TNFα-induced necroptosis and autophagy via supression of the p38-NF-κB survival pathway in L929 cells.

Tumor necrosis factor alpha (TNFα) has been reported to induce necroptosis and autophagy, but its mechanisms remain unclear. In this study, we found that TNFα significantly induced necroptosis and autophagy in murine fibrosarcoma L929 cells. The necroptosis inhibitor necrostatin-1 (Nec-1) completely blocked TNFα-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 TNFα-induced necroptosis. The cytotoxicity of TNFα was accompanied by decreased expressions of phosphorylated p38 mitogen-activated protein kinase (p-p38) and nuclear factor-kappa B (NF-κB), and inhibition of p38 and NF-κB activation by chemical inhibitors or siRNA augmented these necroptotic and autophagic responses to TNFα in the cells. The pan-caspase inhibitor z-VAD-fmk (zVAD) exacerbated TNFα-induced necroptosis and autophagy. Combined treatment with TNFα and zVAD further decreased the expressions of p-p38 and NF-κB compared with TNFα alone treatment. Consequently, these results indicated that suppression of the p38-NF-κB survivial signaling pathway promoted necroptotic and autophagic cell death in TNFα-treated L929 cells.