Exogenous serpin B1 restricts immune complex-mediated NET formation via inhibition of a chymotrypsin-like protease and enhances microbial phagocytosis.

Immune complex (IC)-driven formation of neutrophil extracellular traps (NETs) is a major contributing factor to the pathogenesis of autoimmune diseases including systemic lupus erythematosus (SLE). Exogenous recombinant human serpin B1 (rhsB1) can regulate NET formation; however, its mechanism(s) of action is currently unknown as is its ability to regulate IC-mediated NET formation and other neutrophil effector functions. To investigate this, we engineered or post-translationally modified rhsB1 proteins that possessed specific neutrophil protease inhibitory activities and pretreated isolated neutrophils with them prior to inducing NET formation with ICs derived from patients with SLE, PMA, or the calcium ionophore A23187. Neutrophil activation and phagocytosis assays were also performed with rhsB1 pretreated and IC-activated neutrophils. rhsB1 dose-dependently inhibited NET formation by all three agents in a process dependent on its chymotrypsin-like inhibitory activity, most likely cathepsin G. Only one variant (rhsB1 C344A) increased surface levels of neutrophil adhesion/activation markers on IC-activated neutrophils and boosted intracellular ROS production. Further, rhsB1 enhanced complement-mediated neutrophil phagocytosis of opsonized bacteria but not ICs. In conclusion, we have identified a novel mechanism of action by which exogenously administered rhsB1 inhibits IC, PMA, and A2138-mediated NET formation. Cathepsin G is a well-known contributor to autoimmune disease but to our knowledge, this is the first report implicating it as a potential driver of NET formation. We identified the rhsB1 C334A variant as a candidate protein that can suppress IC-mediated NET formation, boost microbial phagocytosis, and potentially impact additional neutrophil effector functions including ROS-mediated microbial killing in phagolysosomes.

Calcinosis in dermatomyositis.

PURPOSE OF REVIEW: To provide the most recent literature on our understanding behind the pathogenesis and the treatment of calcinosis in dermatomyositis. RECENT FINDINGS: Early diagnosis and controlling the overall disease activity are cornerstones to prevent calcinosis in juvenile dermatomyositis. Observational cohort studies showed that prolonged state of inflammation and features of vascular dysfunction like digital ulcers and abnormal nailfold capillaries are associated with calcinosis. Neutrophil activation and mitochondrial dysfunction have recently emerged as potential mechanistic pathways involved in calcinosis pathogenesis. Few recent case series have alluded to the efficacy of topical and intralesional sodium thiosulfate, while JAK inhibitors appear to be newer promising therapy in juvenile dermatomyositis. SUMMARY: Calcinosis in dermatomyositis consists of deposition of insoluble calcium compounds in the skin and other tissues. It is prevalent in up to 75% of patients with juvenile dermatomyositis and up to 20% in adult dermatomyositis. While it leads to significant patient morbidity, we do not yet understand the pathogenesis in its entirety. Surgical excision although palliative is the mainstay of treatment and should be offered to patients. All available treatment options are only based on very low level of evidence.

Mitochondrial transfer and implications for muscle function in idiopathic inflammatory myopathies.

Impairment in cellular bioenergetics as either the cause, consequence, or major contributor of tissue damage has drawn increasing scientific curiosity across aging and chronic health conditions, with mitochondrial dysfunction emerging as a central mechanism in the pathogenesis of a variety of inflammatory and degenerative disorders. Beyond bioenergetics, mitochondria play critical regulatory roles in programmed cell death of dysfunctional/defective cells as well as in metabolite synthesis and metabolic signalling. Further, extra-cellular exposure to fragmentation of injured mitochondria is associated with incitement of systemic and organ-based inflammation. Thus, mitochondrial function has recently drawn intense, spectral scientific interest as an integral component across maladies.In muscle, mitochondrial dysfunction is clinically associated with atrophy and diminished endurance. Direct myo-histopathological evidence characterising loss of mitochondrial integrity as a hallmark of muscle compromise was first noticed in inclusion body myositis (IBM). This was followed by the discovery of multiple deletions in mitochondrial DNA in sarcopenia, IBM, and other inflammatory myopathies, like dermatomyositis. Though fraught with bioethical considerations, the transplant technology of mitochondrial transfer is swiftly gaining prominence in cellular biology and muscle physiology to remediate mitochondrial diminution and dysfunction. Assembling seminal works and recent developments, this review ventures into the rapidly evolving landscape of mitochondrial transfer, focusing on its implications on muscle function, and offers an integrated perspective on the potential roles of mitochondrial transfer and its implications for preserving and restoring muscle health. Presented here is a consolidated viewpoint on mitochondrial transfer in idiopathic inflammatory myopathies.

Mental health in paediatric and adult myositis-related diseases: current state of research, interventions, and future steps from the MIHRA Psychological Impact Scientific Working Group.

Psychological and emotional well-being are critical aspects of overall health for individuals with chronic rheumatologic conditions. Mental health-related literature, however, predominantly focuses on systemic lupus erythematosus or rheumatoid arthritis, with limited emphasis on idiopathic inflammatory myopathies (IIMs). High proportions of those with juvenile myositis report psychological distress at levels warranting mental health referral. Adults with dermatomyositis diagnosed with depression or anxiety do not receive adequate mental health care. Mental health symptoms in those with IIMs are associated with worse health-related quality of life, medication adherence, and disease outcomes. Despite demonstrated high rates of mental health burden, access to mental health care remains severely lacking.Data related to mental health burden is limited by small sample size, limited generalisability, variable methods of assessment, and inconsistent diagnosis codes to define mental health conditions. Additional research is needed to validate current screening tools in myositis populations. Other relevant measurable factors include disease severity, non-health- and health-related trauma exposure, loneliness, isolation, loss of control, sleep difficulties, fatigue, pain, self-esteem, body image, sexual health, and health inequities. Studiesare needed investigating the efficacy of therapeutic and pharmacologic interventions among patients with myositis who experience depression and anxiety. Currently, knowledge and resources are limited around mental health burden and potential intervention for those living with IIMs. The Myositis International Health & Research Collaborative Alliance (MIHRA) Psychological Impact Scientific Working Group offers a preliminary road map to characterise and prioritise the work ahead to understand baseline mental health burden and compare avenues for intervention.

Collaborative research in myositis-related disorders: MIHRA, a global shared community model.

Myositis International Health and Research Collaborative Alliance (MIHRA) is a newly formed purpose-built non-profit charitable research organization dedicated to accelerating international clinical trial readiness, global professional and lay education, career development and rare disease advocacy in IIM-related disorders. In its long form, the name expresses the community's scope of engagement and intent. In its abbreviation, MIHRA, conveys linguistic roots across many languages, that reflects the IIM community's spirit with meanings such as kindness, community, goodness, and peace. MIHRA unites the global multi-disciplinary community of adult and pediatric healthcare professionals, researchers, patient advisors and networks focused on conducting research in and providing care for pediatric and adult IIM-related disorders to ultimately find a cure. MIHRA serves as a resourced platform for collaborative efforts in investigator-initiated projects, consensus guidelines for IIM assessment and treatment, and IIM-specific career development through connecting research networks.MIHRA's infrastructure, mission, programming and operations are designed to address challenges unique to rare disease communities and aspires to contribute toward transformative models of rare disease research such as global expansion and inclusivity, utilization of community resources, streamlining ethics and data-sharing policies to facilitate collaborative research. Herein, summarises MIHRA operational cores, missions, vision, programming and provision of community resources to sustain, accelerate and grow global collaborative research in myositis-related disorders.

Neutrophil extracellular trap formation in anti-neutrophil cytoplasmic antibody-associated and large-vessel vasculitis.

Levels of neutrophil extracellular traps (NETs) were measured in plasma of healthy controls (HC, n = 30) and patients with granulomatosis with polyangiitis (GPA, n = 123), microscopic polyangiitis (MPA, n = 61), Takayasu's arteritis (TAK, n = 58), and giant cell arteritis (GCA, n = 68), at times of remission or activity and correlated with levels of the platelet-derived thrombospondin-1 (TSP-1). Levels of NETs were elevated during active disease in patients with GPA (p < 0.0001), MPA (p = 0.0038), TAK (p < 0.0001), and GCA (p < 0.0001), and in remission for GPA, p < 0.0001, MPA, p = 0.005, TAK, p = 0.03, and GCA, p = 0.0009. All cohorts demonstrated impaired NET degradation. Patients with GPA (p = 0.0045) and MPA (p = 0.005) had anti-NET IgG antibodies. Patients with TAK had anti-histone antibodies (p < 0.01), correlating with presence of NETs. Levels of TSP-1 were increased in all patients with vasculitis, and associated with NET formation. NET formation is a common process in vasculitides. Targeting NET formation or degradation could be potential therapeutic approaches for vasculitides.

Mitochondrial-mediated inflammation and platelet activation in giant cell arteritis.

Markers of extracellular mitochondria are present in giant cell arteritis (GCA) patients. However, their role in promoting inflammation and platelet activation is no known. To investigate this, isolated mitochondria were opsonized with plasma from GCA patients or healthy individuals and incubated with peripheral blood mononuclear cells (PBMCs) or platelets and assessed for inflammatory cytokine production and platelet activation. Plasma from GCA patients promoted increased mitochondrial-mediated cytokine production by PBMCs as compared to healthy controls (p < 0.05). Mitochondria opsonized with plasma factors from patients with GCA induced higher platelet activation as compared to mitochondria opsonized with plasma factors from healthy individuals (p = 0.0015). Platelet levels of P-selectin were associated with disease activity in GCA (r = 0.34, p = 0.01). GCA patients have impaired ability to regulate the clearance of extracellular mitochondria, possibly contributing to excessive inflammation and platelet activation. Targeting key drivers of mitochondrial extrusion and/or their clearance could lead to new therapeutic interventions in GCA.

Calcinosis in systemic sclerosis.

PURPOSE OF REVIEW: To provide updated information on the prevalence, pathogenesis, diagnostics, and therapeutics of calcinosis cutis associated with systemic sclerosis (SSc). RECENT FINDINGS: Observational studies show ethnic and geographical differences in the prevalence of calcinosis. In addition to clinical and serological associations, biochemical studies and in-vivo models have attempted to explain theories behind its pathogenesis, including prolonged state of inflammation, mechanical stress, hypoxia, and dysregulation in bone and phosphate metabolism. Long-term use of proton pump inhibitors may increase the risk for calcinosis in SSc. Few single center observational studies have shown mild benefit with minocycline and topical sodium thiosulfate. SUMMARY: Calcinosis cutis is the deposition of insoluble calcium in the skin and subcutaneous tissues. It affects up to 40% of SSc patients and causes significant morbidity. Long disease duration, features of vascular dysfunction, and osteoporosis have been associated with calcinosis. Altered levels of inorganic pyrophosphate and fibroblast growth factor-23 have been implicated in dysregulated phosphate metabolism that may lead to calcinosis in SSc. Plain radiography can help with diagnosis and quantifying the calcinosis burden. Surgical treatment remains the most effective therapy when feasible. At present, no medical therapies have proven efficacy in large randomized controlled trials.

Role of mitochondria in the myopathy of juvenile dermatomyositis and implications for skeletal muscle calcinosis.

OBJECTIVES: To elucidate mechanisms contributing to skeletal muscle calcinosis in patients with juvenile dermatomyositis. METHODS: A well-characterized cohorts of JDM (n = 68), disease controls (polymyositis, n = 7; juvenile SLE, n = 10, and RNP + overlap syndrome, n = 12), and age-matched health controls (n = 17) were analyzed for circulating levels of mitochondrial (mt) markers including mtDNA, mt-nd6, and anti-mitochondrial antibodies (AMAs) using standard qPCR, ELISA, and novel-in-house assays, respectively. Mitochondrial calcification of affected tissue biopsies was confirmed using electron microscopy and energy dispersive X-ray analysis. A human skeletal muscle cell line, RH30, was used to generate an in vitro calcification model. Intracellular calcification is measured by flow cytometry and microscopy. Mitochondria were assessed for mtROS production and membrane potential by flow cytometry and real-time oxygen consumption rate by Seahorse bioanalyzer. Inflammation (interferon-stimulated genes) was measured by qPCR. RESULTS: In the current study, patients with JDM exhibited elevated levels of mitochondrial markers associated with muscle damage and calcinosis. Of particular interest are AMAs predictive of calcinosis. Human skeletal muscle cells undergo time- and dose-dependent accumulation of calcium phosphate salts with preferential localization to mitochondria. Calcification renders skeletal muscle cells mitochondria stressed, dysfunctional, destabilized, and interferogenic. Further, we report that inflammation induced by interferon-alpha amplifies mitochondrial calcification of human skeletal muscle cells via the generation of mitochondrial reactive oxygen species (mtROS). CONCLUSIONS: Overall, our study demonstrates the mitochondrial involvement in the skeletal muscle pathology and calcinosis of JDM and mtROS as a central player in the calcification of human skeletal muscle cells. Therapeutic targeting of mtROS and/or upstream inducers, such as inflammation, may alleviate mitochondrial dysfunction, leading to calcinosis. AMAs can potentially identify patients with JDM at risk for developing calcinosis.

Immune complex-mediated neutrophil activation in patients with polymyalgia rheumatica.

OBJECTIVE: Neutrophils are important in host defence. However, neutrophils are also linked to inflammation and organ damage. The purpose of this study was to assess whether markers of neutrophil activation are increased in PMR. METHODS: Levels of immune complexes (IC), calprotectin and neutrophil extracellular traps (NETs) were measured in plasma of healthy individuals (n = 30) and patients with PMR (n = 60), at flare and upon treatment with glucocorticoids using ELISA. Plasma-mediated neutrophil activation was assessed in presence of an FcγRIIA inhibitory antibody (IV.3). RESULTS: Plasma levels of calprotectin and NETs were elevated in PMR (P < 0.001). Mechanistically, neutrophil activation was driven by ICs, present in plasma, able to up-regulate neutrophil activation markers CD66b and CD11b (P < 0.0001) in an FcγRIIA-dependent manner (P < 0.01). Of note, circulating levels of IC correlated with plasma induced CD66b and CD11b (r = 0.51, P = 0.004, and r = 0.46, P = 0.01, respectively) and decreased after glucocorticoid therapy. In contrast to NETs, calprotectin significantly decreased after glucocorticoid therapy (P < 0.001) and was higher in PMR without overlapping GCA compared with patients with overlapping disease (P = 0.014). Interestingly, musculoskeletal involvement was associated with elevated levels of calprotectin before initiation of glucocorticoid therapy (P = 0.036). CONCLUSIONS: Neutrophil activation, including NET formation, is increased in PMR, through IC-mediated engagement of FcγRIIA. Clinically, neutrophil activation is associated with musculoskeletal involvement, with calprotectin, but not NETs, being a biomarker of treatment response in PMR patients. In all, IC-mediated neutrophil activation is a central process in PMR pathogenesis identifying potential novel therapeutic targets (FcγRIIA), as well as soluble markers for disease monitoring (calprotectin).

The emerging role of Growth Differentiation Factor 15 as a potential disease biomarker in juvenile dermatomyositis.

OBJECTIVE: We aimed to investigate the potential of Growth Differentiation Factor 15 (GDF-15) as a novel biomarker for disease activity in Juvenile Dermatomyositis (JDM). METHODS: We recruited children with juvenile myositis including juvenile dermatomyositis (n = 77), polymyositis (n = 6), and healthy controls (n = 22). GDF-15 levels in plasma were measured using ELISA. Statistical analyses were performed using non-parametric tests. RESULTS: Levels of GDF-15 were significantly elevated in JDM compared with healthy controls (p< 0.001). GDF-15 levels exhibited strong positive correlations with disease activity scores, including the Disease Activity Score (DAS) total score, DAS skin score, DAS muscle score, and Childhood Myositis Assessment Scale (CMAS). Additionally, GDF-15 levels could differentiate between active disease and remission based on the Physician Global Assessment of muscle score. Positive correlations were observed between levels of GDF-15 and creatine kinase, neopterin, and nailfold end row loops, indicating the potential involvement of GDF-15 in muscle damage, immune activation, and vascular pathology. ROC curve analysis showed GDF-15 to be more effective in assessing disease activity in JDM than creatine kinase (AUC 0.77, p= 0.001 and AUC 0.6369, p= 0.0738, respectively). CONCLUSION: GDF-15 may serve as a valuable biomarker for assessing disease activity in JDM. It exhibits better sensitivity and specificity than creatine kinase, and the levels correlate with various disease activity scores and functional measures. GDF-15 may provide valuable information for treatment decision-making and monitoring disease progression in JDM.

Argonaute, Vault, and Ribosomal Proteins Targeted by Autoantibodies in Systemic Lupus Erythematosus.

OBJECTIVE: To expand, in an unbiased manner, our knowledge of autoantigens and autoantibodies in patients with systemic lupus erythematosus (SLE) and evaluate their associations with serological and clinical variables. METHODS: Human proteome arrays (> 21,000 proteins) were screened with serum from patients with SLE (n = 12) and healthy controls (n = 6) for IgG and IgA binding. Top hits were validated with 2 cohorts of patients with SLE (cohort 1, n = 49; cohort 2, n = 46) and other rheumatic diseases by ELISA. Clinical associations of the autoantibodies were tested. RESULTS: Ro60 was the top hit in the screen, and the 10 following proteins included 2 additional known SLE autoantigens plus 8 novel autoantigens involved in microRNA processing (Argonaute protein 1 [AGO1], AGO2, and AGO3), ribosomes (ribosomal protein lateral stalk subunit P2 and ovarian tumor deubiquitinase 5 [OTUD5]), RNA transport by the vault (major vault protein), and the immune proteasome (proteasome activator complex subunit 3). Patient serum contained IgG reactive with these proteins and IgA against the AGO proteins. Using the 95th percentile of healthy donor reactivity, 5-43% were positive for the novel antigens, with OTUD5 and AGO1 showing the highest percentages of positivity. Autoantibodies against AGO1 proteins were more prevalent in patients with oral ulcers in a statistically significant manner. IgG autoantibodies against AGO proteins were also seen in other rheumatic diseases. CONCLUSION: We discovered new autoantigens existing in cytosolic macromolecular protein assemblies containing RNA (except the proteasome) in cells. A more comprehensive list of autoantigens will allow for a better analysis of how proteins are targeted by the autoimmune response. Future research will also reveal whether specific autoantibodies have utility in the diagnosis or management of SLE.

Calcinosis in systemic sclerosis.

PURPOSE OF REVIEW: The aim of this study was to provide updated information on the prevalence, pathogenesis, diagnostics and therapeutics of calcinosis cutis associated with systemic sclerosis (SSc). RECENT FINDINGS: Observational studies show ethnic and geographical differences in the prevalence of calcinosis. In addition to clinical and serological associations, biochemical studies and in-vivo models have attempted to explain theories behind its pathogenesis, including prolonged state of inflammation, mechanical stress, hypoxia and dysregulation in bone and phosphate metabolism. Long-term use of proton pump inhibitors may increase the risk for calcinosis in SSc. Few single-centre observational studies have shown mild benefit with minocycline and topical sodium thiosulfate. SUMMARY: Calcinosis cutis is the deposition of insoluble calcium in the skin and subcutaneous tissues. It affects up to 40% of SSc patients and causes significant morbidity. Long disease duration, features of vascular dysfunction and osteoporosis have been associated with calcinosis. Altered levels of inorganic pyrophosphate and fibroblast growth factor-23 have been implicated in dysregulated phosphate metabolism that may lead to calcinosis in SSc. Plain radiography can help with diagnosis and quantifying the calcinosis burden. Surgical treatment remains the most effective therapy when feasible. At present, no medical therapies have proven efficacy in large randomized controlled trials.

FcγRIIA expression accelerates nephritis and increases platelet activation in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease characterized by deposits of immune complexes (ICs) in organs and tissues. The expression of FcγRIIA by human platelets, which is their unique receptor for immunoglobulin G antibodies, positions them to ideally respond to circulating ICs. Whereas chronic platelet activation and thrombosis are well-recognized features of human SLE, the exact mechanisms underlying platelet activation in SLE remain unknown. Here, we evaluated the involvement of FcγRIIA in the course of SLE and platelet activation. In patients with SLE, levels of ICs are associated with platelet activation. Because FcγRIIA is absent in mice, and murine platelets do not respond to ICs in any existing mouse model of SLE, we introduced the FcγRIIA (FCGR2A) transgene into the NZB/NZWF1 mouse model of SLE. In mice, FcγRIIA expression by bone marrow cells severely aggravated lupus nephritis and accelerated death. Lupus onset initiated major changes to the platelet transcriptome, both in FcγRIIA-expressing and nonexpressing mice, but enrichment for type I interferon response gene changes was specifically observed in the FcγRIIA mice. Moreover, circulating platelets were degranulated and were found to interact with neutrophils in FcγRIIA-expressing lupus mice. FcγRIIA expression in lupus mice also led to thrombosis in lungs and kidneys. The model recapitulates hallmarks of human SLE and can be used to identify contributions of different cellular lineages in the manifestations of SLE. The study further reveals a role for FcγRIIA in nephritis and in platelet activation in SLE.

Autoantibodies against the envelope proteins of endogenous retroviruses K102 and K108 in patients with systemic lupus erythematosus correlate with active disease.

OBJECTIVES: To determine if patients with systemic lupus erythematosus (SLE), a disease characterised by elevated type I interferons reminiscent of anti-viral immunity, have expression of human endogenous retrovirus K (HERV-K) proviruses capable of producing envelope (Env) protein, as well as associated autoantibodies against the Env protein. METHODS: ELISAs were conducted with recombinant Env protein and sera from SLE patients with active (n=60) or inactive (n=49) disease, healthy controls (n=47), other rheumatic disorders (n=59), as well as plasma from paediatric lupus patients with active (n=30) or inactive (n=30) disease, and 17 healthy children. Antibody reactivity was evaluated for correlations with clinical and laboratory parameters of the patients. Expression of HERV-K transcripts were profiled in SLE leukocytes by RNA-Seq. RESULTS: Both adult and paediatric SLE patients had autoantibodies against HERV-K Env with higher titres than healthy controls or patients with Sjögren's syndrome, small- or large-vessel vasculitis, or psoriatic arthritis. Transcripts from only two HERV-K loci capable of producing Env, HERV-K102 and -K108, were detected among the 10 expressed loci in SLE patients. CONCLUSIONS: Our data reveal that HERV-K proviruses are expressed in SLE and that the HERV-K-encoded Env protein elicits an immune response in patients, particularly during active disease.

Calpain drives pyroptotic vimentin cleavage, intermediate filament loss, and cell rupture that mediates immunostimulation.

Pyroptosis is an inflammatory form of programmed cell death following cellular damage or infection. It is a lytic process driven by gasdermin D-mediated cellular permeabilization and presumed osmotic forces thought to induce swelling and rupture. We found that pyroptotic cells do not spontaneously rupture in culture but lose mechanical resilience. As a result, cells were susceptible to rupture by extrinsic forces, such as shear stress or compression. Cell analyses revealed that all major cytoskeleton components were disrupted during pyroptosis and that sensitivity to rupture was calpain-dependent and linked with cleavage of vimentin and loss of intermediate filaments. Moreover, while release of lactate dehydrogenase (LDH), HMGB1, and IL-1ß occurred without rupture, rupture was required for release of large inflammatory stimuli-ASC specks, mitochondria, nuclei, and bacteria. Importantly, supernatants from ruptured cells were more immunostimulatory than those from nonruptured cells. These observations reveal undiscovered cellular events occurring during pyroptosis, define the mechanisms driving pyroptotic rupture, and highlight the immunologic importance of this event.

Mitochondrial N-formyl methionine peptides associate with disease activity as well as contribute to neutrophil activation in patients with rheumatoid arthritis.

OBJECTIVES: Literature suggests that neutrophils of patients with rheumatoid arthritis (RA) are primed to respond to N-formyl methionine group (formylated peptides). Animal models indicate that formylated peptides contribute to joint damage via neutrophil recruitment and inflammation in joints. Non-steroidal anti-inflammatory drugs are also known to inhibit formyl peptide-induced neutrophil activation. The predominant source of formylated peptides in sterile inflammatory conditions like RA is mitochondria, organelles with prokaryotic molecular signatures. However, there is no direct evidence of mitochondrial formyl peptides (mtNFPs) in the circulation of patients with RA and their potential role in neutrophil-mediated inflammation in RA, including their clinical significance. METHODS: Levels of mtNFPs (total fMet, MT-ND6) were analyzed using ELISA in plasma and serum obtained from patients in 3 cross-sectional RA cohorts (n = 275), a longitudinal inception cohort (n = 192) followed for a median of 8 years, and age/gender-matched healthy controls (total n = 134). Neutrophil activation assays were done in the absence or presence of formyl peptide receptor 1 (FPR1) inhibitor cyclosporine H. RESULTS: Elevated levels of total fMet were observed in the circulation of patients with RA as compared to healthy controls (p < 0.0001) associating with disease activity and could distinguish patients with the active disease from patients with inactive disease or patients in remission. Baseline levels of total fMet correlated with current and future joint involvement, respectively and predicted the development of rheumatoid nodules (OR = 1.2, p = 0.04). Further, total fMet levels improved the prognostic ability of ACPA in predicting erosive disease (OR of 7.9, p = 0.001). Total fMet levels correlated with markers of inflammation and neutrophil activation. Circulating mtNFPs induced neutrophil activation in vitro through FPR1-dependent mechanisms. CONCLUSIONS: Circulating mtNFPs could be novel biomarkers of disease monitoring and prognosis for RA and in investigating neutrophil-mediated inflammation in RA. We propose, FPR1 as a novel therapeutic target for RA.

A neutrophil signature is strongly associated with increased cardiovascular risk in gout.

OBJECTIVE: To investigate the association between neutrophil activation and cardiovascular risk in gout patients. We hypothesize that neutrophil activation mediates inflammation and therefore takes part in atherogenesis in gout patients. METHOD: Patient data were collected from 75 consecutive gout patients participating in the Reade gout cohort Amsterdam. Levels of neutrophil extracellular traps (NETs) and neutrophil activation (calprotectin and peroxidase activity) were analysed by ELISA and fluorimetry in plasma and compared with healthy controls. Markers of neutrophil activation were related to clinical markers of cardiovascular risk, including BMI, smoking, blood pressure, lipid profile and 10 year risk of cardiovascular mortality (EU-SCORE). RESULTS: Increased levels of NETs were found in gout patients, although increased levels were not associated with cardiovascular risk. However, markers of neutrophil activation, including peroxidase activity correlated with waist:hip ratio (ß = 0.33, P < 0.001), cholesterol ratio (ß = 0.46, P < 0.005) and triglycerides (ß = 0.60, P < 0.001) as well as the 10 year risk of cardiovascular mortality (ß = 0.44, P = 0.001). Calprotectin levels were elevated in hypertension (P = 0.005) and diabetes (P = 0.02). Finally, gout patients with high levels of both peroxidase and calprotectin ('neutrophil activation signature') had a markedly elevated cardiovascular risk score (P = 0.001), with 68% of the patients having high cardiovascular risk (odds ratio 2.9, P = 0.03). CONCLUSION: We demonstrated elevated levels of neutrophil activation markers, MPO and calprotectin in gout patients as compared with healthy controls. Of note, neutrophil activation markers were associated with several risk factors for cardiovascular disease, including hyperlipidaemia, hypertension and diabetes. Finally, the presence of a neutrophil activation signature was strongly associated with an increased 10 year risk of cardiovascular mortality. Further studies are needed to determine whether gout-specific factors and/or cardiovascular risk factors contribute to the elevated neutrophil activation observed in these patients.

An interferon-gamma release assay as a novel biomarker in systemic lupus erythematosus.

OBJECTIVE: The mycobacterium tuberculosis (TB) IFN-γ release assay (TB-IGRA) assesses peripheral blood cell release of IFN-γ upon ex vivo exposure to mitogen (IGRA-MT), TB antigen or a negative/nil control (IGRA-NL); IGRA-NL is a measure of spontaneous IFN-γ release (SIR). Here, we investigate the diagnostic associations of elevated SIR and the potential use of IGRA-NL as a novel biomarker in SLE. METHODS: We analysed diagnostic code frequencies among 11 823 individuals undergoing TB-IGRA testing between 2010 and 2015 in a large urban US health-care system. To study the relationship between IGRA-NL and SLE, we identified 99 individuals with SLE and TB-IGRA test results then assessed correlations between IGRA-NL, normalized IGRA-NL (the quotient of IGRA-NL/IGRA-MT), disease manifestations and disease activity. RESULTS: We identified a discovery cohort of 108 individuals with elevated SIR (>5 S.d. above median) that was significantly enriched for a limited set of diagnoses, including SLE, TB infection, haemophagocytic lymphohistiocytosis and HIV infection. In SLE patients undergoing TB-IGRA testing, normalized IGRA-NL correlated better with disease activity than did anti-dsDNA or complement levels. This relationship appeared to reflect interactions between normalized IGRA-NL and the presence of acute skin disease, hypocomplementemia, fever and thrombocytopenia. CONCLUSION: Elevated SIR appears to be associated with a limited number of disease processes, including SLE. The diagnostic utility of SIR remains to be determined. IFN-γ activation, as measured by the TB-IGRA test, may offer a readily available tool for assessing disease activity in patients with SLE.

Complement deposition, C4d, on platelets is associated with vascular events in systemic lupus erythematosus.

OBJECTIVE: Complement components, including C4d, can be found on activated platelets, a process associated with vascular disease in SLE. We investigated whether platelet C4d (PC4d) adds additional value to traditional and known lupus-associated risk factors when identifying SLE patients with vascular disease. METHODS: This cross-sectional study included 308 well-characterized SLE patients and 308 matched general population controls. PC4d deposition was analysed using flow cytometry. Values >95% of controls were considered as PC4d positive (+). aPL were determined by Luminex, and the LA test was performed by DRVVT. History of vascular disease (composite and as separate outcomes) was defined at inclusion. RESULTS: SLE patients had increased PC4d deposition as compared with population controls (50 vs 5%, P < 0.0001). PC4d+ positively associated with any vascular events, and separately with venous and cerebrovascular events, and also with all investigated aPL profiles. The association for any vascular event remained statistically significant after adjustment for traditional and SLE-associated risk factors (odds ratio: 2.3, 95% CI: 1.3, 4.3, P = 0.008). Compared with patients negative for both PC4d and LA, patients with double positivity were more likely to have vascular disease (odds ratio: 12.3, 95% CI: 5.4, 29.3; attributable proportion due to interaction 0.8, 95% CI: 0.4, 1.1). CONCLUSION: PC4d+ is associated with vascular events in SLE, independently of traditional and SLE-associated risk factors. Concurrent presence of PC4d and LA seem to interact to further increase the odds for vascular events. Prospective studies should examine whether the aPL/PC4d combination can improve prediction of vascular events in SLE and/or APS.