Phospholipid composition and organization in model β-thalassemic erythrocytes

Abstract

The membrane phospholipid organization in human red blood cells (RBC) is rigidly maintained by a complex system of enzymes. However, several elements of this system are sensitive to oxidative damage. An important component in the destruction of pthaiasse-mic RBC is the generation of reactive oxygen species and the release of redox-active iron by the unpaired a-hemoglobin chains. Consequently, we hypothesized that the presence of this oxidative stress to the RBC membrane could lead to alterations in membrane lipid organization. Model p thaiassemic RBC, prepared by the introduction of excess agiobin in the cell, have previously been shown to exhibit structural and functional changes almost identical to those observed in p-thaiassemic cells. After 24 hr at 3PC, the model p thaiassemic cells exhibited a significant loss of deformabiiity, as measured by ektacyto-metric analysis, indicative of extensive membrane damage. However, a normal steady-state distribution of endogenous phospholipids was found, as evidenced by the accessibility of membrane phospholipids to hydrolysis by phosphoiipases. Similarly, the kinetics of transbilayer movement of spin-labeled phosphatidylserine (PS) and phosphatidyietha-noiamine (PE) in ail samples was in the normal range and was not affected by the presence of excess a-globin chains. In contrast, a faster rate of spin-labeled phosphatidylcholine (PC) transbiiayer movement was observed in these cells. While control RBC exhibited a complete loss of their initial (2 moi%) iysophosphatidyichoiine (LPC) levels following 24 hr of incubation at 37% 1.5 mol% LPC was still present in model p-thaiassemic cells, suggesting an altered phospholipid molecular species turnover, possibly as a result of an increased repair of oxidatively damaged phospholipids.

Microfluidic analysis of cellular deformability of normal and oxidatively damaged red blood cells

“…Indeed, pharmacologic agents or hemoglobin, cytoskeletal, metabolic or lipid abnormalities that impair the deformability of the RBC will give rise to the premature clearance of the cell and, potentially, anemia. Because of the crucial biological importance of RBC deformability, numerous methodologies have been devised to measure both cellular and membrane deformability [3,[26][27][28][29][30][31][32][33]. These approaches include ektacytometry, micropore transit analyses, and micropipette aspiration.…”

“…To understand the pathophysiology of disease, previous investigators have used techniques such as ektacytometry and the cell transit analyzer to measure cellular deformability [3,[26][27][28][29][30][31][32][33]. Ektacytometry measures deformability by subjecting RBC suspended in a viscous solution to rotational shear stress such that the normal cells form ellipsoids.…”

Reduced oxidative-stress response in red blood cells from p45NFE2-deficient mice

“…Similar changes in the osmotic deformability profile and a decrease in the deformability index due to oxidation-induced changes in RBC membranes were previously observed in hemoglobinopathies such as thalassemia. [32][33][34] The oxidant-induced decreased deformability in the hypertonic arm of the profile indicates changes in the mechanical properties of the membrane 35 and For personal use only. on April 4, 2019. by guest www.bloodjournal.org From suggests that mutant cells may be more rigid than normal cells.…”

Red blood cells from patients with homozygous sickle cell disease provide a catalytic surface for factor Va inactivation by activated protein C

“…In these conditions, the mean value of the rate of factor Va inactivation at the surface of SS RBCs approached the rate of the reaction as measured on the surface of synthetic phospholipids vesicles with 10% phosphatidylserine. The promoting effect of SS RBCs was more than expected as, upon complete loss of asymmetry, phosphatidylserine present in the outer part of a red cell membrane would represent, at the most, 7% of total phospholipids (Kuypers et al , 1996b), but exposure is restricted to the small subpopulation of sickle cells. Incorporation of phosphatidylethanolamine in phosphatidylserine‐containing vesicles increases the rate of factor Va inactivation approximately 10‐fold, whatever the factor Va and phospholipids vesicles concentrations used (Smirnov & Esmon, 1994), and it is therefore possible that simultaneous exposure of phosphatidylethanolamine upon sickling could help to promote APC anticoagulant activity.…”