Enhancement of nickel elution by lipopolysaccharide-induced inflammation

BackgroundImplantations of metallic biomedical devices into bodies are increasing. The elution of Ni ions from these devices can lead to metal allergies. However, the molecular mechanisms of the elution have not been fully examined. Furthermore, it is not clear whether infection and inflammation affect the corrosion of metals.ObjectiveWe examined whether the elution of Ni from metal wires and plates was enhanced by inflammation in vivo and in vitro.MethodsA Ni or SUS316L wire was implanted subcutaneously in the dorsum of mice. Lipopolysaccharide (LPS) was injected at the site immediately following the implantation. After 8, 24, and 72 h, the tissue around the wire was excised. RAW 264 cells were seeded on a Ni plate and incubated for 24 h in medium containing LPS. The amount of Ni in the tissue or conditioned medium was determined fluorometrically.ResultsThe release of Ni ions from the wire was significantly increased from 8 to 72 h, and further increased by LPS. LPS also enhanced the release of Ni ions by the cells, but only when they were attached to the Ni plate. Chloroquine, bafilomycin A1 and amiloride markedly inhibited the effects of LPS.ConclusionThe activation of inflammatory cells on metals enhanced the elution of Ni probably via the release of protons at the interface of the cells and material.