Transbilayer movement of phospholipids in red cell and platelet membranes

Selective Blood Cell Hitchhiking in Whole Blood with Ionic Liquid-Coated PLGA Nanoparticles to Redirect Biodistribution After Intravenous Injection

Less than 5% of intravenously-injected nanoparticles (NPs) reach destined sites in the body due to opsonization and immune-based clearance in vascular circulation. By hitchhiking in situ onto specific blood components post-injection, NPs can selectively target tissue sites for unprecedentedly high drug delivery rates. Choline carboxylate ionic liquids (ILs) are biocompatible liquid salts <100X composed of bulky asymmetric cations and anions. This class of ILs has been previously shown to significantly extend circulation time and redirect biodistribution in BALB/c mice post-IV injection via hitchhiking on red blood cell (RBC) membranes. Herein, we synthesized & screened 60 choline carboxylic acid-based ILs to coat PLGA NPs and present the impact of structurally engineering the coordinated anion identity to selectively interface and hitchhike lymphocytes, monocytes, granulocytes, platelets, and RBCs in whole mouse blood for in situ targeted drug delivery. Furthermore, we find this nanoparticle platform to be biocompatible (non-cytotoxic), translate to human whole blood by resisting serum uptake and maintaining modest hitchhiking, and also significantly extend circulation retention over 24 hours in BALB/c healthy adult mice after IV injection. Because of their altered circulation profiles, we additionally observe dramatically different organ accumulation profiles compared to bare PLGA NPs. This study establishes an initial breakthrough platform for a modular and transformative targeting technology to hitchhike onto blood components with high efficacy and safety in the bloodstream post-IV administration.

The Bone Cement Hypercoagulation Syndrome: Pathophysiology, Mortality, and Prevention

Since Charnley introduced acrylic cement to seal metallic hip prostheses in the 1950s, reports of perioperative fatal cardiorespiratory and vascular dysfunctions have been published. Studies on humans and animals have shown neurogenic stimulation and substantial local and systemic activation of coagulation are caused by surgical bone marrow damage and chemical cell destruction by toxic monomeric methyl methacrylate from the implanted cement and other tissue-released substances. Venous blood-borne cell fragments and conjugates of activated cells from the surgical site are sequestered and trapped in the pulmonary microcirculation. A substantial hypercoagulation occurs in the lung circulation. Hypercoagulable blood is passed over to the arterial side and may cause vessel obliteration and organ damage. This process may affect the brain, heart, and kidneys and, through the release of vasoactive substances, introduce hemodynamic imbalances that can lead to fatal outcomes in susceptible populations such as elderly patients with hip fractures. The main underlying pathophysiologic processes leading to these occasionally devastating outcomes are a substantial activation of coagulation and cell destruction caused by the toxic substance released by curing bone cement and several vasoactive substances.

Sex-Specific Differences of Adenosine Triphosphate Levels in Red Blood Cells Isolated From ApoE/LDLR Double-Deficient Mice

In this study for the first time, we investigated the correlation between sex-specific differences in adenosine triphosphate (ATP) levels in red blood cells (RBCs) and their mechanical, biochemical, and morphological alterations during the progression of atherosclerosis in ApoE/LDLR double-deficient (ApoE/LDLR^−/−) mice. Our results indicate that both sex and age affect alterations in RBCs of both ApoE/LDLR^−/− and C57BL/6J mice. When compared with male RBCs, female RBCs were characterized by lower basal ATP and mean corpuscular hemoglobin concentration (MCHC), higher hemoglobin concentration (HGB), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), deformability, and phosphatidylserine (PS) exposure levels, regardless of age in both, ApoE/LDLR^−/− and C57BL/6J mice. ApoE/LDLR^−/− mice compared with age-matched controls showed lower basal ATP levels regardless of age and sex. Intracellular ATP level of RBCs was decreased solely in senescent female C57BL/6J mice, while it was elevated in males. Basal extracellular ATP levels were 400 times lower than corresponding intracellular level. In conclusion, basal ATP levels, RBC morphology, deformability, PS exposure levels alterations are sex-dependent in mice. Changes in basal ATP levels were correlated with PS exposure and trends of changes in MCV. Trends of changes of the most RBC parameters were similar in both sexes of ApoE/LDLR^−/− mice compared with age-matched controls; however, their kinetics and levels vary greatly between different stages of disease progression.

The role of phosphatidylserine on the membrane in immunity and blood coagulation

The negatively charged aminophospholipid, phosphatidylserine (PtdSer), is located in the inner leaflet of the plasma membrane in normal cells, and may be exposed to the outer leaflet under some immune and blood coagulation processes. Meanwhile, Ptdser exposed to apoptotic cells can be recognized and eliminated by various immune cells, whereas on the surface of activated platelets Ptdser interacts with coagulation factors prompting enhanced production of thrombin which significantly facilitates blood coagulation. In the case where PtdSer fails in exposure or mistakenly occurs, there are occurrences of certain immunological and haematological diseases, such as the Scott syndrome and Systemic lupus erythematosus. Besides, viruses (e.g., Human Immunodeficiency Virus (HIV), Ebola virus (EBOV)) can invade host cells through binding the exposed PtdSer. Most recently, the Corona Virus Disease 2019 (COVID-19) has been similarly linked to PtdSer or its receptors. Therefore, it is essential to comprehensively understand PtdSer and its functional characteristics. Therefore, this review summarizes Ptdser, its eversion mechanism; interaction mechanism, particularly with its immune receptors and coagulation factors; recognition sites; and its function in immune and blood processes. This review illustrates the potential aspects for the underlying pathogenic mechanism of PtdSer-related diseases, and the discovery of new therapeutic strategies as well.

IVS I-5 (G>C) is associated with changes to RBC membrane lipidome in response to Hydroxyurea treatment in β-thalassemia patients

Red Blood Cell’s membrane loses its integrity during hemoglobinopathies like β-thalassemia and sickle cell disease. Various mutations have been associated with β-thalassemia, the most prevalent of which is the IVS-1-5...

Calcium-sensing receptor promotes calcium oxalate crystal adhesion and renal injury in Wistar rats by promoting ROS production and subsequent regulation of PS ectropion, OPN, KIM-1, and ERK expression

OBJECTIVES

To explore the mechanism of calcium-sensing receptors (CaSRs) during the development of nephrolithiasis.

MATERIALS AND METHODS

Wistar rats were treated with ethylene glycol to induce calcium oxalate crystallization, and gadolinium chloride (GdCl₃, an agonist of CaSR) and NPS 2390 (an antagonist of CaSR) were added. Oxidative stress (OS) and calcium oxalate crystals in the kidney were observed. CaSR expression and the expression of extracellular signal-regulated protein kinase (ERK), OPN, and KIM-1 were determined by western blotting. In addition, renal tubular epithelial cells were isolated from the kidney to observe phosphatidylserine (PS) ectropion using flow cytometric analysis. Various biochemical parameters were assessed in serum and urine at the end of the experiment.

RESULTS

Calcium oxalate increased OS, crystal adhesion, PS ectropion, and the expression of CaSR and ERK, OPN, and KIM-1 in vivo. In addition, lower levels of urine citrate as well as increased serum creatinine and urea levels were observed after treatment with calcium oxalate (p < .05). Compared with calcium oxalate treatment alone, the above deleterious changes were further significantly confirmed by GdCl₃ but were reversed by NPS-2390. However, urine calcium excretion was decreased after ethylene glycol treatment but was significantly reduced by NPS 2390 and increased by GdCl₃ (p < .05).

CONCLUSIONS

The results suggest that CaSR might play significant roles in the induction of nephrolithiasis in rats by regulating reactive oxygen species (ROS) and PS ectropion and the composition of urine, OPN, KIM-1, and ERK expression.

Comparison of pathological clotting using haematological, functional and morphological investigations in HIV-positive and HIV-negative patients with deep vein thrombosis

BACKGROUND

Patients infected with the human immunodeficiency virus (HIV) are more prone to systemic inflammation and pathological clotting, and many may develop deep vein thrombosis (DVT) as a result of this dysregulated inflammatory profile. Coagulation tests are not routinely performed unless there is a specific reason.

METHODS

We recruited ten healthy control subjects, 35 HIV negative patients with deep vein thrombosis (HIV negative-DVT), and 13 HIV patients with DVT (HIV positive-DVT) on the primary antiretroviral therapy (ARV) regimen-emtricitabine, tenofovir and efavirenz. Serum inflammatory markers, haematological results, viscoelastic properties using thromboelastography (TEG) and scanning electron microscopy (SEM) of whole blood (WB) were used to compare the groups.

RESULTS

The DVT patients (HIV positive and HIV negative) had raised inflammatory markers. The HIV positive-DVT group had anaemia in keeping with anaemia of chronic disorders. DVT patients had a hypercoagulable profile on the TEG but no significant difference between HIV negative-DVT and HIV positive-DVT groups. The TEG analysis compared well and supported our ultrastructural results. Scanning electron microscopy of DVT patient's red blood cells (RBCs) and platelets demonstrated inflammatory changes including abnormal cell shapes, irregular membranes and microparticle formation. All the ultrastructural changes were more prominent in the HIV positive-DVT patients.

CONCLUSIONS

Although there were trends that HIV-positive patients were more hypercoagulable on functional tests (viscoelastic profile) compared to HIV-negative patients, there were no significant differences between the 2 groups. The sample size was, however, small in number. Morphologically there were inflammatory changes in patients with DVT. These ultrastructural changes, specifically with regard to platelets, appear more pronounced in HIV-positive patients which may contribute to increased risk for hypercoagulability and deep vein thrombosis.

Lipidomics Analysis of Timosaponin BII in INS-1 Cells Induced by Glycolipid Toxicity and Its Relationship with Inflammation

Anemarrhena asphodeloides Bunge is a traditional Chinese medicine. The timosaponin BII is one of the most abundant and widely studied active ingredients in Anemarrhena asphodeloides Bunge. Related studies have shown that timosaponin BII has potential value for development and further utilization. The protective effect of timosaponin BII on islet β cells under type 2 diabetes was investigated in the glycolipid toxic INS-1 cell model and possible biomarkers were explored by lipidomics analysis. Timosaponin BII was isolated from Anemarrhena asphodeloides Bunge by polyamide resin and Sephadex LH-20. Then, the glycolipid toxicity INS-1 cell model was established to investigate the protective effect of timosaponin BII. The results showed that timosaponin BII could significantly influence the levels of malondialdehyde (MDA) and glutathione (GSH), thereby restoring the insulin secretion ability and cell viability of model cells. Lipidomics analysis was combined with multivariate statistical analysis for marker selection. The four most common pathological and pharmacological lipid markers were phosphatidylserine (PS), suggesting that timosaponin BII had protective effects on model cells related to the reduction oxidative stress and macrophage inflammation. RAW264.7 macrophages were stimulated by LPS to establish a model of inflammation and study the effect of timosaponin BII on the nodes of NOD-like receptor P3 (NLRP3) inflammasome pathway in the model cells. In conclusion, timosaponin BII may have the effect of protecting INS-1 pancreatic β cells through reducing IL-1β (interleukin-1β) production by inhibiting the NLRP3 inflammasome in macrophage and restoring the insulin secretion ability and cell viability by reducing oxidative stress.

Mass spectrometry strategies to unveil modified aminophospholipids of biological interest

The biological functions of modified aminophospholipids (APL) have become a topic of interest during the last two decades, and distinct roles have been found for these biomolecules in both physiological and pathological contexts. Modifications of APL include oxidation, glycation, and adduction to electrophilic aldehydes, altogether contributing to a high structural variability of modified APL. An outstanding technique used in this challenging field is mass spectrometry (MS). MS has been widely used to unveil modified APL of biological interest, mainly when associated with soft ionization methods (electrospray and matrix-assisted laser desorption ionization) and coupled with separation techniques as liquid chromatography. This review summarizes the biological roles and the chemical mechanisms underlying APL modifications, and comprehensively reviews the current MS-based knowledge that has been gathered until now for their analysis. The interpretation of the MS data obtained by in vitro-identification studies is explained in detail. The perspective of an analytical detection of modified APL in clinical samples is explored, highlighting the fundamental role of MS in unveiling APL modifications and their relevance in pathophysiology.

Protective effect of phosphatidylserine blockade in sepsis induced organ dysfunction

BACKGROUND

Phosphatidylserine is usually an intracellularly oriented cell membrane phospholipid. Externalized phosphatidylserine on activated cells is a signal for phagocytosis. In sepsis, persistent phosphatidylserine exposure is also a signal for activation of the coagulation and inflammatory cascades. As such, phosphatidylserine may be a key molecule in sepsis induced cellular and organ injury. We hypothesize that phosphatidylserine blockade provides a protective effect in sepsis induced organ dysfunction.

METHODS

Sepsis was induced in adult female rats using an endotoxin model. Diannexin, a homodimer of annexin A5, was administered for phosphatidylserine blockade. Rats were allocated to control (n = 5), sepsis (n = 6), or sepsis and phosphatidylserine blockade (n = 9) groups. Gut, pulmonary, renal, and hematologic dysfunctions were evaluated by mesenteric microvascular fluid leak, partial pressure of oxygen, serum creatinine, activated clotting time, and glomerular fibrin deposition, respectively.

RESULTS

Rats in the sepsis group demonstrated gut, renal, and hematologic dysfunction. Phosphatidylserine blockade reversed signs of gut dysfunction and mesenteric microvascular leak (P < .01). In addition, phosphatidylserine blockade corrected systemic coagulopathy, as measured by activated clotting time (P = .03) and glomerular fibrin deposition (P = .008). There was no difference in renal dysfunction (P = .1) or pulmonary dysfunction in any of the groups (P = .6).

CONCLUSION

In sepsis, phosphatidylserine blockade had a protective effect on gut dysfunction and coagulopathy. Increased phosphatidylserine exposure may be a key mediator of organ dysfunction and coagulopathy during sepsis. These data may provide insights into novel treatment options for septic patients.

Comparison of the systemic phospholipid profile in dogs diagnosed with idiopathic inflammatory bowel disease or food-responsive diarrhea before and after treatment

BACKGROUND

Inflammatory bowel disease (IBD) and food-responsive diarrhea (FRD) are common chronic enteropathies in dogs, of which the exact pathogenesis has not been fully understood. In people dyslipidemia has been reported in patients with IBD, and potential therapeutic benefits of polyunsaturated fatty acids (PUFA) in the treatment of IBD have been investigated. Studies on the phospholipid profile in dogs with IBD and FRD are still lacking.

AIM

To investigate the systemic phospholipid profile of dogs with IBD or FRD and to evaluate possible differences in phospholipids before and after treatment.

METHODS

The phospholipids in whole blood and EDTA plasma of 32 dogs diagnosed with either IBD (n = 16) or FRD (n = 16) were analyzed by hydrophilic interaction liquid chromatography (HILIC) prior to and after initiation of treatment, which included an elimination diet enriched with PUFAs.

RESULTS

A clear separation of the phospholipids between whole blood and plasma was demonstrated on principal component analysis plots. In addition to the type of specimen, treatment and disease severity were the most significant factors determining the variance of the phospholipid profile. An increase in lysolipids was observed after treatment. The phosphatidylcholine (PC) species changed from PC 38:4 before treatment to mainly lysophosphatidylcholine 18:0 after treatment. Furthermore, several differences in the abundance of individual phospholipids were identified between dogs with IBD and dogs with FRD and between treatment statuses using random forest analysis.

CONCLUSION

Significant variances were identified in the phospholipid profiles of dogs with IBD and FRD. These were particularly determined by type of specimen used, disease severity and treatment status. After treatment, a shift of phospholipid species towards lysophosphatidylcholine 18:0 was observed. Future studies should further investigate the role of lipids in the pathophysiology of IBD and FRD as well as their potential therapeutic benefits.

The P4-ATPase ATP9A is a novel determinant of exosome release

Extracellular vesicles (EVs) released by cells have a role in intercellular communication to regulate a wide range of biological processes. Two types of EVs can be recognized. Exosomes, which are released from multi-vesicular bodies upon fusion with the plasma membrane, and ectosomes, which directly bud from the plasma membrane. How cells regulate the quantity of EV release is largely unknown. One of the initiating events in vesicle biogenesis is the regulated transport of phospholipids from the exoplasmic to the cytosolic leaflet of biological membranes. This process is catalyzed by P4-ATPases. The role of these phospholipid transporters in intracellular vesicle transport has been established in lower eukaryotes and is slowly emerging in mammalian cells. In Caenorhabditis elegans (C. elegans), deficiency of the P4-ATPase member TAT-5 resulted in enhanced EV shedding, indicating a role in the regulation of EV release. In this study, we investigated whether the mammalian ortholog of TAT-5, ATP9A, has a similar function in mammalian cells. We show that knockdown of ATP9A expression in human hepatoma cells resulted in a significant increase in EV release that was independent of caspase-3 activation. Pharmacological blocking of exosome release in ATP9A knockdown cells did significantly reduce the total number of EVs. Our data support a role for ATP9A in the regulation of exosome release from human cells.

Modulation of the inflammatory response of immune cells in human peripheral blood by oxidized arachidonoyl aminophospholipids

Aminophospholipids (APL), phosphatidylethanolamine (PE) and phosphatidylserine (PS), can be oxidized upon oxidative stress. Oxidized PE and PS have been detected in clinical samples of different pathologies and may act as modulators of the inflammatory response. However, few studies have focused on the effects of oxidized APL (ox-APL) esterified with arachidonic acid, even though a considerable number of studies have assessed the modulation of the immune system by oxidized 1-palmitoyl-2-arachidonoyl-sn-3-glycerophosphocholine (OxPAPC). In the present study, we have used flow cytometry to evaluate the ability of oxidized PAPE (OxPAPE) and PAPS (OxPAPS) to promote or suppress an inflammatory phenotype on monocytes subsets and myeloid dendritic cells (mDCs). The results indicate that OxPAPE increases the frequency of all monocyte subpopulations expressing TNF-α, which promotes an inflammatory response. However, immune cell stimulation with OxPAPE in the presence of LPS results in a decrease of TNF-α expressed by classical monocytes. Incubation with OxPAPS and LPS induces a decrease in TNF-α produced by monocytes, and a significant decrease in IL-1β expressed by monocytes and mDCs, indicating that OxPAPS reduces the LPS-induced pro-inflammatory expression in these populations. These results show the importance of OxPAPE and OxPAPS as modulators of the inflammatory response and demonstrate their possible contribution to the onset and resolution of human diseases related to oxidative stress and inflammation.

Role of red blood cells in haemostasis and thrombosis

In contrast to an obsolete notion that erythrocytes, or red blood cells (RBCs), play a passive and minor role in hemostasis and thrombosis, over the past decades there has been increasing evidence that RBCs have biologically and clinically important functions in blood clotting and its disorders. This review summarizes the main mechanisms that underlie the involvement of RBCs in hemostasis and thrombosis in vivo, such as rheological effects on blood viscosity and platelet margination, aggregation and deformability of RBCs; direct adhesion and indirect biochemical interactions with endothelial cells and platelets, etc. The ability of stored and pathologically altered RBCs to generate thrombin through exposure of phosphatidylserine has been emphasized. The procoagulant and prothrombotic potential of RBC-derived microparticles transfused with stored RBCs or formed in various pathological conditions associated with hemolysis has been described along with prothrombotic effects of free hemoglobin and heme. Binding of fibrinogen or fibrin to RBCs may influence their effects on fibrin network structure, clot mechanical properties, and fibrinolytic resistance. Recent data on platelet-driven clot contraction show that RBCs compressed by platelets pulling on fibrin form a tightly packed array of polyhedral erythrocytes, or polyhedrocytes, which comprises a nearly impermeable barrier important for hemostasis and wound healing. RBCs may perform dual roles, both helping to stem bleeding but at the same time contributing to thrombosis in a variety of ways.

Neo1 and phosphatidylethanolamine contribute to vacuole membrane fusion in Saccharomyces cerevisiae

NEO1 is an essential gene in budding yeast and belongs to a highly conserved subfamily of P-type ATPase genes that encode phospholipid flippases. Inactivation of temperature sensitive neo1^ts alleles produces pleiomorphic defects in the secretory and endocytic pathways, including fragmented vacuoles. A screen for multicopy suppressors of neo1-2^ts growth defects yielded YPT7, which encodes a Rab7 homolog involved in SNARE-dependent vacuolar fusion. YPT7 suppressed the vacuole fragmentation phenotype of neo1-2, but did not suppress Golgi-associated protein trafficking defects. Neo1 localizes to Golgi and endosomal membranes and was only observed in the vacuole membrane, where Ypt7 localizes, in retromer mutants or when highly overexpressed in wild-type cells. Phosphatidylethanolamine (PE) has been implicated in Ypt7-dependent vacuolar membrane fusion in vitro and is a potential transport substrate of Neo1. Strains deficient in PE synthesis (psd1Δ psd2Δ) displayed fragmented vacuoles and the neo1-2 fragmented vacuole phenotype was also suppressed by overexpression of PSD2, encoding a phosphatidylserine decarboxylase that produces PE at endosomes. In contrast, neo1-2 was not suppressed by overexpression of VPS39, an effector of Ypt7 that forms a membrane contact site potentially involved in PE transfer between vacuoles and mitochondria. These results support the crucial role of PE in vacuole membrane fusion and implicate Neo1 in concentrating PE in the cytosolic leaflet of Golgi and endosomes, and ultimately the vacuole membrane.

State-of-the-Art-Review: Microvesicles in Blood Components: Laboratory and Clinical Aspects

There is ample evidence for the presence of microvesicles (MV) of different sizes and functions in various blood components. A variety of mechanisms have been proposed for the formation of MV. These include mechanical injury, shear stress, cell activation, activation of complements, hypoxia, and the cell aging process. While MV share many biological properties and surface receptors of their parental cells, they demonstrate significant differences in membrane asymmetry of the inner membrane phospholipid, in particular phosphatidylserine (PS). This provides high-affinity binding sites for the components of the prothrombinase complex. To what extent these MV contribute to hemostatic effectiveness, immudomodulation, and some untoward effects of the transfused blood components remains to be fully elucidated. Several methods for qualitative and semiquantitative characterization of MV are now available. Although in most cases it is necessary to separate MV from the intact cells for improved characterization, recent advances in flow cytometry make it possible to accurately differentiate MV in the presence of their parental cells on the basis of light scattering and fluorescent intensity. This review focuses on four main areas of MV in blood components: (1) the proposed mechanisms of platelet vesiculation, (2) factors influencing the formation of MV, (3) laboratory analysis of MV, and (4) the clinical impact of the presence of MV in blood components. Key Words: Microvesicte—Vesicutation—Biood component—Ptatelets—Transfusion.

Insights into the properties of the two enantiomers of trans-δ-viniferin, a resveratrol derivative: antioxidant activity, biochemical and molecular modeling studies of its interactions with hemoglobin

Resveratrol is widely known as an antioxidant and anti-inflammatory molecule. The present study first reports the effects of trans-δ-viniferin (TVN), a dimer of resveratrol, on human erythrocytes. The antioxidant activity of TVN was tested using in vitro model systems such as hydroxy radical scavenging, DPPH and lipid peroxidation. In addition we have examined the influence of the 15R,22R- and 15S,22S-enantiomers (abbreviated R,R-TVN, and S,S-TVN, respectively) on anion transport, ATP release, caspase 3 activation. Given that hemoglobin (Hb) redox reactions are the major source of RBC oxidative stress, we also explored the effects of TVN on hemoglobin function. TVN showed moderate antioxidant properties and good protective activity from hemoglobin oxidation. Potential binding sites of R,R-TVN and S,S-TVN with oxy- and deoxy-Hb were also investigated through an extensive in silico docking approach and molecular dynamics calculations. The whole molecular modeling studies indicate that binding of R,R-TVN and S,S-TVN to Hb lacks of specific ligand-target interactions. This is the first report on the biological activity of the individual enantiomers of a resveratrol-related dimer.

DIANNEXIN DOWN-MODULATES TNF-INDUCED ENDOTHELIAL MICROPARTICLE RELEASE BY BLOCKING MEMBRANE BUDDING PROCESS

BACKGROUND

Microparticles are now recognised as true biological effectors with a role in immunopathology through their ability to disseminate functional properties. Diannexin, a homodimer of annexin V, binds to PS with a higher affinity and longer blood half-life than the monomer, inhibits prothrombinase complex activity thereby diminishing coagulation and reperfusion injury mediators and prevent microvesicle-mediated material transfer. Our aim was to determine if Diannexin could modulate microparticle production by endothelial cells by interacting with the phosphatidylserine exposure occurring during the release of these vesicles.

RESULTS

In this study we showed that fluorescently labelled Diannexin binds to calcimycin-activated endothelial cells but not to resting cells. After overnight incubation, Diannexin enters cells and their released MP carry Diannexin. Some Diannexin seems to be processed via early endosomes and later is found in lysosomes. Both unlabelled Diannexin and fluorescent Diannexin inhibit MP release from TNF-activated endothelial cells. However, Diannexin treatment does not prevent endothelial activation by TNF. In addition, the inhibitory effect of Diannexin on MP release could be observed when cells were pre-, concomitantly or post-treated with cytokines. Scanning electron microscopy showed differences in the numbers and types of protuberances at the cell surface when cells were treated or not with Diannexin. Finally, there is no apparent congruency between fluorescent Diannexin labelling and surface protuberances as shown by correlative microscopy.

CONCLUSIONS

Altogether these data suggest that Diannexin can inhibit endothelial vesiculation by binding PS present either at the cell surface or at the level of the inner leaflet of the plasma membrane.

Thrombin generation: biochemical possibilities and clinical reality

In this issue of Blood, under the unassuming title “Sample conditions determine the ability of thrombin generation parameters to identify bleeding phenotype in FXI deficiency,” Pike et al publish observations on a very rare condition, but the results validate the real-life importance of a scheme of thrombin generation that has been emerging from biochemical research over the last decades and that challenges such stereotypes as the “clotting cascade” and “primary and secondary hemostasis.” Moreover, this article shows how a bleeding phenotype is best recognized in the laboratory.

Differential roles of tissue factor and phosphatidylserine in activation of coagulation

It has been suggested that the main physiological trigger of coagulation, tissue factor, possesses limited procoagulant activity and occurs in an inactive or so-called encrypted state. For the conversion of encrypted into decrypted tissue factor with sufficient procoagulant activity, four distinct models have been proposed: 1; dimer formation, 2; lipid rafts, 3; disulfide bonds, and 4; phosphatidylserine exposure. Pro and cons can be given for each of these mechanisms of tissue factor encryption/decryption, however, it seems most likely that two or more mechanisms act together in activating the procoagulant activity. The exposure of phosphatidylserine in the outer layer of cell membranes supports coagulation through enhanced formation of the tenase (factors IXa, VIIIa and X) and prothrombinase (factors Xa, Va and prothrombin) complexes. The proposed role for phosphatidylserine in decryption of tissue factor could contribute to the correct orientation of the tissue factor - factor VII complex. Overall, the contribution of both tissue factor and phosphatidylserine to coagulation seems distinct with tissue factor being the physiological activator and phosphatidylserine the driving force of propagation of coagulation.

Follicular fluid lipid fingerprinting from women with PCOS and hyper response during IVF treatment

PURPOSE

Polycystic ovary syndrome (PCOS) is an endocrine-metabolic disorder that leads to lower natural reproductive potential and presents a challenge for assisted reproductive medicine because patients may exhibit immature oocyte retrieval and a higher risk of ovarian hyper stimulation syndrome during in vitro fertilization (IVF) treatment. This study aimed to identify potential lipid biomarkers for women with PCOS and a hyper response to controlled ovarian stimulation.

METHODS

Follicular fluid samples were collected from patients who underwent IVF, including normal responder women who became pregnant (control group, n = 11), women with PCOS and a hyper response to gonadotropins (PCOS group, n = 7) and women with only hyper response to gonadotropins (HR group, n = 7). A lipidomic analysis was performed by electrospray ionization mass spectrometry, and candidate biomarkers were analyzed by tandem mass spectrometry experiment.

RESULTS

The lipid profiles indicated particularities related to differences in phosphatidylcholine (PCOS and HR), phosphatidylserine, phosphatydilinositol and phosphatidylglycerol (control), sphingolipids (PCOS) and phosphatidylethanolamine (control and HR).

CONCLUSIONS

These findings contribute to the understanding of the molecular mechanisms associated with lipid metabolism in the PCOS-related hyper response, and strongly suggest that these lipids may be useful as biomarkers, leading to the development of more individualized treatment for pregnancy outcome.

Platelet activation by riboflavin and UV light: is it really the other side of the coin?

INTRODUCTION

Nowadays transfusion safety is still put at risk by contamination of pathogens. The Mirasol PRT System blocks the replication of pathogens and white blood cells. Our goal was to quantify the activation of platelets after treatment with the Mirasol device.

MATERIALS AND METHODS

From September to December 2013, 131 platelet collections were studied using a simple flow cytometric strategy.

RESULTS

There was a significant correlation between the percentage of platelet activated before and after the treatment.

CONCLUSION

Our results induced us to think that the activation of platelets after treatment was acceptable.

Non-enzymatic modification of aminophospholipids by carbonyl-amine reactions

Non-enzymatic modification of aminophospholipids by lipid peroxidation-derived aldehydes and reducing sugars through carbonyl-amine reactions are thought to contribute to the age-related deterioration of cellular membranes and to the pathogenesis of diabetic complications. Much evidence demonstrates the modification of aminophospholipids by glycation, glycoxidation and lipoxidation reactions. Therefore, a number of early and advanced Maillard reaction-lipid products have been detected and quantified in different biological membranes. These modifications may be accumulated during aging and diabetes, introducing changes in cell membrane physico-chemical and biological properties.

A new look at the lipid composition of the plasma membrane of human blood platelets relative to the GPIIb/IIIa (integrin cxIIβ3) content

The total lipids of the human platelet plasma membrane (HPPM) from 50 ml of blood of healthy subjects were extracted, quantified and related to the mass content of the major intrinsic membrane protein, the glycoprotein IIb/IIIa (GPIIb/IIIa). The HPPM total lipid/GPIIb/IIIa weight ratio determined was 5.40 ± 0.20, independently of the membrane washing procedure used, with the cholesterol/GPIIb/IIIa and phospholipid/GPIIb/IIIa molar ratios of 800 ± 50 and 1200 ± 40, respectively. If the distribution of lipids around each intrinsic protein were proportional to its mass, the lipids around a molecule of GPIIb/IIIa will occupy about 120 nm(2) of the membrane plane, which is about one and a half times the cross-sectional area of the extracellular head of GPIIb/IIIa, as estimated by electron microscopy. The lipid extracts were further subjected to thin-layer chromatography to separate and quantify the different phospholipid fractions, the free fatty acids and the neutral lipid fraction and the distribution of fatty acids in each fraction was determined by gas chromatography after methanolysis. The phospholipid molar distribution was SPM(22.3 ± 0.9%), PC(36.2 ± 1.0%), PE(24.9 ± 0.9%), PS(12.1 ± 0.6%) and PI(4.5 ± 0.4%) and the free fatty acid fraction represented 2.9 ± 0.4% of the total fatty acids in HPPM. The fatty acid chain length ranged from 14 to 24 carbons, comprising unsaturated fatty acids (47.3% molar per cent of the total) of which 40.7 ± 2.0% were monosaturated and 40.7 ± 0.9% tetraunsaturated. Palmitic, stearic, oleic and arachidonic acids represent 66% of the total fatty acids of HPPM, being: 68.9 ± 5.3% of palmitic acid and 63.3 ± 6.9% of oleic acid in PC; 50.9 ± 3.8% of arachidonic acid in PE; and 30.5 ± 2.4% of stearic acid in PS. We discuss the methodological modifications and the new data in relation with the major differences in HPPM lipid composition found in the literature. The data obtained provides a comprehensive and accurate description of the lipid composition of HPPM on which to rely as a reference for basic and medical studies.

Platelet signaling-a primer

OBJECTIVE

To review the receptors and signal transduction pathways involved in platelet plug formation and to highlight links between platelets, leukocytes, endothelium, and the coagulation system.

DATA SOURCES

Original studies, review articles, and book chapters in the human and veterinary medical fields.

DATA SYNTHESIS

Platelets express numerous surface receptors. Critical among these are glycoprotein VI, the glycoprotein Ib-IX-V complex, integrin α(IIb) β(3) , and the G-protein-coupled receptors for thrombin, ADP, and thromboxane. Activation of these receptors leads to various important functional events, in particular activation of the principal adhesion receptor α(IIb) β(3) . Integrin activation allows binding of ligands such as fibrinogen, mediating platelet-platelet interaction in the process of aggregation. Signals activated by these receptors also couple to 3 other important functional events, secretion of granule contents, change in cell shape through cytoskeletal rearrangement, and procoagulant membrane expression. These processes generate a stable thrombus to limit blood loss and promote restoration of endothelial integrity.

CONCLUSIONS

Improvements in our understanding of how platelets operate through their signaling networks are critical for diagnosis of unusual primary hemostatic disorders and for rational antithrombotic drug design.

Evaluation of rapamycin-induced cell death

Mammalian target of rapamycin (mTOR) is an evolutionarily conserved kinase that integrates signals from nutrients and growth factors for the coordinate regulation of many cellular processes, including proliferation and cell death. Constitutive mTOR signaling characterizes multiple human malignancies, and pharmacological inhibitors of mTOR such as the immunosuppressant rapamycin and some of its nonimmunosuppressive derivatives not only have been ascribed with promising anticancer properties in vitro and in vivo but are also being extensively evaluated in clinical trials. mTOR inhibition rapidly leads to the activation of autophagy, which most often exerts prosurvival effects, although in some cases it accompanies cell death. Thus, depending on the specific experimental setting (cell type, concentration, stimulation time, and presence of concurrent stimuli), rapamycin can activate/favor a wide spectrum of cellular responses/phenotypes, ranging from adaptation to stress and survival to cell death. The (at least partial) overlap among the biochemical and morphological responses triggered by rapamycin considerably complicates the study of cell death-associated variables. Moreover, rapamycin presumably triggers acute cell death mainly via off-target mechanisms. Here, we describe a set of assays that can be employed for the routine quantification of rapamycin-induced cell death in vitro, as well as a set of guidelines that should be applied for their correct interpretation.

Aspirin: pharmacology and clinical applications

Antiplatelet therapy has been documented to reduce risks of cardiovascular disease after acute myocardial infarction, coronary artery bypass graft, and in chronic atrial fibrillation patients, amongst other risk factors. Conventional management of thrombosis-based disorders includes the use of heparin, oral anticoagulants, and the preferred antiplatelet agent aspirin. Interestingly, aspirin was not intended to be used as an antiplatelet agent; rather, after being repurposed, it has become one of the most widely prescribed antithrombotic drugs. To this end, there have been several milestones in the development of antiplatelet agents in the last few decades, such as adenosine diphosphate receptor inhibitors, phosphodiesterase inhibitors, and GPIIb/IIIa inhibitors. However, given some of the limitations of these therapies, aspirin continues to play a major role in the management of thrombotic and cardiovascular disorders and is expected to do so for years to come.

Oxalate impairs aminophospholipid translocase activity in renal epithelial cells via oxidative stress: implications for calcium oxalate urolithiasis

PURPOSE

We evaluated the possible involvement of phospholipid transporters and reactive oxygen species in the oxalate induced redistribution of renal epithelial cell phosphatidylserine.

MATERIALS AND METHODS

Madin-Darby canine kidney cells were labeled with the fluorescent phospholipid NBD-PS in the inner or outer leaflet of the plasma membrane and then exposed to oxalate in the presence or absence of antioxidant. This probe was tracked using a fluorescent quenching assay to assess the bidirectional transmembrane movement of phosphatidylserine. Surface expressed phosphatidylserine was detected by annexin V binding assay. The cell permeable fluorogenic probe DCFH-DA was used to measure the intracellular reactive oxygen species level.

RESULTS

Oxalate produced a time and concentration dependent increase in phosphatidylserine, which may have resulted from impaired aminophospholipid translocase mediated, inward directed phosphatidylserine transport and from enhanced phosphatidylserine outward transport. Adding the antioxidant N-acetyl-L-cysteine significantly attenuated phosphatidylserine externalization by effectively rescuing aminophospholipid translocase activity.

CONCLUSIONS

To our knowledge our findings are the first to show that oxalate induced increased reactive oxygen species generation impairs aminophospholipid translocase activity and decreased aminophospholipid translocase activity has a role in hyperoxaluria promoted calcium oxalate urolithiasis by facilitating phosphatidylserine redistribution in renal epithelial cells.

Molecular determinants of phospholipid synergy in blood clotting

Many regulatory processes in biology involve reversible association of proteins with membranes. Clotting proteins bind to phosphatidylserine (PS) on cell surfaces, but a clear picture of this interaction has yet to emerge. We present a novel explanation for membrane binding by GLA domains of clotting proteins, supported by biochemical studies, solid-state NMR analyses, and molecular dynamics simulations. The model invokes a single “phospho-l-serine-specific” interaction and multiple “phosphate-specific” interactions. In the latter, the phosphates in phospholipids interact with tightly bound Ca²⁺ in GLA domains. We show that phospholipids with any headgroup other than choline strongly synergize with PS to enhance factor X activation. We propose that phosphatidylcholine and sphingomyelin (the major external phospholipids of healthy cells) are anticoagulant primarily because their bulky choline headgroups sterically hinder access to their phosphates. Following cell damage or activation, exposed PS and phosphatidylethanolamine collaborate to bind GLA domains by providing phospho-l-serine-specific and phosphate-specific interactions, respectively.

Annexin A5-functionalized bimodal nanoparticles for MRI and fluorescence imaging of atherosclerotic plaques

Apoptosis and macrophage burden are believed to correlate with atherosclerotic plaque vulnerability and are therefore considered important diagnostic and therapeutic targets for atherosclerosis. These cell types are characterized by the exposure of phosphatidylserine (PS) at their surface. In the present study, we developed and applied a small micellar fluorescent annexin A5-functionalized nanoparticle for noninvasive magnetic resonance imaging (MRI) of PS exposing cells in atherosclerotic lesions. Annexin A5-mediated target-specificity was confirmed with ellipsometry and in vitro binding to apoptotic Jurkat cells. In vivo T(1)-weighted MRI of the abdominal aorta in atherosclerotic ApoE(-/-) mice revealed enhanced uptake of the annexin A5-micelles as compared to control-micelles, which was corroborated with ex vivo near-infrared fluorescence images of excised whole aortas. Confocal laser scanning microscopy (CLSM) demonstrated that the targeted agent was associated with macrophages and apoptotic cells, whereas the nonspecific control agent showed no clear uptake by such cells. In conclusion, the annexin A5-conjugated bimodal micelles displayed potential for noninvasive assessment of cell types that are considered to significantly contribute to plaque instability and therefore may be of great value in the assessment of atherosclerotic lesion phenotype.

Current applications of nanotechnology for magnetic resonance imaging of apoptosis

Apoptosis, or programmed cell death, is a morphologically and biochemically distinct form of cell death, which together with proliferation plays an important role in tissue development and homeostasis. Insufficient apoptosis is important in the pathology of various disorders such as cancer and autoimmune diseases, whereas a high apoptotic activity is associated with myocardial infarction, neurodegenerative diseases, and advanced atherosclerotic lesions. Consequently, apoptosis is recognized as an important therapeutic target, which should be either suppressed, e.g., during an ischemic cardiac infarction, or promoted, e.g., in the treatment of cancerous lesions. Imaging tools to address location, amount, and time course of apoptotic activity non-invasively in vivo are therefore of great clinical use in the evaluation of such therapies. This chapter reviews current literature and new developments in the application of nanoparticles for non-invasive apoptosis imaging. Focus is on functionalized nanoparticle contrast agents for MR imaging and bimodal nanoparticle agents that combine magnetic and fluorescent properties.

Phospholipids: key players in apoptosis and immune regulation

Phosphatidylserine (PS), a phospholipid predominantly found in the inner leaflet of eukaryotic cellular membranes, plays important roles in many biological processes. During apoptosis, the asymmetric distribution of phospholipids of the plasma membrane gets lost and PS is translocated to the outer leaflet of the plasma membrane. There, PS acts as one major “eat me” signal that ensures efficient recognition and uptake of apoptotic cells by phagocytes. PS recognition of activated phagocytes induces the secretion of anti-inflammatory cytokines like interleukin-10 and transforming grow factor-beta. Deficiencies in the clearance of apoptotic cells result in the occurrence of secondarily necrotic cells. The latter have lost the membrane integrity and release immune activating danger signals, which may induce inflammatory responses. Accumulation of dead cells containing nuclear autoantigens in sites of immune selection may provide survival signals for autoreactive B-cells. The production of antibodies against nuclear structures determines the initiation of chronic autoimmunity in systemic lupus erythematosus. Since PS on apoptotic cells is an important modulator of the immune response, natural occurring ligands for PS like annexinA5 have profound effects on immune responses against dead and dying cells, including tumour cells. In this review we will focus on the role of PS exposure in the clearance process of dead cells and its implications in clinical situations where apoptosis plays a relevant role, like in cancer, chronic autoimmunity, and infections. Relevance of other phospholipids during the apoptosis process is also discussed.

Erythrocyte membrane phosphatidylserine exposure in obesity

It has been suggested that increased erythrocyte membrane phosphatidylserine (PS) exposure could contribute to hypercoagulability and hemorheological disturbances in obesity. The aim of our study was to evaluate PS exposure in obese patients and in a control group and to correlate this with hemorheological properties, i.e., erythrocyte aggregability (EA) and deformability, and to evaluate the effect of weight loss on these parameters. An anthropometric and analytical evaluation was performed at baseline and after 3 months on a diet (very low-calorie diet for 4 weeks and low-calorie diet for 2 months) on 49 severe or morbid obese patients (37 women, 12 men) and 55 healthy volunteers (39 women, 16 men). PS exposure on erythrocyte membrane was performed by flow cytometry. Erythrocyte aggregation was measured using the Myrenne MA(1) and the Sefam aggregometer. Erythrocyte deformability was determined in a stress diffractometer. Prothrombin fragment F1+2 (F1+2) was determined as a marker of the hypercoagulable state, and plasma malondialdehyde (MDA) as an indicator of oxidative stress. Obese patients had a higher EA index, higher PS exposure on erythrocyte membranes and higher levels of MDA and F1+2. The differences in erythrocyte aggregation and F1+2 between obese patients and the control group were maintained after adjusting for PS exposure. After 3 months of diet, a significant reduction in PS exposure on erythrocyte membrane was observed. Obese patients show increased PS exposure on erythrocyte membrane, with no effect on rheological properties. Increased PS exposure could contribute to hypercoagulability in these patients. Weight loss obtained with diet treatment reduces PS exposure on erythrocyte membrane.

Phosphatidylserine and phosphatidylethanolamine in mammalian cells: two metabolically related aminophospholipids

Phosphatidylserine (PS) and phosphatidylethanolamine (PE) are two aminophospholipids whose metabolism is interrelated. Both phospholipids are components of mammalian cell membranes and play important roles in biological processes such as apoptosis and cell signaling. PS is synthesized in mammalian cells by base-exchange reactions in which polar head groups of preexisting phospholipids are replaced by serine. PS synthase activity resides primarily on mitochondria-associated membranes and is encoded by two distinct genes. Studies in mice in which each gene has been individually disrupted are beginning to elucidate the importance of these two synthases for biological functions in intact animals. PE is made in mammalian cells by two completely independent major pathways. In one pathway, PS is converted into PE by the mitochondrial enzyme PS decarboxylase. In addition, PE is made via the CDP-ethanolamine pathway, in which the final reaction occurs on the endoplasmic reticulum and nuclear envelope. The relative importance of these two pathways of PE synthesis has been investigated in knockout mice. Elimination of either pathway is embryonically lethal, despite the normal activity of the other pathway. PE can also be generated from a base-exchange reaction and by the acylation of lyso-PE. Cellular levels of PS and PE are tightly regulated by the implementation of multiple compensatory mechanisms.

Study on the effect of eicosapentaenoic acid on phospholipids composition in membrane microdomains of tight junctions of epithelial cells by liquid chromatography/electrospray mass spectrometry

Tight junctions of epithelial cells determine epithelial membrane integrity and play an important role in selective paracellular permeability to ions and macromolecules. In this work, we investigated the effect of one of n-3 series polyunsaturated fatty acids, eicosapentaenoic acid (EPA) on the phospholipid composition of membrane microdomains of tight junctions. After treated by EPA, membrane microdomains of tight junctions were isolated by discontinuous sucrose density gradient ultracentrifugation, and raft phospholipids were extracted. The PE, PI, PS, PC and SM were separated and determined by high-performance liquid chromatography/quadrupole-linear ion trap mass spectrometry (HPLC Qtrap-MS), and were further identified by HPLC-MS/MS. It was found that EPA altered the fatty acyl substitution of phospholipids that constituted membrane microdomains of tight junctions by enriching the unsaturated fatty acyl chains of the phospholipids. It provides a new visual angle to explaining the intracellular mechanism involved in n-3 polyunsaturated fatty acids (PUFAs) modulation of intestinal tight junction barrier.

Beta-thalassaemia and sickle cell anaemia as paradigms of hypercoagulability

Thalassaemia and sickle cell disease (SCD) represent the most common forms of hereditary haemolytic anaemia and result from a partial or complete lack of synthesis of one of the major alpha- or beta-globin chains of haemoglobin A or from a single amino acid mutation (beta(6Glu-->Val)) of the beta-globin chain respectively. Although they have different pathophysiologies, patients with these conditions manifest both biochemical and clinical evidence of hypercoagulability. While the frequency of various thrombotic complications may vary in beta-thalassaemia and homozygous SCD [sickle cell anaemia (SCA)], patients with both diseases manifest decreased levels of natural anticoagulant proteins, as well as increased markers of thrombin generation and platelet activation. The abnormal phospholipid membrane assymetry present in the red blood cells of beta-thalassaemia and SCA patients, with resultant phosphatidylserine exposure appears to play a significant role in the aetiology of the observed hypercoagulable state. This review presents the available data on the aetiology and clinical manifestations of the coagulation and platelet activation that exist in both beta-thalassaemia and SCA, as well as the potential therapeutic implications resulting from this hypercoagulability.