EFFECTS OF CONTACT SENSITIZERS NEOMYCIN SULFATE, BENZOCAINE AND 2,4-DINITROBENZENE 1-SULFONATE, SODIUM-SALT ON VIABILITY, MEMBRANE INTEGRITY AND IL-1-ALPHA MESSENGER-RNA EXPRESSION OF CULTURED NORMAL HUMAN KERATINOCYTES

The toxic effect of three potential contact sensitization chemicals [t he aminoglycosidic antibiotic neomycin sulfate, the local anaesthetic benzocaine and the primary sensitizer 2,4-dinitrobenzene 1-sulfonate, sodium salt (DNBS)], on cultured human keratinocytes was examined. The three chemicals were compared with respect to their cytotoxic potenti al (determined by crystal violet staining assay), their membrane disru ptive potential ([H-3]arachidonic acid release assay), and their effec ts on interleukin 1 alpha (IL-1 alpha) mRNA expression [reverse transc ription-polymerase chain reaction (RT-PCR)]. At the concentrations use d, neomycin sulfate (0.004-0.32%) and benzocaine (0.0165-0.165%) did n ot show relevant cytotoxicity or membrane perturbation. On the other h and, DNBS (0.001-1%) caused a significant dose-dependent cytotoxic res ponse at concentrations higher than 0.1%, while the [H-3]arachidonic a cid release assay indicated absence of membrane perturbation activity in all the range of DNBS concentrations examined. The effects of the t hree sensitizers on IL-1 alpha mRNA expression were varied; neomycin s ulfate caused a dose-dependent induction of IL-1 alpha mRNA, benzocain e did not significantly affect its signal, and DNBS suppressed IL-1 al pha gene expression.