CXCL4-RNA Complexes Circulate in Systemic Sclerosis and Amplify Inflammatory/Pro-Fibrotic Responses by Myeloid Dendritic Cells |
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Authors: | Immacolata Pietraforte Alessia Butera Lucia Gaddini Anna Mennella Raffaella Palazzo Doriana Campanile Katia Stefanantoni Valeria Riccieri Roberto Lande Loredana Frasca |
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Affiliation: | 1.Istituto Superiore di Sanità, Department of Oncology and Molecular Medicine, 00161 Rome, Italy;2.Istituto Superiore di Sanità, National Center for Drug Research and Evaluation, 00161 Rome, Italy;3.Department of Clinical, Internal, Anesthesiological and Cardiovascular Sciences, Sapienza University of Rome, 00185 Roma, Italy |
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Abstract: | 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. |
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Keywords: | CXCL4 RNA systemic sclerosis inflammation myeloid dendritic cells (mDCs) |
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