Icariin ameliorates gonadotropin dysregulation in an ovariectomy model: Therapeutic effect and mechanism.

BACKGROUND

MicroRNA-7 (miR-7) suppresses pituitary gonadotropins, while icariin, an active compound from Epimedium brevicornu Maxim., exhibits estrogen-like properties. However, whether icariin regulates gonadotropins via miR-7 remains unclear.

PURPOSE: This study investigated whether icariin regulates gonadotropins through miR-7 and elucidated the underlying molecular mechanisms.

STUDY

DESIGN

An integrated approach combining ovariectomized mouse model, primary pituitary cell cultures, and molecular techniques was employed.

METHODS

In vivo, ovariectomized C57BL/6 mice received intragastric icariin (20, 40, 80 mg·kg-1·d-1), 17β-estradiol (20 μg·kg-1·d-1), or vehicle for 28 days. Serum and pituitary tissues were collected. In vitro, primary pituitary cells were treated with icariin (0.1 to 1000 nM) for 12 h. Effects on miR-7 and gonadotropins were assessed. Mechanistic studies were examined using mimic/inhibitor, antagonists, small interfering RNAs, bioinformatics, luciferase reporter assay, quantitative real-time polymerase chain reaction and western blot.

RESULTS

Icariin at medium and high doses increased miR-7 expression and reversed ovariectomy-induced gonadotropin elevation, with effects comparable to 17β-estradiol. In primary pituitary cells, icariin (100 nM) similarly up-regulated miR-7 and suppressed gonadotropins. Mechanistically, our data suggest the involvement of G protein-coupled estrogen receptor in icariin action. Mitogen-activated protein kinase kinase 4 (Map2k4) was identified as a miR-7 target. Map2k4 knockdown attenuated icariin's inhibition of luteinizing hormone beta subunit and blocked icariin-induced suppression of c-Jun N-terminal kinase phosphorylation.

CONCLUSION

Icariin regulates pituitary gonadotropins via a membrane estrogen receptor-mediated pathway that upregulates miR-7 to directly target Map2k4, a mechanism contributing to gonadotropin subunit regulation, with differential involvement of downstream pathways revealing its estrogenic activity.