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 during 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 mumol/L of synthetic ceramide. The apoptotic signaling pathway activated by TNF-alpha was examined in MC3T3-E1 cells. Endogenous cellular ceramide concentrations increased within 3 min, and comparable peak levels were observed for 30 min after TNF-alpha treatment. Activation of nuclear factor-kappa B (NF-kappa B) was detected after TNF-alpha or synthetic ceramide stimulation. The concentration of NF-kappa B increased in the perinuclear region after 5 min of treatment and translocation into the nucleus was observed within 15 min of treatment. Degradation of I kappa B alpha/MAD-3 was observed after 60 min of ceramide treatment. These results indicate that nuclear translocation and activation of NF-kappa B through TNF-alpha generated ceramide may be one important apoptotic signaling pathway in MC3T3-E1 cells. The osteoblastic apoptosis triggered by TNF-alpha-generated ceramide may explain the inhibition of bone formation during severe bone inflammation.