Sirt3-mediated mitochondrial dysfunction is involved in fluoride-induced cognitive deficits.

Excessive fluoride is capable of inducing cognitive deficits, but the mechanisms remain elusive. This study aimed to investigate the effects and underlying mechanisms of fluoride on mitochondrial dysfunction and neurobiological alterations, as well as cognitive impairment. C57BL/6 mice were orally administered 25, 50, and 100 mg/L NaF for 90 days. Cultured human neuroblastoma SH-SY5Y cells were exposed to NaF (110 mg/L) for 24 h in the presence or absence of Sirt3 overexpression. The results demonstrated that chronic exposure to high fluoride induced cognitive deficits and neural/synaptic injury in mice. Fluoride reduced mitochondrial antioxidant enzyme activities and elevated SOD2 acetylation by downregulating Sirt3 expression in the brains of mice and NaF-treated SH-SY5Y cells. Moreover, fluoride lowered mtDNA transcription and induced mitochondrial dysfunction along with increased FoxO3A acetylation in the brains of mice and NaF-treated SH-SY5Y cells. Subsequent experiments revealed that overexpression of Sirt3 significantly attenuated the adverse effects of fluoride on radical scavenging capabilities and mtDNA transcription, as well as mitochondrial function in SH-SY5Y cells. These results suggest that chronic long-term fluoride exposure evokes neural/synaptic injury and cognitive impairment through mitochondrial dysfunction and its associated oxidative stress, which is, at least partly, mediated by Sirt3 inhibition in the mouse brain.