157 Sodium Fluoride Exposure Exerts Toxic Effects on Porcine Oocyte Maturation

Abstract

Excessive long-term fluoride intake is associated with several health problems, including infertility. However, limited information is available on the toxic effects of fluoride exposure on the female reproductive system, especially oocyte maturation. In this study, we investigated the toxic effect of sodium fluoride (NaF) exposure on porcine oocyte maturation and its possible underlying mechanisms. The level of reactive oxygen species, glutathione (GSH), mitochondrial membrane potential, apoptosis, and DNA damage and cathepsin B in the blastocysts were observed by staining with 2′,7′-dichlorodihydrofluorescein diacetate (H2DCF-DA), 4-chloromethyl-6.8-difluoro-7-hydroxycoumarin (CMF₂HC, Invitrogen, Carlsbad, CA, USA), 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethyl-imidacarbocyanine iodide (JC-1), annexin V-fluorescein isothiocyanate (FITC) apoptosis detection kit, anti-γH2A.X (Ser139) and Magic Red cathepsin B assay kit, respectively. Data obtained from the experimental groups were compared using Student’s t-test. Our results showed that treatment with 60, 100, and 150 μg mL⁻¹ NaF significantly decreased the degree of cumulus cell expansion (CEI: 2.64 ± 0.27, 1.32 ± 0.52, and 0.57 ± 0.15 v. 3.58 ± 0.19; P < 0.05) and the rate of maturation (74.33% ± 4.32%, 57.83% ± 7.14%, 44.00% ± 5.93% v. 84.50% ± 3.62%; P < 0.05) in a dose-dependent manner during in vitro maturation for 44 h. Cell cycle analysis showed that NaF exposure blocked meiotic resumption, disturbed spindle dynamics, disrupted chromosome separation, and increased aneuploidy in porcine oocytes. Moreover, NaF exposure disturbed mitochondrial function, triggered DNA damage response, and induced early apoptosis in porcine oocytes. Exposure to NaF also induced oxidative stress, decreased GSH level, and increased cathepsin B activity in and impaired the further development potential of porcine oocytes, as indicated by a decrease in blastocyst formation rate, increase in apoptosis, and inhibition of cell proliferation. Together, these results indicate that NaF exposure impairs the maturation capacity of porcine oocytes by inhibiting cumulus cell expansion, disturbing cytoskeletal dynamics, and blocking nuclear and cytoplasmic maturation, thus decreasing the quality and affecting the subsequent embryonic development potential of porcine oocytes.