A simple, novel, procedure for monitoring membrane scrambling and permeability in microparticles, platelets, and leukocytes in whole blood samples

The 6-kilodalton peptide 1 in plant viruses of the family Potyviridae is a viroporin

Potyviridae, the largest family of plant RNA viruses, includes many important pathogens that significantly reduce the yields of many crops worldwide. In this study, we report that the 6-kilodalton peptide 1 (6K1), one of the least characterized potyviral proteins, is an endoplasmic reticulum-localized protein. AI-assisted structure modeling and biochemical assays suggest that 6K1 forms pentamers with a central hydrophobic tunnel, can increase the cell membrane permeability of Escherichia coli and Nicotiana benthamiana, and can conduct potassium in Saccharomyces cerevisiae. An infectivity assay showed that viral proliferation is inhibited by mutations that affect 6K1 multimerization. Moreover, the 6K1 or its homologous 7K proteins from other viruses of the Potyviridae family also have the ability to increase cell membrane permeability and transmembrane potassium conductance. Taken together, these data reveal that 6K1 and its homologous 7K proteins function as viroporins in viral infected cells.

Light-Enhanced Cytotoxicity of Doxorubicin by Photoactivation

The combination of photodynamic therapy with chemotherapy (photochemotherapy, PCT) can lead to additive or synergistic antitumor effects. Usually, two different molecules, a photosensitizer (PS) and a chemotherapeutic drug are used in PCT. Doxorubicin is one of the most successful chemotherapy drugs. Despite its high efficacy, two factors limit its clinical use: severe side effects and the development of chemoresistance. Doxorubicin is a chromophore, able to absorb light in the visible range, making it a potential PS. Here, we exploited the intrinsic photosensitizing properties of doxorubicin to enhance its anticancer activity in leukemia, breast, and epidermoid carcinoma cells, upon irradiation. Light can selectively trigger the local generation of reactive oxygen species (ROS), following photophysical pathways. Doxorubicin showed a concentration-dependent ability to generate peroxides and singlet oxygen upon irradiation. The underlying mechanisms leading to the increase in its cytotoxic activity were intracellular ROS generation and the induction of necrotic cell death. The nuclear localization of doxorubicin represents an added value for its use as a PS. The use of doxorubicin in PCT, simultaneously acting as a chemotherapeutic agent and a PS, may allow (i) an increase in the anticancer effects of the drug, and (ii) a decrease in its dose, and thus, its dose-related adverse effects.

Impact of Pre-Analytical and Analytical Variables Associated with Sample Preparation on Flow Cytometric Stainings Obtained with EuroFlow Panels

Simple Summary

Objective interpretation of flow cytometry may be hampered by a lack of standardized sample preparation procedures. The EuroFlow consortium conducted a series of experiments to determine the potential impact of different pre-analytical and analytical factors on the variability of results in terms of relative cell populations distribution and marker expression levels. The experiments were performed on healthy donors and patients with different hematological malignancies (e.g., acute leukemia, lymphoma, multiple myeloma, and myelodysplastic syndrome) to mimic real-world clinical settings. Overall, the results showed that sample storage conditions, anticoagulant use, and sample processing protocol might need to be tailored for sample and cell type(s), as well as to the specific markers evaluated. However, defining of well-balanced boundaries for storage time to 24 h, staining-acquisition delay to 3 h, and choosing a washing buffer of pH within the range of 7.2 to 7.8 would be a valid recommendation for most applications and circumstances described herein.

Abstract

Objective interpretation of FC results may still be hampered by limited technical standardization. The EuroFlow consortium conducted a series of experiments to determine the impact of different variables on the relative distribution and the median fluorescence intensity (MFI) of markers stained on different cell populations, from both healthy donors and patients’ samples with distinct hematological malignancies. The use of different anticoagulants; the time interval between sample collection, preparation, and acquisition; pH of washing buffers; and the use of cell surface membrane-only (SM) vs. cell surface plus intracytoplasmic (SM+CY) staining protocols, were evaluated. Our results showed that only monocytes were represented at higher percentages in EDTA- vs. heparin-anticoagulated samples. Application of SM or SM+CY protocols resulted in slight differences in the percentage of neutrophils and debris determined only with particular antibody combinations. In turn, storage of samples for 24 h at RT was associated with greater percentage of debris and cell doublets when the plasma cell disorder panel was used. Furthermore, 24 h storage of stained cells at RT was selectively detrimental for MFI levels of CD19 and CD45 on mature B- and T-cells (but not on leukemic blasts, clonal B- and plasma cells, neutrophils, and NK cells). The obtained results showed that the variables evaluated might need to be tailored for sample and cell type(s) as well as to the specific markers compared; however, defining of well-balanced boundaries for storage time, staining-to-acquisition delay, and pH of washing buffer would be a valid recommendation for most applications and circumstances described herein.

Microparticle formation after co-culture of human whole blood and umbilical artery in a novel in vitro model of flow

Cardiovascular disease (CVD) is now the largest killer in western society, and the importance of interactions between vascular endothelium and circulating blood components in disease pathogenesis is well established. Microparticles are a heterogeneous population of <1 μm blood borne particles that arise from blebbing or shedding of cell membranes. The microparticle population includes several classes of apoptotic bodies; however, increased numbers of procoagulant microparticles have been described in plasma from people with CVD. We have previously demonstrated that interactions of monocytes and platelets with isolated inflamed endothelial cells lead to production of pro-coagulant tissue factor bearing microparticles under laminar flow conditions. Here we have investigated microparticle production after perfusion of human whole blood through intact inflamed human umbilical artery. When blood was perfused through umbilical arteries which had been pre-stimulated with tumour necrosis factor (TNFα) for 18 h under flow conditions, there was significantly increased production of microparticles from both platelet and non-platelet sources, in particular from erythrocytes. To determine whether microparticles generated during interactions with inflamed endothelium could induce a pro-inflammatory response in trans, we isolated microparticles by centrifugation after co-culture and incubated with isolated quiescent endothelial cells followed by measurement of reactive oxygen species formation. Microparticles derived from co-culture with inflamed endothelium induced significantly enhanced levels of reactive oxygen species (ROS). These data suggest that presence of an inflamed endothelium causes release of pro-inflammatory microparticles from circulating blood cells, which could contribute to prolonged endothelial activation and subsequent atherosclerotic changes in blood vessels subjected to inflammatory insult.

Age, gender and disease-related platelet and neutrophil activation ex vivo in whole blood samples from patients with Behçet's disease

OBJECTIVES

Behçet's disease (BD) is more severe among young males and disease severity decreases with age. Therefore, the effect of disease activity, gender and age on platelet and neutrophil activation in whole blood taken from patients with BD was investigated.

METHODS

Using an anti-coagulant Tripotassium ethylenediaminetetra acetic acid (K3EDTA) plus citrate-theophylline-adenosine-dipyridamole (CTAD) (K3EDTA/CTAD) that preserves the degree of platelet activation that exists in vivo, we assessed neutrophil and platelet activation, microparticles, and monocyte and neutrophil-platelet aggregate formation in 43 BD patients using flow cytometry. This is the first description of platelet activation and microparticles in BD patients using this methodology.

RESULTS

Inactive [2.78 (0.56)%, P = 0.0009; 3.11 (0.78)%, P < 0.0001] and active [2.28 (0.84)%, P < 0.0001; 3.071 (0.67)%, P = 0.0031] BD patients had significantly higher percentages of CD62P-expressing platelets and CD62P+ platelet microparticles as compared with healthy controls (HCs) [0.84 (0.1)% and 1.23 (0.14)%], respectively. The percentages of CD62P+ platelets and CD62P+ platelet microparticles in female and male BD patients were also significantly higher than those expressed by female and male HCs. The percentages of CD62P+ microparticles were significantly increased in the 20-30-(P = 0.0301) and 31-50-(P < 0.0162) year age ranges, but not in the >50-year age group of BD patients.

CONCLUSION

BD is a rare, chronic multi-systemic vasculitis and interaction of activated platelets with leucocytes has been linked to pathological disorders associated with vascular inflammation. Importantly, this study demonstrates that platelet microparticle activation is increased in BD. Also, this is the first report in which changes in platelet activation in BD are concordant with the observations that BD disease activity diminishes with age.

Flow cytometric analysis of microparticle phenotype and their role in thrombin generation

BACKGROUND

Microparticles may be generated from a number of cell types and are known to play a role in haemostasis by a variety of mechanisms. We investigated the role of platelet, red cell, and leucocyte-derived microparticles in the measurement of thrombin generation.

METHODS

Four parameters of thrombin generation (the endogenous thrombin potential (ETP), lag time, time to peak, peak height) and microparticle content was determined in 35 plasma samples from normal individuals pre and post filtration to remove microparticles. Immunofluorescent flow cytometry was used to identify and enumerate platelet, leucocyte, monocyte and red cell derived microparticles in plasma samples based on the expression of CD42b, CD45, CD15, and Glycophorin A respectively. Expression of phosphatidylserine and tissue factor by microparticles was determined by Annexin V and anti CD142 binding. The pre and post filtration results were compared.

RESULTS

There was a significant decrease in ETP and Peak Height, and an increase in the time to peak post filtration (P < 0.001). A significant decrease in the number of CD42+, CD45+, CD15+, CD142+, and Annexin V+ microparticles was also observed. The change in CD42b+ microparticles correlated highly with the change in Annexin V+ microparticles (r = 0.68). Whilst the change in ETP correlated best with the change in CD15+ microparticles (r = 0.45) and the change in time to peak correlated with the change in Annexin V binding (r = 0.52) (P < 0.01).

CONCLUSION

The presence of micropartcles in plasma significantly affects thrombin generation.

Microparticle formation after exposure of blood to activated endothelium under flow

Increased numbers of circulating microparticles (MPs) are indicative of poor clinical outcome in a number of inflammatory disorders, including atherosclerosis. Platelets and megakaryocytes are a major source of MP and are identified by presence of CD42b on the MP surface. MP shed from activated platelets can be identified by presence of P-selectin (CD62P). Tissue factor (TF) is the principal initiator of blood coagulation and its activity has been identified in MPs derived from patient plasma, which may contribute to thrombosis. Here, we have investigated by flow cytometry the expression of TF and CD62P on MP after exposure of diluted whole blood to TNF-activated endothelial cells (EC) both under static conditions and in our newly established model of flow. MPs were significantly increased in blood subjected to flow and this was further enhanced after exposure of blood to TNF-activated EC. MP surface expression of CD62P or TF was upregulated following exposure to TNF-activated EC under flow compared with flow with nonactivated EC or after static coculture with and without prior EC activation. These data strongly suggest that interactions of blood with inflamed EC can modulate production of CD62P and TF bearing MP under flow conditions, and thus may contribute to a prothrombotic environment.

Platelet activation and endogenous thrombin potential in pre-eclampsia

INTRODUCTION

Platelets and the coagulation system may be involved in the pathogenesis of pre-eclampsia. We investigated whether platelet and coagulation activation markers, are elevated in pre-eclampsia.

MATERIALS/METHODS

Case-control study in which activated platelets, platelet-monocyte/ neutrophil aggregates, platelet microparticles (measured by flow cytometry) and four markers of thrombin generation capacity (endogenous thrombin potential (ETP), peak height, lag time and time to peak) using the Calibrated Automated Thrombogram system were assessed in pregnant women of similar gestational age with (n=46) and without (n=46) pre-eclampsia, and in healthy non-pregnant women (n=42).

RESULTS

The percentage of, CD62P+ platelets (p=0.013), CD62P+ platelet microparticles (p=0.029) and platelet-monocyte aggregates (p=0.019) were significantly higher in women with pre-eclampsia than the pregnant controls. Both groups of pregnant women had significantly higher ETP and peak height (p <0.001) than the healthy non pregnant group and the women with pre-eclampsia had significantly higher ETP and peak height (p<0.001) than the normotensive pregnant controls.

CONCLUSION

In the most comprehensive laboratory analysis to date, we found evidence of both platelet and coagulation activation in women with pre-eclampsia.