Exposure of human keratinocytes and fibroblasts in vitro to nickel sulphate ions induces synthesis of stress proteins Hsp72 and Hsp90

Exposure of the epidermis to nickel-containing compounds is one of the most common causes of contact allergy and may indicate that exposure of skin cells to nickel ions causes stress. In this study, cytotoxicity assays upon human keratinocytes and fibroblasts in monolayer culture indicated a 50% decrease in viability of both cell types at nickel sulphate concentrations in excess of 10(-3) M. To investigate the possible induction of a stress response within these cell types, monolayer cultures were exposed to concentrations of nickel sulphate for 1 h, followed by 35S-methionine labelling. Whole cell lysates were analysed by SDS-PAGE and immunoblotting with specific monoclonal antibodies, or by fluorography. For keratinocytes, increased synthesis of Hsp90 at concentrations of 10(-5) M and above and induction of the stress-inducible Hsp72 at concentrations of 10(-4) M and above were observed. For fibroblasts, increased induction of Hsp90 at all concentrations under test and a dose-responsive increase in Hsp72 synthesis were detected. These results indicate that both keratinocytes and fibroblasts react to the toxic effects of nickel ions by mounting a stress response involving the up-regulation of synthesis of key stress proteins.