Interaction of phosphatidylcholine liposomes and plasma lipoproteins with sheep erythrocyte membranes. Preferential transfer of phosphatidylcholine containing unsaturated fatty acids

Effect of Liposome Treatment on Hemorheology and Metabolic Profile of Human Red Blood Cells During Hypothermic Storage

BACKGROUND

Ex vivo cold storage of red blood cells (RBCs) for transfusion has long been associated with hypothermic storage lesions. It has been proposed that liposomes can be used to mitigate hemorheological elements of RBC membrane storage lesions. This study aimed to determine the appropriate liposome treatment time and assess the effects of liposome treatment on RBC's hemorheological and metabolic profiles.

MATERIALS AND METHODS

Unilamellar liposomes were synthesized to contain a bilayer of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC):cholesterol (7:3 mol%). Packed human RBCs (n = 4) were divided into untreated control (HEPES-NaCl solution) and liposome-treated samples (2 mM DOPC liposomes) and treated at days 2, 21, and 42 of hypothermic storage. RBC quality assessment included percent hemolysis, deformability, aggregation, hematological indices, microvesiculation, supernatant potassium, adenosine triphosphate (ATP), and 2,3-diphosphoglycerate (2,3-DPG).

RESULTS

Among the parameters affected by liposome treatment time were deformability, aggregation amplitude (Amp), mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and microparticle mean fluorescence intensity. After 6 weeks of storage, aggregation index (AI) and Amp were significantly increased in liposome-treated RBCs (AI: 45.38 ± 1.92% vs. 41.54 ± 4.10%, p = 0.020; Amp: 16.38 ± 2.17 arbitrary units [au] vs. 12.22 ± 3.29 au, p = 0.019). Despite comparable hemolysis levels at 3 and 6 weeks, DOPC-treated RBCs showed significantly increased potassium levels for the same time points (3 weeks: 31.2 ± 2.7 mmol/L vs. 30.8 ± 2.7 mmol/L, p = 0.007; 6 weeks: 45.0 ± 3.0 mmol/L vs. 43.8 ± 3.4 mmol/L, p = 0.013). ATP and 2,3-DPG levels were comparable throughout storage.

CONCLUSIONS

Liposome treatment seemed to be more beneficial when performed at the beginning of storage up to day 21. DOPC liposome treatment resulted in an improvement in human RBC hemorheology upon storage, with no significant impact on metabolic profile.

Arachidonic acid levels in serum phospholipids of patients with angina pectoris or fatal myocardial infarction

The fatty acid composition and concentrations of serum phospholipids (PL) were examined in 14 normal subjects (NS), 10 patients with coronary heart disease (CHD) and stable angina pectoris, and in 12 patients with acute, fatal myocardial infarction (MI). The NS and patients with CHD and stable angina pectoris were matched with respect to age, height, body weight, blood pressure and serum cholesterol. Serum PL of patients with CHD and of patients with acute, fatal MI contained significantly more arachidonic acid (20:4n6, AA) than serum PL of the NS. Docosahexaenoic acid (22:6n3, DHA) was also increased in serum PL of patients with acute, fatal MI. AA and DHA levels in serum PL reflect changes in lipid metabolism that may relate to the cause and/or consequences of CHD.

Reduction of the in vitro hemolytic activity of soybean lecithin liposomes by treatment with a block copolymer

The in vitro hemolytic activity of liposomes made of soybean L-alpha-lecithin towards diluted (0.0086 v/v) human erythrocytes was used to investigate the effect of surface coating on the interaction of liposomes with cells. The increase in apparent volume of the block copolymer of ethylene glycol and propylene glycol, Pluronic F-127, in the presence of liposomes supports the hypothesis of either adsorption or penetration of the copolymer at the surface of the liposomes. When the liposomes are pre-incubated with Pluronic F-127, their lytic activity towards fresh erythrocytes is significantly reduced while it remains unchanged towards erythrocytes aged in vitro. It is also found that aging the liposomes has little effect on their lytic activity while aging of the erythrocytes makes them more fragile towards the liposomes. The results are discussed in terms of steric hindrance.

Kinetics of phospholipid transfer between liposomes (neutral or negatively charged) and high-density lipoproteins: a spin-label study of early events

The kinetics of spin-labeled phosphatidylcholine transfer between vesicles and HDL particles exhibited a two-phase process, as seen by ESR spectroscopy. The results were analyzed by considering several possible steps in the overall transfer, whose aspects were also studied: (i) micellar complex formation after HDL apolipoprotein-vesicle mixture, (ii) the rate of PC transfer from the micellar complex to HDL, (iii) the rate of the reverse reaction between overloaded HDL particles and other particles such as HDLs, LDLs, and lipid vesicles. The results agree most convincingly with a mechanism in which the diffusion of phospholipids into the HDL-endogenous lipids is the limiting step, occurring as a two-step process. In addition, we observed a negative charge effect on the lipid transfer rates and yields.