Changes of phosphatidylserine distribution in human red blood cells during the process of loading sugars

Achieving high intracellular trehalose in hRBCs by reversible membrane perturbation of maltopyranosides with synergistic membrane protection of macromolecular protectants

Trehalose is considered as a biocompatible cryoprotectant for solvent-free cryopreservation of cells, but the difficulty of the current trehalose delivery platforms to human red blood cells (hRBCs) limits its wide applications. Due to cell injuries caused by incubation at 37 °C and low intracellular loading efficiency, development of novel methods to facilitate trehalose entry in hRBCs is essential. Herein, a reversible membrane perturbation and synergistic membrane stabilization system based on maltopyranosides and macromolecular protectants was constructed, demonstrating the ability of efficient trehalose loading in hRBCs at 4 °C. Results of confocal laser scanning microscopy exhibited that the intracellular loading with the assistance of maltopyranosides was a reversible process, while the membrane protective effect of macromolecular protectants on trehalose loading in hRBCs was necessary. It was suggested that introduction of 30 mM poly(vinyl pyrrolidone) 8000 combined with 1 mM dodecyl-β-D-maltopyranoside and 0.8 M trehalose could increase the intracellular trehalose to 84.0 ± 11.3 mM in hRBCs, whereas poly(ethylene glycol), dextran, human serum albumin or hydroxyethyl starch had a weak effect. All the macromolecular protectants could promote the cryosurvival of hRBCs, exhibiting membrane stabilization, and incubation and followed by cryopreservation did not change the basic functions and normal morphology of hRBCs substantially. This study provided an alternative strategy for glycerol-free cryopreservation of cells and the delivery of membrane-impermeable cargos.

NonFreezable Preservation of Human Red Blood Cells at -8 °C

Red blood cell (RBC) preservation is very important in human health. The RBCs are usually preserved at 4 ± 2 °C without freezing or at a very low temperature (-80 °C or liquid nitrogen) with deep freezing. Herein, non freezable preservation of RBCs at a subzero temperature is reported to prolong the preservation time compared with that at 4 ± 2 °C. By adding glycerol and poly(ethylene glycol) (PEG) (average number molecular weight 400, PEG-400) into the preservation solution, the freezing point is decreased and the hemolysis is kept low. The cell metabolism of stored RBCs at -8 °C is reduced, and the shelf life of RBCs extends up to at least 70 days. At the end of preservation, the pH decreases a little bit to demonstrate the low metabolic rate of RBCs stored at subzero temperatures. After quick washing, the RBC survival rate is ca. 95%. The adenosine triphosphate, 2,3-diphosphoglycerate, and cell deformation ability of the washed RBCs are maintained at a high level, while the malondialdehyde is relatively low, which verifies the high quality of RBCs stored at this condition.

Facilitating trehalose entry into hRBCs at 4 °C by alkylated ε-poly(L-lysine) for glycerol-free cryopreservation

Currently, glycerol is a conventional cryoprotectant of human red blood cells (hRBCs), but the time-consuming thawing and deglycerolization processes are essential before transfusion. Much of the research up to now has been conducted on the delivery of impermeable trehalose to hRBCs at 37 °C, but the cryoprotective effect of trehalose and deterioration of cells still remain challenging. Encouraged by the interaction of hydrophobic or cationic groups on cell membranes and osmotic stabilization, herein, we propose a novel cryopreservation system to facilitate trehalose entry into hRBCs at 4 °C and pH 7.4. High intracellular trehalose contents and cryosurvival of hRBCs were achieved with small function variations via the assistance of self-assembled nanoparticles of alkylated ε-poly(L-lysine) (ε-PL) along with poly(vinyl pyrrolidone) (PVP). The effect of amphipathic alkylated ε-PL with various alkyl chains and grafting ratios on membrane perturbation with protection of PVP was systematically investigated. Overall, by the combination of alkylated ε-PL and PVP, the intracellular trehalose could be enhanced to 109.7 ± 6.1 mM and subsequently hRBC cryosurvival reached 91.7 ± 5.5%, significantly higher than those containing trehalose only, 11.9 ± 1.1 mM and 50.0 ± 2.1%, respectively. It was observed that the biocompatible trehalose-loading system could benefit glycerol-free cryopreservation of hRBCs and also provide a feasible way for impermeable biomacromolecule delivery.

Cryopreservation of human erythrocytes through high intracellular trehalose with membrane stabilization of maltotriose-grafted ε-poly(L-lysine)

Cryopreservation of human erythrocytes via suitable cryoprotectants is essential for transfusion at emergency, but the conventional glycerolization method requires a tedious thawing-deglycerolization process. Alternatively, trehalose, a nonreducing disaccharide, has gained...

Protective Effects of Ferulic Acid on High Glucose-Induced Protein Glycation, Lipid Peroxidation, and Membrane Ion Pump Activity in Human Erythrocytes

Ferulic acid (FA) is the ubiquitous phytochemical phenolic derivative of cinnamic acid. Experimental studies in diabetic models demonstrate that FA possesses multiple mechanisms of action associated with anti-hyperglycemic activity. The mechanism by which FA prevents diabetes-associated vascular damages remains unknown. The aim of study was to investigate the protective effects of FA on protein glycation, lipid peroxidation, membrane ion pump activity, and phosphatidylserine exposure in high glucose-exposed human erythrocytes. Our results demonstrated that FA (10-100 μM) significantly reduced the levels of glycated hemoglobin (HbA1c) whereas 0.1-100 μM concentrations inhibited lipid peroxidation in erythrocytes exposed to 45 mM glucose. This was associated with increased glucose consumption. High glucose treatment also caused a significant reduction in Na⁺/K⁺-ATPase activity in the erythrocyte plasma membrane which could be reversed by FA. Furthermore, we found that FA (0.1-100 μM) prevented high glucose-induced phosphatidylserine exposure. These findings provide insights into a novel mechanism of FA for the prevention of vascular dysfunction associated with diabetes.

Increased cation conductance in human erythrocytes artificially aged by glycation

Excessive glucose concentrations foster glycation and thus premature aging of erythrocytes. The present study explored whether glycation-induced erythrocyte aging is paralleled by features of suicidal erythrocyte death or eryptosis, which is characterized by cell membrane scrambling with subsequent phosphatidylserine exposure at the cell surface and cell shrinkage. Both are triggered by increases of cytosolic Ca(2+) concentration ([Ca(2+)](i)), which may result from activation of Ca(2+) permeable cation channels. Glycation was accomplished by exposure to high glucose concentrations (40 and 100 mM), phosphatidylserine exposure estimated from annexin binding, cell shrinkage from decrease of forward scatter, and [Ca(2+)](i) from Fluo3-fluorescence in analysis via fluorescence-activated cell sorter. Cation channel activity was determined by means of whole-cell patch clamp. Glycation of total membrane proteins, immunoprecipitated TRPC3/6/7, and immunoprecipitated L-type Ca(2+) channel proteins was estimated by Western blot testing with polyclonal antibodies used against advanced glycation end products. A 30-48-h exposure of the cells to 40 or 100 mM glucose in Ringer solution (at 37 degrees C) significantly increased glycation of membrane proteins, hemoglobin (HbA(1c)), TRPC3/6/7, and L-type Ca(2+) channel proteins, enhanced amiloride-sensitive, voltage-independent cation conductance, [Ca(2+)](i), and phosphatidylserine exposure, and led to significant cell shrinkage. Ca(2+) removal and addition of Ca(2+) chelator EGTA prevented the glycation-induced phosphatidylserine exposure and cell shrinkage after glycation. Glycation-induced erythrocyte aging leads to eryptosis, an effect requiring Ca(2+) entry from extracellular space.

Inhibition of high glucose-induced erythrocyte phosphatidylserine exposure by leupeptin and disaccharides

High glucose can lead to serious phosphatidylserine exposure of erythrocytes which may influence the protective effect of glucose on lyophilization of erythrocytes. In this study, caspase activation has not occurred during phosphatidylserine exposure of erythrocytes. However, leupeptin can efficiently inhibit phosphatidylserine exposure of erythrocytes induced by high glucose. With increase of the leupeptin concentrations, the percentages of cells with exposed phosphatidylserine were decreased steadily. In addition, trehalose and sucrose can significantly inhibit phosphatidylserine exposure and cell shrinkage of erythrocytes induced by high glucose through increasing tolerance to osmotic shock. When the disaccharide concentrations were more than 100 mM, the percentages of cells with exposed phosphatidylserine were similar to those of control cells. Moreover, addition of disaccharides in the glucose buffer can result in high osmotic pressure which may facilitate uptake of glucose and disaccharides into erythrocytes and higher cellular glucose and disaccharide concentrations can provide more protection for lyophilized erythrocytes. Although disaccharides can increase the osmotolerance and decrease the phosphatidylserine exposure of erythrocytes exposed to high glucose, whether disaccharides can prevent phosphatidylserine exposure of lyophilized erythrocytes still needs further researches.