Attenuation of AH26-induced apoptosis by inhibition of SAPK/JNK pathway in MC-3T3 E1 cells

Introduction: The cytotoxicity of AH26, a resin-based sealer, induces apoptosis in osteoblast cells. However, the apoptosis pathway is not completely understood. This study examined the apoptosis pathway and its regulation of AH26 through mitogen-activated protein kinase (MAPKs), which may play a role in reducing the cytotoxicity of AH26. Methods: Using mouse osteoblasts cells (MC-3T3-E1), specimens of AH26 were eluted with the culture medium for 1, 3, 5, and 7 days. The cytotoxicity was tested using an 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. The induction of apoptosis was detected by Hoechst33258 staining and poly (ADP-ribose) polymerase (PARP) activation. The AH26-involved signal pathway was analyzed by immunoblotting with a specific antibody. Results: AH26 exhibited cytotoxicity toward MC-3T3-E1 cells, which resulted in mitochondria-mediated apoptosis, as confirmed by Bax expression and the displacement of cytochrome c from mitochondria to cytosol. As evidence of MAPKs activation, the cells treated with AH26 expressed stress-activated protein/c-jun N-terminal kinase (SAPK/JNK) and extracellular signal-regulated protein kinase (ERK1/2). SAPK/JNK activation appears to regulate apoptosis, whereas ERK activation protects cell survival. Conclusions: From these results, the toxicity of AH26 can be decreased by controlling the apoptosis signals. This approach might have potential applications for reducing the long-term stress of periapical tissue that improves endodontic treatment.