Effects of contact sensitizers neomycin sulfate, benzocaine and 2,4-dinitrobenzene 1-sulfonate, sodium salt on viability, membrane integrity and IL-1α mRNA expression of cultured normal human keratinocytes

The toxic effect of three potential contact sensitization chemicals [the aminoglycosidic antibiotic neomycin sulfate, the local anaesthetic benzocaine and the primary sensitizer 2,4-dinitrobenzene l-sulfonate, sodium salt (DNBS)], on cultured human keratinocytes was examined. The three chemicals were compared with respect to their cytotoxic potential (determined by crystal violet staining assay), their membrane disruptive potential ([ 3h]arachidonic acid release assay), and their effects on interleukin 1α (IL-1α) mRNA expression [reverse transcription-polymerase chain reaction (RT-PCR)]. At the concentrations used, neomycin sulfate (0.004–0.32%) and benzocaine (0.0165-0.165%) did not show relevant cytotoxicity or membrane perturbation. On the other hand, DNBS (0.001-1%) caused a significant dose-dependent cytotoxic response at concentrations higher than 0.1%, while the [ 3h]arachidonic acid release assay indicated absence of membrane perturbation activity in all the range of DNBS concentrations examined. The effects of the three sensitizers on IL-1α mRNA expression were varied; neomycin sulfate caused a dose-dependent induction of IL-1α mRNA, benzocaine did not significantly affect its signal, and DNBS suppressed IL-1α gene expression.