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The effect of porphyrin and radiation on ferrochelatase and 5‐aminolevulinic acid synthase in epidermal cells

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The effects of ultraviolet A (UVA) and blue light on ferrochelatase protein, and its mRNA level, in 5‐aminolevulinic acid (ALA)‐loaded A431 cells was evaluated. Western blot analysis of ferrochelatase protein showed a protein band of 43 kDa. There was a decrease in the protein concentration 24 h and 48 h after irradiation of these cells. In contrast, as judged by Northern blot analysis, there was no change in ferorchelatase mRNA level. Measurement of ALA synthase activity showed an ALA dose‐dependent but radiation‐independent decrease of enzyme activity, suggesting an end‐product feedback inhibition. Since reactive oxygen species generated by porphyrin‐induced photochemical reaction may be involved in the decrease in ferrochelatase protein, the effect of scavengers of reactive oxygen species was evaluated by measuring porphyrin accumulation in irradiated, ALA‐loaded A431 cells. Porphyrin accumulation was significantly decreased in the presence of singlet oxygen scavenger sodium azide (0.05 mM, 40.6% suppression) or hydroxyl radical scavenger mannitol (5.0 mM, 45.0% suppression). These data suggest that the photochemical reaction induced by porphyrin and irradiation resulted in a decrease in ferrochelatase protein content, but had no effect on ferrochelatase mRNA level nor on ALA synthase activity. The decrease in protein was partly mediated by the reactive oxygen species.
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Document Type: Original Article

Affiliations: 1: Dermatology Service, Department of Veterans Affairs Medical Center, and Ronald O. Perelman Department of Dermatology, New York University School of Medicine 2: The Rockefeller University, New York, New York, USA 3: Kansai Medical University, Moriguchi, Japan

Publication date: 1995-02-01

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