GnRH Triggers a Transient Inflammatory-Like Response in Pituitary Cells During Ovulation

The hormonal surge that triggers ovulation does more than release gonadotropins. According to a new open-access study published on 20 October 2026 in Cell Communication and Signaling, the preovulatory surge of gonadotropin-releasing hormone (GnRH) is accompanied by a transient inflammatory-like response in the rat pituitary gland, driven in large part by the hormone’s direct action on gonadotrope cells.

Pituitary gonadotrope cells are central regulators of reproduction, secreting the gonadotropins that control the ovaries and testes under GnRH instruction from the hypothalamus. While the preovulatory GnRH surge is known to trigger massive gonadotropin release, the molecular mechanisms supporting this process have remained incompletely understood. The research team, led by authors including Ghislaine Garrel, Joëlle Cohen-Tannoudji and David L’Hôte, set out to characterize what happens in the pituitary during this critical reproductive window.

Using single-cell and temporal analyses of the rat pituitary gland, combined with in situ and in vitro analyses, the researchers demonstrated that the preovulatory period is associated with a transient inflammatory-like response. This response is characterized by increased expression of pro-inflammatory mediators, including the genes Tnf, Il6 and Ptgs2. Notably, the team found no evidence of increased leukocyte infiltration into the pituitary, indicating that the inflammatory signature arises from the gland’s own cells rather than from invading immune cells.

The study also revealed a coordinated shift in a second regulatory axis. Expression of the anti-inflammatory gene Elovl2 decreased during the preovulatory period, while expression of Sat1 rose concomitantly. Sat1 encodes the rate-limiting enzyme of polyamine catabolism, linking the inflammatory-like state to a previously unrecognized change in polyamine metabolism within the pituitary.

Single-cell analysis identified gonadotrope cells as key contributors to this process. In LβT2 gonadotrope cells grown in vitro, GnRH directly induced inflammatory gene expression via the ERK and PI3K signaling pathways. The response showed distinct sensitivity to pulsatile patterns of GnRH exposure, and sustained GnRH exposure, mimicking the preovulatory surge, was required to induce a subset of inflammatory-related genes, including Sat1.

Promoter analyses provided a mechanistic explanation for the Sat1 increase. GnRH regulates Sat1 transcription through a proximal promoter region involving FOXO transcription factors, which act as repressors that are relieved upon GnRH signaling. In other words, the hormone’s signaling cascade lifts a brake on the gene, allowing polyamine catabolism to ramp up alongside the inflammatory program.

Functional experiments clarified what this means for pituitary physiology. Although modulation of polyamine metabolism did not affect gonadotropin secretion, SAT1 contributed to GnRH-induced expression of inflammatory mediators, as evidenced by SAT1 loss-of-function and pharmacological experiments. The enzyme therefore appears to shape the inflammatory-like response rather than the release of reproductive hormones itself.

Together, these findings uncover a previously unrecognized regulation of polyamine metabolism and inflammatory pathways by GnRH in gonadotrope cells. The authors suggest that a controlled inflammatory-like state contributes to pituitary plasticity during ovulation, offering a new molecular dimension to a process long studied almost exclusively through the lens of gonadotropin secretion. Because the work was performed in rat pituitary tissue and in a gonadotrope cell line, its direct relevance to human reproduction remains to be tested in future studies.

Subject of Research: GnRH-induced inflammatory-like signaling and SAT1 upregulation in pituitary gonadotrope cells during the preovulatory surge

Article Title: GnRH drives an inflammatory process with concomitant SAT1 upregulation through ERK/PI3K signaling pathways in pituitary gonadotrope cells during the preovulatory surge

Article References: Garrel, G., Le Ciclé, C., Rios, T., Nizard, P., Cohen-Tannoudji, J., & L’Hôte, D. (2026). GnRH drives an inflammatory process with concomitant SAT1 upregulation through ERK/PI3K signaling pathways in pituitary gonadotrope cells during the preovulatory surge. Cell Communication and Signaling. https://doi.org/10.1186/s12964-026-03317-w

Image Credits: AI Generated

DOI: 10.1186/s12964-026-03317-w

Keywords: GnRH, pituitary, gonadotrope cells, inflammation, SAT1, polyamine metabolism, ERK signaling, PI3K signaling, ovulation, preovulatory surge, FOXO transcription factors, reproductive endocrinology