Ceramide-induced nuclear translocation of NF-κB is a potential mediator of the apoptotic response to TNF-α in murine clonal osteoblasts

Osteoblasts are affected by TNF-α 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-α and 10 μmol/L of synthetic ceramide. The apoptotic signaling pathway activated by TNF-α 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-α treatment. Activation of nuclear factor-κB (NF-κB) was detected after TNF-α or synthetic ceramide stimulation. The concentration of NF-κB increased in the perinuclear region after 5 min of treatment and translocation into the nucleus was observed within 15 min of treatment. Degradation of IκBα/MAD-3 was observed after 60 min of ceramide treatment. These results indicate that nuclear translocation and activation of NF-κB through TNF-α generated ceramide may be one important apoptotic signaling pathway in MC3T3-E1 cells. The osteoblastic apoptosis triggered by TNF-α-generated ceramide may explain the inhibition of bone formation during severe bone inflammation.