Effect of cyclooxygenase inhibition on acute ultraviolet B irradiated mice skin

DANIEL H. GONZÁLEZ MAGLIO; MARIELA L. PAZ; ALEJANDRO FERRARI; JORGE NIETO; JULIANA LEONI

St. Louis, Missouri, USA

Congreso; 66th SID Annual Meeting (Society for Investigative Dermatology; 2005

In the present study we examined the effect of the topical application of a non steroid anti-inflammatory drug (naproxen) on the epidermal damage after an acute dose of ultraviolet B (UVB) radiation. We evaluated the expression of cyclooxygenases (COX) 1 and 2 and the inducible nitric oxide synthase (iNOS), as well as prostaglandin E2 (PGE2) synthesis and histological alterations.Female SKH-1 hairless mice were divided into 4 groups according to the treatment: 1, non irradiated control; 2, irradiated; 3, irradiated plus naproxen (0 hours post UVB); 4, irradiated plus naproxen (6 hours post UVB). Mice were irradiated with a dose of 200 mJ/cm2 and sacrificed 24 hours later to remove dorsal skin. One fraction was processed for histological analysis and the rest was treated to scrape the epidermis in order to make homogenates. The expression of the enzymes was studied by western blot and the PGE2 levels were assessed by ELISA. To perform the histological analysis 15 mm skin sections were fixed in p-formaldehyde and stained with hematoxilin-eosin. The epidermal integrity features as well as the number of sun burn cells were evaluated performing an histological blind assay.The results show that the epidermal expression of COX-1 and COX-2 are not affected in any of the studied conditions whereas the level of their product, PGE2, is significantly decreased in groups 3 and 4 compared with groups 1 and 2 (19.5 and 10.9 vs 328.6 and 1032.9 mg/mg of protein). iNOS expression is clearly suppressed by naproxen as shown by the results, expressed as ratios relative to the control group; the values are from group 1 to 4 respectively: 1, 2.49,1.63 and 0.77. The naproxen treatment produces a slight improvement in the epidermal integrity features, but it does not affect the number of epidermal sun burn cells.Topical application of naproxen reduces epidermal damage after UVB irradiation, since it decreases the levels of inflammatory-related molecules like PGE2 and iNOS.