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Costa AR, Tavares I, Martins I. How do opioids control pain circuits in the brainstem during opioid-induced disorders and in chronic pain? Implications for the treatment of chronic pain. Pain 2024; 165:324-336. [PMID: 37578500 DOI: 10.1097/j.pain.0000000000003026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 07/07/2023] [Indexed: 08/15/2023]
Abstract
ABSTRACT Brainstem areas involved in descending pain modulation are crucial for the analgesic actions of opioids. However, the role of opioids in these areas during tolerance, opioid-induced hyperalgesia (OIH), and in chronic pain settings remains underappreciated. We conducted a revision of the recent studies performed in the main brainstem areas devoted to descending pain modulation with a special focus on the medullary dorsal reticular nucleus (DRt), as a distinctive pain facilitatory area and a key player in the diffuse noxious inhibitory control paradigm. We show that maladaptive processes within the signaling of the µ-opioid receptor (MOR), which entail desensitization and a switch to excitatory signaling, occur in the brainstem, contributing to tolerance and OIH. In the context of chronic pain, the alterations found are complex and depend on the area and model of chronic pain. For example, the downregulation of MOR and δ-opioid receptor (DOR) in some areas, including the DRt, during neuropathic pain likely contributes to the inefficacy of opioids. However, the upregulation of MOR and DOR, at the rostral ventromedial medulla, in inflammatory pain models, suggests therapeutic avenues to explore. Mechanistically, the rationale for the diversity and complexity of alterations in the brainstem is likely provided by the alternative splicing of opioid receptors and the heteromerization of MOR. In conclusion, this review emphasizes how important it is to consider the effects of opioids at these circuits when using opioids for the treatment of chronic pain and for the development of safer and effective opioids.
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Affiliation(s)
- Ana Rita Costa
- Department of Biomedicine, Unit of Experimental Biology, Faculty of Medicine, University of Porto, Porto, Portugal
- IBMC-Institute of Molecular and Cell Biology, University of Porto, Porto, Portugal
- I3S- Institute of Investigation and Innovation in Health, University of Porto, Porto, Portugal. Costa is now with the Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden and Science for Life Laboratory, Solna, Sweden
| | - Isaura Tavares
- Department of Biomedicine, Unit of Experimental Biology, Faculty of Medicine, University of Porto, Porto, Portugal
- IBMC-Institute of Molecular and Cell Biology, University of Porto, Porto, Portugal
- I3S- Institute of Investigation and Innovation in Health, University of Porto, Porto, Portugal. Costa is now with the Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden and Science for Life Laboratory, Solna, Sweden
| | - Isabel Martins
- Department of Biomedicine, Unit of Experimental Biology, Faculty of Medicine, University of Porto, Porto, Portugal
- IBMC-Institute of Molecular and Cell Biology, University of Porto, Porto, Portugal
- I3S- Institute of Investigation and Innovation in Health, University of Porto, Porto, Portugal. Costa is now with the Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden and Science for Life Laboratory, Solna, Sweden
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Bouchet CA, McPherson KB, Coutens B, Janowsky A, Ingram SL. Monoacylglycerol Lipase Protects the Presynaptic Cannabinoid 1 Receptor from Desensitization by Endocannabinoids after Persistent Inflammation. J Neurosci 2023; 43:5458-5467. [PMID: 37414560 PMCID: PMC10376933 DOI: 10.1523/jneurosci.0037-23.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 06/08/2023] [Accepted: 06/28/2023] [Indexed: 07/08/2023] Open
Abstract
Cannabinoid-targeted pain therapies are increasing with the expansion of cannabis legalization, however, their efficacy may be limited by pain-induced adaptations in the cannabinoid system. Cannabinoid receptor subtype 1 (CB1R) inhibition of spontaneous, GABAergic miniature IPSCs (mIPSCs) and evoked IPSCs (eIPSCs) in the ventrolateral periaqueductal gray (vlPAG) were compared in slices from naive and inflamed male and female Sprague Dawley rats. Complete Freund's Adjuvant (CFA) injections into the hindpaw induced persistent inflammation. In naive rats, exogenous cannabinoid agonists robustly reduce both eIPSCs and mIPSCs. After 5-7 d of inflammation, the effects of exogenous cannabinoids are significantly reduced because of CB1R desensitization via GRK2/3, as function is recovered in the presence of the GRK2/3 inhibitor, Compound 101 (Cmp101). Inhibition of GABA release by presynaptic μ-opioid receptors in the vlPAG does not desensitize with persistent inflammation. Unexpectedly, while CB1R desensitization significantly reduces the inhibition produced by exogenous agonists, depolarization-induced suppression of inhibition protocols that promote 2-arachidonoylglycerol (2-AG) synthesis exhibit prolonged CB1R activation after inflammation. 2-AG tone is detected in slices from CFA-treated rats when GRK2/3 is blocked, suggesting an increase in 2-AG synthesis after persistent inflammation. Inhibiting 2-AG degradation with the monoacylglycerol lipase (MAGL) inhibitor JZL184 during inflammation results in the desensitization of CB1Rs by endocannabinoids that is reversed with Cmp101. Collectively, these data indicate that persistent inflammation primes CB1Rs for desensitization, and MAGL degradation of 2-AG protects CB1Rs from desensitization in inflamed rats. These adaptations with inflammation have important implications for the development of cannabinoid-based pain therapeutics targeting MAGL and CB1Rs.SIGNIFICANCE STATEMENT Presynaptic G-protein-coupled receptors are resistant to desensitization. Here we find that persistent inflammation increases endocannabinoid levels, priming presynaptic cannabinoid 1 receptors for desensitization on subsequent addition of exogenous agonists. Despite the reduced efficacy of exogenous agonists, endocannabinoids have prolonged efficacy after persistent inflammation. Endocannabinoids readily induce cannabinoid 1 receptor desensitization if their degradation is blocked, indicating that endocannabinoid concentrations are maintained at subdesensitizing levels and that degradation is critical for maintaining endocannabinoid regulation of presynaptic GABA release in the ventrolateral periaqueductal gray during inflammatory states. These adaptations with inflammation have important implications for the development of cannabinoid-based pain therapies.
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Affiliation(s)
- Courtney A Bouchet
- Department of Neurological Surgery, Oregon Health & Science University, Portland, Oregon 97239
- Neuroscience Graduate Program, Vollum Institute, Portland, Oregon 97239
| | - Kylie B McPherson
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045
| | - Basile Coutens
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045
| | - Aaron Janowsky
- Research Service, VA Portland Health Care System, Portland, Oregon 97239
- Departments of Psychiatry, and Behavioral Neuroscience, Oregon Health & Science University, Portland, Oregon 97239
| | - Susan L Ingram
- Department of Neurological Surgery, Oregon Health & Science University, Portland, Oregon 97239
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045
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3
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Ma R, Kutchy NA, Wang Z, Hu G. Extracellular vesicle-mediated delivery of anti-miR-106b inhibits morphine-induced primary ciliogenesis in the brain. Mol Ther 2023; 31:1332-1345. [PMID: 37012704 PMCID: PMC10188913 DOI: 10.1016/j.ymthe.2023.03.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 03/27/2023] [Accepted: 03/29/2023] [Indexed: 04/05/2023] Open
Abstract
Repeated use of opioids such as morphine causes changes in the shape and signal transduction pathways of various brain cells, including astrocytes and neurons, resulting in alterations in brain functioning and ultimately leading to opioid use disorder. We previously demonstrated that extracellular vesicle (EV)-induced primary ciliogenesis contributes to the development of morphine tolerance. Herein, we aimed to investigate the underlying mechanisms and potential EV-mediated therapeutic approach to inhibit morphine-mediated primary ciliogenesis. We demonstrated that miRNA cargo in morphine-stimulated-astrocyte-derived EVs (morphine-ADEVs) mediated morphine-induced primary ciliogenesis in astrocytes. CEP97 is a target of miR-106b and is a negative regulator of primary ciliogenesis. Intranasal delivery of ADEVs loaded with anti-miR-106b decreased the expression of miR-106b in astrocytes, inhibited primary ciliogenesis, and prevented the development of tolerance in morphine-administered mice. Furthermore, we confirmed primary ciliogenesis in the astrocytes of opioid abusers. miR-106b-5p in morphine-ADEVs induces primary ciliogenesis via targeting CEP97. Intranasal delivery of ADEVs loaded with anti-miR-106b ameliorates morphine-mediated primary ciliogenesis and prevents morphine tolerance. Our findings bring new insights into the mechanisms underlying primary cilium-mediated morphine tolerance and pave the way for developing ADEV-mediated small RNA delivery strategies for preventing substance use disorders.
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Affiliation(s)
- Rong Ma
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China; Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198-5880, USA.
| | - Naseer A Kutchy
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198-5880, USA; Department of Animal Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901- 8525, USA
| | - Zhongbin Wang
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198-5880, USA
| | - Guoku Hu
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198-5880, USA.
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4
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Coutens B, Ingram SL. Key differences in regulation of opioid receptors localized to presynaptic terminals compared to somas: Relevance for novel therapeutics. Neuropharmacology 2023; 226:109408. [PMID: 36584882 PMCID: PMC9898207 DOI: 10.1016/j.neuropharm.2022.109408] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 12/05/2022] [Accepted: 12/27/2022] [Indexed: 12/29/2022]
Abstract
Opioid receptors are G protein-coupled receptors (GPCRs) that regulate activity within peripheral, subcortical and cortical circuits involved in pain, reward, and aversion processing. Opioid receptors are expressed in both presynaptic terminals where they inhibit neurotransmitter release and postsynaptic locations where they act to hyperpolarize neurons and reduce activity. Agonist activation of postsynaptic receptors at the plasma membrane signal via ion channels or cytoplasmic second messengers. Agonist binding initiates regulatory processes that include phosphorylation by G protein receptor kinases (GRKs) and recruitment of beta-arrestins that desensitize and internalize the receptors. Opioid receptors also couple to effectors from endosomes activating intracellular enzymes and kinases. In contrast to postsynaptic opioid receptors, receptors localized to presynaptic terminals are resistant to desensitization such that there is no loss of signaling in the continuous presence of opioids over the same time scale. Thus, the balance of opioid signaling in circuits expressing pre- and postsynaptic opioid receptors is shifted toward inhibition of presynaptic neurotransmitter release during continuous opioid exposure. The functional implication of this shift is not often acknowledged in behavioral studies. This review covers what is currently understood about regulation of opioid/nociceptin receptors, with an emphasis on opioid receptor signaling in pain and reward circuits. Importantly, the review covers regulation of presynaptic receptors and the critical gaps in understanding this area, as well as the opportunities to further understand opioid signaling in brain circuits. This article is part of the Special Issue on "Opioid-induced changes in addiction and pain circuits".
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Affiliation(s)
- Basile Coutens
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA
| | - Susan L Ingram
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA.
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5
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McPherson KB, Ingram SL. Cellular and circuit diversity determines the impact of endogenous opioids in the descending pain modulatory pathway. Front Syst Neurosci 2022; 16:963812. [PMID: 36045708 PMCID: PMC9421147 DOI: 10.3389/fnsys.2022.963812] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 07/15/2022] [Indexed: 01/31/2023] Open
Abstract
The descending pain modulatory pathway exerts important bidirectional control of nociceptive inputs to dampen and/or facilitate the perception of pain. The ventrolateral periaqueductal gray (vlPAG) integrates inputs from many regions associated with the processing of nociceptive, cognitive, and affective components of pain perception, and is a key brain area for opioid action. Opioid receptors are expressed on a subset of vlPAG neurons, as well as on both GABAergic and glutamatergic presynaptic terminals that impinge on vlPAG neurons. Microinjection of opioids into the vlPAG produces analgesia and microinjection of the opioid receptor antagonist naloxone blocks stimulation-mediated analgesia, highlighting the role of endogenous opioid release within this region in the modulation of nociception. Endogenous opioid effects within the vlPAG are complex and likely dependent on specific neuronal circuits activated by acute and chronic pain stimuli. This review is focused on the cellular heterogeneity within vlPAG circuits and highlights gaps in our understanding of endogenous opioid regulation of the descending pain modulatory circuits.
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Affiliation(s)
- Kylie B. McPherson
- Division of Neuroscience and Clinical Pharmacology, Department of Biomedical Sciences, University of Cagliari, Monserrato, Italy,Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, United States
| | - Susan L. Ingram
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, United States,*Correspondence: Susan L. Ingram
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6
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Adhikary S, Williams JT. Cellular Tolerance Induced by Chronic Opioids in the Central Nervous System. Front Syst Neurosci 2022; 16:937126. [PMID: 35837149 PMCID: PMC9273719 DOI: 10.3389/fnsys.2022.937126] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 06/08/2022] [Indexed: 01/21/2023] Open
Abstract
Opioids are powerful analgesics that elicit acute antinociceptive effects through their action the mu opioid receptor (MOR). However opioids are ineffective for chronic pain management, in part because continuous activation of MORs induces adaptive changes at the receptor level and downstream signaling molecules. These adaptations include a decrease in receptor-effector coupling and changes to second messenger systems that can counteract the persistent activation of MORs by opioid agonists. Homeostatic regulation of MORs and downstream signaling cascades are viewed as precursors to developing tolerance. However, despite numerous studies identifying crucial mechanisms that contribute to opioid tolerance, no single regulatory mechanism that governs tolerance in at the cellular and systems level has been identified. Opioid tolerance is a multifaceted process that involves both individual neurons that contain MORs and neuronal circuits that undergo adaptations following continuous MOR activation. The most proximal event is the agonist/receptor interaction leading to acute cellular actions. This review discusses our understanding of mechanisms that mediate cellular tolerance after chronic opioid treatment that, in part, is mediated by agonist/receptor interaction acutely.
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Adhikary S, Koita O, Lebowitz JJ, Birdsong WT, Williams JT. Agonist-Specific Regulation of G Protein-Coupled Receptors after Chronic Opioid Treatment. Mol Pharmacol 2022; 101:300-308. [PMID: 35193934 PMCID: PMC9092468 DOI: 10.1124/molpharm.121.000453] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Accepted: 02/16/2022] [Indexed: 01/21/2023] Open
Abstract
Chronic treatment of animals with morphine results in a long lasting cellular tolerance in the locus coeruleus and alters the kinase dependent desensitization of opioid and nonopioid G protein-coupled receptors (GPCRs). This study examined the development of tolerance and altered regulation of kinase activity after chronic treatment of animals with clinically relevant opioids that differ in efficacy at the µ-opioid receptors (MOR). In slices from oxycodone treated animals, no tolerance to opioids was observed when measuring the MOR induced increase in potassium conductance, but the G protein receptor kinase 2/3 blocker, compound 101, no longer inhibited desensitization of somatostatin (SST) receptors. Chronic fentanyl treatment induced a rightward shift in the concentration response to [Met5]enkephalin, but there was no change in the kinase regulation of desensitization of the SST receptor. When total phosphorylation deficient MORs that block desensitization, internalization, and tolerance were virally expressed, chronic treatment with fentanyl resulted in the altered kinase regulation of SST receptors. The results suggest that sustained opioid receptor signaling initiates the process that results in altered kinase regulation of not only opioid receptors, but also other GPCRs. This study highlights two very distinct downstream adaptive processes that are specifically regulated by an agonist dependent mechanism. SIGNIFICANCE STATEMENT: Persistent signaling of MORs results in altered kinase regulation of nonopioid GPCRs after chronic treatment with morphine and oxycodone. Profound tolerance develops after chronic treatment with fentanyl without affecting kinase regulation. The homeostatic change in the kinase regulation of nonopioid GPCRs could account for the systems level in vivo development of tolerance that is seen with opioid agonists, such as morphine and oxycodone, that develop more rapidly than the tolerance induced by efficacious agonists, such as fentanyl and etorphine.
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Affiliation(s)
- Sweta Adhikary
- Vollum Institute, Oregon Health and Science University, Portland, Oregon (S.A., O.K., J.J.L., J.T.W.) and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan (W.T.B.)
| | - Omar Koita
- Vollum Institute, Oregon Health and Science University, Portland, Oregon (S.A., O.K., J.J.L., J.T.W.) and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan (W.T.B.)
| | - Joseph J Lebowitz
- Vollum Institute, Oregon Health and Science University, Portland, Oregon (S.A., O.K., J.J.L., J.T.W.) and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan (W.T.B.)
| | - William T Birdsong
- Vollum Institute, Oregon Health and Science University, Portland, Oregon (S.A., O.K., J.J.L., J.T.W.) and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan (W.T.B.)
| | - John T Williams
- Vollum Institute, Oregon Health and Science University, Portland, Oregon (S.A., O.K., J.J.L., J.T.W.) and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan (W.T.B.)
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8
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Patel M, Matti C, Grimsey NL, Legler DF, Javitch JA, Finlay DB, Glass M. Delineating the interactions between the cannabinoid CB 2 receptor and its regulatory effectors; β-arrestins and G protein-coupled receptor kinases. Br J Pharmacol 2021; 179:2223-2239. [PMID: 34811740 DOI: 10.1111/bph.15748] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 10/20/2021] [Accepted: 11/10/2021] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND AND PURPOSE The cannabinoid CB2 receptor (CB2 ) is a promising therapeutic target for modulating inflammation. However, little is known surrounding the mechanisms underpinning CB2 desensitisation and regulation, particularly the role of G protein-coupled receptor kinases (GRKs). Here, we evaluated the role of six GRK isoforms in β-arrestin recruitment to CB2 . Mutagenesis of several distal C-terminal aspartic acid residues was also performed in an attempt to delineate additional structural elements involved in the regulation of CB2 . EXPERIMENTAL APPROACH In CB2 -expressing HEK 293 cells, β-arrestin translocation was measured using real-time BRET assays. G protein dissociation BRET assays were performed to assess the activation and desensitisation of CB2 in the presence of β-arrestin 2. KEY RESULTS Overexpression of GRK isoforms 1-6 failed to considerably improve translocation of either β-arrestin 1 or β-arrestin 2 to CB2 . Consistent with this, inhibition of endogenous GRK2/3 did not substantially reduce β-arrestin 2 translocation. Mutagenesis of C-terminal aspartic acid residues resulted in attenuation of β-arrestin 2 translocation, which translated to a reduction in desensitisation of G protein activation. CONCLUSION AND IMPLICATIONS Our findings suggest that CB2 does not adhere to the classical GPCR regulatory paradigm, entailing GRK- and β-arrestin-mediated desensitisation. Instead, C-terminal aspartic acid residues may act as phospho-mimics to induce β-arrestin activation. This study provides novel insights into the regulatory mechanisms of CB2 , which may aid in our understanding of drug tolerance and dependence.
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Affiliation(s)
- Monica Patel
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Christoph Matti
- Biotechnology Institute Thurgau (BITg) at the University of Konstanz, Kreuzlingen, Switzerland
| | - Natasha L Grimsey
- Department of Pharmacology and Clinical Pharmacology, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Daniel F Legler
- Biotechnology Institute Thurgau (BITg) at the University of Konstanz, Kreuzlingen, Switzerland.,Faculty of Biology, University of Konstanz, Konstanz, Germany.,Theodor Kocher Institute, University of Bern, Bern, Switzerland
| | - Jonathan A Javitch
- Department of Psychiatry and Pharmacology, Columbia University Vagelos College of Physicians and Surgeons, New York, New York, United States.,Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York, United States
| | - David B Finlay
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Michelle Glass
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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9
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He XJ, Patel J, Weiss CE, Ma X, Bloodgood BL, Banghart MR. Convergent, functionally independent signaling by mu and delta opioid receptors in hippocampal parvalbumin interneurons. eLife 2021; 10:69746. [PMID: 34787079 PMCID: PMC8716102 DOI: 10.7554/elife.69746] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 11/16/2021] [Indexed: 11/13/2022] Open
Abstract
Functional interactions between G protein-coupled receptors are poised to enhance neuronal sensitivity to neuromodulators and therapeutic drugs. Mu and Delta opioid receptors (MORs and DORs) can interact when overexpressed in the same cells, but whether co-expression of endogenous MORs and DORs in neurons leads to functional interactions is unclear. Here, in mice, we show that both MORs and DORs inhibit parvalbumin-expressing basket cells (PV-BCs) in hippocampal CA1 through partially occlusive signaling pathways that terminate on somato-dendritic potassium channels and presynaptic calcium channels. Using photoactivatable opioid neuropeptides, we find that DORs dominate the response to enkephalin in terms of both ligand-sensitivity and kinetics, which may be due to relatively low expression levels of MOR. Opioid-activated potassium channels do not show heterologous desensitization, indicating that MORs and DORs signal independently. In a direct test for heteromeric functional interactions, the DOR antagonist TIPP-Psi does not alter the kinetics or potency of either the potassium channel or synaptic responses to photorelease of the MOR agonist DAMGO. Thus, aside from largely redundant and convergent signaling, MORs and DORs do not functionally interact in PV-BCs in a way that impacts somato-dendritic potassium currents or synaptic transmission. These findings imply that crosstalk between MORs and DORs, either in the form of physical interactions or synergistic intracellular signaling, is not a preordained outcome of co-expression in neurons.
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Affiliation(s)
- Xinyi Jenny He
- Biological Sciences, University of California San Diego, La Jolla, United States
| | - Janki Patel
- University of California San Diego, San Diego, United States
| | - Connor E Weiss
- University of California San Diego, San Diego, United States
| | - Xiang Ma
- University of California San Diego, San Diego, United States
| | - Brenda L Bloodgood
- Biological Sciences, University of California San Diego, La Jolla, United States
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10
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Gledhill LJ, Babey AM. Synthesis of the Mechanisms of Opioid Tolerance: Do We Still Say NO? Cell Mol Neurobiol 2021; 41:927-948. [PMID: 33704603 DOI: 10.1007/s10571-021-01065-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Accepted: 02/12/2021] [Indexed: 10/21/2022]
Abstract
The use of morphine as a first-line agent for moderate-to-severe pain is limited by the development of analgesic tolerance. Initially opioid receptor desensitization in response to repeated stimulation, thought to underpin the establishment of tolerance, was linked to a compensatory increase in adenylate cyclase responsiveness. The subsequent demonstration of cross-talk between N-methyl-D-aspartate (NMDA) glutamate receptors and opioid receptors led to the recognition of a role for nitric oxide (NO), wherein blockade of NO synthesis could prevent tolerance developing. Investigations of the link between NO levels and opioid receptor desensitization implicated a number of events including kinase recruitment and peroxynitrite-mediated protein regulation. Recent experimental advances and the identification of new cellular constituents have expanded the potential signaling candidates to include unexpected, intermediary compounds not previously linked to this process such as zinc, histidine triad nucleotide-binding protein 1 (HINT1), micro-ribonucleic acid (mi-RNA) and regulator of G protein signaling Z (RGSZ). A further complication is a lack of consistency in the protocols used to create tolerance, with some using acute methods measured in minutes to hours and others using days. There is also an emphasis on the cellular changes that are extant only after tolerance has been established. Although a review of the literature demonstrates a lack of spatio-temporal detail, there still appears to be a pivotal role for nitric oxide, as well as both intracellular and intercellular cross-talk. The use of more consistent approaches to verify these underlying mechanism(s) could provide an avenue for targeted drug development to rescue opioid efficacy.
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Affiliation(s)
- Laura J Gledhill
- CURA Pharmacy, St. John of God Hospital, Bendigo, VIC, 3550, Australia
| | - Anna-Marie Babey
- Faculty of Medicine and Health, University of New England, Armidale, NSW, 2351, Australia.
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11
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Abreu N, Acosta-Ruiz A, Xiang G, Levitz J. Mechanisms of differential desensitization of metabotropic glutamate receptors. Cell Rep 2021; 35:109050. [PMID: 33910009 PMCID: PMC9750234 DOI: 10.1016/j.celrep.2021.109050] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 03/04/2021] [Accepted: 04/07/2021] [Indexed: 12/16/2022] Open
Abstract
G protein-coupled receptors (GPCRs) interact with intracellular transducers to control both signal initiation and desensitization, but the distinct mechanisms that control the regulation of different GPCR subtypes are unclear. Here we use fluorescence imaging and electrophysiology to examine the metabotropic glutamate receptor (mGluR) family. We find distinct properties across subtypes in both rapid desensitization and internalization, with striking differences between the group II mGluRs. mGluR3, but not mGluR2, undergoes glutamate-dependent rapid desensitization, internalization, trafficking, and recycling. We map differences between mGluRs to variable Ser/Thr-rich sequences in the C-terminal domain (CTD) that control interaction with both GPCR kinases and β-arrestins. Finally, we identify a cancer-associated mutation, G848E, within the mGluR3 CTD that enhances β-arrestin coupling and internalization, enabling an analysis of mGluR3 β-arrestin-coupling properties and revealing biased variants. Together, this work provides a framework for understanding the distinct regulation and functional roles of mGluR subtypes.
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Affiliation(s)
- Nohely Abreu
- Biochemistry, Cell and Molecular Biology Graduate Program, Weill Cornell Medicine, New York, NY, USA; Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA
| | - Amanda Acosta-Ruiz
- Biochemistry, Cell and Molecular Biology Graduate Program, Weill Cornell Medicine, New York, NY, USA; Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA
| | - Guoqing Xiang
- Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA
| | - Joshua Levitz
- Biochemistry, Cell and Molecular Biology Graduate Program, Weill Cornell Medicine, New York, NY, USA; Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA.
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12
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Ehrlich AT, Darcq E. Recent advances in basic science methodology to evaluate opioid safety profiles and to understand opioid activities. Fac Rev 2021; 10:15. [PMID: 33718932 PMCID: PMC7946392 DOI: 10.12703/r/10-15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Opioids are powerful drugs used by humans for centuries to relieve pain and are still frequently used as pain treatment in current clinical practice. Medicinal opioids primarily target the mu opioid receptor (MOR), and MOR activation produces unmatched pain-alleviating properties, as well as side effects such as strong rewarding effects, and thus abuse potential, and respiratory depression contributing to death during overdose. Therefore, the ultimate goal is to create opioid pain-relievers with reduced respiratory depression and thus fewer chances of lethality. Efforts are also underway to reduce the euphoric effects of opioids and avoid abuse liability. In this review, recent advances in basic science methodology used to understand MOR pharmacology and activities will be summarized. The focus of the review will be to describe current technological advances that enable the study of opioid analgesics from subcellular mechanisms to mesoscale network responses. These advances in understanding MOR physiological responses will help to improve knowledge and future design of opioid analgesics.
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Affiliation(s)
- Aliza T Ehrlich
- Department of Psychiatry and Behavioral Sciences, University of California, San Francisco, CA, USA
| | - Emmanuel Darcq
- Department of Psychiatry, Douglas Research Center, McGill University, Montréal, Canada
- INSERM U1114, UNISTRA University of Strasbourg, Strasbourg, France
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Puthenveedu MA. Editorial: 50 Years of Opioid Research and the International Narcotics Research Conference. Mol Pharmacol 2020; 98:386-388. [PMID: 32788221 PMCID: PMC7562969 DOI: 10.1124/molpharm.120.000132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 08/04/2020] [Indexed: 11/22/2022] Open
Abstract
In the past 50 years, scientists have made considerable strides toward understanding how opioids act. This special issue of Molecular Pharmacology celebrates these 50 years of opioid research and the role that the International Narcotics Research Conference has played in driving this research, by bringing together review and original research articles that present historical highlights, the current state of the art, and perspectives on the future of opioid research. SIGNIFICANCE STATEMENT: Opioids have been used for thousands of years to manage pain and cause euphoria, but their use has been highly limited due to serious side effects. Deciphering the mechanisms of how opioids mediate beneficial and adverse physiological outcomes is essential for developing better treatments for pain and for opioid addiction.
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