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.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
1R01NS022911-01
Application #
3405712
Study Section
Physiology Study Section (PHY)
Project Start
1986-08-01
Project End
1989-07-31
Budget Start
1986-08-01
Budget End
1987-07-31
Support Year
1
Fiscal Year
1986
Total Cost
Indirect Cost
Name
Emory University
Department
Type
Schools of Medicine
DUNS #
042250712
City
Atlanta
State
GA
Country
United States
Zip Code
30322