Src kinases in systemic sclerosis: Central roles in fibroblast activation and in skin fibrosis

Authors

  • Catherine Skhirtladze,

    1. Department of Internal Medicine 3 and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
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    • Drs. Skhirtladze and Oliver Distler contributed equally to this work.

  • Oliver Distler,

    1. Zurich Center of Integrative Human Physiology, Switzerland
    2. University Hospital Zurich, Switzerland
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    • Drs. Skhirtladze and Oliver Distler contributed equally to this work.

    • Dr. Oliver Distler has received consulting fees, speaking fees, and/or honoraria (less than $10,000) from Array BioPharma. Dr. Jörg H. W. Distler has received consulting fees, speaking fees, and/or honoraria (less than $10,000 each) from Encysive and Actelion.

  • Clara Dees,

    1. Department of Internal Medicine 3 and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
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  • Alfiya Akhmetshina,

    1. Department of Internal Medicine 3 and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
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  • Nicole Busch,

    1. Department of Internal Medicine 3 and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
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  • Paulius Venalis,

    1. Department of Internal Medicine 3 and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
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  • Jochen Zwerina,

    1. Department of Internal Medicine 3 and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
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  • Bernd Spriewald,

    1. Department of Internal Medicine 3 and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
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  • Margarita Pileckyte,

    1. Kaunas Medical University Hospital, Kaunas, Lithuania
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  • Georg Schett,

    1. Department of Internal Medicine 3 and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
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  • Jörg H. W. Distler

    Corresponding author
    1. Department of Internal Medicine 3 and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
    • Department of Internal Medicine 3, University of Erlangen-Nuremberg, Universitätsstrasse 29, Erlangen 91054, Germany
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    • Dr. Oliver Distler has received consulting fees, speaking fees, and/or honoraria (less than $10,000) from Array BioPharma. Dr. Jörg H. W. Distler has received consulting fees, speaking fees, and/or honoraria (less than $10,000 each) from Encysive and Actelion.


Abstract

Objective

Src kinases are nonreceptor tyrosine kinases, which have been implicated in cytoskeletal organization and cell mobility. This study was undertaken to evaluate the potential of Src kinases as novel targets of antifibrotic therapies.

Methods

Fibroblast cultures were obtained from 10 patients with systemic sclerosis (SSc) and 5 healthy subjects. Src signaling was inhibited using small-molecule inhibitors and overexpression of a dominant-negative mutant of Src and of the endogenous inhibitor Csk. The expression of extracellular matrix proteins was analyzed by real-time polymerase chain reaction and by SirCol collagen assay. Toxic effects were excluded by MTT assay and staining for annexin V and propidium iodide. The mouse model of bleomycin-induced dermal fibrosis was used to assess the role of Src kinases in dermal fibrosis in vivo.

Results

Stimulation with transforming growth factor β and platelet-derived growth factor activated Src signaling in dermal fibroblasts from patients with SSc and healthy donors. Incubation with the Src kinase inhibitors or overexpressed mutant Src or Csk reduced the synthesis of messenger RNA for COL1A1, COL1A2, and fibronectin 1. A dose-dependent reduction in collagen release was also observed at the protein level. No inhibitory effects on proliferation and no increase in the number of apoptotic or necrotic fibroblasts were observed. Consistent with the in vitro data, inhibition of Src kinases prevented experimental dermal fibrosis. Dermal thickness, the amount of collagen protein, and the number of myofibroblasts were reduced in a dose-dependent manner.

Conclusion

These findings indicate that Src kinases play important roles in the activation of fibroblasts and in the development of experimental fibrosis. Thus, Src kinases might be interesting targets for novel antifibrotic therapies in SSc.

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