Effects of sodium fluoride on hyperactivation and Ca2+ signaling pathway in sperm from mice: an in vivo study

Sperm hyperactivation is crucial for a successful fertilization; however, the influence of fluoride (F) to hyperactivation is still in its infancy. The purpose of this study was to investigate the effect of sodium fluoride (NaF) on sperm hyperactivation, Ca2+/CALM-CAMK2 signaling, and CatSper1 and CatSper2 mRNA expression in mice sperm. Adult male Kunming mice were administrated with 30, 70, and 150 mg NaF/l (corresponding to 2.84 +/- 0.29, 6.28 +/- 0.61, and 14.18 +/- 1.00 mg F/kg body weight per day) through drinking water for 49 days. The results showed that NaF reduced the sperm hyperactivated motility in a dose-dependent manner. Compared with the controls, intracellular Ca2+ concentration and CAMK2 protein were significantly decreased in mice treated with 70 and 150 mg NaF/l, while no effect on CALM was determined in all treatment groups. Furthermore, decreased sperm CatSper1 mRNA expression was also observed in response to middle and higher doses of NaF (70, 150 mg/l) with comparison to the control group, whereas no change in the mRNA expression of CatSper2 was detected in NaF administrated groups. Treatment with 30 mg NaF/l exhibited slight effects on the above indexes with no statistical difference. These findings indicated that exposure to 70 and 150 mg/l NaF for 49 days could result in low hyperactivation via alteration of Ca2+ signaling pathway involving CatSper1 in sperm from mice.