Differentiation of skin sensitizers from irritant chemicals by interleukin-1α and macrophage inflammatory protein-2 in murine keratinocytes.

The development of novel alternative testing methods is required to identify the sensitizing capacity of chemicals as a replacement for animal experimentation. We aimed to evaluate in vitro assays as screening tools for detecting skin sensitizers. The murine epidermal keratinocyte cell line HEL-30 was exposed to 16 relevant skin sensitizers and 6 skin irritants. The dose causing 75% cell viability (CV(75)) measured by an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was chosen as a highest dose and three more doses (0.5×, 0.1×, and 0.01× of CV(75)) were tested. As parameters, levels of interleukin 1α (IL-1α), macrophage inflammatory protein 2 (MIP-2), IL-6, and IL-18 production were measured using 4 different doses. The accuracy of detecting sensitizers or irritants by IL-1α or MIP-2 alone was exactly same: 75% (12 out of 16) for sensitizers, 83% (5 out of 6) for irritants, and overall 77% (17 out of 22). However, combination of IL-1α and MIP-2 showed better accuracy: 94% (15 out of 16), 67% (4 out of 6), and overall 86% (19 out of 22). IL-6 and IL-18 could not differentiate sensitizers from irritants. This study suggests that the combination of pro-inflammatory cytokines IL-1α and MIP-2 in murine HEL-30 cells can be a reliable in vitro method for identifying chemicals that may act as skin sensitizers.