Involvement of nuclear factor of activated T cells in granulocyte-macrophage colony-stimulating factor production in canine keratinocytes stimulated with a cysteine protease.

BACKGROUND: A previous study demonstrated that the cysteine protease of Dermatophagoides farinae induced production of granulocyte-macrophage colony-stimulating factor (GM-CSF) in a canine epidermal keratinocyte progenitor cell line (CPEK); however, the molecular mechanism has not been elucidated. HYPOTHESIS/OBJECTIVES: Given that the transcription of GM-CSF mRNA in human lymphocytes is mainly regulated by the nuclear factor of activated T cells (NFAT), it is hypothesized that NFAT also contributes to GM-CSF production in canine keratinocytes stimulated with a cysteine protease. METHODS: Nuclear translocation of NFAT was evaluated in CPEK cells in the absence or presence of the cysteine protease papain. We also investigated whether blockade of NFAT could inhibit GM-CSF production. RESULTS: Papain-induced nuclear translocation of NFAT, producing GM-CSF, was partly inhibited by ciclosporin. CONCLUSIONS AND CLINICAL IMPORTANCE: The results suggest that GM-CSF production mediated by the cysteine protease is regulated not only by NFAT but also by unknown signalling pathways in canine keratinocytes.

Production of GM-CSF mediated by cysteine protease of Der f in canine keratinocytes.

House dust mite (HDM) allergens are the most common allergens for induction of IgE-mediated hypersensitivity. Recently, epicutaneous sensitization with HDM allergens has been emphasized in the development of atopic dermatitis (AD) by producing various soluble factors in keratinocytes. Among the soluble factors, GM-CSF is a key molecule that activates Langerhans cells, antigen-presenting cells in the epidermis. In the present study, we investigated the effects of Dermatophagoides farinae (Der f) on GM-CSF production in a canine keratinocyte cell line, CPEK. CPEKs were found to produce GM-CSF upon stimulation by Der f. The GM-CSF production was suppressed by addition of a cysteine protease inhibitor. The present results suggest that cysteine protease-derived Der f may be an initiator of allergic inflammation by inducing the production of GM-CSF in keratinocytes.