Long-Acting β2-Agonists in Asthma: Enantioselective Safety Studies are Needed.

PubMed

Jacobson, Glenn A; Raidal, Sharanne; Hostrup, Morten; Calzetta, Luigino; Wood-Baker, Richard; Farber, Mark O; Page, Clive P; Walters, E Haydn

2018-05-01

Long-acting β2-agonists (LABAs) such as formoterol and salmeterol are used for prolonged bronchodilatation in asthma, usually in combination with inhaled corticosteroids (ICSs). Unexplained paradoxical asthma exacerbations and deaths have been associated with LABAs, particularly when used without ICS. LABAs clearly demonstrate effective bronchodilatation and steroid-sparing activity, but long-term treatment can lead to tolerance of their bronchodilator effects. There are also concerns with regard to the effects of LABAs on bronchial hyperresponsiveness (BHR), where long-term use is associated with increased BHR and loss of bronchoprotection. A complicating factor is that formoterol and salmeterol are both chiral compounds, usually administered as 50:50 racemic (rac-) mixtures of two enantiomers. The chiral nature of these compounds has been largely forgotten in the debate regarding LABA safety and effects on BHR, particularly that (S)-enantiomers of β2-agonists may be deleterious to asthma control. LABAs display enantioselective pharmacokinetics and pharmacodynamics. Biological plausibility of the deleterious effects of β2-agonists (S)-enantiomers is provided by in vitro and in vivo studies from the short-acting β2-agonist (SABA) salbutamol. Supportive clinical findings include the fact that patients in emergency departments who demonstrate a blunted response to salbutamol are more likely to benefit from (R)-salbutamol than rac-salbutamol, and resistance to salbutamol appears to be a contributory mechanism in rapid asthma deaths. More effort should therefore be applied to investigating potential enantiospecific effects of LABAs on safety, specifically bronchoprotection. Safety studies directly assessing the effects of LABA (S)-enantiomers on BHR are long overdue.

Alpha 2-adrenoceptor blockade, pituitary-adrenal hormones, and agonistic interactions in rats.

PubMed

Haller, J; Barna, I; Kovács, J L

1994-08-01

The effects of adrenergic activation on aggressiveness and the aggression induced endocrine changes were tested in rats. Alpha 2 adrenoceptor blockers were used for enhancing activation of the adrenergic system, and changes in aggressiveness were tested in resident-intruder contests. Three experiments were conducted. In experiment 1, saline injected rats responded to the presence of an opponent by aggression and the increase in plasma ACTH and corticosterone. Intraperitoneal administration of 1 mg/kg CH-38083 (an alpha 2 adrenoceptor antagonist) produced a several fold increase in clinch fighting and mutual upright scores, and also further enhanced the plasma ACTH and corticosterone response. In experiment 2, the effect of three doses (0.5, 1 and 2 mg/kg) of three different alpha 2 adrenoceptor blockers CH-38083, idazoxan and yohimbine were tested. All the substances increased aggression at 0.5 and 1 mg/kg; at 2 mg/kg the effect of idazoxan and yohimbine disappeared, while with CH-38083 an additional increase was obtained. In yohimbine treated animals the enhancement of aggression was reduced already at 1 mg/kg. In experiment 3, indomethacin, a potent inhibitor of the catecholamine-induced ACTH release completely abolished the effects of the alpha 2 adrenoceptor antagonist CH-38083: the intensity of agonistic interactions, as well as ACTH and corticosterone plasma concentrations, returned to control levels. The possible role of catecholamines and the stress hormones in the activation of aggression is discussed.

Adverse reactions of α2-adrenoceptor agonists in cats reported in 2003-2013 in Finland.

PubMed

Raekallio, Marja R; Virtanen, Marika; Happonen, Irmeli; Vainio, Outi M

2017-07-01

To describe suspected adverse drug reactions in cats associated with use of α 2 -adrenoceptor agonists. Retrospective study. A total of 90 cats. Data were collected from reports on adverse reactions to veterinary medicines sent to the Finnish Medicines Agency during 2003-2013. All reports of suspected adverse reactions associated with use of α 2 -adrenoceptor agonists in cats were included. Probable pulmonary oedema was diagnosed based on post mortem or radiological examination, or presence of frothy or excess fluid from the nostrils or trachea. If only dyspnoea and crackles on auscultation were reported, possible pulmonary oedema was presumed. Pulmonary oedema was suspected in 61 cases. Of these cats, 37 were categorised as probable and 24 as possible pulmonary oedema. The first clinical signs had been noted between 1 minute and 2 days (median, 15 minutes) after α 2 -adrenoceptor agonist administration. Many cats probably had no intravenous overhydration when the first clinical signs were detected, as either they presumably had no intravenous cannula or the signs appeared before, during or immediately after cannulation. Of the 61 cats, 43 survived, 14 died and for four the outcome was not clearly stated. Pulmonary oedema is a perilous condition that may appear within minutes of an intramuscular administration of sedative or anaesthetic agent in cats. The symptoms were not caused by intravenous overhydration, at least in cats having no venous cannula when the first clinical signs were detected. Copyright © 2017 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.

β2-adrenoceptor-induced modulation of transglutaminase 2 transamidase activity in cardiomyoblasts.

PubMed

Vyas, Falguni S; Nelson, Carl P; Freeman, Fiona; Boocock, David J; Hargreaves, Alan J; Dickenson, John M

2017-10-15

Tissue transglutaminase 2 (TG2) is modulated by protein kinase A (PKA) mediated phosphorylation: however, the precise mechanism(s) of its modulation by G-protein coupled receptors coupled to PKA activation are not fully understood. In the current study we investigated the potential regulation of TG2 activity by the β 2 -adrenoceptor in rat H9c2 cardiomyoblasts. Transglutaminase transamidation activity was assessed using amine-incorporating and protein cross-linking assays. TG2 phosphorylation was determined via immunoprecipitation and Western blotting. The long acting β 2 -adrenoceptor agonist formoterol induced time- and concentration-dependent increases in TG2 transamidation. Increases in TG2 activity were reduced by the TG2 inhibitors Z-DON (Benzyloxycarbonyl-(6-Diazo-5-oxonorleucinyl)-L-valinyl-L-prolinyl-L-leucinmethylester) and R283 ((1,3,dimethyl-2[2-oxo-propyl]thio)imidazole chloride). Responses to formoterol were blocked by pharmacological inhibition of PKA, extracellular signal-regulated kinase 1 and 2 (ERK1/2), or phosphatidylinositol 3-kinase (PI-3K) signalling. Furthermore, the removal of extracellular Ca 2+ also attenuated formoterol-induced TG2 activation. Fluorescence microscopy demonstrated TG2-induced biotin-X-cadaverine incorporation into proteins. Formoterol increased the levels of TG2-associated phosphoserine and phosphothreonine, which were blocked by inhibition of PKA, ERK1/2 or PI-3K signalling. Subsequent proteomic analysis identified known (e.g. lactate dehydrogenase A chain) and novel (e.g. Protein S100-A6) protein substrates for TG2. Taken together, the data obtained suggest that β 2 -adrenoceptor-induced modulation of TG2 represents a novel paradigm in β 2 -adrenoceptor cell signalling, expanding the repertoire of cellular functions responsive to catecholamine stimulation. Copyright © 2017 Elsevier B.V. All rights reserved.

Distribution and types of adrenoceptors in the guinea-pig ileum: the action of α-and β-adrenoceptor agonists

PubMed Central

Bauer, V.

1981-01-01

1 Segments of guinea-pig ileum and the myenteric plexus-longitudinal smooth muscle preparation were used for a study of the actions of adrenaline, noradrenaline, isoprenaline, ephedrine and phenylephrine on the responses of coaxially stimulated ileum at different distances from the ileocaecal valve. 2 The responses of the ileum to electrical stimulation were suppressed by adrenaline, nonadrenaline and ephedrine, while phenylephrine and isoprenaline inhibited them only partially. 3 The twitch inhibition elicited by these adrenoceptor agonists was the same at all distances from the ileocaecal valve. There was no significant difference between their cumulative and non-cumulative concentration-response curves. 4 Smooth muscle relaxation was induced only by isoprenaline and contraction only by phenylephrine at all distances from the ileocaecal junction. Adrenaline and noradrenaline evoked smooth muscle contraction in the terminal (0 to 20 cm), a concentration-dependent, biphasic response in the intermediate part (21 to 50 cm) and a relaxation in the proximal ileum (> 50 cm from the ilecocaecal valve). Ephedrine did not change significantly the smooth muscle tension in the terminal and the intermediate segments and induced smooth muscle relaxation in the proximal ones. 5 Ouabain and a potassium-free solution did not appear to influence the prejunctional action of noradrenaline nor the amplitude of smooth muscle relaxation in the proximal ileum, whereas the concentration-contractor response curves were significantly depressed and shifted to the right by ouabain and in a potassium-free solution. 6 The brief initial (phasic) contraction induced by acetylcholine was not influenced during the sustained increase or decrease in tension induced by catecholamines. On the contrary, the stimulatory catecholamine actions disappeared or were changed to smooth muscle relaxation by acetylcholine pretreatment. Potassium chloride pretreatment did not change the character of the

Stereochemistry of an agonist determines coupling preference of beta2-adrenoceptor to different G proteins in cardiomyocytes.

PubMed

Woo, Anthony Yiu-Ho; Wang, Tian-Bing; Zeng, Xiaokun; Zhu, Weizhong; Abernethy, Darrell R; Wainer, Irving W; Xiao, Rui-Ping

2009-01-01

A fundamental question regarding receptor-G protein interaction is whether different agonists can lead a receptor to different intracellular signaling pathways. Our previous studies have demonstrated that although most beta(2)-adrenoceptor agonists activate both G(s) and G(i) proteins, fenoterol, a full agonist of beta(2)-adrenoceptor, selectively activates G(s) protein. Fenoterol contains two chiral centers and may exist as four stereoisomers. We have synthesized a series of stereoisomers of fenoterol and its derivatives and characterized their receptor binding and pharmacological properties. We tested the hypothesis that the stereochemistry of an agonist determines selectivity of receptor coupling to different G protein(s). We found that the R,R isomers of fenoterol and methoxyfenoterol exhibited more potent effects to increase cardiomyocyte contraction than their S,R isomers. It is noteworthy that although (R,R)-fenoterol and (R,R)-methoxyfenoterol preferentially activate G(s) signaling, their S,R isomers were able to activate both G(s) and G(i) proteins as evidenced by the robust pertussis toxin sensitivities of their effects on cardiomyocyte contraction and on phosphorylation of extracellular signal-regulated kinase 1/2. The differential G protein selectivities of the fenoterol stereoisomers were further confirmed by photoaffinity labeling studies on G(s),G(i2), and G(i3) proteins. The inefficient G(i) signaling with the R,R isomers is not caused by the inability of the R,R isomers to trigger the protein kinase A (PKA)-mediated phosphorylation of the beta(2)-adrenoceptor, because the R,R isomers also markedly increased phosphorylation of the receptor at serine 262 by PKA. We conclude that in addition to receptor subtype and phosphorylation status, the stereochemistry of a given agonist plays an important role in determining receptor-G protein selectivity and downstream signaling events.

Evidence for alpha 2-adrenoceptor agonist activity of minoxidil.

PubMed

Sharma, N; Mehta, A A; Santani, D D; Goyal, R K

1997-09-01

The present investigation was undertaken to study the mechanism of action of minoxidil using various smooth muscle preparations. Minoxidil (4.7 x 10(-6) M to 4.7 x 10(-4) M) produced a concentration-dependent inhibition of field stimulation-evoked responses in rat anococcygeus muscle and vas deferens. The inhibition produced by minoxidil was antagonized by yohimbine (2.5 x 10(-7) M). Minoxidil (1.4 x 10(-5) M to 4.7 x 10(-4) M) also produced a concentration-dependent relaxation in oestrogen-primed potassium chloride-depolarized rat uterus. These responses were blocked not only by yohimbine but also by glibenclamide (2.02 x 10(-8) M). Our results suggest that minoxidil possesses alpha 2-adrenoceptor agonist activity in addition to potassium-channel-opening activity.

Role of alpha2C-adrenoceptor subtype in spatial working memory as revealed by mice with targeted disruption of the alpha2C-adrenoceptor gene.

PubMed

Tanila, H; Mustonen, K; Sallinen, J; Scheinin, M; Riekkinen, P

1999-02-01

The role of the alpha2C-adrenoceptor subtype in mediating the beneficial effect of alpha2-adrenoceptor agonists on spatial working memory was studied in adult mice with targeted inactivation of the alpha2C-receptor gene (KO) and their wild-type controls (WT). A delayed alternation task was run in a T-maze with mixed delays varying from 20 s to 120 s. Dexmedetomidine, a specific but subtype nonselective alpha2-adrenoceptor agonist, dose-dependently decreased the total number of errors. The effect was strongest at the dose of 5 microg/kg (s.c.), and was observed similarly in KO and WT mice. KO mice performed inferior to WT mice due to a higher number of perseverative errors. Dexmedetomidine slowed initiation of the motor response in the start phase at lower doses in WT mice than in KO mice but no such difference was observed in the return phase of the task, suggesting involvement of alpha2C-adrenoceptors in the cognitive aspect of response preparation or in response sequence initiation. According to these findings, enhancement of spatial working memory is best achieved with alpha2-adrenoceptor agonists which have neither agonistic nor antagonistic effects at the alpha2C-adrenoceptor subtype.

Inhibition by fenoterol of human eosinophil functions including beta2-adrenoceptor-independent actions.

PubMed

Tachibana, A; Kato, M; Kimura, H; Fujiu, T; Suzuki, M; Morikawa, A

2002-12-01

Agonists at beta2 adrenoceptors are used widely as bronchodilators in treating bronchial asthma. These agents also may have important anti-inflammatory effects on eosinophils in asthma. We examined whether widely prescribed beta2-adrenoceptor agonists differ in ability to suppress stimulus-induced eosinophil effector functions such as superoxide anion (O2-) generation and degranulation. To examine involvement of cellular adhesion in such responses, we also investigated effects of beta2 agonists on cellular adhesion and on CD11b expression by human eosinophils. O2- was measured using chemiluminescence. Eosinophil degranulation and adhesion were assessed by a radioimmunoassay for eosinophil protein X (EPX). CD11b expression was measured by flow cytometry. Fenoterol inhibited platelet-activating factor (PAF)-induced O2- generation by eosinophils significantly more than salbutamol or procaterol. Fenoterol partially inhibited PAF-induced degranulation by eosinophils similarly to salbutamol or procaterol. Fenoterol inhibited phorbol myristate acetate (PMA)-induced O2- generation and degranulation by eosinophils, while salbutamol or procaterol did not. Fenoterol inhibition of PMA-induced O2- generation was not reversed by ICI-118551, a selective beta2-adrenoceptor antagonist. Fenoterol, but not salbutamol or procaterol, significantly inhibited PAF-induced eosinophil adhesion. Fenoterol inhibited O2- generation and degranulation more effectively than salbutamol or procaterol; these effects may include a component involving cellular adhesion. Inhibition also might include a component not mediated via beta2 adrenoceptors.

Epinephrine increases contextual learning through activation of peripheral β2-adrenoceptors.

PubMed

Alves, Ester; Lukoyanov, Nikolay; Serrão, Paula; Moura, Daniel; Moreira-Rodrigues, Mónica

2016-06-01

Phenylethanolamine-N-methyltransferase knockout (Pnmt-KO) mice are unable to synthesize epinephrine and display reduced contextual fear. However, the precise mechanism responsible for impaired contextual fear learning in these mice is unknown. Our aim was to study the mechanism of epinephrine-dependent contextual learning. Wild-type (WT) or Pnmt-KO (129x1/SvJ) mice were submitted to a fear conditioning test either in the absence or in the presence of epinephrine, isoprenaline (non-selective β-adrenoceptor agonist), fenoterol (selective β2-adrenoceptor agonist), epinephrine plus sotalol (non-selective β-adrenoceptor antagonist), and dobutamine (selective β1-adrenoceptor agonist). Catecholamines were separated by reverse-phase HPLC and quantified by electrochemical detection. Blood glucose was measured by coulometry. Re-exposure to shock context induced higher freezing in WT and Pnmt-KO mice treated with epinephrine and fenoterol than in mice treated with vehicle. In addition, freezing response in Pnmt-KO mice was much lower than in WT mice. Freezing induced by epinephrine was blocked by sotalol in Pnmt-KO mice. Epinephrine and fenoterol treatment restored glycemic response in Pnmt-KO mice. Re-exposure to shock context did not induce a significant difference in freezing in Pnmt-KO mice treated with dobutamine and vehicle. Aversive memories are best retained if moderately high plasma epinephrine concentrations occur at the same moment as the aversive stimulus. In addition, epinephrine increases context fear learning by acting on peripheral β2-adrenoceptors, which may induce high levels of blood glucose. Since glucose crosses the blood-brain barrier, it may enhance hippocampal-dependent contextual learning.

Inhibition by fenoterol of human eosinophil functions including β2-adrenoceptor-independent actions

PubMed Central

TACHIBANA, A; KATO, M; KIMURA, H; FUJIU, T; SUZUKI, M; MORIKAWA, A

2002-01-01

Agonists at β2 adrenoceptors are used widely as bronchodilators in treating bronchial asthma. These agents also may have important anti-inflammatory effects on eosinophils in asthma. We examined whether widely prescribed β2-adrenoceptor agonists differ in ability to suppress stimulus-induced eosinophil effector functions such as superoxide anion (O2−) generation and degranulation. To examine involvement of cellular adhesion in such responses, we also investigated effects of β2 agonists on cellular adhesion and on CD11b expression by human eosinophils. O2− was measured using chemiluminescence. Eosinophil degranulation and adhesion were assessed by a radioimmunoassay for eosinophil protein X (EPX). CD11b expression was measured by flow cytometry. Fenoterol inhibited platelet-activating factor (PAF)-induced O2− generation by eosinophils significantly more than salbutamol or procaterol. Fenoterol partially inhibited PAF-induced degranulation by eosinophils similarly to salbutamol or procaterol. Fenoterol inhibited phorbol myristate acetate (PMA)-induced O2− generation and degranulation by eosinophils, while salbutamol or procaterol did not. Fenoterol inhibition of PMA-induced O2− generation was not reversed by ICI-118551, a selective β2-adrenoceptor antagonist. Fenoterol, but not salbutamol or procaterol, significantly inhibited PAF-induced eosinophil adhesion. Fenoterol inhibited O2− generation and degranulation more effectively than salbutamol or procaterol; these effects may include a component involving cellular adhesion. Inhibition also might include a component not mediated via β2 adrenoceptors. PMID:12452831

Influenza A virus infection and cigarette smoke impair bronchodilator responsiveness to β-adrenoceptor agonists in mouse lung.

PubMed

Donovan, Chantal; Seow, Huei Jiunn; Bourke, Jane E; Vlahos, Ross

2016-05-01

β2-adrenoceptor agonists are the mainstay therapy for patients with asthma but their effectiveness in cigarette smoke (CS)-induced lung disease such as chronic obstructive pulmonary disease (COPD) is limited. In addition, bronchodilator efficacy of β2-adrenoceptor agonists is decreased during acute exacerbations of COPD (AECOPD), caused by respiratory viruses including influenza A. Therefore, the aim of the present study was to assess the effects of the β2-adrenoceptor agonist salbutamol (SALB) on small airway reactivity using mouse precision cut lung slices (PCLS) prepared from CS-exposed mice and from CS-exposed mice treated with influenza A virus (Mem71, H3N1). CS exposure alone reduced SALB potency and efficacy associated with decreased β2-adrenoceptor mRNA expression, and increased tumour necrosis factor α (TNFα) and interleukin-1β (IL-1β) expression. This impaired relaxation was restored by day 12 in the absence of further CS exposure. In PCLS prepared after Mem71 infection alone, responses to SALB were transient and were not well maintained. CS exposure prior to Mem71 infection almost completely abolished relaxation, although β2-adrenoceptor and TNFα and IL-1β expression were unaltered. The present study has shown decreased sensitivity to SALB after CS or a combination of CS and Mem71 occurs by different mechanisms. In addition, the PCLS technique and our models of CS and influenza infection provide a novel setting for assessment of alternative bronchodilators. © 2016 The Author(s).

Comparative 3D QSAR study on β1-, β2-, and β3-adrenoceptor agonists

PubMed Central

Senthil Kumar, P.

2009-01-01

A quantitative structure–activity relationship study of tryptamine-based derivatives of β1-, β2-, and β3-adrenoceptor agonists was conducted using comparative molecular field analysis (CoMFA). Correlation coefficients (cross-validated r2) of 0.578, 0.595, and 0.558 were obtained for the three subtypes, respectively, in three different CoMFA models. All three CoMFA models have different steric and electrostatic contributions, implying different requirements inside the binding cavity. The CoMFA coefficient contour plots of the three models and comparisons among these plots provide clues regarding the main chemical features responsible for the biological activity variations and also result in predictions which correlate very well with the observed biological activity. Based on the analysis, a summary regeospecific description of the requirements for improving β-adrenoceptor subtype selectivity is given. PMID:21170122

The β3 -adrenoceptor agonist mirabegron increases human atrial force through β1 -adrenoceptors: an indirect mechanism?

PubMed

Mo, Weilan; Michel, Martin C; Lee, Xiang Wen; Kaumann, Alberto J; Molenaar, Peter

2017-08-01

Mirabegron has been classified as a β 3 -adrenoceptor agonist approved for overactive bladder syndrome. We investigated possible cardiac effects of mirabegron in the absence or presence of β-adrenoceptor subtype antagonists. In view of its phenylethanolamine structure, we investigated whether mirabegron has indirect sympathomimetic activity by using neuronal uptake blockers. Right atrial trabeculae, from non-failing hearts, were paced and contractile force measured at 37°C. Single concentrations of mirabegron were added in the absence or presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), β 3 (L-748,337), β 1 (CGP 20712A), β 2 (ICI 118,551) -adrenoceptor antagonists, neuronal uptake inhibitors desipramine or phenoxybenzamine. Mirabegron significantly increased contractile force in human right atrium (1 μM, 7.6 ± 2.6%, n = 7; 10 μM, 10.2 ± 1.5%, n = 22 compared with (-)-isoprenaline P < 0.05). In the presence of IBMX, mirabegron (10 μM) caused a greater contraction. L-748,337 (100 nM) had no effect on the increase in contractile force caused by mirabegron (10 μM). In contrast, mirabegron (10 μM) reduced contractile force in the presence of CGP 20712A, which was not affected by L-748,337 (100 nM) or ICI 118,551 (50 nM). Mirabegron (10 μM) also reduced contractile force in the presence of desipramine or phenoxybenzamine. Mirabegron increases human atrial force through β 1 - but not β 3 -adrenoceptors. Desipramine and phenoxybenzamine block neuronal uptake and conceivably prevent mirabegron from releasing noradrenaline. A non-specific cardiodepressant effect is not mediated through β 3 (or β 2 )-adrenoceptors, consistent with lack of β 3 -adrenoceptor function on human atrial contractility. © 2017 The British Pharmacological Society.

Beta2-adrenoceptor agonist fenoterol enhances functional repair of regenerating rat skeletal muscle after injury.

PubMed

Beitzel, Felice; Gregorevic, Paul; Ryall, James G; Plant, David R; Sillence, Martin N; Lynch, Gordon S

2004-04-01

Beta(2)-adrenoceptor agonists such as fenoterol are anabolic in skeletal muscle, and because they promote hypertrophy and improve force-producing capacity, they have potential application for enhancing muscle repair after injury. No previous studies have measured the beta(2)-adrenoceptor population in regenerating skeletal muscle or determined whether fenoterol can improve functional recovery in regenerating muscle after myotoxic injury. In the present study, the extensor digitorum longus (EDL) muscle of the right hindlimb of deeply anesthetized rats was injected with bupivacaine hydrochloride, which caused complete degeneration of all muscle fibers. The EDL muscle of the left hindlimb served as the uninjured control. Rats received either fenoterol (1.4 mg x kg(-1) x day(-1)) or an equal volume of saline for 2, 7, 14, or 21 days. Radioligand binding assays identified a approximately 3.5-fold increase in beta(2)-adrenoceptor density in regenerating muscle at 2 days postinjury. Isometric contractile properties of rat EDL muscles were measured in vitro. At 14 and 21 days postinjury, maximum force production (P(o)) of injured muscles from fenoterol-treated rats was 19 and 18% greater than from saline-treated rats, respectively, indicating more rapid restoration of function after injury. The increase in P(o) in fenoterol-treated rats was due to increases in muscle mass, fiber cross-sectional area, and protein content. These findings suggest a physiological role for beta(2)-adrenoceptor-mediated mechanisms in muscle regeneration and show clearly that fenoterol hastens recovery after injury, indicating its potential therapeutic application.

The β2 agonist terbutaline specifically decreases pulmonary arterial pressure under normoxia and hypoxia via α adrenoceptor antagonism.

PubMed

Neumann, Vanessa; Knies, Ralf; Seidinger, Alexander; Simon, Annika; Lorenz, Kristina; Matthey, Michaela; Breuer, Johannes; Wenzel, Daniela

2018-05-01

Pulmonary hypertension is a severe, incurable disease with a poor prognosis. Although treatment regimens have improved during the last 2 decades, current pharmacologic strategies are limited and focus on the modulation of only a few pathways related to endothelin, NO, and prostacyclin signaling. Therefore, the identification of novel molecular targets is urgently needed. We found that the β 2 adrenoceptor (AR) agonists terbutaline (TER) and salbutamol induced a dose-dependent vasorelaxation in large pulmonary arteries but not aortas of mouse. This effect was found to be independent of β ARs and the endothelium but was determined by the type of the preconstrictor. Vasodilation by β 2 AR agonists occurred after pretreatment of pulmonary arteries with phenylephrine and serotonin, both agonists of α 1 ARs, but was absent after preconstriction with the thromboxane analog U46619. These data indicated α-adrenolytic activity of β 2 AR agonists, which was confirmed by a right shift of the phenylephrine dose-response curve by TER. This effect was physiologically relevant because TER also relaxed small intrapulmonary arteries in lung slices and diminished pulmonary arterial pressure in an isolated perfused lung model under normoxia and hypoxia. Finally, TER applied as an aerosol also selectively decreased pulmonary arterial pressure without effects on systemic blood pressure and heart rate in mouse in vivo. Thus, β 2 AR agonists display α-adrenolytic activity in pulmonary arteries ex vivo and in vivo, and may provide a novel option to reduce pulmonary arterial pressure in pulmonary hypertension.-Neumann, V., Knies, R., Seidinger, A., Simon, A., Lorenz, K., Matthey, M., Breuer, J., Wenzel, D. The β 2 agonist terbutaline specifically decreases pulmonary arterial pressure under normoxia and hypoxia via α adrenoceptor antagonism.

The pharmacological rationale for combining muscarinic receptor antagonists and β-adrenoceptor agonists in the treatment of airway and bladder disease☆

PubMed Central

Dale, Philippa R; Cernecka, Hana; Schmidt, Martina; Dowling, Mark R; Charlton, Steven J; Pieper, Michael P; Michel, Martin C

2014-01-01

Muscarinic receptor antagonists and β-adrenoceptor agonists are used in the treatment of obstructive airway disease and overactive bladder syndrome. Here we review the pharmacological rationale for their combination. Muscarinic receptors and β-adrenoceptors are physiological antagonists for smooth muscle tone in airways and bladder. Muscarinic agonism may attenuate β-adrenoceptor-mediated relaxation more than other contractile stimuli. Chronic treatment with one drug class may regulate expression of the target receptor but also that of the opposing receptor. Prejunctional β2-adrenoceptors can enhance neuronal acetylcholine release. Moreover, at least in the airways, muscarinic receptors and β-adrenoceptors are expressed in different locations, indicating that only a combined modulation of both systems may cause dilatation along the entire bronchial tree. While all of these factors contribute to a rationale for a combination of muscarinic receptor antagonists and β-adrenoceptor agonists, the full value of such combination as compared to monotherapy can only be determined in clinical studies. PMID:24682092

α2A- and α2C-Adrenoceptors as Potential Targets for Dopamine and Dopamine Receptor Ligands.

PubMed

Sánchez-Soto, Marta; Casadó-Anguera, Verònica; Yano, Hideaki; Bender, Brian Joseph; Cai, Ning-Sheng; Moreno, Estefanía; Canela, Enric I; Cortés, Antoni; Meiler, Jens; Casadó, Vicent; Ferré, Sergi

2018-03-18

The poor norepinephrine innervation and high density of Gi/o-coupled α 2A - and α 2C -adrenoceptors in the striatum and the dense striatal dopamine innervation have prompted the possibility that dopamine could be an effective adrenoceptor ligand. Nevertheless, the reported adrenoceptor agonistic properties of dopamine are still inconclusive. In this study, we analyzed the binding of norepinephrine, dopamine, and several compounds reported as selective dopamine D 2 -like receptor ligands, such as the D 3 receptor agonist 7-OH-PIPAT and the D 4 receptor agonist RO-105824, to α 2 -adrenoceptors in cortical and striatal tissue, which express α 2A -adrenoceptors and both α 2A - and α 2C -adrenoceptors, respectively. The affinity of dopamine for α 2 -adrenoceptors was found to be similar to that for D 1 -like and D 2 -like receptors. Moreover, the exogenous dopamine receptor ligands also showed high affinity for α 2A - and α 2C -adrenoceptors. Their ability to activate Gi/o proteins through α 2A - and α 2C -adrenoceptors was also analyzed in transfected cells with bioluminescent resonance energy transfer techniques. The relative ligand potencies and efficacies were dependent on the Gi/o protein subtype. Furthermore, dopamine binding to α 2 -adrenoceptors was functional, inducing changes in dynamic mass redistribution, adenylyl cyclase activity, and ERK1/2 phosphorylation. Binding events were further studied with computer modeling of ligand docking. Docking of dopamine at α 2A - and α 2C -adrenoceptors was nearly identical to its binding to the crystallized D 3 receptor. Therefore, we provide conclusive evidence that α 2A - and α 2C -adrenoceptors are functional receptors for norepinephrine, dopamine, and other previously assumed selective D 2 -like receptor ligands, which calls for revisiting previous studies with those ligands.

Rilmenidine produces mydriasis in cats by stimulation of CNS alpha 2-adrenoceptors.

PubMed

Koss, M C

2003-02-01

1. Experiments were undertaken to determine if the imidazoline/alpha2-adrenoceptor agonist, rilmenidine, would produce mydriasis in cats and, if so, to delineate its site of action and determine if this effect is mediated by imidazoline receptors or alpha2-adrenoceptors. 2. Rilmenidine produced dose-related pupillary dilator responses in pentobarbital anaesthetized cats that were independent of sympathetic innervation to the iris but were dependent upon intact parasympathetic neuronal tone. The ED50 for rilmenidine-induced pupillary dilation was approximately 200 microg kg(-1), i.v., and was sustained for at least 1 h. 3. The highly selective alpha2-adrenoceptor antagonist, RS-79948, administered either before or after rilmenidine, antagonized rilmenidine-induced mydriasis. Neuronally induced reflex inhibition of parasympathetic nerve activity was also inhibited by administration of RS-79948. 4. These results suggest that rilmenidine acts like clonidine to produce pupillary dilation by inhibition of parasympathetic tone to the iris sphincter and that this central nervous system parasympatho-inhibition is mediated by alpha2-adrenoceptors, rather than imidazoline receptors.

β2-Adrenoceptors and non-β-adrenoceptors mediate effects of BRL37344 and clenbuterol on glucose uptake in soleus muscle: studies using knockout mice

PubMed Central

Ngala, Robert A; O'Dowd, Jacqueline; Wang, Steven J; Stocker, Claire; Cawthorne, Michael A; Arch, Jonathan RS

2009-01-01

Background and purpose: In previous work, 10 pM BRL37344 and 10 pM clenbuterol stimulated glucose uptake in mouse soleus muscle. Ten nM BRL37344 also stimulated uptake but 100 nM clenbuterol inhibited uptake. Antagonist studies suggested that the opposite effects of 10 nM BRL37344 and 100 nM clenbuterol are mediated by the β2-adrenoceptor. BRL37344 and clenbuterol have been studied in muscles that lack β3-, β2- or all three β-adrenoceptors. Effects of β-adrenoceptor antagonists on responses to the agonists have been studied further using muscles from wild-type mice. Experimental approach: Soleus muscles of wild-type or β-adrenoceptor knockout mice were incubated with 2-deoxy[1-14C]-glucose, and β-adrenoceptor ligands. Formation of 2-deoxy[1-14C]-glucose-6-phosphate was measured. Key results: Concentration–response relationships were similar for BRL37344 and clenbuterol in normal muscle and muscle lacking β3-adrenoceptors. Ten pM BRL37344 and clenbuterol stimulated glucose uptake in muscle lacking β2-adrenoceptors or all three β-adrenoceptors, but 10 nM BRL37344 did not stimulate uptake in either case, and 100 nM clenbuterol stimulated, rather than inhibited, uptake in muscle lacking β2-adrenoceptors. One hundred nM clenbuterol also stimulated glucose uptake in normal muscle when β2-adrenoceptors were blocked with ICI118551, and this was not prevented by antagonism of β1- or β3-adrenoceptors. Conclusions and implications: Ten nM BRL37344 and 100 nM clenbuterol have opposite effects on glucose uptake but both effects are mediated by the β2-adrenoceptor – apparently an example of agonist-directed signalling. Ten pM BRL37344, 10 pM clenbuterol and 100 nM clenbuterol in the presence of ICI118551 stimulate glucose uptake via β-adrenoceptor-independent mechanisms, demonstrating unknown properties for the agonists. PMID:19912225

Agonist-induced β2-adrenoceptor desensitization and downregulation enhance pro-inflammatory cytokine release in human bronchial epithelial cells.

PubMed

Oehme, Susanne; Mittag, Anja; Schrödl, Wieland; Tarnok, Attila; Nieber, Karen; Abraham, Getu

2015-02-01

It is not clear whether increased asthma severity associated with long-term use of β2-adrenoceptor (β2-AR) agonists can be attributed to receptor degradation and increased inflammation. We investigated the cross-talk between β-AR agonist-mediated effects on β2-AR function and expression and cytokine release in human bronchial epithelial cells. In 16HBE14o(-) cells grown in the presence and absence of β-AR agonists and/or antagonists, the β2-AR density was assessed by radioligand binding; the receptor protein and mRNA was determined using laser scanning cytometer and RT-PCR; cAMP generation, the cytokines IL-6 and IL-8 release were determined using AlphaScreen Assay and ELISA, respectively. Isoprenaline (ISO) and salbutamol (Salbu) induced a concentration- and time-dependent significant decrease in β2-AR density. Both Salbu and ISO reduced cAMP generation in a concentration-dependent manner while in same cell culture the IL-6 and IL-8 release was significantly enhanced. These effects were antagonized to a greater extent by ICI 118.551 than by propranolol, but CGP 20712A had no effect. Reduction of the β2-AR protein and mRNA could be seen when cells were treated with ISO for 24 h. Our findings indicate a direct link between cytokine release and altered β2-AR expression and function in airway epithelial cells. β2-AR desensitization and downregulation induced by long-term treatment with β2-AR agonists during asthma may account for adverse reactions also due to enhanced release of pro-inflammatory mediators and should, thus, be considered in asthma therapy. Copyright © 2014 Elsevier Ltd. All rights reserved.

β1 -Adrenoceptor, but not β2 -adrenoceptor, subtype regulates heart rate in type 2 diabetic rats in vivo.

PubMed

Cook, Rosalind F; Bussey, Carol T; Mellor, Kimberley M; Cragg, Patricia A; Lamberts, Regis R

2017-08-01

What is the central question of the study? The sympathetic system regulates heart rate via β-adrenoceptors; this is impaired during diabetes. However, the specific β-adrenoceptor subtype contributions in heart rate regulation in diabetes in vivo are unknown. What is the main finding and its importance? Telemetric recordings in conscious non-diabetic and type 2 diabetic rats demonstrated that the β 1 -adrenoceptor subtype, and not the β 2 -adrenoceptor, regulated the lower resting heart rate and increased β-adrenoceptor responsiveness in diabetes in vivo. This provides new physiological insight into the dysregulation of heart rate in type 2 diabetes, which is important for improving therapeutic strategies targeting the diabetic chronotropic incompetence. β-Adrenoceptor blockers are widely used to reduce heart rate, the strongest predictor of mortality in cardiac patients, but are less effective in diabetic patients. This study aimed to determine the specific contributions of β 1 - and β 2 -adrenoceptor subtypes to chronotropic responses in type 2 diabetes in vivo, which are currently unknown. Type 2 diabetic and non-diabetic rats were implanted with radiotelemeters to measure arterial blood pressure and derive heart rate in conscious conditions. Vascular access ports were implanted to inject isoprenaline (β 1 - and β 2 -adrenoceptor agonist, 0.1-300 μg kg -1 ) in the presence of atenolol (β 1 -adrenoceptor antagonist, 2000 μg kg -1 ) or nadolol (β 1 - and β 2 -adrenoceptor agonist, 4000 μg kg -1 ) to determine the chronotropic contributions of the β-adrenoceptor subtypes. Resting heart rate was reduced in diabetic rats (388 ± 62 versus 290 ± 37 beats min -1 non-diabetic versus diabetic, P < 0.05, mean ± SD), which remained after atenolol or nadolol administration. Overall β-adrenoceptor chronotropic responsiveness was increased in diabetic rats (change in heart rate at highest dose of isoprenaline: 135 ± 66 versus 205 ± 28�

Inhibition of basal and stimulated release of endothelin-1 from guinea pig tracheal epithelial cells in culture by beta 2-adrenoceptor agonists and cyclic AMP enhancers.

PubMed

Yang, Quan; Battistini, Bruno; Pelletier, Stéphane; Sirois, Pierre

2007-10-01

The effects of cyclic AMP-related compounds and beta adrenoceptor agonists on the basal and lipopolysaccharide (LPS)-stimulated release of endothelin-1 (ET-1) from guinea-pig tracheal epithelial cells (GPTEpCs) in culture were studied. Forskolin (a potent activator of adenylyl cyclase), 8-bromo-cyclic AMP (a cyclic AMP analogue), salbutamol and salmeterol (two beta 2-adrenoceptor agonists), were used to increase cyclic AMP levels. Cultured GPTEpCs released ET-1 continuously over a 24 h incubation period. The values reached 1,938 +/- 122 pg/mg of total cell proteins after 24 h. LPS (10 microg/ml) significantly stimulated the release of ET-1 by 1.6- to 1.8-fold, up to 1,262 +/- 56 pg/mg total cell proteins after an 8 h incubation period. Compound 8-bromo-cyclic AMP (10(-5), 10(-4) and 10(-3) M) reduced the basal release of ET-1 from GPTEpCs by up to 31% (P < 0.01) and the LPS stimulated release by up to 42% (P < 0.05), after an 8 h incubation period. Forskolin (10(-6), 10(-5) and 10(-4) M) also inhibited the basal release of ET-1 by up to 28% (P < 0.05) and LPS-stimulated release of ET-1 by up to 50% (P < 0.05), after an 8 h incubation period. At the concentration of 10(-5) M, forskolin increased cyclic AMP levels in GPTEpCs by 17-fold (P < 0.001) in the medium, 15 min after the beginning of the incubation. Salbutamol (10(-8) to 10(-6) M) had no effect on the basal production and release of ET-1 after 8 h. Conversely, this short acting beta 2-adrenoceptor agonist significantly reduced LPS-mediated increase of ET-1 production by up to 55% (P < 0.05) after an 8 h incubation period. Salmeterol (10(-9) M to 10(-5) M) inhibited basal and LPS-stimulated production and release of ET-1 after an 8 h incubation period (between 44 and 51%, P < 0.01). Both salbutamol and salmeterol (10(-6) M) increase cyclic AMP levels by five- and twofold, respectively (P < 0.05). In summary, these observations indicate that beta 2-adrenoceptor agonists or cyclic AMP enhancers can modulate both

Thermodynamics and docking of agonists to the β(2)-adrenoceptor determined using [(3)H](R,R')-4-methoxyfenoterol as the marker ligand.

PubMed

Toll, Lawrence; Pajak, Karolina; Plazinska, Anita; Jozwiak, Krzysztof; Jimenez, Lucita; Kozocas, Joseph A; Tanga, Mary J; Bupp, James E; Wainer, Irving W

2012-06-01

G protein-coupled receptors (GPCRs) are integral membrane proteins that change conformation after ligand binding so that they can transduce signals from an extracellular ligand to a variety of intracellular components. The detailed interaction of a molecule with a G protein-coupled receptor is a complicated process that is influenced by the receptor conformation, thermodynamics, and ligand conformation and stereoisomeric configuration. To better understand the molecular interactions of fenoterol analogs with the β(2)-adrenergic receptor, we developed a new agonist radioligand for binding assays. [(3)H](R,R')-methoxyfenoterol was used to probe the binding affinity for a series of fenoterol stereoisomers and derivatives. The results suggest that the radioligand binds with high affinity to an agonist conformation of the receptor, which represents approximately 25% of the total β(2)-adrenoceptor (AR) population as determined with the antagonist [(3)H]CGP-12177. The β(2)-AR agonists tested in this study have considerably higher affinity for the agonist conformation of the receptor, and K(i) values determined for fenoterol analogs model much better the cAMP activity of the β(2)-AR elicited by these ligands. The thermodynamics of binding are also different when interacting with an agonist conformation, being purely entropy-driven for each fenoterol isomer, rather than a mixture of entropy and enthalpy when the fenoterol isomers binding was determined using [(3)H]CGP-12177. Finally, computational modeling identified the molecular interactions involved in agonist binding and allow for the prediction of additional novel β(2)-AR agonists. The study underlines the possibility of using defined radioligand structure to probe a specific conformation of such shape-shifting system as the β(2)-adrenoceptor.

Thermodynamics and Docking of Agonists to the β2-Adrenoceptor Determined Using [3H](R,R′)-4-Methoxyfenoterol as the Marker Ligand

PubMed Central

Pajak, Karolina; Plazinska, Anita; Jozwiak, Krzysztof; Jimenez, Lucita; Kozocas, Joseph A.; Tanga, Mary J.; Bupp, James E.; Wainer, Irving W.

2012-01-01

G protein-coupled receptors (GPCRs) are integral membrane proteins that change conformation after ligand binding so that they can transduce signals from an extracellular ligand to a variety of intracellular components. The detailed interaction of a molecule with a G protein-coupled receptor is a complicated process that is influenced by the receptor conformation, thermodynamics, and ligand conformation and stereoisomeric configuration. To better understand the molecular interactions of fenoterol analogs with the β2-adrenergic receptor, we developed a new agonist radioligand for binding assays. [3H](R,R′)-methoxyfenoterol was used to probe the binding affinity for a series of fenoterol stereoisomers and derivatives. The results suggest that the radioligand binds with high affinity to an agonist conformation of the receptor, which represents approximately 25% of the total β2-adrenoceptor (AR) population as determined with the antagonist [3H]CGP-12177. The β2-AR agonists tested in this study have considerably higher affinity for the agonist conformation of the receptor, and Ki values determined for fenoterol analogs model much better the cAMP activity of the β2-AR elicited by these ligands. The thermodynamics of binding are also different when interacting with an agonist conformation, being purely entropy-driven for each fenoterol isomer, rather than a mixture of entropy and enthalpy when the fenoterol isomers binding was determined using [3H]CGP-12177. Finally, computational modeling identified the molecular interactions involved in agonist binding and allow for the prediction of additional novel β2-AR agonists. The study underlines the possibility of using defined radioligand structure to probe a specific conformation of such shape-shifting system as the β2-adrenoceptor. PMID:22434858

Metabolic responses to BRL37344 and clenbuterol in soleus muscle and C2C12 cells via different atypical pharmacologies and β2-adrenoceptor mechanisms

PubMed Central

Ngala, R A; O'Dowd, J; Wang, S J; Agarwal, A; Stocker, C; Cawthorne, M A; Arch, J R S

2008-01-01

Background and purpose: Picomolar concentrations of the β3-adrenoceptor agonist BRL37344 stimulate 2-deoxyglucose uptake in soleus muscle via undefined receptors. Higher concentrations alter uptake, apparently via β2-adrenoceptors. Effects of BRL37344 and β2-adrenoceptor agonists are compared. Experimental approach: Mouse soleus muscles were incubated with 2-deoxy[1-14C]-glucose, [1-14C]-palmitate or [2-14C]-pyruvate, and BRL37344, β2-adrenoceptor agonists and selective β-adrenoceptor antagonists. Formation of 2-deoxy[1-14C]-glucose-6-phosphate or 14CO2 was measured. 2-Deoxy[1-14C]-glucose uptake and β-adrenoceptor mRNA were measured in C2C12 cells. Key results: 10 pM BRL37344, 10 pM clenbuterol and 100 pM salbutamol stimulated 2-deoxyglucose uptake in soleus muscle by 33–54%. The effect of BRL37344 was prevented by 1 μM atenolol but not by 300 nM CGP20712A or IC3118551, or 1 μM SR59230A; that of clenbuterol was prevented by ICI118551 but not atenolol. 10 nM BRL37344 st4mulated 2-deoxyglucose uptake, whereas 100 nM clenbuterol and salbutamol inhibited uptake. These effects were blocked by ICI118551. Similar results were obtained in C2C12 cells, in which only β2-adrenoceptor mRNA could be detected by RT-PCR. 10 nM BRL37344 and 10 pM clenbuterol stimulated muscle palmitate oxidation. In the presence of palmitate, BRL37344 no longer stimulated 2-deoxyglucose uptake and the effect of clenbuterol was not significant. Conclusions and implications: Stimulation of glucose uptake by 10 pM BRL37344 and clenbuterol involves different atypical pharmacologies. Nanomolar concentrations of BRL37344 and clenbuterol, probably acting via β2-adrenoceptors, have opposite effects on glucose uptake. The agonists preferentially stimulate fat rather than carbohydrate oxidation, but stimulation of endogenous fat oxidation cannot explain why 100 nM clenbuterol inhibited 2-deoxyglucose uptake. PMID:18552870

Actions of alpha2 adrenoceptor ligands at alpha2A and 5-HT1A receptors: the antagonist, atipamezole, and the agonist, dexmedetomidine, are highly selective for alpha2A adrenoceptors.

PubMed

Newman-Tancredi, A; Nicolas, J P; Audinot, V; Gavaudan, S; Verrièle, L; Touzard, M; Chaput, C; Richard, N; Millan, M J

1998-08-01

This study examined the activity of chemically diverse alpha2 adrenoceptor ligands at recombinant human (h) and native rat (r) alpha2A adrenoceptors compared with 5-HT1A receptors. First, in competition binding experiments at h alpha2A and h5-HT1A receptors expressed in CHO cells, several compounds, including the antagonists 1-(2-pyrimidinyl)piperazine (1-PP), (+/-)-idazoxan, benalfocin (SKF 86466), yohimbine and RX 821,002, displayed preference for h alpha2A versus h5-HT1A receptors of only 1.4-, 3.6-, 4-, 10- and 11-fold, respectively (based on differences in pKi values). Clonidine, brimonidine (UK 14304), the benzopyrrolidine fluparoxan and the guanidines guanfacine and guanabenz exhibited intermediate selectivity (22- to 31-fold) for h alpha2A receptors. Only the antagonist atipamezole and the agonist dexmedetomidine (DMT) displayed high preference for alpha2 adrenoceptors (1290- and 91-fold, respectively). Second, the compounds were tested for their ability to induce h5-HT1A receptor-mediated G-protein activation, as indicated by the stimulation of [35S]GTPgammaS binding. All except atipamezole and RX 821,002 exhibited agonist activity, with potencies which correlated with their affinity for h5-HT1A receptors. Relative efficacies (Emax values) were 25-35% for guanabenz, guanfacine, WB 4101 and benalfocin, 50-65% for 1-PP, (+/-)-idazoxan and clonidine, and over 70% for fluparoxan, oxymetazoline and yohimbine (relative to 5-HT = 100%). Yohimbine-induced [35S]GTPgammaS binding was inhibited by the selective 5-HT1A receptor antagonist WAY 100,635. In contrast, RX 821,002 was the only ligand which exhibited antagonist activity at h5-HT1A receptors, inhibiting 5-HT-stimulated [35S]GTPgammaS binding. Atipamezole, which exhibited negligeable affinity for 5-HT1A receptors, was inactive. Third, the affinities for r alpha2A differed considerably from the affinities for h alpha2A receptors whereas the affinities for r5-HT1A differed much less from the affinities for h5-HT

Alpha2-adrenoceptor blockade accelerates the neurogenic, neurotrophic, and behavioral effects of chronic antidepressant treatment.

PubMed

Yanpallewar, Sudhirkumar U; Fernandes, Kimberly; Marathe, Swananda V; Vadodaria, Krishna C; Jhaveri, Dhanisha; Rommelfanger, Karen; Ladiwala, Uma; Jha, Shanker; Muthig, Verena; Hein, Lutz; Bartlett, Perry; Weinshenker, David; Vaidya, Vidita A

2010-01-20

Slow-onset adaptive changes that arise from sustained antidepressant treatment, such as enhanced adult hippocampal neurogenesis and increased trophic factor expression, play a key role in the behavioral effects of antidepressants. alpha(2)-Adrenoceptors contribute to the modulation of mood and are potential targets for the development of faster acting antidepressants. We investigated the influence of alpha(2)-adrenoceptors on adult hippocampal neurogenesis. Our results indicate that alpha(2)-adrenoceptor agonists, clonidine and guanabenz, decrease adult hippocampal neurogenesis through a selective effect on the proliferation, but not the survival or differentiation, of progenitors. These effects persist in dopamine beta-hydroxylase knock-out (Dbh(-/-)) mice lacking norepinephrine, supporting a role for alpha(2)-heteroceptors on progenitor cells, rather than alpha(2)-autoreceptors on noradrenergic neurons that inhibit norepinephrine release. Adult hippocampal progenitors in vitro express all the alpha(2)-adrenoceptor subtypes, and decreased neurosphere frequency and BrdU incorporation indicate direct effects of alpha(2)-adrenoceptor stimulation on progenitors. Furthermore, coadministration of the alpha(2)-adrenoceptor antagonist yohimbine with the antidepressant imipramine significantly accelerates effects on hippocampal progenitor proliferation, the morphological maturation of newborn neurons, and the increase in expression of brain derived neurotrophic factor and vascular endothelial growth factor implicated in the neurogenic and behavioral effects of antidepressants. Finally, short-duration (7 d) yohimbine and imipramine treatment results in robust behavioral responses in the novelty suppressed feeding test, which normally requires 3 weeks of treatment with classical antidepressants. Our results demonstrate that alpha(2)-adrenoceptors, expressed by progenitor cells, decrease adult hippocampal neurogenesis, while their blockade speeds up antidepressant action

α2-adrenoceptor blockade accelerates the neurogenic, neurotrophic, and behavioral effects of chronic antidepressant treatment

PubMed Central

Yanpallewar, Sudhirkumar U.; Fernandes, Kimberly; Marathe, Swananda V.; Vadodaria, Krishna C.; Jhaveri, Dhanisha; Rommelfanger, Karen; Ladiwala, Uma; Jha, Shanker; Muthig, Verena; Hein, Lutz; Bartlett, Perry; Weinshenker, David; Vaidya, Vidita A.

2010-01-01

Slow-onset adaptive changes that arise from sustained antidepressant treatment, such as enhanced adult hippocampal neurogenesis and increased trophic factor expression, play a key role in the behavioral effects of antidepressants. α2-adrenoceptors contribute to the modulation of mood and are potential targets for the development of faster acting antidepressants. We investigated the influence of α2-adrenoceptors on adult hippocampal neurogenesis. Our results indicate that α2-adrenoceptor agonists, clonidine and guanabenz, decrease adult hippocampal neurogenesis through a selective effect on the proliferation, but not the survival or differentiation, of progenitors. These effects persist in dopamine β-hydroxylase knockout (Dbh −/−) mice lacking norepinephrine, supporting a role for α2-heteroceptors on progenitor cells, rather than α2-autoreceptors on noradrenergic neurons that inhibit norepinephrine release. Adult hippocampal progenitors in vitro express all the α2-adrenoceptor subtypes, and decreased neurosphere frequency and BrdU incorporation indicate direct effects of α2-adrenoceptor stimulation on progenitors. Further, co-administration of the α2-adrenoceptor antagonist yohimbine with the antidepressant imipramine significantly accelerates effects on hippocampal progenitor proliferation, the morphological maturation of newborn neurons, and the increase in expression of brain derived neurotrophic factor and vascular endothelial growth factor implicated in the neurogenic and behavioral effects of antidepressants. Finally, short duration (7 day) yohimbine and imipramine treatment results in robust behavioral responses in the novelty suppressed feeding test, which normally requires 3 weeks of treatment with classical antidepressants. Our results demonstrate that α2-adrenoceptors, expressed by progenitor cells, decrease adult hippocampal neurogenesis, while their blockade speeds up antidepressant action, highlighting their importance as targets for

The design, synthesis and pharmacological characterization of novel β2-adrenoceptor antagonists

PubMed Central

Hothersall, J Daniel; Black, James; Caddick, Stephen; Vinter, Jeremy G; Tinker, Andrew; Baker, James R

2011-01-01

BACKGROUND AND PURPOSE Selective and potent antagonists for the β2-adrenoceptor are potentially interesting as experimental and clinical tools, and we sought to identify novel ligands with this pharmacology. EXPERIMENTAL APPROACH A range of pharmacological assays was used to assess potency, affinity, selectivity (β2-adrenoceptor vs. β1-adrenoceptor) and efficacy. KEY RESULTS Ten novel compounds were identified but none had as high affinity as the prototypical β2-adrenoceptor blocker ICI-118,551, although one of the novel compounds was more selective for β2-adrenoceptors. Most of the ligands were inverse agonists for β2-adrenoceptor-cAMP signalling, although one (5217377) was a partial agonist and another a neutral antagonist (7929193). None of the ligands were efficacious with regard to β2-adrenoceptor-β-arrestin signalling. The (2S,3S) enantiomers were identified as the most active, although unusually the racemates were the most selective for the β2-adrenoceptors. This was taken as evidence for some unusual enantiospecific behaviour. CONCLUSIONS AND IMPLICATIONS In terms of improving on the pharmacology of the ligand ICI-118,551, one of the compounds was more selective (racemic JB-175), while one was a neutral antagonist (7929193), although none had as high an affinity. The results substantiate the notion that β-blockers do more than simply inhibit receptor activation, and differences between the ligands could provide useful tools to investigate receptor biology. PMID:21323900

Homologous regulation of the α2C-adrenoceptor subtype in human hepatocarcinoma, HepG2

PubMed Central

Cayla, Cécile; Schaak, Stéphane; Roquelaine, Cyril; Gales, Céline; Quinchon, Françoise; Paris, Hervé

1999-01-01

Previous studies of the regulation of the α2C-adrenoceptor in OK and in transfected cells have led to discrepant conclusions. In the present work, we examined the homologous regulation of the human α2C-adrenoceptor in the hepatocarcinoma cell-line, HepG2; a model which expresses this subtype spontaneously.Short-period treatment of the cells with UK14304 provoked neither a diminution of the potency of the α2-agonist to inhibit forskolin-induced cyclic AMP-accumulation nor a change in the degree of receptor coupling to G-proteins.Long-period exposure to UK14304 resulted in a large reduction of [3H]MK912 binding sites (55% decrease). The action of UK14304 was dose-dependent (EC50=190±45 nM), rapid (t1/2 =4.2 h) and reversible. Receptor down-regulation was also observed with clonidine or (−)adrenaline (38 and 36% decrease, respectively) and was blocked by the addition of α2-antagonists.Conversely to that observed with α2-agonists, treatment of the cells with RX821002 or yohimbine alone, but not with phentolamine, promoted a significant increase of the receptor expression.The observed alterations of receptor density are not the reflection of changes at the α2C4 mRNA level. Estimation of the receptor protein turnover and measurement of its half-life demonstrated that down-regulation by α2-agonists and up-regulation by α2-antagonists, with inverse-agonist efficacy, are respectively the consequence of increased and decreased rate of receptor degradation.In conclusion, our data show that α2C-adrenoceptor does not undergo desensitization but is down-regulated in HepG2. The lack of desensitization agrees with previous results obtained in cells transfected with the α2C4 gene, but not with observations made in OK cells. Inversely, down-regulation fits with results obtained in OK but not in transfected cells. The reasons for these discrepancies are discussed. Our results also demonstrated that certain α2-antagonists behave as inverse agonist on the HepG2 model

ICI D7114 a novel selective beta-adrenoceptor agonist selectively stimulates brown fat and increases whole-body oxygen consumption.

PubMed Central

Holloway, B. R.; Howe, R.; Rao, B. S.; Stribling, D.; Mayers, R. M.; Briscoe, M. G.; Jackson, J. M.

1991-01-01

1. ICI D7114 is a novel, beta-adrenoceptor agonist which stimulates whole body oxygen consumption in conscious rats, cats and dogs and brown adipose tissue (BAT) activity in conscious rats. Treatment of rats with ICI D7114 stimulated oxygen consumption (ED50, 0.04 mg kg-1, p.o.) and BAT mitochondrial guanosine diphosphate (GDP)-binding (ED50, 0.15 mg kg-1, p.o.) with no chronotropic effects on the heart at these doses. 2. Reference beta-adrenoceptor agonists, isoprenaline and clenbuterol, also stimulated oxygen consumption and BAT activity but were less selective because they also produced effects on heart rate at these doses. 3. Treatment of conscious rats with ICI D7114 did not attenuate the chronotropic effects on the heart of a subsequent isoprenaline challenge. 4. Administration of ICI D7114 or of its acid metabolite had no effect in a cat soleus muscle model of tremor or on blood potassium levels in the conscious dog, indicating lack of effects at beta 2-adrenoceptors. 5. The results indicate that ICI D7114 may have activity at atypical beta-adrenoceptors in brown adipose tissue leading to increased whole body oxygen consumption. PMID:1686210

A Role for Presynaptic alpha(sub 2)-Adrenoceptors in Angiotensin 2-Induced Drinking in Rats

NASA Technical Reports Server (NTRS)

Fregly, Melvin J.; Rowland, Neil E.; Greenleaf, John E.

1984-01-01

Studies from this laboratory have shown that either central or peripheral administration of clonidine, the alpha(sub 2)-adrenoceptor agonist, can attenuate a variety of dipsogenic stimuli in rats. Further, yohimbine and tolazoline, alpha(sub 2)-adrenoceptor antagonists, augment the drinking response to both peripherally administered isoproterenol and angiotensin 2. Studies reported here establish a dose-inhibition relationship between the dose of clonidine administered (2 to 32 micrograms/kg) intracerebroventricularly (IVT) and inhibition of the drinking response to peripherally administered angiotensin 2 (200 micrograms/kg, SC). DI(sub 50) was approximately 4 micrograms/kg. Yohimbine (300 micrograms/kg, SC) reversed the antidipsogenic effect of centrally administered clonidine (32 micrograms/kg, IVT) on angiotensin 2-induced (200 micrograms/kg, SC) water intake. Phenylephrine, an alpha(sub 2)-adrenoceptor agonist, administered IVT (40 and 80 micrograms/kg) also inhibited angiotensin 2-induced drinking in a dose-related fashion. The antidipsogenic effect of phenylephfine (80 micrograms/kg) was blocked by administration of yohimbine (100 micrograms/kg, SC). Thus, this effect of phenylephrine most likely occurs by way of alpha(sub 2)- adrenoceptors. These results support a role for the pre-synaptic alpha(sub 2)-adrenoceptor in the mediation of drinking in rats. Activation of alpha(sub 2)-adrenoceptors is accompanied by reduced water intake while inhibition of these receptors enhances water intake.

Antinociceptive synergism of MD-354 and clonidine. Part II. The alpha-adrenoceptor component.

PubMed

Young, Shawquia; Vainio, Minna; Scheinin, Mika; Dukat, Małgorzata

2010-08-01

Previously, we reported that antinociceptive synergism of a 5-HT(3)/alpha(2)-adrenoceptor ligand MD-354 (m-chlorophenylguanidine) and clonidine combination occurs, in part, through a 5-HT(3) receptor antagonist mechanism. In the present investigation, a possible role for alpha(2)-adrenoceptors was examined. Mechanistic studies using yohimbine (a subtype non-selective alpha(2)-adrenoceptor antagonist), BRL 44408 (a preferential alpha(2A)-adrenoceptor antagonist) and imiloxan (a preferential alpha(2B/C)-adrenoceptor antagonist) on the antinociceptive actions of a MD-354/clonidine combination were conducted. Subcutaneous pre-treatment with all three antagonists inhibited the antinociceptive synergism of MD-354 and clonidine in the mouse tail-flick assay in a dose-dependent manner (AD(50) = 0.33, 2.1, and 0.17 mg/kg, respectively). Enhancement of clonidine antinociception by MD-354 did not potentiate clonidine's locomotor suppressant activity in a mouse locomotor assay. When [ethyl-3H]RS-79948-197 was used as radioligand, MD-354 displayed almost equal affinity to alpha(2A)- and alpha(2B)-adrenoceptors (K(i) = 110 and 220 nM) and showed lower affinity at alpha(2C)-adrenoceptors (K(i) = 4,700 nM). MD-354 had no subtype-selectivity for the alpha(2)-adrenoceptor subtypes as an antagonist in functional [35S]GTPgammaS binding assays. MD-354 was a weak partial agonist at alpha(2A)-adrenoceptors. Overall, in addition to the 5-HT(3) receptor component, the present investigation found MD-354 to be a weak partial alpha(2A)-adrenoceptor agonist that enhances clonidine's thermal antinociceptive actions through an alpha(2)-adrenoceptor-mediated mechanism without augmenting sedation.

OPC-28326, a selective femoral vasodilator, is an alpha2C-adrenoceptor-selective antagonist.

PubMed

Sun, B; Lockyer, S; Li, J; Chen, R; Yoshitake, M; Kambayashi, J I

2001-11-01

OPC-28326 has been reported to selectively increase femoral blood flow in open-chest dogs and autoperfused canine femoral artery preparations. Preliminary data indicated that OPC-28326 has a high affinity at the alpha2-adrenoceptor. In the present study, we tested OPC-28326 in isoflurane anesthetized rats at a dose of 3 mg/kg of body weight, given intraduodenally. OPC-28326 significantly increased femoral blood flow, by 44.7 +/- 13.8%, 45 min after drug administration, whereas carotid blood flow increased by only 3.6 +/- 5.5% (n = 6). Chinese hamster ovary cell lines overexpressing rat alpha2D-, alpha2B-, or alpha2C-adrenoceptor were established. These cells also coexpress luciferase, driven by cAMP elevation. In radioligand binding assays using cell membrane preparations, OPC-28326 dose dependently competed with [3H]RX821002 binding, with calculated K(i) values of 3840 +/- 887, 633 +/- 46, and 13.7 +/- 1.9 nM on alpha2D-, alpha2B-, and alpha2C-adrenoceptor, respectively. A similar affinity and rank order of potency were also found for OPC-28326 on the alpha2-subtypes using epinephrine as agonist in luciferase assays. No agonistic effect of OPC-28326 was detected on any of the alpha2-adrenoceptors. Finally, in situ hybridization performed on skeletal muscle tissue sections collected from rat hind limb (musculus gastrocnemius) demonstrated a high level expression of alpha2C in the vascular tissues. Thus, the abundance of alpha2C in the skeletal muscle may account for the selective effect of OPC-28326 in increasing femoral blood flow.

Interaction of berberine with human platelet. alpha. sub 2 adrenoceptors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hui, Ka Kit; Yu, Jun Liang; Chan, Wai Fong A.

1991-01-01

Berberine was found to inhibit competitively the specific binding of ({sup 3}H)-yohimbine. The displacement curve was parallel to those of clonidine, epinephrine, norepinephrine, with the rank order of potency (IC{sub 50}) being clonidine {gt} epinephrine {gt} norepinephrine (14.5 {mu}M) = berberine. Increasing concentrations of berberine from 0.1 {mu}M to 10 {mu}M inhibited ({sup 3}H)-yohimbine binding, shifting the saturation binding curve to the right without decreasing the maximum binding capacity. In platelet cyclic AMP accumulation experiments, berberine at concentrations of 0.1 {mu}M to 0.1 mM inhibited the cAMP accumulation induced by 10 {mu}M prostaglandin E{sub 1} in a dose dependent manner,more » acting as an {alpha}{sub 2} adrenoceptor agonist. In the presence of L-epinephrine, berberine blocked the inhibitory effect of L-epinephrine behaving as an {alpha}{sub 2} adrenoceptor antagonist.« less

In vitro desensitization of beta-adrenoceptors in guinea pig trachea: interactions between beta-adrenoceptor agonists and influence of adenosine and other drugs.

PubMed

Matran, R; Naline, E; Advenier, C; Duroux, P

1989-01-01

The aim of this study was to investigate quantitatively the action of and the interaction between beta-adrenergic receptor agonists in desensitizing guinea pig isolated trachea. It was also to evaluate the influence of substances whose effects on desensitization are either disputed (theophylline, indomethacin, ketotifen, hydrocortisone) or unknown (nicardipine, Bay K 8644, fenspiride, adenosine). Tracheal strips were contracted with histamine (5 x 10(-5) M) or acetylcholine (5.10(-5) M) and concentration-response (C/R) curves for various beta-adrenoceptor agonists were determined before and after incubation (20 min to 4 h) with the same beta-adrenoceptor agonist (autodesensitization), with other beta-adrenoceptor agonists (cross-desensitization), or with a beta-adrenoceptor agonist and another substance. Our results show that the autodesensitization induced by isoprenaline is concentration dependent and that concentration dependence is more pronounced with salbutamol and fenoterol than with isoprenaline and adrenaline with respect to autodesensitization: shifts (log unit) of the C/R curves were 0.59 +/- 0.06 (N = 5) for salbutamol (10(-5) M), 0.78 +/- 0.09 (N = 5) for fenoterol (10(-6) M), 0.30 +/- 0.04 (N = 9) for isoprenaline (10(-5) M), and 0.33 +/- 0.05 (N = 5) for adrenaline (10(-5) M). Our studies of cross-desensitization (desensitization to isoprenaline, adrenaline, salbutamol, and fenoterol induced by incubation with isoprenaline 10(-5) M) showed a significantly greater shift in the C/R curves for fenoterol (0.56 +/- 0.08, N = 5) and salbutamol (0.62 +/- 0.05, N = 5) than for adrenaline (0.35 +/- 0.07, N = 5) and isoprenaline itself (0.30 +/- 0.05, N = 9). Of the substances we studied, none modified the desensitization induced by isoprenaline except hydrocortisone and adenosine. Hydrocortisone (10(-8) M) reduced it significantly, although to a negligible extent. Adenosine (3 x 10(-4) M) did not shift the C/R curve to isoprenaline by itself, but incubation

Depression of NMDA receptor-mediated synaptic transmission by four α2 adrenoceptor agonists on the in vitro rat spinal cord preparation

PubMed Central

Faber, E S L; Chambers, J P; Evans, R H

1998-01-01

α2-Adrenoceptor agonists have a spinal site of analgesic action. In the current study the synaptic depressant actions of xylazine, detomidine, romifidine and dexmedetomidine have been compared on segmental reflexes containing NMDA receptor-mediated components in the neonatal rat hemisected spinal cord preparation in vitro.Reflexes were evoked in the ventral root following either supramaximal electrical stimulation of the corresponding ipsilateral lumbar dorsal root to evoke the high intensity excitatory postsynaptic potential (e.p.s.p.) involving all primary afferent fibres, or low intensity stimulation to evoke the solely A fibre-mediated low intensity e.p.s.p. The high intensity e.p.s.p. contains a greater NMDA receptor-mediated component.Xylazine, romifidine, detomidine and dexmedetomidine all depressed both the high intensity e.p.s.p. and the low intensity e.p.s.p. giving respective EC50 values of 0.91±0.2 μM (n=12), 23.4±3 nM (n=12), 37.7±7 nM (n=8) and 0.84±0.1 nM (n=4) for depression of the high intensity e.p.s.p. and 0.76±0.1 μM (n=12), 22.0±3 nM (n=12), 24.9±6 nM (n=4) and 2.7±0.6 nM (n=4) for depression of the low intensity e.p.s.p., respectively. Unlike the other three drugs, the two values for dexmedetomidine, showing a greater selectivity for the high intensity e.p.s.p., are significantly different.Each of these depressant actions was reversed by the selective α2-adrenoceptor antagonist atipamezole (1 μM).In contrast to previous reports of the actions of α2-adrenoceptor agonists on the in vitro spinal cord preparation, at concentrations ten fold higher than the above EC50 values xylazine, romifidine, detomidine and dexmedetomidine depressed the initial population spike of motoneurons (MSR). This depression was not reversed by atipamezole.Comparison of the rank order of the present EC50 values for depression of the high intensity e.p.s.p. with potency ratios from in vivo analgesic tests in previous studies show a close

alpha(2)-adrenoceptor antagonist properties of OPC-28326, a novel selective peripheral vasodilator.

PubMed

Orito, K; Kishi, M; Imaizumi, T; Nakazawa, T; Hashimoto, A; Mori, T; Kambe, T

2001-10-01

1. Antagonistic properties of OPC-28326 ([4-(N-methyl-2-phenylethylamino)-1-(3,5-dimethyl-4-propionyl-aminobenzoyl)] piperidine hydrochloride monohydrate), a selective peripheral vasodilator, were investigated by analysing the data from functional studies in various tissues from the rat and binding studies of the drug to alpha(2)-adrenoceptor subtypes. 2. Using a human recombinant receptor and rat kidney cortex, we found that OPC-28326 displays affinities to alpha(2A)-, alpha(2B)- and alpha(2C)-adrenoceptors with K(i) values of 2040, 285, and 55 nM, respectively. The K(i) values of yohimbine for alpha(2A)-, alpha(2B)-, and alpha(2C)-adrenoceptors were 3.0, 2.0 and 11.0 nM, respectively. 3. B-HT 920, an alpha(2)-adrenoceptor agonist, produced a pressor response via peripheral postsynaptic alpha(2)-adrenoceptor stimulation (thought to be an alpha(2B)-subtype) in a reserpine-pretreated pithed rat preparation. OPC-28326 (3 - 30 mg kg(-1), i.v.) and yohimbine (0.3 - 3 mg kg(-1), i.v.) caused dose-dependent rightward shift in the pressor dose-response curve induced by B-HT 920. The apparent pA(2) values were 1.55 (0.87 - 2.75, 95% confidence interval) and 0.11 (0.06 - 0.21) mg kg(-1), respectively. The potency of OPC-28326 was about 14 times less than that of yohimbine. 4. Clonidine inhibited the tension developed by electrical stimulation, of the rat vas deferens, by its peripheral presynaptic alpha(2A/D)-adrenoceptor action. OPC-28326 (1 - 100 microM) and yohimbine (10 - 1000 nM) caused a rightward shift in the concentration-response curve of clonidine. The pA(2) values were 5.73 (5.54 - 5.91) and 7.92 (7.84 - 8.01), respectively, providing evidence for a potency of OPC-28326 of about 155 times less than that of yohimbine. 5. Mydriasis was induced by brimonidine via stimulation of central alpha(2A/D)-adrenoceptors in anaesthetized rats. Intravenous OPC-28326 had no effect on this action, even at a very high dose of 10 mg kg(-1) i.v., while yohimbine (0.1 - 0.3 mg kg(-1

Effect of fenoterol-induced constitutive beta(2)-adrenoceptor activity on contractile receptor function in airway smooth muscle.

PubMed

de Vries, B; Roffel, A F; Zaagsma, J; Meurs, H

2001-11-23

In the present study, we investigated the effect of fenoterol-induced constitutive beta(2)-adrenoceptor activity on muscarinic receptor agonist- and histamine-induced bovine tracheal smooth muscle contractions. Bovine tracheal smooth muscle strips were incubated with 10 microM fenoterol or vehicle for various periods of time (5, 30 min, 18 h) at 37 degrees C. After extensive washout (3 h, 37 degrees C), isometric contractions were measured to the full muscarinic receptor agonist methacholine, the partial muscarinic receptor agonist 4-(m-chlorophenyl-carbamoyloxy)-2-butynyltrimethylammonium (McN-A-343) and histamine. Fenoterol treatment significantly reduced the sensitivity (pEC(50)) to methacholine in a time-dependent manner, without affecting maximal contraction (E(max)). Fenoterol treatment similarly reduced the pEC(50) of McN-A-343 and histamine; however, E(max) values were also reduced, to approximately 70% of control after 18-h treatment. The inverse agonist timolol, having no effect on control preparations, consistently restored the reduced pEC(50) and E(max) values of the contractile agonists. Remarkably, in the presence of timolol the pEC(50) values of McN-A-343 and histamine in fenoterol-treated airways were significantly enhanced compared to controls. In conclusion, fenoterol-induced constitutive beta(2)-adrenoceptor activity reduces muscarinic receptor agonist- and histamine-induced contractions of bovine tracheal smooth muscle, which can be reversed by the inverse agonist timolol. Moreover, after beta(2)-adrenoceptor agonist treatment, inverse agonism by beta-adrenoceptor antagonists may cause enhanced airway reactivity to contractile mediators.

Icilin-evoked behavioral stimulation is attenuated by alpha2-adrenoceptor activation

PubMed Central

Kim, Jae; Cowan, Alan; Lisek, Renata; Raymondi, Natalie; Rosenthal, Aaron; Hirsch, Daniel D.; Rawls, Scott M.

2011-01-01

Icilin is a transient receptor potential cation channel subfamily M (TRPM8) agonist that produces behavioral activation in rats and mice. Its hallmark overt pharmacological effect is wet-dog shakes (WDS) in rats. The vigorous shaking associated with icilin is dependent on NMDA receptor activation and nitric oxide production, but little else is known about the biological systems that modulate the behavioral phenomenon. The present study investigated the hypothesis that alpha2-adrenoceptor activation inhibits icilin-induced WDS. Rats injected with icilin (0.5, 1, 2.5, 5 mg/kg, i.p.) displayed dose-related WDS that were inhibited by pretreatment with a fixed dose of clonidine (0.15 mg/kg, s.c.). Shaking behavior caused by a fixed dose (2.5 mg/kg) of icilin was also inhibited in a dose-related manner by clonidine pretreatment (0.03–0.15 mg/kg, s.c.) and reduced by clonidine posttreatment (0.15 mg/kg, s.c.). Pretreatment with a peripherally restricted alpha2-adrenoceptor agonist, ST91 (0.075, 0.15 mg/kg), also decreased the incidence of shaking elicited by 2.5 mg/kg of icilin. Pretreatment with yohimbine (2 mg/kg, i.p.) enhanced the shaking induced by a low dose of icilin (0.5 mg/kg). The imidazoline site agonists, agmatine (150 mg/kg, i.p.) and 2-BFI (7 mg/kg, i.p.), did not affect icilin-evoked shaking. These results suggest that alpha2-adrenoceptor activation inhibits shaking induced by icilin and that increases in peripheral, as well as central, alpha2-adrenoceptor signaling oppose the behavioral stimulant effect of icilin. PMID:21315691

Interaction of fenoterol stereoisomers with β2-adrenoceptor-G sα fusion proteins: antagonist and agonist competition binding.

PubMed

Reinartz, Michael T; Kälble, Solveig; Wainer, Irving W; Seifert, Roland

2015-05-01

The specific interaction between G-protein-coupled receptors and ligand is the starting point for downstream signaling. Fenoterol stereoisomers were successfully used to probe ligand-specific activation (functional selectivity) of the β2-adrenoceptor (β2AR) (Reinartz et al. 2015). In the present study, we extended the pharmacological profile of fenoterol stereoisomers using β2AR-Gsα fusion proteins in agonist and antagonist competition binding assays. Dissociations between binding affinities and effector potencies were found for (R,S')- and (S,S')-isomers of 4'-methoxy-1-naphthyl-fenoterol. Our data corroborate former studies on the importance of the aminoalkyl moiety of fenoterol derivatives for functional selectivity.

Behaviour of beta 2-adrenoceptors on lymphocytes under continuous and pulsatile tocolysis with Fenoterol.

PubMed

Schmidt-Rhode, Peter; Brunke, Björn; Schröer, Heinrich; Obert, Kirstin; Schlegel, Kerstin; Sturm, Gerhard; Schulz, Klaus-Dieter; von Wichert, Peter

2003-01-01

The present study investigates the population of beta 2-receptors on lymphocytes in pregnant women with premature labor between the 29th and 34th week of pregnancy. The population of receptors on lymphocytes correlates with that on the myometrium, which is not accessible for study during pregnancy. Fourteen patients received a pulsatile tocolysis, while ten women received a continuous tocolysis with Fenoterol. Assuming an equal population of receptors in both groups before commencement of therapy, the numbers of receptors in the patients with continuous tocolysis fell to about 35% of the initial value after 72 hours. Under pulsatile tocolysis, the numbers of receptors remained unchanged for a period of three days and was still only just below 70% of the initial value by the seventh day. Our data demonstrate that continuous administration of the short-acting beta 2-agonist Fenoterol resulted in a substantial loss of beta 2-adrenoceptors on lymphocytes. In contrast, intermittent administration of the same beta 2-adrenergic agonist prevented the onset of receptor down-regulation in pregnant women with preterm labor. Further studies are required to investigate the impact of the decreased loss of beta 2-adrenoceptor density on the good clinical experience with intermittent tocolysis.

Activation of beta- and alpha-2-adrenoceptors in the basolateral amygdala has opposing effects on hippocampal-prefrontal long-term potentiation.

PubMed

Lim, Ee Peng; Dawe, Gavin S; Jay, Thérèse M

2017-01-01

Noradrenaline (NA), released by the locus coeruleus (LC), plays a key role in mediating the effects of stress on memory functions. The LC provides diffuse projections to many forebrain nuclei including the hippocampus, the prefrontal cortex (PFC), and the basolateral amygdala (BLA). These three structures are intricately interlinked. The hippocampal-prefrontal (H-PFC) pathway is involved in various cognitive functions. The first aim of this study was to examine the role of BLA in H-PFC plasticity by infusion of drugs to activate and inactivate the BLA and studying the effects on H-PFC long-term potentiation (LTP) in the rat in vivo. Activation of the BLA with glutamate impaired, while inactivation with muscimol augmented, H-PFC LTP. This study also aimed to demonstrate how directly applying noradrenaline and other noradrenergic agents in the BLA can affect H-PFC LTP. Noradrenaline at 1μg/0.2μl enhanced H-PFC LTP. Stimulating alpha-2-adrenoceptors in the BLA with clonidine enhanced LTP while blocking alpha-2 adrenoceptors with idazoxan impaired it. Propranolol, a non-selective beta antagonist, enhanced H-PFC LTP while isoprenaline, a non-selective beta agonist, decreased H-PFC LTP. These results suggest that the BLA regulates H-PFC plasticity negatively and also provide a mechanism by which noradrenaline in the BLA can affect H-PFC plasticity via alpha-2 and beta adrenoceptors. Copyright © 2016 Elsevier Inc. All rights reserved.

Time Trends of Period Prevalence Rates of Patients with Inhaled Long-Acting Beta-2-Agonists-Containing Prescriptions: A European Comparative Database Study

PubMed Central

Rottenkolber, Marietta; Voogd, Eef; van Dijk, Liset; Primatesta, Paola; Becker, Claudia; Schlienger, Raymond; de Groot, Mark C. H.; Alvarez, Yolanda; Durand, Julie; Slattery, Jim; Afonso, Ana; Requena, Gema; Gil, Miguel; Alvarez, Arturo; Hesse, Ulrik; Gerlach, Roman; Hasford, Joerg; Fischer, Rainald; Klungel, Olaf H.; Schmiedl, Sven

2015-01-01

Background Inhaled, long-acting beta-2-adrenoceptor agonists (LABA) have well-established roles in asthma and/or COPD treatment. Drug utilisation patterns for LABA have been described, but few studies have directly compared LABA use in different countries. We aimed to compare the prevalence of LABA-containing prescriptions in five European countries using a standardised methodology. Methods A common study protocol was applied to seven European healthcare record databases (Denmark, Germany, Spain, the Netherlands (2), and the UK (2)) to calculate crude and age- and sex-standardised annual period prevalence rates (PPRs) of LABA-containing prescriptions from 2002–2009. Annual PPRs were stratified by sex, age, and indication (asthma, COPD, asthma and COPD). Results From 2002–2009, age- and sex-standardised PPRs of patients with LABA-containing medications increased in all databases (58.2%–185.1%). Highest PPRs were found in men ≥ 80 years old and women 70–79 years old. Regarding the three indications, the highest age- and sex-standardised PPRs in all databases were found in patients with “asthma and COPD” but with large inter-country variation. In those with asthma or COPD, lower PPRs and smaller inter-country variations were found. For all three indications, PPRs for LABA-containing prescriptions increased with age. Conclusions Using a standardised protocol that allowed direct inter-country comparisons, we found highest rates of LABA-containing prescriptions in elderly patients and distinct differences in the increased utilisation of LABA-containing prescriptions within the study period throughout the five European countries. PMID:25706152

α2-Adrenoceptor Functionality in Postmortem Frontal Cortex of Depressed Suicide Victims

PubMed Central

Valdizán, Elsa M.; Díez-Alarcia, Rebeca; González-Maeso, Javier; Pilar-Cuéllar, Fuencisla; García-Sevilla, Jesús A.; Meana, J. Javier; Pazos, Angel

2013-01-01

Background Alterations in brain density and signaling associated with monoamine receptors are believed to play a role in depressive disorders. This study evaluates the functional status of α2A-adrenoceptors in postmortem frontal cortex of depressed subjects. Methods G-protein activation and inhibition of adenylyl cyclase (AC) activity induced by the α2-adrenoceptor agonist UK14304 were measured in triplicate in samples from 15 suicide victims with an antemortem diagnosis of major depression and 15 matched control subjects. Results Basal [35S] guanosine γ thio-phosphate (GTPγS) binding and cyclic adenosine monophosphate accumulation did not differ between groups. In depressed victims, an increase in [35S] GTPγS binding potency (EC50 = .58 μmol/L vs. EC50 = 3.31 μmol/L; p < .01; depressed vs. control) and a significant reduction in the maximal inhibition of AC activity (Imax = 27 ± 4% vs. Imax = 47 ± 5%; p < .01) were observed after incubation with the α2-adrenoceptor agonist UK14304. No differences were found between antidepressant-free and antidepressant-treated subjects. A significant relationship between EC50 values for [35S] GTPγS and Imax values for AC assay was found (n = 30; r = −.43; p < .05). Conclusions The dual regulation of α2A-adrenoceptor signaling pathways raises the possibility that factors affecting the G-protein cycle and/or selective access of Gαi/o–protein to AC might be relevant to receptor abnormalities in depression, providing further support for the involvement of α2A-adrenoceptors in the pathogenesis of depression. PMID:20864091

The costo-uterine muscle of the rat contains a homogeneous population of beta-adrenoceptors.

PubMed Central

Hartley, M. L.; Pennefather, J. N.

1985-01-01

The effects of two selective beta-adrenoceptor antagonists on the inhibitory responses to some sympathomimetic amines of electrically-stimulated preparations of costo-uterine muscle, taken from virgin rats, have been examined quantitatively. pA2 values for the antagonist, atenolol (beta 1-selective) and ICI 118,551 (beta 2-selective) were obtained using as agonists, fenoterol (beta 2-selective agonist) and noradrenaline (alpha- and beta-adrenoceptor agonist, beta 1-selective); and in addition, with ICI 118,551 only, isoprenaline (beta-agonist, non-selective) and adrenaline (alpha- and beta-adrenoceptor agonist, beta 2-selective). Catecholamine uptake mechanisms and alpha-adrenoceptors were not blocked in any of these experiments. Atenolol competitively antagonized the effects of fenoterol and noradrenaline to a similar extent, the pA2 values being 5.4 and 5.7, respectively. ICI 118,551 competitively antagonized the effects of fenoterol, isoprenaline, adrenaline and noradrenaline to a similar extent; pA2 values ranged from 8.7 with noradrenaline to 9.1 with isoprenaline. These results extend our previous observations which indicated that the adrenoceptors mediating inhibition of electrically-evoked contractions of costo-uterine muscle of the virgin rat are homogeneous and of the beta 2-subtype. The potency of the beta 1-selective agonist RO 363 in producing inhibition of electrically-evoked contractions of this tissue was also examined. RO 363 was 200 times less potent than isoprenaline but was a full agonist. This indicates that there is efficient coupling between beta 2-adrenoceptor activation and tissue response in this non-innervated preparation. PMID:2858239

Long-acting muscarinic antagonists vs. long-acting β 2 agonists in COPD exacerbations: a systematic review and meta-analysis

PubMed Central

Maia, Israel Silva; Pincelli, Mariângela Pimentel; Leite, Victor Figueiredo; Amadera, João; Buehler, Anna Maria

2017-01-01

ABSTRACT Objective: To determine whether long-acting muscarinic antagonists (LAMAs) provide superior therapeutic effects over long-acting β2 agonists (LABAs) for preventing COPD exacerbations. Methods: This was a systematic review and meta-analysis of randomized clinical trials involving patients with stable, moderate to severe COPD according to the Global Initiative for Chronic Obstructive Lung Disease criteria, treated with a LAMA (i.e., tiotropium bromide, aclidinium, or glycopyrronium), followed for at least 12 weeks and compared with controls using a LABA in isolation or in combination with a corticosteroid. Results: A total of 2,622 studies were analyzed for possible inclusion on the basis of their title and abstract; 9 studies (17,120 participants) were included in the analysis. In comparison with LABAs, LAMAs led to a greater decrease in the exacerbation rate ratio (relative risk [RR] = 0.88; 95% CI: 0.84-0.93]; a lower proportion of patients who experienced at least one exacerbation (RR = 0.90; 95% CI: 0.87-0.94; p < 0.00001); a lower risk of exacerbation-related hospitalizations (RR = 0.78; 95% CI: 0.69-0.87; p < 0.0001); and a lower number of serious adverse events (RR = 0.81; 95% CI: 0.67-0.96; p = 0.0002). The overall quality of evidence was moderate for all outcomes. Conclusions: The major findings of this systematic review and meta-analysis were that LAMAs significantly reduced the exacerbation rate (exacerbation episodes/year), as well as the number of exacerbation episodes, of hospitalizations, and of serious adverse events. PMID:28767773

Role of transglutaminase 2 in A1 adenosine receptor- and β2-adrenoceptor-mediated pharmacological pre- and post-conditioning against hypoxia-reoxygenation-induced cell death in H9c2 cells.

PubMed

Vyas, Falguni S; Nelson, Carl P; Dickenson, John M

2018-01-15

Pharmacologically-induced pre- and post-conditioning represent attractive therapeutic strategies to reduce ischaemia/reperfusion injury during cardiac surgery and following myocardial infarction. We have previously reported that transglutaminase 2 (TG2) activity is modulated by the A 1 adenosine receptor and β 2 -adrenoceptor in H9c2 cardiomyoblasts. The primary aim of this study was to determine the role of TG2 in A 1 adenosine receptor and β 2 -adrenoceptor-induced pharmacological pre- and post-conditioning in the H9c2 cells. H9c2 cells were exposed to 8h hypoxia (1% O 2 ) followed by 18h reoxygenation, after which cell viability was assessed by monitoring mitochondrial reduction of MTT, lactate dehydrogenase release and caspase-3 activation. N 6 -cyclopentyladenosine (CPA; A 1 adenosine receptor agonist), formoterol (β 2 -adrenoceptor agonist) or isoprenaline (non-selective β-adrenoceptor agonist) were added before hypoxia/reoxygenation (pre-conditioning) or at the start of reoxygenation following hypoxia (post-conditioning). Pharmacological pre- and post-conditioning with CPA and isoprenaline significantly reduced hypoxia/reoxygenation-induced cell death. In contrast, formoterol did not elicit protection. Pre-treatment with pertussis toxin (G i/o -protein inhibitor), DPCPX (A 1 adenosine receptor antagonist) or TG2 inhibitors (Z-DON and R283) attenuated the A 1 adenosine receptor-induced pharmacological pre- and post-conditioning. Similarly, pertussis toxin, ICI 118,551 (β 2 -adrenoceptor antagonist) or TG2 inhibition attenuated the isoprenaline-induced cell survival. Knockdown of TG2 using small interfering RNA (siRNA) attenuated CPA and isoprenaline-induced pharmacological pre- and post-conditioning. Finally, proteomic analysis following isoprenaline treatment identified known (e.g. protein S100-A6) and novel (e.g. adenine phosphoribosyltransferase) protein substrates for TG2. These results have shown that A 1 adenosine receptor and β 2 -adrenoceptor

Comparisons of the effects of long-acting and short-acting GnRH agonists on embryo quality, endometrial thickness and pregnancy rate in human in vitro fertilization.

PubMed

Mao, Gen-Hong; Feng, Zonggang; He, Yan; Huang, Yu-Rong

2014-02-24

The aim was to compare the efficacy of long-acting and short-acting gonadotropin-releasing hormone (GnRH) agonists by long protocol on embryo quality, endometrial thickness and pregnancy rate in in vitro fertilization. In this retrospective study, long-term pituitary downregulation, achieved with long- and short-acting GnRH agonists (GnRHa), was performed for patients undergoing in vitro fertilization (n = 175). There were no significant differences between the long and short-acting GnRH group (63.16% vs. 66.26%, p > 0.05), and the secondary and primary infertility group (63.47% vs. 66.86%, p > 0.05) in embryo quality. Logistic regression analysis showed that type of infertility and endometrial thickness were significantly associated with pregnancy outcome. Patients in the long-acting GnRHa group had a thicker endometrium on the day of human chorionic gonadotrophin (hCG) administration (10.79 ±2.62 mm vs. 9.64 ±1.97 mm, p < 0.01), lower serum luteinizing hormone (LH) concentration (1.21 ±1.13 vs. 2.53 ±3.39) and a higher pregnancy rate (59.60% vs. 43.42%, p < 0.05) than those of patients in the short-acting GnRHa group. This work suggests that types of agonist protocol and infertility may not affect embryo quality. Type of infertility and endometrial thickness may be positive predictors for clinical pregnancy, but the key finding is that the long-acting GnRHa protocol may be an effective method of improving endometrial thickness, endometrial receptivity and pregnancy rate in in vitro fertilization.

Divergent agonist selectivity in activating β1- and β2-adrenoceptors for G-protein and arrestin coupling.

PubMed

Casella, Ida; Ambrosio, Caterina; Grò, Maria Cristina; Molinari, Paola; Costa, Tommaso

2011-08-15

The functional selectivity of adrenergic ligands for activation of β1- and β2-AR (adrenoceptor) subtypes has been extensively studied in cAMP signalling. Much less is known about ligand selectivity for arrestin-mediated signalling pathways. In the present study we used resonance energy transfer methods to compare the ability of β1- and β2-ARs to form a complex with the G-protein β-subunit or β-arrestin-2 in response to a variety of agonists with various degrees of efficacy. The profiles of β1-/β2-AR selectivity of the ligands for the two receptor-transducer interactions were sharply different. For G-protein coupling, the majority of ligands were more effective in activating the β2-AR, whereas for arrestin coupling the relationship was reversed. These data indicate that the β1-AR interacts more efficiently than β2-AR with arrestin, but less efficiently than β2-AR with G-protein. A group of ligands exhibited β1-AR-selective efficacy in driving the coupling to arrestin. Dobutamine, a member of this group, had 70% of the adrenaline (epinephrine) effect on arrestin via β1-AR, but acted as a competitive antagonist of adrenaline via β2-AR. Thus the structure of such ligands appears to induce an arrestin-interacting form of the receptor only when bound to the β1-AR subtype. © The Authors Journal compilation © 2011 Biochemical Society

The changes in beta-adrenoceptor-mediated cardiac function in experimental hypothyroidism: the possible contribution of cardiac beta3-adrenoceptors.

PubMed

Arioglu, E; Guner, S; Ozakca, I; Altan, V M; Ozcelikay, A T

2010-02-01

Thyroid hormone deficiency has been reported to decrease expression and function of both beta(1)- and beta(2)-adrenoceptor in different tissues including heart. The purpose of this study was to examine the possible contribution of beta(3)-adrenoceptors to cardiac dysfunction in hypothyroidism. In addition, effect of this pathology on beta(1)- and beta(2)-adrenoceptor was investigated. Hypothyroidism was induced by adding methimazole (300 mg/l) to drinking water of rats for 8 weeks. Cardiac hemodynamic parameters were measured in anesthetised rats in vivo. Responses to beta-adrenoceptor agonists were examined in rat papillary muscle in vitro. We also studied the effect of hypotyroidism on mRNA expression of beta-adrenoceptors, Gialpha, GRK, and eNOS in rat heart. All of the hemodynamic parameters (systolic, diastolic and mean arterial pressure, left ventricular pressure, heart rate, +dp/dt, and -dp/dt) were significantly reduced by the methimazole treatment. The negative inotropic effect elicited by BRL 37344 (a beta(3)-adrenoceptor preferential agonist) and positive inotropic effects produced by isoprenaline and noradrenaline, respectively, were significantly decreased in papillary muscle of hypothyroid rats as compared to those of controls. On the other hand, hypothyroidism resulted in increased cardiac beta(2)- and beta(3)-adrenoceptor, Gialpha(2), Gialpha(3), GRK3, and eNOS mRNA expressions. However, beta(1)-adrenoceptor and GRK2 mRNA expressions were not changed significantly in this pathology. These results show that mRNA expression of beta(3)-adrenoceptors as well as the signalling pathway components mediated through beta(3)-adrenoceptors are significantly increased in hypothyroid rat heart. Since we could not correlate these alternates with the decreased negative inotropic response mediated by this receptor subtype, it is not clear whether these changes are important for hypothyroid induced reduction in cardiac function.

Different mechanisms of action of beta2-adrenergic receptor agonists: a comparison of reproterol, fenoterol and salbutamol on monocyte cyclic-AMP and leukotriene B4 production in vitro.

PubMed

Juergens, Uwe R; Stöber, M; Libertus, H; Darlath, W; Gillissen, A; Vetter, H

2004-07-30

Beta2-adrenergic receptor agonists have several effects on airway function, most of which are mediated in a variety of cell types resulting in increased c-AMP-production and inhibition of inflammatory mediator production. However, their stimulating effects on cAMP-production became known to be inversed by increasing phosphodiesterase (PDE) activity and degradation of cAMP. Therefore, in this study we have evaluated the efficacy of reproterol, a dual acting beta2-adrenoceptor agonist and PDE-inhibitor, as compared to salbutamol and fenoterol with respect to production of cAMP and LTB4 in cultured monocytes. Isolated human monocytes (10(5)/ml) were incubated (n = 9) in suspension with beta2-adrenoceptor agonists (10(-10) -10(-4) M) for 30 minutes with and without IBMX. Then, cAMP production was determined following treatment with Triton-X100. Production of LTB4 was measured following incubation of beta2-adrenoceptor agonists for 4 hrs in the presence of LPS (10 mg/ml). cAMP and LTB subset 4 were measured in culture supernatants by enzyme immunoassay. At 10(-5) M, production of cAMP was significantly stimulated by reproterol > fenoterol > salbutamol in a dose-dependent manner to an extent of *128%, *65%, 13% (*p<0.04) respectively. In contrast, LTB4-production was inhibited significantly to a similar degree by salbutamol and reproterol in a dose-dependent manner by 59% and 49% (10(-5) M, p<0.03), respectively, with decreasing inhibition (15%) after fenoterol. Following co-incubation with IBMX, cAMP production only increased significantly (p<0.002) after fenoterol (+110%) compared to salbutamol (+29%) and reproterol (+50%) (ANOVA, p<0.001). These data suggest effects of the theophylline constituent of reproterol to inhibit adenylyl cyclase induced phosphodiesterase activity. The advantageous synergistic effects of reproterol on cAMP-production need to be further explored in trials.

Evaluation of the alpha-1 and alpha-2 adrenoceptor-mediated effects of a series of dimethoxy-substituted tolazoline derivatives in the cardiovascular system of the pithed rat.

PubMed

Ruffolo, R R; Messick, K

1985-01-01

The alpha-1 and alpha-2 adrenoceptor-mediated effects of a series of dimethoxy-substituted tolazoline derivatives were investigated in the cardiovascular system of the pithed rat. The 2,5- and 3,5-dimethoxy-substituted tolazoline derivatives produced vasopressor responses that were inhibited by the alpha-1 adrenoceptor antagonist, prazosin (0.1 mg/kg i.v.), and were not affected by the alpha-2 adrenoceptor antagonist, yohimbine (1 mg/kg i.v.), suggesting that these derivatives selectively activate postsynaptic vascular alpha-1 adrenoceptors. The 2,5- and 3,5-dimethoxy-substituted derivatives of tolazoline did not produce an alpha-2 adrenoceptor-mediated inhibition of neurogenic tachycardia in cord-stimulated pithed rats and were therefore presumed to be devoid of alpha-2 adrenoceptor agonist activity. In contrast, 2,3-dimethoxytolazoline produced a vasopressor effect that was inhibited by yohimbine but not by prazosin, suggesting selective activation of postsynaptic vascular alpha-2 adrenoceptors. Consistent with this observation is the fact that 2,3-dimethoxytolazoline elicited a dose-dependent, alpha-2 adrenoceptor-mediated inhibition of neurogenic tachycardia in cord-stimulated pithed rat. 3,4-Dimethoxytolazoline was a weak alpha-1 adrenoceptor agonist in the vasculature of the pithed rat and was devoid of agonist activity at alpha-2 adrenoceptors. However, 3,4-dimethoxytolazoline was found to be an alpha-2 adrenoceptor antagonist of similar potency as yohimbine. The results of the present study indicate that dimethoxy-substituted derivatives of tolazoline possess different activities and selectivities at alpha-1 and alpha-2 adrenoceptors depending upon the positions of substitution.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphodiesterase 4 Inhibitors Attenuate the Asthma Phenotype Produced by β2-Adrenoceptor Agonists in Phenylethanolamine N-Methyltransferase-Knockout Mice.

PubMed

Forkuo, Gloria S; Kim, Hosu; Thanawala, Vaidehi J; Al-Sawalha, Nour; Valdez, Daniel; Joshi, Radhika; Parra, Sergio; Pera, Tonio; Gonnella, Patricia A; Knoll, Brian J; Walker, Julia K L; Penn, Raymond B; Bond, Richard A

2016-08-01

Mice lacking the endogenous β2-adrenoceptor (β2AR) agonist epinephrine (phenylethanolamine N-methyltransferase [PNMT]-knockout mice) are resistant to developing an "asthma-like" phenotype in an ovalbumin sensitization and challenge (Ova S/C) model, and chronic administration of β2AR agonists to PNMT-KO mice restores the phenotype. Based on these and other studies showing differential effects of various β2AR ligands on the asthma phenotype, we have speculated that the permissive effect of endogenous epinephrine and exogenous β2AR agonists on allergic lung inflammation can be explained by qualitative β2AR signaling. The β2AR can signal through at least two pathways: the canonical Gαs-cAMP pathway and a β-arrestin-dependent pathway. Previous studies suggest that β-arrestin-2 is required for allergic lung inflammation. On the other hand, cell-based assays suggest antiinflammatory effects of Gαs-cAMP signaling. This study was designed to test whether the in vitro antiinflammatory effects of phosphodiesterase 4 inhibitors, known to increase intracellular cAMP in multiple airway cell types, attenuate the asthma-like phenotype produced by the β2AR agonists formoterol and salmeterol in vivo in PNMT-KO mice, based on the hypothesis that skewing β2AR signaling toward Gαs-cAMP pathway is beneficial. Airway inflammatory cells, epithelial mucus production, and airway hyperresponsiveness were quantified. In Ova S/C PNMT-KO mice, formoterol and salmeterol restored the asthma-like phenotype comparable to Ova S/C wild-type mice. However, coadministration of either roflumilast or rolipram attenuated this formoterol- or salmeterol-driven phenotype in Ova S/C PNMT-KO. These findings suggest that amplification of β2AR-mediated cAMP by phosphodiesterase 4 inhibitors attenuates the asthma-like phenotype promoted by β-agonists.

Characterization of the hypothermic effects of imidazoline I2 receptor agonists in rats

PubMed Central

Thorn, David A; An, Xiao-Fei; Zhang, Yanan; Pigini, Maria; Li, Jun-Xu

2012-01-01

BACKGROUND AND PURPOSE Imidazoline I2 receptors have been implicated in several CNS disorders. Although several I2 receptor agonists have been described, no simple and sensitive in vivo bioassay is available for studying I2 receptor ligands. This study examined I2 receptor agonist-induced hypothermia as a functional in vivo assay of I2 receptor agonism. EXPERIMENTAL APPROACH Different groups of rats were used to examine the effects of I2 receptor agonists on the rectal temperature and locomotion. The pharmacological mechanisms were investigated by combining I2 receptor ligands and different antagonists. KEY RESULTS All the selective I2 receptor agonists examined (2-BFI, diphenyzoline, phenyzoline, CR4056, tracizoline, BU224 and S22687, 3.2–56 mg·kg–1, i.p.) dose-dependently and markedly decreased the rectal temperature (hypothermia) in rats, with varied duration of action. Pharmacological mechanism of the observed hypothermia was studied by combining the I2 receptor agonists (2-BFI, BU224, tracizoline and diphenyzoline) with imidazoline I2 receptor/ α2 adrenoceptor antagonist idazoxan, selective I1 receptor antagonist efaroxan, α2 adrenoceptor antagonist/5-HT1A receptor agonist yohimbine. Idazoxan but not yohimbine or efaroxan attenuated the hypothermic effects of 2-BFI, BU224, tracizoline and diphenyzoline, supporting the I2 receptor mechanism. In contrast, both idazoxan and yohimbine attenuated hypothermia induced by the α2 adrenoceptor agonist clonidine. Among all the I2 receptor agonists studied, only S22687 markedly increased the locomotor activity in rats. CONCLUSIONS AND IMPLICATIONS Imidazoline I2 receptor agonists can produce hypothermic effects, which are primarily mediated by I2 receptors. These data suggest that I2 receptor agonist-induced hypothermia is a simple and sensitive in vivo assay for studying I2 receptor ligands. PMID:22324428

Modulation of fear/anxiety responses, but not food intake, following α-adrenoceptor agonist microinjections in the nucleus accumbens shell of free-feeding rats.

PubMed

Kochenborger, Larissa; Zanatta, Débora; Berretta, Luigi Marins; Lopes, Ana Paula Fraga; Wunderlich, Bruna Luiza; Januário, Ana Cláudia; Neto, José Marino; Terenzi, Mariana Graciela; Paschoalini, Marta Aparecida; Faria, Moacir Serralvo

2012-01-01

This study investigated the effect of α-adrenoceptor agonists microinjected into the shell region of the accumbens nucleus (AcbSh) on feeding and anxiety-related behaviors in free-feeding rats. Male Wistar rats with a chronically implanted cannula into the AcbSh were unilaterally microinjected with either clonidine (CLON, α(2)-adrenoceptor agonist) or phenylephrine (PHEN, α(1)-adrenoceptor agonist) at the doses of 6 and 20 nmol and submitted to the elevated plus-maze (EPM), a pre-clinical test of anxiety. Immediately after the EPM test, the animals underwent food intake evaluation for 30 min. The data showed that rats microinjected with CLON (20 nmol/0.2 μl) into the AcbSh exhibited increased %Open arm time, which is compatible with an anxiolytic-like effect. The CLON-induced anxiolysis was corroborated by increased head-dipping and decreased stretched-attend posture, two ethologically derived behaviors which are fear/anxiety-motivated. The animal's locomotor activity was not changed by 20 nmol CLON microinjection into the AcbSh. However, neither dose of PHEN microinjected into the AcbSh was able to alter either the spatial-temporal or ethological variables representative of fear/anxiety and locomotion. Food intake was not altered by any dose of CLON and PHEN microinjected into the AcbSh, but the 20 nmol CLON microinjection induced increased motor activity in the feeding test. The data suggests that noradrenergic projections to the AcbSh may underlie fear/anxiety modulation through α(2)-adrenoceptor in the AcbSh, while feeding behavior was unaffected by noradrenergic modulation in the AcbSh of free-feeding rats. This article is part of a Special Issue entitled 'Anxiety and Depression'. Copyright © 2011 Elsevier Ltd. All rights reserved.

Dual interaction of agmatine with the rat α2D-adrenoceptor: competitive antagonism and allosteric activation

PubMed Central

Molderings, G J; Menzel, S; Kathmann, M; Schlicker, E; Göthert, M

2000-01-01

In segments of rat vena cava preincubated with [3H]-noradrenaline and superfused with physiological salt solution, the influence of agmatine on the electrically evoked [3H]-noradrenaline release, the EP3 prostaglandin receptor-mediated and the α2D-adrenoceptor-mediated inhibition of evoked [3H]-noradrenaline release was investigated. Agmatine (0.1–10 μM) by itself was without effect on evoked [3H]-noradrenaline release. In the presence of 10 μM agmatine, the prostaglandin E2(PGE2)-induced EP3-receptor-mediated inhibition of [3H]-noradrenaline release was not modified, whereas the α2D-adrenoceptor-mediated inhibition of [3H]-noradrenaline release induced by noradrenaline, moxonidine or clonidine was more pronounced than in the absence of agmatine. However, 1 mM agmatine antagonized the moxonidine-induced inhibition of [3H]-noradrenaline release. Agmatine concentration-dependently inhibited the binding of [3H]-clonidine and [3H]-rauwolscine to rat brain cortex membranes (Ki values 6 μM and 12 μM, respectively). In addition, 30 and 100 μM agmatine increased the rate of association and decreased the rate of dissociation of [3H]-clonidine resulting in an increased affinity of the radioligand for the α2D-adrenoceptors. [14C]-agmatine labelled specific binding sites on rat brain cortex membranes. In competition experiments. [14C]-agmatine was inhibited from binding to its specific recognition sites by unlabelled agmatine, but not by rauwolscine and moxonidine. In conclusion, the present data indicate that agmatine both acts as an antagonist at the ligand recognition site of the α2D-adrenoceptor and enhances the effects of α2-adrenoceptor agonists probably by binding to an allosteric binding site of the α2D-adrenoceptor which seems to be labelled by [14C]-agmatine. PMID:10928978

Thiophene/thiazole-benzene replacement on guanidine derivatives targeting α2-Adrenoceptors.

PubMed

Flood, Aoife; Trujillo, Cristina; Sanchez-Sanz, Goar; Kelly, Brendan; Muguruza, Carolina; Callado, Luis F; Rozas, Isabel

2017-09-29

Searching for improved antagonists of α 2 -adrenoceptors, a thorough theoretical study comparing the aromaticity of phenyl-, pyridinyl-, thiophenyl- and thiazolylguanidinium derivatives has been carried out [at M06-2X/6-311++G(p,d) computational level] confirming that thiophene and thiazole will be good 'ring equivalents' to benzene in these guanidinium systems. Based on these results, a small but chemically diverse library of guanidine derivatives (15 thiophenes and 2 thiazoles) were synthesised to explore the effect that the bioisosteric change has on affinity and activity at α 2 -adrenoceptors in comparison with our previously studied phenyl derivatives. All compounds were tested for their α 2 -adrenoceptor affinity and unsubstituted guanidinothiophenes displayed the strongest affinities in the same range as the phenyl analogues. In the case of cycloakyl systems, thiophenes with 6-membered rings showed the largest affinities, while for the thiazoles the 5-membered analogue presented the strongest affinity. From all the compounds tested for noradrenergic activity, only one compound exhibited agonistic activity, while two compounds showed very promising antagonism of α 2 -adrenoceptors. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Investigation of the prejunctional α2-adrenoceptor mediated actions of MDMA in rat atrium and vas deferens

PubMed Central

Lavelle, Aisling; Honner, Valerie; Docherty, J R

1999-01-01

We have investigated the effects of methylenedioxymethamphetamine (MDMA, ‘ecstasy') on peripheral noradrenergic neurotransmission in the rat.In rat atrial slices pre-incubated with [3H]-noradrenaline and in the presence of desipramine (1 μM) to prevent effects of MDMA on basal outflow of tritium, MDMA (10 μM) significantly inhibited the release of tritium evoked by short trains of six pulses at 100 Hz every 10 s for 3 min. This effect did not occur in the presence of the α2-adrenoceptor antagonist yohimbine (1 μM).In epididymal portions of rat vas deferens in the presence of nifedipine (10 μM), MDMA produced a concentration-dependent inhibition of single pulse nerve stimulation-evoked contractions with a pD2 of 5.88±0.16 (n=4). Inhibitory effects of MDMA were antagonized by the α2-adrenoceptor antagonist yohimbine (0.3 μM), but not by the 5-hydroxytryptamine receptor antagonist cyanopindolol in a concentration (1 μM) which markedly antagonized the inhibitory actions of the 5-HT-1 receptor agonist 5-carboxamidotryptamine.In prostatic portions of rat vas deferens in the presence of cocaine (3 μM), MDMA produced a concentration-dependent inhibition of single pulse nerve stimulation-evoked contractions with a pD2 of 5.12±0.21 (n=4). In the absence of cocaine, only the highest concentration of MDMA (30 μM) produced an inhibition, but the α2-adrenoceptor antagonist yohimbine (0.3 μM) converted the response to MDMA from inhibition to potentiation of the stimulation-evoked contraction.In radioligand binding studies, MDMA showed similar affinities for α2B, α2C and α2D-adrenoceptor sites, with pKi values of 5.14±0.16, 5.11±0.05 and 5.31±0.14, respectively.It is concluded that MDMA has significant α2-adrenoceptor agonist actions. PMID:10556934

Alpha-2A Adrenoceptor Agonist Guanfacine Restores Diuretic Efficiency in Experimental Cirrhotic Ascites: Comparison with Clonidine

PubMed Central

Sansoè, Giovanni; Aragno, Manuela; Mastrocola, Raffaella; Mengozzi, Giulio; Parola, Maurizio

2016-01-01

Background In human cirrhosis, adrenergic hyperfunction causes proximal tubular fluid retention and contributes to diuretic-resistant ascites, and clonidine, a sympatholytic drug, improves natriuresis in difficult-to-treat ascites. Aim To compare clonidine (aspecific α2-adrenoceptor agonist) to SSP-002021R (prodrug of guanfacine, specific α2A-receptor agonist), both associated with diuretics, in experimental cirrhotic ascites. Methods and Results Six groups of 12 rats were studied: controls (G1); controls receiving furosemide and potassium canrenoate (G2); rats with ascitic cirrhosis due to 14-week CCl4 treatment (G3); cirrhotic rats treated (over the 11th-14th CCl4 weeks) with furosemide and canrenoate (G4), furosemide, canrenoate and clonidine (G5), or diuretics and SSP002021R (G6). Three rats of each group had their hormonal status and renal function assessed at the end of 11th, 12th, 13th, and 14th weeks of respective treatments.Cirrhotic rats in G3 and G4 gained weight over the 12th-14th CCl4 weeks. In G4, brief increase in sodium excretion over the 11th-12th weeks preceded worsening of inulin clearance and natriuresis (diuretic resistance). In comparison with G4, the addition of clonidine (G5) or guanfacine (G6) to diuretics improved, respectively, sodium excretion over the 11th-12th CCl4 weeks, or GFR and electrolytes excretion over the 13th-14th CCl4 weeks. Natriuretic responses in G5 and G6 were accompanied by reduced catecholamine serum levels. Conclusions α2A-receptor agonists restore glomerular filtration rate and natriuresis, and delay diuretic-resistant ascites in experimental advanced cirrhosis. Clonidine ameliorates diuretic-dependent natriuresis just for a short time. PMID:27384184

Xenopus-derived glucagon-like peptide-1 and polyethylene-glycosylated glucagon-like peptide-1 receptor agonists: long-acting hypoglycaemic and insulinotropic activities with potential therapeutic utilities.

PubMed

Han, Jing; Fei, Yingying; Zhou, Feng; Chen, Xinyu; Zhang, Ying; Liu, Lin; Fu, Junjie

2018-02-01

Incretin-based therapies based on glucagon-like peptide-1 (GLP-1) receptor agonists are effective treatments of type 2 diabetes. Abundant research has focused on the development of long-acting GLP-1 receptor agonists. However, all GLP-1 receptor agonists in clinical use or development are based on human or Gila GLP-1. We have identified a potent GLP-1 receptor agonist, xGLP-1B, based on Xenopus GLP-1. To further modify the structure of xGLP-1B, alanine scanning was performed to study the structure -activity relationship of xGLP-1B. Two strategies were then employed to improve bioactivity. First, the C-terminal tail of lixisenatide was appended to cysteine-altered xGLP-1B analogues. Second, polyethylene glycol (PEG) chains with different molecular weights were conjugated with the peptides, giving a series of PEGylated conjugates. Comprehensive bioactivity studies of these conjugates were performed in vitro and in vivo. From the in vitro receptor activation potency and in vivo acute hypoglycaemic activities of conjugates 25 -36, 33 was identified as the best candidate for further biological assessments. Conjugate 33 exhibited prominent hypoglycaemic and insulinotropic activities, as well as improved pharmacokinetic profiles in vivo. The prolonged antidiabetic duration of 33 was further confirmed by pre-oral glucose tolerance tests (OGTT) and multiple OGTT. Furthermore, chronic treatment of db/db mice with 33 ameliorated non-fasting blood glucose and insulin levels, reduced HbA1c values and normalized their impaired glucose tolerance. Importantly, no in vivo toxicity was observed in mice treated with 33. Peptide 33 is a promising long-acting type 2 diabetes therapeutic deserving further investigation. © 2017 The British Pharmacological Society.

Modulation of 3H-noradrenaline release by presynaptic opioid, cannabinoid and bradykinin receptors and β-adrenoceptors in mouse tissues

PubMed Central

Trendelenburg, A U; Cox, S L; Schelb, V; Klebroff, W; Khairallah, L; Starke, K

2000-01-01

Release-modulating opioid and cannabinoid (CB) receptors, β-adrenoceptors and bradykinin receptors at noradrenergic axons were studied in mouse tissues (occipito-parietal cortex, heart atria, vas deferens and spleen) preincubated with 3H-noradrenaline. Experiments using the OP1 receptor-selective agonists DPDPE and DSLET, the OP2-selective agonists U50488H and U69593, the OP3-selective agonist DAMGO, the ORL1 receptor-selective agonist nociceptin, and a number of selective antagonists showed that the noradrenergic axons innervating the occipito-parietal cortex possess release-inhibiting OP3 and ORL1 receptors, those innervating atria OP1, ORL1 and possibly OP3 receptors, and those innervating the vas deferens all four opioid receptor types. Experiments using the non-selective CB agonists WIN 55,212-2 and CP 55,940 and the CB1-selective antagonist SR 141716A indicated that the noradrenergic axons of the vas deferens possess release-inhibiting CB1 receptors. Presynaptic CB receptors were not found in the occipito-parietal cortex, in atria or in the spleen. Experiments using the non-selective β-adrenoceptor agonist isoprenaline and the β2-selective agonist salbutamol, as well as subtype-selective antagonists, demonstrated the occurrence of release-enhancing β2-adrenoceptors at the sympathetic axons of atria and the spleen, but demonstrated their absence in the occipito-parietal cortex and the vas deferens. Experiments with bradykinin and the B2-selective antagonist Hoe 140 showed the operation of release-enhancing B2 receptors at the sympathetic axons of atria, the vas deferens and the spleen, but showed their absence in the occipito-parietal cortex. The experiments document a number of new presynaptic receptor locations. They confirm and extend the existence of marked tissue and species differences in presynaptic receptors at noradrenergic neurons. PMID:10807669

Nitric oxide donor beta2-agonists: furoxan derivatives containing the fenoterol moiety and related furazans.

PubMed

Buonsanti, M Federica; Bertinaria, Massimo; Stilo, Antonella Di; Cena, Clara; Fruttero, Roberta; Gasco, Alberto

2007-10-04

The structure of fenoterol, a beta2-adrenoceptor agonist used in therapy, has been joined with furoxan NO-donor moieties to give new NO-donor beta2-agonists. The furazan analogues, devoid of the property to release NO, were also synthesized for comparison. All the compounds retained beta2-agonistic activity at micromolar or submicromolar concentration when tested on guinea pig tracheal rings precontracted with carbachol. Among the furoxan derivatives, the NO contribution to trachea relaxation was evident with product 15b at micromolar concentrations. All the new NO-donor hybrids were able to dilate rat aortic strips precontracted with phenylephrine. Both furoxan and furazan derivatives displayed antioxidant activity greater than that of fenoterol.

Discovery of olodaterol, a novel inhaled beta2-adrenoceptor agonist with a 24 h bronchodilatory efficacy.

PubMed

Bouyssou, Thierry; Hoenke, Christoph; Rudolf, Klaus; Lustenberger, Philipp; Pestel, Sabine; Sieger, Peter; Lotz, Ralf; Heine, Claudia; Büttner, Frank H; Schnapp, Andreas; Konetzki, Ingo

2010-02-15

Compound 4p was identified from a series of 6-hydroxy-4H-benzo[1,4]oxazin-3-ones as potent agonist of the human beta2-adrenoceptor with a high beta1/beta2-selectivity. A complete reversal of acetylcholine-induced bronchoconstriction which lasted over the whole study period of 5h was demonstrated for 4p in a guinea pig in vivo model without any signs of cardiovascular effects up to 10-fold above the first dose reaching 100% bronchoprotection. The enantiomerically pure (R)-form of 4p exerted a bronchodilatory efficacy over 24 h in dogs and guinea pigs in the absence of systemic pharmacodynamic effects. Formoterol which was tested as comparator in the same in vivo models of acetylcholine-induced bronchoconstriction did not retain efficacy after 24 h. In summary, the preclinical profile of compound (R)-4p (olodaterol, also known as BI 1744 CL) suggests a potential for once-daily dosing in man accompanied with an improved safety profile. Copyright 2010 Elsevier Ltd. All rights reserved.

Effects of fenoterol on beta-adrenoceptor and muscarinic M2 receptor function in bovine tracheal smooth muscle.

PubMed

De Vries, B; Roffel, A F; Kooistra, J M; Meurs, H; Zaagsma, J

2001-05-11

Prolonged (18 h) incubation of isolated bovine tracheal smooth muscle with the beta2-adrenoceptor agonist fenoterol (10 microM) induced desensitization of isoprenaline-induced adenylyl cyclase activity in bovine tracheal smooth muscle membranes, characterized by a 25% decrease in maximal effect (Emax) (P < 0.05), while the sensitivity to the agonist (pEC50) was unchanged. The Emax value of isoprenaline-induced smooth muscle relaxation of submaximal methacholine-induced contractile tones was similarly reduced by about 25% (P < 0.001), while the pEC50 value was diminished by 1.0 log unit (P < 0.001). As determined by 30 microM gallamine-induced muscarinic M2 receptor antagonism and pertussis toxin-induced inactivation of G(i alpha), muscarinic M2 receptor-mediated functional antagonism did not play a role in isoprenaline-induced relaxation of bovine tracheal smooth muscle contracted by methacholine, both in control and in 18-h fenoterol-treated tissue. In line with these observations, we found no enhanced muscarinic M2 receptor-mediated inhibition of 1 microM forskolin-stimulated adenylyl cyclase activity after 18-h fenoterol treatment. These data indicate that 18-h fenoterol treatment of bovine tracheal smooth muscle induces beta2-adrenoceptor desensitization and reduced functional antagonism of methacholine-induced contraction by beta-adrenoceptor agonists, without a change of muscarinic M2 receptor function.

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

PubMed

Sisley, Stephanie; Smith, Kathleen; Sandoval, Darleen A; Seeley, Randy J

2014-08-01

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 exendin-4 in the brain, little data exists on the central effects of liraglutide, a long-acting GLP-1R agonist with much closer structural homology to native GLP-1. In lean, Long-Evans rats, we found that direct intra-third cerebroventricular (i3vt) administration of 0.26 nmol liraglutide caused a 50% reduction in food intake. However, exendin-4 produced the same reduction in food intake with 10-fold greater potency (0.02 nmol). These data are supported by similar c-Fos immunoreactivity in the hypothalamic paraventricular nuclei by exendin-4 as compared to liraglutide despite differing doses. The anorectic effects of both drugs were blocked with i3vt pre-treatment of a GLP-1R competitive antagonist, exendin(9-39), indicating that both drugs required the GLP-1R for their effects. Exendin-4, and not liraglutide, caused hyperglycemia when given i3vt prior to an oral glucose tolerance test, although liraglutide did not lower glucose. Thus, these data show that GLP-1R agonists have differing anorectic potencies in the CNS, which may account for some of their clinical differences. Additionally, we show here that the glucose lowering properties of acute administration of GLP-1R agonists are not accounted for by their central effects. Copyright © 2014 Elsevier Inc. All rights reserved.

Inhalation by design: novel ultra-long-acting β(2)-adrenoreceptor agonists for inhaled once-daily treatment of asthma and chronic obstructive pulmonary disease that utilize a sulfonamide agonist headgroup.

PubMed

Glossop, Paul A; Lane, Charlotte A L; Price, David A; Bunnage, Mark E; Lewthwaite, Russell A; James, Kim; Brown, Alan D; Yeadon, Michael; Perros-Huguet, Christelle; Trevethick, Michael A; Clarke, Nicholas P; Webster, Robert; Jones, Rhys M; Burrows, Jane L; Feeder, Neil; Taylor, Stefan C J; Spence, Fiona J

2010-09-23

A novel series of potent and selective sulfonamide derived β(2)-adrenoreceptor agonists are described that exhibit potential as inhaled ultra-long-acting bronchodilators for the treatment of asthma and chronic obstructive pulmonary disease. Analogues from this series mediate very long-lasting smooth muscle relaxation in guinea pig tracheal strips. The sulfonamide agonist headgroup confers high levels of intrinsic crystallinity that could relate to the acidic sulfonamide motif supporting a zwitterionic form in the solid state. Optimization of pharmacokinetic properties was achieved through targeted introduction of a phenolic moiety to support rapid phase II clearance, thereby minimizing systemic exposure following inhalation and reducing systemically mediated adverse events. Compound 38 (PF-610355) is identified as a clinical candidate from this series, with in vivo duration of action studies confirming its potential for once-daily use in humans. Compound 38 is currently in advanced phase II clinical studies.

Myricetin: a potent approach for the treatment of type 2 diabetes as a natural class B GPCR agonist

PubMed Central

Li, Ying; Zheng, Xuemin; Yi, Xiulin; Liu, Changxiao; Kong, Dexin; Zhang, Jianning; Gong, Min

2017-01-01

The physiologic properties of glucagon-like peptide 1 (GLP-1) make it a potent candidate drug target in the treatment of type 2 diabetes mellitus (T2DM). GLP-1 is capable of regulating the blood glucose level by insulin secretion after administration of oral glucose. The advantages of GLP-1 for the avoidance of hypoglycemia and the control of body weight are attractive despite its poor stability. The clinical efficacies of long-acting GLP-1 derivatives strongly support discovery pursuits aimed at identifying and developing orally active, small-molecule GLP-1 receptor (GLP-1R) agonists. The purpose of this study was to identify and characterize a novel oral agonist of GLP-1R (i.e., myricetin). The insulinotropic characterization of myricetin was performed in isolated islets and in Wistar rats. Long-term oral administration of myricetin demonstrated glucoregulatory activity. The data in this study suggest that myricetin might be a potential drug candidate for the treatment of T2DM as a GLP-1R agonist. Further structural modifications on myricetin might improve its pharmacology and pharmacokinetics.—Li, Y., Zheng, X., Yi, X., Liu, C., Kong, D., Zhang, J., Gong, M. Myricetin: a potent approach for the treatment of type 2 diabetes as a natural class B GPCR agonist. PMID:28270518

Isoproterenol Acts as a Biased Agonist of the Alpha-1A-Adrenoceptor that Selectively Activates the MAPK/ERK Pathway

PubMed Central

Copik, Alicja. J.; Baldys, Aleksander; Nguyen, Khanh; Sahdeo, Sunil; Ho, Hoangdung; Kosaka, Alan; Dietrich, Paul J.; Fitch, Bill; Raymond, John R.; Ford, Anthony P. D. W.; Button, Donald; Milla, Marcos E.

2015-01-01

The α1A-AR is thought to couple predominantly to the Gαq/PLC pathway and lead to phosphoinositide hydrolysis and calcium mobilization, although certain agonists acting at this receptor have been reported to trigger activation of arachidonic acid formation and MAPK pathways. For several G protein-coupled receptors (GPCRs) agonists can manifest a bias for activation of particular effector signaling output, i.e. not all agonists of a given GPCR generate responses through utilization of the same signaling cascade(s). Previous work with Gαq coupling-defective variants of α1A-AR, as well as a combination of Ca2+ channel blockers, uncovered cross-talk between α1A-AR and β2-AR that leads to potentiation of a Gαq-independent signaling cascade in response to α1A-AR activation. We hypothesized that molecules exist that act as biased agonists to selectively activate this pathway. In this report, isoproterenol (Iso), typically viewed as β-AR-selective agonist, was examined with respect to activation of α1A-AR. α1A-AR selective antagonists were used to specifically block Iso evoked signaling in different cellular backgrounds and confirm its action at α1A-AR. Iso induced signaling at α1A-AR was further interrogated by probing steps along the Gαq /PLC, Gαs and MAPK/ERK pathways. In HEK-293/EBNA cells transiently transduced with α1A-AR, and CHO_α1A-AR stable cells, Iso evoked low potency ERK activity as well as Ca2+ mobilization that could be blocked by α1A-AR selective antagonists. The kinetics of Iso induced Ca2+ transients differed from typical Gαq- mediated Ca2+ mobilization, lacking both the fast IP3R mediated response and the sustained phase of Ca2+ re-entry. Moreover, no inositol phosphate (IP) accumulation could be detected in either cell line after stimulation with Iso, but activation was accompanied by receptor internalization. Data are presented that indicate that Iso represents a novel type of α1A-AR partial agonist with signaling bias toward MAPK

Adrenoceptor function and expression in bladder urothelium and lamina propria.

PubMed

Moro, Christian; Tajouri, Lotti; Chess-Williams, Russ

2013-01-01

To investigate the role of adrenoceptor subtypes in regulating the spontaneous contractile activity of the inner lining of the urinary bladder (urothelium/lamina propria). The responses of isolated strips of porcine urothelium/lamina propria to noradrenaline, phenylephrine, and isoprenaline were obtained in the absence and presence of receptor subtype-selective antagonists. Quantitative reverse-transcriptase polymerase chain reaction was undertaken to assess the expression of adrenoceptor genes. The tissues expressed all α1- and β-adrenoceptor subtypes, with the α1A-, α1B-, and β2-adrenoceptors the predominant receptors at the messenger RNA level. In the functional experiments, the rate of phasic contractions and the basal tension were increased by the α1-adrenoceptor agonists phenylephrine (100 μM) and A61603 (10 μM). The rate and tension responses to phenylephrine were reduced by low concentrations of tamsulosin (3 nM) and RS100329 (10 nM) but were unaffected by BMY7378 (100 nM), prazosin (10 nM), and RS17053 (1 μM). In contrast, isoprenaline and salbutamol (both 1 μM) induced a relaxation of tissues and slowing of phasic contractions. The rate and tension responses to isoprenaline were inhibited by propranolol (100 nM) or a combination of CGP20712A (30 nM) and ICI118551 (70 nM). The rate responses were also significantly inhibited by ICI118551 alone (70 nM). Although all α1- and β-adrenoceptor subtypes were expressed in the pig urothelium/lamina propria, the α1A/L-adrenoceptor appeared to mediate increases in the contractile rate and tension. The β-adrenoceptor induced inhibition of spontaneous contractile activity appears to be predominately mediated by β2-adrenoceptors, with β1- and β2-adrenoceptors possibly involved in the tension responses. Copyright © 2013 Elsevier Inc. All rights reserved.

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 ...

Prevention of neutrophil extravasation by α2-adrenoceptor-mediated endothelial stabilization.

PubMed

Herrera-García, Ada María; Domínguez-Luis, María Jesús; Arce-Franco, María; Armas-González, Estefanía; Álvarez de La Rosa, Diego; Machado, José David; Pec, Martina K; Feria, Manuel; Barreiro, Olga; Sánchez-Madrid, Francisco; Díaz-González, Federico

2014-09-15

Adrenergic receptors are expressed on the surface of inflammation-mediating cells, but their potential role in the regulation of the inflammatory response is still poorly understood. The objectives of this work were to study the effects of α2-adrenergic agonists on the inflammatory response in vivo and to determine their mechanism of action. In two mouse models of inflammation, zymosan air pouch and thioglycolate-induced peritonitis models, the i.m. treatment with xylazine or UK14304, two α2-adrenergic agonists, reduced neutrophil migration by 60%. The α2-adrenergic antagonist RX821002 abrogated this effect. In flow cytometry experiments, the basal surface expression of L-selectin and CD11b was modified neither in murine nor in human neutrophils upon α2-agonist treatment. Similar experiments in HUVEC showed that UK14304 prevented the activation-dependent upregulation of ICAM-1. In contrast, UK14304 augmented electrical resistance and reduced macromolecular transport through a confluent HUVEC monolayer. In flow chamber experiments, under postcapillary venule-like flow conditions, the pretreatment of HUVECs, but not neutrophils, with α2-agonists decreased transendothelial migration, without affecting neutrophil rolling. Interestingly, α2-agonists prevented the TNF-α-mediated decrease in expression of the adherens junctional molecules, VE-cadherin, β-catenin, and plakoglobin, and reduced the ICAM-1-mediated phosphorylation of VE-cadherin by immunofluorescence and confocal analysis and Western blot analysis, respectively. These findings indicate that α2-adrenoceptors trigger signals that protect the integrity of endothelial adherens junctions during the inflammatory response, thus pointing at the vascular endothelium as a therapeutic target for the management of inflammatory processes in humans. Copyright © 2014 by The American Association of Immunologists, Inc.

Cholesterol regulates contractility and inotropic response to β2-adrenoceptor agonist in the mouse atria: Involvement of Gi-protein-Akt-NO-pathway.

PubMed

Odnoshivkina, Yulia G; Sytchev, Vaycheslav I; Petrov, Alexey M

2017-06-01

Majority of cardiac β2-adrenoceptors is located in cholesterol-rich microdomains. Here, we have investigated the underlying mechanisms by which a slight to moderate cholesterol depletion with methyl-β-cyclodextrin (MβCD, 1 and 5mM) interferes with contractility and inotropic effect of β2-adrenergic agonist (fenoterol, 50μM) in the mouse atria. Treatment with MβCD itself increased amplitude of Ca 2+ transient but did not change the contraction amplitude due to a clamping action of elevated NO. Cholesterol depletion significantly attenuated the positive inotropic response to fenoterol which is accompanied by increase in NO generation and decrease in Ca 2+ transient. Influence of 1mM MβCD on the fenoterol-driven changes in both contractility and NO level was strongly attenuated by inhibition of G i -protein (pertussis toxin), Akt (Akt 1/2 kinase inhibitor) or NO-synthase (L-NAME). After exposure to 5mM MβCD, pertussis toxin or Akt inhibitor could recover the β2-agonist effects on contractility, NO production and Ca 2+ transient, while L-NAME only reduced NO level. An adenylyl cyclase activator (forskolin, 50nM) had no influence on the MβCD-induced changes in the β2-agonist effects. Obtained results suggest that slight cholesterol depletion upregulates G i -protein/Akt/NO-synthase signaling that attenuates the positive inotropic response to β2-adrenergic stimulation without altering the Ca 2+ transient. Whilst moderate cholesterol depletion additionally could suppress the enhancement of the Ca 2+ transient amplitude caused by the β2-adrenergic agonist administration in G i -protein/Akt-dependent but NO-independent manner. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impaired activation of adenylyl cyclase in lung of the Basenji-greyhound model of airway hyperresponsiveness: decreased numbers of high affinity beta-adrenoceptors.

PubMed Central

Emala, C. W.; Aryana, A.; Hirshman, C. A.

1996-01-01

1. To evaluate mechanisms involved in the impaired beta-adrenoceptor stimulation of adenylyl cyclase in tissues from the Basenji-greyhound (BG) dog model of airway hyperresponsiveness, we compared agonist and antagonist binding affinity of beta-adrenoceptors, beta-adrenoceptor subtypes, percentage of beta-adrenoceptors sequestered, and coupling of the beta-adrenoceptor to Gs alpha in lung membranes from BG and control mongrel dogs. We found that lung membranes from the BG dog had higher total numbers of beta-adrenoceptors with a greater percentage of receptors of the beta 2 subtype as compared to mongrel lung membranes. 2. Agonist and antagonist binding affinity and the percentage of beta-adrenoceptors sequestered were not different in BG and mongrel dog lung membranes. However, the percentage of beta-adrenoceptors in the high affinity state for agonist was decreased in BG lung membranes suggesting an uncoupling of the receptor from Gs alpha. 3. Impaired coupling between the beta-adrenoceptor and G protein documented by the decreased numbers of beta-adrenoceptors in the high affinity state in BG lung membranes, is a plausible explanation for the reduced stimulation of adenylyl cyclase and the resultant reduction in airway smooth muscle relaxation in this model. PMID:8864536

Comparison Review of Short-Acting and Long-Acting Glucagon-like Peptide-1 Receptor Agonists.

PubMed

Uccellatore, Annachiara; Genovese, Stefano; Dicembrini, Ilaria; Mannucci, Edoardo; Ceriello, Antonio

2015-09-01

Glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1 RAs) are useful tools for treating type 2 diabetes mellitus. In their recent position statement, the American Diabetes Association and European Association for the Study of Diabetes recommend GLP1-RAs as add-on to metformin when therapeutic goals are not achieved with monotherapy, particularly for patients who wish to avoid weight gain or hypoglycemia. GLP1-RAs differ substantially in their duration of action, frequency of administration and clinical profile. Members of this class approved for clinical use include exenatide twice-daily, exenatide once-weekly, liraglutide and lixisenatide once-daily. Recently, two new once-weekly GLP1-RAs have been approved: dulaglutide and albiglutide. This article summarizes properties of short- and long-acting GLP-1 analogs, and provides useful information to help choose the most appropriate compound for individual patients.

The novel β3-adrenoceptor agonist mirabegron reduces carbachol-induced contractile activity in detrusor tissue from patients with bladder outflow obstruction with or without detrusor overactivity.

PubMed

Svalø, Julie; Nordling, Jørgen; Bouchelouche, Kirsten; Andersson, Karl-Erik; Korstanje, Cees; Bouchelouche, Pierre

2013-01-15

β(3)-Adrenoceptors are major players in detrusor relaxation and have been suggested as a new putative target for the treatment of overactive bladder syndrome. We determined the effects of mirabegron (YM178), a novel β(3)-adrenoceptor agonist, on carbachol-induced tone in isolated human detrusor preparations from patients with bladder outflow obstruction (BOO) with and without detrusor overactivity (DO), and from patients with normal bladder function. We compared the effects to those of isoprenaline, a non-selective β-adrenoceptor agonist. Detrusor specimens were obtained from patients with benign prostatic hyperplasia undergoing cystoscopy and from patients undergoing radical prostatectomy/cystectomy (in total 33 donors). Detrusor contractility was evaluated by organ bath studies and strips were incubated with carbachol (1μM) to induce and enhance tension. Both mirabegron and isoprenaline reduced carbachol-induced tone in tissues from all groups. Isoprenaline decreased tension with higher potency than mirabegron in normal, BOO and BOO+DO detrusor strips with pIC(50) values of 7.49 ± 0.16 vs. 6.23 ± 0.26 (P=0.0002), 6.89 ± 0.34 vs. 6.04 ± 0.31 (P=0.01), and 6.57 ± 0.20 vs. 5.41 ± 0.08 (P<0.0001, n=4), respectively. The maximal relaxant effect of isoprenaline and mirabegron in the normal, BOO and BOO+DO detrusor was 37.7 ± 14.4% and 36.1 ± 23.3%, 14.4 ± 12.2% vs. 33.4 ± 21.0% and 18.3 ± 10.0% vs. 28.3 ± 12.2% (n=4, P>0.05), respectively. Mirabegron and isoprenaline reduced carbachol-induced tone in both normal bladders and obstructed bladder with and without DO. Isoprenaline had higher potency than mirabegron, but the efficacy of mirabegron effect was the same as that of isoprenaline. Copyright © 2012 Elsevier B.V. All rights reserved.

The beta2- and beta3-adrenoceptor-mediated relaxation induced by fenoterol in guinea pig taenia caecum.

PubMed

Akimoto, Yurie; Horinouchi, Takahiro; Tanaka, Yoshio; Koike, Katsuo

2002-10-01

Fenoterol, a beta2-adrenoceptor selective agonist, belongs to the arylethanolamine class. To understand the receptor subtypes responsible for beta-adrenoceptor-mediated relaxation of guinea pig taenia caecum, we investigated the effect of fenoterol. Fenoterol caused concentration-dependent relaxation of the guinea pig taenia caecum. Propranolol, bupranolol and butoxamine produced shifts of the concentration-response curve for fenoterol. Schild regression analyses carried out for propranolol, butoxamine and bupranolol against fenoterol gave pA2 values of 8.41, 6.33 and 8.44, respectively. However, in the presence of 3 x 10(-4) M atenolol, 10(-4) M butoxamine and 10(-6) M phentolamine to block the beta1-, beta2- and a-adrenoceptor effects, respectively, Schild regression analysis carried out for bupranolol against fenoterol gave pA2 values of 5.80. These results suggest that the relaxant response to fenoterol in the guinea pig taenia caecum is mediated by both the beta2- and the beta3-adrenoceptors.

Portal hypertension and liver cirrhosis in rats: effect of the β3-adrenoceptor agonist SR58611A

PubMed Central

Vasina, Valentina; Giannone, Ferdinando; Domenicali, Marco; Latorre, Rocco; Berzigotti, Annalisa; Caraceni, Paolo; Zoli, Marco; De Ponti, Fabrizio; Bernardi, Mauro

2012-01-01

BACKGROUND AND PURPOSE β3-Adrenoceptors participate in the regulation of vascular tone in physiological and pathological conditions. We aimed to assess the effect of pharmacological modulation of β3-adrenoceptors on portal pressure (PP) and systemic haemodynamics and their expression in the liver and mesenteric vessels of cirrhotic rats. EXPERIMENTAL APPROACH PP, central venous pressure (CVP) and systemic haemodynamics were invasively assessed in control and CCl4-treated cirrhotic rats before and during infusion of the selective β3-adrenoceptor agonist, SR58611A. Tissue samples were also collected from liver, heart, portal vein and mesenteric artery for immunohistochemistry and molecular biology analysis. The effect of SR58611A on isolated portal vein was assessed. KEY RESULTS At baseline, cirrhotic rats showed portal hypertension, reduced CVP and hyperdynamic circulation. SR58611A induced a significant, dose-dependent decrease in PP in cirrhotic rats, but not in controls. Although both groups manifested a dose-dependent reduction in mean arterial pressure, this effect was associated with decreased cardiac index (CI) and unchanged indicized peripheral vascular resistance (PVRI) in cirrhotic rats and increased CI and decreased PVRI in control animals. Pretreatment with the selective β3-adrenoceptor antagonist SR59230 prevented all SR58611A-induced changes in cirrhotic rats. SR58611A concentration-dependently relaxed portal vein in cirrhotic rats to a significantly greater extent than in healthy rats; pretreatment with SR59230A completely prevented SR58611A-induced cirrhotic portal vein relaxation. Finally, β3-adrenoceptors were identified in the liver, heart and portal vein of cirrhotic and control animals; their expression was increased in cirrhotic rats. CONCLUSIONS AND IMPLICATIONS β3-Adrenoceptors are altered in portal hypertension of experimental cirrhosis and may represent a novel therapeutic target. PMID:22708587

Functional human antibody CDR fusions as long-acting therapeutic endocrine agonists.

PubMed

Liu, Tao; Zhang, Yong; Liu, Yan; Wang, Ying; Jia, Haiqun; Kang, Mingchao; Luo, Xiaozhou; Caballero, Dawna; Gonzalez, Jose; Sherwood, Lance; Nunez, Vanessa; Wang, Danling; Woods, Ashley; Schultz, Peter G; Wang, Feng

2015-02-03

On the basis of the 3D structure of a bovine antibody with a well-folded, ultralong complementarity-determining region (CDR), we have developed a versatile approach for generating human or humanized antibody agonists with excellent pharmacological properties. Using human growth hormone (hGH) and human leptin (hLeptin) as model proteins, we have demonstrated that functional human antibody CDR fusions can be efficiently engineered by grafting the native hormones into different CDRs of the humanized antibody Herceptin. The resulting Herceptin CDR fusion proteins were expressed in good yields in mammalian cells and retain comparable in vitro biological activity to the native hormones. Pharmacological studies in rodents indicated a 20- to 100-fold increase in plasma circulating half-life for these antibody agonists and significantly extended in vivo activities in the GH-deficient rat model and leptin-deficient obese mouse model for the hGH and hLeptin antibody fusions, respectively. These results illustrate the utility of antibody CDR fusions as a general and versatile strategy for generating long-acting protein therapeutics.

Blood eosinophils and inhaled corticosteroid/long-acting β-2 agonist efficacy in COPD

PubMed Central

Pavord, Ian D; Lettis, Sally; Locantore, Nicholas; Pascoe, Steve; Jones, Paul W; Wedzicha, Jadwiga A; Barnes, Neil C

2016-01-01

Objective We performed a review of studies of fluticasone propionate (FP)/salmeterol (SAL) (combination inhaled corticosteroid (ICS)/long-acting β2-agonist (LABA)) in patients with COPD, which measured baseline (pretreatment) blood eosinophil levels, to test whether blood eosinophil levels ≥2% were associated with a greater reduction in exacerbation rates with ICS therapy. Methods Three studies of ≥1-year duration met the inclusion criteria. Moderate and severe exacerbation rates were analysed according to baseline blood eosinophil levels (<2% vs ≥2%). At baseline, 57–75% of patients had ≥2% blood eosinophils. Changes in FEV1 and St George's Respiratory Questionnaire (SGRQ) scores were compared by eosinophil level. Results For patients with ≥2% eosinophils, FP/SAL was associated with significant reductions in exacerbation rates versus tiotropium (INSPIRE: n=719, rate ratio (RR)=0.75, 95% CI 0.60 to 0.92, p=0.006) and versus placebo (TRISTAN: n=1049, RR=0.63, 95% CI 0.50 to 0.79, p<0.001). No significant difference was seen in the <2% eosinophil subgroup in either study (INSPIRE: n=550, RR=1.18, 95% CI 0.92 to 1.51, p=0.186; TRISTAN: n=354, RR=0.99, 95% CI 0.67 to 1.47, p=0.957, respectively). In SCO30002 (n=373), no significant effects were observed (FP or FP/SAL vs placebo). No relationship was observed in any study between eosinophil subgroup and treatment effect on FEV1 and SGRQ. Discussion Baseline blood eosinophil levels may represent an informative marker for exacerbation reduction with ICS/LABA in patients with COPD and a history of moderate/severe exacerbations. PMID:26585525

Novelty response of rats determines the effect of prefrontal alpha-2 adrenoceptor modulation on anxiety.

PubMed

Uzsoki, B; Tóth, M; Hernádi, I

2011-07-25

In this study we provide evidence that animals of the same population, although identical in age and sex, have individual reactions to the prefrontal modulation of adrenoceptors. We have examined the dose-dependent action of α(2)-adrenoceptor agents on the anxiety of rats with different response to novelty in the elevated plus maze (EPM) apparatus. Rats were divided into high (HR) and low responder (LR) groups based on their locomotor activity in a novel open field environment. HR rats also showed increased locomotion and low anxiety in the EPM. Prefrontal injection of α(2)-receptor antagonist yohimbine, BRL44408 or imiloxan caused anxiety only in HR rats. The α(2A/D)-receptor agonist guanfacine increased anxiety levels of both groups. However, the effective dose was lower in HR rats. The present results propose different prefrontal adrenoceptor sensitivity of rats showing distinct baseline activity levels. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Long-acting β-agonist prescribing in people with asthma in primary care.

PubMed

Morales, Daniel R; Jackson, Cathy; Fielding, Shona; Guthrie, Bruce

2013-02-01

Long-acting β2-agonist (LABA) monotherapy is contraindicated in asthma following reports of serious adverse events. Anonymised Scottish health data were used to determine the prevalence of LABA prescribing and LABA monotherapy (sustained and episodic) in asthma during 2006. Of 73 486 asthma patients identified, 5592 (7.6%; 95% CI 7.4% to 7.8%) were prescribed LABAs as a separate inhaler of which 991 patients had LABA monotherapy (17.7% (95% CI 16.7% to 18.7%) of patients at risk). Asthma reviews were associated with reductions in sustained (OR 0.44; 95% CI 0.32 to 0.61) but not episodic monotherapy (OR 1.16; 95% CI 0.85 to 1.57). These findings support recent changes in UK asthma guidelines recommending LABAs in fixed-dose combination inhalers.

Formoterol versus short-acting beta-agonists as relief medication for adults and children with asthma

PubMed Central

Welsh, Emma J; Cates, Christopher J

2014-01-01

Background Formoterol is a long-acting beta2-agonist but because it has a fast onset of action it can also be used as a relief medication. Objectives To asses the efficacy and safety of formoterol as reliever therapy in comparison to short-acting beta2-agonists in adults and children with asthma. Search methods We searched the Cochrane Airways Group Specialised Register and websites of clinical trial registers (for unpublished trial data), and we checked the Food and Drug Administration (FDA) submissions in relation to formoterol. The date of the most recent search was February 2010. Selection criteria Randomised, parallel-arm trials of at least 12 weeks duration in patients of any age and severity of asthma. Studies randomised patients to any dose of as-needed formoterol versus short-acting beta2-agonist. Concomitant use of inhaled corticosteroids or other maintenance medication was allowed, as long as this was not part of the randomised treatment regimen. Data collection and analysis Two authors independently selected trials for inclusion in the review. Outcome data were extracted by one author and checked by the second author. We sought unpublished data on primary outcomes. Main results This review includes eight studies conducted in 22,604 participants (mostly adults). Six studies compared formoterol as-needed to terbutaline whilst two studies compared formoterol with salbutamol as-needed. Background maintenance therapy varied across the trials. Asthma exacerbations and serious adverse events showed a direction of treatment effect favouring formoterol, of which one outcome reached statistical significance (exacerbations requiring a course of oral corticosteroids). In patients on short-acting beta2-agonists, 117 people out of 1000 had exacerbations requiring oral corticosteroids over 30 weeks, compared to 101 (95% CI 93 to 108) out of 1000 for patients on formoterol as-needed. In patients on maintenance inhaled corticosteroids there were also significantly fewer

Conopeptide ρ-TIA defines a new allosteric site on the extracellular surface of the α1B-adrenoceptor.

PubMed

Ragnarsson, Lotten; Wang, Ching-I Anderson; Andersson, Åsa; Fajarningsih, Dewi; Monks, Thea; Brust, Andreas; Rosengren, K Johan; Lewis, Richard J

2013-01-18

The G protein-coupled receptor (GPCR) superfamily is an important drug target that includes over 1000 membrane receptors that functionally couple extracellular stimuli to intracellular effectors. Despite the potential of extracellular surface (ECS) residues in GPCRs to interact with subtype-specific allosteric modulators, few ECS pharmacophores for class A receptors have been identified. Using the turkey β(1)-adrenergic receptor crystal structure, we modeled the α(1B)-adrenoceptor (α(1B)-AR) to help identify the allosteric site for ρ-conopeptide TIA, an inverse agonist at this receptor. Combining mutational radioligand binding and inositol 1-phosphate signaling studies, together with molecular docking simulations using a refined NMR structure of ρ-TIA, we identified 14 residues on the ECS of the α(1B)-AR that influenced ρ-TIA binding. Double mutant cycle analysis and docking confirmed that ρ-TIA binding was dominated by a salt bridge and cation-π between Arg-4-ρ-TIA and Asp-327 and Phe-330, respectively, and a T-stacking-π interaction between Trp-3-ρ-TIA and Phe-330. Water-bridging hydrogen bonds between Asn-2-ρ-TIA and Val-197, Trp-3-ρ-TIA and Ser-318, and the positively charged N terminus and Glu-186, were also identified. These interactions reveal that peptide binding to the ECS on transmembrane helix 6 (TMH6) and TMH7 at the base of extracellular loop 3 (ECL3) is sufficient to allosterically inhibit agonist signaling at a GPCR. The ligand-accessible ECS residues identified provide the first view of an allosteric inhibitor pharmacophore for α(1)-adrenoceptors and mechanistic insight and a new set of structural constraints for the design of allosteric antagonists at related GPCRs.

[Beta-1 adrenoceptor blockade decreases the firing rate to painful stimuli in spinal wide-dynamic range neurons in rats].

PubMed

Lamothe-Molina, Paul J; Lamothe-Molina, Pedro A; López-Ávila, Alberto

2014-01-01

It is known that epinephrine/norepinephrine inhibit acute pain transmission. However, the role of ß-adrenoceptors is not clear. Thus, we analyzed if beta-1 and/or beta-2 adrenoceptors can modulate acute pain transmission by performing in vivo single unit recordings during painful and non-painful peripheral stimulation in rats. Longitudinal study in which we analyzed seven groups of male rats Wistar: control group (n = 11): saline (0.9 %); EPI group (n = 8): epinephrine 100 mcg; beta-1 agonist group (n = 8): dobutamine 125 mcg; beta-1-antagonist group (n = 9): metoprolol 100 mcg; beta-2-agonist group (n = 7): clenbuterol 100 mcg; beta-2-antagonist group (n = 8): butoxamine 100 mcg; beta-1-antagonist + EPI group (n = 10): metoprolol 100 mcg + epinephrine 100 mcg. For the statistical analysis we used ANOVA. Epinephrine significantly reduced the basal firing rate (BFR) in 34.1 % (p < 0.05) and also the evoked response by painful stimulation in 56 % (p < 0.05). No change was observed in the evoked response by non-painful stimulation. ANTß1 was the only beta-adrenoceptor acting drug that significantly reduced the evoked response by painful stimulation in 41 % (p < 0.05). None of the other drugs alone affected either the BFR or the evoked response to non-painful or painful stimulation. It is the first time that a beta-1-adrenoceptor antagonist (metoprolol) probes to be effective in reducing the response to painful stimulation in WDR neurons.

β2-adrenoceptor blockage induces G1/S phase arrest and apoptosis in pancreatic cancer cells via Ras/Akt/NFκB pathway.

PubMed

Zhang, Dong; Ma, Qingyong; Wang, Zheng; Zhang, Min; Guo, Kun; Wang, Fengfei; Wu, Erxi

2011-11-26

Smoking and stress, pancreatic cancer (PanCa) risk factors, stimulate nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and catecholamines production respectively. NNK and catecholamine bind the β-adrenoceptors and induce PanCa cell proliferation; and we have previously suggested that β-adrenergic antagonists may suppress proliferation and invasion and stimulate apoptosis in PanCa. To clarify the mechanism of apoptosis induced by β2-adrenergic antagonist, we hypothesize that blockage of the β2-adrenoceptor could induce G1/S phase arrest and apoptosis and Ras may be a key player in PanCa cells. The β1 and β2-adrenoceptor proteins were detected on the cell surface of PanCa cells from pancreatic carcinoma specimen samples by immunohistochemistry. The β2-adrenergic antagonist ICI118,551 significantly induced G1/S phase arrest and apoptosis compared with the β1-adrenergic antagonist metoprolol, which was determined by the flow cytometry assay. β2-adrenergic antagonist therapy significantly suppressed the expression of extracellular signal-regulated kinase, Akt, Bcl-2, cyclin D1, and cyclin E and induced the activation of caspase-3, caspase-9 and Bax by Western blotting. Additionally, the β2-adrenergic antagonist reduced the activation of NFκB in vitro cultured PanCa cells. The blockage of β2-adrenoceptor markedly induced PanCa cells to arrest at G1/S phase and consequently resulted in cell death, which is possibly due to that the blockage of β2-adrenoceptor inhibited NFκB, extracellular signal-regulated kinase, and Akt pathways. Therefore, their upstream molecule Ras may be a key factor in the β2-adrenoceptor antagonist induced G1/S phase arrest and apoptosis in PanCa cells. The new pathway discovered in this study may provide an effective therapeutic strategy for PanCa.

Characterization and autoradiographic localization of beta-adrenoceptor subtypes in human cardiac tissues.

PubMed Central

Buxton, B. F.; Jones, C. R.; Molenaar, P.; Summers, R. J.

1987-01-01

1 Receptor autoradiography using (-)-[125I]-cyanopindolol (CYP) was used to study the distribution of beta-adrenoceptor subtypes in human right atrial appendage, left atrial free wall, left ventricular papillary muscle and pericardium. 2 The binding of (-)-[125I]-CYP to slide-mounted tissue sections of human right atrial appendage was time-dependent (K1 = 4.11 +/- 1.01 X 10(8) M-1 min-1, K-1 = 1.47 +/- 0.25 X 10(-3) min-1, n = 3), saturable (42.02 +/- 2.96 pM, n = 4) and stereoselective with respect to the optical isomers of propranolol (pKD (-):8.97 +/- 0.02, (+):6.88 +/- 0.06, n = 3). 3 The proportions of beta-adrenoceptor subtypes were determined in slide-mounted tissue sections using the antagonists CGP 20712A (beta 1-selective) and ICI 118,551 (beta 2-selective). In right atrial appendage and left ventricular papillary muscle 40% (34-45%) of the beta-adrenoceptors were of the beta 2-subtype. 4 Images from X-ray film and nuclear emulsion coated coverslips exposed to (-)-[125I]-CYP-labelled sections showed an even distribution of beta-adrenoceptor subtypes over the myocardium of the right atrial appendage, left ventricular papillary muscle and left atrial free wall. Sections of pericardium exhibited predominantly beta 2-adrenoceptors. beta 2-Adrenoceptors were localized to the intimal surface of coronary arteries. 5 The selective beta 1-adrenoceptor agonist RO363 and beta 2-selective agonist procaterol produced concentration-dependent inotropic responses in right atrial appendage strips. Responses to RO363 were antagonized by CGP 20712A (pKB = 9.29) suggesting an interaction with beta 1-adrenoceptors. Responses to procaterol were antagonized by ICI 118,551 (pKB = 9.06) suggesting an interaction at beta 2-adrenoceptors. 6 The finding that a significant proportion of human myocardial adrenoceptors are of the beta 2-subtype has important clinical implications for the involvement of these receptors in the control of heart rate and force, and the autoradiographic

Selective inhibition of alpha1B-adrenergic receptor expression and function using a phosphorothioate antisense oligodeoxynucleotide.

PubMed

Gonzalez-Cabrera, P J; Iversen, P L; Liu, M F; Scofield, M A; Jeffries, W B

1998-06-01

To investigate alpha1B-adrenoceptor function, we developed a phosphorothioate antisense oligodeoxynucleotide (AO) to inhibit the expression of the alpha1B-adrenoceptor subtype in DDT1 MF2 cells. We measured the cellular uptake of the AO and its effect on alpha1B-adrenoceptor mRNA expression, protein density, and coupling to phospholipase C. Cells treated with either a control oligodeoxynucleotide (CO) or medium alone served as control groups. Confocal microscopy demonstrated that DDT1 MF2 cells internalized carboxyfluorescein-labeled (FAM) AO within 30 min. Analysis of cellular lysates showed that approximately 50% of the intracellular FAM-AO was present as an intact 18-mer for up to 48 hr. Incubation of cells with AO for 48 hr decreased alpha1B-adrenoceptor density ([3H]prazosin Bmax) versus control groups by 12% (1 microM AO) and 72% (10 microM AO). In time course experiments, AO (10 microM) reduced alpha1B-adrenoceptor density by 28, 64, and 68% versus controls after 24, 48, and 72 hr of exposure, respectively. alpha1B-Adrenoceptor mRNA concentration (measured by RT-PCR) was reduced by 25% in cells treated for 48 hr with 10 microM AO versus controls. AO pretreatment (10 microM, 48 hr) reduced the maximum response to agonist-stimulated [3H]inositol phosphate accumulation. The maximal response of the full agonist norepinephrine was reduced by 30% after AO treatment, and by 73% for the partial agonist naphazoline. In contrast, AO did not affect histamine-stimulated total [3H]inositol phosphate accumulation. Thus, AO effectively reduced alpha1B-adrenoceptor subtype expression and function in vitro, suggesting a potential to selectively inhibit alpha1B-adrenoceptor function in vivo.

Structure-activity relationship studies of (+/-)-terbutaline and (+/-)-fenoterol on beta3-adrenoceptors in the guinea pig gastric fundus.

PubMed

Horinouchi, T; Nakagawa, Y; Wakabayashi, M; Koike, K

2001-08-01

(+/-)-Terbutaline and (+/-)-fenoterol are both arylethanolamine analogs that have tertbutyl and aryliso-propyl substituents respectively at the a position on the nitrogen of the ethanolamine side chain. In the present study, we have investigated the structure-activity relationships of (+/-)-terbutaline and (+/-)-fenoterol as beta3-adrenoceptor agonists in the guinea pig gastric fundus. (+/-)-Terbutaline and (+/-)-fenoterol induced concentration-dependent relaxation of the precontracted gastric fundus with pD2 values of 4.45+/-0.10 and 5.90+/-0.09, and intrinsic activities of 1.00+/-0.03 and 0.99+/-0.01 respectively. The combination of the selective beta1-adrenoceptor antagonist (+/-)-atenolol (100 microM), and the selective beta2-adrenoceptor antagonist (+/-)-butoxamine (100 microM), produced a 2 and 6 fold rightward shift of the concentration-response curves for (+/-)-terbutaline and (+/-)-fenoterol respectively, without depressing the maximal responses. The order of potency of these agonists was (pD2 value): (+/-)-fenoterol (5.09+/-0.10) > (+/-)-terbutaline (4.13+/-0.08). In the presence of (+/-)-atenolol and (+/-)-butoxamine, however, the non-selective beta1, beta2- and beta3-adrenoceptor antagonist (+/-)-bupranolol caused a concentration-dependent rightward shift of the concentration-response curves for (+/-)-terbutaline and (+/-)-fenoterol. Schild plot analyses of the effects of (+/-)-bupranolol against these agonists gave pA2 values of 6.21+/-0.07 ((+/-)-terbutaline) and 6.37+/-0.06 ((+/-)-fenoterol) respectively, and the slopes of the Schild plot were not significantly different from unity (p>0.05). These results suggest that the relaxant responses to (+/-)-terbutaline and (+/-)-fenoterol are mainly mediated through beta3-adrenoceptors in the guinea pig gastric fundus. The beta3-adrenoceptor agonist potencies of arylethanolamine analogs depend on the size of the end of the alkylamine side chain.

Blood eosinophils and inhaled corticosteroid/long-acting β-2 agonist efficacy in COPD.

PubMed

Pavord, Ian D; Lettis, Sally; Locantore, Nicholas; Pascoe, Steve; Jones, Paul W; Wedzicha, Jadwiga A; Barnes, Neil C

2016-02-01

We performed a review of studies of fluticasone propionate (FP)/salmeterol (SAL) (combination inhaled corticosteroid (ICS)/long-acting β2-agonist (LABA)) in patients with COPD, which measured baseline (pretreatment) blood eosinophil levels, to test whether blood eosinophil levels ≥2% were associated with a greater reduction in exacerbation rates with ICS therapy. Three studies of ≥1-year duration met the inclusion criteria. Moderate and severe exacerbation rates were analysed according to baseline blood eosinophil levels (<2% vs ≥2%). At baseline, 57-75% of patients had ≥2% blood eosinophils. Changes in FEV1 and St George's Respiratory Questionnaire (SGRQ) scores were compared by eosinophil level. For patients with ≥2% eosinophils, FP/SAL was associated with significant reductions in exacerbation rates versus tiotropium (INSPIRE: n=719, rate ratio (RR)=0.75, 95% CI 0.60 to 0.92, p=0.006) and versus placebo (TRISTAN: n=1049, RR=0.63, 95% CI 0.50 to 0.79, p<0.001). No significant difference was seen in the <2% eosinophil subgroup in either study (INSPIRE: n=550, RR=1.18, 95% CI 0.92 to 1.51, p=0.186; TRISTAN: n=354, RR=0.99, 95% CI 0.67 to 1.47, p=0.957, respectively). In SCO30002 (n=373), no significant effects were observed (FP or FP/SAL vs placebo). No relationship was observed in any study between eosinophil subgroup and treatment effect on FEV1 and SGRQ. Baseline blood eosinophil levels may represent an informative marker for exacerbation reduction with ICS/LABA in patients with COPD and a history of moderate/severe exacerbations. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Selective regulation of beta 1- and beta 2-adrenoceptors in the human heart by chronic beta-adrenoceptor antagonist treatment.

PubMed Central

Michel, M. C.; Pingsmann, A.; Beckeringh, J. J.; Zerkowski, H. R.; Doetsch, N.; Brodde, O. E.

1988-01-01

1. In 44 patients undergoing coronary artery bypass grafting, the effect of chronic administration of the beta-adrenoceptor antagonists sotalol, propranolol, pindolol, metoprolol and atenolol on beta-adrenoceptor density in right atria (containing 70% beta 1- and 30% beta 2-adrenoceptors) and in lymphocytes (having only beta 2-adrenoceptors) was studied. 2. beta-Adrenoceptor density in right atrial membranes and in intact lymphocytes was assessed by (-)-[125I]-iodocyanopindolol (ICYP) binding; the relative amount of right atrial beta 1- and beta 2-adrenoceptors was determined by inhibition of ICYP binding by the selective beta 2-adrenoceptor antagonist ICI 118,551 and analysis of the resulting competition curves by the iterative curve fitting programme LIGAND. 3. With the exception of pindolol, all beta-adrenoceptor antagonists increased right atrial beta-adrenoceptor density compared to that observed in atria from patients not treated with beta-adrenoceptor antagonists. 4. All beta-adrenoceptor antagonists increased right atrial beta 1-adrenoceptor density; on the other hand, only sotalol and propranolol also increased right atrial beta 2-adrenoceptor density, whereas metoprolol and atenolol did not affect it and pindolol decreased it. 5. Similarly, in corresponding lymphocytes, only sotalol or propranolol increased beta 2-adrenoceptor density, while metoprolol and atenolol did not affect it and pindolol decreased it. 6. It is concluded that beta-adrenoceptor antagonists subtype-selectively regulate cardiac and lymphocyte beta-adrenoceptor subtypes. The selective increase in cardiac beta 1-adrenoceptor density evoked by metoprolol and atenolol may be one of the reasons for the beneficial effects observed in patients with end-stage congestive cardiomyopathy following intermittent treatment with low doses of selective beta 1-adrenoceptor antagonists. PMID:2902891

Contribution of β-adrenoceptor subtypes to relaxation of colon and oesophagus and pacemaker activity of ureter in wildtype and β3-adrenoceptor knockout mice

PubMed Central

Oostendorp, Jaap; Preitner, Frédéric; Moffatt, James; Jimenez, Maria; Giacobino, Jean Paul; Molenaar, Peter; Kaumann, Alberto Julio

2000-01-01

The smooth muscle relaxant responses to the mixed β3-, putative β4-adrenoceptor agonist, (−)-CGP 12177 in rat colon are partially resistant to blockade by the β3-adrenoceptor antagonist SR59230A suggesting involvement of β3- and putative β4-adrenoceptors. We now investigated the function of the putative β4-adrenoceptor and other β-adrenoceptor subtypes in the colon, oesophagus and ureter of wildtype (WT) and β3-adrenoceptor knockout (β3KO) mice.(−)-Noradrenaline and (−)-adrenaline relaxed KCl (30 mM)-precontracted colon mostly through β1-and β3-adrenoceptors to a similar extent and to a minor extent through β2-adrenoceptors. In colon from β3KO mice, (−)-noradrenaline was as potent as in WT mice but the effects were mediated entirely through β1-adrenoceptors. (−)-CGP 12177 relaxed colon from β3KO mice with 2 fold greater potency than in WT mice. The maintenance of potency for (−)-noradrenaline and increase for (−)-CGP 12177 indicate compensatory increases in β1- and putative β4-adrenoceptor function in β3KO mice.In oesophagi precontracted with 1 μM carbachol, (−)-noradrenaline caused relaxation mainly through β1-and β3-adrenoceptors. (−)-CGP 12177 (2 μM) relaxed oesophagi from WT by 61.4±5.1% and β3KO by 67.3±10.1% of the (−)-isoprenaline-evoked relaxation, consistent with mediation through putative β4-adrenoceptors.In ureter, (−)-CGP 12177 (2 μM) reduced pacemaker activity by 31.1±2.3% in WT and 31.3±7.5% in β3KO, consistent with mediation through putative β4-adrenoceptors.Relaxation of mouse colon and oesophagus by catecholamines are mediated through β1- and β3-adrenoceptors in WT. The putative β4-adrenoceptor, which presumably is an atypical state of the β1-adrenoceptor, mediates the effects of (−)-CGP 12177 in colon, oesophagus and ureter. PMID:10864880

Conopeptide ρ-TIA Defines a New Allosteric Site on the Extracellular Surface of the α1B-Adrenoceptor*♦

PubMed Central

Ragnarsson, Lotten; Wang, Ching-I Anderson; Andersson, Åsa; Fajarningsih, Dewi; Monks, Thea; Brust, Andreas; Rosengren, K. Johan; Lewis, Richard J.

2013-01-01

The G protein-coupled receptor (GPCR) superfamily is an important drug target that includes over 1000 membrane receptors that functionally couple extracellular stimuli to intracellular effectors. Despite the potential of extracellular surface (ECS) residues in GPCRs to interact with subtype-specific allosteric modulators, few ECS pharmacophores for class A receptors have been identified. Using the turkey β1-adrenergic receptor crystal structure, we modeled the α1B-adrenoceptor (α1B-AR) to help identify the allosteric site for ρ-conopeptide TIA, an inverse agonist at this receptor. Combining mutational radioligand binding and inositol 1-phosphate signaling studies, together with molecular docking simulations using a refined NMR structure of ρ-TIA, we identified 14 residues on the ECS of the α1B-AR that influenced ρ-TIA binding. Double mutant cycle analysis and docking confirmed that ρ-TIA binding was dominated by a salt bridge and cation-π between Arg-4-ρ-TIA and Asp-327 and Phe-330, respectively, and a T-stacking-π interaction between Trp-3-ρ-TIA and Phe-330. Water-bridging hydrogen bonds between Asn-2-ρ-TIA and Val-197, Trp-3-ρ-TIA and Ser-318, and the positively charged N terminus and Glu-186, were also identified. These interactions reveal that peptide binding to the ECS on transmembrane helix 6 (TMH6) and TMH7 at the base of extracellular loop 3 (ECL3) is sufficient to allosterically inhibit agonist signaling at a GPCR. The ligand-accessible ECS residues identified provide the first view of an allosteric inhibitor pharmacophore for α1-adrenoceptors and mechanistic insight and a new set of structural constraints for the design of allosteric antagonists at related GPCRs. PMID:23184947

Fenoterol inhibits superoxide anion generation by human polymorphonuclear leukocytes via beta-adrenoceptor-dependent and -independent mechanisms.

PubMed

Mirza, Zafar Nazir; Kato, Masahiko; Kimura, Hirokazu; Tachibana, Atsushi; Fujiu, Toru; Suzuki, Masato; Mochizuki, Hiroyuki; Tokuyama, Kenichi; Morikawa, Akihiro

2002-05-01

Beta2-adrenoceptor agonists, used widely as bronchodilator in treating bronchial asthma, may have anti-inflammatory activity. We examined whether various widely prescribed beta2-adrenoceptor agonists differ in anti-inflammatory mechanisms. We investigated effects of these drugs on superoxide anion generation by stimulated human polymorphonuclear leukocytes in vitro using chemiluminescence. At high concentrations, fenoterol significantly inhibited both N-formylmethionyl-leucyl-phenylalanine- and phorbol myristate acetate-induced superoxide generation by neutrophils. In contrast, salbutamol or procaterol partially inhibited generation with the former stimulus but not the latter. Inhibition by salbutamol or procaterol was completely reversed by either propranolol, a nonselective beta-adrenoceptor antagonist, or ICI-118551, a beta2-adrenoceptor-selective antagonist. In contrast, the effect of fenoterol at concentrations exceeding 10(-6) M against superoxide generation with the former stimulus was only partially reversed by antagonists, and the effect of high concentrations of fenoterol against generation with the latter stimulus was not reversed. No drugs scavenged superoxide at the highest concentration used (10(-5) M). Fenoterol at high concentrations has an inhibitory effect on superoxide generation that includes a component not mediated via beta2-adrenoceptors. Direct inhibition at or downstream from protein kinase C may be involved.

alpha2-Adrenergic agonists antagonise the anxiolytic-like effect of antidepressants in the four-plate test in mice.

PubMed

Massé, Fabienne; Hascoët, Martine; Bourin, Michel

2005-10-14

Selective serotonin reuptake inhibitors (SSRIs) and serotonin/noradrenaline reuptake inhibitors (SNRIs) has been reported to be efficient in anxiety disorders. Some animal models have demonstrated an anxiolytic-like effect following acute administration, however, it is not yet known how noradrenergic receptors are implicated in the therapeutic effects of antidepressants (ADs) in anxiety. The effects of two alpha(2)-adrenoceptor agonists (clonidine, guanabenz) on anxiolytic-like effect of two SSRIs (paroxetine and citalopram) and two SNRIs (venlafaxine and milnacipran) were evaluated in the four-plate test (FPT) in mice. Paroxetine (4 mg/kg), citalopram (8 mg/kg), venlafaxine (8 mg/kg), and milnacipran (8 mg/kg) administered intraperitoneally (i.p.) increased the number of punishments accepted by mice in the FPT. Clonidine (0.0039-0.5 mg/kg) and guanabenz (0.03-0.5mg/kg) had no effect on the number of punishments accepted by mice. Clonidine (0.03 and 0.06 mg/kg) and guanabenz (0.125 and 0.5 mg/kg) (i.p. -45 min) reversed the anti-punishment effect of paroxetine, citalopram, venlafaxine and milnacipran (i.p. -30 min). But if the antidepressants are administered 45 min before the test and alpha(2)-adrenoceptor agonists 30 min before the test, alpha(2)-adrenoceptor agonists failed to alter the anti-punishment effect of antidepressants. The results of this present study indicate that alpha(2)-adrenoceptor agonists antagonise the anxiolytic-like effect of antidepressants in mice when they are administered 15 min before the administration of antidepressant suggesting a close inter-regulation between noradrenergic and serotoninergic system in the mechanism of SSRIs and SNRIs in anxiety-like behaviour.

Effects of Synephrine and B-Phenethylamine on Human a-Adrenoceptor Subtypes

USDA-ARS?s Scientific Manuscript database

Synephrine and B-phenethylamine are structurally related to ephedrine. In this study, the effects of synephrine and B-phenethylamine are investigated on a-adrenoceptor (a-AR) subtypes expressed in human embroyonic kidney (HEK293) or Chinese hamster ovary (CHO) cells, and compared to that of 1R,2S-no...

Proliferation of the human urothelium is induced by atypical β1 -adrenoceptors.

PubMed

Winder, M; Wasén, C; Aronsson, P; Giglio, D

2015-09-01

We wanted to assess whether β-adrenoceptors mediate proliferation in the normal and malignant urothelial cell lines UROtsa and T24, respectively. Urothelial cells were cultured for 24 h in the presence of the β-adrenoceptor agonists isoprenaline (β1/2/3 ), dobutamine (β1 ), salbutamol (β2 ), BRL 37344 (β3 ), CGP 12177 (a partial β-agonist) or β-adrenoceptor antagonists (metoprolol; β1 , propranolol; β1/2 ). Phosphorylation of kinases was screened with a Human Phospho-Kinase Array Kit (R&D systems). Intracellular pathways activated by proliferation of urothelial cells were characterized by incubating cells with the MEK1/2 inhibitor PD 98,059, the p38 kinase inhibitor losmapimod or with the Akt 1/2 kinase inhibitor. Proliferation was assessed with the MTT proliferation assay (ATCC). Western blot and immunocytochemistry were used for detection of the β1 -adrenoceptor. Isoprenaline and dobutamine induced proliferation, while salbutamol and BRL 37344 did not. Dobutamine-induced proliferation was not affected by metoprolol or propranolol but was instead antagonized by CGP 12177 in T24 but not in UROtsa. In response to stimulation with dobutamine, Akt1/2/3 was phosphorylated in UROtsa, while ERK1/2 and p38 were phosphorylated in T24. MEK1/2 inhibition blocked basal and dobutamine-induced proliferation in T24 but only basal proliferation in UROtsa. Losmapimod slightly inhibited basal proliferation in T24 but not dobutamine-induced proliferation. Akt 1/2 inhibitor blocked basal and dobutamine-induced proliferation in UROtsa. Immunocytochemistry and Western blot revealed expression of β1 -adrenoceptors in both urothelial cell lines. The present data show that the urothelium expresses atypical β1-adrenoceptors that activate intracellular kinases inducing urothelial proliferation. © 2016 John Wiley & Sons Ltd.

The effects of SB 216469, an antagonist which discriminates between the alpha 1A-adrenoceptor and the human prostatic alpha 1-adrenoceptor.

PubMed Central

Chess-Williams, R.; Chapple, C. R.; Verfurth, F.; Noble, A. J.; Couldwell, C. J.; Michel, M. C.

1996-01-01

1. The affinity of the alpha 1-adrenoceptor antagonist SB 216469 (also known as REC 15/2739) has been determined at native and cloned alpha 1-adrenoceptor subtypes by radioligand binding and at functional alpha 1-adrenoceptor subtypes in isolated tissues. 2. In radioligand binding studies with [3H]-prazosin, SB 216469 had a high affinity at the alpha 1A-adrenoceptors of the rat cerebral cortex and kidney (9.5-9.8) but a lower affinity at the alpha 1B-adrenoceptors of the rat spleen and liver (7.7-8.2). 3. At cloned rat alpha 1-adrenoceptor subtypes transiently expressed in COS-1 cells and also at cloned human alpha 1-adrenoceptor subtypes stably transfected in Rat-1 cells, SB 216469 exhibited a high affinity at the alpha 1a-adrenoceptors (9.6-10.4) with a significantly lower affinity at the alpha 1b-adrenoceptor (8.0-8.4) and an intermediate affinity at the alpha 1d-adrenoceptor (8.7-9.2). 4. At functional alpha 1-adrenoceptors, SB 216469 had a similar pharmacological profile, with a high affinity at the alpha 1A-adrenoceptors of the rat vas deferens and anococcygeus muscle (pA2 = 9.5-10.0), a low affinity at the alpha 1B-adrenoceptors of the rat spleen (6.7) and guinea-pig aorta (8.0), and an intermediate affinity at the alpha 1D-adrenoceptors of the rat aorta (8.8). 5. Several recent studies have concluded that the alpha 1-adrenoceptor present in the human prostate has the pharmacological characteristics of the alpha 1A-adrenoceptor subtype. However, the affinity of SB 216469 at human prostatic alpha 1-adrenoceptors (pA2 = 8.1) determined in isolated tissue strips, was significantly lower than the values obtained at either the cloned alpha 1a-adrenoceptors (human, rat, bovine) or the native alpha 1A-adrenoceptors in radioligand binding and functional studies in the rat. 6. Our results with SB 216469, therefore, suggest that the alpha 1-adrenoceptor mediating contractile responses of the human prostate has properties which distinguish it from the cloned alpha 1a-adrenoceptor

Autoradiographic localization of beta-adrenoceptors in asthmatic human lung

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spina, D.; Rigby, P.J.; Paterson, J.W.

1989-11-01

The autoradiographic distribution and density of beta-adrenoceptors in human non-diseased and asthmatic bronchi were investigated using (125I)iodocyanopindolol (I-CYP). Analysis of the effects of the beta-adrenoceptor antagonists on I-CYP binding demonstrated that betaxolol (20 nM, beta 1-selective) had no significant effect on specific grain density in either nonasthmatic or asthmatic human bronchus, whereas ICI-118551 (20 nM, beta 2-selective) inhibited I-CYP binding by 85 +/- 9% and 89 +/- 3%, respectively. Thus, homogeneous populations of beta 2-adrenoceptors existed in bronchi from both sources. Large populations of beta-adrenoceptors were localized to the bronchial epithelium, submucosal glands, and airway smooth muscle. Asthmatic bronchial tissuemore » featured epithelial damage with exfoliated cells associated with luminal mucus plugs. A thickened basement membrane and airway smooth muscle hyperplasia were also evident. High levels of specific I-CYP binding were also detected over asthmatic bronchial smooth muscle, as assessed by autoradiography and quantitation of specific grain densities. Isoproterenol and fenoterol were 10- and 13-fold less potent, respectively, in bronchi from asthmatic lung than in those from nonasthmatic lung. However, this attenuated responsiveness to beta-adrenoceptor agonists was not caused by reduced beta-adrenoceptor density in asthmatic airways. A defect may exist in the coupling between beta-adrenoceptors and postreceptor mechanisms in severely asthmatic lung.« less

α1-Adrenoceptors in the hippocampal dentate gyrus involved in learning-dependent long-term potentiation during active-avoidance learning in rats.

PubMed

Lv, Jing; Zhan, Su-Yang; Li, Guang-Xie; Wang, Dan; Li, Ying-Shun; Jin, Qing-Hua

2016-11-09

The hippocampus is the key structure for learning and memory in mammals and long-term potentiation (LTP) is an important cellular mechanism responsible for learning and memory. The influences of norepinephrine (NE) on the modulation of learning and memory, as well as LTP, through β-adrenoceptors are well documented, whereas the role of α1-adrenoceptors in learning-dependent LTP is not yet clear. In the present study, we measured extracellular concentrations of NE in the hippocampal dentate gyrus (DG) region using an in-vivo brain microdialysis and high-performance liquid chromatography techniques during the acquisition and extinction of active-avoidance behavior in freely moving conscious rats. Next, the effects of prazosin (an antagonist of α1-adrenoceptor) and phenylephrine (an agonist of the α1-adrenoceptor) on amplitudes of field excitatory postsynaptic potential were measured in the DG region during the active-avoidance behavior. Our results showed that the extracellular concentration of NE in the DG was significantly increased during the acquisition of active-avoidance behavior and gradually returned to the baseline level following extinction training. A local microinjection of prazosin into the DG significantly accelerated the acquisition of the active-avoidance behavior, whereas a local microinjection of phenylephrine retarded the acquisition of the active-avoidance behavior. Furthermore, in all groups, the changes in field excitatory postsynaptic potential amplitude were accompanied by corresponding changes in active-avoidance behavior. Our results suggest that NE activation of α1-adrenoceptors in the hippocampal DG inhibits active-avoidance learning by modulation of synaptic efficiency in rats.

Computer-assisted determination of minimum energy conformations. 7: A pharmacophore model of the active region of the alpha2-adrenoceptor

NASA Astrophysics Data System (ADS)

Ashman, William P.; Mickiewicz, A. P.; Nelson, Todd M.

1992-09-01

Molecular modeling and computational chemistry techniques are used to analyze compounds in developing pharmacophores of biological receptors to use as templates in structure activity relationship studies and to design new chemicals having physiological activity of interest. In this study, the results of x-ray crystal analyses and PM3 semi-empirical molecular orbital conformational analyses are used to determine the three-dimensional representations of selected adrenergic compounds known to be agonists with the alpha2-adrenoceptor in achieving optimized geometries and electrostatic parameters. The alpha2-adrenergic agonists interact with the adrenergic system receptors to produce various increases or decreases in hemodynamic responses (i.e., hypertension, hypotension, and bradycardia) and sedation. A pharmacophore model of the active region of the alpha2-adrenoceptor is described based on the superimposition of common structural, electrostatic, and physicochemical features of the compounds. Using the model to predict compound adrenergic activity and to design alpha2-adrenergic compounds is discussed.

Effect of (R)-2-(2-aminothiazol-4-yl)-4'-{2-[(2-hydroxy-2-phenylethyl)amino]ethyl} acetanilide (YM178), a novel selective beta3-adrenoceptor agonist, on bladder function.

PubMed

Takasu, Toshiyuki; Ukai, Masashi; Sato, Shuichi; Matsui, Tetsuo; Nagase, Itsuro; Maruyama, Tatsuya; Sasamata, Masao; Miyata, Keiji; Uchida, Hisashi; Yamaguchi, Osamu

2007-05-01

We evaluated the pharmacological characteristics of (R)-2-(2-aminothiazol-4-yl)-4'-{2-[(2-hydroxy-2-phenylethyl)amino]-ethyl} acetanilide (YM178). YM178 increased cyclic AMP accumulation in Chinese hamster ovary (CHO) cells expressing human beta3-adrenoceptor (AR). The half-maximal effective concentration (EC50) value was 22.4 nM. EC50 values of YM178 for human beta1- and beta2-ARs were 10,000 nM or more, respectively. The ratio of intrinsic activities of YM178 versus maximal response induced by isoproterenol (nonselective beta-AR agonist) was 0.8 for human beta3-ARs, 0.1 for human beta1-ARs, and 0.1 for human beta2-ARs. The relaxant effects of YM178 were evaluated in rats and humans bladder strips precontracted with carbachol (CCh) and compared with those of isoproterenol and 4-[3-[(1,1-dimethylethyl)amino]-2-hydroxypropoxy]-1,3-dihydro-2H-benzimidazol-2-one hydrochloride (CGP-12177A) (beta3-AR agonist). EC50 values of YM178 and isoproterenol in rat bladder strips precontracted with 10(-6) M CCh were 5.1 and 1.4 microM, respectively, whereas those in human bladder strips precontracted with 10(-7) M CCh were 0.78 and 0.28 microM, respectively. In in vivo study, YM178 at a dose of 3 mg/kg i.v. decreased the frequency of rhythmic bladder contraction induced by intravesical filling with saline without suppressing its amplitude in anesthetized rats. These findings suggest the suitability of YM178 as a therapeutic drug for the treatment of symptoms of overactive bladder such as urinary frequency, urgency, and urge incontinence.

Effect of Selective Prostaglandin E2 EP2 Receptor Agonist CP-533,536 on Voiding Efficiency in Rats with Midodrine-Induced Functional Urethral Obstruction.

PubMed

Kurihara, Ryoko; Imazumi, Katsunori; Takamatsu, Hajime; Ishizu, Kenichiro; Yoshino, Taiji; Masuda, Noriyuki

2016-05-01

We investigated the effect of the selective prostaglandin E2 EP2 receptor agonist CP-533,536 on voiding efficiency in rats with midodrine-induced functional urethral obstruction. The effect of CP-533,536 (0.03-0.3 mg/kg, intravenous [i.v.]) on urethral perfusion pressure (UPP) was investigated in anesthetized rats pre-treated with midodrine (1 mg/kg, i.v.), which forms an active metabolite that acts as an α1 -adrenoceptor agonist. The effect of CP-533,536 (0.03-0.3 mg/kg, i.v.) on cystometric parameters was also investigated in anesthetized rats. In addition, the effect of CP-533,536 (0.03-0.3 mg/kg, i.v.) on residual urine volume (RV) and voiding efficiency (VE) was investigated in conscious rats treated with midodrine (1 mg/kg, i.v.). CP-533,536 dose-dependently decreased UPP elevated by midodrine in anesthetized rats. In contrast, CP-533,536 did not affect maximum voiding pressure, intercontraction interval, or intravesical threshold pressure. In conscious rats, midodrine (1 mg/kg, i.v.) markedly increased RV and reduced VE. CP-533,536 dose-dependently ameliorated increases in RV and decreases in VE induced by midodrine. These results suggest that a selective EP2 receptor agonist could ameliorate the elevation of RV and improve the reduction of VE in rats with functional urethral obstruction caused by stimulation of α1 -adrenoceptors. The mechanism of action might be not potentiation of bladder contraction but rather preferential relief of urethral constriction. © 2014 Wiley Publishing Asia Pty Ltd.

Contribution of α-adrenoceptor stimulation by phenylephrine to basal nitric oxide production in the isolated mouse aorta.

PubMed

van Langen, Johanna T H; Van Hove, Cor E; Schrijvers, Dorien M; Martinet, Wim; De Meyer, Guido R Y; Fransen, Paul; Bult, Hidde

2013-04-01

In the mouse aorta, contractions evoked by the α(1)-adrenoceptor agonist phenylephrine are strongly suppressed by the continuous production of nitric oxide (NO). We investigated whether phenylephrine itself stimulated NO production by activating endothelial α(2)-adrenoceptors. On a prostaglandin F(2α) contraction, the α(2)-adrenoceptor agonist 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine (UK14304) induced 29.3 ± 7.4% relaxation, which was inhibited by 0.1 μM 2-[(4,5-Dihydro-1H-imidazol-2-yl)methyl]-2,3-dihydro-1-methyl-1H-isoindole (BRL44408) with a pKB' corresponding to α(2)-antagonism. In the presence of NO synthase blockers, UK14304 elicited small contractions above 1 μM that were inhibited by 0.1 μM prazosin, but not influenced by 0.1 μM rauwolscine. At 3 μM or higher concentrations, phenylephrine caused only modest relaxation (up to 7.4 ± 2.3%) of segments constricted with prostaglandin F(2α) in the presence of prazosin, which was abolished with 0.1 μM BRL44408. Furthermore, BRL44408 did not increase contractions induced with 1 μM phenylephrine. These results confirm that α(1)- but not α(2)-adrenoceptors are expressed on aortic smooth muscle cells, whereas endothelial cells only express α(2)-adrenoceptors. Moreover, phenylephrine exerted a very modest relaxing effect through nonspecific stimulation of α(2)-adrenoceptors, but only at concentrations higher than 1 μM. It is concluded that the high basal output of NO in the isolated mouse aorta is not due to stimulation of α-adrenoceptors.

Agonist-Directed Desensitization of the β2-Adrenergic Receptor

PubMed Central

Goral, Vasiliy; Jin, Yan; Sun, Haiyan; Ferrie, Ann M.; Wu, Qi; Fang, Ye

2011-01-01

The β2-adrenergic receptor (β2AR) agonists with reduced tachyphylaxis may offer new therapeutic agents with improved tolerance profile. However, receptor desensitization assays are often inferred at the single signaling molecule level, thus ligand-directed desensitization is poorly understood. Here we report a label-free biosensor whole cell assay with microfluidics to determine ligand-directed desensitization of the β2AR. Together with mechanistic deconvolution using small molecule inhibitors, the receptor desensitization and resensitization patterns under the short-term agonist exposure manifested the long-acting agonism of salmeterol, and differentiated the mechanisms of agonist-directed desensitization between a full agonist epinephrine and a partial agonist pindolol. This study reveals the cellular mechanisms of agonist-selective β2AR desensitization at the whole cell level. PMID:21541288

Association of a beta-2 adrenoceptor (ADRB2) gene variant with a blunted in vivo lipolysis and fat oxidation.

PubMed

Jocken, J W E; Blaak, E E; Schiffelers, S; Arner, P; van Baak, M A; Saris, W H M

2007-05-01

Obesity is associated with a blunted beta-adrenoceptor-mediated lipolysis and fat oxidation. We investigated whether polymorphisms in codon 16, 27 and 164 of the beta (2)-adrenoceptor gene (ADRB2) and exon 10 of the G protein beta (3)-subunit gene (GNB3) are associated with alterations in in vivo lipolysis and fat oxidation. Sixty-five male and 43 female overweight and obese subjects (body mass index (BMI) range: 26.1-48.4 kg/m(2)) were included. Energy expenditure (EE), respiratory quotient (RQ), circulating free fatty acid (FFA) and glycerol levels were determined after stepwise infusion of increasing doses of the non-selective beta-agonist isoprenaline (ISO). In women, the Arg16 allele of the ADRB2 gene was associated with a blunted increase in circulating FFA, glycerol and a decreased fat oxidation during ISO stimulation. In men, the Arg16 allele was significantly associated with a blunted increase in FFA but not in glycerol or fat oxidation. These results suggest that genetic variation in the ADRB2 gene is associated with disturbances in in vivo beta-adrenoceptor-mediated lipolysis and fat oxidation during beta-adrenergic stimulation in overweight and obese subjects; these effects are influenced by gene-gender interactions.

Mathematical modeling physiological effects of the overexpression of β2-adrenoceptors in mouse ventricular myocytes.

PubMed

Rozier, Kelvin; Bondarenko, Vladimir E

2018-03-01

Transgenic (TG) mice overexpressing β 2 -adrenergic receptors (β 2 -ARs) demonstrate enhanced myocardial function, which manifests in increased basal adenylyl cyclase activity, enhanced atrial contractility, and increased left ventricular function in vivo. To gain insights into the mechanisms of these effects, we developed a comprehensive mathematical model of the mouse ventricular myocyte overexpressing β 2 -ARs. We found that most of the β 2 -ARs are active in control conditions in TG mice. The simulations describe the dynamics of major signaling molecules in different subcellular compartments, increased basal adenylyl cyclase activity, modifications of action potential shape and duration, and the effects on L-type Ca 2+ current and intracellular Ca 2+ concentration ([Ca 2+ ] i ) transients upon stimulation of β 2 -ARs in control, after the application of pertussis toxin, upon stimulation with a specific β 2 -AR agonist zinterol, and upon stimulation with zinterol in the presence of pertussis toxin. The model also describes the effects of the β 2 -AR inverse agonist ICI-118,551 on adenylyl cyclase activity, action potential, and [Ca 2+ ] i transients. The simulation results were compared with experimental data obtained in ventricular myocytes from TG mice overexpressing β 2 -ARs and with simulation data on wild-type mice. In conclusion, a new comprehensive mathematical model was developed that describes multiple experimental data on TG mice overexpressing β 2 -ARs and can be used to test numerous hypotheses. As an example, using the developed model, we proved the hypothesis of the major contribution of L-type Ca 2+ current to the changes in the action potential and [Ca 2+ ] i transient upon stimulation of β 2 -ARs with zinterol. NEW & NOTEWORTHY We developed a new mathematical model for transgenic mouse ventricular myocytes overexpressing β 2 -adrenoceptors that describes the experimental findings in transgenic mice. The model reveals mechanisms of the

Saw palmetto extracts potently and noncompetitively inhibit human alpha1-adrenoceptors in vitro.

PubMed

Goepel, M; Hecker, U; Krege, S; Rübben, H; Michel, M C

1999-02-15

We wanted to test whether phytotherapeutic agents used in the treatment of lower urinary tract symptoms have alpha1-adrenoceptor antagonistic properties in vitro. Preparations of beta-sitosterol and extracts of stinging nettle, medicinal pumpkin, and saw palmetto were obtained from several pharmaceutical companies. They were tested for their ability to inhibit [3H]tamsulosin binding to human prostatic alpha1-adrenoceptors and [3H]prazosin binding to cloned human alpha1A- and alpha1B-adrenoceptors. Inhibition of phenylephrine-stimulated [3H]inositol phosphate formation by cloned receptors was also investigated. Up to the highest concentration which could be tested, preparations of beta-sitosterol, stinging nettle, and medicinal pumpkin were without consistent inhibitory effect in all assays. In contrast, all tested saw palmetto extracts inhibited radioligand binding to human alpha1-adrenoceptors and agonist-induced [3H]inositol phosphate formation. Saturation binding experiments in the presence of a single saw palmetto extract concentration indicated a noncompetitive antagonism. The relationship between active concentrations in vitro and recommended therapeutic doses for the saw palmetto extracts was slightly lower than that for several chemically defined alpha1-adrenoceptor antagonists. Saw palmetto extracts have alpha1-adrenoceptor-inhibitory properties. If bioavailability and other pharmacokinetic properties of these ingredients are similar to those of the chemically defined alpha1-adrenoceptor antagonists, alpha1-adrenoceptor antagonism might be involved in the therapeutic effects of these extracts in patients with lower urinary tract symptoms suggestive of benign prostatic obstruction.

The estrogen receptor antagonist ICI 182,780 can act both as an agonist and an inverse agonist when estrogen receptor α AF-2 is modified.

PubMed

Movérare-Skrtic, Sofia; Börjesson, Anna E; Farman, Helen H; Sjögren, Klara; Windahl, Sara H; Lagerquist, Marie K; Andersson, Annica; Stubelius, Alexandra; Carlsten, Hans; Gustafsson, Jan-Åke; Ohlsson, Claes

2014-01-21

The bone-sparing effect of estrogen is primarily mediated via estrogen receptor (ER) α, which stimulates target gene transcription through two activation functions (AFs), AF-1 in the N-terminal and AF-2 in the ligand-binding domain. It was recently demonstrated that the ER antagonist ICI 182,780 (ICI) acts as an ER agonist in uterus of mice with mutations in the ERα AF-2. To evaluate the estrogen-like effects of ICI in different tissues, ovariectomized wild-type mice and mice with mutations in the ERα AF-2 (ERαAF-2(0)) were treated with ICI, estradiol, or vehicle for 3 wk. Estradiol increased the trabecular and cortical bone mass as well as the uterine weight, whereas it reduced fat mass, thymus weight, and the growth plate height in wild-type but not in ERαAF-2(0) mice. Although ICI had no effect in wild-type mice, it exerted tissue-specific effects in ERαAF-2(0) mice. It acted as an ERα agonist on trabecular bone mass and uterine weight, whereas no effect was seen on cortical bone mass, fat mass, or thymus weight. Surprisingly, a pronounced inverse agonistic activity was seen on the growth plate height, resulting in enhanced longitudinal bone growth. In conclusion, ICI uses ERα AF-1 in a tissue-dependent manner in mice lacking ERαAF-2, resulting in no effect, agonistic activity, or inverse agonistic activity. We propose that ERα lacking AF-2 is constitutively active in the absence of ligand in the growth plate, enabling ICI to act as an inverse agonist.

Suppressive effects of formoterol and salmeterol on eotaxin-1 in bronchial epithelial cells.

PubMed

Chu, Yu-Te; Chang, Tai-Tsung; Jong, Yuh-Jyh; Kuo, Po-Lin; Lee, Hsi-Ming; Lee, Min-Sheng; Chang, Hui-Wen; Hung, Chih-Hsing

2010-03-01

Eotaxin-1 (CCL11), an eosinophil-specific C-C chemokine, is a potent chemoattractant for mobilization of eosinophils into airways after allergic stimulation. Eotaxin-1 recruits eosinophils into inflammatory sites, and may play a role in the pathogenesis of asthma. Formoterol and salmeterol are two inhaled long acting beta(2) adrenoceptor agonists (LABAs), widely used for the local treatment of asthma. However, little is known about their effects on the eotaxin-1 expression of bronchial epithelial cells. BEAS-2B cells were stimulated by adding IL-4 with or without 2 h pre-treatment of formoterol or salmeterol. The protein and mRNA expression of eotaxin-1 were measured by ELISA assay and real-time PCR, respectively. Effects of formoterol and salmeterol on nuclear and cytosolic pSTAT-6 expression were evaluated by Western blot and immunofluorescence study. Formoterol and salmeterol (10(-7)-10(-10) m) significantly down-regulated IL-4- induced eotaxin-1 expression in BEAS-2B cells. A specific beta(2) adrenoceptor antagonist (ICI 118,551) reversed their suppression of eotaxin-1 production. Forskolin, an cAMP activator, could also suppress the expression of eotaxin-1 by IL-4 in a dose dependent manner (10(-7)-10(-10 )m). The western blot and immunofluorescence studies demonstrated that formoterol 10(-7 )m suppressed the nuclear expression of pSTAT-6. Formoterol and salmeterol, two inhaled long-acting beta(2) agonists, down-regulated IL-4- induced eotaxin-1 expression in BEAS-2B cells. The effect was mediated via the beta(2) adrenoceptor, and cAMP. Formoterol significantly down-regulated pSTAT6 at higher concentration, and further turned off the IL-4 signaling pathway.

The estrogen receptor antagonist ICI 182,780 can act both as an agonist and an inverse agonist when estrogen receptor α AF-2 is modified

PubMed Central

Movérare-Skrtic, Sofia; Börjesson, Anna E.; Farman, Helen H.; Sjögren, Klara; Windahl, Sara H.; Lagerquist, Marie K.; Andersson, Annica; Stubelius, Alexandra; Carlsten, Hans; Gustafsson, Jan-Åke; Ohlsson, Claes

2014-01-01

The bone-sparing effect of estrogen is primarily mediated via estrogen receptor (ER) α, which stimulates target gene transcription through two activation functions (AFs), AF-1 in the N-terminal and AF-2 in the ligand-binding domain. It was recently demonstrated that the ER antagonist ICI 182,780 (ICI) acts as an ER agonist in uterus of mice with mutations in the ERα AF-2. To evaluate the estrogen-like effects of ICI in different tissues, ovariectomized wild-type mice and mice with mutations in the ERα AF-2 (ERαAF-20) were treated with ICI, estradiol, or vehicle for 3 wk. Estradiol increased the trabecular and cortical bone mass as well as the uterine weight, whereas it reduced fat mass, thymus weight, and the growth plate height in wild-type but not in ERαAF-20 mice. Although ICI had no effect in wild-type mice, it exerted tissue-specific effects in ERαAF-20 mice. It acted as an ERα agonist on trabecular bone mass and uterine weight, whereas no effect was seen on cortical bone mass, fat mass, or thymus weight. Surprisingly, a pronounced inverse agonistic activity was seen on the growth plate height, resulting in enhanced longitudinal bone growth. In conclusion, ICI uses ERα AF-1 in a tissue-dependent manner in mice lacking ERαAF-2, resulting in no effect, agonistic activity, or inverse agonistic activity. We propose that ERα lacking AF-2 is constitutively active in the absence of ligand in the growth plate, enabling ICI to act as an inverse agonist. PMID:24395795

Using long-acting beta2-agonists safely: What will be the impact of the US Food and Drug Administration's panel recommendations?

PubMed

Smart, Brian A

2009-01-01

The US Food and Drug Administration (FDA) has launched an investigation into the safety of long-acting beta(2)-agonists (LABAs). While the impact of this investigation is yet to be seen, clinicians should be circumspect in the use of these agents and prescribe them according to the recommendations of current asthma guidelines, informing patients and their caretakers about potential risks. As clinical trials attempt to address the question of whether LABAs are safe for use in pediatric and adult populations, current data provide no clear answers. A special hearing of the FDA's Pulmonary-Allergy Drugs Advisory Committee, Drug Safety and Risk Management Advisory Committee, and Pediatric Advisory Committee attempted to seek consensus on the matter as it reviewed the results of controlled clinical trials and conducted a benefit:risk assessment of LABAs to make recommendations on their safety.

Brain α2-adrenoceptors in monoamine-depleted rats: increased receptor density, G coupling proteins, receptor turnover and receptor mRNA

PubMed Central

Ribas, Catalina; Miralles, Antonio; Busquets, Xavier; García-Sevilla, Jesús A

2001-01-01

This study was designed to assess the molecular and cellular events involved in the up-regulation (and receptor supersensitivity) of brain α2-adrenoceptors as a result of chronic depletion of noradrenaline (and other monoamines) by reserpine. Chronic reserpine (0.25 mg kg−1 s.c., every 48 h for 6 – 14 days) increased significantly the density (Bmax values) of cortical α2-adrenoceptor agonist sites (34 – 48% for [3H]-UK14304, 22 – 32% for [3H]-clonidine) but not that of antagonist sites (11 – 18% for [3H]-RX821002). Competition of [3H]-RX821002 binding by (−)-adrenaline further indicated that chronic reserpine was associated with up-regulation of the high-affinity state of α2-adrenoceptors. In cortical membranes of reserpine-treated rats (0.25 mg kg−1 s.c., every 48 h for 20 days), the immunoreactivities of various G proteins (Gαi1/2, Gαi3, Gαo and Gαs) were increased (25 – 34%). Because the high-affinity conformation of the α2-adrenoceptor is most probably related to the complex with Gαi2 proteins, these results suggested an increase in signal transduction through α2-adrenoceptors (and other monoamine receptors) induced by chronic reserpine. After α2-adrenoceptor alkylation, the analysis of receptor recovery (Bmax for [3H]-UK14304) indicated that the increased density of cortical α2-adrenoceptors in reserpine-treated rats was probably due to a higher appearance rate constant of the receptor (Δr=57%) and not to a decreased disappearance rate constant (Δk=7%). Northern- and dot-blot analyses of RNA extracted from the cerebral cortex of saline- and reserpine-treated rats (0.25 mg kg−1, s.c., every 48 h for 20 days) revealed that reserpine markedly increased the expression of α2a-adrenoceptor mRNA in the brain (125%). This transcriptional activation of the receptor gene expression appears to be the cellular mechanism by which reserpine induces up-regulation in the density of brain α2-adrenoceptors

Possible mechanism of the negative inotropic effect of α1-adrenoceptor agonists in rat isolated left atria after exposure to free radicals

PubMed Central

Peters, Stephan L M; Batink, Harry D; Michel, Martin C; Pfaffendorf, Martin; van Zwieten, Pieter A

1998-01-01

This study was designed to investigate the mechanism(s) of the negative inotropic effects of α1-adrenoceptor agonists observed in rat isolated left atria after exposure to free radicals.Ouabain and calphostin C were used in contraction experiments to block the sodium pump and protein kinase C. Methoxamine-induced phospholipase C and Na+/K+ ATPase activities were measured.Methoxamine (300 μM) increased contractile force by 1.6±0.2 mN in control atria but decreased contractile force in electrolysis-treated atria by 2.0±0.1 mN (P<0.05), as determined 10 min after methoxamine addition. In contrast, the positive inotropic effects of endothelin-1 (30 nM) and isoprenaline (10 μM) were reduced from 2.6±0.3 to 1.3±0.1 mN and from 2.6±0.3 to 1.7±0.2 mN, respectively, by electrolysis treatment (P<0.05), but not converted into a negative inotropic action.In an inositol phosphate assay we observed that the stimulation of phospholipase C by methoxamine was attenuated by electrolysis when the (electrolyzed) medium from the organ bath was used, but the phospholipase C responses were restored by the use of fresh medium. However, fresh medium did not counteract the negative inotropic effect of methoxamine. Accordingly, the negative inotropic effect of methoxamine is not directly related to the impaired phospholipase C responses seen in atria subjected to electrolysis.Ouabain (10 μM) and the protein kinase C inhibitor calphostin C (50 nM), completely prevented the negative inotropic effect of 300 μM methoxamine in electrolysis-treated atria.Measurement of the Na+/K+ ATPase activity, revealed that in control atria, α1-adrenoceptor stimulation with 300 μM methoxamine, decreased the Na+/K+ ATPase activity by 14.4±7.7%. In contrast, methoxamine increased the Na+/K+ ATPase activity by 48.8±8.9% (P<0.05) in electrolysis-treated atria. Interestingly, this increase in Na+/K+ ATPase activity was completely counteracted by calphostin C (1.4±0.1% over

Beta-adrenoceptor dysfunction after inhibition of NO synthesis

NASA Technical Reports Server (NTRS)

Whalen, E. J.; Johnson, A. K.; Lewis, S. J.

2000-01-01

G(s) protein-coupled beta-adrenoceptors rapidly desensitize on exposure to agonists in reconstituted membrane preparations, whereas rapid tachyphylaxis to beta-adrenoceptor-mediated vasodilation does not readily occur in vivo. This study examined the possibility that endothelium-derived nitrosyl factors prevent the rapid desensitization of beta-adrenoceptors in the vascular smooth muscle of resistance arteries in pentobarbital-anesthetized rats. The fall in mean arterial blood pressure and in hindquarter vascular resistance produced by the beta-adrenoceptor agonist isoproterenol (ISO, 0.1 to 10 microg/kg IV) was slightly but significantly smaller in rats treated with the NO synthase inhibitor N:(G)-nitro-L-arginine methyl ester (L-NAME, 100 micromol/kg IV) than in saline-treated rats. The ISO-induced fall in mesenteric resistance was similar in L-NAME-treated and in saline-treated rats. The fall in hindquarter vascular resistance and in mesenteric resistance produced by ISO (8 x 10 microg/kg IV) was subject to tachyphylaxis on repeated injection in rats treated with L-NAME (100 micromol/kg IV) but not in rats treated with saline. Injections of L-S:-nitrosocysteine (1200 nmol/kg IV), a lipophobic S:-nitrosothiol, before each injection of ISO (10 microg/kg IV) prevented tachyphylaxis to ISO in L-NAME-treated rats. The vasodilator effects of ISO (0.1 to 10 microg/kg IV) in L-NAME-treated rats that received 8 injections of ISO (10 microg/kg IV) were markedly smaller than in L-NAME-treated rats that received 8 injections of saline. These results indicate that (1) the vasodilator actions of ISO in pentobarbital-anesthetized rats only minimally involve the release of endothelium-derived nitrosyl factors, (2) the effects of ISO are subject to development of tachyphylaxis in L-NAME-treated rats, and (3) tachyphylaxis to ISO is prevented by L-S:-nitrosocysteine. These findings suggest that endothelium-derived nitrosyl factors may prevent desensitization of beta-adrenoceptors

Inhibition of agonist-induced smooth muscle contraction by picotamide in the male human lower urinary tract outflow region.

PubMed

Hennenberg, Martin; Tamalunas, Alexander; Wang, Yiming; Keller, Patrick; Schott, Melanie; Strittmatter, Frank; Herlemann, Annika; Yu, Qingfeng; Rutz, Beata; Ciotkowska, Anna; Stief, Christian G; Gratzke, Christian

2017-05-15

Male lower urinary tract symptoms (LUTS) due to bladder outlet obstruction are characterized by abnormal smooth muscle contractions in the lower urinary tract. Alpha 1 -adrenoceptor antagonists may induce smooth muscle relaxation in the outflow region and represent the current gold standard of medical treatment. However, results may be unsatisfactory or inadequate. Apart from α 1 -adrenoceptor agonists, smooth muscle contraction in the outflow region may be induced by thromboxane A 2 (TXA 2 ), endothelins, or muscarinic receptor agonists. Here, we studied effects of the thromboxane A 2 receptor (TP receptor) antagonist picotamide on contraction in the human male bladder trigone and prostate. Carbachol, the α 1 -adrenoceptor agonist phenylephrine, the thromboxane A 2 analog U46619, and electric field stimulation (EFS) induced concentration- or frequency-dependent contractions of trigone tissues in an organ bath. Picotamide (300µM) inhibited carbachol-, phenylephrine-, U46619-, and EFS-induced contractions. Endothelins 1-3 induced concentration-dependent contractions of prostate tissues, which were inhibited by picotamide. Analyses using real time polymerase chain reaction and antibodies suggested expression of thromboxane A 2 receptors and synthase in trigone smooth muscle cells. Thromboxane B 2 (the stable metabolite of thromboxane A 2 ) was detectable by enzyme immune assay in trigone samples, with most values ranging between 50 and 150pg/mg trigone protein. Picotamide inhibits contractions induced by different stimuli in the human lower urinary tract, including cholinergic, adrenergic, thromboxane A 2 - and endothelin-induced, and neurogenic contractions in different locations of the outflow region. This distinguishes picotamide from current medical treatments for LUTS, and suggests that picotamide may induce urodynamic effects in vivo. Copyright © 2017. Published by Elsevier B.V.

Comparative efficacy of fixed-dose combinations of long-acting muscarinic antagonists and long-acting β2-agonists: a systematic review and network meta-analysis

PubMed Central

Schlueter, Max; Gonzalez-Rojas, N; Baldwin, Michael; Groenke, Lars; Voss, Florian; Reason, Tim

2016-01-01

Background: A number of long-acting muscarinic antagonist (LAMA)/long-acting β2-agonist (LABA) fixed-dose combinations (FDCs) for treatment of moderate-to-very severe chronic obstructive pulmonary disease (COPD) have recently become available, but none have been directly compared in head-to-head randomized controlled trials (RCTs). The purpose of this study was to assess the relative clinical benefit of all currently available LAMA/LABA FDCs using a Bayesian network meta-analysis (NMA). Methods: A systematic literature review identified RCTs investigating the efficacy, safety and quality of life associated with licensed LAMA/LABA FDCs for the treatment of moderate-to-very severe COPD. RCTs were screened for inclusion in the NMA using prespecified eligibility criteria. Data were extracted for outcomes of interest, including change in trough forced expiratory volume in 1 second (tFEV1) from baseline, St. George Respiratory Questionnaire (SGRQ) percentage of responders, Transition Dyspnea Index (TDI) percentage of responders, change in SGRQ score from baseline, change in TDI focal score from baseline, moderate-to-severe exacerbations, all-cause discontinuation, and discontinuation due to adverse events. Results: Following screening, a total of 27 trials from 26 publications with 30,361 subjects were eligible for inclusion in the NMA. Nonsignificant results were seen in most analyses comparing efficacy, exacerbations and discontinuation rates of included LAMA/LABA FDCs (i.e. aclidinium/formoterol 400/12 µg, glycopyrronium/indacaterol 110/50 µg, tiotropium + olodaterol 5/5 µg, umeclidinium/vilanterol 62.5/25 µg). Meta-regression controlling for post-bronchodilator percentage of tFEV1 predicted at baseline as well as meta-regression adjusting for concomitant use of inhaled corticosteroids at baseline was performed to assess the magnitude of effect modification and produced similar results as observed in the base case analysis. Conclusion: All LAMA/LABA FDCs were

Inhibition by alpha- and beta-adrenoceptors of the twitch response to transmural stimulation in the guinea-pig vas deferens.

PubMed

Hedqvist, P; Von Euler, U S

1976-11-01

Noradrenaline as well as the indirectly acting amines tyramine and phenethylamine either enhance or inhibit the twitch response of the transmurally stimulated, isolated guine-pig vas deferens, thus partly confirming previous reports. In both cases enhancement is annulled by alpha-adrenoceptor blockers. The twitch inhibition caused by noradrenaline is abolished by alpha- + beta2-adrenoceptor blockers, but not by either blocker alone. The inhibition caused by the indirectly acting amines is largely abolished by alpha-adrenoceptor blockers. Clonidine strongly inhibits the twitch. This effect if promptly removed by phentolamine. After blockade of the neurally induced twitch by tetrodotoxin, noradrenaline and the indirectly acting amines have no effect or slightly enhance the twitch elicited by transmural stimulation of the smooth muscle. It is concluded that exogenous noradrenaline acts on postjunctional stimulatory alpha-adrenoceptors and on inhibitory alpha- and beta2-adrenoceptors, which are presumably prejunctional. In the unstimulated preparation contracted by acetylcholine, noradrenaline causes further contraction which is changed into relaxation after phentolamine. This relaxation is abolished by butoxamine, suggesting that noradrenaline may also act on inhibitory postjunctional beta2-adrenoceptors. The twitch-inhibiting effect of endogenous noradrenaline, released by nerve stimulation or by indirectly acting amines, appears to be primarily mediated by prejunctional alpha-adrenoceptors.

Modulatory effects of the basolateral amygdala α2-adrenoceptors on nicotine-induced anxiogenic-like behaviours of rats in the elevated plus maze.

PubMed

Bashiri, Hamideh; Rezayof, Ameneh; Sahebgharani, Mousa; Tavangar, Seyed Mohammad; Zarrindast, Mohammad-Reza

2016-06-01

The present study was designed to clarify whether α2-adrenoceptors of the basolateral amygdala (BLA) are involved in nicotine-induced anxiogenic-like behaviours. Adult male Wistar rats were bilaterally cannulated in the BLA and anxiety-like behaviours were assessed in an elevated plus maze (EPM) task. Systemic intraperitoneal (i.p.) administration of nicotine (0.3, 0.5 and 0.7 mg/kg) dose-dependently decreased open arm time (%OAT) and open arm entry (%OAE), indicating the anxiogenic-like effect of nicotine. The activation of the BLA α2-adrenoceptors by the injection of α2-receptor agonist, clonidine (0.1, 0.3 and 0.5 μg/rat) into the BLA (intra-BLA) reversed nicotine-induced anxiogenic-like behaviours. It is important to note that intra-BLA injection of a higher dose of clonidine (0.5 μg/rat) by itself increased %OAT, but not %OAE which showed an anxiolytic effect of the agonist. On the other hand, intra-BLA injection of different doses of α2-adrenoceptor antagonist, yohimbine (1, 3 and 5 μg/rat) in combination with an ineffective dose of nicotine (0.3 mg/kg) decreased %OAT and %OAE, suggesting a potentiative effect of the antagonist on nicotine response. In addition, intra-BLA injection of the same doses of yohimbine did not alter %OAT and %OAE. Interestingly, intra-BLA injection of yohimbine (0.5 and 1 μg/rat) significantly reversed the inhibitory effect of clonidine on nicotine-induced anxiogenic-like behaviours. It should be considered that the drug treatments had no effect on locomotor activity in all experiments. Taken together, it can be concluded that nicotine produces anxiogenic-like behaviours which may be mediated through the BLA α2-adrenoceptor mechanism. Copyright © 2016. Published by Elsevier Ltd.

Comparison of alpha 1A- and alpha 1B-adrenoceptor coupling to inositol phosphate formation in rat kidney.

PubMed

Büscher, R; Erdbrügger, W; Philipp, T; Brodde, O E; Michel, M C

1994-12-01

We have compared the coupling mechanisms of rat renal alpha 1A- and alpha 1B-like adrenoceptors to inositol phosphate formation. The experiments were performed in parallel in native renal tissue preparations and in those where alpha 1B-adrenoceptors had been inactivated by treatment with 10 mumol/l chloroethylclonidine for 30 min at 37 degrees C; renal slices were used in most experiments but isolated renal cells were also used in some cases. The Ca2+ chelating agent, EGTA (5 mmol/l), reduced noradrenaline-stimulated inositol phosphate formation in native but enhanced it in chloroethylclonidine-treated renal slices. The inhibitory effect of EGTA was not mimicked by 100 nmol/l nifedipine. Inactivation of 87% of cellular Gi by 16-20 h treatment with 500 ng/ml pertussis toxin did not significantly affect noradrenaline-stimulated inositol phosphate formation in isolated renal cells but abolished the inhibitory effect of chloroethylclonidine. The adenylate cyclase activator, forskolin (20 mumol/l), inhibited noradrenaline-stimulated inositol phosphate formation in native and chloroethylclonidine-treated slices, and the inhibitory effects of chloroethylclonidine treatment and forskolin were additive. We conclude that in rat kidney inositol phosphate formation via alpha 1B-like adrenoceptors may involve the influx of extracellular Ca2+ and a pertussis toxin-sensitive G-protein but is insensitive to inhibition by forskolin. In contrast alpha 1A-like adrenoceptor-mediated inositol phosphate formation does not require the presence of extracellular Ca2+ or of Gi and is sensitive to inhibition by forskolin. In comparison to published data from other model systems we further conclude that the signaling mechanisms of alpha 1-adrenoceptor subtypes may depend on their cellular environment.

Wnt/β-catenin signaling modulates human airway sensitization induced by β2-adrenoceptor stimulation.

PubMed

Faisy, Christophe; Grassin-Delyle, Stanislas; Blouquit-Laye, Sabine; Brollo, Marion; Naline, Emmanuel; Chapelier, Alain; Devillier, Philippe

2014-01-01

Regular use of β2-agonists may enhance non-specific airway responsiveness. The wingless/integrated (Wnt) signaling pathways are responsible for several cellular processes, including airway inflammation and remodeling while cAMP-PKA cascade can activate the Wnt signaling. We aimed to investigate whether the Wnt signaling pathways are involved in the bronchial hyperresponsiveness induced by prolonged exposure to β2-adrenoceptor agonists in human isolated airways. Bronchi were surgically removed from 44 thoracic surgery patients. After preparation, bronchial rings and primary cultures of bronchial epithelial cells were incubated with fenoterol (0.1 µM, 15 hours, 37 °C), a β2-agonist with high intrinsic efficacy. The effects of inhibitors/blockers of Wnt signaling on the fenoterol-induced airway sensitization were examined and the impact of fenoterol exposure on the mRNA expression of genes interacting with Wnt signaling or cAMP-PKA cascade was assessed in complete bronchi and in cultured epithelial cells. Compared to paired controls, fenoterol-sensitization was abolished by inhibition/blockage of the Wnt/β-catenin signaling, especially the cell-surface LRP5/6 co-receptors or Fzd receptors (1 µM SFRP1 or 1 µM DKK1) and the nuclear recruitment of TCF/LEF transcriptions factors (0.3 µM FH535). Wnt proteins secretion did not seem to be involved in the fenoterol-induced sensitization since the mRNA expression of Wnt remained low after fenoterol exposure and the inactivator of Wnt secretion (1 µM IWP2) had no effect on the fenoterol-sensitization. Fenoterol exposure did not change the mRNA expression of genes regulating Wnt signaling or cAMP-PKA cascade. Collectively, our pharmacological investigations indicate that fenoterol-sensitization is modulated by the inhibition/blockage of canonical Wnt/β-catenin pathway, suggesting a phenomenon of biased agonism in connection with the β2-adrenoceptor stimulation. Future experiments based on the results of the present

Fenoterol functionally activates the β₃-adrenoceptor in human urinary bladder, comparison with rat and mouse: implications for drug discovery.

PubMed

Palea, Stefano; Rekik, Moèz; Rouget, Céline; Camparo, Philippe; Botto, Henri; Rischmann, Pascal; Lluel, Philippe; Westfall, Timothy D

2012-09-05

Fenoterol has been reported to be a potent and selective β(2)-adrenoceptor agonist and is currently used clinically to treat asthma. Electrical field stimulation (EFS) of isolated urinary bladder mimics the voiding contraction by stimulating parasympathetic nerves, resulting in neurogenic contractions. To determine if stimulation of β(2)-adrenoceptors can inhibit this response, fenoterol was tested against EFS-induced contractions in human isolated urinary bladder and compared with mouse and rat. Bladder strips were mounted in organ baths and reproducible contractions induced by EFS. Fenoterol was added cumulatively in the presence of the β(2)-adrenoceptor antagonist ICI118551 or the β(3)-adrenoceptor antagonist L-748337. Fenoterol inhibited neurogenic contractions in all three species in a concentration-dependent manner with pEC(50) values of 6.66 ± 0.11, 6.86 ± 0.06 and 5.71 ± 0.1 in human, mouse and rat respectively. In human bladder strips ICI118551 (100 nM) did not affect responses to fenoterol, while L-748337 (0.3-3 μM) produced rightward shifts of the concentration-response curves with a pA(2) value of 8.10. In mouse bladder strips ICI118551 (30 nM) blocked the inhibitory effect of fenoterol (pA(2)=8.80), while L-748337 (10 μM) inhibited the response with a pA(2) of 5.79. In rat bladder ICI118551 (30 nM) was without effect, while L-748,337 (10 μM) inhibited the response to fenoterol with a pA(2) of 5.40. From these results it is clear that fenoterol potently activates β(3)-adrenoceptors in human isolated urinary bladder to inhibit EFS-induced contractions. Fenoterol also activates β(3)-adrenoceptors in rat, but β(2)-adrenoceptors in mouse bladder to inhibit EFS-induced contractions. Copyright © 2012 Elsevier B.V. All rights reserved.

Synthesis and in Vitro and in Vivo Characterization of Highly β1-Selective β-Adrenoceptor Partial Agonists

PubMed Central

2013-01-01

β-Adrenoceptor antagonists boast a 50-year use for symptomatic control in numerous cardiovascular diseases. One might expect highly selective antagonists are available for the human β-adrenoceptor subtype involved in these diseases, yet few truly β1-selective molecules exist. To address this clinical need, we re-evaluated LK 204-545 (1),1 a selective β1-adrenoceptor antagonist, and discovered it possessed significant partial agonism. Removal of 1’s aromatic nitrile afforded 19, a ligand with similar β1-adrenoceptor selectivity and partial agonism (log KD of −7.75 and −5.15 as an antagonist of functional β1- and β2-mediated responses, respectively, and 34% of the maximal response of isoprenaline (β1)). In vitro β-adrenoceptor selectivity and partial agonism of 19 were mirrored in vivo. We designed analogues of 19 to improve affinity, selectivity, and partial agonism. Although partial agonism could not be fully attenuated, SAR suggests that an extended alkoxyalkoxy side chain, alongside substituents at the meta- or para-positions of the phenylurea, increases ligand affinity and β1-selectivity. PMID:23614528

Comparative Evaluation of Partial α2 -Adrenoceptor Agonist and Pure α2 -Adrenoceptor Antagonist on the Behavioural Symptoms of Withdrawal after Chronic Alcohol Administration in Mice.

PubMed

Arora, Shivani; Vohora, Divya

2016-08-01

As an addictive drug, alcohol produces withdrawal symptoms if discontinued abruptly after chronic use. Clonidine (CLN), a partial α2 -adrenergic agonist, and mirtazapine (MRT), an antagonist of α2 -adrenoceptor, both clinically aid alcohol withdrawal. Considering different mechanisms of action of the two drugs, this study was designed to see how far these two mechanistically different drugs differ in their ability to decrease the severity of ethanol withdrawal syndrome. The effect of CLN and MRT on ethanol withdrawal-induced anxiety, depression and memory impairment was analysed using EPM, FST and PAR tests, respectively. Animals received distilled water, ethanol and/or either of the drugs (CLN and MRT) in different doses. Relapse to alcohol use was analysed by CPP test. Animals received ethanol as a conditioning drug and distilled water, CLN or MRT as test drug. CLN and MRT both alleviated anxiety in a dose-dependent manner. MRT (4 mg/kg) was more effective than CLN (0.1 mg/kg) in ameliorating the anxiogenic effect of alcohol withdrawal. However, CLN treatment increased depression. It significantly decreased swimming time and increased immobility time, whereas MRT treatment decreased immobility time and increased climbing and swimming time during abstinence. The effect was dose dependent for both drugs. The results of PAR test show that CLN treatment worsens working memory. Significant increase in SDE and TSZ and decrease in SDL were observed in CLN-treated animals. MRT treatment, on the other hand, improved working memory at both doses. Further, both CLN and MRT alleviated craving. A significant decrease in time spent in the ethanol-paired chamber was seen. MRT treatment at both doses showed better effect than CLN in preventing the development of preference in CPP test. These findings indicate a potential therapeutic use and better profile of mirtazapine over clonidine in improving memory, as well as in alleviating depression, anxiety and craving associated

Modification of certain pharmacological effects of ethanol by lipophilic alpha-1 adrenergic agonists

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menon, M.K.; Dinovo, E.C.; Haddox, V.G.

The influence of four centrally-acting alpha-1 adrenoceptor agonists, namely, 2(2-chloro-5-trifluoromethylphenylimino) imidazolidine (St 587), cirazoline, (-) 1,2,3,4-tetrahydro-8-methoxy-5-methylthio-2-naphthalenamine ((-)SKF 89748A) and 2-(2-methylindazol-4-imino)imidazolidine (Sgd 101/75) on the pharmacological effects of ethanol was investigated. All four drugs reduced the duration of ethanol-induced hypnosis in C57B1/6 mice, this effect being proportional to their relative potencies to exert central alpha-1 agonism. In prazosin-pretreated mice, St 587 failed to reduce the hypnotic effect of ethanol, which provided strong evidence for the role of alpha-1 agonism for the hypnosis reducing effect of St 587. Hyperactivity induced in C57B1/6 mice by a subhypnotic dose of ethanol and St 587more » was reported earlier. In the present study, St 587, cirazoline and (-)SKF 89748A produced similar response, but no correlation between this effect and ethanol hypnosis blockade could be established. 19 references, 8 figures, 2 tables.« less

An investigation into the selectivity of a novel series of benzoquinolizines for alpha 2-adrenoceptors in vivo.

PubMed Central

Paciorek, P. M.; Pierce, V.; Shepperson, N. B.; Waterfall, J. F.

1984-01-01

The potencies and selectivities of a novel series of benzoquinolizines for the alpha 2-adrenoceptor have been investigated in the rat in comparison with yohimbine and indoramin. Peripheral postjunctional alpha 2- and alpha 1-adrenoceptor blockade was measured as the reversal of B-HT 933 and methoxamine-induced pressor responses, respectively, in the pithed rat. Peripheral prejunctional alpha 2-adrenoceptor blockade was measured as the reversal of B-HT 933-induced inhibition of an electrically evoked tachycardia in the pithed rat. Central alpha 2-adrenoceptor blockade was measured as a reversal of the hypotension induced in anaesthetized rats by central (i.c.v.) administration of clonidine. Wy 25309, Wy 26392, Wy 26703 and yohimbine (0.3-3 mg kg-1 i.v.) evoked dose-dependent shifts to the right of the dose-response curves to B-HT 933 whilst having minimal effects on the methoxamine dose-response curve. The selectivity for alpha 2-adrenoceptors increased with the dose of antagonist administered. In general, the order of selectivity was Wy 25309 greater than Wy 26392 greater than Wy 26703 greater than yohimbine. Indoramin (1 mg kg-1 i.v.) shifted the methoxamine pressor dose-response curve to the right without affecting the B-HT 933 dose-response curves, confirming its selective alpha 1-antagonist activity. Peripheral administration of all three benzoquinolizines (1-100 micrograms kg-1 i.v.) led to a dose-dependent reversal of the hypotension evoked by central administration of clonidine (500 ng i.c.v.). The reversal was incomplete, higher doses causing a further decrease in blood pressure. (ABSTRACT TRUNCATED AT 250 WORDS) PMID:6329385

Alpha 2B adrenoceptor genotype moderates effect of reboxetine on negative emotional memory bias in healthy volunteers.

PubMed

Gibbs, Ayana A; Bautista, Carla E; Mowlem, Florence D; Naudts, Kris H; Duka, Theodora

2013-10-23

Evidence suggests that emotional memory plays a role in the pathophysiology of depression/anxiety disorders. Noradrenaline crucially modulates emotional memory. Genetic variants involved in noradrenergic signaling contribute to individual differences in emotional memory and vulnerability to psychopathology. A functional deletion polymorphism in the α-2B adrenoceptor gene (ADRA2B) has been linked to emotional memory and post-traumatic stress disorder. The noradrenaline reuptake inhibitor reboxetine attenuates enhanced memory for negative stimuli in healthy and depressed individuals. We examined whether the effect of reboxetine on emotional memory in healthy individuals would be moderated by ADRA2B genotype. ADRA2B deletion carriers demonstrated enhanced emotional memory for negative stimuli compared with deletion noncarriers, consistent with prior studies. Reboxetine attenuated enhanced memory for negative stimuli in deletion noncarriers but had no significant effect in deletion carriers. This is the first demonstration of genetic variation influencing antidepressant drug effects on emotional processing in healthy humans.

Formoterol, a long-acting β2 adrenergic agonist, improves cognitive function and promotes dendritic complexity in a mouse model of Down syndrome.

PubMed

Dang, Van; Medina, Brian; Das, Devsmita; Moghadam, Sarah; Martin, Kara J; Lin, Bill; Naik, Priyanka; Patel, Devan; Nosheny, Rachel; Wesson Ashford, John; Salehi, Ahmad

2014-02-01

Down syndrome is associated with significant failure in cognitive function. Our previous investigation revealed age-dependent degeneration of locus coeruleus, a major player in contextual learning, in the Ts65Dn mouse model of Down syndrome. We studied whether drugs already available for use in humans can be used to improve cognitive function in these mice. We studied the status of β adrenergic signaling in the dentate gyrus of the Ts65Dn mouse model of Down syndrome. Furthermore, we used fear conditioning to study learning and memory in these mice. Postmortem analyses included the analysis of synaptic density, dendritic arborization, and neurogenesis. We found significant atrophy of dentate gyrus and failure of β adrenergic signaling in the hippocampus of Ts65Dn mice. Our behavioral analyses revealed that formoterol, a long-acting β2 adrenergic receptor agonist, caused significant improvement in the cognitive function in Ts65Dn mice. Postmortem analyses revealed that the use of formoterol was associated with a significant improvement in the synaptic density and increased complexity of newly born dentate granule neurons in the hippocampus of Ts65Dn mice. Our data suggest that targeting β2 adrenergic receptors is an effective strategy for restoring synaptic plasticity and cognitive function in these mice. Considering its widespread use in humans and positive effects on cognition in Ts65Dn mice, formoterol or similar β2 adrenergic receptor agonists with ability to cross the blood brain barrier might be attractive candidates for clinical trials to improve cognitive function in individuals with Down syndrome. Published by Elsevier Inc.

The involvement of peripheral alpha 2-adrenoceptors in the antihyperalgesic effect of oxcarbazepine in a rat model of inflammatory pain.

PubMed

Tomić, Maja A; Vucković, Sonja M; Stepanović-Petrović, Radica M; Ugresić, Nenad D; Paranos, Sonja Lj; Prostran, Milica S; Bosković, Bogdan

2007-11-01

We studied whether peripheral alpha2-adrenergic receptors are involved in the antihyperalgesic effects of oxcarbazepine by examining the effects of yohimbine (selective alpha2-adrenoceptor antagonist), BRL 44408 (selective alpha(2A)-adrenoceptor antagonist), MK-912 (selective alpha2C-adrenoceptor antagonist), and clonidine (alpha2-adrenoceptor agonist) on the antihyperalgesic effect of oxcarbazepine in the rat model of inflammatory pain. Rats were intraplantarly (i.pl.) injected with the proinflammatory compound concanavalin A (Con A). A paw-pressure test was used to determine: 1) the development of hyperalgesia induced by Con A; 2) the effects of oxcarbazepine (i.pl.) on Con A-induced hyperalgesia; and 3) the effects of i.pl. yohimbine, BRL 44408, MK-912 and clonidine on the oxcarbazepine antihyperalgesia. Both oxcarbazepine (1000-3000 nmol/paw; i.pl.) and clonidine (1.9-7.5 nmol/paw; i.pl.) produced a significant dose-dependent reduction of the paw inflammatory hyperalgesia induced by Con A. Yohimbine (260 and 520 nmol/paw; i.pl.), BRL 44408 (100 and 200 nmol/paw; i.pl.) and MK-912 (10 and 20 nmol/paw; i.pl.) significantly depressed the antihyperalgesic effects of oxcarbazepine (2000 nmol/paw; i.pl.) in a dose-dependent manner. The effects of antagonists were due to local effects since they were not observed after administration into the contralateral hindpaw. Oxcarbazepine and clonidine administered jointly in fixed-dose fractions of the ED(50) (1/4, 1/2, and 3/4) caused significant and dose-dependent reduction of hyperalgesia induced by Con A. Isobolographic analysis revealed an additive antihyperalgesic effect. Our results indicate that the peripheral alpha2A and alpha2C adrenoceptors could be involved in the antihyperalgesic effects of oxcarbazepine in a rat model of inflammatory hyperalgesia.

Appropriate use of inhaled corticosteroid and long-acting beta(2)-adrenergic agonist combination therapy among asthma patients in a US commercially insured population.

PubMed

Ye, Xin; Gutierrez, Benjamin; Zarotsky, Victoria; Nelson, Michael; Blanchette, Christopher M

2009-09-01

To examine health care utilization measures indicating which asthma patients are appropriate for inhaled corticosteroid and long-acting beta(2)-adrenergic agonist (ICS/LABA) therapy and determine whether two ICS/LABA therapies were initiated in accordance with guidelines. A retrospective cohort study of commercially insured asthma patients aged > or =12 years that initiated fluticasone propionate/salmeterol (FSC) or budesonide/formoterol fumarate dihydrate (BFC) combination therapy in 2007 was conducted. Use was considered appropriate if patients met any of the following during a 1-year period before ICS/LABA initiation: ICS or leukotriene receptor antagonist (LTRA) use; an asthma-related emergency department (ED) visit or hospitalization; > or =2 oral corticosteroids (OCS) courses; or > or =6 short-acting beta(2)-adrenergic agonist (SABA) canisters. Multivariate logistic regression was used to assess factors associated with appropriate ICS/LABA use. Certain limitations inherent to the use of claims data for research apply to this study. Of 24,231 patients who initiated ICS/LABA therapy, 993 received BFC and 23,238 received FSC. Among all patients, 37.6% met > or =1 criteria for appropriate use. However, compared with FSC users, BFC users had a significantly higher likelihood of meeting > or =1 of these criteria (odds ratio, 2.01; 95% CI, 1.76-2.30; p < 0.001), and a higher proportion of BFC than FSC patients met 4 of the 5 appropriate use criteria. In total, 58.4% of BFC patients versus 36.7% of FSC patients met > or =1 criteria for appropriate use. Other factors associated with appropriate use included age, region, Charlson comorbidity score, number of medications, and prescriber specialty. Fewer than half of all patients fulfilled the specified criteria for being appropriate for ICS/LABA therapy. However, a significantly higher proportion of BFC than FSC users met the criteria for appropriate use of ICS/LABA therapy. These results may suggest a need for improved

Modelling the Interaction of Catecholamines with the α1A Adrenoceptor Towards a Ligand-induced Receptor Structure

NASA Astrophysics Data System (ADS)

Kinsella, Gemma K.; Rozas, Isabel; Watson, Graeme W.

2005-06-01

Adrenoceptors are members of the important G protein coupled receptor family for which the detailed mechanism of activation remains unclear. In this study, we have combined docking and molecular dynamics simulations to model the ligand induced effect on an homology derived human α1A adrenoceptor. Analysis of agonist/α1A adrenoceptor complex interactions focused on the role of the charged amine group, the aromatic ring, the N-methyl group of adrenaline, the beta hydroxyl group and the catechol meta and para hydroxyl groups of the catecholamines. The most critical interactions for the binding of the agonists are consistent with many earlier reports and our study suggests new residues possibly involved in the agonist-binding site, namely Thr-174 and Cys-176. We further observe a number of structural changes that occur upon agonist binding including a movement of TM-V away from TM-III and a change in the interactions of Asp-123 of the conserved DRY motif. This may cause Arg-124 to move out of the TM helical bundle and change the orientation of residues in IC-II and IC-III, allowing for increased affinity of coupling to the G-protein.

Central α- and β-adrenoceptors modifying arterial blood pressure and heart rate in conscious cats

PubMed Central

Day, M.D.; Roach, A.G.

1974-01-01

1 In conscious unrestrained cats noradrenaline, α-methylnoradrenaline and clonidine, infused into the lateral cerebral ventricles (i.c.v.) caused dose-related falls in blood pressure and heart rate; both effects were abolished after i.c.v. phentolamine. 2 In 12 out of 20 cats, i.c.v. isoprenaline and salbutamol when given caused dose-related pressor responses and tachycardias. These effects were abolished after i.c.v. β-adrenoceptor blocking drugs but were unaffected by α-adrenoceptor blocking agents. 3 In 5 out of 20 cats, i.c.v. isoprenaline regularly produced dose-related falls in blood pressure with associated tachycardias; both effects were abolished after i.c.v. β-adrenoceptor blocking agents. 4 Intracerebroventricular dopamine produced cardiovascular responses which were qualitatively similar to those produced by i.c.v. isoprenaline. 5 Intracerebroventricular adrenaline produced complex responses in untreated animals but typical α-effects were obtained after prior i.c.v. treatment with a β-adrenoceptor blocking agent and typical β-effects after i.c.v. pretreatment with an α-adrenoceptor blocking agent. 6 The cardiovascular changes produced by i.c.v. β-adrenoceptor agonists were abolished after systemic administration of hexamethonium or bethanidine. 7 The results are discussed in the light of the mode of action of β-adrenoceptor stimulants and β-adrenoceptor blocking agents in the treatment of hypertension. PMID:4451747

Wnt/β-Catenin Signaling Modulates Human Airway Sensitization Induced by β2-Adrenoceptor Stimulation

PubMed Central

Faisy, Christophe; Grassin-Delyle, Stanislas; Blouquit-Laye, Sabine; Brollo, Marion; Naline, Emmanuel; Chapelier, Alain; Devillier, Philippe

2014-01-01

Background Regular use of β2-agonists may enhance non-specific airway responsiveness. The wingless/integrated (Wnt) signaling pathways are responsible for several cellular processes, including airway inflammation and remodeling while cAMP–PKA cascade can activate the Wnt signaling. We aimed to investigate whether the Wnt signaling pathways are involved in the bronchial hyperresponsiveness induced by prolonged exposure to β2-adrenoceptor agonists in human isolated airways. Methods Bronchi were surgically removed from 44 thoracic surgery patients. After preparation, bronchial rings and primary cultures of bronchial epithelial cells were incubated with fenoterol (0.1 µM, 15 hours, 37°C), a β2-agonist with high intrinsic efficacy. The effects of inhibitors/blockers of Wnt signaling on the fenoterol-induced airway sensitization were examined and the impact of fenoterol exposure on the mRNA expression of genes interacting with Wnt signaling or cAMP–PKA cascade was assessed in complete bronchi and in cultured epithelial cells. Results Compared to paired controls, fenoterol-sensitization was abolished by inhibition/blockage of the Wnt/β-catenin signaling, especially the cell-surface LRP5/6 co-receptors or Fzd receptors (1 µM SFRP1 or 1 µM DKK1) and the nuclear recruitment of TCF/LEF transcriptions factors (0.3 µM FH535). Wnt proteins secretion did not seem to be involved in the fenoterol-induced sensitization since the mRNA expression of Wnt remained low after fenoterol exposure and the inactivator of Wnt secretion (1 µM IWP2) had no effect on the fenoterol-sensitization. Fenoterol exposure did not change the mRNA expression of genes regulating Wnt signaling or cAMP–PKA cascade. Conclusions Collectively, our pharmacological investigations indicate that fenoterol-sensitization is modulated by the inhibition/blockage of canonical Wnt/β-catenin pathway, suggesting a phenomenon of biased agonism in connection with the β2-adrenoceptor stimulation. Future

Long-term studies of dopamine agonists.

PubMed

Hubble, Jean P

2002-02-26

Dopamine agonists have long been used as adjunctive therapy for the treatment of Parkinson's disease (PD). In more recent years these drugs have also been proved safe and effective as initial therapy in lieu of levodopa in the treatment of PD. Long-term levodopa therapy is associated with motor complications, including fluctuating response patterns and dyskinesia. By initially introducing a dopamine agonist as symptomatic drug therapy, it may be possible to postpone the use of levodopa and delay or prevent the development of motor complications. Recently, four clinical trials have explored this hypothesis by comparing the long-term response and side effects of levodopa with dopamine agonist therapy. The drugs studied have included ropinirole, pramipexole, cabergoline, and pergolide. In each of these projects, the occurrence of motor complications, such as wearing off and dyskinesia, was significantly less in the subjects assigned to initiation of therapy with a dopamine agonist. The addition of levodopa could be postponed by many months or even several years. Therefore, these long-term studies of dopamine agonists support the initiation of a dopamine agonist instead of levodopa in an effort to postpone levodopa-related motor complications. This therapeutic approach may be particularly appropriate in PD patients with a long treatment horizon on the basis of age and general good health. The extension phase of the long-term study comparing pramipexole with levodopa is ongoing, and follow-up information may help to establish the value of this treatment strategy.

Treatment options for the management of exercise-induced asthma and bronchoconstriction.

PubMed

Millward, David T; Tanner, Lindsay G; Brown, Mark A

2010-12-01

Treatment for exercise-induced bronchospasm and exercise-induced asthma includes both pharmacologic and nonpharmacologic options. Pharmacologic agents that have been proven to be effective for treating these conditions include short- and long-acting β2-adrenoceptor agonists, mast cell-stabilizing agents, anticholinergics, leukotriene receptor antagonists, and inhaled corticosteroids (ICS). When selecting the most appropriate medication, factors to consider include the effectiveness of each, the duration of action, frequency of administration, potential side effects, and tolerance level. Long-acting β2-adrenoceptor agonists should not be used without ICS. Nonpharmacologic treatments include physical conditioning, incorporating a warm-up before and a cool-down period after exercise, performing nasal breathing, avoiding cold weather or environmental allergens, using a face mask or other aid to warm and humidify inhaled air, and modifying dietary intake. The data to support nonpharmacologic treatments are limited; however, they are routinely recommended because of the low risk associated with their use. This article highlights the advantages and limitations of each treatment option.

Interactions of xylazine and detomidine with alpha2-adrenoceptors in brain tissue from cattle, swine and rats.

PubMed

Törneke, K; Bergström, U; Neil, A

2003-06-01

Xylazine is an alpha2-adrenoceptor agonist sedative with a much higher interspecies variability in effect than detomidine, another alpha2-agonist used in veterinary practice. In the present study, we have used radioligand binding in brain tissue to investigate if the high species variation in sensitivity to xylazine could be explained in terms of receptor interactions. Species known to be more (cattle) or less (swine and rats) sensitive to xylazine were used. There was no variation in the density or the subtype pattern of the alpha2-adrenoceptors that could explain the species variation recorded in vivo, as a homogenous population of the alpha2A/D-subtype (200-300 fmol/mg protein) was found in all species. The species differences in the affinities of xylazine and detomidine were minor and similar for the two drugs. The only parameter investigated where a significant species difference was found for xylazine but not for detomidine was the slope of the inhibition binding curve when the G-protein coupling was diminished. For xylazine this slope was considerably lower than unity (i.e. 0.77 +/- 0.075) using cattle preparations compared with 0.92 +/- 0.037 (mean +/- SE) and 0.90 +/- 0.028, respectively for swine and rats, while for detomidine this parameter was close to unity in all species (cattle, swine, rat). This finding indicates that the species variation in effect for xylazine could be due to differences at the G-protein level or further down-stream in the effect cascade.

Beta 2-agonist fenoterol has greater effects on contractile function of rat skeletal muscles than clenbuterol.

PubMed

Ryall, James G; Gregorevic, Paul; Plant, David R; Sillence, Martin N; Lynch, Gordon S

2002-12-01

Potential treatments for skeletal muscle wasting and weakness ideally possess both anabolic and ergogenic properties. Although the beta(2)-adrenoceptor agonist clenbuterol has well-characterized effects on skeletal muscle, less is known about the therapeutic potential of the related beta(2)-adrenoceptor agonist fenoterol. We administered an equimolar dose of either clenbuterol or fenoterol to rats for 4 wk to compare their effects on skeletal muscle and tested the hypothesis that fenoterol would produce more powerful anabolic and ergogenic effects. Clenbuterol treatment increased fiber cross-sectional area (CSA) by 6% and maximal isometric force (P(o)) by 20% in extensor digitorum longus (EDL) muscles, whereas fiber CSA in soleus muscles decreased by 3% and P(o) was unchanged, compared with untreated controls. In the EDL muscles, fenoterol treatment increased fiber CSA by 20% and increased P(o) by 12% above values achieved after clenbuterol treatment. Soleus muscles of fenoterol-treated rats exhibited a 13% increase in fiber CSA and a 17% increase in P(o) above that of clenbuterol-treated rats. These data indicate that fenoterol has greater effects on the functional properties of rat skeletal muscles than clenbuterol.

Anti-inflammatory actions of clonidine, guanfacine and B-HT 920 against various inflammagen-induced acute paw oedema in rats.

PubMed

Kulkarni, S K; Mehta, A K; Kunchandy, J

1986-02-01

Clonidine (0.1-1.0 mg/kg, i.p.) exhibited anti-inflammatory activity in carrageenan-, formalin-, 5-HT- and histamine-induced paw oedema in rats. Similarly, other two alpha 2-adrenoceptor agonists, guanfacine and B-HT 920, also displayed an anti-inflammatory action in these models. The anti-inflammatory effect of all the three alpha 2-adrenoceptor agonists was reversed by yohimbine. However, prazosin failed to block the anti-inflammatory effect of clonidine. Intracerebroventricularly administered clonidine had a delayed onset of anti-inflammatory action, starting only from 60 min post carrageenan administration. This was in contrast to the systemically administered clonidine which was effective against both phases of carrageenan-induced oedema. On the other hand, irrespective of the route of administration, i.e. peripheral or central, guanfacine and B-HT 920 were effective against the early as well as against the delayed phases of the inflammatory reaction. The studies suggest that it is not the imidazoline moiety but the activation of alpha 2-adrenoceptors which is essential for the anti-inflammatory action of these agents.

Additive anticonvulsant effects of agmatine and lithium chloride on pentylenetetrazole-induced clonic seizure in mice: involvement of α₂-adrenoceptor.

PubMed

Bahremand, Arash; Ziai, Pouya; Payandemehr, Borna; Rahimian, Reza; Amouzegar, Afsaneh; Khezrian, Mina; Montaser-Kouhsari, Laleh; Meibodi, Maryam Aghaei; Ebrahimi, Ali; Ghasemi, Abbas; Ghasemi, Mehdi; Dehpour, Ahmad Reza

2011-09-01

After 60 years, lithium is still the mainstay in the treatment of mood disorders and widely used in clinic. In addition to its mood stabilizer effects, lithium also shows some anticonvulsant properties. Similar to lithium, agmatine also plays a protective role in the CNS against seizures and has been reported to enhance the effect of different antiepileptic agents. Moreover, both agmatine and lithium have modulatory effects on α(2)-adrenoceptors. So, we designed this study: 1) to investigate whether agmatine and lithium show an additive effect against clonic seizures induced by pentylenetetrazole; 2) to assess whether this additive effect is mediated through the α(2)-adrenoceptor or not. In our study, acute administration of a single effective dose of lithium chloride (30 mg/kg, i.p.) increased the seizure threshold. Pre-treatment with low and, per se, non-effective doses of agmatine (1 and 3mg/kg) potentiated a sub-effective dose of lithium (10mg/kg). Interestingly, the anticonvulsant effects of these effective combinations of lithium and agmatine were prevented by pre-treatment with low and non-effective doses of yohimbine [α(2)-adrenoceptor antagonist] (0.1 and 0.5mg/kg). On the other hand, clonidine [α(2)-adrenoceptor agonist] augmented the anticonvulsant effect of a sub-effective combination of lithium (5mg/kg i.p.) and agmatine (1mg/kg) at relatively low doses (0.1 and 0.25mg/kg). In summary, our findings demonstrate that agmatine and lithium chloride exhibit additive anticonvulsant properties which seem to be mediated through α(2)-adrenoceptor. Copyright © 2011. Published by Elsevier B.V.

The influence of hormonal and neuronal factors on rat heart adrenoceptors

PubMed Central

Kunos, George; Mucci, Lucia; O'Regan, Seana

1980-01-01

1 The influence of hormonal and neuronal factors on adrenoceptors mediating increased cardiac force and rate of contraction were studied in rat isolated atria. The pharmacological properties of these receptors were deduced from the relative potencies of agonists and from the effects of selective α- and β-adrenoceptor antagonists. The numbers and affinities of α- and β-adrenoceptors were also determined by radioligand binding to ventricular membrane fragments. 2 Hypophysectomy reduced the inotropic potency of isoprenaline and increased the potency of phenylephrine and methoxamine in left atria. The effect of phenylephrine was inhibited by propranolol less effectively and by phentolamine or phenoxybenzamine more effectively in hypophysectomized than in control rats. The difference in block was smaller at low than at high antagonist concentrations. Similar but smaller changes were observed for chronotropic responses of right atria. 3 The decreased β- and increased α-receptor response after hypophysectomy was similar to that observed earlier in thyroidectomized rats (Kunos, 1977). These changes developed slowly after hypophysectomy (>2 weeks), they were both reversed within 2 days of thyroxine treatment (0.2 mg/kg daily), but were not affected by cortisone treatment (50 mg/kg every 12 h for 4 days). 4 Treatment of hypophysectomized rats for 2 days with thyroxine increased the density of [3H]-dihydroalprenolol ([3H]-DHA) binding sites from 27.5 ± 2.7 to 45.5 ± 5.7 fmol/mg protein and decreased the density of [3H]-WB-4101 binding sites from 38.7 ± 3.1 to 18.7 ± 2.5 fmol/mg protein. The affinity of either type of binding site for agonists or antagonist was not significantly altered by thyroxine treatment and the sum total of α1- and β-receptors remained the same. 5 Sympathetic denervation of thyroidectomized rats by 6-hydroxydopamine increased the inotropic potency of isoprenaline and noradrenaline and the blocking effect of propranolol, and decreased the

Antileukotriene Agents Versus Long-Acting Beta-Agonists in Older Adults with Persistent Asthma: A Comparison of Add-On Therapies.

PubMed

Altawalbeh, Shoroq M; Thorpe, Carolyn T; Zgibor, Janice C; Kane-Gill, Sandra; Kang, Yihuang; Thorpe, Joshua M

2016-08-01

To compare the effectiveness and cardiovascular safety of long-acting beta-agonists (LABAs) with those of leukotriene receptor antagonists (LTRAs) as add-on treatments in older adults with asthma already taking inhaled corticosteroids (ICSs). Retrospective cohort study. Medicare fee-for-service (FFS) claims (2009-10) for a 10% random sample of beneficiaries continuously enrolled in Parts A, B, and D in 2009. Medicare beneficiaries aged 66 and older continuously enrolled in FFS Medicare with Part D coverage with a diagnosis of asthma before 2009 treated exclusively with ICSs plus LABAs or ICSs plus LTRAs (N = 14,702). The augmented inverse propensity-weighted estimator was used to compare the effect of LABA add-on therapy with that of LTRA add-on therapy on asthma exacerbations requiring inpatient, emergency, or outpatient care and on cardiovascular (CV) events, adjusting for demographic characteristics, comorbidities, and county-level healthcare-access variables. The primary analysis showed that LTRA add-on treatment was associated with greater odds of asthma-related hospitalizations or emergency department visits (odds ratio (OR) = 1.4, P < .001), as well as outpatient exacerbations requiring oral corticosteroids or antibiotics (OR = 1.41, P < .001) than LABA treatment. LTRA add-on therapy was also less effective in controlling acute symptoms, as indicated by greater use of short-acting beta agonists (rate ratio = 1.58, P < .001). LTRA add-on treatment was associated with lower odds of experiencing a CV event than LABA treatment (OR = 0.86, P = .006). This study provides new evidence specific to older adults to help healthcare providers weigh the risks and benefits of these add-on treatments. Further subgroup analysis is needed to personalize asthma treatments in this high-risk population. © 2016, Copyright the Authors Journal compilation © 2016, The American Geriatrics Society.

Differential agonist and inverse agonist profile of antipsychotics at D2L receptors coupled to GIRK potassium channels.

PubMed

Heusler, Peter; Newman-Tancredi, Adrian; Castro-Fernandez, Annabelle; Cussac, Didier

2007-03-01

The D(2) dopaminergic receptor represents a major target of antipsychotic drugs. Using the coupling of the human D(2long) (hD(2L)) receptor to G protein-coupled inward rectifier potassium (GIRK) channels in Xenopus laevis oocytes, we examined the activity of antipsychotic agents of different classes - typical, atypical, and a "new generation" of compounds, exhibiting a preferential D(2) and 5-HT(1A) receptor profile. When the hD(2L) receptor was coexpressed with GIRK channels, a series of reference compounds exhibited full agonist (dopamine, and quinpirole), partial agonist (apomorphine, (-)3-PPP, and (+)-UH232) or inverse agonist (raclopride, and L741626) properties. Sarizotan exhibited only very weak partial agonist action. At higher levels of receptor cRNA injected per oocyte, both partial agonist activity and inverse agonist properties were generally more pronounced. The inverse agonist action of L741626 was reversed by interaction with sarizotan, thus confirming the constitutive activity of wild-type hD(2L) receptors in the oocyte expression system. When antipsychotic agents were tested for their actions at the hD(2L) receptor, typical (haloperidol) as well as atypical (nemonapride, ziprasidone, and clozapine) compounds acted as inverse agonists. In contrast, among D(2)/5-HT(1A) antipsychotics, only SLV313 and F15063 behaved as inverse agonists, whilst the other members of this group (bifeprunox, SSR181507 and the recently marketed antipsychotic, aripiprazole) exhibited partial agonist properties. Thus, the X. laevis oocyte expression system highlights markedly different activity of antipsychotics at the hD(2L) receptor. These differential properties may translate to distinct therapeutic potential of these compounds.

Suppressive effects of RXR agonist PA024 on adrenal CYP11B2 expression, aldosterone secretion and blood pressure.

PubMed

Suzuki, Dai; Saito-Hakoda, Akiko; Ito, Ryo; Shimizu, Kyoko; Parvin, Rehana; Shimada, Hiroki; Noro, Erika; Suzuki, Susumu; Fujiwara, Ikuma; Kagechika, Hiroyuki; Rainey, William E; Kure, Shigeo; Ito, Sadayoshi; Yokoyama, Atsushi; Sugawara, Akira

2017-01-01

The effects of retinoids on adrenal aldosterone synthase gene (CYP11B2) expression and aldosterone secretion are still unknown. We therefore examined the effects of nuclear retinoid X receptor (RXR) pan-agonist PA024 on CYP11B2 expression, aldosterone secretion and blood pressure, to elucidate its potential as a novel anti-hypertensive drug. We demonstrated that PA024 significantly suppressed angiotensin II (Ang II)-induced CYP11B2 mRNA expression, promoter activity and aldosterone secretion in human adrenocortical H295R cells. Human CYP11B2 promoter functional analyses using its deletion and point mutants indicated that the suppression of CYP11B2 promoter activity by PA024 was in the region from -1521 (full length) to -106 including the NBRE-1 and the Ad5 elements, and the Ad5 element may be mainly involved in the PA024-mediated suppression. PA024 also significantly suppressed the Ang II-induced mRNA expression of transcription factors NURR1 and NGFIB that bind to and activate the Ad5 element. NURR1 overexpression demonstrated that the decrease of NURR1 expression may contribute to the PA024-mediated suppression of CYP11B2 transcription. PA024 also suppressed the Ang II-induced mRNA expression of StAR, HSD3β2 and CYP21A2, a steroidogenic enzyme group involved in aldosterone biosynthesis. Additionally, the PA024-mediated CYP11B2 transcription suppression was shown to be exerted via RXRα. Moreover, the combination of PPARγ agonist pioglitazone and PA024 caused synergistic suppressive effects on CYP11B2 mRNA expression. Finally, PA024 treatment significantly lowered both the systolic and diastolic blood pressure in Tsukuba hypertensive mice (hRN8-12 x hAG2-5). Thus, RXR pan-agonist PA024 may be a candidate anti-hypertensive drugs that acts via the suppression of aldosterone synthesis and secretion.

Alpha-adrenoceptor antagonistic and calcium antagonistic effects of nicergoline in the rat isolated aorta.

PubMed

Heitz, C; Descombes, J J; Miller, R C; Stoclet, J C

1986-04-16

The activity of the alpha-adrenoceptor antagonist nicergoline, a molecule composed of two constituent parts, ergoline and bromonicotinic acid, was investigated in the rat isolated aorta. Nicergoline (10 nM-0.1 microM) displaced concentration-effect curves elicited by noradrenaline and phenylephrine to the right and inhibited maximal responses elicited by both alpha-adrenoceptor agonists without significantly affecting prostaglandin F2 alpha-induced contractions. Higher concentrations of nicergoline (1 microM-50 microM) displaced to the right the concentration-effect curves elicited by calcium in a depolarizing medium. This calcium antagonist activity was not shared by either of the constituent parts. Nicergoline 100 microM abolished the 45Ca influx induced into rat aorta by 100 mM K+-containing physiological solution. The selectivity of nicergoline for alpha 1-adrenoceptors seen in binding experiments also depends on the presence of the bromonicotinic moiety of the molecule. It is concluded that nicergoline, but not its substituent parts, displays both alpha 1-adrenoceptor and calcium antagonism. The latter property may account for some of the observed effects of this compound.

Mild prenatal protein malnutrition increases alpha2C-adrenoceptor density in the cerebral cortex during postnatal life and impairs neocortical long-term potentiation and visuo-spatial performance in rats.

PubMed

Soto-Moyano, Rubén; Valladares, Luis; Sierralta, Walter; Pérez, Hernán; Mondaca, Mauricio; Fernández, Victor; Burgos, Héctor; Hernández, Alejandro

2005-06-01

Mild reduction in the protein content of the mother's diet from 25 to 8% casein, calorically compensated by carbohydrates, does not alter body and brain weights of rat pups at birth, but leads to significant enhancements in the concentration and release of cortical noradrenaline during early postnatal life. Since central noradrenaline and some of its receptors are critically involved in long-term potentiation (LTP) and memory formation, this study evaluated the effect of mild prenatal protein malnutrition on the alpha2C-adrenoceptor density in the frontal and occipital cortices, induction of LTP in the same cortical regions and the visuo-spatial memory. Pups born from rats fed a 25% casein diet throughout pregnancy served as controls. At day 8 of postnatal age, prenatally malnourished rats showed a threefold increase in neocortical alpha2C-adrenoceptor density. At 60 days-of-age, alpha2C-adrenoceptor density was still elevated in the neocortex, and the animals were unable to maintain neocortical LTP and presented lower visuo-spatial memory performance. Results suggest that overexpression of neocortical alpha2C-adrenoceptors during postnatal life, subsequent to mild prenatal protein malnutrition, could functionally affect the synaptic networks subserving neocortical LTP and visuo-spatial memory formation.

Effects of long-acting beta adrenergic agonists on vocal fold ion transport.

PubMed

Sivasankar, Mahalakshmi; Blazer-Yost, Bonnie

2009-03-01

Inhaled medications prescribed for the hypersensitive airway typically combine corticosteroids and long-acting beta2 adrenergic agonists (LABAs). The phonatory side effects of these combination treatments are widely recognized. However, there is limited understanding of the physiological changes induced by these medications that underlie the phonatory side effects. The objective of this study was to investigate the distinct effects of corticosteroids and LABAs on vocal fold mucosal physiology. Understanding the physiological changes to the vocal folds after corticosteroid and LABA treatments is necessary to prevent the prevalent vocal decrement associated with these medications. Experimental in vitro design with treatment and control groups. Native porcine vocal fold mucosae (N = 38) were exposed to corticosteroid or LABA treatments. Ion transport was measured continuously at baseline and after treatment. To quantify the nature of ion transport, vocal folds were also treated with chloride and sodium channel inhibitors. Corticosteroid treatment did not alter ion transport. Conversely, exposure to LABAs significantly increased ion transport. This increase in ion transport was transient, observed immediately after treatment in all tissue and associated with increased chloride secretion. The distinct effects of corticosteroids and LABAs on vocal fold physiology have not been examined to date. This study demonstrates that short-term treatment with LABAs, but not corticosteroids, significantly increases ion transport. These findings suggest that one underlying physiological mechanism for phonatory changes associated with inhaled treatments may be related to acute alterations in vocal fold ion transport and surface hydration.

Combined corticosteroid and long-acting beta-agonist in one inhaler versus placebo for chronic obstructive pulmonary disease

PubMed Central

Nannini, Luis Javier; Cates, Christopher J; Lasserson, Toby J; Poole, Phillippa

2014-01-01

Background Long-acting beta-agonists and inhaled corticosteroids have both been recommended in guidelines for the treatment of chronic obstructive pulmonary disease. Their co-administration in a combined inhaler may facilitate adherence to medication regimens, and improve efficacy. Objectives To assess the efficacy of combined inhaled corticosteroid and long-acting beta-agonist preparations, compared to placebo, in the treatment of adults with chronic obstructive pulmonary disease. Search methods We searched the Cochrane Airways Group Specialised Register of trials. The date of the most recent search is April 2007. Selection criteria Studies were included if they were randomised and double-blind. Studies could compare any combined inhaled corticosteroids and long-acting beta-agonist preparation with placebo. Data collection and analysis Two authors independently assessed study risk of bias and extracted data. The primary outcomes were exacerbations, mortality and pneumonia. Health-related quality of life (measured by validated scales), lung function and side-effects were secondary outcomes. Dichotomous data were analysed as fixed effect odds ratios or rate ratios with 95% confidence intervals, and continuous data as mean differences and 95% confidence intervals. Main results Eleven studies met the inclusion criteria (6427 participants randomised). Two different combination preparations (fluticasone/salmeterol and budesonide/formoterol) were used. Study quality was good. Fluticasone/salmeterol and budesonide/formoterol both reduced the rate of exacerbations. Pooled analysis of both combination therapies indicated that exacerbations were less frequent when compared with placebo, Rate Ratio: 0.74 (95% CI 0.7 to 0.8). The clinical impact of this effect depends on the frequency of exacerbations experienced by patients. The patients included in these trials had on average 1-2 exacerbations per year which means that treatment with combination therapy would lead to a

Blockade of hyperpolarization-activated channels modifies the effect of beta-adrenoceptor stimulation.

PubMed

Zefirov, T L; Ziyatdinova, N I; Gainullin, A A; Zefirov, A L

2002-05-01

Experiments on rats showed that blockade of hyperpolarization-activated currents moderates tachycardia induced by beta-adrenoceptor agonist isoproterenol and potentiates the increase in stroke volume produced by this agonist. Electrical stimulation of the vagus nerve against the background of isoproterenol treatment augmented bradycardia and increased stroke volume. Blockade of hyperpolarization-activated currents followed by application of isoproterenol moderated vagus-induced bradycardia and had no effect on the dynamics of stroke volume.

Impact of multiple-dose versus single-dose inhaler devices on COPD patients’ persistence with long-acting β2-agonists: a dispensing database analysis

PubMed Central

van Boven, Job FM; van Raaij, Joost J; van der Galiën, Ruben; Postma, Maarten J; van der Molen, Thys; Dekhuijzen, PN Richard; Vegter, Stefan

2014-01-01

Background: With a growing availability of different devices and types of medication, additional evidence is required to assist clinicians in prescribing the optimal medication in relation to chronic obstructive pulmonary disease (COPD) patients’ persistence with long-acting β2-agonists (LABAs). Aims: To assess the impact of the type of inhaler device (multiple-dose versus single-dose inhalers) on 1-year persistence and switching patterns with LABAs. Methods: A retrospective observational cohort study was performed comparing a cohort of patients initiating multiple-dose inhalers and a cohort initiating single-dose inhalers. The study population consisted of long-acting bronchodilator naive COPD patients, initiating inhalation therapy with mono-LABAs (formoterol, indacaterol or salmeterol). Analyses were performed using pharmacy dispensing data from 1994 to 2012, obtained from the IADB.nl database. Study outcomes were 1-year persistence and switching patterns. Results were adjusted for initial prescriber, initial medication, dosing regimen and relevant comorbidities. Results: In all, 575 patients initiating LABAs were included in the final study cohort. Among them, 475 (83%) initiated a multiple-dose inhaler and 100 (17%) a single-dose inhaler. Further, 269 (47%) initiated formoterol, 9 (2%) indacaterol and 297 (52%) salmeterol. There was no significant difference in persistence between users of multiple-dose or single-dose inhalers (hazard ratio: 0.98, 95% confidence interval: 0.76–1.26, P=0.99). Over 80% re-started or switched medication. Conclusions: There seems no impact of inhaler device (multiple-dose versus single-dose inhalers) on COPD patients’ persistence with LABAs. Over 80% of patients who initially seemed to discontinue LABAs, re-started their initial medication or switched inhalers or medication within 1 year. PMID:25274453

Effects of E2HSA, a Long-Acting Glucagon Like Peptide-1 Receptor Agonist, on Glycemic Control and Beta Cell Function in Spontaneous Diabetic db/db Mice.

PubMed

Hou, Shaocong; Li, Caina; Huan, Yi; Liu, Shuainan; Liu, Quan; Sun, Sujuan; Jiang, Qian; Jia, Chunming; Shen, Zhufang

2015-01-01

Glucagon like peptide-1 (GLP-1) receptor agonists such as exendin-4 have been widely used but their short half-life limits their therapeutic value. The recombinant protein, E2HSA, is a novel, long-acting GLP-1 receptor agonist generated by the fusion of exendin-4 with human serum albumin. In mouse pancreatic NIT-1 cells, E2HSA activated GLP-1 receptor with similar efficacy as exendin-4. After single-dose administration in ICR mice, E2HSA showed prolonged glucose lowering effects which lasted up to four days and extended inhibition on gastric emptying for at least 72 hours. Chronic E2HSA treatment in db/db mice significantly improved glucose tolerance, reduced elevated nonfasting and fasting plasma glucose levels, and also decreased HbA1c levels. E2HSA also increased insulin secretion and decreased body weight and appetite. Furthermore, immunofluorescence analysis showed that E2HSA increased β-cell area, improved islet morphology, and reduced β-cell apoptosis. In accordance with the promotion of β-cell function and survival, E2HSA upregulated genes such as Irs2, Pdx-1, Nkx6.1, and MafA and downregulated the expression levels of FoxO1 and proapoptotic Bcl-2 family proteins. In conclusion, with prolonged glucose lowering effects and promoting β-cell function and survival, the fusion protein, E2HSA, is a promising new therapeutic for once weekly treatment of type 2 diabetes.

Effects of E2HSA, a Long-Acting Glucagon Like Peptide-1 Receptor Agonist, on Glycemic Control and Beta Cell Function in Spontaneous Diabetic db/db Mice

PubMed Central

Hou, Shaocong; Li, Caina; Liu, Shuainan; Liu, Quan; Sun, Sujuan; Jia, Chunming; Shen, Zhufang

2015-01-01

Glucagon like peptide-1 (GLP-1) receptor agonists such as exendin-4 have been widely used but their short half-life limits their therapeutic value. The recombinant protein, E2HSA, is a novel, long-acting GLP-1 receptor agonist generated by the fusion of exendin-4 with human serum albumin. In mouse pancreatic NIT-1 cells, E2HSA activated GLP-1 receptor with similar efficacy as exendin-4. After single-dose administration in ICR mice, E2HSA showed prolonged glucose lowering effects which lasted up to four days and extended inhibition on gastric emptying for at least 72 hours. Chronic E2HSA treatment in db/db mice significantly improved glucose tolerance, reduced elevated nonfasting and fasting plasma glucose levels, and also decreased HbA1c levels. E2HSA also increased insulin secretion and decreased body weight and appetite. Furthermore, immunofluorescence analysis showed that E2HSA increased β-cell area, improved islet morphology, and reduced β-cell apoptosis. In accordance with the promotion of β-cell function and survival, E2HSA upregulated genes such as Irs2, Pdx-1, Nkx6.1, and MafA and downregulated the expression levels of FoxO1 and proapoptotic Bcl-2 family proteins. In conclusion, with prolonged glucose lowering effects and promoting β-cell function and survival, the fusion protein, E2HSA, is a promising new therapeutic for once weekly treatment of type 2 diabetes. PMID:26351642

The effect of prolonged ethanol administration on central alpha 2-adrenoceptors sensitivity.

PubMed

Szmigielski, A; Szmigielska, H; Wejman, I

1989-01-01

The response of an endogenous inhibitor of protein kinases (type II inhibitor) to clonidine was used as an index of sensitivity of central alpha 2-adrenoceptors. Low doses of clonidine (20-50 micrograms/kg) induced an increase in type II inhibitor activity in the nucleus accumbens, hippocampus and in the anterior and posterior hypothalamus by stimulating presynaptic alpha 2-adrenoceptors. Stimulation of postsynaptic alpha 2-adrenoceptors by high doses of clonidine 0.5-1.0 mg/kg resulted in a dose-dependent decrease in type II inhibitor activity. Prolonged treatment with ethanol (5 g/kg/day po for 21 days) greatly reduced the action of high doses of clonidine in all the examined brain areas, suggesting subsensitivity of postsynaptic alpha 2-adrenoceptors lasting for at least 48 h after the last ethanol administration. A single dose of ethanol induced a short lasting subsensitivity of postsynaptic alpha 2-adrenoceptors in the anterior hypothalamus. 12 h after administration of alcohol the response of type II inhibitor to high doses of clonidine in this brain area was the same as in untreated rats.

Combined corticosteroid and long-acting beta2-agonist in one inhaler versus long-acting beta2-agonists for chronic obstructive pulmonary disease

PubMed Central

Nannini, Luis Javier; Lasserson, Toby J; Poole, Phillippa

2014-01-01

Background Both inhaled steroids (ICS) and long-acting beta2-agonists (LABA) are used in the management of chronic obstructive pulmonary disease (COPD). This updated review compared compound LABA plus ICS therapy (LABA/ICS) with the LABA component drug given alone. Objectives To assess the efficacy of ICS and LABA in a single inhaler with mono-component LABA alone in adults with COPD. Search methods We searched the Cochrane Airways Group Specialised Register of trials. The date of the most recent search was November 2011. Selection criteria We included randomised, double-blind controlled trials. We included trials comparing compound ICS and LABA preparations with their component LABA preparations in people with COPD. Data collection and analysis Two authors independently assessed study risk of bias and extracted data. The primary outcomes were exacerbations, mortality and pneumonia, while secondary outcomes were health-related quality of life (measured by validated scales), lung function, withdrawals due to lack of efficacy, withdrawals due to adverse events and side-effects. Dichotomous data were analysed as random-effects model odds ratios or rate ratios with 95% confidence intervals (CIs), and continuous data as mean differences and 95% CIs. We rated the quality of evidence for exacerbations, mortality and pneumonia according to recommendations made by the GRADE working group. Main results Fourteen studies met the inclusion criteria, randomising 11,794 people with severe COPD. We looked at any LABA plus ICS inhaler (LABA/ICS) versus the same LABA component alone, and then we looked at the 10 studies which assessed fluticasone plus salmeterol (FPS) and the four studies assessing budesonide plus formoterol (BDF) separately. The studies were well-designed with low risk of bias for randomisation and blinding but they had high rates of attrition, which reduced our confidence in the results for outcomes other than mortality. Primary outcomes There was low quality

Complete reversal of muscle wasting in experimental cancer cachexia: Additive effects of activin type II receptor inhibition and β-2 agonist.

PubMed

Toledo, Míriam; Busquets, Sílvia; Penna, Fabio; Zhou, Xiaolan; Marmonti, Enrica; Betancourt, Angelica; Massa, David; López-Soriano, Francisco J; Han, H Q; Argilés, Josep M

2016-04-15

Formoterol is a highly potent β2-adrenoceptor-selective agonist, which is a muscle growth promoter in many animal species. Myostatin/activin inhibition reverses skeletal muscle loss and prolongs survival of tumor-bearing animals. The aim of this investigation was to evaluate the effects of a combination of the soluble myostatin receptor ActRIIB (sActRIIB) and the β2-agonist formoterol in the cachectic Lewis lung carcinoma model. The combination of formoterol and sActRIIB was extremely effective in reversing muscle wasting associated with experimental cancer cachexia in mice. Muscle weights from tumor-bearing animals were completely recovered following treatment and this was also reflected in the measured grip strength. This combination increased food intake in both control and tumor-bearing animals. The double treatment also prolonged survival significantly without affecting the weight and growth of the primary tumor. In addition, it significantly reduced the number of metastasis. Concerning the mechanisms for the preservation of muscle mass during cachexia, the effects of formoterol and sActRIIB seemed to be additive, since formoterol reduced the rate of protein degradation (as measured in vitro as tyrosine release, using incubated isolated individual muscles) while sActRIIB only affected protein synthesis (as measured in vivo using tritiated phenylalanine). Formoterol also increased the rate of protein synthesis and this seemed to be favored by the presence of sActRIIB. Combining formoterol and sActRIIB seemed to be a very promising treatment for experimental cancer cachexia. Further studies in human patients are necessary and may lead to a highly effective treatment option for muscle wasting associated with cancer. © 2015 UICC.

Characterizations of the α1-adrenoceptor subtypes mediating contractions of the human internal anal sphincter.

PubMed

Owaki, Hiroyuki; Sadahiro, Sotaro; Takaki, Miyako

2015-04-01

Human internal anal sphincter (IAS) is contracted by α1-adrenoceptor stimulation and thus α1-adrenoceptor agonists may be useful in treating fecal incontinence. This study characterizes the contribution of α1-adrenoceptor subtypes in contraction of human IAS and to investigate the age-related risk of patients with fecal incontinence. IAS and inferior mesenteric artery (IMA), as a predictor of systemic arterial pressure, were obtained from 11 patients. Both muscle strips were assessed by isometric-contraction experiments using phenylephrine, further in IAS, in the presence of various subtype selective α1-adrenoceptor antagonists. Immunohistochemistry and gene expression studies were performed in the same samples. The mean pEC50 values with SEM of phenylephrine in IAS (6.30 ± 0.13) were higher than those of IMA (5.60 ± 0.10). Furthermore, the age-related pEC50 change of IAS was observed between age <70 and ≥70 (6.58 ± 0.13 and 6.07 ± 0.16, respectively (P < 0.05)). In IAS, rightward shift of the concentration-response curves of phenylephrine was observed with three α1-adrenoceptor antagonists. Each pKB value of silodosin, BMY-7378 and prazosin was 9.36 ± 0.53, 7.28 ± 0.20 and 8.89 ± 0.12, respectively. These pKB values and gene expression studies indicated that α1A-adrenoceptor subtypes predominantly contributed to human IAS contraction. Copyright © 2015 The Authors. Production and hosting by Elsevier B.V. All rights reserved.

Acute systemic effects of inhaled salbutamol in asthmatic subjects expressing common homozygous beta2-adrenoceptor haplotypes at positions 16 and 27.

PubMed

Lee, Daniel K C; Bates, Caroline E; Lipworth, Brian J

2004-01-01

The relationship between beta2-adrenoceptor polymorphisms at positions 16 and 27, and the acute systemic beta2-adrenoceptor effects of inhaled salbutamol is unclear. We therefore elected to evaluate the influence of common homozygous beta2-adrenoceptor haplotypes on the acute systemic beta2-adrenoceptor effects following inhaled salbutamol in asthmatic subjects. An initial database search of 531 asthmatic subjects identified the two commonest homozygous haplotypes at positions 16 and 27 to be Arg16-Gln27 (12%) and Gly16-Glu27 (19%). After a 1-week washout period where all beta2-adrenoceptor agonists were withdrawn, 16 Caucasian subjects (Arg16-Gln27: n = 8 and Gly16-Glu27: n = 8) were given a single dose of inhaled salbutamol (1200 microg), followed by serial blood sampling for serum potassium, along with measurements of diastolic blood pressure and heart rate, at 5-min intervals for 20 min. The two groups were well matched for age, sex, FEV1, and inhaled corticosteroid dose. Baseline values for serum potassium, diastolic blood pressure and heart rate were not significantly different comparing Arg16-Gln27 vs Gly16-Glu27. The mean +/- SEM maximum serum potassium change from baseline over 20 min was significantly greater (P = 0.04) for Arg16-Gln27: -0.37 +/- 0.05 mmol l(-1) vs Gly16-Glu27: -0.23 +/- 0.04 mmol l(-1); 95% CI for difference: -0.01 to -0.28 mmol l(-1). The maximum diastolic blood pressure change from baseline over 20 min was significantly greater (P = 0.0008) for Arg16-Gln27: -13 +/- 1 mmHg vs Gly16-Glu27: -4 +/- 2 mmHg; 95% CI for difference: -5, 14 mmHg. There was no significant difference comparing the maximum heart rate change from baseline for Arg16-Gln27: 10 +/- 3 beats min(-1) vs Gly16-Glu27: 10 +/- 3 beats min(-1). Caucasian asthmatic subjects with the Arg16-Gln27 haplotype exhibited a greater systemic response to inhaled salbutamol, compared with those with the Gly16-Glu27 haplotype. The attenuated beta2-adrenoceptor response in the Gly16-Glu27

Serelaxin Elicits Bronchodilation and Enhances β-Adrenoceptor-Mediated Airway Relaxation

PubMed Central

Lam, Maggie; Royce, Simon G.; Donovan, Chantal; Jelinic, Maria; Parry, Laura J.; Samuel, Chrishan S.; Bourke, Jane E.

2016-01-01

Treatment with β-adrenoceptor agonists does not fully overcome the symptoms associated with severe asthma. Serelaxin elicits potent uterine and vascular relaxation via its cognate receptor, RXFP1, and nitric oxide (NO) signaling, and is being clinically evaluated for the treatment of acute heart failure. However, its direct bronchodilator efficacy has yet to be explored. Tracheal rings were prepared from male Sprague-Dawley rats (250–350 g) and tricolor guinea pigs, and precision cut lung slices (PCLSs) containing intrapulmonary airways were prepared from rats only. Recombinant human serelaxin (rhRLX) alone and in combination with rosiglitazone (PPARγ agonist; recently described as a novel dilator) or β-adrenoceptor agonists (isoprenaline, salbutamol) were added either to pre-contracted airways, or before contraction with methacholine or endothelin-1. Regulation of rhRLX responses by epithelial removal, indomethacin (cyclooxygenase inhibitor), L-NAME (nitric oxide synthase inhibitor), SQ22536 (adenylate cyclase inhibitor) and ODQ (guanylate cyclase inhibitor) were also evaluated. Immunohistochemistry was used to localize RXFP1 to airway epithelium and smooth muscle. rhRLX elicited relaxation in rat trachea and PCLS, more slowly than rosiglitazone or isoprenaline, but potentiated relaxation to both these dilators. It markedly increased β-adrenoceptor agonist potency in guinea pig trachea. rhRLX, rosiglitazone, and isoprenaline pretreatment also inhibited the development of rat tracheal contraction. Bronchoprotection by rhRLX increased with longer pre-incubation time, and was partially reduced by epithelial removal, indomethacin and/or L-NAME. SQ22536 and ODQ also partially inhibited rhRLX-mediated relaxation in both intact and epithelial-denuded trachea. RXFP1 expression in the airways was at higher levels in epithelium than smooth muscle. In summary, rhRLX elicits large and small airway relaxation via epithelial-dependent and -independent mechanisms, likely

Potentiation of carbachol-induced detrusor smooth muscle contractions by beta-adrenoceptor activation.

PubMed

Klausner, Adam P; Rourke, Keith F; Miner, Amy S; Ratz, Paul H

2009-03-15

In strips of rabbit bladder free of urothelium, the beta-adrenoceptor agonist, isoproterenol, significantly reduced basal detrusor smooth muscle tone and inhibited contractions produced by low concentrations of the muscarinic receptor agonist, carbachol. During a carbachol concentration-response curve, instead of inhibiting, isoproterenol strengthened contractions produced by high carbachol concentrations. Thus, the carbachol concentration-response curve was shifted by isoproterenol from a shallow, graded relationship, to a steep, switch-like relationship. The tyrosine kinase inhibitor, genistein, inhibited carbachol-induced contractions only in the presence of isoproterenol. Contraction produced by a single high carbachol concentration (1 microM) displayed 1 fast and 1 slow peak. In the presence of isoproterenol, the slow peak was not strengthened, but was delayed, and U-0126 (mitogen-activated protein kinase kinase inhibitor) selectively inhibited this delay concomitantly with inhibition of extracellular signal-regulated kinase (ERK) phosphorylation. Isoproterenol reduced ERK phosphorylation only in the absence of carbachol. These data support the concept that, by inhibiting weak contractions, potentiating strong contractions, and producing a more switch-like concentration-response curve, beta-adrenoceptor stimulation enhanced the effectiveness of muscarinic receptor-induced detrusor smooth muscle contraction. Moreover, beta-adrenoceptor stimulation changed the cellular mechanism by which carbachol produced contraction. The potential significance of multi-receptor and multi-cell crosstalk is discussed.

Activation of β-adrenoceptor facilitates active avoidance learning through enhancement of glutamate levels in the hippocampal dentate gyrus.

PubMed

Lv, Jing; Feng, Hao; Chen, Ling; Wang, Wei-Yao; Yue, Xue-Ling; Jin, Qing-Hua

2017-10-18

Long-term potentiation (LTP) is widely accepted as the best studied model for neurophysiological mechanisms that could underlie learning and memory formation. Despite a number of studies indicating that β-adrenoceptors in the hippocampal dentate gyrus (DG) is involved in the modulation of learning and memory as well as LTP, few studies have used glutamate release as a visual indicator in awake animals to explore the role of β-adrenoceptors in learning-dependent LTP. Therefore, in the present study, the effects of propranolol (an antagonist of β-adrenoceptor) and isoproterenol (an agonist of β-adrenoceptor) on extracellular concentrations of glutamate and amplitudes of field excitatory postsynaptic potential were measured in the DG region during active avoidance learning in freely moving conscious rats. In the control group, the glutamate level in the DG was significantly increased during the acquisition of active avoidance behavior and returned to basal level following extinction training. In propranolol group, antagonism of β-adrenoceptors in the DG significantly reduced the change in glutamate level, and the acquisition of the active avoidance behavior was significantly inhibited. In contrast, the change in glutamate level was significantly enhanced by isoproterenol, and the acquisition of the active avoidance behavior was significantly accelerated. Furthermore, in all groups, the changes in glutamate level were accompanied by corresponding changes in field excitatory postsynaptic potential amplitude and active avoidance behavior. Our results suggest that activation of β-adrenoceptors in the hippocampal DG facilitates active avoidance learning by modulations of glutamate level and synaptic efficiency in rats.

Mild prenatal protein malnutrition increases alpha 2C-adrenoceptor expression in the rat cerebral cortex during postnatal life.

PubMed

Sierralta, Walter; Hernández, Alejandro; Valladares, Luis; Pérez, Hernán; Mondaca, Mauricio; Soto-Moyano, Rubén

2006-05-15

Mild reduction in the protein content in the diet of pregnant rats from 25 to 8% casein, calorically compensated by carbohydrates, does not alter body and brain weights of rat pups at birth, but results in significant changes of the concentration and release of cortical noradrenaline during postnatal life, together with impaired long-term potentiation and memory formation. Since some central noradrenergic receptors are critically involved in neuroplasticity, the present study evaluated, by utilizing immunohistochemical methods, the effect of mild prenatal protein malnutrition on the alpha 2C-adrenoceptor expression in the frontal and occipital cortices of 8- and 60-day-old rats. At day 8 of postnatal age, prenatally malnourished rats exhibited a three-fold increase of alpha 2C-adrenoceptor expression in both the frontal and the occipital cortices, as compared to well-nourished controls. At 60 days of age, prenatally malnourished rats showed normal expression levels scores of alpha 2C-adrenoceptor in the neocortex. Results suggest that overexpression of neocortical alpha 2C-adrenoceptors during early postnatal life, subsequent to mild prenatal protein malnutrition, could in part be responsible for neural and behavioral disturbances showing prenatally malnourished animals during the postnatal life.

Agonist-induced modulation of inverse agonist efficacy at the beta 2-adrenergic receptor.

PubMed

Chidiac, P; Nouet, S; Bouvier, M

1996-09-01

Sustained stimulation of several G protein-coupled receptors is known to lead to a reduction in the signaling efficacy. This phenomenon, named agonist-induced desensitization, has been best studied for the beta 2-adrenergic receptor (AR) and is characterized by a decreased efficacy of beta-adrenergic agonists to stimulate the adenylyl cyclase activity. Recently, several beta-adrenergic ligands were found to inhibit the spontaneous agonist-independent activity of the beta 2AR. These compounds, termed inverse agonists, have different inhibitory efficacies, ranging from almost neutral antagonists to full inverse agonists. The current study was undertaken to determine whether, as is the case for agonists, desensitization can affect the efficacies of inverse agonists. Agonist-promoted desensitization of the human beta 2AR expressed in Sf9 cells potentiated the inhibitory actions of the inverse agonists, with the extent of the potentiation being inversely proportional to their intrinsic activity. For example, desensitization increased the inhibitory action of the weak inverse agonist labetalol by 29%, whereas inhibition of the spontaneous activity by the strong inverse agonist timolol was not enhanced by the desensitizing stimuli. Interestingly, dichloroisoproterenol acted stochastically as either a weak partial agonist or a weak inverse agonist in control conditions but always behaved as an inverse agonist after desensitization. These data demonstrate that like for agonists, the efficacies of inverse agonists can be modulated by a desensitizing treatment. Also, the data show that the initial state of the receptor can determine whether a ligand behaves as a partial agonist or an inverse agonist.

Optimization of a Small Tropomyosin-related Kinase B (TrkB) Agonist 7,8-Dihydroxyflavone Active in Mouse Models of Depression

PubMed Central

Liu, Xia; Chan, Chi-Bun; Qi, Qi; Xiao, Ge; Luo, Hongbo R.; He, Xiaolin; Ye, Keqiang

2012-01-01

Structure-activity relationship study shows that the catechol group in 7,8-dihdyroxyflavone, a selective small TrkB receptor agonist, is critical for the agonistic activity. To improve the poor pharmacokinetic profiles intrinsic to catechol-containing molecules and elevate the agonistic effect of the lead compound, we initiated the lead optimization campaign by synthesizing various bioisosteric derivatives. Here we show that the optimized 2-methyl-8-(4′-(pyrrolidin-1-yl)phenyl)chromeno[7,8-d]imidazol-6(1H)-one derivative possesses the enhanced TrkB stimulatory activity. Chronic oral administration of this compound significantly reduces the immobility in forced swim test and tail suspension test, two classical antidepressant behavioral animal models, which is accompanied by robust TrkB activation in hippocampus of mouse brain. Further, in vitro ADMET studies demonstrate that this compound possesses the improved features compared to the previous lead compound. Hence, this optimized compound may act as a promising lead candidate for in-depth drug development for treating various neurological disorders including depression. PMID:22984948

Selective blockade by nicergoline of vascular responses elicited by stimulation of alpha 1A-adrenoceptor subtype in the rat.

PubMed

Alvarez-Guerra, M; Bertholom, N; Garay, R P

1999-01-01

The alpha 1-adrenergic blocking activity of nicergoline was re-examined in rats, with a particular emphasis on alpha 1-adrenoceptor subtypes. In pithed rats, nicergoline and prazosin infused at a single small dose (0.5 microgram/kg/min i.v.) produced a substantial and identical shift to the right of the control dose pressor response curve to the specific alpha 1-agonist cirazoline (ED50 = 4.0 +/- 0.1, 4.0 +/- 0.1 and 0.9 +/- 0.01 microgram/kg i.v. for nicergoline, prazosin and vehicle respectively). In the isolated perfused mesenteric vascular bed, nicergoline strongly inhibited the pressor responses elicited by cirazoline, with approximately 40-fold higher potency (pA2 = 11.1 +/- 0.3) than prazosin (pA2 = 9.5 +/- 0.3). Conversely, nicergoline was 20-fold less potent than prazosin to antagonize the contractile effects of cirazoline in isolated endothelium-denuded aorta (pA2 = 8.6 +/- 0.2 and 9.9 +/- 0.2 for nicergoline and prazosin respectively). Pretreatment of mesenteric vascular beds with chloroethylclonidine did not significantly modify nicergoline antagonistic potency (pA2 = 10.6 +/- 0.2). Nicergoline displaced [3H]-prazosin bound to rat forebrain membranes pretreated with chloroethylclonidine (pKi = 9.9 +/- 0.2) at concentrations 60-fold lower than in rat liver membranes (pKi = 8.1 +/- 0.2). Finally, of the nicergoline metabolites studied, lumilysergol acted as a modest alpha 1 antagonist (bromonicotinic acid was devoid of alpha 1 antagonist activity). In conclusion, nicergoline is a potent and selective alpha 1A-adrenoceptor subtype antagonist, an alpha 1-adrenoceptor subtype which is mainly represented in resistance arteries.

Rational Design of Dual Agonist-Antibody Fusions as Long-acting Therapeutic Hormones.

PubMed

Liu, Yan; Wang, Ying; Zhang, Yong; Liu, Tao; Jia, Haiqun; Zou, Huafei; Fu, Qiangwei; Zhang, Yuhan; Lu, Lucy; Chao, Elizabeth; Parker, Holly; Nguyen-Tran, Van; Shen, Weijun; Wang, Danling; Schultz, Peter G; Wang, Feng

2016-11-18

Recent studies have suggested that modulation of two or more signaling pathways can achieve substantial weight loss and glycemic stability. We have developed an approach to the generation of bifunctional antibody agonists that activate leptin receptor and GLP-1 receptor. Leptin was fused into the complementarity determining region 3 loop of the light chain alone, or in combination with exendin-4 (EX4) fused at the N-terminus of the heavy chain of Herceptin. The antibody fusions exhibit similar or increased in vitro activities on their cognate receptors, but 50-100-fold longer circulating half-lives in rodents compared to the corresponding native peptides/proteins. The efficacy of the leptin/EX4 dual antibody fusion on weight loss, especially fat mass loss, was enhanced in ob/ob mice and DIO mice compared to the antibody fusion of either EX4 or leptin alone. This work demonstrates the versatility of this combinatorial fusion strategy for generating dual antibody agonists with long half-lives.

Biomarker-guided clinical development of the first-in-class anti-inflammatory FPR2/ALX agonist ACT-389949.

PubMed

Stalder, Anna K; Lott, Dominik; Strasser, Daniel S; Cruz, Hans G; Krause, Andreas; Groenen, Peter M A; Dingemanse, Jasper

2017-03-01

The main objectives of these two phase I studies were to investigate safety and tolerability as well as the pharmacokinetic/pharmacodynamic profile of the novel potent and selective formyl peptide receptor type 2 (FPR2)/Lipoxin A 4 receptor (ALX) agonist ACT-389949. A challenge model was used to assess the drug's anti-inflammatory potential, with the aim of selecting a dosing regimen for future patient studies. Two double-blind, randomized phase I studies investigated the safety, tolerability, pharmacokinetics and pharmacodynamics of ACT-389949 at different doses and dosing regimens. Drug exposure was correlated with target engagement markers such as receptor internalization and cytokine measurements. The effect of FPR2/ALX agonism on neutrophil migration was studied in a lipopolysaccharide (LPS) inhalation model. ACT-389949 was well tolerated. Maximum concentrations were reached around 2 h after dosing, with a mean terminal half-life of 29.3 h [95% confidence interval (CI) 25.5, 33.7]. After multiple-dose administration, exposure increased by 111% (95% CI 89, 136), indicating drug accumulation. Administration of ACT-389949 resulted in a dose-dependent, long-lasting internalization of FPR2/ALX into leukocytes. Pro- and anti-inflammatory cytokines were dose-dependently but transiently upregulated only after the first dose. No pharmacological effect on neutrophil count was observed in the LPS challenge test performed at steady state. FPR2/ALX agonism with ACT-389949 was shown to be safe and well tolerated in healthy subjects. Receptor internalization and downstream mediators pointed towards a desensitization of the system, which may explain the lack of effect on neutrophil recruitment in the LPS challenge model. © 2016 The British Pharmacological Society.

Chronic β2 -adrenoceptor agonist treatment alters muscle proteome and functional adaptations induced by high intensity training in young men.

PubMed

Hostrup, Morten; Onslev, Johan; Jacobson, Glenn A; Wilson, Richard; Bangsbo, Jens

2018-01-15

While several studies have investigated the effects of exercise training in human skeletal muscle and the chronic effect of β 2 -agonist treatment in rodent muscle, their effects on muscle proteome signature with related functional measures in humans are still incompletely understood. Herein we show that daily β 2 -agonist treatment attenuates training-induced enhancements in exercise performance and maximal oxygen consumption, and alters muscle proteome signature and phenotype in trained young men. Daily β 2 -agonist treatment abolished several of the training-induced enhancements in muscle oxidative capacity and caused a repression of muscle metabolic pathways; furthermore, β 2 -agonist treatment induced a slow-to-fast twitch muscle phenotype transition. The present study indicates that chronic β 2 -agonist treatment confounds the positive effect of high intensity training on exercise performance and oxidative capacity, which is of interest for the large proportion of persons using inhaled β 2 -agonists on a daily basis, including athletes. Although the effects of training have been studied for decades, data on muscle proteome signature remodelling induced by high intensity training in relation to functional changes in humans remains incomplete. Likewise, β 2 -agonists are frequently used to counteract exercise-induced bronchoconstriction, but the effects β 2 -agonist treatment on muscle remodelling and adaptations to training are unknown. In a placebo-controlled parallel study, we randomly assigned 21 trained men to 4 weeks of high intensity training with (HIT+β 2 A) or without (HIT) daily inhalation of β 2 -agonist (terbutaline, 4 mg dose -1 ). Of 486 proteins identified by mass-spectrometry proteomics of muscle biopsies sampled before and after the intervention, 32 and 85 were changing (false discovery rate (FDR) ≤5%) with the intervention in HIT and HIT+β 2 A, respectively. Proteome signature changes were different in HIT and HIT+β 2 A (P�

A Novel Aminotetralin-Type Serotonin (5-HT) 2C Receptor-Specific Agonist and 5-HT2A Competitive Antagonist/5-HT2B Inverse Agonist with Preclinical Efficacy for Psychoses

PubMed Central

Morgan, Drake; Felsing, Daniel; Kondabolu, Krishnakanth; Rowland, Neil E.; Robertson, Kimberly L.; Sakhuja, Rajeev; Booth, Raymond G.

2014-01-01

Development of 5-HT2C agonists for treatment of neuropsychiatric disorders, including psychoses, substance abuse, and obesity, has been fraught with difficulties, because the vast majority of reported 5-HT2C selective agonists also activate 5-HT2A and/or 5-HT2B receptors, potentially causing hallucinations and/or cardiac valvulopathy. Herein is described a novel, potent, and efficacious human 5-HT2C receptor agonist, (−)-trans-(2S,4R)-4-(3′[meta]-bromophenyl)-N,N-dimethyl-1,2,3,4-tetrahydronaphthalen-2-amine (−)-MBP), that is a competitive antagonist and inverse agonist at human 5-HT2A and 5-HT2B receptors, respectively. (−)-MBP has efficacy comparable to the prototypical second-generation antipsychotic drug clozapine in three C57Bl/6 mouse models of drug-induced psychoses: the head-twitch response elicited by [2,5]-dimethoxy-4-iodoamphetamine; hyperlocomotion induced by MK-801 [(5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (dizocilpine maleate)]; and hyperlocomotion induced by amphetamine. (−)-MBP, however, does not alter locomotion when administered alone, distinguishing it from clozapine, which suppresses locomotion. Finally, consumption of highly palatable food by mice was not increased by (−)-MBP at a dose that produced at least 50% maximal efficacy in the psychoses models. Compared with (−)-MBP, the enantiomer (+)-MBP was much less active across in vitro affinity and functional assays using mouse and human receptors and also translated in vivo with comparably lower potency and efficacy. Results indicate a 5-HT2C receptor-specific agonist, such as (−)-MBP, may be pharmacotherapeutic for psychoses, without liability for obesity, hallucinations, heart disease, sedation, or motoric disorders. PMID:24563531

Recent advances in COPD disease management with fixed-dose long-acting combination therapies.

PubMed

Bateman, Eric D; Mahler, Donald A; Vogelmeier, Claus F; Wedzicha, Jadwiga A; Patalano, Francesco; Banerji, Donald

2014-06-01

Combinations of two long-acting bronchodilators and long-acting bronchodilators with inhaled corticosteroids (ICS) are recommended therapies in the management of chronic obstructive pulmonary disease (COPD). Three fixed-dose combination products have recently been approved for the treatment of COPD (the long-acting β2-agonist plus long-acting muscarinic antagonist [LABA/LAMA] combinations glycopyrronium/indacaterol [QVA149] and umeclidinium/vilanterol, and the LABA/ICS fluticasone furoate/vilanterol), with others currently in late-stage development. LABA/LAMA and LABA/ICS combination therapies demonstrate positive effects on both lung function and patient-reported outcomes, with significant improvements observed with LABA/LAMA combinations compared with placebo, each component alone and other comparators in current use. No new safety concerns have been observed with combinations of long-acting bronchodilators. Combinations of two long-acting bronchodilators represent a new and convenient treatment option in COPD. This review summarizes published efficacy and safety data from clinical trials of both LABA/LAMA and novel LABA/ICS combinations in patients with COPD.

Oxysterol, 5α-cholestan-3-one, modulates a contractile response to β2-adrenoceptor stimulation in the mouse atria: Involvement of NO signaling.

PubMed

Sytchev, Vaycheslav I; Odnoshivkina, Yulia G; Ursan, Roman V; Petrov, Alexey M

2017-11-01

Atrial β2-adrenoceptors provide an important mechanism for regulation of cardiac function and changes in their downstream signaling are involved in processes underlying heart disorders. We have investigated the mechanism by which the cholesterol metabolite 5α-cholestan-3-one (5ɑCh3) modulates inotropic effect of β2-adrenoceptor agonist fenoterol. Atria from mice were electrically stimulated and changes in contraction amplitude in response to fenoterol were studied in 5ɑCh3-pretreated samples. Intracellular Ca 2+ and NO levels were estimated using fluorescent dyes Fluo-4 and DAF-FM, respectively. By itself 5αCh3 that appears in the circulation under some pathological conditions had a negligible influence on contraction, Ca 2+ -transient and NO production. However, pretreatment with 5αCh3 markedly attenuated the positive inotropic effect of fenoterol which was accompanied by an increase in the NO synthesis. Unexpectedly, the oxysterol also augmented an enhancement of Ca 2+ -transient amplitude in response to fenoterol. Under conditions of a pharmacological inhibition of G i -protein/Akt/NO synthase/protein kinase G signaling, 5αCh3 augmented the inotropic effect of fenoterol. Herein, Akt antagonist suppressed the increase in NO production, while inhibition of NO synthesis did not modify the increased amplitude of the Ca 2+ -transient. Along similar lines, enrichment of plasma membranes with cholesterol reduced the stimulatory effect of 5αCh3 on β2-adrenoceptor-evoked NO production, but not on the Ca2+-transient amplitude, leading to an elevation of the positive inotropic response to fenoterol. These data suggest that 5ɑCh3 potentiates the effect of pharmacological β2-adrenoceptor activation on both NO production and Ca 2+ transient via independent mechanisms, thereby affecting the positive inotropy. Copyright © 2017 Elsevier Inc. All rights reserved.

Impaired structural and functional regeneration of skeletal muscles from β2-adrenoceptor knockout mice

PubMed Central

Silva, M T; Wensing, L A; Brum, P C; Câmara, N O; Miyabara, E H

2014-01-01

Aims β2-adrenergic stimulation causes beneficial effects on structure and function of regenerating muscles; thus, the β2-adrenoceptor may play an important role in the muscle regenerative process. Here, we investigated the role of the β2-adrenoceptor in skeletal muscle regeneration. Methods Tibialis anterior (TA) muscles from β2-adrenoceptor knockout (β2KO) mice were cryolesioned and analysed after 1, 3, 10 and 21 days. The role of β2-adrenoceptor on regenerating muscles was assessed through the analysis of morphological and contractile aspects, M1 and M2 macrophage profile, cAMP content, and activation of TGF-β signalling elements. Results Regenerating muscles from β2KO mice showed decreased calibre of regenerating myofibres and reduced muscle contractile function at 10 days when compared with those from wild type. The increase in cAMP content in muscles at 10 days post-cryolesion was attenuated in the absence of the β2-adrenoceptor. Furthermore, there was an increase in inflammation and in the number of macrophages in regenerating muscles lacking the β2-adrenoceptor at 3 and 10 days, a predominance of M1 macrophage phenotype, a decrease in TβR-I/Smad2/3 activation, and in the Smad4 expression at 3 days, while akirin1 expression increased at 10 days in muscles from β2KO mice when compared to those from wild type. Conclusions Our results suggest that the β2-adrenoceptor contributes to the regulation of the initial phases of muscle regeneration, especially in the control of macrophage recruitment in regenerating muscle through activation of TβR-I/Smad2/3 and reduction in akirin1 expression. These findings have implications for the future development of better therapeutic approaches to prevent or treat muscle injuries. PMID:24938737

Do saw palmetto extracts block human alpha1-adrenoceptor subtypes in vivo?

PubMed

Goepel, M; Dinh, L; Mitchell, A; Schäfers, R F; Rübben, H; Michel, M C

2001-02-15

To test whether saw palmetto extracts, which act as alpha1-adrenoceptor antagonists in vitro, also do so in vivo in man. In a placebo-controlled, double-blind, four-way cross-over study 12 healthy young men were treated with three different saw palmetto extract preparations (320 mg o.d.) for 8 days each. On the last day, before and 2, 4 and 6 hr after drug intake blood pressure and heart rate were determined and blood samples obtained, which were used in an ex vivo radioreceptor assay with cloned human alpha1-adrenoceptor subtypes. Saw palmetto extract treatment did not result in alpha1-adrenoceptor subtype occupancy in the radioreceptor assay. Although the saw palmetto extracts caused minor reductions of supine blood pressure, they did not affect blood pressure during orthostatic stress testing and did not alter heart rate under either condition. Moreover, plasma catecholamines remained largely unaltered. Despite their alpha1-adrenoceptor antagonist effects in vitro, therapeutically used doses of saw palmetto extracts do not cause alpha1-adrenoceptor antagonism in man in vivo. Copyright 2001 Wiley-Liss, Inc.

Long-Acting β-Agonist in Combination or Separate Inhaler as Step-Up Therapy for Children with Uncontrolled Asthma Receiving Inhaled Corticosteroids.

PubMed

Turner, Steve; Richardson, Kathryn; Murray, Clare; Thomas, Mike; Hillyer, Elizabeth V; Burden, Anne; Price, David B

Adding a long-acting β 2 -agonist (LABA) to inhaled corticosteroids (ICS) using a fixed-dose combination (FDC) inhaler is the UK guideline recommendation for children aged more than 4 years with uncontrolled asthma. The evidence of benefit of adding an FDC inhaler over a separate LABA inhaler is limited. The objective of this study was to compare the effectiveness of a LABA added as an FDC inhaler, and as a separate inhaler, in children with uncontrolled asthma. Two UK primary care databases were used to create a matched cohort study with a 2-year follow-up period. We included children prescribed their first step-up from ICS monotherapy. Two cohorts were formed for children receiving an add-on LABA as an FDC inhaler, or a separate LABA inhaler. Matching variables and confounders were identified by comparing characteristics during a baseline year of follow-up. Outcomes were examined during the subsequent year. The primary outcome was an adjusted odds ratio for overall asthma control (defined as follows: no asthma-related hospital admission or emergency room visit, prescription for oral corticosteroids or antibiotic with evidence of respiratory consultation, and ≤2 puffs of short-acting β-agonist daily). The final study consisted of 1330 children in each cohort (mean age 9 years; 59% male). In the separate ICS+LABA cohort, the odds of achieving overall asthma control were lower (adjusted odds ratio, 0.77 [95% confidence interval, 0.66-0.91]; P = .001) compared with the FDC cohort. The study demonstrates a small but significant benefit in achieving asthma control from an add-on LABA as an FDC, compared with a separate inhaler and this supports current guideline recommendations. Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

Clebopride enhances contractility of the guinea pig stomach by blocking peripheral D2 dopamine receptor and alpha-2 adrenoceptor.

PubMed

Takeda, K; Taniyama, K; Kuno, T; Sano, I; Ishikawa, T; Ohmura, I; Tanaka, C

1991-05-01

The mechanism of action of clebopride on the motility of guinea pig stomach was examined by the receptor binding assay for bovine brain membrane and by measuring gastric contractility and the release of acetylcholine from the stomach. The receptor binding assay revealed that clebopride bound to the D2 dopamine receptor with a high affinity and to the alpha-2 adrenoceptor and 5-HT2 serotonin receptor with relatively lower affinity, and not to D1 dopamine, alpha-1 adrenergic, muscarinic acetylcholine, H1 histamine, or opioid receptor. In strips of the stomach, clebopride at 10(-8) M to 10(-5) M enhanced the electrical transmural stimulation-evoked contraction and the release of acetylcholine. This enhancement was attributed to the blockade of the D2 dopamine receptor and alpha-2 adrenoceptor because: 1) Maximum responses obtained with specific D2 dopamine receptor antagonist, domperidone, and with specific alpha-2 adrenoceptor antagonist, yohimbine, were smaller than that with clebopride, and the sum of the effects of these two specific receptor antagonists is approximately equal to the effect of clebopride. 2) The facilitatory effect of clebopride was partially eliminated by pretreatment of the sample with domperidone or yohimbine, and the facilitatory effect of clebopride was not observed in preparations treated with the combination of domperidone and yohimbine. Clebopride also antagonized the inhibitory effects of dopamine and clonidine on the electrical transmural stimulation-evoked responses. These results indicate that clebopride acts on post ganglionic cholinergic neurons at D2 and alpha-2 receptors in this preparation to enhance enteric nervous system stimulated motility.

beta. -Adrenoceptors in human tracheal smooth muscle: characteristics of binding and relaxation

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Koppen, C.J.; Hermanussen, M.W.; Verrijp, K.N.

1987-06-29

Specific binding of (/sup 125/I)-(-)-cyanopindolol to human tracheal smooth muscle membranes was saturable, stereo-selective and of high affinity (K/sub d/ = 5.3 +/- 0.9 pmol/l and R/sub T/ = 78 +/- 7 fmol/g tissue). The ..beta../sub 1/-selective antagonists atenolol and LK 203-030 inhibited specific (/sup 125/I)-(-)-cyanopindolol binding according to a one binding site model with low affinity in nearly all subjects, pointing to a homogeneous BETA/sub 2/-adrenoceptor population. In one subject using LK 203-030 a small ..beta../sub 1/-adrenoceptor subpopulation could be demonstrated. The beta-mimetics isoprenaline, fenoterol, salbutamol and terbutaline recognized high and low affinity agonist binding sites. Isoprenaline's pK/sub H/-more » and pK/sub L/-values for the high and low affinity sites were 8.0 +/- 0.2 and 5.9 +/- 0.3 respectively. In functional experiments isoprenaline relaxed tracheal smooth muscle strips having intrinsic tone with a pD/sub 2/-value of 6.63 +/- 0.19. 32 references, 4 figures, 2 tables.« less

Alpha-1 adrenoceptor hyperresponsiveness in three neuropathic pain states: complex regional pain syndrome 1, diabetic peripheral neuropathic pain and central pain states following spinal cord injury.

PubMed

Teasell, Robert W; Arnold, J Malcolm O

2004-01-01

The pathophysiology of the pain associated with complex regional pain syndrome, spinal cord injury and diabetic peripheral neuropathy is not known. The pain of complex regional pain syndrome has often been attributed to abnormal sympathetic nervous system activity based on the presence of vasomotor instability and a frequently reported positive response, albeit a temporary response, to sympathetic blockade. In contrast, the pain below the level of spinal cord injury and diabetic peripheral neuropathy are generally seen as deafferentation phenomena. Each of these pain states has been associated with abnormal sympathetic nervous system function and increased peripheral alpha-1 adrenoceptor activity. This increased responsiveness may be a consequence of alpha-1 adrenoceptor postsynaptic hypersensitivity, or alpha-2 adrenoceptor presynaptic dysfunction with diminished noradrenaline reuptake, increased concentrations of noradrenaline in the synaptic cleft and increased stimulation of otherwise normal alpha-1 adrenoceptors. Plausible mechanisms based on animal research by which alpha-1 adrenoceptor hyperresponsiveness can lead to chronic neuropathic-like pain have been reported. This raises the intriguing possibility that sympathetic nervous system dysfunction may be an important factor in the generation of pain in many neuropathic pain states. Although results to date have been mixed, there may be a greater role for new drugs which target peripheral alpha-2 adrenoceptors (agonists) or alpha-1 adrenoceptors (antagonists).

Use of GnRH agonist implants for long-term suppression of fertility in extensively managed heifers and cows.

PubMed

D'Occhio, Michael J; Fordyce, Geoffry; Whyte, Tim R; Jubb, Tristan F; Fitzpatrick, Lee A; Cooper, Neil J; Aspden, William J; Bolam, Matt J; Trigg, Timothy E

2002-12-16

The ability of gonadotrophin releasing hormone (GnRH) agonist implants to suppress ovarian activity and prevent pregnancies, long-term, was examined in heifers and cows maintained under extensive management. At three cattle stations, heifers (2-year-old) and older cows (3- to 16-year-old) were assigned to a control group that received no treatment, or were treated with high-dose (12 mg, Station A) or low-dose (8 mg, Station B and Station C) GnRH agonist implants. The respective numbers of control and GnRH agonist-treated animals (heifers + cows) at each station were: Station A, 20 and 99; Station B, 19 and 89; Station C, 20 and 76. Animals were maintained with 4% bulls and monitored for pregnancy at 2-monthly intervals for approximately 12 months. Pregnancy rates for control heifers and control cows ranged from 60-90% and 80-100%, respectively, depending on the study site. The respective number of animals (heifers + cows) treated with GnRH agonist that conceived, and days to first conception, were: Station A, 9 (9%) and 336 +/- 3 days; Station B, 8 (10%) and 244 +/- 13 days; Station C, 20 (26%) and 231 +/- 3 days. Treatment with high-dose GnRH agonist prevented pregnancies for longer (approximately 300 days) than treatment with low-dose GnRH agonist (approximately 200 days). In the majority of heifers and cows treated with GnRH agonist, ovarian follicular growth was restricted to early antral follicles (2-4mm). The findings indicate that GnRH agonist implants have considerable potential as a practical technology to suppress ovarian activity and control reproduction in female cattle maintained in extensive rangelands environments. The technology also has broader applications in diverse cattle production systems. Copyright 2002 Elsevier Science B.V.

The effects of alpha2-adrenoceptor agents on anti-hyperalgesic effects of carbamazepine and oxcarbazepine in a rat model of inflammatory pain.

PubMed

Vucković, Sonja M; Tomić, Maja A; Stepanović-Petrović, Radica M; Ugresić, Nenad; Prostran, Milica S; Bosković, Bogdan

2006-11-01

In this study, the effects of yohimbine (alpha2-adrenoceptor antagonist) and clonidine (alpha2-adrenoceptor agonist) on anti-hyperalgesia induced by carbamazepine and oxcarbazepine in a rat model of inflammatory pain were investigated. Carbamazepine (10-40 mg/kg; i.p.) and oxcarbazepine (40-160 mg/kg; i.p.) caused a significant dose-dependent reduction of the paw inflammatory hyperalgesia induced by concanavalin A (Con A, intraplantarly) in a paw pressure test in rats. Yohimbine (1-3 mg/kg; i.p.) significantly depressed the anti-hyperalgesic effects of carbamazepine and oxcarbazepine, in a dose- and time-dependent manner. Both drug mixtures (carbamazepine-clonidine and oxcarbazepine-clonidine) administered in fixed-dose fractions of the ED50 (1/2, 1/4 and 1/8) caused significant and dose-dependent reduction of the hyperalgesia induced by Con A. Isobolographic analysis revealed a significant synergistic (supra-additive) anti-hyperalgesic effect of both combinations tested. These results indicate that anti-hyperalgesic effects of carbamazepine and oxcarbazepine are, at least partially, mediated by activation of adrenergic alpha2-receptors. In addition, synergistic interaction for anti-hyperalgesia between carbamazepine and clonidine, as well as oxcarbazepine and clonidine in a model of inflammatory hyperalgesia, was demonstrated.

beta(2)-adrenoceptor antagonist ICI 118,551 decreases pulmonary vascular tone in mice via a G(i/o) protein/nitric oxide-coupled pathway.

PubMed

Wenzel, Daniela; Knies, Ralf; Matthey, Michaela; Klein, Alexandra M; Welschoff, Julia; Stolle, Vanessa; Sasse, Philipp; Röll, Wilhelm; Breuer, Johannes; Fleischmann, Bernd K

2009-07-01

beta(2)-adrenoceptors are important modulators of vascular tone, particularly in the pulmonary circulation. Because neurohormonal activation occurs in pulmonary arterial hypertension, we have investigated the effect of different adrenergic vasoactive substances on tone regulation in large and small pulmonary arteries, as well as in systemic vessels of mice. We found that the beta(2)-adrenoceptor antagonist ICI 118,551 (ICI) evoked a decrease of vascular tone in large pulmonary arteries and reduced the sensitivity of pulmonary arteries toward different contracting agents, eg, norepinephrine, serotonin, or endothelin. ICI proved to act specifically on pulmonary vessels, because it shifted the dose-response curve of norepinephrine to the right in pulmonary arteries, whereas there was no effect in the aorta. Pharmacological experiments proved that the right shift of the norepinephrine dose-response curve by ICI was mediated via a beta(2)-adrenoceptor/G(i/o) protein-dependent pathway enhancing NO production in the endothelium; these results were corroborated in beta-adrenoceptor and endothelial NO synthase knockout mice where ICI had no effect. ICI increased vascular lumen diameter in lung sections and reduced pulmonary arterial pressure under normoxia and under hypoxia in the isolated perfused lung model. These effects were found to be physiologically relevant, because ICI specifically decreased pulmonary but not systemic blood pressure in vivo. Thus, the beta(2)-adrenoceptor antagonist ICI is a pulmonary arterial-specific vasorelaxant and, therefore, a potentially interesting novel therapeutic agent for the treatment of pulmonary arterial hypertension.

Involvement of α2-adrenoceptors in inhibitory and facilitatory pain modulation processes.

PubMed

Vo, L; Drummond, P D

2016-03-01

In healthy humans, high-frequency electrical stimulation (HFS) of the forearm not only produces hyperalgesia at the site of stimulation but also reduces sensitivity to pressure-pain on the ipsilateral side of the forehead. In addition, HFS augments the ipsilateral trigeminal nociceptive blink reflex and intensifies the ipsilateral component of conditioned pain modulation. The aim of this study was to determine whether α2-adrenoceptors mediate these ipsilateral nociceptive influences. The α2-adrenoceptor antagonist yohimbine was administered to 22 participants in a double-blind, placebo-controlled crossover study. In each session, thermal and mechanical sensitivity in the forearms and forehead was assessed before and after HFS. In addition, the combined effect of HFS and yohimbine on the nociceptive blink reflex and on conditioned pain modulation was explored. In this paradigm, the conditioning stimulus was cold pain in the ipsilateral or contralateral temple, and the test stimulus was electrically evoked pain in the forearm. Blood pressure and electrodermal activity increased for several hours after yohimbine administration, consistent with blockade of central α2-adrenoceptors. Yohimbine not only augmented the nociceptive blink reflex ipsilateral to HFS but also intensified the inhibitory influence of ipsilateral temple cooling on electrically evoked pain at the HFS-treated site in the forearm. Yohimbine had no consistent effect on primary or secondary hyperalgesia in the forearm or on pressure-pain in the ipsilateral forehead. These findings imply involvement of α2-adrenoceptors both in ipsilateral antinociceptive and pronociceptive pain modulation processes. However, a mechanism not involving α2-adrenoceptors appears to mediate analgesia in the ipsilateral forehead after HFS. © 2015 European Pain Federation - EFIC®

p38 Mitogen-Activated Protein Kinase-γ Inhibition by Long-Acting β2 Adrenergic Agonists Reversed Steroid Insensitivity in Severe Asthma

PubMed Central

Mercado, Nicholas; To, Yasuo; Kobayashi, Yoshiki; Adcock, Ian M.; Barnes, Peter J.

2011-01-01

Corticosteroid insensitivity (CI) is a major barrier to treating severe asthma. Despite intensive research, the molecular mechanism of CI remains uncertain. The aim of this study was to determine abnormality in corticosteroid action in severe asthma and to identify the molecular mechanism of the long-acting β2-adrenergic agonists (LABAs) formoterol and salmeterol on restoration of corticosteroid sensitivity in severe asthma in vitro. Peripheral blood mononuclear cells (PBMCs) were obtained from 16 subjects with severe corticosteroid-insensitive asthma, 6 subjects with mild corticosteroid-sensitive asthma, and 11 healthy volunteers. Corticosteroid (dexamethasone) sensitivity was determined on tumor necrosis factor-α (TNF-α)-induced interleukin (IL)-8 production. Glucocorticoid receptor (GR) phosphorylation and kinase phosphorylation were evaluated by immunoprecipitation-Western blotting analysis and kinase phosphorylation array in IL-2/IL-4-treated corticosteroid insensitive model in PBMCs. In vitro corticosteroid sensitivity on TNF-α-induced IL-8 production was significantly lower in patients with severe asthma than in healthy volunteers and patients with mild asthma. This CI seen in severe asthma was associated with reduced GR nuclear translocation and with hyperphosphorylation of GR, which were reversed by LABAs. In IL-2/IL-4-treated PBMCs, LABAs inhibited phosphorylation of Jun-NH2-terminal kinase and p38 mitogen-activated protein kinase-γ (p38MAPK-γ) as well as GR. In addition, cells with p38MAPK-γ knockdown by RNA interference did not develop CI in the presence of IL-2/IL-4. Furthermore, p38MAPK-γ protein expression was up-regulated in PBMCs from some patients with severe asthma. In conclusion, p38 MAPK-γ activation impairs corticosteroid action and p38 MAPK-γ inhibition by LABAs has potential for the treatment of severe asthma. PMID:21917909

Long-acting muscarinic antagonist (LAMA) plus long-acting beta-agonist (LABA) versus LABA plus inhaled corticosteroid (ICS) for stable chronic obstructive pulmonary disease (COPD).

PubMed

Horita, Nobuyuki; Goto, Atsushi; Shibata, Yuji; Ota, Erika; Nakashima, Kentaro; Nagai, Kenjiro; Kaneko, Takeshi

2017-02-10

Three classes of inhaler medications are used to manage chronic obstructive pulmonary disease (COPD): long-acting beta-agonists (LABA), long-acting muscarinic antagonists (LAMA), and inhaled corticosteroids (ICS). When two classes of medications are required, LAMA plus LABA (LAMA+LABA) and LABA plus ICS (LABA+ICS) are often selected because these combinations can be administered via a single medication device. The previous Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidance recommended LABA+ICS as the first-line treatment for managing stable COPD in high-risk people of categories C and D. However, the updated GOLD 2017 guidance recommends LAMA+LABA over LABA+ICS. To compare the benefits and harms of LAMA+LABA versus LABA+ICS for treatment of people with stable COPD. We performed an electronic search of the Cochrane Airways Group Specialised Register (2 February 2016), ClinicalTrials.gov (4 June 2016), and the World Health Organization Clinical Trials Search Portal (4 June 2016), followed by a handsearch (5 June 2016). Two review authors screened and scrutinised the selected articles. We included individual randomised controlled trials, parallel-group trials, and cross-over trials comparing LAMA+LABA and LABA+ICS for stable COPD. The minimum accepted trial duration was one month and trials should have been conducted in an outpatient setting. Two review authors independently extracted data and evaluated risk of bias. We resolved any discrepancies through discussion. We analysed dichotomous data as odds ratios (OR), and continuous data as mean differences (MD), with 95% confidence interval (CI) using Review Manager 5. Exacerbations were measured by counting the number of people experiencing one or more exacerbation. We included 11 studies comprising 9839 participants in our quantitative analysis. Most studies included people with moderate to severe COPD, without recent exacerbations. One pharmaceutical sponsored trial that included only people with

Involvement of alpha-adrenoceptors in myometrial responses in the pro-oestral rat.

PubMed Central

Acritopoulou-Fourcroy, S.; Marçais-Collado, H.

1988-01-01

1. Myometrial responses to different agents acting on adrenoceptors were examined in vivo in the pro-oestrous rat. Changes in spontaneous uterine mechanical activity were recorded isometrically and evaluated in terms of amplitude and duration of uterine contractions. 2. Phenylephrine (10 micrograms kg-1) markedly increased the amplitude and duration of contractions and 40 micrograms kg-1 gave rise to tetanic contractions. 3. Administration of either nicergoline (400 micrograms kg-1) or phentolamine (1000 micrograms kg-1) to phenylephrine-primed rat uterus reduced the strength of contractions and phentolamine abolished the phenylephrine-induced uterine contracture. 4. Following blockade of alpha 2-adrenoceptors by yohimbine (1000 micrograms kg-1) and beta-adrenoceptors by propranolol (2400 micrograms kg-1), a single injection of phenylephrine (100 micrograms kg-1) increased the amplitude of uterine contractions by 30%. 5. Noradrenaline reduced the amplitude of contractions and caused elevation of the baseline level. The response of myometrium to the combination of both propranolol and noradrenaline was the establishment of uterine contracture with subsequent increase of the duration of contractions. 6. These results clearly demonstrate the involvement of alpha-adrenoceptors in the myometrial activity of the rat in vivo during pro-oestrus. PMID:2832026

β-Adrenoceptor-Mediated Relaxation of Carbachol-Pre-Contracted Mouse Detrusor.

PubMed

Propping, Stefan; Newe, Manja; Lorenz, Kristina; Wirth, Manfred P; Ravens, Ursula

2015-01-01

To study the β-adrenoceptor subtypes involved in the relaxation responses to (-)-isoprenaline in carbachol-pre-contracted (CCh) mouse detrusor muscle with intact and denuded mucosa. Isolated muscle strips from the urinary bladder of male C57BL6 mice or β2-adrenoceptor knockout mice were pre-contracted with CCh, 1 µM and relaxed with increasing concentrations of the β-adrenoceptor (β-AR) agonist (-)-isoprenaline and forskolin. For estimating the β-AR subtypes involved, subtype-selective receptor blockers were used, that is, CGP 20712A (β1-ARs), ICI 118,551 (β2-ARs), and L748,337 (β3-ARs). Unlike in KCl-pre-contracted muscle, the mucosa did not affect the sensitivity of the relaxation response to (-)-isoprenaline in CCh-pre-contracted murine detrusor strips. Increasing concentrations of (-)-isoprenaline produced a biphasic concentration-relaxation response without any difference both during the presence and absence of mucosa. The relaxation fraction produced by low (-)-isoprenaline concentrations was mediated by β2-AR as evidenced by a shift of the concentration-response curve to higher concentrations with ICI 118,551, but not with CGP 20712A and L748,337, and by the absence of this fraction in β2-AR-KO mice. The relaxation response with low sensitivity to (-)-isoprenaline was not affected by any of the β-AR subtype-selective blockers and was the only response detected in detrusor strips from β2-AR-KO mice. In CCh-pre-contracted mouse detrusor, β2-ARs are responsible for the relaxation component with high sensitivity to (-)-isoprenaline as indicated by the conversion of a biphasic into a monophasic CRC with ICI 118,551 or by its absence in β2-AR KO mice. The mucosa does not impair relaxation under these conditions. © 2015 S. Karger AG, Basel.

Lack of effect of the alpha2C-adrenoceptor Del322-325 polymorphism on inhibition of cyclic AMP production in HEK293 cells.

PubMed

Montgomery, M D; Bylund, D B

2010-02-01

The alpha(2C)-adrenoceptor has multiple functions, including inhibiting release of noradrenaline from presynaptic nerve terminals. A human alpha(2C) polymorphism, Del322-325, a potential risk factor for heart failure, has been reported to exhibit reduced signalling in CHO cells. To further understand the role of the Del322-325 polymorphism on receptor signalling, we attempted to replicate and further study the reduced signalling in HEK293 cells. Human alpha(2C) wild-type (WT) and Del322-325 adrenoceptors were stably transfected into HEK293 cells. Radioligand binding was performed to determine affinities for both receptors. In intact cells, inhibition of forskolin-stimulated cyclic AMP production by WT and Del322-325 clones with a range of receptor densities (200-2320 fmol.mg(-1) protein) was measured following agonist treatment. Noradrenaline, brimonidine and clonidine exhibited similar binding affinities for WT and Del322-325. Brimonidine and clonidine also had similar efficacies and potencies for both receptors for the inhibition of cyclic AMP production at all receptor densities tested. A linear regression analysis comparing efficacy and potency with receptor expression levels showed no differences in slopes between WT and Del322-325. The alpha(2C) WT and Del322-325 adrenoceptors exhibited similar binding properties. Additionally, inhibition of cyclic AMP production by Del322-325 was similar to that of WT over a range of receptor densities. Therefore, in intact HEK293 cells, the alpha(2C)-Del322-325 polymorphism does not exhibit reduced signalling to adenylyl cyclase and may not represent a clinically important phenotype.

Association of blood eosinophils and plasma periostin with FEV1 response after 3-month inhaled corticosteroid and long-acting beta2-agonist treatment in stable COPD patients

PubMed Central

Park, Hye Yun; Lee, Hyun; Koh, Won-Jung; Kim, Seonwoo; Jeong, Ina; Koo, Hyeon-Kyoung; Kim, Tae-Hyung; Kim, Jin Woo; Kim, Woo Jin; Oh, Yeon-Mok; Sin, Don D; Lim, Seong Yong; Lee, Sang-Do

2016-01-01

Background COPD patients with increased airway eosinophilic inflammation show a favorable response to inhaled corticosteroids (ICS) in combination with a long-acting bronchodilator. Recent studies have demonstrated a significant correlation of sputum eosinophilia with blood eosinophils and periostin. We investigated whether high blood eosinophils and plasma periostin were associated with an improvement in forced expiratory volume in 1 second (FEV1) after 3-month treatment with ICS/long-acting beta2-agonist (LABA) in stable COPD patients. Patients and methods Blood eosinophils and plasma periostin levels were measured in 130 stable COPD subjects selected from the Korean Obstructive Lung Disease cohort. Subjects began a 3-month ICS/LABA treatment after washout period. Results High blood eosinophils (>260/µL, adjusted odds ratio =3.52, P=0.009) and high plasma periostin (>23 ng/mL, adjusted odds ratio =3.52, P=0.013) were significantly associated with FEV1 responders (>12% and 200 mL increase in FEV1 from baseline after treatment). Moreover, the addition of high blood eosinophils to age, baseline positive bronchodilator response, and FEV1 <50% of the predicted value significantly increased the area under the curve for prediction of FEV1 responders (from 0.700 to 0.771; P=0.045). Conclusion High blood eosinophils and high plasma periostin were associated with improved lung function after 3-month ICS/LABA treatment. In particular, high blood eosinophils, in combination with age and baseline lung function parameters, might be a possible biomarker for identification of COPD patients with favorable FEV1 improvement in response to ICS/LABA treatment. PMID:26730185

Association of blood eosinophils and plasma periostin with FEV1 response after 3-month inhaled corticosteroid and long-acting beta2-agonist treatment in stable COPD patients.

PubMed

Park, Hye Yun; Lee, Hyun; Koh, Won-Jung; Kim, Seonwoo; Jeong, Ina; Koo, Hyeon-Kyoung; Kim, Tae-Hyung; Kim, Jin Woo; Kim, Woo Jin; Oh, Yeon-Mok; Sin, Don D; Lim, Seong Yong; Lee, Sang-Do

2016-01-01

COPD patients with increased airway eosinophilic inflammation show a favorable response to inhaled corticosteroids (ICS) in combination with a long-acting bronchodilator. Recent studies have demonstrated a significant correlation of sputum eosinophilia with blood eosinophils and periostin. We investigated whether high blood eosinophils and plasma periostin were associated with an improvement in forced expiratory volume in 1 second (FEV1) after 3-month treatment with ICS/long-acting beta2-agonist (LABA) in stable COPD patients. Blood eosinophils and plasma periostin levels were measured in 130 stable COPD subjects selected from the Korean Obstructive Lung Disease cohort. Subjects began a 3-month ICS/LABA treatment after washout period. High blood eosinophils (>260/µL, adjusted odds ratio =3.52, P=0.009) and high plasma periostin (>23 ng/mL, adjusted odds ratio =3.52, P=0.013) were significantly associated with FEV1 responders (>12% and 200 mL increase in FEV1 from baseline after treatment). Moreover, the addition of high blood eosinophils to age, baseline positive bronchodilator response, and FEV1 <50% of the predicted value significantly increased the area under the curve for prediction of FEV1 responders (from 0.700 to 0.771; P=0.045). High blood eosinophils and high plasma periostin were associated with improved lung function after 3-month ICS/LABA treatment. In particular, high blood eosinophils, in combination with age and baseline lung function parameters, might be a possible biomarker for identification of COPD patients with favorable FEV1 improvement in response to ICS/LABA treatment.

Association of Inhaled Corticosteroids and Long-Acting β-Agonists as Controller and Quick Relief Therapy With Exacerbations and Symptom Control in Persistent Asthma: A Systematic Review and Meta-analysis.

PubMed

Sobieraj, Diana M; Weeda, Erin R; Nguyen, Elaine; Coleman, Craig I; White, C Michael; Lazarus, Stephen C; Blake, Kathryn V; Lang, Jason E; Baker, William L

2018-04-10

Combined use of inhaled corticosteroids and long-acting β-agonists (LABAs) as the controller and the quick relief therapy termed single maintenance and reliever therapy (SMART) is a potential therapeutic regimen for the management of persistent asthma. To conduct a systematic review and meta-analysis of the effects of SMART in patients with persistent asthma. The databases of MEDLINE via OVID, EMBASE, the Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Reviews were searched from database inception through August 2016 and updated through November 28, 2017. Two reviewers selected randomized clinical trials or observational studies evaluating SMART vs inhaled corticosteroids with or without a LABA used as the controller therapy and short-acting β-agonists as the relief therapy for patients aged 5 years or older with persistent asthma and reporting on an outcome of interest. Meta-analyses were conducted using a random-effects model to calculate risk ratios (RRs), risk differences (RDs), and mean differences with corresponding 95% CIs. Citation screening, data abstraction, risk assessment, and strength of evidence grading were completed by 2 independent reviewers. Asthma exacerbations. The analyses included 16 randomized clinical trials (N = 22 748 patients), 15 of which evaluated SMART as a combination therapy with budesonide and formoterol in a dry-powder inhaler. Among patients aged 12 years or older (n = 22 524; mean age, 42 years; 14 634 [65%] were female), SMART was associated with a reduced risk of asthma exacerbations compared with the same dose of inhaled corticosteroids and LABA as the controller therapy (RR, 0.68 [95% CI, 0.58 to 0.80]; RD, -6.4% [95% CI, -10.2% to -2.6%]) and a higher dose of inhaled corticosteroids and LABA as the controller therapy (RR, 0.77 [95% CI, 0.60 to 0.98]; RD, -2.8% [95% CI, -5.2% to -0.3%]). Similar results were seen when SMART was compared with inhaled corticosteroids alone

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

PubMed

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

2016-05-03

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

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

PubMed Central

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

2016-01-01

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

Vasodilators and α-adrenoceptor antagonists in hypertension and heart failure

PubMed Central

Taylor, S. H.

1981-01-01

1 The mechanism of the increase in arteriolar resistance in hypertension and heart failure is differently derived. In hypertension, venous compliance is normal and the concentric narrowing of the arteriolar resistance vessels is `anatomical'; it is not due to increased stimulation or enhanced sensitivity of the vascular smooth muscle. In heart failure narrowing of both the arteriolar resistance and venous capacitance vessels derives predominantly from increased sympathoadrenal stimulation of α1-adrenoceptors in the vascular smooth muscle. 2 Vasodilator drugs which relax vascular smooth muscle differ widely in their site of activity. None are entirely specific for arteries, arterioles or veins, but they may be grouped for therapeutic convenience into those predominantly acting on arterioles (for example hydralazine) and those acting on veins (for example nitrates). 3 Control of the resting blood pressure in stable essential hypertension appears to be equally well achieved with non-specific arteriolar dilators (for example hydralazine, minoxidil, calcium antagonists) as those with specific α1-adrenoceptor blocking properties (for example prazosin, indoramin). Pressure surges due to dynamic exercise and mental stress are little influenced by either category of drug. In contrast, α-adrenoceptor antagonists appear to be capable of partly suppressing increase in ambulatory pressure and the pressor responses to isometric exercise and cold, particularly in patients pre-treated with β-blocking drugs. 4 In acute heart failure, non-selective α-blocking drugs (for example phentolamine) produce an equal reduction in left ventricular filling pressure but greater increase in cardiac output than vasodilator drugs with a more balanced relaxing effect on arterioles and venules. 5 In chronic heart failure, the little information available indicates that non-selective arteriolar dilatation is probably associated with a greater increase in cardiac output lesser reduction in left

beta2-Agonist modulates epithelial gene expression involved in the T- and B-cell chemotaxis and induces airway sensitization in human isolated bronchi.

PubMed

Faisy, Christophe; Pinto, Francisco M; Blouquit-Laye, Sabine; Danel, Claire; Naline, Emmanuel; Buenestado, Amparo; Grassin Delyle, Stanislas; Burgel, Pierre-Régis; Chapelier, Alain; Advenier, Charles; Candenas, Maria-Luz; Devillier, Philippe

2010-02-01

Regular use of beta(2)-adrenoceptor agonists may enhance non-specific airway responsiveness and inflammation. In earlier experimental studies, we showed that prolonged in vitro fenoterol exposure induced airway sensitization via perturbed epithelial regulation of bronchoconstriction. The aim of the present work was to examine the involvement of inflammatory mediator genes and proinflammatory cells and to investigate the role of the bronchial epithelium in these untoward effects. Bronchial tissues were surgically removed from 17 ex-smokers. Bronchial rings and primary cultures of bronchial epithelial cells were incubated with 0.1microM fenoterol for 15h. Levels of mRNA-expression were analyzed using a real-time quantitative reverse transcription-polymerase chain reaction array. Bronchial rings were contracted with endothelin-1 and immune cell infiltration was assessed by immunohistochemistry. Compared to paired controls, fenoterol up-regulated the mRNAs of cytokines/proteins implicated in the recruitment of T and B cells or the activation and proliferation of bronchial epithelial cells (CCL20/MIP-3alpha, FOXA2, PPAR-gamma) in isolated bronchi and in cultured epithelial cells. Fenoterol exposure significantly enhanced CD8(+)-T and differentiated CD138(+)-B-cells infiltration into the bronchi, especially the subepithelial area. Increase in CD8 or CD138 labeling-intensity strongly correlated with rise in maximal contraction to endothelin-1 induced by fenoterol exposure. In summary, our results show that fenoterol modulates the T and B cells chemotaxis possibly via the epithelial chemokine secretion in isolated bronchi from ex-smokers. They also suggest that the infiltration of resident T and B cells into the subepithelial area is associated with an increase in airway responsiveness due to fenoterol exposure. Copyright 2009 Elsevier Ltd. All rights reserved.

Phosphorylation-induced conformation of β2-adrenoceptor related to arrestin recruitment revealed by NMR.

PubMed

Shiraishi, Yutaro; Natsume, Mei; Kofuku, Yutaka; Imai, Shunsuke; Nakata, Kunio; Mizukoshi, Toshimi; Ueda, Takumi; Iwaï, Hideo; Shimada, Ichio

2018-01-15

The C-terminal region of G-protein-coupled receptors (GPCRs), stimulated by agonist binding, is phosphorylated by GPCR kinases, and the phosphorylated GPCRs bind to arrestin, leading to the cellular responses. To understand the mechanism underlying the formation of the phosphorylated GPCR-arrestin complex, we performed NMR analyses of the phosphorylated β 2 -adrenoceptor (β 2 AR) and the phosphorylated β 2 AR-β-arrestin 1 complex, in the lipid bilayers of nanodisc. Here we show that the phosphorylated C-terminal region adheres to either the intracellular side of the transmembrane region or lipids, and that the phosphorylation of the C-terminal region allosterically alters the conformation around M215 5.54 and M279 6.41 , located on transemembrane helices 5 and 6, respectively. In addition, we found that the conformation induced by the phosphorylation is similar to that corresponding to the β-arrestin-bound state. The phosphorylation-induced structures revealed in this study propose a conserved structural motif of GPCRs that enables β-arrestin to recognize dozens of GPCRs.

Effects of ovarian steroids upon responses mediated by adrenoceptors in separated layers of the myometrium and in the costo-uterine muscle of the guinea-pig

PubMed Central

Hartley, Margaret L.; Pennefather, Jocelyn N.; Story, Margot E.

1983-01-01

1 This study describes the effects of ovarian steroid hormones upon the responses to adrenoceptor agonists of isolated myometrium, separated into its longitudinal and circular layers, and of costo-uterine muscle from guinea-pigs. The preparations were field-stimulated at 100 s intervals, and the adrenoceptor agonists phenylephrine and isoprenaline produced enhancement or inhibition of the evoked contractions. 2 Isoprenaline produced propranolol-sensitive inhibitory effects in longitudinal and circular myometrium and costo-uterine muscle preparations from animals from all experimental groups: i.e. from nonsteroid-treated animals (ovariectomized and intact); intact animals treated with either oestrogen or progesterone alone; ovariectomized animals treated with oestrogen; ovariectomized and intact animals treated with progesterone following oestrogen priming; and from animals 1-4 days post-partum. Longitudinal myometrial preparations from progesterone-treated oestrogen-primed and from post-partum animals were most sensitive to this agonist. 3 Phenylephrine produced phentolamine-sensitive excitatory effects in circular myometrial and costo-uterine muscle preparations from animals from all the experimental groups. In contrast, propranolol-sensitive inhibitory responses to phenylephrine occurred in longitudinal myometrial preparations taken from animals treated with progesterone following oestrogen priming, and from post-partum animals. Longitudinal myometrium from animals from the remaining experimental groups exhibited phentolamine-sensitive excitatory responses to phenylephrine. 4 The basis for the selective effect upon the longitudinal myometrium of exposure to progesterone following a period of oestrogen priming, is discussed. The results described are consistent with the possibility that in the longitudinal layer of guinea-pig uterus exposed to progesterone following oestrogen priming there is an increase in the proportion of β-adrenoceptors in this layer. This

[(35)S]-GTPgammaS autoradiography reveals alpha(2) adrenoceptor-mediated G-protein activation in amygdala and lateral septum.

PubMed

Newman-Tancredi, A; Chaput, C; Touzard, M; Millan, M J

2000-04-03

alpha(2)-adrenoceptor-mediated G-protein activation was examined by [(35)S]-GTPgammaS autoradiography. In alpha(2)-adrenoceptor-rich regions (amygdala, lateral septum), noradrenaline stimulated [(35)S]-GTPgammaS binding. These actions were abolished by the selective alpha(2) antagonist, atipamezole. Conversely, in caudate nucleus, which expresses few alpha(2) receptors, noradrenaline-induced stimulation was not inhibited by atipamezole, suggesting that it is not mediated by alpha(2)-adrenoceptors.

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

Real-world effects of two inhaled corticosteroid/long-acting β₂-agonist combinations in the treatment of asthma.

PubMed

Yatera, Kazuhiro; Yamasaki, Kei; Nishida, Chinatsu; Noguchi, Shingo; Oda, Keishi; Akata, Kentarou; Nagata, Shuya; Kawanami, Yukiko; Kawanami, Toshinori; Ishimoto, Hiroshi; Mukae, Hiroshi

2014-09-01

There are several inhaled corticosteroid/long-acting β2-agonist (ICS/LABA) combinations currently used to treat asthmatic patients, but the differences in the clinical effects of these ICS/LABAs are currently unknown. We herein evaluated the effects of two currently available ICS/LABA combinations in a real-world setting. A fluticasone propionate/salmeterol combined Discus inhaler (FP/SM; 250/50 μg bid) was switched to a budesonide/formoterol Turbuhaler inhaler (BUD/FM; 160/4.5 μg two inhalations bid) and FP/SM (500/50 μg bid) was also switched to BUD/FM (160/4.5 μg four inhalations bid) in symptomatic asthmatic patients treated with FP/SM over 20 years of age. Sixty patients were enrolled in this study, and the scores of the asthma control test (ACT) and asthma control questionnaire-5 item version (ACQ5) were significantly improved 4 and 8 weeks after the switch to ICS/LABA treatments, and well-controlled asthma (ACQ5 score <0.75) and good control (ACT score >20) was achieved in 54 (90%) and 40 (66.7%) patients, respectively, at 8 weeks. The spirometric analysis revealed significant improvements of the values of the peak expiratory flow (PEF) and forced expiratory volume in one second (FEV1) after switching from FP/SM to BUD/FM, and significantly improved small airway impairments ([Formula: see text]50 and [Formula: see text]25) were observed in patients treated with high-dose ICS/LABA. These subjective and objective improvements were also seen in patients aged over 65 years old. These data demonstrated that changing the combined ICS/LABA inhaler from FP/SM to BUD/FM can lead to more effective management of symptomatic patients with asthma, especially in patients treated with high-dose ICS/LABA.

Co-agonists differentially tune GluN2B-NMDA receptor trafficking at hippocampal synapses

PubMed Central

Ferreira, Joana S; Papouin, Thomas; Ladépêche, Laurent; Yao, Andrea; Langlais, Valentin C; Bouchet, Delphine; Dulong, Jérôme; Mothet, Jean-Pierre; Sacchi, Silvia; Pollegioni, Loredano; Paoletti, Pierre; Oliet, Stéphane Henri Richard; Groc, Laurent

2017-01-01

The subunit composition of synaptic NMDA receptors (NMDAR), such as the relative content of GluN2A- and GluN2B-containing receptors, greatly influences the glutamate synaptic transmission. Receptor co-agonists, glycine and D-serine, have intriguingly emerged as potential regulators of the receptor trafficking in addition to their requirement for its activation. Using a combination of single-molecule imaging, biochemistry and electrophysiology, we show that glycine and D-serine relative availability at rat hippocampal glutamatergic synapses regulate the trafficking and synaptic content of NMDAR subtypes. Acute manipulations of co-agonist levels, both ex vivo and in vitro, unveil that D-serine alter the membrane dynamics and content of GluN2B-NMDAR, but not GluN2A-NMDAR, at synapses through a process requiring PDZ binding scaffold partners. In addition, using FRET-based FLIM approach, we demonstrate that D-serine rapidly induces a conformational change of the GluN1 subunit intracellular C-terminus domain. Together our data fuels the view that the extracellular microenvironment regulates synaptic NMDAR signaling. DOI: http://dx.doi.org/10.7554/eLife.25492.001 PMID:28598327

Activation of alpha2 adrenergic receptors suppresses fear conditioning: expression of c-Fos and phosphorylated CREB in mouse amygdala.

PubMed

Davies, M Frances; Tsui, Janet; Flannery, Judy A; Li, Xiangqi; DeLorey, Timothy M; Hoffman, Brian B

2004-02-01

alpha(2) adrenergic agonists such as dexmedetomidine generally suppress noradrenergic transmission and have sedative, analgesic, and antihypertensive properties. Considering the importance of the neurotransmitter norepinephrine in forming memories for fearful events, we have investigated the acute and chronic effects of dexmedetomidine on discrete cue and contextual fear conditioning in mice. When administered before training, dexmedetomidine (10-20 microg/kg, i.p.) selectively suppressed discrete cue fear conditioning without affecting contextual memory. This behavioral change was associated with a decrease in memory retrieval-induced expression of c-Fos and P-CREB in the lateral, basolateral, and central nuclei of the amygdala. Dexmedetomidine's action on discrete cue memory did not occur in alpha(2A) adrenoceptor knockout (KO) mice. When dexmedetomidine was administered after training, it suppressed contextual memory, an effect that did not occur in alpha(2A) adrenoceptor KO mice. We conclude that dexmedetomidine, acting at alpha(2A) adrenoceptors, must be present during the encoding process to decrease discrete cue fear memory; however, its ability to suppress contextual memory is likely the result of blocking the consolidation process. The ability of alpha(2) agonists to suppress fear memory may be a valuable property clinically in order to suppress the formation of memories during stressful situations.

Aucubin protects against pressure overload-induced cardiac remodelling via the β3 -adrenoceptor-neuronal NOS cascades.

PubMed

Wu, Qing-Qing; Xiao, Yang; Duan, Ming-Xia; Yuan, Yuan; Jiang, Xiao-Han; Yang, Zheng; Liao, Hai-Han; Deng, Wei; Tang, Qi-Zhu

2018-05-01

Aucubin, the predominant component of Eucommia ulmoides Oliv., has been shown to have profound effects on oxidative stress. As oxidative stress has previously been demonstrated to contribute to acute and chronic myocardial injury, we tested the effects of aucubin on cardiac remodelling and heart failure. Initially, H9c2 cardiomyocytes and neonatal rat cardiomyocytes pretreated with aucubin (1, 3, 10, 25 and 50 μM) were challenged with phenylephrine. Secondly, the transverse aorta was constricted in C57/B6 and neuronal NOS (nNOS)-knockout mice, then aucubin (1 or 5 mg·kg -1 body weight day -1 ) was injected i.p. for 25 days. Hypertrophy was evaluated by assessing morphological changes, echocardiographic parameters, histological analyses and hypertrophic markers. Oxidative stress was evaluated by examining ROS generation, oxidase activity and NO generation. NOS expression was determined by Western blotting. Aucubin effectively suppressed cardiac remodelling; in mice, aucubin substantially inhibited pressure overload-induced cardiac hypertrophy, fibrosis and inflammation, whereas knocking out nNOS abolished these cardioprotective effects of aucubin. Blocking or knocking down the β 3 -adrenoceptor abolished the protective effects of aucubin in vitro. Furthermore, aucubin enhanced the protective effects of a β 3 -adrenoceptor agonist in vitro by increasing cellular cAMP levels, whereas treatment with an adenylate cyclase (AC) inhibitor abolished the cardioprotective effects of aucubin. Aucubin suppresses oxidative stress during cardiac remodelling by increasing the expression of nNOS in a process that requires activation of the β 3 -adrenoceptor/AC/cAMP pathway. These findings suggest that aucubin could have potential as a treatment for cardiac remodelling and heart failure. © 2018 The British Pharmacological Society.

Agonists and antagonists acting at P2X receptors: selectivity profiles and functional implications.

PubMed

Lambrecht, G

2000-11-01

P2X receptors are nucleotide-gated cation channels composed of homomeric or heteromeric assemblies of three subunits. In the past 7 years, an extended series (P2X1-7) of P2X subunits has been cloned from vertebrate tissues. In this rapidly expanding field, one of the main current challenges is to relate the cloned P2X receptor subtypes to the diverse physiological responses mediated by the native P2X receptors. However, the paucity of useful ligands, especially subtype-selective agonists and antagonists as well as radioligands, acts as a considerable impediment to progress. Most of the ligands available are highly limited in terms of their kinetics of action, receptor-affinity, subtype-selectivity and P2X receptor-specificity. Their suspected ability to be a substrate for ecto-nucleotidases or to inhibit these enzymes also complicates their use. A number of new antagonists at P2X receptors have recently been described which to some degree are more potent and more selective than earlier antagonists like suramin or pyridoxal-5'-phosphate-6-azophenyl 2',4'-disulfonate (PPADS). This work moves us closer to the ideal goal of classifying the recombinant and native P2X receptor subtypes on the basis of antagonist profiles. This review begins with a brief account of the current status of P2X receptors. It then focuses on the pharmacological properties of a series of key P2 receptor agonists and antagonists and will finish with the discussion of some related therapeutic possibilities.

Putative β4-adrenoceptors in rat ventricle mediate increases in contractile force and cell Ca2+: comparison with atrial receptors and relationship to (−)-[3H]-CGP 12177 binding

PubMed Central

Sarsero, Doreen; Molenaar, Peter; Kaumann, Alberto J; Freestone, Nicholas S

1999-01-01

We identified putative β4-adrenoceptors by radioligand binding, measured increases in ventricular contractile force by (−)-CGP 12177 and (±)-cyanopindolol and demonstrated increased Ca2+ transients by (−)-CGP 12177 in rat cardiomyocytes.(−)-[3H]-CGP 12177 labelled 13–22 fmol mg−1 protein ventricular β1, β2-adrenoceptors (pKD ∼9.0) and 50–90 fmol mg−1 protein putative β4-adrenoceptors (pKD ∼7.3). The affinity values (pKi) for (β1,β2-) and putative β4-adrenoceptors, estimated from binding inhibition, were (−)-propranolol 8.4, 5.7; (−)-bupranolol 9.7, 5.8; (±)-cyanopindolol 10.0,7.4.In left ventricular papillary muscle, in the presence of 30 μM 3-isobutyl-1-methylxanthine, (−)-CGP 12177 and (±)-cyanopindolol caused positive inotropic effects, (pEC50, (−)-CGP 12177, 7.6; (±)-cyanopindolol, 7.0) which were antagonized by (−)-bupranolol (pKB 6.7–7.0) and (−)-CGP 20712A (pKB 6.3–6.6). The cardiostimulant effects of (−)-CGP 12177 in papillary muscle, left and right atrium were antagonized by (±)-cyanopindolol (pKP 7.0–7.4).(−)-CGP 12177 (1 μM) in the presence of 200 nM (−)-propranolol increased Ca2+ transient amplitude by 56% in atrial myocytes, but only caused a marginal increase in ventricular myocytes. In the presence of 1 μM 3-isobutyl-1-methylxanthine and 200 nM (−)-propranolol, 1 μM (−)-CGP 12177 caused a 73% increase in Ca2+ transient amplitude in ventricular myocytes. (−)-CGP 12177 elicited arrhythmic transients in some atrial and ventricular myocytes.Probably by preventing cyclic AMP hydrolysis, 3-isobutyl-1-methylxanthine facilitates the inotropic function of ventricular putative β4-adrenoceptors, suggesting coupling to Gs protein-adenylyl cyclase. The receptor-mediated increases in contractile force are related to increases of Ca2+ in atrial and ventricular myocytes. The agreement of binding affinities of agonists with cardiostimulant potencies is consistent with mediation

Activation of β-adrenoceptors in the bed nucleus of the stria terminalis induces food intake reduction and anxiety-like behaviors.

PubMed

Naka, Tomonori; Ide, Soichiro; Nakako, Tomokazu; Hirata, Mikie; Majima, Yuki; Deyama, Satoshi; Takeda, Hiroshi; Yoshioka, Mitsuhiro; Minami, Masabumi

2013-04-01

We previously demonstrated the critical role of noradrenergic transmission within the ventral part of the bed nucleus of the stria terminalis (vBNST) in pain-induced aversion. We showed that activation of β-adrenoceptors in this brain region by intra-vBNST injection of isoproterenol, a β-adrenoceptor agonist, produced aversive responses. In the present study, we examined the effects of a β-adrenoceptor agonist injected into the vBNST on food intake and anxiety-like behaviors in male Sprague-Dawley rats. Bilateral intra-vBNST injection of isoproterenol (3 and 10 nmol/side) caused a dose-dependent decrease in food intake; this suppressive effect was reversed by co-administration of timolol, a β-adrenoceptor antagonist. Dose-dependent (10 and 30 nmol/side) induction of anxiety-like behaviors by isoproterenol was observed in the elevated plus maze (EPM) test, which was also reversed by co-administration of timolol. Off-site control injections of isoproterenol into the lateral ventricle did not show any significant effect in the food consumption and EPM tests. These results suggest that the vBNST is one of the neuroanatomical substrates which may be involved in the close relationship between negative affective states and reduction of food intake, and that noradrenergic transmission within this brain region plays a critical role in inducing anxiety-like behaviors and reduced food intake. Copyright © 2012 Elsevier Ltd. All rights reserved.

Pharmacological characterization of ATPM [(-)-3-aminothiazolo[5,4-b]-N-cyclopropylmethylmorphinan hydrochloride], a novel mixed kappa-agonist and mu-agonist/-antagonist that attenuates morphine antinociceptive tolerance and heroin self-administration behavior.

PubMed

Wang, Yu-Jun; Tao, Yi-Min; Li, Fu-Ying; Wang, Yu-Hua; Xu, Xue-Jun; Chen, Jie; Cao, Ying-Lin; Chi, Zhi-Qiang; Neumeyer, John L; Zhang, Ao; Liu, Jing-Gen

2009-04-01

ATPM [(-)-3-amino-thiazolo[5,4-b]-N-cyclopropylmethylmorphinan hydrochloride] was found to have mixed kappa- and mu-opioid activity and identified to act as a full kappa-agonist and a partial mu-agonist by in vitro binding assays. The present study was undertaken to characterize its in vivo effects on morphine antinociceptive tolerance in mice and heroin self-administration in rats. ATPM was demonstrated to yield more potent antinociceptive effects than (-)U50,488H (trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamide). It was further found that the antinociceptive effects of ATPM were mediated by kappa- and mu-, but not delta-opioid, receptors. In addition to its agonist profile on the mu-receptor, ATPM also acted as a mu-antagonist, as measured by its inhibition of morphine-induced antinociception. It is more important that ATPM had a greater ratio of the ED(50) value of sedation to that of antinociception than (-)U50,488 (11.8 versus 3.7), indicative of a less sedative effect than (-)U50,488H. In addition, ATPM showed less potential to develop antinociceptive tolerance relative to (-)U50,488H and morphine. Moreover, it dose-dependently inhibited morphine-induced antinociceptive tolerance. Furthermore, it was found that chronic treatment of rats for 8 consecutive days with ATPM (0.5 mg/kg s.c.) produced sustained decreases in heroin self-administration. (-)U50,488H (2 mg/kg s.c.) also produced similar inhibitory effect. Taken together, our findings demonstrated that ATPM, a novel mixed kappa-agonist and mu-agonist/-antagonist, could inhibit morphine-induced antinociceptive tolerance, with less potential to develop tolerance and reduce heroin self-administration with less sedative effect. kappa-Agonists with some mu-activity appear to offer some advantages over selective kappa-agonists for the treatment of heroin abuse.

Blunted beta-adrenoceptor-mediated fat oxidation in overweight subjects: a role for the hormone-sensitive lipase gene.

PubMed

Jocken, Johan W E; Blaak, Ellen E; van der Kallen, Carla J H; van Baak, Marleen A; Saris, Wim H M

2008-03-01

Obesity is associated with blunted beta-adrenoceptor-mediated lipolysis and fat oxidation, which persist after weight reduction. We investigated whether dinucleotide (CA)(n) repeat polymorphisms in intron 6 (i6) or 7 (i7) and a C-60G promoter substitution of the hormone-sensitive lipase (HSL) gene are associated with a blunted in vivo beta-adrenoceptor-mediated increase in circulating fatty acids and glycerol (estimation of lipolytic response) and fat oxidation in overweight-obese subjects. A total of 103 overweight (25 kg/m(2) < or = body mass index < 30 kg/m(2)) and obese (body mass index > or =30 kg/m(2)) subjects (62 men, 41 women) were included. Energy expenditure, respiratory quotient (RQ), and circulating fatty acid and glycerol were determined after stepwise infusion of increasing doses of the nonselective beta-agonist isoprenaline. The i6, i7 (CA)(n) repeat polymorphisms were determined by size-resolved capillary electrophoresis; and a C-60G promoter substitution was determined by restriction enzyme digestion assay. Female noncarriers of allele 184 i7 (n = 18) and female carriers of allele 240 i6 (n = 12) showed an overall reduced fat oxidation (as indicated by changes in RQ) after beta-adrenoceptor-mediated stimulation, explaining, respectively, 6.9% and 20.8% of the variance in RQ. These effects were not seen in male subjects. In conclusion, our results suggest that variation in i7 and i6 of the HSL gene might be associated with a physiological effect on in vivo beta-adrenoceptor-mediated fat oxidation, at least in overweight-obese female subjects.

Trek2a regulates gnrh3 expression under control of melatonin receptor Mt1 and α2-adrenoceptor.

PubMed

Loganathan, Kavinash; Moriya, Shogo; Parhar, Ishwar S

2018-02-12

Gonadotrophin-releasing hormone (GnRH) expression is associated with the two-pore domain potassium ion (K + ) channel-related K + (TREK) channel trek2a expression and melatonin levels. We aimed to investigate correlation of trek2a expression with gnrh3 expression, and regulatory mechanisms of trek2a expression by the melatonin receptor Mt1 and α 2 -adrenoceptor which are regulated by melatonin. trek2a specific siRNA, Mt1 antagonist luzindole and α 2 -adrenoceptor antagonist prazosin were administered into the adult zebrafish brain and gene expressions were examined by real-time PCR. trek2a specific siRNA administration significantly reduced expression levels of trek2a, gnrh3 and mt1. Luzindole administration suppressed trek2a and gnrh3 expressions. Prazosin administration reduced trek2a and gnrh3 expressions. It is suggested that Trek2a regulates gnrh3 expression under the control of Mt1 and α 2 -adrenoceptor. Copyright © 2018 Elsevier Inc. All rights reserved.

Adrenoceptors in Brain: Cellular Gene Expression and Effects on Astrocytic Metabolism and [Ca2+]i

PubMed Central

Hertz, Leif; Lovatt, Ditte; Goldman, Steven A.; Nedergaard, Maiken

2010-01-01

Recent in vivo studies have established astrocytes as a major target for locus coeruleus activation (Bekar et al., Cereb. Cortex 18, 2789–2795), renewing interest in cell culture studies on noradrenergic effects on astrocytes in primary cultures and calling for additional information about the expression of adrenoceptor subtypes on different types of brain cells. In the present communication, mRNA expression of α1-, α2- and β-adrenergic receptors and their subtypes was determined in freshly-isolated, cell marker-defined populations of astrocytes, NG2-positive cells, microglia, endothelial cells, and Thy1-positive neurons (mainly glutamatergic projection neurons) in murine cerebral cortex. Immediately after dissection of frontal, parietal and occipital cortex of 10–12-week-old transgenic mice, which combined each cell-type marker with a specific fluorescent signal, the tissue was digested, triturated and centrifuged, yielding a solution of dissociated cells of all types, which were separated by fluorescence-activated cell sorting (FACS). mRNA expression in each cell fraction was determined by microarray analysis. α1A-Receptors were unequivocally expressed in astrocytes and NG2-positive cells, but absent in other cell types, and α1B-receptors were not expressed in any cell population. Among α2-receptors only α2A-receptors were expressed, unequivocally in astrocytes and NG-positive cells, tentatively in microglia and questionably in Thy1-positive neurons and endothelial cells. β1-Receptors were unequivocally expressed in astrocytes, tentatively in microglia, and questionably in neurons and endothelial cells, whereas β2-adrenergic receptors showed tentative expression in neurons and astrocytes and unequivocal expression in other cell types. This distribution was supported by immunochemical data and its relevance established by previous studies in well-differentiated primary cultures of mouse astrocytes, showing that stimulation of α2-adrenoceptors

5-Methoxy-N,N-dimethyltryptamine-induced analgesia is blocked by alpha-adrenoceptor antagonists in rats.

PubMed Central

Archer, T.; Danysz, W.; Jonsson, G.; Minor, B. G.; Post, C.

1986-01-01

The effects of the alpha-adrenoceptor antagonists prazosin, phentolamine and yohimbine upon 5-methoxy-N,N-dimethyltryptamine (5-MeODMT)-induced analgesia were tested in the hot-plate, tail-flick and shock-titration tests of nociception with rats. Intrathecally injected yohimbine and phentolamine blocked or attenuated the analgesia produced by systemic administration of 5-MeODMT in all three nociceptive tests. Intrathecally administered prazosin attenuated the analgesic effects of 5-MeODMT in the hot-plate and tail-flick tests, but not in the shock titration test. Intrathecal yohimbine showed a dose-related lowering of pain thresholds in saline and 5-MeODMT-treated animals. Phentolamine and prazosin produced normal dose-related curves in the hot-plate test and biphasic effects in the shock titration and tail-flick tests. These results demonstrate a functional interaction between alpha 2-adrenoceptors and 5-HT agonist-induced analgesia at a spinal level in rats. PMID:2877697

Effect of RareGenetic Variants in the β2 Adrenergic Receptor Geneon the Risk for Exacerbations and Symptom Control During Long-Acting Beta Agonist Treatment in a Multi-Ethnic Asthma Population

PubMed Central

Ortega, Victor E.; Hawkins, Gregory A.; Moore, Wendy C.; Hastie, Annette T.; Ampleford, Elizabeth J.; Busse, William W.; Castro, Mario; Chardon, Domingo; Erzurum, Serpil C.; Israel, Elliot; Montealegre, Federico; Wenzel, Sally E.; Peters, Stephen P.; Meyers, Deborah A.; Bleecker, Eugene R.

2014-01-01

Background Severe adverse life-threatening events associated with long-acting beta agonists (LABA) use have caused the FDA to review LABA safety which has resulted in a boxed warning and a mandatory LABA safety study in 46,800 asthmatics. Identification of an at-risk, susceptible subpopulation using predictive biomarkers is critical in understanding LABA safety. The β2-adrenergic receptor gene (ADRB2) contains a common, nonsynonymous single nucleotide polymorphism, Gly16Arg, that is unlikely to account for rare, life-threatening events. We hypothesize that rare ADRB2 variants with strong effects modulate therapeutic responses to long-acting beta agonist (LABA) therapy and contribute to rare, severe adverse events. Methods ADRB2 was sequenced in 197 African Americans, 191 non-Hispanic Whites, and 73 Puerto Ricans. Sequencing identified six rare variants which were genotyped in 1,165 asthmatics (total=1,626). The primary hypothesis was that severe asthma exacerbations requiring hospitalization were associated with rare ADRB2 variants. Replication was performed in 659 non-Hispanic White asthma subjects. Findings Asthmatics receiving LABA with a rare variant had increased asthma-related hospitalizations (meta-analysis for all ethnic groups: p=2·83 × 10−4), specifically LABA-treated non-Hispanic Whites with the rare Ile164 allele (only rare variant in Whites, OR4·48, 95% CI 1·40–14·0, p=0·01) and African Americans with a 25 base-pair promoter polynucleotide insertion (OR 13·43, 95% CI 2·02–265·4, p=0·006). The subset of non-Hispanic Whites and African Americans receiving LABAs with these rare variants had increased exacerbations requiring urgent outpatient healthcare visits (non-Hispanic Whites with or without the rare Ile164 allele: 2·6 visits versus 1·1 visits, p=8·4 × 10−7 and African Americans with or without the rare insertion: 3·7 visits versus 2·4 visits, 0·01), and more frequently were treated with chronic systemic corticosteroids (OR4�

Molecular cloning and functional expression of the guinea pig alpha(1a)-adrenoceptor.

PubMed

González-Espinosa, C; Romero-Avila, M T; Mora-Rodríguez, D M; González-Espinosa, D; García-Sáinz, J A

2001-08-31

In the present paper, the cloning and expression of the guinea pig alpha(1A)-adrenoceptor is presented. The nucleotide sequence had an open reading frame of 1401 bp that encoded a 466 amino-acid protein with an estimated molecular mass of approximately 51.5 kDa. When the clone was expressed in Cos-1 cells, specific high-affinity binding of [(3)H]prazosin and [(3)H]tamsulosin was observed. Chloroethylclonidine treatment of membranes slightly decreased the total binding with both radioligands. Binding competition experiments using [(3)H]tamsulosin showed the following potency order: (a) for agonists: oxymetazoline >epinephrine>norepinephrine>methoxamine, and (b) for antagonists: prazosin> or 5-methyl-urapidil=benoxathian>phentolamine>BMY 7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4,5]decane-7,9-dione). Photoaffinity labeling using [(125)I-aryl]azido-prazosin revealed a major broad band with a molecular mass between 70 and 80 kDa. The receptor was functional, as evidenced by an epinephrine-increased production of [(3)H]inositol phosphates that was blocked by prazosin.

In vivo dopamine agonist properties of rotigotine: Role of D1 and D2 receptors.

PubMed

Fenu, Sandro; Espa, Elena; Pisanu, Augusta; Di Chiara, Gaetano

2016-10-05

Rotigotine acts in vitro as a full agonist of dopamine D1 receptors at concentrations almost superimposable to those at which it acts on D2 receptors. However in vivo evidence of the differences between the agonist activity of rotigotine at D1 receptors from that on the D2 receptors has not been provided yet. In order to test the ability of rotigotine to stimulate dopamine D1 and D2 receptors in vivo, we studied the effect of SCH39166 and eticlopride, selective dopamine D1 and D2/D3 receptor antagonists respectively, on rotigotine-induced contralateral turning behavior in 6-hydroxydopamine lesioned rats. Furthermore, the expression of the immediate-early gene c-fos in the caudate-putamen, was evaluated. As a comparison, we tested the D2/D3 agonist pramipexole. In primed rats, rotigotine (0.035, 0.1 and 0.35mg/kg) induced dose-dependent contralateral turning. Turning induced by 0.1mg/kg of rotigotine was reduced by pretreatment with the D1 antagonist SCH39166 and the D2 antagonist eticlopride. In drug-naive rats, rotigotine was less effective in eliciting turning but SCH39166 still reduced turning induced by rotigotine (0.35mg/kg). Pramipexole induced contralateral turning only in primed rats. SCH39166 potentiated and eticlopride abolished pramipexole-induced turning. Rotigotine induced Fos expression in the caudate-putamen and SCH39166 completely blocked it. Pramipexole failed to induce Fos. These results indicate that rotigotine acts in vivo as an agonist of D1 and D2 receptors while pramipexole is devoid of D1 activity in vivo. Given their differing DA receptor profiles, rotigotine and pramipexole might differ in their spectrum of application to the therapy of Parkinson's disease. Copyright © 2016 Elsevier B.V. All rights reserved.

Activation of 5-hydroxytryptamine1B/1D/1F receptors as a mechanism of action of antimigraine drugs.

PubMed

Ramírez Rosas, Martha B; Labruijere, Sieneke; Villalón, Carlos M; Maassen Vandenbrink, Antoinette

2013-08-01

The introduction of the triptans (5-hydroxytryptamine (5-HT)1B/1D receptor agonists) was a great improvement in the acute treatment of migraine. However, shortcomings of the triptans have prompted research on novel serotonergic targets for the treatment of migraine. In this review the different types of antimigraine drugs acting at 5-HT receptors, their discovery and development are discussed. The first specific antimigraine drugs were the ergot alkaloids, consisting of ergotamine, dihydroergotamine and methysergide, which are agonists at 5-HT receptors, but can also bind α-adrenoceptors and dopamine receptors. In the 1990s, the triptans became available on the market. They are 5-HT1B/1D receptor agonists, showing fewer side effects due to their receptor specificity. In the last years, compounds that bind specifically to 5-HT1D, 5-HT1F and 5-HT7 receptors have been explored for their antimigraine potential. Furthermore, the serotonergic system seems to act in tight connection with the glutamatergic as well as the CGRP-ergic systems, which may open novel therapeutic avenues. Although the triptans are very effective in treating migraine attacks, their shortcomings have stimulated the search for novel drugs. Currently, the focus is on 5-HT1F receptor agonists, which seem devoid of vascular side effects. Moreover, novel compounds that affect multiple transmitter and/or neuropeptide systems that are involved in migraine could be of therapeutic relevance.

Metabolic benefits of 1-(3-(4-(o-tolyl)piperazin-1-yl)propyl)pyrrolidin-2-one: a non-selective α-adrenoceptor antagonist.

PubMed

Kotańska, Magdalena; Kulig, Katarzyna; Marcinkowska, Monika; Bednarski, Marek; Malawska, Katarzyna; Zaręba, Paula

2018-05-01

Previous studies have shown that several components of the metabolic syndrome, such as hypertension, obesity or imbalanced lipid and carbohydrate homeostasis, are associated with the sympathetic nervous system overactivity. Therefore, the inhibition of the adrenergic nervous system seems to be a reasonable and appropriate therapeutic approach for the treatment of metabolic disturbances. It has been suggested that non-selective adrenoceptor antagonists could be particularly beneficial, since α 1 -adrenoceptor antagonists can improve disrupted lipid and carbohydrate profiles, while the inhibition of the α 2 -adrenoceptor may contribute to body weight reduction. The aim of the present study was to investigate the metabolic benefits deriving from administration of a non-selective α-adrenoceptor antagonist from the group of pyrrolidin-2-one derivatives. The aim of the present study was to investigate the potential metabolic benefits deriving from chronic administration of a non-selective α-adrenoceptor antagonist, from the group of pyrrolidin-2-one derivatives. The α 1 - and α 2 -adrenoreceptor affinities of the tested compound-1-(3-(4-(o-tolyl)piperazin-1-yl)propyl)pyrrolidin-2-one had been investigated previously by means of the radioligand binding assay. In the present study, we extended the pharmacological profile characteristics of the selected molecule by additional intrinistic activity assays. Next, we investigated the influence of the tested compound on body weight, hyperglycemia, hypertriglyceridemia, blood pressure in the animal model of obesity induced by a high-fat diet, and additionally we measured the spontaneous activity and body temperature. The intrinistic activity studies revealed that the tested compound is a potent, non-selective antagonist of α 1B and α 2A -adrenoceptors. After the chronic administration of the tested compound, we observed reduced level of triglycerides and glucose in the rat plasma. Interestingly, the tested did not reduce

Alpha 2-adrenoceptors and endothelium-dependent relaxation in canine large arteries.

PubMed Central

Angus, J. A.; Cocks, T. M.; Satoh, K.

1986-01-01

Ring preparations from the carotid, coronary, renal, mesenteric and femoral arteries of the dog were precontracted with the thromboxane mimetic U46619, after ensuring that the resting conditions were comparable from the Laplace relationship. In the presence of prazosin (1 microM) and propranolol (3 microM), noradrenaline (NA) relaxed the arteries in the order coronary greater than carotid greater than femoral greater than renal = mesenteric. When maximum relaxation to nitroglycerin (10 microM) was taken to be 100% the maximum relaxation to noradrenaline in each artery was: coronary 70%; carotid 34%; femoral 19%; renal 7% and mesenteric 2%. In endothelium-intact arteries UK14304 mimicked the relaxation responses to NA and idazoxan shifted the curves to both agonists to the right, consistent with an alpha 2-adrenoceptor classification. Substance P relaxed the arteries in the same order as for NA but showed higher efficacy i.e.: coronary 100%; carotid 80%; femoral 71% renal 49%; and mesenteric 41%. Removal of the endothelium abolished the relaxation to NA. We conclude that endothelium-dependent relaxation to NA and substance P varies greatly across 5 large arteries of the dog. This may indicate that endothelium-derived relaxing factor (EDRF) release is site-dependent or that the efficacy of EDRF on smooth muscle varies; being greatest in the coronary and weakest in the renal and mesenteric arteries. PMID:2427147

Structure-bias relationships for fenoterol stereoisomers in six molecular and cellular assays at the β2-adrenoceptor.

PubMed

Reinartz, Michael T; Kälble, Solveig; Littmann, Timo; Ozawa, Takeaki; Dove, Stefan; Kaever, Volkhard; Wainer, Irving W; Seifert, Roland

2015-01-01

Functional selectivity is well established as an underlying concept of ligand-specific signaling via G protein-coupled receptors (GPCRs). Functionally, selective drugs could show greater therapeutic efficacy and fewer adverse effects. Dual coupling of the β2-adrenoceptor (β2AR) triggers a signal transduction via Gsα and Giα proteins. Here, we examined 12 fenoterol stereoisomers in six molecular and cellular assays. Using β2AR-Gsα and β2AR-Giα fusion proteins, (R,S')- and (S,S')-isomers of 4'-methoxy-1-naphthyl-fenoterol were identified as biased ligands with preference for Gs. G protein-independent signaling via β-arrestin-2 was disfavored by these ligands. Isolated human neutrophils constituted an ex vivo model of β2AR signaling and demonstrated functional selectivity through the dissociation of cAMP accumulation and the inhibition of formyl peptide-stimulated production of reactive oxygen species. Ligand bias was calculated using an operational model of agonism and revealed that the fenoterol scaffold constitutes a promising lead structure for the development of Gs-biased β2AR agonists.

A2B Adenosine Receptor Agonist Improves Erectile Function in Diabetic Rats.

PubMed

Wen, Jiaming; Wang, Bohan; Du, Chuanjun; Xu, Gang; Zhang, Zhewei; Li, Yi; Zhang, Nan

2015-10-01

Diabetes is an important risk factor for erectile dysfunction (ED). Recent studies have indicated that A2B adenosine receptor (ADORA2B) signaling is essential for penile erection. Thus, we hypothesize that diabetic ED may be attributed to impaired A2B adenosine signaling. To test this hypothesis, we generated diabetic rats by injecting streptozocin as animal model. After 12 weeks, immunohistochemistry staining was used to localize the expression of ADORA2B. Western Blot and quantitative PCR were employed to determine ADORA2B expression level. Intracavernosal pressure (ICP) measurement was used to evaluate erectile function. Diabetic rats received a single intravenous injection of BAY 60-6583, an ADORA2B agonist, or vehicle solution, at 60 min before the ICP measurement. The results showed that ADORA2B expressed in the nerve bundle, smooth muscle, and endothelium in penile tissue of control mice. Western Blot and quantitative PCR results indicated that the expression levels of ADORA2B protein and mRNA were significantly reduced in penile tissues of diabetic rats. Functional studies showed that the erectile response induced by electrical stimulation was remarkably decreased in diabetic rats, compared with age-matched control rats. However, at 60 min after BAY 60-6583 treatment, the erectile function was improved in diabetic rats, suggesting that enhancement of ADORA2B signaling may improve erectile function in diabetic ED. This preclinical study has revealed a previously unrecognized therapeutic possibility of BAY 60-6583 as an effective and mechanism-based drug to treat diabetic ED. In conclusion, we propose that impaired A2B adenosine signaling is one of the pathological mechanisms of diabetic ED.

The beta-3 adrenoceptor agonist, mirabegron relaxes isolated prostate from human and rabbit: new therapeutic indication?

PubMed

Calmasini, Fabiano B; Candido, Tuany Z; Alexandre, Eduardo C; D'Ancona, Carlos A; Silva, Daniel; de Oliveira, Marco Antonio; De Nucci, Gilberto; Antunes, Edson; Mónica, Fabíola Z

2015-03-01

Alpha1 (α1)-blockers, 5-alpha reductase and phosphodiesterase type-5 inhibitors are pharmacological classes currently available for benign prostatic hyperplasia (BPH) treatment. Mirabegron, a beta-3 adrenoceptor (β3-AR) agonist has been approved for the therapy of overactive bladder and may constitute a new therapeutic option for BPH treatment. This study is aimed to evaluate the in vitro effects of mirabegron in human and rabbit prostatic smooth muscle. In rabbit prostate, electrical field stimulation (EFS)-induced contraction and concentration-response curve (CRC) to mirabegron in phenylephrine pre-contracted tissues were carried out. The potency (pEC50 ) and maximal response (Emax ) values were determined. In human prostate, CRC to phenylephrine was carried out in the absence and presence of mirabegron. Immunohistochemistry analysis for β3-AR was also carried out. In human prostate, immunohistochemistry analysis revealed the presence of β3-AR on the transition zone and mirabegron reduced by 42% the phenylephrine-induced contractions. In rabbit prostate, mirabegron produced concentration-dependent relaxations (pEC50 : 6.01 ± 0.12; Emax : 106 ± 3%), which were fully resistant to the blockade of β1-AR and β2-AR. The β3-AR blocker L748,337 caused a six-fold rightward shift in mirabegron-induced relaxations. Mirabegron (10 μM) reduced by 63% the EFS-induced contractions. Inhibitors of nitric oxide (L-NAME) and of soluble guanylate cyclase (ODQ) along with a cocktail of K+ channel blockers (apamin, charybdotoxin, glibenclamide, tetraethylammonium) all failed to significantly affect the mirabegron-induced rabbit relaxations. Mirabegron relaxes prostatic smooth muscle, providing an experimental support for the clinical investigation of its combination with an α1-blockers or PDE5 inhibitors in the treatment of BPH. Prostate 75:440-447, 2015. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc.

Beta-2 adrenoceptor genotype and progress in term and late preterm active labor

PubMed Central

MILLER, Russell S.; SMILEY, Richard M.; DANIEL, Danette; WENG, Chunhua; EMALA, Charles W.; BLOUIN, Jean-Louis; FLOOD, Pamela D.

2011-01-01

OBJECTIVE To evaluate whether beta-2 adrenoceptor genotype at a functional polymorphic site encoding for amino acid residue 16 influences rate of cervical dilatation in term and late preterm active labor. STUDY DESIGN Subjects that underwent vaginal delivery at 34 or greater weeks gestational age between May, 2006, and August, 2007, were identified. Each subject had provided venous blood from which DNA was extracted for beta-2 adrenoceptor genotyping. Digital cervical examinations with paired examination times were collected from intrapartum records. Rate of cervical dilatation in active labor was determined using linear regression and rates were compared between genotype groups. RESULTS Among 401 subjects with satisfactory genotype and intrapartum data, overall rate of active labor was 0.76+/−0.01 cm/hr. When labor was compared by genotype, homozygous Arg/Arg16 subjects progressed at a slower rate (0.64+/−0.03 cm/hr) than all other pooled genotypes (0.8+/−0.02 cm/hr). CONCLUSION Homozygous beta-2 adrenoceptor genotype encoding for Arg/Arg16 was associated with slower progress in active labor. PMID:21600547

Membrane Potential Controls the Efficacy of Catecholamine-induced β1-Adrenoceptor Activity*

PubMed Central

Birk, Alexandra; Rinne, Andreas; Bünemann, Moritz

2015-01-01

G protein-coupled receptors (GPCRs) are membrane-located proteins and, therefore, are exposed to changes in membrane potential (VM) in excitable tissues. These changes have been shown to alter receptor activation of certain Gi-and Gq-coupled GPCRs. By means of a combination of whole-cell patch-clamp and Förster resonance energy transfer (FRET) in single cells, we demonstrate that the activation of the Gs-coupled β1-adrenoreceptor (β1-AR) by the catecholamines isoprenaline (Iso) and adrenaline (Adr) is regulated by VM. This voltage-dependence is also transmitted to G protein and arrestin 3 signaling. Voltage-dependence of β2-AR activation, however, was weak compared with β1-AR voltage-dependence. Drug efficacy is a major target of β1-AR voltage-dependence as depolarization attenuated receptor activation, even under saturating concentrations of agonists, with significantly faster kinetics than the deactivation upon agonist withdrawal. Also the efficacy of the endogenous full agonist adrenaline was reduced by depolarization. This is a unique finding since reports of natural full agonists at other voltage-dependent GPCRs only show alterations in affinity during depolarization. Based on a Boltzmann function fit to the relationship of VM and receptor-arrestin 3 interaction we determined the voltage-dependence with highest sensitivity in the physiological range of membrane potential. Our data suggest that under physiological conditions voltage regulates the activity of agonist-occupied β1-adrenoceptors on a very fast time scale. PMID:26408198

7,8-dihydroxyflavone, a TrkB receptor agonist, blocks long-term spatial memory impairment caused by immobilization stress in rats.

PubMed

Andero, Raül; Daviu, Núria; Escorihuela, Rosa Maria; Nadal, Roser; Armario, Antonio

2012-03-01

Post-traumatic stress disorder (PTSD) patients show cognitive deficits, but it is unclear whether these are a consequence of the pathology or a pre-existing factor of vulnerability to PTSD. Animal models may help to demonstrate whether or not exposure to certain stressors can actually induce long-lasting (LL; days) impairment of hippocampus-dependent memory tasks and to characterize neurobiological mechanisms. Adult male rats were exposed to 2-h immobilization on boards (IMO), a severe stressor, and spatial learning in the Morris water maze (MWM) was studied days later. Exposure to IMO did not modify learning or short-term memory in the MWM when learning started 3 or 9 days after IMO, but stressed rats did show impaired long-term memory at both times, in accordance with the severity of the stressor. New treatments to prevent PTSD symptoms are needed. Thus, considering the potential protective role of brain-derived neurotrophic factor (BDNF) on hippocampal function, 7,8-dihydroxyflavone (7,8-DHF), a recently characterized agonist of the BDNF receptor TrkB, was given before or after IMO in additional experiments. Again, exposure to IMO resulted in LL deficit in long-term memory, and such impairment was prevented by the administration of 7,8-DHF either 2 h prior IMO or 8 h after the termination of IMO. The finding that IMO-induced impairment of spatial memory was prevented by pharmacological potentiation of TrkB pathway with 7,8-DHF even when the drug was given 8 h after IMO suggests that IMO-induced impairment is likely to be a LL process that is strongly dependent on the integrity of the BDNF-TrkB system and is susceptible to poststress therapeutic interventions. 7,8-DHF may represent a new therapeutic approach for early treatment of subjects who have suffered traumatic experiences. Copyright © 2010 Wiley Periodicals, Inc.

Novel kinin B1 receptor agonists with improved pharmacological profiles.

PubMed

Côté, Jérôme; Savard, Martin; Bovenzi, Veronica; Bélanger, Simon; Morin, Josée; Neugebauer, Witold; Larouche, Annie; Dubuc, Céléna; Gobeil, Fernand

2009-04-01

There is some evidence to suggest that inducible kinin B1 receptors (B1R) may play beneficial and protecting roles in cardiovascular-related pathologies such as hypertension, diabetes, and ischemic organ diseases. Peptide B1R agonists bearing optimized pharmacological features (high potency, selectivity and stability toward proteolysis) hold promise as valuable therapeutic agents in the treatment of these diseases. In the present study, we used solid-phase methodology to synthesize a series of novel peptide analogues based on the sequence of Sar[dPhe(8)]desArg(9)-bradykinin, a relatively stable peptide agonist with moderate affinity for the human B1R. We evaluated the pharmacological properties of these peptides using (1) in vitro competitive binding experiments on recombinant human B1R and B2R (for index of selectivity determination) in transiently transfected human embryonic kidney 293 cells (HEK-293T cells), (2) ex vivo vasomotor assays on isolated human umbilical veins expressing endogenous human B1R, and (3) in vivo blood pressure tests using anesthetized lipopolysaccharide-immunostimulated rabbits. Key chemical modifications at the N-terminus, the positions 3 and 5 on Sar[dPhe(8)]desArg(9)-bradykinin led to potent analogues. For example, peptides 18 (SarLys[Hyp(3),Cha(5), dPhe(8)]desArg(9)-bradykinin) and 20 (SarLys[Hyp(3),Igl(5), dPhe(8)]desArg(9)-bradykinin) outperformed the parental molecule in terms of affinity, functional potency and duration of action in vitro and in vivo. These selective agonists should be valuable in future animal and human studies to investigate the potential benefits of B1R activation.

Acute orexigenic effect of agmatine involves interaction between central α2-adrenergic and GABAergic receptors.

PubMed

Taksande, Brijesh Gulabrao; Sharma, Omi; Aglawe, Manish Manohar; Kale, Mayur Bhimrao; Gawande, Dinesh Yugraj; Umekar, Milind Janraoji; Kotagale, Nandkishor Ramdas

2017-09-01

Agmatine and GABA have been abundantly expressed in brain nuclei involved in regulation of energy homeostasis and promoting stimulation of food intake in rodents. However, their mutual interaction, if any, in the elicitation of feeding behavior is largely remains unclear. The current study provides experimental evidence for the possible interaction of agmatine, adrenergic and GABAergic systems in stimulation of feeding in satiated rats. Satiated rats fitted with intracerebroventricular (i.c.v.) cannulae and were administered agmatine, alone or jointly with (a) GABA A receptor agonist, muscimol, diazepam or antagonist bicuculline and flumazenil, GABA A positive modulator, allopregnanolone or negative modulator of GABA A receptor, dehydroepiandrosterone (b) In view of the high affinity of agmatine for α 2 -adrenoceptors and the close association between α 2 -adrenoceptors and GABAergic system, the effect of their modulators on feeding elicited by agmatine/GABAergic agonists were also examined. I.c.v. administration of agmatine (40-80μg/rat) induces the significant orexigenic effect in satiated rats. The orexigenic effect of agmatine was potentiated by muscimol (25ng/rat, i.c.v.); diazepam (0.5mg/kg, i.p.); allopregnanolone (0.5mg/kg, s.c.) and blocked by bicuculline (1mg/kg, i.p.) and dehydroepiandrosterone (4mg/kg,s.c.). However, it remained unaffected in presence of flumazenil (25ng/rat, i.c.v.). The orexigenic effect of agmatine and GABAergic agonists was potentiated by a α 2 -adrenoceptors agonist, clonidine (10ng/rat, i.c.v.) and blocked by its antagonist, yohimbine (5μg/rat, i.c.v.). Yohimbine also blocked the hyperphagic effect elicited by ineffective dose combination of agmatine (5μg/rat, i.c.v.) with muscimol (25ng/rat, i.c.v.) or diazepam (0.5mg/kg, i.p.) or allopregnanolone (0.5mg/kg,s.c.). The results of the present study suggest that agmatine induced α 2 -adrenoceptors activation might facilitate GABAergic activity to stimulate food intake in

The role of serotonin-2 (5-HT2) and dopamine receptors in the behavioral actions of the 5-HT2A/2C agonist, DOI, and putative 5-HT2C inverse agonist, SR46349B.

PubMed

Scarlota, Laura C; Harvey, John A; Aloyo, Vincent J

2011-02-01

Atypical antipsychotic efficacy is often attributed to actions at serotonin-2 (5-HT(2)) and dopamine receptors, indicating a potential benefit of understanding the interplay between these systems. Currently, it is known that 5-HT(2) receptors modulate dopamine release, although the role of specific dopamine receptors in 5-HT(2)-mediated behavior is not well understood. We examined the role of 5-HT(2A), 5-HT(2C), and dopamine (D1 and D2) receptors in the behavioral response to a 5-HT(2A/2C) agonist (DOI) and 5-HT(2A/2C) antagonist (SR46349B). Effects were assessed by measuring rabbit head bobs (previously characterized as 5-HT(2A) receptor-mediated) and body shakes (5-HT(2C)-mediated). As expected, DOI produced head bobs and body shakes, and these DOI-elicited behaviors were attenuated by the SR46349B pretreatment. Unexpectedly, SR46349B also induced head bobs when administered alone. However, SR46349B-elicited head bobs are distinguishable from those produced by DOI since the 5-HT(2A) antagonist, ketanserin, only attenuated DOI-elicited head bobs. Conversely, 5-HT(2C) ligands (SB242084 and SB206553) inhibited SR46349B but not DOI-induced head bobs. Furthermore, when administered alone, SB206553 (a 5-HT(2C) inverse agonist) produced head bobs, indicating the behavior can be either 5-HT(2A) or 5-HT(2C) mediated. Next, it was revealed that D1 and D2 receptors play a role in DOI-elicited head bobs, but only D1 receptors are required for SR46349B-elicited head bobs. 5-HT(2A) receptor agonism and 5-HT(2C) inverse agonism produce the same behavior, likely due to similar downstream actions at D1 receptors. Consequently, 5-HT(2C) agonism or D1 agonism may be effective therapies for disorders, such as schizophrenia, currently being treated with 5-HT(2A) antagonists.

Functional β2-adrenoceptors in rat left atria: effect of foot-shock stress.

PubMed

Moura, André Luiz de; Hyslop, Stephen; Grassi-Kassisse, Dora M; Spadari, Regina C

2017-09-01

Altered sensitivity to the chronotropic effect of catecholamines and a reduction in the β 1 /β 2 -adrenoceptor ratio have previously been reported in right atria of stressed rats, human failing heart, and aging. In this report, we investigated whether left atrial inotropism was affected by foot-shock stress. Male rats were submitted to 3 foot-shock sessions and the left atrial inotropic response, adenylyl cyclase activity, and β-adrenoceptor expression were investigated. Left atria of stressed rats were supersensitive to isoprenaline when compared with control rats and this effect was abolished by ICI118,551, a selective β 2 -receptor antagonist. Schild plot slopes for the antagonism between CGP20712A (a selective β 1 -receptor antagonist) and isoprenaline differed from unity in atria of stressed but not control rats. Atrial sensitivity to norepinephrine, as well as basal and forskolin- or isoprenaline-stimulated adenylyl cyclase activities were not altered by stress. The effect of isoprenaline on adenylyl cyclase stimulation was partially blocked by ICI118,551 in atrial membranes of stressed rats. These findings indicate that foot-shock stress equally affects inotropism and chronotropism and that β 2 -adrenoceptor upregulation contributes to the enhanced inotropic response to isoprenaline.

Renal denervation improves cardiac function in rats with chronic heart failure: Effects on expression of β-adrenoceptors

PubMed Central

Zheng, Hong; Liu, Xuefei; Sharma, Neeru M.

2016-01-01

Chronic activation of the sympathetic drive contributes to cardiac remodeling and dysfunction during chronic heart failure (HF). The present study was undertaken to assess whether renal denervation (RDN) would abrogate the sympathoexcitation in HF and ameliorate the adrenergic dysfunction and cardiac damage. Ligation of the left coronary artery was used to induce HF in Sprague-Dawley rats. Four weeks after surgery, RDN was performed, 1 wk before the final measurements. At the end of the protocol, cardiac function was assessed by measuring ventricular hemodynamics. Rats with HF had an average infarct area >30% of the left ventricle and left ventricular end-diastolic pressure (LVEDP) >20 mmHg. β1- and β2-adrenoceptor proteins in the left ventricle were reduced by 37 and 49%, respectively, in the rats with HF. RDN lowered elevated levels of urinary excretion of norepinephrine and brain natriuretic peptide levels in the hearts of rats with HF. RDN also decreased LVEDP to 10 mmHg and improved basal dP/dt to within the normal range in rats with HF. RDN blunted loss of β1-adrenoceptor (by 47%) and β2-adrenoceptor (by 100%) protein expression and improved isoproterenol (0.5 μg/kg)-induced increase in +dP/dt (by 71%) and −dP/dt (by 62%) in rats with HF. RDN also attenuated the increase in collagen 1 expression in the left ventricles of rats with HF. These findings demonstrate that RDN initiated in chronic HF condition improves cardiac function mediated by adrenergic agonist and blunts β-adrenoceptor expression loss, providing mechanistic insights for RDN-induced improvements in cardiac function in the HF condition. PMID:27288440

Inward rectifier K+ channel and T-type Ca2+ channel contribute to enhancement of GABAergic transmission induced by β1-adrenoceptor in the prefrontal cortex.

PubMed

Luo, Fei; Zheng, Jian; Sun, Xuan; Tang, Hua

2017-02-01

The functions of prefrontal cortex (PFC) are sensitive to norepinephrine (NE). Endogenously released NE influences synaptic transmission through activation of different subtypes of adrenergic receptors in PFC including α 1 , α 2 , β 1 or β 2 -adrenoceptor. Our recent study has revealed that β 1 -adrenoceptor (β 1 -AR) activation modulates glutamatergic transmission in the PFC, whereas the roles of β 1 -AR in GABAergic transmission are elusive. In the current study, we probed the effects of the β 1 -AR agonist dobutamine (Dobu) on GABAergic transmission onto pyramidal neurons in the PFC of juvenile rats. Dobu increased both the frequency and amplitude of miniature IPSCs (mIPSCs). Ca 2+ influx through T-type voltage-gated Ca 2+ channel was required for Dobu-enhanced mIPSC frequency. We also found that Dobu facilitated GABA release probability and the number of releasable vesicles through regulating T-type Ca 2+ channel. Dobu depolarized GABAergic fast-spiking (FS) interneurons with no effects on the firing rate of action potentials (APs) of interneurons. Dobu-induced depolarization of FS interneurons required inward rectifier K + channel (Kir). Our results suggest that Dobu increase GABA release via inhibition of Kir, which further depolarizes FS interneurons resulting in Ca 2+ influx via T-type Ca 2+ channel. Copyright © 2016 Elsevier Inc. All rights reserved.

Initial Assessment of β3-Adrenoceptor-Activated Brown Adipose Tissue in Streptozotocin-Induced Type 1 Diabetes Rodent Model Using [18F]Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography.

PubMed

Baranwal, Aparna; Mirbolooki, M Reza; Mukherjee, Jogeshwar

2015-01-01

Metabolic activity of brown adipose tissue (BAT) is activated by β3-adrenoceptor agonists and norepinephrine transporter (NET) blockers and is measurable using [(18)F]fluorodeoxyglucose ([(18)F]FDG) positron emission tomography/computed tomography (PET/CT) in rats. Using the streptozotocin (STZ)-treated rat model of type 1 diabetes mellitus (T1DM), we investigated BAT activity in this rat model under fasting and nonfasting conditions using [(18)F]FDG PET/CT. Drugs that enhance BAT activity may have a potential for therapeutic development in lowering blood sugar in insulin-resistant diabetes. Rats were rendered diabetic by administration of STZ and confirmed by glucose measures. [(18)F]FDG was injected in the rats (fasted or nonfasted) pretreated with either saline or β3-adrenoceptor agonist CL316,243 or the NET blocker atomoxetine for PET/CT scans. [(18)F]FDG metabolic activity was computed as standard uptake values (SUVs) in interscapular brown adipose tissue (IBAT) and compared across the different drug treatment conditions. Blood glucose levels > 500 mg/dL were established for the STZ-treated diabetic rats. Under fasting conditions, average uptake of [(18)F]FDG in the IBAT of STZ-treated diabetic rats was approximately 70% lower compared to that of normal rats. Both CL316,243 and atomoxetine activated IBAT in normal rats had an SUV > 5, whereas activation in STZ-treated rats was significantly lower. The agonist CL316,243 activated IBAT up to threefold compared to saline in the fasted STZ-treated rat. In the nonfasted rat, the IBAT activation was up by twofold by CL316243. Atomoxetine had a greater effect on lowering blood sugar levels compared to CL316,243 in the nonfasted rats. A significant reduction in metabolic activity was observed in the STZ-treated diabetic rodent model. Increased IBAT activity in the STZ-treated diabetic rat under nonfasted conditions using the β3-adrenoceptor agonist CL316,243 suggests a potential role of BAT in modulating blood

The effects of lower than conventional doses of oral nadolol on relative beta 1/beta 2-adrenoceptor blockade.

PubMed

Wheeldon, N M; McDevitt, D G; Lipworth, B J

1994-08-01

1. The aim of the present study was to evaluate the relative beta 1/beta 2 antagonist selectivity of the beta-adrenoceptor blocker nadolol, in lower than conventional clinical doses. 2. Eight normal volunteers received single oral doses of either placebo (PL), nadolol 5 mg (N5), 20 mg (N20) or 80 mg (N80) in a single-blind, randomised crossover design. beta 1-adrenoceptor antagonism was assessed by attenuation of exercise tachycardia, and beta 2-adrenoceptor blockade by effects on salbutamol-induced chronotropic, hypokalaemic and finger tremor responses. The relative percentage attenuation of beta 2 and beta 1-mediated responses was calculated and expressed as beta 2:beta 1 selectivity ratios. 3. Nadolol produced dose-related reductions in exercise tachycardia in keeping with increasing beta 1-adrenoceptor blockade; mean % reduction (95% CI) compared with placebo: N5 10.7 (6.6 to 14.8), N20 21.4 (17.3 to 25.4), N80 38.9 (34.8 to 42.9). However, even the lowest dose of nadolol (5 mg) produced almost complete blunting of beta 2-mediated effects and significantly increase exercise hyperkalaemia; peak exercise hyperkalaemia (mmol l-1) (means and 95% CI): PL 4.88 (4.68 to 5.07), N5 5.36 (5.17 to 5.55), N20 5.48 (5.28 to 5.67), N80 5.42 (5.22 to 5.61). beta 2:beta 1 selectivity ratios significantly increased as the dose of nadolol was reduced. 4. These data suggest that whereas in the clinical dose range nadolol behaves as a non-selective beta-adrenoceptor antagonist, as the dose is reduced this drug demonstrates an increasing degree of selectivity for the beta 2-adrenoceptor.(ABSTRACT TRUNCATED AT 250 WORDS)

The beta-adrenergic agonist salbutamol modulates neuromuscular junction formation in zebrafish models of human myasthenic syndromes.

PubMed

McMacken, Grace; Cox, Dan; Roos, Andreas; Müller, Juliane; Whittaker, Roger; Lochmüller, Hanns

2018-05-01

Inherited defects of the neuromuscular junction (NMJ) comprise an increasingly diverse range of disorders, termed congenital myasthenic syndromes (CMS). Therapies acting on the sympathetic nervous system, including the selective β2 adrenergic agonist salbutamol and the α and β adrenergic agonist ephedrine, have become standard treatment for several types of CMS. However, the mechanism of the therapeutic effect of sympathomimetics in these disorders is not understood. Here, we examined the effect of salbutamol on NMJ development using zebrafish with deficiency of the key postsynaptic proteins Dok-7 and MuSK. Treatment with salbutamol reduced motility defects in zebrafish embryos and larvae. In addition, salbutamol lead to morphological improvement of postsynaptic acetycholine receptor (AChR) clustering and size of synaptic contacts in Dok-7-deficient zebrafish. In MuSK-deficient zebrafish, salbutamol treatment reduced motor axon pathfinding defects and partially restored the formation of aneural prepatterned AChRs. In addition, the effects of salbutamol treatment were prevented by pre-treatment with a selective β2 antagonist. Treatment with the cyclic adenosine monophosphate (cAMP) activator forskolin, replicated the effects of salbutamol treatment. These results suggest that sympathomimetics exert a direct effect on neuromuscular synaptogenesis and do so via β2 adrenoceptors and via a cAMP-dependent pathway.

The beta-adrenergic agonist salbutamol modulates neuromuscular junction formation in zebrafish models of human myasthenic syndromes

PubMed Central

McMacken, Grace; Cox, Dan; Roos, Andreas; Müller, Juliane; Whittaker, Roger; Lochmüller, Hanns

2018-01-01

Abstract Inherited defects of the neuromuscular junction (NMJ) comprise an increasingly diverse range of disorders, termed congenital myasthenic syndromes (CMS). Therapies acting on the sympathetic nervous system, including the selective β2 adrenergic agonist salbutamol and the α and β adrenergic agonist ephedrine, have become standard treatment for several types of CMS. However, the mechanism of the therapeutic effect of sympathomimetics in these disorders is not understood. Here, we examined the effect of salbutamol on NMJ development using zebrafish with deficiency of the key postsynaptic proteins Dok-7 and MuSK. Treatment with salbutamol reduced motility defects in zebrafish embryos and larvae. In addition, salbutamol lead to morphological improvement of postsynaptic acetycholine receptor (AChR) clustering and size of synaptic contacts in Dok-7-deficient zebrafish. In MuSK-deficient zebrafish, salbutamol treatment reduced motor axon pathfinding defects and partially restored the formation of aneural prepatterned AChRs. In addition, the effects of salbutamol treatment were prevented by pre-treatment with a selective β2 antagonist. Treatment with the cyclic adenosine monophosphate (cAMP) activator forskolin, replicated the effects of salbutamol treatment. These results suggest that sympathomimetics exert a direct effect on neuromuscular synaptogenesis and do so via β2 adrenoceptors and via a cAMP-dependent pathway. PMID:29462491

Antihypertensive effect of formononetin through regulating the expressions of eNOS, 5-HT2A/1B receptors and α1-adrenoceptors in spontaneously rat arteries.

PubMed

Sun, Tao; Wang, Jie; Huang, Lin-Hong; Cao, Yong-Xiao

2013-01-15

One of the main pathological changes of hypertension is the dysfunction of blood vessels. We have found in our previous study that formononetin, one kind of phytoestrogens, has an acute antihypertensive effect. Therefore, we hypothesized that formononetin might produce a chronic antihypertensive effect through regulating the expressions of contractile receptors and endothelial nitric oxide synthase (eNOS) in artery. The present study was conducted to verify this effect. Male spontaneously hypertensive rats (SHRs) were divided into two groups, orally administrated formononetin (50mg/kg per day) and Tween 80 vehicle, respectively, for 8 weeks. The blood pressure was measured by tail-cuff method. Isometric tension of arterial rings was recorded by a myograph system. The mRNA and protein expression in arteries was determined with quantitative real-time polymerase chain reaction and immunohistochemistry, respectively. Results showed that the systolic blood pressure of SHRs decreased significantly in formononetin group compared to Tween 80 group. The vasoconstriction induced by phenylephrine or 5-hydroxytryptamine (5-HT) in the mesenteric artery segments in formononetin group was decreased, and the relaxation induced by acetylcholine was increased compared with that in Tween 80 group. In the mesenteric arteries of the formononetin-treated SHRs, the expressions of α(1)-adrenoceptors and 5-HT(2A/1B) receptors at both mRNA and protein levels decreased, while the mRNA and protein expressions of eNOS increased. In conclusion, formononetin has a chronic antihypertensive effect in SHRs. The antihypertensive mechanism may be associated with the down-regulation of α(1)-adrenoceptors and 5-HT(2A/1B) receptors, and the up-regulation of eNOS expression in arteries. Copyright © 2012 Elsevier B.V. All rights reserved.

Actin isoform and alpha 1B-adrenoceptor gene expression in aortic and coronary smooth muscle is influenced by cyclical stretch.

PubMed

Lundberg, M S; Sadhu, D N; Grumman, V E; Chilian, W M; Ramos, K S

1995-09-01

The occurrence of vascular domains with specific biological and pharmacological characteristics suggests that smooth muscle cells in different arteries may respond differentially to a wide range of environmental stimuli. To determine if some of these vessel-specific differences may be attributable to mechano-sensitive gene regulation, the influence of cyclical stretch on the expression of actin isoform and alpha 1B-adrenoceptor genes was examined in aortic and coronary smooth muscle cells. Cells were seeded on an elastin substrate and subjected to maximal stretching (24% elongation) and relaxation cycles at a frequency of 120 cycles/min in a Flexercell strain unit for 72 h. Total RNA was extracted and hybridized to radiolabeled cDNA probes to assess gene expression. Stretch caused a greater reduction of actin isoform mRNA levels in aortic smooth muscle cells as compared to cells from the coronary artery. Steady-state mRNA levels of alpha 1B-adrenoceptor were also decreased by cyclical stretch in both cell types but the magnitude of the response was greater in coronary smooth muscle cells. No changes in alpha 1B-adrenoceptor or beta/gamma-actin steady-state mRNA levels were observed in H4IIE cells, a nonvascular, immortalized cell line. The relative gene expression of heat shock protein 70 was not influenced by the cyclic stretch regimen in any of these cell types. These results suggest that stretch may participate in the regulation of gene expression in vascular smooth muscle cells and that this response exhibits some degree of cell-specificity.

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.

Neural control of renal function: role of renal alpha adrenoceptors.

PubMed

DiBona, G F

1985-01-01

Adrenoceptors of various subtypes mediate the renal functional responses to alterations in efferent renal sympathetic nerve activity, the neural component, and renal arterial plasma catecholamine concentrations, the humoral component, of the sympathoadrenergic nervous system. Under normal physiologic as well as hypertensive conditions, the influence of the renal sympathetic nerves predominates over that of circulating plasma catecholamines. In most mammalian species, increases in efferent renal sympathetic nerve activity elicit renal vasoconstrictor responses mediated predominantly by renal vascular alpha-1 adrenoceptors, increases in renin release mediated largely by renal juxtaglomerular granular cell beta-1 adrenoceptors with involvement of renal vascular alpha-1 adrenoceptors only when renal vasoconstriction occurs, and direct increases in renal tubular sodium and water reabsorption mediated predominantly by renal tubular alpha-1 adrenoceptors. In most mammalian species, alpha-2 adrenoceptors do not play a significant role in the renal vascular or renin release responses to renal sympathoadrenergic stimulation. Although renal tubular alpha-2 adrenoceptors do not mediate the increases in renal tubular sodium and water reabsorption produced by increases in efferent renal sympathetic nerve activity, they may be involved through their inhibitory effect on adenylate cyclase in modulating the response to other hormonal agents that influence renal tubular sodium and water reabsorption via stimulation of adenylate cyclase.

Effect of beta-agonists on LAM progression and treatment.

PubMed

Le, Kang; Steagall, Wendy K; Stylianou, Mario; Pacheco-Rodriguez, Gustavo; Darling, Thomas N; Vaughan, Martha; Moss, Joel

2018-01-30

Lymphangioleiomyomatosis (LAM), a rare disease of women, is associated with cystic lung destruction resulting from the proliferation of abnormal smooth muscle-like LAM cells with mutations in the tuberous sclerosis complex (TSC) genes TSC1 and/or TSC2 The mutant genes and encoded proteins are responsible for activation of the mechanistic target of rapamycin (mTOR), which is inhibited by sirolimus (rapamycin), a drug used to treat LAM. Patients who have LAM may also be treated with bronchodilators for asthma-like symptoms due to LAM. We observed stabilization of forced expiratory volume in 1 s over time in patients receiving sirolimus and long-acting beta-agonists with short-acting rescue inhalers compared with patients receiving only sirolimus. Because beta-agonists increase cAMP and PKA activity, we investigated effects of PKA activation on the mTOR pathway. Human skin TSC2 +/- fibroblasts or LAM lung cells incubated short-term with isoproterenol (beta-agonist) showed a sirolimus-independent increase in phosphorylation of S6, a downstream effector of the mTOR pathway, and increased cell growth. Cells incubated long-term with isoproterenol, which may lead to beta-adrenergic receptor desensitization, did not show increased S6 phosphorylation. Inhibition of PKA blocked the isoproterenol effect on S6 phosphorylation. Thus, activation of PKA by beta-agonists increased phospho-S6 independent of mTOR, an effect abrogated by beta-agonist-driven receptor desensitization. In agreement, retrospective clinical data from patients with LAM suggested that a combination of bronchodilators in conjunction with sirolimus may be preferable to sirolimus alone for stabilization of pulmonary function.

β3-Adrenoceptor activation upregulates apolipoprotein A-I expression in HepG2 cells, which might further promote cholesterol efflux from macrophage foam cells.

PubMed

Gao, Xia-Qing; Li, Yan-Fang; Jiang, Zhi-Li

2017-01-01

The aim of this study was to explore the effects of β 3 -adrenoceptor (β 3 -AR) activation on HepG2 cells and its influence on cholesterol efflux from macrophage foam cells. HepG2 cells were cultured and treated with the β 3 -AR agonist, BRL37344, and antagonist, SR52390A, and the expression of apolipoprotein (Apo) A-I, ApoA-II, ApoB, and β 3 -AR in the supernatants and cells was determined. The expression of peroxisome proliferator-activated receptor (PPAR) γ and PPARα in the HepG2 cells was also assessed. Next, using the RAW264.7 macrophage foam cell model, we also assessed the influence of the HepG2 cell supernatants on lipid efflux. The cholesterol content of the foam cells was also measured, and the cholesterol efflux from the macrophages was examined by determining 3 H-labeled cholesterol levels. Expression of ATP-binding cassette transporter (ABC) A1 and ABCG1 of the macrophage foam cells was also assessed. β 3 -AR activation increased ApoA-I expression in both the HepG2 cells and the supernatants; PPARγ expression was upregulated, but PPARα expression was not. Treatment with GW9662 abolished the increased expression of ApoA-I induced by the β 3 -AR agonist. The HepG2 cell supernatants decreased the lipid accumulation and increased the cholesterol efflux from the macrophage foam cells. ABCA1 expression, but not ABCG1 expression, increased in the macrophage foam cells treated with BRL37344-treated HepG2 cell supernatants. Activation of β 3 -AR in HepG2 cells upregulates ApoA-I expression, which might further promote cholesterol efflux from macrophage foam cells. PPARγ might be required for the induction of ApoA-I expression.

Contribution of beta 1- and beta 2-adrenoceptors of human atrium and ventricle to the effects of noradrenaline and adrenaline as assessed with (-)-atenolol.

PubMed Central

Lemoine, H.; Schönell, H.; Kaumann, A. J.

1988-01-01

1. (-)-Atenolol was used as a tool to assess the function of beta 1- and beta 2-adrenoceptors in human heart. Right atrial and left ventricular preparations from patients undergoing open heart surgery were set up to contract isometrically. Membrane particles were prepared for beta-adrenoceptor labelling with [3H]-(-)-bupranolol and adenylate cyclase assays. 2. The positive inotropic effects of (-)-noradrenaline were antagonized to a similar extent by (-)-atenolol in atrial and ventricular preparations. (-)-Atenolol consistently antagonized the effects of (-)-adrenaline to a lesser extent than those of (-)-noradrenaline in atrial preparations. In ventricular preparations (-)-atenolol antagonized the effects of low concentrations of (-)-adrenaline to a lesser extent than those of high concentrations. 3. pKB values (M) of (-)-atenolol, estimated with non-linear analysis from the blockade of the positive inotropic effects of the catecholamines, were 7.4 for beta 1-adrenoceptors and 6.0 for beta 2-adrenoceptors. 4. (-)-Atenolol inhibited the binding of [3H]-(-)-bupranolol to ventricular beta 1-adrenoceptors with a pKD (M) of 5.9 and to ventricular beta 2-adrenoceptors with a pKD of 4.6. 5. (-)-Atenolol inhibited the catecholamine-induced adenylate cyclase stimulation in the atrium and ventricle with pKB values of 5.8-6.4 for beta 1- and pKB values of 4.7-5.7 for beta 2-adrenoceptors. The binding and cyclase assays suggest a partial affinity loss for (-)-atenolol inherent to membrane preparations. 6. beta 1-Adrenoceptors mediate the maximum positive inotropic effects of (-)-noradrenaline in both the atrium and ventricle of man. beta 2-Adrenoceptors appear to be capable of mediating maximal positive inotropic effects of (-)-adrenaline in atrium. In contrast, ventricular beta 2-adrenoceptors mediated only submaximal effects of (-)-adrenaline. PMID:2851354

Adrenoceptor Polymorphisms in Hypertension and Diabetes with obesity-update in 2014.

PubMed

Masuo, K

2014-08-12

Hypertension, diabetes mellitus (especially type 2 diabetes mellitus) and metabolic syndrome associated with obesity are rapidly growing public health problems. Sympathetic nerve activation is well documented in hypertension, diabetes mellitus, and obesity, hypertension and diabetes are determined by genetic background and environmental factors. Reduced energy expenditure and resting metabolic rate are predictive of weight gain, and the sympathetic nervous system participates in regulating energy balance through thermogenesis. The thermogenic effects of sympathetic nervous system in obesity have been mainly mediated via the β2 and β3-adrenergic receptors in humans. Further, β2-adrenoceptors importantly influence vascular reactivity and may regulate blood pressure. Genetic polymorphisms of the -adrenoceptor gene have been shown to alter the function of several adrenoceptor subtype and thus to modify the response to catecholamine. Among β2-adrenoceptor polymorphisms, Arg16Gly, Gln27Glu, and Thr164Ile are considered the most functionally important. β2-adrenoceptor genes have been studied in relation to hypertension. Genetic variations in the β3-adrenoceptor, such as the Try64Arg variant, are also associated with both obesity and hypertension. This review is an update of several versions published of the relationships between adrenoceptor polymorphisms and hypertension, diabetes and obesiy based on the my own review on the relationship with obesity in 2011 in "Journal of Obesity" [1], and another of my own reviews on the relationships with hypertension in 2010 in "International journal of Hypertension" [2], with 37 articles provided by the "PubMed" with the keywords of "adrenoceptor polymorphisms, obesity, hypertension and diabetes" searched on December 2013. However, the relationships of the polymorphisms of β2- and β3-adrenoceptor genes with sympathetic nervous system activity, hypertension and metabolic syndrome have been still discordant, it might be

Efficacy and safety of the CRTh2 antagonist AZD1981 as add-on therapy to inhaled corticosteroids and long-acting β2-agonists in patients with atopic asthma.

PubMed

Bateman, Eric D; O'Brien, Christopher; Rugman, Paul; Luke, Sally; Ivanov, Stefan; Uddin, Mohib

2018-01-01

To evaluate the efficacy and safety of AZD1981, a potent, specific antagonist of the CRTh2 receptor, as add-on therapy to inhaled corticosteroids (ICS) and long-acting β 2 -agonists (LABA), in patients with persistent asthma with an allergic component. In this placebo-controlled, parallel-group Phase IIb study, patients with persistent atopic asthma on ICS and LABA were randomized to receive 12 weeks of treatment with placebo or AZD1981 (80 mg daily, 200 mg daily, and 10 mg, 40 mg, 100 mg, or 400 mg twice daily [BID]). The primary end point was the mean change from baseline in predose, prebronchodilator forced expiratory volume in 1 second (FEV 1 ) averaged over weeks 2, 4, 8, and 12 in the AZD1981-treatment group vs the placebo group. Secondary end points included other measures of lung function, symptoms, and asthma control, as well as standard measures of safety. In total, 1,140 patients (99.7%) received study treatment. There were improvements in the primary end point across all treatment groups over 12 weeks of treatment. However, the improvement for the highest AZD1981 dose (400 mg BID) vs placebo was not statistically significant (0.02 L, P =0.58), preventing interpretation of statistical testing for the lower doses. AZD1981 was well tolerated, and the incidence of adverse events was comparable across placebo and treatment groups. In patients with allergic asthma receiving ICS and LABA therapy, the addition of AZD1981 at doses up to 400 mg BID failed to produce a clinically relevant improvement in lung function or any other measured end point, but appeared to have an acceptable safety profile. This clinical study is registered with ClinicalTrials.gov (NCT01197794).

Comparison of changes in the extracellular concentration of noradrenaline in rat frontal cortex induced by sibutramine or d-amphetamine: modulation by α2-adrenoceptors

PubMed Central

Wortley, K E; Hughes, Z A; Heal, D J; Stanford, S C

1999-01-01

The effects of sibutramine (0.25–10 mg kg−1, i.p.) on extracellular noradrenaline concentration in the frontal cortex of halothane-anaesthetized rats were compared with those of d-amphetamine (1–3 mg kg−1, i.p.) using in vivo microdialysis. The role of presynaptic α2-adrenoceptors in modulating the effects of these drugs on extracellular noradrenaline concentration were also investigated by pretreating rats with the selective α2-adrenoceptor antagonist, RX821002.Sibutramine induced a gradual and sustained increase in extracellular noradrenaline concentration. The dose-response relationship was described by a bell-shaped curve with a maximum effect at 0.5 mg kg−1. In contrast, d-amphetamine induced a rapid increase in extracellular noradrenaline concentration, the magnitude of which paralleled drug dose.Pretreatment with the α2-adrenoceptor antagonist, RX821002 (dose 3 mg kg−1, i.p.) increased by 5 fold the accumulation of extracellular noradrenaline caused by sibutramine (10 mg kg−1) and reduced the latency of sibutramine to reach its maximum effect from 144–56 min.RX821002-pretreatment increased by only 2.5 fold the increase in extracellular noradrenaline concentration caused by d-amphetamine alone (10 mg kg−1) and had no effect on the latency to reach maximum.These findings support evidence that sibutramine acts as a noradrenaline uptake inhibitor in vivo and that the effects of this drug are blunted by indirect activation of presynaptic α2-adreno-ceptors. In contrast, the rapid increase in extracellular noradrenaline concentration induced by d-amphetamine is consistent with this being mainly due to an increase in Ca2+-independent release of noradrenaline. PMID:10482917

Clenbuterol Induces Cell Cycle Arrest in C2C12 Myoblasts by Delaying p27 Degradation through β-arrestin 2 Signaling

PubMed Central

Chen, Min; Liu, Chuncheng; Wang, Meng; Wang, Hong; Zhang, Kuo; Zheng, Yu; Yu, Zhengquan; Li, Xiangdong; Guo, Wei; Li, Ning; Meng, Qingyong

2017-01-01

β2-Adrenoceptor (β2-AR) agonists promote muscle growth. The aim of this study was to elucidate some effects of the selective β2-adrenoceptor agonist clenbuterol (CLB) on myoblast proliferation. We found that CLB induces cell cycle arrest in C2C12 myoblasts. This effect is partly due to the enhanced stability of p27, rather than the increased gene transcription via cAMP response element-binding protein (CREB). Specifically, CLB treatment enhanced the accumulation of p27 in the nucleus while depleting it from the cytosol via a mechanism that requires β2-AR. Surprisingly, p27 accumulation was not reversed by the protein kinase A (PKA) inhibitor H-89, but interestingly, was alleviated by the knockdown of β-arrestin 2. Thus, our work provides a basis for β2-AR agonists inhibit myoblasts proliferation through signaling via β2-AR, β-arrestin 2, and p27. PMID:29104500

Modulation of intracellular Ca2+ via L-type calcium channels in heart cells by the autoantibody directed against the second extracellular loop of the alpha1-adrenoceptors.

PubMed

Bkaily, Ghassan; El-Bizri, Nesrine; Bui, Michel; Sukarieh, Rami; Jacques, Danielle; Fu, Michael L X

2003-03-01

The effects of methoxamine, a selective alpha1-adrenergic receptor agonist, and the autoantibody directed against the second extracellular loop of alpha1-adrenoceptors were studied on intracellular free Ca2+ levels using confocal microscopy and ionic currents using the whole-cell patch clamp technique in single cells of 10-day-old embryonic chick and 20-week-old fetal human hearts. We observed that like methoxamine, the autoantibody directed against the second extracellular loop of alpha1-adrenoreceptors significantly increased the L-type calcium current (I(Ca(L))) but had no effect on the T-type calcium current (I(Ca(T))), the delayed outward potassium current, or the fast sodium current. This effect of the autoantibody was prevented by a prestimulation of the receptors with methoxamine and vice versa. Moreover, treating the cells with prazosin, a selective alpha1-adrenergic receptor antagonist blocked the methoxamine and the autoantibody-induced increase in I(Ca(L)), respectively. In absence of prazosin, both methoxamine and the autoantibody showed a substantial enhancement in the frequency of cell contraction and that of the concomitant cytosolic and nuclear free Ca2+ variations. The subsequent addition of nifedipine, a specific L-type Ca2+ channel blocker, reversed not only the methoxamine or the autoantibody-induced effect but also completely abolished cell contraction. These results demonstrated that functional alpha1-adrenoceptors exist in both 10-day-old embryonic chick and 20-week-old human fetal hearts and that the autoantibody directed against the second extracellular loop of this type of receptors plays an important role in stimulating their activity via activation of L-type calcium channels. This loop seems to have a functional significance by being the target of alpha1-receptor agonists like methoxamine.

The Arrestin-selective Angiotensin AT1 Receptor Agonist [Sar1,Ile4,Ile8]-AngII Negatively Regulates Bradykinin B2 Receptor Signaling via AT1-B2 Receptor Heterodimers*

PubMed Central

Wilson, Parker C.; Lee, Mi-Hye; Appleton, Kathryn M.; El-Shewy, Hesham M.; Morinelli, Thomas A.; Peterson, Yuri K.; Luttrell, Louis M.; Jaffa, Ayad A.

2013-01-01

The renin-angiotensin and kallikrein-kinin systems are key regulators of vascular tone and inflammation. Angiotensin II, the principal effector of the renin-angiotensin system, promotes vasoconstriction by activating angiotensin AT1 receptors. The opposing effects of the kallikrein-kinin system are mediated by bradykinin acting on B1 and B2 bradykinin receptors. The renin-angiotensin and kallikrein-kinin systems engage in cross-talk at multiple levels, including the formation of AT1-B2 receptor heterodimers. In primary vascular smooth muscle cells, we find that the arrestin pathway-selective AT1 agonist, [Sar1,Ile4,Ile8]-AngII, but not the neutral AT1 antagonist, losartan, inhibits endogenous B2 receptor signaling. In a transfected HEK293 cell model that recapitulates this effect, we find that the actions of [Sar1,Ile4, Ile8]-AngII require the AT1 receptor and result from arrestin-dependent co-internalization of AT1-B2 heterodimers. BRET50 measurements indicate that AT1 and B2 receptors efficiently heterodimerize. In cells expressing both receptors, pretreatment with [Sar1,Ile4,Ile8]-AngII blunts B2 receptor activation of Gq/11-dependent intracellular calcium influx and Gi/o-dependent inhibition of adenylyl cyclase. In contrast, [Sar1,Ile4,Ile8]-AngII has no effect on B2 receptor ligand affinity or bradykinin-induced arrestin3 recruitment. Both radioligand binding assays and quantitative microscopy-based analysis demonstrate that [Sar1,Ile4,Ile8]-AngII promotes internalization of AT1-B2 heterodimers. Thus, [Sar1,Ile4,Ile8]-AngII exerts lateral allosteric modulation of B2 receptor signaling by binding to the orthosteric ligand binding site of the AT1 receptor and promoting co-sequestration of AT1-B2 heterodimers. Given the opposing roles of the renin-angiotensin and kallikrein-kinin systems in vivo, the distinct properties of arrestin pathway-selective and neutral AT1 receptor ligands may translate into different pharmacologic actions. PMID:23661707

The arrestin-selective angiotensin AT1 receptor agonist [Sar1,Ile4,Ile8]-AngII negatively regulates bradykinin B2 receptor signaling via AT1-B2 receptor heterodimers.

PubMed

Wilson, Parker C; Lee, Mi-Hye; Appleton, Kathryn M; El-Shewy, Hesham M; Morinelli, Thomas A; Peterson, Yuri K; Luttrell, Louis M; Jaffa, Ayad A

2013-06-28

The renin-angiotensin and kallikrein-kinin systems are key regulators of vascular tone and inflammation. Angiotensin II, the principal effector of the renin-angiotensin system, promotes vasoconstriction by activating angiotensin AT1 receptors. The opposing effects of the kallikrein-kinin system are mediated by bradykinin acting on B1 and B2 bradykinin receptors. The renin-angiotensin and kallikrein-kinin systems engage in cross-talk at multiple levels, including the formation of AT1-B2 receptor heterodimers. In primary vascular smooth muscle cells, we find that the arrestin pathway-selective AT1 agonist, [Sar(1),Ile(4),Ile(8)]-AngII, but not the neutral AT1 antagonist, losartan, inhibits endogenous B2 receptor signaling. In a transfected HEK293 cell model that recapitulates this effect, we find that the actions of [Sar(1),Ile(4), Ile(8)]-AngII require the AT1 receptor and result from arrestin-dependent co-internalization of AT1-B2 heterodimers. BRET50 measurements indicate that AT1 and B2 receptors efficiently heterodimerize. In cells expressing both receptors, pretreatment with [Sar(1),Ile(4),Ile(8)]-AngII blunts B2 receptor activation of Gq/11-dependent intracellular calcium influx and Gi/o-dependent inhibition of adenylyl cyclase. In contrast, [Sar(1),Ile(4),Ile(8)]-AngII has no effect on B2 receptor ligand affinity or bradykinin-induced arrestin3 recruitment. Both radioligand binding assays and quantitative microscopy-based analysis demonstrate that [Sar(1),Ile(4),Ile(8)]-AngII promotes internalization of AT1-B2 heterodimers. Thus, [Sar(1),Ile(4),Ile(8)]-AngII exerts lateral allosteric modulation of B2 receptor signaling by binding to the orthosteric ligand binding site of the AT1 receptor and promoting co-sequestration of AT1-B2 heterodimers. Given the opposing roles of the renin-angiotensin and kallikrein-kinin systems in vivo, the distinct properties of arrestin pathway-selective and neutral AT1 receptor ligands may translate into different pharmacologic

Effects of oxytocin on serotonin 1B agonist-induced autism-like behavior in mice.

PubMed

Lawson, Sarah K; Gray, Andrew C; Woehrle, Nancy S

2016-11-01

Social impairments in autism remain poorly understood and without approved pharmacotherapies. Novel animals models are needed to elucidate mechanisms and evaluate novel treatments for the social deficits in autism. Recently, serotonin 1B receptor (5-HT1B) agonist challenge in mice was shown to induce autism-like behaviors including perseveration, reduced prepulse inhibition, and delayed alternation deficits. However, the effects of 5-HT1B agonists on autism-related social behaviors in mice remain unknown. Here, we examine the effects of 5-HT1B agonist challenge on sociability and preference for social novelty in mice. We also examine the effects of 5-HT1B agonist treatment on average rearing duration, a putative rodent measure of non-selective attention. Non-selective attention is an associated feature of autism that is also not well understood. We show that 5-HT1B receptor activation reduces sociability, preference for social novelty, and rearing in mice. In addition, we examine the ability of oxytocin, an off-label treatment for the social impairments in autism, to reverse 5-HT1B agonist-induced social and attention deficits in mice. We show that oxytocin restores social novelty preference in mice treated with a 5-HT1B agonist. We also show that oxytocin attenuates 5-HT1B agonist-induced sociability and rearing deficits in mice. Our results suggest that 5-HT1B agonist challenge provides a useful pharmacological mouse model for aspects of autism, and implicate 5-HT1B in autism social and attention deficits. Moreover, our findings suggest that oxytocin may treat the social deficits in autism through a mechanism involving 5-HT1B. Copyright © 2016 Elsevier B.V. All rights reserved.

Retigabine diminishes the effects of acetylcholine, adrenaline and adrenergic agonists on the spontaneous activity of guinea pig smooth muscle strips in vitro.

PubMed

Apostolova, Elisaveta; Zagorchev, Plamen; Kokova, Vesela; Peychev, Lyudmil

2017-03-01

The aim of this study is to evaluate the effect of retigabine on the smooth muscle response to acetylcholine, adrenaline, α-and β-adrenoceptor agonists. We studied the change in the spontaneous smooth muscle contraction of guinea pig gastric corpus strips before and after 20-min treatment with 2μM retigabine. We also evaluated the effect of retigabine on the smooth muscle response to 10μM acetylcholine, 1 and 10μM adrenaline, 1μM methoxamine, 0.1μM p-iodoclonidine and 10μM isoproterenol. We observed a significant reduction in the effects of all studied mediators and agonists when they were added to organ baths in the presence of retigabine. Retigabine diminished the effect of acetylcholine on the spontaneous smooth muscle activity. The effect was fully antagonized by XE-991 (Kv7 channel blocker), which supports our hypothesis about the role of KCNQ channels in the registered changes. The increase in the contraction force after adding of 1μM adrenaline, methoxamine, and 0.1μM p-iodoclonidine was also significantly smaller in presence of retigabine. However, comparing the effect of 10μM adrenaline on the contractility before and after treatment with retigabine, we observed increased contractility when retigabine was present in the organ baths. A possible explanation for the observed diminished effects of mediators and receptor agonists is that the effect of retigabine on smooth muscle contractility is complex. The membrane hyperpolarization, the interaction between Kv7 channels and adrenoceptors, and the influence on signaling pathways may contribute to the summary smooth muscle response. Copyright © 2016 Elsevier B.V. All rights reserved.

Relative myotoxic and haemodynamic effects of the beta-agonists fenoterol and clenbuterol measured in conscious unrestrained rats.

PubMed

Burniston, Jatin G; Tan, Lip-Bun; Goldspink, David F

2006-11-01

The beta(2)-adrenoceptor (beta(2)-AR) agonists clenbuterol and fenoterol have similar beneficial effects in animal models of heart failure. However, large doses of clenbuterol can induce cardiomyocyte death, and it is not known which of these agents has the most favourable therapeutic profile. We have investigated the cardiotoxicity of clenbuterol and fenoterol alongside that of isoprenaline, and compared their haemodynamic effects. Wistar rats (n = 6 per group) were subcutaneously injected with each beta-agonist (0.003-3 mmol kg(-1)) or saline, and cardiomyocyte apoptosis was detected by caspase 3 immunohistochemistry. In a separate experiment, rats (n = 4) were given equivalent doses to those used in the myotoxicity studies, in a randomized cross-over design, and their blood pressure recorded via radiotelemetry. Injection of 0.3 mmol kg(-1) fenoterol or isoprenaline, but not clenbuterol, induced significant cardiomyocyte apoptosis (0.4 +/- 0.05%; P < 0.05). At 3 mmol kg(-1), all agonists induced apoptosis (fenoterol, 1.1 +/- 0.1%; isoprenaline, 0.9 +/- 0.8%; and clenbuterol, 0.4 +/- 0.07%; P < 0.05). beta(1)-Adrenoceptor antagonism (10 mg kg(-1) bisoprolol) prevented 92% (P < 0.05) of apoptosis induced by all three agonists, but clenbuterol-induced apoptosis could also be prevented by 96% (P < 0.05) by beta(2)-AR antagonism (10 mg kg(-1) ICI 118 551). Clenbuterol decreased diastolic (1.3- to 1.6-fold; P < 0.05) and systolic blood pressure (1.3-fold; P < 0.05), and doses > 0.3 mmol kg(-1) increased heart rate (1.4-fold; P < 0.05). Fenoterol increased heart rate (1.2- to 1.4-fold; P < 0.05), and doses > 0.3 mmol kg(-1) decreased diastolic blood pressure (1.3-fold; P < 0.05). In conclusion, the cardiotoxicity of fenoterol was similar to isoprenaline and greater than clenbuterol, and fenoterol had less desirable haemodynamic effects.

β1-adrenergic receptor stimulation by agonist Compound 49b restores insulin receptor signal transduction in vivo

PubMed Central

Jiang, Youde; Zhang, Qiuhua; Ye, Eun-Ah

2014-01-01

Purpose Determine whether Compound 49b treatment ameliorates retinal changes due to the lack of β2-adrenergic receptor signaling. Methods Using retinas from 3-month-old β2-adrenergic receptor-deficient mice, we treated mice with our novel β1-/β2-adrenergic receptor agonist, Compound 49b, to assess the effects of adrenergic agonists acting only on β1-adrenergic receptors due to the absence of β2-adrenergic receptors. Western blotting or enzyme-linked immunosorbent assay (ELISA) analyses were performed for β1- and β2-adrenergic receptors, as well as key insulin resistance proteins, including TNF-α, SOCS3, IRS-1Ser307, and IRTyr960. Analyses were also performed on key anti- and proapoptotic proteins: Akt, Bcl-xL, Bax, and caspase 3. Electroretinogram analyses were conducted to assess functional changes, while histological assessment was conducted for changes in retinal thickness. Results A 2-month treatment of β2-adrenergic receptor-deficient mice with daily eye drops of 1 mM Compound 49b, a novel β1- and β2-adrenergic receptor agonist, reversed the changes in insulin resistance markers (TNF-α and SOCS3) observed in untreated β2-adrenergic receptor-deficient mice, and concomitantly increased morphological integrity (retinal thickness) and functional responses (electroretinogram amplitude). These results suggest that stimulating β1-adrenergic receptors on retinal endothelial cells or Müller cells can compensate for the loss of β2-adrenergic receptor signaling on Müller cells, restore insulin signal transduction, reduce retinal apoptosis, and enhance retinal function. Conclusions Since our previous studies with β1-adrenergic receptor knockout mice confirmed that the reverse also occurs (β2-adrenergic receptor stimulation can compensate for the loss of β1-adrenergic receptor activity), it appears that increased activity in either of these pathways alone is sufficient to block insulin resistance–based retinal cell apoptosis. PMID:24966659

Impact and benefit of A(2B)-adenosine receptor agonists for the respiratory tract: mucociliary clearance, ciliary beat frequency, trachea muscle tonus and cytokine release.

PubMed

Walaschewski, Robin; Begrow, Frank; Verspohl, Eugen J

2013-01-01

Adenosine is known to induce a bronchospasm in asthma- and COPD patients. The role of A(2B) receptors was investigated with respect to several parameters of the respiratory tract: tonus of smooth muscle, ciliary beat frequency as measured by high-speed video camera connected to a microscope (both in rats) and mucociliary clearance (MCC; transport of a fluorescent dye using a microdialysis procedure) in mice.  NECA (5'-N-ethylcarboxamidoadenosine) (a non-selective adenosine receptor agonist) was able to acutely induce a contraction, which was reversed to a relaxation after repeated dosing. This relaxation was completely abolished by PSB-1115, an A(2B) receptor antagonist. IL-13 (cytokine) was not involved mediating acute contractility effects. MCC was increased by BAY 60-6583 (A(2B) receptor agonist) and NECA (counteracted by the A(2B) receptor antagonist PSB-1115). Activation of A(2B) adenosine receptors by BAY 60-6583 induced an increase of the ciliary beat frequency, which could be reduced by administration of PSB-1115. Several cytokines were increased by NECA although only some are relevant because they are not blocked by A(2B) receptor antagonism. The A(2B) receptors are involved in airway relaxation, MCC improvement and ciliary beat frequency. A(2B) receptor agonists may be of therapeutic value and should be developed. © 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.

Long-acting peptidomimergic control of gigantism caused by pituitary acidophilic stem cell adenoma.

PubMed

Maheshwari, H G; Prezant, T R; Herman-Bonert, V; Shahinian, H; Kovacs, K; Melmed, S

2000-09-01

Gigantism is caused by GH hypersecretion occurring before epiphyseal long bone closure and usually is associated with pituitary adenoma. A 15-yr-old female patient presented with accelerated growth due to a large pituitary tumor that was surgically resected to relieve pressure effects. Second surgery to remove residual tumor tissue was followed by administration of octreotide LAR, a long-acting depot somatostatin analog, together with long-acting cabergoline. Height was over the 95th percentile, with evidence of a recent growth spurt. Serum GH levels were more than 60 ng/mL (normal, <10 ng/mL) with no suppression to 75 g oral glucose, and serum PRL (>8,000 ng/mL; normal, <23 ng/mL) and insulin-like growth factor I levels (845 ng/mL; age-matched normal, 242-660 ng/mL) were elevated. Histology, immunostaining, and electron microscopy demonstrated a pituitary acidophil stem cell adenoma. Tumor tissue expressed both somatostatin receptor type 2 and dopamine receptor type 2. The Gs alpha subunit, GHRH receptor, and MEN1 genes were intact, and tumor tissue abundantly expressed pituitary tumor transforming gene (PTTG). Serum GH and PRL levels were controlled after two surgeries, and with continued cabergoline and octreotide LAR GH, PRL, and insulin-like growth factor I levels were normalized. In conclusion, administration of long-acting somatostatin analog every 4 weeks in combination with a long-acting dopamine agonist biweekly controlled biochemical parameters and accelerated growth in a patient with gigantism caused by a rare pituitary acidophil stem cell adenoma.

A review of dopamine agonist therapy in type 2 diabetes and effects on cardio-metabolic parameters.

PubMed

Lamos, E M; Levitt, D L; Munir, K M

2016-02-01

Dopamine action appears to play a role in changes that are seen in obesity, metabolic syndrome and type 2 diabetes mellitus. Bromocriptine-QR (Quick Release), a dopamine agonist, is approved for use in treatment of type 2 diabetes. It has demonstrated modest improvement in glycemic parameters, cholesterol and weight in certain cohorts. Limited data using cabergoline, a long-acting dopamine agonist, also demonstrate glycemic efficacy. Additionally, bromocriptine-QR appears to have a favorable cardiovascular risk reduction. The direct mechanism by which bromocriptine-QR, or central dopamine agonism, achieves modest glycemic control and favorable cardio-metabolic profile is unclear. This relationship appears to be more complex than the historical explanation of "resetting" the circadian clock and may further be elucidated using data in individuals with hyperprolactinemia and prolactinoma. Copyright © 2015 Primary Care Diabetes Europe. Published by Elsevier Ltd. All rights reserved.

Mixed Kappa/Mu Opioid Receptor Agonists: The 6β-Naltrexamines

PubMed Central

Cami-Kobeci, Gerta; Neal, Adrian P.; Bradbury, Faye A.; Purington, Lauren C.; Aceto, Mario D.; Harris, Louis S.; Lewis, John W.; Traynor, John R.; Husbands, Stephen M.

2011-01-01

Ligands from the naltrexamine series have consistently demonstrated agonist activity at kappa opioid receptors (KOR), with varying activity at the mu opioid receptor (MOR). Various 6β-cinnamoylamino derivatives were made with the aim of generating ligands with a KOR agonist/MOR partial agonist profile, as ligands with this activity may be of interest as treatment agents for cocaine abuse. The ligands all displayed the desired high affinity, non-selective binding in vitro and in the functional assays were high efficacy KOR agonists with some partial agonist activity at MOR. Two of the new ligands (12a, 12b) have been evaluated in vivo, with 12a acting as a KOR agonist, and therefore somewhat similar to the previously evaluated analogues 3–6, while 12b displayed predominant MOR agonist activity. PMID:19253970

Effect of partial agonist activity in beta blockers in severe angina pectoris: a double blind comparison of pindolol and atenolol.

PubMed Central

Quyyumi, A A; Wright, C; Mockus, L; Fox, K M

1984-01-01

The use of beta adrenoceptor blockade in the treatment of rest angina is controversial, and the effects on severe angina of partial agonist activity in beta blockers are unknown. Eight patients with effort angina and seven with effort and nocturnal angina and severe coronary artery disease were studied initially when they were not taking any antianginal drugs. Pindolol 5 mg thrice daily (with partial agonist activity) and atenolol 100 mg daily (without partial agonist activity) were given for five days each in a double blind randomised manner. Diaries of angina were kept and treadmill exercise testing and ambulatory ST monitoring performed during the last 48 hours of each period of treatment. Daytime and nocturnal resting heart rates and the frequency of angina were significantly reduced by atenolol compared with pindolol (p less than 0.01). The duration of exercise was significantly increased and the frequency, duration, and magnitude of daytime and nocturnal episodes of ST segment depression on ambulatory monitoring were reduced by atenolol. Reduction in resting heart rate is important in the treatment of both effort and nocturnal angina. Partial agonist activity in beta adrenoceptor antagonists may be deleterious in patients with severe angina pectoris. PMID:6148991

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

PubMed

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

2015-08-01

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.

Langerhans cells beta 2-adrenoceptors: role in migration, cytokine production, Th priming and contact hypersensitivity.

PubMed

Maestroni, Georges J M; Mazzola, Paola

2003-11-01

We showed that norepinephrine (NE) hampers IL-12 and stimulates IL-10 production via adrenoceptors (ARs) in bone marrow-derived dendritic cells (BMDC) influencing their Th priming ability. Others have shown that Langerhans cells (LC) express mRNA for beta1-, beta2- and alpha1(A)-(ARs) and that catecholamines may inhibit the antigen-presenting capability via beta2-ARs. Here, we show that also BMDC express mRNA for beta1-, beta2-, alpha2(A)- and alpha2(C)-ARs. Inhibition of IL-12 is mediated by both beta2- and alpha2(A)-ARs, while stimulation of IL-10 by beta2-ARs only. In addition, LC migration, the contact hypersensitivity response (CHS) and production of IFN-gamma and IL-2 in draining lymph node cells is increased in mice treated topically with the beta2-AR antagonist ICI 118,551 during FITC sensitization. Activation of beta2-ARs in BMDC before adoptive transfer could reduce both migration and CHS response to FITC. Finally, preincubation of BMDC with LPS in presence of the specific beta2-AR agonist salbutamol impaired their chemotactic response to CCL19 and CCL21 and this effect was neutralized by anti-IL-10 mAb. We suggest that the physiological activation of beta2-ARs in DC (LC) results in stimulation of IL-10 which in turn restrains DC (LC) migration influencing antigen presentation and the consequent CHS response.

A PET Tracer for Brain α2C Adrenoceptors, (11)C-ORM-13070: Radiosynthesis and Preclinical Evaluation in Rats and Knockout Mice.

PubMed

Arponen, Eveliina; Helin, Semi; Marjamäki, Päivi; Grönroos, Tove; Holm, Patrik; Löyttyniemi, Eliisa; Någren, Kjell; Scheinin, Mika; Haaparanta-Solin, Merja; Sallinen, Jukka; Solin, Olof

2014-07-01

We report the development of a PET tracer for α2C adrenoceptor imaging and its preliminary preclinical evaluation. α2C adrenoceptors in the human brain may be involved in various neuropsychiatric disorders, such as depression, schizophrenia, and neurodegenerative diseases. PET tracers are needed for imaging of this receptor system in vivo. High-specific-activity (11)C-ORM-13070 (1-[(S)-1-(2,3-dihydrobenzo[1,4]dioxin-2-yl)methyl]-4-(3-(11)C-methoxymethylpyridin-2-yl)-piperazine) was synthesized by (11)C-methylation of O-desmethyl-ORM-13070 with (11)C-methyl triflate, which was prepared from cyclotron-produced (11)C-methane via (11)C-methyl iodide. Rats and mice were investigated in vivo with PET and ex vivo with autoradiography. The specificity of (11)C-ORM-13070 binding to α2 adrenoceptors was demonstrated in rats pretreated with atipamezole, an α2 adrenoceptor antagonist. The α2C adrenoceptor selectivity of the tracer was determined by comparing tracer binding in wild-type and α2A- and α2AC adrenoceptor knockout (KO) mice. (11)C-ORM-13070 and its radioactive metabolites in rat plasma and brain tissue were analyzed with radio-high-performance liquid chromatography and mass spectroscopy. Human radiation dose estimates were extrapolated from rat biodistribution data. The radiochemical yield, calculated from initial cyclotron-produced (11)C-methane, was 9.6% ± 2.7% (decay-corrected to end of bombardment). The specific activity of the product was 640 ± 390 GBq/μmol (decay-corrected to end of synthesis). The radiochemical purity exceeded 99% in all syntheses. The highest levels of tracer binding were observed in the striatum and olfactory tubercle of rats and control and α2A KO mice-that is, in the brain regions known to contain the highest densities of α2C adrenoceptors. In rats pretreated with atipamezole and in α2AC KO mice, (11)C tracer binding in the striatum and olfactory tubercle was low, similar to that of the frontal cortex and thalamus, regions

Thieno[3,2-b]- and thieno[2,3-b]pyrrole bioisosteric analogues of the hallucinogen and serotonin agonist N,N-dimethyltryptamine.

PubMed

Blair, J B; Marona-Lewicka, D; Kanthasamy, A; Lucaites, V L; Nelson, D L; Nichols, D E

1999-03-25

The synthesis and biological activity of 6-[2-(N, N-dimethylamino)ethyl]-4H-thieno[3,2-b]pyrrole (3a) and 4-[2-(N, N-dimethylamino)ethyl]-6H-thieno[2,3-b]pyrrole (3b), thienopyrroles as potential bioisosteres of N,N-dimethyltryptamine (1a), are reported. Hallucinogen-like activity was evaluated in the two-lever drug discrimination paradigm using LSD- and DOI-trained rats. Neither 3a nor 3b substituted for LSD or DOI up to doses of 50 micromol/kg. By comparison, 1a fully substituted in LSD-trained rats. However, 3a and 3b fully substituted for the 5-HT1A agonist LY293284 ((-)-(4R)-6-acetyl-4-(di-n-propylamino)-1,3,4, 5-tetrahydrobenz[c,d]indole). Both 3a and 3b induced a brief "serotonin syndrome" and salivation, an indication of 5-HT1A receptor activation. At the cloned human 5-HT2A receptor 3b had about twice the affinity of 3a. At the cloned human 5-HT2B and 5-HT2C receptors, however, 3a had about twice the affinity of 3b. Therefore, thiophene lacks equivalence as a replacement for the phenyl ring in the indole nucleus of tryptamines that bind to 5-HT2 receptor subtypes and possess LSD-like behavioral effects. Whereas both of the thienopyrroles had lower affinity than the corresponding 1a at 5-HT2 receptors, 3a and 3b had significantly greater affinity than 1a at the 5-HT1A receptor. Thus, thienopyrrole does appear to serve as a potent bioisostere for the indole nucleus in compounds that bind to the serotonin 5-HT1A receptor. These differences in biological activity suggest that serotonin receptor isoforms are very sensitive to subtle changes in the electronic character of the aromatic systems of indole compounds.

Structure/function relationships of calcitonin analogues as agonists, antagonists, or inverse agonists in a constitutively activated receptor cell system.

PubMed

Pozvek, G; Hilton, J M; Quiza, M; Houssami, S; Sexton, P M

1997-04-01

The structure/function relationship of salmon calcitonin (sCT) analogues was investigated in heterologous calcitonin receptor (CTR) expression systems. sCT analogues with progressive amino-terminal truncations intermediate of sCT-(1-32) to sCT-(8-32) were examined for their ability to act as agonists, antagonists, or inverse agonists. Two CTR cell clones, B8-H10 and G12-E12, which express approximately 5 million and 25,000 C1b receptors/cell, respectively, were used for this study. The B8-H10 clone has an approximately 80-fold increase in basal levels of intracellular cAMP due to constitutive activation of the overexpressed receptor. In whole-cell competition binding studies, sCT-(1-32) was more potent than any of its amino-terminally truncated analogues in competition for 125I-sCT binding. In cAMP accumulation studies, sCT-(1-32) and modified analogues sCT-(2-32) and sCT-(3-32) had agonist activities. SDZ-216-710, with an amino-terminal truncation of four amino acids, behaved as a partial agonist/antagonist, whereas amino-terminal truncations of six or seven amino acid residues produced a 16-fold reduction in basal cAMP levels and attenuated the response to the agonist sCT-(1-32) in the constitutively active CTR system. This inverse agonist effect was insensitive to pertussis toxin inhibition. In contrast, the inverse agonist activity of these peptides was not observed in the nonconstitutively active CTR system, in which sCT analogues with amino-terminal truncations of four or more amino acids behaved as neutral competitive antagonists. These results suggest that the inverse agonist activity is mediated by stabilization of the inactive state of the receptor, which does not couple to G protein, and attenuates basal signaling initiated by ligand-independent activation of the effector adenylyl cyclase.

Interaction between alpha 2-adrenergic and angiotensin II systems in the control of glomerular hemodynamics as assessed by renal micropuncture in the rat

NASA Technical Reports Server (NTRS)

Thomson, S. C.; Gabbai, F. B.; Tucker, B. J.; Blantz, R. C.

1992-01-01

The hypothesis that renal alpha 2 adrenoceptors influence nephron filtration rate (SNGFR) via interaction with angiotensin II (AII) was tested by renal micropuncture. The physical determinants of SNGFR were assessed in adult male Munich Wistar rats 5-7 d after ipsilateral surgical renal denervation (DNX). DNX was performed to isolate inhibitory central and presynaptic alpha 2 adrenoceptors from end-organ receptors within the kidney. Two experimental protocols were employed: one to test whether prior AII receptor blockade with saralasin would alter the glomerular hemodynamic response to alpha 2 adrenoceptor stimulation with the selective agonist B-HT 933 under euvolemic conditions, and the other to test whether B-HT 933 would alter the response to exogenous AII under conditions of plasma volume expansion. In euvolemic rats, B-HT 933 caused SNGFR to decline as the result of a decrease in glomerular ultrafiltration coefficient (LpA), an effect that was blocked by saralasin. After plasma volume expansion, B-HT 933 showed no primary effect on LpA but heightened the response of arterial blood pressure, glomerular transcapillary pressure gradient, and LpA to AII. The parallel results of these converse experiments suggest a complementary interaction between renal alpha 2-adrenergic and AII systems in the control of LpA.

Role of α1-adrenoceptor subtypes in the effects of methylenedioxy methamphetamine (MDMA) on body temperature in the mouse

PubMed Central

Bexis, S; Docherty, J R

2007-01-01

Background and purpose: We have investigated the ability of α1-adrenoceptor antagonists to affect the hyperthermia produced by methylenedioxy methamphetamine (MDMA) in conscious mice. Experimental approach: Mice were implanted with temperature probes under ether anaesthesia and allowed 2 weeks recovery. MDMA (20 mg kg−1) was administered subcutaneously 30 min after vehicle or test antagonist or combination of antagonists and effects on body temperature monitored. Key results: Following vehicle, MDMA produced a hyperthermia, reaching a maximum increase of 1.8 °C at 140 min. Prazosin (0.1 mg kg−1) revealed an early significant hypothermia to MDMA of −1.94 °C. The α1A-adrenoceptor antagonist RS 100329 (0.1 mg kg−1), or the α1D-adrenoceptor antagonist BMY 7378 (0.5 mg kg−1) given alone, did not reveal a hypothermia to MDMA, but the combination of the two antagonists revealed a significant hypothermia to MDMA. The putative α1B-adrenoceptor anatagonist cyclazosin (1 mg kg−1) also revealed a significant hypothermia to MDMA, but actions of cyclazosin at the other α1-adrenoceptor subtypes cannot be excluded. Conclusions and implications: More than one subtype of α1-adrenoceptor is involved in a component of the hyperthermic response to MDMA in mouse, probably both α1A- and α1D-adrenoceptors, and removal of this α1-adrenoceptor-mediated component reveals an initial hypothermia. PMID:18037913

Bronchoprotection in conscious guinea pigs by budesonide and the NO-donating analogue, TPI 1020, alone and combined with tiotropium or formoterol

PubMed Central

Turner, DL; Ferrari, N; Ford, WR; Kidd, EJ; Nevin, B; Paquet, L; Renzi, P; Broadley, KJ

2012-01-01

BACKGROUND AND PURPOSE Inhaled corticosteroids, anticholinergics and β2-adrenoceptor agonists are frequently combined for treating chronic respiratory diseases. We examine the corticosteroid, budesonide, and novel NO-donating derivative, TPI 1020, against histamine- and methacholine-induced bronchoconstriction and whether they enhance the β2-adrenoceptor agonist formoterol or muscarinic antagonist tiotropium in conscious guinea pigs. EXPERIMENTAL APPROACH Dunkin-Hartley guinea pigs received inhaled histamine (3 mM) or methacholine (1.5 mM) and specific airway conductance (sGaw) was measured before and 15 or 75 min after treatment with budesonide, TPI 1020, tiotropium or formoterol alone or in combinations. KEY RESULTS Formoterol (0.7–10 µM) and budesonide (0.11–0.7 mM) inhibited histamine-induced bronchoconstriction and tiotropium (2–20 µM) inhibited methacholine-induced bronchoconstriction by up to 70.8 ± 16.6%, 34.9 ± 4.4% and 85.1 ± 14.3%, respectively. Formoterol (2.5 µM) or tiotropium (2 µM) alone exerted small non-significant bronchoprotection. However, when co-administered with TPI 1020 0.11 mM, which alone had no significant effect, there was significant inhibition of the bronchoconstriction (45.7 ± 12.2% and 79.7 ± 21.4%, respectively). Co-administering budesonide (0.11 mM) with tiotropium (2 µM), which alone had no effect, also significantly inhibited the methacholine bronchoconstriction (36.5 ± 13.0%), but there was no potentiation of formoterol against histamine. The NO scavenger, CPTIO, prevented the bronchoprotection by SNAPand TPI 1020. CONCLUSIONS AND IMPLICATIONS TPI 1020 potentiated the bronchoprotection by formoterol and tiotropium. Budesonide also enhanced the effects of tiotropium but not formoterol. Combination of TPI 1020 with a long-acting β2-adrenoceptor agonist or muscarinic receptor antagonist may therefore be a more potent therapeutic approach for treatment of chronic respiratory diseases. PMID:22563753

The antagonistic effect of antipsychotic drugs on a HEK293 cell line stably expressing human alpha1A1-adrenoceptors.

PubMed

Nourian, Zahra; Mulvany, Michael J; Nielsen, Karsten Bork; Pickering, Darryl S; Kristensen, Torsten

2008-10-31

Antipsychotic drugs often cause orthostatic hypotension, probably through antagonist action on resistance vessel alpha(1A)-adrenoceptors. Here we have tested this possibility directly using cells transfected with a relevant human alpha(1A)-adrenoceptor splice variant. To determine a splice variant which was relevant, we used quantitative real-time polymerase chain reaction (qPCR) to determine the prevalence in human subcutaneous small arteries of three of the five splice variants ADRA1A_v1-5, which encode functional protein: alpha(1A1)-, alpha(1A3)-, alpha(1A4)-adrenoceptors. Our statistical analysis showed higher transcription levels of alpha(1A1)- than of alpha(1A3)- and alpha(1A4)-adrenoceptors (1.6 and 5.8 times, respectively). We therefore chose to study the alpha(1A1)-adrenoceptor, and the cDNA encoding it was transfected into the Flp-In-293 (modified from HEK-293) cell line to produce a cell line stably expressing a functional form of this splice variant. The expression of recombinant alpha(1A1)-adrenoceptor subtype was confirmed by Western immunoblot analysis, and its functionality demonstrated using a Fura-2 assay by a rise in intracellular calcium concentration ([Ca(2+)](i)) when challenged with phenylephrine (EC(50)=1.61x10(-8) M). From Schild analysis, prazosin, sertindole, risperidone, and haloperidol caused a concentration-dependent, rightward shift of the cumulative concentration-response curves for phenylephrine in cells expressing human recombinant alpha(1A1)-adrenoceptors to yield pK(B) values of 8.40, 8.05, 8.26 and 7.38, respectively. In [7-methoxy-(3)H]-prazosin binding experiments, high expression was seen (B(max)=48.5+/-16.7 pmol/mg protein, +/-S.E.M.) along with high affinity binding to a single site (K(d)=0.210+/-0.034 nM). The pharmacological profiles of recombinant human alpha(1A1)-adrenoceptors in competition binding studies confirmed much higher antagonist affinity of sertindole and risperidone than haloperidol for these receptors. In

Effect of adrenaline and alpha-agonists on net rate of liquid absorption from the pleural space of rabbits.

PubMed

Zocchi, L; Raffaini, A; Agostoni, E

1997-05-01

Indirect evidence supporting a solute-coupled liquid absorption from the pleural space of rabbits has recently been provided; moreover, the beta 2-adrenoceptor agonist terbutaline has been found to increase this absorption. In this study the effect of adrenaline and alpha-adrenoceptor agonists on net rate of liquid absorption (Jnet) from albumin Ringer hydrothoraces of various sizes has been determined in anaesthetized rabbits. In hydrothoraces with adrenaline (5 x 10(-6) M) the relationship between Jnet and volume of liquid injected was displaced upwards by 0.09 ml h-1 relative to that in control hydrothoraces (P < 0.01). This displacement did not occur with lower adrenaline concentrations or after pretreatment with the beta-blocker propranolol. Hence, this increase in Jnet is mediated by stimulation of beta-receptors. It seems to be caused by an increase in solute-coupled liquid absorption, since beta-agonists inhibit lymphatic activity while, at relatively high concentrations, they may increase active transport. Conversely, the strong stimulation of lymphatic alpha-receptors that should occur with adrenaline after beta-blockade may fail to increase lymphatic drainage, because it has been shown that the increase in contraction frequency of lymphatics may be balanced by the decrease in their stroke volume. Arterial blood pressure during the hydrothoraces with adrenaline was unchanged. In hydrothoraces with the alpha 2-agonist clonidine (5 x 10(-6) M; a less potent agent than adrenaline) the slope of the relationship between Jnet and volume injected increased by 26% (P < 0.01), while its origin did not change. This increase in slope did not occur with a lower clonidine concentration or after pretreatment with the alpha-blocker phentolamine. Hence, it is caused by stimulation of alpha 2-receptors, which probably lead to an increase in lymphatic drainage related to liquid load. In hydrothoraces with the alpha 1-agonist phenylephrine (5 x 10(-6) or 10(-7) M) Jnet was

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

Choline+ is a low-affinity ligand for alpha 1-adrenoceptors.

PubMed

Unelius, L; Cannon, B; Nedergaard, J

1994-10-07

The effect of choline+, a commonly used Na+ substitute, on ligand binding to alpha 1-adrenoceptors was investigated. It was found that replacement of 25% of the Na+ in a Krebs-Ringer bicarbonate buffer with choline+ led to a 3-fold decrease in the apparent affinity of [3H]prazosin for its binding site (i.e. the alpha 1-receptor) in a membrane preparation from brown adipose tissue, while no decrease in the total number of binding sites was observed. Similar effects were seen in membrane preparations from liver and brain. In competition experiments, it was found that choline+ could inhibit [3H]prazosin binding; from the inhibition curve, an affinity (Ki) of 31 mM choline+ for the [3H]prazosin-binding site could be calculated. In fully choline(+)-substituted buffers, where the level of [3H]prazosin binding was substantially reduced, both phentolamine and norepinephrine could still compete with [3H]prazosin for its binding site, with virtually unaltered affinity; thus choline+ did not substantially affect the characteristics of those receptors to which it did not bind. Choline+ did not affect the binding characteristics of the beta 1/beta 2 radioligand [3H]CGP-12177; thus, the effect on alpha 1-receptors was not due to general, unspecific effects on the membrane preparations. It is concluded that choline+ possesses characteristics similar to those of a competitive ligand for the alpha 1-adrenoceptor; it has a low affinity but the competitive type of interaction of choline may nonetheless under experimental conditions interfere with agonist interaction with the alpha 1-receptor.

Pharmacokinetics of Mirabegron, a β3-Adrenoceptor Agonist for Treatment of Overactive Bladder, in Healthy East Asian Subjects.

PubMed

Iitsuka, Hiromi; van Gelderen, Marcel; Katashima, Masataka; Takusagawa, Shin; Sawamoto, Taiji

2015-05-01

The objective of these studies was to evaluate the pharmacokinetic profile, safety, and tolerability of mirabegron, a β3-adrenoceptor agonist for the treatment of overactive bladder, including food effects (low- or high-fat meals) and sex, in healthy East Asian subjects. In total, 5 pharmacokinetic studies of mirabegron were conducted in healthy East Asian subjects. Food effects were assessed in 3 randomized, single-dose studies in young Japanese male subjects (study 1), male and female subjects (study 2), and young Taiwanese male and female subjects (study 3). In the other 2 single- and multiple-dose studies in young Chinese male and female subjects (study 4 and study 5), mirabegron was administered as a single dose under fasted conditions. After the washout period, mirabegron was administered once daily under fed conditions for 8 days. Pharmacokinetic parameters were determined using noncompartmental methods. Safety and tolerability assessments included physical examinations, vital signs, 12-lead ECG, clinical laboratory tests (biochemistry, hematology, and urinalysis), and adverse event monitoring. After administration of single oral doses of mirabegron, exposure under fed conditions was lower than under fasted conditions in Japanese and Taiwanese subjects. In Japanese subjects, a greater reduction in mirabegron Cmax and AUC0-∞ was observed after a low-fat meal compared with a high-fat meal. In Chinese subjects, Cmax was reached at approximately 4.0 hours after single oral doses. Mirabegron accumulated 2- to 3-fold on once-daily dosing of multiple-dose relative to single-dose data. Steady state was reached within 7 days. After administration of mirabegron, mean values for Cmax and AUC in female subjects were higher than those in male subjects. Mirabegron was well tolerated in Japanese, Taiwanese, and Chinese subjects. Our studies confirm the higher exposure levels of mirabegron in female compared with male East Asian subjects as found earlier in Western

Modulation of resistance artery tone by the trace amine β-phenylethylamine: dual indirect sympathomimetic and α1-adrenoceptor blocking actions.

PubMed

Narang, Deepak; Kerr, Paul M; Lunn, Stephanie E; Beaudry, Rhys; Sigurdson, Julie; Lalies, Margaret D; Hudson, Alan L; Light, Peter E; Holt, Andrew; Plane, Frances

2014-10-01

The trace amine β-phenylethylamine (PEA) is normally present in the body at low nanomolar concentrations but can reach micromolar levels after ingestion of drugs that inhibit monoamine oxidase and primary amine oxidase. In vivo, PEA elicits a robust pressor response, but there is no consensus regarding the underlying mechanism, with both vasodilation and constriction reported in isolated blood vessels. Using functional and biochemical approaches, we found that at low micromolar concentrations PEA (1-30 μM) enhanced nerve-evoked vasoconstriction in the perfused rat mesenteric bed but at a higher concentration (100 μM) significantly inhibited these responses. The α2-adrenoceptor antagonist rauwolscine (1 µM) also enhanced nerve-mediated vasoconstriction, but in the presence of both rauwolscine (1 µM) and PEA (30 µM) together, nerve-evoked responses were initially potentiated and then showed time-dependent rundown. PEA (10 and 100 μM) significantly increased noradrenaline outflow from the mesenteric bed as determined by high-pressure liquid chromatography coupled with electrochemical detection. In isolated endothelium-denuded arterial segments, PEA (1 µM to 1 mM) caused concentration-dependent reversal of tone elicited by the α1-adrenoceptor agonists noradrenaline (EC50 51.69 ± 10.8 μM; n = 5), methoxamine (EC50 68.21 ± 1.70 μM; n = 5), and phenylephrine (EC50 67.74 ± 16.72 μM; n = 5) but was ineffective against tone induced by prostaglandin F2 α or U46619 (9,11-dideoxy-9α,11α-methanoepoxyprostaglandin F2 α). In rat brain homogenates, PEA displaced binding of both [(3)H]prazosin (Ki ≈ 25 μM) and [(3)H]rauwolscine (Ki ≈ 1.2 μM), ligands for α1- and α2-adrenoceptors, respectively. These data provide the first demonstration that dual indirect sympathomimetic and α1-adrenoceptor blocking actions underlie the vascular effects of PEA in resistance arteries. Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics.

Is Slow-Onset Long-Acting Monoamine Transport Blockade to Cocaine as Methadone is to Heroin? Implication for Anti-Addiction Medications

PubMed Central

Peng, Xiao-Qing; Xi, Zheng-Xiong; Li, Xia; Spiller, Krista; Li, Jie; Chun, Lauren; Wu, Kuo-Ming; Froimowitz, Mark; Gardner, Eliot L

2010-01-01

The success of methadone in treating opiate addiction has suggested that long-acting agonist therapies may be similarly useful for treating cocaine addiction. Here, we examined this hypothesis, using the slow-onset long-acting monoamine reuptake inhibitor 31,345, a trans-aminotetralin analog, in a variety of addiction-related animal models, and compared it with methadone's effects on heroin's actions in the same animal models. Systemic administration of 31,345 produced long-lasting enhancement of electrical brain-stimulation reward (BSR) and extracellular nucleus accumbens (NAc) dopamine (DA). Pretreatment with 31,345 augmented cocaine-enhanced BSR, prolonged cocaine-enhanced NAc DA, and produced a long-term (24-48 h) reduction in cocaine self-administration rate without obvious extinction pattern, suggesting an additive effect of 31,345 with cocaine. In contrast, methadone pretreatment not only dose-dependently inhibited heroin self-administration with an extinction pattern but also dose-dependently inhibited heroin-enhanced BSR and NAc DA, suggesting functional antagonism by methadone of heroin's actions. In addition, 31,345 appears to possess significant abuse liability, as it produces dose-dependent enhancement of BSR and NAc DA, maintains a low rate of self-administration behavior, and dose-dependently reinstates drug-seeking behavior. In contrast, methadone only partially maintains self-administration with an extinction pattern, and fails to induce reinstatement of drug-seeking behavior. These findings suggest that 31,345 is a cocaine-like slow-onset long-acting monoamine transporter inhibitor that may act as an agonist therapy for cocaine addiction. However, its pattern of action appears to be significantly different from that of methadone. Ideal agonist substitutes for cocaine should fully emulate methadone's actions, that is, functionally antagonizing cocaine's action while blocking monoamine transporters to augment synaptic DA. PMID:20827272

Does lower dose of long-acting triptorelin maintain pituitary suppression and produce good live birth rate in long down-regulation protocol for in-vitro fertilization?

PubMed

Chen, Xin; Feng, Shu-xian; Guo, Ping-ping; He, Yu-xia; Liu, Yu-dong; Ye, De-sheng; Chen, Shi-ling

2016-04-01

The effects of pituitary suppression with one-third depot of long-acting gonadotropin-releasing hormone (GnRH) agonist in GnRH agonist long protocol for in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) were investigated. A retrospective cohort study was performed on 3186 cycles undergoing IVF/ICSI with GnRH agonist long protocol in a university-affiliated infertility center. The pituitary was suppressed with depot triptorelin of 1.25 mg or 1.875 mg. There was no significant difference in live birth rate between 1.25 mg triptorelin group and 1.875 mg triptorelin group (41.2% vs. 43.7%). The mean luteinizing hormone (LH) level on follicle-stimulating hormone (FSH) starting day was significantly higher in 1.25 mg triptorelin group. The mean LH level on the day of human chorionic gonadotrophin (hCG) administration was slightly but statistically higher in 1.25 mg triptorelin group. There was no significant difference in the total FSH dose between the two groups. The number of retrieved oocytes was slightly but statistically less in 1.25 mg triptorelin group than in 1.875 mg triptorelin group (12.90±5.82 vs. 13.52±6.97). There was no significant difference in clinical pregnancy rate between the two groups (50.5% vs. 54.5%). It was suggested that one-third depot triptorelin can achieve satisfactory pituitary suppression and produce good live birth rates in a long protocol for IVF/ICSI.

Identification of novel selective V2 receptor non-peptide agonists.

PubMed

Del Tredici, Andria L; Vanover, Kim E; Knapp, Anne E; Bertozzi, Sine M; Nash, Norman R; Burstein, Ethan S; Lameh, Jelveh; Currier, Erika A; Davis, Robert E; Brann, Mark R; Mohell, Nina; Olsson, Roger; Piu, Fabrice

2008-10-30

Peptides with agonist activity at the vasopressin V(2) receptor are used clinically to treat fluid homeostasis disorders such as polyuria and central diabetes insipidus. Of these peptides, the most commonly used is desmopressin, which displays poor bioavailability as well as potent activity at the V(1b) receptor, with possible stress-related adverse effects. Thus, there is a strong need for the development of small molecule chemistries with selective V(2) receptor agonist activity. Using the functional cell-based assay Receptor Selection and Amplification Technology (R-SAT((R))), a screening effort identified three small molecule chemotypes (AC-94544, AC-88324, and AC-110484) with selective agonist activity at the V(2) receptor. One of these compounds, AC-94544, displayed over 180-fold selectivity at the V(2) receptor compared to related vasopressin and oxytocin receptors and no activity at 28 other G protein-coupled receptors (GPCRs). All three compounds also showed partial agonist activity at the V(2) receptor in a cAMP accumulation assay. In addition, in a rat model of central diabetes insipidus, AC-94544 was able to significantly reduce urine output in a dose-dependent manner. Thus, AC-94544, AC-88324, and AC-110484 represent novel opportunities for the treatment of disorders associated with V(2) receptor agonist deficiency.

Combination inhaled steroid and long-acting beta₂-agonist in addition to tiotropium versus tiotropium or combination alone for chronic obstructive pulmonary disease.

PubMed

Rojas-Reyes, Maria Ximena; García Morales, Olga M; Dennis, Rodolfo J; Karner, Charlotta

2016-06-06

The long-acting bronchodilator tiotropium and single-inhaler combination therapy of inhaled corticosteroids and long-acting beta2-agonists (ICS/LABA) are commonly used for maintenance treatment of patients with chronic obstructive pulmonary disease (COPD). Combining these treatments, which have different mechanisms of action, may be more effective than administering the individual components. To assess relative effects of the following treatments on markers of exacerbations, symptoms, quality of life and lung function in patients with COPD.• Tiotropium plus LABA/ICS versus tiotropium.• Tiotropium plus LABA/ICS versus LABA/ICS. We searched the Cochrane Airways Group Specialised Register of Trials (April 2015), ClinicalTrials.gov (www.ClinicalTrials.gov), the World Health Organization (WHO) trials portal and reference lists of relevant articles. We included parallel, randomised controlled trials (RCTs) lasting three months or longer conducted to compare ICS and LABA combination therapy in addition to inhaled tiotropium versus tiotropium alone or combination therapy alone. We independently assessed trials for inclusion, then extracted data on trial quality and outcome results. We contacted study authors to ask for additional information. We collected trial information on adverse effects. Tiotropium plus LABA/ICS versus tiotropiumWe included six studies (1902 participants) with low risk of bias that compared tiotropium in addition to inhaled corticosteroid and long-acting beta2-agonist combination therapy versus tiotropium alone. Investigators found no statistically significant differences in mortality between treatments (odds ratio (OR) 1.80, 95% confidence interval (CI) 0.55 to 5.91; two studies; 961 participants), a reduction in all-cause hospitalisations with the use of combined therapy (tiotropium + LABA/ICS) (OR 0.61, 95% CI 0.40 to 0.92; two studies; 961 participants; number needed to treat for an additional beneficial outcome (NNTB) 19.7, 95% CI 10.75 to

Downregulation of kinin B1 receptor function by B2 receptor heterodimerization and signaling.

PubMed

Zhang, Xianming; Brovkovych, Viktor; Zhang, Yongkang; Tan, Fulong; Skidgel, Randal A

2015-01-01

Signaling through the G protein-coupled kinin receptors B1 (kB1R) and B2 (kB2R) plays a critical role in inflammatory responses mediated by activation of the kallikrein-kinin system. The kB2R is constitutively expressed and rapidly desensitized in response to agonist whereas kB1R expression is upregulated by inflammatory stimuli and it is resistant to internalization and desensitization. Here we show that the kB1R heterodimerizes with kB2Rs in co-transfected HEK293 cells and natively expressing endothelial cells, resulting in significant internalization and desensitization of the kB1R response in cells pre-treated with kB2R agonist. However, pre-treatment of cells with kB1R agonist did not affect subsequent kB2R responses. Agonists of other G protein-coupled receptors (thrombin, lysophosphatidic acid) had no effect on a subsequent kB1R response. The loss of kB1R response after pretreatment with kB2R agonist was partially reversed with kB2R mutant Y129S, which blocks kB2R signaling without affecting endocytosis, or T342A, which signals like wild type but is not endocytosed. Co-endocytosis of the kB1R with kB2R was dependent on β-arrestin and clathrin-coated pits but not caveolae. The sorting pathway of kB1R and kB2R after endocytosis differed as recycling of kB1R to the cell surface was much slower than that of kB2R. In cytokine-treated human lung microvascular endothelial cells, pre-treatment with kB2R agonist inhibited kB1R-mediated increase in transendothelial electrical resistance (TER) caused by kB1R stimulation (to generate nitric oxide) and blocked the profound drop in TER caused by kB1R activation in the presence of pyrogallol (a superoxide generator). Thus, kB1R function can be downregulated by kB2R co-endocytosis and signaling, suggesting new approaches to control kB1R signaling in pathological conditions. Copyright © 2014 Elsevier Inc. All rights reserved.

Downregulation of kinin B1 receptor function by B2 receptor heterodimerization and signaling

PubMed Central

Zhang, Xianming; Brovkovych, Viktor; Zhang, Yongkang; Tan, Fulong; Skidgel, Randal A.

2014-01-01

Signaling through the G protein-coupled kinin receptors B1 (kB1R) and B2 (kB2R) plays a critical role in inflammatory responses mediated by activation of the kallikrein-kinin system. The kB2R is constitutively expressed and rapidly desensitized in response to agonist whereas kB1R expression is upregulated by inflammatory stimuli and it is resistant to internalization and desensitization. Here we show that the kB1R heterodimerizes with kB2Rs in co-transfected HEK293 cells and natively expressing endothelial cells, resulting in significant internalization and desensitization of the kB1R response in cells pre-treated with kB2R agonist. However, pre-treatment of cells with kB1R agonist did not affect subsequent kB2R responses. Agonists of other G protein-coupled receptors (thrombin, lysophosphatidic acid) had no effect on a subsequent kB1R response. The loss of kB1R response after pretreatment with kB2R agonist was partially reversed with kB2R mutant Y129S, which blocks kB2R signaling without affecting endocytosis, or T342A, which signals like wild type but is not endocytosed. Co-endocytosis of the kB1R with kB2R was dependent on β-arrestin and clathrin-coated pits but not caveolae. The sorting pathway of kB1R and kB2R after endocytosis differed as recycling of kB1R to the cell surface was much slower than that of kB2R. In cytokine-treated human lung microvascular endothelial cells, pre-treatment with kB2R agonist inhibited kB1R-mediated increase in transendothelial electrical resistance (TER) caused by kB1R stimulation (to generate nitric oxide) and blocked the profound drop in TER caused by kB1R activation in the presence of pyrogallol (a superoxide generator). Thus, kB1R function can be downregulated by kB2R co-endocytosis and signaling, suggesting new approaches to control kB1R signaling in pathological conditions. PMID:25289859

Dexmedetomidine: a novel sedative-analgesic agent

PubMed Central

2001-01-01

Since the first report of clonidine, an α2-adrenoceptor agonist, the indications for this class of drugs have continued to expand. In December 1999, dexmedetomidine was approved as the most recent agent in this group and was introduced into clinical practice as a short-term sedative (<24 hours). α2-Adrenoceptor agonists have several beneficial actions during the perioperative period. They decrease sympathetic tone, with attenuation of the neuroendocrine and hemodynamic responses to anesthesia and surgery; reduce anesthetic and opioid requirements; and cause sedation and analgesia. They allow psychomotoric function to be preserved while letting the patient rest comfortably. With this combination of effects, α2-adrenoceptor agonists may offer benefits in the prophylaxis and adjuvant treatment of perioperative myocardial ischemia. Furthermore, their role in pain management and regional anesthesia is expanding. Side effects consist of mild to moderate cardiovascular depression, with slight decreases in blood pressure and heart rate. The development of new, more selective α2-adrenoceptor agonists with improved side effect profiles may provide a new concept for the administration of perioperative anesthesia and analgesia. This review aims to give background information to improve understanding of the properties and applications of the novel α2-adrenoceptor agonist, dexmedetomidine. PMID:16369581

Small-molecule-biased formyl peptide receptor agonist compound 17b protects against myocardial ischaemia-reperfusion injury in mice

PubMed Central

Qin, Cheng Xue; May, Lauren T.; Li, Renming; Cao, Nga; Rosli, Sarah; Deo, Minh; Alexander, Amy E.; Horlock, Duncan; Bourke, Jane E.; Yang, Yuan H.; Stewart, Alastair G.; Kaye, David M.; Du, Xiao-Jun; Sexton, Patrick M.; Christopoulos, Arthur; Gao, Xiao-Ming; Ritchie, Rebecca H.

2017-01-01

Effective treatment for managing myocardial infarction (MI) remains an urgent, unmet clinical need. Formyl peptide receptors (FPR) regulate inflammation, a major contributing mechanism to cardiac injury following MI. Here we demonstrate that FPR1/FPR2-biased agonism may represent a novel therapeutic strategy for the treatment of MI. The small-molecule FPR1/FPR2 agonist, Compound 17b (Cmpd17b), exhibits a distinct signalling fingerprint to the conventional FPR1/FPR2 agonist, Compound-43 (Cmpd43). In Chinese hamster ovary (CHO) cells stably transfected with human FPR1 or FPR2, Compd17b is biased away from potentially detrimental FPR1/2-mediated calcium mobilization, but retains the pro-survival signalling, ERK1/2 and Akt phosphorylation, relative to Compd43. The pathological importance of the biased agonism of Cmpd17b is demonstrable as superior cardioprotection in both in vitro (cardiomyocytes and cardiofibroblasts) and MI injury in mice in vivo. These findings reveal new insights for development of small molecule FPR agonists with an improved cardioprotective profile for treating MI. PMID:28169296

A Deletion Variant of the α2b-Adrenoceptor Modulates the Stress-Induced Shift from "Cognitive" to "Habit" Memory.

PubMed

Wirz, Lisa; Wacker, Jan; Felten, Andrea; Reuter, Martin; Schwabe, Lars

2017-02-22

Stress induces a shift from hippocampus-based "cognitive" toward dorsal striatum-based "habitual" learning and memory. This shift is thought to have important implications for stress-related psychopathologies, including post-traumatic stress disorder (PTSD). However, there is large individual variability in the stress-induced bias toward habit memory, and the factors underlying this variability are completely unknown. Here we hypothesized that a functional deletion variant of the gene encoding the α2b-adrenoceptor ( ADRA2B ), which has been linked to emotional memory processes and increased PTSD risk, modulates the stress-induced shift from cognitive toward habit memory. In two independent experimental studies, healthy humans were genotyped for the ADRA2B deletion variant. After a stress or control manipulation, participants completed a dual-solution learning task while electroencephalographic (Study I) or fMRI measurements (Study II) were taken. Carriers compared with noncarriers of the ADRA2B deletion variant exhibited a significantly reduced bias toward habit memory after stress. fMRI results indicated that, whereas noncarriers of the ADRA2B deletion variant showed increased functional connectivity between amygdala and putamen after stress, this increase in connectivity was absent in carriers of the deletion variant, who instead showed overall enhanced connectivity between amygdala and entorhinal cortex. Our results indicate that a common genetic variation of the noradrenergic system modulates the impact of stress on the balance between cognitive and habitual memory systems, most likely via altered amygdala orchestration of these systems. SIGNIFICANCE STATEMENT Stressful events have a powerful effect on human learning and memory. Specifically, accumulating evidence suggests that stress favors more rigid dorsal striatum-dependent habit memory, at the expense of flexible hippocampus-dependent cognitive memory. Although this shift may have important implications

Use of a potent, long acting agonist of gonadotropin-releasing hormone in the treatment of precocious puberty.

PubMed

Boepple, P A; Mansfield, M J; Wierman, M E; Rudlin, C R; Bode, H H; Crigler, J F; Crawford, J D; Crowley, W F

1986-02-01

Studies utilizing the administration of GnRH in various GnRH-deficient models have revealed the critical importance of the dose and mode of delivery of this releasing factor in determining the subsequent pituitary response. Chronic administration of long acting GnRH agonists (GnRHa), like continuous infusion of high doses of the native peptide, results in suppression of pituitary gonadotropin secretion. This selective and reversible suppression of gonadotropin secretion suggested several therapeutic applications for these analogs, particularly in the treatment of central precocious puberty (CPP), a disorder for which the previously available therapies lacked uniform efficacy and were associated with potential side effects. In our series, 74 children with CPP have been treated during the last 5 yr with the potent GnRH agonist, [D-Trp6, Pro9-ethylamide(NEt)]GnRH. Having selected a dose and route of administration that produced uniform suppression of spontaneous and stimulated pituitary gonadotropin secretion, GnRHa therapy resulted in a fall of gonadal sex steroid levels into the prepubertal range, a halting or regression of secondary sexual development, and a complete cessation of menses. Growth velocity slowed during therapy, with this slowing more pronounced during prolonged treatment periods and among those patients with more advanced chronological and skeletal ages. Skeletal maturation was retarded to a greater degree than linear growth, with resultant increases in the predictions for adult stature. Moreover, these benefits have been achieved in the absence of significant side effects. Complete reversal of the suppression of gonadarche has followed discontinuation of therapy; however, patterns of growth and skeletal maturation after discontinuation of GnRHa administration remain to be characterized. Thus, the impact of GnRHa therapy on final height must await further longitudinal study. The selective nature of GnRHa suppression of gonadarche also permits an

Effect of 7,8-Dihydroxyflavone, a Small-Molecule TrkB Agonist, on Emotional Learning

PubMed Central

Andero, Raul; Heldt, Scott A.; Ye, Keqiang; Liu, Xia; Armario, Antonio; Ressler, Kerry J.

2013-01-01

Objective Despite increasing awareness of the many important roles played by brain-derived neurotrophic factor (BDNF) activation of TrkB, a fuller understanding of this system and the use of potential TrkB-acting therapeutic agents has been limited by the lack of any identified small-molecule TrkB agonists that fully mimic the actions of BDNF at brain TrkB receptors in vivo. However, 7,8-dihydroxyflavone (7,8-DHF) has recently been identified as a specific TrkB agonist that crosses the blood-brain barrier after oral or intra-peritoneal administration. The authors combined pharmacological, biochemical, and behavioral approaches in a preclinical study examining the role of 7,8-DHF in modulating emotional memory in mice. Method The authors first examined the ability of systemic 7,8-DHF to activate TrkB receptors in the amygdala. They then examined the effects of systemic 7,8-DHF on acquisition and extinction of conditioned fear, using specific and well-characterized BDNF-dependent learning paradigms in several models using naive mice and mice with prior traumatic stress exposure. Results Amygdala TrkB receptors, which have previously been shown to be required for emotional learning, were activated by systemic 7,8-DHF (at 5 mg/kg i.p.). 7,8-DHF enhanced both the acquisition of fear and its extinction. It also appeared to rescue an extinction deficit in mice with a history of immobilization stress. Conclusions These data suggest that 7,8-DHF may be an excellent agent for use in understanding the effects of TrkB activation in learning and memory paradigms and may be attractive for use in reversing learning and extinction deficits associated with psychopathology. PMID:21123312

Design and Discovery of Functionally Selective Serotonin 2C (5-HT2C) Receptor Agonists.

PubMed

Cheng, Jianjun; McCorvy, John D; Giguere, Patrick M; Zhu, Hu; Kenakin, Terry; Roth, Bryan L; Kozikowski, Alan P

2016-11-10

On the basis of the structural similarity of our previous 5-HT 2C agonists with the melatonin receptor agonist tasimelteon and the putative biological cross-talk between serotonergic and melatonergic systems, a series of new (2,3-dihydro)benzofuran-based compounds were designed and synthesized. The compounds were evaluated for their selectivity toward 5-HT 2A , 5-HT 2B , and 5-HT 2C receptors in the calcium flux assay with the ultimate goal to generate selective 5-HT 2C agonists. Selected compounds were studied for their functional selectivity by comparing their transduction efficiency at the G protein signaling pathway versus β-arrestin recruitment. The most functionally selective compound (+)-7e produced weak β-arrestin recruitment and also demonstrated less receptor desensitization compared to serotonin in both calcium flux and phosphoinositide (PI) hydrolysis assays. We report for the first time that selective 5-HT 2C agonists possessing weak β-arrestin recruitment can produce distinct receptor desensitization properties.

Long-acting muscarinic antagonist use in adults with asthma: real-life prescribing and outcomes of add-on therapy with tiotropium bromide.

PubMed

Price, David; Kaplan, Alan; Jones, Rupert; Freeman, Daryl; Burden, Anne; Gould, Shuna; von Ziegenweidt, Julie; Ali, Muzammil; King, Christine; Thomas, Mike

2015-01-01

Randomized controlled trials indicate that addition of a long-acting muscarinic antagonist (LAMA) such as tiotropium may improve asthma control and reduce exacerbation risk in patients with poorly controlled asthma, but broader clinical studies are needed to investigate the effectiveness of LAMA in real-life asthma care. Medical records of adults with asthma (aged ≥18 years) prescribed tiotropium were obtained from the UK Optimum Patient Care Research Database for the period 2001-2013. Patients diagnosed with chronic obstructive pulmonary disease were excluded, but no other clinical exclusions were applied. Two primary outcomes were compared in the year before (baseline) and the year after (outcome) addition of tiotropium: exacerbations (asthma-related hospital emergency department attendance or inpatient admission, or acute oral corticosteroid course) and acute respiratory events (exacerbation or antibiotic prescription with lower respiratory consultation). Secondary outcomes included lung function test results and short-acting β2 agonist usage. The Wilcoxon signed-rank test was used for variables measured on the interval scale, the marginal homogeneity test for categorized variables, and the paired t-test for lung function indices. Of the 2,042 study patients, 83% were prescribed an inhaled corticosteroid and 68% a long-acting β2 agonist during the baseline year; 67% were prescribed both. Comparing baseline and outcome years, the percentage of patients having at least one exacerbation decreased from 37% to 27% (P<0.001) and the percentage having at least one acute respiratory event decreased from 58% to 47% (P<0.001). There were no significant changes in lung function, and usage of short-acting β2 agonists (in salbutamol/albuterol equivalents) increased from a median (interquartile range) of 274 (110, 548) to 329 (110, 603) μg/day (P=0.01). In this real-life asthma population, addition of LAMA therapy was associated with significant decreases in the

Effects of age and hypertension on α1-adrenoceptors in the major source arteries of the rat bladder and penis.

PubMed

Yono, Makoto; Tanaka, Takanori; Tsuji, Shigeki; Irie, Shin; Sakata, Yukikuni; Otani, Masayuki; Yoshida, Masaki; Latifpour, Jamshid

2011-11-16

α(1)-Adrenoceptors regulate blood pressure, regional vascular resistance and tissue blood flow. As aging and hypertension may impact pelvic arterial blood flow resulting in bladder and penile dysfunction, we investigated effects of age and hypertension on α(1)-adrenoceptors in the major source arteries of the rat bladder and penis. Using radioligand receptor binding, real-time reverse transcription-polymerase chain reaction (RT-PCR) and fluorescent microsphere infusion techniques, we compared 3 and 22-month-old male Fischer rats, and male normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs). Twenty-two-month-old rats and SHRs had significantly higher total α(1)-adrenoceptor density in the internal iliac artery and lower blood flow to the bladder and penis than 3-month-old and WKY rats, respectively. RT-PCR data showed an age and hypertension related increase in the expression of α(1B)-adrenoceptor mRNA in the internal iliac, vesical and internal pudendal arteries and a switch from α(1A) predominance in 3-month-old and WKY rats to α(1B)>α(1A) in 22-month-old rats and SHRs. Our data indicate the presence of age and hypertension related alterations in vascular α(1)-adrenoceptor subtype distribution and in blood flow to the rat bladder and penis. These findings suggest that pharmacological blockade of the vascular α(1B)-adrenoceptor, which could increase pelvic blood flow, may contribute to the improvement of bladder and penile dysfunctions in animal models for aging and hypertension. Copyright © 2011 Elsevier B.V. All rights reserved.

Lack of α2C-Adrenoceptor Results in Contrasting Phenotypes of Long Bones and Vertebra and Prevents the Thyrotoxicosis-Induced Osteopenia

PubMed Central

Cruz Grecco Teixeira, Marilia Bianca; Martins, Gisele Miyamura; Miranda-Rodrigues, Manuela; De Araújo, Iasmin Ferreira; Oliveira, Ricardo; Brum, Patrícia Chakur; Azevedo Gouveia, Cecilia Helena

2016-01-01

A series of studies have demonstrated that activation of the sympathetic nervous system (SNS) causes osteopenia via β2-adrenoceptor (β2-AR) signaling. However, in a recent study, we found an unexpected and generalized phenotype of high bone mass in female mice with chronic sympathetic hyperactivity, due to double gene inactivation of adrenoceptors that negatively regulate norepinephrine release, α2A-and α2C-AR (α2A/2C-AR-/-). These findings suggest that β2-AR is not the single adrenoceptor involved in bone turnover regulation and show that α2-AR signaling may also mediate the SNS actions in the skeleton. In addition, we found that α2A/2C-AR-/- animals are resistant to the thyrotoxicosis-induced osteopenia, suggesting that thyroid hormone (TH), when in supraphysiological levels, interacts with the SNS to control bone mass and structure, and that this interaction may also involve α2-AR signaling. In the present study, to further investigate these hypotheses and to discriminate the roles of α2-AR subtypes, we have evaluated the bone phenotype of mice with the single gene inactivation of α2C-AR subtype, which mRNA expression was previously shown to be down regulated by triiodothyronine (T3). A cohort of 30 day-old female α2CAR-/- mice and their wild-type (WT) controls were treated with a supraphysiological dose of T3 for 30 or 90 days, which induced a thyrotoxic state in both mouse lineages. The micro-computed tomographic (μCT) analysis showed that α2C-AR-/- mice present lower trabecular bone volume (BV/TV) and number (Tb.N), and increased trabecular separation (Tb.Sp) in the femur compared with WT mice; which was accompanied by decreased bone strength (determined by the three-point bending test) in the femur and tibia. The opposite was observed in the vertebra, where α2C-AR-/- mice show increased BV/TV, Tb.N and trabecular thickness (Tb.Th), and decreased Tb.Sp, compared with WT animals. In spite of the contrasting bone phenotypes of the femur and L5

Lack of α2C-Adrenoceptor Results in Contrasting Phenotypes of Long Bones and Vertebra and Prevents the Thyrotoxicosis-Induced Osteopenia.

PubMed

Cruz Grecco Teixeira, Marilia Bianca; Martins, Gisele Miyamura; Miranda-Rodrigues, Manuela; De Araújo, Iasmin Ferreira; Oliveira, Ricardo; Brum, Patrícia Chakur; Azevedo Gouveia, Cecilia Helena

2016-01-01

A series of studies have demonstrated that activation of the sympathetic nervous system (SNS) causes osteopenia via β2-adrenoceptor (β2-AR) signaling. However, in a recent study, we found an unexpected and generalized phenotype of high bone mass in female mice with chronic sympathetic hyperactivity, due to double gene inactivation of adrenoceptors that negatively regulate norepinephrine release, α2A-and α2C-AR (α2A/2C-AR-/-). These findings suggest that β2-AR is not the single adrenoceptor involved in bone turnover regulation and show that α2-AR signaling may also mediate the SNS actions in the skeleton. In addition, we found that α2A/2C-AR-/- animals are resistant to the thyrotoxicosis-induced osteopenia, suggesting that thyroid hormone (TH), when in supraphysiological levels, interacts with the SNS to control bone mass and structure, and that this interaction may also involve α2-AR signaling. In the present study, to further investigate these hypotheses and to discriminate the roles of α2-AR subtypes, we have evaluated the bone phenotype of mice with the single gene inactivation of α2C-AR subtype, which mRNA expression was previously shown to be down regulated by triiodothyronine (T3). A cohort of 30 day-old female α2CAR-/- mice and their wild-type (WT) controls were treated with a supraphysiological dose of T3 for 30 or 90 days, which induced a thyrotoxic state in both mouse lineages. The micro-computed tomographic (μCT) analysis showed that α2C-AR-/- mice present lower trabecular bone volume (BV/TV) and number (Tb.N), and increased trabecular separation (Tb.Sp) in the femur compared with WT mice; which was accompanied by decreased bone strength (determined by the three-point bending test) in the femur and tibia. The opposite was observed in the vertebra, where α2C-AR-/- mice show increased BV/TV, Tb.N and trabecular thickness (Tb.Th), and decreased Tb.Sp, compared with WT animals. In spite of the contrasting bone phenotypes of the femur and L5

The tremorolytic action of beta-adrenoceptor blockers in essential, physiological and isoprenaline-induced tremor is mediated by beta-adrenoceptors located in a deep peripheral compartment.

PubMed

Abila, B; Wilson, J F; Marshall, R W; Richens, A

1985-10-01

The effects of intravenous propranolol 100 micrograms kg-1, sotalol 500 micrograms kg-1, timolol 7.8 micrograms kg-1, atenolol 125 micrograms kg-1 and placebo on essential, physiological and isoprenaline-induced tremor were studied. These beta-adrenoceptor blocker doses produced equal reduction of standing-induced tachycardia in essential tremor patients. Atenolol produced significantly less reduction of essential and isoprenaline-induced tremor than the non-selective drugs, confirming the importance of beta 2-adrenoceptor blockade in these effects. Propranolol and sotalol produced equal maximal inhibition of isoprenaline-induced tremor but propranolol was significantly more effective in reducing essential tremor. The rate of development of the tremorolytic effect was similar in essential, physiological and isoprenaline-induced tremors but all tremor responses developed significantly more slowly than the heart rate responses. It is proposed that these results indicate that the tremorolytic activity of beta-adrenoceptor blockers in essential, physiological and isoprenaline-induced tremor is exerted via the same beta 2-adrenoceptors located in a deep peripheral compartment which is thought to be in the muscle spindles.

The tremorolytic action of beta-adrenoceptor blockers in essential, physiological and isoprenaline-induced tremor is mediated by beta-adrenoceptors located in a deep peripheral compartment.

PubMed Central

Abila, B; Wilson, J F; Marshall, R W; Richens, A

1985-01-01

The effects of intravenous propranolol 100 micrograms kg-1, sotalol 500 micrograms kg-1, timolol 7.8 micrograms kg-1, atenolol 125 micrograms kg-1 and placebo on essential, physiological and isoprenaline-induced tremor were studied. These beta-adrenoceptor blocker doses produced equal reduction of standing-induced tachycardia in essential tremor patients. Atenolol produced significantly less reduction of essential and isoprenaline-induced tremor than the non-selective drugs, confirming the importance of beta 2-adrenoceptor blockade in these effects. Propranolol and sotalol produced equal maximal inhibition of isoprenaline-induced tremor but propranolol was significantly more effective in reducing essential tremor. The rate of development of the tremorolytic effect was similar in essential, physiological and isoprenaline-induced tremors but all tremor responses developed significantly more slowly than the heart rate responses. It is proposed that these results indicate that the tremorolytic activity of beta-adrenoceptor blockers in essential, physiological and isoprenaline-induced tremor is exerted via the same beta 2-adrenoceptors located in a deep peripheral compartment which is thought to be in the muscle spindles. PMID:2866785

Aripiprazole once-monthly long-acting injectable for the treatment of schizophrenia.

PubMed

Potkin, Steven G; Preda, Adrian

2016-01-01

Patient non-adherence increases the risk for relapse and the long-term care of schizophrenia. Long-acting injectable (LAI) antipsychotics can decrease this risk by ensuring adherence. An extended formulation, aripiprazole 400 mg once-monthly (AOM 400) LAI (AOM LAI), received regulatory approval in the year 2013 for the treatment of schizophrenia. AOM LAI is the first dopamine D2 partial agonist available in a long-acting formulation for the treatment of schizophrenia. This review covers data on the efficacy and tolerability/safety of AOM LAI. AOM LAI is a lyophilized powder of aripiprazole, with an elimination half-life of 29.9 - 46.5 days, allowing for a 4-week injection interval. Antipsychotic efficacy was documented in a 12-week double-blind trial (n = 340) and in two maintenance-of-effect trials: a 38-week trial (n = 662) and a 52-week trial (n = 403). The side effect profile is similar to that of oral aripiprazole. Adverse events (≥5% and at least twice that for placebo) were typically mild or moderate and did not lead to discontinuation: increased weight, akathisia, injection site pain and sedation. The 400 mg dose is tolerated by >90% of patients. Injection does not require additional training of health personnel or post-injection observation. AOM LAI is an efficacious and well-tolerated antipsychotic treatment for schizophrenia.

Prescription of oral short-acting beta 2-agonist for asthma in non-resource poor settings: A national study in Malaysia.

PubMed

Chin, May Chien; Sivasampu, Sheamini; Khoo, Ee Ming

2017-01-01

Use of oral short-acting beta 2-agonist (SABA) persists in non-resource poor countries despite concerns for its lower efficacy and safety. Utilisation and reasons for such use is needed to support the effort to discourage the use of oral SABA in asthma. This study examined the frequency of oral short-acting Beta 2-agonist (SABA) usage in the management of asthma in primary care and determined correlates of its usage. Data used were from the 2014 National Medical Care Survey in Malaysia, a nationally representative survey of primary care encounters (weighted n = 325818). Using methods of analysis of data for complex surveys, we determined the frequency of asthma diagnosis in primary care and the rate of asthma medication prescription, which includes oral SABA. Multivariate logistic regression models were built to assess associations with the prescription of oral SABA. A weighted estimate of 9241 encounters presented to primary care with asthma in 2014. The mean age of the patients was 39.1 years. The rate of oral SABA, oral steroids, inhaled SABA and inhaled corticosteroids prescriptions were 33, 33, 50 and 23 per 100 asthma encounters, respectively. It was most commonly used in patients with the age ranged between 20 to less than 40 years. Logistic regression models showed that there was a higher odds of oral SABA usage in the presence of respiratory infection, prescription of oral corticosteroids and in the private sector. Oral SABA use in asthma is found to be common in a non- resource poor setting and its use could be attributed to a preference for oral medicines along undesirable clinical practices within a fragmented health system.

Prescription of oral short-acting beta 2-agonist for asthma in non-resource poor settings: A national study in Malaysia

PubMed Central

Sivasampu, Sheamini; Khoo, Ee Ming

2017-01-01

Objective Use of oral short-acting beta 2-agonist (SABA) persists in non-resource poor countries despite concerns for its lower efficacy and safety. Utilisation and reasons for such use is needed to support the effort to discourage the use of oral SABA in asthma. This study examined the frequency of oral short-acting Beta 2-agonist (SABA) usage in the management of asthma in primary care and determined correlates of its usage. Methods Data used were from the 2014 National Medical Care Survey in Malaysia, a nationally representative survey of primary care encounters (weighted n = 325818). Using methods of analysis of data for complex surveys, we determined the frequency of asthma diagnosis in primary care and the rate of asthma medication prescription, which includes oral SABA. Multivariate logistic regression models were built to assess associations with the prescription of oral SABA. Results A weighted estimate of 9241 encounters presented to primary care with asthma in 2014. The mean age of the patients was 39.1 years. The rate of oral SABA, oral steroids, inhaled SABA and inhaled corticosteroids prescriptions were 33, 33, 50 and 23 per 100 asthma encounters, respectively. It was most commonly used in patients with the age ranged between 20 to less than 40 years. Logistic regression models showed that there was a higher odds of oral SABA usage in the presence of respiratory infection, prescription of oral corticosteroids and in the private sector. Conclusion Oral SABA use in asthma is found to be common in a non- resource poor setting and its use could be attributed to a preference for oral medicines along undesirable clinical practices within a fragmented health system. PMID:28662193

Detection of receptor ligands by monitoring selective stabilization of a Renilla luciferase-tagged, constitutively active mutant, G-protein-coupled receptor

PubMed Central

Ramsay, Douglas; Bevan, Nicola; Rees, Stephen; Milligan, Graeme

2001-01-01

The wild-type β2-adrenoceptor and a constitutively active mutant of this receptor were C-terminally tagged with luciferase from the sea pansy Renilla reniformis. C-terminal addition of Renilla luciferase did not substantially alter the levels of expression of either form of the receptor, the elevated constitutive activity of the mutant β2-adrenoceptor nor the capacity of isoprenaline to elevate cyclic AMP levels in intact cells expressing these constructs. Treatment of cells expressing constitutively active mutant β2-adrenoceptor-Renilla luciferase with antagonist/inverse agonist ligands resulted in upregulation of levels of this polypeptide which could be monitored by the elevated luciferase activity. The pEC50 for ligand-induced luciferase upregulation and ligand affinity to bind the receptor were highly correlated. Similar upregulation could be observed following sustained treatment with agonist ligands. These effects were only observed at a constitutively active mutant of the β2-adrenoceptor. Co-expression of the wild-type β2-adrenoceptor C-terminally tagged with the luciferase from Photinus pyralis did not result in ligand-induced upregulation of the levels of activity of this luciferase. Co-expression of the constitutively active mutant β2-adrenoceptor-Renilla luciferase and an equivalent mutant of the α1b-adrenoceptor C-terminally tagged with green fluorescent protein allowed pharmacological selectivity of adrenoceptor antagonists to be demonstrated. This approach offers a sensitive and convenient means, which is amenable to high throughput analysis, to monitor ligand binding to a constitutively active mutant receptor. As no prior knowledge of receptor ligands is required this approach may be suitable to identify ligands at orphan G protein-coupled receptors. PMID:11350868

A Long-Acting BMP-2 Release System Based on Poly(3-hydroxybutyrate) Nanoparticles Modified by Amphiphilic Phospholipid for Osteogenic Differentiation

PubMed Central

Peng, Xiaochun; Chen, Yunsu; Li, Yamin; Wang, Yiming

2016-01-01

We explored a novel poly(3-hydroxybutyrate) (PHB) nanoparticle loaded with hydrophilic recombinant human BMP-2 with amphiphilic phospholipid (BPC-PHB NP) for a rapid-acting and long-acting delivery system of BMP-2 for osteogenic differentiation. The BPC-PHB NPs were prepared by a solvent evaporation method and showed a spherical particle with a mean particle size of 253.4 nm, mean zeta potential of −22.42 mV, and high entrapment efficiency of 77.18%, respectively. For BPC-PHB NPs, a short initial burst release of BMP-2 from NPs in 24 h was found and it has steadily risen to reach about 80% in 20 days for in vitro test. BPC-PHB NPs significantly reduced the burst release of BMP-2, as compared to that of PHB NPs loading BMP-2 without PL (B-PHB NPs). BPC-PHB NPs maintained the content of BMP-2 for a long-term osteogenic differentiation. The OCT-1 cells with BPC-PHB NPs have high ALP activity in comparison with others. The gene markers for osteogenic differentiation were significantly upregulated for sample with BPC-PHB NPs, implying that BPC-PHB NPs can be used as a rapid-acting and long-acting BMP-2 delivery system for osteogenic differentiation. PMID:27379249

Interactions of nitric oxide with α2 -adrenoceptors within the locus coeruleus underlie the facilitation of inhibitory avoidance memory by agmatine.

PubMed

Shelkar, Gajanan P; Gakare, Sukanya G; Chakraborty, Suwarna; Dravid, Shashank M; Ugale, Rajesh R

2016-09-01

Agmatine, a putative neurotransmitter, plays a vital role in learning and memory. Although it is considered an endogenous ligand of imidazoline receptors, agmatine exhibits high affinity for α-adrenoceptors, NOS and NMDA receptors. These substrates within the locus coeruleus (LC) are critically involved in learning and memory processes. The hippocampus and LC of male Wistar rat were stereotaxically cannulated for injection. Effects of agmatine, given i.p. or intra-LC, on acquisition, consolidation and retrieval of inhibitory avoidance (IA) memory were measured. The NO donor S-nitrosoglutathione, non-specific (L-NAME) and specific NOS inhibitors (L-NIL, 7-NI, L-NIO), the α2 -adrenoceptor antagonist (yohimbine) or the corresponding agonist (clonidine) were injected intra-LC before agmatine. Intra-hippocampal injections of the NMDA antagonist, MK-801 (dizocilpine), were used to modify the memory enhancing effects of agmatine, SNG and yohimbine. Expression of tyrosine hydroxylase (TH) and eNOS in the LC was assessed immunohistochemically. Agmatine (intra-LC or i.p.) facilitated memory retrieval in the IA test. S-nitrosoglutathione potentiated, while L-NAME and L-NIO decreased, these effects of agmatine. L-NIL and 7-NI did not alter the effects of agmatine. Yohimbine potentiated, whereas clonidine attenuated, effects of agmatine within the LC. The effects of agmatine, S-nitrosoglutathione and yohimbine were blocked by intra-hippocampal MK-801. Agmatine increased the population of TH- and eNOS-immunoreactive elements in the LC. The facilitation of memory retrieval in the IA test by agmatine is probably mediated by interactions between eNOS, NO and noradrenergic pathways in the LC. © 2016 The British Pharmacological Society.

Agemone mexicana flavanones; apposite inverse agonists of the β2-adrenergic receptor in asthma treatment.

PubMed

Eniafe, Gabriel O; Metibemu, Damilohun S; Omotuyi, Olaposi I; Ogunleye, Adewale J; Inyang, Olumide K; Adelakun, Niyi S; Adeniran, Yakubu O; Adewumi, Bamidele; Enejoh, Ojochenemi A; Osunmuyiwa, Joseph O; Shodehinde, Sidiqat A; Oyeneyin, Oluwatoba E

2018-01-01

Asthma is an inflammatory disease of the airway that poses a major threat to human health. With increase industrialization in the developed and developing countries, the incidence of asthma is on the rise. The β2-adrenergic receptor is an important target in designing anti-asthmatic drugs. The synthetic agonists of the β2-adrenergic receptor used over the years proved effective, but with indispensable side effects, thereby limiting their therapeutic use on a long-term scale. Inverse agonists of this receptor, although initially contraindicated, had been reported to have long-term beneficial effects. Phytochemicals from Agemone mexicana were screened against the human β2-adrenergic receptor in the agonist, inverse agonist, covalent agonist, and the antagonist conformations. Molecular docking of the phyto-constituents showed that the plant constituents bind better to the inverse agonist bound conformation of the protein, and revealed two flavanones; eriodictyol and hesperitin, with lower free energy (ΔG) values and higher affinities to the inverse agonist bound receptor than the co-crystallized ligand. Eriodictyol and hesperitin bind with the glide score of -10.684 and - 9.958 kcal/mol respectively, while the standard compound ICI-118551, binds with glide score of -9.503 kcal/mol. Further interaction profiling at the protein orthosteric site and ADME/Tox screening confirmed the drug-like properties of these compounds.

Identification and characterization of (/sup 3/H)-rauwolscine binding to alpha2-adrenoceptors in the canine saphenous vein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gout, B.

1988-01-01

The biochemical exploration of the alpha2-adrenergic receptors was investigated in the canine saphenous vein using the highly selective alpha2-adrenergic antagonist rauwolscine as a tritiated ligand. Following an enzymatic digestive pretreatment, the authors isolated a purified smooth muscle cell membranes fraction from saphenous veins in quantity sufficient to permit them to study the venous alpha2-adrenoreceptor content. The binding of tritiated rauwolscine was rapid, specific, saturable and reversible. The presence of high affinity sites with a density of binding Bmax of 125.2 /+ -/ 43.1 fmol/mg protein was demonstrated on a unique class of non interacting sites. The kinetically derived Kd wasmore » 1.28 nM, in good agreement with the value obtained from saturation isotherms. The pharmacological profile of these sites was assessed by the comparison of the potency of alpha-adrenergic agonists and antagonists to inhibit 1 nM (/sup 3/H)-rauwolscine. Their efficacy was respectively: rauwolscine > phentolamine > RX 781094 > clonidine >> prazosin > (-)-phenylephrine > (-)-noradrenaline. The results showed that (/sup 3/H)-rauwolscine bound specifically to sites in their membranal preparation, which had the pharmacological characteristics of the alpha2-adrenoceptors. The correlation between biochemical and pharmacological data revealed the usefulness of binding methods in the further study of adrenergic mechanisms in the canine saphenous vein.« less

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.

[Side effects of treatment with the long-acting gonadorelin agonist triptorelin in a case of paraphilia].

PubMed

Hoogeveen, J H; van der Veer, E

2007-01-01

A 35-year-old man with a paraphilia was treated with long-acting gonadorelin. The desired result was reduced preoccupation with sexuality, but there were various side effects including a serious amount of bone loss. We believe that more attention should be given to the adverse effects of long-term treatment with triptorelin. In our view the drug regimen needs to be revised.

Multiple mechanisms underlying the long duration of action of thienorphine, a novel partial opioid agonist for the treatment of addiction.

PubMed

Yu, Gang; Li, Shu-Hui; Cui, Meng-Xun; Yan, Ling-Di; Yong, Zheng; Zhou, Pei-Lan; Su, Rui-Bin; Gong, Ze-Hui

2014-03-01

It is considered that a long-acting therapy would be advantageous in the treatment of addiction. In a search for novel buprenorphine analogues, thienorphine was demonstrated to be an extremely long-acting orally active partial opioid agonist. This study explored the mechanisms underlying the long-lasting effects of thienorphine. The binding kinetics of [(3) H]thienorphine were measured in membrane preparations expressing cloned rat opioid receptors. Flow cytometric analysis was used to determine the effect of thienorphine on the surface opioid receptor number. The long-lasting effects of thienorphine were also confirmed at the tissue level and in vivo. At 37°C, [(3) H]thienorphine showed rapid association with μ- and κ-opioid receptors, while its dissociation was sluggish and biphasic (K-1 = 0.21 min(-1) , K-2 = 0.0078 min(-1) for the μ-receptor; K-1 = 0.17 min(-1) , K-2 = 0.0042 min(-1) for the κ-receptor). Treatment with thienorphine for 24, 48, and 72 h downregulated surface μ-receptor in a dose- and time-dependent manner. The inhibitory effect of thienorphine on guinea pig ileum persisted for more than 120 min after prolonged washing. In vivo, thienorphine exhibited significant antagonism of morphine-induced antinociception for more than 7 days. These results indicate that multiple factors, including persistent receptor occupation and enhanced receptor downregulation, may contribute to the long-lasting effects of thienorphine that would be beneficial for its application in addiction treatment. © 2013 John Wiley & Sons Ltd.

Involvement of α₂-adrenoceptors, imidazoline, and endothelin-A receptors in the effect of agmatine on morphine and oxycodone-induced hypothermia in mice.

PubMed

Bhalla, Shaifali; Andurkar, Shridhar V; Gulati, Anil

2013-10-01

Potentiation of opioid analgesia by endothelin-A (ET(A)) receptor antagonist, BMS182874, and imidazoline receptor/α₂-adrenoceptor agonists such as clonidine and agmatine are well known. It is also known that agmatine blocks morphine hyperthermia in rats. However, the effect of agmatine on morphine or oxycodone hypothermia in mice is unknown. The present study was carried out to study the role of α₂-adrenoceptors, imidazoline, and ET(A) receptors in morphine and oxycodone hypothermia in mice. Body temperature was determined over 6 h in male Swiss Webster mice treated with morphine, oxycodone, agmatine, and combination of agmatine with morphine or oxycodone. Yohimbine, idazoxan, and BMS182874 were used to determine involvement of α₂-adrenoceptors, imidazoline, and ET(A) receptors, respectively. Morphine and oxycodone produced significant hypothermia that was not affected by α₂-adrenoceptor antagonist yohimbine, imidazoline receptor/α₂ adrenoceptor antagonist idazoxan, or ET(A) receptor antagonist, BMS182874. Agmatine did not produce hypothermia; however, it blocked oxycodone but not morphine-induced hypothermia. Agmatine-induced blockade of oxycodone hypothermia was inhibited by idazoxan and yohimbine. The blockade by idazoxan was more pronounced compared with yohimbine. Combined administration of BMS182874 and agmatine did not produce changes in body temperature in mice. However, when BMS182874 was administered along with agmatine and oxycodone, it blocked agmatine-induced reversal of oxycodone hypothermia. This is the first report demonstrating that agmatine does not affect morphine hypothermia in mice, but reverses oxycodone hypothermia. Imidazoline receptors and α₂-adrenoceptors are involved in agmatine-induced reversal of oxycodone hypothermia. Our findings also suggest that ET(A) receptors may be involved in blockade of oxycodone hypothermia by agmatine. © 2012 The Authors Fundamental and Clinical Pharmacology © 2012 Société Française de