Relationship between the ability of sunscreens containing 2-ethylhexyl-4′-methoxycinnamate to protect against UVR-induced inflammation, depletion of epidermal Langerhans (Ia +) cells and suppression of alloactivating capacity of murine skin in vivo

Abstract

The UVB sunscreen 2-ethylhexyl-4′-methoxycinnamate was evaluated in hairless albino mouse skin for its ability to inhibit UVR-induced (i) oedema, (ii) epidermal Langerhans cell (Ia +) depletion and (iii) suppression of the alloactivating capacity of epidermal cells (mixed epidermal cell—lymphocyte reaction, MECLR). The sunscreen, prepared at 9% in ethanol or a cosmetic lotion, was applied prior to UVB/UVA irradiation. In some experiments there was a second application halfway through the irradiation. Single applications in both vehicles gave varying degrees of protection from oedema and Langerhans cell depletion but afforded no protection from suppression of MECLR. When the sunscreens were applied twice there was improved protection from oedema and Langerhans cell depletion and complete protection was afforded from suppression of MECLR. There was a clear linear relationship between Langerhans cell numbers and oedema with and without sunscreen application. The relationship between Langerhans cell numbers and MECLR was more complex. These data confirm published discrepancies between protection from oedema (a model for human erythema) and endpoints with immunological significance, but show that 2-ethylhexyl-4′-methoxycinnamate can afford complete immunoprotection, although protection is dependent on the application rate and vehicle.