Pascal Portes

Refinement of the Episkin protocol for the assessment of acute skin irritation of chemicals: follow-up to the ECVAM prevalidation study.

The Episkin model took part in the prevalidation study on in vitro tests for acute skin irritation of chemicals, which was carried out during 1999 and 2000. This prevalidation study was co-ordinated and supported by the European Centre for the Validation of Alternative Methods (ECVAM). During Phase 1 and Phase 2 of this study, reproducibility and transferability of the method were verified. Unfortunately, the performance of the method in terms of predictive ability was considered insufficient, due to a low specificity. In order to improve the performance of the Episkin method, the existing protocol was refined. This refinement consisted in reducing the exposure time of epidermis with chemicals. Sensitivity, specificity and accuracy of the new method were 70, 80 and 75%, respectively, thus meeting the acceptance criteria as defined by the Management Team. The Episkin method is now ready to enter a validation study of in vitro tests for acute skin irritation.

Use of human reconstituted epidermis Episkin® for assessment of weak phototoxic potential of chemical compounds

Background/purpose: Drug‐induced phototoxicity is a non‐immunological inflammatory skin reaction, caused by concurrent topical or systemic exposure to a specific molecule and ultraviolet radiation. Most of phototoxic compounds absorb energy particularly from UVA light leading to activated derivatives, which can induce cellular damage. This type of adverse cutaneous response can be reproduced, in vitro, using human skin models. In this study, we investigated the ability of human reconstituted epidermis Episkin® to assess skin phototoxicity of weak phototoxic compounds such as 6‐methylcoumarin and ofloxacin, compared to a strong one, chlorpromazine, and two negative controls (sodium dodecyl sulphate (SDS), sulisobenzone).

Skin cell protection against UVA by Sideroxyl, a new antioxidant complementary to sunscreens

Oxidative stress resulting from photosensitized ROS production in skin is widely accepted as the main contributor to the deleterious effects of UVA exposure. Among the mechanisms known to be involved in UVA-induced oxidative damage, iron plays a central role. UVA radiation of skin cells induces an immediate release of iron, which can then act as a catalyst for uncontrolled oxidation reactions of cell components. Such site-specific damage can scarcely be counteracted by classical antioxidants. In contrast, iron chelators potentially offer an effective way to protect skin against UVA insults. However, iron chelation is very difficult to achieve without disturbing iron homeostasis or inducing iron depletion. A novel compound was developed to avoid these potentially harmful side effects. Sideroxyl was designed to acquire its strong chelating capability only during oxidative stress according to an original process of intramolecular hydroxylation. Herein, we describe in vitro results demonstrating the protective efficiency of Sideroxyl against deleterious effects of UVA at the molecular, cellular, and tissular levels. First, the Sideroxyl diacid form protects a model protein against UVA-induced photosensitized carbonylation. Second, intracellular ROS are dose-dependently decreased in the presence of Sideroxyl in both human cultured fibroblasts and human keratinocytes. Third, Sideroxyl protects normal human fibroblasts against UVA-induced DNA damage as measured by the comet assay and MMP-1 production. Finally, Sideroxyl provides protection against UVA-induced alterations in human reconstructed skin. These results suggest that Sideroxyl may prevent UVA-induced damage in human skin as a complement to sunscreens, especially in the long-wavelength UVA range.

Iron chelation can modulate UVA-induced lipid peroxidation and ferritin expression in human reconstructed epidermis.

Background/Purpose: As ferritin has been identified as an important factor in antioxidant defense in cultured human skin cells, we evaluated UVA‐induced lipid hydroperoxides (LPO) production and ferritin expression in reconstructed human epidermis in vitro.