Unraveling IFN-I response dynamics and TNF crosstalk in the pathophysiology of systemic lupus erythematosus.

Introduction: The innate immune system serves the crucial first line of defense against a wide variety of potential threats, during which the production of pro-inflammatory cytokines IFN-I and TNFα are key. This astonishing power to fight invaders, however, comes at the cost of risking IFN-I-related pathologies, such as observed during autoimmune diseases, during which IFN-I and TNFα response dynamics are dysregulated. Therefore, these response dynamics must be tightly regulated, and precisely matched with the potential threat. This regulation is currently far from understood. Methods: Using droplet-based microfluidics and ODE modeling, we studied the fundamentals of single-cell decision-making upon TLR signaling in human primary immune cells (n = 23). Next, using biologicals used for treating autoimmune diseases [i.e., anti-TNFα, and JAK inhibitors], we unraveled the crosstalk between IFN-I and TNFα signaling dynamics. Finally, we studied primary immune cells isolated from SLE patients (n = 8) to provide insights into SLE pathophysiology. Results: single-cell IFN-I and TNFα response dynamics display remarkable differences, yet both being highly heterogeneous. Blocking TNFα signaling increases the percentage of IFN-I-producing cells, while blocking IFN-I signaling decreases the percentage of TNFα-producing cells. Single-cell decision-making in SLE patients is dysregulated, pointing towards a dysregulated crosstalk between IFN-I and TNFα response dynamics. Discussion: We provide a solid droplet-based microfluidic platform to study inherent immune secretory behaviors, substantiated by ODE modeling, which can challenge the conceptualization within and between different immune signaling systems. These insights will build towards an improved fundamental understanding on single-cell decision-making in health and disease.

Suppression of IL-12/IL-23 p40 subunit in the skin and blood of psoriasis patients by Tofacitinib is dependent on active interferon-γ signaling in dendritic cells: Implications for the treatment of psoriasis and interferon-driven diseases.

Interleukin (IL)-12 and IL-23 are pro-inflammatory cytokines produced by dendritic cells (DCs) and associated with Psoriasis (Pso) and Psoriatic Arthritis (PsA) pathogenesis. Tofacitinib, a Janus kinase inhibitor, effectively suppresses inflammatory cascades downstream the IL-12/IL-23 axis in Pso and PsA patients. Here, we investigated whether Tofacitinib directly regulates IL-12/IL-23 production in DCs, and how this regulation reflects responses to Tofacitinib in Pso patients. We treated monocyte-derived dendritic cells and myeloid dendritic cells with Tofacitinib and stimulated cells with either lipopolysaccharide (LPS) or a combination of LPS and IFN-γ. We assessed gene expression by qPCR, obtained skin microarray and blood Olink data and clinical parameters of Pso patients treated with Tofacitinib from public data sets. Our results indicate that in DCs co-stimulated with LPS and IFN-γ, but not with LPS alone, Tofacitinib leads to the decreased expression of IL-23/IL-12 shared subunit IL12B (p40). In Tofacitinib-treated Pso patients, IL-12 expression and psoriasis area and severity index (PASI) are significantly reduced in patients with higher IFN-γ at baseline. These findings demonstrate for the first time that Tofacitinib suppresses IL-23/IL-12 shared subunit IL12B in DCs upon active IFN-γ signaling, and that Pso patients with higher IFN-γ baseline levels display improved clinical response after Tofacitinib treatment.

RegEnrich gene regulator enrichment analysis reveals a key role of the ETS transcription factor family in interferon signaling.

Changes in a few key transcriptional regulators can lead to different biological states. Extracting the key gene regulators governing a biological state allows us to gain mechanistic insights. Most current tools perform pathway/GO enrichment analysis to identify key genes and regulators but tend to overlook the gene/protein regulatory interactions. Here we present RegEnrich, an open-source Bioconductor R package, which combines differential expression analysis, data-driven gene regulatory network inference, enrichment analysis, and gene regulator ranking to identify key regulators using gene/protein expression profiling data. By benchmarking using multiple gene expression datasets of gene silencing studies, we found that RegEnrich using the GSEA method to rank the regulators performed the best. Further, RegEnrich was applied to 21 publicly available datasets on in vitro interferon-stimulation of different cell types. Collectively, RegEnrich can accurately identify key gene regulators from the cells under different biological states, which can be valuable in mechanistically studying cell differentiation, cell response to drug stimulation, disease development, and ultimately drug development.

ZFP36 Family Members Regulate the Proinflammatory Features of Psoriatic Dermal Fibroblasts.

Dermal fibroblasts are strategically positioned underneath the basal epidermis layer to support keratinocyte proliferation and extracellular matrix production. In inflammatory conditions, these fibroblasts produce cytokines and chemokines that promote the chemoattraction of immune cells into the dermis and the hyperplasia of the epidermis, two characteristic hallmarks of psoriasis. However, how dermal fibroblasts specifically contribute to psoriasis development remains largely uncharacterized. In this study, we investigated through which cytokines and signaling pathways dermal fibroblasts contribute to the inflammatory features of psoriatic skin. We show that dermal fibroblasts from lesional psoriatic skin are important producers of inflammatory mediators, including IL-6, CXCL8, and CXCL2. This increased cytokine production was found to be regulated by ZFP36 family members ZFP36, ZFP36L1, and ZFP36L2, RNA-binding proteins with mRNA-degrading properties. In addition, the expression of ZFP36 family proteins was found to be reduced in chronic inflammatory conditions that mimic psoriatic lesional skin. Collectively, these results indicate that dermal fibroblasts are important producers of cytokines in psoriatic skin and that reduced expression of ZFP36 members in psoriasis dermal fibroblasts contributes to their inflammatory phenotype.

Immune checkpoint inhibitor-associated sarcoidosis: A usually benign disease that does not require immunotherapy discontinuation.

OBJECTIVE: To analyse the clinical patterns of sarcoidosis triggered by immune checkpoint inhibitors (ICIs) in patients with cancer. PATIENTS AND METHODS: The ImmunoCancer International Registry is a big data-sharing multidisciplinary network from 18 countries dedicated to evaluating the clinical research of immune-related adverse events related to cancer immunotherapies. RESULTS: We identified 32 patients with biopsy-proven sarcoidosis. Underlying cancer included mainly melanoma (n = 24). Cancer immunotherapy consisted of monotherapy in 19 cases (anti-PD-1 in 18 and ipilimumab in 1) or combined ipilimumab + nivolumab in 13. The time median interval between initiation of ICI and sarcoidosis diagnosis was 3 months (range, 2-29 months). The use of combined ICI was associated with a shorter delay in developing sarcoidosis symptoms. The disease was symptomatic in 19 (59%) cases with mostly cutaneous, respiratory and general symptoms. The organs involved included mainly the mediastinal lymph nodes (n = 32), the lungs (n = 11), the skin (n = 10) and the eyes (n = 5). Pulmonary computed tomography studies showed bilateral hilar lymphadenopathy in all cases. There was no severe manifestation. Specific systemic therapy was required in only 12 patients (37%): oral glucocorticoids in 9, and hydroxychloroquine in 3. ICIs were held in 25 patients (78%) and definitively discontinued in 18 (56%) patients. Seven patients continued ICI treatment with a second flare in one case. In six additional patients, an ICI was reintroduced with no harm, and sarcoidosis relapsed in one of them. CONCLUSION: Our study shows that ICI-related sarcoidosis seems to have a specific profile, possibly more benign than that of idiopathic sarcoidosis, and does not necessarily imply ICI discontinuation.

Tissue-Resident Memory CD8+ T Cells From Skin Differentiate Psoriatic Arthritis From Psoriasis.

OBJECTIVE: To compare immune cell phenotype and function in psoriatic arthritis (PsA) versus psoriasis in order to better understand the pathogenesis of PsA. METHODS: In-depth immunophenotyping of different T cell and dendritic cell subsets was performed in patients with PsA, psoriasis, or axial spondyloarthritis and healthy controls. Subsequently, we analyzed cells from peripheral blood, synovial fluid (SF), and skin biopsy specimens using flow cytometry, along with high-throughput transcriptome analyses and functional assays on the specific cell populations that appeared to differentiate PsA from psoriasis. RESULTS: Compared to healthy controls, the peripheral blood of patients with PsA was characterized by an increase in regulatory CD4+ T cells and interleukin-17A (IL-17A) and IL-22 coproducing CD8+ T cells. One population specifically differentiated PsA from psoriasis: i.e., CD8+CCR10+ T cells were enriched in PsA. CD8+CCR10+ T cells expressed high levels of DNAX accessory molecule 1 and were effector memory cells that coexpressed skin-homing receptors CCR4 and cutaneous lymphocyte antigen. CD8+CCR10+ T cells were detected under inflammatory and homeostatic conditions in skin, but were not enriched in SF. Gene profiling further revealed that CD8+CCR10+ T cells expressed GATA3, FOXP3, and core transcriptional signature of tissue-resident memory T cells, including CD103. Specific genes, including RORC, IFNAR1, and ERAP1, were up-regulated in PsA compared to psoriasis. CD8+CCR10+ T cells were endowed with a Tc2/22-like cytokine profile, lacked cytotoxic potential, and displayed overall regulatory function. CONCLUSION: Tissue-resident memory CD8+ T cells derived from the skin are enhanced in the circulation of patients with PsA compared to patients with psoriasis alone. This may indicate that aberrances in cutaneous tissue homeostasis contribute to arthritis development.

Multiomics and Machine Learning Accurately Predict Clinical Response to Adalimumab and Etanercept Therapy in Patients With Rheumatoid Arthritis.

OBJECTIVE: To predict response to anti-tumor necrosis factor (anti-TNF) prior to treatment in patients with rheumatoid arthritis (RA), and to comprehensively understand the mechanism of how different RA patients respond differently to anti-TNF treatment. METHODS: Gene expression and/or DNA methylation profiling on peripheral blood mononuclear cells (PBMCs), monocytes, and CD4+ T cells obtained from 80 RA patients before they began either adalimumab (ADA) or etanercept (ETN) therapy was studied. After 6 months, treatment response was evaluated according to the European League Against Rheumatism criteria for disease response. Differential expression and methylation analyses were performed to identify the response-associated transcription and epigenetic signatures. Using these signatures, machine learning models were built by random forest algorithm to predict response prior to anti-TNF treatment, and were further validated by a follow-up study. RESULTS: Transcription signatures in ADA and ETN responders were divergent in PBMCs, and this phenomenon was reproduced in monocytes and CD4+ T cells. The genes up-regulated in CD4+ T cells from ADA responders were enriched in the TNF signaling pathway, while very few pathways were differential in monocytes. Differentially methylated positions (DMPs) were strongly hypermethylated in responders to ETN but not to ADA. The machine learning models for the prediction of response to ADA and ETN using differential genes reached an overall accuracy of 85.9% and 79%, respectively. The models using DMPs reached an overall accuracy of 84.7% and 88% for ADA and ETN, respectively. A follow-up study validated the high performance of these models. CONCLUSION: Our findings indicate that machine learning models based on molecular signatures accurately predict response before ADA and ETN treatment, paving the path toward personalized anti-TNF treatment.

EULAR points to consider for the diagnosis and management of rheumatic immune-related adverse events due to cancer immunotherapy with checkpoint inhibitors.

BACKGROUND: Rheumatic and musculoskeletal immune-related adverse events (irAEs) are observed in about 10% of patients with cancer receiving checkpoint inhibitors (CPIs). Given the recent emergence of these events and the lack of guidance for rheumatologists addressing them, a European League Against Rheumatism task force was convened to harmonise expert opinion regarding their identification and management. METHODS: First, the group formulated research questions for a systematic literature review. Then, based on literature and using a consensus procedure, 4 overarching principles and 10 points to consider were developed. RESULTS: The overarching principles defined the role of rheumatologists in the management of irAEs, highlighting the shared decision-making process between patients, oncologists and rheumatologists. The points to consider inform rheumatologists on the wide spectrum of musculoskeletal irAEs, not fulfilling usual classification criteria of rheumatic diseases, and their differential diagnoses. Early referral and facilitated access to rheumatologist are recommended, to document the target organ inflammation. Regarding therapeutic, three treatment escalations were defined: (1) local/systemic glucocorticoids if symptoms are not controlled by symptomatic treatment, then tapered to the lowest efficient dose, (2) conventional synthetic disease-modifying antirheumatic drugs, in case of inadequate response to glucocorticoids or for steroid sparing and (3) biological disease-modifying antirheumatic drugs, for severe or refractory irAEs. A warning has been made on severe myositis, a life-threatening situation, requiring high dose of glucocorticoids and close monitoring. For patients with pre-existing rheumatic disease, baseline immunosuppressive regimen should be kept at the lowest efficient dose before starting immunotherapies. CONCLUSION: These statements provide guidance on diagnosis and management of rheumatic irAEs and aim to support future international collaborations.

DNAM1 and TIGIT balance the T cell response, with low T cell TIGIT expression corresponding to inflammation in psoriatic disease.

Objectives: Signals at the contact site of antigen-presenting cells (APCs) and T cells help orchestrate the adaptive immune response. CD155 on APCs can interact with the stimulatory receptor DNAM1 or inhibitory receptor TIGIT on T cells. The CD155/DNAM1/TIGIT axis is under extensive investigation as immunotherapy target in inflammatory diseases including cancer, chronic infection and autoimmune diseases. We investigated a possible role for CD155/DNAM1/TIGIT signaling in psoriatic disease. Methods: By flow cytometry, we analyzed peripheral blood mononuclear cells of patients with psoriasis (n = 20) or psoriatic arthritis (n = 21), and healthy individuals (n = 7). We measured CD155, TIGIT, and DNAM1 expression on leukocyte subsets and compared activation-induced cytokine production between CD155-positive and CD155-negative APCs. We assessed the effects of TIGIT and DNAM1 blockade on T cell activation, and related the expression of CD155/DNAM1/TIGIT axis molecules to measures of disease activity. Results: High CD155 expression associates with tumor necrosis factor (TNF) production in myeloid and plasmacytoid dendritic cells (DC). In CD1c+ myeloid DC, activation-induced CD155 expression associates with increased HLA-DR expression. CD8 T cells - but not CD4 T cells - express high levels of TIGIT. DNAM1 blockade decreases T cell pro-inflammatory cytokine production, while TIGIT blockade increased T cell proliferation. Finally, T cell TIGIT expression shows an inverse correlation with inflammation biomarkers in psoriatic disease. Conclusion: CD155 is increased on pro-inflammatory APCs, while the receptors DNAM1 and TIGIT expressed on T cells balance the inflammatory response by T cells. In psoriatic disease, low TIGIT expression on T cells is associated with systemic inflammation.

First-line csDMARD monotherapy drug retention in psoriatic arthritis: methotrexate outperforms sulfasalazine.

OBJECTIVES: Conventional synthetic DMARDs (csDMARDs) are the first-line treatment for PsA, but there is conflicting data regarding their efficacy and scarce reports describing the duration of use (drug retention) of csDMARD in this population. Their position in treatment recommendations is a matter of growing debate due to the availability of alternative treatment options with higher levels of evidence. We aimed to study drug retention and predictors for drug retention among PsA patients receiving first-line csDMARD monotherapy. METHODS: Retrospective cohort study in DMARD-naïve adult PsA patients in whom a first csDMARD was prescribed as monotherapy primarily to treat PsA-related symptoms. The main outcome was time to failure of the csDMARD (i.e. stopping the csDMARD or adding another DMARD). RESULTS: A total of 187 patients were included, who were mainly prescribed MTX (n = 163) or SSZ (n = 21). The pooled median drug retention time was 31.8 months (interquartile range 9.04-110). Drug retention was significantly higher in MTX (median 34.5 months; interquartile range 9.60-123) as compared with SSZ-treated patients (median 12.0 months; interquartile range 4.80- 55.7) (P =0.016, log-rank test). In multivariable Cox regression, the use of MTX and older age were associated with increased retention. The main reasons for treatment failure were inefficacy (52%) and side effects (28%). Upon failure, MTX treated patients were more commonly, subsequently treated with a biologic DMARD compared with SSZ (P < 0.05). CONCLUSION: MTX outperforms SSZ as a first-line csDMARD in DMARD-naïve PsA patients with respect to monotherapy drug retention in daily clinical practice.

Biomarker profiles of endothelial activation and dysfunction in rare systemic autoimmune diseases: implications for cardiovascular risk.

OBJECTIVES: Vasculopathy is an important hallmark of systemic chronic inflammatory connective tissue diseases (CICTD) and is associated with increased cardiovascular risk. We investigated disease-specific biomarker profiles associated with endothelial dysfunction, angiogenic homeostasis and (tissue) inflammation, and their relation to disease activity in rare CICTD. METHODS: A total of 38 serum proteins associated with endothelial (dys)function and inflammation were measured by multiplex-immunoassay in treatment-naive patients with localized scleroderma (LoS, 30), eosinophilic fasciitis (EF, 8) or (juvenile) dermatomyositis (34), 119 (follow-up) samples during treatment, and 65 controls. Data were analysed by unsupervised clustering, Spearman correlations, non-parametric t test and ANOVA. RESULTS: The systemic CICTD, EF and dermatomyositis, had distinct biomarker profiles, with 'signature' markers galectin-9 (dermatomyositis) and CCL4, CCL18, CXCL9, fetuin, fibronectin, galectin-1 and TSP-1 (EF). In LoS, CCL18, CXCL9 and CXCL10 were subtly increased. Furthermore, dermatomyositis and EF shared upregulation of markers related to interferon (CCL2, CXCL10), endothelial activation (VCAM-1), inhibition of angiogenesis (angiopoietin-2, sVEGFR-1) and inflammation/leucocyte chemo-attraction (CCL19, CXCL13, IL-18, YKL-40), as well as disturbance of the Angiopoietin-Tie receptor system and VEGF-VEGFR system. These profiles were related to disease activity, and largely normalized during treatment. However, a subgroup of CICTD patients showed continued elevation of CXCL10, CXCL13, galectin-9, IL-18, TNFR2, VCAM-1, and/or YKL-40 during clinically inactive disease, possibly indicating subclinical interferon-driven inflammation and/or endothelial dysfunction. CONCLUSION: CICTD-specific biomarker profiles revealed an anti-angiogenic, interferon-driven environment during active disease, with incomplete normalization under treatment. This warrants further investigation into monitoring of vascular biomarkers during clinical follow-up, or targeted interventions to minimize cardiovascular risk in the long term.

Comparison of the Heel Enthesitis MRI Scoring System (HEMRIS) with clinical enthesitis and local metabolic activity on PET-CT.

OBJECTIVE: To compare the Heel Enthesitis MRI Scoring model (HEMRIS) with clinical and PET/CT outcomes in patients with cutaneous psoriasis (Pso), psoriatic arthritis (PsA) or ankylosing spondylitis (AS). METHODS: This prospective, observational study included 38 patients with Pso, PsA and AS. Patients were included regardless of presence or absence of clinical heel enthesitis. MRI-scans of both ankles and a whole-body 18F-FDG PET/CT were acquired. MRIs were assessed for enthesitis by two independent and blinded observers according to the HEMRIS. A physician, blinded for imaging results, performed clinical evaluations of enthesitis at the Achilles tendon and plantar fascia. RESULTS: In total, 146 entheses were scored according to the HEMRIS and clinically assessed for enthesitis (6 entheses were clinically affected). In Achilles tendons with clinical enthesitis, the HEMRIS structural damage score was significantly higher, compared to Achilles tendons without clinical enthesitis (respective median scores 1.0 and 0.5; p=0.04). In clinically unaffected entheses, HEMRIS abnormalities occurred in 44/70 (63%) of Achilles tendons and in 23/70 (33%) of plantar fascia. At the Achilles tendon, local metabolic activity measured on PET/CT was weakly associated with the structural (rs=0.25, p=0.03) and total HEMRIS (rs=0.26, p=0.03). CONCLUSION: This study revealed a high prevalence of subclinical HEMRIS abnormalities and discrepancy between HEMRIS and clinical and PET/CT findings. This may suggest that the HEMRIS is a sensitive method for detection of inflammatory and structural disease of enthesitis at the Achilles tendon and plantar fascia, although the clinical significance of these MRI findings remains to be determined in longitudinal studies.

Whole Transcriptome Analysis Reveals Heterogeneity in B Cell Memory Populations in Patients With Juvenile Idiopathic Arthritis-Associated Uveitis.

Purpose: Patients with juvenile idiopathic arthritis (JIA) are prone to developing chronic anterior uveitis (JIA-U+). Although several risk factors for JIA-U+ have been identified, the underlying etiology is poorly understood. Histopathological studies demonstrate B cell infiltrates in eye tissues of patients with JIA-U+. Methods: We performed transcriptome profiling of peripheral blood CD19-positive B cells taken from 14 cases with JIA-U+, 13 JIA cases without uveitis (JIA-U-), and five healthy controls. Deconvolution-based estimation was used to determine the immune cell fractions for each sample. Results: Deconvolution results revealed that naive B cells made up on average 71% of the CD19-positive cell fractions analyzed. Differential expression analysis identified 614 differentially expressed genes (DEGs) between the groups at nominal significance and six genes at a false discovery rate of 5% (FDR < 0.05). Head-to-head comparison of all JIA-U- versus JIA-U+ revealed no DEGs in the CD19+ B cell pool (FDR < 0.05). However, principal component analysis based on a panel of key genes for B cell subsets revealed that JIA-U+ cases bifurcate into distinct clusters, characterized by markedly disparate expression for genes associated with specific memory B cell populations. CIBERSORT analysis of the overall transcriptome of the new uveitis cluster identified an increased proportion of memory B cells. Conclusion: These data show that JIA-U- and JIA-U+ have a globally similar transcriptome considering the global peripheral CD19-positive B cell pool. However, heterogeneity in B cell memory genes among cases with uveitis suggests a role for specific memory B cell subsets in the etiology of JIA-U+.

Leukocyte Associated Immunoglobulin Like Receptor 1 Regulation and Function on Monocytes and Dendritic Cells During Inflammation.

Inhibitory receptors are crucial immune regulators and are essential to prevent exacerbated responses, thus contributing to immune homeostasis. Leukocyte associated immunoglobulin like receptor 1 (LAIR-1) is an immune inhibitory receptor which has collagen and collagen domain containing proteins as ligands. LAIR-1 is broadly expressed on immune cells and has a large availability of ligands in both circulation and tissues, implicating a need for tight regulation of this interaction. In the current study, we sought to examine the regulation and function of LAIR-1 on monocyte, dendritic cell (DC) and macrophage subtypes, using different in vitro models. We found that LAIR-1 is highly expressed on intermediate monocytes as well as on plasmacytoid DCs. LAIR-1 is also expressed on skin immune cells, mainly on tissue CD14+ cells, macrophages and CD1c+ DCs. In vitro, monocyte and type-2 conventional DC stimulation leads to LAIR-1 upregulation, which may reflect the importance of LAIR-1 as negative regulator under inflammatory conditions. Indeed, we demonstrate that LAIR-1 ligation on monocytes inhibits toll like receptor (TLR)4 and Interferon (IFN)-α- induced signals. Furthermore, LAIR-1 is downregulated on GM-CSF and IFN-γ monocyte-derived macrophages and monocyte-derived DCs. In addition, LAIR-1 triggering during monocyte derived-DC differentiation results in significant phenotypic changes, as well as a different response to TLR4 and IFN-α stimulation. This indicates a role for LAIR-1 in skewing DC function, which impacts the cytokine expression profile of these cells. In conclusion, we demonstrate that LAIR-1 is consistently upregulated on monocytes and DC during the inflammatory phase of the immune response and tends to restore its expression during the resolution phase. Under inflammatory conditions, LAIR-1 has an inhibitory function, pointing toward to a potential intervention opportunity targeting LAIR-1 in inflammatory conditions.

CXCL4 triggers monocytes and macrophages to produce PDGF-BB, culminating in fibroblast activation: Implications for systemic sclerosis.

OBJECTIVE: To analyze how monocyte and macrophage exposure to CXCL4 induces inflammatory and fibrotic processes observed in Systemic sclerosis (SSc) patients. METHODS: In six independent experiments, monocytes of healthy controls (HC) and SSc patients were stimulated with CXCL4, TLR-ligands, IFNɑ or TGFß and the secretion of cytokines in the supernatant was assessed by multiplex immunoassays. PDGF-BB production by monocyte-derived macrophages was quantified using immunoassays. The number of monocytes and PDGF-BB in circulation was quantified in HC and SSc patients with the Sysmex XT-1800i haematology counter and immunoassays. Intracellular PDGF-BB was quantified in monocytes by Western blot. PDGF-receptor inhibition was achieved using siRNA-mediated knockdown or treatment with Crenolanib. The production of inflammatory mediators and extracellular matrix (ECM) components by dermal fibroblasts was analyzed by qPCR, ELISA and ECM deposition assays. RESULTS: SSc and HC monocytes released PDGF-BB upon stimulation with CXCL4. Conversely, TLR ligands, IFNɑ or TGFß did not induce PDGF-bb release. PDGF-BB plasma levels were significantly (P = 0.009) higher in diffuse SSc patients (n = 19), compared with HC (n = 21). In healthy dermal fibroblasts, PDGF-BB enhanced TNFɑ-induced expression of inflammatory cytokines and increased ECM production. Comparable results were observed in fibroblasts cultured in supernatant taken from macrophages stimulated with CXCL4. This effect was almost completely abrogated by inhibition of the PDGF-receptor using Crenolanib. CONCLUSION: Our findings demonstrate that CXCL4 can drive fibroblast activation indirectly via PDGF-BB production by myeloid cells. Hence, targeting PDGF-BB or CXCL4-induced PDGF-BB release could be clinically beneficial for patients with SSc.

A cross-disease meta-GWAS identifies four new susceptibility loci shared between systemic sclerosis and Crohn's disease.

Genome-wide association studies (GWASs) have identified a number of genetic risk loci associated with systemic sclerosis (SSc) and Crohn's disease (CD), some of which confer susceptibility to both diseases. In order to identify new risk loci shared between these two immune-mediated disorders, we performed a cross-disease meta-analysis including GWAS data from 5,734 SSc patients, 4,588 CD patients and 14,568 controls of European origin. We identified 4 new loci shared between SSc and CD, IL12RB2, IRF1/SLC22A5, STAT3 and an intergenic locus at 6p21.31. Pleiotropic variants within these loci showed opposite allelic effects in the two analysed diseases and all of them showed a significant effect on gene expression. In addition, an enrichment in the IL-12 family and type I interferon signaling pathways was observed among the set of SSc-CD common genetic risk loci. In conclusion, through the first cross-disease meta-analysis of SSc and CD, we identified genetic variants with pleiotropic effects on two clinically distinct immune-mediated disorders. The fact that all these pleiotropic SNPs have opposite allelic effects in SSc and CD reveals the complexity of the molecular mechanisms by which polymorphisms affect diseases.

Promotion of macrophage activation by Tie2 in the context of the inflamed synovia of rheumatoid arthritis and psoriatic arthritis patients.

OBJECTIVE: To examine the role of Tie2 signalling in macrophage activation within the context of the inflammatory synovial microenvironment present in patients with RA and PsA. METHODS: Clinical responses and macrophage function were examined in wild-type and Tie2-overexpressing (Tie2-TG) mice in the K/BxN serum transfer model of arthritis. Macrophages derived from peripheral blood monocytes from healthy donors, RA and PsA patients, and RA and PsA synovial tissue explants were stimulated with TNF (10 ng/ml), angiopoietin (Ang)-1 or Ang-2 (200 ng/ml), or incubated with an anti-Ang2 neutralizing antibody. mRNA and protein expression of inflammatory mediators was analysed by quantitative PCR, ELISA and Luminex. RESULTS: Tie2-TG mice displayed more clinically severe arthritis than wild-type mice, accompanied by enhanced joint expression of IL6, IL12B, NOS2, CCL2 and CXCL10, and activation of bone marrow-derived macrophages in response to Ang-2 stimulation. Ang-1 and Ang-2 significantly enhanced TNF-induced expression of pro-inflammatory cytokines and chemokines in macrophages from healthy donors differentiated with RA and PsA SF and peripheral blood-derived macrophages from RA and PsA patients. Both Ang-1 and Ang-2 induced the production of IL-6, IL-12p40, IL-8 and CCL-3 in synovial tissue explants of RA and PsA patients, and Ang-2 neutralization suppressed the production of IL-6 and IL-8 in the synovial tissue of RA patients. CONCLUSION: Tie2 signalling enhances TNF-dependent activation of macrophages within the context of ongoing synovial inflammation in RA and PsA, and neutralization of Tie2 ligands might be a promising therapeutic target in the treatment of these diseases.

Increased intra-articular granzyme M may trigger local IFN-λ1/IL-29 response in rheumatoid arthritis.

OBJECTIVES: Granzymes are serine proteases involved in eliminating tumour cells and virally infected cells. In addition, extracellular granzyme levels are elevated in inflammatory conditions, including several types of infection and autoimmune diseases, such as rheumatoid arthritis (RA). While GrA and GrB have been associated with RA, a role for the other three granzymes (GrH, GrK, and GrM) in this disease remains unclear. Here, we aimed to investigate the presence and role of GrM and GrK in serum and synovial fluid of patients with RA, psoriatic arthritis, and osteoarthritis. METHODS: Granzyme levels were determined in serum, synovial fluid, peripheral blood mononuclear cells (PBMCs) and synovial fluid mononuclear cells (SFMCs) of RA patients and relevant control groups. In addition, the link between GrM and inflammatory cytokines in synovial fluid was investigated. RESULTS: Serum GrM and GrK levels were not affected in RA. GrM, but not GrK, levels were elevated in synovial fluid of RA patients. GrM was mainly expressed by cytotoxic lymphocytes in SFMCs with a similar expression pattern as compared with PBMCs. Intra-articular GrM expression correlated with IL-25, IL-29, XCL1, and TNFα levels. Intriguingly, purified GrM triggered the release of IL-29 (IFN-λ1) from human fibroblasts in vitro. CONCLUSIONS: These data indicate that GrM levels are increased in RA synovial fluid and that GrM can stimulate proinflammatory IL-29 release from fibroblasts, suggesting a role of GrM in the pathogenesis of RA.

Extracellular SPARC cooperates with TGF-ß signalling to induce pro-fibrotic activation of systemic sclerosis patient dermal fibroblasts.

OBJECTIVES: SSc is an autoimmune disease characterized by inflammation, vascular injury and excessive fibrosis in multiple organs. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular glycoprotein that regulates processes involved in SSc pathology, such as inflammation and fibrosis. In vivo and in vitro studies have implicated SPARC in SSc, but it is unclear if the pro-fibrotic effects of SPARC on fibroblasts are a result of intracellular signalling or fibroblast interactions with extracellular SPARC hampering further development of SPARC as a potential therapeutic target. This study aimed to analyse the potential role of exogenous SPARC as a regulator of fibrosis in SSc. METHODS: Dermal fibroblasts from both healthy controls and SSc patients were stimulated with SPARC alone or in combination with TGF-ß1, in the absence or presence of a TGF receptor 1 inhibitor. mRNA and protein expression of extracellular matrix components and other fibrosis-related mediators were measured by quantitative PCR and western blot. RESULTS: Exogenous SPARC induced mRNA and protein expression of collagen I, collagen IV, fibronectin 1, TGF-ß and SPARC by dermal fibroblasts from SSc patients, but not from healthy controls. Importantly, exogenous SPARC induced the activation of the tyrosine kinase SMAD2 and pro-fibrotic gene expression induced by SPARC in SSc fibroblasts was abrogated by inhibition of TGF-ß signalling. CONCLUSION: These results indicate that exogenous SPARC is an important pro-fibrotic mediator contributing to the pathology driving SSc but in a TGF-ß dependent manner. Therefore, SPARC could be a promising therapeutic target for reducing fibrosis in SSc patients, even in late states of the disease.