Mifepristone mechanism of action
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Mifepristone Mechanism of Action: Progesterone and Glucocorticoid Receptor Antagonism
Mifepristone acts primarily as an antagonist of the progesterone receptor and the glucocorticoid receptor. It binds with high affinity to these intracellular receptors, blocking the action of their natural hormones. This antagonism prevents the normal transcription of progesterone-dependent genes, which is crucial for maintaining pregnancy, and also interferes with glucocorticoid signaling pathways Baulieu1997Cadepond1997Mahajan1997+1 MORE.
Molecular Interactions and Receptor Binding
At the molecular level, mifepristone’s effectiveness is due to its strong binding to the receptor, particularly involving its phenyl-aminodimethyl group at the 11 beta-position, which interacts with a specific region of the receptor binding pocket. This binding causes a change in the shape (transconformation) of the receptor’s ligand-binding domain, which disrupts normal receptor function compared to hormone agonists Baulieu1997Cadepond1997Mahajan1997.
Effects on Reproductive Function and Emergency Contraception
When used for emergency contraception, mifepristone’s main effect is to block or delay ovulation by preventing or delaying the luteinizing hormone (LH) surge, rather than inhibiting implantation. This makes it effective in preventing pregnancy if taken soon after unprotected intercourse . Additionally, mifepristone blocks progesterone receptors in the placenta, leading to the termination of pregnancy when used as an abortifacient .
Additional Cellular and Metabolic Effects
Mifepristone also acts as a glucocorticoid receptor antagonist, which can influence other physiological processes. For example, it can reverse the reduction of adult neurogenesis caused by high corticosterone levels, suggesting a role in treating certain mood disorders . It also inhibits dietary lipid digestion by blocking glucocorticoid receptor-mediated transcription of lipase enzymes, affecting lipid metabolism and potentially offering benefits in metabolic diseases .
Impact on Cell Permeability, Angiogenesis, and Cancer
Mifepristone increases cell permeability, angiogenesis, and the expression of aquaporin 1 (AQP1) through the ERK MAPK pathway, which is part of its anti-implantation contraceptive effect . In cancer research, mifepristone has shown the ability to inhibit cell proliferation and induce ferroptosis (a type of cell death) in meningioma cells via the PR/p53/HO1/GPX4 axis, highlighting its potential in cancer therapy Chen2014Dai2025.
Enzyme Inactivation
Mifepristone is also a potent and selective inactivator of the liver enzyme cytochrome P-450-3A4 (CYP-3A4). It irreversibly modifies the enzyme at its active site, which can affect the metabolism of other drugs processed by this enzyme .
Conclusion
Mifepristone’s mechanism of action is primarily based on its antagonism of progesterone and glucocorticoid receptors, leading to effects on reproductive function, metabolism, and cell signaling. Its unique molecular interactions and broad physiological impacts make it useful not only for medical abortion and emergency contraception but also for potential applications in metabolic disorders, neurogenesis, and cancer therapy.
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