RESUMEN
K2P2.1 (TREK1), a two-pore domain potassium channel, has emerged as regulator of leukocyte transmigration into the central nervous system. In the context of skeletal muscle, immune cell infiltration constitutes the pathogenic hallmark of idiopathic inflammatory myopathies (IIMs). However, the underlying mechanisms remain to be elucidated. In this study, we investigated the role of K2P2.1 in the autoimmune response of IIMs. We detected K2P2.1 expression in primary skeletal muscle and endothelial cells of murine and human origin. We observed an increased pro-inflammatory cell response, adhesion and transmigration by pharmacological blockade or genetic deletion of K2P2.1 in vitro and in in vivo myositis mouse models. Of note, our findings were not restricted to endothelial cells as skeletal muscle cells with impaired K2P2.1 function also demonstrated a strong pro-inflammatory response. Conversely, these features were abrogated by activation of K2P2.1 and improved the disease course of a myositis mouse model. In humans, K2P2.1 expression was diminished in IIM patients compared to non-diseased controls arguing for the translatability of our findings. In summary, K2P2.1 may regulate the inflammatory response of skeletal muscle. Further research is required to understand whether K2P2.1 could serve as novel therapeutic target.
Asunto(s)
Células Endoteliales , Miositis , Humanos , Animales , Ratones , Células Endoteliales/patología , Miositis/genética , Músculo Esquelético/patología , Leucocitos/patologíaRESUMEN
Myasthenia gravis is a chronic antibody-mediated autoimmune disease disrupting neuromuscular synaptic transmission. Informative biomarkers remain an unmet need to stratify patients with active disease requiring intensified monitoring and therapy; their identification is the primary objective of this study. We applied mass spectrometry-based proteomic serum profiling for biomarker discovery. We studied an exploration and a prospective validation cohort consisting of 114 and 140 anti-acetylcholine receptor antibody (AChR-Ab)-positive myasthenia gravis patients, respectively. For downstream analysis, we applied a machine learning approach. Protein expression levels were confirmed by ELISA and compared to other myasthenic cohorts, in addition to myositis and neuropathy patients. Anti-AChR-Ab levels were determined by a radio receptor assay. Immunohistochemistry and immunofluorescence of intercostal muscle biopsies were employed for validation in addition to interactome studies of inter-alpha-trypsin inhibitor heavy chain H3 (ITIH3). Machine learning identified ITIH3 as potential serum biomarker reflective of disease activity. Serum levels correlated with disease activity scores in the exploration and validation cohort and were confirmed by ELISA. Lack of correlation between anti-AChR-Ab levels and clinical scores underlined the need for biomarkers. In a subgroup analysis, ITIH3 was indicative of treatment responses. Immunostaining of muscle specimens from these patients demonstrated ITIH3 localization at the neuromuscular endplates in myasthenia gravis but not in controls, thus providing a structural equivalent for our serological findings. Immunoprecipitation of ITIH3 and subsequent proteomics lead to identification of its interaction partners playing crucial roles in neuromuscular transmission. This study provides data on ITIH3 as a potential pathophysiological-relevant biomarker of disease activity in myasthenia gravis. Future studies are required to facilitate translation into clinical practice.
Asunto(s)
Biomarcadores , Miastenia Gravis , Humanos , Miastenia Gravis/sangre , Miastenia Gravis/diagnóstico , Miastenia Gravis/patología , Miastenia Gravis/metabolismo , Biomarcadores/sangre , Biomarcadores/metabolismo , Masculino , Femenino , Persona de Mediana Edad , Adulto , Anciano , Autoanticuerpos/sangre , Receptores Colinérgicos/inmunología , Receptores Colinérgicos/metabolismo , Proteómica/métodos , Estudios de Cohortes , Adulto Joven , Proteínas Inhibidoras de Proteinasas Secretoras/sangre , Aprendizaje AutomáticoRESUMEN
Inclusion body myositis (IBM) is unique across the spectrum of idiopathic inflammatory myopathies (IIM) due to its distinct clinical presentation and refractoriness to current treatment approaches. One explanation for this resistance may be the engagement of cell-autonomous mechanisms that sustain or promote disease progression of IBM independent of inflammatory activity. In this study, we focused on senescence of tissue-resident cells as potential driver of disease. For this purpose, we compared IBM patients to non-diseased controls and immune-mediated necrotizing myopathy patients. Histopathological analysis suggested that cellular senescence is a prominent feature of IBM, primarily affecting non-myogenic cells. In-depth analysis by single nuclei RNA sequencing allowed for the deconvolution and study of muscle-resident cell populations. Among these, we identified a specific cluster of fibro-adipogenic progenitors (FAPs) that demonstrated key hallmarks of senescence, including a pro-inflammatory secretome, expression of p21, increased ß-galactosidase activity, and engagement of senescence pathways. FAP function is required for muscle cell health with changes to their phenotype potentially proving detrimental. In this respect, the transcriptomic landscape of IBM was also characterized by changes to the myogenic compartment demonstrating a pronounced loss of type 2A myofibers and a rarefication of acetylcholine receptor expressing myofibers. IBM muscle cells also engaged a specific pro-inflammatory phenotype defined by intracellular complement activity and the expression of immunogenic surface molecules. Skeletal muscle cell dysfunction may be linked to FAP senescence by a change in the collagen composition of the latter. Senescent FAPs lose collagen type XV expression, which is required to support myofibers' structural integrity and neuromuscular junction formation in vitro. Taken together, this study demonstrates an altered phenotypical landscape of muscle-resident cells and that FAPs, and not myofibers, are the primary senescent cell type in IBM.
Asunto(s)
Miositis por Cuerpos de Inclusión , Miositis , Humanos , Miositis por Cuerpos de Inclusión/metabolismo , Adipogénesis , Colágeno/metabolismo , Músculo Esquelético/metabolismoRESUMEN
BACKGROUND: Cladribine is a synthetic purine analogue that interferes with DNA synthesis and repair next to disrupting cellular proliferation in actively dividing lymphocytes. The compound is approved for the treatment of multiple sclerosis (MS). Cladribine can cross the blood-brain barrier, suggesting a potential effect on central nervous system (CNS) resident cells. Here, we explored compartment-specific immunosuppressive as well as potential direct neuroprotective effects of oral cladribine treatment in experimental autoimmune encephalomyelitis (EAE) mice. METHODS: In the current study, we compare immune cell frequencies and phenotypes in the periphery and CNS of EAE mice with distinct grey and white matter lesions (combined active and focal EAE) either orally treated with cladribine or vehicle, using flow cytometry. To evaluate potential direct neuroprotective effects, we assessed the integrity of the primary auditory cortex neuronal network by studying neuronal activity and spontaneous synaptic activity with electrophysiological techniques ex vivo. RESULTS: Oral cladribine treatment significantly attenuated clinical deficits in EAE mice. Ex vivo flow cytometry showed that cladribine administration led to peripheral immune cell depletion in a compartment-specific manner and reduced immune cell infiltration into the CNS. Histological evaluations revealed no significant differences for inflammatory lesion load following cladribine treatment compared to vehicle control. Single cell electrophysiology in acute brain slices was performed and showed an impact of cladribine treatment on intrinsic cellular firing patterns and spontaneous synaptic transmission in neurons of the primary auditory cortex. Here, cladribine administration in vivo partially restored cortical neuronal network function, reducing action potential firing. Both, the effect on immune cells and neuronal activity were transient. CONCLUSIONS: Our results indicate that cladribine exerts a neuroprotective effect after crossing the blood-brain barrier independently of its peripheral immunosuppressant action.
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Encefalomielitis Autoinmune Experimental , Encefalomielitis , Fármacos Neuroprotectores , Ratones , Animales , Encefalomielitis Autoinmune Experimental/patología , Cladribina/uso terapéutico , Fármacos Neuroprotectores/farmacología , Ratones Endogámicos C57BL , Modelos Animales de Enfermedad , Inmunosupresores/uso terapéuticoRESUMEN
BACKGROUND: Vaccination has proven to be effective in preventing SARS-CoV-2 transmission and severe disease courses. However, immunocompromised patients have not been included in clinical trials and real-world clinical data point to an attenuated immune response to SARS-CoV-2 vaccines among patients with multiple sclerosis (MS) receiving immunomodulatory therapies. METHODS: We performed a retrospective study including 59 ocrelizumab (OCR)-treated patients with MS who received SARS-CoV-2 vaccination. Anti-SARS-CoV-2-antibody titres, routine blood parameters and peripheral immune cell profiles were measured prior to the first (baseline) and at a median of 4 weeks after the second vaccine dose (follow-up). Moreover, the SARS-CoV-2-specific T cell response and peripheral B cell subsets were analysed at follow-up. Finally, vaccination-related adverse events were assessed. RESULTS: After vaccination, we found anti-SARS-CoV-2(S) antibodies in 27.1% and a SARS-CoV-2-specific T cell response in 92.7% of MS cases. T cell-mediated interferon (IFN)-γ release was more pronounced in patients without anti-SARS-CoV-2(S) antibodies. Antibody titres positively correlated with peripheral B cell counts, time since last infusion and total IgM levels. They negatively correlated with the number of previous infusion cycles. Peripheral plasma cells were increased in antibody-positive patients. A positive correlation between T cell response and peripheral lymphocyte counts was observed. Moreover, IFN-γ release was negatively correlated with the time since the last infusion. CONCLUSION: In OCR-treated patients with MS, the humoral immune response to SARS-CoV-2 vaccination is attenuated while the T cell response is preserved. However, it is still unclear whether T or B cell-mediated immunity is required for effective clinical protection. Nonetheless, given the long-lasting clinical effects of OCR, monitoring of peripheral B cell counts could facilitate individualised treatment regimens and might be used to identify the optimal time to vaccinate.
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COVID-19 , Esclerosis Múltiple , Vacunas Virales , Anticuerpos Monoclonales Humanizados , Anticuerpos Antivirales , COVID-19/prevención & control , Vacunas contra la COVID-19/uso terapéutico , Humanos , Inmunidad , Esclerosis Múltiple/tratamiento farmacológico , Estudios Retrospectivos , SARS-CoV-2 , VacunaciónRESUMEN
Myasthenia gravis (MG) is a prototypical autoimmune disease of the neuromuscular junction (NMJ). The study of the underlying pathophysiology has provided novel insights into the interplay of autoantibodies and complement-mediated tissue damage. Experimental autoimmune myasthenia gravis (EAMG) emerged as a valuable animal model, designed to gain further insight and to test novel therapeutic approaches for MG. However, the availability of native acetylcholine receptor (AChR) protein is limited favouring the use of recombinant proteins. To provide a simplified platform for the study of MG, we established a model of EAMG using a recombinant protein containing the immunogenic sequence of AChR in mice. This model recapitulates key features of EAMG, including fatigable muscle weakness, the presence of anti-AChR-antibodies, and engagement of the NMJ by complement and a reduced NMJ density. Further characterization of this model demonstrated a prominent B cell immunopathology supported by T follicular helper cells. Taken together, the herein-presented EAMG model may be a valuable tool for the study of MG pathophysiology and the pre-clinical testing of therapeutic applications.
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Miastenia Gravis Autoinmune Experimental , Receptores Colinérgicos , Ratones , Animales , Miastenia Gravis Autoinmune Experimental/tratamiento farmacológico , Miastenia Gravis Autoinmune Experimental/metabolismo , Unión Neuromuscular/patología , Proteínas del Sistema Complemento , Autoanticuerpos , InmunizaciónRESUMEN
BACKGROUND: The clinical heterogeneity of myasthenia gravis (MG), an autoimmune disease defined by antibodies (Ab) directed against the postsynaptic membrane, constitutes a challenge for patient stratification and treatment decision making. Novel strategies are needed to classify patients based on their biological phenotypes aiming to improve patient selection and treatment outcomes. METHODS: For this purpose, we assessed the serum proteome of a cohort of 140 patients with anti-acetylcholine receptor-Ab-positive MG and utilised consensus clustering as an unsupervised tool to assign patients to biological profiles. For in-depth analysis, we used immunogenomic sequencing to study the B cell repertoire of a subgroup of patients and an in vitro assay using primary human muscle cells to interrogate serum-induced complement formation. FINDINGS: This strategy identified four distinct patient phenotypes based on their proteomic patterns in their serum. Notably, one patient phenotype, here named PS3, was characterised by high disease severity and complement activation as defining features. Assessing a subgroup of patients, hyperexpanded antibody clones were present in the B cell repertoire of the PS3 group and effectively activated complement as compared to other patients. In line with their disease phenotype, PS3 patients were more likely to benefit from complement-inhibiting therapies. These findings were validated in a prospective cohort of 18 patients using a cell-based assay. INTERPRETATION: Collectively, this study suggests proteomics-based clustering as a gateway to assign patients to a biological signature likely to benefit from complement inhibition and provides a stratification strategy for clinical practice. FUNDING: CN and CBS were supported by the Forschungskommission of the Medical Faculty of the Heinrich Heine University Düsseldorf. CN was supported by the Else Kröner-Fresenius-Stiftung (EKEA.38). CBS was supported by the Deutsche Forschungsgemeinschaft (DFG-German Research Foundation) with a Walter Benjamin fellowship (project 539363086). The project was supported by the Ministry of Culture and Science of North Rhine-Westphalia (MODS, "Profilbildung 2020" [grant no. PROFILNRW-2020-107-A]).
Asunto(s)
Autoanticuerpos , Miastenia Gravis , Fenotipo , Proteómica , Receptores Colinérgicos , Humanos , Miastenia Gravis/sangre , Miastenia Gravis/diagnóstico , Miastenia Gravis/inmunología , Miastenia Gravis/metabolismo , Receptores Colinérgicos/inmunología , Receptores Colinérgicos/metabolismo , Autoanticuerpos/sangre , Autoanticuerpos/inmunología , Proteómica/métodos , Femenino , Masculino , Persona de Mediana Edad , Adulto , Análisis por Conglomerados , Proteoma , Anciano , Linfocitos B/metabolismo , Linfocitos B/inmunología , Activación de ComplementoRESUMEN
Experimental autoimmune encephalomyelitis (EAE) is the most common murine model for multiple sclerosis (MS) and is frequently used to further elucidate the still unknown etiology of MS in order to develop new treatment strategies. The myelin oligodendrocyte glycoprotein peptide 35-55 (MOG35-55) EAE model reproduces a self-limiting monophasic disease course with ascending paralysis within 10 days after immunization. The mice are examined daily using a clinical scoring system. MS is driven by different pathomechanisms with a specific temporal pattern, thus the investigation of the role of central nervous system (CNS)-resident cell types during disease progression is of great interest. The unique feature of this protocol is the simultaneous isolation of all principal CNS-resident cell types (microglia, oligodendrocytes, astrocytes, and neurons) applicable in adult EAE and healthy mice. The dissociation of the brain and the spinal cord from adult mice is followed by magnetic-activated cell sorting (MACS) to isolate microglia, oligodendrocytes, astrocytes, and neurons. Flow cytometry was used to perform quality analyses of the purified single-cell suspensions confirming viability after cell isolation and indicating the purity of each cell type of approximately 90%. In conclusion, this protocol offers a precise and comprehensive way to analyze complex cellular networks in healthy and EAE mice. Moreover, required mice numbers can be substantially reduced as all four cell types are isolated from the same mice.
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Encefalomielitis Autoinmune Experimental , Encefalomielitis , Esclerosis Múltiple , Ratones , Animales , Encefalomielitis Autoinmune Experimental/etiología , Ratones Endogámicos C57BL , Sistema Nervioso Central/metabolismo , Médula Espinal/metabolismo , Glicoproteína Mielina-Oligodendrócito , Encefalomielitis/complicaciones , Fragmentos de PéptidosRESUMEN
BACKGROUND AND PURPOSE: Myotonic dystrophy type 1 (DM1) is the most common form of adult-onset muscular dystrophy and is caused by an repeat expansion [r(CUG)exp] located in the 3' untranslated region of the DMPK gene. Symptoms include skeletal and cardiac muscle dysfunction and fibrosis. In DM1, there is a lack of established biomarkers in routine clinical practice. Thus, we aimed to identify a blood biomarker with relevance for DM1-pathophysiology and clinical presentation. METHODS: We collected fibroblasts from 11, skeletal muscles from 27, and blood samples from 158 DM1 patients. Moreover, serum, cardiac, and skeletal muscle samples from DMSXL mice were included. We employed proteomics, immunostaining, qPCR and ELISA. Periostin level were correlated with CMRI-data available for some patients. RESULTS: Our studies identified Periostin, a modulator of fibrosis, as a novel biomarker candidate for DM1: proteomic profiling of human fibroblasts and murine skeletal muscles showed significant dysregulation of Periostin. Immunostaining on skeletal and cardiac muscles from DM1 patients and DMSXL mice showed an extracellular increase of Periostin, indicating fibrosis. qPCR studies indicated increased POSTN expression in fibroblasts and muscle. Quantification of Periostin in blood samples from DMSXL mice and two large validation cohorts of DM1 patients showed decreased levels in animals and diseased individuals correlating with repeat expansion and disease severity and presence of cardiac symptoms identified by MRI. Analyses of longitudinal blood samples revealed no correlation with disease progression. CONCLUSIONS: Periostin might serve as a novel stratification biomarker for DM1 correlating with disease severity, presence of cardiac malfunction and fibrosis.
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Cardiomiopatías , Distrofia Miotónica , Adulto , Humanos , Ratones , Animales , Distrofia Miotónica/genética , Expansión de Repetición de Trinucleótido , Proteómica , Músculo Esquelético , Células Musculares/metabolismo , Cardiomiopatías/genética , Cardiomiopatías/metabolismo , Gravedad del Paciente , Proteína Quinasa de Distrofia Miotónica/genéticaRESUMEN
Chronic inflammation of skeletal muscle is the common feature of idiopathic inflammatory myopathies (IIM). Given the rarity of the disease and potential difficulty of routinely obtaining target tissue, i.e., standardized skeletal muscle, our understanding of immune signatures of the IIM spectrum remains incomplete. Further insight into the immune topography of IIM is needed to determine specific treatment targets according to clinical and immunological phenotypes. Thus, we used high-dimensional flow cytometry to investigate the immune phenotypes of anti-synthetase syndrome (ASyS), dermatomyositis (DM) and inclusion-body myositis (IBM) patients as representative entities of the IIM spectrum and compared them to healthy controls. We studied the CD8, CD4 and B cell compartments in the blood aiming to provide a contemporary overview of the immune topography of the IIM spectrum. ASyS was characterized by altered CD4 composition and expanded T follicular helper cells supporting B cell-mediated autoimmunity. For DM, unsupervised clustering identified expansion of distinct B cell subtypes highly expressing immunoglobulin G4 (IgG4) and CD38. Lastly, terminally differentiated, cytotoxic CD8 T cells distinguish IBM from other IIM. Interestingly, these terminally differentiated CD8 T cells highly expressed the integrin CD18 mediating cellular adhesion and infiltration. The distinct immune cell topography of IIM might provide the framework for targeted treatment approaches potentially improving therapeutic outcomes.
Asunto(s)
Miositis por Cuerpos de Inclusión , Miositis , Humanos , Miositis/metabolismo , Músculo Esquelético/metabolismo , Integrinas/metabolismo , Inmunoglobulina G/metabolismoRESUMEN
BACKGROUND & AIMS: The 2-pore potassium channel subfamily K member 9 (KCNK9) regulates intracellular calcium concentration and thus modulates cell survival and inflammatory signaling pathways. It also was recognized as a risk allele for inflammatory bowel disease. However, it remains unclear whether KCNK9 modulates inflammatory bowel disease via its impact on immune cell function or whether its influence on calcium homeostasis also is relevant in intestinal epithelial cells. METHODS: Kcnk9-/- mice were challenged with 3% dextran sulfate sodium (DSS) to induce experimental acute colitis. Primary cultures of intestinal epithelial cells were generated, and expression of potassium channels as well as cytosolic calcium levels and susceptibility to apoptosis were evaluated. Furthermore, we evaluated whether KCNK9 deficiency was compensated by the closely related 2-pore potassium channel KCNK3 in vivo or in vitro. RESULTS: Compared with controls, KCNK9 deficiency or its pharmacologic blockade were associated with aggravated DSS-induced colitis compared with wild-type animals. In the absence of KCNK9, intestinal epithelial cells showed increased intracellular calcium levels and were more prone to mitochondrial damage and caspase-9-dependent apoptosis. We found that expression of KCNK3 was increased in Kcnk9-/- mice but did not prevent apoptosis after DSS exposure. Conversely, increased levels of KCNK9 in Kcnk3-/- mice were associated with an ameliorated course of DSS-induced colitis. CONCLUSIONS: KCNK9 enhances mitochondrial stability, reduces apoptosis, und thus supports epithelial cell survival after DSS exposure in vivo and in vitro. Conversely, its increased expression in Kcnk3-/- resulted in less mitochondrial damage and apoptosis and was associated with beneficial outcomes in DSS-induced colitis.