Nitric-oxide-dependent activation of pig oocytes: the role of the cGMP-signalling pathway

Abstract

Pig oocytes matured in vitro were parthenogenetically activated (78%) after treatment with 2 mM nitric oxide-donor (+/-)-S-nitroso-N-acetylpenicillamine (SNAP) for 24 h. Inhibition of soluble guanylyl cyclase with the specific inhibitors 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) or 6-anilino-5,8-quinolinequinone (LY83583) suppressed the SNAP-induced activation in a dose-dependent manner (23% of activated oocytes after treatment with 400 microM ODQ; 12% of activated oocytes after treatment with 40 microM LY83583). 8-Bromo-cyclic guanosine monophosphate (8-Br-cGMP), a phosphodiesterase-resistant analogue of cGMP, enhances the effect of suboptimal doses (0.1 or 0.5 mM) of the NO donor SNAP. DT3, a specific inhibitor of cGMP-dependent protein kinase (PKG, PKG), is also able to inhibit the activation of pig oocytes after NO donor treatment. Involvement of the cGMP-dependent signalling pathway is specific for NO-induced oocyte activation, because both the guanylyl cyclase inhibitor ODQ and the PKG inhibitor DT3 are unable to inhibit activation in oocytes treated with the calcium ionophore A23187. These data indicate that the activation of pig oocytes with an NO donor is cGMP-dependent and that PKG plays an important role in this mode of oocyte activation.

The endothelial nitric oxide synthase/nitric oxide system is involved in the defective quality of bovine oocytes from low mid-antral follicle count ovaries1

“…In fact, the effect of NO on oocyte maturation can be stimulatory or inhibitory depending on its concentration (Bu et al, 2003(Bu et al, , 2004Bilodeau-Goeseels, 2007). Positive effects of SNAP administration during IVM were observed in the mouse (Goud et al, 2005), rat , and pig (Petr et al, 2005(Petr et al, , 2006. In our IVM system, the addition of 100 µM SNAP slightly increased blastocyst and hatching rates of oocytes derived from Lo ovaries to a percentage comparable with that observed in oocytes isolated from Hi ovaries; conversely, it negatively affected the hatching rate of oocytes from Hi ovaries.…”

The role of nitric oxide in parthenogenetic activation of pig oocytes: A review

“…sGC and cGMP also play an important role in the ovary (Grasselli et al, 2001;LaPolt et al, 2003;Shi et al, 2004) and it was proved that they are also involved in the regulation of meiosis (Tornell et al, 1984(Tornell et al, , 1990. Petr et al (2006) demonstrated that the activation of in vitro matured pig oocytes via the NO-dependent signalling pathway was mediated through cGMP. This suggestion is supported by an observation that sGC inhibitors effectively suppressed oocyte activation after the treatment of oocyte with an NO-donor and this is further supported by an observation that 8-Br-cGMP -an analogue of cGMP more resistant to phosphodiesteraseenhances the effects of a suboptimal dose of the NO-donor SNAP on oocyte activation.…”

Effects of cycloheximide or 6-dimethyl aminopurine on the parthenogenetic activation of pig oocytes using pulsatile treatment with nitric oxide donor

“…Changes in intracellular signalling by free calcium ions seem to be important for oocyte activation using NO-donor, and these changes are at least partially triggered by the cGMP-dependent signalling cascade (Kuo et al, 2000;Petr et al, 2005bPetr et al, , 2006Petr et al, , 2007a. These effects on calcium signalling could mimic the intracellular oscillation of free calcium ions which is induced by phospholipase C-zeta after fertilization of the oocyte by sperm (Jones et al, 1998;Parrington et al, 2002;Fujimoto et al, 2004;Konig et al, 2006).…”