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Abstract

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 degrees 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 (lambdaex = 365 nm, lambdaem = 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.

Anomalous change of viscosity and conductivity in blood plasma lipoproteins in the physiological temperature range

“…Calculation of the viscous flow enthalpy for the lipoprotein 32, 33 on either side of T c and the difference in these values relative to this point (Δ H trans. , the conventional heat of transition) demonstrated that with a rather high ionic force of the solution the activation energy of viscous flow was small both before T c and after it.…”

“…In addition, an about 5 cm −1 frequency shift of the absorption band of the mentioned bond to the long wave region was observed, which was reflected on the differential curve by the appearance of asymmetry and a weak maximum at 1733 cm −1 . This can be explained by an increase in the number of hydrogen bonds that are likely to form between unesterified cholesterol and human apoA‐I in native HDL 32.…”

“…At the same time, in rat lipoproteins it was noted the process of despiralization and decreasing of the tangle against the background of increasing β‐structure moiety, i.e., the α‐helix → β‐structure and tangle → β‐structure transitions occurred. In addition, the lipid ordering in human proceeded through the formation of new hydrogen bonds, probably of phospholipids with proteins and cholesterol or of cholesterol molecules with apoproteins 32. At the same time, in rats the lipid ordering was not attended by changing the number of hydrogen bonds, which is likely to be caused by the lipid ordering in deeper layers of the lipoprotein particle, where contact with proteins is weaker or absent.…”

“…Numerous works report on the interaction of apoA, C, and E with phospholipids and cholesterol resulting in the change of the secondary protein structure, in particular, the tangle ↔ α‐helix transition 31, 32. Upon interaction of human HDL with cortisol, the tangle → β‐structure transition is recorded along with the tangle → α‐helix transition 44.…”

The proteome of sickle cell disease: insights from exploratory proteomic profiling

“…ApoA-II, along with acute-phase SAA, impairs the antioxidant properties of HDL by displacing paraoxonase-1, a HDL-associated enzyme [109,110]. Paraoxonase-1 enables HDL to accept and inactivate oxidized phospholipids from cell membranes [111]. Impairment of this function might be especially problematic in a setting of severe oxidative stress such as SCD.…”