Sunscreens containing the broad-spectrum UVA absorber, Mexoryl SX, prevent the cutaneous detrimental effects of UV exposure: a review of clinical study results.
BACKGROUND
UVA exposure of human skin mainly produces reactive oxygen species (ROS) leading to DNA, cell and tissue damage. It alters immune function, pigmentation and it is certainly responsible for a large part of photoaging changes. Moreover UVA is implicated in the etiology of several photodermatoses. As a consequence, to provide adequate protection, sunscreens or skin care products for daily use protective products need UVA absorbers combined with UVB ones.


OBJECTIVE
To assess the efficacy of sunscreens containing a broad-spectrum UVA absorber the Mexoryls SX or ecamsule and to compare formulations with and without it through a large number of clinical studies in human volunteers and patients.


METHODS
The following assessments were conducted: *Prevention of excessive pigmentation induced by UV exposure in Caucasian and Asian skins using a method that measures pigmentation protection factors (PPF). *Efficacy against DNA damage by measurement of pyrimidine dimer formation and p53 protein accumulation. *Protection of immune system using delayed type hypersensitivity (DTH) reactions to recall antigens, isomerization of urocanic acid (UCA), alteration of Langerhans cells (LC) density, morphology and function. *Reduction of epidermal and dermal alterations induced by repeated UVA or UV solar simulated radiation (SSR) using histology or immunohistology. *Prevention of the polymorphous light eruption (PMLE) in patients prone to develop this disease.


RESULTS
Mexoryls SX-containing formulations showed a dose-dependent level of protection against pigmentation. For a same sun protection factor (SPF) the higher the UVA protection was, the higher was the PPF. Pyrimidine dimer formation and p53 accumulation were significantly reduced by formulations with Mexoryls SX. In the studies looking at the suppression of DTH reactions to recall antigens by the different UV spectra, the LC alterations and the cis UCA formation, Mexoryls SX formulations always showed a higher protective potency than sunscreen without it even when the protection against erythema was similar (products with same SPF). Mexoryls SX formulations also prevented or significantly decreased to minimal, ferritin, tenascin and lysozyme expression induced by repeated UVA or SSR exposure. It also reduced the enhancement of collagenase 2 mRNA expression induced by SSR exposure. Finally PMLE study demonstrated that UVA protection was essential for the prevention of this photodermatose.


CONCLUSIONS
Mexoryls SX formulated in sunscreens or daily use products have been shown to be an effective UV absorber, leading to an increased efficacy of these products against a large number of biological damage induced by UVA, SSR or sun exposure.
Fourtanier
Anny
A
L'Oréal Recherche, Clichy, France. afourtanier@rd.loreal.com
Moyal
Dominique
D
Seité
Sophie
S
D001892:Camphanes / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use*; D006801:Humans; D006968:Hypersensitivity, Delayed / Q000188:drug therapy / Q000209:etiology; D007108:Immune Tolerance / Q000187:drug effects / Q000528:radiation effects; D010787:Photosensitivity Disorders / Q000517:prevention & control*; D011740:Pyrimidine Dimers / Q000378:metabolism; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000517:prevention & control*; D012867:Skin / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000528:radiation effects*; D015595:Skin Aging / Q000187:drug effects / Q000473:pathology / Q000528:radiation effects; D012880:Skin Pigmentation / Q000187:drug effects / Q000528:radiation effects; D013451:Sulfonic Acids / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use*; D013473:Sunscreening Agents / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014466:Ultraviolet Rays / Q000009:adverse effects* / Q000145:classification
D001892:Camphanes; D011740:Pyrimidine Dimers; D013451:Sulfonic Acids; D013473:Sunscreening Agents; D016159:Tumor Suppressor Protein p53; C075352:terephthalylidene dicamphor sulfonic acid