Title:Metal Toxicity and Speciation: A Review
Volume: 28
Issue: 35
Author(s): Massimiliano Peana*, Alessio Pelucelli, Serenella Medici, Rosita Cappai, Valeria Marina Nurchi and Maria Antonietta Zoroddu*
Affiliation:
- Department of Chemistry and Pharmacy, University of Sassari, Sassari,Italy
- Department of Chemistry and Pharmacy, University of Sassari, Sassari,Italy
Keywords:
Metal speciation, metal toxicity, chelation therapy, toxic metals, metal poisoning, oxidation states.
Abstract:
Background: Essential metal ions play a specific and fundamental role in human
metabolism. Their homeostasis is finely tuned, and any concentration imbalance in
the form of deficiency or excess could lead to a progressive reduction and failure of normal
biological function, to severe physiological and clinical outcomes, may eventually
causing death. Conversely, non-essential metals are not necessary for life, and only
noxious effects could arise after their exposure. Large environmental amounts of such
chemicals come from both natural and anthropogenic sources, with the latter being predominant
because of human activities. The dissipation of toxic metals contaminates water,
air, soil, and food, causing a series of chronic and acute syndromes.
Objective: This review discusses the toxicity of non-essential metals considering their peculiar
chemical characteristics, such as different forms, hard-soft character, oxidation
states, binding capabilities, and solubility, which can influence their speciation in biological
systems, and subsequently, the main cellular targets. Particular focus is given to selected
toxic metals, major non-essential metals, or semimetals related to toxicity, such as
mercury, lead, cadmium, chromium, nickel, and arsenic. In addition, we provide indications
on the possible treatments/interventions for metal poisoning based on chelation therapy.
Conclusion: Toxic metal ions can exert their peculiar harmful effects in several ways.
They strongly coordinate with important biological molecules on the basis of their chemical-
physical characteristics (mainly HSAB properties) or replace essential metal ions
from their natural locations in proteins, enzymes, or hard structures, such as bones or
teeth. Metals with redox properties could be key inducers of reactive oxygen species,
leading to oxidative stress and cellular damage. Therapeutic detoxification, through complexation
of toxic metal ions by specific chelating agents, appears an efficacious clinical
strategy, mainly in acute cases of metal intoxication.
