Sodium fluoride causes oxidative stress and apoptosis in cementoblasts

Objectives: 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.

Methods: 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.

Results: 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.

Conclusions: 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.

Clinical significance: 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.

Apoptosis; Caspase-3; Caspase-8; Caspase-9; Cementum; Sodium fluoride.