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Chew WS, Ong WY. Regulation of Calcium-Independent Phospholipase A2 Expression by Adrenoceptors and Sterol Regulatory Element Binding Protein-Potential Crosstalk Between Sterol and Glycerophospholipid Mediators. Mol Neurobiol 2014; 53:500-517. [PMID: 25482049 DOI: 10.1007/s12035-014-9026-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 11/21/2014] [Indexed: 01/02/2023]
Abstract
Calcium-independent phospholipase A2 (iPLA2) is an 85-kDa enzyme that releases docosahexaenoic acid (DHA) from glycerophospholipids. DHA can be metabolized to resolvins and neuroprotectins that have anti-inflammatory properties and effects on neural plasticity. Recent studies show an important role of prefrontal cortical iPLA2 in hippocampo-prefrontal cortical LTP and antidepressant-like effect of the norepinephrine reuptake inhibitor (NRI) antidepressant, maprotiline. In this study, we elucidated the cellular mechanisms through which stimulation of adrenergic receptors could lead to increased iPLA2 expression. Treatment of SH-SY5Y neuroblastoma cells with maprotiline, another tricyclic antidepressant with noradrenaline reuptake inhibiting properties, nortriptyline, and the adrenergic receptor agonist, phenylephrine, resulted in increased iPLA2β mRNA expression. This increase was blocked by inhibitors to alpha-1 adrenergic receptor, mitogen-activated protein (MAP) kinase or extracellular signal-regulated kinase (ERK) 1/2, and sterol regulatory element-binding protein (SREBP). Maprotiline and phenylephrine induced binding of SREBP-2 to sterol regulatory element (SRE) region on the iPLA2 promoter, as determined by electrophoretic mobility shift assay (EMSA). Together, results indicate that stimulation of adrenoreceptors causes increased iPLA2 expression via MAP kinase/ERK 1/2 and SREBP, and suggest a possible mechanism for effect of CNS noradrenaline on neural plasticity and crosstalk between sterol and glycerophospholipid mediators, that may play a role in physiological or pathophysiological processes in the brain and other organs.
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Affiliation(s)
- Wee-Siong Chew
- Department of Anatomy, National University of Singapore, Singapore, 119260, Singapore
| | - Wei-Yi Ong
- Department of Anatomy, National University of Singapore, Singapore, 119260, Singapore. .,Neurobiology and Ageing Research Programme, National University of Singapore, Singapore, 119260, Singapore.
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Kurko D, Kapui Z, Nagy J, Lendvai B, Kolok S. Analysis of functional selectivity through G protein-dependent and -independent signaling pathways at the adrenergic α(2C) receptor. Brain Res Bull 2014; 107:89-101. [PMID: 25080296 DOI: 10.1016/j.brainresbull.2014.07.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 07/15/2014] [Accepted: 07/17/2014] [Indexed: 01/01/2023]
Abstract
Although G protein-coupled receptors (GPCRs) are traditionally categorized as Gs-, Gq-, or Gi/o-coupled, their signaling is regulated by multiple mechanisms. GPCRs can couple to several effector pathways, having the capacity to interact not only with more than one G protein subtype but also with alternative signaling or effector proteins such as arrestins. Moreover, GPCR ligands can have different efficacies for activating these signaling pathways, a characteristic referred to as biased agonism or functional selectivity. In this work our aim was to detect differences in the ability of various agonists acting at the α2C type of adrenergic receptors (α2C-ARs) to modulate cAMP accumulation, cytoplasmic Ca(2+) release, β-arrestin recruitment and receptor internalization. A detailed comparative pharmacological characterization of G protein-dependent and -independent signaling pathways was carried out using adrenergic agonists (norepinephrine, phenylephrine, brimonidine, BHT-920, oxymetazoline, clonidine, moxonidine, guanabenz) and antagonists (MK912, yohimbine). As initial analysis of agonist Emax and EC50 values suggested possible functional selectivity, ligand bias was quantified by applying the relative activity scale and was compared to that of the endogenous agonist norepinephrine. Values significantly different from 0 between pathways indicated an agonist that promoted different level of activation of diverse effector pathways most likely due to the stabilization of a subtly different receptor conformation from that induced by norepinephrine. Our results showed that a series of agonists acting at the α2C-AR displayed different degree of functional selectivity (bias factors ranging from 1.6 to 36.7) through four signaling pathways. As signaling via these pathways seems to have distinct functional and physiological outcomes, studying all these stages of receptor activation could have further implications for the development of more selective therapeutics with improved efficacy and/or fewer side effects.
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Affiliation(s)
- Dalma Kurko
- Pharmacological and Drug Safety Research, Gedeon Richter Plc., Budapest, Hungary.
| | - Zoltán Kapui
- Pharmacological and Drug Safety Research, Gedeon Richter Plc., Budapest, Hungary
| | - József Nagy
- Pharmacological and Drug Safety Research, Gedeon Richter Plc., Budapest, Hungary
| | - Balázs Lendvai
- Pharmacological and Drug Safety Research, Gedeon Richter Plc., Budapest, Hungary
| | - Sándor Kolok
- Pharmacological and Drug Safety Research, Gedeon Richter Plc., Budapest, Hungary
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Dexamethasone in the presence of desipramine enhances MAPK/ERK1/2 signaling possibly via its interference with β-arrestin. J Neural Transm (Vienna) 2013; 121:289-98. [PMID: 24132698 DOI: 10.1007/s00702-013-1099-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 10/05/2013] [Indexed: 01/07/2023]
Abstract
Antidepressant medication is the standard treatment for major depression disorder (MDD). However, the response to these treatments is often incomplete and many patients remain refractory. In the present study, we show that the glucocorticoid receptor (GR) agonist dexamethasone (DEX) increased MAPK/ERK1/2 signaling in the presence of the noradrenergic antidepressant, desipramine (DMI), while no such effect was induced by DEX or DMI alone in human neuroblastoma SH-SY5Y cells. This enhancement was dependent on the activation of both α(2) adrenergic receptors (AR) and GR. The timing of MAPK/ERK1/2 activation as well as DEX-induced reduction in membranous α(2) AR suggests the involvement of a β-arrestin-dependent mechanism. In line with the latter, DEX increased cytosolic and decreased membranous levels of β-arrestin. Concomitantly, DEX induced a time-dependent increase in cytosolic α(2) AR-β-arrestin interaction and a decrease in β-arrestin interaction with Mdm2 E3 ubiquitin ligase. All of these effects of DEX were prevented by the GR antagonist RU486. Our data suggest an additional intracellular role for DEX, in which activation of GR interferes with the trafficking and degradation of β-arrestin-α2c-AR complex. We suggest that such an interaction in the presence of DMI can enhance MAPK/ERK1/2 signaling, a key player in neural plasticity and neurogenesis processes, which is impaired in MDD, while stimulated by antidepressants.
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Yaniv SP, Lucki A, Klein E, Ben-Shachar D. Dexamethasone enhances the norepinephrine-induced ERK/MAPK intracellular pathway possibly via dysregulation of the α2-adrenergic receptor: Implications for antidepressant drug mechanism of action. Eur J Cell Biol 2010; 89:712-22. [DOI: 10.1016/j.ejcb.2010.05.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Revised: 05/16/2010] [Accepted: 05/17/2010] [Indexed: 11/25/2022] Open
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Kurko D, Bekes Z, Gere A, Baki A, Boros A, Kolok S, Bugovics G, Nagy J, Szombathelyi Z, Ignácz-Szendrei G. Comparative pharmacology of adrenergic alpha(2C) receptors coupled to Ca(2+) signaling through different Galpha proteins. Neurochem Int 2009; 55:467-75. [PMID: 19426776 DOI: 10.1016/j.neuint.2009.04.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Revised: 04/24/2009] [Accepted: 04/28/2009] [Indexed: 10/20/2022]
Abstract
Adrenergic alpha(1), alpha(2) and beta receptors are members of the G-protein-coupled receptor families (GPCRs) mediating physiological responses to adrenaline (epinephrine) and noradrenaline (norepinephrine). Since GPCRs are major targets for potential therapeutic agents, development of robust, reliable and cost effective functional screening methods for these receptors is in the focus of pharmacological research. For this reason, the aim of the present study was to develop an intracellular calcium assay for investigating the pharmacology of the alpha(2C) type of adrenergic receptors (alpha(2C)-AR). Although activation of alpha(2C)-AR is not linked to calcium mobilization, co-expression of these receptors with the chimeric Galpha(qi5) protein, containing the five carboxyl-terminal amino acids from G(i), or promiscuosus Galpha(16) protein can divert receptor signaling to the G(q) pathway generating Ca(2+) release from intracellular stores. In order to assess the functional potency of alpha(2)-AR agonists and antagonists, we established a fluorometric Ca(2+) assay using cell lines stably and constitutively co-expressing alpha(2C)-AR and Galpha(qi5) or Galpha(16) proteins (Galpha(qi5)/alpha(2C) and Galpha(16)/alpha(2C)). As part of the pharmacological characterization, we measured the changes in cytoplasmic Ca(2+) levels due to activation of the chimeric Galpha(qi5) or Galpha(16) coupled recombinant alpha(2C) receptors as a function of increasing concentration of several agonists (noradrenaline, brimonidine, oxymetazoline, clonidine, moxonidine) and antagonists (MK912, yohimbine). The binding affinities of alpha(2)-AR agonist and antagonists and the inhibition of the forskolin-stimulated cAMP accumulation in alpha(2C)-AR expressing cells were also measured. These results confirmed that the Galpha(qi5)/alpha(2C) and Galpha(16)/alpha(2C) recombinant systems can be useful for modelling the native G(i)-coupled system. Our results indicate that a plate-reader based fluorometric Ca(2+) assay may be suitable in high-throughput screening for alpha(2C)-AR ligands as well.
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Affiliation(s)
- Dalma Kurko
- Pharmacological and Drug Safety Research, Budapest, Hungary.
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Yaniv SP, Ben-Shachar D, Klein E. Norepinephrine–glucocorticoids interaction does not annul the opposite effects of the individual treatments on cellular plasticity in neuroblastoma cells. Eur J Pharmacol 2008; 596:14-24. [DOI: 10.1016/j.ejphar.2008.08.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Revised: 07/27/2008] [Accepted: 08/08/2008] [Indexed: 11/25/2022]
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Donnici L, Tiraboschi E, Tardito D, Musazzi L, Racagni G, Popoli M. Time-dependent biphasic modulation of human BDNF by antidepressants in neuroblastoma cells. BMC Neurosci 2008; 9:61. [PMID: 18601743 PMCID: PMC2483719 DOI: 10.1186/1471-2202-9-61] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Accepted: 07/05/2008] [Indexed: 11/10/2022] Open
Abstract
Background Recent rodent studies reported that antidepressant treatments affect the expression of brain-derived neurotrophic factor (BDNF) mRNA in a way that is dependent on treatment duration, by selective modulation of different BDNF transcripts. However, no data are available for the human BDNF gene. We studied the effect of different antidepressants on BDNF mRNA expression in human neuroblastoma SH-SY5Y cells. Results Cultured cells were treated with the antidepressants fluoxetine, reboxetine and desipramine for different time lengths (6, 24, 48 hours). Expression of total BDNF mRNA was analyzed by reverse transcription PCR and levels of different BDNF transcripts were detected by hemi-nested PCR with specific primers. Short-term treatment (6 hours) with reboxetine or desipramine reduced total BDNF, whereas long-term treatment (48 hours) significantly increased total BDNF mRNA levels. These changes were accounted for by differential regulation of BDNF IV and VIa/b transcripts. Fluoxetine showed no significant effects. Conclusion This is the first study showing biphasic changes in the expression of total and specific BDNF transcripts in human cells following antidepressant treatments. These findings suggest that biphasic induction of BDNF by antidepressants could be a feature common to rodents and humans and encourage the use of SH-SY5Y cells as a tool for investigation of drug effects on human genes.
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Affiliation(s)
- Lorena Donnici
- Center of Neuropharmacology, Department of Pharmacological Sciences and Center of Excellence on Neurodegenerative Diseases, University of Milano, Italy.
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Bawa-Khalfe T, Altememi GF, Mandyam CD, Schwarz LA, Eikenburg DC, Standifer KM. The presence of beta2-adrenoceptors sensitizes alpha2A-adrenoceptors to desensitization after chronic epinephrine treatment. BMC Pharmacol 2007; 7:16. [PMID: 18096057 PMCID: PMC2234403 DOI: 10.1186/1471-2210-7-16] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2007] [Accepted: 12/20/2007] [Indexed: 11/23/2022] Open
Abstract
Background In addition to the regulation of blood pressure, α2- and β-adrenoceptor (AR) subtypes play an important role in the modulation of noradrenergic neurotransmission in the human CNS and PNS. Several studies suggest that the α2-AR responsiveness in cells and tissues after chronic epinephrine (EPI) or norepinephrine (NE) exposure may vary, depending on the β-AR activity present there. Recently, we reported that in BE(2)-C human neuroblastoma cells (endogenously expressing α2A- and β2-AR), chronic EPI treatment (300 nM) produced a dramatic β-adrenoceptor-dependent desensitization of the α2A-AR response. The aim of this study is to determine if stable addition of a β2-AR to a second neuroblastoma cell line (SH-SY5Y), that normally expresses only α2A-ARs that are not sensitive to 300 nM EPI exposure, would suddenly render α2A-ARs in that cell line sensitive to treatment with the same EPI concentration. Methods These studies employed RT-PCR, receptor binding and inhibition of cAMP accumulation to confirm α2-AR subtype expression. Stable clones of SH-SY5Y cells transfected to stably express functional β2-ARs (SHβ2AR4) were selected to compare sensitivity of α2-AR to EPI in the presence or absence of β2-ARs. Results A series of molecular, biochemical and pharmacological studies indicated that the difference between the cell lines could not be attributed to α2-AR heterogeneity. We now report that after transfection of functional β2-AR into SH-SY5Y cells (SHβ2AR4), chronic treatment with modest levels of EPI desensitizes the α2A-AR. This effect results from a β2-AR dependent down-regulation of native α2A-ARs by EPI accompanied by enhanced translocation of GRK2 and GRK3 to the membrane (required for GRK-mediated phosphorylation of agonist-occupied receptors). Conclusion This study further supports the hypothesis that the presence of the β-AR renders the α2A-AR more susceptible to desensitization with physiological levels of EPI.
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Affiliation(s)
- Tasneem Bawa-Khalfe
- Research Center for Cardiovascular Diseases, Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, The University of Texas-Houston Health Science Center, Houston, TX, USA.
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Fischer W, Neubert RHH, Brandsch M. Clonidine accumulation in human neuronal cells. Eur J Pharm Sci 2007; 32:291-5. [PMID: 17869491 DOI: 10.1016/j.ejps.2007.08.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Revised: 08/06/2007] [Accepted: 08/07/2007] [Indexed: 11/25/2022]
Abstract
After transport across several epithelial barriers including the blood-brain barrier, clonidine interacts with alpha(2)-adrenergic receptors and imidazoline binding sites in the brain. We hypothesized that neuronal cells take up clonidine thereby removing the drug from the extracellular fluid compartment. Uptake of [(3)H]clonidine into SH-SY5Y neuroblastoma cells was linear for up to 1 min, unaffected by inside directed Na(+) or Cl(-) gradients but strongly inhibited by an outside pH of 6.0. The cells accumulated [(3)H]clonidine 50-70-fold uphill against a concentration gradient. Unlabeled clonidine, guanabenz, imipramine, diphenhydramine, maprotiline, quinine and the endogenous monoamine phenylethylamine (2 mM) strongly inhibited the [(3)H]clonidine uptake by 60-95%. Tetraethylammonium, choline and N-methyl-4-phenylpyridinium had no effect. The accumulation at pH 7.5 was saturable with an apparent Michaelis-Menten constant (K(t)) of 0.7 mM. We conclude that SH-SY5Y cells not only bind clonidine to extracellular receptors but also take up the drug rapidly by a specific and concentrative mechanism.
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Affiliation(s)
- Wiebke Fischer
- Membrane Transport Group, Biozentrum, Martin-Luther-University Halle-Wittenberg, Weinbergweg 22, D-06120 Halle, Germany
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Moncada A, Cendán CM, Baeyens JM, Del Pozo E. Inhibitors of serine/threonine protein phosphatases antagonize the antinociception induced by agonists of alpha 2 adrenoceptors and GABAB but not kappa-opioid receptors in the tail flick test in mice. Pain 2005; 114:212-20. [PMID: 15733647 DOI: 10.1016/j.pain.2004.12.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2004] [Revised: 12/01/2004] [Accepted: 12/13/2004] [Indexed: 11/22/2022]
Abstract
We previously reported that serine/threonine protein phosphatases (PPs) play a role in the antinociception induced by the mu-opioid receptor agonist morphine. In this study we evaluated the possible involvement of PPs on the antinociception induced by agonists of others G protein-coupled receptors in the tail flick test in mice. The subcutaneous administration of clonidine (0.25-4 mg/kg), baclofen (2-32 mg/kg) or U50,488H (2-16 mg/kg) (agonists of alpha(2) adrenoceptors, GABA(B) and kappa-opioid receptors, respectively) produced dose-dependent antinociception. The antinociceptive effects of clonidine and baclofen were antagonized in a dose-dependent way by the protein phosphatase inhibitors okadaic acid (0.001-10 pg/mouse, i.c.v.) and cantharidin (0.001-10 ng/mouse, i.c.v.), and okadaic acid was 1000 times more potent than cantharidin in producing this effect. The effects of these drugs appear to be specifically due to the blockade of PPs, since L-norokadaone (an analogue of okadaic acid that has no effect on PPs) did not modify clonidine- or baclofen-induced antinociception over the wide range of doses used (0.001-1000 pg/mouse, i.c.v.). On the other hand, the antinociception induced by activation of kappa-opioid receptors with U50,488H was not modified by okadaic acid or cantharidin. In conclusion, our data support the idea that serine/threonine PPs are differentially involved in the antinociceptive effects of several agonists of G protein-coupled receptors in mice.
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Affiliation(s)
- Ana Moncada
- Department of Pharmacology and Neurosciences Institute, School of Medicine, University of Granada, Avenida de Madrid 12, E-18012 Granada, Spain
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Corboz MR, Varty LM, Rizzo CA, Mutter JC, Rivelli MA, Wan Y, Umland S, Qiu H, Jakway J, McCormick KD, Berlin M, Hey JA. Pharmacological characterization of alpha 2-adrenoceptor-mediated responses in pig nasal mucosa. ACTA ACUST UNITED AC 2004; 23:208-19. [PMID: 15084187 DOI: 10.1111/j.1474-8673.2003.00298.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
1. Pig nasal mucosal strips were incubated with alpha-adrenoceptor antagonists followed by alpha2-adrenoceptor agonist concentration-response curves. 2. Contractions elicited by the alpha2-adrenoceptor agonists BHT-920 (pD2 = 6.16 +/- 0.07), UK 14,304 (pD2 = 6.89 +/- 0.13) and PGE-6201204 (pD2 = 7.12 +/- 0.21) were blocked by the alpha2-adrenoceptor antagonist yohimbine (0.1 microm). In contrast, the alpha1-adrenoceptor antagonist prazosin (0.03 microm) had no effect on the BHT-920-, UK 14,304- and PGE-6201204-induced contractions, but blocked the contractile response to the alpha(1)-adrenoceptor agonist phenylephrine (pD2 = 5.38 +/- 0.04) and the mixed alpha1- and alpha2-adrenoceptor agonist oxymetazoline (pD(2) = 6.30 +/- 0.22). 3. The alpha2-adrenoceptor antagonist yohimbine (0.01-0.1 microm, pA2 = 8.04), alpha2B/C-adrenoceptor antagonist ARC 239 (10 microm, pK(b) = 6.33 +/- 0.21), alpha2A/C-adrenoceptor antagonist WB 4101 (0.3 microm, pK(b) = 8.01 +/- 0.24), alpha2A-adrenoceptor antagonists BRL44408 (0.1 microm, pK(b) = 6.82 +/- 0.34) and RX 821002 (0.1 microm, pKb = 8.31 +/- 0.35), alpha2C-adrenoceptor antagonists spiroxatrine (1 microm, pKb = 7.32 +/- 0.32), rauwolscine (0.1 microm, pKb = 8.16 +/- 0.14) and HV 723 (0.3 microm, pKb = 7.68 +/- 0.14) inhibited BHT-920-induced contractions in pig nasal mucosa. 4. The present antagonist potencies showed correlations with binding affinity estimates (pKi) obtained for these antagonists at the human recombinant alpha2A- and alpha2C-adrenoceptors (r = 0.78 and 0.83, respectively) and with binding affinity estimates (pKd) obtained in pig native alpha2A- and alpha2C-monoreceptor assays (r = 0.85 and 0.78, respectively). No correlation was observed for the alpha2B-subtype. 5. In conclusion, contractile responses to phenylephrine, BHT-920, UK 14,304, PGE-6201204 and oxymetazoline indicate that alpha1- and alpha2-adrenoceptors are present and mediate vasoconstriction in pig nasal mucosa. Furthermore, correlation analysis comparing antagonist potency in pig nasal mucosa with affinities for human recombinant alpha2-adrenoceptors and native pig alpha2-adrenoceptors suggest that alpha2A- and alpha2C-adrenoceptor subtypes constrict pig nasal mucosa vasculature.
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Affiliation(s)
- M R Corboz
- Allergy Department, Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
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Renauld AE, Ignatowski TA, Spengler RN. Alpha 2-adrenergic receptor inhibition of cAMP accumulation is transformed to facilitation by tumor necrosis factor-alpha. Brain Res 2004; 1004:212-6. [PMID: 15033439 DOI: 10.1016/j.brainres.2004.01.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/02/2004] [Indexed: 11/26/2022]
Abstract
Activation of the alpha(2)-adrenergic receptor on neurons regulates the activity of neurons. Inhibition of forskolin-stimulated cAMP accumulation induced by alpha(2)-adrenergic receptor activation is altered following exposure of the neuron SH-SY5Y cell line to tumor necrosis factor-alpha (TNF). Acute (5 and 15 min) exposure to TNF induces a transformation in alpha(2)-adrenergic regulation of cAMP accumulation from inhibition to facilitation. These findings support an autocrine role for the regulation of TNF production from neurons.
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Affiliation(s)
- Amy E Renauld
- Department of Pathology and Anatomical Sciences, School of Medicine and Biomedical Sciences, SUNY at Buffalo, 206 Farber Hall, 3435 Main Street, Buffalo, NY 14214, USA
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Song ZM, Abou-Zeid O, Fang YY. α2a adrenoceptors regulate phosphorylation of microtubule-associated protein-2 in cultured cortical neurons. Neuroscience 2004; 123:405-18. [PMID: 14698748 DOI: 10.1016/j.neuroscience.2003.09.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Adrenoceptors have been suggested to mediate neuronal development. This study revealed the expression of alpha2A adrenoceptors in the cortical plate of fetal mouse cerebral wall. The effects of alpha2A adrenoceptor on dendrite growth were investigated in primary neuronal cultures. Application of alpha2 adrenoceptor agonists, BHT 933 or UK 14304 for 24 or 72 h resulted in a 1.5-2-fold increase in dendrite lengths. This effect was blocked by alpha2 adrenergic antagonists, RX 821002 or yohimbine, as well as a alpha2A selective antagonist, BRL 44408, but not by alpha2B/alpha2C selective antagonists ARC 239, imiloxan and rauwolscine. Guanfacine, a alpha2A selective agonists, also significantly increased the dendrite lengths in culture. These results suggest that the morphological effect is wholly attributable to alpha2A adrenoceptor activation. We further tested the hypothesis that alpha2A adrenoceptors act through altering the phosphorylation state of microtubule-associated protein 2. The results showed that the phosphorylation of microtubule-associated protein 2 was significantly reduced on both serine and threonine residues by over 40% after 2 h of application of guanfacine and was maintained at this low level for a prolonged time up to 96 h. These findings suggest that alpha2A adrenoceptors regulate the phosphorylation of microtubule-associated protein 2, which in turn mediates dendrite growth of cortical neurons.
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Affiliation(s)
- Z-M Song
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Building 54, Mills Road, Canberra, ACT 0200, Australia.
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Sarkar S, Tsai SW, Nguyen TT, Plevyak M, Padbury JF, Rubin LP. Inhibition of placental 11beta-hydroxysteroid dehydrogenase type 2 by catecholamines via alpha-adrenergic signaling. Am J Physiol Regul Integr Comp Physiol 2001; 281:R1966-74. [PMID: 11705783 DOI: 10.1152/ajpregu.2001.281.6.r1966] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The placenta expresses high levels of 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2) that converts cortisol into inactive 11-keto metabolites and effectively protects the developing fetus from maternal cortisol during pregnancy. Impairment of this glucocorticoid barrier has adverse effects on fetal outcomes. A similar spectrum of adverse fetal effects is induced by antenatal stress during pregnancy. To examine the hypothesis that physiological stress may regulate placental 11betaHSD2 gene expression, we examined the effects of the catecholamines norepinephrine (NE) and epinephrine (E) on 11betaHSD2 expression in human trophoblastic cells. With the use of Northern blotting and semiquantitative RT-PCR, we determined that NE and E rapidly downregulate 11betaHSD2 steady-state mRNA levels in early- and late-gestation human trophoblasts and BeWo trophoblastic cells. Experiments using different adrenoceptor subtype-selective agonists and antagonists demonstrated that this catecholamine suppression of 11betaHSD2 mRNA expression is mediated via both alpha(1)- and alpha(2)-adrenoceptors and is independent of beta-adrenergic stimulation. To examine transcriptional regulation, BeWo cells were transiently transfected with a reporter construct in which an 11betaHSD2 human promoter sequence was inserted upstream of the luciferase gene. Treatment with 10(-7) M NE decreased luciferase activity by ~60% (n = 3, P < 0.01). These results suggest the NE/E-mediated decrease in placental 11betaHSD2 gene expression is an instance of alpha-adrenoceptor-specific rapid transcriptional inhibition of an adrenergic target gene. This molecular mechanism may be involved in the deleterious effects of antenatal physiological stress on fetoplacental growth and development.
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Affiliation(s)
- S Sarkar
- Department of Pediatrics, Brown Medical School, Providence, Rhode Island 02905-2499, USA
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Rizzo CA, Ruck LM, Corboz MR, Umland SP, Wan Y, Shah H, Jakway J, Cheng L, McCormick K, Egan RW, Hey JA. Postjunctional alpha(2C)-adrenoceptor contractility in human saphenous vein. Eur J Pharmacol 2001; 413:263-9. [PMID: 11226402 DOI: 10.1016/s0014-2999(01)00772-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The postjunctional alpha(2)-adrenoceptor-mediated contractility was characterized in human saphenous vein derived from coronary artery bypass graft surgery. Human saphenous vein contracted to alpha(2)-adrenoceptor selective agonists BHT-920 (5,6,7,8-Tetrahydro-6-(2-propenyl)-4H-thiazolo[4,5-d]azepin-2-amine dihydrochloride; pD(2)=6.7+/-0.1) and UK 14,304 (5-Bromo-6-(2-imidazolin-2-ylamino)quinoxaline; pD(2)=7.2+/-0.1). BHT-920-induced contractions were inhibited by the alpha(2)-adrenoceptor antagonist yohimbine (17-Hydroxy-yohimban-16-carboxylic acid methyl ester hydrochloride; pA(2)=8.7+/-0.5), but not by the alpha(1)-adrenoceptor antagonist prazosin (1-[4-Amino-6,7-dimethoxy-2-quinazolinyl]-4-[2-furanylcarbonyl]-piperazine hydrochloride; 300 nM). In contrast, prazosin (pK(b)=7.9+/-0.2) potently antagonized contractions elicited by the alpha(1)-adrenoceptor agonist phenylephrine ((R)-3-Hydroxy-alpha-[(methylamino)methyl] benzenemethanol hydrochloride; pD(2)=4.9+/-0.1), indicating that both alpha(2)- and alpha(1)-adrenoceptor evoke human saphenous vein contractions. Functional antagonist activity estimates (pA(2) or pK(b)) obtained for the alpha-adrenoceptor antagonists ARC 239 (2-[2-(4-(2-Methoxyphenyl)piperazin-1-yl)ethyl]-4,4-dimethyl-1,3-(2H,4H)-isoquinolindione dihydrochloride), WB 4101 (2-(2,6-Dimethoxyphenoxyethyl)aminomethyl-1,4-benzodioxane hydrochloride) and HV 723 (alpha-ethyl-3,4,5-trimethoxy-alpha-(3-((2-(2-methoxyphenoxy) ethyl)amino)propyl)benzeneacetonitrile) against BHT-920-induced human saphenous vein contractions were 7.0+/-0.6, 8.3+/-0.6 and 7.7+/-0.3, respectively. The alpha(2)-adrenoceptor subtype affinities (pK(i)) obtained in recombinant human alpha(2A)-, alpha(2B)- and alpha(2C)-adrenoceptor competition binding assays were 8.6, 8.3 and 8.6 for yohimbine; 6.3, 8.4 and 7.0 for ARC 239; 8.4, 7.5 and 8.4 for WB 4101 and 7.5, 7.4 and 7.9 for HV 723, respectively. Taken together, the binding and functional antagonist activity estimates obtained in these investigations indicate that alpha(2C)-adrenoceptor is the predominant postjunctional alpha(2)-adrenoceptor subtype in human saphenous vein.
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Affiliation(s)
- C A Rizzo
- Schering-Plough Research Institute, Allergy, K-15-1-1600, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA.
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Umland SP, Wan Y, Shah H, Billah M, Egan RW, Hey JA. Receptor reserve analysis of the human alpha(2C)-adrenoceptor using. Eur J Pharmacol 2001; 411:211-21. [PMID: 11164378 DOI: 10.1016/s0014-2999(00)00909-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Here we determine for norepinephrine, (5-bromo-6-(2-imidazolin-2-ylamino)quinoxaline) (UK14,304), 5,6,7,8-tetrahydro-6-(2-propenyl)-4H-thiazolo[4,5-d]azepin-2-amine dihydrochloride (BHT-920), (2-[3-hydroxy-2,6-dimethyl-4-t-butylbenzyl]-2-imidazoline) (oxymetazoline), and ((R)-3-Hydroxy-alpha-[(methylamino)methyl]-benzenemethanol hydrochloride) (phenylephrine), affinities using a radiolabeled agonist and antagonist, and potency and efficacy values in membrane [(35)S]guanosine-5'-O-(3-thiotriphosphate) ([(35)S]GTP gamma S) binding and cAMP cellular inhibition assays, in Chinese hamster ovary cells (CHO-K1) expressing the human alpha(2c)-adrenoceptor. These cells express a high ratio of receptor to G-protein because each agonist, but not several antagonists, displaced [(3)H]UK14,304 with higher affinity than [(3)H]rauwolscine. The rank order of potency of high affinity K(i) and EC(50) in both functional assays was norepinephrine > or =UK14,304>BHT-920>oxymetazoline>phenylephrine. The receptor reserve of G-protein activation and cAMP responses was measured with the irreversible antagonist, benextramine; K(A) values of norepinephrine or UK14,304 were similar (289, 271 or 150, 163 nM, respectively). A 20-fold greater receptor occupancy was required for agonist-induced half-maximal [(35)S]GTP gamma S binding compared to cAMP inhibition, indicating significant signal amplification in cells. Therefore, the G-protein activation assay is better at distinguishing full and partial agonists.
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Affiliation(s)
- S P Umland
- Schering-Plough Research Institute, 2015 Galloping Hill Road, K15-1-1700, Kenilworth, NJ 07033, USA.
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