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.
Inhibition of Glycogen Synthase Kinase 3 Induces Dermal Fibrosis by Activation of the Canonical Wnt Pathway.
Bergmann1, Christina, Akhmetshina2, Alfiya, Dees1, Clara, Palumbo1, Katrin, Zerr1, Pawel, Beyer3, Christian, Zwerina1, Jochen
Department of Internal Medicine 3 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
University of Erlangen-Nuremberg, Erlangen, Germany
University Hospital Zurich, Zurich, Switzerland
Wnt signaling plays a critical role in embryogenesis and in adult tissue homeostasis. The abnormal activation of Wnt signaling is associated with a wide range of diseases and might also play a role in SSc. Glykogen Synthase Kinase 3b (GSK-3) is a crucial regulator of the canonical Wnt signaling. In the absence of Wnt proteins, GSK-3 promotes the phosphorylation and subsequent degradation of b-catenin. Thus, the aberrant activation of the canonical Wnt pathway is prevented. However, in the presence of Wnt, GSK-3 becomes inactive and b-catenin is not degraded but stimulates the transcription of Wnt target genes. The aim of the present study was to define the role of GSK-3 as a central regulator of canonical Wnt signaling for fibroblast activation and in experimental models of SSc.
We used siRNA and two specific inhibitors, SB216763 and AR-A014418, to inhibit GSK-3 in cultured fibroblasts and in mice. The activation of the canonical Wnt signaling was analyzed by determining the levels of nuclear b-catenin and by measuring the mRNA levels of the Wnt target gene Axin2. The effects of GSK-3 on the release of collagen were evaluated in human dermal fibroblasts, in the mouse model of bleomycin induced dermal fibrosis and in the tight-skin-1 (tsk-1) mice. To investigate whether inhibition of GSK-3 alone is sufficient to induce fibrosis, SB216763 was applied to mice without additional profibrotic stimuli.
Targeting GSK-3 potently activated the canonical Wnt pathway in fibroblasts in vitro and in vivo with a prominent accumulation of nuclear b-catenin and induction of Axin2. Incubation with inhibitors of GSK-3 dose-dependently upregulated the expression of col1a1 from cultured fibroblasts by up to 2.6 fold (p<0.05) and increased the release of collagen protein. Similar results were also obtained upon knockdown of GSK-3 with siRNA. The increased release of collagen was completely abolished by siRNA mediated knockdown of b-catenin suggesting that the pro-fibrotic effects of inhibition of GSK-3 are mediated by the canonical Wnt pathway. In vivo, inactivation of GSK-3 exacerbated bleomycin induced dermal fibrosis with increased dermal thickening by 84±15%(p<0.05) compared to bleomycin treatment alone. Inactivation of GSK-3 also aggravated the tsk-1 phenotype. Moreover, inhibition of GSK-3 was sufficient to induce progressive dermal fibrosis in mice with increases in dermal thickening by up to 65±9% within 8 weeks (p<0.05).
We demonstrated that GSK-3 is a crucial regulator of the canonical Wnt pathway in dermal fibroblasts. Inhibition of GSK-3 stimulates the release of collagen from dermal fibroblasts in a b-catenin dependant manner and aggravates experimental fibrosis in different mouse models. Of note, inhibition of GSK-3 alone was sufficient to induce dermal fibrosis. These results highlight the key-role of canonical Wnt signaling in fibrosis and underline the importance of proper control of the canonical Wnt pathway.
To cite this abstract, please use the following information:
Bergmann, Christina, Akhmetshina, Alfiya, Dees, Clara, Palumbo, Katrin, Zerr, Pawel, Beyer, Christian, et al; Inhibition of Glycogen Synthase Kinase 3 Induces Dermal Fibrosis by Activation of the Canonical Wnt Pathway. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :2539