Inclusion Body Myositis Patients Research Articles

Comparison of Serum rAAV Serotype-Specific Antibodies in Patients with Duchenne Muscular Dystrophy, Becker Muscular Dystrophy, Inclusion Body Myositis, or GNE Myopathy

Recombinant adeno-associated virus (rAAV) is a commonly used gene therapy vector for the delivery of therapeutic transgenes in a variety of human diseases, but pre-existing serum antibodies to viral capsid proteins can greatly inhibit rAAV transduction of tissues. Serum was assayed from patients with Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), inclusion body myositis (IBM), and GNE myopathy (GNE). These were compared to serum from otherwise normal human subjects to determine the extent of pre-existing serum antibodies to rAAVrh74, rAAV1, rAAV2, rAAV6, rAAV8, and rAAV9. In almost all cases, patients with measurable titers to one rAAV serotype showed titers to all other serotypes tested, with average titers to rAAV2 being highest in all instances. Twenty-six percent of all young normal subjects (<18 years old) had measurable rAAV titers to all serotypes tested, and this percentage increased to almost 50% in adult normal subjects (>18 years old). Fifty percent of all IBM and GNE patients also had antibody titers to all rAAV serotypes, while only 18% of DMD and 0% of BMD patients did. In addition, serum-naïve macaques treated systemically with rAAVrh74 could develop cross-reactive antibodies to all other serotypes tested at 24 weeks post treatment. These data demonstrate that most DMD and BMD patients should be amenable to vascular rAAV-mediated treatment without the concern of treatment blockage by pre-existing serum rAAV antibodies, and that serum antibodies to rAAVrh74 are no more common than those for rAAV6, rAAV8, or rAAV9.

Clinical and Electrophysiological Findings in Hereditary Inclusion Body Myopathy Compared With Sporadic Inclusion Body Myositis

To compare the clinical and electrophysiological findings in hereditary inclusion body myopathy (hIBM) and sporadic inclusion body myositis (sIBM) patients. We retrospectively identified 8 genetically proven hIBM patients and 1 DNAJB6 myopathy with pathological features of hIBM, and compared their clinical, electromyographic, and serological data with a group of 51 pathologically proven sIBM patients. hIBM patients had a younger mean age of onset (36 vs. 60 years, P = 0.0001). Diagnostic delay was shorter in sIBM (6 vs. 15 years, P = 0.0003). Wrist flexors (P = 0.02), digit flexors (P = 0.01), digit extensors (P = 0.02), and quadriceps (P = 0.008) muscles were more frequently affected in sIBM. Fibrillation potentials were more common in sIBM patients (P = 0.03). Electrical myotonia was found in 4 hIBM patients, not significantly different from sIBM patients (P = 0.45). Creatinine kinase was higher in sIBM patients (799 vs 232, P = 0.03). sIBM and hIBM seem to have similar electromyographic changes. The combination of clinical, serological, and histopathological findings can guide genetic testing to the final diagnosis.

Clinical features and prognosis in anti-SRP and anti-HMGCR necrotising myopathy

ObjectiveTo elucidate the common and distinct clinical features of immune-mediated necrotising myopathy (IMNM), also known as necrotising autoimmune myopathy associated with autoantibodies against signal recognition particle (SRP) and 3-hydroxy-3-methylglutaryl-coenzyme A...

Molecular treatment effects of alemtuzumab in skeletal muscles of patients with IBM.

BackgroundMechanisms of inflammation and protein accumulation are crucial in inclusion body myositis (IBM). Recent evidence demonstrated that intravenous immunoglobulin failed to suppress cell-stress mediators in IBM. Here we studied the molecular changes in skeletal muscle biopsies from patients with IBM before and after treatment with alemtuzumab.MethodsRelevant inflammatory and degeneration-associated markers were assessed by quantitative-PCR and immunohistochemistry in repeated muscle biopsy specimens from patients with IBM, which had been treated in a previously published uncontrolled proof-of-concept trial with alemtuzumab.ResultsThere were no significant changes of the mRNA expression levels of the pro-inflammatory chemokines CXCL-9, CCL-4, and the cytokines IFN-γ, TGF-β, TNF-α, and IL-1β. Similarly, the degeneration-associated molecules ubiquitin, APP and αB-crystallin did not substantially change. Although no overall beneficial treatment effect was noted except for a 6-month stabilization, some patients experienced a transient improvement in muscle strength. In such responders, a trend towards reduced expression of inflammatory markers was noted. In contrast, the expression remained unchanged in the others who did not experience any change. The expression levels of IL-1β and MHC-I correlated with the positive clinical effect. By immunohistochemistry, some inflammatory mediators like CD8, CXCL-9, and MHC-I were downmodulated. However, no consistent changes were noted for ubiquitin, nitrotyrosin and β-amyloid.ConclusionsAlemtuzumab showed a trend towards downregulation of the expression of some inflammatory molecules in skeletal muscle of IBM patients but has no effect on several crucial markers of cell stress and degeneration. The data are helpful to explain the molecular treatment effects of future lymphocyte-targeted immunotherapies in IBM.

Economic Burden of Sporadic Inclusion Body Myositis Patients in the United States (P1.135)

Economic Burden of Sporadic Inclusion Body Myositis Patients in the United States (P1.135)

Association of inclusion body myositis with T cell large granular lymphocytic leukaemia.

SEE HOHLFELD AND SCHULZE-KOOPS DOI101093/BRAIN/AWW053 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: Inclusion body myositis and T cell large granular lymphocytic leukaemia are rare diseases involving pathogenic cytotoxic CD8+ T cells. After encountering four patients with both disorders, we prospectively screened 38 patients with inclusion body myositis for the presence of expanded large granular lymphocyte populations by standard clinical laboratory methods (flow cytometry, examination of blood smears, and T cell receptor gene rearrangements), and performed muscle immunohistochemistry for CD8, CD57, and TIA1. Most (22/38; 58%) patients with inclusion body myositis had aberrant populations of large granular lymphocytes in their blood meeting standard diagnostic criteria for T cell large granular lymphocytic leukaemia. These T cell populations were clonal in 20/20 patients and stably present on follow-up testing in 15 patients a median of 350 days later. T cell aberrant loss of CD5 or gain of expression of CD16 and CD94 were common (19/42, 45%). In comparison, 2/15 (14%) age-matched patients with dermatomyositis, polymyositis, or necrotizing myopathy, and 0/20 (0%) age-matched healthy subjects had large granular lymphocyte expansions, with none of these patients having T cell aberrant expression of CD5, CD16 or CD94. Reduced blood CD4/CD8 ratio, increased blood CD8 count, and lymphocytosis were additional biomarkers highly correlated with flow cytometry-measured large granular lymphocyte expansions. Cross-sectional data suggested more aggressive disease in patients with such expansions than without. Muscle immunohistochemistry demonstrated invasion of large granular lymphocytes into muscle in 15/15 inclusion body myositis patients but in only 1/28 patients with dermatomyositis or polymyositis. The extent of CD8+ and CD57+ cells in inclusion body myositis muscle correlated with the size of blood large granular lymphocyte populations. Myofibre-invading cells expressed CD57, a marker of persistent T cell exposure to antigen and T cell aggressiveness. In many patients with inclusion body myositis, the autoimmune T cell expansion has evolved into a neoplastic-like or overtly neoplastic disorder, perhaps contributing to its relative refractoriness to immune-directed therapies previously reported.

Chapter 25 - Autoimmune muscle disease

Patients with polymyositis (PM), dermatomyositis (DM), and immune-mediated necrotizing myopathy (IMNM) present with the subacute onset of symmetric proximal muscle weakness, elevated muscle enzymes, myopathic findings on electromyography, and autoantibodies. DM patients are distinguished by their cutaneous manifestations. Characteristic features on muscle biopsy include the invasion of nonnecrotic muscle fibers by T cells in PM, perifascicular atrophy in DM, and myofiber necrosis without prominent inflammation in IMNM. Importantly, these are regarded as autoimmune diseases and most patients respond partially, if not completely, to immunosuppressive therapy. Patients with inclusion body myositis (IBM) usually present with the insidious onset of asymmetric weakness in distal muscles (e.g., wrist flexors, and distal finger flexors), often when more proximal muscle groups are relatively preserved. Although IBM muscle biopsies usually have focal invasion of myofibers by lymphocytes, the majority of IBM biopsies also include rimmed vacuoles. While most IBM patients do have autoantibodies, treatment with immunosuppressive agents does not improve their clinical course. Along with the presence of abnormally aggregated proteins on muscle biopsy, the refractory nature and relentless course of IBM suggest that the underlying pathophysiology may include a dominant myodegenerative component. This chapter will focus on the epidemiology, clinical presentation, and treatment of the autoimmune myopathies and IBM. An emphasis will be placed on recent advances, indicating that these are a diverse family of diseases and that each of more than a dozen myositis autoantibodies is associated with a distinct clinical phenotype.

Magnetic resonance imaging pattern recognition in sporadic inclusion-body myositis.

In sporadic inclusion-body myositis (IBM), additional tools are needed to confirm the diagnosis, particularly in clinically atypical or pathologically unproven patients. The aims of this study were to define the pattern of muscle MRI in IBM and to assess its accuracy in differentiating IBM from other myopathies that overlap with it clinically or pathologically. Blind assessment was done on the scans of 17 definite IBM, 2 possible IBM, and 118 patients with other myopathies. The diagnostic accuracy to detect definite IBM was 95% for the typical pattern (with 100% specificity) and 97% for both typical and consistent patterns (with 97% specificity). Muscle MRI is an accurate tool for diagnostic work-up of suspected IBM patients and may be particularly helpful in patients with early disease or who lack the classical IBM pathology.

Subcutaneous immunoglobulin in treating inflammatory neuromuscular disorders.

Intravenous immunoglobulin administration has long been used in the treatment of autoimmune neuromuscular disorders. Immunoglobulins may be administered by intramuscular, intravenous or subcutaneous routes. This is a report on the long-term clinical follow up of six patients with inflammatory neuromuscular disorders, that is, three chronic inflammatory demyelinating polyneuropathy (CIDP), one multifocal motor neuropathy (MMN), one inclusion body myositis (IBM) and one myasthenia gravis (MG), treated with subcutaneous immunoglobulins for a mean of 3.25 years. One MMN and two CIDP patients received a weekly dose of subcutaneous immunoglobulins equivalent to intravenous immunoglobulin. One CIDP patient received a 50% dose reduction, the IBM patient received a 30% reduction and the MG patient a 20% reduction. The lower dose chosen in the majority of patients was based not only on clinical effects, but also on studies of primary immunodeficiency syndromes. One patient with CIDP showed clinical fluctuation, which was successfully treated with an adaptation of the dose of subcutaneous immunoglobulins, while the remaining patients with neuromuscular disorders had a stable clinical course for 2 years. No serious side effects were observed. Our results suggest that subcutaneous immunoglobulins can be an attractive alternative therapy in autoimmune neuromuscular disorders.

Idiopathic inflammatory myopathies evaluated by near-infrared spectroscopy.

In this study we evaluated whether near-infrared spectroscopy (NIRS) can determine the metabolic patterns of dermatomyositis (DM), polymyositis (PM), and inclusion-body myositis (IBM). We enrolled 10 consecutive patients affected by DM, 11 by PM, and 9 by IBM, and 3 groups of healthy controls. We measured changes in oxygenated and deoxygenated hemoglobin/myoglobin in the extensor digitorum communis during venous and arterial occlusion testing (VOT) and post-occlusion hyperemia. DM showed lower oxygen consumption (P=0.04) during VOT and reduced oxygen supply after VOT (P=0.04) compared with controls. IBM patients showed higher oxygen consumption (P=0.04) during VOT and higher oxygen supply after VOT (P=0.03) than controls. DM patients showed reduced oxidative metabolism compared with IBM (P=0.001), and an impaired ability to supply oxygen compared with PM (P=0.03) and IBM (P=0.001) patients. NIRS differentiated samples of DM and IBM patients from controls, but it could not distinguish PM patients from a sample of healthy subjects.

Mitochondrial pathology in inclusion body myositis

Inclusion body myositis (IBM) is usually associated with a large number of cytochrome c oxidase (COX)-deficient muscle fibers and acquired mitochondrial DNA (mtDNA) deletions.We studied the number of COX-deficient fibers and the amount of mtDNA deletions, and if variants in nuclear genes involved in mtDNA maintenance may contribute to the occurrence of mtDNA deletions in IBM muscle.Twenty-six IBM patients were included. COX-deficient fibers were assayed by morphometry and mtDNA deletions by qPCR. POLG was analyzed in all patients by Sanger sequencing and C10orf2 (Twinkle), DNA2, MGME1, OPA1, POLG2, RRM2B, SLC25A4 and TYMP in six patients by next generation sequencing.Patients with many COX-deficient muscle fibers had a significantly higher proportion of mtDNA deletions than patients with few COX-deficient fibers. We found previously unreported variants in POLG and C10orf2 and IBM patients had a significantly higher frequency of an RRM2B variant than controls. POLG variants appeared more common in IBM patients with many COX-deficient fibers, but the difference was not statistically significant.We conclude that COX-deficient fibers in inclusion body myositis are associated with multiple mtDNA deletions. In IBM patients we found novel and also previously reported variants in genes of importance for mtDNA maintenance that warrants further studies.

BACE-1, PS-1 and sAPPβ Levels Are Increased in Plasma from Sporadic Inclusion Body Myositis Patients: Surrogate Biomarkers among Inflammatory Myopathies.

Sporadic inclusion body myositis (sIBM) is a rare disease that is difficult to diagnose. Muscle biopsy provides three prominent pathological findings: inflammation, mitochondrial abnormalities and fibber degeneration, represented by the accumulation of protein depots constituted by β-amyloid peptide, among others. We aim to perform a screening in plasma of circulating molecules related to the putative etiopathogenesis of sIBM to determine potential surrogate biomarkers for diagnosis. Plasma from 21 sIBM patients and 20 age- and gender-paired healthy controls were collected and stored at -80°C. An additional population of patients with non-sIBM inflammatory myopathies was also included (nine patients with dermatomyositis and five with polymyositis). Circulating levels of inflammatory cytokines (interleukin [IL]-6 and tumor necrosis factor [TNF]-α), mitochondrial-related molecules (free plasmatic mitochondrial DNA [mtDNA], fibroblast growth factor-21 [FGF-21] and coenzyme-Q10 [CoQ]) and amyloidogenic-related molecules (beta-secretase-1 [BACE-1], presenilin-1 [PS-1], and soluble Aβ precursor protein [sAPPβ]) were assessed with magnetic bead-based assays, real-time polymerase chain reaction, enzyme-linked immunosorbent assay (ELISA) and high-pressure liquid chromatography (HPLC). Despite remarkable trends toward altered plasmatic expression of inflammatory and mitochondrial molecules (increased IL-6, TNF-α, circulating mtDNA and FGF-21 levels and decreased content in CoQ), only amyloidogenic degenerative markers including BACE-1, PS-1 and sAPPβ levels were significantly increased in plasma from sIBM patients compared with controls and other patients with non-sIBM inflammatory myopathies (p < 0.05). Inflammatory, mitochondrial and amyloidogenic degeneration markers are altered in plasma of sIBM patients confirming their etiopathological implication in the disease. Sensitivity and specificity analysis show that BACE-1, PS-1 and sAPPβ represent a good predictive noninvasive tool for the diagnosis of sIBM, especially in distinguishing this disease from polymyositis.

Sporadic inclusion body myositis: new insights and potential therapy.

To describe new insights and developments in the pathogenesis, diagnosis and treatment of sporadic inclusion body myositis (IBM). Various hypothesis about the pathogenesis of IBM continue to be investigated, including autoimmune factors, mitochondrial dysfunction, protein dyshomeostasis, altered nucleic acid metabolism, myonuclear degeneration and the role of the myostatin pathway. Serum autoantibodies against cytosolic 5'-nucleotidase 1A have been identified in IBM showing moderate diagnostic performance. The differential diagnostic value of histopathological features, including different protein aggregates, continues to be evaluated. MRI may also be of monitoring value in IBM. New therapeutic strategies are being tested in IBM patients, namely the upregulation of the heat shock response and the antagonism of myostatin. Recent important advances have occurred in IBM. These advances, including recent and ongoing clinical trials, may lead to earlier diagnosis and improved understanding and treatment of the disease. Despite improved knowledge, IBM continues to be a puzzling disease and the pathogenesis remains to be clarified. An interdisciplinary, bench to bedside translational research approach is crucial for the successful identification of novel treatments for this debilitating, currently untreatable disorder.

Cytoplasmic 5′‐nucleotidase autoantibodies in inclusion body myositis: Isotypes and diagnostic utility

Recent studies have identified circulating immunoglobulin (Ig) G autoantibodies against cytoplasmic 5'-nucleotidase 1A (cN1A; NT5C1A) in patients with inclusion body myositis (IBM), whose detection provides for an IBM blood diagnostic test. Whether or not anti-cN1A autoantibody isotypes other than IgG are present in IBM has not previously been reported. Plasma and serum samples from 205 patients (50 with and155 without IBM) were studied for the presence of IgM and IgA, in addition to IgG, anti-cN1A autoantibodies using immunoblots and enzyme-linked immunoassays (ELISAs). IgM, IgA, and IgG anti-cN1A autoantibodies were detected by ELISA with similar sensitivities (49-53%) and specificities (94-96%), but with differing patterns of autoantibody isotype presence. Combination assays of all 3 autoantibody levels improved diagnostic sensitivity to 76%. In addition to previously recognized IgG anti-cN1A autoantibodies, IBM patients have circulating IgM and IgA anti-cN1A autoantibodies. Differing patterns of these isotypes may be present and useful for diagnosis.

G.P.65: Obstructive sleep apnoea and subclinical impairment of respiratory function are common in sporadic inclusion body myositis

To examine the occurrence of respiratory dysfunction in sporadic inclusion body myositis (IBM) and its relationship to peripheral muscle strength and ventilation during sleep. Anthropometric, muscle strength, dyspnoea, daytime sleepiness and dysphagia data were collected. Spirometry, respiratory muscle strength and arterial blood gas tensions were measured. Ventilation during sleep was assessed by dual channel (oximetry, nasal pressure) home monitoring. Sixteen patients with biopsy-proven IBM were studied (10 males, 6 females; age 68.1±9.9years; disease duration 11.9±5.0years; body mass index 28.5±4.0kg/m²). Four patients reported excessive daytime sleepiness (Epworth Sleepiness Scale ⩾10); 8 had at least mild dysphagia (Dysphagia Outcome Severity Scale ⩽5); forced vital capacity was <80% of the predicted normal in 7; sniff nasal inspiratory pressure was reduced (<60cm H₂O) in 3; daytime hypoxemia (PaO₂<80mmHg) was present in 10 and hypercapnia (PaCO₂>45mmHg) in one. Sleep study was performed in 15 patients and revealed sleep hypoxemia (⩾2% of total sleep time at or below a saturation <90% (TST⩽90)) in 10 and obstructive sleep apnoea (respiratory disturbance index 23.4±12.8 (range 7–50.3) events/h) in all 15. Daytime PaO₂ was related to TST⩽90 (<i>r</i>=−0.55, <i>p</i>=0.04). Asymptomatic impairment of wakeful respiratory function was common and obstructive sleep apnoea was observed in all patients tested, irrespective of daytime respiratory function. This high occurrence probably reflects the combined effects of pharyngeal muscle weakness and sleep-related reduction in muscle activation and ventilatory drive. These findings suggest that tests of respiratory function, including an overnight sleep study, should be performed routinely in IBM patients, irrespective of peripheral muscle function or other non-respiratory disease severity parameters.

G.P.66: Real-time MRI for the evaluation of dysphagia in inclusion body myositis (IBM)

Inclusion body myositis (IBM) is the most common acquired myopathy in patients over 50years and is characterized by a progressive muscle weakness and dysphagia. The aim of this study was to compare a novel real-time MRI technique with the standard assessments for dysphagia. The evaluation of symptoms of dysphagia and of the swallowing quality of life was performed by a standardized questionnaire (SWAL-QoL) in 20 non-selected, consecutive patients with IBM. Technical testing included flexible endoscopic evaluation of swallowing (FEES), videofluoroscopy (VF) and real-time MRI. The clinical parameters included the IBM-functional rating score (IBM-FRS), a patient reported functional assessment (sIFA) and the strength of different muscles (MRC-score). Dysphagia was noted in SWAL-QoL in 72% of the patients and it revealed a higher frequency of dysphagia and a poorer swallowing quality of life in IBM patients compared to reference values of healthy elderly. The SWAL-QoL significantly correlated with the IBM-FRS and the MRC score. Swallowing in a supine position during MRI was well tolerated by all patients and no aspiration occurred. In some patients, during swallowing a muscle propulsion in the area of the cricopharygeal muscle was seen on MRI and VF. The MRI showed a significant increase of the oral and pharyngeal transit times and the esophageal opening time in patients compared to healthy controls from a prior published study. The pharyngeal transit time significantly correlated to the eating duration per SWAL-QoL. Symptoms of dysphagia were found in the majority of IBM patients. Dynamic real-time MRI is highly suitable for the assessment of dysphagia in IBM. Besides avoiding exposure to X-rays, MRI advantages are additional information such as morphology and time lapse, which are not provided by standard methods. Improved diagnostic tools for evaluating swallowing in IBM may help to prevent aspiration and subsequent pneumonia.

G.P.256: The German patient registry for inclusion body myositis

Although inclusion body myositis (IBM) is the most common acquired myopathy in patients aged over 50 years, it is a very rare disease with an estimated prevalence between 4.5 and 9.5/million rising up to 50/million for individuals over 50 years with high variability in different populations and ethnic groups. Patients suffer from slowly progressive muscle weakness and pharyngeal impairment resulting in severe disability. No causative treatment is currently available but new therapeutic strategies are investigated and innovative clinical trials are considered for the next years. A German patient registry for IBM is being established to overcome the bottlenecks of data fragmentation, lack of harmonization and lack of trial readiness for this disease. We aim to include harmonized datasets of preferably all German patients diagnosed with IBM based on standardized clinical and histopathological findings (revised Hilton–Jones criteria). A harmonized dataset including clinical data and muscle biopsy reports is recorded using a dual patient and professional online report system ( www.ibm-register.de ). National legislation, data protection laws and ethical recommendations are strictly followed in this process. Approval of the project by the Munich University Ethics Board is awaited within 2014. The registry will start upon IRB approval and aims at collecting high-quality, curated and regularly updated longitudinal data of the majority of German IBM patients in the mid- and long-term. In addition, the registry may help to address research questions like prevalence, natural history and disease characterization. The IBM registry will provide a unique opportunity not only to effectively recruit German patients for international clinical trials and to support the translation of new therapies from “bench to bedside”, but also to improve patient care by assessing standards of diagnosis and care.

Altered RIG‐I/DDX58‐mediated innate immunity in dermatomyositis

We investigated the molecular mechanisms involved in the pathogenesis of three inflammatory myopathies, dermatomyositis (DM), polymyositis (PM) and inclusion body myositis (IBM). We performed microarray experiments(†) using microdissected pathological muscle fibres from 15 patients with these disorders and five controls. Differentially expressed candidate genes were validated by immunohistochemistry on muscle biopsies, and the altered pathways were analysed in human myotube cultures. Up-regulation of genes involved in viral and nucleic acid recognition were found in the three myopathies but not in controls. In DM, retinoic acid-inducible gene 1 (RIG-I, DDX58) and the novel antiviral factor DDX60, which promotes RIG-I-mediated signalling, were significantly up-regulated, followed by IFIH1 (MDA5) and TLR3. Immunohistochemistry confirmed over-expression of RIG-I in pathological muscle fibres in 5/5 DM, 0/5 PM and 0/5 IBM patients, and in 0/5 controls. Stimulation of human myotubes with a ligand of RIG-I produced a significant secretion of interferon-β (IFNβ; p < 0.05) and up-regulation of class I MHC, RIG-I and TLR3 (p < 0.05) by IFNβ-dependent and TLR3-independent mechanisms. RIG-I-mediated innate immunity, triggered by a viral or damage signal, plays a significant role in the pathogenesis of DM, but not in that of PM or IBM.

Mechanistic effects of IVIg in neuroinflammatory diseases: conclusions based on clinicopathologic correlations.

The mechanisms of action of IVIg on immunoregulatory and neuroinflammatory network have been predominantly based on in vitro experiments and animal studies, rather than direct effects on human tissues. Based on clinicopathologic correlations and tissues obtained before and after IVIg therapy, the better documented and clinically-relevant in-vivo actions of IVIg include effects on: a) Antibodies. An extracted antigen-specific anti-immunoglobulin (idiotypic) fraction appears partially responsible for its effect in myasthenia gravis and GBS; b) Complement. Sera from Dermatomyositis (DM) patients responding to IVIg, inhibit complement consumption and intercept MAC formation leading to disappearance of MAC deposits in the repeated muscle biopsies and normalization of muscle tissue; c) Genes. In repeated muscle biopsies from DM patients who improved after IVIg, but not from Inclusion-Body-Myositis (IBM) who did not improve, there is a 2-fold alteration of 2206 tissue genes associated with inflammation, fibrosis, tissue remodeling and regeneration; and d) degenerative-proinflammatory molecules and β-amyloid, implicated in neurodegenerative CNS diseases and IBM. In repeated muscle biopsies of IBM patients who did not respond to IVIg, the mRNA or protein expression for chemokines, IFN-γ, TGF-ß, IL-10, Ubiquitin and aB-crystallin is reduced, but not for the key molecules ICOS, ICOSL, IL-6, IL1-β, perforin, APP, nitric oxide synthase and nitrotyrosine, in spite of good IVIg penetration in muscles. Collectively, the selective effectiveness of IVIg in human diseases seems to correlate in vivo with inhibition of causative inflammatory mediators. Study of accessible tissues before and after therapy and clinicopathologic correlations, may help explain the differential effect of IVIg in autoimmune or neuroinflammatory diseases.

Phosphorylation of NBR1 by GSK3 modulates protein aggregation

The autophagy receptor NBR1 (neighbor of BRCA1 gene 1) binds UB/ubiquitin and the autophagosome-conjugated MAP1LC3/LC3 (microtubule-associated protein 1 light chain 3) proteins, thereby ensuring ubiquitinated protein degradation. Numerous neurodegenerative and neuromuscular diseases are associated with inappropriate aggregation of ubiquitinated proteins and GSK3 (glycogen synthase kinase 3) activity is involved in several of these proteinopathies. Here we show that NBR1 is a substrate of GSK3. NBR1 phosphorylation by GSK3 at Thr586 prevents the aggregation of ubiquitinated proteins and their selective autophagic degradation. Indeed, NBR1 phosphorylation decreases protein aggregation induced by puromycin or by the DES/desmin N342D mutant found in desminopathy patients and stabilizes ubiquitinated proteins. Importantly, decrease of protein aggregates is due to an inhibition of their formation and not to their autophagic degradation as confirmed by data on Atg7 knockout mice. The relevance of NBR1 phosphorylation in human pathology was investigated. Analysis of muscle biopsies of sporadic inclusion body myositis (sIBM) patients revealed a strong decrease of NBR1 phosphorylation in muscles of sIBM patients that directly correlated with the severity of protein aggregation. We propose that phosphorylation of NBR1 by GSK3 modulates the formation of protein aggregates and that this regulation mechanism is defective in a human muscle proteinopathy.