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 (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-kappaB) 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-kappaB inhibitors prevented upregulation of the cell adhesion molecule ICAM-1 in KTC indicating a direct role of NF-kappaB in PAR2-mediated upregulation of ICAM-1. Fluorescence-activated cell sorter analysis confirmed PAR2-induced and NF-kappaB-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-kappaB 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.