Yifan Yang1, Jan Kroon1, Onno Meijer1
(1) Dept. of Medicine, Division of Endocrinology, Leiden University Medical Center, Leiden, Netherlands.
Glucocorticoids (GCs) exert negative feedback on the hypothalamic–pituitary–adrenal (HPA) axis through both genomic and rapid non-genomic mechanisms. Within the anterior pituitary, Annexin A1 (ANXA1) has been proposed to contribute to the early GC-induced inhibition of adrenocorticotropic hormone (ACTH) release.
This study aimed to establish an in vitro model for ANXA1-mediated pituitary negative feedback to investigate non-genomic effects of GCs. AtT-20 cells were used as mouse ACTH-secreting corticotrophs, TtT/GF cells as a mouse folliculo-stellate-like cell line, and A549 cells as a human reference model. Glucocorticoid receptor (GR) activity was first validated in TtT/GF cells by RT-qPCR on GR target genes, followed by ACTH measurements in AtT-20 monocultures and AtT-20/TtT-GF co-cultures treated with vehicle or dexamethasone. To explore early ANXA1 responses, ANXA1 phosphorylation was assessed in TtT/GF cells and A549 cells after dexamethasone exposure by Western blotting.
Our results demonstrated that TtT/GF cells displayed functional GR activity, and 24-hour dexamethasone treatment significantly inhibited ACTH release in the co-culture system, while no suppression was observed in AtT-20 monocultures. Dexamethasone induced rapid ANXA1 phosphorylation in TtT/GF cells within 30 minutes, and a response was also observed in A549 cells and independent of new protein synthesis.
In summary, these findings indicate that ANXA1 contributes to the early non-genomic effects of GCs within the anterior pituitary, though its specific role in ACTH regulation remains to be clarified. Our future work will focus on determining how ANXA1 and GR are involved in the underlying mechanisms of HPA-axis negative feedback and disinhibition.