Egarit Noulsri

Flow cytometric quantitation of red blood cell vesicles in thalassemia

Thalassemia is a hereditary hemolytic anemia caused by mutations in the globin gene complex. Circulatory disturbances including arterial and venous thrombosis have also been noted in these patients. Aggregability of abnormal RBC and the high level of membrane‐derived microparticles stemming from activated platelets and other blood cells are thought to be responsible for the associated thrombotic risk. Destruction of RBC is also thought to be an important pathophysiological consequence, particularly through the formation of circulating vesicles. To our knowledge, there has been no attempt to quantitatively evaluate the number of RBC vesicles in thalassemia. This prompted us to study the level of RBC vesicles in the peripheral blood of thalassemia patients using quantitative flow cytometry.

Platelet Inhibition by Nitrite Is Dependent on Erythrocytes and Deoxygenation

Background Nitrite is a nitric oxide (NO) metabolite in tissues and blood, which can be converted to NO under hypoxia to facilitate tissue perfusion. Although nitrite is known to cause vasodilation following its reduction to NO, the effect of nitrite on platelet activity remains unclear. In this study, the effect of nitrite and nitrite+erythrocytes, with and without deoxygenation, on platelet activity was investigated. Methodology/Finding Platelet aggregation was studied in platelet-rich plasma (PRP) and PRP+erythrocytes by turbidimetric and impedance aggregometry, respectively. In PRP, DEANONOate inhibited platelet aggregation induced by ADP while nitrite had no effect on platelets. In PRP+erythrocytes, the inhibitory effect of DEANONOate on platelets decreased whereas nitrite at physiologic concentration (0.1 µM) inhibited platelet aggregation and ATP release. The effect of nitrite+erythrocytes on platelets was abrogated by C-PTIO (a membrane-impermeable NO scavenger), suggesting an NO-mediated action. Furthermore, deoxygenation enhanced the effect of nitrite as observed from a decrease of P-selectin expression and increase of the cGMP levels in platelets. The ADP-induced platelet aggregation in whole blood showed inverse correlations with the nitrite levels in whole blood and erythrocytes. Conclusion Nitrite alone at physiological levels has no effect on platelets in plasma. Nitrite in the presence of erythrocytes inhibits platelets through its reduction to NO, which is promoted by deoxygenation. Nitrite may have role in modulating platelet activity in the circulation, especially during hypoxia.

Activated platelet-derived microparticles in thalassaemia.

Thromboembolic complications have been documented in thalassaemia patients. The aggregability of abnormal red blood cells and the high level of membrane‐derived microparticles (MPs) stemming from blood cells are thought to be responsible for the associated thrombotic risk. We investigated the number of MPs, their cellular origin and their procoagulant properties in β‐thalassaemia. Fresh whole blood was simultaneously stained for annexin V, cellular antigens and the known density beads. The procoagulant properties of these phosphatidylserine (PS)‐bearing MPs were also measured by assessing the platelet factor‐3‐like activity in the blood. Flow cytometric results showed that splenectomised β‐thalassaemia/HbE patients had significantly higher levels of PS‐bearing MPs than non‐splenectomised β‐thalassaemia/HbE patients and normal individuals (P < 0·0001). There was a good correlation between PS‐bearing MPs and PS‐bearing platelets, reflecting the existence of chronic platelet activation in β‐thalassaemia/HbE patients (rs = 0·511, P < 0·001). The cellular origin of PS‐bearing MPs showed mostly activated‐platelet origin with adhesion (CD41a/CD62P/CD36). Moreover, the platelet procoagulant activity was higher in splenectomised β‐thalassaemia/HbE patients when compared with non‐splenectomised (P < 0·05) and normal individuals (P < 0·01), and the amount correlated with PS‐bearing MPs (rs = 0·560, P < 0·001). These findings suggest that MPs originate from activated platelets with a potential to aggravate thrombotic events when the numbers are excessive, as is commonly seen in splenectomised β‐thalassaemia/HbE patients.

Antitumor activity and mechanism of action of the iron chelator, Dp44mT, against leukemic cells

Iron chelators have been reported to induce apoptosis and cell cycle arrest in cancer cells. Recent studies suggest broad and selective antitumor activity of the new iron chelator, di‐2‐pyridylketone‐4,4‐dimethyl‐3‐thiosemicarbazone (Dp44mT; Whitnall et al., Proc Natl Acad Sci USA 2006;103:14901–14906). However, little is known concerning its effects on hematological malignancies. Using acute leukemia cells, the effect of Dp44mT on apoptosis, cell cycle, caspase‐3 activation, and mitochondrial trans‐membrane potential has been examined by flow cytometry. Dp44mT acted to induce a G1/S arrest in NB4 promyelocytic leukemia cells at low concentrations (0.5–2.5 μM), being far more effective than the clinically used chelator, desferrioxamine (DFO). Moreover, Dp44mT induced apoptosis of NB4 cells in a dose‐ and time‐dependent manner with markedly less effect on nonproliferating cells. The apoptosis‐inducing activity of Dp44mT was significantly more effective than DFO. Furthermore, this study also showed that Dp44mT had broad activity, inducing apoptosis in several types of acute leukemia and also multiple myeloma cell lines. Additional studies examining the cytotoxic mechanisms of Dp44mT showed that a reduction in the mitochondrial trans‐membrane potential and caspase‐3 activation could be involved in the mechanism of apoptosis. Our results suggest that Dp44mT possesses potential as an effective cytotoxic agent for the chemotherapeutic treatment of acute leukemia. Am. J. Hematol. 2009.

Iron Chelator-Mediated Alterations in Gene Expression: Identification of Novel Iron-Regulated Molecules That Are Molecular Targets of Hypoxia-Inducible Factor-1α and p53

Iron deficiency affects 500 million people, yet the molecular role of iron in gene expression remains poorly characterized. In addition, the alterations in global gene expression after iron chelation remain unclear and are important to assess for understanding the molecular pathology of iron deficiency and the biological effects of chelators. Considering this, we assessed the effect on whole genome gene expression of two iron chelators (desferrioxamine and 2-hydroxy-1-napthylaldehyde isonicotinoyl hydrazone) that have markedly different permeability properties. Sixteen genes were significantly regulated by both ligands, whereas a further 50 genes were significantly regulated by either compound. Apart from iron-mediated regulation of expression via hypoxia inducible factor-1α, it was noteworthy that the transcription factor p53 was also involved in iron-regulated gene expression. Examining 16 genes regulated by both chelators in normal and neoplastic cells, five genes (APP, GDF15, CITED2, EGR1, and PNRC1) were significantly differentially expressed between the cell types. In view of their functions in tumor suppression, proliferation, and apoptosis, these findings are important for understanding the selective antiproliferative effects of chelators against neoplastic cells. Most of the genes identified have not been described previously to be iron-regulated and are important for understanding the molecular and cellular effects of iron depletion.

A multicenter evaluation of the PanLeucogating method and the use of generic monoclonal antibody reagents for CD4 enumeration in HIV-infected patients in Thailand

The current method of CD4 enumeration in Thailand, based on the three‐tube, three‐color method recommended by the Centers for Disease Control and Prevention, is expensive and thus unavailable to most patients who have the human immunodeficiency virus (HIV). Less expensive, simpler protocols (i.e., PanLeucogating and primary CD4 gating) have been described but require more published validation data to gain widespread acceptance. We describe a multicenter evaluation of the PanLeucogating method.

Evaluation of a New Single-Parameter Volumetric Flow Cytometer (CyFlowgreen) for Enumeration of Absolute CD4+ T Lymphocytes in Human Immunodeficiency Virus Type 1-Infected Thai Patients

ABSTRACT Use of the standard dual-platform flow cytometric method for determination of CD4+ T-lymphocyte counts, which needs both a flow cytometer (FCM) and hematological analyzer, would inevitably lead to increased variability. The development of new single-platform (SP) FCMs that provide direct CD4+ T-lymphocyte counts for improved assay precision and accuracy have recently attracted attention. This study evaluated one of those systems, CyFlowgreen (Partec), a single-parameter SP volumetric FCM. The performance of CyFlowgreen was compared with those of two reference standard SP microbead-based technologies of the three-color TruCOUNT tube with the FACScan FCM and a two-color FACSCount system (Becton Dickinson Biosciences). Absolute CD4+ and CD8+ T-lymphocyte counts in 200 human immunodeficiency virus type 1-seropositive blood specimens were determined. Statistical analysis for correlation and agreement were performed. A high correlation of absolute CD4 counts was shown when those obtained with CyFlowgreen were compared with those obtained with the bead-based three-color TruCOUNT system (R2 = 0.96; mean bias, −69.1 cells/μl; 95% confidence interval [CI], −225.7 to +87.5 cells/μl) and the FACSCount system (R2 = 0.97; mean bias, −40.0 cells/μl; 95% CI, −165.1 to +85.1 cells/μl). The correlation of the CD4+ T-lymphocyte counts obtained by the two bead-based systems was high (R2 = 0.98). Interestingly, CyFlowgreen yielded CD4+ T-lymphocyte counts that were 21.8 and 7.2 cells/μl lower than those obtained with the TruCOUNT and the FACSCount systems, respectively, when CD4+ T-lymphocyte counts were <250 CD4+ T-lymphocyte counts/μl range or 17.3 and 5.8 cells/μl less, respectively, when CD4+ T-lymphocyte counts were <200 cells/μl. The single-parameter CyFlowgreen volumetric technology performed well in comparison with the performance of the standard SP bead-based FCM system. However, a multicenter comparative study is needed before this FCM machine is implemented in resource-limited settings.

Evaluation of a single-platform microcapillary flow cytometer for enumeration of absolute CD4+ T-lymphocyte counts in HIV-1 infected Thai patients.

Various assays are used to enumerate peripheral blood absolute CD4+ T‐lymphocytes. Flow cytometry is considered the gold standard for this purpose. However, the high cost of available flow cytometers and monoclonal antibody reagents make it difficult to implement such methods in the resource‐poor settings. In this study, we evaluated a cheaper, recently developed single‐platform microcapillary cytometer for CD4+ T‐lymphocyte enumeration, the personal cell analyzer (PCA), from Guava® Technologies.

Low cost CD4 enumeration using generic monoclonal antibody reagents and a two-color user-defined multiset™ protocol

The standard three‐tube, three‐color flow cytometric method utilizing the TriTEST™ reagents in conjunction with the MultiSET™ software commonly used in most laboratories in Thailand for CD4 enumeration is expensive and thus unavailable to most HIV‐infected patients. A more affordable method, i.e., the PanLeucogating protocol using only two monoclonal antibody reagents, has been described but requires the use of the CellQUEST™ software that does not have automatic gating and reporting facilities. We describe a simple protocol that utilizes a two‐color user‐defined protocol with the automated MultiSET™ software for the acquisition, analysis, and reporting of CD4 results.

Differences in levels of platelet-derived microparticles in platelet components prepared using the platelet rich plasma, buffy coat, and apheresis procedures

BACKGROUND There has been an increased interest in platelet-derived microparticles (PMPs) in transfusion medicine. Little is known about PMP status during the preparation of platelet concentrates for transfusion. AIM The aim of this study is to compare the PMP levels in platelet components prepared using the buffy coat (BC), platelet-rich plasma platelet concentrate (PRP-PC), and apheresis (AP) processes. METHODS Platelet components were prepared using the PRP-PC and BC processes. Apheresis platelets were prepared using the Trima Accel and Amicus instruments. The samples were incubated with annexin A5-FITC, CD41-PE, and CD62P-APC. At day 1 after processing, the PMPs and activated platelets were determined using flow cytometry. RESULTS Both the percentage and number of PMPs were higher in platelet components prepared using the Amicus instrument (2.6±1.8, 32802±19036 particles/μL) than in platelet components prepared using the Trima Accel instrument (0.5±0.4, 7568±5298 particles/μL), BC (1.2±0.6, 12,920±6426 particles/μL), and PRP-PC (0.9±0.6, 10731±5514 particles/μL). Both the percentage and number of activated platelets were higher in platelet components prepared using the Amicus instrument (33.2±13.9, 427553±196965 cells/μL) than in platelet components prepared using the Trima Accel instrument (16.2±6.1, 211209±87706 cells/μL), BC (12.9±3.2, 140624±41003 cells/μL), and PRP-PC (21.1±6.3, 265210±86257 cells/μL). CONCLUSIONS The study suggests high variability of PMPs and activated platelets in platelet components prepared using different processes. This result may be important in validating the instruments involved in platelet blood collection and processing.