First report in a dog model of atopic dermatitis: expression patterns of protease-activated receptor-2 and thymic stromal lymphopoietin.

Abstract

BACKGROUND: Protease-activated receptor (PAR)-2 plays a crucial role in inflammation and the skin barrier. Protease-activated receptor-2 is activated by proteolytic enzymes of allergens and stimulates thymic stromal lymphopoietin (TSLP), promoting T-helper 2 cytokines. In humans with atopic dermatitis (AD), increased expression of PAR-2 and TSLP has been reported. HYPOTHESIS/OBJECTIVES: To compare the pattern of staining of PAR-2 and TSLP between normal and atopic beagle dogs. The hypothesis tested was that increased expression is present in atopic dog skin compared with healthy control skin. ANIMALS: Eight atopic and five normal dogs were challenged for 3 days with house dust mites. METHODS: Skin biopsies were taken to measure the intensity, distribution, integrity and cell staining pattern on days 0, 3 and 10, both objectively and subjectively. Clinical signs were scored and compared between groups. RESULTS: Atopic dogs showed a significant increase in clinical scores on days 3 (peak of challenge) and 10 (resolution) and a significant condensed staining pattern for TSLP in the stratum basale at all times in comparison to normal dogs. They showed a significant patchy pattern for PAR-2 on days 0 and 3 and for TSLP at all times compared with normal dogs. The intensity itself was not significantly increased in atopic dogs compared with normal animals for both PAR-2 and TSLP. CONCLUSIONS AND CLINICAL IMPORTANCE: These preliminary findings do not confirm a difference in the amount of expression but rather in its pattern. Studies using PAR-2 or TSLP inhibitors could shed light on their clinical relevance.