Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


The Transcription Factor AP-1 Mediates the Pro-Fibrotic Effects of TGF and Contributes to the Development of Experimental Dermal Fibrosis.

Avouac3,  Jerome, Palumbo2,  Katrin, Tomcik4,  Michal, Zerr2,  Pawel, Dees2,  Clara, Horn2,  Angelika, Akhmetshina2,  Alfiya

Center of Experimental Rheumatology and Zurich Center of Integrative Human Physiology, University Hospital Zurich, Zurich, Switzerland
Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany, Paris Descartes University, Rheumatology A Department, Cochin Hospital and INSERM U781, Necker Hospital,
Department of Internal Medicine III, University of Erlangen-Nuremberg, Erlangen, Germany and Institute of Rheumatology and Connective Tissue Research Laboratory, Department of Rheumatology of the First Faculty of Medicine, Charles U
Division of Rheumatology, Department of Medicine, Kobe University Graduate School of Medicine, Kobe University Hospital, Kobe, Japan
Friedrich Alexander Univ, Erlangen, Germany
Paris Descartes University, Rheumatology A Department, Cochin Hospital and INSERM U781, Necker Hospital, Paris, France
University of Erlangen, Erlangen, Germany

Background:

Tissue fibrosis caused by pathological activation of fibroblasts is a major hallmark of systemic sclerosis (SSc). The activation of the transcription factor AP-1, composed of members of Jun and Fos families, regulates cell proliferation, apoptosis, inflammation, wound healing and tumorigenesis. AP-1 is also one of the transcriptional targets of TGFb signaling, one of the key growth factors in SSc.

Objectives:

The aims of the present study were to investigate whether AP-1 contributes to the pathologic activation of fibroblasts in SSc and to evaluate the anti-fibrotic potential of AP-1 inhibition for treatment of SSc.

Methods:

Activation of AP-1 in human skin was determined by real-time PCR for c-Jun and c-Fos and immunohistochemistry for N-terminal residues of human c-Jun. SSc and healthy dermal fibroblasts were stimulated with TGFb and incubated with T5224, a small-molecule inhibitor of c-Fos/AP-1 (1). Collagen synthesis was quantified by real-time PCR and hydroxyproline assay. Differentiation of resting fibroblasts into myofibroblasts was assessed by staining for a-smooth muscle actin and stress fibers. To evaluate the anti-fibrotic potential of specific AP-1 inhibition by T5224 in vivo, we used the mouse model of bleomycin induced dermal fibrosis or attenuated adenoviruses overexpressing a constitutively active TGFb receptor I.

Results:

Increased levels of AP-1 were detected in the skin of SSc patients. The overactivation of AP-1 persisted in cultured SSc fibroblasts. Inhibition of AP-1 reduced the basal mRNA levels of col1a1 and col1a2 in SSc fibroblasts by up to 46±3% (p<0.05) but did not reduce the collagen synthesis in resting healthy dermal fibroblasts. Similar results were obtained on the protein level. Stimulation of healthy fibroblasts with TGFb lead to AP-1 activation and inhibition of AP-1 abrogated the stimulatory effects of TGFb on collagen synthesis. Inhibition of AP-1 also prevented the differentiation of resting fibroblasts into myofibroblasts. Consistently, inhibition of AP-1 exerted potent anti-fibrotic effects in different models of experimental fibrosis. In the mouse model of bleomycin-induced fibrosis, inhibition of AP-1 decreased dermal thickening by 53±3% (p<0.05). In addition, the collagen content and the number of myofibroblasts were significantly reduced (respectively 46±2% and 66±4%, p<0.05). In the TGFbRI model, selective inhibition of AP-1 also exerted potent anti-fibrotic effects and reduced dermal thickening, collagen content and myofibroblast counts by 70±5%, 52±3% and 51±2%, respectively (p<0.05). T5224 was well tolerated: no weight loss, alterations of the skin texture or affected activity were recorded during the whole treatment period.

Conclusion:

We demonstrate that AP-1 is activated in a TGFb dependent manner in SSc and that inhibition of AP-1 specifically reduces collagen synthesis in activated SSc fibroblasts. The specific AP-1 inhibitor T5224 efficiently prevented the development of dermal fibrosis in different mouse models of SSc and was well tolerated. Thus, AP-1 might be a promising new molecular target for the treatment of SSc.

(1)Aikawa, Y, Morimoto, K & Yamamoto, T et al, Nat Biotechnol 2008;26:817-23

To cite this abstract, please use the following information:
Avouac, Jerome, Palumbo, Katrin, Tomcik, Michal, Zerr, Pawel, Dees, Clara, Horn, Angelika, et al; The Transcription Factor AP-1 Mediates the Pro-Fibrotic Effects of TGF and Contributes to the Development of Experimental Dermal Fibrosis. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :616
DOI: 10.1002/art.28384

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