Subacute exposure to Roundup® changes steroidogenesis and gene expression of the glutathione-glutaredoxin system in rat ovaries: Implications for ovarian toxicity of this glyphosate-based herbicide.

Studies have indicated that glyphosate induces endocrine disruption and may adversely affect the male reproductive system. However, evidence of its effects on ovarian function is poorly understood so far, making further studies necessary on the mechanisms of the glyphosate toxicity in the female reproductive system. The aim of this work was to evaluate the effect of a subacute exposure (28 days) to the glyphosate-based formulation Roundup® (1.05, 10.5 and 105 µg/kg b.w. of glyphosate) on steroidogenesis, oxidative stress, systems involved in cell redox control and histopathological parameters in rat ovaries. Hence we quantify plasma estradiol and progesterone by chemiluminescence; non-protein thiol levels, TBARS, superoxide dismutase and catalase activity by spectrophotometry; gene expression of steroidogenic enzymes and redox systems by real-time PCR; and ovarian follicles by optical microscopy. Our results demonstrated that oral exposure increased progesterone levels and the mRNA expression of 3ß-hydroxysteroid dehydrogenase. Histopathological analysis revealed a decrease in the number of primary follicles and an increase in the number of corpus luteum in rats exposed to Roundup®. An imbalance of the oxidative status was also evidenced by decreasing the catalase activity at all groups exposed to the herbicide. Increased lipid peroxidation and gene expression of glutarredoxin and decreased of glutathione reductase were also observed. Our results indicate that Roundup® causes endocrine disruption of hormones related to female fertility and reproduction and changes the oxidative status by altering antioxidant activity, inducing lipid peroxidation, as well as changing the gene expression of the glutathione-glutarredoxin system in rat ovaries.

Effects of the mycotoxin metabolite de-epoxy-deoxynivalenol (DOM-1) on embryo development and sperm motility in cattle.

Contamination of animal feed with Fusarium spp results in accumulation of mycotoxins including deoxynivalenol. In animals, deoxynivalenol is metabolized to de-epoxy deoxynivalenol (DOM-1), which is generally considered to be a non-toxic metabolite; however, recent studies demonstrated that DOM-1 can reduce steroid production and induce apoptosis in the bovine ovary. The objectives of this study were to assess the effects of DOM-1 on applied aspects of reproductive function in cattle, specifically sperm function and embryo development in vitro and follicle growth and superovulatory responses in vivo. The effect of naturally contaminated feed on superovulatory responses was assessed; a dose of 6 ppm deoxynivalenol increased blood DOM-1 concentrations to 20 ng/ml, but this did not alter the number of viable embryos recovered on day 7. However, intrafollicular injection of DOM-1 (100 ng/ml) directly into the growing dominant follicle resulted in cessation of follicular growth over the subsequent 3 days. Treatment with DOM-1 reduced motility of bull spermatozoa over a 10-h period in vitro. Addition of DOM-1 to oocytes in vitro during IVM did not alter rates of cumulus expansion and nuclear maturation, but treatment during IVF reduced the rate of blastocyst formation. These data illustrate that DOM-1 is more biologically active than previously thought and negatively impacted reproductive outcomes in cattle.

The role of fibroblast growth factor-18 in follicular atresia in cattle.

Although the various members of the fibroblast growth factor (FGF) family are generally mitotic, one member, FGF18, has been shown to increase the rate of apoptosis of ovarian granulosa cells. In the present study, we first determined whether granulosa cells express FGF18 and we then explored the mechanism through which FGF18 increases apoptosis in vitro. Under culture conditions that favored estradiol secretion and CYP19A1 expression, granulosa FGF18 mRNA levels were barely detectable; however, withdrawing gonadotropic support (follicle-stimulating hormone or insulin-like growth factor 1) reduced levels of CYP19A1 mRNA and increased abundance of mRNA encoding the death ligand FASLG and FGF18. Addition of FGF18, but not FGF2, FGF10, or EGF, increased the proportion of apoptotic cells and frequency of caspase 3 activation, and these effects were abrogated by coculture with estradiol. Addition of FGF18 decreased abundance of mRNA encoding the antiapoptotic proteins GADD45B and MDM2, and increased that encoding the proapoptotic protein BBC3; these effects were reversed by coculture with estradiol. The physiological relevance of FGF18 was determined using an in vivo model: injection of FGF18 directly into growing bovine dominant follicles caused cessation of follicle growth by 24 h after injection. Collectively, these data demonstrate that FGF18 is proapoptotic in vivo and may act through a mechanism involving the BBC3-MDM2 pathway.

Evidence that the effect of angiotensin II on bovine oocyte nuclear maturation is mediated by prostaglandins E2 and F2alpha.

Angiotensin II (AngII) prevents the inhibitory effect of follicular cells on oocyte maturation, but its involvement in LH-induced meiotic resumption remains unknown. The aim of this study was to assess the involvement of AngII in LH-induced meiotic resumption and of prostaglandins (PGs) in the action of AngII. In the experiment I, seven cows were superovulated, intrafollicularly injected with 10 muM saralasin (a competitive AngII antagonist) or saline when the follicles reached a diameter larger than 12 mm, and challenged with a GnRH agonist to induce an LH surge. Fifteen hours after GnRH, the animals were ovariectomized and the oocytes were recovered to determine the stage of meiosis. The oocytes from follicles that received saline were in germinal vesicle (GV) breakdown (30.8%) or metaphase I (MI; 69.2%) stage while those that received saralasin were in the GV stage (100%; P<0.001) 15 h after GnRH agonist. In another experiment, oocytes were co-cultured with follicular hemisections for 15 h to determine whether PGs mediate the effect of AngII on meiotic resumption. Indomethacin (10 microM) inhibited AngII-induced meiotic resumption (13.4 vs 77.5% MI without indomethacin; P<0.001). Furthermore, the GV oocytes progressed to MI at a similar rate when PGE(2), PGF(2alpha) or AngII was present in the co-culture system with follicular cells (PGE(2) 77.4%, PGF(2alpha) 70.0%, and AngII 75.0% MI). In conclusion, our results provide strong evidence that AngII mediates the resumption of meiosis induced by an LH surge in bovine oocytes and that this event is dependent on PGE(2) or PGF(2alpha) produced by follicular cells.