The Induction of Heme Oxygenase-1 Modulates Bismuth Oxide-induced Cytotoxicity in Human Dental Pulp Cells

The aim of this study was to investigate the cytotoxic and nitric oxide (NO)-inducing effects of bismuth oxide (Bi2O3)-containing Portland cement (BPC) on human dental pulp cells. We also assessed whether heme oxygenase-1 (HO-1) is involved in BPC-induced cytotoxicity in dental pulp cells. Cytotoxicity and NO production induced by BPC were higher than those induced by Portland cement at 12 and 24 hours, and the former gradually decreased to the level observed for PC. HO-1 and inducible nitric oxide synthase messenger RNA expressions in the BPC group showed maximal increase at 24 hours, and it gradually decreased with increasing cultivation time. Hemin treatment reversed the BPC-induced cytotoxicity, whereas zinc protoporphyrin IX treatment increased the cytotoxicity. These results suggested that NO production by BPC correlates with HO-1 expression in dental pulp cells. Moreover, BPC-induced HO-1 expression in dental pulp cells plays a protective role against the cytotoxic effects of BPC.