DUOX2 is a Generator of ROS in the Ovary and a Potential Mediator of Ovulation

Background: Ovulation is triggered by the preovulatory surge of the pituitary luteinizing hormone (LH). LH/hCG induction of reactive oxygen species (ROS) is required for successful ovulation. H2O2, one of ROS species, was shown to fully mimic the effect of LH/hCG in mice ovulation. However, the molecular process that generates H2O2 in the ovary during ovulation remains largely unknown. DUOX2, a member of the NOX/DUOX family of NADPH oxidase, is capable of generating H2O2. Results: Using global transcriptome RNAseq, we identified that DUOX2 is one of the transcripts that was markedly upregulated in granulosa cells during ovulation. Treatment with human chorionic gonadotropin (hCG), an ovulatory trigger, significantly increases the expression of DUOX2 mRNA and protein in human GCs both in vivo and in vitro. hCG-induced up-regulation of DUOX2 is mediated by the cAMP-PKA and the PKC pathway. A functional test reveals that DUOX2 chemical inhibitor, Diphenyleneiodonium (DPI), an NADPH oxidase inhibitor, decreased H2O2 levels in MGCs (Mural Granulosa Cells) treated with hCG. The inhibition of H2O2 by DPI suggests that DUOX2 activity is required for hCG-induced elevation of extracellular H2O2 in MGCs. In vivo treatment of mice with DPI significantly decreases the number of ovulated oocytes and markedly attenuates the expression of key ovulatory genes. These results support the putative role of DUOX2 in ovulation. Conclusions: DUOX2 is a ROS generator during the ovulatory process and is involved in the LH/hCG-induced signaling cascades leading to ovulation. Treatment with DUOX2 inhibitors may affect late folliculogenesis and ovulation and thus may serve for fertility control.