Solar-simulated irradiation evokes a persistent and biphasic IL-1α response

Abstract

Exposure of skin to solar-simulated irradiation generates a multitude of adaptive responses including cytokine transcription, synthesis and secretion. Interleukin-1 (IL-1) is one of the cytokines induced in epidermal cells in response to UV irradiation. It displays a broad range of mitogenic and inflammatory activities including fibroblast proliferation and T-cell activation. There are two forms, IL-1α and IL-1β and IL-1α is the predominant form secreted by epidermal keratinocytes. UV-induced modulations of IL-1α message levels have been extensively studied within the first 48 h after irradiation, but longer term changes and impact on IL-1α cellular protein levels are virtually unexplored. We now report that cells of keratinocyte origin (SCC 12F) respond to a single physiologic dose of solar-simulated irradiation with both early (8 h) and late (72 h) peaks of IL-1α mRNA induction. UV-stimulated IL-1α secretion is increased above sham-irradiated control secretion for at least 96 h after irradiation. Our study provides evidence that UV-induced adaptive cutaneous responses persist for at least several days, and suggests that different mechanisms may mediate the early vs. late inductions. © Blackwell Munksgaard, 2004.