TNFα-Induced Necroptosis and Autophagy via Supression of the p38-NF-κB Survival Pathway in L929 Cells

Tumor necrosis factor alpha (TNF alpha) has been reported to induce necroptosis and autophagy, but its mechanisms remain unclear. In this study, we found that TNF alpha significantly induced necroptosis and autophagy in murine fibrosarcoma L929 cells. The necroptosis inhibitor necrostatin-1 (Nec-1) completely blocked TNF alpha-induced necroptosis and autophagy, but inhibition of autophagy with 3-methyladenine (3MA) or Beclin 1 small interfering RNA (siRNA) promoted necroptosis, indicating that autophagy acted as a negative regulator of TNF alpha-induced necroptosis. The cytotoxicity of TNF alpha was accompanied by decreased expressions of phosphorylated p38 mitogen-activated protein kinase (p-p38) and nuclear factor-kappa B (NF-kappa B), and inhibition of p38 and NF-kappa B activation by chemical inhibitors or siRNA augmented these necroptotic and autophagic responses to TNF alpha in the cells. The pan-caspase inhibitor z-VAD-fmk (zVAD) exacerbated TNF alpha-induced necroptosis and autophagy. Combined treatment with TNF alpha and zVAD further decreased the expressions of p-p38 and NE-kappa B compared with TNF alpha alone treatment. Consequently, these results indicated that suppression of the p38 NE-kappa B survivial signaling pathway promoted necroptotic and autophagic cell death in TNF alpha-treated L929 cells. [Supplementary Figures: available only at http://dx.doi.org/10.1254/jphs.11105FP]