Abstract
Objectives: Considering the critical role of microRNAs (miRNAs) in regulation of cell activation, we investigated their role in circulating type-2 conventional dendritic cells (cDC2s) of patients with primary Sjögren's syndrome (pSS) compared to healthy controls (HC).Methods: CD1c-expressing cDC2s were isolated from peripheral blood. A discovery cohort (15 pSS, 6 HC) was used to screen the expression of 758 miRNAs and a replication cohort (15 pSS, 11 HC) was used to confirm differential expression of 18 identified targets. Novel targets for two replicated miRNAs were identified by SILAC in HEK-293T cells and validated in primary cDC2s. Differences in cytokine production between pSS and HC cDC2s were evaluated by intracellular flow-cytometry. cDC2s were cultured in the presence of MSK1-inhibitors to investigate their effect on cytokine production.Results: Expression of miR-130a and miR-708 was significantly decreased in cDC2s from pSS patients compared to HC in both cohorts, and both miRNAs were downregulated upon stimulation via endosomal TLRs. Upstream mediator of cytokine production MSK1 was identified as a novel target of miR-130a and overexpression of miR-130a reduced MSK1 expression in cDC2s. pSS cDC2s showed higher MSK1 expression and an increased fraction of IL-12 and TNF-α-producing cells. MSK1-inhibition reduced cDC2 activation and production of IL-12, TNF-α, and IL-6.Conclusions: The decreased expression of miR-130a and miR-708 in pSS cDC2s seems to reflect cell activation. miR-130a targets MSK1, which regulates pro-inflammatory cytokine production, and we provide proof-of-concept for MSK1-inhibition as a therapeutic avenue to impede cDC2 activity in pSS.
Highlights
Primary Sjögren’s syndrome is an autoimmune disease characterized by keratoconjunctivitis sicca, xerostomia, and lymphocytic infiltration of salivary and lacrimal glands [1, 2]. pSS is associated with multiple factors such as genetic predisposition and environmental factors including viral infection [3]
Hierarchical clustering of the 39 differentially-expressed miRNAs between pSS patients and healthy controls (HC) using Euclidean distance and Ward’s method (B). miR-708 and miR-130a expression was consistently downregulated in pSS patients compared to HC in both cohorts (C). cDC2s stimulated with TLR3 (25 μg/mL) and TLR7/8 (1 μg/mL) ligands for 24 h showed a reduced expression of miR-708 and miR-130a measured by qPCR compared to medium control (D)
Using two independent cohorts of patients and controls (Table 1) we identified differentially expressed miRNAs in cDC2s from pSS patients compared to HC
Summary
Primary Sjögren’s syndrome (pSS) is an autoimmune disease characterized by keratoconjunctivitis sicca, xerostomia, and lymphocytic infiltration of salivary and lacrimal glands [1, 2]. pSS is associated with multiple factors such as genetic predisposition and environmental factors including viral infection [3]. Activated autoreactive B cells and T cells as well as increased levels of pro-inflammatory cytokines drive chronic inflammation of the exocrine glands, associated with loss of function [4]. CDC2s are the most predominant in human blood, tissues and lymphoid organs [5] They produce a variety of cytokines (e.g., IL-12, IL-6, and TNF-α) and chemokines (e.g., CXCL8, CCL3, CCL4, CCL5, and CXCL10) [6] and present antigen to potently activate T cells [7, 8]. CDC2s are suspected to play an important role in driving salivary gland inflammation [11, 12], their molecular regulation has not yet been studied in pSS
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