The proinflammatory cytokine tumor necrosis factor (TNF)-α has been implicated in the attenuation of neutrophil spontaneous apoptosis during sepsis. Antiapoptotic signaling is principally mediated through the p60TNF receptor (p60TNFR). In neutrophils, TNF-α is an incomplete secretagogue and requires input from a ligated integrin(s) for neutrophil activation. In adherent neutrophils, TNF-α triggers association of both protein kinase C (PKC)-δ and phosphatidylinositol (PI) 3-kinase with the p60TNFR. In this study, a role for PKC-δ and PI 3-kinase in TNF-α-mediated antiapoptotic signaling was examined. TNF-α inhibited spontaneous apoptosis in fibronectin-adherent neutrophils, and this antiapoptotic signaling was blocked by the PKC-δ inhibitor rottlerin, but not by an inhibitor of Ca2+-dependent PKC isotypes, Go-6976. Inhibition of PI 3-kinase by LY-294002 also inhibited TNF-α-mediated antiapoptotic signaling. Cycloheximide blocked TNF-α-mediated antiapoptotic signaling, suggesting protein synthesis is required. Inhibition of either PKC-δ or PI 3-kinase attenuated TNF-α-mediated activation of the antiapoptotic transcription factor NFκB. Thus both PKC-δ and PI 3-kinase have essential roles in TNF-α-mediated antiapoptotic signaling in adherent neutrophils.
Bcl-2 Activates the Transcription Factor NFκB through the Degradation of the Cytoplasmic Inhibitor IκBα
