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Cao B, Xu Q, Shi Y, Zhao R, Li H, Zheng J, Liu F, Wan Y, Wei B. Pathology of pain and its implications for therapeutic interventions. Signal Transduct Target Ther 2024; 9:155. [PMID: 38851750 PMCID: PMC11162504 DOI: 10.1038/s41392-024-01845-w] [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] [Received: 05/12/2023] [Revised: 04/08/2024] [Accepted: 04/25/2024] [Indexed: 06/10/2024] Open
Abstract
Pain is estimated to affect more than 20% of the global population, imposing incalculable health and economic burdens. Effective pain management is crucial for individuals suffering from pain. However, the current methods for pain assessment and treatment fall short of clinical needs. Benefiting from advances in neuroscience and biotechnology, the neuronal circuits and molecular mechanisms critically involved in pain modulation have been elucidated. These research achievements have incited progress in identifying new diagnostic and therapeutic targets. In this review, we first introduce fundamental knowledge about pain, setting the stage for the subsequent contents. The review next delves into the molecular mechanisms underlying pain disorders, including gene mutation, epigenetic modification, posttranslational modification, inflammasome, signaling pathways and microbiota. To better present a comprehensive view of pain research, two prominent issues, sexual dimorphism and pain comorbidities, are discussed in detail based on current findings. The status quo of pain evaluation and manipulation is summarized. A series of improved and innovative pain management strategies, such as gene therapy, monoclonal antibody, brain-computer interface and microbial intervention, are making strides towards clinical application. We highlight existing limitations and future directions for enhancing the quality of preclinical and clinical research. Efforts to decipher the complexities of pain pathology will be instrumental in translating scientific discoveries into clinical practice, thereby improving pain management from bench to bedside.
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Affiliation(s)
- Bo Cao
- Department of General Surgery, First Medical Center, Chinese PLA General Hospital, Beijing, 100853, China
| | - Qixuan Xu
- Department of General Surgery, First Medical Center, Chinese PLA General Hospital, Beijing, 100853, China
- Medical School of Chinese PLA, Beijing, 100853, China
| | - Yajiao Shi
- Neuroscience Research Institute and Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience, Ministry of Education/National Health Commission, Peking University, Beijing, 100191, China
| | - Ruiyang Zhao
- Department of General Surgery, First Medical Center, Chinese PLA General Hospital, Beijing, 100853, China
- Medical School of Chinese PLA, Beijing, 100853, China
| | - Hanghang Li
- Department of General Surgery, First Medical Center, Chinese PLA General Hospital, Beijing, 100853, China
- Medical School of Chinese PLA, Beijing, 100853, China
| | - Jie Zheng
- Neuroscience Research Institute and Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience, Ministry of Education/National Health Commission, Peking University, Beijing, 100191, China
| | - Fengyu Liu
- Neuroscience Research Institute and Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience, Ministry of Education/National Health Commission, Peking University, Beijing, 100191, China.
| | - You Wan
- Neuroscience Research Institute and Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience, Ministry of Education/National Health Commission, Peking University, Beijing, 100191, China.
| | - Bo Wei
- Department of General Surgery, First Medical Center, Chinese PLA General Hospital, Beijing, 100853, China.
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Endocannabinoid 2-Arachidonoylglycerol Levels in the Anterior Cingulate Cortex, Caudate Putamen, Nucleus Accumbens, and Piriform Cortex Were Upregulated by Chronic Restraint Stress. Cells 2023; 12:cells12030393. [PMID: 36766735 PMCID: PMC9913316 DOI: 10.3390/cells12030393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 01/18/2023] [Accepted: 01/19/2023] [Indexed: 01/24/2023] Open
Abstract
Endocannabinoid 2-arachidonoylglycerol (2-AG) has been implicated in habituation to stress, and its augmentation reduces stress-induced anxiety-like behavior. Chronic restraint stress (CRS) changes the 2-AG levels in some gross brain areas, such as the forebrain. However, the detailed spatial distribution of 2-AG and its changes by CRS in stress processing-related anatomical structures such as the anterior cingulate cortex (ACC), caudate putamen (CP), nucleus accumbens (NAc), and piriform cortex (PIR) are still unclear. In this study, mice were restrained for 30 min in a 50 mL-centrifuge tube for eight consecutive days, followed by imaging of the coronal brain sections of control and stressed mice using desorption electrospray ionization mass spectrometry imaging (DESI-MSI). The results showed that from the forebrain to the cerebellum, 2-AG levels were highest in the hypothalamus and lowest in the hippocampal region. 2-AG levels were significantly (p < 0.05) upregulated and 2-AG precursors levels were significantly (p < 0.05) downregulated in the ACC, CP, NAc, and PIR of stressed mice compared with control mice. This study provided direct evidence of 2-AG expression and changes, suggesting that 2-AG levels are increased in the ACC CP, NAc, and PIR when individuals are under chronic stress.
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Kelly R, Bemelmans AP, Joséphine C, Brouillet E, McKernan DP, Dowd E. Time-Course of Alterations in the Endocannabinoid System after Viral-Mediated Overexpression of α-Synuclein in the Rat Brain. Molecules 2022; 27:507. [PMID: 35056822 PMCID: PMC8778740 DOI: 10.3390/molecules27020507] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 01/06/2022] [Accepted: 01/12/2022] [Indexed: 11/16/2022] Open
Abstract
Since the discovery of α-synuclein as the major component in Lewy bodies, research into this protein in the context of Parkinson's disease pathology has been exponential. Cannabinoids are being investigated as potential therapies for Parkinson's disease from numerous aspects, but still little is known about the links between the cannabinoid system and the pathogenic α-synuclein protein; understanding these links will be necessary if cannabinoid therapies are to reach the clinic in the future. Therefore, the aim of this study was to investigate the time-course of alterations in components of the endocannabinoid system after viral-mediated α-synuclein overexpression in the rat brain. Rats were given unilateral intranigral injections of AAV-GFP or AAV-α-synuclein and sacrificed 4, 8 and 12 weeks later for qRT-PCR and liquid chromatography-mass spectrometry analyses of the endocannabinoid system, in addition to histological visualization of α-synuclein expression along the nigrostriatal pathway. As anticipated, intranigral delivery of AAV-α-synuclein induced widespread overexpression of human α-synuclein in the nigrostriatal pathway, both at the mRNA level and the protein level. However, despite this profound α-synuclein overexpression, we detected no differences in CB1 or CB2 receptor expression in the nigrostriatal pathway; however, interestingly, there was a reduction in the expression of neuroinflammatory markers. Furthermore, there was a reduction in the levels of the endocannabinoid 2-AG and the related lipid immune mediator OEA at week 12 post-surgery, indicating that α-synuclein overexpression triggers dysregulation of the endocannabinoid system. Although this research does show that the endocannabinoid system is impacted by α-synuclein, further research is necessary to more comprehensively understand the link between the cannabinoid system and the α-synuclein aspect of Parkinson's disease pathology in order for cannabinoid-based therapies to be feasible for the treatment of this disease in the coming years.
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Affiliation(s)
- Rachel Kelly
- Department of Pharmacology & Therapeutics and Galway Neuroscience Centre, National University of Ireland Galway, H91 W5P7 Galway, Ireland; (R.K.); (D.P.M.)
| | - Alexis-Pierre Bemelmans
- Neurodegenerative Diseases Laboratory, Molecular Imaging Research Center, Paris-Saclay University, CEA, CNRS, F-92265 Fontenay-aux-Roses, France; (A.-P.B.); (C.J.); (E.B.)
| | - Charlène Joséphine
- Neurodegenerative Diseases Laboratory, Molecular Imaging Research Center, Paris-Saclay University, CEA, CNRS, F-92265 Fontenay-aux-Roses, France; (A.-P.B.); (C.J.); (E.B.)
| | - Emmanuel Brouillet
- Neurodegenerative Diseases Laboratory, Molecular Imaging Research Center, Paris-Saclay University, CEA, CNRS, F-92265 Fontenay-aux-Roses, France; (A.-P.B.); (C.J.); (E.B.)
| | - Declan P. McKernan
- Department of Pharmacology & Therapeutics and Galway Neuroscience Centre, National University of Ireland Galway, H91 W5P7 Galway, Ireland; (R.K.); (D.P.M.)
| | - Eilís Dowd
- Department of Pharmacology & Therapeutics and Galway Neuroscience Centre, National University of Ireland Galway, H91 W5P7 Galway, Ireland; (R.K.); (D.P.M.)
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Sexually Dimorphic Expression of Fear-conditioned Analgesia in Rats and Associated Alterations in the Endocannabinoid System in the Periaqueductal Grey. Neuroscience 2021; 480:117-130. [PMID: 34774710 DOI: 10.1016/j.neuroscience.2021.11.005] [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: 06/18/2021] [Revised: 10/16/2021] [Accepted: 11/02/2021] [Indexed: 11/20/2022]
Abstract
The endocannabinoid system within the periaqueductal grey (PAG) has been implicated in fear-conditioned analgesia (FCA), the profound suppression of pain upon re-exposure to a context previously paired with an aversive stimulus. Since the endocannabinoid and nociceptive systems exhibit sexual dimorphism, the aim of the present study was to assess possible sex differences in the expression of FCA, fear in the presence of nociceptive tone, and associated sex-dependent alterations in the endocannabinoid system within the PAG. Male and female Sprague-Dawley rats received footshock (10 × 1s; 0.4 mA; every 60 s) or no-footshock in a conditioning arena and 23.5 h later received intraplantar injection of formalin (2.5%) under brief isoflourane anaesthetic into the right hind paw. Nociceptive and fear-related behaviours were assessed 30 min later. Levels of endocannabinoids, N-acylethanolamines and neurotransmitters in the PAG were assessed by LC-MS/MS and expression of endocannabinoid system-related proteins by Western immunoblotting. Male, but not female, rats exhibited robust FCA and greater expression of fear-related behaviours than females. Fear-conditioned formalin-treated males, but not females, had higher levels of N-oleoylethanolamine (OEA) and γ-aminobutyric acid (GABA) in the PAG, compared with non-fear-conditioned controls. There was no effect of fear conditioning on the levels of FAAH or CB1 receptor expression (CB1R) in the PAG of male or female formalin-treated rats. Non-fear-conditioned females had higher levels of CB1R and PPARγ expression than non-fear-conditioned male counterparts. In summary, our results provide evidence of sexual dimorphism in the expression of FCA and fear-related behaviours, and associated alterations in components of the endocannabinoid system and GABA within the PAG.
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Boullon L, Finn DP, Llorente-Berzal Á. Sex Differences in a Rat Model of Peripheral Neuropathic Pain and Associated Levels of Endogenous Cannabinoid Ligands. FRONTIERS IN PAIN RESEARCH 2021; 2:673638. [PMID: 35295501 PMCID: PMC8915733 DOI: 10.3389/fpain.2021.673638] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 05/10/2021] [Indexed: 11/16/2022] Open
Abstract
Chronic neuropathic pain is a major unmet clinical need affecting 10% of the world population, the majority of whom suffer from co-morbid mood disorders. Sex differences have been reported in pain prevalence, perception and response to analgesics. However, sexual dimorphism in chronic neuropathic pain and the associated neurobiology, are still poorly understood. The lack of efficacy and the adverse effects associated with current pharmacological treatments, further underline the need for new therapeutic targets. The endocannabinoid system (ECS) is a lipid signalling system which regulates a large number of physiological processes, including pain. The aim of this study was to investigate sexual dimorphism in pain-, anxiety- and depression-related behaviours, and concomitant alterations in supraspinal and spinal endocannabinoid levels in the spared nerve injury (SNI) animal model of peripheral neuropathic pain. Sham or SNI surgery was performed in adult male and female Sprague-Dawley rats. Mechanical and cold allodynia was tested weekly using von Frey and acetone drop tests, respectively. Development of depression-related behaviours was analysed using sucrose splash and sucrose preference tests. Locomotor activity and anxiety-related behaviours were assessed with open field and elevated plus maze tests. Levels of endocannabinoid ligands and related N-acylethanolamines in supraspinal regions of the descending inhibitory pain pathway, and spinal cord, were analysed 42 days post-surgery. SNI surgery induced allodynia in rats of both sexes. Female-SNI rats exhibited earlier onset and greater sensitivity to cold and mechanical allodynia than their male counterparts. In male rats, SNI induced a significant reduction of rearing, compared to sham controls. Trends for depressive-like behaviours in females and for anxiety-like behaviours in males were observed after SNI surgery but did not reach statistical significance. No concomitant alterations in levels of endogenous cannabinoid ligands and related N-acylethanolamines were observed in the regions analysed. Our results demonstrate differential development of SNI-induced nociceptive behaviour between male and female rats suggesting important sexually dimorphic modifications in pain pathways. SNI had no effect on depression- or anxiety-related behaviours in animals of either sex, or on levels of endocannabinoid ligands and related N-acylethanolamines across the regions involved in the descending modulation of nociception at the time points investigated.
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O'Sullivan G, Humphrey RM, Thornton AM, Kerr DM, McGuire BE, Caes L, Roche M. Maternal presence or absence alters nociceptive responding and cortical anandamide levels in juvenile female rats. Behav Brain Res 2020; 392:112712. [PMID: 32479851 DOI: 10.1016/j.bbr.2020.112712] [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: 02/28/2020] [Revised: 04/21/2020] [Accepted: 05/16/2020] [Indexed: 10/24/2022]
Abstract
The influence of parental support on child pain experiences is well recognised. Accordingly, animal studies have revealed both short- and long-term effects of early life stress on nociceptive responding and neural substrates such as endocannabinoids. The endocannabinoid system plays an important role in mediating and modulating stress, social interaction, and nociception. This study examined the effects of maternal support or acute isolation on nociceptive responding of female rats to a range of stimuli during the juvenile pre-adolescent period and accompanying changes in the endocannabinoid system. The data revealed that juvenile female Sprague Dawley rats (PND21-24) isolated from the dam for 1 h prior to nociceptive testing exhibited increased latency to withdraw in the hot plate test and increased mechanical withdrawal threshold in the Von Frey test, compared to rats tested in the presence of the dam. Furthermore, isolated rats exhibited reduced latency to respond in the acetone drop test and enhanced nociceptive responding in the formalin test when compared to dam-paired counterparts. Anandamide, but not 2-AG, levels were reduced in the prefrontal cortex of dam-paired, but not isolated, juvenile rats following nociceptive testing. There was no change in the expression of CB1, FAAH or MAGL; however, CB2 receptor expression was reduced in both dam-paired and isolated rats following nociceptive testing. Taken together the data demonstrate that brief social isolation or the presence of the dam modulates nociceptive responding of juvenile rat pups in a modality specific manner, and suggest a possible role for the endocannabinoid system in the prefrontal cortex in sociobehavioural pain responses during early life.
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Affiliation(s)
- Grace O'Sullivan
- Centre for Pain Research, National University of Ireland Galway, Ireland; School of Psychology, National University of Ireland Galway, Ireland
| | - Rachel M Humphrey
- Physiology, School of Medicine, National University of Ireland Galway, Ireland; Centre for Pain Research, National University of Ireland Galway, Ireland; Galway Neuroscience Centre, National University of Ireland Galway, Ireland
| | - Aoife M Thornton
- Physiology, School of Medicine, National University of Ireland Galway, Ireland; Galway Neuroscience Centre, National University of Ireland Galway, Ireland
| | - Daniel M Kerr
- Galway Neuroscience Centre, National University of Ireland Galway, Ireland; Pharmacology, School of Medicine, National University of Ireland Galway, Ireland
| | - Brian E McGuire
- Centre for Pain Research, National University of Ireland Galway, Ireland; School of Psychology, National University of Ireland Galway, Ireland
| | - Line Caes
- Psychology, Faculty of Natural Sciences, University of Stirling, Scotland, UK
| | - Michelle Roche
- Physiology, School of Medicine, National University of Ireland Galway, Ireland; Centre for Pain Research, National University of Ireland Galway, Ireland; Galway Neuroscience Centre, National University of Ireland Galway, Ireland.
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Corcoran L, Mattimoe D, Roche M, Finn DP. Attenuation of fear-conditioned analgesia in rats by monoacylglycerol lipase inhibition in the anterior cingulate cortex: Potential role for CB 2 receptors. Br J Pharmacol 2020; 177:2240-2255. [PMID: 31967664 PMCID: PMC7174879 DOI: 10.1111/bph.14976] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Revised: 12/01/2019] [Accepted: 12/19/2019] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND AND PURPOSE Improved understanding of brain mechanisms regulating endogenous analgesia is important from a fundamental physiological perspective and for identification of novel therapeutic strategies for pain. The endocannabinoid system plays a key role in stress-induced analgesia, including fear-conditioned analgesia (FCA), a potent form of endogenous analgesia. Here, we studied the role of the endocannabinoid 2-arachidonoyl glycerol (2-AG) within the anterior cingulate cortex (ACC; a brain region implicated in the affective component of pain) in FCA in rats. EXPERIMENTAL APPROACH FCA was modelled in male Lister-hooded rats by assessing formalin-evoked nociceptive behaviour in an arena previously paired with footshock. The effects of intra-ACC administration of MJN110 (inhibitor of monoacylglycerol lipase [MGL], the primary enzyme catabolizing 2-AG), AM630 (CB2 receptor antagonist), AM251 (CB1 receptor antagonist) or MJN110 + AM630 on FCA were assessed. KEY RESULTS MJN110 attenuated FCA when microinjected into the ACC, an effect associated with increased levels of 2-AG in the ACC. This effect of MJN110 on FCA was unaltered by co-administration of AM251 but was blocked by AM630, which alone reduced nociceptive behaviour in non-fear-conditioned rats. RT-qPCR confirmed that mRNA encoding CB1 and CB2 receptors was detectable in the ACC of formalin-injected rats and unchanged in those expressing FCA. CONCLUSION AND IMPLICATIONS These results suggest that an MGL substrate in the ACC, likely 2-AG, modulates FCA and that within the ACC, 2-AG-CB2 receptor signalling may suppress this form of endogenous analgesia. These results may facilitate increased understanding and improved treatment of pain- and fear-related disorders and their co-morbidity.
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Affiliation(s)
- Louise Corcoran
- Pharmacology and Therapeutics, School of MedicineNational University of Ireland GalwayGalwayIreland
- Galway Neuroscience Centre and Centre for Pain ResearchNational University of Ireland GalwayGalwayIreland
| | - Darragh Mattimoe
- Pharmacology and Therapeutics, School of MedicineNational University of Ireland GalwayGalwayIreland
- Galway Neuroscience Centre and Centre for Pain ResearchNational University of Ireland GalwayGalwayIreland
| | - Michelle Roche
- Physiology, School of MedicineNational University of Ireland GalwayGalwayIreland
- Galway Neuroscience Centre and Centre for Pain ResearchNational University of Ireland GalwayGalwayIreland
| | - David P. Finn
- Pharmacology and Therapeutics, School of MedicineNational University of Ireland GalwayGalwayIreland
- Galway Neuroscience Centre and Centre for Pain ResearchNational University of Ireland GalwayGalwayIreland
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