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Oladosu FA, Maixner W, Nackley AG. Alternative Splicing of G Protein-Coupled Receptors: Relevance to Pain Management. Mayo Clin Proc 2015; 90:1135-51. [PMID: 26250730 PMCID: PMC5024555 DOI: 10.1016/j.mayocp.2015.06.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 06/13/2015] [Accepted: 06/26/2015] [Indexed: 01/01/2023]
Abstract
Drugs that target G protein-coupled receptors (GPCRs) represent the primary treatment strategy for patients with acute and chronic pain; however, there is substantial individual variability in both the efficacy and adverse effects associated with these drugs. Variability in drug responses is due, in part, to individuals' diversity in alternative splicing of pain-relevant GPCRs. G protein-coupled receptor alternative splice variants often exhibit distinct tissue distribution patterns, drug-binding properties, and signaling characteristics that may impact disease pathology as well as the extent and direction of analgesic effects. We review the importance of GPCRs and their known splice variants to the management of pain.
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Affiliation(s)
- Folabomi A Oladosu
- Center for Pain Research and Innovation, University of North Carolina, Chapel Hill
| | - William Maixner
- Center for Pain Research and Innovation, University of North Carolina, Chapel Hill
| | - Andrea G Nackley
- Center for Pain Research and Innovation, University of North Carolina, Chapel Hill.
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52
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Wang PC, Ho IK, Lee CWS. Buprenorphine-elicited alteration of adenylate cyclase activity in human embryonic kidney 293 cells coexpressing κ-, μ-opioid and nociceptin receptors. J Cell Mol Med 2015; 19:2587-96. [PMID: 26153065 PMCID: PMC4627564 DOI: 10.1111/jcmm.12644] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 05/28/2015] [Indexed: 02/03/2023] Open
Abstract
Buprenorphine, a maintenance drug for heroin addicts, exerts its pharmacological function via κ- (KOP), μ-opioid (MOP) and nociceptin/opioid receptor-like 1 (NOP) receptors. Previously, we investigated its effects in an in vitro model expressing human MOP and NOP receptors individually or simultaneously (MOP, NOP, and MOP+NOP) in human embryonic kidney 293 cells. Here, we expanded this cell model by expressing human KOP, MOP and NOP receptors individually or simultaneously (KOP, KOP+MOP, KOP+NOP and KOP+MOP+NOP). Radioligand binding with tritium-labelled diprenorphine confirmed the expression of KOP receptors. Immunoblotting and immunocytochemistry indicated that the expressed KOP, MOP and NOP receptors are N-linked glycoproteins and colocalized in cytoplasmic compartments. Acute application of the opioid receptor agonists— U-69593, DAMGO and nociceptin— inhibited adenylate cyclase (AC) activity in cells expressing KOP, MOP and NOP receptors respectively. Buprenorphine, when applied acutely, inhibited AC activity to ~90% in cells expressing KOP+MOP+NOP receptors. Chronic exposure to buprenorphine induced concentration-dependent AC superactivation in cells expressing KOP+NOP receptors, and the level of this superactivation was even higher in KOP+MOP+NOP-expressing cells. Our study demonstrated that MOP receptor could enhance AC regulation in the presence of coexpressed KOP and NOP receptors, and NOP receptor is essential for concentration-dependent AC superactivation elicited by chronic buprenorphine exposure.
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Affiliation(s)
- Pei-Chen Wang
- Neuropsychiatric Center, National Health Research Institutes, Miaoli County, Taiwan
| | - Ing-Kang Ho
- Neuropsychiatric Center, National Health Research Institutes, Miaoli County, Taiwan.,Graduate Institute of Clinical Medical Science, China Medical University, Taichung, Taiwan.,Center for Drug Abuse and Addiction, China Medical University Hospital, Taichung, Taiwan
| | - Cynthia Wei-Sheng Lee
- Center for Drug Abuse and Addiction, China Medical University Hospital, Taichung, Taiwan.,China Medical University, Taichung, Taiwan
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Kim HJ, Kim JS, Woo JT, Lee IS, Cha BY. Hyperpigmentation mechanism of methyl 3,5-di-caffeoylquinate through activation of p38 and MITF induction of tyrosinase. Acta Biochim Biophys Sin (Shanghai) 2015; 47:548-56. [PMID: 26018825 DOI: 10.1093/abbs/gmv040] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 03/20/2015] [Indexed: 11/13/2022] Open
Abstract
Methyl 3,5-di-caffeoylquinate (3,5-diCQM) has been used for the treatment of various diseases in oriental medicine, but its effect on melanogenesis has not been reported yet. In this study, the molecular mechanism of 3,5-diCQM-induced melanogenesis was investigated. It was found that 3,5-diCQM induced synthesis of melanin pigments in murine B16F10 melanoma cells in a concentration-dependent manner. Treatment of cells with 3,5-diCQM for 48 h increased extracellular and intracellular melanin production and tyrosinase activity. The expressions of tyrosinase, tyrosinase-related protein 1 (TRP1), and TRP2 were up-regulated in a dose-dependent manner 48 h after 3,5-diCQM treatment. Western blot analysis showed that 3,5-diCQM increased the phosphorylation of p38 mitogen-activated protein kinase and cAMP responsive element binding as well as the expression of microphthalmia-associated transcription factor. In addition, 3,5-diCQM-stimulated cAMP production, and 3,5-diCQM-induced tyrosinase activity and melanin synthesis were attenuated by H89, a protein kinase A inhibitor. These results suggested that 3,5-diCQM-mediated activation of the p38 pathway may represent a novel approach for an effective therapy for vitiligo and hair graying.
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Affiliation(s)
- Hyo Jung Kim
- Research Institute for Biological Functions, Chubu University, Kasugai, Aichi 487-8501, Japan
| | - Jin Sook Kim
- KM Convergence Research Division, Korea Institute of Oriental Medicine, Daejeon 305-811, Republic of Korea
| | - Je-Tae Woo
- Research Institute for Biological Functions, Chubu University, Kasugai, Aichi 487-8501, Japan Department of Research and Development, Erina Co., Inc., Minato-ku, Tokyo 105-0021, Japan
| | - Ik-Soo Lee
- KM Convergence Research Division, Korea Institute of Oriental Medicine, Daejeon 305-811, Republic of Korea
| | - Byung-Yoon Cha
- Research Institute for Biological Functions, Chubu University, Kasugai, Aichi 487-8501, Japan
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Franklin C, Fortepiani L, Nguyen T, Rangel Y, Strong R, Gottlieb HB. Renal responses produced by microinjection of the kappa opioid receptor agonist, U50-488H, into sites within the rat lamina terminalis. Pharmacol Res Perspect 2015; 3:e00117. [PMID: 26038693 PMCID: PMC4448977 DOI: 10.1002/prp2.117] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 11/18/2014] [Accepted: 11/24/2014] [Indexed: 01/01/2023] Open
Abstract
Activation of central kappa opioid receptors (KOR) has been demonstrated to produce marked free water diuresis with a concurrent increase in renal sympathetic nerve activity (RSNA). This study investigated the cardiovascular (CV) and renal effects evoked by central activation of KOR in two lamina terminalis sites, the median preoptic area (MPA) and anterolateral division of the bed nuclei of the stria terminalis (BST). Rats anesthetized with urethane alpha-chloralose were instrumented to record mean arterial pressure, heart rate, RSNA, and urine output (V). Rats were infused with isotonic saline (25 μL/min) and urine samples were collected during two 10-min control periods and six consecutive 10-min experimental periods following microinjection of vehicle, U50-448H (U50, KOR agonist) alone or norbinaltorphimine (nor-BNI, KOR antagonist) plus U50. Microinjection of U50 into the BST increased V (peak at 30 min, 84.8 ± 12.9 μL/min) as compared to its respective control, vehicle, or nor-BNI plus U50. This diuretic effect occurred without any significant changes in CV parameters, RSNA, or urinary sodium excretion. In contrast, U50 injection into the MPA significantly increased RSNA (peak at 20 mins: 129 ± 9.9) without increasing the other parameters. This study demonstrated novel sites through which activation of KOR selectively increases V and RSNA. The ability of U50 to increase V without affecting sodium excretion and RSNA raises the possibility that LT neurons could be an important substrate through which drugs targeting KOR could selectively facilitate water excretion in sodium-retaining diseases such as congestive heart failure.
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Affiliation(s)
- Cynthia Franklin
- Department of Pharmaceutical Sciences, Feik School of Pharmacy, University of Incarnate Word San Antonio, Texas, 78209
| | - Lourdes Fortepiani
- Rosenberg School of Optometry, University of Incarnate Word San Antonio, Texas, 78209
| | - Tin Nguyen
- Department of Pharmaceutical Sciences, Feik School of Pharmacy, University of Incarnate Word San Antonio, Texas, 78209
| | - Yolanda Rangel
- Department of Physical Therapy, University of Texas Health Science Center at San Antonio San Antonio, Texas, 78229
| | - Randy Strong
- Department of Pharmacology and the Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio and the South Texas Veterans Health Care System San Antonio, Texas, 78229
| | - Helmut B Gottlieb
- Department of Pharmaceutical Sciences, Feik School of Pharmacy, University of Incarnate Word San Antonio, Texas, 78209
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Lohman RJ, Harrison RS, Ruiz-Gómez G, Hoang HN, Shepherd NE, Chow S, Hill TA, Madala PK, Fairlie DP. Helix-constrained nociceptin peptides are potent agonists and antagonists of ORL-1 and nociception. VITAMINS AND HORMONES 2015; 97:1-55. [PMID: 25677767 DOI: 10.1016/bs.vh.2014.10.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Nociceptin (orphanin FQ) is a 17-residue neuropeptide hormone with roles in both nociception and analgesia. It is an opioid-like peptide that binds to and activates the G-protein-coupled receptor opioid receptor-like-1 (ORL-1, NOP, orphanin FQ receptor, kappa-type 3 opioid receptor) on central and peripheral nervous tissue, without activating classic delta-, kappa-, or mu-opioid receptors or being inhibited by the classic opioid antagonist naloxone. The three-dimensional structure of ORL-1 was recently published, and the activation mechanism is believed to involve capture by ORL-1 of the high-affinity binding, prohelical C-terminus. This likely anchors the receptor-activating N-terminus of nociception nearby for insertion in the membrane-spanning helices of ORL-1. In search of higher agonist potency, two lysine and two aspartate residues were strategically incorporated into the receptor-binding C-terminus of the nociceptin sequence and two Lys(i)→Asp(i+4) side chain-side chain condensations were used to generate lactam cross-links that constrained nociceptin into a highly stable α-helix in water. A cell-based assay was developed using natively expressed ORL-1 receptors on mouse neuroblastoma cells to measure phosphorylated ERK as a reporter of agonist-induced receptor activation and intracellular signaling. Agonist activity was increased up to 20-fold over native nociceptin using a combination of this helix-inducing strategy and other amino acid modifications. An NMR-derived three-dimensional solution structure is described for a potent ORL-1 agonist derived from nociceptin, along with structure-activity relationships leading to the most potent known α-helical ORL-1 agonist (EC₅₀ 40 pM, pERK, Neuro-2a cells) and antagonist (IC₅₀ 7 nM, pERK, Neuro-2a cells). These α-helix-constrained mimetics of nociceptin(1-17) had enhanced serum stability relative to unconstrained peptide analogues and nociceptin itself, were not cytotoxic, and displayed potent thermal analgesic and antianalgesic properties in rats (ED₅₀ 70 pmol, IC₅₀ 10 nmol, s.c.), suggesting promising uses in vivo for the treatment of pain and other ORL-1-mediated responses.
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Affiliation(s)
- Rink-Jan Lohman
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
| | - Rosemary S Harrison
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
| | - Gloria Ruiz-Gómez
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
| | - Huy N Hoang
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
| | - Nicholas E Shepherd
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
| | - Shiao Chow
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
| | - Timothy A Hill
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
| | - Praveen K Madala
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
| | - David P Fairlie
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia.
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56
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Knapman A, Connor M. Cellular signalling of non-synonymous single-nucleotide polymorphisms of the human μ-opioid receptor (OPRM1). Br J Pharmacol 2014; 172:349-63. [PMID: 24527749 DOI: 10.1111/bph.12644] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Revised: 01/21/2014] [Accepted: 02/07/2014] [Indexed: 12/15/2022] Open
Abstract
UNLABELLED There is significant variability in individual responses to opioid drugs, which is likely to have a significant genetic component. A number of non-synonymous single-nucleotide polymorphisms (SNPs) in the coding regions of the μ-opioid receptor gene (OPRM1) have been postulated to contribute to this variability. Although many studies have investigated the clinical influences of these μ-opioid receptor variants, the outcomes are reported in the context of thousands of other genes and environmental factors, and we are no closer to being able to predict individual response to opioids based on genotype. Investigation of how μ-opioid receptor SNPs affect their expression, coupling to second messengers, desensitization and regulation is necessary to understand how subtle changes in receptor structure can impact individual responses to opioids. To date, the few functional studies that have investigated the consequences of SNPs on the signalling profile of the μ-opioid receptor in vitro have shown that the common N40D variant has altered functional responses to some opioids, while other, rarer, variants display altered signalling or agonist-dependent regulation. Here, we review the data available on the effects of μ-opioid receptor polymorphisms on receptor function, expression and regulation in vitro, and discuss the limitations of the studies to date. Whether or not μ-opioid receptor SNPs contribute to individual variability in opioid responses remains an open question, in large part because we have relatively little good data about how the amino acid changes affect μ-opioid receptor function. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
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Affiliation(s)
- Alisa Knapman
- Australian School of Advanced Medicine, Macquarie University, Sydney, NSW, Australia
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Actin filament reorganization in astrocyte networks is a key functional step in neuroinflammation resulting in persistent pain: novel findings on network restoration. Neurochem Res 2014; 40:372-9. [PMID: 24952067 DOI: 10.1007/s11064-014-1363-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 06/09/2014] [Accepted: 06/13/2014] [Indexed: 10/25/2022]
Abstract
In recent years, the importance of glial cell activation in the generation and maintenance of long-term pain has been investigated. One novel mechanism underlying long-lasting pain is injury-induced inflammation in the periphery, followed by microglial activation in the dorsal horn of the spinal cord, which results in local neuroinflammation. An increase in neuronal excitability may follow, with intense signaling along the pain tracts to the thalamus and the parietal cortex along with other cortical regions for the identification and recognition of the injury. If the local neuroinflammation develops into a pathological state, then the astrocytes become activated. Previous studies in which lipopolysaccharide (LPS) was used to induce inflammation have shown that in a dysfunctional astrocyte network, the actin cytoskeleton is reorganized from the normally occurring F-actin stress fibers into the more diffusible, disorganized, ring-form globular G-actin. In addition, Ca(2+) signaling systems are altered, Na(+)- and glutamate transporters are downregulated, and pro-inflammatory cytokines, particularly IL-1β, are released in dysfunctional astrocyte networks. In a series of experiments, we have demonstrated that these LPS-induced changes in astrocyte function can be restored by stimulation of Gi/o and inhibition of Gs with a combination of a μ-receptor agonist and ultralow concentrations of a μ-receptor antagonist and by inhibition of cytokine release, particularly IL-1β, by the antiepileptic drug levetiracetam. These findings could be of clinical significance and indicate a novel treatment for long-term pain.
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58
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Brewer KL, Baran CA, Whitfield BR, Jensen AM, Clemens S. Dopamine D3 receptor dysfunction prevents anti-nociceptive effects of morphine in the spinal cord. Front Neural Circuits 2014; 8:62. [PMID: 24966815 PMCID: PMC4052813 DOI: 10.3389/fncir.2014.00062] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 05/23/2014] [Indexed: 01/11/2023] Open
Abstract
Dopamine (DA) modulates spinal reflexes, including nociceptive reflexes, in part via the D3 receptor subtype. We have previously shown that mice lacking the functional D3 receptor (D3KO) exhibit decreased paw withdrawal latencies from painful thermal stimuli. Altering the DA system in the CNS, including D1 and D3 receptor systems, reduces the ability of opioids to provide analgesia. Here, we tested if the increased pain sensitivity in D3KO might result from a modified μ-opioid receptor (MOR) function at the spinal cord level. As D1 and D3 receptor subtypes have competing cellular effects and can form heterodimers, we tested if the changes in MOR function may be mediated in D3KO through the functionally intact D1 receptor system. We assessed thermal paw withdrawal latencies in D3KO and wild type (WT) mice before and after systemic treatment with morphine, determined MOR and phosphorylated MOR (p-MOR) protein expression levels in lumbar spinal cords, and tested the functional effects of DA and MOR receptor agonists in the isolated spinal cord. In vivo, a single morphine administration (2 mg/kg) increased withdrawal latencies in WT but not D3KO, and these differential effects were mimicked in vitro, where morphine modulated spinal reflex amplitudes (SRAs) in WT but not D3KO. Total MOR protein expression levels were similar between WT and D3KO, but the ratio of pMOR/total MOR was higher in D3KO. Blocking D3 receptors in the isolated WT cord precluded morphine's inhibitory effects observed under control conditions. Lastly, we observed an increase in D1 receptor protein expression in the lumbar spinal cord of D3KO. Our data suggest that the D3 receptor modulates the MOR system in the spinal cord, and that a dysfunction of the D3 receptor can induce a morphine-resistant state. We propose that the D3KO mouse may serve as a model to study the onset of morphine resistance at the spinal cord level, the primary processing site of the nociceptive pathway.
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Affiliation(s)
- Kori L Brewer
- Department of Physiology, Brody School of Medicine, East Carolina University Greenville, NC, USA
| | - Christine A Baran
- Department of Emergency Medicine, Brody School of Medicine, East Carolina University Greenville, NC, USA
| | - Brian R Whitfield
- Department of Emergency Medicine, Brody School of Medicine, East Carolina University Greenville, NC, USA
| | - A Marley Jensen
- Department of Physiology, Brody School of Medicine, East Carolina University Greenville, NC, USA
| | - Stefan Clemens
- Department of Physiology, Brody School of Medicine, East Carolina University Greenville, NC, USA
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59
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Bajo M, Madamba SG, Roberto M, Siggins GR. Acute morphine alters GABAergic transmission in the central amygdala during naloxone-precipitated morphine withdrawal: role of cyclic AMP. Front Integr Neurosci 2014; 8:45. [PMID: 24926240 PMCID: PMC4044973 DOI: 10.3389/fnint.2014.00045] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2014] [Accepted: 05/14/2014] [Indexed: 01/23/2023] Open
Abstract
The central amygdala (CeA) plays an important role in opioid addiction. Therefore, we examined the effects of naloxone-precipitated morphine withdrawal (WD) on GABAergic transmission in rat CeA neurons using whole-cell recordings with naloxone in the bath. The basal frequency of miniature inhibitory postsynaptic currents (mIPSCs) increased in CeA neurons from WD compared to placebo rats. Acute morphine (10 μ M) had mixed effects (≥20% change from baseline) on mIPSCs in placebo and WD rats. In most CeA neurons (64%) from placebo rats, morphine significantly decreased mIPSC frequency and amplitude. In 32% of placebo neurons, morphine significantly increased mIPSC amplitudes but had no effect on mIPSC frequency. In WD rats, acute morphine significantly increased mIPSC frequency but had no effect on mIPSC amplitude in 41% of CeA neurons. In 45% of cells, acute morphine significantly decreased mIPSC frequency and amplitude. Pre-treatment with the cyclic AMP inhibitor (R)-adenosine, cyclic 3',5'-(hydrogenphosphorothioate) triethylammonium (RP), prevented acute morphine-induced potentiation of mIPSCs. Pre-treatment of slices with the Gi/o G-protein subunit inhibitor pertussis toxin (PTX) did not prevent the acute morphine-induced enhancement or inhibition of mIPSCs. PTX and RP decreased basal mIPSC frequencies and amplitudes only in WD rats. The results suggest that inhibition of GABAergic transmission in the CeA by acute morphine is mediated by PTX-insensitive mechanisms, although PTX-sensitive mechanisms cannot be ruled out for non-morphine responsive cells; by contrast, potentiation of GABAergic transmission is mediated by activated cAMP signaling that also mediates the increased basal GABAergic transmission in WD rats. Our data indicate that during the acute phase of WD, the CeA opioid and GABAergic systems undergo neuroadaptative changes conditioned by a previous chronic morphine exposure and dependence.
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Affiliation(s)
- Michal Bajo
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute La Jolla, CA, USA
| | - Samuel G Madamba
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute La Jolla, CA, USA
| | - Marisa Roberto
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute La Jolla, CA, USA
| | - George R Siggins
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute La Jolla, CA, USA
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μ-Opioid inhibition of Ca2+ currents and secretion in isolated terminals of the neurohypophysis occurs via ryanodine-sensitive Ca2+ stores. J Neurosci 2014; 34:3733-42. [PMID: 24599471 DOI: 10.1523/jneurosci.2505-13.2014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
μ-Opioid agonists have no effect on calcium currents (I(Ca)) in neurohypophysial terminals when recorded using the classic whole-cell patch-clamp configuration. However, μ-opioid receptor (MOR)-mediated inhibition of I(Ca) is reliably demonstrated using the perforated-patch configuration. This suggests that the MOR-signaling pathway is sensitive to intraterminal dialysis and is therefore mediated by a readily diffusible second messenger. Using the perforated patch-clamp technique and ratio-calcium-imaging methods, we describe a diffusible second messenger pathway stimulated by the MOR that inhibits voltage-gated calcium channels in isolated terminals from the rat neurohypophysis (NH). Our results show a rise in basal intracellular calcium ([Ca(2+)]i) in response to application of [D-Ala(2)-N-Me-Phe(4),Gly5-ol]-Enkephalin (DAMGO), a MOR agonist, that is blocked by D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP), a MOR antagonist. Buffering DAMGO-induced changes in [Ca(2+)]i with BAPTA-AM completely blocked the inhibition of both I(Ca) and high-K(+)-induced rises in [Ca(2+)]i due to MOR activation, but had no effect on κ-opioid receptor (KOR)-mediated inhibition. Given the presence of ryanodine-sensitive stores in isolated terminals, we tested 8-bromo-cyclic adenosine diphosphate ribose (8Br-cADPr), a competitive inhibitor of cyclic ADP-ribose (cADPr) signaling that partially relieves DAMGO inhibition of I(Ca) and completely relieves MOR-mediated inhibition of high-K(+)-induced and DAMGO-induced rises in [Ca(2+)]i. Furthermore, antagonist concentrations of ryanodine completely blocked MOR-induced increases in [Ca(2+)]i and inhibition of I(Ca) and high-K(+)-induced rises in [Ca(2+)]i while not affecting KOR-mediated inhibition. Antagonist concentrations of ryanodine also blocked MOR-mediated inhibition of electrically-evoked increases in capacitance. These results strongly suggest that a key diffusible second messenger mediating the MOR-signaling pathway in NH terminals is [Ca(2+)]i released by cADPr from ryanodine-sensitive stores.
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Zambelli VO, Fernandes ACDO, Gutierrez VP, Ferreira JCB, Parada CA, Mochly-Rosen D, Cury Y. Peripheral sensitization increases opioid receptor expression and activation by crotalphine in rats. PLoS One 2014; 9:e90576. [PMID: 24594607 PMCID: PMC3942445 DOI: 10.1371/journal.pone.0090576] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 02/04/2014] [Indexed: 11/19/2022] Open
Abstract
Inflammation enhances the peripheral analgesic efficacy of opioid drugs, but the mechanisms involved in this phenomenon have not been fully elucidated. Crotalphine (CRP), a peptide that was first isolated from South American rattlesnake C.d. terrificus venom, induces a potent and long-lasting anti-nociceptive effect that is mediated by the activation of peripheral opioid receptors. Because the high efficacy of CRP is only observed in the presence of inflammation, we aimed to elucidate the mechanisms involved in the CRP anti-nociceptive effect induced by inflammation. Using real-time RT-PCR, western blot analysis and ELISA assays, we demonstrate that the intraplantar injection of prostaglandin E2 (PGE2) increases the mRNA and protein levels of the µ- and κ-opioid receptors in the dorsal root ganglia (DRG) and paw tissue of rats within 3 h of the injection. Using conformation state-sensitive antibodies that recognize activated opioid receptors, we show that PGE2, alone does not increase the activation of these opioid receptors but that in the presence of PGE2, the activation of specific opioid receptors by CRP and selective µ- and κ-opioid receptor agonists (positive controls) increases. Furthermore, PGE2 down-regulated the expression and activation of the δ-opioid receptor. CRP increased the level of activated mitogen-activated protein kinases in cultured DRG neurons, and this increase was dependent on the activation of protein kinase Cζ. This CRP effect was much more prominent when the cells were pretreated with PGE2. These results indicate that the expression and activation of peripheral opioid receptors by opioid-like drugs can be up- or down-regulated in the presence of an acute injury and that acute tissue injury enhances the efficacy of peripheral opioids.
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MESH Headings
- Analgesics, Opioid/isolation & purification
- Analgesics, Opioid/pharmacology
- Analgesics, Opioid/therapeutic use
- Animals
- Crotalus/metabolism
- Dinoprostone
- Ganglia, Spinal/drug effects
- Ganglia, Spinal/immunology
- Ganglia, Spinal/metabolism
- Gene Expression Regulation/drug effects
- Hyperalgesia/chemically induced
- Hyperalgesia/drug therapy
- Hyperalgesia/genetics
- Hyperalgesia/immunology
- Male
- Peptides/isolation & purification
- Peptides/pharmacology
- Peptides/therapeutic use
- Rats
- Rats, Wistar
- Receptors, Opioid/agonists
- Receptors, Opioid/genetics
- Receptors, Opioid/immunology
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Affiliation(s)
| | | | | | | | - Carlos Amilcar Parada
- Departamento de Fisiologia e Biofísica, Instituto de Biociências (UNICAMP) Rua Monteiro Lobato, Cidade Universitária, Campinas, SP, Brazil
| | - Daria Mochly-Rosen
- Department of Chemical and Systems Biology, Stanford University, School of Medicine, Stanford, California, United States of America
| | - Yara Cury
- Laboratório Especial de Dor e Sinalização, Instituto Butantan, São Paulo, SP, Brazil
- * E-mail:
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62
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Ujcikova H, Eckhardt A, Kagan D, Roubalova L, Svoboda P. Proteomic analysis of post-nuclear supernatant fraction and percoll-purified membranes prepared from brain cortex of rats exposed to increasing doses of morphine. Proteome Sci 2014; 12:11. [PMID: 24528483 PMCID: PMC3936806 DOI: 10.1186/1477-5956-12-11] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 02/03/2014] [Indexed: 11/10/2022] Open
Abstract
Background Proteomic analysis was performed in post-nuclear supernatant (PNS) and Percoll-purified membranes (PM) prepared from fore brain cortex of rats exposed to increasing doses of morphine (10–50 mg/kg) for 10 days. Results In PNS, the 10 up (↑)- or down (↓)-regulated proteins exhibiting the largest morphine-induced change were selected, excised manually from the gel and identified by MALDI-TOF MS/MS: 1-(gi|148747414, Guanine deaminase), ↑2.5×; 2-(gi|17105370, Vacuolar-type proton ATP subunit B, brain isoform), ↑2.6×; 3-(gi|1352384, Protein disulfide-isomerase A3), ↑3.4×; 4-(gi|40254595, Dihydropyrimidinase-related protein 2), ↑3.6×; 5-(gi|149054470, N-ethylmaleimide sensitive fusion protein, isoform CRAa), ↑2.0×; 6-(gi|42476181, Malate dehydrogenase, mitochondrial precursor), ↑1.4×; 7-(gi|62653546, Glyceraldehyde-3-phosphate dehydrogenase), ↑1.6×; 8-(gi|202837, Aldolase A), ↑1.3×; 9-(gi|31542401, Creatine kinase B-type), ↓0.86×; 10-(gi|40538860, Aconitate hydratase, mitochondrial precursor), ↑1.3×. The identified proteins were of cytoplasmic (1, 4, 5, 7, 9), cell membrane (2), endoplasmic reticulum (3) and mitochondrial (6, 8, 10) origin and 9 of them were significantly increased, 1.3-3.6×. The 4 out of 9 up-regulated proteins (4, 6, 7, 10) were described as functionally related to oxidative stress; the 2 proteins participate in genesis of apoptotic cell death. In PM, the 18 up (↑)- or down (↓)-regulated proteins were identified by LC-MS/MS and were of plasma membrane [Brain acid soluble protein, ↓2.1×; trimeric Gβ subunit, ↓2.0x], myelin membrane [MBP, ↓2.5×], cytoplasmic [Internexin, ↑5.2×; DPYL2, ↑4.9×; Ubiquitin hydrolase, ↓2.0×; 60S ribosomal protein, ↑2.7×; KCRB, ↓2.6×; Sirtuin-2, ↑2.5×; Peroxiredoxin-2, ↑2.2×; Septin-11, ↑2.2×; TERA, ↑2.1×; SYUA, ↑2.0×; Coronin-1A, ↓5.4×] and mitochondrial [Glutamate dehydrogenase 1, ↑2.7×; SCOT1, ↑2.2×; Prohibitin, ↑2.2×; Aspartate aminotransferase, ↓2.2×] origin. Surprisingly, the immunoblot analysis of the same PM resolved by 2D-ELFO indicated that the “active”, morphine-induced pool of Gβ subunits represented just a minor fraction of the total signal of Gβ which was decreased 1.2x only. The dominant signal of Gβ was unchanged. Conclusion Brain cortex of rats exposed to increasing doses of morphine is far from being adapted. Significant up-regulation of proteins functionally related to oxidative stress and apoptosis suggests a major change of energy metabolism resulting in the state of severe brain cell “discomfort” or even death.
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Affiliation(s)
| | | | | | | | - Petr Svoboda
- Laboratories of Biochemistry of Membrane Receptors, Institute of Physiology, v,v,i,, Academy of Sciences of the Czech Republic, Videnska 1083, Prague 4 14220, Czech Republic.
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UJČÍKOVÁ H, BREJCHOVÁ J, VOŠAHLÍKOVÁ M, KAGAN D, DLOUHÁ K, SÝKORA J, MERTA L, DRASTICHOVÁ Z, NOVOTNÝ J, OSTAŠOV P, ROUBALOVÁ L, PARENTI M, HOF M, SVOBODA P. Opioid-Receptor (OR) Signaling Cascades in Rat Cerebral Cortex and Model Cell Lines: the Role of Plasma Membrane Structure. Physiol Res 2014; 63:S165-76. [DOI: 10.33549/physiolres.932638] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Large number of extracellular signals is received by plasma membrane receptors which, upon activation, transduce information into the target cell interior via trimeric G-proteins (GPCRs) and induce activation or inhibition of adenylyl cyclase enzyme activity (AC). Receptors for opioid drugs such as morphine (μ-OR, δ-OR and κ-OR) belong to rhodopsin family of GPCRs. Our recent results indicated a specific up-regulation of AC I (8-fold) and AC II (2.5-fold) in plasma membranes (PM) isolated from rat brain cortex exposed to increasing doses of morphine (10-50 mg/kg) for 10 days. Increase of ACI and ACII represented the specific effect as the amount of ACIII-ACIX, prototypical PM marker Na, K-ATPase and trimeric G-protein α and β subunits was unchanged. The up-regulation of ACI and ACII faded away after 20 days since the last dose of morphine. Proteomic analysis of these PM indicated that the brain cortex of morphine-treated animals cannot be regarded as being adapted to this drug because significant up-regulation of proteins functionally related to oxidative stress and alteration of brain energy metabolism occurred. The number of δ-OR was increased 2-fold and their sensitivity to monovalent cations was altered. Characterization of δ-OR-G-protein coupling in model HEK293 cell line indicated high ability of lithium to support affinity of δ-OR response to agonist stimulation. Our studies of PM structure and function in context with desensitization of GPCRs action were extended by data indicating participation of cholesterol-enriched membrane domains in agonist-specific internalization of δ-OR. In HEK293 cells stably expressing δ-OR-Gi1α fusion protein, depletion of PM cholesterol was associated with the decrease in affinity of G-protein response to agonist stimulation, whereas maximum response was unchanged. Hydrophobic interior of isolated PM became more “fluid”, chaotically organized and accessible to water molecules. Validity of this conclusion was supported by the analysis of an immediate PM environment of cholesterol molecules in living δ-OR-Gi1α-HEK293 cells by fluorescent probes 22- and 25-NBD-cholesterol. The alteration of plasma membrane structure by cholesterol depletion made the membrane more hydrated. Understanding of the positive and negative feedback regulatory loops among different OR-initiated signaling cascades (µ-, δ-, and κ-OR) is crucial for understanding of the long-term mechanisms of drug addiction as the decrease in functional activity of µ-OR may be compensated by increase of δ-OR and/or κ-OR signaling.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | - P. SVOBODA
- Department of Biochemistry of Membrane Receptors, Institute of Physiology Academy of Sciences of the Czech Republic
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Schönberger M, Trauner D. A photochromic agonist for μ-opioid receptors. Angew Chem Int Ed Engl 2014; 53:3264-7. [PMID: 24519993 DOI: 10.1002/anie.201309633] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 12/05/2013] [Indexed: 01/09/2023]
Abstract
Opioid receptors (ORs) are widely distributed in the brain, the spinal cord, and the digestive tract and play an important role in nociception. All known ORs are G-protein-coupled receptors (GPCRs) of family A. Another well-known member of this family, rhodopsin, is activated by light through the cis/trans isomerization of a covalently bound chromophore, retinal. We now show how an OR can be combined with a synthetic azobenzene photoswitch to gain light sensitivity. Our work extends the reach of photopharmacology and outlines a general strategy for converting Family A GPCRs, which account for the majority of drug targets, into photoreceptors.
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Affiliation(s)
- Matthias Schönberger
- Department of Chemistry, Ludwig-Maximilians-University (LMU) Munich and Center of Integrated Protein Science, Butenandtstrasse 5-13, 81377 Munich (Germany)
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66
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Chen M, Zhang X, Xu H, Ma X, Jiang W, Xu T. Inhibitory effect of spinal mGlu(5) receptor antisense oligonucleotide on the up-regulated expression of spinal G protein associated with chronic morphine treatment. Eur J Pharmacol 2013; 723:253-8. [PMID: 24296320 DOI: 10.1016/j.ejphar.2013.11.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 11/12/2013] [Accepted: 11/20/2013] [Indexed: 11/19/2022]
Abstract
Knockdown of spinal metabotropic glutamate 5 (mGlu5) receptor was shown to inhibit the development of intrathecal morphine antinociceptive tolerance. The present work was designed to evaluate the expression of spinal G-protein during morphine tolerance and knockdown of spinal mGlu5 receptor with antisense oligonucleotide (ODN). Rats were treated with saline, morphine, mGlu5 receptor antisense or mismatch ODN intrathecally. Behavioral tests were employed to test the thermal and mechanical pain thresholds. Five days later, rats were scarified and spinal expression of spinal Gαi, Gαo, Gαq and Gβ were detected. Consistent with the previous results, knockdown of spinal mGlu5 receptor could inhibit spinal morphine antinociceptive tolerance in behavioral tests (P<0.05). The mGlu5 receptor antisense ODN produced a significant reduction in mGlu5 receptor protein of about 56.6% compared with the control group (P<0.05). Expression of spinal Gαi, Gαo, Gαq and Gβ were up-regulated while morphine tolerance developed (P<0.05). Antisense ODN of spinal mGlu5 receptor, but not mismatched ODN, reduced the spinal dorsal horn levels of Gαi, Gαo, Gαs, Gαq and Gβ (P<0.05). We conclude that expression of spinal G (αi, αo, αs, αq and β) protein may be up-regulated after chronic morphine treatment which could be attenuated by knockdown of spinal mGlu5 receptor with antisense ODN.
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Affiliation(s)
- Moxi Chen
- Department of Anesthesiology, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiaotong University, 600 Yi Shan Road, Shanghai 200233, China
| | - Xiaoli Zhang
- Department of Anesthesiology, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiaotong University, 600 Yi Shan Road, Shanghai 200233, China
| | - Hao Xu
- Department of Anesthesiology, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiaotong University, 600 Yi Shan Road, Shanghai 200233, China
| | - Xiaqing Ma
- Department of Anesthesiology, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiaotong University, 600 Yi Shan Road, Shanghai 200233, China
| | - Wei Jiang
- Department of Anesthesiology, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiaotong University, 600 Yi Shan Road, Shanghai 200233, China.
| | - Tao Xu
- Department of Anesthesiology, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiaotong University, 600 Yi Shan Road, Shanghai 200233, China.
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67
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Lee CWS, Ho IK. Pharmacological Profiles of Oligomerized μ-Opioid Receptors. Cells 2013; 2:689-714. [PMID: 24709876 PMCID: PMC3972655 DOI: 10.3390/cells2040689] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Revised: 09/30/2013] [Accepted: 10/09/2013] [Indexed: 01/21/2023] Open
Abstract
Opioids are widely prescribed pain relievers with multiple side effects and potential complications. They produce analgesia via G-protein-protein coupled receptors: μ-, δ-, κ-opioid and opioid receptor-like 1 receptors. Bivalent ligands targeted to the oligomerized opioid receptors might be the key to developing analgesics without undesired side effects and obtaining effective treatment for opioid addicts. In this review we will update the biological effects of μ-opioids on homo- or hetero-oligomerized μ-opioid receptor and discuss potential mechanisms through which bivalent ligands exert beneficial effects, including adenylate cyclase regulation and receptor-mediated signaling pathways.
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Affiliation(s)
- Cynthia Wei-Sheng Lee
- Center for Drug Abuse and Addiction, China Medical University Hospital, Taichung 40447, Taiwan.
| | - Ing-Kang Ho
- Center for Drug Abuse and Addiction, China Medical University Hospital, Taichung 40447, Taiwan.
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68
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Block L, Björklund U, Westerlund A, Jörneberg P, Biber B, Hansson E. A new concept affecting restoration of inflammation-reactive astrocytes. Neuroscience 2013; 250:536-45. [DOI: 10.1016/j.neuroscience.2013.07.033] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 07/15/2013] [Accepted: 07/15/2013] [Indexed: 01/30/2023]
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69
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Knapman A, Abogadie F, McIntrye P, Connor M. A real-time, fluorescence-based assay for measuring μ-opioid receptor modulation of adenylyl cyclase activity in Chinese hamster ovary cells. ACTA ACUST UNITED AC 2013; 19:223-31. [PMID: 23989451 DOI: 10.1177/1087057113501391] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Inhibition of adenylyl cyclase (AC) activity is frequently used to measure µ-opioid receptor (MOR) activation. We sought to develop a simple, rapid assay of AC activity in whole cells that could be used to study MOR signaling. Chinese hamster ovary cells expressing human MOR (CHO-MOR cells) were grown in 96-well plates and loaded with membrane potential-sensitive fluorescent dye. CHO-MOR cells were treated with the AC activator forskolin (FSK), with or without simultaneous application of MOR agonists, and the resulting change in fluorescence was measured. CHO-MOR cells hyperpolarized in response to application of FSK (pEC₅₀, 7.3) or calcitonin (pEC₅₀, 9.4). A submaximally effective concentration of FSK (300 nM) caused a 52% ± 2% decrease in fluorescence. Simultaneous application of the opioids DAMGO (pEC₅₀, 7.4; E(max), 56%), morphine (pEC₅₀, 7.0; E(max), 61%); and buprenorphine (pEC₅₀, 8.6; E(max), 24%) inhibited the FSK response in a dose-dependent manner while having no effect by themselves. The effects of DAMGO were blocked by pertussis toxin. This assay represents a simple, robust method for real-time observation of AC inhibition by MOR in CHO cells. It represents an appealing alternative to end-point assays that rely on cAMP accumulation and can avoid potential confounds associated with rapid desensitization of MOR signaling.
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Affiliation(s)
- Alisa Knapman
- 1Australian School of Advanced Medicine, Macquarie University, NSW Australia
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70
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Marquez P, Hamid A, Lutfy K. The role of NOP receptors in psychomotor stimulation and locomotor sensitization induced by cocaine and amphetamine in mice. Eur J Pharmacol 2013; 707:41-5. [PMID: 23524092 PMCID: PMC3652801 DOI: 10.1016/j.ejphar.2013.03.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Revised: 03/12/2013] [Accepted: 03/13/2013] [Indexed: 01/22/2023]
Abstract
We have previously shown that orphanin FQ (also known as nociceptin; OFQ/N) attenuates the motor stimulatory effect of cocaine and blocks locomotor sensitization induced by cocaine. Furthermore, we have shown that cocaine treatment altered the level of endogenous OFQ/N, raising the possibility that endogenous OFQ/N and its receptor (NOP) may be crucial in these actions of cocaine. Accordingly, in the present study, we sought to determine the role of NOP receptors in psychomotor stimulation and locomotor sensitization induced by cocaine or amphetamine. Mice lacking the NOP receptor and their wild-type littermates were habituated to motor activity chambers for 1h, injected with cocaine (0, 15 or 30 mg/kg) or amphetamine (0, 1 or 3mg/kg), and motor activity was recorded for 1h. For sensitization induced by these drugs, mice were treated with saline or the highest dose of each drug once daily for three consecutive days and tested on day 8. On this day, mice were habituated to the chambers for 1h, then received a challenge dose of cocaine (15 mg/kg) or amphetamine (1mg/kg), and motor activity was recorded for 1h. Cocaine and amphetamine each induced hyperlocomotion but the extent of this response was not different between NOP receptor null mice and their controls. Sensitization developed to the motor stimulatory action of each drug, but the magnitude of cocaine-induced sensitization was only higher in null mice compared to their controls. Together, the present results suggest that the endogenous OFQ/N/NOP receptor system may modulate the development of cocaine-induced locomotor sensitization.
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Affiliation(s)
- Paul Marquez
- Dept. of Pharm. Sci., Coll of Pharmacy, Western Univ. of Health Sci., Pomona, CA 91766
- Dept. of Endocrinology/Medicine, Charles Drew University, Los Angeles, CA 90059
| | - Abdul Hamid
- Dept. of Endocrinology/Medicine, Charles Drew University, Los Angeles, CA 90059
| | - Kabirullah Lutfy
- Dept. of Pharm. Sci., Coll of Pharmacy, Western Univ. of Health Sci., Pomona, CA 91766
- Dept. of Endocrinology/Medicine, Charles Drew University, Los Angeles, CA 90059
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71
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Paldy E, Borcel E, Higuera-Matas A, López-Montoya G, Wenger T, Toth G, Borsodi A, Ambrosio E. CNR1 gene deletion affects the density of endomorphin-2 binding sites in the mouse brain in a hemisphere-specific manner. Eur J Pharmacol 2013; 698:220-7. [DOI: 10.1016/j.ejphar.2012.10.043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2012] [Revised: 10/27/2012] [Accepted: 10/31/2012] [Indexed: 11/29/2022]
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72
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Sirohi S, Bakalkin G, Walker BM. Alcohol-induced plasticity in the dynorphin/kappa-opioid receptor system. Front Mol Neurosci 2012; 5:95. [PMID: 23060746 PMCID: PMC3459013 DOI: 10.3389/fnmol.2012.00095] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 08/29/2012] [Indexed: 01/02/2023] Open
Abstract
Alcoholism is a chronic relapsing disorder characterized by continued alcohol use despite numerous adverse consequences. Alcohol has been shown to interact with numerous neurotransmitter systems to exert its pharmacological effects. The endogenous opioid system (EOS) has been strongly implicated in the positive and negative reinforcing effects of alcohol. Traditionally recognized as dysphoric/anhedonic in nature, the dynorphin/kappa-opioid receptor (DYN/KOR) system has recently received considerable attention due to evidence suggesting that an upregulated DYN/KOR system may be a critical contributor to the complex factors that result in escalated alcohol consumption once dependent. The present review will discuss alcohol-induced plasticity in the DYN/KOR system and how these neuroadaptations could contribute to excessive alcohol seeking and consumption.
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Affiliation(s)
- Sunil Sirohi
- Laboratory of Alcoholism and Addictions Neuroscience, Department of Psychology, Washington State University Pullman, WA, USA
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73
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Szentirmay AK, Király KP, Lenkey N, Lackó E, Al-Khrasani M, Friedmann T, Timár J, Gyarmati S, Tóth G, Fürst S, Riba P. Spinal interaction between the highly selective μ agonist DAMGO and several δ opioid receptor ligands in naive and morphine-tolerant mice. Brain Res Bull 2012; 90:66-71. [PMID: 22995282 DOI: 10.1016/j.brainresbull.2012.09.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 09/10/2012] [Indexed: 12/11/2022]
Abstract
Since the discovery of opioid receptor dimers their possible roles in opioid actions were intensively investigated. Here we suggest a mechanism that may involve the μ-δ opioid heterodimers. The exact role of δ opioid receptors in antinociception and in the development of opioid tolerance is still unclear. While receptor up-regulation can be observed during the development of opioid tolerance no μ receptor down-regulation could be detected within five days. In our present work we investigated how the selective δ opioid receptor agonists and antagonists influence the antinociceptive effect of the selective μ receptor agonist DAMGO in naïve and morphine-tolerant mice. We treated male NMRI mice with 200 μmol/kg subcutaneous (s.c.) morphine twice daily for three days. On the fourth day we measured the antinociceptive effect of DAMGO alone and combined with delta ligands: DPDPE, deltorphin II (agonists), TIPP and TICPψ (antagonists), respectively, administered intrathecally (i.t.) in mouse tail-flick test. In naive control mice none of the δ ligands caused significant changes in the antinociceptive action of DAMGO. The treatment with s.c. morphine resulted in approximately four-fold tolerance to i.t. DAMGO, i.e. the ED₅₀ value of DAMGO was four times as high as in naive mice. 500 and 1000 pmol/mouse of the δ₁ selective agonist DPDPE enhanced the tolerance to DAMGO while 1000 pmol/mouse of the δ₂ selective agonist deltorphin II did not influence the degree of tolerance. However, both δ antagonists TIPP and TICPψ potentiated the antinociceptive effect of i.t. DAMGO, thus they restored the potency of DAMGO to the control level. The inhibitory action of DPDPE against the antinociceptive effect of DAMGO could be antagonized by TIPP and TICPψ. We hypothesize that during the development of morphine tolerance the formation of μδ heterodimers may contribute to the spinal opioid tolerance. δ ligands may affect the dimer formation differently. Those, like DPDPE may facilitate the dimer formation hence inhibit the antinociceptive effect of DAMGO by causing virtual μ receptor down-regulation. Ligands that do not affect the dimer formation do not influence antinociception either but ligands with the presumed capability of disconnecting the dimers may decrease the spinal tolerance to DAMGO.
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Affiliation(s)
- A K Szentirmay
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvárad Tér 4, P.O. Box 370, H-1445 Budapest, Hungary
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Wilson-Poe AR, Morgan MM, Aicher SA, Hegarty DM. Distribution of CB1 cannabinoid receptors and their relationship with mu-opioid receptors in the rat periaqueductal gray. Neuroscience 2012; 213:191-200. [PMID: 22521830 DOI: 10.1016/j.neuroscience.2012.03.038] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Revised: 02/15/2012] [Accepted: 03/13/2012] [Indexed: 11/15/2022]
Abstract
The periaqueductal gray (PAG) is part of a descending pain modulatory system that, when activated, produces widespread and profound antinociception. Microinjection of either opioids or cannabinoids into the PAG elicits antinociception. Moreover, microinjection of the cannabinoid 1 (CB1) receptor agonist HU-210 into the PAG enhances the antinociceptive effect of subsequent morphine injections, indicating a direct relationship between these two systems. The objective of this study was to characterize the distribution of CB1 receptors in the dorsolateral and ventrolateral PAG in relationship to mu-opioid peptide (MOP) receptors. Immunocytochemical analysis revealed extensive and diffuse CB1 receptor labeling in the PAG, 60% of which was found in somatodendritic profiles. CB1 and MOP receptor immunolabeling were co-localized in 32% of fluorescent Nissl-stained cells that were analyzed. Eight percent (8%) of PAG neurons that were MOP receptor-immunoreactive (-ir) received CB1 receptor-ir appositions. Ultrastructural analysis confirmed the presence of CB1 receptor-ir somata, dendrites and axon terminals in the PAG. These results indicate that behavioral interactions between cannabinoids and opioids may be the result of cellular adaptations within PAG neurons co-expressing CB1 and MOP receptors.
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Affiliation(s)
- A R Wilson-Poe
- Department of Neuroscience, Washington State University, 14204 NE Salmon Creek Avenue, Vancouver, WA 98686, USA.
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Block L, Forshammar J, Westerlund A, Björklund U, Lundborg C, Biber B, Hansson E. Naloxone in ultralow concentration restores endomorphin-1-evoked Ca²⁺ signaling in lipopolysaccharide pretreated astrocytes. Neuroscience 2012; 205:1-9. [PMID: 22245502 DOI: 10.1016/j.neuroscience.2011.12.058] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 12/28/2011] [Indexed: 12/19/2022]
Abstract
Long-term pain is a disabling condition that affects thousands of people. Pain may be sustained for a long time even after the physiological trigger has resolved. Possible mechanisms for this phenomenon include low-grade inflammation in the CNS. Astrocytes respond to inflammatory stimuli and may play an important role as modulators of the inflammatory response in the nervous system. This study aimed first to assess how astrocytes in a primary culture behave when exposed to the endogenous μ-opioid receptor agonist endomorphin-1 (EM-1), in a concentration-dependent manner, concerning intracellular Ca²⁺ responses. EM-1 stimulated the μ-opioid receptor from 10⁻¹⁵ M up to 10⁻⁴ M with increasing intensity, usually reflected as one peak at low concentrations and two peaks at higher concentrations. Naloxone, pertussis toxin (PTX), or the μ-opioid receptor antagonists CTOP did not totally block the EM-1-evoked Ca²⁺ responses. However, a combination of ultralow concentration naloxone (10⁻¹² M) and PTX (100 ng/ml) totally blocked the EM-1-evoked Ca²⁺ responses. This suggests that ultralow (picomolar) concentrations of naloxone should block the μ-opioid receptor coupled G(s) protein, and that PTX should block the μ-opioid receptor coupled G(i/o) protein. The second aim was to investigate exposure of astrocytes with the inflammatory agent lipopolysaccharide (LPS). After 4 h of LPS incubation, the EM-1-evoked Ca²⁺ transients were attenuated, and after 24 h of LPS incubation, the EM-1-evoked Ca²⁺ transients were oscillated. To restore the EM-1-evoked Ca²⁺ transients, naloxone was assessed as a proposed anti-inflammatory substance. In ultralow picomolar concentration, naloxone demonstrated the ability to restore the Ca²⁺ transients.
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Affiliation(s)
- L Block
- Department of Anesthesiology and Intensive Care Medicine, Institute of Clinical Sciences, The Sahlgrenska Academy, University of Gothenburg, SE 41345 Gothenburg, Sweden
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Lee CWS, Yan JY, Chiang YC, Hung TW, Wang HL, Chiou LC, Ho IK. Differential pharmacological actions of methadone and buprenorphine in human embryonic kidney 293 cells coexpressing human μ-opioid and opioid receptor-like 1 receptors. Neurochem Res 2011; 36:2008-21. [PMID: 21671107 PMCID: PMC3183316 DOI: 10.1007/s11064-011-0525-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/03/2011] [Indexed: 11/26/2022]
Abstract
Methadone and buprenorphine are used in maintenance therapy for heroin addicts. In this study, we compared their effects on adenylate cyclase (AC) activity in human embryonic kidney (HEK) 293 cells stably overexpressing human μ-opioid receptor (MOR) and nociceptin/opioid receptor-like 1 receptor (ORL1) simultaneously. After acute exposure, methadone inhibited AC activity; however, buprenorphine induced compromised AC inhibition. When naloxone was introduced after 30 min incubation with methadone, the AC activity was enhanced. This was not observed in the case of buprenorphine. Enhancement of the AC activity was more significant when the incubation lasted for 4 h, and prolonged exposure to buprenorphine elevated the AC activity as well. The removal of methadone and buprenorphine by washing also obtained similar AC superactivation as that revealed by naloxone challenge. The study demonstrated that methadone and buprenorphine exert initially different yet eventually convergent adaptive changes of AC activity in cells coexpressing human MOR and ORL1 receptors.
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Affiliation(s)
- Cynthia Wei-Sheng Lee
- Division of Mental Health and Addiction Medicine, Institute of Population Health Sciences, National Health Research Institutes, 35 Keyan Road, Zhunan, Miaoli County, 35053 Taiwan
| | - Jia-Ying Yan
- Division of Mental Health and Addiction Medicine, Institute of Population Health Sciences, National Health Research Institutes, 35 Keyan Road, Zhunan, Miaoli County, 35053 Taiwan
| | - Yao-Chang Chiang
- Division of Mental Health and Addiction Medicine, Institute of Population Health Sciences, National Health Research Institutes, 35 Keyan Road, Zhunan, Miaoli County, 35053 Taiwan
| | - Tsai-Wei Hung
- Division of Mental Health and Addiction Medicine, Institute of Population Health Sciences, National Health Research Institutes, 35 Keyan Road, Zhunan, Miaoli County, 35053 Taiwan
| | - Hung-Li Wang
- Department of Physiology, Chang Gung University School of Medicine, Kwei-San, Taoyuan, 33302 Taiwan
| | - Lih-Chu Chiou
- Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, 10051 Taiwan
| | - Ing-Kang Ho
- Division of Mental Health and Addiction Medicine, Institute of Population Health Sciences, National Health Research Institutes, 35 Keyan Road, Zhunan, Miaoli County, 35053 Taiwan
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Abstract
Opioid analgesics elicit their effects via activation of the mu-opioid receptor (MOR), a G protein-coupled receptor known to interact with Gα(i/o)-type G proteins. Work in vitro has suggested that MOR couples preferentially to the abundant brain Gα(i/o) isoform, Gα(o). However, studies in vivo evaluating morphine-mediated antinociception have not supported these findings. The aim of the present work was to evaluate the contribution of Gα(o) to MOR-dependent signaling by measuring both antinociceptive and biochemical endpoints in a Gα(o) null transgenic mouse strain. Male wild-type and Gα(o) heterozygous null (Gα(o) ⁺/⁻) mice were tested for opioid antinociception in the hot plate test or the warm-water tail withdrawal test as measures of supraspinal or spinal antinociception, respectively. Reduction in Gα(o) levels attenuated the supraspinal antinociception produced by morphine, methadone, and nalbuphine, with the magnitude of suppression dependent on agonist efficacy. This was explained by a reduction in both high-affinity MOR expression and MOR agonist-stimulated G protein activation in whole brain homogenates from Gα(o) ⁺/⁻ and Gα(o) homozygous null (Gα(o)⁻/⁻) mice, compared with wild-type littermates. On the other hand, morphine spinal antinociception was not different between Gα(o) ⁺/⁻ and wild-type mice and high-affinity MOR expression was unchanged in spinal cord tissue. However, the action of the partial agonist nalbuphine was compromised, showing that reduction in Gα(o) protein does decrease spinal antinociception, but suggesting a higher Gα(o) protein reserve. These results provide the first in vivo evidence that Gα(o) contributes to maximally efficient MOR signaling and antinociception.
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Dietis N, Rowbotham DJ, Lambert DG. Opioid receptor subtypes: fact or artifact? Br J Anaesth 2011; 107:8-18. [PMID: 21613279 DOI: 10.1093/bja/aer115] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
There is a vast amount of pharmacological evidence favouring the existence of multiple subtypes of opioid receptors. In addition to the primary classification of µ (mu: MOP), δ (delta: DOP), κ (kappa: KOP) receptors, and the nociceptin/orphanin FQ peptide receptor (NOP), various groups have further classified the pharmacological µ into µ(1-3), the δ into δ(1-2)/δ(complexed/non-complexed), and the κ into κ(1-3). From an anaesthetic perspective, the suggestions that µ(1) produced analgesia and µ(2) produced respiratory depression are particularly important. However, subsequent to the formal identification of the primary opioid receptors (MOP/DOP/KOP/NOP) by cloning and the use of this information to produce knockout animals, evidence for these additional subtypes is lacking. Indeed, knockout of a single gene (and hence receptor) results in a loss of all function associated with that receptor. In the case of MOP knockout, analgesia and respiratory depression is lost. This suggests that further sub-classification of the primary types is unwise. So how can the wealth of pharmacological data be reconciled with new molecular information? In addition to some simple misclassification (κ(3) is probably NOP), there are several possibilities which include: (i) alternate splicing of a common gene product, (ii) receptor dimerization, (iii) interaction of a common gene product with other receptors/signalling molecules, or (iv) a combination of (i)-(iii). Assigning variations in ligand activity (pharmacological subtypes) to one or more of these molecular suggestions represents an interesting challenge for future opioid research.
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Affiliation(s)
- N Dietis
- Department of Cardiovascular Sciences (Pharmacology and Therapeutics Group), Division of Anaesthesia, Critical Care and Pain Management, University of Leicester, Leicester Royal Infirmary, Leicester LE1 5WW, UK
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79
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Pappas SS, Kennedy T, Goudreau JL, Lookingland KJ. Opioid-mediated regulation of A11 diencephalospinal dopamine neurons: pharmacological evidence of activation by morphine. Neuropharmacology 2011; 61:614-21. [PMID: 21605572 DOI: 10.1016/j.neuropharm.2011.05.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Revised: 04/30/2011] [Accepted: 05/03/2011] [Indexed: 11/17/2022]
Abstract
Dopamine (DA) neurons of the A11 diencephalospinal system represent the sole source of DA innervation to the spinal cord in mice, serving neuromodulatory roles in the processing of nociceptive input and movement. These neurons originate in the dorso-caudal diencephalon and project axons unilaterally throughout the rostrocaudal extent of the spinal cord, terminating predominantly in the dorsal horn. The density of A11 DA axon terminals in the lumbar region is greater in males compared to females, while in both sexes the activity of neurons terminating in the thoracic spinal cord is greater than those terminating in the lumbar region. The present study was designed to test the hypothesis that A11 DA neurons are activated by opioids. To test this hypothesis, male and female mice were systemically treated with agonists or antagonists acting at the μ-opioid receptor, and spinal cord concentrations of DA and its metabolite DOPAC were determined in the thoracic and lumbar spinal cord using high performance liquid chromatography coupled with electrochemical detection. Systemic administration of the μ-opioid agonist morphine led to a dose- and time-dependent increase in spinal cord DOPAC/DA ratio (an estimate of DA neuronal activity) in both male and female mice, with greater changes occurring in the lumbar segment. Blockade of opioid receptors with the opioid antagonist naloxone reversed the stimulatory effects of morphine on A11 DA neurons in both male and female mice, but had little to no effect on the activity of these neurons when administered alone. Present findings are consistent with the conclusion that spinal cord-projecting axon terminals of A11 DA neurons are activated by opioids in both male and female mice, most likely through a dis-inhibitory mechanism.
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Affiliation(s)
- Samuel S Pappas
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA
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80
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Wang Y, Kong Y, Shei GJ, Kang L, Cvijic ME. Development of a cyclic adenosine monophosphate assay for Gi-coupled G protein-coupled receptors by utilizing the endogenous calcitonin activity in Chinese hamster ovary cells. Assay Drug Dev Technol 2011; 9:522-31. [PMID: 21561374 DOI: 10.1089/adt.2010.0361] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Activation of G(i)-coupled G protein-coupled receptor (GPCRs) by their ligands leads to inhibition of adenylyl cyclase (AC) and reduction of cyclic adenosine monophosphate (cAMP) levels in cells. The traditional cAMP assay for G(i)-coupled GPCRs commonly uses forskolin, a nonspecific AC activator, to increase the basal cAMP level in cells to create an assay window for ligand detection. However, there is still a need to develop a nonforskolin-based cAMP assay because of the challenges inherent in titrating the concentration of forskolin to achieve a reliable assay window, along with issues related to the cAMP-independent effects of forskolin. Herein, we describe such an assay by utilizing the endogenous activity of the calcitonin receptor in Chinese hamster ovary (CHO) cells. The calcitonin receptor is a G(s)-coupled GPCR that, when activated by calcitonin, leads to the stimulation of AC and increases cAMP in cells. Thus, we use calcitonin, instead of forskolin, to increase the basal cAMP level in CHO cells to achieve an assay window. We demonstrated that calcitonin peptides robustly increased cAMP accumulation in several CHO cell lines stably expressing well-known G(i)-coupled GPCRs, such as the Dopamine D2 receptor, the Opioid μ receptor, or the Cannabinoid receptor-1. Agonists of these G(i)-coupled GPCRs attenuated calcitonin-induced cAMP production in their receptor stable cell lines. On the other hand, antagonists and/or inverse agonists blocked the effects of their agonists on calcitonin-induced cAMP production. This calcitonin-based cAMP assay has been demonstrated to be sensitive and robust and exhibited acceptable assay windows (signal/noise ratio) and, thus, can be applied to screen for agonists and antagonists/inverse agonists of G(i)-coupled GPCRs in high-throughput screening formats.
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Affiliation(s)
- Yuren Wang
- Metabolic Disease Research, Bristol-Myers Squibb Company, 311 Pennington-Rocky Hill Road, Pennington, NJ 08534, USA.
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81
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Thorpe AJ, Clair A, Hochman S, Clemens S. Possible Sites of Therapeutic Action in Restless Legs Syndrome: Focus on Dopamine and α 2δ Ligands. Eur Neurol 2011; 66:18-29. [DOI: 10.1159/000328431] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 04/11/2011] [Indexed: 01/01/2023]
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82
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Ficus deltoidea (Mas cotek) extract exerted anti-melanogenic activity by preventing tyrosinase activity in vitro and by suppressing tyrosinase gene expression in B16F1 melanoma cells. Arch Dermatol Res 2010; 303:161-70. [DOI: 10.1007/s00403-010-1089-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2010] [Revised: 09/29/2010] [Accepted: 10/04/2010] [Indexed: 11/27/2022]
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83
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Velázquez-Marrero CM, Marrero HG, Lemos JR. Voltage-dependent kappa-opioid modulation of action potential waveform-elicited calcium currents in neurohypophysial terminals. J Cell Physiol 2010; 225:223-32. [PMID: 20506396 DOI: 10.1002/jcp.22247] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Release of neurotransmitter is activated by the influx of calcium. Inhibition of Ca(2+) channels results in less calcium influx into the terminals and presumably a reduction in transmitter release. In the neurohypophysis (NH), Ca(2+) channel kinetics, and the associated Ca(2+) influx, is primarily controlled by membrane voltage and can be modulated, in a voltage-dependent manner, by G-protein subunits interacting with voltage-gated calcium channels (VGCCs). In this series of experiments we test whether the kappa- and micro-opioid inhibition of Ca(2+) currents in NH terminals is voltage-dependent. Voltage-dependent relief of G-protein inhibition of VGCC can be achieved with either a depolarizing square pre-pulse or by action potential waveforms. Both protocols were tested in the presence and absence of opioid agonists targeting the kappa- and micro-receptors in neurohypophysial terminals. The kappa-opioid VGCC inhibition is relieved by such pre-pulses, suggesting that this receptor is involved in a voltage-dependent membrane delimited pathway. In contrast, micro-opioid inhibition of VGCC is not relieved by such pre-pulses, indicating a voltage-independent diffusible second-messenger signaling pathway. Furthermore, relief of kappa-opioid inhibition during a physiologic action potential (AP) burst stimulation indicates the possibility of activity-dependent modulation in vivo. Differences in the facilitation of Ca(2+) channels due to specific G-protein modulation during a burst of APs may contribute to the fine-tuning of Ca(2+)-dependent neuropeptide release in other CNS terminals, as well.
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Affiliation(s)
- Cristina M Velázquez-Marrero
- Department of Physiology and Program in Neuroscience, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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84
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Molecular assays for characterization of alternatively spliced isoforms of the u opioid receptor (MOR). Methods Mol Biol 2010; 617:421-35. [PMID: 20336438 DOI: 10.1007/978-1-60327-323-7_30] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Mu-opioid receptor (MOR) belongs to a family of heptahelical G-protein-coupled receptors (GPCRs). Studies in humans and rodents demonstrated that the OPRM1 gene coding for MOR undergoes extensive alternative splicing afforded by the genetic complexity of OPRM1. Evidence from rodent studies also demonstrates an important role of these alternatively spliced forms in mediating opiate analgesia via their differential signaling properties. MOR signaling is predominantly G(ia) coupled. Release of the alpha subunit from G-protein complex results in the inhibition of adenylyl cyclase/cAMP pathway, whereas release of the betagamma subunits activates G-protein-activated inwardly rectifying potassium channels and inhibits voltage-dependent calcium channels. These molecular events result in the suppression of cellular activities that diminish pain sensations. Recently, a new isoform of OPRM1, MOR3, has been identified that shows an increase in the production of nitric oxide (NO) upon stimulation with morphine. Hence, there is a need to describe molecular techniques that enable the functional characterization of MOR isoforms. In this review, we describe the methodologies used to assay key mediators of MOR activation including cellular assays for cAMP, free Ca(2+), and NO, all of which have been implicated in the pharmacological effects of MOR agonists.
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85
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Gris P, Gauthier J, Cheng P, Gibson DG, Gris D, Laur O, Pierson J, Wentworth S, Nackley AG, Maixner W, Diatchenko L. A novel alternatively spliced isoform of the mu-opioid receptor: functional antagonism. Mol Pain 2010; 6:33. [PMID: 20525224 PMCID: PMC2894766 DOI: 10.1186/1744-8069-6-33] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Accepted: 06/02/2010] [Indexed: 01/05/2023] Open
Abstract
Background Opioids are the most widely used analgesics for the treatment of clinical pain. They produce their therapeutic effects by binding to μ-opioid receptors (MORs), which are 7 transmembrane domain (7TM) G-protein-coupled receptors (GPCRs), and inhibiting cellular activity. However, the analgesic efficacy of opioids is compromised by side-effects such as analgesic tolerance, dependence and opioid-induced hyperalgesia (OIH). In contrast to opioid analgesia these side effects are associated with cellular excitation. Several hypotheses have been advanced to explain these phenomena, yet the molecular mechanisms underlying tolerance and OIH remain poorly understood. Results We recently discovered a new human alternatively spliced isoform of MOR (MOR1K) that is missing the N-terminal extracellular and first transmembrane domains, resulting in a 6TM GPCR variant. To characterize the pattern of cellular transduction pathways activated by this human MOR1K isoform, we conducted a series of pharmacological and molecular experiments. Results show that stimulation of MOR1K with morphine leads to excitatory cellular effects. In contrast to stimulation of MOR1, stimulation of MOR1K leads to increased Ca2+ levels as well as increased nitric oxide (NO) release. Immunoprecipitation experiments further reveal that unlike MOR1, which couples to the inhibitory Gαi/o complex, MOR1K couples to the stimulatory Gαs complex. Conclusion The major MOR1 and the alternative MOR1K isoforms mediate opposite cellular effects in response to morphine, with MOR1K driving excitatory processes. These findings warrant further investigations that examine animal and human MORK1 expression and function following chronic exposure to opioids, which may identify MOR1K as a novel target for the development of new clinically effective classes of opioids that have high analgesic efficacy with diminished ability to produce tolerance, OIH, and other unwanted side-effects.
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Affiliation(s)
- Pavel Gris
- Center for Neurosensory Disorders, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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86
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β-Arrestin2 influences the response to methadone in opioid-dependent patients. THE PHARMACOGENOMICS JOURNAL 2010; 11:258-66. [PMID: 20514076 DOI: 10.1038/tpj.2010.37] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
β-Arrestin2 (ARRB2) is a component of the G-protein-coupled receptor complex and is involved in μ-opioid and dopamine D(2) receptor signaling, two central processes in methadone signal transduction. We analyzed 238 patients in methadone maintenance treatment (MMT) and identified a haplotype block (rs34230287, rs3786047, rs1045280 and rs2036657) spanning almost the entire ARRB2 locus. Although none of these single nucleotide polymorphisms (SNPs) leads to a change in amino-acid sequence, we found that for all the SNPs analyzed, with exception of rs34230287, homozygosity for the variant allele confers a nonresponding phenotype (n=73; rs1045280C and rs2036657G: OR=3.1, 95% CI=1.5-6.3, P=0.004; rs3786047A: OR=2.5, 95% CI=1.2-5.1, P=0.02) also illustrated by a 12-fold shorter period of negative urine screening (P=0.01). The ARRB2 genotype may thus contribute to the interindividual variability in the response to MMT and help to predict response to treatment.
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87
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Cortez AM, Charntikov S, Der-Ghazarian T, Horn LR, Crawford CA, McDougall SA. Age-dependent effects of kappa-opioid receptor stimulation on cocaine-induced stereotyped behaviors and dopamine overflow in the caudate-putamen: an in vivo microdialysis study. Neuroscience 2010; 169:203-13. [PMID: 20435099 DOI: 10.1016/j.neuroscience.2010.04.052] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Revised: 04/07/2010] [Accepted: 04/23/2010] [Indexed: 11/28/2022]
Abstract
kappa-Opioid receptor stimulation attenuates psychostimulant-induced increases in extracellular dopamine in the caudate-putamen (CPu) and nucleus accumbens of adult rats, while reducing cocaine-induced locomotor activity and stereotyped behaviors. Because kappa-opioid receptor agonists (e.g., U50,488 or U69,593) often affect the behavior of preweanling rats in a paradoxical manner, the purpose of the present study was to determine whether kappa-opioid receptor stimulation differentially affects dopaminergic functioning in the CPu depending on age. In vivo microdialysis was used to determine whether U50,488 (5 mg/kg) attenuates cocaine-induced dopamine overflow in the dorsal CPu on postnatal day (PD) 17 and PD 85. In the microinjection experiment, cocaine-induced stereotyped behaviors were assessed in adult and preweanling rats after bilateral infusions of vehicle or U50,488 (1.6 or 6.4 microg per side) into the CPu. Results showed that U50,488 attenuated the cocaine-induced increases in CPu dopamine overflow on PD 85, while the same dose of U50,488 did not alter dopamine dialysate levels on PD 17. Cocaine also increased stereotyped behaviors (repetitive motor movements, behavioral intensity scores, and discrete behaviors) at both ages, but adult rats appeared to exhibit more intense stereotypic responses than the younger animals. Consistent with the microdialysis findings, bilateral infusions of U50,488 into the dorsal CPu decreased the cocaine-induced stereotypies of adult rats, while leaving the behaviors of preweanling rats unaffected. These results suggest that the neural mechanisms underlying kappa-opioid/dopamine interactions in the CPu are not fully mature during the preweanling period. This lack of functional maturity may explain why kappa-opioid receptor agonists frequently induce different behavioral effects in young and adult rats.
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Affiliation(s)
- A M Cortez
- Department of Psychology, California State University, San Bernardino, CA 92407, USA
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88
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Protein kinase C mediates the synergistic interaction between agonists acting at alpha2-adrenergic and delta-opioid receptors in spinal cord. J Neurosci 2009; 29:13264-73. [PMID: 19846714 DOI: 10.1523/jneurosci.1907-09.2009] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Coactivation of spinal alpha(2)-adrenergic receptors (ARs) and opioid receptors produces antinociceptive synergy. Antinociceptive synergy between intrathecally administered alpha(2)AR and opioid agonists is well documented, but the mechanism underlying this synergy remains unclear. The delta-opioid receptor (DOP) and the alpha(2A)ARs are coexpressed on the terminals of primary afferent fibers in the spinal cord where they may mediate this phenomenon. We evaluated the ability of the DOP-selective agonist deltorphin II (DELT), the alpha(2)AR agonist clonidine (CLON) or their combination to inhibit calcitonin gene-related peptide (CGRP) release from spinal cord slices. We then examined the possible underlying signaling mechanisms involved through coadministration of inhibitors of phospholipase C (PLC), protein kinase C (PKC) or protein kinase A (PKA). Potassium-evoked depolarization of spinal cord slices caused concentration-dependent release of CGRP. Coadministration of DELT and CLON inhibited the release of CGRP in a synergistic manner as confirmed statistically by isobolograpic analysis. Synergy was dependent on the activation of PLC and PKC, but not PKA, whereas the effect of agonist administration alone was only dependent on PLC. The importance of these findings was confirmed in vivo, using a thermal nociceptive test, demonstrating the PKC dependence of CLON-DELT antinociceptive synergy in mice. That inhibition of CGRP release by the combination was maintained in the presence of tetrodotoxin in spinal cord slices suggests that synergy does not rely on interneuronal signaling and may occur within single subcellular compartments. The present study reveals a novel signaling pathway underlying the synergistic analgesic interaction between DOP and alpha(2)AR agonists in the spinal cord.
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89
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Georgescu M, Sabongui C, Del Corpo A, Marsan L, Pfaus JG. Vaginocervical stimulation induces Fos in glutamate neurons in the ventromedial hypothalamus: attenuation by estrogen and progesterone. Horm Behav 2009; 56:450-6. [PMID: 19665463 DOI: 10.1016/j.yhbeh.2009.07.014] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Revised: 07/30/2009] [Accepted: 07/30/2009] [Indexed: 10/20/2022]
Abstract
Vaginocervical stimulation (VCS) induces the immediate-early gene product Fos in the ventromedial hypothalamus (VMH) of female rats. However, this induction is lower in ovariectomized rats that receive estradiol benzoate (EB) and progesterone (P) relative to an oil vehicle. We have observed that a substantial proportion of cells activated in the VMH by VCS stain for glutamate, and infusions of glutamate or its selective receptor agonists to the VMH inhibit both appetitive and consummatory sexual behaviors in females. This raises the possibility that VCS activates an inhibitory glutamate system in the VMH, and that ovarian steroids blunt the activation, although it is not known whether EB or P, alone or in combination, lead to this effect. The present experiment examined the ability of VCS to induce Fos in glutamate neurons in the VMH of ovariectomized rats under 4 hormonal regimens: oil, EB alone, P alone, or EB+P, following 1 or 50 distributed VCSs administered with a lubricated glass rod over the course of 1 h. Treatment with EB or P alone significantly reduced the number of glutamate neurons activated by 1 VCS, with P being more effective than EB. Treatment with EB+P also produced a significant reduction, but not to the extent of EB or P alone. Although EB and P work in synergy to activate sexual behavior in female rats, actions of EB or P alone are sufficient to blunt the ability of VCS to activate glutamate neurons in the VMH. It thus appears that ovarian steroids may "disinhibit" sexual responding, in part, by dampening the ability of VCS to activate glutamate neurons in the VMH. In turn, this may allow females to receive a sufficient number of intromissions for the activation of sexual reward and the facilitation of pregnancy.
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Affiliation(s)
- Michaela Georgescu
- Center for Studies in Behavioral Neurobiology, Department of Psychology, Concordia University, Montréal, QC, Canada
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90
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Grilli M, Neri E, Zappettini S, Massa F, Bisio A, Romussi G, Marchi M, Pittaluga A. Salvinorin A exerts opposite presynaptic controls on neurotransmitter exocytosis from mouse brain nerve terminals. Neuropharmacology 2009; 57:523-30. [DOI: 10.1016/j.neuropharm.2009.07.023] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 07/13/2009] [Accepted: 07/15/2009] [Indexed: 10/20/2022]
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91
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Fontana F, Bernardi P, Pizzi C, Spampinato S, Bedini A, Pich EM. Plasma nociceptin/orphanin FQ levels rise after spontaneous episodes of angina, but not during induced myocardial ischemia. Peptides 2009; 30:1705-9. [PMID: 19560501 DOI: 10.1016/j.peptides.2009.06.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Revised: 06/16/2009] [Accepted: 06/17/2009] [Indexed: 10/20/2022]
Abstract
The aim of our study was to evaluate the effects of repeated episodes of angina and induced myocardial ischemia on plasma nociceptin/orphanin FQ (N/OFQ) levels. Patients with unstable angina (23 with new onset severe angina or accelerated angina and 18 with subacute angina at rest) who had had repeated spontaneous episodes of chest pain in the last week before the study underwent myocardial perfusion single-photon emission computed tomography using adenosine infusion. Twenty subjects without clinical symptoms of angina matched for age, sex and cardiac risk factors served as a control group. N/OFQ levels were significantly (P<0.01) higher in the patients (15.2+/-2.1 pg/ml) than in the control group (8.5+/-2.6 pg/ml). Blood pressure and heart rate did not significantly differ. All patients showed transient adenosine infusion myocardial ischemia that did not induce chest pain or significantly modify plasma N/OFQ levels or hemodynamic parameters. Our findings show that unstable angina is associated with a significant increase in circulating N/OFQ levels unrelated to intervening transient myocardial ischemia or hemodynamic changes. This increase is probably related to the chest pain repeatedly occurring in the course of coronary artery disease, but absent during transient adenosine-induced myocardial ischemia.
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Affiliation(s)
- Fiorella Fontana
- Dipartimento di Medicina Interna, dell'Invecchiamento e Malattie Nefrologiche, Ospedale S. Orsola, Via Massarenti 9, Bologna, Italy.
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92
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Lopez A, Salomé L. Membrane functional organisation and dynamic of mu-opioid receptors. Cell Mol Life Sci 2009; 66:2093-108. [PMID: 19300905 PMCID: PMC11115522 DOI: 10.1007/s00018-009-0008-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2008] [Revised: 02/17/2009] [Accepted: 02/18/2009] [Indexed: 12/30/2022]
Abstract
The activation and signalling activity of the membrane mu-opioid receptor (MOP-R) involve interactions among the receptor, G-proteins, effectors and many other membrane or cytosolic proteins. Decades of investigation have led to identification of the main biochemical processes, but the mechanisms governing the successive protein-protein interactions have yet to be established. We will need to unravel the dynamic membrane organisation of this complex and multifaceted molecular machinery if we are to understand these mechanisms. Here, we review and discuss advances in our understanding of the signalling mechanism of MOP-R resulting from biochemical or biophysical studies of the organisation of this receptor in the plasma membrane.
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Affiliation(s)
- André Lopez
- CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, 31077 Toulouse, France
- Université de Toulouse, UPS, IPBS, 31077 Toulouse, France
| | - Laurence Salomé
- CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, 31077 Toulouse, France
- Université de Toulouse, UPS, IPBS, 31077 Toulouse, France
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93
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Abstract
Opioid efficacy on mu-receptor may be influenced by various Gi/o-G-protein subunits interacting with intracellular face of receptor. Pertussis toxin-insensitive Galphai1 and Galphai2 subunits tethered with mu-receptor were stably transfected into AtT20 cells to (i) determine coupling of different alpha-subunits on opioid efficacy, and (ii) determine coupling to downstream effectors, for example, calcium and potassium channels. After pertussis toxin, stimulation of [35S]GTP-gamma-S incorporation persisted. Both constructs were able to couple to native calcium and potassium channels, with endomorphins 1 and 2 equally effective. However, pertussis toxin abolished opioid actions on calcium and potassium channels suggesting strong coupling to endogenous G-proteins, and that differences in coupling efficacy to Galphai1 and Galphai2 previously observed are restricted to initial step of signaling cascade.
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Stein C, Clark JD, Oh U, Vasko MR, Wilcox GL, Overland AC, Vanderah TW, Spencer RH. Peripheral mechanisms of pain and analgesia. ACTA ACUST UNITED AC 2008; 60:90-113. [PMID: 19150465 DOI: 10.1016/j.brainresrev.2008.12.017] [Citation(s) in RCA: 184] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/29/2008] [Indexed: 12/23/2022]
Abstract
This review summarizes recent findings on peripheral mechanisms underlying the generation and inhibition of pain. The focus is on events occurring in peripheral injured tissues that lead to the sensitization and excitation of primary afferent neurons, and on the modulation of such mechanisms. Primary afferent neurons are of particular interest from a therapeutic perspective because they are the initial generator of noxious impulses traveling towards relay stations in the spinal cord and the brain. Thus, if one finds ways to inhibit the sensitization and/or excitation of peripheral sensory neurons, subsequent central events such as wind-up, sensitization and plasticity may be prevented. Most importantly, if agents are found that selectively modulate primary afferent function and do not cross the blood-brain-barrier, centrally mediated untoward side effects of conventional analgesics (e.g. opioids, anticonvulsants) may be avoided. This article begins with the peripheral actions of opioids, turns to a discussion of the effects of adrenergic co-adjuvants, and then moves on to a discussion of pro-inflammatory mechanisms focusing on TRP channels and nerve growth factor, their signaling pathways and arising therapeutic perspectives.
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Affiliation(s)
- Christoph Stein
- Department of Anesthesiology and Critical Care Medicine, Charité Campus Benjamin Franklin, Freie Universität Berlin, Germany
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95
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Suder P, Nawrat D, Bielawski A, Zelek-Molik A, Raoof H, Dylag T, Kotlinska J, Nalepa I, Silberring J. Cryptic peptide derived from the rat neuropeptide FF precursor affects G-proteins linked to opioid receptors in the rat brain. Peptides 2008; 29:1988-93. [PMID: 18706462 DOI: 10.1016/j.peptides.2008.07.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2008] [Revised: 07/01/2008] [Accepted: 07/15/2008] [Indexed: 11/22/2022]
Abstract
Recently, we reported the discovery of a novel amino acid sequence derived from the NPFF precursor NAWGPWSKEQLSPQA, which blocked the expression of conditioned place preference induced by morphine and reversed the antinociceptive activity of morphine (5mg/kg, s.c.) in the tail-immersion test in rats. Here, we name it as NPNA (Neuropeptide NA from its flanking amino acid residues). The synthetic peptide influenced the expression of mRNA coding for Galpha(i1), (i2), and (i3) subunits. The results provide further evidence that yet another bioactive sequence might be present within the NPFF precursor.
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Affiliation(s)
- Piotr Suder
- Department of Neurobiochemistry, Faculty of Chemistry and Regional Laboratory, Jagiellonian University, Ingardena 3 Street, 30-060 Krakow, Poland.
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96
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The novel inhibitor of the heterotrimeric G-protein complex, BIM-46187, elicits anti-hyperalgesic properties and synergizes with morphine. Eur J Pharmacol 2008; 594:70-6. [DOI: 10.1016/j.ejphar.2008.07.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Accepted: 07/10/2008] [Indexed: 01/03/2023]
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97
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Margas W, Sedeek K, Ruiz-Velasco V. Coupling specificity of NOP opioid receptors to pertussis-toxin-sensitive Galpha proteins in adult rat stellate ganglion neurons using small interference RNA. J Neurophysiol 2008; 100:1420-32. [PMID: 18562551 PMCID: PMC2544458 DOI: 10.1152/jn.90405.2008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Accepted: 06/15/2008] [Indexed: 01/18/2023] Open
Abstract
The opioid receptor-like 1 (NOP or ORL1) receptor is a G-protein-coupled receptor the endogenous ligand of which is the heptadecapeptide, nociceptin (Noc). NOP receptors are known to modulate pain processing at spinal, supraspinal, and peripheral levels. Previous work has demonstrated that NOP receptors inhibit N-type Ca2+ channel currents in rat sympathetic stellate ganglion (SG) neurons via pertussis toxin (PTX)-sensitive Galphai/o subunits. However, the identification of the specific Galpha subunit that mediates the Ca2+ current modulation is unknown. The purpose of the present study was to examine coupling specificity of Noc-activated NOP receptors to N-type Ca2+ channels in SG neurons. Small interference RNA (siRNA) transfection was employed to block the expression of PTX-sensitive Galpha subunits. RT-PCR results showed that siRNA specifically decreased the expression of the intended Galpha subunit. Evaluation of cell surface protein expression and Ca2+ channel modulation were assessed by immunofluorescence staining and electrophysiological recordings, respectively. Furthermore, the presence of mRNA of the intended siRNA target Galpha protein was examined by RT-PCR experiments. Fluorescence imaging showed that Galphai1, Galphai3, and Galphao were expressed in SG neurons. The transfection of Galphai1-specific siRNA resulted in a significant decrease in Noc-mediated Ca2+ current inhibition, while silencing of either Galphai3 or Galphao was without effect. Taken together, these results suggest that in SG neurons Galphai1 subunits selectively couple NOP receptors to N-type Ca2+ channels.
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Affiliation(s)
- Wojciech Margas
- Department of Anesthesiology, Penn State University College of Medicine, Hershey, PA 17033-0850, USA
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98
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Schoultz BW, Arstad E, Marton J, Willoch F, Drzezga A, Wester HJ, Henriksen G. A New Method for Radiosynthesis of C-Labeled Carbamate Groups and its Application for a Highly Efficient Synthesis of the Kappa-Opioid Receptor Tracer [C]GR103545. THE OPEN MEDICINAL CHEMISTRY JOURNAL 2008; 2:72-4. [PMID: 19662146 PMCID: PMC2704583 DOI: 10.2174/1874104500802010072] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Revised: 07/01/2008] [Accepted: 07/01/2008] [Indexed: 12/04/2022]
Abstract
11C-labeled carbamates can be obtained in a three-component coupling reaction of primary or secondary amines with CO2 and 11C-methylation reagents. [11C]Methyl-triflate mediated methylation of carbamino adducts provides the corresponding 11C-labeled carbamate groups in excellent yields under mild conditions (temperatures ≤ 40°C, 2 min reaction time). The utility of the method has been demonstrated by a highly efficient radiosynthesis of [11C]GR103545.
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Affiliation(s)
- B W Schoultz
- Department of Chemistry, University of Oslo, Norway
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99
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Abstract
G protein betagamma subunits are central participants in G protein-coupled receptor signaling pathways. They interact with receptors, G protein alpha subunits and downstream targets to coordinate multiple, different GPCR functions. Much is known about the biology of Gbetagamma subunits but mysteries remain. Here, we will review what is known about general aspects of structure and function of Gbetagamma as well as discuss emerging mechanisms for regulation of Gbetagamma signaling. Recent data suggest that Gbetagamma is a potential therapeutic drug target. Thus, a thorough understanding of the molecular and physiological functions of Gbetagamma has significant implications.
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Affiliation(s)
- A V Smrcka
- Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.
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100
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Smrcka AV, Lehmann DM, Dessal AL. G protein betagamma subunits as targets for small molecule therapeutic development. Comb Chem High Throughput Screen 2008; 11:382-95. [PMID: 18537559 PMCID: PMC2688719 DOI: 10.2174/138620708784534761] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
G proteins mediate the action of G protein coupled receptors (GPCRs), a major target of current pharmaceuticals and a major target of interest in future drug development. Most pharmaceutical interest has been in the development of selective GPCR agonists and antagonists that activate or inhibit specific GPCRs. Some recent thinking has focused on the idea that some pathologies are the result of the actions of an array of GPCRs suggesting that targeting single receptors may have limited efficacy. Thus, targeting pathways common to multiple GPCRs that control critical pathways involved in disease has potential therapeutic relevance. G protein betagamma subunits released from some GPCRs upon receptor activation regulate a variety of downstream pathways to control various aspects of mammalian physiology. There is evidence from cell- based and animal models that excess Gbetagamma signaling can be detrimental and blocking Gbetagamma signaling has salutary effects in a number of pathological models. Gbetagamma regulates downstream pathways through modulation of enzymes that produce cellular second messengers or through regulation of ion channels by direct protein-protein interactions. Thus, blocking Gbetagamma functions requires development of small molecule agents that disrupt Gbetagamma protein interactions with downstream partners. Here we discuss evidence that small molecule targeting Gbetagamma could be of therapeutic value. The concept of disruption of protein-protein interactions by targeting a "hot spot" on Gbetagamma is delineated and the biochemical and virtual screening strategies for identification of small molecules that selectively target Gbetagamma functions are outlined. Evaluation of the effectiveness of virtual screening indicates that computational screening enhanced identification of true Gbetagamma binding molecules. However, further refinement of the approach could significantly improve the yield of Gbetagamma binding molecules from this screen that could result in multiple candidate leads for future drug development.
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Affiliation(s)
- Alan V Smrcka
- Department of Pharmacology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
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