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.


The Nuclear Receptor CAR Mediates the Pro-Fibrotic Effects of TGF- and Contributes to the Development of Experimental Dermal Fibrosis.

Avouac1,  Jerome, Tomcik2,  Michal, Palumbo1,  Katrin, Zerr1,  Pawel, Dees1,  Clara, Akhmetshina1,  Alfiya, Beyer1,  Christian

Department of Internal Medicine 3 and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
Institute of Rheumatology, Department of Clinical and Experimental Rheumatology, 1st Faculty of Medicine, Charles University, Prague, Czech Republic
University Hospital Zurich, Zurich, Switzerland
Paris Descartes University, Rheumatology A department, Cochin Hospital, Paris, France

Background/Purpose:

Tissue fibrosis caused by pathological activation of fibroblasts is a major hallmark of systemic sclerosis (SSc). The constitutive androstane receptor (CAR), a member of the nuclear receptor superfamily, is involved in shear and xenobiotic stress. CAR regulates target genes involved in drug metabolism, such as cytochrome P450 family members. CAR activation has also recently been shown to exacerbate hepatic fibrosis. We aim in the present study to investigate whether CAR might contribute to the pathologic activation of fibroblasts in SSc and to the development of experimental dermal fibrosis.

Methods:

Expression of CAR was determined in human skin by immunohistochemistry and in fibroblasts by real time PCR and western blots. SSc and healthy dermal fibroblasts were stimulated with TGFb and incubated with CITCO, a potent and selective agonist for the human CAR. Collagen release from fibroblasts was evaluated by mRNA levels of col1a1 and col1a2 and by the SirCol collagen assay. Col1a2 transcriptional activity was assessed by transfection assays performed with a luciferase reporter construct under control of the -772-bp to +58-bp col1a2 promoter. The synthetic agonist of mouse CAR TCPOBOP was used to evaluate the profibrotic potential of CAR in vivo in the mouse model of bleomycin induced dermal fibrosis or in the model of dermal fibrosis induced by local injections of replication deficient adenoviruses overexpressing a constitutively active TGF-b receptor I.

Results:

Upregulation of CAR was detected in the skin and dermal fibroblasts of SSc patients. Stimulation of healthy fibroblasts with TGFb increased the expression of CAR mRNA by 93±11% and protein by 81±14% (p<0.05 for both). Treatment of healthy or SSc fibroblasts with CITCO significantly increased the stimulatory effects of TGF-b on collagen synthesis. CITCO also amplified the stimulatory effects of TGF-b on col1a2 transcriptional activity by up to 41±5% (p=0.03). Consistently, activation of CAR with TCPOBOP exerted potent profibrotic effects in different models of experimental fibrosis. In the mouse model of bleomycin-induced fibrosis, activation of CAR increased dermal thickening by 35±1% (p<0.05). In addition, the collagen content and the number of myofibroblasts were significantly increased (respectively 42±3% and 69±11%, p<0.05). In the TGFbRI model, activation of CAR also exerted potent profibrotic effects and increased dermal thickening, collagen content and myofibroblast counts by 51±5%, 46±7% and 42±3%, respectively (p<0.05).

Conclusion:

We demonstrate that CAR is activated in a TGFb dependent manner in SSc and mediates the effects of TGF-b on collagen synthesis. In addition, activation of CAR contributed to the development of dermal fibrosis in different mouse models of SSc. Thus, CAR might be a promising new molecular target for the treatment of SSc and other fibrotic processes.

To cite this abstract, please use the following information:
Avouac, Jerome, Tomcik, Michal, Palumbo, Katrin, Zerr, Pawel, Dees, Clara, Akhmetshina, Alfiya, et al; The Nuclear Receptor CAR Mediates the Pro-Fibrotic Effects of TGF- and Contributes to the Development of Experimental Dermal Fibrosis. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :2540
DOI:

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