Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.


RNAi Mediated Silencing of the Autoantigen hnRNP-A2 Dcreases Inflammatory Arthritis by Inhibiting Activation of Cells of the Mononuclear Phagocytic System.

Herman1,  Sonja, Presumey2,  Jessy, Pfatschbacher1,  Juergen, Vandenberg3,  Wim B., Apparailley2,  Florence, Steiner1,  Gunter

Medical University of Vienna, Vienna, Austria
Hôpital Saint Eloi, Montpellier, France
Radboud University Nijmegen Med Center, Nijmegen, Netherlands

Background/Purpose:

HnRNP-A2 belongs to a heterogenous family of nuclear proteins importantly involved in mRNA trafficking, transcriptional and translational processes. Recent evidence let suggest that hnRNPs posttranscriptionally modulate expression of inflammatory mediators such as COX-2, TNF-a, IL-1b and iNOS by affecting mRNA stability and translation. Strong upregulation of hnRNP-A2 at sites of inflammation and the generation of antibodies and autoreactive T-cells against hnRNP-A2 in patients with rheumatoid arthritis (RA) and various arthritis models points towards a potential involvement of this protein in the pathogenesis of inflammatory arthritis.

Methods:

Expression of hnRNP-A2 in tissues and cells was analysed by flow cytometry and immunoblotting. In-vitro silencing of hnRNP-A2 was studied in J77.4 cells. Collagen-induced arthritis (CIA) in DBA1 mice and K/BxN serum transfer arthritis in BL/6 mice were used as arthritis models. For silencing of hnRNP-A2 expression, siRNA containing lipoplexes were used, which were injected intravenously once a week. Control animals were treated with unspecifc siRNA/lipoplexes or PBS. Silencing efficiency was analyzed by immunobloting and real-time PCR. Arthritis was measured by an established clinical scoring system, inflammation and bone erosions were analyzed by histomorphometry.

Results:

HnRNP-A2 was highly expressed in lymphoid organs such as lymph-nodes, spleen and thymus. Among cells of the immune system monocytes/macrophages showed the strongest expression of hnRNP-A2. Silencing of hnRNP-A2 in a monocytic cell line diminished the proliferative capacity of transfected cells.

Silencing of hnRNP-A2 in vivo revealed a 60%–70% silencing efficiency in lymph nodes and spleen of injected mice. Remarkably, incidence of arthritis in those mice, which were injected with hnRNP-A2 specific siRNA-lipoplexes, was only 20% as compared to 70 and 80%, respectively, in the control groups. Moreover, arthritis scores and weight loss differed significantly from control animals. Histological analysis of paws confirmed that both inflammation and bone erosion were significantly reduced in animals treated with hnRNP-A2 specific siRNA. Serum levels of cytokines typically produced by cells of the mononuclear phagocytic system such as TNF-a, IL-23 and IL-1 were strongly reduced. The effects observed were similar in both arthritis models indicating that hnRNP-A2 is crucially involved in the effector arm of autoimmune arthritis.

Conclusion:

In-vivo silencing of hnRNP-A2 largely prevents induction of arthritis development by inhibiting activation of the mononuclear phagocyte system thereby diminishing the inflammatory immune response.

To cite this abstract, please use the following information:
Herman, Sonja, Presumey, Jessy, Pfatschbacher, Juergen, Vandenberg, Wim B., Apparailley, Florence, Steiner, Gunter; RNAi Mediated Silencing of the Autoantigen hnRNP-A2 Dcreases Inflammatory Arthritis by Inhibiting Activation of Cells of the Mononuclear Phagocytic System. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :2428
DOI:

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