JOURNAL OF COSMETIC SCIENCE 104 ANTIOXIDANT PROPERTIES MTPC is a versatile antioxidant, scavenging hydroxyl radicals (CUPRAC method: 5.72 × 109 M/s), limiting hydrogen peroxide cell toxicity, and preventing photosen- sitization reactions. Accordingly, it could limit intracellular oxidative stress induc- tion in UVA-irradiated keratinocytes (monitoring with the CM-DCFDA probe, data not shown). PHOTOPROTECTIVE PROPERTIES Cell viability improvement. MTPC dose-dependently reduces UVB-induced cytotoxicity, when applied during irradiation (100 mJ/cm2), as shown in Figure 4. Improved cell viability was confi rmed in RHE experiments by histological analysis (he- motoxylin and eosin staining) that showed that topical application of MTPC preserves epidermis integrity (data not shown). Inhibition of UVB-induced DNA damages. DNA represents the most important cellular chromophore for UVB and absorption causes DNA damage, preferentially CPDs and Figure 9. Monitoring of Galectin-7 secretion by HaCaT keratinocytes (A) or RHE (B) exposed to UVB. All experiments were performed in triplicates. t-test was used for statistical analysis with *p 0.05, **p 0.01, ***p 0.001, and ND: not determined. Figure 10. Monitoring of Galectin-7 effect on the production of IL-2 (A) and IFN-γ (B) by activated and nonactivated jurkat T lymphocytes.

UROCANIC ACID MIMIC AS SUNSCREEN 105 pyrimidine (6-4) pyrimidone photoproducts (6-4PP). We found that MTPC very effi - ciently prevents UVB-induced DNA damages as revealed by CPD monitoring in irradi- ated HaCaT keratinocytes (Figure 5) and RHE (Figure 6). Inhibition of UVB-induced pro-infl ammatory cytokines release. As UVB is well known to induce pro-infl ammatory cytokines release in skin, we measured IL-8, TNFα, and IL-6 secretion from UVB-irradiated HaCaT keratinocytes. We found that MTPC dose-dependently in- hibits the production of these three cytokines (data not shown). This inhibition of pro- infl ammatory cytokines release was also observed when irradiated RHEs were topically treated with MTPC (Figure 7). Anti-infl ammatory property of Entadamide A (trans MTPC). In line with previous in vitro results (1) showing that Entadamide A inhibits 5-LOX, a key infl ammatory enzyme of the arachidonic acid cascade, we found that the MTPC isomerisation product dose-dependently inhibits 5-LOX catalytic activity (Figure 8). INHIBITION OF UVB-INDUCED IMMUNOSUPPRESSIVE SIGNALLING The MTPC properties presented above support the hypothesis that MTPC strongly op- poses UVB-induced immunosuppression because it interferes with several signalling pathways of this process (Figure 2): cis UCA formation (4), DNA damages induction [as CPDs formation is directly involved in immunosuppressive signalling (5)], and TNFα overexpression, which was recently shown to act downstream DNA damage (5).We thus chose to monitor the recently identifi ed mediator Galectin-7 (Gal7), as it is involved in both cis UCA and DNA damages immunosuppressive signalling (Figure 2). In our two-dimensional (HaCaT keratinocytes) or three-dimensional (RHE) in vitro mod- els, UVB strongly increases Gal7 expression. Addition of MTPC abrogates this overex- pression (Figure 9). Because UVB also impairs T-cell-mediated immune function, we set up a more specifi c model. Activated Jurkat T-lymphocyte cells were exposed to Gal7, and we monitored IL-2 and interferon-γ (IFN-γ, two signalling cytokines of the immune system. We used a recombinant Gal7 as HaCaT cells produce too low amounts, and because some constitu- ents of RHE culture medium interfere with the assay. When exposed to a recombinant Gal7, Jurkat T-lymphocytes produce less IL-2 and IFN-γ (Figure 10). This fi nding shows that Gal7 overexpression can impair T-cell-mediated immunity, and supports an impor- tant role for Gal7 in UVB immunosuppressive property. CONCLUSION Our experiments have shown that MTPC, a nature-inspired molecule, protects the skin from the deleterious effect of UVB thanks to a combination of three mechanisms (UV absorption, antioxidation, and anti-infl ammation). These fi ndings support the usefulness of MTPC for sun care or photoaging prevention. REFERENCES (1) F. Ikegami, T. Sekine, M. Aburada, Y. Fujii, Y. Komatsu, and I. Murakoshi, Purifi cation and Properties of a Plant β-D-Glucuronidase from Scutellaria Root.Chem. Pharm. Bull., 37, 1932–1933 (1989).