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Kim K, Nan G, Bak H, Kim HY, Kim J, Cha M, Lee BH. Insular cortex stimulation alleviates neuropathic pain through changes in the expression of collapsin response mediator protein 2 involved in synaptic plasticity. Neurobiol Dis 2024; 194:106466. [PMID: 38471625 DOI: 10.1016/j.nbd.2024.106466] [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: 01/12/2024] [Revised: 03/03/2024] [Accepted: 03/04/2024] [Indexed: 03/14/2024] Open
Abstract
In recent studies, brain stimulation has shown promising potential to alleviate chronic pain. Although studies have shown that stimulation of pain-related brain regions can induce pain-relieving effects, few studies have elucidated the mechanisms of brain stimulation in the insular cortex (IC). The present study was conducted to explore the changes in characteristic molecules involved in pain modulation mechanisms and to identify the changes in synaptic plasticity after IC stimulation (ICS). Following ICS, pain-relieving behaviors and changes in proteomics were explored. Neuronal activity in the IC after ICS was observed by optical imaging. Western blotting was used to validate the proteomics data and identify the changes in the expression of glutamatergic receptors associated with synaptic plasticity. Experimental results showed that ICS effectively relieved mechanical allodynia, and proteomics identified specific changes in collapsin response mediator protein 2 (CRMP2). Neuronal activity in the neuropathic rats was significantly decreased after ICS. Neuropathic rats showed increased expression levels of phosphorylated CRMP2, alpha amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR), and N-methyl-d-aspartate receptor (NMDAR) subunit 2B (NR2B), which were inhibited by ICS. These results indicate that ICS regulates the synaptic plasticity of ICS through pCRMP2, together with AMPAR and NR2B, to induce pain relief.
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Affiliation(s)
- Kyeongmin Kim
- Department of Physiology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea; Department of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Guanghai Nan
- Department of Physiology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea; Department of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Hyeji Bak
- Department of Physiology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Hee Young Kim
- Department of Physiology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Junesun Kim
- Rehabilitation Science Program, Department of Health Science, Graduate School, Korea University, Seoul 02841, Republic of Korea; Department of Health and Environment Science, College of Health Science, Korea University, Seoul 02841, Republic of Korea
| | - Myeounghoon Cha
- Department of Physiology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea.
| | - Bae Hwan Lee
- Department of Physiology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea; Department of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul 03722, Republic of Korea.
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Yao D, Chen Y, Chen G. The role of pain modulation pathway and related brain regions in pain. Rev Neurosci 2023; 34:899-914. [PMID: 37288945 DOI: 10.1515/revneuro-2023-0037] [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: 03/25/2023] [Accepted: 05/18/2023] [Indexed: 06/09/2023]
Abstract
Pain is a multifaceted process that encompasses unpleasant sensory and emotional experiences. The essence of the pain process is aversion, or perceived negative emotion. Central sensitization plays a significant role in initiating and perpetuating of chronic pain. Melzack proposed the concept of the "pain matrix", in which brain regions associated with pain form an interconnected network, rather than being controlled by a singular brain region. This review aims to investigate distinct brain regions involved in pain and their interconnections. In addition, it also sheds light on the reciprocal connectivity between the ascending and descending pathways that participate in pain modulation. We review the involvement of various brain areas during pain and focus on understanding the connections among them, which can contribute to a better understanding of pain mechanisms and provide opportunities for further research on therapies for improved pain management.
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Affiliation(s)
- Dandan Yao
- Department of Anesthesiology, School of Medicine, Shaoxing University, Shaoxing, Zhejiang, China
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Yeru Chen
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Gang Chen
- Department of Anesthesiology, School of Medicine, Shaoxing University, Shaoxing, Zhejiang, China
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310058, China
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Islam J, Kc E, Kim S, Chung MY, Park KS, Kim HK, Park YS. Optogenetic Inhibition of Glutamatergic Neurons in the Dysgranular Posterior Insular Cortex Modulates Trigeminal Neuropathic Pain in CCI-ION Rat. Neuromolecular Med 2023; 25:516-532. [PMID: 37700212 DOI: 10.1007/s12017-023-08752-3] [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: 06/02/2023] [Accepted: 08/15/2023] [Indexed: 09/14/2023]
Abstract
In individuals with chronic neuropathic pain, the posterior insular cortex (PIC) has been found to exhibit increased glutamatergic activity, and the dysgranular portion of PIC (DPIC) has been investigated as a novel cortical target for pain modulation. However, the role of DPIC glutamatergic neurons (DPICg) in trigeminal neuropathic pain (TNP) remains unclear. Here, we examined the outcomes of DPICg inhibition in a rat model of chronic constriction injury of the infraorbital nerve (CCI-ION). Animals were randomly divided into TNP, sham, and control groups. TNP animals underwent CCI-ION surgery. Either optogenetic or null viruses were delivered to the contralateral DPICg of TNP and sham animals. In vivo single-unit extracellular recordings from the ipsilateral spinal trigeminal nucleus caudalis (TNC) and contralateral ventral posteromedial (VPM) thalamus were obtained under both "ON" and "OFF" stimulation states. Behavioral responses during the stimulation-OFF and stimulation-ON phases were examined. Expression of c-Fos, pERK, and CREB immunopositive neurons were also observed. Optogenetic inhibition of contralateral DPICg decreased the neural firing rate in both TNC and VPM thalamus, the expression of sensory-responsive cell bodies, and transcriptional factors in the DPIC of TNP group. Improvements in hyperalgesia, allodynia, and anxiety-like responses in TNP animals were also observed during stimulation-ON condition. In fine, descending pain processing is influenced by neuroanatomical projections from the DPIC to the pain matrix areas, and DPICg could play a necessary role in this neural circuitry. Therefore, the antinociceptive effect of DPICg inhibition in this study may provide evidence for the therapeutic potential of DPICg in TNP.
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Affiliation(s)
- Jaisan Islam
- Department of Medical Neuroscience, College of Medicine, Chungbuk National University, Cheongju, Chungbuk, Korea
| | - Elina Kc
- Department of Medical Neuroscience, College of Medicine, Chungbuk National University, Cheongju, Chungbuk, Korea
| | - Soochong Kim
- Department of Veterinary Medicine, College of Veterinary Medicine, Chungbuk National University, Cheongju, Korea
| | - Moon Young Chung
- Department of Neurosurgery, Soonchunhyang University, Bucheon, Korea
| | - Ki Seok Park
- Department of Neurosurgery, Eulji University Hospital, Daejeon, Korea
| | - Hyong Kyu Kim
- Department of Medicine and Microbiology, College of Medicine, Chungbuk National University, Cheongju, Korea
| | - Young Seok Park
- Department of Medical Neuroscience, College of Medicine, Chungbuk National University, Cheongju, Chungbuk, Korea.
- Department of Neurosurgery, Chungbuk National University Hospital, 776, 1 Sunhwanro, Seowon-gu, Cheongju, 28644, Korea.
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Kim K, Nan G, Kim L, Kwon M, Lee KH, Cha M, Lee BH. Insular cortex stimulation alleviates neuropathic pain via ERK phosphorylation in neurons. CNS Neurosci Ther 2023; 29:1636-1648. [PMID: 36806498 PMCID: PMC10173725 DOI: 10.1111/cns.14126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 11/13/2022] [Accepted: 12/09/2022] [Indexed: 02/22/2023] Open
Abstract
AIMS The clinical use of brain stimulation is attractive for patients who have side effects or tolerance. However, studies on insular cortex (IC) stimulation are lacking in neuropathic pain. The present study aimed to investigate the effects of IC stimulation (ICS) on neuropathic pain and to determine how ICS modulates pain. METHODS Changes in pain behaviors were observed following ICS with various parameters in neuropathic rats. Western blotting was performed to assess molecular changes in the expression levels of phosphorylated extracellular signal-regulated kinase (pERK), neurons, astrocytes, and microglia between experimental groups. Immunohistochemistry was performed to investigate the colocalization of pERK with different cell types. RESULTS The most effective pain-relieving effect was induced at 50 Hz-120 μA in single trial of ICS and it maintained 4 days longer after the termination of repetitive ICS. The expression levels of pERK, astrocytes, and microglia were increased in neuropathic rats. However, after ICS, the expression levels of pERK were decreased, and colocalization of pERK and neurons was reduced in layers 2-3 of the IC. CONCLUSION These results indicated that ICS attenuated neuropathic pain by the regulation of pERK in neurons located in layers 2-3 of the IC. This preclinical study may enhance the potential use of ICS and identify the therapeutic mechanisms of ICS in neuropathic pain.
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Affiliation(s)
- Kyeongmin Kim
- Department of Physiology, Yonsei University College of Medicine, Seoul, Korea
| | - Guanghai Nan
- Department of Physiology, Yonsei University College of Medicine, Seoul, Korea.,Department of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, Korea
| | - Leejeong Kim
- Department of Physiology, Yonsei University College of Medicine, Seoul, Korea.,Department of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, Korea
| | - Minjee Kwon
- Department of Nursing, Kyungil University, Gyeongsan, Korea
| | - Kyung Hee Lee
- Department of Dental Hygiene, Division of Health Science, Dongseo University, Busan, Korea
| | - Myeounghoon Cha
- Department of Physiology, Yonsei University College of Medicine, Seoul, Korea
| | - Bae Hwan Lee
- Department of Physiology, Yonsei University College of Medicine, Seoul, Korea.,Department of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, Korea
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Choi S, Kim K, Kwon M, Bai SJ, Cha M, Lee BH. Modulation of Neuropathic Pain by Glial Regulation in the Insular Cortex of Rats. Front Mol Neurosci 2022; 15:815945. [PMID: 35493331 PMCID: PMC9043281 DOI: 10.3389/fnmol.2022.815945] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 02/22/2022] [Indexed: 12/12/2022] Open
Abstract
The insular cortex (IC) is known to process pain information. However, analgesic effects of glial inhibition in the IC have not yet been explored. The aim of this study was to investigate pain alleviation effects after neuroglia inhibition in the IC during the early or late phase of pain development. The effects of glial inhibitors in early or late phase inhibition in neuropathic pain were characterized in astrocytes and microglia expressions in the IC of an animal model of neuropathic pain. Changes in withdrawal responses during different stages of inhibition were compared, and morphological changes in glial cells with purinergic receptor expressions were analyzed. Inhibition of glial cells had an analgesic effect that persisted even after drug withdrawal. Both GFAP and CD11b/c expressions were decreased after injection of glial inhibitors. Morphological alterations of astrocytes and microglia were observed with expression changes of purinergic receptors. These findings indicate that inhibition of neuroglia activity in the IC alleviates chronic pain, and that purinergic receptors in glial cells are closely related to chronic pain development.
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Affiliation(s)
- Songyeon Choi
- Department of Physiology, Yonsei University College of Medicine, Seoul, South Korea
- Department of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, South Korea
| | - Kyeongmin Kim
- Department of Physiology, Yonsei University College of Medicine, Seoul, South Korea
- Department of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, South Korea
| | - Minjee Kwon
- Department of Nursing, Kyungil University, Gyeongsan, South Korea
| | - Sun Joon Bai
- Department of Anesthesiology and Pain Medicine, Yonsei University College of Medicine, Seoul, South Korea
| | - Myeounghoon Cha
- Department of Physiology, Yonsei University College of Medicine, Seoul, South Korea
- *Correspondence: Myeounghoon Cha,
| | - Bae Hwan Lee
- Department of Physiology, Yonsei University College of Medicine, Seoul, South Korea
- Department of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, South Korea
- Bae Hwan Lee,
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Wang Z, Huang S, Yu X, Li L, Yang M, Liang S, Liu W, Tao J. Altered thalamic neurotransmitters metabolism and functional connectivity during the development of chronic constriction injury induced neuropathic pain. Biol Res 2020; 53:36. [PMID: 32843088 PMCID: PMC7448455 DOI: 10.1186/s40659-020-00303-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Accepted: 08/08/2020] [Indexed: 11/17/2022] Open
Abstract
Background To investigate the thalamic neurotransmitters and functional connections in the development of chronic constriction injury (CCI)-induced neuropathic pain. Methods The paw withdrawal threshold was measured by mechanical stimulation the right hind paw with the von frey hair in the rats of CCI-induced neuropathic pain. The N-acetylaspartate (NAA) and Glutamate (Glu) in thalamus were detected by magnetic resonance spectrum (MRS) process. The thalamic functional connectivity with other brain regions was scanned by functional magnetic resonance image (fMRI). Results The paw withdrawal threshold of the ipsilateral side showed a noticeable decline during the pathological process. Increased concentrations of Glu and decreased levels of NAA in the thalamus were significantly correlated with mechanical allodynia in the neuropathic pain states. The thalamic regional homogeneity (ReHo) decreased during the process of neuropathic pain. The functional connectivity among the thalamus with the insula and somatosensory cortex were significantly increased at different time points (7, 14, 21 days) after CCI surgery. Conclusion Our study suggests that dynamic changes in thalamic NAA and Glu levels contribute to the thalamic functional connection hyper-excitation during CCI-induced neuropathic pain. Enhanced thalamus-insula functional connection might have a significant effect on the occurrence of neuropathic pain.
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Affiliation(s)
- Zhifu Wang
- College of Integrated Traditional Chinese and Western Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, 350122, China
| | - Sheng Huang
- National-Local Joint Engineering Research Center of Rehabilitation Medicine Technology, Fujian University of Traditional Chinese Medicine, Fuzhou, 350122, Fujian, China.,Fujian Collaborative Innovation Center for Rehabilitation Technology, Fuzhou, 350122, Fujian, China
| | - Xiangmei Yu
- College of Integrated Traditional Chinese and Western Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, 350122, China
| | - Long Li
- National-Local Joint Engineering Research Center of Rehabilitation Medicine Technology, Fujian University of Traditional Chinese Medicine, Fuzhou, 350122, Fujian, China.,Fujian Collaborative Innovation Center for Rehabilitation Technology, Fuzhou, 350122, Fujian, China
| | - Minguang Yang
- National-Local Joint Engineering Research Center of Rehabilitation Medicine Technology, Fujian University of Traditional Chinese Medicine, Fuzhou, 350122, Fujian, China.,Fujian Collaborative Innovation Center for Rehabilitation Technology, Fuzhou, 350122, Fujian, China
| | - Shengxiang Liang
- National-Local Joint Engineering Research Center of Rehabilitation Medicine Technology, Fujian University of Traditional Chinese Medicine, Fuzhou, 350122, Fujian, China.,Fujian Collaborative Innovation Center for Rehabilitation Technology, Fuzhou, 350122, Fujian, China
| | - Weilin Liu
- College of Rehabilitation Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, 350122, China
| | - Jing Tao
- College of Rehabilitation Medicine, Fujian University of Traditional Chinese Medicine, Fuzhou, 350122, China.
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Kim K, Choi S, Cha M, Lee BH. Effects of mTOR inhibitors on neuropathic pain revealed by optical imaging of the insular cortex in rats. Brain Res 2020; 1733:146720. [PMID: 32061737 DOI: 10.1016/j.brainres.2020.146720] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 01/22/2020] [Accepted: 02/07/2020] [Indexed: 11/24/2022]
Abstract
In the pain matrix, the insular cortex (IC) is mainly involved in discriminative sensory and motivative emotion. Abnormal signal transmission from injury site causes neuropathic pain, which generates enhanced synaptic plasticity. The mammalian target of rapamycin (mTOR) complex is the key regulator of protein synthesis; it is involved in the modulation of synaptic plasticity. To date, there has been no report on the changes in optical signals in the IC under neuropathic condition after treatment with mTOR inhibitors, such as Torin1 and XL388. Therefore, we aimed to determine the pain-relieving effect of mTOR inhibitors (Torin1 and XL388) and observe the changes in optical signals in the IC after treatment. Mechanical threshold was measured in adult male Sprague-Dawley rats after neuropathic surgery, and therapeutic effect of inhibitors was assessed on post-operative day 7 following the microinjection of Torin1 or XL388 into the IC. Optical signals were acquired to observe the neuronal activity of the IC in response to peripheral stimulation before and after treatment with mTOR inhibitors. Consequently, the inhibitors showed the most effective alleviation 4 h after microinjection into the IC. In optical imaging, peak amplitudes of optical signals and areas of activated regions were reduced after treatment with Torin1 and XL388. However, there were no significant optical signal changes in the IC before and after vehicle application. These findings suggested that Torin1 and XL388 are associated with the alleviation of neuronal activity that is excessively manifested in the IC, and is assumed to diminish synaptic plasticity.
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Affiliation(s)
- Kyeongmin Kim
- Department of Physiology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea; Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Songyeon Choi
- Department of Physiology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea; Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Myeounghoon Cha
- Department of Physiology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Bae Hwan Lee
- Department of Physiology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea; Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Republic of Korea.
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Jee Kim M, Tanioka M, Woo Um S, Hong SK, Hwan Lee B. Analgesic effects of FAAH inhibitor in the insular cortex of nerve-injured rats. Mol Pain 2018; 14:1744806918814345. [PMID: 30380982 PMCID: PMC6247483 DOI: 10.1177/1744806918814345] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Revised: 08/10/2018] [Accepted: 09/30/2018] [Indexed: 01/04/2023] Open
Abstract
The insular cortex is an important region of brain involved in the processing of pain and emotion. Recent studies indicate that lesions in the insular cortex induce pain asymbolia and reverse neuropathic pain. Endogenous cannabinoids (endocannabinoids), which have been shown to attenuate pain, are simultaneously degraded by fatty acid amide hydrolase (FAAH) that halts the mechanisms of action. Selective inhibitor URB597 suppresses FAAH activity by conserving endocannabinoids, which reduces pain. The present study examined the analgesic effects of URB597 treatment in the insular cortex of an animal model of neuropathic pain. Under pentobarbital anesthesia, male Sprague-Dawley rats were subjected to nerve injury and cannula implantation. On postoperative day 14, rodents received microinjection of URB597 into the insular cortex. In order to verify the analgesic mechanisms of URB597, cannabinoid 1 receptor (CB1R) antagonist AM251, peroxisome proliferator-activated receptor alpha (PPAR alpha) antagonist GW6471, and transient receptor potential vanilloid 1 (TRPV1) antagonist Iodoresiniferatoxin (I-RTX) were microinjected 15 min prior to URB597 injection. Changes in mechanical allodynia were measured using the von-Frey test. Expressions of CB1R, N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD), and TRPV1 significantly increased in the neuropathic pain group compared to the sham-operated control group. Mechanical threshold and expression of NAPE-PLD significantly increased in groups treated with 2 nM and 4 nM URB597 compared with the vehicle-injected group. Blockages of CB1R and PPAR alpha diminished the analgesic effects of URB597. Inhibition of TRPV1 did not effectively reduce the effects of URB597 but attenuated expression of NAPE-PLD compared with the URB597-injected group. In addition, optical imaging demonstrated that neuronal activity of the insular cortex was reduced following URB597 treatment. Our results suggest that microinjection of FAAH inhibitor into the insular cortex causes analgesic effects by decreasing neural excitability and increasing signals related to the endogenous cannabinoid pathway in the insular cortex.
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Affiliation(s)
- Min Jee Kim
- Department of Physiology and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Motomasa Tanioka
- Department of Physiology and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Sun Woo Um
- Department of Physiology and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Seong-Karp Hong
- Division of Bio and Health Sciences, Mokwon University, Daejeon, Republic of Korea
| | - Bae Hwan Lee
- Department of Physiology and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea
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Kwon M, Han J, Kim UJ, Cha M, Um SW, Bai SJ, Hong SK, Lee BH. Inhibition of Mammalian Target of Rapamycin (mTOR) Signaling in the Insular Cortex Alleviates Neuropathic Pain after Peripheral Nerve Injury. Front Mol Neurosci 2017; 10:79. [PMID: 28377693 PMCID: PMC5359287 DOI: 10.3389/fnmol.2017.00079] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 03/06/2017] [Indexed: 12/30/2022] Open
Abstract
Injury of peripheral nerves can trigger neuropathic pain, producing allodynia and hyperalgesia via peripheral and central sensitization. Recent studies have focused on the role of the insular cortex (IC) in neuropathic pain. Because the IC is thought to store pain-related memories, translational regulation in this structure may reveal novel targets for controlling chronic pain. Signaling via mammalian target of rapamycin (mTOR), which is known to control mRNA translation and influence synaptic plasticity, has been studied at the spinal level in neuropathic pain, but its role in the IC under these conditions remains elusive. Therefore, this study was conducted to determine the role of mTOR signaling in neuropathic pain and to assess the potential therapeutic effects of rapamycin, an inhibitor of mTORC1, in the IC of rats with neuropathic pain. Mechanical allodynia was assessed in adult male Sprague-Dawley rats after neuropathic surgery and following microinjections of rapamycin into the IC on postoperative days (PODs) 3 and 7. Optical recording was conducted to observe the neural responses of the IC to peripheral stimulation. Rapamycin reduced mechanical allodynia and downregulated the expression of postsynaptic density protein 95 (PSD95), decreased neural excitability in the IC, thereby inhibiting neuropathic pain-induced synaptic plasticity. These findings suggest that mTOR signaling in the IC may be a critical molecular mechanism modulating neuropathic pain.
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Affiliation(s)
- Minjee Kwon
- Department of Physiology, Yonsei University College of MedicineSeoul, South Korea; Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of MedicineSeoul, South Korea
| | - Jeongsoo Han
- Department of Physiology, Yonsei University College of MedicineSeoul, South Korea; Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of MedicineSeoul, South Korea
| | - Un Jeng Kim
- Department of Physiology, Yonsei University College of Medicine Seoul, South Korea
| | - Myeounghoon Cha
- Department of Physiology, Yonsei University College of Medicine Seoul, South Korea
| | - Sun Woo Um
- Department of Physiology, Yonsei University College of MedicineSeoul, South Korea; Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of MedicineSeoul, South Korea
| | - Sun Joon Bai
- Department of Anesthesiology and Pain Medicine, Yonsei University College of Medicine Seoul, South Korea
| | - Seong-Karp Hong
- Division of Bio and Health Sciences, Mokwon University Daejeon, South Korea
| | - Bae Hwan Lee
- Department of Physiology, Yonsei University College of MedicineSeoul, South Korea; Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of MedicineSeoul, South Korea; Brain Research Institute and Epilepsy Research Institute, Yonsei University College of MedicineSeoul, South Korea
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Cha M, Chae Y, Bai SJ, Lee BH. Spatiotemporal changes of optical signals in the somatosensory cortex of neuropathic rats after electroacupuncture stimulation. BMC COMPLEMENTARY AND ALTERNATIVE MEDICINE 2017; 17:33. [PMID: 28068994 PMCID: PMC5223459 DOI: 10.1186/s12906-016-1510-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/24/2016] [Accepted: 12/01/2016] [Indexed: 12/20/2022]
Abstract
Background Peripheral nerve injury causes physiological changes in primary afferent neurons. Neuropathic pain associated with peripheral nerve injuries may reflect changes in the excitability of the nervous system, including the spinothalamic tract. Current alternative medical research indicates that acupuncture stimulation has analgesic effects in various pain symptoms. However, activation changes in the somatosensory cortex of the brain by acupuncture stimulation remain poorly understood. The present study was conducted to monitor the changes in cortical excitability, using optical imaging with voltage-sensitive dye (VSD) in neuropathic rats after electroacupuncture (EA) stimulation. Methods Male Sprague–Dawley rats were divided into three groups: control (intact), sham injury, and neuropathic pain rats. Under pentobarbital anesthesia, rats were subjected to nerve injury with tight ligation and incision of the tibial and sural nerves in the left hind paw. For optical imaging, the rats were re-anesthetized with urethane, and followed by craniotomy. The exposed primary somatosensory cortex (S1) was stained with VSD for one hour. Optical signals were recorded from the S1 cortex, before and after EA stimulation on Zusanli (ST36) and Yinlingquan (SP9). Results After peripheral stimulation, control and sham injury rats did not show significant signal changes in the S1 cortex. However, inflamed and amplified neural activities were observed in the S1 cortex of nerve-injured rats. Furthermore, the optical signals and region of activation in the S1 cortex were reduced substantially after EA stimulation, and recovered in a time-dependent manner. The peak fluorescence intensity was significantly reduced until 90 min after EA stimulation (Pre-EA: 0.25 ± 0.04 and Post-EA 0 min: 0.01 ± 0.01), and maximum activated area was also significantly attenuated until 60 min after EA stimulation (Pre-EA: 37.2 ± 1.79 and Post-EA 0 min: 0.01 ± 0.10). Conclusion Our results indicate that EA stimulation has inhibitory effects on excitatory neuronal signaling in the S1 cortex, caused by noxious stimulation in neuropathic pain. These findings suggest that EA stimulation warrants further study as a potential adjuvant modulation of neuropathic pain.
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