Sodium azide induces necrotic cell death in rat squamous cell carcinoma SCC131

Sodium azide (NaN₃) is widely used in industry and agriculture, and also in laboratories as a potent preservative. NaN₃ induces cell death when applied to cultured cells. However, whether the mode of cell death is apoptosis or necrosis remains a subject of debate. There have been no previous reports on NaN₃-induced cell death in squamous cell carcinoma (SCC), and so we studied the mode of cell death induced by NaN₃ using the rat SCC cell line, SCC131. In this experiment, SCC131 cells died 48–72 h after NaN₃ treatment with concentrations greater than 5 mM. The NaN₃ treatment reduced the mitochondrial membrane potential and ATP content. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and DNA ladder detection assay indicated that no DNA fragmentation occurred. In addition, phosphatidyl serine did not appear on the cell surface, according to the findings of dye-uptake bioassay and flow cytometric analysis of Annexin V labeling. Electron microscopic analysis revealed that the NaN₃-treated cells showed mitochondrial swelling and rupture of the cell membrane. In conclusion, NaN₃ induces necrotic cell death in SCC131. This experimental model may be used in the study of necrotic cell death.