Overgrowth of rheumatoid synoviocytes, which results in joint destruction, is due to impaired balance between cell proliferation and cell death (apoptosis). Ceramide is an important lipid messenger involved in mediating a variety of cell functions including apoptosis. We investigated the effects of ceramide on growth-promoting anti-apoptotic signals in rheumatoid synovial cells. Human synovial cells isolated from patients with rheumatoid arthritis (RA) were stimulated with platelet-derived growth factor (PDGF) in the presence or absence of C2-ceramide. The kinase activity of Akt, MEK, and ERK1/2 was analyzed in PDGF-stimulated synovial cells by Western blot analysis. Pretreatment with C2-ceramide completely inhibited PDGF-induced cell cycle progression of rheumatoid synovial cells. PDGF stimulation induced phosphorylation and activation of Akt, MEK, and ERK1/2 in rheumatoid synovial cells. C2-ceramide inhibited the activation of Akt, MEK and ERK1/2 in PDGF-stimulated synovial cells. Our data demonstrated that inhibition of anti-apoptotic kinases, such as Akt and ERK1/2, may play an important role in ceramide-mediated apoptosis of rheumatoid synovial cells.
Copyright 2000 Academic Press.