EVIDENCE THAT FERRITIN IS UV INDUCIBLE IN HUMAN SKIN - PART OF A PUTATIVE DEFENSE-MECHANISM

As ferritin has been identified as an important factor in antioxidant defense in cultured human skin cells we evaluated the presence of ferr itin in human skin in vivo and the modifications following irradiation with UVA I, UVA I + II, and solar simulating light by immunohistochem ical analysis. We report that the putative protective protein ferritin is regularly present in the basal layer of unirradiated epidermis in vivo and that the induction of ferritin was dependent on wavelength an d cell type. Following UVA I radiation, ferritin increased both in epi dermal and in dermal tissue. The same response occurred, although to a lesser extent, with UVA I + II but did not occur following solar simu lating radiation. Quantitative analysis for ferritin in cultured kerat inocytes and fibroblasts from seven individuals following each UV spec tra were also assessed by enzyme-linked immunosorbent assay. The induc tion of ferritin by UV was highly dependent on the waveband and cell t ype. UVA I and UVA I + II radiations induced ferritin expression in de rmal fibroblasts up to 260% and 200% over basal levels, respectively. Solar simulating radiation produced only a small induction of approxim ate to 130% over basal ferritin levels in dermal fibroblasts. Ferritin increased in cultured fibroblasts as early as 3 h post-UVA with a pea k at 6 h that remained until 48 h; there was no observable qualitative or quantitative increase seen in the undifferentiated cultured epider mal keratinocytes. Our findings indicate that the putative defense sys tem of ferritin exists in human skin in vivo and its induction is depe ndent on UV spectra and cell type. The increased concentrations of thi s antioxidant in human skin following acute UV radiation could afford increased protection against subsequent oxidative stress.