In situ demonstration of phosphorylated c-jun and p38 MAP kinase in epidermal keratinocytes following ultraviolet B irradiation of human skin

Ultraviolet B (UVB) irradiation is known to induce activation of cellular s tress response pathways in cultured cells or intact human skin, as demonstr ated by phosphorylation of MAP kinase family members and up- or down-stream targets, using biochemical assays. This study demonstrates by immunohistoc hemistry that low-dose UVB irradiation of normal human skin induces rapid a nd reversible phosphorylation of c-jun (a target of c-jun N-terminal kinase ) and p38 mitogen activated protein kinase (p38 MAP kinase), Phosphorylatio n was maximal at 4-8 h and returned to normal levels at 48 h after irradiat ion. Nuclear localization of these phosphorylated substrates was found usin g antisera against the epitope containing the phosphorylated serine-73 of c -jun, and the dually phosphorylated epitope (threonine-180 and tyrosine-182 ) of p38 MAP kinase, Nearly all epidermal cells were positive for c-jun pho sphorylation, whereas p38 phosphorylation was seen predominantly in the dif ferentiated layers, In contrast to the massive activation of c-jun and p38, only a small population of the suprabasal cells showed nuclear translocati on of nuclear factor kappa B (NF kappaB), and a few scattered cells became apoptotic, as determined by TUNEL (TdT mediated dUTP nick end labelling) st aining, The expression of involucrin and skin-derived anti-leukoproteinase (SKALP)/elafin, two genes putatively under control of the c-jun and p38 pat hways, was found to be increased. These findings establish the first cellul ar localization of UVB-induced protein phosphorylation of stress response p roteins in human epidermis, thereby providing a link between cellular activ ation and gene expression in defined cell populations, Copyright (C) 2000 J ohn Wiley Br Sons, Ltd.