Tumor necrosis factor-α protects synovial cells from nitric oxide induced apoptosis through phosphoinositide 3-kinase Akt signal transduction

Objective. To investigate the anti-apoptotic role of tumor necrosis factor-α (TNF-α) and its signaling pathways in cultured human fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis. Methods. FLS were cultured in Dulbecco's modified Eagle's medium. Apoptotic cells were identified by TUNEL assay and Hoechst staining. Cell viability was determined by the MTT method. Expression of phospho-Akt and phospho-BAD was measured by Western blotting. Results. A 24-h TNF-α treatment prevented FLS apoptosis induced by nitric oxide (NO) donor sodium nitroprusside dihydrate (SNP), achieving 70% protection. At 1-10 ng·ml ^-1 concentrations, TNF-α induced phosphorylation of Akt and BAD in a time and concentration-dependent manner. This effect was blocked by treatment with both LY294002 and nuclear factor-κB inhibitor pyrrolidine-dithiocarbamate. Conclusion. TNF-α has an anti-apoptotic effect in human FLS. Activation of Akt and BAD may have an important role in this process.