This proposal seeks to understand the mechanism of phototoxicity manifested at the level of cell plasma membranes. The long-range goal is to explain the factors that make potent photosensitizers phototoxic and to define how the function of photomodified membranes differs from normal. This work will contribute to the understanding of diseases of phototoxicity such as the porphyrias and of drug-induced phototoxicity. It will also help in the development of photodynamic therapy for the treatment of malignant tumors. The focus of this proposal is on the remarkable ability of the isothiocyano derivative of eosin to sensitize human red blood cell membranes relative to the underivatized eosin. A comprehensive comparison will be made of the physicochemical properties and membrane-modifying action of these two sensitizers. Their physicochemical properties in terms of ability to generate singlet oxygen and their behavior in non-aqueous solvents will be assessed. Their ability to sensitize the creation of cation leaks in red blood cells will be measured by tracking the kinetics of the ensuing colloid osmotic hemolysis spectrophotometrically. Their ability to sensitize the loss of acetylcholinesterase activity in erythrocyte ghost membranes will be measured by Ellman's assay. For these processes the light dose dependence, relative potency, temperature dependence, and inhibition by anion transport inhibitors will be defined. The loading and location of these sensitizers on membrane proteins and their inhibition by anion transport inhibitors will be assessed by the fluorescence signals on SDS-poly-acrylamide gels. Parallel experiments will measure some of these same properties using erythrosin (FD and C red #3) and its isothiocyano derivative. Auxiliary experiments will compare the sensitizing potency of these sensitizers for the light-induced block of sodium channel gating on giant axons from lobsters.
| Pooler, J P (1989) Photooxidation of cell membranes using eosin derivatives that locate in lipid or protein to study the role of diffusible intermediates. Photochem Photobiol 50:55-68 |
| Pooler, J P (1988) Photomodification of human erythrocytes: external heavy atom effect, selective permeability and properties of the anion permeation pathway. Photochem Photobiol 47:369-76 |
