Polymorphonuclear leukocyte chemotaxis induced by zinc, copper and nickel in vitro

Metallic dental restorations and prosthetic constructions are susceptible to corrosion in oral environment, resulting in the release of various heavy metal ions. Chloride salts of zinc, copper, nickel, chromium, iron and gold were tested for their ability to promote the migration of polymorphonuclear leukocytes (PMNs). Using a modified Boyden chamber assay for chemotaxis zinc, copper and nickel enhanced the migration of PMN cells in concentration range of 0.5-1.0 mM, whereas no augmentation in migratory activity was noted using chromium or iron. In contrast, an inhibition in migratory activity was observed in cells directed toward gold ions. Exposure of cells to zinc, copper or nickel ions induced an orientation reaction in leukocytes in a similar fashion as the polarization reaction induced by a potent peptide chemoattractant, N-formylmethionylleucylphenylalanine (fMLP), in these cells. Exposure of PMN cells to zinc or nickel in chemotactic concentrations stimulated the chemotaxis of these cells to fMLP 2-fold, whereas pretreatment of the cells with zinc prior to assay markedly decreased the subsequent chemotactic migration of the cells to this metal or to fMLP. The enhanced locomotion of PMN cells induced by zinc, copper or nickel ions was found to be in greater extent due to an increase in directed migration (chemotaxis) rather than an augmentation in random movement (chemokinesis) as assessed by Zigmond-Hirsch checkerboard analysis. These results suggest that zinc, copper and nickel ions attract leukocytes by inducing and promoting the chemotactic response in these cells, which may modulate the inflammatory response of host tissue around such metals.