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Jacob S. Treating myasthenia gravis beyond the eye clinic. Eye (Lond) 2024:10.1038/s41433-024-03133-x. [PMID: 38789789 DOI: 10.1038/s41433-024-03133-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Revised: 02/17/2024] [Accepted: 05/07/2024] [Indexed: 05/26/2024] Open
Abstract
Myasthenia gravis (MG) is one of the most well characterised autoimmune disorders affecting the neuromuscular junction with autoantibodies targeting the acetylcholine receptor (AChR) complex. The vast majority of patients present with ocular symptoms including double vision and ptosis, but may progress on to develop generalised fatiguable muscle weakness. Severe involvement of the bulbar muscles can lead to dysphagia, dysarthria and breathing difficulties which can progress to myasthenic crisis needing ventilatory support. Given the predominant ocular onset of the disease, it is important that ophthalmologists are aware of the differential diagnosis, investigations and management including evolving therapies. When the disease remains localised to the extraocular muscles (ocular MG) IgG1 and IgG3 antibodies against the AChR (including clustered AChR) are present in nearly 50% of patients. In generalised MG this is seen in nearly 90% patients. Other antibodies include those against muscle specific tyrosine kinase (MuSK) and lipoprotein receptor related protein 4 (LRP4). Even though decremental response on repetitive nerve stimulation is the most well recognised neurophysiological abnormality, single fibre electromyogram (SFEMG) in experienced hands is the most sensitive test which helps in the diagnosis. Initial treatment should be using cholinesterase inhibitors and then proceeding to immunosuppression using corticosteroids and steroid sparing drugs. Patients requiring bulbar muscle support may need rescue therapies including plasma exchange and intravenous immunoglobulin (IVIg). Newer therapeutic targets include those against the B lymphocytes, complement system, neonatal Fc receptors (FcRn) and various other elements of the immune system.
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Affiliation(s)
- Saiju Jacob
- University Hospitals Birmingham, Birmingham, UK.
- Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, UK.
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Wang B, Zhu Y, Liu D, Hu C, Zhu R. The intricate dance of non-coding RNAs in myasthenia gravis pathogenesis and treatment. Front Immunol 2024; 15:1342213. [PMID: 38605954 PMCID: PMC11007667 DOI: 10.3389/fimmu.2024.1342213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 03/11/2024] [Indexed: 04/13/2024] Open
Abstract
Myasthenia gravis (MG) stands as a perplexing autoimmune disorder affecting the neuromuscular junction, driven by a multitude of antibodies targeting postsynaptic elements. However, the mystery of MG pathogenesis has yet to be completely uncovered, and its heterogeneity also challenges diagnosis and treatment. Growing evidence shows the differential expression of non-coding RNAs (ncRNAs) in MG has played an essential role in the development of MG in recent years. Remarkably, these aberrantly expressed ncRNAs exhibit distinct profiles within diverse clinical subgroups and among patients harboring various antibody types. Furthermore, they have been implicated in orchestrating the production of inflammatory cytokines, perturbing the equilibrium of T helper 1 cells (Th1), T helper 17 cells (Th17), and regulatory T cells (Tregs), and inciting B cells to generate antibodies. Studies have elucidated that certain ncRNAs mirror the clinical severity of MG, while others may hold therapeutic significance, showcasing a propensity to return to normal levels following appropriate treatments or potentially foretelling the responsiveness to immunosuppressive therapies. Notably, the intricate interplay among these ncRNAs does not follow a linear trajectory but rather assembles into a complex network, with competing endogenous RNA (ceRNA) emerging as a prominent hub in some cases. This comprehensive review consolidates the landscape of dysregulated ncRNAs in MG, briefly delineating their pivotal role in MG pathogenesis. Furthermore, it explores their promise as prospective biomarkers, aiding in the elucidation of disease subtypes, assessment of disease severity, monitoring therapeutic responses, and as novel therapeutic targets.
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Affiliation(s)
| | | | | | | | - Ruixia Zhu
- Department of Neurology, The First Affiliated Hospital of China Medical University, Shenyang, China
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Iorio R. Myasthenia gravis: the changing treatment landscape in the era of molecular therapies. Nat Rev Neurol 2024; 20:84-98. [PMID: 38191918 DOI: 10.1038/s41582-023-00916-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/06/2023] [Indexed: 01/10/2024]
Abstract
Myasthenia gravis (MG) is an autoimmune disorder that affects the neuromuscular junction, leading to muscle weakness and fatigue. MG is caused by antibodies against the acetylcholine receptor (AChR), the muscle-specific kinase (MuSK) or other AChR-related proteins that are expressed in the postsynaptic muscle membrane. The standard therapeutic approach for MG has relied on acetylcholinesterase inhibitors, corticosteroids and immunosuppressants, which have shown good efficacy in improving MG-related symptoms in most people with the disease; however, these therapies can carry a considerable burden of long-term adverse effects. Moreover, up to 15% of individuals with MG exhibit limited or no response to these standard therapies. The emergence of molecular therapies, including monoclonal antibodies, B cell-depleting agents and chimeric antigen receptor T cell-based therapies, has the potential to revolutionize the MG treatment landscape. This Review provides a comprehensive overview of the progress achieved in molecular therapies for MG associated with AChR antibodies and MuSK antibodies, elucidating both the challenges and the opportunities these therapies present to the field. The latest developments in MG treatment are described, exploring the potential for personalized medicine approaches.
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Affiliation(s)
- Raffaele Iorio
- Department of Neuroscience, Università Cattolica del Sacro Cuore, Rome, Italy.
- Neurology Unit, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy.
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San PP, Jacob S. Role of complement in myasthenia gravis. Front Neurol 2023; 14:1277596. [PMID: 37869140 PMCID: PMC10585143 DOI: 10.3389/fneur.2023.1277596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 09/18/2023] [Indexed: 10/24/2023] Open
Abstract
Myasthenia gravis is a prototypic neuroimmune disorder with autoantibodies targeting the acetylcholine receptor complex at the neuromuscular junction. Patients present with mainly ocular muscle weakness and tend to have a generalized muscle weakness later in the clinical course. The weakness can be severe and fatal when bulbar muscles are heavily involved. Acetylcholine receptor antibodies are present in the majority of patients and are of IgG1 and IgG3 subtypes which can activate the complement system. The complement involvement plays a major role in the neuromuscular junction damage and the supporting evidence in the literature is described in this article. Complement therapies were initially studied and approved for paroxysmal nocturnal hemoglobinuria and in the past decade, those have also been studied in myasthenia gravis. The currently available randomized control trial and real-world data on the efficacy and safety of the approved and investigational complement therapies are summarized in this review.
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Affiliation(s)
- Pyae Phyo San
- Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, United Kingdom
| | - Saiju Jacob
- Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, United Kingdom
- Department of Neurology, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom
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Iwasa K, Furukawa Y, Yoshikawa H, Yamada M, Ono K. CD59 Expression in Skeletal Muscles and Its Role in Myasthenia Gravis. NEUROLOGY - NEUROIMMUNOLOGY NEUROINFLAMMATION 2023; 10:10/1/e200057. [DOI: 10.1212/nxi.0000000000200057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 09/19/2022] [Indexed: 11/18/2022]
Abstract
Background and ObjectivesComplement regulatory proteins at the neuromuscular junction (NMJ) could offer protection against complement-mediated damage in myasthenia gravis (MG). However, there is limited information on their expression at the human NMJ. Thus, this study aimed at investigating the expression of the cluster of differentiation 59 (CD59) at the NMJ of human muscle specimens and demonstrating the overexpression ofCD59mRNA and protein in the muscles of patients with MG.MethodsIn this observational study, muscle specimens from 16 patients with MG (9 and 7 patients with and without thymoma, respectively) and 6 nonmyopathy control patients were examined. Immunohistochemical stains, Western blot analysis, and quantitative real-time reverse transcription PCR were used to evaluate the CD59 expression.ResultsA strong localized expression of CD59 was observed at the NMJ in both patients with and without MG. Moreover, the CD59/glyceraldehyde-3-phosphate dehydrogenase protein ratio in patients with MG was significantly higher than that in the nonmyopathy controls (MG; n = 16, median 0.16, interquartile range (IQR) 0.08–0.26 and nonmyopathy controls; n = 6, median 0.03, IQR 0.02–0.11,p= 0.01). The proportion ofCD59mRNA expression relative toAChRmRNA expression (ΔCtCD59/AChR) was associated with the quantitative MG score, MG activities of daily living score, and MG of Foundation of America Clinical Classification (r= 0.663,p= 0.01;r= 0.638,p= 0.014; andr= 0.715,p= 0.003, respectively).DiscussionCD59, which acts as a complement regulator, may protect the NMJ from complement attack. Our findings could provide a basis for further research that investigates the underlying pathogenesis in MG and the immunomodulating interactions of the muscle cells.
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Sikorski PM, Kusner LL, Kaminski HJ. Myasthenia Gravis. Clin Immunol 2023. [DOI: 10.1016/b978-0-7020-8165-1.00065-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
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Obaid AH, Zografou C, Vadysirisack DD, Munro-Sheldon B, Fichtner ML, Roy B, Philbrick WM, Bennett JL, Nowak RJ, O'Connor KC. Heterogeneity of Acetylcholine Receptor Autoantibody-Mediated Complement Activity in Patients With Myasthenia Gravis. NEUROLOGY(R) NEUROIMMUNOLOGY & NEUROINFLAMMATION 2022; 9:9/4/e1169. [PMID: 35473886 PMCID: PMC9128035 DOI: 10.1212/nxi.0000000000001169] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 03/08/2022] [Indexed: 11/24/2022]
Abstract
BACKGROUND AND OBJECTIVES Autoantibodies targeting the acetylcholine receptor (AChR), found in patients with myasthenia gravis (MG), mediate pathology through 3 mechanisms: complement-directed tissue damage, blocking of the acetylcholine binding site, and internalization of the AChR. Clinical assays, used to diagnose and monitor patients, measure only autoantibody binding. Consequently, they are limited in providing association with disease burden, understanding of mechanistic heterogeneity, and monitoring therapeutic response. The objective of this study was to develop a cell-based assay that measures AChR autoantibody-mediated complement membrane attack complex (MAC) formation. METHODS An HEK293T cell line-modified using CRISPR/Cas9 genome editing to disrupt expression of the complement regulator genes (CD46, CD55, and CD59)-was used to measure AChR autoantibody-mediated MAC formation through flow cytometry. RESULTS Serum samples (n = 155) from 96 clinically confirmed AChR MG patients, representing a wide range of disease burden and autoantibody titer, were tested along with 32 healthy donor (HD) samples. AChR autoantibodies were detected in 139 of the 155 (89.7%) MG samples through a cell-based assay. Of the 139 AChR-positive samples, autoantibody-mediated MAC formation was detected in 83 (59.7%), whereas MAC formation was undetectable in the HD group or AChR-positive samples with low autoantibody levels. MAC formation was positively associated with autoantibody binding in most patient samples; ratios (mean fluorescence intensity) of MAC formation to AChR autoantibody binding ranged between 0.27 and 48, with a median of 0.79 and an interquartile range of 0.43 (0.58-1.1). However, the distribution of ratios was asymmetric and included extreme values; 16 samples were beyond the 10-90 percentile, with high MAC to low AChR autoantibody binding ratio or the reverse. Correlation between MAC formation and clinical disease scores suggested a modest positive association (rho = 0.34, p = 0.0023), which included a subset of outliers that did not follow this pattern. MAC formation did not associate with exposure to immunotherapy, thymectomy, or MG subtypes defined by age-of-onset. DISCUSSION A novel assay for evaluating AChR autoantibody-mediated complement activity was developed. A subset of patients that lacks association between MAC formation and autoantibody binding or disease burden was identified. The assay may provide a better understanding of the heterogeneous autoantibody molecular pathology and identify patients expected to benefit from complement inhibitor therapy.
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Sirin T, Karaaslan Z, Arkali B, Bekdik P, Akinci T, Candan F, Akarsu E, Baslo MB, Orhan E, Oge AE. Is Video-Oculography a Predictive Test for Myasthenia Gravis with Ocular Symptoms? Neurol India 2022; 70:80-86. [DOI: 10.4103/0028-3886.336330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Mantegazza R, Vanoli F, Frangiamore R, Cavalcante P. Complement Inhibition for the Treatment of Myasthenia Gravis. Immunotargets Ther 2020; 9:317-331. [PMID: 33365280 PMCID: PMC7751298 DOI: 10.2147/itt.s261414] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Accepted: 12/02/2020] [Indexed: 12/11/2022] Open
Abstract
Generalized myasthenia gravis (gMG) is a rare autoimmune disorder affecting the neuromuscular junction (NMJ). Approximately 80-90% of patients display antibodies directed against the nicotinic acetylcholine receptor (AChR). A major drive of AChR antibody-positive MG pathology is represented by complement activation. The role of the complement cascade has been largely demonstrated in patients and in MG animal models. Complement activation at the NMJ leads to focal lysis of the post-synaptic membrane, disruption of the characteristic folds, and reduction of AChR. Given that the complement system works as an activation cascade, there are many potential targets that can be considered for therapeutic intervention. Preclinical studies have confirmed the efficacy of complement inhibition in ameliorating MG symptoms. Eculizumab, an antibody directed towards C5, has recently been approved for the treatment of AChR antibody-positive gMG. Other complement inhibitors, targeting C5 as well, are currently under phase III study. Complement inhibitors, however, may present prohibitive costs. Therefore, the identification of a subset of patients more or less prone to respond to such therapies would be beneficial. For such purpose, there is a critical need to identify possible biomarkers predictive of therapeutic response, a field not yet sufficiently explored in MG. This review aims to give an overview of the complement cascade involvement in MG, the evolution of complement-inhibiting therapies and possible biomarkers useful to tailor and monitor complement-directed therapies.
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Affiliation(s)
- Renato Mantegazza
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Fiammetta Vanoli
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Rita Frangiamore
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Paola Cavalcante
- Neurology IV - Neuroimmunology and Neuromuscular Diseases Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
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Evoli A, Iorio R. Controversies in Ocular Myasthenia Gravis. Front Neurol 2020; 11:605902. [PMID: 33329368 PMCID: PMC7734350 DOI: 10.3389/fneur.2020.605902] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Accepted: 10/26/2020] [Indexed: 12/12/2022] Open
Abstract
Myasthenia gravis (MG) with symptoms limited to eye muscles [ocular MG (OMG)] is a rare disease. OMG incidence varies according to ethnicity and age of onset. In recent years, both an increase in incidence rate, particularly in the elderly, and a lower risk for secondary generalization may have contributed to the growing disease prevalence in Western countries. OMG should be considered in patients with painless ptosis and extrinsic ophthalmoparesis. Though asymmetric muscle involvement and symptom fluctuations are typical, in some cases, OMG can mimic isolated cranial nerve paresis, internuclear ophthalmoplegia, and conjugate gaze palsy. Diagnostic confirmation can be challenging in patients negative for anti-acetylcholine receptor and anti-muscle-specific tyrosine kinase antibodies on standard radioimmunoassay. Early treatment is aimed at relieving symptoms and at preventing disease progression to generalized MG. Despite the absence of high-level evidence, there is general agreement on the efficacy of steroids at low to moderate dosage; immunosuppressants are considered when steroid high maintenance doses are required. The role of thymectomy in non-thymoma patients is controversial. Prolonged exposure to immunosuppressive therapy has a negative impact on the health-related quality of life in a proportion of these patients. OMG is currently excluded from most of the treatments recently developed in generalized MG.
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Affiliation(s)
- Amelia Evoli
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy.,Department of Neuroscience, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Raffaele Iorio
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy.,Department of Neuroscience, Università Cattolica del Sacro Cuore, Rome, Italy
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Cetin H, Beeson D, Vincent A, Webster R. The Structure, Function, and Physiology of the Fetal and Adult Acetylcholine Receptor in Muscle. Front Mol Neurosci 2020; 13:581097. [PMID: 33013323 PMCID: PMC7506097 DOI: 10.3389/fnmol.2020.581097] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 08/13/2020] [Indexed: 12/31/2022] Open
Abstract
The neuromuscular junction (NMJ) is a highly developed synapse linking motor neuron activity with muscle contraction. A complex of molecular cascades together with the specialized NMJ architecture ensures that each action potential arriving at the motor nerve terminal is translated into an action potential in the muscle fiber. The muscle-type nicotinic acetylcholine receptor (AChR) is a key molecular component located at the postsynaptic muscle membrane responsible for the generation of the endplate potential (EPP), which usually exceeds the threshold potential necessary to activate voltage-gated sodium channels and triggers a muscle action potential. Two AChR isoforms are found in mammalian muscle. The fetal isoform is present in prenatal stages and is involved in the development of the neuromuscular system whereas the adult isoform prevails thereafter, except after denervation when the fetal form is re-expressed throughout the muscle. This review will summarize the structural and functional differences between the two isoforms and outline congenital and autoimmune myasthenic syndromes that involve the isoform specific AChR subunits.
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Affiliation(s)
- Hakan Cetin
- Department of Neurology, Medical University of Vienna, Vienna, Austria.,Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Richard Webster
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
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Albazli K, Kaminski HJ, Howard JF. Complement Inhibitor Therapy for Myasthenia Gravis. Front Immunol 2020; 11:917. [PMID: 32582144 PMCID: PMC7283905 DOI: 10.3389/fimmu.2020.00917] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Accepted: 04/20/2020] [Indexed: 01/01/2023] Open
Abstract
Complement activation as a driver of pathology in myasthenia gravis (MG) has been appreciated for decades. The terminal complement component [membrane attack complex (MAC)] is found at the neuromuscular junctions of patients with MG. Animals with experimental autoimmune MG are dependent predominantly on an active complement system to develop weakness. Mice deficient in intrinsic complement regulatory proteins demonstrate a significant increase in the destruction of the neuromuscular junction. As subtypes of MG have been better defined, it has been appreciated that acetylcholine receptor antibody-positive disease is driven by complement activation. Preclinical assessments have confirmed that complement inhibition would be a viable therapeutic approach. Eculizumab, an antibody directed toward the C5 component of complement, was demonstrated to be effective in a Phase 3 trial with subsequent approval by the Federal Drug Administration of the United States and other worldwide regulatory agencies for its use in acetylcholine receptor antibody-positive MG. Second- and third-generation complement inhibitors are in development and approaching pivotal efficacy evaluations. This review will summarize the history and present the state of knowledge of this new therapeutic modality.
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Affiliation(s)
- Khaled Albazli
- Department of Neurology, George Washington University, Washington, DC, United States
| | - Henry J. Kaminski
- Department of Neurology, George Washington University, Washington, DC, United States
| | - James F. Howard
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
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Increased serum acetylcholine receptor α1 subunit protein in anti-acetylcholine receptor antibody-positive myasthenia gravis. J Neuroimmunol 2020; 339:577125. [DOI: 10.1016/j.jneuroim.2019.577125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 12/06/2019] [Accepted: 12/06/2019] [Indexed: 11/22/2022]
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14
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de Meel RHP, Raadsheer WF, van Zwet EW, Tannemaat MR, Verschuuren JJGM. Ocular Weakness in Myasthenia Gravis: Changes in Affected Muscles are a Distinct Clinical Feature. J Neuromuscul Dis 2019; 6:369-376. [PMID: 31424417 PMCID: PMC6839603 DOI: 10.3233/jnd-190407] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Introduction: In this study we quantitatively describe ocular weakness patterns in myasthenia gravis (MG) to help neurologists in making the clinical diagnosis and to investigate how the current outcome measures reflect ocular weakness in MG. Methods: We investigated ptosis and diplopia patterns in a retro- and prospective cohort of 306 MG patients. Diplopia was systematically examined by testing extra-ocular muscle (EOM) fatigability in two horizontal and four oblique directions for 60 seconds. Results: Of patients with initial symmetric ptosis, 40% developed asymmetric ptosis at the second visit. Changes in form of ptosis occurred less often in seronegative MG patients (50%) than in patients with acetylcholine receptor (AChR) antibodies (70%) or muscle-specific kinase (MuSK) antibodies (69%) (p = 0.038). Of patients with diplopia on the first visit, double vision contained both a vertical and horizontal component in 95%. At the second visit, 83% manifested diplopia in other gaze directions. The mean time (in seconds) to diplopia was 11.6±14.0 and the mean time to ptosis was 27.6±19.8. Diplopia or ptosis manifested within 30 seconds in 87% and 58%, respectively. Patients who manifested diplopia after 30 seconds, reported no limitations due to diplopia. Discussion: Changes in the gaze directions in which diplopia occurs or ptosis side occur frequently in MG. In diagnostically challenging cases, we recommend testing ptosis and diplopia in multiple gaze directions for 30–60 seconds during at least two follow-up visits to maximize the chance of observing changes in ocular weakness patterns.
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Affiliation(s)
- Robert H P de Meel
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
| | - Wouter F Raadsheer
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
| | - Erik W van Zwet
- Department of Biostatistics, Leiden University Medical Center, Leiden, The Netherlands
| | - Martijn R Tannemaat
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
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Heterogeneity and shifts in distribution of muscle weakness in myasthenia gravis. Neuromuscul Disord 2019; 29:664-670. [PMID: 31488385 DOI: 10.1016/j.nmd.2019.07.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 07/06/2019] [Accepted: 07/19/2019] [Indexed: 01/26/2023]
Abstract
The distribution of muscle weakness in myasthenia gravis (MG) patients with acetylcholine receptor (AChR) antibodies is highly variable. As muscle groups respond differently to therapeutic interventions, it is important to acknowledge this variability. We analysed the distribution of muscle weakness in 225 AChR MG patients over time. On the basis of combinations of muscle weakness, seven phenotypes were defined: 'ocular' (O), 'bulbar' (B), 'neck/limbs/respiratory' (NLR), or a combination (O+B, O+NLR, B+NLR and O+B+NLR). MG remained restricted to ocular weakness in 5%, whereas 7% never had ocular weakness. At last follow-up, ocular or bulbar weakness had resolved more frequently than NLR weakness (40%, 38% and 25%; p = 0.003, respectively). Patients with O, B or OB phenotype at baseline had a higher age at onset and were more frequently male than patients with NLR, ONLR, BNLR or OBNLR phenotype (52.7 ± 17.5 vs. 44.0 ± 18.9; p = 0.007 and 64% vs. 37%; p = 0.002, respectively). MG patients have heterogeneous distributions of muscle weakness and frequently shift between phenotypes. The phenotypic variations found in AChR MG suggest that also other factors aside from the AChR antibody mediated immune response are of importance in determining the disease expression in MG.
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16
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Nel M, Mulder N, Europa TA, Heckmann JM. Using Whole Genome Sequencing in an African Subphenotype of Myasthenia Gravis to Generate a Pathogenetic Hypothesis. Front Genet 2019; 10:136. [PMID: 30881381 PMCID: PMC6406016 DOI: 10.3389/fgene.2019.00136] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 02/11/2019] [Indexed: 12/25/2022] Open
Abstract
Myasthenia gravis (MG) is a rare, treatable antibody-mediated disease which is characterized by muscle weakness. The pathogenic antibodies are most frequently directed at the acetylcholine receptors (AChRs) at the skeletal muscle endplate. An ophthalmoplegic subphenotype of MG (OP-MG), which is characterized by treatment resistant weakness of the extraocular muscles (EOMs), occurs in a proportion of myasthenics with juvenile symptom onset and African genetic ancestry. Since the pathogenetic mechanism(s) underlying OP-MG is unknown, the aim of this study was to use a hypothesis-generating genome-wide analysis to identify candidate OP-MG susceptibility genes and pathways. Whole genome sequencing (WGS) was performed on 25 AChR-antibody positive myasthenic individuals of African genetic ancestry sampled from the phenotypic extremes: 15 with OP-MG and 10 individuals with control MG (EOM treatment-responsive). Variants were called according to the Genome Analysis Toolkit (GATK) best practice guidelines using the hg38 reference genome. In addition to single variant association analysis, variants were mapped to genes (±200 kb) using VEGAS2 to calculate gene-based test statistics and HLA allele group assignment was inferred through "best-match" alignment of reads against the IMGT/HLA database. While there were no single variant associations that reached genome-wide significance in this exploratory sample, several genes with significant gene-based test statistics and known to be expressed in skeletal muscle had biological functions which converge on muscle atrophy signaling and myosin II function. The closely linked HLA-DPA1 and HLA-DPB1 genes were associated with OP-MG subjects (gene-based p < 0.05) and the frequency of a functional A > G SNP (rs9277534) in the HLA-DPB1 3'UTR, which increases HLA-DPB1 expression, differed between the two groups (G-allele 0.30 in OP-MG vs. 0.60 in control MG; p = 0.04). Furthermore, we show that rs9277534 is an HLA-DBP1 expression quantitative trait locus in patient-derived myocytes (p < 1 × 10-3). The application of a SNP to gene to pathway approach to this exploratory WGS dataset of African myasthenic individuals, and comparing dichotomous subphenotypes, resulted in the identification of candidate genes and pathways that may contribute to OP-MG susceptibility. Overall, the hypotheses generated by this work remain to be verified by interrogating candidate gene and pathway expression in patient-derived extraocular muscle.
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Affiliation(s)
- Melissa Nel
- Neurology Research Group, Division of Neurology, Department of Medicine, University of Cape Town, Cape Town, South Africa
| | - Nicola Mulder
- Computational Biology Division, Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Tarin A Europa
- Neurology Research Group, Division of Neurology, Department of Medicine, University of Cape Town, Cape Town, South Africa
| | - Jeannine M Heckmann
- Neurology Research Group, Division of Neurology, Department of Medicine, University of Cape Town, Cape Town, South Africa
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Kusner LL, Sengupta M, Kaminski HJ. Acetylcholine receptor antibody-mediated animal models of myasthenia gravis and the role of complement. Ann N Y Acad Sci 2018; 1413:136-142. [PMID: 29356015 DOI: 10.1111/nyas.13555] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 10/23/2017] [Accepted: 10/25/2017] [Indexed: 12/22/2022]
Abstract
Because of the failure of many promising therapeutics identified in preclinical evaluation, funding sources have established guidelines for increased rigor in animal evaluations. The myasthenia gravis (MG) community of scientists has developed guidelines for preclinical assessment for potential MG treatments. Here, we provide a focused summary of these recommendations and the role of complement in disease development in experimental models of MG.
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Affiliation(s)
- Linda L Kusner
- Department of Pharmacology and Physiology, George Washington University School of Medicine and Health Sciences, Washington, DC
| | - Manjistha Sengupta
- Department of Neurology, George Washington University School of Medicine and Health Sciences, Washington, DC
| | - Henry J Kaminski
- Department of Neurology, George Washington University School of Medicine and Health Sciences, Washington, DC
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Du A, Huang S, Zhao X, Feng K, Zhang S, Huang J, Miao X, Baggi F, Ostrom RS, Zhang Y, Chen X, Xu C. Suppression of CHRN endocytosis by carbonic anhydrase CAR3 in the pathogenesis of myasthenia gravis. Autophagy 2017; 13:1981-1994. [PMID: 28933591 PMCID: PMC5788490 DOI: 10.1080/15548627.2017.1375633] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Myasthenia gravis is an autoimmune disorder of the neuromuscular junction manifested as fatigable muscle weakness, which is typically caused by pathogenic autoantibodies against postsynaptic CHRN/AChR (cholinergic receptor nicotinic) in the endplate of skeletal muscle. Our previous studies have identified CA3 (carbonic anhydrase 3) as a specific protein insufficient in skeletal muscle from myasthenia gravis patients. In this study, we investigated the underlying mechanism of how CA3 insufficiency might contribute to myasthenia gravis. Using an experimental autoimmune myasthenia gravis animal model and the skeletal muscle cell C2C12, we find that inhibition of CAR3 (the mouse homolog of CA3) promotes CHRN internalization via a lipid raft-mediated pathway, leading to accelerated degradation of postsynaptic CHRN. Activation of CAR3 reduces CHRN degradation by suppressing receptor endocytosis. CAR3 exerts this effect by suppressing chaperone-assisted selective autophagy via interaction with BAG3 (BCL2-associated athanogene 3) and by dampening endoplasmic reticulum stress. Collectively, our study illustrates that skeletal muscle cell CAR3 is critical for CHRN homeostasis in the neuromuscular junction, and its deficiency leads to accelerated degradation of CHRN and development of myasthenia gravis, potentially revealing a novel therapeutic approach for this disorder.
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Affiliation(s)
- Ailian Du
- a Department of Neurology, Tongren Hospital , Shanghai Jiao Tong University School of Medicine (SJTUSM) , Shanghai , China
| | - Shiqian Huang
- b Shanghai Institute of Immunology, Institutes of Medical Sciences , Shanghai Jiao Tong University School of Medicine , Shanghai , China
| | - Xiaonan Zhao
- b Shanghai Institute of Immunology, Institutes of Medical Sciences , Shanghai Jiao Tong University School of Medicine , Shanghai , China
| | - Kuan Feng
- c Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences & SJTUSM , Shanghai , China
| | - Shuangyan Zhang
- b Shanghai Institute of Immunology, Institutes of Medical Sciences , Shanghai Jiao Tong University School of Medicine , Shanghai , China
| | - Jiefang Huang
- c Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences & SJTUSM , Shanghai , China
| | - Xiang Miao
- c Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences & SJTUSM , Shanghai , China
| | - Fulvio Baggi
- d Neurology IV-Neuroimmunology and Neuromuscular Diseases Unit, Fondazione Istituto Neurologico "Carlo Besta" , Milan , Italy
| | - Rennolds S Ostrom
- e Department of Biomedical and Pharmaceutical Sciences , Chapman University School of Pharmacy , Irvine , CA , USA
| | - Yanyun Zhang
- b Shanghai Institute of Immunology, Institutes of Medical Sciences , Shanghai Jiao Tong University School of Medicine , Shanghai , China.,c Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences & SJTUSM , Shanghai , China
| | - Xiangjun Chen
- f Department of Neurology , Fudan University Huashan Hospital, and Institute of Neurology, Fudan University , Shanghai , China
| | - Congfeng Xu
- b Shanghai Institute of Immunology, Institutes of Medical Sciences , Shanghai Jiao Tong University School of Medicine , Shanghai , China.,c Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences & SJTUSM , Shanghai , China
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Kaminski HJ, Himuro K, Alshaikh J, Gong B, Cheng G, Kusner LL. Differential RNA Expression Profile of Skeletal Muscle Induced by Experimental Autoimmune Myasthenia Gravis in Rats. Front Physiol 2016; 7:524. [PMID: 27891095 PMCID: PMC5102901 DOI: 10.3389/fphys.2016.00524] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 10/24/2016] [Indexed: 01/14/2023] Open
Abstract
The differential susceptibility of skeletal muscle by myasthenia gravis (MG) is not well understood. We utilized RNA expression profiling of extraocular muscle (EOM), diaphragm (DIA), and extensor digitorum (EDL) of rats with experimental autoimmune MG (EAMG) to evaluate the hypothesis that muscles respond differentially to injury produced by EAMG. EAMG was induced in female Lewis rats by immunization with acetylcholine receptor purified from the electric organ of the Torpedo. Six weeks later after rats had developed weakness and serum antibodies directed against the AChR, animals underwent euthanasia and RNA profiling performed on DIA, EDL, and EOM. Profiling results were validated by qPCR. Across the three muscles between the experiment and control groups, 359 probes (1.16%) with greater than 2-fold changes in expression in 7 of 9 series pairwise comparisons from 31,090 probes were identified with approximately two-thirds being increased. The three muscles shared 16 genes with increased expression and 6 reduced expression. Functional annotation demonstrated that these common expression changes fell predominantly into categories of metabolism, stress response, and signaling. Evaluation of specific gene function indicated that EAMG led to a change to oxidative metabolism. Genes related to muscle regeneration and suppression of immune response were activated. Evidence of a differential immune response among muscles was not evident. Each muscle had a distinct RNA profile but with commonality in gene categories expressed that are focused on muscle repair, moderation of inflammation, and oxidative metabolism.
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Affiliation(s)
- Henry J Kaminski
- Department of Neurology, George Washington University Washington, DC, USA
| | - Keiichi Himuro
- Department of Neurology, Graduate School of Medicine, Chiba University Chiba, Japan
| | - Jumana Alshaikh
- Department of Neurology, George Washington University Washington, DC, USA
| | - Bendi Gong
- Department of Pediatrics, Washington University St. Louis, MO, USA
| | - Georgiana Cheng
- Department of Pathobiology, Cleveland Clinic Cleveland, OH, USA
| | - Linda L Kusner
- Pharmacology and Physiology, George Washington University Washington, DC, USA
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Baruca M, Leonardis L, Podnar S, Hojs-Fabjan T, Grad A, Jerin A, Blagus R, Šega-Jazbec S. Single fiber EMG as a prognostic tool in myasthenia gravis. Muscle Nerve 2016; 54:1034-1040. [DOI: 10.1002/mus.25174] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 04/27/2016] [Accepted: 05/02/2016] [Indexed: 11/06/2022]
Affiliation(s)
- Mateja Baruca
- University Medical Centre Ljubljana, Department of Neurology; Zaloška cesta 2,1000 Ljubljana Slovenia
| | - Lea Leonardis
- University Medical Centre Ljubljana, Institute of Clinical Neurophysiology; Ljubljana Slovenia
| | - Simon Podnar
- University Medical Centre Ljubljana, Institute of Clinical Neurophysiology; Ljubljana Slovenia
| | | | - Anton Grad
- General Hospital of Isola; Isola Slovenia
| | - Aleš Jerin
- University Medical Centre Ljubljana, Clinical institute of Clinical Chemistry and biochemistry; Ljubljana Slovenia
| | - Rok Blagus
- Institute for Biostatistics and Medical Informatics; University of Ljubljana, Faculty of Medicine; Ljubljana Slovenia
| | - Saša Šega-Jazbec
- University Medical Centre Ljubljana, Department of Neurology; Zaloška cesta 2,1000 Ljubljana Slovenia
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Hamdoon MNT, Fattouh M, El-Din AN, Elnady HM. The potential role of cell surface complement regulators and circulating CD4+ CD25+ T-cells in the development of autoimmune myasthenia gravis. Electron Physician 2016; 8:1718-26. [PMID: 26955441 PMCID: PMC4768919 DOI: 10.19082/1718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 12/13/2015] [Indexed: 11/20/2022] Open
Abstract
INTRODUCTION CD4+CD25+ regulatory T-lymphocytes (T-regs) and regulators of complement activity (RCA) involving CD55 and CD59 play an important role in the prevention of autoimmune diseases. However, their role in the pathogenesis of human autoimmune myasthenia gravis (MG) remains unclear. This study aimed to determine the frequency of peripheral blood T-regs and CD4+ T-helper (T-helper) cells and the red blood cells (RBCs) level of expression of CD55 and CD59 in MG patients. METHODS Fourteen patients with MG in neurology outpatient clinics of Sohag University Hospital and Sohag General Hospital from March 2014 to December 2014, and 10 age-matched healthy controls participated in this case-control study. We did flowcytometric assessments of the percentage of peripheral T-regs and T-helper cells and the level of expression of CD55 and CD59 on RBCs in the peripheral blood of patients and controls. RESULTS There was a statistically significant decrease in the percentage of peripheral blood T-regs and T-regs/T-helper cell ratio in the MG patients group. Moreover, the level of expression of CD55, CD59, and dual expression of CD55/CD59 on RBCs were statistically significantly lower in MG patients than those of healthy controls. However, regression analysis indicated that there was no significant correlation between all the measured parameters and disease duration or staging. CONCLUSION Functional defects in the T-regs and RCA may play a role in the pathogenesis of autoimmune MG and their functional modulation may represent an alternative therapeutic strategy for MG treatment.
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Affiliation(s)
| | - Mona Fattouh
- Department of Microbiology and Immunology, Sohag University Hospital, Sohag, Egypt
| | - Asmaa Nasr El-Din
- Department of Microbiology and Immunology, Sohag University Hospital, Sohag, Egypt
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The African-387 C>T TGFB1 variant is functional and associates with the ophthalmoplegic complication in juvenile myasthenia gravis. J Hum Genet 2015; 61:307-16. [PMID: 26632886 DOI: 10.1038/jhg.2015.146] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 11/07/2015] [Accepted: 11/10/2015] [Indexed: 02/03/2023]
Abstract
Although extraocular muscles are commonly affected by myasthenia gravis (MG) at presentation, a treatment-resistant ophthalmoplegic complication of MG (OP-MG) occurs in younger patients with African-genetic ancestry. In MG, pathogenic antibodies activate complement-mediated muscle damage and this may be potentiated in some OP-MG cases because of relative deficiency of decay-accelerating factor/CD55. Extending this argument, we hypothesized that OP-MG individuals may harbor African-specific polymorphisms in key genes influencing extraocular muscle remodeling. We screened the regulatory region of the transforming growth factor beta-1 (TGFB1) gene encoding the cytokine pivotal in muscle healing responses. We show the frequency of an African-specific polymorphism TGFB1 c.-387 T (rs11466316) among South Africans with African-genetic ancestry is higher than 1000 Genomes African controls (17.2% vs 4.8%; P<1 × 10(-7)), and associates with juvenile OP-MG (28%; P=0.043). Further, TGFB1 -387 C>T is functional because it represses the TGFB1 promoter construct basal activity by fivefold, and OP-MG fibroblasts (-387 C/T or T/T) have lower basal TGFB1 mRNA transcripts compared with controls (-387 C/C)(P=0.001). Co-transfections with Sp1 show less responsiveness of the -387 T promoter compared with wild-type -387 C (P=0.015). Our findings suggest that population-specific alleles may lower TGFB1 expression, thereby influencing OP-MG susceptibility by inhibiting extraocular muscle CD55 upregulation and/or altered endplate remodeling.
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Endoplasmic reticulum stress contributes to acetylcholine receptor degradation by promoting endocytosis in skeletal muscle cells. J Neuroimmunol 2015; 290:109-14. [PMID: 26711579 DOI: 10.1016/j.jneuroim.2015.11.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 11/24/2015] [Accepted: 11/25/2015] [Indexed: 12/20/2022]
Abstract
After binding by acetylcholine released from a motor neuron, a nicotinic acetylcholine receptor at the neuromuscular junction produces a localized end-plate potential, which leads to muscle contraction. Improper turnover and renewal of acetylcholine receptors contributes to the pathogenesis of myasthenia gravis. In the present study, we demonstrate that endoplasmic reticulum (ER) stress contributes to acetylcholine receptor degradation in C2C12 myocytes. We further show that ER stress promotes acetylcholine receptor endocytosis and lysosomal degradation, which was dampened by blocking endocytosis or treating with lysosome inhibitor. Knockdown of ER stress proteins inhibited acetylcholine receptor endocytosis and degradation, while rescue assay restored its endocytosis and degradation, confirming the effects of ER stress on promoting endocytosis-mediated degradation of junction acetylcholine receptors. Thus, our studies identify ER stress as a factor promoting acetylcholine receptor degradation through accelerating endocytosis in muscle cells. Blocking ER stress and/or endocytosis might provide a novel therapeutic approach for myasthenia gravis.
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Guidelines for pre-clinical assessment of the acetylcholine receptor--specific passive transfer myasthenia gravis model-Recommendations for methods and experimental designs. Exp Neurol 2015; 270:3-10. [PMID: 25743217 DOI: 10.1016/j.expneurol.2015.02.025] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 02/13/2015] [Accepted: 02/17/2015] [Indexed: 11/21/2022]
Abstract
Antibodies against the muscle acetylcholine receptor (AChR) are the most common cause of myasthenia gravis (MG). Passive transfer of AChR antibodies from MG patients into animals reproduces key features of human disease, including antigenic modulation of the AChR, complement-mediated damage of the neuromuscular junction, and muscle weakness. Similarly, AChR antibodies generated by active immunization in experimental autoimmune MG models can subsequently be passively transferred to other animals and induce weakness. The passive transfer model is useful to test therapeutic strategies aimed at the effector mechanism of the autoantibodies. Here we summarize published and unpublished experience using the AChR passive transfer MG model in mice, rats and rhesus monkeys, and give recommendations for the design of preclinical studies in order to facilitate translation of positive and negative results to improve MG therapies.
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Suzuki S, Murai H, Imai T, Nagane Y, Masuda M, Tsuda E, Konno S, Oji S, Nakane S, Motomura M, Suzuki N, Utsugisawa K. Quality of life in purely ocular myasthenia in Japan. BMC Neurol 2014; 14:142. [PMID: 24996227 PMCID: PMC4088302 DOI: 10.1186/1471-2377-14-142] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 07/01/2014] [Indexed: 11/10/2022] Open
Abstract
Background Since there has been no conclusive evidence regarding the treatment of ocular myasthenia, treatment guidelines were recently issued by the European Federation of Neurological Societies/European Neurological Society (EFNS/ENS). However, the therapeutic outcomes concerning the quality-of-life (QOL) of patients with ocular myasthenia are not yet fully understood. Methods We investigated the therapeutic outcomes of patients with purely ocular myasthenia in a multicenter cross-sectional survey in Japan. To evaluate the severity of ocular symptoms, we used the ocular-quantitative MG (QMG) score advocated by Myasthenia Gravis Foundation of America. We used the Japanese translated version of the MG-QOL15, a self-appraised scoring system. Results Of 607 myasthenia gravis (MG) patients with an observation-duration of illness ≥ 2 years, the cases of 123 patients (20%) were limited to ocular muscles (purely ocular myasthenia). During the entire clinical course, 81 patients experienced both ptosis and diplopia, 36 had ptosis alone, and six had diplopia alone. Acetyl-cholinesterase inhibitors and prednisolone were used in 98 and 52 patients, respectively. Treatment improved ocular symptoms, with the mean reduction in ocular-QMG score of 2.3 ± 1.8 points. However, 47 patients (38%) failed to gain minimal manifestation or a better status. Patients with unfavorable outcomes also self-reported severe QOL impairment. Multivariate analyses showed that the pretreatment ocular-QMG score was associated with unfavorable outcomes, but not associated with the patient’s QOL. Conclusion A treatment strategy designed in accord with a patient's ocular presentation must be considered in order to improve ocular symptoms and the patient's QOL.
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Affiliation(s)
- Shigeaki Suzuki
- Department of Neurology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
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Zhou Y, Kaminski HJ, Gong B, Cheng G, Feuerman JM, Kusner L. RNA expression analysis of passive transfer myasthenia supports extraocular muscle as a unique immunological environment. Invest Ophthalmol Vis Sci 2014; 55:4348-59. [PMID: 24917137 DOI: 10.1167/iovs.14-14422] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
PURPOSE Myasthenia gravis demonstrates a distinct predilection for involvement of the extraocular muscles (EOM), and we have hypothesized that this may be due to a unique immunological environment. To assess this hypothesis, we took an unbiased approach to analyze RNA expression profiles in EOM, diaphragm, and extensor digitorum longus (EDL) in rats with experimentally acquired myasthenia gravis (EAMG). METHODS Experimentally acquired myasthenia gravis was induced in rats by intraperitoneal injection of antibody directed against the acetylcholine receptor (AChR), whereas control rats received antibody known to bind the AChR but not induce disease. After 48 hours, animals were killed and muscles analyzed by RNA expression profiling. Profiling results were validated using qPCR and immunohistochemical analysis. RESULTS Sixty-two genes common among all muscle groups were increased in expression. These fell into four major categories: 12.8% stress response, 10.5% immune response, 10.5% metabolism, and 9.0% transcription factors. EOM expressed 212 genes at higher levels, not shared by the other two muscles, and a preponderance of EOM gene changes fell into the immune response category. EOM had the most uniquely reduced genes (126) compared with diaphragm (26) and EDL (50). Only 18 downregulated genes were shared by the three muscles. Histological evaluation and disease load index (sum of fold changes for all genes) demonstrated that EOM had the greatest degree of pathology. CONCLUSIONS Our studies demonstrated that consistent with human myasthenia gravis, EOM demonstrates a distinct RNA expression signature from EDL and diaphragm, which is based on differences in the degree of muscle injury and inflammatory response.
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Affiliation(s)
- Yuefang Zhou
- Department of Ophthalmology and Visual Sciences, Washington University, St. Louis, Missouri, United States
| | - Henry J Kaminski
- Departments of Neurology, Pharmacology, and Physiology, George Washington University, Washington, DC, United States
| | - Bendi Gong
- Department of Pediatrics, Washington University, St. Louis, Missouri, United States
| | - Georgiana Cheng
- Department of Pathobiology, Cleveland Clinic, Cleveland, Ohio, United States
| | - Jason M Feuerman
- Department of Ophthalmology, Baylor College of Medicine, Houston, Texas, United States
| | - Linda Kusner
- Departments of Neurology, Pharmacology, and Physiology, George Washington University, Washington, DC, United States
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The effects of prednisone and steroid-sparing agents on decay accelerating factor (CD55) expression: implications in myasthenia gravis. Neuromuscul Disord 2014; 24:499-508. [PMID: 24703255 DOI: 10.1016/j.nmd.2014.02.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Accepted: 02/24/2014] [Indexed: 12/11/2022]
Abstract
Decay accelerating factor (DAF) expression at the muscle endplate is an important defence against complement-mediated damage in myasthenia gravis. Previously we implicated the c.-198C>G DAF polymorphism with the development of treatment-resistant myasthenia-associated ophthalmoplegia by showing that the C>G DAF polymorphism prevented lipopolysaccharide-induced upregulation of lymphoblast DAF. We postulated that drugs used in myasthenia gravis may increase the susceptibility of extraocular muscles to complement-mediated damage and studied their effects on endogenous DAF using patient-derived lymphoblasts as well as mouse myotubes. We show that prednisone repressed C>G DAF expression in lymphoblasts and increased their susceptibility to cytotoxicity. Methotrexate, but not azathioprine or cyclosporine, increased DAF in C>G lymphoblasts. In mouse myotubes expressing wild-type Daf, prednisone also repressed Daf expression. Although cyclosporine, azathioprine, and methotrexate increased muscle Daf levels when used alone, upon co-treatment with prednisone only azathioprine maintained myotube Daf levels close to basal. Therefore, prednisone negatively influences DAF expression in C>G lymphoblasts and in myotubes expressing wild-type Daf. We speculate that myasthenic individuals at risk of developing the ophthalmoplegic complication, such as those with C>G DAF, may have inadequate endogenous levels of complement regulatory protein protection in their extraocular muscle in response to prednisone, increasing their susceptibility to complement-mediated damage.
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Tüzün E, Christadoss P. Complement associated pathogenic mechanisms in myasthenia gravis. Autoimmun Rev 2013; 12:904-11. [DOI: 10.1016/j.autrev.2013.03.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/12/2013] [Indexed: 12/26/2022]
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Kusner LL, Kaminski HJ. The role of complement in experimental autoimmune myasthenia gravis. Ann N Y Acad Sci 2013; 1274:127-32. [PMID: 23252907 DOI: 10.1111/j.1749-6632.2012.06783.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Complement plays an important role in the pathophysiology of experimental autoimmune myasthenia gravis (EAMG). The deposition of IgG at the neuromuscular junction, followed by the activation and observance of C3 at the site, and finally the insertion of the membrane attack complex results in the destruction of the plasma membrane at the neuromuscular junction. Animal models of complement-deficient components show the importance of the mediated lysis in EAMG. These events have regulators that allow for the limitation in the cascade and the ability of the cell to inhibit complement at many places along the pathway. The complement regulatory proteins have many roles in reducing the activation of the complement cascade and the inflammatory pathways. Mice deficient in complement regulatory proteins, decay accelerating factor, and CD59 demonstrate a significant increase in the destruction at the neuromuscular junction. Inhibition of complement-mediated lysis is an attractive therapeutic in MG.
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Affiliation(s)
- Linda L Kusner
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC, USA.
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Huda R, Tüzün E, Christadoss P. Complement C2 siRNA mediated therapy of myasthenia gravis in mice. J Autoimmun 2013; 42:94-104. [PMID: 23410585 DOI: 10.1016/j.jaut.2013.01.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 12/17/2012] [Accepted: 01/02/2013] [Indexed: 01/17/2023]
Abstract
Activation of complement components is crucial in the progression and severity of myasthenia gravis and experimental autoimmune myasthenia gravis (EAMG). Mice deficient in complement component C4 or treated with monoclonal antibody to C1q are resistant to EAMG. In this study, we show that inhibition of complement cascade activation by suppressing the expression of a critical low-abundant protein, C2, in the classical complement pathway, significantly improved clinical and immunopathological manifestations of EAMG. Two weeks after a second booster immunization with acetylcholine receptor, when mice exhibit muscle weakness, i.p. injection of C2 siRNA significantly suppressed C2 mRNA in the blood cells and liver of EAMG mice. Treatment of EAMG mice with C2 siRNA, once a week for 5 weeks, significantly improved muscle strength, which was further evidenced by functional AChR preservation in muscle, reduction in number of C3 and membrane-attack complexes at neuro-muscular junctions in forelimb muscle sections, and a transient decrease in serum IgG2b levels. Our study shows for the first time that siRNA-mediated suppression of C2, a component of the classical complement system, following established disease, can effectively contribute to the remission of EAMG. Therefore, C2 siRNA mediated therapy can be applied in all complement mediated autoimmune diseases.
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Affiliation(s)
- Ruksana Huda
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1070, USA
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Liu R, Xu H, Wang G, Li J, Gou L, Zhang L, Miao J, Li Z. Extraocular muscle characteristics related to myasthenia gravis susceptibility. PLoS One 2013; 8:e55611. [PMID: 23409007 PMCID: PMC3568149 DOI: 10.1371/journal.pone.0055611] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 01/02/2013] [Indexed: 11/30/2022] Open
Abstract
Background The pathogenesis of extraocular muscle (EOM) weakness in myasthenia gravis might involve a mechanism specific to the EOM. The aim of this study was to investigate characteristics of the EOM related to its susceptibility to myasthenia gravis. Methods Female F344 rats and female Sprague-Dawley rats were assigned to experimental and control groups. The experimental group received injection with Ringer solution containing monoclonal antibody against the acetylcholine receptor (AChR), mAb35 (0.25 mg/kg), to induce experimental autoimmune myasthenia gravis, and the control group received injection with Ringer solution alone. Three muscles were analyzed: EOM, diaphragm, and tibialis anterior. Tissues were examined by light microscopy, fluorescence histochemistry, and transmission electron microscopy. Western blot analysis was used to assess marker expression and ELISA analysis was used to quantify creatine kinase levels. Microarray assay was conducted to detect differentially expressed genes. Results In the experimental group, the EOM showed a simpler neuromuscular junction (NMJ) structure compared to the other muscles; the NMJ had fewer synaptic folds, showed a lesser amount of AChR, and the endplate was wider compared to the other muscles. Results of microarray assay showed differential expression of 54 genes in the EOM between the experimental and control groups. Conclusion Various EOM characteristics appear to be related to the increased susceptibility of the EOM and the mechanism of EOM weakness in myasthenia gravis.
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Affiliation(s)
- Rui Liu
- Department of Geratology, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi Province, P. R. China
| | - Hanpeng Xu
- LONI, Department of Neurology, UCLA, Los Angeles, California, United States of America
| | - Guiping Wang
- Department of Neurosurgery, 208th Hospital of PLA, Changchun, Jilin Province, P. R. China
| | - Jie Li
- Department of Endocrinology, 451 Hospital of PLA,Xi'an, Shaanxi Province, P. R. China
| | - Lin Gou
- LONI, Department of Neurology, UCLA, Los Angeles, California, United States of America
| | - Lihua Zhang
- Department of Geratology, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi Province, P. R. China
| | - Jianting Miao
- Department of Neurology, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi Province, P. R. China
- * E-mail: (ZL); (JM)
| | - Zhuyi Li
- Department of Neurology, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi Province, P. R. China
- * E-mail: (ZL); (JM)
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Kusner LL, Halperin JA, Kaminski HJ. Cell surface complement regulators moderate experimental myasthenia gravis pathology. Muscle Nerve 2012; 47:33-40. [PMID: 23042232 DOI: 10.1002/mus.23448] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/01/2012] [Indexed: 01/01/2023]
Abstract
INTRODUCTION Intrinsic mouse complement regulators influence the severity of passively induced experimental acquired myasthenia gravis (EAMG). To assess the potential influence of CD59b in the absence of CD59a background, we used the mCD59ab(-/-) mouse model to re-evaluate mCD59 in protecting the neuromuscular junction (NMJ). METHODS EAMG was induced with monoclonal antibody to the acetylcholine receptor (AChR) in Daf1(-/-) , CD59ab(-/-) , Daf1(-/-) CD59ab(-/-) , and wild-type C57Bl/6 mice. Animals were monitored throughout the experiment. Diaphragms were analyzed for NMJ injury. RESULTS Daf1(-/-) CD59ab(-/-) mice required euthanasia 24 hours after disease induction because of severe weakness. Histological assessment demonstrated reduced AChR density, simplification of synaptic folds, and disrupted mitochondria. CD59ab-deficient mice demonstrated mild weakness and reduction in weight after 24 hours. In contrast, Daf1(-/-) had more severe weakness at 60 hours. The NMJ of EAMG-induced Daf1(-/-) and CD59ab(-/-) mice demonstrated similar AChR density. CONCLUSION NMJs of CD59 and DAF mice are protected from complement-mediated injury of passive EAMG.
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Affiliation(s)
- Linda L Kusner
- Department of Pharmacology and Physiology, George Washington University, Washington, DC, USA.
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Soltys J, Wu X. Complement regulatory protein Crry deficiency contributes to the antigen specific recall response in experimental autoimmune myasthenia gravis. JOURNAL OF INFLAMMATION-LONDON 2012; 9:20. [PMID: 22642809 PMCID: PMC3524051 DOI: 10.1186/1476-9255-9-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Accepted: 04/18/2012] [Indexed: 12/20/2022]
Abstract
UNLABELLED BACKGROUND Myasthenia gravis (MG) and animal model of experimental autoimmune myasthenia gravis (EAMG) is the most common autoimmune disorder of neuromuscular transmission. The disease is caused by the breakdown of the acetylcholine receptor (AChR) which is largely due to complement activation at the neuromuscular junction (NMJ). Limited knowledge exists to the extent that complement receptor 1-related gene/protein y deficiency (Crry -/-) modulates the adaptive immune response and EAMG outcome. METHODS Mouse EAMG was induced by s.c. administrations of purified acetylcholine receptor (AChR) to Crry -/- and age- matched WT (C57BL/6) mice. Disease severity was assessed by clinical score assessment and muscle grip strength measurements. Serum complement activity was determined by hemolytic assay. ELISA was used to detect the level of AChR specific antibodies. Splenic cells were analyzed for T and B cells subsets distribution, release of cytokines and AChR specific recall responses. Deposition of complement components at the NMJ was assessed by immunofluorescence staining. RESULTS In comparison to WT EAMG, Crry -/- EAMG mice showed signs of augmented muscle weakness but differences, except for one time point, were not statistically significant. Serum complement activity was reduced in Crry -/- EAMG mice and no substantial changes in deposition of C3, C3b/iC3b and C5b-9 (MAC) at the NMJ between WT EAMG and Crry -/- EAMG mice were detected. Lack of Crry affected adaptive immune response. Crry -/- EAMG mice showed increases in the number of AChR specific splenic T-cells secreting IFN-γ and IL-4. Production of complement fixing antibodies (IgG2b, IgG2c) was also augmented. More Th1, Th2 and Th17 cytokines were released into the bloodstream of Crry -/- EAMG mice. CONCLUSIONS Data suggest that Crry deficiency modulates the adaptive immune response in EAMG, but its effect on disease outcome is limited. This was due to the generally lower serum complement level caused by increased C3 turnover. Modulation of complement activity with soluble or membrane bound regulators of complement activity represents a potentially effective approach to modify autoimmune processes in MG and EAMG.
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Affiliation(s)
- Jindrich Soltys
- Department of Neurology & Psychiatry, 1438 South Grand Boulevard, Saint Louis University School of Medicine, Saint Louis, MO, 63104, USA.
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Soltys J, Halperin JA, Xuebin Q. DAF/CD55 and Protectin/CD59 modulate adaptive immunity and disease outcome in experimental autoimmune myasthenia gravis. J Neuroimmunol 2012; 244:63-9. [PMID: 22325826 DOI: 10.1016/j.jneuroim.2012.01.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Revised: 12/13/2011] [Accepted: 01/09/2012] [Indexed: 01/14/2023]
Abstract
The role of regulators of complement activity (RCA) involving CD55 and CD59 in the pathogenesis of experimental autoimmune myasthenia gravis (EAMG) remains unclear. CD55 and CD59 restrict complement activation by inhibiting C3/C5 convertases' activities and membrane attack complex formation, respectively. Actively immunized EAMG mice deficient in either CD55 or CD59 showed significant differences in adaptive immune responses and worsened disease outcome associated with increased levels of serum cytokines, modified production of acetylcholine receptor antibodies, and more complement deposition at the neuromuscular junction. We conclude that modulation of complement activity by RCA represents an alternative in controlling of autoimmune processes in EAMG.
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Affiliation(s)
- Jindrich Soltys
- Department of Neurology & Psychiatry, Saint Louis University School of Medicine, Saint Louis, MO 63104, United States.
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Kauling ALC, de Almeida MCS, Locks GDF, Brunharo GM. Myasthenia gravis: two case reports and review of the literature. Rev Bras Anestesiol 2011; 61:748-63. [PMID: 22063376 DOI: 10.1016/s0034-7094(11)70084-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Accepted: 02/21/2011] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND AND OBJECTIVES Myasthenia gravis (MG) is an autoimmune neurologic disease that affects the postsynaptic portion of the neuromuscular junction. It represents a challenge for anesthesiologists due to the diversity of disease manifestations and possibility of postoperative respiratory complications. The objective of this study was to demonstrate the importance of adequate monitoring of the neuromuscular blockade (NMB) due to the multiple presentations of MG. CONTENTS In this paper we report two cases of patients with MG. The first patient presented with the classical sensitivity to the neuromuscular blocker (NMB) and the second had a similar response to that of a normal patient. The literature review will be restricted to disease characteristics, while the description of its pathophysiology will focus on its reactions to NMB. CONCLUSIONS We suggest that, due to the multiple presentation and treatment of MG, neuromuscular transmission monitors are fundamental when using NMB.
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Tüzün E, Huda R, Christadoss P. Complement and cytokine based therapeutic strategies in myasthenia gravis. J Autoimmun 2011; 37:136-43. [PMID: 21636248 DOI: 10.1016/j.jaut.2011.05.006] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Accepted: 05/02/2011] [Indexed: 01/17/2023]
Abstract
Myasthenia gravis (MG) is a T cell-dependent and antibody-mediated disease in which the target antigen is the skeletal muscle acetylcholine receptor (AChR). In the last few decades, several immunological factors involved in MG pathogenesis have been discovered mostly by studies utilizing the experimental autoimmune myasthenia gravis (EAMG) model. Nevertheless, MG patients are still treated with non-specific global immunosuppression that is associated with severe chronic side effects. Due to the high heterogeneity of AChR epitopes and antibody responses involved in MG pathogenesis, the specific treatment of MG symptoms have to be achieved by inhibiting the complement factors and cytokines involved in anti-AChR immunity. EAMG studies have clearly shown that inhibition of the classical and common complement pathways effectively and specifically diminish the neuromuscular junction destruction induced by anti-AChR antibodies. The inborn or acquired deficiencies of IL-6, TNF-α and TNF receptor functions are associated with the lowest EAMG incidences. Th17-type immunity has recently emerged as an important contributor of EAMG pathogenesis. Overall, these results suggest that inhibition of the complement cascade and the cytokine networks alone or in combination might aid in development of future treatment models that would reduce MG symptoms with highest efficacy and lowest side effect profile.
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Affiliation(s)
- Erdem Tüzün
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1070, USA
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Pal J, Rozsa C, Komoly S, Illes Z. Clinical and biological heterogeneity of autoimmune myasthenia gravis. J Neuroimmunol 2011; 231:43-54. [DOI: 10.1016/j.jneuroim.2010.10.020] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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Kusner LL, Kaminski HJ, Soltys J. Effect of complement and its regulation on myasthenia gravis pathogenesis. Expert Rev Clin Immunol 2010; 4:43-52. [PMID: 20477586 DOI: 10.1586/1744666x.4.1.43] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Myasthenia gravis (MG) is primarily caused by antibodies directed towards the skeletal muscle acetylcholine receptor, leading to muscle weakness. Although these antibodies may induce compromise of neuromuscular transmission by blocking acetylcholine receptor function or antigenic modulation, the predominant mechanism of injury to the neuromuscular junction is complement-mediated lysis of the postsynaptic membrane. The vast majority of data to support the role of complement derives from experimentally acquired MG (EAMG). In this article, we review studies that demonstrate the central role of complement in EAMG and MG pathogenesis along with the emerging role of complement in T- and B-cell function, as well as the potential for complement inhibitor-based therapy to treat human MG.
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Affiliation(s)
- Linda L Kusner
- Department of Neurology & Psychiatry, Saint Louis University, 1438 South Grand Blvd, St Louis, MO 63104, USA.
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Hoek RM, de Launay D, Kop EN, Yilmaz-Elis AS, Lin F, Reedquist KA, Verbeek JS, Medof ME, Tak PP, Hamann J. Deletion of either CD55 or CD97 ameliorates arthritis in mouse models. ACTA ACUST UNITED AC 2010; 62:1036-42. [PMID: 20131275 DOI: 10.1002/art.27347] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
OBJECTIVE CD55 (decay-accelerating factor) is best known for its role in the negative regulation of the complement system. Indeed, lack of this molecule leads to disease aggravation in many autoimmune disease models. However, CD55 is abundantly present on fibroblast-like synoviocytes and is also a ligand of the adhesion-class heptahelical receptor CD97, which is expressed by infiltrating macrophages. Treatment with antibodies to CD97 ameliorates the collagen-induced model of rheumatoid arthritis (RA) in DBA/1 mice, but the net contribution of CD55 is unknown. This study was undertaken to investigate the role of CD55 in experimental RA. METHODS Arthritis was induced in wild-type, CD55(-/-), and CD97(-/-) mice using collagen-induced and K/BxN serum-transfer models. Incidence of arthritis was monitored over time, and disease activity was assessed by clinical and immunohistochemical evaluation. RESULTS In contrast to observations in many inflammatory disease models, lack of CD55 resulted in decreased arthritis in experimental models of RA. Consistent with the previously reported effects of anti-CD97 antibody treatment, CD97(-/-) mice had reduced arthritis activity compared with wild-type controls. CONCLUSION Our findings indicate that the lack of CD55 or CD97 in 2 different models of arthritis increases resistance to the disease. These findings provide insight into a role for CD55 interaction with CD97 in the pathogenesis of RA and suggest that therapeutic strategies that disrupt CD55/CD97 may be clinically beneficial.
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Affiliation(s)
- Robert M Hoek
- Academic Medical Center, Amsterdam, The Netherlands.
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Abstract
Current therapy for myasthenia gravis is directed towards generalized modulation and suppression of the immune system. These approaches have been extensively studied and are effective in many patients with myasthenia, but at the cost of significant adverse effects due to the global effects on the immune system. Future directions in therapy are geared towards focused immunotherapies that aim to improve outcomes while lessening the burden of side effects. This paper reviews both the current accepted treatments for myasthenia gravis as well as promising targeted therapies in development.
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Affiliation(s)
- Hans D Katzberg
- Department of Neurology, Stanford University, Palo Alto, CA, USA
| | - Vera Bril
- University Health Network, University of Toronto, Toronto, Canada
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Heckmann JM, Uwimpuhwe H, Ballo R, Kaur M, Bajic VB, Prince S. A functional SNP in the regulatory region of the decay-accelerating factor gene associates with extraocular muscle pareses in myasthenia gravis. Genes Immun 2009; 11:1-10. [PMID: 19675582 PMCID: PMC2834500 DOI: 10.1038/gene.2009.61] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Complement activation in myasthenia gravis (MG) may damage muscle endplate and complement regulatory proteins such as decay-accelerating factor (DAF) or CD55 may be protective. We hypothesize that the increased prevalence of severe extraocular muscle (EOM) dysfunction among African MG subjects reported earlier may result from altered DAF expression. To test this hypothesis, we screened the DAF gene sequences relevant to the classical complement pathway and found an association between myasthenics with EOM paresis and the DAF regulatory region c.-198C>G SNP (odds ratio=8.6; P=0.0003). This single nucleotide polymorphism (SNP) results in a twofold activation of a DAF 5′-flanking region luciferase reporter transfected into three different cell lines. Direct matching of the surrounding SNP sequence within the DAF regulatory region with the known transcription factor-binding sites suggests a loss of an Sp1-binding site. This was supported by the observation that the c.-198C>G SNP did not show the normal lipopolysaccharide-induced DAF transcriptional upregulation in lymphoblasts from four patients. Our findings suggest that at critical periods during autoimmune MG, this SNP may result in inadequate DAF upregulation with consequent complement-mediated EOM damage. Susceptible individuals may benefit from anti-complement therapy in addition to immunosuppression.
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Affiliation(s)
- J M Heckmann
- Neurology Research Group, Department of Medicine, University of Cape Town, Cape Town, South Africa.
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Farrugia ME, Jacob S, Sarrigiannis PG, Kennett RP. Correlating extent of neuromuscular instability with acetylcholine receptor antibodies. Muscle Nerve 2009; 39:489-93. [PMID: 19260064 DOI: 10.1002/mus.21156] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In a retrospective study of 86 patients with myasthenia gravis (MG), we correlated the acetylcholine receptor (AChR) antibody titers with single-fiber EMG studies to explore whether a relationship exists between these parameters. We found that the AChR antibody titers correlated significantly with the mean of the mean consecutive difference of orbicularis oculi (OO, P<0.0001) and extensor digitorum communis (EDC, P<0.0001). The correlation was found to be stronger in OO. The antibody titers also correlated with the percentage of potential pairs with increased jitter in both muscles and, again, the correlation was more significant in OO (P<0.0001) than in EDC (P=0.001). We speculate that this relationship is stronger in OO than in the limb muscles, because the architectural and immunological differences in the motor unit render OO more vulnerable and sensitive to disturbances in neuromuscular transmission.
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Affiliation(s)
- Maria E Farrugia
- Department of Clinical Neurophysiology, West Wing, John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK.
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Abstract
Acquired myasthenia gravis (MG) is an autoimmune disorder of the neuromuscular junction in which patients experience fluctuating skeletal muscle weakness that often affects selected muscle groups preferentially. The target of the autoimmune attack in most cases is the skeletal muscle acetylcholine receptor (AChR), but in others, non-AChR components of the neuromuscular junction, such as the muscle-specific receptor tyrosine kinase, are targeted. The pathophysiological result is muscle endplate dysfunction and consequent fatigable muscle weakness. Clinical presentations vary substantially, both for anti-AChR positive and negative MG, and accurate diagnosis and selection of effective treatment depends on recognition of less typical as well as classic disease phenotypes. Accumulating evidence suggests that clinical MG subgroups might respond differently to treatment. In this Review, we provide current information about the epidemiology, immunopathogenesis, clinical presentations, diagnosis, and treatment of MG, including emerging therapeutic strategies.
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Affiliation(s)
- Matthew N Meriggioli
- Department of Neurology and Rehabilitation, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
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Griffiths MR, Neal JW, Fontaine M, Das T, Gasque P. Complement factor H, a marker of self protects against experimental autoimmune encephalomyelitis. THE JOURNAL OF IMMUNOLOGY 2009; 182:4368-77. [PMID: 19299737 DOI: 10.4049/jimmunol.0800205] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The CNS innate immune response is a "double-edged sword" representing a fine balance between protective antipathogen responses and detrimental neurocytotoxic effects. Hence, it is important to identify the key regulatory mechanisms involved in the control of CNS innate immunity and which could be harnessed to explore novel therapeutic avenues. In analogy to the newly described neuroimmune regulatory proteins also known as "don't eat me" signals (CD200, CD47, CD22, fractalkine, semaphorins), we herein identify the key role of complement regulator factor H (fH) in controlling neuroinflammation initiated in an acute mouse model of Ab-dependent experimental autoimmune encephalomyelitis. Mouse fH was found to be abundantly expressed by primary cultured neurons and neuronal cell lines (N1E115 and Neuro2a) at a level comparable to BV2 microglia and CLTT astrocytes. Mouse neurons expressed other complement regulators crry and low levels of CD55. In the brain, the expression of fH was localized to neuronal bodies and axons, endothelial cells, microglia but not oligodendrocytes and myelin sheaths and was dramatically reduced in inflammatory experimental autoimmune encephalomyelitis settings. When exogenous human fH was administered to disease Ab-dependent experimental autoimmune encephalomyelitis animals, there was a significant decrease in clinical score, inflammation, and demyelination, as compared with PBS-injected animals. We found that the accumulation of human fH in the brain parenchyma protected neurons from complement opsonization, axonal injury, and leukocyte infiltration. Our data argue for a key regulatory activity of fH in neuroprotection and provide novel therapeutic avenues for CNS chronic inflammatory diseases.
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Affiliation(s)
- Mark R Griffiths
- Department of Medical Biochemistry, Cardiff University, United Kingdom
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Soltys J, Gong B, Kaminski HJ, Zhou Y, Kusner LL. Extraocular muscle susceptibility to myasthenia gravis: unique immunological environment? Ann N Y Acad Sci 2008; 1132:220-4. [PMID: 18567871 DOI: 10.1196/annals.1405.037] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Extraocular muscle (EOM) is susceptible to neuromuscular junction disorders, in particular, myasthenia gravis (MG). While EOM physiological characteristics and the ocular motor system requirements contribute to the propensity of ocular motor deficits observed among patients with MG, the authors propose that EOM have immunological features that place the muscles at risk for immune attack. Genomic profiling studies have demonstrated that genes associated with the immune response are differentially expressed in EOM, with particular differences in both classical and alternative complement-mediated immune response pathways. Intrinsic complement regulators are expressed at lower levels at rodent EOM neuromuscular junctions, which would put them at risk for the complement-mediated injury that occurs in MG. In fact, systemic C inhibition in experimental autoimmune MG (EAMG) induced by administration of acetylcholine receptor (AChR) antibodies or immunization with AChR will eliminate complement deposition at junctions of other skeletal muscle, but not EOM. Also, EOM junctions have greater injury in active and passive EAMG by several measures, suggesting that the lack of complement inhibition puts the EOM at risk. Among ocular myasthenia patients, serum AChR antibody levels are low, which would support the concept that EOM junctions are more susceptible to antibody injury than are other junctions. These observations suggest that complement inhibitory therapies may prove to be particularly effective in treatment of ocular myasthenia.
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Affiliation(s)
- Jindrich Soltys
- Department of Neurology & Psychiatry, Saint Louis University, 1438 South Grand Avenue, St. Louis, MO 63104, USA
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Losen M, Martínez-Martínez P, Phernambucq M, Schuurman J, Parren PW, De Baets MH. Treatment of Myasthenia Gravis by Preventing Acetylcholine Receptor Modulation. Ann N Y Acad Sci 2008; 1132:174-9. [DOI: 10.1196/annals.1405.034] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Heckmann JM, Owen EP, Little F. Myasthenia gravis in South Africans: Racial differences in clinical manifestations. Neuromuscul Disord 2007; 17:929-34. [PMID: 17720497 DOI: 10.1016/j.nmd.2007.07.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Revised: 06/24/2007] [Accepted: 07/16/2007] [Indexed: 11/20/2022]
Abstract
We present data on the phenotypic variation in myasthenia gravis of 205 subjects from a multi-racial South African cohort. Consecutive subjects seen more than twice from 1996 to 2006, were included. Documented observational data included a myasthenia gravis and extra-ocular eye muscle score. Results showed Black subjects were more likely than Whites to develop treatment-resistant complete ophthalmoplegia and ptosis (18% vs. 2%; p=0.041). Of the 14 patients with this phenotype, 13 had generalised disease and positive AChR antibodies. Despite similar sized cohorts, White subjects were more likely than Blacks to develop generalised myasthenia poorly responsive to therapy (p=0.005). There were no significant racial differences in the time between diagnosis to initiation of therapy, or the performance and timing of thymectomy. The racial variation in some phenotypic features of myasthenia gravis and outcome to therapy, highlights the need to study biological factors in different subgroups to develop a more rational approach to immuno-suppressive therapy.
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Affiliation(s)
- J M Heckmann
- Division of Neurology, E8-74, Groote Schuur Hospital and University of Cape Town Observatory, 7925, South Africa.
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Leite MI, Jones M, Ströbel P, Marx A, Gold R, Niks E, Verschuuren JJGM, Berrih-Aknin S, Scaravilli F, Canelhas A, Morgan BP, Vincent A, Willcox N. Myasthenia gravis thymus: complement vulnerability of epithelial and myoid cells, complement attack on them, and correlations with autoantibody status. THE AMERICAN JOURNAL OF PATHOLOGY 2007; 171:893-905. [PMID: 17675582 PMCID: PMC1959483 DOI: 10.2353/ajpath.2007.070240] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In early-onset myasthenia gravis, the thymus contains lymph node-type infiltrates with frequent acetylcholine receptor (AChR)-specific germinal centers. Our recent evidence/two-step hypothesis implicates hyperplastic medullary thymic epithelial cells (expressing isolated AChR subunits) in provoking infiltration and thymic myoid cells (with intact AChR) in germinal center formation. To test this, we screened for complement attack in a wide range of typical generalized myasthenia patients. Regardless of the exact serology, thymi with sizeable infiltrates unexpectedly showed patchy up-regulation of both C5a receptor and terminal complement regulator CD59 on hyperplastic epithelial cells. These latter also showed deposits of activated C3b complement component, which appeared even heavier on infiltrating B cells, macrophages, and especially follicular dendritic cells. Myoid cells appeared particularly vulnerable to complement; few expressed the early complement regulators CD55, CD46, or CR1, and none were detectably CD59(+). Indeed, when exposed to infiltrates, and especially to germinal centers, myoid cells frequently labeled for C1q, C3b (25 to 48%), or even the terminal C9, with some showing obvious damage. This early/persistent complement attack on both epithelial and myoid cells strongly supports our hypothesis, especially implicating exposed myoid cells in germinal center formation/autoantibody diversification. Remarkably, the similar changes place many apparent AChR-seronegative patients in the same spectrum as the AChR-seropositive patients.
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Affiliation(s)
- Maria I Leite
- Department of Clinical Neurology, University of Oxford, Oxford, United Kingdom
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