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Xu Q, Jin L, Wang L, Tang Y, Wu H, Chen Q, Sun L. The role of gonadal hormones in regulating opioid antinociception. Ann Med 2024; 56:2329259. [PMID: 38738380 PMCID: PMC11095291 DOI: 10.1080/07853890.2024.2329259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 03/06/2024] [Indexed: 05/14/2024] Open
Abstract
Opioids are the most prescribed drugs for the alleviation of pain. Both clinical and preclinical studies have reported strong evidence for sex-related divergence regarding opioid analgesia. There is an increasing amount of evidence indicating that gonadal hormones regulate the analgesic efficacy of opioids. This review presents an overview of the importance of gonadal steroids in modulating opioid analgesic responsiveness and focuses on elaborating what is currently known regarding the underlyingmechanism. We sought to identify the link between gonadal hormones and the effect of oipiod antinociception.
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Affiliation(s)
- Qi Xu
- Department of Anesthesiology, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, China
| | - Lin Jin
- Department of Anesthesiology, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, China
| | - LuYang Wang
- Department of Anesthesiology, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, China
| | - YingYing Tang
- Department of Anesthesiology, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, China
| | - Hui Wu
- Department of Anesthesiology, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, China
| | - Qing Chen
- Department of Anesthesiology, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, China
| | - LiHong Sun
- Department of Anesthesiology, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, China
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Mussetto V, Teuchmann HL, Heinke B, Trofimova L, Sandkühler J, Drdla-Schutting R, Hogri R. Opioids Induce Bidirectional Synaptic Plasticity in a Brainstem Pain Center in the Rat. THE JOURNAL OF PAIN 2023; 24:1664-1680. [PMID: 37150382 DOI: 10.1016/j.jpain.2023.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 04/27/2023] [Accepted: 05/02/2023] [Indexed: 05/09/2023]
Abstract
Opioids are powerful analgesics commonly used in pain management. However, opioids can induce complex neuroadaptations, including synaptic plasticity, that ultimately drive severe side effects, such as pain hypersensitivity and strong aversion during prolonged administration or upon drug withdrawal, even following a single, brief administration. The lateral parabrachial nucleus (LPBN) in the brainstem plays a key role in pain and emotional processing; yet, the effects of opioids on synaptic plasticity in this area remain unexplored. Using patch-clamp recordings in acute brainstem slices from male and female Sprague Dawley rats, we demonstrate a concentration-dependent, bimodal effect of opioids on excitatory synaptic transmission in the LPBN. While a lower concentration of DAMGO (0.5 µM) induced a long-term depression of synaptic strength (low-DAMGO LTD), abrupt termination of a higher concentration (10 µM) induced a long-term potentiation (high-DAMGO LTP) in a subpopulation of cells. LTD involved a metabotropic glutamate receptor (mGluR)-dependent mechanism; in contrast, LTP required astrocytes and N-methyl-D-aspartate receptor (NMDAR) activation. Selective optogenetic activation of spinal and periaqueductal gray matter (PAG) inputs to the LPBN revealed that, while LTD was expressed at all parabrachial synapses tested, LTP was restricted to spino-parabrachial synapses. Thus, we uncovered previously unknown forms of opioid-induced long-term plasticity in the parabrachial nucleus that potentially modulate some adverse effects of opioids. PERSPECTIVE: We found a previously unrecognized site of opioid-induced plasticity in the lateral parabrachial nucleus, a key region for pain and emotional processing. Unraveling opioid-induced adaptations in parabrachial function might facilitate the identification of new therapeutic measures for addressing adverse effects of opioid discontinuation such as hyperalgesia and aversion.
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Affiliation(s)
- Valeria Mussetto
- Department of Neurophysiology, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria
| | - Hannah Luise Teuchmann
- Department of Neurophysiology, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria
| | - Bernhard Heinke
- Department of Neurophysiology, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria
| | - Lidia Trofimova
- Department of Neurophysiology, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria
| | - Jürgen Sandkühler
- Department of Neurophysiology, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria
| | - Ruth Drdla-Schutting
- Department of Neurophysiology, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria
| | - Roni Hogri
- Department of Neurophysiology, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria.
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Miller S, Abrahante JE, Roopra A, Dougherty BJ. A transcriptome dataset for gonadectomy-induced changes in rat spinal cord. Sci Data 2022; 9:789. [PMID: 36581616 PMCID: PMC9800375 DOI: 10.1038/s41597-022-01917-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Accepted: 12/15/2022] [Indexed: 12/30/2022] Open
Abstract
Circulating sex steroid hormones are critical for neural function and development of neuroplasticity in many regions of the central nervous system. In the spinal cord, our knowledge of steroid hormone influence mostly derives from mechanistic studies of pain processing in dorsal spinal cord circuits; less is known regarding hormonal influence of ventral spinal motor function. Gonadectomy (surgical removal of the testes in males and ovaries in females) rapidly and persistently reduces circulating sex steroids in both females and males, providing a means to interrogate the role of hormones on neural function. Here we provide a next-generation RNA sequencing (RNA-seq) data set to evaluate the impact of gonadectomy on the transcriptome of ventral spinal cord tissue of adult female and male rats.
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Affiliation(s)
- Shawn Miller
- Divisions of Physical Therapy and Rehabilitation Science, Department of Rehabilitation Medicine, University of Minnesota Medical School, Minneapolis, MN, 55455, USA
| | - Juan E Abrahante
- University of Minnesota Informatics Institute, Minneapolis, MN, 55455, USA
| | - Avtar Roopra
- Department of Neuroscience, University of Wisconsin, Madison, WI, 53705, USA
| | - Brendan J Dougherty
- Divisions of Physical Therapy and Rehabilitation Science, Department of Rehabilitation Medicine, University of Minnesota Medical School, Minneapolis, MN, 55455, USA.
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Mazzitelli M, Presto P, Antenucci N, Meltan S, Neugebauer V. Recent Advances in the Modulation of Pain by the Metabotropic Glutamate Receptors. Cells 2022; 11:2608. [PMID: 36010684 PMCID: PMC9406805 DOI: 10.3390/cells11162608] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 08/16/2022] [Accepted: 08/18/2022] [Indexed: 01/22/2023] Open
Abstract
Metabotropic glutamate receptors (mGluR or mGlu) are G-protein coupled receptors activated by the binding of glutamate, the main classical neurotransmitter of the nervous system. Eight different mGluR subtypes (mGluR1-8) have been cloned and are classified in three groups based on their molecular, pharmacological and signaling properties. mGluRs mediate several physiological functions such as neuronal excitability and synaptic plasticity, but they have also been implicated in numerous pathological conditions including pain. The availability of new and more selective allosteric modulators together with the canonical orthosteric ligands and transgenic technologies has led to significant advances in our knowledge about the role of the specific mGluR subtypes in the pathophysiological mechanisms of various diseases. Although development of successful compounds acting on mGluRs for clinical use has been scarce, the subtype-specific-pharmacological manipulation might be a compelling approach for the treatment of several disorders in humans, including pain; this review aims to summarize and update on preclinical evidence for the roles of different mGluRs in the pain system and discusses knowledge gaps regarding mGluR-related sex differences and neuroimmune signaling in pain.
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Affiliation(s)
- Mariacristina Mazzitelli
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Peyton Presto
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Nico Antenucci
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Shakira Meltan
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Garrison Institute on Aging, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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Storman EM, Liu NJ, Gintzler AR. Relevance of c-Src and protein phosphatase 2A to aromatase activity: Evidence of an acute self-regulating oestrogenic signalling complex in rat central nervous system. J Neuroendocrinol 2022; 34:e13089. [PMID: 35043508 PMCID: PMC9038631 DOI: 10.1111/jne.13089] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 12/30/2021] [Accepted: 12/30/2021] [Indexed: 12/27/2022]
Abstract
We previously reported that aromatase protein levels do not parallel aromatase enzyme activity. This suggests that oestrogenic signalling may be modulated via post-translational modification of aromatase protein. The tyrosine and serine phosphorylation state of aromatase are known to influence its activity. To investigate the possible relevance of aromatase phosphorylation to the incongruity observed between aromatase protein and its activity, we explored interactions between aromatase and the tyrosine kinase c-Src and the serine protein phosphatases 2A and 5 (PP2A and PP5), as well as the relationship between levels of tyrosine-phosphorylated aromatase and the extrapolated aromatase activity. We found that (a) hypothalamic aromatase was significantly more heavily tyrosine-phosphorylated than spinal aromatase; (b) aromatase was oligomerized with c-Src and PP2A/PP5, potentially activating aromatase via tyrosine-phosphorylation and serine-dephosphorylation; (c) the associations of c-Src and PP2A/PP5 with hypothalamic aromatase were substantially greater than with spinal aromatase; and (d) aromatase, oestrogen receptor α, PP2A, and c-Src were present in a common membrane oligomer. The existence of c-Src and PP2A in an oligomer that also contains aromatase and membrane oestrogen receptor α (and presumably other signalling molecules) indicates the presence in the CNS of a potentially self-regulating oestrogenic signalling unit. The degree to which such a complex operates autonomously and the regulatory factors thereof are likely to have substantial physiological implications and clinical relevance.
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Affiliation(s)
- Emiliya M Storman
- Department of Obstetrics and Gynecology, State University of New York, Downstate Health Sciences University, Brooklyn, New York, USA
| | - Nai-Jiang Liu
- Department of Obstetrics and Gynecology, State University of New York, Downstate Health Sciences University, Brooklyn, New York, USA
| | - Alan R Gintzler
- Department of Obstetrics and Gynecology, State University of New York, Downstate Health Sciences University, Brooklyn, New York, USA
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Arbiters of endogenous opioid analgesia: role of CNS estrogenic and glutamatergic systems. Transl Res 2021; 234:31-42. [PMID: 33567346 PMCID: PMC8217383 DOI: 10.1016/j.trsl.2021.02.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 02/01/2021] [Accepted: 02/02/2021] [Indexed: 11/24/2022]
Abstract
Nociception and opioid antinociception in females are pliable processes, varying qualitatively and quantitatively over the reproductive cycle. Spinal estrogenic signaling via membrane estrogen receptors (mERs), in combination with multiple other signaling molecules [spinal dynorphin, kappa-opioid receptors (KOR), glutamate and metabotropic glutamate receptor 1 (mGluR1)], appears to function as a master coordinator, parsing functionality between pronociception and antinociception. This provides a window into pharmacologically accessing intrinsic opioid analgesic/anti-allodynic systems. In diestrus, membrane estrogen receptor alpha (mERα) signals via mGluR1 to suppress spinal endomorphin 2 (EM2) analgesia. Strikingly, in the absence of exogenous opioids, interfering with this suppression in a chronic pain model elicits opioid anti-allodynia, revealing contributions of endogenous opioid(s). In proestrus, robust spinal EM2 analgesia is manifest but this requires spinal dynorphin/KOR and glutamate-activated mGluR1. Furthermore, spinal mGluR1 blockade in a proestrus chronic pain animal (eliminating spinal EM2 analgesia) exacerbates mechanical allodynia, revealing tempering by endogenous opioid(s). A complex containing mu-opioid receptor, KOR, aromatase, mGluRs, and mERα are foundational to eliciting endogenous opioid anti-allodynia. Aromatase-mERα oligomers are also plentiful, in a central nervous system region-specific fashion. These can be independently regulated and allow estrogens to act intracellularly within the same signaling complex in which they are synthesized, explaining asynchronous relationships between circulating estrogens and central nervous system estrogen functionalities. Observations with EM2 highlight the translational relevance of extensively characterizing exogenous responsiveness to endogenous opioids and the neuronal circuits that mediate them along with the multiplicity of estrogenic systems that concomitantly function in phase and out-of-phase with the reproductive cycle.
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Abstract
Aromatase CYP19A1 catalyzes the synthesis of estrogens in endocrine, reproductive and central nervous systems. Higher levels of 17β-estradiol (E2) are associated with malignancies and diseases of the breast, ovary and endometrium, while low E2 levels increase the risk for osteoporosis, cardiovascular diseases and cognitive disorders. E2, the transcriptional activator of the estrogen receptors, is also known to be involved in non-genomic signaling as a neurotransmitter/neuromodulator, with recent evidence for rapid estrogen synthesis (RES) within the synaptic terminal. Although regulation of brain aromatase activity by phosphorylation/dephosphorylation has been suggested, it remains obscure in the endocrine and reproductive systems. RES and overabundance of estrogens could stimulate the genomic and non-genomic signaling pathways, and genotoxic effects of estrogen metabolites. Here, by utilizing biochemical, cellular, mass spectrometric, and structural data we unequivocally demonstrate phosphorylation of human placental aromatase and regulation of its activity. We report that human aromatase has multiple phosphorylation sites, some of which are consistently detectable. Phosphorylation of the residue Y361 at the reductase-coupling interface significantly elevates aromatase activity. Other sites include the active site residue S478 and several at the membrane interface. We present the evidence that two histidine residues are phosphorylated. Furthermore, oxidation of two proline residues near the active site may have implications in regulation. Taken together, the results demonstrate that aromatase activity is regulated by phosphorylation and possibly other post-translational modifications. Protein level regulation of aromatase activity not only represents a paradigm shift in estrogen-mediated biology, it could also explain unresolved clinical questions such as aromatase inhibitor resistance.
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Abstract
This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, CUNY, 65-30 Kissena Blvd., Flushing, NY, 11367, United States.
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9
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Gintzler AR, Storman EM, Liu NJ. Estrogens as arbiters of sex-specific and reproductive cycle-dependent opioid analgesic mechanisms. VITAMINS AND HORMONES 2019; 111:227-246. [PMID: 31421702 PMCID: PMC7136895 DOI: 10.1016/bs.vh.2019.06.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The organization of estrogenic signaling in the CNS is exceedingly complex. It is comprised of peripherally and centrally synthesized estrogens, and a plethora of types of estrogen receptor that can localize to both the nucleus and the plasma membrane. Moreover, CNS estrogen receptors can exist independent of aromatase (aka estrogen synthase) as well as oligomerize with it, along with a host of other membrane signaling proteins. This ability of CNS estrogen receptors to either to physically pair or exist separately enables locally produced estrogens to act on multiple spatial levels, with a high degree of gradated regulation and plasticity, signaling either in-phase or out-of phase with circulating estrogens. This complexity explains the numerous contradictory findings regarding sex-dependent pain processing and sexually dimorphic opioid antinociception. This review highlights the increasing awareness that estrogens are major endogenous arbiters of both opioid analgesic actions and the mechanisms used to achieve them. This behooves us to understand, and possibly intercede at, the points of intersection of estrogenic signaling and opioid functionality. Factors that integrate estrogenic actions at subcellular, synaptic, and CNS regional levels are likely to be prime drug targets for novel pharmacotherapies designed to modulate CNS estrogen-dependent opioid functionalities and possibly circumvent the current opioid epidemic.
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MESH Headings
- Analgesia
- Analgesics, Opioid/pharmacology
- Animals
- Aromatase
- Brain/physiology
- Dynorphins/physiology
- Estrogens/physiology
- Female
- Humans
- Male
- Neurosecretory Systems/physiology
- Nociception/drug effects
- Nociception/physiology
- Receptors, Estrogen/physiology
- Receptors, Opioid, kappa/drug effects
- Receptors, Opioid, kappa/physiology
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/physiology
- Reproduction/physiology
- Sex Characteristics
- Signal Transduction/physiology
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Affiliation(s)
- Alan R Gintzler
- Department of Obstetrics and Gynecology, State University of New York, Downstate Medical Center, Brooklyn, NY, United States.
| | - Emiliya M Storman
- Department of Obstetrics and Gynecology, State University of New York, Downstate Medical Center, Brooklyn, NY, United States
| | - Nai-Jiang Liu
- Department of Obstetrics and Gynecology, State University of New York, Downstate Medical Center, Brooklyn, NY, United States
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Gintzler AR, Liu NJ, Storman EM, Wessendorf MW. Exploiting endogenous opioids: Lessons learned from endomorphin 2 in the female rat. Peptides 2019; 112:133-138. [PMID: 30557590 PMCID: PMC7173356 DOI: 10.1016/j.peptides.2018.12.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 11/30/2018] [Accepted: 12/03/2018] [Indexed: 02/06/2023]
Abstract
Effective management of chronic pain is demanded by ethical as well as medical considerations. Although opioid analgesics remain among the most effective pharmacotherapies for ameliorating many types of pain, their use is clouded by concerns regarding their addictive properties, underscored by the current epidemic of prescription opioid abuse and attendant deaths. Medicinal harnessing of endogenous opioid antinociception could provide a strategy for continuing to take advantage of the powerful antinociceptive properties of opioids while avoiding their abuse potential. Based on our studies of endogenous mechanism that suppress and facilitate spinal endomorphin 2 antinociception over the rat reproductive cycle, we identified multiple signaling molecules that could serve as targets for activating endogenous opioid analgesia for chronic pain management in women. Our findings emphasize the need for a precision medicine approach that includes stage of menstrual cycle as an important determinant of drug targets for (activating/harnessing) endogenous opioid antinociceptive systems/ capabilities. Utilization of drugs that harness endogenous opioid antinociception in accordance with varying physiological states represents a novel approach for effective pain management.
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Affiliation(s)
- Alan R Gintzler
- Department of Obstetrics and Gynecology, State University of New York, Downstate Medical Center, 450 Clarkson Ave, Brooklyn, NY, 11203, USA.
| | - Nai-Jiang Liu
- Department of Obstetrics and Gynecology, State University of New York, Downstate Medical Center, 450 Clarkson Ave, Brooklyn, NY, 11203, USA
| | - Emiliya M Storman
- Department of Obstetrics and Gynecology, State University of New York, Downstate Medical Center, 450 Clarkson Ave, Brooklyn, NY, 11203, USA
| | - Martin W Wessendorf
- Department of Neuroscience, School of Medicine, University of Minnesota, Minneapolis, MN 55455, USA
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Gintzler AR, Liu NJ. Harnessing endogenous opioids for pain relief: Fantasy vs reality. J Opioid Manag 2019; 16:67-72. [PMID: 32091619 PMCID: PMC8244826 DOI: 10.5055/jom.2020.0552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
OBJECTIVE To review evidence demonstrating efficacy and feasibility of harnessing the activity of endogenous opioid analgesic systems for pain management. METHODS The authors sought to summarize a wealth of data that establish proof of concept that the analgesic activity of endogenous opioids can be exploited to clinically benefit from the enormous pain-relieving abilities of these peptides without contributing to the current crisis of death by synthetic opioid overdose. RESULTS There is a plethora of studies demonstrating that not only can endogenous opioids mediate placebo-induced antinociception but they are also active in modulating clinical pain. Earlier studies convincingly demonstrate the effec-tiveness of psychological strategies to coopt endogenous opioid analgesic systems to produce pain relief. The challenge is to define pharmacological targets for activating endogenous opioid analgesia reliably in a clinical setting. Based on insights gleaned from mechanisms underlying the ebb and flow of analgesic responsiveness to the spinal application of endomorphin 2, multiple signaling proteins were identified that activate endogenous spinal opioid analgesia. Notably, this was achieved in the absence of any exogenous synthetic opioid. CONCLUSIONS Utilization of drugs that harness endogenous opioid antinociception in accordance with varying physiological states represents a novel approach for effective pain management while mitigating the present epidemic of death by synthetic opioid overdose.
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Affiliation(s)
- Alan R Gintzler
- Department of Obstetrics and Gynecology, State University of New York, Downstate Medical Center, Brooklyn, New York
| | - Nai-Jiang Liu
- Department of Obstetrics and Gynecology, State University of New York, Downstate Medical Center, Brooklyn, New York
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Liu NJ, Storman EM, Gintzler AR. Pharmacological Modulation of Endogenous Opioid Activity to Attenuate Neuropathic Pain in Rats. THE JOURNAL OF PAIN 2018; 20:235-243. [PMID: 30366152 DOI: 10.1016/j.jpain.2018.10.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 09/12/2018] [Accepted: 10/17/2018] [Indexed: 12/23/2022]
Abstract
We showed previously that spinal metabotropic glutamate receptor 1 (mGluR1) signaling suppresses or facilitates (depending on the stage of estrous cycle) analgesic responsiveness to intrathecal endomorphin 2, a highly mu-opioid receptor-selective endogenous opioid. Spinal endomorphin 2 antinociception is suppressed during diestrus by mGluR1 when it is activated by membrane estrogen receptor alpha (mERα) and is facilitated during proestrus when mGluR1 is activated by glutamate. In the current study, we tested the hypothesis that in female rats subjected to spinal nerve ligation (SNL), the inhibition of spinal estrogen synthesis or blockade of spinal mERα/mGluR1 would be antiallodynic during diestrus, whereas during proestrus, mGluR1 blockade would worsen the mechanical allodynia. As postulated, following SNL, aromatase inhibition or mERα/mGluR1 blockade during diestrus markedly lessened the mechanical allodynia. This was observed only on the paw ipsilateral to SNL and was eliminated by naloxone, implicating endogenous opioid mediation. In contrast, during proestrus, mGluR1 blockade worsened the SNL-induced mechanical allodynia of the ipsilateral paw. Findings suggest menstrual cycle stage-specific drug targets for and the putative clinical utility of harnessing endogenous opioids for chronic pain management in women, as well as the value of, if not the necessity for, considering menstrual cycle stage in clinical trials thereof. PERSPECTIVE: Intrathecal treatments that enhance spinal endomorphin 2 analgesic responsiveness under basal conditions lessen mechanical allodynia in a chronic pain model. Findings provide a foundation for developing drugs that harness endogenous opioid antinociception for chronic pain relief, lessening the need for exogenous opioids and thus prescription opioid abuse.
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Affiliation(s)
- Nai-Jiang Liu
- Department of Obstetrics and Gynecology, State University of New York, Downstate Medical Center, Brooklyn, New York
| | - Emiliya M Storman
- Department of Obstetrics and Gynecology, State University of New York, Downstate Medical Center, Brooklyn, New York
| | - Alan R Gintzler
- Department of Obstetrics and Gynecology, State University of New York, Downstate Medical Center, Brooklyn, New York..
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14
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Estrogen Regulation of GRK2 Inactivates Kappa Opioid Receptor Signaling Mediating Analgesia, But Not Aversion. J Neurosci 2018; 38:8031-8043. [PMID: 30076211 DOI: 10.1523/jneurosci.0653-18.2018] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 07/11/2018] [Accepted: 07/21/2018] [Indexed: 12/12/2022] Open
Abstract
Activation of κ opioid receptors (KORs) produces analgesia and aversion via distinct intracellular signaling pathways, but whether G protein-biased KOR agonists can be designed to have clinical utility will depend on a better understanding of the signaling mechanisms involved. We found that KOR activation produced conditioned place aversion and potentiated CPP for cocaine in male and female C57BL/6N mice. Consistent with this, males and females both showed arrestin-mediated increases in phospho-p38 MAPK following KOR activation. Unlike in males, however, KOR activation had inconsistent analgesic effects in females and KOR increased Gβγ-mediated ERK phosphorylation in males, but not females. KOR desensitization was not responsible for the lack of response in females because neither Grk3 nor Pdyn gene knock-out enhanced analgesia. Instead, responsiveness was estrous cycle dependent because KOR analgesia was evident during low estrogen phases of the cycle and in ovariectomized (OVX) females. Estradiol treatment of OVX females suppressed KOR-mediated analgesia, demonstrating that estradiol was sufficient to blunt Gβγ-mediated KOR signals. G protein-coupled receptor kinase 2 (GRK2) is known to regulate ERK activation, and we found that the inhibitory, phosphorylated form of GRK2 was significantly higher in intact females. GRK2/3 inhibition by CMPD101 increased KOR stimulation of phospho-ERK in females, decreased sex differences in KOR-mediated inhibition of dopamine release, and enhanced mu opioid receptor and KOR-mediated analgesia in females. In OVX females, estradiol increased the association between GRK2 and Gβγ. These studies suggest that estradiol, through increased phosphorylation of GRK2 and possible sequestration of Gβγ by GRK2, blunts G protein-mediated signals.SIGNIFICANCE STATEMENT Chronic pain disorders are more prevalent in females than males, but opioid receptor agonists show inconsistent analgesic efficacy in females. κ opioid receptor (KOR) agonists have been tested in clinical trials for treating pain disorders based on their analgesic properties and low addictive potential. However, the molecular mechanisms underlying sex differences in KOR actions were previously unknown. Our studies identify an intracellular mechanism involving estradiol regulation of G protein-coupled receptor kinase 2 that is responsible for sexually dimorphic analgesic responses following opioid receptor activation. Understanding this mechanism will be critical for developing effective nonaddictive opioid analgesics for use in women and characterizing sexually dimorphic effects in other inhibitory G protein-coupled receptor signaling responses.
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