Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Functional Significance of mTor in FLS Proliferation and Its Role in the Pathogenesis of Psoriatic Arthritis.

Raychaudhuri2,  Siba P., Saxena1,  Ankit, Raychaudhuri3,  Smriti K.

UC Davis
UC Davis/VAMC Sacramento, Davis, CA
UC Davis/VAMC Sacramento

Purpose:

Hyperproliferation and impaired apoptosis of resident synoviocytes (FLS) are critical pathologic events in the pathogenesis of autoimmune inflammatory arthritis like in rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Synovial hyperplasia leads to cartilage and bone damage in the inflamed joints. Increasing evidence places mammalian target of rapamycin (mTOR) as a central regulator of both cell growth (size) and proliferation, this is achieved in part by regulation of translation initiation. We hypothesize that mTOR signaling cascade proteins are upregulated in the FLS obtained from PsA patients and thus maintains proliferation and survival of these cells causing disease pathology. The aim of this study was to investigate the association of mTOR signaling proteins in regulating the proliferation and survival of these synoviocytes of psoriatic arthritis.

Methods:

FLS were isolated and prepared from the synovial tissue collected from PsA patients (n=5). FLS obtained from OA (n=5) were used as control. Cell lysates were prepared from these FLS. By western blot assay denovo expression of mTOR and its phosphorylated downstream signaling protein p-mTOR was determined. Also effect of mTOR inhibitors were observed on the proliferation and survival of these FLS. FLS were cultured with rapamycin (10nM) and NVP-BEZ235 (50nM) for 3–5 days at 37°C in 5% CO2. FACS based CFSE dilution and MTT assays were used for proliferation studies.

Results:

We found enhanced expression of mTOR (relative intensity (R.I.)= 1.9±0.1) and its downstream activated signaling protein p-mTOR (R.I.= 0.73 ±0.02) in FLS obtained from PsA in comparison to the non inflammatory OA FLS (R.I.= 0.9 ± 0.05; p-mTOR R.I.= 0.26±0.05). The difference of mTOR and p-mTOR was found to be significant at p<0.01. Also the FLS proliferation was found to be significantly reduced when cultured in presence of rapamycin [proliferation index (PI)=.35±0.04) and NVP-BEZ 235 (PI=0.28± 0.02), in comparison to untreated cells (1.2±0.035), data were found to be significantly different between treated and untreated groups at p<0.01.

Conclusions:

We observed high expression of mTOR signaling cascade proteins in the FLS obtained from PsA in comparison to noninflammatory OA cells. We used FLS from RA patients as positive controls and observations were similar to that of FLS of PsA. Further inhibition of proliferation of these cells in presence of mTOR inhibitors rapamycin and NVP-BEZ235 substantiates the role of mTOR signaling pathway in regulating the proliferation of FLS cell. Proliferating FLS is the major component of the invading pannus in inflammatory arthritis. The novel observations described herein provide new insights for the molecular mechanism of FLS proliferation as well as provides new avenues for treatment of psoriatic disease and RA.

To cite this abstract, please use the following information:
Raychaudhuri, Siba P., Saxena, Ankit, Raychaudhuri, Smriti K.; Functional Significance of mTor in FLS Proliferation and Its Role in the Pathogenesis of Psoriatic Arthritis. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :1971
DOI: 10.1002/art.29736

Abstract Supplement

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