Hydrogen peroxide-induced liver cell necrosis is dependent on AP-1 activation

To deter-mine whether intracellular signaling events involved in apoptosis may also mediate necrosis, the role of the transcription factor AP-1 was investigated in a hepatoma cell model of cellular necrosis induced by oxidant stress. Treatment of the human hepatoma cell line HuH-7 with H₂O₂ caused dose-dependent necrosis as determined by light microscopy, fluorescent staining, and an absence of DNA fragmentation. H₂O₂ treatment led to increases in c-fos and c-jun mRNA levels, Jun nuclear kinase activity, and AP-1 DNA binding. AP-1 transcriptional activity measured with an AP-1-driven luciferase reporter gene was also increased. To determine whether this AP-1 activation contributed to H₂O₂-induced cell necrosis, HuH-7 cells were stably transfected with an antisense c-jun expression vector. Cells expressing antisense c-jun had decreased levels of AP-1 activation and significantly increased survival after H₂O₂ exposure. These data indicate that AP-1 activation occurs during oxidant-induced cell necrosis and contributes to cell death. Necrosis is therefore not always a passive process but may involve the activation of intracellular signaling pathways similar to those that mediate apoptosis.