Extracellular regulated kinase and c-Jun N-terminal kinase are activated in psoriatic involved epidermis.

Psoriatic skin shows markedly increased keratinocyte proliferation and altered differentiation with various abnormal signalling pathways. In the present study, we investigated the expression of mitogen-activated protein kinases in psoriatic skin. Immunohistochemical study showed increased extracellular regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) expression in the nuclei of involved epidermis. Western blot analyses confirmed the increased active phospho-ERK and phospho-JNK expression in the involved epidermis. In contrast, expression pattern of p38 was not different between the involved and uninvolved epidermis, which was confirmed by western blot analysis. These results indicate that psoriatic epidermis shows selective activation of ERK and JNK, which might be related to hyperproliferation and abnormal differentiation of psoriatic epidermis.