Potential method to determine irritant potency in vitro – Comparison of two reconstructed epidermal culture models with different barrier competency

Testing chemicals for their ability to cause skin irritation is required for all ingredients of products that come into contact with the skin. Here, we describe a potential method for determining the irritant potency of a chemical in vitro and apply the method to two different reconstructed epidermis models which exhibit different barrier properties. Two surfactants: sodium dodecyl sulphate, Triton X100 and two non-surfactants: 2-4-di-nitro-chloro-benzene, cinnamaldehyde were applied topically in a dose response for 24 h. Biomarkers IL-1alpha, IL-1RA, IL-8 and MTT were assessed and EC50 values determined. Variation in barrier properties between the epidermal models led to variation in the extent of penetration of surfactants, but not of non-surfactants which in turn influenced the EC50 value obtained from surfactants. Furthermore, EC50 values showed that no single biomarker could be classed as the most sensitive biomarker since biomarker sensitivity differed between the different chemicals studied. However, the ranking of the chemicals in order of strong to weak irritant was the same irrespective of the model used and also independent of the biomarker used (Triton X100 > DNCB > SDS > CA). This study describes a method which not only distinguishes an irritant from a non-irritant but which may possibly also be used to determine irritant potency.