The present Test Guideline addresses the human health hazard endpoint skin sensitisation, following exposure to a test chemical. Skin sensitisation refers to an allergic response following skin contact with the tested chemical, as defined by the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (UN GHS).
This Test Guideline (TG) provides an in vitro procedure (the ARE-Nrf2 luciferase test method) used for supporting the discrimination between skin sensitisers and non-sensitisers in accordance with the UN GHS.
The second key event on the adverse outcome pathway leading to skin sensitisation takes place in the keratinocytes and includes inflammatory responses as well as gene expression associated with specific cell signalling pathways such as the antioxidant/electrophile response element (ARE)-dependent pathways. The test method described in this Test Guideline (ARE-Nrf2 luciferase test method) is proposed to address this second key event. The cell line contains the luciferase gene under the transcriptional control of a constitutive promoter fused with an ARE element from a gene that is known to be up-regulated by contact sensitisers. The luciferase signal reflects the activation by sensitisers of endogenous Nrf2 dependent genes. This allows quantitative measurement (by luminescence detection) of luciferase gene induction, using well established light producing luciferase substrates, as an indicator of the activity of the Nrf2 transcription factor in cells following exposure to electrophilic test substances.
Currently, the only in vitro ARE-Nrf2 luciferase test method covered by this Test Guideline is the KeratinoSensTM test method. Performance standards have been developed to enable the validation of similar test methods.