Effects of fluoride on liver apoptosis and Bcl-2, Bax protein expression in freshwater teleost, Cyprinus carpio

Fish take up fluoride directly from water and are the target organisms for fluoride pollution in the aquatic ecosystems. This study was conducted to evaluate oxidative stress, histopathological changes, apoptosis and Bcl-2, Bax expression in the livers of the common carp (Cyprinus carpio) chronically exposed to fluoride. Our results showed that after 90 d of exposure, the inhibition of SOD, GSH activities and a dose-dependent stimulation of MDA levels in the liver tissues indicated that fluoride caused oxidative stress in the fish. Microscopic examinations showed that damages to the liver tissues and cell organelles in the liver tissues increased with exposure concentration. A positive correlation was observed between the apoptosis index and fluoride levels in the livers (r = 0.995). There was a negative correlation between the fluoride concentration of water and the expression of Bcl-2, Bcl-2/Bax (r = −0.98, r = −0.96). A positive correlation was showed between the fluoride concentration of water and the expression of Bax (r = 0.96) after 90 d of exposure. Our results suggested that the common carp could tolerate relatively high levels of fluoride but adverse effects of fluoride occurred in the livers of the fish after 90 d of exposure. The apoptosis of liver cells had an important causative role in the process of fluoride-induced pathological changes of liver.

► Fluoride caused oxidative stress in the livers of carp.
► Damages of fluoride to liver tissues and cell organelles increased.
► Oxidative damage promoted apoptosis after exposed to fluoride.
► The expression of Bcl-2 and Bcl-2/Bax decreased, the expression of Bax increased.