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  • Title: The transcription factor JunD mediates transforming growth factor {beta}-induced fibroblast activation and fibrosis in systemic sclerosis.
    Author: Palumbo K, Zerr P, Tomcik M, Vollath S, Dees C, Akhmetshina A, Avouac J, Yaniv M, Distler O, Schett G, Distler JH.
    Journal: Ann Rheum Dis; 2011 Jul; 70(7):1320-6. PubMed ID: 21515915.
    Abstract:
    OBJECTIVES: Transforming growth factor β (TGFβ) has been identified as a key player in fibrotic diseases. However, the molecular mechanisms by which TGFβ activates fibroblasts are incompletely understood. Here, the role of JunD, a member of the activator protein 1 (AP-1) family of transcription factors, as a downstream mediator of TGFβ signalling in systemic sclerosis (SSc), was investigated. METHODS: The expression of JunD was analysed by real-time PCR, immunofluorescence, western blotting and immunohistochemistry. The canonical Smad pathway was specifically targeted by small interfering (si)RNA. The expression of extracellular matrix proteins in JunD deficient (JunD(-/-)) fibroblasts was analysed by real-time PCR and hydroxyproline assays. The mouse model of bleomycin-induced dermal fibrosis was used to assess the role of JunD in experimental fibrosis. RESULTS: JunD was overexpressed in SSc skin and in cultured fibroblasts in a TGFβ dependent manner. The expression of JunD colocalised with pSmad 3 in fibrotic skin and silencing of Smad 3 or Smad 4 by siRNA prevented the induction of JunD by TGFβ. JunD(-/-) fibroblasts were less responsive to TGFβ and released less collagen upon stimulation with TGFβ. Moreover, JunD(-/-) mice were protected from bleomycin-induced fibrosis with reduced dermal thickening, decreased myofibroblast counts and lower collagen content of lesional skin. CONCLUSIONS: These data demonstrate that JunD is overexpressed in SSc and that JunD is a mediator of the profibrotic effects of TGFβ. Considering that inhibitors of AP-1 signalling have recently been developed and are available for clinical trials in SSc, these findings may have translational implications.
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