2-hydroxy ethylmethacrylate activates the extrinsic and intrinsic apoptotic processes through mitogen-activated protein kinase signaling pathways in cementoblasts - An in vitro study

Background/purpose 2-Hydroxy ethylmethacrylate (HEMA) is a hydrophilic monomer that may be released from composite resin after polymerization. Little is known about the adverse effects of HEMA on cementoblasts. Therefore, this study investigated the possible mechanisms underlying the cytotoxicity engendered by HEMA on murine cementoblast cell line (OCCM.30). Materials and methods OCCM.30 cells were cultured with HEMA (0, 2, 4, and 8 mM) for 24 h. Cell viability was determined by microculture tetrazolium assay. Flow cytometry with annexin V-FITC/propidium iodide apoptosis staining was conducted to evaluate the cell cycle distribution and the type of cell death. Western blot was employed to investigate the caspase-mediated apoptotic cell death and mitogen-activated protein kinase (MAPK) pathways. Results The concentrations of HEMA≧4 mM significantly inhibited cell viability in a concentration-dependent manner ( P < 0.05). HEMA dose-dependently induced apoptosis by the increase of sub-G1 population, early apoptotic cells, and later apoptotic cells, respectively. HEMA-induced apoptotic mechanisms were found to activate executioner caspase-3, extrinsic caspase-8, and intrinsic caspase-9, respectively ( P < 0.05). In addition, HEMA increased the phosphorylation of extracellular signal-regulated protein kinases (ERK), c-Jun N-terminal kinases (JNK), and p38, respectively ( P < 0.05). Using inhibitors of ERK (U0128), JNK (JNK-in-8), and p38 (SB203580), HEMA’s increases of cleaved caspases-3, -8, and -9 could be expectedly suppressed ( P < 0.05). Conclusion The results demonstrated that HEMA decreased cell viability and induced caspase-mediated apoptosis in cementoblast by activating both extrinsic and intrinsic apoptotic pathways through ERK, JNK, and p38 signaling. These results may provide the preliminary information for the development of less cytotoxic composite resin.