Session Information
Title: Systemic Sclerosis, Fibrosing Syndromes and Raynaud’s – Pathogenesis, Animal Models and Genetics
Session Type: Abstract Submissions (ACR)
Background/Purpose: We have recently demonstrated that stimulation of the soluble guanylate cyclase (sGC) has potent anti-fibrotic activity in different models of fibrosis. sGC stimulation increases levels of cGMP, which acts as a second messenger to induce various cellular effects. The molecular mechanisms, however, by which sGC stimulation exerts its anti-fibrotic effects have not been characterized yet. In the present work, we investigated interactions between sGC signaling and the TGF-β pathway.
Methods: Normal and SSc fibroblasts as well as sGC-knockout fibroblasts were pre-treated with the sGC stimulator BAY41-2272 or 8-Bromo-cGMP and stimulated with TGF-β. sGC-knockout fibroblasts were generated by isolation of dermal fibroblasts from sGCIfl/fl mice and recombination induced by Cre-adenovirus. In vivo, we studied anti-fibrotic effects of BAY41-2272 in mice challenged with either bleomycin or an adenovirus expressing a constitutively active TGFβI receptor (TBR model).
Results: sGC stimulation by BAY41-2272 effectively inhibited TGFβ-dependent collagen release (mRNA and protein levels) from normal and SSc dermal fibroblasts. In sGC-knockout fibroblasts, pre-treatment with the sGC stimulator BAY41-2272 did not reduce collagen release, demonstrating that the anti-fibrotic effects of BAY41-2272 are indeed mediated exclusively via sGC. To demonstrate that the second messenger cGMP is the central mediator of the sGC effects, we used the stable cGMP analogon 8-Bromo-cGMP. 8-Bromo-cGMP was effective in reducing TGFβ-dependent increase of collagen mRNA levels and collagen release in normal and SSc fibroblasts as well as in sGC-knockout fibroblasts. To further elucidate the novel link between sGC- and TGFβ-signaling, we studied nuclear p-smad2/3 levels: BAY41-2272 or 8-Bromo-cGMP prevented the TGFβ-induced increase in nuclear p-smad2/3 in normal and SSc fibroblasts. In sGC-knockout fibroblasts, only 8-Bromo-cGMP reduced p-smad2/3 levels, while BAY41-2272 had no effects. In vivo, we examined the antifibrotic effects of sGC stimulation in TGFβ-dependent, experimental dermal fibrosis (TBR model). BAY41-2272 dose-dependently reduced dermal thickening, hydroxyproline content and myofibroblast counts as well as p-smad2/3 levels, suggesting that sGC stimulation inhibited fibrogenesis via blocking TGFβ-signaling. We confirmed these findings in the more general disease model of bleomycin-induced dermal fibrosis, in which TGFβ is one of several important pro-fibrotic mediators.
Conclusion: We elucidated the molecular mechanisms underlying the anti-fibrotic effects of sGC signaling. Stimulation of sGC increases cGMP levels, which inhibits smad phosphorylation and results in decreased fibroblast activation and collagen release. Importantly, sGC stimulators have vasodilatory and anti-remodeling effects and are in phase 3 clinical trials for pulmonary arterial hypertension (PAH). Thus, sGC stimulators may soon become available for clinical trials and may provide simultaneous treatment of vascular disease and fibrosis in SSc.
Disclosure:
C. Beyer,
None;
S. C. Schindler,
None;
A. Distler,
None;
C. Dees,
None;
H. Reichert,
None;
H. Akan,
None;
P. Sandner,
Bayer Health Care,
3;
O. Distler,
Actelion, Pfizer, Boehringer-Ingelheim, Bayer, Roche, Ergonex, BMS, Sanofi-Aventis, United BioSource Corporation, medac, Biovitrium, Novartis and Active Biotec,
2,
Actelion, Pfizer, Boehringer-Ingelheim, Bayer, Roche, Ergonex, BMS, Sanofi-Aventis, United BioSource Corporation, medac, Biovitrium, Novartis and Active Biotec,
5,
Actelion, Pfizer and Ergonex,
8;
G. Schett,
None;
J. H. Distler,
None.
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