1. ^*Department of Dermatology and Ludwig Boltzmann Institute for Cell Biology and Immunobiology of the Skin, University of Münster, Münster, Germany
2. ^†Department of Experimental Dermatology, Institute of Immunology & Cell Biology, University of Münster, Münster, Germany
3. ^‡Department of Pharmacology & Experimental Therapeutics, University of Calgary, Calgary, Canada
4. ^§Max-Planck Institute for Vascular Biology & Center for Molecular Biology of Inflammation (ZMBE), University of Münster, Münster, Germany

Correspondence: Martin Steinhoff MD PhD, Department of Dermatology, University of Münster, von-Esmarch-Str. 58, 48149 Münster, Germany. Email: msteinho@uni-muenster.de

Received 1 August 2003; Revised 14 June 2004; Accepted 21 June 2004; Published online 21 December 2004.

Abstract

Proteinase-activated receptor-2 (PAR₂) belongs to a new G protein-coupled receptor subfamily that is activated by various serine proteases. Recent knowledge indicates that PAR₂ is involved in cutaneous inflammation and immune response. PAR₂ is highly expressed by human keratinocytes (KTC). The underlying mechanisms of PAR₂-mediated KTC function and cutaneous immune response are, however, still incomplete. Therefore, we investigated the activation of important signaling cascades in primary human KTC after PAR₂-stimulation using specific agonists. Moreover, we compared PAR₂-immunoreactivity in the epidermis of inflammatory dermatoses and normal human skin. Electrophoretic mobility shift assays and morphological transduction studies revealed PAR₂-induced activation and translocation of nuclear factor kappa B (NF-B) in primary human KTC with a maximum after 1 h. Supershift analysis demonstrated acivation of the p50/p65 heterodimer complex. PAR₂ agonists also induced upregulation of intercellular adhesion molecule-1 (ICAM-1) RNA, as shown by RT-PCR. Use of NF-B inhibitors prevented upregulation of the cell adhesion molecule ICAM-1 in KTC indicating a direct role of NF-B in PAR₂-mediated upregulation of ICAM-1. Fluorescence-activated cell sorter analysis confirmed PAR₂-induced and NF-B-mediated upregulation of ICAM-1 protein after 13 h. Moreover, increased expression of PAR₂ was detected in KTC of patients with atopic dermatitis suggesting a role of PAR₂ in human skin inflammation. In conclusion, PAR₂ induces upregulation of cell adhesion molecules such as ICAM-1 in primary human KTC via NF-B activation, and is upregulated in KTC during cutaneous inflammation. Thus, PAR₂ may play an important regulatory role of human KTC during inflammation and immune response.