Induction of DNA damage by porphyrin photosensitizers

The photosensitizing effects of hematoporphyrin derivative, meso-tetra(p-sulfonatophenyl)porphine, meso-tetra(p-carboxyphenyl)porphine, and meso-tetra(4-N-methylpyridyl)-porphine on ColE1 supercoiled DNA were studied using agarose gel electrophoresis. Photoinduced single- and double-strand breaks were observed to form under neutral conditions. Singlet oxygen was shown to predominate in the mechanism of the induction of these lesions in the case of hematoporphyrin derivative, meso-tetra(p-sulfonatophenyl)porphine, and meso-tetra(p-carboxyphenyl)porphine and to play a significant role in the case of meso-tetra(4-N-methylpyridyl)porphine. The results suggest the possibility that the risk of photodynamic carcinogenesis may accompany photochemotherapy and fluorescence endoscopic procedures involving porphyrin photosensitizers.