The inhibitional effect of calreticulin on tumour necrosis factor-related apoptosis-inducing ligand-mediated T cell apoptosis in rheumatoid arthritis

Abstract

Objective To investigate the anti-apotoptic effects of calreticulin (CRT) on tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated T cells apoptosis in rheumatoid arthritis (RA). Methods Levels of CRT in the synovial fluid from patients with RA (23 cases) and osteoarthritis (OA) (36 cases) were detected with enzyme-linked immunosorbent assay (ELISA); the expression and localization of CRT in RA and OA synovial tissue were detected by immunohistochemistry. The capacity of CRT binding to TRAIL was measured by ELISA; the effect of TRAIL on Jurkat T cell proliferation was determined by the methylthiazolyl tetrazolium (MTT) assay, CRT on TRAIL-mediated apoptosis by flow cytometry analysis. The t-test and SNK-q test were used for statistical analysis. Results ① CRT were significantly up-regulated both in synovial fluid and tissue from RA than those from OA [ (5.6±2.5) ng/ml and (3.2±1.3) ng/ml, t=6.233, P<0.05; 32 787±18 294 and 7 945±2 765, t=15.662, P<0.01]. ② Binding rate of CRT-TRAIL increased to (117±9)% and(155±14)% with TRAIL stimulation (1 μg/ml and 2 μg/ml, respectively) compared to the controls (q=3.858, 8.647; P<0.01). ③ The proliferation of Jurkat T cell was inhibited after co-cultured with TRAIL, at 12 hours, 100ng/ml TRAIL treated cell showed a significant decreased survival rate and at 24 hours(q=7.532, P<0.05), and the similar results were shown both with 50 ng/ml and 100 ng/ml TRAIL (q=9.211, 12.879; P<0.01). ④ T cell early apoptosis was suppressed by the combination of CRT and TRAIL: with CRT (4, 8 and 16 ng/ml), the corresponding apoptotic rates were (30.7±1.1)%, (24.5±1.1)% and (22.3±1.5)% respectively, which showed significant differences compared with the control group (32.5±1.4)% (q=3.82, 12.17, 15.39; P<0.05). Conclusion Increased levels of CRT are detected in the synovial fluid and tissue in RA; and CRT is expressed in inflammatory cells in synovial tissue from RA patients. In addition, CRT can partly inhibit TRAIL-mediated apoptosis of Jurkat T cells via binding to TRAIL, which may suggest its potential role in the pathogenesis especially in inflammation of RA. Key words: Arthritis, rheumatoid; Calreticulin; Tumor necrosis factor-related apoptosis-inducing ligand