Intracellular zinc stores protect the intestinal epithelium from Ochratoxin A toxicity

Ochratoxin A (OTA) is a harmful mycotoxin frequently contaminating foods, feeds and beverages. OTA was reported to be nephrotoxic, immunotoxic, hepatotoxic and a potential carcinogen, with yet poorly characterized mechanisms. Although intestinal cells are relatively resistant to high concentrations of OTA, interaction with other dietary factors or specific nutritional conditions may increase OTA toxicity to the intestinal mucosa. The role of intracellular zinc stores in protecting the integrity of intestinal mucosa has been investigated in human Caco-2/TC7 cells challenged with OTA. Zinc depletion of cells incubated with TPEN, a specific zinc chelator, caused an increase of tight junction permeability in OTA treated cells, accompanied by increased apoptosis. These effects were fully reverted by zinc supplementation during TPEN treatment, showing a specific role for this micronutrient in enterocyte defence mechanisms from OTA toxicity. A complex perturbation of zinc homeostasis was also demonstrated by analyzing the expression of genes coding for proteins involved in cellular zinc. In particular, zinc-dependent up-regulation of the metallothionein gene MT2A upon OTA treatment may indicate that the mycotoxin acts through generation of redox imbalance and that zinc deprivation reduces the intracellular defence mechanisms against noxious insults.