Human keratinocyte cultures in an in vitro approach for the assessment of surfactant-induced irritation

A specific, mechanistic, in vitro approach for the assessment of human skin irritation potential is outlined for the evaluation of surfactants and the results compared with in vivo human patch test data. The level of free available surfactant monomer and the solubilization of the corn protein zein in vitro were confirmed to be related to surfactant in vivo human skin irritation potential. In vitro cytotoxicity to monolayer keratinocyte cultures could not discriminate between the moderate human skin irritant sodium dodecyl sulfate (SDS) and the mild irritants cocamidopropylbetaine (CA) and Polysorbate 20 (P20). An in vitro stratified differentiated human epidermal equivalent (HEE) exhibited reduced cytotoxicity to the test chemicals, compared with monolayer culture responses, and was able to discriminate between the toxic potential of SDS and CA. Stimulation of interleukin-1α release from the A431 human keratinocyte cell line reflected in vivo erythema scores more closely than cytotoxic potential, and coincided with nitric oxide production by macrophages upon exposure to A431-conditioned medium. Combination of these mechanistic assays has allowed a profile of likely in vivo human responses to be approximated. Additional knowledge of skin penetrability and rate of recovery from toxic damage would affirm these predictions.