TNF-α protects human primary articular chondrocytes from nitric oxide-induced apoptosis via nuclear factor-κB

Abstract

TNF-α plays a key role in rheumatoid arthritis, but its effect on chondrocyte survival is still conflicting. In the present study, we tested how TNF-α influences chondrocyte survival in response to nitric oxide (NO)-related apoptotic signals, which are abundant during rheumatoid arthritis. Human primary articular chondrocytes or cartilage explants were pretreated with TNF-α for 24 hours and then treated with the proapoptotic NO donor sodium-nitro-prusside (SNP) for an additional 24 hours. TNF-α pretreatment markedly protected chondrocytes from SNP-induced cell death. Preincubation of chondrocytes with TNF-α inhibited both SNP-induced high-molecular weight DNA fragmentation and annexin V-FITC binding. Of interest, TNF-α induced persistent nuclear factor-κB (NF-κB)-DNA binding activity even in the presence of SNP, mirroring apoptosis protection effects. Both the TNF-α antiapoptotic effect and NF-κB-DNA binding activity were significantly inhibited by NF-κB inhibitors, Bay 11 -7085, MG-132, and adenovirus-expressing mutated IκB-α. Phosphatidylinositol-3 kinase inhibitor LY 294002 also markedly inhibited the antiapoptotic effect of TNF-α In primary chondrocytes, TNF-α induced expression of the antiapoptotic protein Cox-2, which persisted in the presence of SNP, and a specific Cox-2 inhibitor significantly blocked the TNF-α protective effect. We therefore conclude that TNF-α-mediated protection of chondrocytes from NO-induced apoptosis acts through NF-κB and requires Cox-2 activity.