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Dvornikova KA, Platonova ON, Bystrova EY. The Role of TRP Channels in Sepsis and Colitis. Int J Mol Sci 2024; 25:4784. [PMID: 38731999 PMCID: PMC11084600 DOI: 10.3390/ijms25094784] [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: 03/31/2024] [Revised: 04/20/2024] [Accepted: 04/24/2024] [Indexed: 05/13/2024] Open
Abstract
To date, several members of the transient receptor potential (TRP) channels which provide a wide array of roles have been found in the gastrointestinal tract (GI). The goal of earlier research was to comprehend the intricate signaling cascades that contribute to TRP channel activation as well as how these receptors' activity affects other systems. Moreover, there is a large volume of published studies describing the role of TRP channels in a number of pathological disorders, including inflammatory bowel disease (IBD) and sepsis. Nevertheless, the generalizability of these results is subject to certain limitations. For instance, the study of IBD relies on various animal models and experimental methods, which are unable to precisely imitate the multifactorial chronic disease. The diverse pathophysiological mechanisms and unique susceptibility of animals may account for the inconsistency of the experimental data collected. The main purpose of this study was to conduct a comprehensive review and analysis of existing studies on transient receptor potential (TRP) channels implicating specific models of colitis and sepsis, with particular emphasis on their involvement in pathological disorders such as IBD and sepsis. Furthermore, the text endeavors to evaluate the generalizability of experimental findings, taking into consideration the limitations posed by animal models and experimental methodologies. Finally, we also provide an updated schematic of the most important and possible molecular signaling pathways associated with TRP channels in IBD and sepsis.
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Affiliation(s)
| | | | - Elena Y. Bystrova
- I.P. Pavlov Institute of Physiology RAS, 199034 St. Petersburg, Russia; (K.A.D.); (O.N.P.)
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Jerram ML, Baker D, Smith TB, Healey P, Taylor L, Black K. A 0.1% L-Menthol Mouth Swill in Elite Male Rugby Players Has Different Effects in Forwards and Backs. Int J Sports Physiol Perform 2023; 18:909-917. [PMID: 36689991 DOI: 10.1123/ijspp.2022-0191] [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: 05/12/2022] [Revised: 09/20/2022] [Accepted: 10/26/2022] [Indexed: 01/24/2023]
Abstract
PURPOSE Menthol mouth swills can improve endurance performance in the heat, which is attributed to attenuations in nonthermally derived thermal sensation (TS) and perception of effort. However, research in elite team-sport athletes is absent. Therefore, this study investigated the performance and TS responses to a 0.1% menthol mouth rinse (MR) or placebo (PLA) among elite male rugby union players. METHOD Twenty-seven (15 Forwards and 12 Backs) elite male Super Rugby players completed two 3-minute 15-a-side rugby-specific conditioning blocks, with MR or PLA provided at the start of training (baseline), at the start of each 3-minute block (swill 1 [S1] and swill 2 [S2]), and at the end of training (swill 3 [S3]). TS was assessed using the American Society of Heating, Refrigerating and Air-Conditioning Engineers 9-point Analog Sensation Scale after each swill and at baseline (preconditioning block). Acceptability was measured after baseline swill and S3 using a 5-question Likert scale. Physical performance was measured throughout training using global positioning system metrics. RESULTS MR attenuated TS from baseline to S1 (P = .003, SD = 1.01) and S2 (P = .002, SD = 1.09) in Forwards only, compared with PLA. Acceptability was higher only for Forwards in MR versus PLA at baseline (P = .003, SD = 1.3) and S3 (P = .004, SD = 0.75). MR had no effect on physical performance metrics (P > .05). CONCLUSION MR attenuated the rise in TS with higher acceptability at S1 and S3 (in Forwards only) with no effect on selected physical performance metrics. Longer-duration exercise (eg, a match) in hot-humid conditions eliciting markedly increased body temperatures could theoretically allow favorable changes in TS to enhance performance-these postulations warrant experimental investigation.
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Affiliation(s)
- Marcia L Jerram
- Department of Human Nutrition, University of Otago, Dunedin,New Zealand
| | - Dane Baker
- Department of Human Nutrition, University of Otago, Dunedin,New Zealand
| | | | - Phil Healey
- Blues Super Rugby Franchise, Auckland,New Zealand
| | - Lee Taylor
- School of Sport, Exercise and Health Sciences, National Centre for Sport and Exercise Medicine (NCSEM), Loughborough University, Loughborough,United Kingdom
- Human Performance Research Centre, University of Technology Sydney (UTS), Sydney, NSW,Australia
- Sport & Exercise Discipline Group, Faculty of Health, University of Technology Sydney (UTS), Sydney, NSW,Australia
| | - Katherine Black
- Department of Human Nutrition, University of Otago, Dunedin,New Zealand
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Zhang M, Ma Y, Ye X, Zhang N, Pan L, Wang B. TRP (transient receptor potential) ion channel family: structures, biological functions and therapeutic interventions for diseases. Signal Transduct Target Ther 2023; 8:261. [PMID: 37402746 DOI: 10.1038/s41392-023-01464-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 03/26/2023] [Accepted: 04/25/2023] [Indexed: 07/06/2023] Open
Abstract
Transient receptor potential (TRP) channels are sensors for a variety of cellular and environmental signals. Mammals express a total of 28 different TRP channel proteins, which can be divided into seven subfamilies based on amino acid sequence homology: TRPA (Ankyrin), TRPC (Canonical), TRPM (Melastatin), TRPML (Mucolipin), TRPN (NO-mechano-potential, NOMP), TRPP (Polycystin), TRPV (Vanilloid). They are a class of ion channels found in numerous tissues and cell types and are permeable to a wide range of cations such as Ca2+, Mg2+, Na+, K+, and others. TRP channels are responsible for various sensory responses including heat, cold, pain, stress, vision and taste and can be activated by a number of stimuli. Their predominantly location on the cell surface, their interaction with numerous physiological signaling pathways, and the unique crystal structure of TRP channels make TRPs attractive drug targets and implicate them in the treatment of a wide range of diseases. Here, we review the history of TRP channel discovery, summarize the structures and functions of the TRP ion channel family, and highlight the current understanding of the role of TRP channels in the pathogenesis of human disease. Most importantly, we describe TRP channel-related drug discovery, therapeutic interventions for diseases and the limitations of targeting TRP channels in potential clinical applications.
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Affiliation(s)
- Miao Zhang
- School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China
- Experiment Center for Science and Technology, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China
- The Center for Microbes, Development and Health; Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Yueming Ma
- School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China
| | - Xianglu Ye
- Institute of Interdisciplinary Integrative Medicine Research, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China
| | - Ning Zhang
- Experiment Center for Science and Technology, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China.
| | - Lei Pan
- The Center for Microbes, Development and Health; Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, 200031, China.
- CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Bing Wang
- School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China.
- Center for Pharmaceutics Research, Shanghai Institute of Materia Medica Chinese Academy of Sciences, Shanghai, 201203, China.
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Leite-Panissi CRA, De Paula BB, Neubert JK, Caudle RM. Influence of TRPV1 on Thermal Nociception in Rats with Temporomandibular Joint Persistent Inflammation Evaluated by the Operant Orofacial Pain Assessment Device (OPAD). J Pain Res 2023; 16:2047-2062. [PMID: 37342611 PMCID: PMC10278653 DOI: 10.2147/jpr.s405258] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 05/05/2023] [Indexed: 06/23/2023] Open
Abstract
Background Temporomandibular joint (TMJ)-associated inflammation contributes to the pain reported by patients with temporomandibular disorders (TMD). It is common for patients diagnosed with TMD to report pain in the masticatory muscles and temporomandibular joints, headache, and jaw movement disturbances. Although TMD can have different origins, including trauma and malocclusion disorder, anxiety/depression substantially impacts the development and maintenance of TMD. In general, rodent studies on orofacial pain mechanisms involve the use of tests originally developed for other body regions, which were adapted to the orofacial area. To overcome limitations and expand knowledge in orofacial pain, our group validated and characterized an operant assessment paradigm in rats with both hot and cold stimuli as well mechanical stimuli. Nevertheless, persistent inflammation of the TMJ has not been evaluated with this operant orofacial pain assessment device (OPAD). Methods We characterized the thermal orofacial sensitivity for cold, neutral, and hot stimuli during the development of TMD using the OPAD behavior test. In addition, we evaluated the role of transient receptor potential vanilloid 1 (TRPV1) expressing nociceptors in rats with persistent TMJ inflammation. The experiments were performed in male and female rats with TMJ inflammation induced by carrageenan (CARR). Additionally, resiniferatoxin (RTX) was administered into the TMJs prior CARR to lesion TRPV1-expressing neurons to evaluate the role of TRPV1-expressing neurons. Results We evidenced an increase in the number of facial contacts and changes in the number of reward licks per stimulus on neutral (37°C) and cold (21°C) temperatures. However, at the hot temperature (42°C), the inflammation did not induce changes in the OPAD test. The prior administration of RTX in the TMJ prevented the allodynia and thermal hyperalgesia induced by CARR. Conclusion We showed that TRPV-expressing neurons are involved in the sensitivity to carrageenan-induced pain in male and female rats evaluated in the OPAD.
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Affiliation(s)
- Christie R A Leite-Panissi
- Department of Psychology, School of Philosophy, Science and Literature of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Bruna B De Paula
- Department of Oral and Maxillofacial Surgery, University of Florida, Gainesville, FL, USA
| | - John K Neubert
- Department of Orthodontics, University of Florida, Gainesville, FL, USA
| | - Robert M Caudle
- Department of Oral and Maxillofacial Surgery, University of Florida, Gainesville, FL, USA
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Liu S, Crawford J, Tao F. Assessing Orofacial Pain Behaviors in Animal Models: A Review. Brain Sci 2023; 13:390. [PMID: 36979200 PMCID: PMC10046781 DOI: 10.3390/brainsci13030390] [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: 08/09/2022] [Revised: 08/25/2022] [Accepted: 02/22/2023] [Indexed: 02/26/2023] Open
Abstract
Orofacial pain refers to pain occurring in the head and face, which is highly prevalent and represents a challenge to clinicians, but its underlying mechanisms are not fully understood, and more studies using animal models are urgently needed. Currently, there are different assessment methods for analyzing orofacial pain behaviors in animal models. In order to minimize the number of animals used and maximize animal welfare, selecting appropriate assessment methods can avoid repeated testing and improve the reliability and accuracy of research data. Here, we summarize different methods for assessing spontaneous pain, evoked pain, and relevant accompanying dysfunction, and discuss their advantages and disadvantages. While the behaviors of orofacial pain in rodents are not exactly equivalent to the symptoms displayed in patients with orofacial pain, animal models and pain behavioral assessments have advanced our understanding of the pathogenesis of such pain.
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Affiliation(s)
| | | | - Feng Tao
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, TX 75246, USA
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Ma W, Sapio MR, Manalo AP, Maric D, Dougherty MK, Goto T, Mannes AJ, Iadarola MJ. Anatomical Analysis of Transient Potential Vanilloid Receptor 1 (Trpv1+) and Mu-Opioid Receptor (Oprm1+) Co-expression in Rat Dorsal Root Ganglion Neurons. Front Mol Neurosci 2022; 15:926596. [PMID: 35875671 PMCID: PMC9302591 DOI: 10.3389/fnmol.2022.926596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 06/09/2022] [Indexed: 11/29/2022] Open
Abstract
Primary afferent neurons of the dorsal root ganglia (DRG) transduce peripheral nociceptive signals and transmit them to the spinal cord. These neurons also mediate analgesic control of the nociceptive inputs, particularly through the μ-opioid receptor (encoded by Oprm1). While opioid receptors are found throughout the neuraxis and in the spinal cord tissue itself, intrathecal administration of μ-opioid agonists also acts directly on nociceptive nerve terminals in the dorsal spinal cord resulting in marked analgesia. Additionally, selective chemoaxotomy of cells expressing the TRPV1 channel, a nonselective calcium-permeable ion channel that transduces thermal and inflammatory pain, yields profound pain relief in rats, canines, and humans. However, the relationship between Oprm1 and Trpv1 expressing DRG neurons has not been precisely determined. The present study examines rat DRG neurons using high resolution multiplex fluorescent in situ hybridization to visualize molecular co-expression. Neurons positive for Trpv1 exhibited varying levels of expression for Trpv1 and co-expression of other excitatory and inhibitory ion channels or receptors. A subpopulation of densely labeled Trpv1+ neurons did not co-express Oprm1. In contrast, a population of less densely labeled Trpv1+ neurons did co-express Oprm1. This finding suggests that the medium/low Trpv1 expressing neurons represent a specific set of DRG neurons subserving the opponent processes of both transducing and inhibiting nociceptive inputs. Additionally, the medium/low Trpv1 expressing neurons co-expressed other markers implicated in pathological pain states, such as Trpa1 and Trpm8, which are involved in chemical nociception and cold allodynia, respectively, as well as Scn11a, whose mutations are implicated in familial episodic pain. Conversely, none of the Trpv1+ neurons co-expressed Spp1, which codes for osteopontin, a marker for large diameter proprioceptive neurons, validating that nociception and proprioception are governed by separate neuronal populations. Our findings support the hypothesis that the population of Trpv1 and Oprm1 coexpressing neurons may explain the remarkable efficacy of opioid drugs administered at the level of the DRG-spinal synapse, and that this subpopulation of Trpv1+ neurons is responsible for registering tissue damage.
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Affiliation(s)
- Wenting Ma
- Department of Perioperative Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, United States
| | - Matthew R. Sapio
- Department of Perioperative Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, United States
| | - Allison P. Manalo
- Department of Perioperative Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, United States
| | - Dragan Maric
- National Institute of Neurological Disorders and Stroke, Flow and Imaging Cytometry Core Facility, Bethesda, MD, United States
| | - Mary Kate Dougherty
- Department of Perioperative Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, United States
| | - Taichi Goto
- Department of Perioperative Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, United States
- Symptoms Biology Unit, National Institute of Nursing Research, National Institutes of Health, Bethesda, MD, United States
| | - Andrew J. Mannes
- Department of Perioperative Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, United States
| | - Michael J. Iadarola
- Department of Perioperative Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, United States
- *Correspondence: Michael J. Iadarola
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Caudle RM, Neubert JK. Effects of Oxaliplatin on Facial Sensitivity to Cool Temperatures and TRPM8 Expressing Trigeminal Ganglion Neurons in Mice. FRONTIERS IN PAIN RESEARCH 2022; 3:868547. [PMID: 35634452 PMCID: PMC9130462 DOI: 10.3389/fpain.2022.868547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 04/18/2022] [Indexed: 12/04/2022] Open
Abstract
The chemotherapeutic agent oxaliplatin is commonly used to treat colorectal cancer. Although effective as a chemotherapeutic, it frequently produces painful peripheral neuropathies. These neuropathies can be divided into an acute sensitivity to cool temperatures in the mouth and face, and chronic neuropathic pain in the limbs and possible numbness. The chronic neuropathy also includes sensitivity to cool temperatures. Neurons that detect cool temperatures are reported to utilize Transient Receptor Potential Cation Channel, Subfamily M, Member 8 (TRPM8). Therefore, we investigated the effects of oxaliplatin on facial nociception to cool temperatures (18°C) in mice and on TRPM8 expressing trigeminal ganglion (TRG) neurons. Paclitaxel, a chemotherapeutic that is used to treat breast cancer, was included for comparison because it produces neuropathies, but acute cool temperature sensitivity in the oral cavity or face is not typically reported. Behavioral testing of facial sensitivity to 18°C indicated no hypersensitivity either acutely or chronically following either chemotherapeutic agent. However, whole cell voltage clamp experiments in TRPM8 expressing TRG neurons indicated that both oxaliplatin and paclitaxel increased Hyperpolarization-Activated Cyclic Nucleotide-Gated channel (HCN), voltage gated sodium channel (Nav), and menthol evoked TRPM8 currents. Voltage gated potassium channel (Kv) currents were not altered. Histological examination of TRPM8 fibers in the skin of the whisker pads demonstrated that the TRPM8 expressing axons and possible Merkel cell-neurite complexes were damaged by oxaliplatin. These findings indicate that oxaliplatin induces a rapid degeneration of TRG neuron axons that express TRPM8, which prevents evoked activation of the sensitized neurons and likely leads to reduced sensitivity to touch and cool temperatures. The changes in HCN, Nav, and TRPM8 currents suggest that spontaneous firing of action potentials may be increased in the deafferented neurons within the ganglion, possibly producing spontaneously induced cooling or nociceptive sensations.
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Affiliation(s)
- Robert M. Caudle
- Department of Oral and Maxillofacial Surgery, University of Florida, Gainesville, FL, United States
| | - John K. Neubert
- Department of Orthodontics, University of Florida, Gainesville, FL, United States
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Tang Z, Zhou J, Long H, Gao Y, Wang Q, Li X, Wang Y, Lai W, Jian F. Molecular mechanism in trigeminal nerve and treatment methods related to orthodontic pain. J Oral Rehabil 2021; 49:125-137. [PMID: 34586644 DOI: 10.1111/joor.13263] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 09/02/2021] [Accepted: 09/23/2021] [Indexed: 02/05/2023]
Abstract
BACKGROUND Orthodontic treatment is the main treatment approach for malocclusion. Orthodontic pain is an inevitable undesirable adverse reaction during orthodontic treatment. It is reported orthodontic pain has become one of the most common reason that patients withdraw from orthodontic treatment. Therefore, understanding the underlying mechanism and finding treatment of orthodontic pain are in urgent need. AIMS This article aims to sort out the mechanisms and treatments of orthodontic pain, hoping to provide some ideas for future orthodontic pain relief. MATERIALS Tooth movement will cause local inflammation. Certain inflammatory factors and cytokines stimulating the trigeminal nerve and further generating pain perception, as well as drugs and molecular targeted therapy blocking nerve conduction pathways, will be reviewed in this article. METHOD We review and summaries current studies related to molecular mechanisms and treatment approaches in orthodontic pain control. RESULTS Orthodontics pain related influencing factors and molecular mechanisms has been introduced. Commonly used clinical methods in orthodontic pain control has been evaluated. DISCUSSION With the clarification of more molecular mechanisms, the direction of orthodontic pain treatment will shift to targeted drugs.
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Affiliation(s)
- Ziwei Tang
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Jiawei Zhou
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Hu Long
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Yanzi Gao
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Qingxuan Wang
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Xiaolong Li
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Yan Wang
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Wenli Lai
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Fan Jian
- State Key Laboratory of Oral Diseases, Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
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Caudle RM, Caudle SL, Flenor ND, Rohrs EL, Neubert JK. Pharmacological Characterization of Orofacial Nociception in Female Rats Following Nitroglycerin Administration. Front Pharmacol 2020; 11:527495. [PMID: 33343340 PMCID: PMC7744726 DOI: 10.3389/fphar.2020.527495] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 10/19/2020] [Indexed: 11/13/2022] Open
Abstract
Rodent models of human disease can be valuable for understanding the mechanisms of a disease and for identifying novel therapies. However, it is critical that these models be vetted prior to committing resources to developing novel therapeutics. Failure to confirm the model can lead to significant losses in time and resources. One model used for migraine headache is to administer nitroglycerin to rodents. Nitroglycerin is known to produce migraine-like pain in humans and is presumed to do the same in rodents. It is not known, however, if the mechanism for nitroglycerin headaches involves the same pathological processes as migraine. In the absence of known mechanisms, it becomes imperative that the model not only translates into successful clinical trials but also successfully reverse translates by demonstrating efficacy of current therapeutics. In this study female rats were given nitroglycerin and nociception was evaluated in OPADs. Estrous was not monitored. Based on the ED50 of nitroglycerin a dose of 10 mg/kg was used for experiments. Sumatriptan, caffeine, buprenorphine and morphine were administered to evaluate the reverse translatability of the model. We found that nitroglycerin did not produce mechanical allodynia in the face of the rats, which is reported to be a consequence of migraine in humans. Nitroglycerin reduced the animals’ participation in the assay. The reduced activity was verified using an assay to measure exploratory behavior. Furthermore, the effects of nitroglycerin were not reversed or prevented by agents that are effective acute therapies for migraine. Two interesting findings from this study, however, were that morphine and nitroglycerin interact to increase the rats’ tolerance of mechanical stimuli on their faces, and they work in concert to slow down the central motor pattern generator for licking on the reward bottle. These interactions suggest that nitroglycerin generated nitric oxide and mu opioid receptors interact with the same neuronal circuits in an additive manner. The interaction of nitroglycerin and morphine on sensory and motor circuits deserves additional examination. In conclusion, based on the results of this study the use of nitroglycerin at these doses in naïve female rats is not recommended as a model for migraine headaches.
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Affiliation(s)
- Robert M Caudle
- Department of Oral and Maxillofacial Surgery, University of Florida, Gainesville, FL, United States
| | - Stephanie L Caudle
- Department of Orthodontics, University of Florida, Gainesville, FL, United States
| | - Natalie D Flenor
- Department of Orthodontics, University of Florida, Gainesville, FL, United States
| | - Eric L Rohrs
- Velocity Laboratories, LLC, Alachua, FL, United States
| | - John K Neubert
- Department of Orthodontics, University of Florida, Gainesville, FL, United States
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Sex differences in mouse Transient Receptor Potential Cation Channel, Subfamily M, Member 8 expressing trigeminal ganglion neurons. PLoS One 2017; 12:e0176753. [PMID: 28472061 PMCID: PMC5417611 DOI: 10.1371/journal.pone.0176753] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 04/17/2017] [Indexed: 01/04/2023] Open
Abstract
The detection of cool temperatures is thought to be mediated by primary afferent neurons that express the cool temperature sensing protein Transient Receptor Potential Cation Channel, Subfamily M, Member 8 (TRPM8). Using mice, this study tested the hypothesis that sex differences in sensitivity to cool temperatures were mediated by differences in neurons that express TRPM8. Ion currents from TRPM8 expressing trigeminal ganglion (TRG) neurons in females demonstrated larger hyperpolarization-activated cyclic nucleotide-gated currents (Ih) than male neurons at both 30° and 18°C. Additionally, female neurons' voltage gated potassium currents (Ik) were suppressed by cooling, whereas male Ik was not significantly affected. At the holding potential tested (-60mV) TRPM8 currents were not visibly activated in either sex by cooling. Modeling the effect of Ih and Ik on membrane potentials demonstrated that at 30° the membrane potential in both sexes is unstable. At 18°, female TRPM8 TRG neurons develop a large oscillating pattern in their membrane potential, whereas male neurons become highly stable. These findings suggest that the differences in Ih and Ik in the TRPM8 TRG neurons of male and female mice likely leads to greater sensitivity of female mice to the cool temperature. This hypothesis was confirmed in an operant reward/conflict assay. Female mice contacted an 18°C surface for approximately half the time that males contacted the cool surface. At 33° and 10°C male and female mice contacted the stimulus for similar amounts of time. These data suggest that sex differences in the functioning of Ih and Ik in TRPM8 expressing primary afferent neurons leads to differences in cool temperature sensitivity.
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Acute and neuropathic orofacial antinociceptive effect of eucalyptol. Inflammopharmacology 2017; 25:247-254. [DOI: 10.1007/s10787-017-0324-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 02/02/2017] [Indexed: 12/19/2022]
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Dussor G, Cao YQ. TRPM8 and Migraine. Headache 2016; 56:1406-1417. [PMID: 27634619 PMCID: PMC5335856 DOI: 10.1111/head.12948] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 05/31/2016] [Accepted: 06/19/2016] [Indexed: 12/27/2022]
Abstract
Migraine is among the most common diseases on earth and one of the most disabling, the latter due in large part to poor treatment efficacy. Development of new therapeutics is dependent on the identification of mechanisms contributing to migraine and discovery of targets for new drugs. Numerous genome-wide association studies (GWAS) have implicated the transient receptor-potential M8 (TRPM8) channel in migraine. This channel is predominantly expressed on peripheral sensory neurons and is known as the sensor for cold temperature in cutaneous tissue but is also expressed on deep visceral afferents where cold is not likely a stimulus. Consequently, a number of alternative endogenous agonists have been proposed. Apart from its role in cold sensation, TRPM8 also contributes to cold allodynia after nerve injury or inflammation, and it is necessary for cooling/menthol-based analgesia. How it might contribute to migraine is less clear. The purpose of this review is to discuss the anatomical and physiological mechanisms by which meningeal TRPM8 may play a role in migraine as well as the potential of TRPM8 as a therapeutic target. TRPM8 is expressed on sensory afferents innervating the meninges, and these neurons are subject to developmental changes that may influence their contribution to migraine. As in viscera, meningeal TRPM8 channels are unlikely to be activated by temperature fluctuations and their endogenous ligands remain unknown. Preclinical migraine studies show that activation of meningeal TRPM8 by exogenous agonists can both cause and alleviate headache behaviors, depending on whether other meningeal afferents concurrently receive noxious stimuli. This is reminiscent of the fact that cold can trigger migraine in humans but menthol can also alleviate headache. We propose that both TRPM8 agonists and antagonists may be potential therapeutics, depending on how migraine is triggered in individual patients. In this regard, TRPM8 may be a novel target for personalized medicine in migraine treatment.
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Affiliation(s)
- Greg Dussor
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX, USA.
| | - Yu-Qing Cao
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
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Schepetkin IA, Kushnarenko SV, Özek G, Kirpotina LN, Sinharoy P, Utegenova GA, Abidkulova KT, Özek T, Başer KHC, Kovrizhina AR, Khlebnikov AI, Damron DS, Quinn MT. Modulation of Human Neutrophil Responses by the Essential Oils from Ferula akitschkensis and Their Constituents. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2016; 64:7156-70. [PMID: 27586050 PMCID: PMC5048753 DOI: 10.1021/acs.jafc.6b03205] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Essential oils were obtained by hydrodistillation of the umbels+seeds and stems of Ferula akitschkensis (FAEOu/s and FAEOstm, respectively) and analyzed by gas chromatography and gas chromatography-mass spectrometry. Fifty-two compounds were identified in FAEOu/s; the primary components were sabinene, α-pinene, β-pinene, terpinen-4-ol, eremophilene, and 2-himachalen-7-ol, whereas the primary components of FAEOstm were myristicin and geranylacetone. FAEOu/s, β-pinene, sabinene, γ-terpinene, geranylacetone, isobornyl acetate, and (E)-2-nonenal stimulated [Ca(2+)]i mobilization in human neutrophils, with the most potent being geranylacetone (EC50 = 7.6 ± 1.9 μM) and isobornyl acetate 6.4 ± 1.7 (EC50 = 7.6 ± 1.9 μM). In addition, treatment of neutrophils with β-pinene, sabinene, γ-terpinene, geranylacetone, and isobornyl acetate desensitized the cells to N-formyl-Met-Leu-Phe (fMLF)- and interleukin-8 (IL-8)-induced [Ca(2+)]i flux and inhibited fMLF-induced chemotaxis. The effects of β-pinene, sabinene, γ-terpinene, geranylacetone, and isobornyl acetate on neutrophil [Ca(2+)]i flux were inhibited by transient receptor potential (TRP) channel blockers. Furthermore, the most potent compound, geranylacetone, activated Ca(2+) influx in TRPV1-transfected HEK293 cells. In contrast, myristicin inhibited neutrophil [Ca(2+)]i flux stimulated by fMLF and IL-8 and inhibited capsaicin-induced Ca(2+) influx in TRPV1-transfected HEK293 cells. These findings, as well as pharmacophore modeling of TRP agonists, suggest that geranylacetone is a TRPV1 agonist, whereas myristicin is a TRPV1 antagonist. Thus, at least part of the medicinal properties of Ferula essential oils may be due to modulatory effects on TRP channels.
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Affiliation(s)
- Igor A Schepetkin
- Department of Microbiology and Immunology, Montana State University , Bozeman, Montana 59717, United States
| | | | - Gulmira Özek
- Department of Pharmacognosy, Faculty of Pharmacy, Anadolu University , Eskisehir 26470, Turkey
| | - Liliya N Kirpotina
- Department of Microbiology and Immunology, Montana State University , Bozeman, Montana 59717, United States
| | - Pritam Sinharoy
- Department of Biological Sciences, Kent State University , Kent, Ohio 44242, United States
| | - Gulzhakhan A Utegenova
- Institute of Plant Biology and Biotechnology , Almaty 050040, Republic of Kazakhstan
- Faculty of Biology and Biotechnology, Al-Farabi Kazakh National University , Almaty 050040, Republic of Kazakhstan
| | - Karime T Abidkulova
- Faculty of Biology and Biotechnology, Al-Farabi Kazakh National University , Almaty 050040, Republic of Kazakhstan
| | - Temel Özek
- Department of Pharmacognosy, Faculty of Pharmacy, Anadolu University , Eskisehir 26470, Turkey
| | - Kemal Hüsnü Can Başer
- Department of Pharmacognosy, Faculty of Pharmacy, Near East University , Nicosia, North Cyprus
| | - Anastasia R Kovrizhina
- Department of Biotechnology and Organic Chemistry, Tomsk Polytechnic University , Tomsk 634050, Russia
| | - Andrei I Khlebnikov
- Department of Biotechnology and Organic Chemistry, Tomsk Polytechnic University , Tomsk 634050, Russia
- Department of Chemistry, Altai State Technical University , Barnaul 656038, Russia
| | - Derek S Damron
- Department of Biological Sciences, Kent State University , Kent, Ohio 44242, United States
| | - Mark T Quinn
- Department of Microbiology and Immunology, Montana State University , Bozeman, Montana 59717, United States
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Hitomi S, Ono K, Yamaguchi K, Terawaki K, Imai R, Kubota K, Omiya Y, Hattori T, Kase Y, Inenaga K. The traditional Japanese medicine hangeshashinto alleviates oral ulcer-induced pain in a rat model. Arch Oral Biol 2016; 66:30-7. [PMID: 26878477 DOI: 10.1016/j.archoralbio.2016.02.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2015] [Revised: 12/15/2015] [Accepted: 02/01/2016] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Recent studies have demonstrated that mouthwash made with the traditional Japanese medicine hangeshashinto exhibits anti-inflammatory action and alleviates oral mucositis scores, including pain complaints, in patients undergoing chemoradiotherapy. However, no study has demonstrated the mechanism underlying how hangeshashinto provides pain relief in oral ulcers. DESIGN The analgesic effects on pain-related behaviors following the topical application of hangeshashinto were evaluated in an oral ulcer rat model treated with acetic acid using recently developed methods. Indomethacin, the representative anti-inflammatory agent, was intraperitoneally administered. The tissue permeability of the oral mucosa was histologically evaluated after applying the fluorescent substance FluoroGold. RESULTS The topical application of hangeshashinto in ulcerative oral mucosa suppressed mechanical pain hypersensitivity over 60 min, without any effects on healthy mucosa. The same drug application also inhibited oral ulcer-induced spontaneous pain. Indomethacin administration failed to block the mechanical pain hypersensitivity, though it did largely block spontaneous pain. Topical anesthesia with lidocaine showed hyposensitivity to mechanical stimulation in healthy mucosa. In the ulcer regions in which the oral epithelial barrier was destroyed, deep parenchyma was stained with FluoroGold, in contrast to healthy oral mucosa, in which staining was limiting to the superficial site. CONCLUSIONS Hangeshashinto leads to long-lasting analgesic effects, specifically in the ulcer region by destroying the epithelial barrier. Hangeshashinto alleviates oral ulcer-induced pain in inflammation-dependent and/or independent manner.
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Affiliation(s)
- Suzuro Hitomi
- Division of Physiology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka 803-8580, Japan
| | - Kentaro Ono
- Division of Physiology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka 803-8580, Japan.
| | - Kiichiro Yamaguchi
- Division of Physiology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka 803-8580, Japan; Division of Dental Anesthesiology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka 803-8580, Japan
| | - Kiyoshi Terawaki
- Tsumura Research Laboratories, Kampo Scientific Strategies Division, Tsumura & Co., 3586 Yoshihara, Amicho, Inashiki-gun, Ibaraki 300-1192, Japan
| | - Ryota Imai
- Tsumura Research Laboratories, Kampo Scientific Strategies Division, Tsumura & Co., 3586 Yoshihara, Amicho, Inashiki-gun, Ibaraki 300-1192, Japan
| | - Kunitsugu Kubota
- Tsumura Research Laboratories, Kampo Scientific Strategies Division, Tsumura & Co., 3586 Yoshihara, Amicho, Inashiki-gun, Ibaraki 300-1192, Japan
| | - Yuji Omiya
- Tsumura Research Laboratories, Kampo Scientific Strategies Division, Tsumura & Co., 3586 Yoshihara, Amicho, Inashiki-gun, Ibaraki 300-1192, Japan
| | - Tomohisa Hattori
- Tsumura Research Laboratories, Kampo Scientific Strategies Division, Tsumura & Co., 3586 Yoshihara, Amicho, Inashiki-gun, Ibaraki 300-1192, Japan
| | - Yoshio Kase
- Tsumura Research Laboratories, Kampo Scientific Strategies Division, Tsumura & Co., 3586 Yoshihara, Amicho, Inashiki-gun, Ibaraki 300-1192, Japan
| | - Kiyotoshi Inenaga
- Division of Physiology, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka 803-8580, Japan
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15
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Burgos-Vega CC, Ahn DDU, Bischoff C, Wang W, Horne D, Wang J, Gavva N, Dussor G. Meningeal transient receptor potential channel M8 activation causes cutaneous facial and hindpaw allodynia in a preclinical rodent model of headache. Cephalalgia 2016; 36:185-93. [PMID: 25944818 PMCID: PMC4635063 DOI: 10.1177/0333102415584313] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 04/05/2015] [Indexed: 01/17/2023]
Abstract
BACKGROUND Migraine headache is a neurological disorder affecting millions worldwide. However, little is known about the mechanisms contributing to migraine. Recent genome-wide association studies have found single nucleotide polymorphisms in the gene encoding transient receptor potential channel M8. Transient receptor potential channel M8 is generally known as a cold receptor but it has been implicated in pain signaling and may play a role in migraine pain. METHODS In order to investigate whether transient receptor potential channel M8 may contribute to the pain of migraine, the transient receptor potential channel M8 activator icilin was applied to the dura mater using a rat behavioral model of headache. Cutaneous allodynia was measured for 5 hours using Von Frey filaments. RESULTS Dural application of icilin produced cutaneous facial and hind paw allodynia that was attenuated by systemic pretreatment with the transient receptor potential channel M8-selective antagonist AMG1161 (10 mg/kg p.o.). Further, the anti-migraine agent sumatriptan (0.6 mg/kg s.c.) or the non-selective NOS inhibitor L-NAME (20 mg/kg i.p.) also attenuated allodynia when given as a pretreatment. CONCLUSIONS These data indicate that transient receptor potential channel M8 activation in the meninges produces behaviors in rats that are consistent with migraine and that are sensitive to pharmacological mechanisms known to have efficacy for migraine in humans. The findings suggest that activation of meningeal transient receptor potential channel M8 may contribute to the pain of migraine.
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Affiliation(s)
| | | | | | | | | | | | | | - Gregory Dussor
- Department of Pharmacology, University of Arizona, USA School of Behavioral and Brain Sciences, University of Texas at Dallas, USA
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Lucius A, Khajavi N, Reinach PS, Köhrle J, Dhandapani P, Huimann P, Ljubojevic N, Grötzinger C, Mergler S. 3-Iodothyronamine increases transient receptor potential melastatin channel 8 (TRPM8) activity in immortalized human corneal epithelial cells. Cell Signal 2015; 28:136-147. [PMID: 26689735 DOI: 10.1016/j.cellsig.2015.12.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 11/25/2015] [Accepted: 12/08/2015] [Indexed: 10/22/2022]
Abstract
3-Iodothyronamine (3T1AM) is an endogenous thyroid hormone metabolite that interacts with the human trace amine-associated receptor 1 (hTAAR1), a G-protein-coupled receptor, to induce numerous physiological responses including dose-dependent body temperature lowering in rodents. 3T1AM also directly activates cold-sensitive transient receptor potential melastatin 8 (TRPM8) channels in human conjunctival epithelial cells (HCjEC) at constant temperature as well as reducing rises in IL-6 release induced by transient receptor potential vanilloid 1 (TRPV1) activation by capsaicin (CAP). Here, we describe that 3T1AM-induced TRPM8 activation suppresses through crosstalk TRPV1 activation in immortalized human corneal epithelial cells (HCEC). RT-PCR and immunofluorescent staining identified TRPM8 gene and protein expression. Increases in Ca(2+) influx induced by the TRPM8 agonists either 3T1AM (0.1-10 μM), menthol (500 μM), icilin (15-60 μM) or temperature lowering (either <17°C or >17°C) were all blocked by 10-20 μM BCTC, a mixed TRPV1/TRPM8 antagonist. BCTC blocked 3T1AM-induced recombinant TRPM8 activation of Ca(2+) transients in an osteosarcoma heterologous expression system. The effects of BCTC in HCEC were attributable to selective TRPM8 inhibition since whole-cell patch-clamp currents underlying Ca(2+) rises induced by 20 μM CAP were BCTC insensitive. On the other hand, Ca(2+) transients induced by activating TRPV1 with either CAP or a hyperosmolar medium were suppressed during exposure to either 1 μM 3T1AM or 15 μM icilin. All of these modulatory effects on intracellular Ca(2+) regulation induced by the aforementioned agents were attributable to changes in underlying inward and outward current. Taken together, TRPM8 activation by 3T1AM markedly attenuates and even eliminates hyperosmolar and CAP induced TRPV1 activation through crosstalk.
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Affiliation(s)
- Alexander Lucius
- Klinik für Augenheilkunde, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Noushafarin Khajavi
- Klinik für Augenheilkunde, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Peter S Reinach
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou 325027, PR China
| | - Josef Köhrle
- Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Priyavathi Dhandapani
- Gastroenterology, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany
| | - Philipp Huimann
- Klinik für Augenheilkunde, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Nina Ljubojevic
- Klinik für Augenheilkunde, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Carsten Grötzinger
- Gastroenterology, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany
| | - Stefan Mergler
- Klinik für Augenheilkunde, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
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Downs CA, Faulkner MS. Toxic stress, inflammation and symptomatology of chronic complications in diabetes. World J Diabetes 2015; 6:554-565. [PMID: 25987953 PMCID: PMC4434076 DOI: 10.4239/wjd.v6.i4.554] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 12/30/2014] [Accepted: 02/12/2015] [Indexed: 02/05/2023] Open
Abstract
Diabetes affects at least 382 million people worldwide and the incidence is expected to reach 592 million by 2035. The incidence of diabetes in youth is skyrocketing as evidenced by a 21% increase in type 1 diabetes and a 30.5% increase in type 2 diabetes in the United States between 2001 and 2009. The effects of toxic stress, the culmination of biological and environmental interactions, on the development of diabetes complications is gaining attention. Stress impacts the hypothalamus-pituitary-adrenal axis and contributes to inflammation, a key biological contributor to the pathogenesis of diabetes and its associated complications. This review provides an overview of common diabetic complications such as neuropathy, cognitive decline, depression, nephropathy and cardiovascular disease. The review also provides a discussion of the role of inflammation and stress in the development and progression of chronic complications of diabetes, associated symptomatology and importance of early identification of symptoms of depression, fatigue, exercise intolerance and pain.
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18
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Assessment of intraoral mucosal pain induced by the application of capsaicin. Arch Oral Biol 2014; 59:1334-41. [PMID: 25189505 DOI: 10.1016/j.archoralbio.2014.08.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 07/10/2014] [Accepted: 08/18/2014] [Indexed: 11/23/2022]
Abstract
OBJECTIVE To develop an objective method for assessing nociceptive behaviour in an animal model of capsaicin-induced intraoral pain. Changes in nociceptive responses were also examined after injury to the inferior alveolar nerve (IAN). DESIGN Nociceptive responses evoked by the intraoral application of various doses of capsaicin were analyzed in lightly anaesthetized rats. The number of c-Fos protein-like immunoreactive (Fos-LI) neurons in the medullary dorsal horn (MDH) induced by the intraoral application of capsaicin was measured. Behavioural and c-Fos responses were also examined 14 days after injury to the IAN. RESULTS Larger doses of intraoral capsaicin (1, 10 and 100μg) induced vigorous licking behaviour and c-Fos response in the MDH in a reproducible manner. The magnitudes of both behavioural activity and the c-Fos response from the 10 and 100μg doses of capsaicin were significantly greater than that by the 1μg dose. Injury to the IAN exaggerated the behavioural and c-Fos responses evoked by intraoral capsaicin. CONCLUSIONS The intraoral application of capsaicin is a valid and reliable method for studying intraoral pain and hyperalgesia following nerve injury.
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