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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., (© 2019 The Authors. Arthritis & Rheumatology published by Wiley Periodicals, Inc. on behalf of American College of Rheumatology.)

Objective: Plasmacytoid dendritic cells (PDCs) are a critical source of type I interferons (IFNs) that can contribute to the onset and maintenance of autoimmunity. Molecular mechanisms leading to PDC dysregulation and a persistent type I IFN signature are largely unexplored, especially in patients with systemic sclerosis (SSc), a disease in which PDCs infiltrate fibrotic skin lesions and produce higher levels of IFNα than those in healthy controls. This study was undertaken to investigate potential microRNA (miRNA)-mediated epigenetic mechanisms underlying PDC dysregulation and type I IFN production in SSc., Methods: We performed miRNA expression profiling and validation in highly purified PDCs obtained from the peripheral blood of 3 independent cohorts of healthy controls and SSc patients. Possible functions of miRNA-618 (miR-618) on PDC biology were identified by overexpression in healthy PDCs., Results: Expression of miR-618 was up-regulated in PDCs from SSc patients, including those with early disease who did not present with skin fibrosis. IFN regulatory factor 8, a crucial transcription factor for PDC development and activation, was identified as a target of miR-618. Overexpression of miR-618 reduced the development of PDCs from CD34+ cells in vitro and enhanced their ability to secrete IFNα, mimicking the PDC phenotype observed in SSc patients., Conclusion: Up-regulation of miR-618 suppresses the development of PDCs and increases their ability to secrete IFNα, potentially contributing to the type I IFN signature observed in SSc patients. Considering the importance of PDCs in the pathogenesis of SSc and other diseases characterized by a type I IFN signature, miR-618 potentially represents an important epigenetic target to regulate immune system homeostasis in these conditions., (© 2017, American College of Rheumatology.)

Objective: Endothelial cell (EC) damage in systemic sclerosis (SSc) is reflected by the shedding of microparticles (MPs). The aim of this study was to show that inhibiting MP release using pantethine or by inactivating ATP-binding cassette transporter A1 (ABCA1) ameliorates murine SSc., Methods: First, the effects of pantethine on MP shedding and on basal oxidative and nitrosative stresses in ECs and fibroblasts were determined in vitro. The effects of pantethine were then tested in vivo. SSc was induced in BALB/c mice by daily intradermal injection of HOCl. Mice were simultaneously treated daily with pantethine by oral gavage., Results: In vitro, pantethine inhibited MP shedding from tumor necrosis factor-stimulated ECs and abrogated MP-induced oxidative and nitrosative stresses in ECs and fibroblasts. Ex vivo, pantethine also restored redox homeostasis in fibroblasts from mice with SSc. In vivo, mice with SSc displayed skin and lung fibrosis associated with increased levels of circulating MPs and markers of oxidative and endothelial stress, which were normalized by administration of pantethine or inactivation of ABCA1., Conclusion: Pantethine is a well-tolerated molecule that represents a potential treatment of human SSc., (© 2015, American College of Rheumatology.)