Anti-Fas IgM monoclonal antibody (anti-Fas mAb) effect on haemophilic arthropathy (HA) synoviocytes

Abstract

Background: Haemophilic arthropathy (HA), which shares some clinical and biological injury characteristics with rheumatoid arthritis (RA), is characterized by chronic proliferative synovitis and cartilage destruction. Anti-Fas mAb specifically targets the Fas molecule, which is expressed and activated on the cell surface of inflammatory synovial cells and plays a key role for induction of apoptosis. Caspases are the final executioners of apoptosis and their activation requires proteolytic processing of inactive zymogen into activated fragments. Aim: To evaluate the effects of anti-Fas mAb on HA synoviocytes and its capacity of inducing apoptosis analysing caspase 3 activity. Methods: HA synoviocytes were incubated with IgM 1000 ng/ml (control), TNFalphalpha 10 ng/ml, FGF 10 ng/ml, CH11 100 ng/ml (positive control of apoptosis) with or without anti-Fas mAb at different concentrations (from 0,1 to 1000 ng/ml) for 24 h. RA and healthy synoviocytes were used as controls. To measure cell proliferation/citotoxicity, the WST-1 assay has been performed. Caspase 3 activity has been evaluated with ELISA kit and western blot. Results: Anti-Fas mAb induced a citotoxic effect in HA (p < 0,001 for any dose), healthy (p < 0,001 at 100 and 1000 ng/ml) and RA synoviocytes (p < 0,05 for any dose) reaching a maximum effect at 1000 ng/ml. After stimulation with anti-Fas mAb combined with TNFalphalpha, there was a citotoxic effect on healthy (p < 0,001 at 10, 100, 1000 ng/ml anti-Fas mAb), RA (p < 0,001 for any dose) and HA synoviocytes (p < 0,005 at 1, 10, 100 and 1000 ng/ml anti-Fas mAb). After stimulation with anti-Fas mAb combined with FGF, there was a citotoxic effect on healthy, RA and HA synoviocytes (p < 0,001 for any dose). Caspase 3 levels were increased in HA synoviocytes after anti-Fas mAb treatment in a dose-dependent manner, even after co-stimulation with TNFalphalpha (p < 0,001 for any stimulus). CH11 induced an increase of caspase 3 levels in HA synoviocytes more than RA synoviocytes. Western blot showed that HA synoviocytes had higher levels of activated caspase 3 compared to RA synoviocytes after stimulation with Anti-Fas mAb, CH11 and costimulation with TNFalphalpha. Conclusion: Anti-Fas mAb has a dose-dependent citotoxic effect on HA synoviocytes, even when associated with TNFalphalpha and FGF. Anti-Fas mAb is effective in increasing caspase 3 levels in HA synoviocytes in a dosedependent manner. HA synoviocytes show higher levels of activated caspase 3 compared to RA synoviocytes. Our results suggest that anti-Fas IgM mAb may favour the induction of apoptosis in HA synoviocytes.