Background:Heavy metals [arsenic, aluminium, cadmium, chromium, cobalt, lead, nickel
(Ni), palladium and titanium] are environmental contaminants able to impact with host human cells,
thus, leading to severe damage.Objective:In this review, the detrimental effects of several heavy metals on human organs will be discussed
and special emphasis will be placed on Ni. In particular, Ni is able to interact with Toll-like
receptor-4 on immune and non-immune cells, thus, triggering the cascade of pro-inflammatory cytokines.
Then, inflammatory and allergic reactions mediated by Ni will be illustrated within different organs,
even including the central nervous system, airways and the gastrointestinal system.Discussion:Different therapeutic strategies have been adopted to mitigate Ni-induced inflammatoryallergic
reactions. In this context, the ability of polyphenols to counteract the inflammatory pathway
induced by Ni on peripheral blood leukocytes from Ni-sensitized patients will be outlined. In particular,
polyphenols are able to decrease serum levels of interleukin (IL)-17, while increasing levels of IL-
10. These data suggest that the equilibrium between T regulatory cells and T helper 17 cells is recovered
with IL-10 acting as an anti-inflammatory cytokine. In the same context, polyphenols reduced
elevated serum levels of nitric oxide, thus, expressing their anti-oxidant potential. Finally, the carcinogenic
potential of heavy metals, even including Ni, will be highlighted.Conclusion:Heavy metals, particularly Ni, are spread in the environment. Nutritional approaches
seem to represent a novel option in the treatment of Ni-induced damage and, among them, polyphenols
should be taken into consideration for their anti-oxidant and anti-inflammatory activities.