Hyperosmotic Stress Induces Cell Death in an Odontoblast-lineage Cell Line

Introduction: Osmotic stress is one of the stimulations related to dental pain caused by caries or dentin hypersensitivity. The mechanism of osmotic-induced dental pain is not completely understood. The purpose of this study was to examine the responses of odontoblasts under sucrose-induced hyperosmotic stress. Methods: We used an odontoblast-lineage cell (OLC) line in our experiments. OLCs were stimulated with sucrose to produce hyperosmotic stress. The expressions of dentin sialophosphoprotein (DSPP) and dentin matrix protein 1 (DMP 1) were detected by using reverse transcriptase polymerase chain reaction assay. The cell viability of OLCs was detected by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium assay. The responses accompanied with cell death were detected by using 4-6-diamidino-2-phenylindole staining, Western blotting of caspase-3, and annexin V assay. The expression of mitogen-activated protein kinases (MAPKs) was detected by using Western blot analysis. Results: DSPP and DMP 1 were not affected by hyperosmotic stress in OLCs. Cell viability decreased over 700 mOsm for 3 hours of cell culture. The shapes of cells and nuclei became irregular and vacuolar under hyperosmotic stress. The expression of cleaved caspase-3 was increased after treatment with hyperosmotic stress. Some propidium iodide-positive cells were detected in flow cytometry analysis. Phosphorylation of 3 MAPKs was induced by hyperosmotic stress. Inhibitors of 3 MAPKs inhibited the hyperosmotic stress-induced decline in cell viability at 500 and 700 mOsm. Conclusions: Hyperosmotic stress induces cell death of OLCs with sucrose through a MAPK pathway. (J Endod 2012;38:931-935)