Heat stress induces alkaline phosphatase activity and heat shock protein 25 expression in cultured pulp cells

Lee M-W, Muramatsu T, Uekusa T, Lee J-H, Shimono M. Heat stress induces alkaline phosphatase activity and heatshock protein 25 expression in cultured pulp cells. InternationalEndodontic Journal, 41, 158–162, 2008. Aim To investigate the responses of cultured rat pulpcells to heat stress.Methodology Pulp cells were obtained from ratincisors and cultured at 37 C. The cells were culturedat 42 C for 30 min and then cultured at 37 C again.Morphology, alkaline phosphatase (ALP) activity andexpression of heat shock protein 25 (HSP25) wereinvestigated at 0, 1, 3, 5, 7, 10 and 14 days followingstimulation. As a control, the cells were maintained at37 C.Results Although there were few cells of apoptosisimmediately after heat stress, there were mitotic cellsfrom day 1 after heat stress. ALP activity in the heatstress group significantly increased at days 7 and 14compared with the control group (about 1.7-fold,P < 0.01, Friedman test). HSP25 expression increasedin both groups, with HSP25 in the heat stress groupbeing expressed earlier than in the control group, andnuclear localization of HSP25 was observed at days 0and 1 in heat-stressed cells.Conclusion These results suggest that heat stressnot only induces HSP25 but also enhances ALP activityin pulp cells.Keywords: alkaline phosphatase activity, dentalpulp, heat shock protein 25, heat stress.