Immunotoxic effects of fluoride on hemocytes of Venerupis philippinarum

The increasing levels of fluoride in the aquatic environments is a matter of concern for freshwater and marine ecosystems. Although data on fluoride toxicity to aquatic organisms are increasing in the scientific literature, few data are available regarding the effects, at cellular level, on freshwater or marine invertebrates. In the present paper, we present data on the effects of in vitro exposure to sodium fluoride (NaF) on the hemocytes of the Manila clam Venerupis philippinarum. Results indicate that NaF reduces cell spreading and phagocytosis in a dose-dependent way, through the alteration of the actin cytoskeleton. In addition, the compound decreases the stability of the lysosomal membranes, as revealed by the Neutral Red assay. In addition, the observed increase in hemocyte mortality and the parallel rise in DNA fragmentation inside their nuclei, as revealed by the TUNEL assay, suggest a NaF-dependent induction of apoptosis, in accordance with the capability of NaF to induce oxidative stress, a known cause of apoptosis, As hemocytes represent the major defence weapon against foreign, potentially pathogenic microbes, the above results indicate a negative effect of NaF on the immune status of V. philippinarum.