Immunomodulation of Skin Cytokine Secretion by House Dust Mite Extracts

Background: Skin contact with house dust mites may contribute to atopic dermatitis and other skin diseases. We sought to determine if molecules from house dust mites could influence the release of proinflammatory cytokines and chemokines from epidermal keratinocytes and dermal fibroblasts grown in a human skin equivalent (HSE) model. Methods: HSEs consisting of an epidermis of keratinocytes with stratum corneum over a dermis of fibroblasts in a collagen matrix were challenged with Dermatophagoides farinae, D. pteronyssinus and Euroglyphus maynei mite extracts. Results: HSEs secreted interleukin (IL)-1 , IL-1 receptor antagonist, IL-6, IL-8, cutaneous T cell-attracting chemokine, transforming growth factor, granulocyte/macrophage and macrophage colony-stimulating factors and vascular endothelial cell growth factor in response to at least 1 mite extract. Extracts of different mite species stimulated HSEs to release different cytokines. Therefore, extracts of different species contained different molecules or different concentrations of similar molecules. The cytokine release profiles of cells in the HSEs were not the same as for monocultured keratinocytes and fibroblasts. Conclusions: Molecules Received: August 19, 2010 Accepted after revision: November 22, 2010 Published online: May 17, 2011 Correspondence to: Dr. Larry G. Arlian Department of Biological Sciences, Wright State University 3640 Colonel Glenn Highway Dayton, OH 45435 (USA) Tel. +1 937 775 2568, Fax +1 937 775 3320, E-Mail larry.arlian @ wright.edu © 2011 S. Karger AG, Basel Accessible online at: www.karger.com/iaa D ow nl oa de d by : 54 .7 0. 40 .1 1 11 /2 3/ 20 17 2 :1 5: 27 P M Arlian/Morgan Int Arch Allergy Immunol 2011;156:171–178 172 pets. There are reports of house dust mites being recovered from human skin and clothing [1–4] . A defective skin barrier may allow penetration of mite molecules into the lower epidermis and dermis [5–10] . Molecules in mite material include both allergens and nonallergens, and some of these are enzymes. House dust mite group 1 allergens are cysteine proteases, and groups 3, 6 and 9 are serine proteases [11] . Protease enzymes from house dust mites, solvents, volatile organics, soaps, detergents, surfactants and abrasive materials can damage the skin epidermal surface barrier, and this can allow penetration of mite molecules into the lower epidermis and dermis [6, 12] . The recombinant allergen Der f 1 is a cysteine protease that has been shown to reduce the barrier function of skin in nude mice [13] . Positive patch test reactions to house dust mites have been reported [14–16] . Serine peptidases from fecal pellets of D. pteronyssinus cleave occludin of epithelial tight junctions of cultured airway epithelial cells [17, 18] . Likewise, D. farinae and D. pteronyssinus extracts cause changes in growth and reduced adhesion in cA549 type II epithelial cells [19] . This chemical and physical disruption may allow penetration of molecules that may induce epidermal and dermal inflammation and immune responses that are mediated by cytokines and chemokines from stimulated keratinocytes, fibroblasts, microvascular endothelial cells and infiltrating cells, including Langerhans cells, lymphocytes and monocytes/macrophages, neutrophils and eosinophils. Stimulated keratinocytes and fibroblasts produce and secrete multiple cytokines that promote cutaneous inflammation. Previous research has shown that house dust mite and stored product mite extracts stimulate the secretion of cytokines from cultured human dermal keratinocytes, fibroblasts and microvascular endothelial cells [20, 21] . Both D. farinae and D. pteronyssinus extracts stimulate cultured keratinocytes to increase secretion of the chemokine growth-related oncogene(GRO  , CXCL1), which is chemotactic for the extravasation of leukocytes during inflammation [20] . Likewise, D. farinae and/or D. pteronyssinus extracts induce cultured normal human dermal fibroblasts to secrete interleukin (IL)-6, IL-8 (CXCL8), monocyte chemoattractant protein-1 (MCP-1, CCL2) and macrophage colony-stimulating factor (M-CSF) [20] . Kato et al. [22] demonstrated that whole-mite culture extract and recombinant Der f 1 and Der p 1 induced the release of IL-8 and granulocyte/ macrophage colony-stimulating factor (GM-CSF) from cultured primary human keratinocytes from infant foreskins and from the human keratinocyte cell line HaCaT. In these previous studies, the effect of mite extracts was investigated using monocultures of epidermal keratinocytes or dermal fibroblasts. In vivo in the skin, fibroblasts and keratinocytes may respond differently to mite extracts because the cytokines secreted by one cell type can influence the function of the others and of the fibroblasts that are associated with a collagen matrix [12, 23] . The cytokines that these 2 cell types produce can mediate the function of many other cells in the skin, including microvascular endothelial cells, which are key to the regulation of extravasation of inflammatory and immune cells. Therefore, the responses of keratinocytes and fibroblasts are important in the progression of inflammatory and immune responses and the manifestation of atopic dermatitis. Here, we report the effect of house dust mite extracts on fibroblasts and keratinocytes together in human skin equivalents (HSEs). The HSE is structurally similar to normal skin. It consists of an epidermis with a stratum corneum over living keratinocytes and a basal layer grown over a dermis consisting of fibroblasts in a collagen matrix [23, 24] .