Comparative study of the in vitro inflammatory activity of three nickel salts on keratinocytes

Nickel, the allergen of contact dermatitis, induces the in vitro production of inflammation markers such as intracellular adhesion molecule-1, interleukin-1 and tumour necrosis factor-alpha by keratinocytes. The purpose of our study was to compare the effect in vitro of different nickel salts on keratinocyte activation in order to determine whether this process depends on the nature of the salt used. Cultured keratinocytes were incubated with three nickel salts for 24 h in MCDB153 medium without hydrocortisone. Nickel gluconate, nickel sulphate and nickel chloride were each used at four concentrations: 5.10(-5) M, 1.10(-4) M and 1.10 (-3) M. Keratinocyte activation was studied through the production of three inflammation markers: intracellular adhesion molecule-1, tumour necrosis factor-alpha and very late antigen-3 (an integrin with increased expression during contact dermatitis). Marker production was detected by immunocytochemistry and flow cytometry. Tumour necrosis factor-alpha production and intracellular adhesion molecule-1 and very late antigen-3 expression increased with addition of the three nickel salts, becoming maximal for nickel gluconate 1.10(-4) M. In a subsequent experiment, zinc gluconate (an anti-inflammatory molecule) at 9 micrograms/ml reduced the very late antigen-3 expression induced by nickel gluconate 1.10(-4) M. Therefore, this study enabled us to determine the concentration of a nickel salt (nickel gluconate) inducing optimal keratinocyte activation in our culture conditions and also indicated the potential interest of very late antigen-3 as an inflammation marker.