Sodium fluoride causes oxidative stress and apoptosis in cementoblasts

Toothpaste with fluoride concentration up to 5000 ppm are recommended to the patients who are susceptible to root caries; however, the effects of fluoride on cementoblasts have received less attention.

The OCCM-30 cells were exposed to 0,0.5, 5, 10 mM NaF respectively. A TUNEL (TdT-mediated dUTP-biotin nick end labeling) assay kit was used to detect the DNA fragmentation. Hoechst staining was used to determine changes of nuclear morphology. Real-time quantitative RT-PCR and Western blotting were performed to investigate the mRNA and protein expression of caspase-3,-8,-9, cleaved Poly (ADP-ribose) polymerase (PARP) and Fas-ligand (Fas-L), a ligand of death receptor. CA-DCF-DA [5 (6)-Carboxy-2',7'-dichlorofluorescein diacetate] was used to measure the generation of reactive oxygen species (ROS) in OCCM-30 cells after the NaF stimulation.

The results showed apoptotic morphological changes and DNA fragmentation in OCCM-30 cells exposed to high concentration of NaF. 10 mM NaF induced the expression of cleaved caspase-3,-8,-9 and cleaved Poly (ADP-ribose) polymerase (PARP). The mRNA expression of the Fas-L was also increased in cells exposed to 5 mM NaF. Furthermore, 10 mM NaF stimulation resulted in a significant generation of ROS in the OCCM-30 cells.

Our research demonstrated that apoptosis is activated by NaF in OCCM-30 cells through both of the extrinsic death receptor-dependent and oxidative stress-related intrinsic apoptotic pathway.

More consideration should be given about the fluoride concentration and the frequency of dental products when used to prevent the root caries for patients with gingival recession.