ATF4 Contributes to Ovulation via Regulating COX2/PGE2 Expression: A Potential Role of ATF4 in PCOS

Abstract

Ovulatory disorder is common in patients with hyperprolactinemia or polycystic ovary syndrome (PCOS). Previous studies have shown that ATF4 plays critical role in apoptosis and glucose homeostasis, but its role in regulating reproductive function was not explored. The present study investigated the role of ATF4 in ovarian ovulatory function. Human granulosa cells (hGCs) from 48 women newly diagnosed with PCOS and 37 controls were used to determine ATF4 expression. In vitro cultured hGCs were used to detect the upstream and downstream genes of ATF4. A shRNA- Atf4 lentiviral vector (shAtf4) was injected into rat ovaries to establish an in vivo gene knockdown model to further assess the in vivo relevance of the results from PCOS women. We found that ATF4 expression was lower in hGCs from PCOS patients than in hGCs from non-PCOS women. Many pivotal transcripts involved in cumulus-oocyte complex (COC) expansion, extracellular matrix (ECM) remodeling, and progesterone production were significantly down-regulated after ATF4 knockdown. ChIP-qPCR assays indicated that ATF4 could directly bind to the COX2 promoter and that ATF4 knockdown could attenuate human chorionic gonadotropin (hCG)-induced COX2 expression and PGE2 production. The in vivo study showed that shRNA-lentivirus mediated Atf4 knockdown in rat ovaries led to reduced number of retrieved oocytes. Collectively, these findings suggested previously unknown roles of ATF4 in ovulation. Furthermore, ATF4 malfunction in PCOS patients may impact the ovulation process, which could contribute, in part, to the pathogenesis of PCOS.

Endocrine and molecular milieus of ovarian follicles are diversely affected by human chorionic gonadotropin and gonadotropin-releasing hormone in prepubertal and mature gilts

“…The cAMP response element-binding protein (CREB1) and activating transcription factor 4 (ATF4, known as CREB2) play a vital role in the control of ovarian steroidogenesis 17 . Thus, mRNA and protein abundance of both cellular transcription factors was evaluated in follicular walls of prepubertal and mature gilts challenged with hormones (hCG or GnRH-A).…”

“…CREB1 and AFT4 play a vital role in the control of ovarian steroidogenesis via cAMP signaling. On the other hand, AFT4 is involved in prostaglandin synthesis by binding to the PTGES2 promoter and increasing PGE 2 production in response to hCG in human granulosa cells 17 .…”

Notch Signaling Induced by Endoplasmic Reticulum Stress Regulates Cumulus-Oocyte Complex Expansion in Polycystic Ovary Syndrome

“…ER stress enhanced COC expansion in vitro, which was accompanied by increased expression of various genes associated with COC expansion, and the effects were abrogated by inhibition of Notch2 signaling. Two reports have evaluated the role of ER stress in COC expansion [ 43 , 44 ], while no study has investigated the role of Notch in this phenomenon. The ER stress inducer thapsigargin enhances murine COC expansion and expression of related genes [ 43 ], consistent with the findings of this study.…”

Up-regulated FHL2 inhibits ovulation through interacting with androgen receptor and ERK1/2 in polycystic ovary syndrome

“…The negative control was the corresponding empty lentiviral vector. The lentivirus vector protocol was modified from the published method [45À47] and combined with our previous experience [19,48]. In brief, we used 293T cells to confirm the transfection efficiency and determined the proper virus titre by examining the expression of FHL2 using qRT-PCR and immunoblotting.…”