Cytokine secretion by peripheral blood mononuclear cells in myasthenia gravis

Targeting autoimmune mechanisms by precision medicine in Myasthenia Gravis

Myasthenia Gravis (MG) is a chronic disabling autoimmune disease caused by autoantibodies to the neuromuscular junction (NMJ), characterized clinically by fluctuating weakness and early fatigability of ocular, skeletal and bulbar muscles. Despite being commonly considered a prototypic autoimmune disorder, MG is a complex and heterogeneous condition, presenting with variable clinical phenotypes, likely due to distinct pathophysiological settings related with different immunoreactivities, symptoms' distribution, disease severity, age at onset, thymic histopathology and response to therapies. Current treatment of MG based on international consensus guidelines allows to effectively control symptoms, but most patients do not reach complete stable remission and require life-long immunosuppressive (IS) therapies. Moreover, a proportion of them is refractory to conventional IS treatment, highlighting the need for more specific and tailored strategies. Precision medicine is a new frontier of medicine that promises to greatly increase therapeutic success in several diseases, including autoimmune conditions. In MG, B cell activation, antibody recycling and NMJ damage by the complement system are crucial mechanisms, and their targeting by innovative biological drugs has been proven to be effective and safe in clinical trials. The switch from conventional IS to novel precision medicine approaches based on these drugs could prospectively and significantly improve MG care. In this review, we provide an overview of key immunopathogenetic processes underlying MG, and discuss on emerging biological drugs targeting them. We also discuss on future direction of research to address the need for patients' stratification in endotypes according with genetic and molecular biomarkers for successful clinical decision making within precision medicine workflow.

LncRNA LINC00680 Acts as a Competing Endogenous RNA and Is Associated With the Severity of Myasthennia Gravis

Background and Purpose

Myasthenia gravis (MG) is a T cell-dependent antibody-mediated autoimmune disorder that can seriously affect patients' quality of life. However, few studies have focused on the severity of MG. Moreover, existing therapeutic efforts, including those targeting biomarkers for MG, remain unsatisfactory. Therefore, it is vital that we investigate the pathogenesis of MG and identify new biomarkers that can not only evaluate the severity of the disease but also serve as potential therapeutic targets. Long noncoding RNA LINC00680 has been found to be associated with the progression of a variety of diseases as a competing endogenous RNA (ceRNA). However, the specific role of LINC00680 in MG has yet to be clarified. Here, we aimed to investigate the association between LINC00680 and the severity of MG.

Methods

Bioinformatics tools, quantitative real-time PCR, Western blotting, and luciferase assays were selected to investigate key signaling pathways and RNA expression in patients with MG. The Quantitative MG Score scale and the MG Composite scale were used to evaluate the severity of MG in the included patients. Cell viability assays and flow cytometry analysis were selected to analyze cell proliferation and apoptosis.

Results

Compared with control subjects, the expression levels of LINC00680 and mitogen-activated protein kinase 1 (MAPK1) in peripheral blood mononuclear cells of patients with MG were both upregulated; the levels of miR-320a were downregulated. A positive correlation was detected between LINC00680 expression and the severity of MG. Luciferase reporter assays identified that LINC00680 acts as a target for miR-320a. The in vitro analysis confirmed that LINC00680 regulates the expression of MAPK1 by sponging miR-320a. Finally, the functional analysis indicated that LINC00680 promoted Jurkat cell proliferation and inhibited cellular apoptosis by sponging miR-320a.

Conclusion

LINC00680 may be associated with the severity of MG as a ceRNA by sponging miR-320a to upregulate MAPK1. These findings suggest that LINC00680 may represent a potential biomarker which evaluates the severity of MG and may serve as a therapeutic target.

Defects of CTLA-4 Are Associated with Regulatory T Cells in Myasthenia Gravis Implicated by Intravenous Immunoglobulin Therapy

Myasthenia gravis (MG) is a CD4⁺ T cell-dependent autoimmune disease resulting from aberrant immune response mediated by circulating autoantibodies at the neuromuscular junction. Intravenous immunoglobulin (IVIg) is an expensive and commonly used immunotherapeutic approach to treat patients with MG. The mechanisms of actions involved in IVIg treatment, however, remain to be investigated. In an effort to examine the roles of various subsets of CD4⁺ T cells in the periphery blood of MG and uncover the mechanisms that contribute to the therapeutical effects of IVIg, we first demonstrated that a subset of CD4⁺ T cells, CTLA-4-expressing regulatory T (Treg) cells, were underrepresented and functionally defective in MG patients. The dynamic profiling during the IVIg therapy course further revealed an inverse relationship between the frequency of CTLA-4⁺ Treg and the quantitative MG (QMG) score that represents disease severity. Our mechanistic studies indicated that IVIg expands CTLA-4-Treg cells via modulating antigen-presenting dendritic cells (DCs). To determine the molecular defects of CTLA-4 in abnormities of Treg in MG patients, we demonstrated hypermethylation at -658 and -793 CpGs of CTLA-4 promoter in MG Tregs. Interestingly, IVIg therapy significantly reduced the methylation level at these two sites in MG patients. Overall, our study may suggest a role of CTLA-4 in functionally defected Treg cells in MG and its actions involved in IVIg therapy.

Identification of the Regulatory Role of lncRNA SNHG16 in Myasthenia Gravis by Constructing a Competing Endogenous RNA Network

Myasthenia gravis (MG) is an autoimmune disorder resulting from antibodies against the proteins at the neuromuscular junction. Emerging evidence indicates that long non-coding RNAs (lncRNAs), acting as competing endogenous RNAs (ceRNAs), are involved in various diseases. However, the regulatory mechanisms of ceRNAs underlying MG remain largely unknown. In this study, we constructed a lncRNA-mediated ceRNA network involved in MG using a multi-step computational strategy. Functional annotation analysis suggests that these lncRNAs may play crucial roles in the immunological mechanism underlying MG. Importantly, through manual literature mining, we found that lncRNA SNHG16 (small nucleolar RNA host gene 16), acting as a ceRNA, plays important roles in the immune processes. Further experiments showed that SNHG16 expression was upregulated in peripheral blood mononuclear cells (PBMCs) from MG patients compared to healthy controls. Luciferase reporter assays confirmed that SNHG16 is a target of the microRNA (miRNA) let-7c-5p. Subsequent experiments indicated that SNHG16 regulates the expression of the key MG gene interleukin (IL)-10 by sponging let-7c-5p in a ceRNA manner. Furthermore, functional assays showed that SNHG16 inhibits Jurkat cell apoptosis and promotes cell proliferation by sponging let-7c-5p. Our study will contribute to a deeper understanding of the regulatory mechanism of MG and will potentially provide new therapeutic targets for MG patients.

CD19+ Tim-1+ B cells are decreased and negatively correlated with disease severity in Myasthenia Gravis patients

T cell immunoglobulin mucin domain-1(Tim-1) was recently identified to be critical and essential for optimal regulatory B cells function in maintaining immune tolerance. We aimed to measure the expression levels of Tim-1 on B cells from patients with Myasthenia Gravis (MG) and to investigate whether the expression of Tim-1 is associated with pathogenesis of MG. A total of 34 patients with MG (18 generalized MG (GMG) and 16 ocular MG (OMG) and 24 healthy donors were recruited in this study. The quantitative myasthenia gravis score (QMGS) was used to evaluate the clinical severity. Real-time PCR and flow cytometry were used to measure the levels of Tim-1 expressed on peripheral B cells. Peripheral CD138+ plasma cells were assayed by flow cytometry. Serum Th17-related cytokines (IL-6, IL-1β and IL-17) and anti-AChR antibody (Ab) titers were tested by enzyme-linked immunosorbent assay (ELISA). Our data demonstrated that the mRNA and protein expression levels of B cell Tim-1 in both the GMG and OMG groups were significantly lower than those in healthy controls, with lower expression in GMG than in OMG. Tim-1 expression on B cells from OMG/GMG was negatively correlated with clinical severity, plasma cells frequency, serum Th17-related cytokines and anti-AChR Ab levels. Our results indicated that aberrant expression of Tim-1 exists on B cells and may contribute to the Th17 polarization and antibody-secreting plasma cells differentiation in MG patients.

A Sensitive Method for Detecting Peptide-specific CD4+ T Cell Responses in Peripheral Blood from Patients with Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune neurological disorder typified by skeletal muscle fatigue and most often production of autoantibodies against the nicotinic acetylcholine receptor (AChR). The present study was undertaken to assess the extent of AChR-peptide recognition in MG patients using co-culturing (DC:TC) of autologous monocyte-derived dendritic cells (moDCs) and highly enriched CD4⁺ T cells from the blood as compared to the traditional whole peripheral blood mononuclear cell (PBMC) cultures. We found that the DC:TC cultures were highly superior to the PBMC cultures for detection of reactivity toward HLA-DQ/DR-restricted AChR-peptides. In fact, whereas DC:TC cultures identified recognition in all MG patients the PBMC cultures failed to detect responsiveness in around 40% of the patients. Furthermore, reactivity to multiple peptides was evident in DC:TC cultures, while PBMC cultures mostly exhibited reactivity to a single peptide. No healthy control (HC) CD4⁺ T cells responded to the peptides in either culture system. Interestingly, whereas spontaneous production of IFNγ and IL-17 was observed in the DC:TC cultures from MG patients, recall responses to peptides enhanced IL-10 production in 9/13 MG patients, while little increase in IFNγ and IL-17 was seen. HCs did not produce cytokines to peptide stimulations. We conclude that the DC: TC culture system is significantly more sensitive and better identifies the extent of responsiveness in MG patients to AChR-peptides than traditional PBMC cultures.

The effect of interleukin (IL)-21 and CD4+ CD25++ T cells on cytokine production of CD4+ responder T cells in patients with myasthenia gravis

Impairment of the suppressive function of regulatory T (T_reg ) cells has been reported in myasthenia gravis (MG). In this study, cytokine-related mechanisms that may lead to the defect of T_reg were investigated in patients with anti-acetylcholine receptor antibody-positive MG (AChR + MG). Proliferation and cytokine production of responder T (T_resp ) cells in response to polyclonal activation were measured in a suppression assay. The effect of interleukin (IL)-21 on suppression was evaluated in vitro in co-culture. IL-21 increased the proliferation of T_resp cells in T_resp /T_reg co-cultures. T_resp cells from patients with MG secreted significantly lower levels of IL-2. In patients with MG, IL-2 levels did not change with the addition of T_reg to cultures, whereas it decreased significantly in controls. In T_resp /T_reg co-cultures, IL-4, IL-6 and IL-10 production increased in the presence of T_reg in patients. Interferon (IFN)-γ was decreased, whereas IL-17A was increased in both patient and control groups. IL-21 inhibited the secretion of IL-4 in MG and healthy controls (HC), and IL-17A in HC only. The results demonstrated that IL-21 enhances the proliferation of T_resp cells in the presence of T_reg . An effect of IL-21 mainly on T_resp cells through IL-2 is implicated.

Differential Cytokine Changes in Patients with Myasthenia Gravis with Antibodies against AChR and MuSK

Neuromuscular transmission failure in myasthenia gravis (MG) is most commonly elicited by autoantibodies (ab) to the acetylcholine receptor or the muscle-specific kinase, constituting AChR-MG and MuSK-MG. It is controversial whether these MG subtypes arise through different T helper (Th) 1, Th2 or Th17 polarized immune reactions and how these reactions are blunted by immunosuppression. To address these questions, plasma levels of cytokines related to various Th subtypes were determined in patients with AChR-MG, MuSK-MG and healthy controls (CON). Peripheral blood mononuclear cells (PBMC) were activated in vitro by anti-CD3, and cytokines were quantified in supernatants. In purified blood CD4⁺ T cells, RNA of various cytokines, Th subtype specific transcription factors and the co-stimulatory molecule, CD40L, were quantified by qRT-PCR. Plasma levels of Th1, Th2 and Th17 related cytokines were overall not significantly different between MG subtypes and CON. By contrast, in vitro stimulated PBMC from MuSK-MG but not AChR-MG patients showed significantly increased secretion of the Th1, Th17 and T follicular helper cell related cytokines, IFN-γ, IL-17A and IL-21. Stimulated expression of IL-4, IL-6, IL-10 and IL-13 was not significantly different. At the RNA level, expression of CD40L by CD4⁺ T cells was reduced in both AChR-MG and MuSK-MG patients while expression of Th subset related cytokines and transcription factors were normal. Immunosuppression treatment had two effects: First, it reduced levels of IL12p40 in the plasma of AChR-MG and MuSK-MG patients, leaving other cytokine levels unchanged; second, it reduced spontaneous secretion of IFN-γ and increased secretion of IL-6 and IL-10 by cultured PBMC from AChR-MG, but not MuSK-MG patients. We conclude that Th1 and Th17 immune reactions play a role in MuSK-MG. Immunosuppression attenuates the Th1 response in AChR-MG and MuSK-MG, but otherwise modulates immune responses in AChR-MG and MuSK-MG patients differentially.

B cells produce less IL-10, IL-6 and TNF-α in myasthenia gravis

B cells from myasthenia gravis (MG) patients with autoantibodies (Aab) against acetylcholine receptor (AChR), muscle-specific kinase (MuSK) or with no detectable Aab were investigated as cytokine producing cells in this study. B cells were evaluated for memory phenotypes and expressions of IL-10, IL-6 and IL-12A. Induced productions of IL-10, IL-6, IL-12p40, TNF-α and LT from isolated B cells in vitro were measured by immunoassays. MG patients receiving immunosuppressive treatment had higher proportions of memory B cells compared with healthy controls and untreated patients. With CD40 stimulation MG patients produced significantly lower levels of IL-10, IL-6. With CD40 and B cell receptor stimulation of B cells, TNF-α production also decreased in addition to these cytokines. The lower levels of these cytokine productions were not related to treatment. Our results confirm a disturbance of B cell subpopulations in MG subgroups on immunosuppressive treatment. B cell derived IL-10, IL-6 and TNF-α are down-regulated in MG, irrespective of different antibody productions. Ineffective cytokine production by B cells may be a susceptibility factor in dysregulation of autoimmune Aab production.

Expression of interleukin-22 in myasthenia gravis

IL-17 and IL-22 are implicated in the pathogenesis of autoimmune diseases. The roles of IL-22 in the pathophysiology of myasthenia gravis (MG) remain unsettled. The aim of this study was to investigate the possible relationship between serum IL-22, IL-17 levels, anti-acetylcholine receptor antibody (anti-AChR Ab) titres and clinical parameters in patients with MG. The serum IL-22, IL-17 levels and anti-AChR Ab titres were tested by enzyme-linked immunosorbent assay (ELISA), while the expression of IL-22 and IL-17 mRNAs in peripheral blood mononuclear cells (PBMC) from healthy and MG subjects were detected by quantitative real-time PCR (qRT-PCR). Furthermore, PBMC from 12 patients with generalized MG were purified and treated with recombinant human IL-22 (rhIL-22), the IL-17 levels of supernatant were detected by ELISA. We found that the IL-17 levels were significantly increased, but IL-22 levels were significantly decreased in the serum of patients with MG compared with healthy controls. Consistantly, a significant decrease in IL-22 mRNA levels and an increase in IL-17 mRNA levels were detected in PBMC collected from patients with MG, compared with healthy controls. A negative correlation between IL-22 mRNA in PBMC, serum IL-22 and serum anti-AChR Ab levels was found in patients with MG. Moreover, in cultured MG PBMC treated with recombinant human IL-22 (rhIL-22), the IL-17 levels were decreased in a dose-dependent manner. Our findings indicated a possible role of IL-22 as a protective factor in MG.

Interleukin-10 promoter polymorphisms in myasthenia gravis

Interleukin 10 (IL-10) is secreted by several hemopoietic cells and suppresses the Th1 mediated immune response, while stimulating B cell differentiation and the humoral immune response. IL-10 expression in Con A-stimulated peripheral blood mononuclear cells is related to three polymorphisms in the promoter region of the IL-10 gene; G/A at position -1082, T/C at position -819 and A/C at position -592. We analyzed the distribution of these IL-10 polymorphisms in 64 MG patients and 87 healthy blood donors to determine any influence on MG susceptibility. MG patients had a significantly higher frequency of the ACC/ACC haplotype (12.5% vs 3.4% in controls), as had the subgroups with late onset MG and thymomatous MG (20.0% and 21.4%, respectively). Early onset MG patients had a high frequency of the ATA/ATA haplotype (19.2% vs 3.4% in controls). Titin Ab-positive MG patients had high ACC/ACC (20.0%). This study indicates a direct link between IL-10 and MG pathogenesis, although the complex role of this multi-faceted cytokine in vivo is as yet not fully elucidated.

Interleukin-5 and interleukin-10 are produced in central nervous system tumor cysts

Interleukin-5 and interleukin-10, as important mediators of vascular permeability, contribute to the development of various pathologic effusions. However, little is known regarding the involvement of these two cytokines in the formation of cysts associated with central nervous system (CNS) tumors. Twenty-eight patients with various cystic CNS tumors were investigated for expression of interleukin-5 and interleukin-10 in cyst fluid and their matched cytokine receptors in tumor tissue. Interleukin-5 and interleukin-10 were detected in cyst fluid, and interleukin-5 concentration was significantly correlated with interleukin-10 concentration (r=0.508, p=0.006). Moreover, both receptors were also detectable in the tumor tissue specimens and high levels of expression were also found in perivascular cells. Therefore, the local production of interleukin-5 and interleukin-10 might be implicated in some types of cyst formation.

Clinical efficacy and cytokine network-modulating effects of tacrolimus in myasthenia gravis

To clarify the long-term efficacy, safety and the cytokine network-modulating effects of tacrolimus in myasthenia gravis, medical records of 86 newly diagnosed consecutive patients and nine steroid-dependent patients were retrospectively reviewed, and peripheral blood mononuclear cells (PBMC) were cultured for the cytokine profile. Steroid reduction effects were observed by using tacrolimus, and no serious adverse effects were observed. The culture study showed reduced IL-12, IL-17, IFN-gamma, GM-CSF, TNF-alpha and MIP-1beta, and elevated IL-10 in the PBMC from patients who received tacrolimus, which suggests inhibition of T cells and macrophages, and enhancement of type 1 regulatory T cells.

Beneficial Effect of Tacrolimus on Myasthenia Gravis With Thymoma

We examined the effect of tacrolimus on myasthenia gravis (MG). Five patients with thymoma and 5 patients without thymoma underwent prior thymectomy but showed persistent myasthenic symptoms. Oral administration with tacrolimus significantly improved MG scores 1, 3, and 6 months following the beginning of treatment in all patients (P < 0.05), and the improvement was significantly higher in the thymoma group compared with the nonthymoma group (P < 0.05). However, there was no significant change in antiacetylcholine receptor titers in either group. This indicates a particular application of immunosuppressive therapy for thymomatous MG following thymectomy.

Interleukine-6 (IL-6) may be a link between myasthenia gravis and myoepithelioma of the parotid gland

Myoepithelioma is a rare benign neoplasm of the salivary glands occurring more frequently in the parotids. Myasthenia gravis (MG) is a chronic, T-cell dependent, antibody and complement-mediated autoimmune neuromuscular transmission disorder. Interleukine-6 (IL-6) is an immune protein belonging to the family of the hematopoietins, liberated in response to infection, burns, trauma, and neoplastic diseases. It seems that an overproduction of IL-6 might play an important role in the pathophysiology of MG. Moreover, it has been discussed the possible role of IL-6 as a modulating factor either in proliferation or in differentiation of pleomorphic adenoma cell line into myoepithelioma. The authors present a rare case of parotid myoepithelioma occurred in a patient affected by myasthenia gravis and suppose a possible IL-6 mediated relationship between myasthenia gravis and parotid myoepithelioma.

Overexpression of phosphodiesterases in experimental autoimmune myasthenia gravis: suppression of disease by a phosphodiesterase inhibitor

Myasthenia gravis (MG) and experimental autoimmune MG (EAMG) are T cell-dependent antibody-mediated autoimmune disorders, in which the nicotinic acetylcholine receptor (AChR) is the major autoantigen. DNA microarray analysis revealed increased levels of several phosphodiesterase (PDE) subtypes in lymph node cells (LNC) and muscles of EAMG rats compared with healthy controls. Quantitative real-time PCR analysis indicated that EAMG is characterized by an increase of PDE subtypes 1, 3, 4, and 7 in LNC and of PDE subtypes 2, 3, 4, and 7 in muscles. Pentoxifylline (PTX), a general PDE inhibitor, inhibited the progression of EAMG when treatment started at either the acute or chronic stages of disease. This suppression was associated with down-regulation of humoral and cellular AChR-specific responses, as well as down-regulation of PDE4, TNF-alpha, IL-18, IL-12, and IL-10 in LNC and of PDEs 1, 4, 7, and TNF-alpha in muscles. The expression of Foxp3, a transcription factor essential for CD4+CD25+ regulatory T cell function, was increased in splenocytes although the number of these cells remained unchanged. PTX also reduced the expression of the endopeptidase cathepsin-l, a marker of muscle damage, in EAMG muscles. This study demonstrates the involvement of PDE regulation in EAMG pathogenesis and suggests that PDE inhibitors may be considered for immunotherapy of MG.

Effects of cytokines on acetylcholine receptor expression: implications for myasthenia gravis

Myasthenia gravis is an autoimmune disease associated with thymic pathologies, including hyperplasia. In this study, we investigated the processes that may lead to thymic overexpression of the triggering Ag, the acetylcholine receptor (AChR). Using microarray technology, we found that IFN-regulated genes are more highly expressed in these pathological thymic tissues compared with age- and sex-matched normal thymus controls. Therefore, we investigated whether proinflammatory cytokines could locally modify AChR expression in myoid and thymic epithelial cells. We found that AChR transcripts are up-regulated by IFN-gamma, and even more so by IFN-gamma and TNF-alpha, as assessed by real-time RT-PCR, with the alpha-AChR subunit being the most sensitive to this regulation. The expression of AChR protein was increased at the cytoplasmic level in thymic epithelial cells and at the membrane in myoid cells. To examine whether IFN-gamma could influence AChR expression in vivo, we analyzed AChR transcripts in IFN-gamma gene knock-out mice, and found a significant decrease in AChR transcript levels in the thymus but not in the muscle, compared with wild-type mice. However, up-regulation of AChR protein expression was found in the muscles of animals with myasthenic symptoms treated with TNF-alpha. Altogether, these results indicate that proinflammatory cytokines influence the expression of AChR in vitro and in vivo. Because proinflammatory cytokine activity is evidenced in the thymus of myasthenia gravis patients, it could influence AChR expression and thereby contribute to the initiation of the autoimmune anti-AChR response.

Comparative study of pre-operative thymic imaging and pathology in patients with myasthenia gravis

The objective of our study is to compare the diagnostic significance of mediastinal CT and (201)Tl-single-photon emission computed tomography (SPECT) with thymic histology in patients with myasthenia gravis (MG). The subjects were 30 patients with MG who were scheduled to receive thymectomy. They did not receive immunosuppressive therapy. The mediastinal CT and (201)Tl-SPECT were performed before the thymectomy. As a consequence, 9 patients had thymoma, 11 had lymphoid follicular hyperplasia (LFH), and 10 had normal thymus on histologic examination after thymectomy. Retrospectively, CT diagnosed the histology of all 9 patients with thymoma, and 5 of 11 with LFH. (201)Tl-SPECT could detect abnormal accumulations in only 6 of 9 cases of thymoma, and 6 of 11 cases of LFH. (201)Tl-SPECT could not distinguish thymoma from LFH. We conclude that a CT study is recommended as an essential study for the detection of thymic abnormalities in pre-operative patients with MG.