Mechanism of action of a lipophilic derivative of salicylic acid on normal skin.
OBJECTIVE
Keratolytics are agents used for a very long period of time to improve various skin disorders such as acne, hyperkeratoses, ichtyose etc. Very little is known about their mechanism of action on healthy skin. On man, the chronic application of a cosmetic cream containing a lipophilic derivative of Salicyclic acid (LSA) markedly improves the aspect and texture of the skin. Different methods were used to investigate the mechanisms of action of this new compound, compared to salicyclic acid.


METHODS
Both non-invasive and histologic methods were used on the dorsal forearm of human volunteers treated with the products. Concerning the non-invasive methods, TEWL, silflo replica and confocal microscopy were used. On shave biopsies, various histometric parameters were measured by image analysis after different staining. The use of antibody MIB-1 reacting with the proliferating nuclear antigen Ki 67 allows one to measure the epidermis proliferation index.


RESULTS
Compared to the excipient alone, presence of LSA 1% improves smoothness and firmness of the skin. The appearance in terms of clearness and healthy complexion is also improved. The thickening of all the living epidermis layers is obtained by both histometric measurement and confocal microscopy. This acanthosis is only recorded on the LSA-treated zones. The Ki 67 labelling study shows that LSA significantly increases the skin proliferation index.


CONCLUSIONS
Salicylic acid, and more markedly its lipophilic derivative (LSA), appear to have a significative effect on the renewal of the living epidermis. This probably explains the cosmetic improvement of the skin obtained after a 1-month treatment with a cream containing this new molecule.
Laboratories de Recherche de L'OREAL, Aulnay-Sous-Bois, FranceLaboratoires de Recherche de L'OREAL, Chevilly-Larue, FranceService de Dermatopathologie/CHU du Sart Tilman, Liège, BelgiumFaculté de Pharmacie/Paris V, Paris, France.
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Lévêque
Laboratories de Recherche de L'OREAL, Aulnay-Sous-Bois, FranceLaboratoires de Recherche de L'OREAL, Chevilly-Larue, FranceService de Dermatopathologie/CHU du Sart Tilman, Liège, BelgiumFaculté de Pharmacie/Paris V, Paris, France.
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Corcuff
Laboratories de Recherche de L'OREAL, Aulnay-Sous-Bois, FranceLaboratoires de Recherche de L'OREAL, Chevilly-Larue, FranceService de Dermatopathologie/CHU du Sart Tilman, Liège, BelgiumFaculté de Pharmacie/Paris V, Paris, France.
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Gonnord
Laboratories de Recherche de L'OREAL, Aulnay-Sous-Bois, FranceLaboratoires de Recherche de L'OREAL, Chevilly-Larue, FranceService de Dermatopathologie/CHU du Sart Tilman, Liège, BelgiumFaculté de Pharmacie/Paris V, Paris, France.
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Montastier
Laboratories de Recherche de L'OREAL, Aulnay-Sous-Bois, FranceLaboratoires de Recherche de L'OREAL, Chevilly-Larue, FranceService de Dermatopathologie/CHU du Sart Tilman, Liège, BelgiumFaculté de Pharmacie/Paris V, Paris, France.
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Renault
Laboratories de Recherche de L'OREAL, Aulnay-Sous-Bois, FranceLaboratoires de Recherche de L'OREAL, Chevilly-Larue, FranceService de Dermatopathologie/CHU du Sart Tilman, Liège, BelgiumFaculté de Pharmacie/Paris V, Paris, France.
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Bazin
Laboratories de Recherche de L'OREAL, Aulnay-Sous-Bois, FranceLaboratoires de Recherche de L'OREAL, Chevilly-Larue, FranceService de Dermatopathologie/CHU du Sart Tilman, Liège, BelgiumFaculté de Pharmacie/Paris V, Paris, France.
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Piérard
Laboratories de Recherche de L'OREAL, Aulnay-Sous-Bois, FranceLaboratoires de Recherche de L'OREAL, Chevilly-Larue, FranceService de Dermatopathologie/CHU du Sart Tilman, Liège, BelgiumFaculté de Pharmacie/Paris V, Paris, France.
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Poelman
aging; confocal microscopy; healthy complexion; histometry; lipophilic salicylic acid