Distinct responses of compartmentalized glutathione redox potentials to pharmacologic quinones targeting NQO1

Area of Science:

• Biochemistry
• Cell Biology
• Pharmacology

Background:

• Deoxynyboquinone (DNQ) is a novel quinone-based antineoplastic agent.
• It selectively targets solid cancers overexpressing cytosolic NAD(P)H:quinone oxidoreductase-1 (NQO1).
• NQO1-mediated excessive ROS production is the proposed mechanism of cancer cell death.

Purpose of the Study:

• To investigate the redox responses induced by DNQ and beta-lapachone (β-lap).
• To monitor intraorganellar glutathione redox potentials (E_GSH) as a measure of oxidative stress.
• To determine the role of NQO1 inhibition in modulating these redox responses.

Main Methods:

• Utilized a genetically encoded redox-sensitive probe to monitor E_GSH in real-time.
• Assessed DNQ and β-lap induced redox changes in human lung A549 and pancreatic MIA-PaCa-2 adenocarcinoma cells.
• Administered NQO1 inhibitors (dicumarol and ES936) to evaluate NQO1-dependent effects.

Main Results:

• Both DNQ and β-lap induced immediate oxidation of E_GSH in the cytosol and mitochondrial matrix.
• DNQ-induced cytosolic oxidation was completely inhibited by NQO1 inhibition.
• Mitochondrial oxidation was NQO1-independent in A549 cells but NQO1-dependent in MIA-PaCa-2 cells.
• Pharmacologic concentrations of β-lap caused off-target reactivity with cellular thiols.

Conclusions:

• DNQ exhibits direct and specific NQO1 substrate specificity, underpinning its therapeutic potency.
• β-lap demonstrates off-target reactivity at effective doses, suggesting a less specific mechanism.
• These findings highlight the importance of NQO1-mediated redox modulation in cancer therapy.