NADPH Oxidases in Dental Cells: Potential Source of ROS

Reactive oxygen species (ROS) have been implicated in causing oxidative damage in dental cells related to dental adhesives, bleaching agents and periodontitis. Nox1, Nox2, Nox3 and Nox4, members of the Nox family of NADPH oxidases, are a source of ROS and play a role in cell proliferation and survival. Dental cells produce ROS; however, the expression profile of NADPH oxidases and whether they are regulated in dental cells has not been explored. Objective:To determine the expression of Nox mRNAs in cultured dental cells and test the effect of fetal bovine serum (FBS) that contains cytokines on Nox family gene expression. Methods:The endogenous pattern of Nox expression was analyzed using total RNA isolated from MEOE-3M (ameloblast), MO6-G3 (odontoblast) and MD10-F2 (dental pulp) cells grown in complete medium. To determine the effect of FBS on Nox expression, cells were initially cultured in serum-free (SF) medium, then incubated with increasing concentrations of FBS (0-10%) for 24 hrs. RT-PCR was performed using specific Nox primers. Results:MEOE-3M expressed Nox2 and Nox4 mRNAs with Nox4 being the most abundant. MD10-F2 expressed Nox4 and, to a lesser extent, Nox1 while differentiated MO6-G3 expressed only Nox4. Nox3 was not expressed by any dental cell type tested. When MEOE-3M cells were placed in SF medium, Nox1 expression was observed and incubation with FBS decreased Nox1 mRNA to non-detectable levels. In contrast, FBS up-regulated Nox4 expression in a dose-dependent manner. Conclusion:Results show, for the first time, that dental cells express NADPH oxidases, with Nox4 being the predominant form. Nox1 and Nox4 showed a distinct pattern of regulation by FBS suggesting that these enzymes may be differentially regulated by cytokines at sites of inflammation and injury. Elucidation of redox pathways in dental cells may provide novel strategies to reduce oxidant stress and enhance dental cell survival and tooth integrity. DE015857 (S.W.)