By Maria Teresa
de Teixeira Cruz Rosete, University of Coimbra
Allergic skin reactions are one of the most common occupational diseases in developed countries, and 19.5% of the general population is sensitive to at least one allergen. A large subset of skin allergens can be found in the environment and in many household products. Metals are one example of a type of skin allergen, with nickel the more prevalent skin allergen in Europe. As a result, before any substance (pharmaceutical compounds, cosmetics, chemicals, etc.) can be brought onto the European market, it must first be evaluated for its skin safety.
Several tests performed in mice have proven accurate in predicting chemicals that possess skin-allergy properties, such as the local lymph node assay. However, skin allergy potential is an endpoint that needs to be assessed within the framework of existing and forthcoming legislation, namely the 7th Amendment to the Cosmetic Directive and, more recently, the new European Cosmetic Regulation, both of which seek to gradually eliminate animal experiments from the safety and toxicity testing of cosmetic ingredients and other chemical substances. The final cut-off date for such testing is March 2013, when cosmetic products containing an ingredient whose safety was tested in animals will not be allowed for sale in Europe. Therefore, the rapid development and validation of testing strategies that do not involve animals is a prerequisite to maintain Europe’s competitiveness in the cosmetic industry. Another legislative piece that is forcing the development of alternative non-animal testing strategies for chemicals toxicological safety is the policy REACH (Registration, Evaluation and Authorization of Chemicals), which went into effect in June 2007. The implementation of this new chemicals policy results in the need for additional toxicological testing of 100,000 already commercialized chemicals, saving an estimated 2 million animals from being sacrificed to skin allergy assessment.
Therefore, for cosmetic and chemistry industries there is an urgent need to find non-animal tests. Despite intense research, non-animal tests for skin sensitization are not available. Currently, the most promising alternative approaches are based on a specific cell type of the skin: dendritic cells. These cells play a pivotal role in the development of skin allergy. In this context, our laboratory (Center for Neuroscience and Cell Biology) developed a non-animal method for predicting whether a compound will provoke skin allergy in humans by using mammalian, dendritic skin cells with a multiple endpoints analysis; this process included the detection of proteins and genes implicated in skin allergy. Based on the results obtained for a large panel of allergens, we constructed a statistical classification model that is programmed and optimized to classify unknown chemicals as either allergens or non-allergens. Our experiments allowed the development of a fast, inexpensive and (high throughput) cell-based test for skin allergy evaluation, which permits the identification of chemicals with skin allergic properties without using animals, as demanded by the new EU legislation. In addition to ethical considerations, this non-animal approach will be of the uttermost importance for the pharmaceutical, chemical, cosmetic, pesticide and food industries.
Maria Teresa de Teixeira Cruz Rosete
University of Coimbra
www.atomiumculture.eu
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