On the Ability of High Density Lipoproteins to Remove Phospholipid Peroxidation Products from Erythrocyte Membranes

A. N. Klimov^*, K. A. Kozhevnikova, A. A. Kuzmin, A. S. Kuznetsov, and E. V. Belova

Institute of Experimental Medicine, Russian Academy of Medical Sciences, ul. Akademika Pavlova 12, St. Petersburg, 197376 Russia; fax: (812) 234-9489; E-mail: bio@bio.iem.ras.spb.ru

^* To whom correspondence should be addressed.

Received May 18, 2000; Revision received September 29, 2000

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To study the transfer of oxidized phospholipids from cell membranes to high-density lipoproteins (HDL), human Cu²⁺-oxidized erythrocyte membranes were incubated with HDL₃ subfraction for 17 h at 37°C followed by isolation of the supernatant, precipitation from it of HDL₃, and determination of lipid peroxide products (LPP) in them. The incubation increased the content of lipid hydroperoxides in HDL₃ significantly (by 32 and 40% calculated per ml of sample or mg of protein) and of malondialdehyde (by 27 and 34%, respectively) compared to control (incubation of HDL₃ alone). The content of conjugated dienes did not change significantly. Fluorescence analyses of isolated HDL₃ particles showed that the content of fluorescent products (lambda_ex = 365 nm, lambda_em = 430 nm) in them was 2.5 times higher than in control, and the number of binding sites for the 1-anilinonaphthalene-8-sulfonic acid probe decreased by 22%. This also confirms accumulation of LPP in the lipoprotein subfraction. It seems likely that an increase in LPP (at least hydroperoxides) in HDL₃ after their incubation with oxidized membranes occurs via transport of phospholipids containing LPP from erythrocyte membranes to lipoproteins. The data on the ability of HDL₃ to accept LPP from erythrocyte membranes in vitro suggest that HDL₃ may have a protective action on cell membranes undergoing oxidation in vivo as well.

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KEY WORDS: lipid peroxidation, lipid hydroperoxides, conjugated dienes, malondialdehyde, high-density lipoproteins, phospholipids

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