APOPTOSIS INDUCTION IN SYNOVIAL FIBROBLASTS BY CERAMIDE - IN-VITRO AND IN-VIVO EFFECTS

Several lipid second messengers are important mediators of extracellul ar signals. Among them ceramide, which is formed by cell membrane sphi ngomyelin, influences the apoptotic signal pathway through Pas antigen , We examined the apoptotic effect of cell-permeable CP-ceramide on rh eumatoid synovial fibroblasts in vitro and in vivo. Exposure of cultur ed human rheumatoid synovial fibroblasts to CP-ceramide for 24 hours p roduced internucleosomal DNA fragmentation and morphologic changes cha racteristic of apoptosis, This C2-ceramide-mediated apoptosis was dose dependent as confirmed by analysis of cytosolic oligonucleosome-bound DNA of treated synovial fibroblasts, We also demonstrated that intraa rticular administration of C2-ceramide into Fas-deficient MRL lpr/lpr mice produced a profound reduction of synovial hyperplasia within 24 h ours, In situ nick end labeling analysis confirmed the induction of ap optosis in synovial lining cells. Our results indicate that CS-ceramid e may function as a potent inducer of apoptosis in the synovium and su ggest that pharmacologically-induced apoptosis may be useful as a new therapeutic modality for rheumatoid arthritis.