Involvement of preexisting lipid hydroperoxides in Cu(2+)-stimulated oxidation of low-density lipoprotein. Arch Biochem Biophys 1994 Dec;315(2):244-54
Date
12/01/1994Pubmed ID
7986064DOI
10.1006/abbi.1994.1496Scopus ID
2-s2.0-0027974212 (requires institutional sign-in at Scopus site) 97 CitationsAbstract
Oxidative modification of human low-density lipoprotein (LDL) is thought to play an important role in the development of atherosclerosis. LDL oxidizability is believed to be strongly influenced by factors such as (a) content of preexisting lipid hydroperoxides (LOOHs) and (b) content of endogenous antioxidants such as alpha-tocopherol and beta-carotene. The purpose of this study was to examine the prooxidant role of preexisting LDL-LOOHs, using a recently developed method for ultrasensitive and selective LOOH analysis: high-performance liquid chromatography with mercury drop electrochemical detection (HPLC-EC). Exceedingly low detection limits for LDL-LOOHs have been achieved by HPLC-EC, e.g., approximately 100 fmol for cholesteryl ester hydroperoxide (CEOOH). This sensitivity has allowed us to monitor LDL-LOOHs at levels that are undetectable by most other methods. Fresh LDL prepared with the utmost care to prevent autoxidation was found to contain small, yet significant amounts of CEOOH, 6-12 pmol/mg protein. Our data suggest that these peroxides could not have arisen during LDL isolation or sample work-up for HPLC-EC. Incubation with GSH and phospholipid hydroperoxide glutathione peroxidase resulted in nearly complete reduction of the CEOOH. This LDL was found to be much more resistant to Cu(2+)-induced peroxidation than starting material, exhibiting a lag period that was at least six times greater. We have also determined that LDL becomes progressively more susceptible to Cu(2+)-induced lipid peroxidation (as evidenced by a shortened lag) when it is preloaded with increasing amounts of photochemically generated LOOHs. Taken together, these results provide strong support for the idea that preexisting LOOHs in LDL are important determinants of its overall oxidizability.
Author List
Thomas JP, Kalyanaraman B, Girotti AWAuthors
Albert W. Girotti PhD Adjunct Professor in the Biochemistry department at Medical College of WisconsinBalaraman Kalyanaraman PhD Professor in the Biophysics department at Medical College of Wisconsin
James 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
AdultCholesterol Esters
Copper
Glutathione Peroxidase
Humans
In Vitro Techniques
Lipid Peroxides
Lipoproteins, LDL
Male
Oxidation-Reduction
Photochemistry