An in vivo Study of Free Radicals Generated in Murine Skin by Protoporphyrin IX and Visible Light

摘要

Lipids extracted from the skin of C57BL/6J mice injected subcutaneously with α-(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 as compared to dark PPIX exposed or vehicle treated controls. Computer analysis of the POBN adduct 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) while 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 as compared to dark or vehicle treated controls. 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.