Inhibition of activator protein 1 signaling abrogates transforming growth factor β-mediated activation of fibroblasts and prevents experimental fibrosis

Arthritis Rheum. 2012 May;64(5):1642-52. doi: 10.1002/art.33501.


Objective: To investigate whether c-Jun and c-Fos contribute to the pathologic activation of fibroblasts in systemic sclerosis (SSc) and to evaluate the antifibrotic potential of selective activator protein 1 (AP-1) inhibition.

Methods: Expression of c-Jun and c-Fos was determined by real-time polymerase chain reaction (PCR) and immunohistochemical analysis. Fibroblasts were stimulated with transforming growth factor β (TGFβ) and incubated with T-5224, a small-molecule inhibitor of AP-1, or were transfected with small interfering RNA (siRNA) duplexes against c-Jun and c-Fos. Collagen synthesis was quantified by real-time PCR and hydroxyproline assay. Differentiation of resting fibroblasts into myofibroblasts was assessed by staining for α-smooth muscle actin and stress fibers. The antifibrotic potential of T-5224 was evaluated in mouse models of dermal fibrosis induced by bleomycin or by adenoviral overexpression of a constitutively active TGFβ receptor type I.

Results: Up-regulation of c-Jun and c-Fos was detected in mouse models of SSc and in the skin and dermal fibroblasts of patients with SSc. Stimulation of healthy fibroblasts with TGFβ induced the expression of c-Jun and c-Fos. Treatment with T-5224 or nucleofection with siRNA directed against c-Jun and c-Fos abrogated the profibrotic effects of TGFβ. T-5224 decreased the release of collagen selectively in SSc fibroblasts. T-5224 was well tolerated and prevented dermal fibrosis induced by bleomycin or by adenoviral activation of TGFβ signaling.

Conclusion: AP-1 is up-regulated in a TGFβ-dependent manner in SSc. The selective AP-1 inhibitor T-5224 reduced collagen synthesis selectively in SSc fibroblasts and efficiently prevented the development of experimental dermal fibrosis. Thus, AP-1 might be a promising new molecular target for the treatment of SSc.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Benzophenones / pharmacology
  • Bleomycin / toxicity
  • Cells, Cultured
  • Collagen / biosynthesis
  • Collagen / drug effects
  • Disease Models, Animal
  • Female
  • Fibroblasts / drug effects
  • Fibroblasts / metabolism*
  • Fibrosis / chemically induced
  • Fibrosis / pathology
  • Fibrosis / prevention & control*
  • Gene Expression / drug effects
  • Humans
  • Isoxazoles / pharmacology
  • JNK Mitogen-Activated Protein Kinases / genetics*
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Male
  • Mice
  • Proto-Oncogene Proteins c-fos / genetics*
  • Proto-Oncogene Proteins c-fos / metabolism
  • RNA, Small Interfering / genetics
  • Scleroderma, Systemic / genetics
  • Scleroderma, Systemic / metabolism
  • Scleroderma, Systemic / pathology
  • Signal Transduction / drug effects
  • Transcription Factor AP-1 / antagonists & inhibitors*
  • Transcription Factor AP-1 / metabolism
  • Transfection
  • Transforming Growth Factor beta / pharmacology*
  • Up-Regulation / drug effects


  • 3-(5-(4-(cyclopentyloxy)-2-hydroxybenzoyl)-2-((3-hydroxy-1,2-benzisoxazol-6-yl)methoxy)phenyl)propionic acid
  • Benzophenones
  • Isoxazoles
  • Proto-Oncogene Proteins c-fos
  • RNA, Small Interfering
  • Transcription Factor AP-1
  • Transforming Growth Factor beta
  • Bleomycin
  • Collagen
  • JNK Mitogen-Activated Protein Kinases