JOURNAL OF COSMETIC SCIENCE 100 factor α (TNFα) also plays a role in UVB-induced immunosuppression, Figure 2D] com- bine to prevent this detrimental mechanism. This study highlights the important role of Galectin-7, a β-galactoside-binding lectin naturally expressed in normal skin, in UVB-mediated immunosuppression. Gal ectin-7 is overexpressed after UVB irradiation and participates to the apoptotic process set up in sunburn keratinocytes (Figure 2E) (3). However, it was recently shown that Galectin-7 overexpression also occurs in the presence of cis UCA, and downregulates T lymphocyte functions (Figure 2F) (2), thus pointing to a potential role in immuno- suppression. METHODS PHOTOISOMERISATION ASSAYS In vitro assays. Reconstructed human epidermis (RHE) obtained from Skinethic Labora- tory (Lyon, France) at day 17 were irradiated at 500 mJ/cm2 with/without (w/wo) ingre- dient. Immediately after irradiation, RHEs were cryofreezed before extraction and high-performance liquid chromatography analysis [in collaboration with Synelvia (Toulouse, France)] for cis- and trans-UCA quantifi cation. ANTI-OXIDANT TESTS The CUPRAC method was used to determine MTPC hydroxyl radical scavenging con- stant. Cytoprotection was assessed in vitro: HaCaT cells were exposed to ultraviolet-A Figure 1. UVB-induced photoisomerisation of trans-UCA and MTPC. Trans MTPC is a natural product (Entadamide A) found in tropical plants of the Entada genus. Figure 2. Signalling pathways involved in UVB-induced immunosuppression.

UROCANIC ACID MIMIC AS SUNSCREEN 101 (UVA) irradiation (Waldmann) and generation of intracellular ROS was visualized after incorporation of the 2’,7’-dichlorodihydrofl uorescein diacetate (CMH2-DCFDA) probe. ASSESSMENT OF PHOTOPROTECTIVE ACTIVITY Cell culture. HaCaT keratinocytes were cultured at 37°C/5% CO2 in growth media con- sisting of DMEM [1 g/l glucose, 10% fetal calf serum (FCS)] supplemented by 1% of antibiotic cocktail. All culture media were obtained from Invitrogen. RHEs were supplied from Skinethic laboratory and have been used starting at 17th day of differentiation. UVB irradiation. HaCaT cells were seeded in 6-well plates at 8000 cells/cm2 3 days before irradiation (100 mJ/cm2, Waldmann lamp) w/wo active ingredient (MTPC) at various Figure 3. In vitro competitive isomerisation assay with human reconstituted epidermis. Dosage of cis and trans UCA in UVB-irradiated RHE topically treated with the active ingredient MTPC or with a reference photoprotective cream (positive control). Figure 4. Cell viability monitoring (MTT assay) in UVB-irradiated HaCaT keratinocytes treated with MTPC. All experiments were performed in triplicates. SEM errors bars are represented in black line and t-test was used for statistical analysis with *p 0.05, **p 0.01, ***p 0.001.