Photostability of sunscreen products influences the efficiency of protection with regard to UV-induced genotoxic or photoageing-related endpoints.
BACKGROUND
Acute as well as chronic sun exposure induces biologically damaging effects in skin including photoageing and cancer. Ultraviolet (UV)A radiation is involved in this process; it is therefore important that sunscreen products provide efficient and stable protection in this range of wavelengths.


OBJECTIVE
This study based on in vitro approaches was performed to demonstrate that photostability is an essential requirement to protect against UVA-induced genetic and dermal alterations.


METHODS
The protection afforded by two sunscreen products, differing with regard to their photostability, was studied using biological markers related to the genotoxic or photoageing impact of UVA or simulated solar UV radiation (UV-SSR). Comet assay was used to assess direct DNA breakage, photo-oxidized purines and lomefloxacin-induced DNA breaks in nuclei of normal human keratinocytes in culture. In similar conditions, detection of p53 accumulation was performed. The use of reconstructed skin in vitro allowed us to use a three-dimensional model to analyse the dermal and epidermal damage induced by UVA or UV-SSR exposure. Abnormal morphological features of the tissue as well as fibroblast alterations and matrix metalloproteinase-1 release induced by UV exposure have been studied after topical application of products on the skin surface.


RESULTS
The results showed that the photostable product afforded better protection with regard to all the criteria studied, compared with the photounstable product.


CONCLUSIONS
These data demonstrate that the loss of absorbing efficiency within the UVA wavelength domain due to photoinstability may have detrimental consequences on cell function and lead to impairments that have been implicated in genotoxic events as well as in the photoageing process.
Marrot
L
L
Genotoxicity Group, L'OREAL Recherche, 1 Avenue E. Schueller, 93600 Aulnay sous Bois, France. lmarrot@recherche.loreal.com
Belaïdi
J P
JP
Lejeune
F
F
Meunier
J R
JR
Asselineau
D
D
Bernerd
F
F
D018929:Cell Culture Techniques; D020552:Comet Assay; D004249:DNA Damage / Q000187:drug effects*; D004307:Dose-Response Relationship, Radiation; D004355:Drug Stability; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000528:radiation effects; D012867:Skin / Q000528:radiation effects; D015595:Skin Aging / Q000187:drug effects* / Q000528:radiation effects; D017768:Skin, Artificial; D013473:Sunscreening Agents / Q000737:chemistry* / Q000494:pharmacology / Q000528:radiation effects; D046509:Tissue Culture Techniques; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014466:Ultraviolet Rays
D013473:Sunscreening Agents; D016159:Tumor Suppressor Protein p53