Assessment of the skin sensitizing potential of chemicals, contained in foods and/or cosmetic ingredients, using a modified local lymph node assay with an elicitation phase (LLNA:DAE) method.

We evaluated the skin sensitizing potential of 10 natural organic chemicals, or their derivatives, which are included in foods and/or skin products, using a modified local lymph node assay (LLNA), with an elicitation phase (LLNA:DAE). The following compounds were tested: carminic acid, esculetin, 4-methyl esculetin, coumarin, quercetin, curcumin, naringenin, chlorogenic acid, isoscopoletin, and shikonin. Esculetin, 4-methyl esculetin, isoscopoletin, and shikonin yielded positive results.

Unsaturated fatty acids show clear elicitation responses in a modified local lymph node assay with an elicitation phase, and test positive in the direct peptide reactivity assay.

The Organisation for Economic Co-operation and Development (OECD) Test Guidelines (TG) adopted the murine local lymph node assay (LLNA) and guinea pig maximization test (GPMT) as stand-alone skin sensitization test methods. However, unsaturated carbon-carbon double-bond and/or lipid acids afforded false-positive results more frequently in the LLNA compared to those in the GPMT and/or in human subjects. In the current study, oleic, linoleic, linolenic, undecylenic, fumaric, maleic, and succinic acid and squalene were tested in a modified LLNA with an elicitation phase (LLNA:DAE), and in a direct peptide reactivity assay (DPRA) to evaluate their skin-sensitizing potential.

Further development of LLNA:DAE method as stand-alone skin-sensitization testing method and applied for evaluation of relative skin-sensitizing potency between chemicals.

To date, there has been no well-established local lymph node assay (LLNA) that includes an elicitation phase. Therefore, we developed a modified local lymph node assay with an elicitation phase (LLNA:DAE) to discriminate true skin sensitizers from chemicals that gave borderline positive results and previously reported this assay. To develop the LLNA:DAE method as a useful stand-alone testing method, we investigated the complete procedure for the LLNA:DAE method using hexyl cinnamic aldehyde (HCA), isoeugenol, and 2,4-dinitrochlorobenzene (DNCB) as test compounds.

Development of LLNA:DAE: a new local lymph node assay that includes the elicitation phase, discriminates borderline-positive chemicals, and is useful for cross-sensitization testing.

We developed a new local lymph node assay (LLNA) that includes the elicitation phase termed LLNA:DAE for discrimination of borderline-positive chemicals as classified by the LLNA modified by Daicel based on ATP content (LLNA:DA) and for cross-sensitization testing. Although the LLNA:DA method could help identify skin sensitizers, some skin irritants classified as non-sensitizers by the LLNA were classified as borderline positive. In addition, the evaluation for the cross-sensitization potential between chemicals was impossible.

A catch-up validation study of an in vitro skin irritation test method using reconstructed human epidermis LabCyte EPI-MODEL24.

Three validation studies were conducted by the Japanese Society for Alternatives to Animal Experiments in order to assess the performance of a skin irritation assay using reconstructed human epidermis (RhE) LabCyte EPI-MODEL24 (LabCyte EPI-MODEL24 SIT) developed by the Japan Tissue Engineering Co., Ltd. (J-TEC), and the results of these studies were submitted to the Organisation for Economic Co-operation and Development (OECD) for the creation of a Test Guideline (TG).