (RAR) agonists by changing the substitution pattern from para to meta or ortho dramatically enhances aqueous solubility by up to 890-fold. We found that meta analogs exhibit similar hydrophobicity to the parent para compound, and have lower melting points, supporting the idea that the increase of aqueous solubility was due to decreased intermolecular interactions in the solid state as a result of the structural changes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Polyyne Hybrid Compounds from Notopterygium incisum with Peroxisome Proliferator-Activated Receptor Gamma Agonistic Effects

    PubMed Central

    2014-01-01

    In the search for peroxisome proliferator-activated receptor gamma (PPARγ) active constituents from the roots and rhizomes of Notopterygium incisum, 11 new polyacetylene derivatives (1–11) were isolated. Their structures were elucidated by NMR and HRESIMS as new polyyne hybrid molecules of falcarindiol with sesquiterpenoid or phenylpropanoid moieties, named notoethers A–H (1–8) and notoincisols A–C (9–11), respectively. Notoincisol B (10) and notoincisol C (11) represent two new carbon skeletons. When tested for PPARγ activation in a luciferase reporter assay with HEK-293 cells, notoethers A–C (1–3), notoincisol A (9), and notoincisol B (10) showed promising agonistic activity (EC50 values of 1.7 to 2.3 μM). In addition, notoincisol A (9) exhibited inhibitory activity on NO production of stimulated RAW 264.7 macrophages. PMID:25333853

  13. Polyyne hybrid compounds from Notopterygium incisum with peroxisome proliferator-activated receptor gamma agonistic effects.

    PubMed

    Liu, Xin; Kunert, Olaf; Blunder, Martina; Fakhrudin, Nanang; Noha, Stefan M; Malainer, Clemens; Schinkovitz, Andreas; Heiss, Elke H; Atanasov, Atanas G; Kollroser, Manfred; Schuster, Daniela; Dirsch, Verena M; Bauer, Rudolf

    2014-11-26

    In the search for peroxisome proliferator-activated receptor gamma (PPARγ) active constituents from the roots and rhizomes of Notopterygium incisum, 11 new polyacetylene derivatives (1-11) were isolated. Their structures were elucidated by NMR and HRESIMS as new polyyne hybrid molecules of falcarindiol with sesquiterpenoid or phenylpropanoid moieties, named notoethers A-H (1-8) and notoincisols A-C (9-11), respectively. Notoincisol B (10) and notoincisol C (11) represent two new carbon skeletons. When tested for PPARγ activation in a luciferase reporter assay with HEK-293 cells, notoethers A-C (1-3), notoincisol A (9), and notoincisol B (10) showed promising agonistic activity (EC50 values of 1.7 to 2.3 μM). In addition, notoincisol A (9) exhibited inhibitory activity on NO production of stimulated RAW 264.7 macrophages.

  14. Slow to fast alterations in skeletal muscle fibers caused by clenbuterol, a beta(2)-receptor agonist

    NASA Technical Reports Server (NTRS)

    Zeman, Richard J.; Ludemann, Robert; Easton, Thomas G.; Etlinger, Joseph D.

    1988-01-01

    The effects of a beta(2)-receptor agonist, clenbuterol, and a beta(2) antagonist, butoxamine, on the skeletal muscle fibers of rats were investigated. It was found that chronic treatment of rats with clenbuterol caused hypertrophy of histochemically identified fast-twitch, but not slow-twitch, fibers within the soleus, while in the extensor digitorum longus the mean areas of both fiber types were increased; in both muscles, the ratio of the number of fast-twitch to slow-twitch fibers was increased. In contrast, a treatment with butoxamine caused a reduction of the fast-twitch fiber size in both muscles, and the ratio of the fast-twitch to slow-twitch fibers was decreased.

  15. Salvinorin A, an active component of the hallucinogenic sage salvia divinorum is a highly efficacious kappa-opioid receptor agonist: structural and functional considerations.

    PubMed

    Chavkin, Charles; Sud, Sumit; Jin, Wenzhen; Stewart, Jeremy; Zjawiony, Jordan K; Siebert, Daniel J; Toth, Beth Ann; Hufeisen, Sandra J; Roth, Bryan L

    2004-03-01

    The diterpene salvinorin A from Salvia divinorum has recently been reported to be a high-affinity and selective kappa-opioid receptor agonist (Roth et al., 2002). Salvinorin A and selected derivatives were found to be potent and efficacious agonists in several measures of agonist activity using cloned human kappa-opioid receptors expressed in human embryonic kidney-293 cells. Thus, salvinorin A, salvinorinyl-2-propionate, and salvinorinyl-2-heptanoate were found to be either full (salvinorin A) or partial (2-propionate, 2-heptanoate) agonists for inhibition of forskolin-stimulated cAMP production. Additional studies of agonist potency and efficacy of salvinorin A, performed by cotransfecting either the chimeric G proteins Gaq-i5 or the universal G protein Ga16 and quantification of agonist-evoked intracellular calcium mobilization, affirmed that salvinorin A was a potent and effective kappa-opioid agonist. Results from structure-function studies suggested that the nature of the substituent at the 2-position of salvinorin A was critical for kappa-opioid receptor binding and activation. Because issues of receptor reserve complicate estimates of agonist efficacy and potency, we also examined the agonist actions of salvinorin A by measuring potassium conductance through G protein-gated K(+) channels coexpressed in Xenopus oocytes, a system in which receptor reserve is minimal. Salvinorin A was found to be a full agonist, being significantly more efficacious than (trans)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl] benzeneacetamide methane-sulfonate hydrate (U50488) or (trans)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl] benzeneacetamide methane-sulfonate hydrate (U69593) (two standard kappa-opioid agonists) and similar in efficacy to dynorphin A (the naturally occurring peptide ligand for kappa-opioid receptors). Salvinorin A thus represents the first known naturally occurring non-nitrogenous full agonist at kappa-opioid receptors.

  16. The Natural Product Magnolol as a Lead Structure for the Development of Potent Cannabinoid Receptor Agonists

    PubMed Central

    Müller, Christa E.

    2013-01-01

    Magnolol (4-allyl-2-(5-allyl-2-hydroxyphenyl)phenol), the main bioactive constituent of the medicinal plant Magnolia officinalis, and its main metabolite tetrahydromagnolol were recently found to activate cannabinoid (CB) receptors. We now investigated the structure-activity relationships of (tetrahydro)magnolol analogs with variations of the alkyl chains and the phenolic groups and could considerably improve potency. Among the most potent compounds were the dual CB1/CB2 full agonist 2-(2-methoxy-5-propyl-phenyl)-4-hexylphenol (61a, K i CB1∶0.00957 µM; K i CB2∶0.0238 µM), and the CB2-selective partial agonist 2-(2-hydroxy-5-propylphenyl)-4-pentylphenol (60, K i CB1∶0.362 µM; K i CB2∶0.0371 µM), which showed high selectivity versus GPR18 and GPR55. Compound 61b, an isomer of 61a, was the most potent GPR55 antagonist with an IC50 value of 3.25 µM but was non-selective. The relatively simple structures, which possess no stereocenters, are easily accessible in a four- to five-step synthetic procedure from common starting materials. The central reaction step is the well-elaborated Suzuki-Miyaura cross-coupling reaction, which is suitable for a combinatorial chemistry approach. The scaffold is versatile and may be fine-tuned to obtain a broad range of receptor affinities, selectivities and efficacies. PMID:24204944

  17. Subunit rotation models activation of serotonin 5-HT3AB receptors by agonists

    NASA Astrophysics Data System (ADS)

    Maksay, Gábor; Simonyi, Miklós; Bikádi, Zsolt

    2004-10-01

    The N-terminal extracellular regions of heterooligomeric 3AB-type human 5-hydroxytryptamine receptors (5-HT 3ABR) were modelled based on the crystal structure of snail acetylcholine binding protein AChBP. Stepwise rotation of subunit A by 5° was performed between -10° and 15° to mimic agonist binding and receptor activation. Anticlockwise rotation reduced the size of the binding cavity in interface AB and reorganised the network of hydrogen bonds along the interface. AB subunit dimers with different rotations were applied for docking of ligands with different efficacies: 5-HT, m-chlorophenylbiguanide, SR 57227, quinolinyl piperazine and lerisetron derivatives. All ligands were docked into the dimer with -10° rotation representing ligand-free, open binding cavities similarly, without pharmacological discrimination. Their ammonium ions were in hydrogen bonding distance to the backbone carbonyl of W183. Anticlockwise rotation and contraction of the binding cavity led to distinctive docking interactions of agonists with E129 and cation-π interactions of their ammonium ions. Side chains of several further amino acids participating in docking (Y143, Y153, Y234 and E236) are in agreement with the effects of point mutations in the binding loops. Our model postulates that 5-HT binds to W183 in a hydrophobic cleft as well as to E236 in a hydrophilic vestibule. Then it elicits anticlockwise rotation to draw in loop C via π-cation-π interactions of␣its ammonium ion with W183 and Y234. Finally, closure of the binding cavity might end in rebinding of 5-HT to E129 in the hydrophilic vestibule.

  18. Catalposide is a natural agonistic ligand of peroxisome proliferator-activated receptor-{alpha}

    SciTech Connect

    Lee, Ji Hae; Jun, Hee-jin; Hoang, Minh-Hien

    2012-06-15

    Highlights: Black-Right-Pointing-Pointer Catalposide is a novel ligand for PPAR{alpha}. Black-Right-Pointing-Pointer Cell stimulated with catalposide improved fatty acid uptake, regulated target genes in fatty acid {beta}-oxidation and synthesis. Black-Right-Pointing-Pointer Catalposdie reduces hepatic triacylglycerides. Black-Right-Pointing-Pointer Theses demonstrate catalposide could ameliorate hyperlipidemia and hepatic steatosis. -- Abstract: Peroxisome proliferator-activated receptor-alpha (PPAR{alpha}) is a nuclear receptor that regulates the expression of genes related to cellular lipid uptake and oxidation. Thus, PPAR{alpha} agonists may be important in the treatment of hypertriglyceridemia and hepatic steatosis. In this study, we demonstrated that catalposide is a novel natural PPAR{alpha} agonist, identified from reporter gene assay-based activity screening withmore » approximately 900 natural plant and seaweed extracts. Results of time-resolved fluorescence resonance energy transfer analyses suggested that the compound interacted directly with the ligand-binding domain of PPAR{alpha}. Cultured hepatocytes stimulated with catalposide exhibited significantly reduced cellular triglyceride concentrations, by 21%, while cellular uptake of fatty acids was increased, by 70% (P < 0.05). Quantitative PCR analysis revealed that the increase in cellular fatty acid uptake was due to upregulation of fatty acid transporter protein-4 (+19% vs. the control) in cells stimulated with catalposide. Additionally, expression of genes related to fatty acid oxidation and high-density lipoprotein metabolism were upregulated, while that of genes related to fatty acid synthesis were suppressed. In conclusion, catalposide is hypolipidemic by activation of PPAR{alpha} via a ligand-mediated mechanism that modulates the expression of in lipid metabolism genes in hepatocytes.« less

  19. The potential and pitfalls of GLP-1 receptor agonists for renal protection in type 2 diabetes.

    PubMed

    Thomas, Merlin C

    2017-04-01

    Glucagon-Like Peptide-1 Receptor agonists (GLP-1 RA) offer substantial benefits for the management of glucose levels in type 2 diabetes. In addition, recent data from clinical trials have demonstrated that treatment with Glucagon-Like Peptide-1 Receptor agonists (GLP-1 RA) are also able to reduce new onset macroalbuminuria. These benefits may be consistent with the known effects of GLP-1 RA on traditional risk factors for progressive kidney disease including glucose lowering, blood pressure lowering, reduced insulin levels and weight reduction. However, emerging evidence suggests that GLP-1 RA can also have direct effects in the kidney, including inhibiting NHE3-dependent sodium reabsorption in the proximal tubule. Additional effects on the intrarenal renin angiotensin system, ischaemia/hypoxia, inflammation, apoptosis and neural signalling may also contribute to renal benefits. The extent to which these effects are mediated by the GLP-1R remains to be established. Recent studies confirm that the metabolic products of GLP-1 retain important antioxidant and anti-apoptotic activities that are GLP-1 R independent. Moreover the divergent peptide sequences of the currently available GLP-1 RA may mean that divergent reno-protective efficacy could be anticipated from different GLP-1 RA on this basis. Kidney disease is an important and deadly clinical outcome, and one worth preventing. Although both experimental and clinical data now support the possibility of renoprotective effects arising from treatment with GLP-1 RA, further work is needed to optimise these effects. A logical synergism with SGLT2 inhibition also exists, and at least in the short term, this combination approach may become the most useful way to protect the kidney in type 2 diabetes. © 2017 Elsevier Masson SAS. All rights reserved.

  20. G protein-coupled receptors: signalling and regulation by lipid agonists for improved glucose homoeostasis.

    PubMed

    Moran, Brian M; Flatt, Peter R; McKillop, Aine M

    2016-04-01

    G protein-coupled receptors (GPCRs) play a pivotal role in cell signalling, controlling many processes such as immunity, growth, cellular differentiation, neurological pathways and hormone secretions. Fatty acid agonists are increasingly recognised as having a key role in the regulation of glucose homoeostasis via stimulation of islet and gastrointestinal GPCRs. Downstream cell signalling results in modulation of the biosynthesis, secretion, proliferation and anti-apoptotic pathways of islet and enteroendocrine cells. GPR40 and GPR120 are activated by long-chain fatty acids (>C12) with both receptors coupling to the Gαq subunit that activates the Ca(2+)-dependent pathway. GPR41 and GPR43 are stimulated by short-chain fatty acids (C2-C5), and activation results in binding to Gαi that inhibits the adenylyl cyclase pathway attenuating cAMP production. In addition, GPR43 also couples to the Gαq subunit augmenting intracellular Ca(2+) and activating phospholipase C. GPR55 is specific for cannabinoid endogenous agonists (endocannabinoids) and non-cannabinoid fatty acids, which couples to Gα12/13 and Gαq proteins, leading to enhancing intracellular Ca(2+), extracellular signal-regulated kinase 1/2 (ERK) phosphorylation and Rho kinase. GPR119 is activated by fatty acid ethanolamides and binds to Gαs utilising the adenylate cyclase pathway, which is dependent upon protein kinase A. Current research indicates that GPCR therapies may be approved for clinical use in the near future. This review focuses on the recent advances in preclinical diabetes research in the signalling and regulation of GPCRs on islet and enteroendocrine cells involved in glucose homoeostasis.

  1. Non-nucleotide Agonists Triggering P2X7 Receptor Activation and Pore Formation.

    PubMed

    Di Virgilio, Francesco; Giuliani, Anna L; Vultaggio-Poma, Valentina; Falzoni, Simonetta; Sarti, Alba C

    2018-01-01

    The P2X7 receptor (P2X7R) is a ligand-gated plasma membrane ion channel belonging to the P2X receptor subfamily activated by extracellular nucleotides. General consensus holds that the physiological (and maybe the only) agonist is ATP. However, scattered evidence generated over the last several years suggests that ATP might not be the only agonist, especially at inflammatory sites. Solid data show that NAD + covalently modifies the P2X7R of mouse T lymphocytes, thus lowering the ATP threshold for activation. Other structurally unrelated agents have been reported to activate the P2X7R via a poorly understood mechanism of action: (a) the antibiotic polymyxin B, possibly a positive allosteric P2X7R modulator, (b) the bactericidal peptide LL-37, (c) the amyloidogenic β peptide, and (d) serum amyloid A. Some agents, such as Alu-RNA, have been suggested to activate the P2X7R acting on the intracellular N- or C-terminal domains. Mode of P2X7R activation by these non-nucleotide ligands is as yet unknown; however, these observations raise the intriguing question of how these different non-nucleotide ligands may co-operate with ATP at inflammatory or tumor sites. New information obtained from the cloning and characterization of the P2X7R from exotic mammalian species (e.g., giant panda) and data from recent patch-clamp studies are strongly accelerating our understanding of P2X7R mode of operation, and may provide hints to the mechanism of activation of P2X7R by non-nucleotide ligands.

  2. Non-nucleotide Agonists Triggering P2X7 Receptor Activation and Pore Formation

    PubMed Central

    Di Virgilio, Francesco; Giuliani, Anna L.; Vultaggio-Poma, Valentina; Falzoni, Simonetta; Sarti, Alba C.

    2018-01-01

    The P2X7 receptor (P2X7R) is a ligand-gated plasma membrane ion channel belonging to the P2X receptor subfamily activated by extracellular nucleotides. General consensus holds that the physiological (and maybe the only) agonist is ATP. However, scattered evidence generated over the last several years suggests that ATP might not be the only agonist, especially at inflammatory sites. Solid data show that NAD+ covalently modifies the P2X7R of mouse T lymphocytes, thus lowering the ATP threshold for activation. Other structurally unrelated agents have been reported to activate the P2X7R via a poorly understood mechanism of action: (a) the antibiotic polymyxin B, possibly a positive allosteric P2X7R modulator, (b) the bactericidal peptide LL-37, (c) the amyloidogenic β peptide, and (d) serum amyloid A. Some agents, such as Alu-RNA, have been suggested to activate the P2X7R acting on the intracellular N- or C-terminal domains. Mode of P2X7R activation by these non-nucleotide ligands is as yet unknown; however, these observations raise the intriguing question of how these different non-nucleotide ligands may co-operate with ATP at inflammatory or tumor sites. New information obtained from the cloning and characterization of the P2X7R from exotic mammalian species (e.g., giant panda) and data from recent patch-clamp studies are strongly accelerating our understanding of P2X7R mode of operation, and may provide hints to the mechanism of activation of P2X7R by non-nucleotide ligands. PMID:29449813

  3. Tetrahydro anthranilic acid as a surrogate for anthranilic acid: application to the discovery of potent niacin receptor agonists.

    PubMed

    Raghavan, Subharekha; Tria, G Scott; Shen, Hong C; Ding, Fa-Xiang; Taggart, Andrew K; Ren, Ning; Wilsie, Larrisa C; Krsmanovic, Mihajlo L; Holt, Tom G; Wolff, Michael S; Waters, M Gerard; Hammond, Milton L; Tata, James R; Colletti, Steven L

    2008-06-01

    The design, synthesis, and biological activity of a series of cycloalkene acid-based niacin receptor agonists are described. This led to the discovery that tetrahydro anthranilic acid is an excellent surrogate for anthranilic acid. Several compounds were identified that were potent against the niacin receptor, had enhanced cytochrome P450 selectivity against subtypes CYP2C8 and CYP2C9, and improved oral exposure in mice.

  4. Black cohosh acts as a mixed competitive ligand and partial agonist of the serotonin receptor.

    PubMed

    Burdette, Joanna E; Liu, Jianghua; Chen, Shao-Nong; Fabricant, Daniel S; Piersen, Colleen E; Barker, Eric L; Pezzuto, John M; Mesecar, Andrew; Van Breemen, Richard B; Farnsworth, Norman R; Bolton, Judy L

    2003-09-10

    extract elevated cAMP levels in 293T-5-HT(7)-transfected HEK cells, suggesting the extract acted as a partial agonist at the receptor. The elevation in cAMP mediated by the black cohosh extract could be reversed in the presence of the antagonist methiothepin, indicating a receptor-mediated process. These data suggest that reductions in hot flashes in some women taking black cohosh may not be due to estrogenic properties. This study identifies other possible biological targets of black cohosh that could account for reported biological effects.

  5. Diazotization and thiocyanate differentiate agonists from antagonists for the high- and low-affinity receptors of gamma-aminobutyric acid.

    PubMed

    Maksay, G; Ticku, M K

    1984-07-01

    The differentiation of high- and low-affinity postsynaptic gamma-aminobutyric acid (GABA) receptors was examined in a washed cortical membrane preparation of the rat. The selective elimination of the high- and low-affinity GABA sites by the chaotropic anion thiocyanate and diazotization by p-diazobenzenesulfonic acid (DSA), respectively, offered two model systems for the separate sites. The [3H]GABA displacing potencies of some GABA agonists [GABA, 4,5,6,7-tetrahydro- isoxazole [4,5c]pyridine-3-ol (THIP), and muscimol] and antagonists [bicuculline methiodide (BCM), 3-alpha-hydroxy-16-imino-5 beta-17-aza-androstan-11-one (R-5135), and d-tubocurarine] and their slope factors were examined in these model systems and in control membranes. The displacing potency of the agonists was increased in the DSA-pretreated membranes and decreased in the presence of thiocyanate. The displacing potency of the antagonists was shifted in an opposite manner. The chaotropic effect of thiocyanate was reversible and not additive with the inhibitory effect of diazotization on the specific binding of GABA. Inhibition of specific GABA binding by pyridoxal-5-phosphate (PLP) could not be protected by GABA antagonists (BCM and R-5135) but only by agonists. The results can be interpreted in the framework of a dual (agonist-antagonist) receptor model, postulating a hydrophobic accessory site at the low-affinity GABA receptor. The effect of thiocyanate on the GABA receptor may result in the exposure of the hydrophobic accessory sites.

  6. Thrombopoietin levels in patients with disorders of platelet production: diagnostic potential and utility in predicting response to TPO receptor agonists.

    PubMed

    Makar, Robert S; Zhukov, Olga S; Sahud, Mervyn A; Kuter, David J

    2013-12-01

    Thrombopoietin (TPO) is the major regulator of megakaryopoiesis. Measurement of serum TPO levels may help distinguish between various causes of thrombocytopenia and predict treatment response to TPO receptor agonists. Serum TPO levels from 118 healthy volunteers and 88 patients with abnormal platelet counts were measured using a quantitative ELISA assay. The mean (range) TPO level in healthy volunteers was 39 (7-99) pg/mL. TPO values were correlated with the patient's diagnosis, platelet count, and response to TPO receptor agonists. 88 patients with history of consumptive thrombocytopenia (39) or hypoproliferative thrombocytopenia (49) were analyzed. Median (interquartile range) TPO level for consumptive thrombocytopenia patients was 63 (48-98) pg/mL with a corresponding median (interquartile range) platelet count of 73 (28-146) × 10(9) /L. In contrast, hypoproliferative thrombocytopenia patients had platelet counts [59 (30-117) × 10(9) /L] comparable with consumptive thrombocytopenia patients, but significantly higher serum TPO levels [706 (358-1546) pg/mL, P < 0.0001]. Analysis of 21 ITP patients treated with TPO receptor agonists demonstrated that a TPO level >95 pg/mL was associated with lack of clinical response (P < 0.002). TPO levels may have diagnostic utility in discriminating between patients with hypoproliferative and consumptive thrombocytopenia. Elevated TPO levels in ITP patients may predict a poor clinical response to treatment with TPO receptor agonists. Copyright © 2013 Wiley Periodicals, Inc.

  7. Cooperative therapeutic action of retinoic acid receptor and retinoid x receptor agonists in a mouse model of Alzheimer's disease.

    PubMed

    Kawahara, Kohichi; Suenobu, Michita; Ohtsuka, Hideyuki; Kuniyasu, Akihiko; Sugimoto, Yukihiko; Nakagomi, Madoka; Fukasawa, Hiroshi; Shudo, Koichi; Nakayama, Hitoshi

    2014-01-01

    Alzheimer's disease (AD) is a neurodegenerative process involving amyloid-β (Aβ) peptide deposition, neuroinflammation, and progressive memory loss. Here, we evaluated whether oral administration of retinoic acid receptor (RAR)α,β agonist Am80 (tamibarotene) or specific retinoid X receptor (RXR) pan agonist HX630 or their combination could improve deficits in an AD model, 8.5-month-old amyloid-β protein precursor 23 (AβPP23) mice. Co-administration of Am80 (0.5 mg/kg) and HX630 (5 mg/kg) for 17 days significantly improved memory deficits (Morris water maze) in AβPP23 mice, whereas administration of either agent alone produced no effect. Only co-administration significantly reduced the level of insoluble Aβ peptide in the brain. These results thus indicate that effective memory improvement via reduction of insoluble Aβ peptide in 8.5-month-old AβPP23 mice requires co-activation of RARα,β and RXRs. RARα-positive microglia accumulated Aβ plaques in the AβPP23 mice. Rat primary microglia co-treated with Am80/HX630 showed increased degradation activity towards 125I-labeled oligomeric Aβ1-42 peptide in an insulin-degrading enzyme (IDE)-dependent manner. The co-administration increased mRNA for IDE and membrane-associated IDE protein in vivo, suggesting that IDE contributes to Aβ clearance in Am80/HX630-treated AβPP23 mice. Am80/HX630 also increased IL-4Rα expression in microglial MG5 cells. The improvement in memory of Am80/HX630-treated AβPP23 mice was correlated with the levels and signaling of hippocampal interleukin-4 (IL-4). Therefore, Am80/HX630 may promote differentiation of IL-4-responsive M2-like microglia and increase their activity for clearance of oligomeric Aβ peptides by restoring impaired IL-4 signaling in AβPP23 mice. Combination treatment with RAR and RXR agonists may be an effective approach for AD therapy.

  8. Differential behavioral reinforcement effects of dopamine receptor agonists in the rat with bilateral lesion of the posterior ventral tegmental area.

    PubMed

    Ouachikh, Omar; Dieb, Wisam; Durif, Franck; Hafidi, Aziz

    2013-09-01

    Dopamine dysregulation syndrome in Parkinson's disease has been attributed to dopamine replacement therapies and/or a lesion of the dopaminergic system. The dopaminergic neuronal loss targets the substantia nigra and the ventral tegmental area (VTA). We hypothesize that dopamine replacement therapy is responsible for the potential reinforcement effect in Parkinson's disease by acting on the neuronal reward circuitry. Therefore this study was designed to explore the potential motivational effect of dopamine replacement therapy in bilateral VTA-lesioned animals. The posterior (p)VTA, which project to the nucleus accumbens (NAc) constitutes the major dopamine neuronal circuitry implicated in addictive disorders. Using the conditioned place preference (CPP) behavioral paradigm, we investigated the motivational effects of dopamine receptor agonists, and cocaine in rat with a 6-OHDA bilateral lesion of the pVTA. Amongst the dopamine receptor agonists used in this study only the D2R and D3R agonists (bromocriptine, PD128907 and pramipexole), induced a significant CPP in pVTA-lesioned animals. Dopamine receptor agonists did not induce behavioral sensitization in sham animals. Moreover, confocal D2R immunostaining analysis showed a significant increase in the number of D2R per cell body in the NAc shell of pVTA lesioned rats compared to sham. This result correlated, for the first time, the dopamine receptor agonists effect with DR2 overexpression in the NAc shell of pVTA-lesioned rats. In addition, cocaine, which is known to increase dopamine release, induced behavioral sensitization in sham group but not in dopamine deprived group. Thus, the later result highlighted the importance of pVTA-NAc dopaminergic pathway in positive reinforcements. Altogether these data suggested that the implication of the dopamine replacement therapy in the appearance of dopamine dysregulation syndrome in Parkinson's disease is probably due to both neuronal degeneration in the posterior VTA and

  9. Dipeptidylpeptidase-4 (DPP-4) inhibitors are favourable to glucagon-like peptide-1 (GLP-1) receptor agonists: yes.

    PubMed

    Scheen, André J

    2012-03-01

    The pharmacological treatment of type 2 diabetes (T2DM) is becoming increasingly complex, especially since the availability of incretin-based therapies. Compared with other glucose-lowering strategies, these novel drugs offer some advantages such as an absence of weight gain and a negligible risk of hypoglycaemia and, possibly, better cardiovascular and β-cell protection. The physician has now multiple choices to manage his/her patient after secondary failure of metformin, and the question whether it is preferable to add an oral dipeptidylpeptidase-4 (DPP-4) inhibitor (gliptin) or an injectable glucagon-like peptide-1 (GLP-1) receptor agonist will emerge. Obviously, DPP-4 inhibitors offer several advantages compared with GLP-1 receptor agonists, especially regarding easiness of use, tolerance profile and cost. However, because they can only increase endogenous GLP-1 concentrations to physiological (rather than pharmacological) levels, they are less potent to improve glucose control, promote weight reduction ("weight neutrality") and reduce blood pressure compared to GLP-1 receptor agonists. Of note, none of the two classes have proven long-term safety and positive impact on diabetic complications yet. The role of DPP-4 inhibitors and GLP-1 receptor agonists in the therapeutic armamentarium of T2DM is rapidly evolving, but their respective potential strengths and weaknesses should be better defined in long-term head-to-head comparative controlled trials. Instead of trying to answer the question whether DPP-4 inhibitors are favourable to GLP-1 receptor agonists (or vice versa), it is probably more clinically relevant to look at which T2DM patient will benefit more from one or the other therapy considering all his/her individual clinical characteristics ("personalized medicine"). Copyright © 2011 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved.

  10. Cannabinoid receptor agonists modulate calcium channels in rat retinal Müller cells.

    PubMed

    Yang, W; Li, Q; Wang, S-Y; Gao, F; Qian, W-J; Li, F; Ji, M; Sun, X-H; Miao, Y; Wang, Z

    2016-01-28

    While activation of cannabinoid CB1 receptor (CB1R) regulates a variety of retinal neuronal functions by modulating ion channels in these cells, effect of activated cannabinoid receptors on Ca(2+) channels in retinal Müller cells is still largely unknown. In the present work we show that three subunits of T-type Ca(2+) channels, CaV3.1, CaV3.2 and CaV3.3, as well as one subunit of L-type Ca(2+) channels, CaV1.2, were expressed in rat Müller cells by immunofluorescent staining. Consistently, nimodipine- and mibefradil-sensitive Na(+) currents through L- and T-type Ca(2+) channels could be recorded electrophysiologically. The cannabinoid receptor agonist WIN55212-2 significantly suppressed Ca(2+) channel currents, mainly the T-type one, in acutely isolated rat Müller cells in a dose-dependent manner, with an IC50 of 3.98μM. The WIN55212-2 effect was not blocked by AM251/SR141716, specific CB1R antagonists. Similar suppression of the currents was observed when anandamide (AEA) and 2-arachidonoyl glycerol (2-AG), endogenous ligands of cannabinoid receptors, were applied. Moreover, even though CB2 receptors (CB2Rs) were expressed in rat Müller cells, the effects of WIN55212-2 and 2-AG on Ca(2+) channel currents were not blocked by AM630, a selective CB2R antagonist. However, the effect of AEA could be partially rescued by AM630. These results suggest that WIN55212-2 and 2-AG receptor-independently suppressed the Ca(2+) channel currents in Müller cells, while AEA suppressed the currents partially through CB2Rs. The existence of receptor-dependent and -independent mechanisms suggests that cannabinoids may modulate Müller cell functions through multiple pathways. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

  11. TRA-418, a thromboxane A2 receptor antagonist and prostacyclin receptor agonist, inhibits platelet-leukocyte interaction in human whole blood.

    PubMed

    Miyamoto, Mitsuko; Ohno, Michihiro; Yamada, Naohiro; Ohtake, Atsushi; Matsushita, Teruo

    2010-10-01

    TRA-418, a compound with both thromboxane A2 receptor (TP receptor) antagonistic and prostacyclin receptor (IP receptor) agonistic activities, was synthesised in our laboratory as a new antithrombotic agent. In this study, we examined the effects of TRA-418 on platelet-leukocyte interactions in human whole blood. Platelet-leukocyte interactions were induced by U-46619 in the presence of epinephrine (U-46619 + epinephrine) or with thrombin receptor agonist peptide 1-6 (TRAP). Platelet-leukocyte interactions were assessed by flow cytometry, with examination of both platelet-neutrophil and platelet-monocyte complexes. In a control experiment, the TP receptor antagonist SQ-29548 significantly inhibited the induction of platelet-leukocyte complexes by the combination of U-46619 and epinephrine, but not TRAP-induced formation of platelet-leukocyte complexes. Conversely, the IP receptor agonist beraprost sodium inhibited platelet-leukocyte complex formation induced by both methods, although the IC50 values of beraprost sodium for U-46619 + epinephrine were at least 10-fold greater than for TRAP. Under such conditions, TRA-418 inhibited both U-46619 + epinephrine-induced and TRAP-induced platelet-leukocyte complex formation in a concentration-dependent manner, in a similar range. These results suggest that TRA-418 exerts its inhibitory effects on platelet-leukocyte interactions by acting as a TP receptor antagonist as well as an IP receptor agonist in an additive or synergistic manner. These inhibitory effects of TRA-418 on formation of platelet-leukocyte complexes suggest the compound is beneficial effects as an antithrombotic agent.

  12. Agonistic monoclonal antibody against CD40 receptor decreases lymphocyte apoptosis and improves survival in sepsis.

    PubMed

    Schwulst, Steven J; Grayson, Mitchell H; DiPasco, Peter J; Davis, Christopher G; Brahmbhatt, Tejal S; Ferguson, Thomas A; Hotchkiss, Richard S

    2006-07-01

    Sepsis causes a marked apoptosis-induced depletion of lymphocytes. The degree of lymphocyte apoptosis during sepsis strongly correlates with survival. CD40, a member of the TNFR family, is expressed on APCs and has potent antiapoptotic activity. In this study we determined whether an agonistic Ab against CD40 could protect lymphocytes from sepsis-induced apoptosis. Secondly, we examined potential antiapoptotic mechanisms of the putative protection. Lastly, we aimed to determine whether anti-CD40 treatment could improve survival in sepsis. CD1 mice were made septic by the cecal ligation and puncture method and treated postoperatively with anti-CD40 Ab. Treatment with anti-CD40 completely abrogated sepsis-induced splenic B cell death and, surprisingly, decreased splenic and thymic T cell death as well (p < 0.001). To investigate the mechanism of protection of anti-CD40 therapy on T cells, CD40 receptor expression was examined. As anticipated, the CD40 receptor was constitutively expressed on B cells, but, unexpectedly, splenic and thymic T cells were found to express CD40 receptor during sepsis. Furthermore, CD4+CD8- T cells were the predominant subtype of T cells expressing CD40 receptor during sepsis. Additionally, the antiapoptotic protein Bcl-x(L) was found to be markedly increased in splenic B and T cells as well as in thymic T cells after treatment with anti-CD40 Ab (p < 0.0025). Lastly, mice that were made septic in a double injury model of sepsis had improved survival after treatment with anti-CD40 as compared with controls (p = 0.05). In conclusion, anti-CD40 treatment increases Bcl-x(L), provides nearly complete protection against sepsis-induced lymphocyte apoptosis, and improves survival in sepsis.

  13. Parallel functional activity profiling reveals valvulopathogens are potent 5-hydroxytryptamine(2B) receptor agonists: implications for drug safety assessment.

    PubMed

    Huang, Xi-Ping; Setola, Vincent; Yadav, Prem N; Allen, John A; Rogan, Sarah C; Hanson, Bonnie J; Revankar, Chetana; Robers, Matt; Doucette, Chris; Roth, Bryan L

    2009-10-01

    Drug-induced valvular heart disease (VHD) is a serious side effect of a few medications, including some that are on the market. Pharmacological studies of VHD-associated medications (e.g., fenfluramine, pergolide, methysergide, and cabergoline) have revealed that they and/or their metabolites are potent 5-hydroxytryptamine(2B) (5-HT(2B)) receptor agonists. We have shown that activation of 5-HT(2B) receptors on human heart valve interstitial cells in vitro induces a proliferative response reminiscent of the fibrosis that typifies VHD. To identify current or future drugs that might induce VHD, we screened approximately 2200 U.S. Food and Drug Administration (FDA)-approved or investigational medications to identify 5-HT(2B) receptor agonists, using calcium-based high-throughput screening. Of these 2200 compounds, 27 were 5-HT(2B) receptor agonists (hits); 14 of these had previously been identified as 5-HT(2B) receptor agonists, including seven bona fide valvulopathogens. Six of the hits (guanfacine, quinidine, xylometazoline, oxymetazoline, fenoldopam, and ropinirole) are approved medications. Twenty-three of the hits were then "functionally profiled" (i.e., assayed in parallel for 5-HT(2B) receptor agonism using multiple readouts to test for functional selectivity). In these assays, the known valvulopathogens were efficacious at concentrations as low as 30 nM, whereas the other compounds were less so. Hierarchical clustering analysis of the pEC(50) data revealed that ropinirole (which is not associated with valvulopathy) was clearly segregated from known valvulopathogens. Taken together, our data demonstrate that patterns of 5-HT(2B) receptor functional selectivity might be useful for identifying compounds likely to induce valvular heart disease.

  14. Impaired β-arrestin recruitment and reduced desensitization by non-catechol agonists of the D1 dopamine receptor.

    PubMed

    Gray, David L; Allen, John A; Mente, Scot; O'Connor, Rebecca E; DeMarco, George J; Efremov, Ivan; Tierney, Patrick; Volfson, Dmitri; Davoren, Jennifer; Guilmette, Edward; Salafia, Michelle; Kozak, Rouba; Ehlers, Michael D

    2018-02-14

    Selective activation of dopamine D1 receptors (D1Rs) has been pursued for 40 years as a therapeutic strategy for neurologic and psychiatric diseases due to the fundamental role of D1Rs in motor function, reward processing, and cognition. All known D1R-selective agonists are catechols, which are rapidly metabolized and desensitize the D1R after prolonged exposure, reducing agonist response. As such, drug-like selective D1R agonists have remained elusive. Here we report a novel series of selective, potent non-catechol D1R agonists with promising in vivo pharmacokinetic properties. These ligands stimulate adenylyl cyclase signaling and are efficacious in a rodent model of Parkinson's disease after oral administration. They exhibit distinct binding to the D1R orthosteric site and a novel functional profile including minimal receptor desensitization, reduced recruitment of β-arrestin, and sustained in vivo efficacy. These results reveal a novel class of D1 agonists with favorable drug-like properties, and define the molecular basis for catechol-specific recruitment of β-arrestin to D1Rs.

  15. A Small Molecule Agonist of EphA2 Receptor Tyrosine Kinase Inhibits Tumor Cell Migration In Vitro and Prostate Cancer Metastasis In Vivo

    PubMed Central

    Guo, Hong; Miao, Hui; Tochtrop, Gregory P.; Hsieh, Jer-Tsong; Page, Phillip; Liu, Lili; Lindner, Daniel J.; Acharya, Chayan; MacKerell, Alexander D.; Ficker, Eckhard; Song, Jianxing; Wang, Bingcheng

    2012-01-01

    During tumor progression, EphA2 receptor can gain ligand-independent pro-oncogenic functions due to Akt activation and reduced ephrin-A ligand engagement. The effects can be reversed by ligand stimulation, which triggers the intrinsic tumor suppressive signaling pathways of EphA2 including inhibition of PI3/Akt and Ras/ERK pathways. These observations argue for development of small molecule agonists for EphA2 as potential tumor intervention agents. Through virtual screening and cell-based assays, we report here the identification and characterization of doxazosin as a novel small molecule agonist for EphA2 and EphA4, but not for other Eph receptors tested. NMR studies revealed extensive contacts of doxazosin with EphA2/A4, recapitulating both hydrophobic and electrostatic interactions recently found in the EphA2/ephrin-A1 complex. Clinically used as an α1-adrenoreceptor antagonist (Cardura®) for treating hypertension and benign prostate hyperplasia, doxazosin activated EphA2 independent of α1-adrenoreceptor. Similar to ephrin-A1, doxazosin inhibited Akt and ERK kinase activities in an EphA2-dependent manner. Treatment with doxazosin triggered EphA2 receptor internalization, and suppressed haptotactic and chemotactic migration of prostate cancer, breast cancer, and glioma cells. Moreover, in an orthotopic xenograft model, doxazosin reduced distal metastasis of human prostate cancer cells and prolonged survival in recipient mice. To our knowledge, doxazosin is the first small molecule agonist of a receptor tyrosine kinase that is capable of inhibiting malignant behaviors in vitro and in vivo. PMID:22916121

  16. Simultaneous Identification and Quantification of 20 β-Receptor Agonists in Feed Using Gas Chromatography-Tandem Mass Spectrometry

    PubMed Central

    Cheng, Jie; Wang, Shi; Su, Xiao-Ou

    2013-01-01

    “Lean meat powder” is a class of toxic chemicals that have structures similar to that of β-adrenergic receptor agonists. At least 16 chemicals from this class have been specifically banned by the 176th bulletin of the Chinese Department of Agriculture on breeding animals, and methods for monitoring the illicit use of β-agonists in animal feed are required. Herein, a method to quantify 20 β-agonists in feed, via analyte derivatization followed by gas chromatography-tandem mass spectrometry, has been developed. The optimized method has a good linear correlation (calibration coefficient > 0.99) between the quantitative ion peak area and the concentration of β-agonists over a large working range (0.05–1 mg/kg). The limit of detection (LOD) was 0.01 mg/kg, the recoveries for three β-agonists spikes (0.05, 0.1, and 1 µg/g) in feed ranged from 75.6 to 102.4%, repeatability ranged from 1.2 to 9.4% for all of the compounds, and intermediate precisions were lower than 13.8%. This precise, accurate method was applied to quantify 20 β-agonists in actual feed samples and represents an excellent complement to existing quantification methods. PMID:24098489

  17. Translational Pharmacology of the Metabotropic Glutamate 2 Receptor-Preferring Agonist LY2812223 in the Animal and Human Brain.

    PubMed

    Felder, Christian C; Schober, Douglas A; Tu, Yuan; Quets, Anne; Xiao, Hongling; Watt, Marla; Siuda, Ed; Nisenbaum, Eric; Xiang, Chuanxi; Heinz, Beverly; Prieto, Lourdes; McKinzie, David L; Monn, James A

    2017-04-01

    LY2812223 [(1 R ,2 S ,4 R ,5 R ,6 R )-2-amino-4-(1 H -1,2,4-triazol-3-ylsulfanyl)bicyclo[3.1.0]hexane-2,6-dicarboxylic acid] was identified via structure-activity studies arising from the potent metabotropic glutamate mGlu2/3 receptor agonist LY354740 [(+)-2-aminobicyclo[3.1.0] hexane-2,6-dicarboxylic acid] as an mGlu2-preferring agonist. This pharmacology was determined using stably transfected cells containing either the human mGlu2 or mGlu3 receptor. We extended the pharmacological evaluation of LY2812223 to native brain tissues derived from relevant species used for preclinical drug development as well as human postmortem brain tissue. This analysis was conducted to ensure pharmacological translation from animals to human subjects in subsequent clinical studies. A guanosine 5'- O -(3-[ 35 S]thio)triphosphate (GTP γ S) functional binding assay, a method for measuring G i -coupled signaling that is inherent to the group 2 mGlu receptors, was used to evaluate LY2812223 pharmacology of native mGlu receptors in mouse, rat, nonhuman primate, and human cortical brain tissue samples. In native tissue membranes, LY2812223 unexpectedly acted as a partial agonist across all species tested. Activity of LY2812223 was lost in cortical membranes collected from mGlu2 knockout mice, but not those from mGlu3 knockout mice, providing additional support for mGlu2-preferring activity. Other signal transduction assays were used for comparison with the GTP binding assay (cAMP, calcium mobilization, and dynamic mass redistribution). In ectopic cell line-based assays, LY2812223 displayed near maximal agonist responses at the mGlu2 receptor across all assay formats, while it showed no functional agonist activity at the mGlu3 receptor except in the cAMP assay. In native brain slices or membranes that express both mGlu2 and mGlu3 receptors, LY2812223 displayed unexpected partial agonist activity, which may suggest a functional interplay between these receptor subtypes in the brain

  18. Adaptability and selectivity of human peroxisome proliferator-activated receptor (PPAR) pan agonists revealed from crystal structures

    SciTech Connect

    Oyama, Takuji; Toyota, Kenji; Waku, Tsuyoshi

    2009-08-01

    The structures of the ligand-binding domains (LBDs) of human peroxisome proliferator-activated receptors (PPARα, PPARγ and PPARδ) in complexes with a pan agonist, an α/δ dual agonist and a PPARδ-specific agonist were determined. The results explain how each ligand is recognized by the PPAR LBDs at an atomic level. Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear hormone receptor family, which is defined as transcriptional factors that are activated by the binding of ligands to their ligand-binding domains (LBDs). Although the three PPAR subtypes display different tissue distribution patterns and distinct pharmacological profiles, they all are essentially related to fatty-acid andmore » glucose metabolism. Since the PPARs share similar three-dimensional structures within the LBDs, synthetic ligands which simultaneously activate two or all of the PPARs could be potent candidates in terms of drugs for the treatment of abnormal metabolic homeostasis. The structures of several PPAR LBDs were determined in complex with synthetic ligands, derivatives of 3-(4-alkoxyphenyl)propanoic acid, which exhibit unique agonistic activities. The PPARα and PPARγ LBDs were complexed with the same pan agonist, TIPP-703, which activates all three PPARs and their crystal structures were determined. The two LBD–ligand complex structures revealed how the pan agonist is adapted to the similar, but significantly different, ligand-binding pockets of the PPARs. The structures of the PPARδ LBD in complex with an α/δ-selective ligand, TIPP-401, and with a related δ-specific ligand, TIPP-204, were also determined. The comparison between the two PPARδ complexes revealed how each ligand exhibits either a ‘dual selective’ or ‘single specific’ binding mode.« less

  19. Potent interleukin 3 receptor agonist with selectively enhanced hematopoietic activity relative to recombinant human interleukin 3.

    PubMed Central

    Thomas, J W; Baum, C M; Hood, W F; Klein, B; Monahan, J B; Paik, K; Staten, N; Abrams, M; McKearn, J P

    1995-01-01

    A systematic evaluation of structure-activity information led to the construction of genetically engineered interleukin 3 (IL-3) receptor agonists (synthokines) with enhanced hematopoietic potency. SC-55494, the most extensively characterized member of this series, exhibits 10- to 20-fold greater biological activity than recombinant human IL-3 (rhIL-3) in human hematopoietic cell proliferation and marrow colony-forming-unit assays. In contrast, SC-55494 is only twice as active as rhIL-3 in priming the synthesis of inflammatory mediators such as leukotriene C4 and triggering the release of histamine from peripheral blood leukocytes. The enhanced hematopoietic activity of SC-55494 correlates with a 60-fold increase in IL-3 alpha-subunit binding affinity and a 20-fold greater affinity for binding to alpha/beta receptor complexes on intact cells relative to rhIL-3. SC-55494 demonstrates a 5- to 10-fold enhanced hematopoietic response relative to its ability to activate the priming and release of inflammatory mediators. Therefore, SC-55494 may ameliorate the myeloablation of cancer therapeutic regimens while minimizing dose-limiting inflammatory side effects. PMID:7537376

  20. Potent interleukin 3 receptor agonist with selectively enhanced hematopoietic activity relative to recombinant human interleukin 3.

    PubMed

    Thomas, J W; Baum, C M; Hood, W F; Klein, B; Monahan, J B; Paik, K; Staten, N; Abrams, M; McKearn, J P

    1995-04-25

    A systematic evaluation of structure-activity information led to the construction of genetically engineered interleukin 3 (IL-3) receptor agonists (synthokines) with enhanced hematopoietic potency. SC-55494, the most extensively characterized member of this series, exhibits 10- to 20-fold greater biological activity than recombinant human IL-3 (rhIL-3) in human hematopoietic cell proliferation and marrow colony-forming-unit assays. In contrast, SC-55494 is only twice as active as rhIL-3 in priming the synthesis of inflammatory mediators such as leukotriene C4 and triggering the release of histamine from peripheral blood leukocytes. The enhanced hematopoietic activity of SC-55494 correlates with a 60-fold increase in IL-3 alpha-subunit binding affinity and a 20-fold greater affinity for binding to alpha/beta receptor complexes on intact cells relative to rhIL-3. SC-55494 demonstrates a 5- to 10-fold enhanced hematopoietic response relative to its ability to activate the priming and release of inflammatory mediators. Therefore, SC-55494 may ameliorate the myeloablation of cancer therapeutic regimens while minimizing dose-limiting inflammatory side effects.