Menadione serves as a substrate for P-glycoprotein: implication in chemosensitizing activity

Area of Science:

• Pharmacology
• Molecular Biology
• Oncology

Background:

• P-glycoprotein (P-gp) is a key efflux transporter involved in multidrug resistance (MDR).
• Menadione exhibits chemosensitizing properties, but its interaction with P-gp is not well understood.

Purpose of the Study:

• To determine if menadione is an inhibitor or substrate of P-gp.
• To investigate the P-gp-dependency of menadione's cellular accumulation and cytotoxicity.

Main Methods:

• Assessed menadione's effect on rhodamine 123 (Rh123) accumulation in P-gp-overexpressing cells.
• Measured intracellular distribution of [(3)H]-menadione in the presence and absence of P-gp inhibitors (verapamil, quinidine).
• Evaluated menadione's cytotoxicity in P-gp-overexpressing and control cells, with and without P-gp inhibitors.

Main Results:

• Menadione increased Rh123 accumulation in P-gp-overexpressing cells, indicating P-gp inhibition.
• Intracellular menadione levels were lower in P-gp-overexpressing cells and restored by P-gp inhibitors.
• P-gp-overexpressing cells showed resistance to menadione cytotoxicity, which was reversed by P-gp inhibitors.

Conclusions:

• Menadione is identified as a substrate of P-gp.
• Menadione's interaction with P-gp likely mediates its chemosensitizing effect.
• Menadione shows promise as a chemotherapeutic enhancer for overcoming drug resistance.