UVA-340 as energy source, mimicking natural sunlight, activates the transcription factor AP-1 in cultured fibroblasts: Evidence for involvement of protein Kinase-C

Ultraviolet radiation (UVR) is known to affect a variety of cellular functi ons, including gene expression. A number of signaling pathways have been su ggested to mediate these effects, including the participation of activator protein-1 (AP-1), activator protein-2 (AP-2) and nuclear factor-kappaB (NF- kappaB). The divergent results from previous studies could be explained, at least in part, by the source of UVR with different spectral characteristic s as well as the type of cells employed as targets. In this study we have u tilized UVA-340 as an energy source with output which closely matches the s pectrum of natural sunlight over the range of 295-350 nm for irradiation of cultured fibroblasts. Combination of electrophoretic mobility shift assays and Northern analyses revealed activation of AP-1 but not NF-kappaB or AP- 2. Inhibition studies further suggested the participation of protein kinase -C, but not protein kinase-A, and that an inhibitor of mitogen-activated pr otein kinase (MEK-1/2) did not alter the AP-1 activation. Free radical quen chers, sodium azide and N-acetylcysteine, did not affect the AP-1 binding a ctivity. Finally, UVA-340 was shown to enhance transcriptional expression o f the type-VII collagen gene (COL7A1), which is endogenously expressed in d ermal fibroblast in an AP-1 dependent manner. Introduction of a mutation in to the AP-1 site of the COL7A1 promoter abolished this activation. Thus, ou r results obtained by utilizing a novel energy source, UVA-340, mimicking n atural sunlight at UVB and lower UVA range indicate a role for AP-1 in medi ating the enhanced gene expression by UVR. Collectively, these results sugg est that AP-I is an important mediator of UVR action in fibroblasts.