A full-UV spectrum absorbing daily use cream protects human skin against biological changes occurring in photoaging

Background: There is overwhelming evidence that exposure of human skin to u ltraviolet radiations (UVR) leads to the development of cutaneous photoagin g and eventually to neoplasia, This study was designed to evaluate in human s the protection afforded by a daily use cream containing a photostable com bination of UVB and UVA absorbers (Uvinul(R) N539, Parsol(R) 1789 and Mexor yl(R) SX) providing a continuous absorption through the entire UV spectrum, against damages induced by repeated daily exposure to solar simulated radi ation (SSR). Methods: Buttock skin of 12 healthy volunteers was exposed 5 days per week for 6 weeks to one minimal erythema dose of solar simulated radiation per e xposure. The following parameters in treated and untreated skin were evalua ted: erythema, pigmentation, skin hydration, skin microtopography, histolog y and immunochemistry, and collagen and metalloproteinase (MMP) mRNA levels . Results: In SSR exposed unprotected skin sites, we observed melanization an d changes in the skin hydration and microtopography. The epidermis revealed a significant increase in stratum corneum and stratum granulosum thickness . In the dermis, an enhanced expression of tenascin and a reduced expressio n of type I pro-collagen were evidenced just below the dermal epidermal jun ction. Although we were unable to visualize any change in elastic fibers in exposed buttock skin, a slightly increased deposition of lysozyme and alph a 1 antitrypsin on these fibers was observed using immunofluorescence techn iques. Furthermore, types I and III collagen mRNA were slightly increased a nd a significant enhancement (up to 2.8-fold) of MMP-2 mRNA level was obser ved. The daily use cream was shown to prevent all these biological changes. Conclusion: Our results show in vivo that an appropriate full-UV spectrum p roduct significantly reduces the solar-UV-induced skin damage, demonstratin g the benefit of daily photoprotection.