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.


Tribbles Homolog 3 Mediates Transforming Growth Factor Beta Driven Dermal Fibrosis In Systemic Sclerosis.

Tomcik1,  Michal, Palumbo2,  Katrin, Avouac3,  Jérôme, Horn2,  Angelika, Khodzhigorova2,  Aisa, Zerr2,  Pawel, Dees2,  Clara

Institute of Rheumatology, Department of Clinical and Experimental Rheumatology, 1st Faculty of Medicine, Charles University, Prague, Czech Republic
Department of Internal Medicine 3 and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
Paris Descartes University, Rheumatology A department, Cochin Hospital, Paris, France
Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
University of Erlangen-Nuremberg, Erlangen, Germany
Institute of Rheumatology, 1st Faculty of Medicine, Charles University, Prague, Czech Republic
University Hospital Zurich, Zurich, Switzerland

Background/Purpose:

Tribbles Homolog 3 (TRB-3), is a member of a family of pseudokinases called Tribbles which regulate activation of a number of intracellular signaling pathways with roles extending from mitosis and cell activation to apoptosis and modulation of gene expression. The aim of this study was to investigate the role of TRB-3 in the pathologic activation of fibroblasts in systemic sclerosis (SSc).

Methods:

Activation of TRB-3 in the skin and dermal fibroblasts was determined by real-time PCR, immunohistochemistry and immunofluorescence. Collagen synthesis of human dermal fibroblasts was quantified by real-time PCR and SirCol collagen assay. The expression of TRB3 was inhibited in cultured fibroblasts and in murine models of fibrosis with siRNA. The mouse models of bleomycin-induced dermal fibrosis and dermal fibrosis induced by attenuated adenovirus overexpressing a constitutively active TGF-b receptor I were used to investigate the role of TRB3 in fibrosis.

Results:

Increased expression of TRB-3 was detected in the upper layer of the dermis of SSc patients. The overexpression of TRB-3 persisted in cultured SSc fibroblasts (4.1±0.4-fold increase, p<0.001). A similar increase in TRB-3 expression was observed in the skin samples from both murine models of experimental dermal fibrosis, both on mRNA and protein level. The upregulation of TRB3 was mediated by TGF-b. Stimulation of cultured fibroblasts with TGF-b increased expression of TRB-3 protein by 4.5±0.2-fold (p<0.001). Knockdown of TRB-3 by siRNA abrogated the stimulatory effects of TGF-b on fibroblasts and completely prevented the stimulatory effects of TGF-b on the release of collagen and the formation of stress fibers. Moreover, mice lacking TRB-3 were protected from experimental fibrosis. In the model of bleomycin-induced dermal fibrosis, siRNA mediated knockdown of TRB-3 decreased dermal thickening by 50±1% (p<0.05), the hydroxyproline content by 76±5% (p<0.01) and the myofibroblast counts by 86±10% (p<0.05). In the model of dermal fibrosis induced by adenoviral overexpression of constitutively active TGF-b receptor I, knockdown of TRB-3 decreased dermal thickening by 91±6% (p<0.05), completely prevented the accumulation of hydroxyproline (p<0.01) and decreased the myofibroblast counts by 82±7% (p<0.05). Consistent with the crucial role of TRB-3 for TGF-b signaling in vitro, knockdown of TRB-3 abrogated the nuclear accumulation of phosphorylated Smad-3 and prevented the induction of TGF-b target genes such as Smad-7 and CTGF in both mouse models.

Conclusion:

We demonstrate for the first time a key-role of TRB-3 in fibroblast activation and tissue fibrosis in SSc. TRB-3 is upregulated in SSc and in experimental fibrosis in a TGF-b dependent manner. TRB-3 is essential for the pro-fibrotic effects of TGF-b and targeting of TRB-3 completely prevents the stimulatory effect of TGF-b on cultured fibroblasts. Moreover, knockdown of TRB-3 protected from experimental dermal fibrosis in different mouse models. Considering the potent anti-fibrotic effects observed in this study, TRB-3 might be a promising candidate for molecular targeted therapies of SSc.

To cite this abstract, please use the following information:
Tomcik, Michal, Palumbo, Katrin, Avouac, Jérôme, Horn, Angelika, Khodzhigorova, Aisa, Zerr, Pawel, et al; Tribbles Homolog 3 Mediates Transforming Growth Factor Beta Driven Dermal Fibrosis In Systemic Sclerosis. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :2538
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