Photooxidation of cell membranes in the presence of hematoporphyrin derivative: reactivity of phospholipid and cholesterol hydroperoxides with glutathione peroxidase. Biochim Biophys Acta 1988 Oct 14;962(3):297-307
Date
10/14/1988Pubmed ID
2971397DOI
10.1016/0005-2760(88)90259-7Scopus ID
2-s2.0-0023755437 (requires institutional sign-in at Scopus site) 52 CitationsAbstract
The susceptibility of photodynamically-generated lipid hydroperoxides to reductive inactivation by glutathione peroxidase (GPX) has been investigated, using hematoporphyrin derivative as a photosensitizing agent and the human erythrocyte ghost as a target membrane. Photoperoxidized ghosts were reactive in a glutathione peroxidase/reductase (GPX/GRD)-coupled assay only after phospholipid hydrolysis by phospholipase A2 (PLA2). However, enzymatically determined lipid hydroperoxide values were consistently approx. 40% lower than iodometrically determined values throughout the course of photooxidation. Moreover, when irradiated ghosts were analyzed iodometrically during PLA2/GSH/GPX treatment, a residual 30-40% of non-reactive lipid hydroperoxide was observed. The possibility that cholesterol product(s) account for the non-reactive lipid hydroperoxide was examined by tracking cholesterol hydroperoxides in [14C]cholesterol-labeled ghosts. The sum of cholesterol hydroperoxides and GPX/GRD-detectable lipid hydroperoxides was found to agree closely with iodometrically determined lipid hydroperoxide throughout the course of irradiation. Thin-layer chromatography of total lipid extracts indicated that cholesterol hydroperoxide was unaffected by PLA2/GSH/GPX treatment, whereas most of the phospholipid peroxides were completely hydrolyzed and the released fatty acid peroxides were reduced to alcohols. It appears, therefore, that the GPX-resistant lipid hydroperoxides in photooxidized ghosts were derived primarily from cholesterol. Ascorbate plus Fe3+ produced a burst of free-radical lipid peroxidation in photooxidized, PLA2-treated ghosts. As expected for fatty acid hydroperoxide inactivation, the lipid peroxidation was inhibited by GSH/GPX, but only partially so, suggesting that cholesterol hydroperoxide-derived radicals play a major role in the reaction.
Author List
Thomas JP, Girotti AWAuthors
Albert W. Girotti PhD Adjunct Professor in the Biochemistry department at Medical College of WisconsinJames P. Thomas MD, PhD Professor in the Medicine department at Medical College of Wisconsin
MESH terms used to index this publication - Major topics in bold
Ascorbic AcidCalcium
Cholesterol
Erythrocyte Membrane
Glutathione Peroxidase
Glutathione Reductase
Hematoporphyrin Derivative
Hematoporphyrins
Humans
Hydrogen Peroxide
Iron
Liposomes
NADP
Oxidation-Reduction
Phospholipases A
Phospholipases A2
Phospholipids
Photochemistry
Radiation-Sensitizing Agents
