Fluvastatin (Fluv) is reported to induce apoptosis in rheumatoid arthritis (RA) synoviocytes through the blocking of protein geranylgeranylation. We report here our investigation of whether geranylgeranylacetone (GGA) induces cell death in RA synoviocytes. Synovial tissues were obtained from patients with RA at the time of total knee arthroplasty. Fibroblast-like synoviocytes (FLS) cultured in three passages were used for the experiments. The FLS were then cultured for 48 h in 48-well flat-bottomed plates containing various concentrations of GGA (0.1-4.0 microg/ml) and either 0.1 or 0.5 microM Fluv. We also examined the effect of GGA and Fluv in human fibroblasts from normal skin (CCD-25SK) and FLS from patients with osteoarthritis (OA). Cells demonstrating cell death were counted following trypan blue staining. In the absence of GGA, there was no apparent cell death, as evidence by trypan blue staining. Concentrations of GGA between 0.1 and 4.0 microg/ml induced cell death in RA FLS, but not in skin fibroblasts (CCD-25SK) nor OA FLS. The number of synoviocytes demonstrating cell death induced by 0.1 or 0.5 microM Fluv was significantly higher than that by the medium alone. In summary, we found that GGA induced cell death in RA FLS, suggesting that GGA may be a potential new therapeutic agent for RA as well as osteoporosis.