Comparative studies of the protein composition of red blood cell membranes from eight mammalian species

Proteomes of Micro- and Nanosized Carriers Engineered from Red Blood Cells

Red blood cell (RBC)-derived systems offer a potential platform for delivery of biomedical cargos. Although the importance of specific proteins associated with the biodistribution and pharmacokinetics of these particles has been recognized, it remains to be explored whether some of the key transmembrane and cytoskeletal proteins responsible for immune-modulatory effects and mechanical integrity of the particles are retained. Herein, using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and quantitative tandem mass tag mass spectrometry in conjunction with bioinformatics analysis, we have examined the proteomes of micro- and nanosized erythrocyte ghosts doped with indocyanine green and compared them with those of RBCs. We identified a total of 884 proteins in each set of RBCs, micro-, and nanosized particles, of which 8 and 45 proteins were expressed at significantly different relative abundances when comparing micro-sized particles vs RBCs and nanosized particles vs RBCs, respectively. We found greater differences in relative abundances of some mechano-modulatory proteins, such as band 3 and protein 4.2, and immunomodulatory proteins like CD44, CD47, and CD55 in nanosized particles as compared to RBCs. Our findings highlight that the methods utilized in fabricating RBC-based systems can induce substantial effects on their proteomes. Mass spectrometry data are available at ProteomeXchange with the identifier PXD038780.

Optimization of the Hemolysis Assay for the Assessment of Cytotoxicity

In vitro determination of hemolytic properties is a common and important method for preliminary evaluation of cytotoxicity of chemicals, drugs, or any blood-contacting medical device or material. The method itself is relatively straightforward, however, protocols used in the literature vary substantially. This leads to significant difficulties both in interpreting and in comparing the obtained values. Here, we examine how the different variables used under different experimental setups may affect the outcome of this assay. We find that certain key parameters affect the hemolysis measurements in a critical manner. The hemolytic effect of compounds tested here varied up to fourfold depending on the species of the blood source. The use of different types of detergents used for generating positive control samples (i.e., 100% hemolysis) produced up to 2.7-fold differences in the calculated hemolysis ratios. Furthermore, we find an expected, but substantial, increase in the number of hemolyzed erythrocytes with increasing erythrocyte concentration and with prolonged incubation time, which in turn affects the calculated hemolysis ratios. Based on our findings we propose an optimized protocol in an attempt to standardize future hemolysis studies.

Traditional and Computational Screening of Non-Toxic Peptides and Approaches to Improving Selectivity

Peptides have positively impacted the pharmaceutical industry as drugs, biomarkers, or diagnostic tools of high therapeutic value. However, only a handful have progressed to the market. Toxicity is one of the main obstacles to translating peptides into clinics. Hemolysis or hemotoxicity, the principal source of toxicity, is a natural or disease-induced event leading to the death of vital red blood cells. Initial screenings for toxicity have been widely evaluated using erythrocytes as the gold standard. More recently, many online databases filled with peptide sequences and their biological meta-data have paved the way toward hemolysis prediction using user-friendly, fast-access machine learning-driven programs. This review details the growing contributions of in silico approaches developed in the last decade for the large-scale prediction of erythrocyte lysis induced by peptides. After an overview of the pharmaceutical landscape of peptide therapeutics, we highlighted the relevance of early hemolysis studies in drug development. We emphasized the computational models and algorithms used to this end in light of historical and recent findings in this promising field. We benchmarked seven predictors using peptides from different data sets, having 7–35 amino acids in length. According to our predictions, the models have scored an accuracy over 50.42% and a minimal Matthew’s correlation coefficient over 0.11. The maximum values for these statistical parameters achieved 100.0% and 1.00, respectively. Finally, strategies for optimizing peptide selectivity were described, as well as prospects for future investigations. The development of in silico predictive approaches to peptide toxicity has just started, but their important contributions clearly demonstrate their potential for peptide science and computer-aided drug design. Methodology refinement and increasing use will motivate the timely and accurate in silico identification of selective, non-toxic peptide therapeutics.

Red Blood Cell Stiffness and Adhesion Are Species-Specific Properties Strongly Affected by Temperature and Medium Changes in Single Cell Force Spectroscopy

Besides human red blood cells (RBC), a standard model used in AFM-single cell force spectroscopy (SCFS), little is known about apparent Young's modulus (Ea) or adhesion of animal RBCs displaying distinct cellular features. To close this knowledge gap, we probed chicken, horse, camel, and human fetal RBCs and compared data with human adults serving as a repository for future studies. Additionally, we assessed how measurements are affected under physiological conditions (species-specific temperature in autologous plasma vs. 25 °C in aqueous NaCl solution). In all RBC types, Ea decreased with increasing temperature irrespective of the suspension medium. In mammalian RBCs, adhesion increased with elevated temperatures and scaled with reported membrane sialic acid concentrations. In chicken only adhesion decreased with higher temperature, which we attribute to the lower AE-1 concentration allowing more membrane undulations. Ea decreased further in plasma at every test temperature, and adhesion was completely abolished, pointing to functional cell enlargement by adsorption of plasma components. This halo elevated RBC size by several hundreds of nanometers, blunted the thermal input, and will affect the coupling of RBCs with the flowing plasma. The study evidences the presence of a RBC surface layer and discusses the tremendous effects when RBCs are probed at physiological conditions.

Effect of ozonation on resistance of ovine and human erythrocytes to hypothermic storage

Long-term hypothermic storage of animal blood can lead to the loss of its quality and can cause complications in recipient animals after transfusion, so the search for new methods of increasing the preservation of erythrocytes after hypothermic storage continues. The article presents the data of the ozonation effect on the preservation rate of ovine and human erythrocytes during hypothermic storage with Alsever’s solution and mannitol medium. Hemolysis, osmotic fragility and distribution density of ovine and human erythrocytes by the sphericity index were determined at different stages of hypothermic storage. The ovine erythrocytes in the control had a lower osmotic resistance compared to human erythrocytes; however, their osmotic fragility did not change significantly after hypothermic storage for 8 weeks, and for human erythrocytes, it significantly increased. Storage of ovine and human erythrocytes longer than 8 weeks led to a sharp hemolysis, while the level of hemolysis of ovine erythrocytes was lower than that of human erythrocytes. Preservation of ozonated erythrocytes is higher than non-ozonated ones during prolonged hypothermic storage. The effect of ozonation on the preservation rate of red blood cells depended on the composition of the preservation media. Hypothermal storage of human erythrocytes in Alsever’s solution for up to 8 weeks led to a shift in the density of distribution according to the sphericity index towards spheroidization of cells; in a medium with mannitol, the number of flattened cell forms increased. After 8 weeks of hypothermic storage of ovine erythrocytes, most of the cells had high sphericity indices. Pretreatment of human and sheep erythrocytes with ozone allows the distribution of cells to be kept closer to the control during long-term storage, which is especially pronounced in mannitol medium. Ovine erythrocytes retained the ability to form rosettes with human T-lymphocytes after hypothermic storage for up to 12 weeks. Thus, ozone pretreatment and the use of mannitol as part of hypothermic storage medium could be an approach to improve the quality of preserved ovine erythrocytes.

Correlation between hemolytic activity, cytotoxicity and systemic in vivo toxicity of synthetic antimicrobial peptides

The use of non-standard toxicity models is a hurdle in the early development of antimicrobial peptides towards clinical applications. Herein we report an extensive in vitro and in vivo toxicity study of a library of 24 peptide-based antimicrobials with narrow spectrum activity towards veterinary pathogens. The haemolytic activity of the compounds was evaluated against four different species and the relative sensitivity against the compounds was highest for canine erythrocytes, intermediate for rat and human cells and lowest for bovine cells. Selected peptides were additionally evaluated against HeLa, HaCaT and HepG2 cells which showed increased stability towards the peptides. Therapeutic indexes of 50–500 suggest significant cellular selectivity in comparison to bacterial cells. Three peptides were administered to rats in intravenous acute dose toxicity studies up to 2–8 × MIC. None of the injected compounds induced any systemic toxic effects in vivo at the concentrations employed illustrating that the correlation between the different assays is not obvious. This work sheds light on the in vitro and in vivo toxicity of this class of promising compounds and provides insights into the relationship between the different toxicity models often employed in different manners to evaluate the toxicity of novel bioactive compounds in general.

Comparative Analysis of Erythrocyte Proteomes of Water Buffalo, Dairy Cattle, and Beef Cattle by Shotgun LC-MS/MS

A number of studies have demonstrated that Babesia orientalis (B. orientalis) can only infect water buffalo (Bubalus bubalis) and not dairy cattle (Bos taurus) or beef cattle (Bos taurus), even though all three belong to the tribe Bovini and have close evolutionary relationships. In addition, Babesia species are intracellular protozoans that obligately parasitize in erythrocytes. This may indicate that the infection specificity is due to differences in erythrocyte proteins. Totals of 491, 1,143, and 1,145 proteins were identified from water buffalo, beef cattle, and dairy cattle, respectively, by searching the Uniprot and NCBI databases. The number of proteins identified for water buffalo was far lower than for beef cattle and dairy cattle, particularly in the range from 15 to 25 kDa. Remarkably, 290 identified proteins were unique to water buffalo, of which putative gamma-globin and putative epsilon-globin had a significant possibility of being relevant to the survival of B. orientalis only in water buffalo. A total of 2,222 proteins were annotated in terms of molecular function, biological process, and cellular component according to GO annotation. The number of proteins of water buffalo in oxygen binding was far higher than for beef cattle and dairy cattle. This is the first time that the protein profiles of water buffalo, beef cattle, and dairy cattle have been comparatively analyzed. The uniquely expressed proteins in water buffalo obtained in this study may provide new insights into the mechanism of B. orientalis infection exclusivity in water buffalo and may be a benefit for the development of strategies against B. orientalis.

Near-Newtonian Blood Behavior - Is It Good to Be a Camel?

From a certain level of exercise-intensity onward, hematocrit increases in horses, which brings more oxygen carriers into the bloodstream. Camels, however, when used in competitive racing could be even in need of iron supplementation and blood transfusions due to a severe reduction of their available hematocrit compared to their resting hematocrit. Since the extrinsic and intrinsic mechanical properties of camel erythrocytes (RBC) are so different compared to RBCs of other mammals, the question arises whether this observation might be a response to endurance exercise aiming at keeping the RBC count low. Rheometry indicated dromedary camel blood to behave almost Newtonian, which is unique amongst mammals. Shear thinning did increase with the hematocrit, but remained marginal compared to horses. As a result, camel whole blood viscosity (WBV) exceeded horse WBV at high shear rates, an effect, which was significantly augmented when the packed cell volume (PCV) was increased. Therefore, in camels any infusion of RBCs into the bloodstream can increase the cardiac work and the energy input into the endothelium more effectively, which should generate vascular remodeling in the long term. Yielding, however, was completely absent in camel blood, confirming low cohesion between its components at quasi-static flow. Camel blood remained a viscous liquid without a threshold even at unphysiologically high PCVs. This can help to washout lactate when camels start to dehydrate and might contribute to the sustained working ability of these animals. The subtle pseudoplastic behavior and the high viscosity contrast across the RBC membrane point to weak coupling between blood flow and red cell behavior. We predict that RBCs flow as separate entities and can show various types of motion, which can lead to friction instead of being collectively aligned to the flow direction. In comparison to horses, this behavior will become relevant at higher RBC counts in front of flow obstacles and possibly cause vascular remodeling if the PCV rises during strenuous exercise, a matter that should be avoided.

Viscoelasticity and structure of blood clots generated in-vitro by rheometry: A comparison between human, horse, rat, and camel

BACKGROUND

Although the coagulation system is evolutionary well preserved, profound species differences exist in viscoelastic as well as in common laboratory tests of coagulation.

OBJECTIVE

Evaluating differences in clot formation and material characterisation of clots of four mammalian species on macro-, micro- and nanoscales by the means of rheometry, scanning electron microscopy (SEM) and small angle x-ray scattering (SAXS).

METHODS

Blood samples were collected from healthy human volunteers, laboratory rats (HL/LE inbred strain), warmblood horses and dromedary camels. Clot formation was observed by oscillating shear rheometry until plateau formation of the shear storage modulus G', at which point selected clots were prepared for scanning electron microscopy. SEM images were analysed for fibre diameter and fractal dimension. Additionally, scattering profiles for plasma and whole blood samples were obtained with SAXS.

RESULTS

Viscoelasticity of clots showed great interspecies variation: clots of rats and horses exhibited shorter clotting times and higher G' plateau values, when compared to human clots. Camel clots showed unique clotting characteristics with no G' plateau formation in the timeframe observed. Less differentiating features were found with SEM and SAXS, although the rat fibre network appears to be more convoluted and dense, which resulted in a higher fractal dimension.

CONCLUSION

Clotting kinetic differs between the species, which is not only of clinical interest, but could also be an important finding for animal models of blood coagulation.

A comparative protein profile of mammalian erythrocyte membranes identified by mass spectrometry

A comparative analysis of erythrocyte membrane proteins of economically important animals, goat (Capra aegagrus hircus), buffalo (Bubalus bubalis), pig (Sus scrofa), cow (Bos tauras), and human (Homo sapiens) was performed. Solubilized erythrocyte membrane proteins were separated by sodium dodecyl sulfate-polyacryamide gel electrophoresis (SDS-PAGE), visualized by staining the gels with Commassie Brilliant Blue (CBB), and identified by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/MS). Emerging results show that all major erythrocyte membrane proteins present in human are also seen in all the animals except for band 4.5 which could not be identified. Band 3 is seen as more intense and compact, band 4.1 appears as a doublet in all the animal erythrocyte membranes, band 4.2 exhibits a slightly higher molecular weight (Mr) in buffalo, and cow and band 4.9 has a higher Mr in all the animals relative to the human protein. In addition, there are two new bands in the goat membrane, band G1, identified as HSP 90α, and band G2 identified as HSP 70. A new band C2 identified as HSP 70 is also seen in cow membranes. Peroxiredoxin II is of lower intensity and/or higher Mr in the animals. The difference in size of the proteins possibly indicates the variations in the composition of the amino acids. The difference in intensity of the proteins among these mammalians highlights the presence of less or more number of copies of that protein per cell. This data complement the earlier observations of differences in the sialoglycoprotein profile and effect of proteases and neuraminidase on agglutination among the mammalian erythrocytes. This study provides a platform to understand the molecular architecture of the individual erythrocytes, and in turn the dependent disorders, their phylogenetic relationship and also generates a database of erythrocyte membrane proteins of mammals. The animals selected for this study are of economic importance as they provide milk for the dairy industry and raw material for leather industry and are routinely sacrificed to obtain non vegetarian food worldwide.

Deep coverage mouse red blood cell proteome: a first comparison with the human red blood cell

Mice have close genetic/physiological relationships to humans, breed rapidly, and can be genetically modified, making them the most used mammal in biomedical research. Because the red blood cell (RBC) is the sole gas transporter in vertebrates, diseases of the RBC are frequently severe; much research has therefore focused on RBC and cardiovascular disorders of mouse and humans. RBCs also host malaria parasites. Recently we presented an in-depth proteome for the human RBC. Here we present directly comparable data for the mouse RBC as membrane-only, soluble-only, and combined membrane-bound/soluble proteomes (comprising, respectively, 247, 232, and 165 proteins). All proteins were identified, validated, and categorized in terms of subcellular localization, protein family, and function, and in comparison with the human RBC, were classified as orthologs, family-related, or unique. Splice isoforms were identified, and polypeptides migrating with anomalous apparent molecular weights were grouped into putatively ubiquitinated or partially degraded complexes. Overall there was close concordance between mouse and human proteomes, confirming the unexpected RBC complexity. Several novel findings in the human proteome have been confirmed here. This comparison sheds light on several open issues in RBC biology and provides a departure point for more comprehensive understanding of RBC function.