Self-recovery Study of Fluoride-Induced Ferroptosis in the Liver of Zebrafish (danio Rerio)

Ferroptosis plays a key role in fluorosis in aquatic organisms, but whether it is involved in fluoride-induced liver damage remains unclear. Previous studies have indicated that fluoride toxicity has the reversible tendency, but the mechanism of self-recovery after fluorosis in aquatic animals has not been elucidated. In this study, adult zebrafish and embryos were exposed to 0, 20, 40, 80 mg/L of fluoride for 30, 60 and 90 d and 3, 4 and 5 d post-fertilization (dpf), respectively. After 90 d, adult zebrafish were transferred to clean water for self-recovery of 30 d. The results showed that fluoride induced the prominent histopathologial changes in liver of adults, and the developmental delay and dark liver area in larvae. Fluoride significantly increased the iron overload, while decreased the expression levels of transferrin (tf), transferrin receptor (tfr), ferroportin (fpn), membrane iron transporter (fpn), and ferritin heavy chain (fth) in adults and larvae. Fluoride also induced the oxidative stress in adults and larvae by increasing the levels of reactive oxygen species (ROS) and malondialdehyde (MDA), while decreasing the glutathione (GSH) content and the levels of glutathione peroxidase 4 (gpx4) and solute carrier family 7 member 11 (slc7a11). Self-recovery relieved fluoride-induced ferroptosis by reducing the histopathological damage and oxidative stress, reversing the expression levels of fth and slc7a11, Fe2+ metabolism and GSH synthesis. Lipid peroxidation and Fe2+ metabolism may be the key factor in alleviating effects of self-recovery on fluoride toxicity. Moreover, males are more sensitive than females. Our results provide a theoretical basis for studying the alleviating effects of self-recovery on fluoride toxicity and the underlying mechanism of its protective effect.