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.
Bosentan Reverses the Profibrotic Phenotype of Systemic Sclerosis Dermal Fibroblasts Through Increasing the DNA Binding Ability of Transcription Factor Fli1.
Akamata1, Kaname, Asano2, Yoshihide, Sato3, Shinichi
Systemic sclerosis (SSc) is a multisystem autoimmune disease characterized by vascular injuries and fibrosis of skin and certain internal organs. Although the pathogenesis of SSc still remains unknown, mounting data have demonstrated the possible contribution of endohtelin-1 (ET-1) to the development of fibrosis and vasculopathy in SSc. ET-1 is indispensable for the profibrotic effect of transforming growth factr-b on fibroblasts and bosentan, a dual ET receptor antagonist, reverses the profibrotic phenotype of SSc fibroblasts. Clinically, bosentan prevents the development of new digital ulcers in SSc. Thus, ET-1 may be involved in the mechanism responsible for the constitutive activation of fibroblasts and endothelial cells in SSc.
Fli1 is a member of Ets transcription factor family, which functions as a potent repressor of type I collagen gene in dermal fibroblasts and as a pivotal regulator of angiogenic process in endothelial cells. In SSc skin, Fli1 levels are constitutively downregulated in these cells, especially through the epigenetic mechanism in dermal fibroblasts, suggesting that Fli1 is one of the genetic factors in SSc. Supporting this idea, gene silencing of Fli1 activates fibroblasts and endothelial cells in vitro and a series of Fli1 mutant mice reproduce the histopathological features of SSc skin, including collagen deposition and abnormal vascular structure.
Based on these backgrounds, the purpose of this study is to clarify the mechanism by which bosentan exerts its anti-fibrotic effect on SSc fibroblasts, especially focusing on Fli1, by using SSc dermal fibroblasts and SSc animal models.
Five strains of SSc dermal fibroblasts and closely matched healthy dermal fibroblasts were used in in vitro studies. Bleomycin-induced SSc mouse model was used to evaluate the anti-fibrotic effect of bosentan in vivo.
mRNA levels of COL1A2 gene were increased by ET-1 around 15 minutes in normal fibroblasts. A responsive element of ET-1 was located between -353 and -264 bp of the COL1A2 promoter, where Fli1 binding site is included, suggesting that ET-1 increases the promoter activity of COL1A2 gene by decreasing the DNA binding ability of Fli1. Consistent with the previous finding that the DNA binding ability of Fli1 is diminished by phosphorylation at threonine 312, ET-1 stimulation increased the phosphorylation levels of Fli1 at threonine 312. In SSc fibroblasts, phosphorylation levels of Fli1 were constitutively elevated compared with normal fibroblasts. Furthermore, a responsive element of bosentan was located between -353 and -264 bp of the COL1A2 promoter in SSc fibroblasts. Moreover, bosentan decreased the phosphorylation levels of Fli1 and increased the DNA binding ability of Fli1 in SSc fibroblasts. Collectively, these results indicate that bosentan reverses profibrotic phenotype of SSc fibroblasts at least partially by increasing the DNA binding ability of Fli1. We also demonstrated that this mechanism is involved in the anti-fibrotic effect of bosentan in vivo using SSc animal models.
Bosentan reverses profibrotic phenotype of SSc fibroblasts at least partially by increasing the DNA binding ability of Fli1.
To cite this abstract, please use the following information:
Akamata, Kaname, Asano, Yoshihide, Sato, Shinichi; Bosentan Reverses the Profibrotic Phenotype of Systemic Sclerosis Dermal Fibroblasts Through Increasing the DNA Binding Ability of Transcription Factor Fli1. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :1480