Do metals and mycotoxins increase demand on glutathione-dependent antioxidant and detoxification pathways?

Metals and certain mycotoxins can place greater functional demand on glutathione (GSH)-dependent antioxidant and detoxification systems. The evidence is strongest for metals, with human biomarker data complementing well-established cellular mechanisms.

Metals: clinical and mechanistic evidence

• Arsenic, cadmium, lead, and mercury bind GSH and other thiol groups, can form GSH conjugates, and impair thiol-dependent antioxidant defenses. Their disruption of mitochondria and antioxidant enzymes also promotes reactive oxygen species (ROS), increasing requirements for GSH-dependent peroxide reduction and redox recycling.
• Oxidative/electrophilic stress can modify Keap1 cysteines and activate Nrf2, increasing expression of genes involved in GSH synthesis and antioxidant defense—an adaptive indication of pathway engagement.
• In chronically exposed Bangladeshi adults, an interquartile-range increase in drinking-water arsenic was associated with a 25.4 µmol/L lower blood GSH. Occupational lead/cadmium exposure and mineworker studies similarly linked cadmium exposure with reduced GSH/GSSG ratios and oxidative-stress alterations.

Mycotoxins: predominantly experimental evidence

• The clearest evidence concerns zearalenone (ZEN). In HepG2 liver cells, ZEN and metabolites increased ROS and oxidative DNA damage while reducing GSH—reported reductions were approximately 25–54% in cellular experiments—sometimes below overtly cytotoxic concentrations.
• Animal and yeast models likewise show oxidative injury, lower hepatic/cellular GSH, and compensatory changes in glutathione peroxidase, glutathione reductase, and glutathione S-transferase activity.
• Some reactive mycotoxin metabolites, notably aflatoxin-derived electrophiles, undergo GST-mediated GSH conjugation. ZEN itself is primarily hydroxylated and glucuronidated, so direct GSH conjugation is not consistently established.

Bottom line

• Metals convincingly increase glutathione-pathway demand; mycotoxins, especially ZEN, plausibly do so through oxidative stress and GSH depletion, but this latter conclusion rests mainly on experimental rather than human exposure evidence.