IL-17 and related cytokines involved in systemic sclerosis: Perspectives

The role of B cells in systemic sclerosis

Systemic sclerosis (SSc) is a rare and refractory systemic disease characterized by fibrosis and vasculopathy in the presence of autoimmune abnormalities. While the exact cause of SSc is incompletely understood, the specific autoantibodies identified in SSc are closely linked to disease severity and prognosis, indicating a significant role of autoimmune abnormalities in the pathogenesis of SSc. Although the direct pathogenic mechanisms of autoantibodies in SSc are not fully elucidated, numerous prior investigations have demonstrated the involvement of B cells in the pathogenesis of SSc through various mechanisms. Additionally, several clinical trials have explored the efficacy of B-cell depletion therapy for SSc, with many reporting positive outcomes. However, the role of B cells in SSc pathogenesis is multifaceted, as they can both promote inflammation and exert inhibitory functions. This article provides an overview of the involvement of B cells in SSc development, incorporating the latest research findings.

PPARγ partial agonist LPSF/GQ-16 prevents dermal and pulmonary fibrosis in HOCl-induced systemic sclerosis (SSc) and modulates cytokine production in PBMC of SSc patients

Thiazolidinediones (TZD) are synthetic molecules that have a range of biological effects, including antifibrotic and anti-inflammatory, and they may represent a promising therapeutic strategy for systemic sclerosis (SSc). The aim of this study was to investigate the immunomodulatory and antifibrotic properties of LPSF/GQ-16, a TZD derivative, in peripheral blood mononuclear cells (PBMC) from SSc patients and in a murine model of SSc HOCl-induced. The PBMC of 20 SSc patients were stimulated with phytohemagglutinin (PHA) and treated with LPSF/GQ-16 for 48 h, later cytokines in the culture supernatants were quantified by sandwich enzyme-linked immunosorbent assay (ELISA) or cytometric bead array (CBA). Experimental SSc was induced by intradermal injections of hypochlorous acid (HOCl) for 6 weeks. HOCl-induced SSc mice received daily treatment with LPSF/GQ-16 (30 mg/kg) through intraperitoneal injections during the same period. Immunological parameters were evaluated by flow cytometry and ELISA, and dermal and pulmonary fibrosis were evaluated by RT-qPCR, hydroxyproline dosage and histopathological analysis. In PBMC cultures, it was possible to observe that LPSF/GQ-16 modulated the secretion of cytokines IL-2 (p < 0.001), IL-4 (p < 0.001), IL-6 (p < 0.001), IL-17A (p = 0.006), TNF (p < 0.001) and IFN-γ (p < 0.001). In addition, treatment with LPSF/GQ-16 in HOCl-induced SSc mice promoted a significant reduction in dermal thickening (p < 0.001), in the accumulation of collagen in the skin (p < 0.001), down-regulated the expression of fibrosis markers in the skin (Col1a1, α-Sma and Tgfβ1, p < 0.001 for all) and lungs (Il4 and Il13, p < 0.001 for both), as well as reduced activation of CD4 + T cells (p < 0.001), B cells (p < 0.001) and M2 macrophages (p < 0.001). In conclusion, LPSF/GQ-16 showed immunomodulatory and antifibrotic properties, demonstrating the therapeutic potential of this molecule for SSc.

Zinc finger protein 189 promotes the differentiation of lamina propria T helper 17.1 cells in dextran sulfate sodium-induced colitis

The factors regulating the heterogeneity of interleukin-17A (IL-17A)-expressing CD4⁺ T cells in inflammatory bowel diseases remain unclear. In the current study, we characterised the expression and function of zinc finger protein 189 (ZFP189) in a murine colitis model. Mice were given dextran sulphate sodium to induce acute colitis. Flow cytometry was applied to recognise and enrich Th17 and Th17.1 cells based on the expression of IL-17A, interferon-γ (IFN-γ), C-X-C motif chemokine receptor 3 (CXCR3), and C-C motif chemokine receptor 4 (CCR4). The expression of ZFP189 in Th17 and Th17.1 cells was determined by Immunoblotting. Lentivirus-mediated ZFP189 knockdown was conducted to evaluate the effect of ZFP189 on the differentiation of Th17 and Th17.1 cells. The adoptive transfer was performed to analyse the pathogenicity of Th17.1 cells in vivo. We found that ZFP189 was mildly up-regulated in IL-17A-expressing CD4⁺ T cells in colonic lamina propria. Lamina propria Th17.1 cells expressed higher ZFP189 than Th17 cells. In vitro ZFP189 knockdown in CD4⁺ T cells did not impact Th17 cell differentiation but suppressed Th17.1 cell differentiation, as evidenced by lower T-box expressed in T cells (T-bet) and IFN-γ. When adoptively transferred into mice, ZFP189-deficient Th17.1 cells produced fewer IFN-γ, tumour necrosis factor-alpha (TNF-α), and granulocyte-macrophage colony-stimulating factor (GM-CSF) than ZFP189-expressing Th17.1 cells. Moreover, ZFP189-deficient Th17.1 cells induced less severe colitis than ZFP189-expressing Th17.1 cells, as evidenced by less body weight loss, a lower disease activity index, and a lower colon histological score. In summary, ZFP189 acts as a positive regulator of the differentiation and pathogenicity of lamina propria Th17.1 cells in colitis.

Type 2 cytokines and scleroderma interstitial lung disease

Interstitial lung disease (ILD) is a life-threatening complication of systemic sclerosis (SSc). Type 2 (Th2) cytokines play a pivotal role in airway disease. Study aim was to evaluate serum level of Th2 interleukin (IL) and chemokine in SSc-ILD. Serum levels of IL-4, IL-5, IL-11, IL-13, IL-21, IL-31 and CXCL-13 were measured by Bio-Plex Multiplex Immunoassays in 60 SSc patients and 20 healthy controls (HC). Pulmonary function tests with diffusion lung capacity for carbon monoxide (DLco) and high resolution computed tomography (HRCT) were performed in SSc patients. ILD is defined as fibrotic changes (ground glass, reticular and honeycombing), assessed by Computer-Aided Lung Informatics for Pathology Evaluation and Ratings (CALIPER) software, affecting at least 10% of the lungs. Serum levels of Th2 cytokines were higher in SSc patients than HC. A linear correlation was observed between ground glass and IL-13 (r = 0.342, p < 0.01), IL-21 (r = 0.345, p < 0.01), IL-31 (r = 0.473, p < 0.001), IL-4 (r = 0.863, p < 0.001), IL-5 (r = 0.249, p < 0.05) and peripheral blood eosinophils (r = 0.463, p < 0.001). We found a negative correlation between DLco and IL-4 (r =  - 0.511, p < 0.001) and peripheral blood eosinophils (r =  - 0.446, p < 0.001). In the logistic regression analysis, IL-4 is associated with DLco ≤ 60% of the predicted [OR 1.039 (CI 95%: 1.015-1.064), p < 0.001], whilst mRSS [OR 1.138 (CI 95%: 1.023-1.266), p < 0.05] and IL-4 [OR 1.017 (CI 95%: 1-1.034), p < 0.05] were associated with ILD. Th2 inflammation could play a key role in early phase of SSc-ILD.

In Systemic Sclerosis Patients, Peripheral Blood CD21low B Cells and Serum IL-4 and IL-21 Influence Joint Involvement

Systemic sclerosis (SSc) patients have an increased frequency of CD21low B cells and of serum interleukin-4 (IL-4) and IL-21, each possible markers of joint involvement in inflammatory arthritis. The aim of this study was to investigate the possible influence of CD21low B cells, IL-4, and IL-21 on joint involvement in a cohort of 52 SSc patients. The DAS28-ESR was correlated with CD21low B cells (r = 0.452, p < 0.001), IL-4 (r = 0.478, p < 0.001), and IL-21 (r = 0.415, p < 0.001). SSc patients with a DAS28-ESR > 3.2 had more CD21low B cells (12.65% (IQR: 7.11-13.79) vs. 5.08% (IQR: 3.76-7.45), p < 0.01), higher IL-4 levels (132.98 pg/mL (IQR: 99.12-164.12) vs. 100.80 pg/mL (IQR: 62.78-121.13), p < 0.05), and higher IL-21 levels (200.77 pg/mL (IQR: 130.13-302.41) vs. 98.83 pg/mL (IQR: 35.70-231.55), p < 0.01) than patients with a DAS28-ESR ≤ 3.2. The logistic regression analysis models showed that the DAI (OR: 2.158 (95% CI: 1.120; 4.156), p < 0.05) and CD21low B cells (OR: 1.301 (95% CI: 1.099; 1.540), p < 0.01), the DAI (OR: 2.060 (95% CI: 1.082; 3.919), p < 0.05) and IL-4 level (OR: 1.026 (95% CI: 1.006; 1.045), p < 0.01), and the DAI (OR: 1.743 (95% CI: 1.022; 2.975), p < 0.05) and IL-21 level (OR: 1.006 (95% CI: 1.000; 1.011), p < 0.05) were independently associated with a DAS28-ESR > 3.2. An elevated CD21low B cell percentage, IL-4 level, and IL-21 level was associated with higher articular disease activity in patients, suggesting a possible role in the pathogenesis of SSc joint involvement.

A comparative study of modulatory interaction between cytokines and apoptotic proteins among Scleroderma patients with and without pulmonary involvement

BACKGROUND

Interstitial lung disease (ILD) and pulmonary arterial hypertension (PAH) are the most eminent forms of pulmonary involvement in Scleroderma. In this study we investigate the interaction between cytokines and apoptotic proteins in treatment naive Scleroderma (SSc) patients with and without pulmonary involvement.

METHODS

Newly diagnosed treatment naïve Scleroderma (SSc) patients (n = 100) and healthy controls (n = 100) were enrolled. Patients were classified as ILD-SSc, PAH-SSc and non-pulmonary SSc (np-SSc). Study variables like mRSS score, autoantibody profile, serum cytokines, serum TGF-β (1,2,3) and apoptotic proteins were assessed for these patients.

RESULTS

Scleroderma patients showed elevated levels of serum cytokines, but significantly lower IL-22 and TGF- β1 when compared to healthy controls (p < 0.05). Apoptotic proteins were significantly elevated among Scleroderma patients, but the patient groups also showed significant lower caspase 1/3/9 levels when compared to healthy controls (p < 0.05). ILD-SSc patients reported higher mRSS score (p = 0.0436) when compared with PAH-SSc and np-SSc. In ILD-SSc patients, finger tightening (p = 0.0481) and calcinosis/lesions (p = 0.0481) were significant clinical presentations whereas, digital ulcers were significantly prominent in np-SSc patients (p = 0.0132). Elevated TGF-β3 levels (p = 0.02) in SSC-ILD and reduced IL-4 levels (p = 0.02) in SSC-PAH were significant cytokines as compared to np-SSc. Significant correlations were obtained among serum cytokines and apoptotic proteins in Scleroderma patients with and without pulmonary involvement. (p < 0.05) CONCLUSION: Our study highlights the correlation between mRSS score, cytokines and apoptotic proteins in SSc patients with pulmonary involvement. A longitudinal follow up in these patients with assessment of these immunological parameters may be helpful in monitoring the disease.

Human dermal fibroblast-derived exosomes induce macrophage activation in systemic sclerosis

OBJECTIVES

Prior work demonstrates that co-cultured macrophages and fibroblasts from patients with SSc engage in reciprocal activation. However, the mechanism by which these cell types communicate and contribute to fibrosis and inflammation in SSc is unknown.

METHODS

Fibroblasts were isolated from skin biopsies obtained from 7 SSc patients or 6 healthy age and gender-matched control subjects following written informed consent. Human donor-derived macrophages were cultured with exosomes isolated from control or SSc fibroblasts for an additional 48 h. Macrophages were immunophenotyped using flow cytometry, qRT-PCR and multiplex. For mutual activation studies, exosome-activated macrophages were co-cultured with SSc or healthy fibroblasts using Transwells.

RESULTS

Macrophages activated with dermal fibroblast-derived exosomes from SSc patients upregulated surface expression of CD163, CD206, MHC Class II and CD16 and secreted increased levels of IL-6, IL-10, IL-12p40 and TNF compared with macrophages incubated with healthy control fibroblasts (n = 7, P < 0.05). Exosome-stimulated macrophages and SSc fibroblasts engaged in reciprocal activation, as production of collagen and fibronectin was significantly increased in SSc fibroblasts receiving signals from SSc exosome-stimulated macrophages (n = 7, P < 0.05).

CONCLUSION

In this work, we demonstrate for the first time that human SSc dermal fibroblasts mediate macrophage activation through exosomes. Our findings suggest that macrophages and fibroblasts engage in cross-talk in SSc skin, resulting in mutual activation, inflammation, and extracellular matrix (ECM) deposition. Collectively, these studies implicate macrophages and fibroblasts as cooperative mediators of fibrosis in SSc and suggest therapeutic targeting of both cell types may provide maximal benefit in ameliorating disease in SSc patients.

Serum levels of interleukin 17 and 22 in patients with systemic sclerosis: a single-center cross-sectional study

Systemic sclerosis (SSc) is a chronic, autoimmune disease characterized by inflammation, vasculopathy, and fibrosis of the skin and internal organs. Immunological response in SSc is still poorly understood. Cytokines play a significant role in this process leading to vasculopathy and fibrosis. In this cross-sectional study, we aimed to investigate serum levels of Th-17-related cytokines, IL-17 and IL-22, and to determine their correlation to the clinical association in SSc patients. Serum IL-17 and IL-22 levels were examined in 42 SSc patients and 29 healthy individuals. Associations between serum IL-17 and IL-22 levels and the duration of the disease, the extent of skin fibrosis, capillaroscopic findings, and involvement of the internal organs were explored. Serum IL-17 levels were not different in SSc and the control group. Serum IL-22 levels were significantly elevated in SSc patients compared to healthy individuals (p = 0.04). A positive correlation was found between the IL-22 sera levels and interstitial lung disease (p = 0.007). These results suggest IL-22 as a potential biomarker in SSc-related interstitial lung disease.

CXCL4-RNA Complexes Circulate in Systemic Sclerosis and Amplify Inflammatory/Pro-Fibrotic Responses by Myeloid Dendritic Cells

CXCL4 is an important biomarker of systemic sclerosis (SSc), an incurable autoimmune disease characterized by vasculopathy and skin/internal organs fibrosis. CXCL4 contributes to the type I interferon (IFN-I) signature, typical of at least half of SSc patients, and its presence is linked to an unfavorable prognosis. The mechanism implicated is CXCL4 binding to self-DNA, with the formation of complexes amplifying TLR9 stimulation in plasmacytoid dendritic cells (pDCs). Here, we demonstrate that, upon binding to self-RNA, CXCL4 protects the RNA from enzymatic degradation. As a consequence, CXCL4-RNA complexes persist in vivo. Indeed, we show for the first time that CXCL4-RNA complexes circulate in SSc plasma and correlate with both IFN-I and TNF-α. By using monocyte-derived DCs (MDDCs) pretreated with IFN-α as a model system (to mimic the SSc milieu of the IFN-I signature), we demonstrate that CXCL4-RNA complexes induce MDDC maturation and increase, in particular, pro-inflammatory TNF-α as well as IL-12, IL-23, IL-8, and pro-collagen, mainly in a TLR7/8-dependent but CXCR3-independent manner. In contrast, MDDCs produced IL-6 and fibronectin independently in their CXCL4 RNA-binding ability. These findings support a role for CXCL4-RNA complexes, besides CXCL4-DNA complexes, in immune amplification via the modulation of myeloid DC effector functions in SSc and also during normal immune responses.

Interleukin-17 Family Cytokines in Metabolic Disorders and Cancer

Interleukin-17 (IL-17) family cytokines are potent drivers of inflammatory responses. Although IL-17 was originally identified as a cytokine that induces protective effects against bacterial and fungal infections, IL-17 can also promote chronic inflammation in a number of autoimmune diseases. Research in the last decade has also elucidated critical roles of IL-17 during cancer development and treatment. Intriguingly, IL-17 seems to play a role in the risk of cancers that are associated with metabolic disorders. In this review, we summarize our current knowledge on the biochemical basis of IL-17 signaling, IL-17′s involvement in cancers and metabolic disorders, and postulate how IL-17 family cytokines may serve as a bridge between these two types of diseases.

Involvement of B cells in the development of systemic sclerosis

Systemic sclerosis (SSc) is a rare intractable systemic disease that causes fibrosis and vasculopathy against a background of autoimmune abnormalities. Although the etiology is not yet fully understood, the type of autoantibodies detected in SSc is closely associated with disease severity and prognosis, supporting that those autoimmune abnormalities play an important role in the pathogenesis of SSc. Although the direct pathogenicity of autoantibodies found in SSc is unknown, many previous studies have shown that B cells are involved in the development of SSc through a variety of functions. Furthermore, a number of clinical studies have been conducted in which B-cell depletion therapy has been tried for SSc, and many of these studies have found B-cell depletion therapy to be effective for SSc. However, the involvement of B cells in pathogenesis is complex, as they not only promote inflammation but also play an inhibitory role. This article outlines the role of B cells in the development of SSc, including the latest research.

A Mechanistic Insight into the Pathogenic Role of Interleukin 17A in Systemic Autoimmune Diseases

Interleukin 17A (IL-17A) has been put forward as a strong ally in our fight against invading pathogens across exposed epithelial surfaces by serving an antimicrobial immunosurveillance role in these tissues to protect the barrier integrity. Amongst other mechanisms that prevent tissue injury mediated by potential microbial threats and promote restoration of epithelial homeostasis, IL-17A attracts effector cells to the site of inflammation and support the host response by driving the development of ectopic lymphoid structures. Accumulating evidence now underscores an integral role of IL-17A in driving the pathophysiology and clinical manifestations in three potentially life-threatening autoimmune diseases, namely, systemic lupus erythematosus, Sjögren’s syndrome, and systemic sclerosis. Available studies provide convincing evidence that the abundance of IL-17A in target tissues and its prime source, which is T helper 17 cells (Th17) and double negative T cells (DNT), is not an innocent bystander but in fact seems to be prerequisite for organ pathology. In this regard, IL-17A has been directly implicated in critical steps of autoimmunity. This review reports on the synergistic interactions of IL-17A with other critical determinants such as B cells, neutrophils, stromal cells, and the vasculature that promote the characteristic immunopathology of these autoimmune diseases. The summary of observations provided by this review may have empowering implications for IL-17A-based strategies to prevent clinical manifestations in a broad spectrum of autoimmune conditions.

Sphingosine 1-phosphate receptor-targeted therapeutics in rheumatic diseases

Sphingosine 1-phosphate (S1P), which acts via G protein-coupled S1P receptors (S1PRs), is a bioactive lipid essential for vascular integrity and lymphocyte trafficking. The S1P-S1PR signalling axis is a key component of the inflammatory response in autoimmune rheumatic diseases. Several drugs that target S1PRs have been approved for the treatment of multiple sclerosis and inflammatory bowel disease and are under clinical testing for patients with systemic lupus erythematosus (SLE). Preclinical studies support the hypothesis that targeting the S1P-S1PR axis would be beneficial to patients with SLE, rheumatoid arthritis (RA) and systemic sclerosis (SSc) by reducing pathological inflammation. Whereas most preclinical research and development efforts are focused on reducing lymphocyte trafficking, protective effects of circulating S1P on endothelial S1PRs, which maintain the vascular barrier and enable blood circulation while dampening leukocyte extravasation, have been largely overlooked. In this Review, we take a holistic view of S1P-S1PR signalling in lymphocyte and vascular pathobiology. We focus on the potential of S1PR modulators for the treatment of SLE, RA and SSc and summarize the rationale, pathobiology and evidence from preclinical models and clinical studies. Improved understanding of S1P pathobiology in autoimmune rheumatic diseases and S1PR therapeutic modulation is anticipated to lead to efficacious and safer management of these diseases.

Autologous hematopoietic stem cell transplantation modifies specific aspects of systemic sclerosis-related microvasculopathy

Objective:

Autologous hematopoietic stem cell transplantation (AHSCT) is a therapeutic option for patients with severe and progressive systemic sclerosis (SSc). Here, we aimed to investigate how AHSCT affects the vasculopathy of SSc patients.

Methods:

Twenty-seven SSc patients were retrospectively assessed, before and after AHSCT, for vessel morphology (nailfold capillaroscopy), skin expression of endothelial markers and serum levels of markers of inflammation, angiogenesis and endothelial activation. Skin biopsies were analyzed by immunohistochemistry (IHC) for expression of CD31, VE-cadherin, E-selectin, angiopoietin-1 (Ang1), angiopoietin-2 (Ang2), Tie-2, vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor receptor 2 (VEGFR2), and endothelin-1 before and 12 months post-AHSCT. Serum samples from SSc patients were assessed before and up to 36 months after AHSCT for IL-6, von Willebrand factor (vWF), CXC Motif Chemokine Ligand 8 (CXCL8), Endothelin-1, epidermal growth factor (EGF), VEGFA, Pentraxin-3, Intercellular Adhesion Molecule 1 (ICAM-1), E-selectin, P-selectin, Thrombomodulin and IL-18 levels, and compared to healthy control samples.

Results:

On nailfold capillaroscopy, the number of capillaries increased at 1 year, while giant capillaries decreased at 6 months and 1 year after AHSCT. In the skin biopsies, expression of E-selectin notably decreased and Ang1 increased after AHSCT. At baseline, all vascular markers evaluated in the serum were significantly higher in SSc patients when compared to healthy controls, except for ICAM-1. When compared at different time points after AHSCT, Thrombomodulin, Pentraxin-3, vWF, and IL-18 levels remained generally stable at high levels until 36 months after AHSCT.

Conclusion:

Our results suggest that AHSCT contributes to improvements of the vessel morphology and dermal microvasculopathy, but does not normalize elevated levels of serum vascular markers in SSc patients. Additional vascular therapeutic approaches might contribute to more effectively treat the endothelial injury.

Therapeutic Options for Systemic Sclerosis: Current and Future Perspectives in Tackling Immune-Mediated Fibrosis

Systemic sclerosis (SSc) is a severe auto-immune, rheumatic disease, characterized by excessive fibrosis of the skin and visceral organs. SSc is accompanied by high morbidity and mortality rates, and unfortunately, few disease-modifying therapies are currently available. Inflammation, vasculopathy, and fibrosis are the key hallmarks of SSc pathology. In this narrative review, we examine the relationship between inflammation and fibrosis and provide an overview of the efficacy of current and novel treatment options in diminishing SSc-related fibrosis based on selected clinical trials. To do this, we first discuss inflammatory pathways of both the innate and acquired immune systems that are associated with SSc pathophysiology. Secondly, we review evidence supporting the use of first-line therapies in SSc patients. In addition, T cell-, B cell-, and cytokine-specific treatments that have been utilized in SSc are explored. Finally, the potential effectiveness of tyrosine kinase inhibitors and other novel therapeutic approaches in reducing fibrosis is highlighted.

The Yin and Yang of IL-17 in Systemic Sclerosis

IL-17 (IL-17A) is a pro-inflammatory cytokine produced by a sub-set of T helper cells termed Th17 cells primarily in response to cytokines like TGF-β and IL-23 and play an important role in host defense. IL-17 signals via the IL-17RA/RC heterodimer and the adaptor protein Act1 to activate both canonical and non-canonical pathways inducing transcriptional activation and stabilization of mRNAs. IL-17 appears to act not directly on immune cells but stimulates stromal cells such as endothelial and epithelial cells and fibroblasts to secrete other immunomodulatory factors. Fibroblast activated by IL-17 can support the growth and differentiation of immune cells. Studies have begun to uncover a dual role for IL-17; on one hand enhancing immune reactions and promoting inflammatory diseases and on the other decreasing responses and immune activity in established disease settings. The balance of double-edged sword effect of IL-17 and autoimmunity is illustrated in a variety of human diseases and experimental models of diseases. Specifically, the emerging interest in autoimmunity in systemic sclerosis (Scleroderma, SSc) has led to potential role of IL-17A as a target therapy in this disease.

Cellular and Molecular Diversity in Scleroderma

With the increasing armamentarium of high-throughput tools available at manageable cost, it is attractive and informative to determine the molecular underpinnings of patient heterogeneity in systemic sclerosis (SSc). Given the highly variable clinical outcomes of patients labelled with the same diagnosis, unravelling the cellular and molecular basis of disease heterogeneity will be crucial to predicting disease risk, stratifying management and ultimately informing a patient-centered precision medicine approach. Herein, we summarise the findings of the past several years in the fields of genomics, transcriptomics, and proteomics that contribute to unraveling the cellular and molecular heterogeneity of SSc. Expansion of these findings and their routine integration with quantitative analysis of histopathology and imaging studies into clinical care promise to inform a scientifically driven patient-centred personalized medicine approach to SSc in the near future.

The role of interleukin-17 in the pathogenesis of systemic sclerosis: Pro-fibrotic or anti-fibrotic?

Systemic sclerosis is characterized by widespread fibrosis of the skin and internal organs, vascular impairment, and dysregulation of innate and adaptive immune system. Growing evidence indicates that T-cell proliferation and cytokine secretion play a major role in the initiation of systemic sclerosis, but the role of T helper 17 cells and of interleukin-17 cytokines in the development and progression of the disease remains controversial. In particular, an equally distributed body of literature supports both pro-fibrotic and anti-fibrotic effects of interleukin-17, suggesting a complex and nuanced role of this cytokine in systemic sclerosis pathogenesis that may vary depending on disease stage, target cells in affected organs, and inflammatory milieu. Although interleukin-17 already represents an established therapeutic target for several immune-mediated inflammatory diseases, more robust experimental evidence is required to clarify whether it may become an attractive therapeutic target for systemic sclerosis as well.

The Anti-Inflammatory Effect of Aptamin C on House Dust Mite Extract-Induced Inflammation in Keratinocytes via Regulation of IL-22 and GDNF Production

Atopic dermatitis (AD), a chronic inflammatory skin disease, is characterized by eczemous lesions on the skin that manifest as severe itching and last a long time. AD is thought to be a response to local allergens, including house dust mites (HDMs). Aptamin C is a modified form of vitamin C comprised of aptamers (DNA fragments) that bind specifically to vitamin C and inhibit its oxidation, thereby increasing its stability and antioxidant effects. It is already known that vitamin C shows an anti-inflammatory effect on skin inflammation. Oxidative stress is one of the major causes of inflammatory diseases, including HDM-induced skin inflammation, suggesting that the antioxidant activity of Aptamin C could regulate inflammatory responses to HDMs in the skin keratinocyte cell line HaCaT and primary skin keratinocytes. Aptamin C not only inhibited HDM-induced proliferation of both type of cells, but suppressed HDM-induced increases in interleukin (IL)-1α and IL-6 production by these cells. In addition, Aptamin C suppressed the production of IL-17 and IL-22 by T cells, which are closely associated with AD pathogenesis, as well as HDM-induced IL-22Rα expression. Aptamin C also reduced the production of thymus and activation-regulated chemokine (TARC) by suppressing the interaction between IL-22 and IL-22Rα, as well as reducing T cell migration. Although HDM treatment markedly increased the expression of glial cell line-derived neurotrophic factor (GDNF), which is associated with itching in AD skin lesions, this increase was reduced by Aptamin C treatment. Taken together, these results suggest that Aptamin C can effectively regulate inflammatory lesions, such as AD, by regulating the production of inflammatory cytokines and GDNF induced by HDM.

Semaphorin4A-Plexin D1 Axis Induces Th2 and Th17 While Represses Th1 Skewing in an Autocrine Manner

Semaphorin (Sema)4A is a transmembrane glycoprotein that is elevated in several autoimmune diseases such as systemic sclerosis, rheumatoid arthritis and multiple sclerosis. Sema4A has a key role in the regulation of Thelper Th1 and Th2 differentiation and we recently demonstrated that CD4⁺ T cell activation induces the expression of Sema4A. However, the autocrine role of Sema4A on Th cell differentiation remains unknown. Naïve Th cells from healthy controls were cell sorted and differentiated into Th1, Th2 and Th17 in the presence or absence of a neutralizing antibody against the Sema4A receptor PlexinD1. Gene expression was determined by quantitative PCR and protein expression by ELISA and flow cytometry. We found that the expression of Sema4A is induced during Th1, Th2 and Th17 differentiation. PlexinD1 neutralization induced the differentiation of Th1 cells, while reduced the Th2 and Th17 skewing. These effects were associated with an upregulation of the transcription factor T-bet by Th1 cells, and to downregulation of GATA3 and RORγt in Th2 cells and Th17 cells, respectively. Finally, PlexinD1 neutralization regulates the systemic sclerosis patients serum-induced cytokine production by CD4⁺ T cells. Therefore, the autocrine Sema4A-PlexinD1 signaling acts as a negative regulator of Th1 skewing but is a key mediator on Th2 and Th17 differentiation, suggesting that dysregulation of this axis might be implicated in the pathogenesis of CD4⁺ T cell-mediated diseases.

Psoriasis and Connective Tissue Diseases

Psoriasis is a chronic systemic inflammatory disease with various co-morbidities, having been recently considered as a comprehensive disease named psoriatic disease or psoriatic syndrome. Autoimmune diseases are one form of its co-morbidities. In addition to the genetic background, shared pathogenesis including innate immunity, neutrophil extracellular trap (NETs), and type I interferon, as well as acquitted immunity such as T helper-17 (Th17) related cytokines are speculated to play a significant role in both psoriasis and connective tissue diseases. On the other hand, there are definite differences between psoriasis and connective tissue diseases, such as their pathomechanisms and response to drugs. Therefore, we cannot expect that one stone kills two birds, and thus caution is necessary when considering whether the administered drug for one disease is effective or not for another disease. In this review, several connective tissue diseases and related diseases are discussed from the viewpoint of their coexistence with psoriasis.

Diagnostic profiles for precision medicine in systemic sclerosis; stepping forward from single biomarkers towards pathophysiological panels

Systemic sclerosis (SSc) is an autoimmune disease which is characterized by vasculopathy, tissue fibrosis and activation of the innate and adaptive immune system. Clinical features of the disease consists of skin thickening and internal organ involvement. Due to the heterogeneous nature of the disease it is difficult to predict disease progression and complications. Despite the discovery of novel autoantibodies associated with SSc, there is an unmet need for biomarkers for diagnosis, disease progression and response to treatment. To date, the use of single (surrogate) biomarkers for these purposes has been unsuccessful. Combining multiple biomarkers in to predictive panels or ultimately algorithms could be more precise. Given the limited therapeutic options and poor prognosis of many SSc patients, a better understanding of the immune-pathofysiological profiles might aid to an adjusted therapeutic approach. Therefore, we set out to explore immunological fingerprints in various clinically defined forms of SSc. We used multilayer profiling to identify unique immune profiles underlying distinct autoantibody signatures. These immune profiles could fill the unmet need for prognosis and response to therapy in SSc. Here, we present 3 pathophysiological fingerprints in SSc based on the expression of circulating antibodies, vascular markers and immunomodulatory mediators.

Invariant natural killer T cells are functionally impaired in patients with systemic sclerosis

Background

Systemic sclerosis (SSc) is a potentially fatal autoimmune disease that leads to extensive fibrosis of the skin and internal organs. Invariant natural killer T (iNKT) cells are potent immunoregulatory T lymphocytes being able to orchestrate dysregulated immune responses. The purpose of this study was to evaluate numbers and function of iNKT cells in patients with SSc and to analyze their correlation with disease parameters.

Methods

Human iNKT cells from 88 patients with SSc and 33 healthy controls were analyzed by flow cytometry. Their proliferative capacity and cytokine production were investigated following activation with CD1d ligand α-galactosylceramide (α-GalCer).

Results

We observed an absolute and relative decrease of iNKT cells in patients with SSc compared with healthy controls. Interestingly, the subtype of SSc, disease severity, or treatment with immunosuppressive drugs did not affect iNKT cell numbers. However, T helper (Th) cell immune polarization was biased towards a Th17 immunophenotype in SSc patients. Moreover, iNKT cells from patients with SSc showed a significantly decreased expansion capacity upon stimulation with α-GalCer.

Conclusion

iNKT cells are deficient and functionally impaired in patients with SSc. Therefore, adoptive transfer strategies using culture-expanded iNKT cells could be a novel approach to treat SSc patients.

Induction of Inflammation and Fibrosis by Semaphorin 4A in Systemic Sclerosis

OBJECTIVE

To analyze the potential role of semaphorin 4A (Sema4A) in inflammatory and fibrotic processes involved in the pathology of systemic sclerosis (SSc).

METHODS

Sema4A levels in the plasma of healthy controls (n = 11) and SSc patients (n = 20) were determined by enzyme-linked immunosorbent assay (ELISA). The expression of Sema4A and its receptors in monocytes and CD4+ T cells from healthy controls and SSc patients (n = 6-7 per group) was determined by ELISA and flow cytometry. Th17 cytokine production by CD4+ T cells (n = 5-7) was analyzed by ELISA and flow cytometry. The production of inflammatory mediators and extracellular matrix (ECM) components by dermal fibroblast cells (n = 6) was analyzed by quantitative polymerase chain reaction, ELISA, Western blotting, confocal microscopy, and ECM deposition assay.

RESULTS

Plasma levels of Sema4A, and Sema4A expression by circulating monocytes and CD4+ T cells, were significantly higher in SSc patients than in healthy controls (P < 0.05). Inflammatory mediators significantly up-regulated the secretion of Sema4A by monocytes and CD4+ T cells from SSc patients (P < 0.05 versus unstimulated SSc cells). Functional assays showed that Sema4A significantly enhanced the expression of Th17 cytokines induced by CD3/CD28 in total CD4+ T cells as well in different CD4+ T cell subsets (P < 0.05 versus unstimulated SSc cells). Finally, Sema4A induced a profibrotic phenotype in dermal fibroblasts from both healthy controls and SSc patients, which was abrogated by blocking or silencing the expression of Sema4A receptors.

CONCLUSION

Our findings indicate that Sema4A plays direct and dual roles in promoting inflammation and fibrosis, 2 main features of SSc, suggesting that Sema4A might be a novel therapeutic target in SSc.

IL-7 is a Key Driver Cytokine in Spondyloarthritis?

The rationale for a type 17 signature in the pathogenesis of spondyloarthritis (SpA) has been increasing and being ratified in studies recently. IL-7 is a cytokine whose ability to stimulate IL-17 production in both innate and adaptive immunity cells has made it a promising target not only for a better understanding of the disease as well as an important potential therapeutic target in patients with SpA.

Dexamethasone inhibits cytokine production in PBMC from systemic sclerosis patients

Glucocorticoids (GC) are widely used in the treatment of SSc, although there is not much evidence to prove the benefits offered by these drugs in this disease. In this study, we evaluated the effects of a GC on cytokine production in peripheral blood mononuclear cells (PBMC) of SSc patients. The effect of dexamethasone (DEX) was evaluated in PBMC of 21 SSc patients and 10 healthy volunteers after stimulation of cells with anti-CD3 and anti-CD28. Cytokines IL-2, IL-4, IL-6, IL-10, IL-17A, IL-17F, IFN-γ, TNF, and IL-1β were quantified in the culture supernatant by CBA or ELISA. Of the patients evaluated in this study, 8 (38%) were taking corticosteroids, and esophageal dysfunction was more frequent in these patients when compared to those who did not take corticosteroids. DEX (1.000 nM) treatment in PBMC of SSc patients stimulated with anti-CD3 and anti-CD28 promoted a significant reduction in IL-2, IL-4, IL-6, IL-10, IL-17A, IFN-γ, TNF, IL-1β (p < 0.001 for all), and IL-17F (p = 0.023) cytokines levels. We did not observe differences in response to in vitro treatment with DEX between groups of patients taking or not taking corticosteroids. In PBMC from healthy volunteers, we observed that DEX treatment significantly reduced IL-4, IFN-γ (p = 0.003 for both), IL-6, IL-10, IL-17A, and TNF (p = 0.002 for all) cytokines. These results show that DEX treatment in PBMC of SSc patients reduced the production of important cytokines involved in the pathogenesis of the disease, suggesting a possible mechanism of action of the CG in the treatment of SSc.