Background/Purpose: The type I interferons (IFN-I) including IFN-a, and IFN-b are key cytokines involved in innate immune response to viral infection. Almost all cells can produce IFN-I, express IFN-I receptor (IFNAR) and induce the transcription of IFN stimulated genes (ISGs), which have anti-proliferative and immunomodulatory activities. Idiopathic inflammatory myopathies (IIMs) are acquired auto-immune diseases. Among the IIMs, Dermatomyositis (DM) is characterized by skin lesions, muscle specific pathologic features combining inflammatory infiltration with HLA-ABC over-expression and vasculopathy. It is known that DM patients express up-regulated ISGs in muscle fibers, endothelial cells (EC), skin tissues and peripheral blood. However, the effect of the IFN-I on myoblasts (MB), myotubes (MT) and EC has not been well determined. Therefore, the aim of this study is to determine if MB, MT and EC present functional changes when exposed to IFN-I.

Methods:

The effect of the activation of IFN-I pathway on the differentiation of MB, and EC and on MT was analyzed in vitro. Thus, those cells were cultured with recombinant IFN-I, IFN-a, IFN-β and Poly (I:C) (PIC), an agonist of TLR3 receptor.

Results:

The results on MB showed that PIC, IFN-a and IFN-β abolished myotube formation and decreased myogenin (MyoG) expression. In differentiated MT, all stimuli induced ISGs (MxA and OAS1). Moreover, IFN-a, IFN-β and PIC dramatically reduced myotube surface. Next, IFN-a and IFN-b neutralization and IFNAR blocking experiments confirmed the specificity of the results. Neutralization and blocking experiments in differentiating MB treated with IFN-I, IFN-a and PIC, reverted the myotube formation and myogenin expression. Along the same lines, the surface area in differentiated MT area was restored. In addition, qPCR results showed the upregulation of genes involved in muscle atrophy such as Murf1 and Atrogin with a decrease of MyoG expression. The overexpression of Murf1 and atrogin was confirmed at the protein level in vivo, in muscle biopsies from DM patients. The presence of both proteins was detected in perifasicular areas, where atrophic fibers cluster. All stimuli induced HLA-ABC and TLR3 expression in differentiated MT and the presence of IFN-I in the supernatants in MB and MT. The activation of IFN-I pathway in EC, led to a decrease in cell proliferation and ISG up-regulation (MxA, RIG-I, ISG15 and TLR3). Tube formation assay with EC in the IFN-I-activated EC showed a disruption of the vascular network formation, indicating that IFN-I impairs angiogenesis in vitro.

Conclusion: In conclusion, in vitro treatment with IFN-I or IFN-I pathway activation recapitulates the characteristic pathological features (muscular and vascular damage) defining DM. This emphasizes the key role of the IFN-I pathway in the pathophysiology of DM, results that potentially may lead to new avenues for therapeutic approaches.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/in-vitro-activation-of-type-i-interferon-pathway-reproduces-the-characteristics-damages-observed-in-dermatomyositis-patients/