Effect of squalene monohydroperoxide on cytotoxicity and cytokine release in a three-dimensional human skin model and human epidermal keratinocytes

In the screening of topical drugs, cosmetics and other chemicals for human use, it is very important, both from a safety and an economic point of view, to have biological markers to discriminate irritant and allergic contact dermatitis that have different impacts on human health. Owing to their anatomical location, keratinocytes are among the first cells to be exposed to various antigens and the use of these cells as a simplified in vitro model to evaluate the potential toxicity of chemicals destined for cutaneous application is amply justified. The purpose of this work was to identify new genes selectively modulated by skin toxicants. Commercially available reconstituted human epidermis (Epiderm) was treated for 18 h with sodium dodecyl sulfate (SDS) 0.4 mg/ml, as reference irritant, or with dinitrochlorobenzene (DNCB) 0.2 mg/ml, as reference allergen, or with vehicle control. Differential display PCR (DD-PCR) was performed. Results identified adipose differentiation-related protein (ADRP) as up-regulated by both irritant and allergen, and KIAA0368 as selectively up-regulated by contact allergen. These data indicate the enormous potential of functional genomic techniques, which allow the identification of genes not immediately connected with the immune response, or even novel genes with unknown functions, which nevertheless may be potential markers of skin irritation and allergy.