Agonists of proteinase-activated receptor-2 stimulate upregulation of intercellular cell adhesion molecule-1 in primary human keratinocytes via activation of NF-kappa B

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