Metals, toxicity and oxidative stress.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing mechanistic, in vitro, and animal studies
PubMed 15892631 · doi:10.2174/0929867053764635
What was done
This narrative review summarizes literature on the cellular and molecular mechanisms of metal-induced toxicity and carcinogenicity. It examines reactive oxygen and nitrogen species generation, lipid peroxidation, DNA adduct formation, glutathione and sulfhydryl depletion, signaling pathway activation (NF-kappaB, AP-1, p53), and the modulation of these pathways by antioxidant molecules including vitamin E, melatonin, vitamin C, and zinc.
What was found
The abstract reports no aggregate quantitative data. Mechanistically, redox-active metals (iron, copper, chromium, vanadium, cobalt) generate hydroxyl and superoxide radicals via Fenton-like chemistry, while non-redox metals (mercury, cadmium, nickel) primarily deplete glutathione and bind protein sulfhydryls. The review notes that intracellular "free pools" of copper are less than one atom per cell, challenging copper's role in in vivo Fenton reactions. It also notes that an epidemiological study linked daily vitamin E intake >400 IU with increased all-cause mortality, and in vitro human data indicate ascorbate functions as an antioxidant rather than a pro-oxidant even alongside redox-active iron or copper.
Why it matters
The review details how disparate toxic and transition metals converge on common pathways of oxidative damage and aberrant transcription factor signaling, helping to explain their carcinogenic and organ-toxic profiles.
Limits
As a narrative review, it lacks a systematic search protocol, predefined inclusion criteria, and formal quality assessment of the cited literature. The presented mechanisms rely heavily on in vitro cell cultures and animal models, which may not directly reflect physiological human exposure dynamics.
Cited by
- supports Copper generates free radicals because it possesses an unpaired d-orbital electron, a characteristic zinc lacks.