Skin sensitisation prediction using read-across, an illustrative next generation risk assessment (NGRA) case study for vanillin.

Skin sensitisation is a key adverse human health effect to be addressed in the safety assessment of cosmetic ingredients. Regulatory demands and scientific progress have led to the development of a Next Generation Risk Assessment (NGRA) framework, relying on the use of New Approach Methodologies (NAM) Defined Approaches (DA) and read-across instead of generating animal data. This case study illustrates the application of read-across for the prediction of the skin sensitisation potential of vanillin at the hypothetical use concentration of 0.5% in a shower gel and face cream. A three-step process was applied to select the most suitable analogues based on their protein reactivity, structural characteristics, physicochemical properties, skin metabolism profile and availability of skin sensitisation data. The applied read-across approach predicted a weak skin sensitiser potential for vanillin corresponding with a Local Lymph Node Assay EC3 value of 10%. Based on this EC3 value a point of departure of 2500 µg/cm2 was derived, resulting in an acceptable exposure level (AEL) of 25 µg/cm2. Because the consumer exposure levels (CEL) for the face cream (13.5 µg/cm2) and shower gel (0.05 µg/cm2) scenarios were lower than the AEL, the NGRA concluded both uses as safe.

Next generation risk assessment for skin sensitisation: A case study with propyl paraben.

Skin sensitisation is a key adverse health effect to be addressed in the safety assessment of cosmetic ingredients. Regulatory demands have urged the development of Next Generation Risk Assessment (NGRA) using New Approach Methodologies (NAM) and Defined Approaches (DA) instead of animal models. An illustrative NGRA case study shall demonstrate if the use of propyl paraben at 0.2% in a face cream was safe for consumers. A sequential stacking tier testing DA based on NAM data predicted propyl paraben to be a non-sensitiser, while some NAM input data showed positive results. To increase confidence, structurally related parabens were considered, which revealed NAM and DA hazard predictions similar to those of propyl paraben, non-sensitiser classifications in animal models and very rare cases of human skin allergy. Based on a weight of evidence it was decided that propyl paraben should be considered a non-sensitiser leading to a favourable NGRA conclusion, in line with traditional risk assessment. Examination of an ab initio NGRA based on NAM and metabolism data resulted in a more conservative weak sensitiser consideration as point of departure, which still led to a favourable conclusion.

Read-across can increase confidence in the Next Generation Risk Assessment for skin sensitisation: A case study with resorcinol.

Historically skin sensitisation risk assessment for cosmetic ingredients was based on animal models, however regulatory demands have led to Next Generation Risk Assessment (NGRA), using data from New Approach Methodologies (NAM) and Defined Approaches (DA). This case study was meant to investigate if the use of resorcinol at 0.2% in a face cream was safe and a maximum use concentration could be defined. The NAM data and DA predictions could not provide sufficient confidence to determine a point of departure (POD). Therefore, the application of read-across was explored to increase the level of confidence. Analogue searches in various tools and databases using "mode of action" and "chemical structural features" retrieved 535 analogues. After refinement by excluding analogues without a defined structure, similar reactivity profile and skin sensitisation data, 39 analogues remained. A final selection was made based on three approaches: expert judgment, chemical similarity or Local Lymph Node Assay data (LLNA). All read-across approaches supported a moderate potency. A POD derived from the LLNA EC3 of 3.6% was determined leading to a favourable NGRA conclusion and a maximum use concentration of 0.36%. This was supported by a traditional risk assessment based on the available animal data for resorcinol.

Glucocorticoid-induced leucine zipper (GILZ) promotes the nuclear exclusion of FOXO3 in a Crm1-dependent manner.

GILZ (glucocorticoid-induced leucine zipper) is an ubiquitous protein whose expression is induced by glucocorticoids in lymphoid cells. We previously showed that GILZ expression is rapidly induced upon interleukin 2 deprivation in T-cells, protecting cells from apoptosis induced by forkhead box subgroup O3 (FOXO3). The aim of this work is to elucidate the molecular mechanism of FOXO factor inhibition by GILZ. We show in the myeloid cell line HL-60 and the lymphoid CTLL-2 T-cell line that GILZ down-regulates the expression of p27(KIP1) and Bim, two FOXO targets involved in cell cycle regulation and apoptosis, respectively. GILZ inhibits FOXO1, FOXO3, and FOXO4 transcriptional activities measured with natural or synthetic FOXO-responsive promoters in HL-60 cells. This inhibitory effect is independent of protein kinase B and IkappaB kinase phosphorylation sites. GILZ does not hinder FOXO3 DNA-binding activity and does not physically interact with FOXO3. However, using fluorescence microscopy, we observe that GILZ expression provokes a Crm-1-dependent nuclear exclusion of FOXO3 leading to its relocalization to the cytoplasm. Moreover, GILZ exclusive cytoplasmic localization is a prerequisite for FOXO3 inhibition and relocalization. We propose that GILZ is a general inhibitor of FOXO factors acting through an original mechanism by preventing them from reaching target genes within the nucleus.

Metallic haptens induce differential phenotype of human dendritic cells through activation of mitogen-activated protein kinase and NF-kappaB pathways.

Dendritic cells (DCs) play a major role in the regulation of immune responses to a variety of antigens (Ag) and haptens which participate in the process of DC maturation. Indeed, metallic haptens are able to induce DC maturation in vitro but the mechanism of this maturation is not well understood. We and others have already shown that NiSO(4) activates p38 mitogen-activated protein kinases (p38MAPK), c-jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and the transcription factor NF-kappaB during the early events of DCs maturation. However, the effect of other metallic haptens on DC maturation is still poorly understood. In the present study, using dendritic cells derived from CD34(+) cord blood cells, we showed that both NiSO(4) and CoCl(2) induced the expression of CD86, CD83, HLA-DR and CD40 and the production of IL-6 in human DCs while K(2)Cr(2)O(7) induced only a slight upregulation of CD86. Interestingly, only NiSO(4) was able to induce the production of IL-12p40. NiSO(4) and CoCl(2) but not K(2)Cr(2)O(7) were able to activate the MAPK pathway and the transcription factor NF-kappaB. The role of MAPKs in metals-induced DC maturation was then evaluated using well-described pharmacological inhibitors. Our results suggest that p38MAPK activation regulates the expression of CD86 and CD83 induced by NiSO(4) while it only affects the expression of CD83 induced by CoCl(2). IL-6 production induced by NiSO(4) and CoCl(2) strongly depended on all MAPKs. IL-12p40 synthesis after NiSO(4) treatment was regulated by both p38MAPK and JNK pathways whereas ERK may play an inhibitory role. Our results show that both NiSO(4) and CoCl(2) activate similar signaling pathways that are playing different roles in DC maturation depending on the hapten used.