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Dhanapalaratnam R, Issar T, Poynten AM, Milner KL, Kwai NCG, Krishnan AV. Progression of axonal excitability abnormalities with increasing clinical severity of diabetic peripheral neuropathy. Clin Neurophysiol 2024; 160:12-18. [PMID: 38367309 DOI: 10.1016/j.clinph.2024.02.002] [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: 08/15/2023] [Revised: 01/18/2024] [Accepted: 02/05/2024] [Indexed: 02/19/2024]
Abstract
OBJECTIVE Diabetic peripheral neuropathy (DPN) is a frequent complication for persons with type 2 diabetes. Previous studies have failed to demonstrate any significant impact of treatment for DPN. The present study assessed the role of axonal ion channel dysfunction in DPN and explored the hypothesis that there may be a progressive change in ion channel abnormalities that varied with disease stage. METHODS Neurophysiological studies were conducted using axonal excitability techniques, a clinical method of assessing ion channel dysfunction. Studies were conducted in 178 persons with type 2 diabetes, with participants allocated into four groups according to clinical severity of neuropathy, assessed using the Total Neuropathy Grade. RESULTS Analysis of excitability data demonstrated a progressive and stepwise reduction in two parameters that are related to the activity of Kv1.1 channels, namely superexcitability and depolarizing threshold electrotonus at 10-20 ms (p < 0.001), and mathematical modelling of axonal excitability findings supported progressive upregulation of Kv1.1 conductances with increasing greater disease severity. CONCLUSION The findings are consistent with a progressive upregulation of juxtaparanodal Kv1.1 conductances with increasing clinical severity of diabetic peripheral neuropathy. SIGNIFICANCE From a translational perspective, the study suggests that blockade of Kv1.1 channels using 4-aminopyridine derivatives such as fampridine may be a potential treatment for DPN.
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Affiliation(s)
- Roshan Dhanapalaratnam
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Neurology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Tushar Issar
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia
| | - Ann M Poynten
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Kerry-Lee Milner
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Natalie C G Kwai
- School of Medical, Indigenous and Health Sciences, University of Wollongong, Australia
| | - Arun V Krishnan
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Neurology, Prince of Wales Hospital, Sydney, NSW 2031, Australia.
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2
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Wang Q, Ye Y, Yang L, Xiao L, Liu J, Zhang W, Du G. Painful diabetic neuropathy: The role of ion channels. Biomed Pharmacother 2024; 173:116417. [PMID: 38490158 DOI: 10.1016/j.biopha.2024.116417] [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: 11/30/2023] [Revised: 03/06/2024] [Accepted: 03/06/2024] [Indexed: 03/17/2024] Open
Abstract
Painful diabetic neuropathy (PDN) is a common chronic complication of diabetes that causes neuropathic pain and negatively affects the quality of life. The management of PDN is far from satisfactory. At present, interventions are primarily focused on symptomatic treatment. Ion channel disorders are a major cause of PDN, and a complete understanding of their roles and mechanisms may provide better options for the clinical treatment of PDN. Therefore, this review summarizes the important role of ion channels in PDN and the current drug development targeting these ion channels.
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Affiliation(s)
- Qi Wang
- Department of Anesthesiology, Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Centre, West China Hospital, Sichuan University, Chengdu, China; National-Local Joint Engineering Research Center of Translational Medicine of Anesthesiology, West China Hospital, Sichuan University, Chengdu, China
| | - Yifei Ye
- Department of Anesthesiology, Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Centre, West China Hospital, Sichuan University, Chengdu, China; National-Local Joint Engineering Research Center of Translational Medicine of Anesthesiology, West China Hospital, Sichuan University, Chengdu, China
| | - Linghui Yang
- Department of Anesthesiology, Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Centre, West China Hospital, Sichuan University, Chengdu, China; National-Local Joint Engineering Research Center of Translational Medicine of Anesthesiology, West China Hospital, Sichuan University, Chengdu, China
| | - Lifan Xiao
- Department of Anesthesiology, Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Centre, West China Hospital, Sichuan University, Chengdu, China; National-Local Joint Engineering Research Center of Translational Medicine of Anesthesiology, West China Hospital, Sichuan University, Chengdu, China
| | - Jin Liu
- Department of Anesthesiology, Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Centre, West China Hospital, Sichuan University, Chengdu, China; National-Local Joint Engineering Research Center of Translational Medicine of Anesthesiology, West China Hospital, Sichuan University, Chengdu, China
| | - Wensheng Zhang
- Department of Anesthesiology, Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Centre, West China Hospital, Sichuan University, Chengdu, China; National-Local Joint Engineering Research Center of Translational Medicine of Anesthesiology, West China Hospital, Sichuan University, Chengdu, China.
| | - Guizhi Du
- Department of Anesthesiology, Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Centre, West China Hospital, Sichuan University, Chengdu, China; National-Local Joint Engineering Research Center of Translational Medicine of Anesthesiology, West China Hospital, Sichuan University, Chengdu, China.
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Tricaud N, Gautier B, Berthelot J, Gonzalez S, Van Hameren G. Traumatic and Diabetic Schwann Cell Demyelination Is Triggered by a Transient Mitochondrial Calcium Release through Voltage Dependent Anion Channel 1. Biomedicines 2022; 10:biomedicines10061447. [PMID: 35740468 PMCID: PMC9220872 DOI: 10.3390/biomedicines10061447] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 06/07/2022] [Accepted: 06/08/2022] [Indexed: 11/16/2022] Open
Abstract
A large number of peripheral neuropathies, among which are traumatic and diabetic peripheral neuropathies, result from the degeneration of the myelin sheath, a process called demyelination. Demyelination does not result from Schwann cell death but from Schwann cell dedifferentiation, which includes reprograming and several catabolic and anabolic events. Starting around 4 h after nerve injury, activation of MAPK/cJun pathways is the earliest characterized step of this dedifferentiation program. Here we show, using real-time in vivo imaging, that Schwann cell mitochondrial pH, motility and calcium content are altered as soon as one hour after nerve injury. Mitochondrial calcium release occurred through the VDAC outer membrane channel and mPTP inner membrane channel. This calcium influx in the cytoplasm induced Schwann-cell demyelination via MAPK/c-Jun activation. Blocking calcium release through VDAC silencing or VDAC inhibitor TRO19622 prevented demyelination. We found that the kinetics of mitochondrial calcium release upon nerve injury were altered in the Schwann cells of diabetic mice suggesting a permanent leak of mitochondrial calcium in the cytoplasm. TRO19622 treatment alleviated peripheral nerve defects and motor deficit in diabetic mice. Together, these data indicate that mitochondrial calcium homeostasis is instrumental in the Schwann cell demyelination program and that blocking VDAC constitutes a molecular basis for developing anti-demyelinating drugs for diabetic peripheral neuropathy.
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Affiliation(s)
- Nicolas Tricaud
- Institut des Neurosciences de Montpellier, Univ. Montpellier, INSERM, 34000 Montpellier, France; (B.G.); (J.B.); (S.G.); (G.V.H.)
- I-Stem, UEVE/UPS U861, INSERM U861, AFM, 91100 Corbeil-Essonnes, France
- Correspondence:
| | - Benoit Gautier
- Institut des Neurosciences de Montpellier, Univ. Montpellier, INSERM, 34000 Montpellier, France; (B.G.); (J.B.); (S.G.); (G.V.H.)
| | - Jade Berthelot
- Institut des Neurosciences de Montpellier, Univ. Montpellier, INSERM, 34000 Montpellier, France; (B.G.); (J.B.); (S.G.); (G.V.H.)
| | - Sergio Gonzalez
- Institut des Neurosciences de Montpellier, Univ. Montpellier, INSERM, 34000 Montpellier, France; (B.G.); (J.B.); (S.G.); (G.V.H.)
| | - Gerben Van Hameren
- Institut des Neurosciences de Montpellier, Univ. Montpellier, INSERM, 34000 Montpellier, France; (B.G.); (J.B.); (S.G.); (G.V.H.)
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Neuro-immune-metabolism: The tripod system of homeostasis. Immunol Lett 2021; 240:77-97. [PMID: 34655659 DOI: 10.1016/j.imlet.2021.10.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 09/30/2021] [Accepted: 10/08/2021] [Indexed: 11/20/2022]
Abstract
Homeostatic regulation of cellular and molecular processes is essential for the efficient physiological functioning of body organs. It requires an intricate balance of several networks throughout the body, most notable being the nervous, immune and metabolic systems. Several studies have reported the interactions between neuro-immune, immune-metabolic and neuro-metabolic pathways. Current review aims to integrate the information and show that neuro, immune and metabolic systems form the triumvirate of homeostasis. It focuses on the cellular and molecular interactions occurring in the extremities and intestine, which are innervated by the peripheral nervous system and for the intestine in particular the enteric nervous system. While the interdependence of neuro-immune-metabolic pathways provides a fallback mechanism in case of disruption of homeostasis, in chronic pathologies of continued disequilibrium, the collapse of one system spreads to the other interacting networks as well. Current review illustrates this domino-effect using diabetes as the main example. Together, this review attempts to provide a holistic picture of the integrated network of neuro-immune-metabolism and attempts to broaden the outlook when devising a scientific study or a treatment strategy.
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Assembly and Function of the Juxtaparanodal Kv1 Complex in Health and Disease. Life (Basel) 2020; 11:life11010008. [PMID: 33374190 PMCID: PMC7824554 DOI: 10.3390/life11010008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 12/21/2020] [Accepted: 12/23/2020] [Indexed: 02/07/2023] Open
Abstract
The precise axonal distribution of specific potassium channels is known to secure the shape and frequency of action potentials in myelinated fibers. The low-threshold voltage-gated Kv1 channels located at the axon initial segment have a significant influence on spike initiation and waveform. Their role remains partially understood at the juxtaparanodes where they are trapped under the compact myelin bordering the nodes of Ranvier in physiological conditions. However, the exposure of Kv1 channels in de- or dys-myelinating neuropathy results in alteration of saltatory conduction. Moreover, cell adhesion molecules associated with the Kv1 complex, including Caspr2, Contactin2, and LGI1, are target antigens in autoimmune diseases associated with hyperexcitability such as encephalitis, neuromyotonia, or neuropathic pain. The clustering of Kv1.1/Kv1.2 channels at the axon initial segment and juxtaparanodes is based on interactions with cell adhesion molecules and cytoskeletal linkers. This review will focus on the trafficking and assembly of the axonal Kv1 complex in the peripheral and central nervous system (PNS and CNS), during development, and in health and disease.
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Lin Y, Lin CS, Chang T, Lee J, Tani J, Chen H, Sung J. Early sensory neurophysiological changes in prediabetes. J Diabetes Investig 2020; 11:458-465. [PMID: 31563156 PMCID: PMC7078118 DOI: 10.1111/jdi.13151] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 09/19/2019] [Accepted: 09/25/2019] [Indexed: 12/14/2022] Open
Abstract
AIMS/INTRODUCTION To elucidate whether axonal changes arise in the prediabetic state and to find a biomarker for early detection of neurophysiological changes. MATERIALS AND METHODS We enrolled asymptomatic diabetes patients, as well as prediabetic and normoglycemic individuals to test sensory nerve excitability, and we analyzed those findings and their correlation with clinical profiles. RESULTS In nerve excitability tests, superexcitability in the recovery cycle showed increasing changes in the normoglycemic, prediabetes and diabetes cohorts (-19.09 ± 4.56% in normoglycemia, -22.39 ± 3.16% in prediabetes and -23.71 ± 5.15% in diabetes, P = 0.002). Relatively prolonged distal sensory latency was observed in the median nerve (3.12 ± 0.29 ms in normoglycemia, 3.23 ± 0.38 ms in prediabetes and 3.45 ± 0.43 ms in diabetes, P = 0.019). Superexcitability was positively correlated with fasting plasma glucose (r = 0.291, P = 0.009) and glycated hemoglobin (r = 0.331, P = 0.003) in all participants. CONCLUSIONS Sensory superexcitability and latencies are the most sensitive parameters for detecting preclinical physiological dysfunction in prediabetes. In addition, changes in favor of superexcitability were positively correlated with glycated hemoglobin for all participants. These results suggest that early axonal changes start in the prediabetic stage, and that the monitoring strategy for polyneuropathy should start as early as prediabetes.
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Affiliation(s)
- Yi‐Chen Lin
- Department of NeurologyTaipei Municipal Wanfang HospitalTaipei Medical UniversityTaipeiTaiwan
- Neuroscience InstituteTaipei Medical UniversityTaipeiTaiwan
| | - Cindy Shin‐Yi Lin
- Neural Regenerative MedicineCollege of Medical Science and TechnologyTaipei Medical University and National Health Research InstitutesTaipeiTaiwan
- The Kam Ling Barbara Lo Chair in Neurodegenerative DisordersCentral Clinical SchoolFaculty of Medicine and Health, Brain and Mind CenterThe University of SydneySydneyAustralia
| | - Tsui‐San Chang
- Department of NeurologyTaipei Municipal Wanfang HospitalTaipei Medical UniversityTaipeiTaiwan
- Neuroscience InstituteTaipei Medical UniversityTaipeiTaiwan
- Department of NeurologySchool of Medicine, College of MedicineTaipei Medical UniversityTaipeiTaiwan
| | - Jing‐Er Lee
- Department of NeurologyTaipei Municipal Wanfang HospitalTaipei Medical UniversityTaipeiTaiwan
- Neuroscience InstituteTaipei Medical UniversityTaipeiTaiwan
| | - Jowy Tani
- Department of NeurologyTaipei Municipal Wanfang HospitalTaipei Medical UniversityTaipeiTaiwan
- Neuroscience InstituteTaipei Medical UniversityTaipeiTaiwan
- Neural Regenerative MedicineCollege of Medical Science and TechnologyTaipei Medical University and National Health Research InstitutesTaipeiTaiwan
- Ph.D. Program for Neural Regenerative MedicineCollege of Medical Science and TechnologyTaipei Medical University and National Health Research InstitutesTaipeiTaiwan
| | - Hung‐Ju Chen
- Department of NeurologyTaipei Municipal Wanfang HospitalTaipei Medical UniversityTaipeiTaiwan
- Neuroscience InstituteTaipei Medical UniversityTaipeiTaiwan
| | - Jia‐Ying Sung
- Department of NeurologyTaipei Municipal Wanfang HospitalTaipei Medical UniversityTaipeiTaiwan
- Neuroscience InstituteTaipei Medical UniversityTaipeiTaiwan
- Department of NeurologySchool of Medicine, College of MedicineTaipei Medical UniversityTaipeiTaiwan
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Meng L, Zhao Y, Qu D, Xie Z, Guo X, Zhu Z, Chen Z, Zhang L, Li W, Cao Z, Tian C, Wu Y. Ion channel modulation by scorpion hemolymph and its defensin ingredients highlights origin of neurotoxins in telson formed in Paleozoic scorpions. Int J Biol Macromol 2020; 148:351-363. [PMID: 31954123 DOI: 10.1016/j.ijbiomac.2020.01.133] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 01/13/2020] [Accepted: 01/14/2020] [Indexed: 12/27/2022]
Abstract
An increasing number of scorpion fossils indicate that the venomous telson developed from the sharp telson in sea scorpions into the extant scorpion-like telson in aquatic scorpions in the Paleozoic Era and then further evolved into the fetal venom system. This hypothesis led us to evaluate the inhibition of scorpion venom-sensitive potassium channels by hemolymph from the scorpion Mesobuthus martensii. Scorpion hemolymph diluted 1:10 inhibited Kv1.1, Kv1.2, Kv1.3 and SK3 potassium channel currents by 76.4%, 90.2%, 85.8%, and 52.8%, respectively. These discoveries encouraged us to investigate the functional similarity between the more ancient defensin ingredients in hemolymph and the evolved neurotoxins in the venom. In addition to the expression of the representative defensin BmKDfsin3 and BmKDfsin5 in both venomous and non-venomous tissues, NMR analysis revealed structural similarities between scorpion defensin and neurotoxin. Functional experiments further indicated that scorpion defensin used the same mechanism as classical neurotoxin to block the neurotoxin-sensitive Kv1.1, Kv1.2, Kv1.3 and SK3 channels. These findings emphasize the likelihood that scorpion defensins evolved into neurotoxins that were adapted to the emergence of the scorpion telson from the sharp telson of sea scorpions into the extant scorpion-like telson in aquatic scorpions in the Paleozoic Era.
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Affiliation(s)
- Lanxia Meng
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, China; State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Yonghui Zhao
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Daliang Qu
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230027, China; School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Zili Xie
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Xingchen Guo
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Zhanyong Zhu
- Department of Plastic Surgery, Renmin Hospital of Wuhan University, Wuhan 430072, China
| | - Zongyun Chen
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Longhua Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230027, China; School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Wenxin Li
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China; Center for BioDrug Research, Wuhan University, Wuhan 430072, China
| | - Zhijian Cao
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China; Center for BioDrug Research, Wuhan University, Wuhan 430072, China
| | - Changlin Tian
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230027, China; School of Life Sciences, University of Science and Technology of China, Hefei 230027, China.
| | - Yingliang Wu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China; Center for BioDrug Research, Wuhan University, Wuhan 430072, China.
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Issar T, Arnold R, Kwai NCG, Walker S, Yan A, Borire AA, Poynten AM, Pussell BA, Endre ZH, Kiernan MC, Krishnan AV. Relative contributions of diabetes and chronic kidney disease to neuropathy development in diabetic nephropathy patients. Clin Neurophysiol 2019; 130:2088-2095. [PMID: 31541986 DOI: 10.1016/j.clinph.2019.08.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 07/04/2019] [Accepted: 08/12/2019] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Chronic kidney disease (CKD) caused by diabetes is known as diabetic kidney disease (DKD). The present study aimed to examine the underlying mechanisms of axonal dysfunction and features of neuropathy in DKD compared to CKD and type 2 diabetes (T2DM) alone. METHODS Patients with DKD (n = 30), CKD (n = 28) or T2DM (n = 40) and healthy controls (n = 41) underwent nerve excitability assessments to examine axonal function. Neuropathy was assessed using the Total Neuropathy Score. A validated mathematical model of human axons was utilised to provide an indication of the underlying causes of nerve pathophysiology. RESULTS Total neuropathy score was significantly higher in patients with DKD compared to those with either CKD or T2DM (p < 0.05). In DKD, nerve excitability measures (S2 accommodation and superexcitability, p < 0.05) were more severely affected compared to both CKD and T2DM and worsened with increasing serum K+ (p < 0.01). Mathematical modelling indicated the basis for nerve dysfunction in DKD was an elevation of extracellular K+ and reductions in Na+ permeability and the hyperpolarisation-activated cation current, which was similar to CKD. CONCLUSIONS Patients with DKD manifested a more severe neuropathy phenotype and shared features of nerve dysfunction to that of CKD. SIGNIFICANCE The CKD, and not diabetes component, appears to underlie axonal pathophysiology in DKD.
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Affiliation(s)
- Tushar Issar
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia
| | - Ria Arnold
- School of Medical Sciences, UNSW Sydney, NSW 2052, Australia
| | - Natalie C G Kwai
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia; Department of Exercise Physiology, UNSW Sydney, NSW 2052, Australia
| | - Susan Walker
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia
| | - Aimy Yan
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia
| | - Adeniyi A Borire
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia
| | - Ann M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Bruce A Pussell
- Department of Nephrology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Zoltan H Endre
- Department of Nephrology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Royal Prince Alfred Hospital, Sydney, NSW 2050, Australia
| | - Arun V Krishnan
- Prince of Wales Clinical School, UNSW Sydney, NSW 2031, Australia.
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Griggs RB, Yermakov LM, Drouet DE, Nguyen DVM, Susuki K. Methylglyoxal Disrupts Paranodal Axoglial Junctions via Calpain Activation. ASN Neuro 2019; 10:1759091418766175. [PMID: 29673258 PMCID: PMC5944142 DOI: 10.1177/1759091418766175] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Nodes of Ranvier and associated paranodal and juxtaparanodal domains along myelinated axons are essential for normal function of the peripheral and central nervous systems. Disruption of these domains as well as increases in the reactive carbonyl species methylglyoxal are implicated as a pathophysiology common to a wide variety of neurological diseases. Here, using an ex vivo nerve exposure model, we show that increasing methylglyoxal produces paranodal disruption, evidenced by disorganized immunostaining of axoglial cell-adhesion proteins, in both sciatic and optic nerves from wild-type mice. Consistent with previous studies showing that increase of methylglyoxal can alter intracellular calcium homeostasis, we found upregulated activity of the calcium-activated protease calpain in sciatic nerves after methylglyoxal exposure. Methylglyoxal exposure altered clusters of proteins that are known as calpain substrates: ezrin in Schwann cell microvilli at the perinodal area and zonula occludens 1 in Schwann cell autotypic junctions at paranodes. Finally, treatment with the calpain inhibitor calpeptin ameliorated methylglyoxal-evoked ezrin loss and paranodal disruption in both sciatic and optic nerves. Our findings strongly suggest that elevated methylglyoxal levels and subsequent calpain activation contribute to the disruption of specialized axoglial domains along myelinated nerve fibers in neurological diseases.
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Affiliation(s)
- Ryan B Griggs
- 1 Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH, USA
| | - Leonid M Yermakov
- 1 Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH, USA
| | - Domenica E Drouet
- 1 Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH, USA
| | - Duc V M Nguyen
- 1 Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH, USA
| | - Keiichiro Susuki
- 1 Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH, USA
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Abstract
The global epidemic of prediabetes and diabetes has led to a corresponding epidemic of complications of these disorders. The most prevalent complication is neuropathy, of which distal symmetric polyneuropathy (for the purpose of this Primer, referred to as diabetic neuropathy) is very common. Diabetic neuropathy is a loss of sensory function beginning distally in the lower extremities that is also characterized by pain and substantial morbidity. Over time, at least 50% of individuals with diabetes develop diabetic neuropathy. Glucose control effectively halts the progression of diabetic neuropathy in patients with type 1 diabetes mellitus, but the effects are more modest in those with type 2 diabetes mellitus. These findings have led to new efforts to understand the aetiology of diabetic neuropathy, along with new 2017 recommendations on approaches to prevent and treat this disorder that are specific for each type of diabetes. In parallel, new guidelines for the treatment of painful diabetic neuropathy using distinct classes of drugs, with an emphasis on avoiding opioid use, have been issued. Although our understanding of the complexities of diabetic neuropathy has substantially evolved over the past decade, the distinct mechanisms underlying neuropathy in type 1 and type 2 diabetes remains unknown. Future discoveries on disease pathogenesis will be crucial to successfully address all aspects of diabetic neuropathy, from prevention to treatment.
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11
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Feldman EL, Callaghan BC, Pop-Busui R, Zochodne DW, Wright DE, Bennett DL, Bril V, Russell JW, Viswanathan V. Diabetic neuropathy. Nat Rev Dis Primers 2019; 5:42. [PMID: 31197183 PMCID: PMC7096070 DOI: 10.1038/s41572-019-0097-9] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The global epidemic of prediabetes and diabetes has led to a corresponding epidemic of complications of these disorders. The most prevalent complication is neuropathy, of which distal symmetric polyneuropathy (for the purpose of this Primer, referred to as diabetic neuropathy) is very common. Diabetic neuropathy is a loss of sensory function beginning distally in the lower extremities that is also characterized by pain and substantial morbidity. Over time, at least 50% of individuals with diabetes develop diabetic neuropathy. Glucose control effectively halts the progression of diabetic neuropathy in patients with type 1 diabetes mellitus, but the effects are more modest in those with type 2 diabetes mellitus. These findings have led to new efforts to understand the aetiology of diabetic neuropathy, along with new 2017 recommendations on approaches to prevent and treat this disorder that are specific for each type of diabetes. In parallel, new guidelines for the treatment of painful diabetic neuropathy using distinct classes of drugs, with an emphasis on avoiding opioid use, have been issued. Although our understanding of the complexities of diabetic neuropathy has substantially evolved over the past decade, the distinct mechanisms underlying neuropathy in type 1 and type 2 diabetes remains unknown. Future discoveries on disease pathogenesis will be crucial to successfully address all aspects of diabetic neuropathy, from prevention to treatment.
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Affiliation(s)
- Eva L. Feldman
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA.,
| | | | - Rodica Pop-Busui
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes (MEND), University of Michigan, Ann Arbor, MI, USA
| | - Douglas W. Zochodne
- Division of Neurology, Department of Medicine and the Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Douglas E. Wright
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS, USA
| | - David L. Bennett
- Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, UK
| | - Vera Bril
- Division of Neurology, Department of Medicine, University of Toronto and University Health Network, Toronto, Ontario, Canada.,Institute for Research and Medical Consultations, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
| | - James W. Russell
- Department of Neurology, University of Maryland and VA Maryland Health Care System, Baltimore, MD, USA
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12
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Sandström J, Kratschmar DV, Broyer A, Poirot O, Marbet P, Chantong B, Zufferey F, Dos Santos T, Boccard J, Chrast R, Odermatt A, Monnet-Tschudi F. In vitro models to study insulin and glucocorticoids modulation of trimethyltin (TMT)-induced neuroinflammation and neurodegeneration, and in vivo validation in db/db mice. Arch Toxicol 2019; 93:1649-1664. [PMID: 30993381 DOI: 10.1007/s00204-019-02455-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 04/09/2019] [Indexed: 02/06/2023]
Abstract
Brain susceptibility to a neurotoxic insult may be increased in a compromised health status, such as metabolic syndrome. Both metabolic syndrome and exposure to trimethyltin (TMT) are known to promote neurodegeneration. In combination the two factors may elicit additive or compensatory/regulatory mechanisms. Combined effects of TMT exposure (0.5-1 μM) and mimicked metabolic syndrome-through modulation of insulin and glucocorticoid (GC) levels-were investigated in three models: tridimensional rat brain cell cultures for neuron-glia effects; murine microglial cell line BV-2 for a mechanistic analysis of microglial reactivity; and db/db mice as an in vivo model of metabolic syndrome. In 3D cultures, low insulin condition significantly exacerbated TMT's effect on GABAergic neurons and promoted TMT-induced neuroinflammation, with increased expression of cytokines and of the regulator of intracellular GC activity, 11β-hydroxysteroid dehydrogenase 1 (11β-Hsd1). Microglial reactivity increased upon TMT exposure in medium combining low insulin and high GC. These results were corroborated in BV-2 microglial cells where lack of insulin exacerbated the TMT-induced increase in 11β-Hsd1 expression. Furthermore, TMT-induced microglial reactivity seems to depend on mineralocorticoid receptor activation. In diabetic BKS db mice, a discrete exacerbation of TMT neurotoxic effects on GABAergic neurons was observed, together with an increase of interleukin-6 (IL-6) and of basal 11β-Hsd1 expression as compared to controls. These results suggest only minor additive effects of the two brain insults, neurotoxicant TMT exposure and metabolic syndrome conditions, where 11β-Hsd1 appears to play a key role in the regulation of neuroinflammation and of its protective or neurodegenerative consequences.
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Affiliation(s)
- Jenny Sandström
- Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 7, 1005, Lausanne, Switzerland.,Swiss Centre for Applied Human Toxicology, Basel, Switzerland
| | - Denise V Kratschmar
- Division of Molecular and Systems Toxicology, Department of Pharmaceutical Sciences, University of Basel, Basel, Switzerland.,Swiss Centre for Applied Human Toxicology, Basel, Switzerland
| | - Alexandra Broyer
- Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 7, 1005, Lausanne, Switzerland
| | - Olivier Poirot
- Department of Medical Genetics, University of Lausanne, Lausanne, Switzerland
| | - Philippe Marbet
- Division of Molecular and Systems Toxicology, Department of Pharmaceutical Sciences, University of Basel, Basel, Switzerland
| | - Boonrat Chantong
- Division of Molecular and Systems Toxicology, Department of Pharmaceutical Sciences, University of Basel, Basel, Switzerland
| | - Fanny Zufferey
- Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 7, 1005, Lausanne, Switzerland.,Swiss Centre for Applied Human Toxicology, Basel, Switzerland
| | - Tania Dos Santos
- Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 7, 1005, Lausanne, Switzerland
| | - Julien Boccard
- Swiss Centre for Applied Human Toxicology, Basel, Switzerland.,School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland
| | - Roman Chrast
- Department of Medical Genetics, University of Lausanne, Lausanne, Switzerland.,Department of Neuroscience and Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden
| | - Alex Odermatt
- Division of Molecular and Systems Toxicology, Department of Pharmaceutical Sciences, University of Basel, Basel, Switzerland.,Swiss Centre for Applied Human Toxicology, Basel, Switzerland
| | - Florianne Monnet-Tschudi
- Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 7, 1005, Lausanne, Switzerland. .,Swiss Centre for Applied Human Toxicology, Basel, Switzerland.
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13
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Borire AA, Issar T, Kwai NC, Visser LH, Simon NG, Poynten AM, Kiernan MC, Krishnan AV. Correlation between markers of peripheral nerve function and structure in type 1 diabetes. Diabetes Metab Res Rev 2018; 34:e3028. [PMID: 29858541 DOI: 10.1002/dmrr.3028] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Revised: 05/20/2018] [Accepted: 05/28/2018] [Indexed: 12/19/2022]
Abstract
BACKGROUND Clinical and experimental studies in patients with type 1 and type 2 diabetes have demonstrated changes in ion channel function and nerve structure. In this study, we investigated the relationship between axonal dysfunction and morphological change in diabetic polyneuropathy by using neuromuscular ultrasound and nerve excitability techniques. We also explored possible differences in this relationship between type 1 and type 2 diabetes. METHODS Nerve ultrasound and corresponding motor excitability studies were undertaken in 110 diabetes patients (50 type 1; 60 type 2) and 60 age-matched controls (30 for each group). Neuropathy severity was assessed by using total neuropathy score. Median and tibial nerve cross-sectional areas were measured at nonentrapment sites by using high-resolution linear probe. RESULTS Median and tibial nerve cross-sectional areas were significantly higher in diabetes patients compared with controls: type 1 (median = 7.6 ± 0.2 mm2 vs 6.3 ± 0.1 mm2 ; tibial = 14.5 ± 0.7 mm2 vs 10.8 ± 0.3 mm2 , P < .05) and type 2 (median = 9.1 ± 0.3 mm2 vs 7.2 ± 0.1 mm2 ; tibial = 18.5 ± 1.0 mm2 vs 12.8 ± 0.5 mm2 , P < .05). In the type 1 cohort, significant correlations were found between nerve cross-sectional area and excitability parameters including resting current-threshold slope (median: r = 0.523, P < .0001; tibial: r = -0.571, P = .004) and depolarizing threshold electrotonus at 90 to 100 ms (median: 0.424, P < .01; tibial: r = 0.435, P = .030). In contrast, there was no relationship between excitability values and nerve cross-sectional area in the type 2 cohort. CONCLUSIONS This study has identified correlation between markers of axonal membrane function and structural abnormalities in peripheral nerves of type 1 diabetes patients. The differential relationship in nerve function and structure between type 1 and type 2 diabetes provides clinical evidence that different pathophysiological mechanisms underlie the development of neuropathy in these patient groups.
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Affiliation(s)
- Adeniyi A Borire
- University of New South Wales, Prince of Wales Clinical School, Sydney, New South Wales, Australia
| | - Tushar Issar
- University of New South Wales, Prince of Wales Clinical School, Sydney, New South Wales, Australia
| | - Natalie C Kwai
- University of New South Wales, School of Medical Sciences, Sydney, New South Wales, Australia
| | - Leo H Visser
- St Elisabeth Ziekenhuis, Tilburg, The Netherlands
| | - Neil G Simon
- University of New South Wales, St Vincent's Clinical School, Sydney, New South Wales, Australia
- University of Sydney, Brain and Mind Centre, Sydney, New South Wales, Australia
| | - Ann M Poynten
- Prince of Wales Hospital, Department of Endocrinology, Sydney, New South Wales, Australia
| | - Matthew C Kiernan
- University of Sydney, Brain and Mind Centre, Sydney, New South Wales, Australia
| | - Arun V Krishnan
- University of New South Wales, Prince of Wales Clinical School, Sydney, New South Wales, Australia
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14
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Gu HF, Li N, Tang YL, Yan CQ, Shi Z, Yi SN, Zhou HL, Liao DF, OuYang XP. Nicotinate-curcumin ameliorates cognitive impairment in diabetic rats by rescuing autophagic flux in CA1 hippocampus. CNS Neurosci Ther 2018; 25:430-441. [PMID: 30260594 DOI: 10.1111/cns.13059] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Revised: 08/09/2018] [Accepted: 08/15/2018] [Indexed: 12/27/2022] Open
Abstract
INTRODUCTION Our previous study has confirmed that a novel curcumin derivate nicotinate-curcumin (NC) can facilitate autophagic flux in THP-1 cells induced by oxidized low-density lipoprotein. AIMS Given that autophagy plays critical roles in neurodegenerative diseases, the present study was carried out to investigate whether NC can improve cognitive function of rats with diabetes mellitus (DM) via restoring autophagic flux in CA1 hippocampus. RESULTS Our results showed that NC treatment improved cognitive deficit and attenuated neuronal loss as well as cellular ultrastructure impairment in the CA1 region of DM rats induced by streptozotocin. Moreover, NC lowered the expressions of the apoptosis-related proteins Bcl-2, Bax, Cyt-c, and cleaved Caspase-3. Notably, NC treatment reversed autophagic flux impairment as evidenced by the deceases in LC3-II and p62 protein levels, and autophagosome accumulation in the hippocampal CA1 region of DM rats. However, these protective effects of NC were abolished by cotreatment with 3-methyladenine (an autophagy inhibitor) and chloroquine (an autophagic flux inhibitor), respectively. Furthermore, NC treatment decreased the expressions of phosphorylated mammalian target of rapamycin (mTOR) and p70 ribosomal protein S6 kinase (p70S6k) proteins in the CA1 region of DM rats. CONCLUSIONS These results indicate that NC ameliorates DM-induced cognitive function impairment via restoring autophagic flux might by inhibiting mTOR/p70S6k activation in the CA1 region, and NC may be a promising agent for diabetic cognitive dysfunction prevention and treatment.
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Affiliation(s)
- Hong-Feng Gu
- Department of Physiology & Institute of Neuroscience, University of South China, Hengyang, China
| | - Na Li
- Department of Physiology & Institute of Neuroscience, University of South China, Hengyang, China
| | - Ya-Ling Tang
- Department of Physiology & Institute of Neuroscience, University of South China, Hengyang, China
| | - Can-Qun Yan
- Department of Endocrine of the Second Affiliated Hospital, University of South China, Hengyang, China
| | - Zhe Shi
- Division of Stem Cell Regulation and Application, State Key Laboratory of Chinese Medicine Powder and Medicine Innovation in Hunan, Hunan University of Chinese Medicine, Changsha, China
| | - Si-Ni Yi
- Department of Endocrine of the Second Affiliated Hospital, University of South China, Hengyang, China
| | - Hao-Ling Zhou
- Department of Endocrine of the Second Affiliated Hospital, University of South China, Hengyang, China
| | - Duan-Fang Liao
- Division of Stem Cell Regulation and Application, State Key Laboratory of Chinese Medicine Powder and Medicine Innovation in Hunan, Hunan University of Chinese Medicine, Changsha, China
| | - Xin-Ping OuYang
- Department of Physiology & Institute of Neuroscience, University of South China, Hengyang, China
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15
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Suarez-Mendez S, Tovilla-Zárate CA, Juárez-Rojop IE, Bermúdez-Ocaña DY. Erythropoietin: A potential drug in the management of diabetic neuropathy. Biomed Pharmacother 2018; 105:956-961. [PMID: 30021390 DOI: 10.1016/j.biopha.2018.06.068] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 06/06/2018] [Accepted: 06/13/2018] [Indexed: 12/28/2022] Open
Abstract
Erythropoietin (EPO) is required for promoting the progress of erythroid differentiation. However, the discovery of EPO and the EPO receptor (EPOR) in the nervous system may contribute to new treatment strategies for the use of EPO in neurodegenerative disorders. Diabetic neuropathy is a neurodegenerative disease that affects a large proportion of diabetic patients and results in alterations in functionality, mood and sleep. The pathogenic mechanisms generating diabetic neuropathy involve: Schwannopathy, polyol pathway activity, advanced glycation end-products (AGEs) accumulation, protein kinase C (PKC) activity, increased hexosamine pathway flux, oxidative stress, nitric oxide and inflammation. In this sense, evidence from both clinical and experimental studies indicates that EPO may reverse diabetic neuropathy through an antioxidant action by decreasing pro-inflammatory cytokines, restoring Na+/K+-ATPase activity, and blocking the generation of pro-apoptotic proteins. The aim of this review is to discuss the neuroprotector effect of EPO on pathogenic mechanisms of diabetic neuropathy.
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Affiliation(s)
- Samuel Suarez-Mendez
- División Académica de Ciencias de la Salud, Universidad Juárez Autónoma de Tabasco, Av. Gregorio Méndez 2838-A. Col. Tamulté, C.P. 86100, Villahermosa, Tabasco, Mexico
| | - Carlos Alfonso Tovilla-Zárate
- División Académica Multidisciplinaria de Comalcalco, Universidad Juárez Autónoma de Tabasco, Ranchería Sur, Cuarta Sección, C.P. 86650, Comalcalco, Tabasco, Mexico
| | - Isela E Juárez-Rojop
- División Académica de Ciencias de la Salud, Universidad Juárez Autónoma de Tabasco, Av. Gregorio Méndez 2838-A. Col. Tamulté, C.P. 86100, Villahermosa, Tabasco, Mexico.
| | - Deysi Y Bermúdez-Ocaña
- División Académica Multidisciplinaria de Comalcalco, Universidad Juárez Autónoma de Tabasco, Ranchería Sur, Cuarta Sección, C.P. 86650, Comalcalco, Tabasco, Mexico.
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16
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Yermakov LM, Drouet DE, Griggs RB, Elased KM, Susuki K. Type 2 Diabetes Leads to Axon Initial Segment Shortening in db/db Mice. Front Cell Neurosci 2018; 12:146. [PMID: 29937715 PMCID: PMC6002488 DOI: 10.3389/fncel.2018.00146] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 05/14/2018] [Indexed: 01/09/2023] Open
Abstract
Cognitive and mood impairments are common central nervous system complications of type 2 diabetes, although the neuronal mechanism(s) remains elusive. Previous studies focused mainly on neuronal inputs such as altered synaptic plasticity. Axon initial segment (AIS) is a specialized functional domain within neurons that regulates neuronal outputs. Structural changes of AIS have been implicated as a key pathophysiological event in various psychiatric and neurological disorders. Here we evaluated the structural integrity of the AIS in brains of db/db mice, an established animal model of type 2 diabetes associated with cognitive and mood impairments. We assessed the AIS before (5 weeks of age) and after (10 weeks) the development of type 2 diabetes, and after daily exercise treatment of diabetic condition. We found that the development of type 2 diabetes is associated with significant AIS shortening in both medial prefrontal cortex and hippocampus, as evident by immunostaining of the AIS structural protein βIV spectrin. AIS shortening occurs in the absence of altered neuronal and AIS protein levels. We found no change in nodes of Ranvier, another neuronal functional domain sharing a molecular organization similar to the AIS. This is the first study to identify AIS alteration in type 2 diabetes condition. Since AIS shortening is known to lower neuronal excitability, our results may provide a new avenue for understanding and treating cognitive and mood impairments in type 2 diabetes.
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Affiliation(s)
- Leonid M Yermakov
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH, United States
| | - Domenica E Drouet
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH, United States
| | - Ryan B Griggs
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH, United States
| | - Khalid M Elased
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, OH, United States
| | - Keiichiro Susuki
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH, United States
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17
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Doppler K, Frank F, Koschker AC, Reiners K, Sommer C. Nodes of Ranvier in skin biopsies of patients with diabetes mellitus. J Peripher Nerv Syst 2017; 22:182-190. [DOI: 10.1111/jns.12224] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Revised: 05/29/2017] [Accepted: 05/30/2017] [Indexed: 01/22/2023]
Affiliation(s)
- Kathrin Doppler
- Department of Neurology; University Hospital Würzburg; Würzburg Germany
| | - Franziska Frank
- Department of Neurology; University Hospital Würzburg; Würzburg Germany
| | - Ann-Cathrin Koschker
- Endocrinology and Diabetes Unit, Department of Medicine I; University of Würzburg; Würzburg Germany
| | - Karlheinz Reiners
- Department of Neurology; University Hospital Würzburg; Würzburg Germany
| | - Claudia Sommer
- Department of Neurology; University Hospital Würzburg; Würzburg Germany
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18
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Feldman EL, Nave KA, Jensen TS, Bennett DLH. New Horizons in Diabetic Neuropathy: Mechanisms, Bioenergetics, and Pain. Neuron 2017; 93:1296-1313. [PMID: 28334605 PMCID: PMC5400015 DOI: 10.1016/j.neuron.2017.02.005] [Citation(s) in RCA: 518] [Impact Index Per Article: 74.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 02/02/2017] [Accepted: 02/02/2017] [Indexed: 12/13/2022]
Abstract
Pre-diabetes and diabetes are a global epidemic, and the associated neuropathic complications create a substantial burden on both the afflicted patients and society as a whole. Given the enormity of the problem and the lack of effective therapies, there is a pressing need to understand the mechanisms underlying diabetic neuropathy (DN). In this review, we present the structural components of the peripheral nervous system that underlie its susceptibility to metabolic insults and then discuss the pathways that contribute to peripheral nerve injury in DN. We also discuss systems biology insights gleaned from the recent advances in biotechnology and bioinformatics, emerging ideas centered on the axon-Schwann cell relationship and associated bioenergetic crosstalk, and the rapid expansion of our knowledge of the mechanisms contributing to neuropathic pain in diabetes. These recent advances in our understanding of DN pathogenesis are paving the way for critical mechanism-based therapy development.
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Affiliation(s)
- Eva L Feldman
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute for Experimental Medicine, 37075 Göttingen, Germany
| | - Troels S Jensen
- Department of Neurology and Danish Pain Research Center, Aarhus University, 8000 Aarhus C, Denmark
| | - David L H Bennett
- Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford OX3 9DU, UK
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19
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Sung JY, Tani J, Chang TS, Lin CSY. Uncovering sensory axonal dysfunction in asymptomatic type 2 diabetic neuropathy. PLoS One 2017; 12:e0171223. [PMID: 28182728 PMCID: PMC5300160 DOI: 10.1371/journal.pone.0171223] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 01/17/2017] [Indexed: 12/02/2022] Open
Abstract
This study investigated sensory and motor nerve excitability properties to elucidate the development of diabetic neuropathy. A total of 109 type 2 diabetes patients were recruited, and 106 were analyzed. According to neuropathy severity, patients were categorized into G0, G1, and G2+3 groups using the total neuropathy score-reduced (TNSr). Patients in the G0 group were asymptomatic and had a TNSr score of 0. Sensory and motor nerve excitability data from diabetic patients were compared with data from 33 healthy controls. Clinical assessment, nerve conduction studies, and sensory and motor nerve excitability testing data were analyzed to determine axonal dysfunction in diabetic neuropathy. In the G0 group, sensory excitability testing revealed increased stimulus for the 50% sensory nerve action potential (P<0.05), shortened strength-duration time constant (P<0.01), increased superexcitability (P<0.01), decreased subexcitability (P<0.05), decreased accommodation to depolarizing current (P<0.01), and a trend of decreased accommodation to hyperpolarizing current in threshold electrotonus. All the changes progressed into G1 (TNSr 1–8) and G2+3 (TNSr 9–24) groups. In contrast, motor excitability only had significantly increased stimulus for the 50% compound motor nerve action potential (P<0.01) in the G0 group. This study revealed that the development of axonal dysfunction in sensory axons occurred prior to and in a different fashion from motor axons. Additionally, sensory nerve excitability tests can detect axonal dysfunction even in asymptomatic patients. These insights further our understanding of diabetic neuropathy and enable the early detection of sensory axonal abnormalities, which may provide a basis for neuroprotective therapeutic approaches.
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Affiliation(s)
- Jia-Ying Sung
- Department of Neurology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.,Department of Neurology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Jowy Tani
- Department of Neurology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.,Ph.D. Program for Neural Regenerative Medicine, College of Medical Science and Technology, Taipei Medical University and National Health Research Institutes
| | - Tsui-San Chang
- Department of Neurology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Cindy Shin-Yi Lin
- Neural Regenerative Medicine, College of Medical Science and Technology, Taipei Medical University and National Health Research Institutes.,Translational Neuroscience, Department of Physiology, School of Medicine Science, Faculty of Medicine, University of New South Wales, Sydney, Australia
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20
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Otani Y, Yermakov LM, Dupree JL, Susuki K. Chronic peripheral nerve compression disrupts paranodal axoglial junctions. Muscle Nerve 2016; 55:544-554. [PMID: 27463510 DOI: 10.1002/mus.25273] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2016] [Revised: 07/13/2016] [Accepted: 07/26/2016] [Indexed: 11/06/2022]
Abstract
INTRODUCTION Peripheral nerves are often exposed to mechanical stress leading to compression neuropathies. The pathophysiology underlying nerve dysfunction by chronic compression is largely unknown. METHODS We analyzed molecular organization and fine structures at and near nodes of Ranvier in a compression neuropathy model in which a silastic tube was placed around the mouse sciatic nerve. RESULTS Immunofluorescence study showed that clusters of cell adhesion complex forming paranodal axoglial junctions were dispersed and overlapped frequently with juxtaparanodal components. These paranodal changes occurred without internodal myelin damage. The distribution and pattern of paranodal disruption suggests that these changes are the direct result of mechanical stress. Electron microscopy confirmed loss of paranodal axoglial junctions. CONCLUSIONS Our data show that chronic nerve compression disrupts paranodal junctions and axonal domains required for proper peripheral nerve function. These results provide important clues toward better understanding of the pathophysiology underlying nerve dysfunction in compression neuropathies. Muscle Nerve 55: 544-554, 2017.
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Affiliation(s)
- Yoshinori Otani
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, 3640 Colonel Glenn Highway, Dayton, Ohio, 45435, USA
| | - Leonid M Yermakov
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, 3640 Colonel Glenn Highway, Dayton, Ohio, 45435, USA
| | - Jeffrey L Dupree
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Keiichiro Susuki
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, 3640 Colonel Glenn Highway, Dayton, Ohio, 45435, USA
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21
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Lv J, Wang M, Xia M. Na v1.7 and Na v1.8: Diabetes-induced Changes in Primary Sensory Neurons in Rats. J Neurogastroenterol Motil 2016; 22:707-708. [PMID: 27703115 PMCID: PMC5056582 DOI: 10.5056/jnm16110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Jianlin Lv
- The First Affiliated Hospital of Guangxi University of Chinese Medicine, Nanning, China
| | - Mingjie Wang
- The First Affiliated Hospital of Guangxi University of Chinese Medicine, Nanning, China.,School of Orthopaedics, Guangxi University of Chinese Medicine, Nanning, China
| | - Meng Xia
- Institute of foundational research of Chinese Medicine, Guangxi University of Chinese Medicine, Nanning, China
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22
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Sun Z, Wu X, Li W, Peng H, Shen X, Ma L, Liu H, Li H. RhoA/rock signaling mediates peroxynitrite-induced functional impairment of Rat coronary vessels. BMC Cardiovasc Disord 2016; 16:193. [PMID: 27724862 PMCID: PMC5057502 DOI: 10.1186/s12872-016-0372-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 09/28/2016] [Indexed: 01/03/2023] Open
Abstract
Background Diabetes-induced vascular dysfunction may arise from reduced nitric oxide (NO) availability, following interaction with superoxide to form peroxynitrite. Peroxynitrite can induce formation of 3-nitrotyrosine-modified proteins. RhoA/ROCK signaling is also involved in diabetes-induced vascular dysfunction. The study aimed to investigate possible links between Rho/ROCK signaling, hyperglycemia, and peroxynitrite in small coronary arteries. Methods Rat small coronary arteries were exposed to normal (NG; 5.5 mM) or high (HG; 23 mM) D-glucose. Vascular ring constriction to 3 mM 4-aminopyridine and dilation to 1 μM forskolin were measured. Protein expression (immunohistochemistry and western blot), mRNA expression (real-time PCR), and protein activity (luminescence-based G-LISA and kinase activity spectroscopy assays) of RhoA, ROCK1, and ROCK2 were determined. Results Vascular ring constriction and dilation were smaller in the HG group than in the NG group (P < 0.05); inhibition of RhoA or ROCK partially reversed the effects of HG. Peroxynitrite impaired vascular ring constriction/dilation; this was partially reversed by inhibition of RhoA or ROCK. Protein and mRNA expressions of RhoA, ROCK1, and ROCK2 were higher under HG than NG (P < 0.05). This HG-induced upregulation was attenuated by inhibition of RhoA or ROCK (P < 0.05). HG increased RhoA, ROCK1, and ROCK2 activity (P < 0.05). Peroxynitrite also enhanced RhoA, ROCK1, and ROCK2 activity; these actions were partially inhibited by 100 μM urate (peroxynitrite scavenger). Exogenous peroxynitrite had no effect on the expression of the voltage-dependent K+ channels 1.2 and 1.5. Conclusions Peroxynitrite-induced coronary vascular dysfunction may be mediated, at least in part, through increased expressions and activities of RhoA, ROCK1, and ROCK2.
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Affiliation(s)
- Zhijun Sun
- Department of Heart Center, Capital Medical University Affiliated Beijing Friendship Hospital, Beijing, China
| | - Xing Wu
- Department of Heart Center, Capital Medical University Affiliated Beijing Friendship Hospital, Beijing, China
| | - Weiping Li
- Department of Heart Center, Capital Medical University Affiliated Beijing Friendship Hospital, Beijing, China
| | - Hui Peng
- Department of Heart Center, Capital Medical University Affiliated Beijing Friendship Hospital, Beijing, China
| | - Xuhua Shen
- Department of Heart Center, Capital Medical University Affiliated Beijing Friendship Hospital, Beijing, China
| | - Lu Ma
- Beijing Key Laboratory of Metabolic Disturbance Related Cardiovascular Disease, Beijing, People's Republic of China
| | - Huirong Liu
- Beijing Key Laboratory of Metabolic Disturbance Related Cardiovascular Disease, Beijing, People's Republic of China
| | - Hongwei Li
- Department of Heart Center, Capital Medical University Affiliated Beijing Friendship Hospital, Beijing, China.
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23
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Griggs RB, Yermakov LM, Susuki K. Formation and disruption of functional domains in myelinated CNS axons. Neurosci Res 2016; 116:77-87. [PMID: 27717670 DOI: 10.1016/j.neures.2016.09.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 09/19/2016] [Accepted: 09/23/2016] [Indexed: 12/15/2022]
Abstract
Communication in the central nervous system (CNS) occurs through initiation and propagation of action potentials at excitable domains along axons. Action potentials generated at the axon initial segment (AIS) are regenerated at nodes of Ranvier through the process of saltatory conduction. Proper formation and maintenance of the molecular structure at the AIS and nodes are required for sustaining conduction fidelity. In myelinated CNS axons, paranodal junctions between the axolemma and myelinating oligodendrocytes delineate nodes of Ranvier and regulate the distribution and localization of specialized functional elements, such as voltage-gated sodium channels and mitochondria. Disruption of excitable domains and altered distribution of functional elements in CNS axons is associated with demyelinating diseases such as multiple sclerosis, and is likely a mechanism common to other neurological disorders. This review will provide a brief overview of the molecular structure of the AIS and nodes of Ranvier, as well as the distribution of mitochondria in myelinated axons. In addition, this review highlights important structural and functional changes within myelinated CNS axons that are associated with neurological dysfunction.
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Affiliation(s)
- Ryan B Griggs
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH, United States
| | - Leonid M Yermakov
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH, United States
| | - Keiichiro Susuki
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH, United States.
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Gonzalez S, Berthelot J, Jiner J, Perrin-Tricaud C, Fernando R, Chrast R, Lenaers G, Tricaud N. Blocking mitochondrial calcium release in Schwann cells prevents demyelinating neuropathies. J Clin Invest 2016; 126:1023-38. [PMID: 26878172 DOI: 10.1172/jci84505] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 12/18/2015] [Indexed: 02/06/2023] Open
Abstract
Schwann cells produce myelin sheath around peripheral nerve axons. Myelination is critical for rapid propagation of action potentials, as illustrated by the large number of acquired and hereditary peripheral neuropathies, such as diabetic neuropathy or Charcot-Marie-Tooth diseases, that are commonly associated with a process of demyelination. However, the early molecular events that trigger the demyelination program in these diseases remain unknown. Here, we used virally delivered fluorescent probes and in vivo time-lapse imaging in a mouse model of demyelination to investigate the underlying mechanisms of the demyelination process. We demonstrated that mitochondrial calcium released by voltage-dependent anion channel 1 (VDAC1) after sciatic nerve injury triggers Schwann cell demyelination via ERK1/2, p38, JNK, and c-JUN activation. In diabetic mice, VDAC1 activity was altered, resulting in a mitochondrial calcium leak in Schwann cell cytoplasm, thereby priming the cell for demyelination. Moreover, reduction of mitochondrial calcium release, either by shRNA-mediated VDAC1 silencing or pharmacological inhibition, prevented demyelination, leading to nerve conduction and neuromuscular performance recovery in rodent models of diabetic neuropathy and Charcot-Marie-Tooth diseases. Therefore, this study identifies mitochondria as the early key factor in the molecular mechanism of peripheral demyelination and opens a potential opportunity for the treatment of demyelinating peripheral neuropathies.
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Wang XC, Wang S, Zhang M, Gao F, Yin C, Li H, Zhang Y, Hu SJ, Duan JH. Α-Dendrotoxin-sensitive Kv1 channels contribute to conduction failure of polymodal nociceptive C-fibers from rat coccygeal nerve. J Neurophysiol 2015; 115:947-57. [PMID: 26609114 DOI: 10.1152/jn.00786.2014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 11/23/2015] [Indexed: 01/20/2023] Open
Abstract
It is known that some patients with diabetic neuropathy are usually accompanied by abnormal painful sensations. Evidence has accumulated that diabetic neuropathic pain is associated with the hyperexcitability of peripheral nociceptors. Previously, we demonstrated that reduced conduction failure of polymodal nociceptive C-fibers and enhanced voltage-dependent sodium currents of small dorsal root ganglion (DRG) neurons contribute to diabetic hyperalgesia. To further investigate whether and how potassium channels are involved in the conduction failure, α-dendrotoxin (α-DTX), a selective blocker of the low-threshold sustained Kv1 channel, was chosen to examine its functional capability in modulating the conduction properties of polymodal nociceptive C-fibers and the excitability of sensory neurons. We found that α-DTX reduced the conduction failure of C-fibers from coccygeal nerve in vivo accompanied by an increased initial conduction velocity but a decreased activity-dependent slowing of conduction velocity. In addition, the number of APs evoked by step currents was significantly enhanced after the treatment with α-DTX in small-diameter sensory neurons. Further study of the mechanism indicates α-DTX-sensitive K(+) current significantly reduced and the activation of this current in peak and steady state shifted to depolarization for diabetic neurons. Expression of Kv channel subunits Kv1.2 and Kv1.6 was downregulated in both small dorsal root ganglion neurons and peripheral C-fibers. Taken together, these results suggest that α-DTX-sensitive Kv1 channels might play an important role in regulating the conduction properties of polymodal nociceptive C-fibers and firing properties of sensory neurons.
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Affiliation(s)
- Xiu-Chao Wang
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China; Department of Psychology, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Shan Wang
- State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Ming Zhang
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Fang Gao
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Chun Yin
- Team Nine, Brigade of Cadets, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Hao Li
- Team Nine, Brigade of Cadets, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Ying Zhang
- Department of Cardiovascular Surgery, Xijing Hospital, Xi'an, People's Republic of China; and
| | - San-Jue Hu
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Jian-Hong Duan
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China; State Key Laboratory of Military Stomatology, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China
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26
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Lauria G, Ziegler D, Malik R, Merkies ISJ, Waxman SG, Faber CG. The role of sodium channels in painful diabetic and idiopathic neuropathy. Curr Diab Rep 2014; 14:538. [PMID: 25142720 DOI: 10.1007/s11892-014-0538-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Painful neuropathies are frequently encountered in clinical practice as an early or late complication of several systemic disorders. Among them, diabetes is one of the most important due to its epidemiology and the relevance for regulatory agencies in the assessment of efficacy of new analgesics. However, the presentation and course of painful neuropathies, as well as the response to available drugs, are highly variable and unpredictable, posing significant challenges in the management of patients. Experimental and clinical studies have suggested that polymorphisms and mutations in pain-related genes are involved in the facilitation or inhibition of nociception, and might modulate neuropathic pain and the response to analgesics in patients. Voltage-gated sodium channel genes are among the most relevant, due to the key role of these membrane proteins in the physiology of nociception and their involvement in the pathogenesis of idiopathic painful small fiber neuropathies. These compelling features make sodium channel candidate targets for a novel approach to painful diabetic and idiopathic neuropathies, which will hopefully allow a new classification of patients and more effective targeted treatments.
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Affiliation(s)
- Giuseppe Lauria
- Neuroalgology and Headache Unit, IRCCS Foundation "Carlo Besta" Neurological Institute, Via Celoria, 11, 20133, Milan, Italy,
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Gu Y, Gu C. Physiological and pathological functions of mechanosensitive ion channels. Mol Neurobiol 2014; 50:339-47. [PMID: 24532247 DOI: 10.1007/s12035-014-8654-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 01/23/2014] [Indexed: 12/11/2022]
Abstract
Rapid sensation of mechanical stimuli is often mediated by mechanosensitve ion channels. Their opening results from conformational changes induced by mechanical forces. It leads to membrane permeation of selected ions and thereby to electrical signaling. Newly identified mechanosensitive ion channels are emerging at an astonishing rate, including some that are traditionally assigned for completely different functions. In this review, we first provide a brief overview of ion channels that are known to play a role in mechanosensation. Next, we focus on three representative ones, including the transient receptor potential channel V4 (TRPV4), Kv1.1 voltage-gated potassium (Kv) channel, and Piezo channels. Their structures, biophysical properties, expression and targeting patterns, and physiological functions are highlighted. The potential role of their mechanosensation in related diseases is further discussed. In sum, mechanosensation appears to be achieved in a variety of ways by different proteins and plays a fundamental role in the function of various organs under normal and abnormal conditions.
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Affiliation(s)
- Yuanzheng Gu
- Department of Neuroscience, Ohio State University, 182 Rightmire Hall, 1060 Carmack Road, Columbus, OH, USA
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28
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Zenker J, Ziegler D, Chrast R. Novel pathogenic pathways in diabetic neuropathy. Trends Neurosci 2013; 36:439-49. [PMID: 23725712 DOI: 10.1016/j.tins.2013.04.008] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2012] [Revised: 04/20/2013] [Accepted: 04/24/2013] [Indexed: 02/08/2023]
Abstract
Diabetic peripheral neuropathy (DPN) is a common complication affecting more than one third of diabetes mellitus (DM) patients. Although all cellular components participating in peripheral nerve function are exposed to and affected by the metabolic consequences of DM, nodal regions, areas of intense interactions between Schwann cells and axons, may be particularly sensitive to DM-induced alterations. Nodes are enriched in insulin receptors, glucose transporters, Na(+) and K(+) channels, and mitochondria, all implicated in the development and progression of DPN. Latest results particularly reinforce the idea that changes in ion-channel function and energy metabolism, both of which depend on axon-glia crosstalk, are among the important contributors to DPN. These insights provide a basis for new therapeutic approaches aimed at delaying or reversing DPN.
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Affiliation(s)
- Jennifer Zenker
- Department of Medical Genetics, University of Lausanne, 1005 Lausanne, Switzerland
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Chang KJ, Rasband MN. Excitable domains of myelinated nerves: axon initial segments and nodes of Ranvier. CURRENT TOPICS IN MEMBRANES 2013; 72:159-92. [PMID: 24210430 DOI: 10.1016/b978-0-12-417027-8.00005-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Neurons are highly polarized cells. They can be subdivided into at least two structurally and functionally distinct domains: somatodendritic and axonal domains. The somatodendritic domain receives and integrates upstream input signals, and the axonal domain generates and relays outputs in the form of action potentials to the downstream target. Demand for quick response to the harsh surroundings prompted evolution to equip vertebrates' neurons with a remarkable glia-derived structure called myelin. Not only Insulating the axon, myelinating glia also rearrange the axonal components and elaborate functional subdomains along the axon. Proper functioning of all theses domains and subdomains is vital for a normal, efficient nervous system.
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Affiliation(s)
- Kae-Jiun Chang
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, USA
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Nadra K, Médard JJ, Quignodon L, Verheijen MHG, Desvergne B, Chrast R. Epineurial adipocytes are dispensable for Schwann cell myelination. J Neurochem 2012; 123:662-7. [PMID: 22849425 DOI: 10.1111/j.1471-4159.2012.07896.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 07/11/2012] [Accepted: 07/12/2012] [Indexed: 12/18/2022]
Abstract
Previous clinical observations and data from mouse models with defects in lipid metabolism suggested that epineurial adipocytes may play a role in peripheral nervous system myelination. We have used adipocyte-specific Lpin1 knockout mice to characterize the consequences of the presence of impaired epineurial adipocytes on the myelinating peripheral nerve. Our data revealed that the capacity of Schwann cells to establish myelin, and the functional properties of peripheral nerves, were not affected by compromised epineurial adipocytes in adipocyte-specific Lpin1 knockout mice. To evaluate the possibility that Lpin1-negative adipocytes are still able to support endoneurial Schwann cells, we also characterized sciatic nerves from mice carrying epiblast-specific deletion of peroxisome proliferator-activated receptor gamma, which develop general lipoatrophy. Interestingly, even the complete loss of adipocytes in the epineurium of peroxisome proliferator-activated receptor gamma knockout mice did not lead to detectable defects in Schwann cell myelination. However, probably as a consequence of their hyperglycemia, these mice have reduced nerve conduction velocity, thus mimicking the phenotype observed under diabetic condition. Together, our data indicate that while adipocytes, as regulators of lipid and glucose homeostasis, play a role in nerve function, their presence in epineurium is not essential for establishment or maintenance of proper myelin.
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Affiliation(s)
- Karim Nadra
- Department of Medical Genetics, University of Lausanne, Lausanne, Switzerland
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