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Perry SK, Emrick JJ. Trigeminal somatosensation in the temporomandibular joint and associated disorders. FRONTIERS IN PAIN RESEARCH 2024; 5:1374929. [PMID: 38784786 PMCID: PMC11111860 DOI: 10.3389/fpain.2024.1374929] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 04/23/2024] [Indexed: 05/25/2024] Open
Abstract
The temporomandibular joint (TMJ) consists of bone, cartilage, ligaments, and associated masticatory muscles and tendons that coordinate to enable mastication in mammals. The TMJ is innervated by the trigeminal nerve (CNV), containing axons of motor and somatosensory neurons. Somatosensation includes touch, temperature, proprioception, and pain that enables mammals to recognize and react to stimuli for survival. The somatosensory innervation of the TMJ remains poorly defined. Disorders of the TMJ (TMD) are of diverse etiology and presentation. Some known symptoms associated with TMD include facial, shoulder, or neck pain, jaw popping or clicking, headaches, toothaches, and tinnitus. Acute or chronic pain in TMD stems from the activation of somatosensory nociceptors. Treatment of TMD may involve over- the-counter and prescription medication, nonsurgical treatments, and surgical treatments. In many cases, treatment achieves only a temporary relief of symptoms including pain. We suggest that defining the sensory innervation of the temporomandibular joint and its associated tissues with a specific focus on the contribution of peripheral innervation to the development of chronic pain could provide insights into the origins of joint pain and facilitate the development of improved analgesics and treatments for TMD.
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Affiliation(s)
| | - Joshua J. Emrick
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI, United States
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Tao J, Wang X, Xu J. Expression of CGRP in the Trigeminal Ganglion and Its Effect on the Polarization of Macrophages in Rats with Temporomandibular Arthritis. Cell Mol Neurobiol 2024; 44:22. [PMID: 38363424 PMCID: PMC10873438 DOI: 10.1007/s10571-024-01456-7] [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: 10/23/2023] [Accepted: 01/19/2024] [Indexed: 02/17/2024]
Abstract
Calcitonin gene-related peptide (CGRP) is synthesized and secreted by trigeminal ganglion neurons, and is a key neuropeptide involved in pain and immune regulation. This study investigates the expression of CGRP in the trigeminal ganglion (TG) and its regulatory role in the polarization of macrophages in rats with temporomandibular arthritis. A rat model of temporomandibular arthritis was established using CFA. Pain behavior was then observed. Temporomandibular joint (TMJ) and the TG were collected, and immunohistochemistry, immunofluorescence (IF) staining, and RT-qPCR were used to examine the expression of CGRP and macrophage-related factors. To investigate the impact of CGRP on macrophage polarization, both CGRP and its antagonist, CGRP 8-37, were separately administered directly within the TG. Statistical analysis revealed that within 24 h of inducing temporomandibular arthritis using CFA, there was a significant surge in CD86 positive macrophages within the ganglion. These macrophages peaked on the 7th day before beginning their decline. In this context, it's noteworthy that administering CGRP to the trigeminal ganglion can prompt these macrophages to adopt the M2 phenotype. Intriguingly, this study demonstrates that injecting the CGRP receptor antagonist (CGRP 8-37) to the ganglion counteracts this shift towards the M2 phenotype. Supporting these in vivo observations, we found that in vitro, CGRP indeed fosters the M2-type polarization of macrophages. CGRP can facilitate the conversion of macrophages into the M2 phenotype. The phenotypic alterations of macrophages within the TG could be instrumental in initiating and further driving the progression of TMJ disorders.
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Affiliation(s)
- Junli Tao
- College of Stomatology, Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory for Oral Diseases and Biomedical Sciences, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing, China
| | - Xiaohui Wang
- College of Stomatology, Chongqing Medical University, Chongqing, China
- Chongqing Key Laboratory for Oral Diseases and Biomedical Sciences, Chongqing, China
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing, China
| | - Jie Xu
- College of Stomatology, Chongqing Medical University, Chongqing, China.
- Chongqing Key Laboratory for Oral Diseases and Biomedical Sciences, Chongqing, China.
- Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing, China.
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Kuramoto E, Fukushima M, Sendo R, Ohno S, Iwai H, Yamanaka A, Sugimura M, Goto T. Three-dimensional topography of rat trigeminal ganglion neurons using a combination of retrograde labeling and tissue-clearing techniques. J Comp Neurol 2024; 532:e25584. [PMID: 38341648 DOI: 10.1002/cne.25584] [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: 09/07/2023] [Revised: 12/28/2023] [Accepted: 01/09/2024] [Indexed: 02/12/2024]
Abstract
The trigeminal nerve is the sensory afferent of the orofacial regions and divided into three major branches. Cell bodies of the trigeminal nerve lie in the trigeminal ganglion and are surrounded by satellite cells. There is a close interaction between ganglion cells via satellite cells, but the function is not fully understood. In the present study, we clarified the ganglion cells' three-dimensional (3D) localization, which is essential to understand the functions of cell-cell interactions in the trigeminal ganglion. Fast blue was injected into 12 sites of the rat orofacial regions, and ganglion cells were retrogradely labeled. The labeled trigeminal ganglia were cleared by modified 3DISCO, imaged with confocal laser-scanning microscopy, and reconstructed in 3D. Histograms of the major axes of the fast blue-positive somata revealed that the peak major axes of the cells innervating the skin/mucosa were smaller than those of cells innervating the deep structures. Ganglion cells innervating the ophthalmic, maxillary, and mandibular divisions were distributed in the anterodorsal, central, and posterolateral portions of the trigeminal ganglion, respectively, with considerable overlap in the border region. The intermingling in the distribution of ganglion cells within each division was also high, in particular, within the mandibular division. Specifically, intermingling was observed in combinations of tongue and masseter/temporal muscles, maxillary/mandibular molars and masseter/temporal muscles, and tongue and mandibular molars. Double retrograde labeling confirmed that some ganglion cells innervating these combinations were closely apposed. Our data provide essential information for understanding the function of ganglion cell-cell interactions via satellite cells.
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Grants
- JP23H03119 Grants-in-Aid from The Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP23K09316 Grants-in-Aid from The Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP19K10058 Grants-in-Aid from The Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP19K10336 Grants-in-Aid from The Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP19KK0419 Grants-in-Aid from The Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP22H05162 Grants-in-Aid from The Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- JP22K09916 Grants-in-Aid from The Ministry of Education, Culture, Sports, Science and Technology (MEXT)
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Affiliation(s)
- Eriko Kuramoto
- Department of Oral Anatomy and Cell Biology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Makoto Fukushima
- Department of Oral Anatomy and Cell Biology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Ryozo Sendo
- Department of Oral Anatomy and Cell Biology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
- Department of Dental Anesthesiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Sachi Ohno
- Department of Dental Anesthesiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Haruki Iwai
- Department of Oral Anatomy and Cell Biology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Atsushi Yamanaka
- Department of Oral Anatomy and Cell Biology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Mitsutaka Sugimura
- Department of Dental Anesthesiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Tetsuya Goto
- Department of Oral Anatomy and Cell Biology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
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Kudsi SQ, Viero FT, Pereira LG, Trevisan G. Involvement of the Transient Receptor Channels in Preclinical Models of Musculoskeletal Pain. Curr Neuropharmacol 2024; 22:72-87. [PMID: 37694792 DOI: 10.2174/1570159x21666230908094159] [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: 04/10/2023] [Revised: 08/14/2023] [Accepted: 08/16/2023] [Indexed: 09/12/2023] Open
Abstract
BACKGROUND Musculoskeletal pain is a condition that affects bones, muscles, and tendons and is present in various diseases and/or clinical conditions. This type of pain represents a growing problem with enormous socioeconomic impacts, highlighting the importance of developing treatments tailored to the patient's needs. TRP is a large family of non-selective cation channels involved in pain perception. Vanilloid (TRPV1 and TRPV4), ankyrin (TRPA1), and melastatin (TRPM8) are involved in physiological functions, including nociception, mediation of neuropeptide release, heat/cold sensing, and mechanical sensation. OBJECTIVE In this context, we provide an updated view of the most studied preclinical models of muscle hyperalgesia and the role of transient receptor potential (TRP) in these models. METHODS This review describes preclinical models of muscle hyperalgesia induced by intramuscular administration of algogenic substances and/or induction of muscle damage by physical exercise in the masseter, gastrocnemius, and tibial muscles. RESULTS The participation of TRPV1, TRPA1, and TRPV4 in different models of musculoskeletal pain was evaluated using pharmacological and genetic tools. All the studies detected the antinociceptive effect of respective antagonists or reduced nociception in knockout mice. CONCLUSION Hence, TRPV1, TRPV4, and TRPA1 blockers could potentially be utilized in the future for inducing analgesia in muscle hypersensitivity pathologies.
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Affiliation(s)
- Sabrina Qader Kudsi
- Programa de Pós-Graduação em Farmacologia, Universidade Federal de Santa Maria (UFSM), Avenida Roraima, 97105-900 Santa Maria (RS), Brazil
| | - Fernanda Tibolla Viero
- Programa de Pós-Graduação em Farmacologia, Universidade Federal de Santa Maria (UFSM), Avenida Roraima, 97105-900 Santa Maria (RS), Brazil
| | - Leonardo Gomes Pereira
- Programa de Pós-Graduação em Farmacologia, Universidade Federal de Santa Maria (UFSM), Avenida Roraima, 97105-900 Santa Maria (RS), Brazil
| | - Gabriela Trevisan
- Programa de Pós-Graduação em Farmacologia, Universidade Federal de Santa Maria (UFSM), Avenida Roraima, 97105-900 Santa Maria (RS), Brazil
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Hovhannisyan AH, Lindquist KA, Belugin S, Mecklenburg J, Ibrahim T, Tram M, Corey TM, Salmon AB, Perez D, Ruparel S, Akopian AN. Sensory innervation of masseter, temporal and lateral pterygoid muscles in common marmosets. Sci Rep 2023; 13:23062. [PMID: 38155190 PMCID: PMC10754842 DOI: 10.1038/s41598-023-49882-9] [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: 04/26/2023] [Accepted: 12/13/2023] [Indexed: 12/30/2023] Open
Abstract
Myogenous temporomandibular disorders is associated with an increased responsiveness of nerves innervating the masseter (MM), temporal (TM), and lateral pterygoid muscles (LPM). This study aimed to examine sensory nerve types innervating MM, TM and LPM of adult non-human primate-common marmosets. Sensory nerves were localized in specific regions of these muscles. Pgp9.5, marker for all nerves, and NFH, a marker for A-fibers, showed that masticatory muscles were primarily innervated with A-fibers. The proportion of C- to A-fibers was highest in LPM, and lowest in MM. All C-fibers (pgp9.5+/NFH-) observed in masticatory muscles were peptidergic (CGRP+) and lacked mrgprD and CHRNA3, a silent nociceptive marker. TrpV1 was register in 17% of LPM nerves. All fibers in masticatory muscles were labeled with GFAP+, a myelin sheath marker. There were substantially more peptidergic A-fibers (CGRP+/NFH+) in TM and LPM compared to MM. MM, TM and LPM NFH+ fibers contained different percentages of trkC+ and parvalbumin+, but not trkB+ fibers. Tyrosine hydroxylase antibodies, which did not label TG, highlighted sympathetic fibers around blood vessels of the masticatory muscles. Overall, masticatory muscle types of marmosets have similarities and differences in innervation patterns.
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Affiliation(s)
- Anahit H Hovhannisyan
- Departments of Endodontics, The School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229-3900, USA
| | - Karen A Lindquist
- Integrated Biomedical Sciences (IBMS) Program, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Sergei Belugin
- Departments of Endodontics, The School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229-3900, USA
| | - Jennifer Mecklenburg
- Departments of Endodontics, The School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229-3900, USA
| | - Tarek Ibrahim
- Departments of Endodontics, The School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229-3900, USA
| | - Meilinn Tram
- Departments of Endodontics, The School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229-3900, USA
- Integrated Biomedical Sciences (IBMS) Program, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Tatiana M Corey
- Departments of Laboratory Animal Resources, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Adam B Salmon
- Departments of Molecular Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
- Sam and Ann Barshop Institute for Longevity and Aging Studies, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
- South Texas Veterans Health Care System, Geriatric Research Education and Clinical Center San Antonio, San Antonio, TX, 78229, USA
| | - Daniel Perez
- Oral and Maxillofacial Surgery, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Shivani Ruparel
- Departments of Endodontics, The School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229-3900, USA
- Integrated Biomedical Sciences (IBMS) Program, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
- Departments of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Armen N Akopian
- Departments of Endodontics, The School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229-3900, USA.
- Integrated Biomedical Sciences (IBMS) Program, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA.
- Departments of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA.
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Mecklenburg J, Shein SA, Malmir M, Hovhannisyan AH, Weldon K, Zou Y, Lai Z, Jin YF, Ruparel S, Tumanov AV, Akopian AN. Transcriptional profiles of non-neuronal and immune cells in mouse trigeminal ganglia. FRONTIERS IN PAIN RESEARCH 2023; 4:1274811. [PMID: 38028432 PMCID: PMC10644122 DOI: 10.3389/fpain.2023.1274811] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 09/29/2023] [Indexed: 12/01/2023] Open
Abstract
Non-neuronal cells constitute 90%-95% of sensory ganglia. These cells, especially glial and immune cells, play critical roles in the modulation of sensory neurons. This study aimed to identify, profile, and summarize the types of trigeminal ganglion (TG) non-neuronal cells in naïve male mice using published and our own data generated by single-cell RNA sequencing, flow cytometry, and immunohistochemistry. TG has five types of non-neuronal cells, namely, glial, fibroblasts, smooth muscle, endothelial, and immune cells. There is an agreement among publications for glial, fibroblasts, smooth muscle, and endothelial cells. Based on gene profiles, glial cells were classified as myelinated and non-myelinated Schwann cells and satellite glial cells. Mpz has dominant expression in Schwann cells, and Fabp7 is specific for SCG. Two types of Col1a2+ fibroblasts located throughout TG were distinguished. TG smooth muscle and endothelial cells in the blood vessels were detected using well-defined markers. Our study reported three types of macrophages (Mph) and four types of neutrophils (Neu) in TG. Mph were located in the neuronal bodies and nerve fibers and were sub-grouped by unique transcriptomic profiles with Ccr2, Cx3cr1, and Iba1 as markers. A comparison of databases showed that type 1 Mph is similar to choroid plexus-low (CPlo) border-associated Mph (BAMs). Type 2 Mph has the highest prediction score with CPhi BAMs, while type 3 Mph is distinct. S100a8+ Neu were located in the dura surrounding TG and were sub-grouped by clustering and expressions of Csf3r, Ly6G, Ngp, Elane, and Mpo. Integrative analysis of published datasets indicated that Neu-1, Neu-2, and Neu-3 are similar to the brain Neu-1 group, while Neu-4 has a resemblance to the monocyte-derived cells. Overall, the generated and summarized datasets on non-neuronal TG cells showed a unique composition of myeloid cell types in TG and could provide essential and fundamental information for studies on cell plasticity, interactomic networks between neurons and non-neuronal cells, and function during a variety of pain conditions in the head and neck regions.
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Affiliation(s)
- Jennifer Mecklenburg
- Department of Endodontics, School of Dentistry, The University of Texas Health Science Center at San Antonio (UTHSCSA), San Antonio, TX, United States
| | - Sergey A. Shein
- Microbiology, Immunology & Molecular Genetics Departments, School of Medicine, UTHSCSA, San Antonio, TX, United States
| | - Mostafa Malmir
- Department of Electrical and Computer Engineering, the University of Texas at San Antonio, San Antonio, TX, United States
| | - Anahit H. Hovhannisyan
- Department of Endodontics, School of Dentistry, The University of Texas Health Science Center at San Antonio (UTHSCSA), San Antonio, TX, United States
| | - Korri Weldon
- Molecular Medicine, School of Medicine, UTHSCSA, San Antonio, TX, United States
| | - Yi Zou
- Molecular Medicine, School of Medicine, UTHSCSA, San Antonio, TX, United States
| | - Zhao Lai
- Molecular Medicine, School of Medicine, UTHSCSA, San Antonio, TX, United States
- Greehey Children’s Cancer Research Institute, UTHSCSA, San Antonio, TX, United States
| | - Yu-Fang Jin
- Department of Electrical and Computer Engineering, the University of Texas at San Antonio, San Antonio, TX, United States
| | - Shivani Ruparel
- Department of Endodontics, School of Dentistry, The University of Texas Health Science Center at San Antonio (UTHSCSA), San Antonio, TX, United States
| | - Alexei V. Tumanov
- Microbiology, Immunology & Molecular Genetics Departments, School of Medicine, UTHSCSA, San Antonio, TX, United States
| | - Armen N. Akopian
- Department of Endodontics, School of Dentistry, The University of Texas Health Science Center at San Antonio (UTHSCSA), San Antonio, TX, United States
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7
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Mecklenburg J, Shein SA, Hovhannisyan AH, Zou Y, Lai Z, Ruparel S, Tumanov AV, Akopian AN. Transcriptional Profiles of Non-neuronal and Immune Cells in Mouse Trigeminal Ganglia. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.18.553897. [PMID: 37645736 PMCID: PMC10462109 DOI: 10.1101/2023.08.18.553897] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Non-neuronal cells constitute 90-95% of sensory ganglia. These cells play critical roles in modulation of nociceptive signal transmissions by sensory neurons. Accordingly, the aim of this review-study was to identify, profile and summarize TG non-neuronal cell types in naïve male mice using published and our own data generated by single-cell RNA sequencing (scRNA-seq), flow cytometry (FC) and immunohistochemistry (IHC). TG contains 5 types of non-neuronal cells: glial, fibroblasts, smooth muscle, endothelial and immune cells. There is agreement among publications for glial, fibroblasts, smooth muscle and endothelial cells. Based on gene profiles, glial cells were classified as Schwann cells and satellite glial cells (SGC). Mpz had dominant expression in Schwann cells, and Fabp7 is specific for SCG. Two types of Col1a2 + fibroblasts located throughout TG were distinguished using gene profiles. TG smooth muscle and endothelial cells representing blood vessels were detected with well recognized markers. Our study split reported single TG immune cell group into 3 types of macrophages and 4 types of neutrophils. Macrophages were located among neuronal bodies and nerve fibers, and were sub-grouped by unique transcriptomic profiles and using Ccr2 , Cx3cr1 and Iba1 as markers. S100a8 + neutrophils were located in dura surrounding TG and were sub-grouped by clustering and expressions of Csf3r , Ly6G, Ngp, Elane and Mpo . Overall, generated and summarized here dataset on non-neuronal TG cells could provide essential and fundamental information for studies on cell plasticity, interactomic network between neurons and non-neuronal cells and function during variety of pain conditions in the head and neck region.
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8
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Ibrahim T, Wu P, Wang LJ, Fang-Mei C, Murillo J, Merlo J, Shein SS, Tumanov AV, Lai Z, Weldon K, Chen Y, Ruparel S. Sex-dependent differences in the genomic profile of lingual sensory neurons in naïve and tongue-tumor bearing mice. Sci Rep 2023; 13:13117. [PMID: 37573456 PMCID: PMC10423281 DOI: 10.1038/s41598-023-40380-6] [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: 05/13/2023] [Accepted: 08/09/2023] [Indexed: 08/14/2023] Open
Abstract
Mechanisms of sex-dependent orofacial pain are widely understudied. A significant gap in knowledge exists about comprehensive regulation of tissue-specific trigeminal sensory neurons in diseased state of both sexes. Using RNA sequencing of FACS sorted retro-labeled sensory neurons innervating tongue tissue, we determined changes in transcriptomic profiles in males and female mice under naïve as well as tongue-tumor bearing conditions Our data revealed the following interesting findings: (1) FACS sorting obtained higher number of neurons from female trigeminal ganglia (TG) compared to males; (2) Naïve female neurons innervating the tongue expressed immune cell markers such as Csf1R, C1qa and others, that weren't expressed in males. This was validated by Immunohistochemistry. (3) Accordingly, immune cell markers such as Csf1 exclusively sensitized TRPV1 responses in female TG neurons. (4) Male neurons were more tightly regulated than female neurons upon tumor growth and very few differentially expressed genes (DEGs) overlapped between the sexes, (5) Male DEGs contained higher number of transcription factors whereas female DEGs contained higher number of enzymes, cytokines and chemokines. Collectively, this is the first study to characterize the effect of sex as well as of tongue-tumor on global gene expression, pathways and molecular function of tongue-innervating sensory neurons.
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Affiliation(s)
- Tarek Ibrahim
- Department of Endodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Ping Wu
- Department of Endodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Li-Ju Wang
- Greehey Children's Cancer Institute, University of Texas Health San Antonio, San Antonio, USA
- Department of Population Health Sciences, University of Texas Health at San Antonio, San Antonio, USA
| | - Chang Fang-Mei
- Department of Endodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Josue Murillo
- Department of Endodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Jaclyn Merlo
- Department of Endodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Sergey S Shein
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas Health San Antonio, San Antonio, USA
| | - Alexei V Tumanov
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas Health San Antonio, San Antonio, USA
| | - Zhao Lai
- Greehey Children's Cancer Institute, University of Texas Health San Antonio, San Antonio, USA
- Department of Molecular Medicine, University of Texas Health at San Antonio, San Antonio, TX, USA
| | - Korri Weldon
- Greehey Children's Cancer Institute, University of Texas Health San Antonio, San Antonio, USA
- Department of Molecular Medicine, University of Texas Health at San Antonio, San Antonio, TX, USA
| | - Yidong Chen
- Greehey Children's Cancer Institute, University of Texas Health San Antonio, San Antonio, USA
- Department of Population Health Sciences, University of Texas Health at San Antonio, San Antonio, USA
| | - Shivani Ruparel
- Department of Endodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA.
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9
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Tram M, Ibrahim T, Hovhannisyan A, Akopian A, Ruparel S. Lingual innervation in male and female marmosets. NEUROBIOLOGY OF PAIN (CAMBRIDGE, MASS.) 2023; 14:100134. [PMID: 38099285 PMCID: PMC10719518 DOI: 10.1016/j.ynpai.2023.100134] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 05/26/2023] [Accepted: 05/26/2023] [Indexed: 12/17/2023]
Abstract
Several gaps in knowledge exists in our understanding of orofacial pain. Some of these include type of peripheral sensory innervation in specific tissues, differences in innervation between sexes and validation of rodent studies in higher order species. The current study addresses these gaps by validating mouse studies for sensory innervation of tongue tissue in non-human primates as well as assesses sex-specific differences. Tongue and trigeminal ganglia were collected from naïve male and female marmosets and tested for nerve fibers using specific markers by immunohistochemistry and number of fibers quantified. We also tested whether specific subgroups of nerve fibers belonged to myelinating or non-myelinating axons. We observed that similar to findings in mice, marmoset tongue was innervated with nerve filaments expressing nociceptor markers like CGRP and TRPV1 as well as non-nociceptor markers like TrkB, parvalbumin (PV) and tyrosine hydroxylase (TH). Furthermore, we found that while portion of TrkB and PV may be sensory fibers, TH-positive fibers were primarily sympathetic nerve fibers. Moreover, number of CGRP, TrkB and TH-positive nerve fibers were similar in both sexes. However, we observed a higher proportion of myelinated TRPV1 positive fibers in females than in males as well as increased number of PV + fibers in females. Taken together, the study for the first time characterizes sensory innervation in non-human primates as well as evaluates sex-differences in innervation of tongue tissue, thereby laying the foundation for future orofacial pain research with new world smaller NHPs like the common marmoset.
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Affiliation(s)
- Meilinn Tram
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Tarek Ibrahim
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Anahit Hovhannisyan
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Armen Akopian
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Shivani Ruparel
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
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Sangalli L, Eli B, Mehrotra S, Sabagh S, Fricton J. Calcitonin Gene-Related Peptide-Mediated Trigeminal Ganglionitis: The Biomolecular Link between Temporomandibular Disorders and Chronic Headaches. Int J Mol Sci 2023; 24:12200. [PMID: 37569575 PMCID: PMC10418780 DOI: 10.3390/ijms241512200] [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: 06/27/2023] [Revised: 07/22/2023] [Accepted: 07/26/2023] [Indexed: 08/13/2023] Open
Abstract
A bidirectional causal relationship has been established between temporomandibular disorders (TMDs) and chronic headaches. Recent advances in the neurobiology of chronic pain offer a framework for understanding the comorbidity between these two conditions that might reside in the shared biomolecular mechanisms of peripheral and central sensitization. The initiation of these processes is inflammatory in nature and is most likely mediated by key molecules, including calcitonin gene-related peptide (CGRP). This scoping review proposes that CGRP-mediated neuroinflammation in the trigeminal ganglion may partly explain the biomolecular bidirectional link between TMDs and chronic headaches. Finally, clinical implications of this neuropathologic process are briefly discussed.
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Affiliation(s)
- Linda Sangalli
- College of Dental Medicine—Illinois, Midwestern University, Downers Grove, IL 60515, USA
| | - Bradley Eli
- Facial Pain Specialists, San Diego, CA 92121,USA; (B.E.); (S.M.); (S.S.)
| | - Sachi Mehrotra
- Facial Pain Specialists, San Diego, CA 92121,USA; (B.E.); (S.M.); (S.S.)
| | - Suzan Sabagh
- Facial Pain Specialists, San Diego, CA 92121,USA; (B.E.); (S.M.); (S.S.)
| | - James Fricton
- Division of TMD and Orofacial Pain, University of Minnesota Schoof of Dentistry, Minneapolis, MN 55455, USA
- Minnesota Head and Neck Pain Clinic, Plymouth, MN 55447, USA
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11
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Ibrahim T, Wu P, Wang LJ, Fang-Mei C, Murillo J, Merlo J, Tumanov A, Lai Z, Weldon K, Chen Y, Ruparel S. Sex-dependent Differences in the Genomic Profile of Lingual Sensory Neurons in Naïve and Tongue-Tumor Bearing Mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.14.524011. [PMID: 36711730 PMCID: PMC9882171 DOI: 10.1101/2023.01.14.524011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Mechanisms of sex-dependent orofacial pain are widely understudied. A significant gap in knowledge exists about comprehensive regulation of tissue-specific trigeminal sensory neurons in diseased state of both sexes. Using RNA sequencing of FACS sorted retro-labeled sensory neurons innervating tongue tissue, we determined changes in transcriptomic profiles in males and female mice under naïve as well as tongue-tumor bearing conditions Our data revealed the following interesting findings: 1) Tongue tissue of female mice was innervated with higher number of trigeminal neurons compared to males; 2) Naïve female neurons innervating the tongue exclusively expressed immune cell markers such as Csf1R, C1qa and others, that weren't expressed in males. This was validated by Immunohistochemistry. 4) Accordingly, immune cell markers such as Csf1 exclusively sensitized TRPV1 responses in female TG neurons. 3) Male neurons were more tightly regulated than female neurons upon tumor growth and very few differentially expressed genes (DEGs) overlapped between the sexes, 5) Male DEGs contained higher number of transcription factors whereas female DEGs contained higher number of enzymes, cytokines and chemokines. Collectively, this is the first study to characterize the effect of sex as well as of tongue-tumor on global gene expression, pathways and molecular function of tongue-innervating sensory neurons.
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Affiliation(s)
- Tarek Ibrahim
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Ping Wu
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Li-Ju Wang
- Greehey Children’s Cancer Institute, University of Texas Health San Antonio, USA
- Department of Population Health Sciences, University of Texas Health at San Antonio, USA
| | - Chang Fang-Mei
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Josue Murillo
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Jaclyn Merlo
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Alexei Tumanov
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas Health San Antonio, USA
| | - Zhao Lai
- Greehey Children’s Cancer Institute, University of Texas Health San Antonio, USA
- Department of Molecular Medicine, University of Texas Health at San Antonio, San Antonio, TX, USA
| | - Korri Weldon
- Greehey Children’s Cancer Institute, University of Texas Health San Antonio, USA
- Department of Molecular Medicine, University of Texas Health at San Antonio, San Antonio, TX, USA
| | - Yidong Chen
- Greehey Children’s Cancer Institute, University of Texas Health San Antonio, USA
- Department of Population Health Sciences, University of Texas Health at San Antonio, USA
| | - Shivani Ruparel
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
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12
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Hovhannisyan AH, Lindquist K, Belugin S, Mecklenburg J, Ibrahim T, Tram M, Corey T, Salmon A, Ruparel S, Ruparel S, Akopian A. Sensory innervation of masseter, temporal and lateral pterygoid muscles in common marmosets. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.10.528062. [PMID: 36798270 PMCID: PMC9934658 DOI: 10.1101/2023.02.10.528062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
Myogenous temporomandibular disorders (TMDM) is associated with an increased responsiveness of nerves innervating the masseter (MM), temporal (TM), medial pterygoid (MPM) and lateral pterygoid muscles (LPM). This study aimed to examine sensory nerve types innervating MM, TM and LPM of adult non-human primate - common marmosets. Sensory nerves are localized in specific regions of these muscles. Pgp9.5, marker for all nerves, and NFH, a marker for A-fibers, showed that masticatory muscles were predominantly innervated with A-fibers. The proportion of C- to A-fibers was highest in LPM, and minimal (6-8%) in MM. All C-fibers (pgp9.5+/NFH-) observed in masticatory muscles were peptidergic (CGRP+) and lacked mrgprD, trpV1 and CHRNA3, a silent nociceptive marker. All fibers in masticatory muscles were labeled with GFAP+, a myelin sheath marker. There were substantially more peptidergic A-fibers (CGRP+/NFH+) in TM and LPM compared to MM. Almost all A-fibers in MM expressed trkC, with some of them having trkB and parvalbumin. In contrast, a lesser number of TM and LPM nerves expressed trkC, and lacked trkB. Tyrosine hydroxylase antibodies, which did not label TG, highlighted sympathetic fibers around blood vessels of the masticatory muscles. Overall, masticatory muscle types of marmosets have distinct and different innervation patterns.
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13
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Wang P, Zhang Q, Dias FC, Suttle A, Dong X, Chen Y. TMEM100, a regulator of TRPV1-TRPA1 interaction, contributes to temporomandibular disorder pain. Front Mol Neurosci 2023; 16:1160206. [PMID: 37033371 PMCID: PMC10077888 DOI: 10.3389/fnmol.2023.1160206] [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: 02/06/2023] [Accepted: 02/27/2023] [Indexed: 04/11/2023] Open
Abstract
There is an unmet need to identify new therapeutic targets for temporomandibular disorder (TMD) pain because current treatments are limited and unsatisfactory. TMEM100, a two-transmembrane protein, was recently identified as a regulator to weaken the TRPA1-TRPV1 physical association, resulting in disinhibition of TRPA1 activity in sensory neurons. Recent studies have also shown that Tmem100, Trpa1, and Trpv1 mRNAs were upregulated in trigeminal ganglion (TG) after inflammation of the temporomandibular joint (TMJ) associated tissues. These findings raise a critical question regarding whether TMEM100 in TG neurons is involved in TMD pain via regulating the TRPA1-TRPV1 functional interaction. Here, using two mouse models of TMD pain induced by TMJ inflammation or masseter muscle injury, we found that global knockout or systemic inhibition of TRPA1 and TRPV1 attenuated pain. In line with their increased genes, mice exhibited significant upregulation of TMEM100, TRPA1, and TRPV1 at the protein levels in TG neurons after TMD pain. Importantly, TMEM100 co-expressed with TRPA1 and TRPV1 in TG neurons-innervating the TMJ and masseter muscle and their co-expression was increased after TMD pain. Moreover, the enhanced activity of TRPA1 in TG neurons evoked by TMJ inflammation or masseter muscle injury was suppressed by inhibition of TMEM100. Selective deletion of Tmem100 in TG neurons or local administration of TMEM100 inhibitor into the TMJ or masseter muscle attenuated TMD pain. Together, these results suggest that TMEM100 in TG neurons contributes to TMD pain by regulating TRPA1 activity within the TRPA1-TRPV1 complex. TMEM100 therefore represents a potential novel target-of-interest for TMD pain.
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Affiliation(s)
- Peng Wang
- Department of Neurology, Duke University, Durham, NC, United States
| | - Qiaojuan Zhang
- Department of Neurology, Duke University, Durham, NC, United States
| | - Fabiana C. Dias
- Department of Neurology, Duke University, Durham, NC, United States
| | - Abbie Suttle
- Department of Neurology, Duke University, Durham, NC, United States
| | - Xinzhong Dong
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Yong Chen
- Department of Neurology, Duke University, Durham, NC, United States
- Center for Translational Pain Medicine, Department of Anesthesiology, Duke University, Durham, NC, United States
- Department of Pathology, Duke University, Durham, NC, United States
- *Correspondence: Yong Chen,
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Bertels Z, Dripps IJ, Shah P, Moye LS, Tipton AF, Siegersma K, Pradhan AA. Delta opioid receptors in Nav1.8 expressing peripheral neurons partially regulate the effect of delta agonist in models of migraine and opioid-induced hyperalgesia. NEUROBIOLOGY OF PAIN 2022; 12:100099. [PMID: 35859654 PMCID: PMC9289726 DOI: 10.1016/j.ynpai.2022.100099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 06/16/2022] [Accepted: 06/18/2022] [Indexed: 11/07/2022]
Abstract
DOR in Nav1.8 cells do not regulate anti-migraine effects of DOR agonist. DOR in Nav1.8 cells is critical for effect of DOR agonist in peripheral OIH. DOR in Nav1.8 cells is not necessary for effect of DOR agonist in cephalic OIH.
Migraine is one of the most common pain disorders and causes disability in millions of people every year. Delta opioid receptors (DOR) have been identified as a novel therapeutic target for migraine and other headache disorders. DORs are present in both peripheral and central regions and it is unclear which receptor populations regulate migraine-associated effects. The aim of this study was to determine if DOR expressed in peripheral nociceptors regulates headache associated endpoints and the effect of delta agonists within these mouse models. We used a conditional knockout, in which DOR was selectively deleted from Nav1.8 expressing cells. Nav1.8-DOR mice and loxP control littermates were tested in models of chronic migraine-associated allodynia, opioid-induced hyperalgesia, migraine-associated negative affect, and aura. Nav1.8-DOR and loxP mice had comparable effect sizes in all of these models. The anti-allodynic effect of the DOR agonist, SNC80, was slightly diminished in the nitroglycerin model of migraine. Intriguingly, in the OIH model the peripheral effects of SNC80 were completely lost in Nav1.8-DOR mice while the cephalic effects remained intact. Regardless of genotype, SNC80 continued to inhibit conditioned place aversion associated with nitroglycerin and decreased cortical spreading depression events associated with migraine aura. These results suggest that DOR in Nav1.8-expressing nociceptors do not critically regulate the anti-migraine effects of delta agonist; and that brain-penetrant delta agonists would be a more effective drug development strategy.
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15
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Kaur S, Hickman TM, Lopez-Ramirez A, McDonald H, Lockhart LM, Darwish O, Averitt DL. Estrogen modulation of the pronociceptive effects of serotonin on female rat trigeminal sensory neurons is timing dependent and dosage dependent and requires estrogen receptor alpha. Pain 2022; 163:e899-e916. [PMID: 35121697 PMCID: PMC9288423 DOI: 10.1097/j.pain.0000000000002604] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 01/28/2022] [Indexed: 11/26/2022]
Abstract
ABSTRACT The role of the major estrogen estradiol (E2) on orofacial pain conditions remains controversial with studies reporting both a pronociceptive and antinociceptive role of E2. E2 modulation of peripheral serotonergic activity may be one mechanism underlying the female prevalence of orofacial pain disorders. We recently reported that female rats in proestrus and estrus exhibit greater serotonin (5HT)-evoked orofacial nocifensive behaviors compared with diestrus and male rats. Further coexpression of 5HT 2A receptor mRNA in nociceptive trigeminal sensory neurons that express transient receptor potential vanilloid 1 ion channels contributes to pain sensitization. E2 may exacerbate orofacial pain through 5HT-sensitive trigeminal nociceptors, but whether low or high E2 contributes to orofacial pain and by what mechanism remains unclear. We hypothesized that steady-state exposure to a proestrus level of E2 exacerbates 5HT-evoked orofacial nocifensive behaviors in female rats, explored the transcriptome of E2-treated female rats, and determined which E2 receptor contributes to sensitization of female trigeminal sensory neurons. We report that a diestrus level of E2 is protective against 5HT-evoked orofacial pain behaviors, which increase with increasing E2 concentrations, and that E2 differentially alters several pain genes in the trigeminal ganglia. Furthermore, E2 receptors coexpressed with 5HT 2A and transient receptor potential vanilloid 1 and enhanced capsaicin-evoked signaling in the trigeminal ganglia through estrogen receptor α. Overall, our data indicate that low, but not high, physiological levels of E2 protect against orofacial pain, and we provide evidence that estrogen receptor α receptor activation, but not others, contributes to sensitization of nociceptive signaling in trigeminal sensory neurons.
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Affiliation(s)
- Sukhbir Kaur
- Department of Biology, Texas Woman’s University, Denton, TX 76204
| | | | | | - Hanna McDonald
- Department of Biology, Texas Woman’s University, Denton, TX 76204
| | | | - Omar Darwish
- Department of Mathematics and Computer Science, Texas Woman’s University, Denton, TX 76204
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16
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Chivers SB, Brackley AD, Jeske NA. Raf kinase inhibitory protein reduces bradykinin receptor desensitization. J Neurochem 2022; 162:156-165. [PMID: 35526109 PMCID: PMC9283312 DOI: 10.1111/jnc.15614] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/05/2022] [Accepted: 04/07/2022] [Indexed: 11/28/2022]
Abstract
Inflammatory hyperalgesia represents a nociceptive phenotype that can become persistent in nature through dynamic protein modifications. However, a large gap in knowledge exists concerning how the integration of intracellular signaling molecules coordinates a persistent inflammatory phenotype. Herein, we demonstrate that Raf Kinase Anchoring Protein (RKIP) interrupts a vital canonical desensitization pathway to maintain bradykinin (BK) receptor activation in primary afferent neurons. Biochemical analyses of primary neuronal cultures indicate bradykinin-stimulated PKC phosphorylation of RKIP at Ser153. Furthermore, BK exposure increases G-protein Receptor Kinase 2 (GRK2) binding to RKIP, inhibiting pharmacological desensitization of the BK receptor. Additional studies found that molecular RKIP down-regulation increases BK receptor desensitization in real-time imaging of primary afferent neurons, identifying a key pathway integrator in the desensitization process that controls multiple GRK2-sensitive G-protein coupled receptors. Therefore, RKIP serves as an integral scaffolding protein that inhibits BK receptor desensitization.
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Affiliation(s)
- Samuel B. Chivers
- Departments of Oral & Maxillofacial SurgeryUniversity of Texas Health San AntonioSan AntonioTexasUSA
| | | | - Nathaniel A. Jeske
- Departments of Oral & Maxillofacial SurgeryUniversity of Texas Health San AntonioSan AntonioTexasUSA
- PhysiologyUniversity of Texas Health San AntonioSan AntonioTexasUSA
- PharmacologyUniversity of Texas Health San AntonioSan AntonioTexasUSA
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17
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Zhang X, Rahman M, Bereiter DA. Estrogen Status and Trigeminal Ganglion Responses to Jaw Movement. J Dent Res 2022; 101:1075-1081. [PMID: 35259995 PMCID: PMC9305844 DOI: 10.1177/00220345221077951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Chronic temporomandibular joint disorders (TMDs) present with pain in the temporomandibular joint (TMJ) and muscles of mastication. Risk factors for TMD include localized joint/muscle inflammation and estrogen status. This study determined whether mild tissue inflammation and estrogen status influenced the responses of trigeminal ganglion neurons to jaw palpation or jaw movement, 2 key diagnostic features of clinical TMD, in adult rats. Neuronal activity was recorded from male rats, ovariectomized (OvX) female rats, and OvX female rats injected with 17β-estradiol 24 h prior to testing (OvXE). Neurons were tested for responses to deep press over the TMJ region and jaw movement in 3 directions (open, protrusion, lateral) 10 d after intra-TMJ injection of a low dose of complete Freund's adjuvant (CFA) or vehicle (sham). Deep press evoked similar responses in all treatment groups. The response magnitude to jaw opening and protrusion was significantly greater for neurons recorded from OvXE CFA-treated rats than from OvX CFA-treated or OvXE sham rats. The responses to lateral movement of the jaw were similar across all treatment groups. Most neurons (70% to 90%) displayed a static response pattern to jaw movement independent of direction. Estradiol treatment also increased the proportion of neurons that were excited by jaw movement in >1 direction as compared with untreated OvX females or males. These results suggest that mild localized inflammation in the TMJ region during periods of elevated estrogen were sufficient to increase the peripheral driving force for jaw movement-evoked hyperalgesia.
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Affiliation(s)
- X Zhang
- Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, USA
| | - M Rahman
- Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, USA
| | - D A Bereiter
- Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, USA
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