Antioxidant effect of zinc in humans

Oxidative stress is known to be an important contributing factor in many chronic diseases. We tested the hypothesis that in healthy normal volunteers zinc acts as an effective anti-inflammatory and antioxidant agent. Ten normal volunteers were administered daily oral zinc supplementation (45 mg zinc as gluconate) and 10 volunteers received placebo for 8 weeks. Plasma zinc, MDA, HAE, and 8-OHdG levels; LPS-induced TNF-α and IL-1β mRNA; and ex vivo TNF-α-induced NF-κB activity in mononuclear cells (MNC) were determined before and after supplementation. In subjects receiving zinc, plasma levels of lipid peroxidation products and DNA adducts were decreased, whereas no change was observed in the placebo group. LPS-stimulated MNC isolated from zinc-supplemented subjects showed reduced mRNA for TNF-α and IL-1β compared to placebo. Ex vivo, zinc protected MNC from TNF-α-induced NF-κB activation. In parallel studies using HL-60, a promyelocytic cell line, we observed that zinc enhances the upregulation of mRNA and DNA-specific binding for A20, a transactivating factor which inhibits the activation of NF-κB. Our results suggest that zinc supplementation may lead to downregulation of the inflammatory cytokines through upregulation of the negative feedback loop A20 to inhibit induced NF-κB activation. Zinc administration to human subjects with conditions associated with increased oxidative stress should be explored.