TNF-α Protects Human Primary Articular Chondrocytes from Nitric Oxide-Induced Apoptosis Via Nuclear Factor-κB

Abstract

SUMMARY:TNF-␣ plays a key role in rheumatoid arthritis, but its effect on chondrocyte survival is still conflicting. In the present study, we tested how TNF-␣ 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-␣ for 24 hours and then treated with the proapoptotic NO donor sodium-nitro-prusside (SNP) for an additional 24 hours. TNF-␣ pretreatment markedly protected chondrocytes from SNP-induced cell death. Preincubation of chondrocytes with TNF-␣ inhibited both SNP-induced high-molecular weight DNA fragmentation and annexin V-FITC binding. Of interest, TNF-␣ induced persistent nuclear factor-B (NF-B)-DNA binding activity even in the presence of SNP, mirroring apoptosis protection effects. Both the TNF-␣ antiapoptotic effect and NF-B-DNA binding activity were significantly inhibited by NF-B inhibitors, Bay 11-7085, MG-132, and adenovirus-expressing mutated IB-␣. Phosphatidylinositol-3 kinase inhibitor LY 294002 also markedly inhibited the antiapoptotic effect of TNF-␣. In primary chondrocytes, TNF-␣ 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-␣ protective effect. We therefore conclude that TNF-␣-mediated protection of chondrocytes from NO-induced apoptosis acts through NF-B and requires Cox-2 activity. (Lab Invest 2002, 82:1661-1672.C artilage loss associated with rheumatoid arthritis (RA) leads to irreversible joint dysfunction. Cartilage destruction results from metalloproteinasedependent matrix degradation and nitric oxide (NO)-induced chondrocyte apoptosis (Amin et al, 1999;Blanco et al, 1995;Lotz et al, 1999;Sakurai et al, 1995). Extracellular matrix modifications may also lead to chondrocyte apoptosis, as was shown in collagen II-deficient mice (Yang et al, 1997). Because chondrocytes are the only cells in the cartilage and the only matrix producers, their survival is the focus of many recent investigations (Blanco et al, 1998;Colnot et al, 2001;Hashimoto et al, 1998;Kim and Song, 1999).The proinflammatory cytokines TNF-␣ and IL-1␤ are indirectly responsible for cartilage degradation and chondrocyte death because they stimulate the synthesis and release of metalloproteinases and NO from monocytes-macrophages, synoviocytes, and chondrocytes. In vitro, however, conflicting results have been reported about the effect of proinflammatory cytokines on chondrocyte apoptosis (Aizawa et al, 2001;Blanco et al, 1995;Fischer et al, 2000;Kuhn et al, 2000;Lotz et al, 1999).Many TNF-␣ biologic activities are mediated by nuclear factor-B (NF-B). NF-B is maintained in the cytoplasm of most cell types under an inactive form associated with an inhibitor from the IB family, such as the ubiquitous IB-␣ protein. After cellular stimulation with TNF-␣, NF-B nuclear activity is rapidly induced as a consequence of IKK kinase activation and IB-␣ phosphory...

Typical cell signaling response to ionizing radiation: DNA damage and extranuclear damage

“…Attenuation of the apoptotic pathway may largely be attributed to the capacity of TNF-α to initiate a preferred NF-κB-dependent signaling. Recently this mechanism has been demonstrated both in vitro using human primary cells [35] and in vivo in hepatic ischemiareperfusion [36] . The initial steps in TNF-α pathway to activate NF-κB are fairly well understood [37] .…”

15-Deoxy-Δ12,14-prostaglandin J2 Inhibits Bay 11-7085-induced Sustained Extracellular Signal-regulated Kinase Phosphorylation and Apoptosis in Human Articular Chondrocytes and Synovial Fibroblasts

“…Phosphorylation in Human Chondrocytes-We and others showed previously that inhibition of NF-B by adenovirusexpressing mutated IB-␣ or by proteasome inhibitor increases human chondrocyte sensitivity to apoptosis (7,8). However, only BAY11-7085, not MG-132 or adenovirus-expressing mutated IB-␣, is itself a proapoptotic agent for chondrocytes.…”

“…NF-B activity, however, also has a protective role against apoptosis of primary (7) and dedifferentiated (8) chondrocytes. Although the proteasome and NF-B inhibitor MG-132 merely sensitized chondrocytes to induced apoptosis, NF-B inhibitor BAY 11-7085 was able to cause chondrocyte apoptosis directly (7). We thus searched for additional pathways triggered by BAY 11-7085 and for an antiinflammatory molecule able to protect chondrocytes from BAY 11-7085-induced apoptosis.…”

Differential Signalling Through ALK-1 and ALK-5 Regulates Leptin Expression in Mesenchymal Stem Cells

“…Informed consents were obtained, and experiments were approved by the ethics committee of our academic hospital (CHU, Liège, Belgium). SVF (n = 10) were isolated as previously explained [16,17]. MSC were cultured in a complete medium consisting of Dulbecco's modified Eagle's medium (DMEM) medium (Cambrex Bio Science), with l-glutamine (2 mM), streptamycin (100 mg/mL), and penicillin (100 U/mL) (BioWhittaker), and supplemented with 10% fetal bovine serum (FBS) (Lonza).…”