Epidermal interleukin-1α generation is amplified at low humidity:: implications for the pathogenesis of inflammatory dermatoses

Background We have previously reported that low humidity amplifies the hyperproliferative and inflammatory response to barrier disruption. Other reports suggest that epidermal interleukin (IL)-1 alpha is stimulated by various factors related to epidermal inflammation and that it may induce other proinflammatory molecules, Objectives To evaluate the generation of IL-1 alpha in the skin of hairless mice kept under various conditions of environmental humidity, Methods We carried out an immunohistochemical study, and evaluated epidermal IL-1 alpha mRNA and protein levels, and release of IL-1 alpha from skin after tape stripping, in hairless mice kept under low or high humidity. Results The immunohistochemical study showed that the amount of IL-1 alpha in the epidermis was higher in animals kept in a low-humidity environment than in a high-humidity one, The epidermal IL-1 alpha mRNA and protein levels increased significantly when the animals were kept under low humidity, Moreover, the release of IL-1 alpha from skin immediately after tape stripping was significantly higher in animals kept in a low-humidity environment than in a high-humidity one. Conclusions These results suggest that IL-1 alpha is an important factor in mediating the relationship between environmental humidity and epidermal pathology.