CERAMIDE-INDUCED NUCLEAR TRANSLOCATION OF NF-KAPPA-B IS A POTENTIAL MEDIATOR OF THE APOPTOTIC RESPONSE TO TNF-ALPHA IN MURINE CLONAL OSTEOBLASTS

Osteoblasts are affected by TNF-alpha overproduction by immune cells d uring inflammation. We demonstrate that apoptosis is induced in murine osteoblastic MC3T3-E1 cells by exceeding the concentrations 100 units /mL of TNF-alpha and 10 mu mol/L of synthetic ceramide. The apoptotic signaling pathway activated by TNF-alpha was examined in MC3T3-E1 cell s. Endogenous cellular ceramide concentrations increased within 3 min, and comparable peak levels were observed for 30 min after TNF-alpha t reatment. Activation of nuclear factor-kappa B (NF-kappa B) was detect ed after TNF-alpha or synthetic ceramide stimulation. The concentratio n of NF-kappa B increased in the perinuclear region after 5 min of tre atment and translocation into the nucleus was observed within 15 min o f treatment. Degradation of I kappa B alpha/MAD-3 was observed after 6 0 min of ceramide treatment. These results indicate that nuclear trans location and activation of NF-kappa B through TNF-alpha generated cera mide may be one important apoptotic signaling pathway in MC3T3-E1 cell s. The osteoblastic apoptosis triggered by TNF-alpha-generated ceramid e may explain the inhibition of bone formation during severe bone infl ammation.