Photodynamic Action of Merocyanine 540 on Artificial and Natural Cell Membranes: Involvement of Singlet Molecular Oxygen

• Published in: Proceedings of the National Academy of Sciences - PNAS 1987-05, Vol.84 (9), p.2999-3003
• Main Authors: Kalyanaraman, B., Feix, J. B., Sieber, F., Thomas, J. P., Girotti, A. W.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Cell Line; Cell Membrane - drug effects; Cell Membrane - metabolism; Cell membranes; Cell physiology; Cholesterols; Dimyristoylphosphatidylcholine; Dyes; Effects of physical and chemical agents; Electron Spin Resonance Spectroscopy; Erythrocyte Membrane - drug effects; Erythrocyte Membrane - metabolism; erythrocytes; Fluorescent Dyes; fluorescent probes; Fundamental and applied biological sciences. Psychology; Humans; Irradiation; Leukemia, Myeloid; Lipid peroxides; Lipids; Liposomes; merocyanine 540; Molecular and cellular biology; Oxygen; Oxygen consumption; Phosphatidylcholines; Photochemistry; Photooxidation; Pyrimidinones - pharmacology; Singlet Oxygen; vesicles
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.84.9.2999

The photochemistry of merocyanine 540 (MC 540), a sensitizing dye that binds preferentially to leukemia and electrically excitable cells, has been investigated. MC 540-mediated photooxidation of histidine, arachidonate, and unsaturated phospholipid vesicles was assessed by spin label oximetry and shown to involve type II (singlet oxygen) chemistry. The dye was also shown to be a potent sensitizer of lipid peroxidation in a natural cell membrane, the erythrocyte ghost. Inhibition by azide, stimulation by2H2O, and identification of the cholesterol product 5α -cholest-6-ene-3β ,5-diol in this system, all were consistent with singlet oxygen intermediacy. Finally, MC 540 was found to be considerably more phototoxic to K-562 leukemia cells in2H2O than in H2O. We conclude that singlet oxygen plays a major role in the phototherapeutic effects of this dye.