Myeloid Dendritic Cells Are Major Producers of IFN-β in Dermatomyositis and May Contribute to Hydroxychloroquine Refractoriness

Recent Advances of Type I Interferon on the Regulation of Immune Cells and the Treatment of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with multiple organ damage. Several studies have found that, in addition to significant production of autoantibodies, the majority of SLE patients exhibit increased expression of type I interferon (IFN-I) regulated genes (also known as IFN-I traits), and that IFN-I plays a crucial role in the pathogenesis of SLE. In SLE, virtually all immune cells are dysregulated, and most of these aberrant dysregulations are directly or indirectly affected by IFN-I. The mechanism of action of IFN-I in these immune cells is multifaceted. In this review, we focus on the immune cell types that produce IFN-I and are affected by IFN-I in SLE. Importantly, we explore the research progress of related drugs in terms of IFN-I production, itself, and downstream. Here we provide the most up-to-date information on the mechanisms that lead to the pathogenesis of SLE, providing the basis for the development of innovative future therapies and future research directions.

Understanding the Role of Type I Interferons in Cutaneous Lupus and Dermatomyositis: Toward Better Therapeutics

A 29-year-old female presented to a rheumatology-dermatology clinic with a pruritic rash that began 6 months prior, after a viral illness. She had previously been diagnosed with eczema and treated with antihistamines and topical steroids without improvement. She also noted fatigue, hair loss, and severe scalp pruritus. Physical examination was notable for violaceous periorbital edema, scaly erythematous papules on the metacarpophalangeal joints of bilateral hands, dilated capillaries of the proximal nail folds, scaly plaques on bilateral elbows, and excoriated erythematous plaques on upper chest, back and hips. The patient reported no muscle weakness, and strength testing and creatinine phosphokinase were normal. Magnetic resonance imaging of the thigh showed no evidence of inflammation or edema. Antibody testing was negative. A diagnosis of clinically amyopathic dermatomyositis was made. Computed tomography scans of the chest, abdomen and pelvis, colonoscopy, and mammogram showed no evidence of cancer. The patient was initiated on methotrexate. Her cutaneous manifestations persisted with debilitating intractable pruritus, and thus, she was transitioned to mycophenolate mofetil, again with minimal improvement. Intravenous immunoglobulin was not approved by insurance given the lack of muscle involvement in her disease. This patient's case highlights a common clinical scenario in rheumatology and dermatology and raises several important issues related to the immunologic underpinnings of cutaneous lupus erythematosus (CLE) and dermatomyositis (DM): What is the role of type I interferon (IFN) in triggering skin disease in CLE and DM? What is the role of IFN in the pathogenesis of skin inflammation in CLE and DM? Can we apply what we know about IFN-targeted therapeutics in CLE and DM to develop better treatments for skin disease?

Topical Mupirocin Treatment Reduces Interferon and Myeloid Signatures in Cutaneous Lupus Erythematous Lesions Through Targeting of Staphyloccal Species

OBJECTIVE

Cutaneous lupus erythematosus (CLE) is an inflammatory skin manifestation of systemic lupus erythematosus. Type I interferons (IFNs) promote inflammatory responses and are elevated in CLE lesions. We recently reported that CLE lesions are frequently colonized with Staphylococcus aureus. Here, we follow up via a proof-of-concept study to investigate whether type I IFN and inflammatory gene signatures in CLE lesions can be modulated with mupirocin, a topical antibiotic treatment against S aureus-mediated skin infections.

METHODS

Participants with active CLE lesions (n = 12) were recruited and randomized into a week of topical treatment with either 2% mupirocin or petroleum jelly vehicle. Paired samples were collected before and after seven days of treatment to assess microbial lesional skin responses. Microbial samples from nares and lesional skin were used to determine baseline and posttreatment Staphylococcus abundance and microbial community profiles by 16S ribosomal RNA gene sequencing. Inflammatory responses were evaluated by bulk RNA sequencing of lesional skin biopsies.

RESULTS

We identified 173 differentially expressed genes in CLE lesions after topical mupirocin treatment. Decreased lesional Staphylococcus burden correlated with decreased IFN pathway signaling and inflammatory gene expression and barrier dysfunction. Interestingly, mupirocin treatment lowered skin monocyte levels, and this mupirocin-associated depletion of monocytes correlated with decreased inflammatory gene expression.

CONCLUSION

Mupirocin treatment decreased lesional Staphylococcus, and this correlated with decreased IFN signaling and inflammatory gene expression. This study suggests a topical antibiotic could be employed to decrease lupus skin inflammation and type I IFN responses by reducing Staphylococcus colonization.

Neutrophil and mononuclear leukocyte pathways and upstream regulators revealed by serum proteomics of adult and juvenile dermatomyositis

OBJECTIVES

Serum protein abundance was assessed in adult and juvenile dermatomyositis (DM and JDM) patients to determine differentially regulated proteins, altered pathways, and candidate disease activity biomarkers.

METHODS

Serum protein expression from 17 active adult DM and JDM patients each was compared to matched, healthy control subjects by a multiplex immunoassay. Pathway analysis and protein clustering of the differentially regulated proteins were examined to assess underlying mechanisms. Candidate disease activity biomarkers were identified by correlating protein expression with disease activity measures.

RESULTS

Seventy-eight of 172 proteins were differentially expressed in the sera of DM and JDM patients compared to healthy controls. Forty-eight proteins were differentially expressed in DM, 32 proteins in JDM, and 14 proteins in both DM and JDM. Twelve additional differentially expressed proteins were identified after combining the DM and JDM cohorts. C-X-C motif chemokine ligand 10 (CXCL10) was the most strongly upregulated protein in both DM and JDM sera. Other highly upregulated proteins in DM included S100 calcium binding protein A12 (S100A12), CXCL9, and nicotinamide phosphoribosyltransferase (NAMPT), while highly upregulated proteins in JDM included matrix metallopeptidase 3 (MMP3), growth differentiation factor 15 (GDF15), and von Willebrand factor (vWF). Pathway analysis indicated that phosphoinositide 3-kinase (PI3K), p38 mitogen-activated protein kinase (MAPK), and toll-like receptor 7 (TLR7) signaling were activated in DM and JDM. Additional pathways specific to DM or JDM were identified. A protein cluster associated with neutrophils and mononuclear leukocytes and a cluster of interferon-associated proteins were observed in both DM and JDM. Twenty-two proteins in DM and 24 proteins in JDM sera correlated with global, muscle, and/or skin disease activity. Seven proteins correlated with disease activity measures in both DM and JDM sera. IL-1 receptor like 1 (IL1RL1) emerged as a candidate global disease activity biomarker in DM and JDM.

CONCLUSION

Coordinate analysis of protein expression in DM and JDM patient sera by a multiplex immunoassay validated previous gene expression studies and identified novel dysregulated proteins, altered signaling pathways, and candidate disease activity biomarkers. These findings may further inform the assessment of DM and JDM patients and aid in the identification of potential therapeutic targets.

Recent Advances in Juvenile Dermatomyositis: Moving toward Integration of Myositis-Specific Antibody Clinical Phenotypes, IFN-Driven Pathogenesis, and Targeted Therapies

Juvenile dermatomyositis (JDM), the most common pediatric inflammatory myopathy, is associated with significant morbidity despite therapeutic advances. Distinct clinical phenotypes have emerged, which can correlate with myositis-specific antibodies. Because translational data solidify the role of type I IFNs in JDM disease pathogenesis, integration of clinical and molecular phenotyping may impact the choice of targeted therapy. This paper reviews clinical and molecular phenotyping in JDM and translational insights into immune pathogenesis that have created emerging options for targeted therapy.

Updates in Dermatomyositis: Newer Treatment Options and Outcome Measures From Dermatologic Perspectives

Dermatomyositis (DM) is a rare autoimmune connective tissue disease with characteristic skin manifestations and possible muscle involvement. Recent advances in classification system to include skin-predominant subtypes, understanding underlying pathogenic mechanisms and the relationship between clinical phenotypes and myositis-specific autoantibodies have led to development of novel therapeutic options. This corresponds with efforts to develop better outcome measures to accurately catch the patients' current disease status and treatment-induced improvements. This report will review the updates in newer treatments and outcome measures of DM, specifically from a dermatologic point of view.

Personalised medicine in juvenile dermatomyositis: From novel insights in disease mechanisms to changes in clinical practice

Juvenile dermatomyositis is characterized by childhood-onset chronic inflammation of the muscles and skin, with potential involvement of other organs. Patients are at risk for long-term morbidity due to insufficient disease control and steroid-related toxicity. Personalised treatment is challenged by a lack of validated tools that can reliably predict treatment response and monitor ongoing (subclinical) inflammation, and by a lack of evidence regarding the best choice of medication for individual patients. A better understanding of the involved disease mechanisms could reveal potential biomarkers and novel therapeutic targets. In this review, we highlight the most relevant immune and non-immune mechanisms, elucidating the effects of interferon overexpression on tissue alongside the interplay between the interferon signature, mitochondrial function, and immune cells. We review mechanism-based biomarkers that are promising for clinical implementation, and the latest advances in targeted therapy development. Finally, we discuss key steps needed for translating these discoveries into clinical practice.

Pandemic-associated pernio harbors footprints of an abortive SARS-CoV-2 infection

Elevated pernio incidence was observed during the COVID-19 pandemic. This prospective study enrolled subjects with pandemic-associated pernio in Wisconsin and Switzerland. Because pernio is a cutaneous manifestation of the interferonopathies, and type I interferon (IFN-I) immunity is critical to COVID-19 recovery, we tested the hypothesis that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-mediated IFN-I signaling might underlie some pernio cases. Tissue-level IFN-I activity and plasmacytoid dendritic cell infiltrates were demonstrated in 100% of the Wisconsin cases. Across both cohorts, sparse SARS-CoV-2 RNA was captured in 25% (6/22) of biopsies, all with high inflammation. Affected patients lacked adaptive immunity to SARS-CoV-2. A hamster model of intranasal SARS-CoV-2 infection was used as a proof-of-principle experiment: RNA was detected in lungs and toes with IFN-I activity at both the sites, while replicating virus was found only in the lung. These data support a viral trigger for some pernio cases, where sustained local IFN-I activity can be triggered in the absence of seroconversion.

[Current update on dermatomyositis]

Dermatomyositis (DM) is a rare autoimmune disease with involvement of skin and muscle that is classified as an idiopathic inflammatory myopathy. In addition to cutaneous lesions as well as weakness and atrophy of muscles, the heart and lungs are the major affected organs. DM occurs in association with malignant tumors in 20% of affected adults. The pathogenesis of the disease is not completely understood. DM is a multifactorial disease influenced by genetic, environmental and immunological factors. The immune response is characterized by activation of innate and adaptive immune mechanisms and a strong activation of the type I interferon pathway. Myositis-specific antibodies are characteristic of DM and allow differential diagnosis. Therapies include corticosteroids, antimalarials, immunoglobulins, biologics such as rituximab or JAK inhibitors. Early diagnosis and treatment are essential for the prognosis.

IFN-beta and EIF2AK2 are potential biomarkers for interstitial lung disease in anti-MDA5 positive dermatomyositis

OBJECTIVE

DM with positive anti-melanoma differentiation-related gene 5 (MDA5) antibody is an autoimmune disease with multiple complications. Interstitial lung diseases (ILDs) are significantly associated with DM and are particularly related to MDA5+ DM. This article aims to explore potential molecular mechanisms and develop new diagnostic biomarkers for MDA5+ DM-ILD.

METHODS

The series matrix files of DM and non-specific interstitial pneumonia (NSIP) were downloaded from the Gene Expression Omnibus (GEO) database to identify the differentially expressed genes (DEGs). Gene set enrichment analysis (GSEA) was used to screen the common enriched pathways related to DM and NSIP. Next, the co-expressed differential expressed genes (co-DEGs) between MDA5+, MDA5- and NSIP groups were identified by Venn plots, and then selected for different enrichment analyses and protein-protein interaction (PPI) network construction. The mRNA expression levels of IFN-beta and EIF2AK2 were measured by RT-qPCR. The protein expression levels of IFN-beta were measured by ELISA.

RESULTS

Using GSEA, the enriched pathway 'herpes simplex virus 1 infection' was both up-regulated in DM and NSIP. Enrichment analysis in MDA5+ DM, MDA5- DM and NSIP reported that the IFN-beta signalling pathway was an important influencing factor in the MDA5+ DM-ILD. We also identified that eukaryotic translation initiation factor 2 alpha kinase 2 (EIF2AK2) was an important gene signature in the MDA5+ DM-ILD by PPI analysis. The expression levels of IFN-beta and EIF2AK2 were significantly increased in MDA5+ DM-ILD patients.

CONCLUSIONS

IFN-beta and EIF2AK2 contributed to the pathogenesis of MDA5+ DM-ILD, which could be used as potential therapeutic targets.

Higher Odds of Adverse Cutaneous Reactions in Patients With Dermatomyositis Treated With Hydroxychloroquine Compared With Methotrexate

OBJECTIVE

Hydroxychloroquine (HCQ) use for the treatment of dermatomyositis (DM) has been associated with adverse cutaneous reactions. We applied a new user, active comparator, retrospective design to assess differences in adverse cutaneous reactions or hospitalizations between HCQ and methotrexate (MTX) use among patients with DM.

METHODS

We used a national network of data from insurance registries (TriNetX), enrolling patients with two International Classification of Diseases (ICD) codes for DM separated by 6 months or more who had a prescription for either (but not both) HCQ or MTX on or after DM diagnosis. Outcomes were adverse cutaneous reactions (ICD codes) or hospital admission (Current Procedural Terminology (CPT) codes) within 4 months from the prescription dispense date. Logistic regression was used to produce adjusted odds ratios (aORs) and 95% confidence intervals (CIs) comparing outcomes in the HCQ group (n = 1364) and the MTX group (n = 1400), adjusted for age at first DM diagnosis, year of birth, sex, and time from DM diagnosis to first prescription.

RESULTS

Overall, we found no significant difference in odds of hospitalization in those taking HCQ (aOR 1.05; 95% CI: 0.79-1.39) compared with those on MTX. Patients with DM on HCQ had 30% higher odds of adverse cutaneous reaction diagnosis compared with patients on MTX (aOR 1.30; 95% CI: 1.02-1.59). Age at DM diagnosis was an effect modifier of this association, with higher odds of adverse cutaneous reaction among patients taking HCQ who were younger at diagnosis.

CONCLUSION

Compared with MTX use, HCQ use, especially in younger patients, may result in higher odds of adverse cutaneous reactions.

The interferon in idiopathic inflammatory myopathies: Different signatures and new therapeutic perspectives. A literature review

Idiopathic inflammatory myopathies (IIM), even though sharing common clinical manifestations, are characterized by diversified molecular pathogenetic mechanisms which may account for the partial inefficacy of currently used immunomodulatory drugs. In the last decades, the role of interferon (IFN) in IIM has been extensively elucidated thanks to genomic and proteomic studies which have assessed the molecular signature at the level of affected tissues or in peripheral blood across distinct IIM subtypes. A predominant type I IFN response has been shown in dermatomyositis (DM), being especially enhanced in MDA5+ DM, while a type 2 IFN profile characterizes anti-synthetase syndrome (ASyS) and inclusion body myositis (IBM); conversely, a less robust IFN footprint has been defined for immune-mediated necrotizing myopathy (IMNM). Intracellular IFN signaling is mediated by the janus kinase/signal transducer and activator of transcription (JAK/STAT) through dedicated transmembrane receptors and specific cytoplasmic molecular combinations. These results may have therapeutic implications and led to evaluating the efficacy of new targeted drugs such as the recently introduced janus kinase inhibitors (JAKi), currently approved for the treatment of rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis. In this review we aim to summarize the most significant evidence of IFN role in IIM pathogenesis and to describe the current state of the art about the ongoing clinical trials on IFN-targeting drugs, with particular focus on JAKi.

Safety and Efficacy of Lenabasum, a Cannabinoid Receptor Type 2 Agonist, in Patients with Dermatomyositis with Refractory Skin Disease: A Randomized Clinical Trial

BACKGROUND

Treatment options are limited for skin disease in dermatomyositis. Lenabasum is a cannabinoid receptor type 2 agonist that triggers the resolution of inflammation.

OBJECTIVE

The objective of this study was to evaluate the safety and efficacy of lenabasum in patients with refractory cutaneous dermatomyositis.

DESIGN

This study was a single-center, double-blind, randomized, placebo-controlled phase 2 study conducted from July 2015 to August 2017.

POPULATION

The population included subjects aged ≥18 years with at least moderately active dermatomyositis skin activity by Cutaneous Dermatomyositis Disease Area and Severity Index activity ≥ 14 and failure or intolerance to hydroxychloroquine.

INTERVENTION

Participants received 20 mg lenabasum daily for 28 days and then 20 mg twice per day for 56 days or placebo.

MAIN OUTCOMES AND MEASURES

The primary outcome was a change in Cutaneous Dermatomyositis Disease Area and Severity Index activity. Safety and other secondary efficacy assessments were performed till day 113.

RESULTS

A total of 22 subjects were randomized to lenabasum (n = 11) or placebo (n = 11). No serious or severe adverse events were related to lenabasum, and no participants discontinued the study. The adjusted least-squares mean for Cutaneous Dermatomyositis Disease Area and Severity Index activity decreased more for lenabasum, and the difference was significant on day 113 (least-squares mean [standard error] difference = ‒6.5 [3.1], P = 0.038). Numerically greater improvements were seen in multiple secondary efficacy outcomes and biomarkers with lenabasum.

CONCLUSION

Lenabasum treatment was well tolerated and was associated with greater improvement in Cutaneous Dermatomyositis Disease Area and Severity Index activity and multiple efficacy outcomes.

TRIAL REGISTRATION

This study was registered at ClinicalTrials.gov, NCT02466243.

Autoimmune Skin Disease Exacerbations Following COVID-19 Vaccination

Background

Vaccination against COVID-19 reduces the risk of severe COVID-19 disease and death. However, few studies have examined the safety of the COVID-19 vaccine in patients with autoimmune skin disease.

Objectives

We sought to determine the incidence of disease exacerbation in this population following COVID-19 vaccination as well as the associated factors.

Methods

We performed a chart review of all patients seen in the autoimmune skin disease clinic of the principal investigator during the study period. All patients included for analysis were systematically and prospectively asked about COVID-19 vaccination status, manufacturers, vaccine dates, autoimmune symptoms after the vaccine, and timing of symptom onset using a standardized template as part of their visit. Demographics and autoimmune disease diagnosis were also collected. Analysis used Chi-square and Fisher's exact tests.

Results

402 subjects were included for analysis. 85.6% of patients were fully vaccinated, with 12.9% unvaccinated and 1.5% partially vaccinated. 14.8% of fully vaccinated patients reported worsening autoimmune signs and symptoms after the vaccine. Fully vaccinated dermatomyositis patients were more likely to report worsening autoimmune signs and symptoms after the vaccine (22.7%) than fully vaccinated lupus erythematosus patients (8.6%) (p=0.009). Patients fully vaccinated with the Moderna vaccine trended towards an increased likelihood of reporting worsening autoimmune signs and symptoms after the vaccine (19.1%) than those with the Pfizer-BioNTech vaccine (12.0%) (p=0.076). Of the patients who had autoimmune symptoms after vaccination, 20% had symptoms after the 1st dose, 82% after the 2nd dose, and 4% after the 3rd dose with median onset (95% confidence interval) of 7 (2,14), 14 (14,21), and 18 (7,28) days later, respectively.

Conclusions

More fully vaccinated dermatomyositis patients had exacerbation of autoimmune signs and symptoms after the vaccine than fully vaccinated lupus erythematosus patients. However, given the risks of COVID-19, clinicians should still promote vaccination in most patients with autoimmune skin disease.

[Translated article] Hydroxychloroquine: An Essential Drug in Dermatology and Its Controversial Use in COVID-19

Hydroxychloroquine is an antimalarial drug with immunomodulatory, anti-inflammatory, antibacterial, and antiviral properties. It has a good safety profile, can be used in children and in pregnant and breastfeeding women, and does not suppress the immune system. Regular screening for retinopathy, one of the drug’s most feared adverse effects, is necessary. Hydroxychloroquine is a widely used, essential drug in dermatology. Clinical response rates are good in lupus erythematous, where it is a first-line therapy, as well in numerous autoimmune/inflammatory diseases, including lichen planus, polymorphic light eruption, porphyria cutanea tarda, granuloma annulare, and sarcoidosis. In 2020, it was widely prescribed both to prevent and to treat COVID-19 caused by SARS-CoV-2. Its increased use led to serious supply shortages and in some cases stocks were entirely depleted. Recent meta-analyses have concluded that hydroxychloroquine is ineffective against COVID-19 and have advised against its use.

[Hydroxychloroquine: An Essential Drug in Dermatology and Its Controversial Use in COVID-19]

Hydroxychloroquine is an antimalarial drug with immunomodulatory, anti-inflammatory, antibacterial, and antiviral properties. It has a good safety profile, can be used in children and in pregnant and breastfeeding women, and does not suppress the immune system. Regular screening for retinopathy, one of the drug's most feared adverse effects, is necessary. Hydroxychloroquine is a widely used, essential drug in dermatology. Clinical response rates are good in lupus erythematous, where it is a first-line therapy, as well in numerous autoimmune/inflammatory diseases, including lichen planus, polymorphic light eruption, porphyria cutanea tarda, granuloma annulare, and sarcoidosis. In 2020, it was widely prescribed both to prevent and to treat COVID-19 caused by SARS-CoV-2. Its increased use led to serious supply shortages and in some cases stocks were entirely depleted. Recent meta-analyses have concluded that hydroxychloroquine is ineffective against COVID-19 and have advised against its use.

Highly multiplexed imaging mass cytometry identifies similarities between antisynthetase syndrome and dermatomyositis skin lesions

OBJECTIVE

Antisynthetase syndrome (AS) and Dermatomyositis (DM) are autoimmune disorders that overlap clinically. Given the presence of DM skin lesions in AS patients, there is debate about whether AS is distinct or a subclassification of DM. Recently studies identified differences in type I interferon (IFN) between AS and DM muscle and finger eruptions. The aim of this study is to elucidate cutaneous disease pathogenic similarities and differences on a single cell level.

METHODS

Five AS and seven DM patients were recruited from a prospectively collected database of well-characterized DM patients. AS patients were clinically confirmed with anti-synthetase syndrome by the Connors and Solomon et al. criteria and aminoacyl-transfer ribonucleic acid synthetase antibodies. Immunophenotyping conducted using immunofluorescence (IF) and imaging mass cytometry (IMC).

RESULTS

IF revealed type I IFN upregulation in AS and DM compared to HC using MxA and IFNβ expression (p<0.05). IMC showed similar macrophages, T cells, B cells, and dendritic cells in AS and DM with no differences in counts (p>0.05), but an increase in myeloid dendritic cell percentage in DM (p<0.05). Key type I IFN, cytokine, and JAK-STAT pathways were similarly expressed in AS and DM (p>0.05). At a single cell level, pSTING+ macrophages in AS expressed increased TNFα, IL17, and IFNβ (p<0.001).

CONCLUSION

IMC is a powerful tool that identifies a role for the type I IFN system in DM-like skin lesions of AS and DM with some differences at a cellular level, but overall significant overlap exists supporting similar therapeutic decision making.

Hydroxychloroquine: An Essential Drug in Dermatology and Its Controversial Use in COVID-19

Hydroxychloroquine is an antimalarial drug with immunomodulatory, anti-inflammatory, antibacterial, and antiviral properties. It has a good safety profile, can be used in children and in pregnant and breastfeeding women, and does not suppress the immune system. Regular screening for retinopathy, one of the drug's most feared adverse effects, is necessary. Hydroxychloroquine is a widely used, essential drug in dermatology. Clinical response rates are good in lupus erythematous, where it is a first-line therapy, as well in numerous autoimmune/inflammatory diseases, including lichen planus, polymorphic light eruption, porphyria cutanea tarda, granuloma annulare, and sarcoidosis. In 2020, it was widely prescribed both to prevent and to treat COVID-19 caused by SARS-CoV-2. Its increased use led to serious supply shortages and in some cases stocks were entirely depleted. Recent meta-analyses have concluded that hydroxychloroquine is ineffective against COVID-19 and have advised against its use.

Plasma-derived DNA containing-extracellular vesicles induce STING-mediated proinflammatory responses in dermatomyositis

Objectives: Extracellular vesicles (EVs) are lipid bilayer membrane vesicles that are present in various bodily fluids and have been implicated in autoimmune disease pathogenesis. Type I interferons (IFN), specifically IFN-β, are uniquely elevated in dermatomyositis (DM). The stimulator of interferon genes (STING) works as a critical nucleic acid sensor and adaptor in type I IFN signaling with possible implications in autoimmune diseases such as DM. In the current study, we investigated whether circulating EVs contribute to proinflammatory effects in DM, whether these proinflammatory responses are mediated by the STING signaling pathway, and if so, by what mechanism STING is activated.

Methods: We collected and characterized EVs from plasma of healthy controls (HC) and DM patients; analyzed their abilities to trigger proinflammatory cytokines release by ELISA, and explored STING signaling pathway activation using immunoblot and immunofluorescent staining. STING signaling pathway inhibitors and RNAi were used to further investigate whether STING was involved in EVs-triggered proinflammatory response. DNase/lipid destabilizing agent was utilized to digest EVs and their captured DNA contents to evaluate how EVs triggered STING-mediated proinflammatory response in DM.

Results: EVs isolated from DM plasma triggered proinflammatory cytokines including type I IFN release with STING signaling pathway activation. The activated STING pathway was preferentially mediated by dsDNA captured by EVs. Suppression of STING or its downstream signaling proteins attenuated the EVs-mediated proinflammatory response.

Conclusions: Plasma-derived, DNA containing-EVs induced STING-mediated proinflammatory effects in DM. Targeting the STING pathway may be a potential therapeutic approach for DM.