House dust mite‐derived serine protease upregulates gene expression of interleukin‐33 in canine keratinocytes via protease‐activated receptor‐2

Abstract

Background -The involvement of interleukin (IL)-33 produced by keratinocytes has been suggested in the pathogenesis of canine atopic dermatitis (cAD). House dust mite (HDM)-derived proteases induce the production of various cytokines and chemokines in keratinocytes via protease-activated receptor-2 (PAR-2); however, their effects on IL-33 mRNA expression in canine keratinocytes have not been determined.Hypothesis/Objective -To clarify whether HDM-derived proteases induce IL-33 mRNA expression in canine keratinocytes via PAR-2.Methods and materials -Expression of IL-33 mRNA was quantified by real-time PCR in a cell line of canine progenitor epidermal keratinocytes (CPEK) stimulated with Dermatophagoides farinae (Der f) whole body extract, Der f pre-treated with cysteine protease and serine protease inhibitors, and trypsin. Trypsin and Der f-mediated IL-33 mRNA expression also was measured in CPEK cells treated with a PAR-2 antagonist.Results -Der f enhanced IL-33 mRNA expression in CPEK cells in incubation time-and dose-dependent manners. Der f pre-treated with a serine protease inhibitor, and not a cysteine protease inhibitor, abrogated an increase in IL-33 mRNA expression in CPEK cells. Trypsin also enhanced IL-33 mRNA expression in CPEK cells. Trypsin-mediated IL-33 mRNA expression was completely abolished by a PAR-2 antagonist, while Der fmediated IL-33 mRNA expression was partially and significantly diminished by it.Conclusions and clinical relevance -Der f-derived serine protease upregulated IL-33 mRNA expression in CPEK cells at least in part via PAR-2. These findings suggest that HDM may be involved in the development of C AD by increasing IL-33 mRNA expression in keratinocytes.

Update on the role of genetic factors, environmental factors and allergens in canine atopic dermatitis

“…1 The findings of a recent study suggest that D. farinae-derived serine can upregulate IL-33 mRNA expression in canine progenitor epidermal keratinocytes (CPEK) via protease-activated receptor-2 (PAR-2) activation and may be involved in cAD. 46 Interleukin (IL)-33 produced by keratinocytes is suspected to be involved in the pathogenesis of cAD. 47 Whether these in vitro findings translate into an in vivo situation needs to be proven.…”

“…Previous studies indicated that house dust mite (HDM) components, such as cysteine (group 1 mite allergens) and serine (group 3, 6 and 9 allergens) proteases may induce a wide variety of inflammatory reactions, which could promote allergic sensitisation 1 . The findings of a recent study suggest that D. farinae ‐derived serine can upregulate IL‐33 mRNA expression in canine progenitor epidermal keratinocytes (CPEK) via protease‐activated receptor‐2 (PAR‐2) activation and may be involved in cAD 46 . Interleukin (IL)‐33 produced by keratinocytes is suspected to be involved in the pathogenesis of cAD 47 .…”