A newly identified long noncoding RNA (lncRNA), named lnc2300, plays a protective role in ovarian granulosa cells but is sharply downregulated under oxidative stress conditions. This study reveals that the transcription factor FoxO1, a known mediator of oxidative damage, directly binds to the promoter of lnc2300 and suppresses its transcription. The repression of lnc2300, in turn, contributes to increased cell apoptosis.
Oxidative stress is widely implicated in reproductive aging and follicular atresia, a process where ovarian follicles degenerate prematurely. The transcription factor FoxO1 is a key effector in oxidative stress response, known to trigger apoptosis in various tissues, including ovarian granulosa cells. While FoxO1's role in regulating protein-coding genes is well established, its interaction with noncoding RNAs, especially in the ovary, remains poorly understood. LncRNA, which are transcripts longer than 200 nucleotides that do not code for proteins, are emerging as important regulatory molecules in stress responses. Due to these unresolved questions, the mechanisms behind lncRNA regulation by FoxO1 and their role in oxidative stress-induced follicular damage require further exploration.
A study (DOI: 10.48130/animadv-0025-0013) published in Animal Advances on 04 June 2025 by Yinxia Li & Qifa Li's team, Nanjing Agricultural University, identifies lnc2300 as a promising target for protecting reproductive function from oxidative damage and offer a new perspective on follicular atresia.
To investigate the regulatory mechanisms of lnc2300, researchers first isolated and characterized its promoter sequence from Yorkshire pigs, revealing a 1,457-bp adenine- and thymine-rich region with high similarity (98.97%) to the Sus scrofa reference genome. They identified classic cis-elements such as a TATA box and CAAT box, and mapped 324 miRNA response elements (MREs), including sites for miR-214 and miR-92a, which are downregulated during follicular atresia. Using JASPAR, they predicted 2,075 transcription factor binding sites (TFBSs) for 254 transcription factors, among which FoxO1 stood out due to its high expression under oxidative stress and inverse correlation with lnc2300 levels in vivo. A specific FoxO1-responsive element (FRE) within the lnc2300 promoter was functionally validated using luciferase reporter assays: overexpressed FoxO1 significantly reduced promoter activity, while mutation of the FRE abolished this effect, confirming direct binding and repression. In granulosa cells, FoxO1 overexpression suppressed lnc2300 expression and promoted apoptosis, as indicated by increased BAX, reduced BCL2, and a lower BCL2/BAX ratio, whereas lnc2300 overexpression reversed these trends. Further, oxidative stress induced by H2O2 reduced lnc2300 transcription and promoter activity in a FoxO1-dependent manner, which was reversed upon FoxO1 silencing. Functionally, lnc2300 overexpression mitigated oxidative stress-induced apoptosis in granulosa cells. Collectively, these results demonstrate that FoxO1 directly binds and represses lnc2300 transcription under oxidative stress, thereby promoting apoptosis in granulosa cells.
This study reveals that oxidative stress induces granulosa cell apoptosis by activating the transcription factor FoxO1, which suppresses the expression of the protective lncRNA lnc2300. Through detailed promoter analysis and functional assays, the researchers show that lnc2300 plays a key anti-apoptotic role, and its downregulation under oxidative stress is mediated by FoxO1. These findings offer new insights into follicular atresia and suggest that lnc2300 could be a potential target for therapies aimed at mitigating reproductive decline caused by oxidative stress.
