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García-Domínguez M. Enkephalins and Pain Modulation: Mechanisms of Action and Therapeutic Perspectives. Biomolecules 2024; 14:926. [PMID: 39199314 PMCID: PMC11353043 DOI: 10.3390/biom14080926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2024] [Revised: 07/28/2024] [Accepted: 07/29/2024] [Indexed: 09/01/2024] Open
Abstract
Enkephalins, a subclass of endogenous opioid peptides, play a pivotal role in pain modulation. Enkephalins primarily exert their effects through opioid receptors located widely throughout both the central and peripheral nervous systems. This review will explore the mechanisms by which enkephalins produce analgesia, emotional regulation, neuroprotection, and other physiological effects. Furthermore, this review will analyze the involvement of enkephalins in the modulation of different pathologies characterized by severe pain. Understanding the complex role of enkephalins in pain processing provides valuable insight into potential therapeutic strategies for managing pain disorders.
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Affiliation(s)
- Mario García-Domínguez
- Faculty of Education and Psychology, Universidad Francisco de Vitoria, 28223 Pozuelo de Alarcón, Spain
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Devarajan J, Mena S, Cheng J. Mechanisms of complex regional pain syndrome. FRONTIERS IN PAIN RESEARCH 2024; 5:1385889. [PMID: 38828388 PMCID: PMC11140106 DOI: 10.3389/fpain.2024.1385889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 04/16/2024] [Indexed: 06/05/2024] Open
Abstract
Complex Regional Pain Syndrome (CRPS) is a chronic pain disorder characterized by a diverse array of symptoms, including pain that is disproportionate to the initial triggering event, accompanied by autonomic, sensory, motor, and sudomotor disturbances. The primary pathology of both types of CRPS (Type I, also known as reflex sympathetic dystrophy, RSD; Type II, also known as causalgia) is featured by allodynia, edema, changes in skin color and temperature, and dystrophy, predominantly affecting extremities. Recent studies started to unravel the complex pathogenic mechanisms of CRPS, particularly from an autoimmune and neuroimmune interaction perspective. CRPS is now recognized as a systemic disease that stems from a complex interplay of inflammatory, immunologic, neurogenic, genetic, and psychologic factors. The relative contributions of these factors may vary among patients and even within a single patient over time. Key mechanisms underlying clinical manifestations include peripheral and central sensitization, sympathetic dysregulation, and alterations in somatosensory processing. Enhanced understanding of the mechanisms of CRPS is crucial for the development of effective therapeutic interventions. While our mechanistic understanding of CRPS remains incomplete, this article updates recent research advancements and sheds light on the etiology, pathogenesis, and molecular underpinnings of CRPS.
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Affiliation(s)
- Jagan Devarajan
- Department of Pain Management, Neurological Institute, Cleveland Clinic, Cleveland, OH, United States
| | - Shayla Mena
- Department of Pain Management, Neurological Institute, Cleveland Clinic, Cleveland, OH, United States
| | - Jianguo Cheng
- Department of Pain Management and Neurosciences, Neurological Institute, Cleveland Clinic, Cleveland, OH, United States
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Bencze N, Scheich B, Szőke É, Wilhelm I, Körmöndi S, Botz B, Helyes Z. Osteosarcoma-Induced Pain Is Mediated by Glial Cell Activation in the Spinal Dorsal Horn, but Not Capsaicin-Sensitive Nociceptive Neurons: A Complex Functional and Morphological Characterization in Mice. Cancers (Basel) 2024; 16:1788. [PMID: 38791867 PMCID: PMC11120600 DOI: 10.3390/cancers16101788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Revised: 04/25/2024] [Accepted: 04/27/2024] [Indexed: 05/26/2024] Open
Abstract
Bone cancer and its related chronic pain are huge clinical problems since the available drugs are often ineffective or cannot be used long term due to a broad range of side effects. The mechanisms, mediators and targets need to be identified to determine potential novel therapies. Here, we characterize a mouse bone cancer model induced by intratibial injection of K7M2 osteosarcoma cells using an integrative approach and investigate the role of capsaicin-sensitive peptidergic sensory nerves. The mechanical pain threshold was assessed by dynamic plantar aesthesiometry, limb loading by dynamic weight bearing, spontaneous pain-related behaviors via observation, knee diameter with a digital caliper, and structural changes by micro-CT and glia cell activation by immunohistochemistry in BALB/c mice of both sexes. Capsaicin-sensitive peptidergic sensory neurons were defunctionalized by systemic pretreatment with a high dose of the transient receptor potential vanilloid 1 (TRPV1) agonist resiniferatoxin (RTX). During the 14- and 28-day experiments, weight bearing on the affected limb and the paw mechanonociceptive thresholds significantly decreased, demonstrating secondary mechanical hyperalgesia. Signs of spontaneous pain and osteoplastic bone remodeling were detected both in male and female mice without any sex differences. Microglia activation was shown by the increased ionized calcium-binding adapter molecule 1 (Iba1) immunopositivity on day 14 and astrocyte activation by the enhanced glial fibrillary acidic protein (GFAP)-positive cell density on day 28 in the ipsilateral spinal dorsal horn. Interestingly, defunctionalization of the capsaicin-sensitive afferents representing approximately 2/3 of the nociceptive fibers did not alter any functional parameters. Here, we provide the first complex functional and morphological characterization of the K7M2 mouse osteosarcoma model. Bone-cancer-related chronic pain and hyperalgesia are likely to be mediated by central sensitization involving neuroinflammation via glial cell activation in the spinal dorsal horn, but not the capsaicin-sensitive sensory neuronal system.
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Affiliation(s)
- Noémi Bencze
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, 7624 Pécs, Hungary; (N.B.); (É.S.); (B.B.)
- National Laboratory for Drug Research and Development, Magyar Tudósok Krt. 2, 1117 Budapest, Hungary
| | - Bálint Scheich
- Department of Pathology and Experimental Cancer Research, Faculty of Medicine, Semmelweis University, Üllői út 26, 1085 Budapest, Hungary;
| | - Éva Szőke
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, 7624 Pécs, Hungary; (N.B.); (É.S.); (B.B.)
- National Laboratory for Drug Research and Development, Magyar Tudósok Krt. 2, 1117 Budapest, Hungary
- Hungarian Research Network, Chronic Pain Research Group (HUN-REN-PTE), 7624 Pécs, Hungary
| | - Imola Wilhelm
- Institute of Biophysics, HUN-REN Biological Research Centre, 6726 Szeged, Hungary;
| | - Sándor Körmöndi
- Department of Traumatology, Faculty of Medicine, University of Szeged, 6720 Szeged, Hungary;
| | - Bálint Botz
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, 7624 Pécs, Hungary; (N.B.); (É.S.); (B.B.)
- Department of Medical Imaging, Medical School, University of Pécs, 7624 Pécs, Hungary
| | - Zsuzsanna Helyes
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, 7624 Pécs, Hungary; (N.B.); (É.S.); (B.B.)
- National Laboratory for Drug Research and Development, Magyar Tudósok Krt. 2, 1117 Budapest, Hungary
- Hungarian Research Network, Chronic Pain Research Group (HUN-REN-PTE), 7624 Pécs, Hungary
- PharmInVivo Ltd., Szondy György Str. 10, 7629 Pécs, Hungary
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Wen B, Zhu H, Xu J, Xu L, Huang Y. NMDA Receptors Regulate Oxidative Damage in Keratinocytes during Complex Regional Pain Syndrome in HaCaT Cells and Male Rats. Antioxidants (Basel) 2024; 13:244. [PMID: 38397842 PMCID: PMC10886417 DOI: 10.3390/antiox13020244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2023] [Revised: 01/29/2024] [Accepted: 02/15/2024] [Indexed: 02/25/2024] Open
Abstract
Complex regional pain syndrome (CRPS), a type of primary chronic pain, occurs following trauma or systemic disease and typically affects the limbs. CRPS-induced pain responses result in vascular, cutaneous, and autonomic nerve alterations, seriously impacting the quality of life of affected individuals. We previously identified the involvement of keratinocyte N-methyl-d-asparagic acid (NMDA) receptor subunit 2 B (NR2B) in both peripheral and central sensitizations in CRPS, although the mechanisms whereby NR2B functions following activation remain unclear. Using an in vivo male rat model of chronic post-ischemia pain (CPIP) and an in vitro oxygen-glucose deprivation/reoxygenation (OGD/R) cell model, we discovered that oxidative injury occurs in rat keratinocytes and HaCaT cells, resulting in reduced cell viability, mitochondrial damage, oxidative damage of nucleotides, and increased apoptosis. In HaCaT cells, OGD/R induced increases in intracellular reactive oxygen species levels and disrupted the balance between oxidation and antioxidation by regulating a series of antioxidant genes. The activation of NMDA receptors via NMDA exacerbated these changes, whereas the inhibition of the NR2B subunit alleviated them. Co-administration of ifenprodil (an NR2B antagonist) and NMDA (an NMDA receptor agonist) during the reoxygenation stage did not result in any significant alterations. Furthermore, intraplantar injection of ifenprodil effectively reversed the altered gene expression that was observed in male CPIP rats, thereby revealing the potential mechanisms underlying the therapeutic effects of peripheral ifenprodil administration in CRPS. Collectively, our findings indicate that keratinocytes undergo oxidative injury in CRPS, with NMDA receptors playing regulatory roles.
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Affiliation(s)
- Bei Wen
- Department of Anesthesiology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China; (B.W.); (H.Z.)
| | - He Zhu
- Department of Anesthesiology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China; (B.W.); (H.Z.)
| | - Jijun Xu
- Department of Pain Management, Cleveland Clinic, Cleveland, OH 44195, USA;
- Department of Inflammation and Immunity, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Li Xu
- Department of Anesthesiology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China; (B.W.); (H.Z.)
| | - Yuguang Huang
- Department of Anesthesiology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China; (B.W.); (H.Z.)
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