title: An in vivo study of free radicals generated in murine skin by protoporphyrin IX and visible light.
abstract: Lipids extracted from the skin of C57BL/6J mice injected subcutaneously with alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN) and exposed to topical protoporphyrin IX (PPIX) and visible light had significantly higher levels of POBN spin adducts compared with dark PPIX exposed or vehicle-treated controls. Computer analysis of the POBN adduct electron paramagnetic (spin) resonance (EPR) spectra indicated that two radical species were present in each extract, one of which was a lipid-derived carbon-centered adduct (1, a(N) = 14.8 G and a(H) = 2.6 G), whereas the other (2, a(N) = 13.8 G and a(H) = 1.8 G) was probably oxygen centered. Adduct 2 was present in greater proportion in lipids extracted from PPIX/light-exposed mice compared with dark or vehicle-treated controls. These findings suggest that PPIX/light generates free radicals in mouse skin, thus providing a radical mechanism for PPIX-induced photosensitivity. Our approach may be useful for the detection of free radicals generated by other skin photosensitizers and may also provide a means for testing putative skin-protecting agents.
authors.affiliation: Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA.
authors.forename: Kozo
authors.initials: K
authors.lastname: Nakai
authors.forename: Ann G
authors.initials: AG
authors.lastname: Motten
authors.forename: Colin F
authors.initials: CF
authors.lastname: Chignell
mesh_terms: D000818:Animals; D005609:Free Radicals / Q000378:metabolism*; D008027:Light; D008055:Lipids / Q000528:radiation effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D017319:Photosensitizing Agents / Q000494:pharmacology; D011524:Protoporphyrins / Q000494:pharmacology*; D012867:Skin / Q000737:chemistry*
chemical_list: D005609:Free Radicals; D008055:Lipids; D017319:Photosensitizing Agents; D011524:Protoporphyrins; C028025:protoporphyrin IX