Does zearalenone bind estrogen receptors and stimulate reproductive tissues?

Zearalenone (ZEN) is a non-steroidal mycoestrogen produced by Fusarium fungi. Structurally resembling 17β-estradiol, it acts as a potent endocrine disruptor by mimicking endogenous estrogens in mammalian tissues.

Receptor binding and mechanistic pathways

• Direct receptor affinity: ZEN binds directly to both estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), with IC50 values of approximately 240.4 nM and 165.7 nM, respectively. It functions as a full agonist at ERα and a mixed agonist-antagonist at ERβ to trigger gene transcription.
• Metabolic activation: Once ingested, ZEN is metabolized into reduced compounds, most notably α-zearalenol. This metabolite exhibits a significantly lower IC50 and higher binding affinity than ZEN, resulting in estrogenic potency that approaches or exceeds that of endogenous estradiol.

Tissue-level effects

• Uterine stimulation: In animal models, receptor activation by ZEN leads to classic uterotropic responses, including marked endometrial epithelial hypertrophy and significant increases in uterine wet weight.
• Proliferative changes: Chronic or low-dose exposure promotes endometrial hyperplasia, myometrial cell proliferation, and altered vulvar size. In mammary tissues, ZEN stimulates ER-mediated cell proliferation, signaling potential disruption in breast tissue homeostasis.

Bottom line

• Zearalenone and its highly potent metabolite, α-zearalenol, directly bind and activate estrogen receptors ERα and ERβ, stimulating estrogen-responsive reproductive and mammary tissues to drive proliferative and hyperplastic changes.