Carbenoxolone reduces cyclic nucleotides level, destabilizes maturation promoting factor and induces meiotic exit from diplotene arrest in rat cumulus oocytes complexes cultured in vitro

Publication date: October 2017
Source:Biomedicine & Pharmacotherapy, Volume 94
Author(s): Meenakshi Tiwari, Shail K. Chaube
BackgroundDisruption of gap junction and transfer of cyclic nucleotides to the oocyte lead to meiotic exit from diplotene arrest (EDA) in mammals. In the present study, we examined whether a gap junction blocker, carbenoxolone (CBX) could induce EDA by reducing cyclic nucleotides level and destabilizing maturation promoting factor (MPF) in rat oocytes cultured in vitro.MethodsDiplotene-arrested cumulus oocyte complexes (COCs) were collected from ovary of immature female rats after 20 IU pregnant mare's serum gonadotropins (PMSG) for 48h. These diplotene-arrested COCs were incubated with various concentration of CBX for 3h in vitro. The morphological changes, meiotic status of oocyte, inducible nitric oxide synthase (iNOS), total nitric oxide (NO), adenosine 3′,5′-cyclic monophosphate (cAMP), guanosine 3′,5′-cyclic monophosphate (cGMP), cell division cycle 25B (Cdc25B), changes in specific phosphorylation status of cyclin-dependent kinase 1 (Cdk1) and cyclin B1 levels were analyzed.ResultsCBX induced EDA in a concentration-dependent manner. The iNOS expression, total NO and cyclic nucleotides level were significantly decreased. The reduced cyclic nucleotides level resulted in the decrease of Cdc25B expression level. The decreased Cdc25B was associated with the increased Thr14/Tyr15 phosphorylated Cdk1 level. However, Thr161 phosphorylated Cdk1 as well as cyclin B1 levels were significantly reduced leading to MPF destabilization. The destabilized MPF finally induced EDA in rat COCs cultured in vitro.ConclusionsOur results suggest that CBX blocked gap junctions interrupted the transfer of cyclic nucleotides to the oocyte. Reduction of cyclic nucleotides level destabilized MPF and induced EDA in vitro. Thus, CBX could be used to induce meiotic maturation under in vitro culture conditions during assisted reproductive technology (ART) programs.

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