Apoptotic Effect of Geniposide on Fibroblast-Like Synoviocytes in Rats with Adjuvant-Induced Arthritis via Inhibiting ERK Signal Pathway In Vitro

Stimulating fibroblast-like synoviocyte (FLS) apoptosis in rheumatoid arthritis (RA) is a promising strategy for clinical treatment. Previous studies have confirmed that geniposide shows a certain anti-arthritic effect in vivo. However, whether geniposide can induce RA FLS apoptosis and the underlying mechanisms has not been elucidated. Herein, adjuvant-induced arthritis (AIA) in rat was induced and FLS was isolated from synovial tissues by tissue explant cultivation method. MTT assay, Hoechst staining, and flow cytometric apoptosis assay were applied to evaluate apoptotic effect of geniposide on AIA FLS. Bcl-2, Bax, and caspase 3 messenger RNA (mRNA) levels, and extracellular-signal-regulated kinases (ERKs) and phosphorylated ERK protein levels were examined by real-time PCR and western blot, respectively. We found that geniposide dose-dependently inhibited AIA FLS proliferation in vitro. AIA FLS treated with geniposide displayed typical apoptotic morphological characteristics including nuclear shrinkage and chromatin condensation. Flow cytometric apoptosis assay indicated that geniposide significantly increased the apoptosis rate of AIA FLS. Additionally, geniposide treatment on AIA FLS decreased Bcl-2 mRNA level and increased Bax and caspase 3 mRNA levels, accompanied by reduced protein levels of phosphorylated-ERK1/2, without affecting total ERK1/2. In conclusion, geniposide effectively induces AIA FLS apoptosis through regulating the apoptosis-related gene expressions and inhibiting ERK signal pathway.