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New In vitro Guidelines from the OECD: h-CLAT and Androgen Receptor Transcriptional Activation (ARTA)

The OECD recently published two new test guidelines for safety assessment. OECD TG 442E details the recommended testing procedure for the human Cell Line Activation Test (h-CLAT) for skin sensitisation. OECD TG 458 outlines assessment of Androgen Receptor Agonists and Antagonists using the Stably Transfected Transactivation method.

The h-CLAT test method is an in vitro assay that determines if a compound is a skin sensitiser or non-sensitiser according the Global Harmonised System (GHS). This assay examines one of the key steps in the Adverse Outcome Pathways (AOP) that occurs during a dermal sensitisation reaction. This assay measures the expression of surface markers CD54 and CD86 in the THP-1 human monocytic cell line. This event is implicated in the induction of type IV hypersensitisation. Flow cytometry is used to measure the change in expression of the surface markers, and the relative fluorescence intensity is compared to control to differentiate between GHS sensitisers and non-sensitisers.

The Stably Transfected Human Androgen Receptor Transcriptional Activation Assay utilises luciferase to determine signal activation or blocking of androgen receptors (AR) caused by AR ligands. Once an agonist interacts with the androgen receptor and a ligand-receptor complex is formed, it translocates to the nucleus of the cell, transactivating a firefly luciferase reporter gene and inducing luciferase expression. Conversely, this process is blocked by antagonists, inhibiting the natural ligand from activating the receptor. While there are several commercially available means to evaluate luciferase activity, TG 458 specifies the AR-EcoScreen™ cell line.

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