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Biomedical subjects

Dai Thi Xuan Trang

Publications and source records attributed to Dai Thi Xuan Trang.

7 recordsLinked to original sources
PubMed2006

Simple colorimetric inhibition assay of heme crystallization for high-throughput screening of antimalarial compounds.

Current assays for screening new antimalarials need initiators of beta-hematin formation that require laborious preparation, special devices, and substrates. In this study, based on reduction of heme absorption in beta-hematin formation, we developed a simple colorimetric assay using Tween 20 as an initiator and a microplate reader for high-throughput screening of inhibitors of beta-hematin formation.

Animals↗
PubMed2005

Inhibition assay of beta-hematin formation initiated by lecithin for screening new antimalarial drugs.

Measurement of heme crystallization provides a tool for screening new antimalarial drugs. Current assays for heme crystallization have employed initiators such as thermo, histidine-rich proteins, and lipids extracted from parasites and infected plasma. These initiators are unnatural or require laborious steps to prepare. In this study, we used a commercially available lipid, lecithin, a kind of phospholipid containing about 50% unsaturated fatty acids, as an initiator for heme crystal (beta-hematin) formation. We demonstrated that the inhibition of lecithin-based beta-hematin formation by antimalarial drugs is highly correlated with the preformed beta-hematin-based method. In addition, the lecithin-based assay is sensitive and convenient for large-scale screening of new novel antimalarials. We also indicated that dimethyl sulfoxide is an ideal solvent for preparation of heme stock solution, which is stable and can be used for 1 month.

Antimalarials↗
PubMed2005

Leukocyte activation by malarial pigment.

Malarial pigment, a unique hemozoin crystal composed of unit cells of heme dimers, is present in large amounts in circulating monocytes and neutrophils and can persist unchanged in macrophages for several months. In the present study, we investigated the effect of hemozoin not only on macrophages, but also on neutrophils. We used beta-hematin (BH), a chemically synthetic crystal structurally identical to hemozoin, for these studies. In vitro, BH up-regulated the expression of tumor necrosis factor-alpha in whole blood and in isolated peritoneal macrophages, indicating that hemozoin is able to stimulate monocytes. BH stimulated murine peritoneal neutrophils to express macrophage inflammatory protein-2 (MIP-2), a homologue of human interleukin-8 that is used as a marker of neutrophil activation. Injecting BH into the peritoneal cavity resulted in a dose-dependent migration of neutrophils and a high level of myeloperoxidase activity of peritoneal cells. Finally, BH directly induced neutrophil chemotaxis in vitro. Taken together, these results suggest that the malarial pigment hemozoin can activate leukocytes and may participate in the pathology of severe malaria.

Animals↗
PubMed2004

One-step concentration of malarial parasite-infected red blood cells and removal of contaminating white blood cells.

BACKGROUND: Isolation of a concentrated, living preparation of malarial parasite-infected red blood cells (PRBCs) that have low contamination of white blood cells (WBCs) facilitates research on the molecular, biochemical and immunological aspects of malarial parasites. This is currently carried out by a two-step method, including the concentration of PRBCs using density gradient centrifugation through Percoll or Nycodenz, followed by the removal of host WBCs using a cellulose powder column or a commercially available filtration unit. These two-step methods can help isolate sufficient PRBCs, but they are laborious. In this study, a simplified one-step procedure that takes advantage of the difference between diamagnetic low-spin oxyhaemoglobin and paramagnetic haemozoin (haem polymer) was described. The paramagnetic polymer is deposited in the food vacuoles of the parasite, allowing the use of magnetic separation to efficiently and rapidly concentrate PRBCs while removing contaminating host WBCs. METHODS: The magnetic removal of WBCs using a commercial LD column (MACS) was evaluated as a new method for concentrating and purifying PRBCs. To compare this method with the two density gradient centrifugation methods using Percoll or Nycodenz, we analysed the quantities of enriched PRBCs and contaminating host WBCs as well as the viability of malarial parasites in the final preparations. RESULTS: The quantity of PRBCs and the viability of malarial parasites in the isolated PRBCs were similar between magnetic and centrifugation methods. However, 90-99% of the contaminating WBCs were removed from the starting material using a magnetic column, whereas WBC content did not change using the Percoll or Nycodenz methods. CONCLUSION: The use of a commercially available magnetic LD column is effective, safe and easy for the one-step purification of PRBCs. This simple method does not affect the viability of malarial parasites.

Animals↗
PubMed2003

Neutralization of toxic heme by Plasmodium falciparum histidine-rich protein 2.

Plasmodium falciparum histidine-rich protein 2 (PfHRP2) has been suggested to be an initiator of the polymerization of heme, which is produced as by-product on the digestion of hemoglobin, and a promoter of the H(2)O(2)-induced degradation of heme in food vacuoles of the malarial parasite. In this work, we have designed PfHRP2 model peptides, R18 and R27 (18 and 27 residues, respectively), and used them for optical and electron spin resonance spectroscopic measurements to confirm that the axial ligands of the heme-PfHRP2 complex are the nitrogenous donors derived from the imidazole moieties of histidine residues of PfHRP2. In addition, we revealed that the affinities of R18 and R27 for heme (K(d) = 2.21 x 10(-6) M and 0.71 x 10(-6) M, respectively) might be as high as that of PfHRP2 (K(d) = 0.94 x 10(-6) M). The R27 peptide can remove heme from membrane-intercalated heme and inhibit heme-induced hemolysis. Therefore, we suggest another function of PfHRP2: it may play an important role in the neutralization of toxic heme in the parasite cytoplasm and infected erythrocytes by removing heme from heme-bound membranes or reducing heme-induced hemolysis.

Amino Acid Sequence↗