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THU0063 Cellular RA-Binding Protein (CRABP)-II Suppression Sensitizes Rheumatoid Fibroblast-Like Synoviocytes to FAS-Induced Apoptosis
  1. N. Mosquera1,2,
  2. J.J. Gomez-Reino1,3,
  3. C. Conde1
  1. 1Laboratorio de Reumatología Experimental y Servicio de Reumatología, IDIS, Hospital Clínico Universitario de Santiago
  2. 2Programa Doctorado Medicina Molecular
  3. 3Departamento de Medicina, Universidad de Santiago de Compostela (USC), Santiago de Compostela, Spain

Abstract

Background Disregulated proliferation and apoptosis of fibroblast-like synoviocytes (FLS) contribute to synovial hyperplasia, chronic inflammation and tissue damage in rheumatoid arthritis (RA). Therefore, FLS are a potential target for therapy given that current treatments, focused against inflammatory factors, are not fully effective in a significant number of patients. An unexplored area includes vitamine A and its metabolites, known as retinoids. They regulate cellular proliferation, differentiation and apoptosis. As such, they have a potent pro-apoptotic and anti-proliferative activity in some types of cancer. The retinoids are transported to the nucleus by the intracellular proteins CRABP-II and FABP5, which expression ratio (CRABP-II/FABP5) determines opposite effects of retinoids. In cells with a high ratio, retinoids signal through RAR and activate pro-apoptotic genes, whereas in cells with a low ratio, they signal through PPARβ/δ and promote survival responses.

Objectives To analyse the role of retinoids, and CRABP-II and FABP5 proteins in proliferation and apoptosis of RA FLS.

Methods FLS were obtained from 7 RA patients. CRABP-II and FABP5 expression was analyzed by real-time PCR and by western blot. TNF-induced proliferation was determined using the CellTiter-Glo luminescent viability assay (Promega). Fas-induced apoptosis was analyzed with the cell death ELISA kit (Roche). Expression of CRABP-II and FABP5 was suppressed in RA FLS by siRNA transfection.

Results CRABP-II and FABP5 expression was analysed in RA FLS. TNF stimulation increased the expression of FABP5 as compared with the baseline (p<0,05), whereas the expression of CRABP-II was unaffected. The treatment with all-trans retinol (ATRA) increased expression of both proteins, although with a higher effect for CRABP-II. We next analysed the effect of ATRA in the basal and TNF-induced proliferation of RA FLS. TNF stimulation significantly increased basal proliferation (p<0,05) whereas the treatment with ATRA induced a significant reduction of proliferation (p<0,05). Interestingly, the combination TNF+ATRA increased 40% the proliferation induced by TNF at 96h (p<0,005).

Next, we analysed the effect of ATRA on Fas-induced apoptosis. Treatment with ATRA decreased RA FLS apoptosis (p<0,05, in the comparison of anti-Fas vs anti-Fas+ATRA, and in the comparison of FasL vs FasL+ATRA).

To distinguish the role of CRABP-II and FABP5 in these effects, we suppressed each of them in RA FLS by siRNA transfection. The lack of CRABP-II sensitized RA FLS to Fas induced apoptosis (p<0,05, in the comparison of anti-Fas sicontrol vs anti-Fas siCRABP-II and in the comparison FasL sicontrol vs FasL siCRABP-II). On the contrary, FABP5 knockdown did not modify the response of RA FLS to Fas-induced apoptosis.

Conclusions Overall these results suggest that retinoid signalling pathway could be involved in the FLS pathogenic changes in RA.

Disclosure of Interest None declared

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