Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Excessive binding of Plasmodium falciparum-infected red blood cells (pRBCs) to the vascular endothelium (cytoadherence) and to uninfected erythrocytes (rosetting) may lead to occlusion of the microvasculature and thereby contribute directly to the acute pathology of severe human malaria. A number of endothelial receptors have been identified as targets for the pRBCs, including CD36, intercellular adhesion molecule-1 (ICAM-1) and chondroitin-4-sulfate (CSA). In vitro, CD36 is the most frequent target of strains from patients with mild as well as severe P. falciparum malaria, but is expressed at low levels on the cerebral microvasculature and therefore seems unlikely to be involved in the evolution of cerebral disease. Strains of P. falciparum that form rosettes are associated both with the occurrence of cerebral malaria and severe anemia. Here we report that malaria-infected RBCs adhere to platelet/endothelial cell adhesion molecule-1 (PECAM-1/CD31) on the vascular endothelium. pRBCs bind to endothelial cells, to PECAM-1/CD31 transfected cells, and directly to recombinant PECAM-1/CD31 absorbed onto plastic. Soluble PECAM-1/CD31 and monoclonal antibodies specific for the amino-terminal segment of PECAM-1/CD31 (domains 1-4) blocked the binding. Interferon-gamma (IFN-gamma)-essential for the development of cerebral malaria in the mouse-was found to augment adhesion of human pRBCs to PECAM-1/CD31 on endothelial cell monolayers. Our results suggest that PECAM-1/CD31 is a virulence-associated endothelial receptor of P. falciparum-infected RBCs.
 ...
PMID:PECAM-1/CD31, an endothelial receptor for binding Plasmodium falciparum-infected erythrocytes. 939 93

In Plasmodium falciparum malaria, large proportions of resident macrophages and circulating monocytes and leukocytes contain massive amounts of the malarial pigment, hemozoin. Previous studies have shown that important functions (e.g., the generation of the oxidative burst, the ability to repeat phagocytosis, and protein kinase C activity) were severely impaired in hemozoin-loaded monocytes. Expression of membrane antigens directly involved in the immune response and in the phagocytic process, and/or under protein kinase C control, in hemozoin-loaded human monocytes was studied. Expression of major histocompatibility complex (MHC) class II after gamma interferon stimulation was blocked in hemozoin-loaded monocytes at the protein expression and gene transcription levels but was preserved in control monocytes loaded with opsonized latex beads or anti-D(Rho)-immunoglobulin G (IgG)-opsonized human erythrocytes. Expression of CD54 (intracellular adhesion molecule 1) and CD11c (p150,95 integrin) was also decreased in hemozoin-loaded monocytes. Expression of MHC class I, CD16 (low-affinity Fc receptor for aggregated IgG), CD32 (low-affinity Fc receptor for aggregated IgG), CD64 (high-affinity receptor for IgG), CD11b (receptor for complement component iC3b [CR3]), CD35 (receptor for complement components C3b and C4b [CR1]), and CD36 (non-class-A scavenger receptor) was not specifically affected by hemozoin loading. These results suggest that hemozoin loading may contribute to the impairment of the immune response and the derangement of antigen presentation reported in previous studies of P. falciparum malaria.
 ...
PMID:Phagocytosis of the malarial pigment, hemozoin, impairs expression of major histocompatibility complex class II antigen, CD54, and CD11c in human monocytes. 952 87

Malaria during pregnancy continues to be a major health problem in endemic countries, with clinical consequences, including death, for both mother and child. Just as cerebral malaria results from parasite sequestration in the brain, maternal malaria results from parasite sequestration in the placenta, and a distinct subpopulation of parasites which bind chondroitin sulfate A but not CD36 causes the syndrome. Women have little or no immunological experience with this parasite prior to first pregnancy, making primigravid women particularly vulnerable to infection. Parasites adhere to the surface of trophoblastic villi, eliciting the accumulation of inflammatory leukocytes in the intervillous space, and the necrosis of adjacent placental tissue. Maternal malaria results in poor pregnancy outcomes, although the responsible mechanisms have not been defined. In holoendemic areas both placental infection and poor outcome decrease in frequency with successive pregnancies; protection may result from control of parasite adhesion, suggesting an attractive target for new therapies.
 ...
PMID:Maternal malaria and parasite adhesion. 953 49

The cerebral form of severe malaria is associated with excessive intravascular sequestration of Plasmodium falciparum-infected erythrocytes (PRBC). Retention and accumulation of PRBC may lead to occlusion of brain microvessels and direct the triggering of acute pathologic changes. Here we report that by selection, cloning, and subcloning, we have identified rare P. falciparum parasites expressing a pan-adhesive phenotype linked to erythrocyte rosetting, a previously identified correlate of cerebral malaria. Rosetting PRBC not only bound uninfected erythrocytes but also formed autoagglutinates, adhered to endothelial cells, and bound to CD36, immunoglobulins, and the blood group A antigen. The linkage of rosetting, autoagglutination, and cytoadherence involved the coexpression on a single PRBC of ligands with multiple specificities and the binding to two or more receptors on erythrocytes and to at least two other cell adhesion molecules, including a new endothelial cell receptor for P. falciparum-infected erythrocytes. Limited proteolysis that differentially cleaved the rosetting ligand PfEMP1 from the PRBC surface abrogated all the binding phenotypes of these parasites, implicating the variant antigen PfEMP1 as a carrier of multiple ligand specificities. The results encourage the further study of pan-adhesion as a potentially important parasite phenotype in the pathogenesis of severe P. falciparum malaria.
 ...
PMID:Multiple adhesive phenotypes linked to rosetting binding of erythrocytes in Plasmodium falciparum malaria. 959 74

Plasmodium falciparum-parasitized red cells attach to endothelial cells through several receptor-adhesin pairs. One of the adhesins on the surface of malaria-infected red blood cell is the modified band 3 molecule. We tested a synthetic peptide (HPLQKTY) based on a peptidic sequence of human band 3 protein to determine whether CD36 or thrombospondin is a receptor for the band 3-related adhesin. Although both CD36 and thrombospondin can bind parasitized cells independently, the HPLQKTY peptide and a monoclonal antibody (3H3) that recognizes the HPLQKTY sequence blocked only the adhesion of parasitized red cells to thrombospondin. The binding of thrombospondin, but not CD36, to the immobilized multiple antigen peptide-conjugated HPLQKTY was dependent on the concentration of the immobilized peptide. It would appear therefore, that thrombospondin is a receptor for the band 3-related cytoadhesion of parasitized erythrocytes.
 ...
PMID:Plasmodium falciparum: thrombospondin mediates parasitized erythrocyte band 3-related adhesin binding. 960 92

Members of the Plasmodium falciparum var gene family encode clonally variant adhesins, which play an important role in the pathogenicity of tropical malaria. Here we employ a selective panning protocol to generate isogenic P.falciparum populations with defined adhesive phenotypes for CD36, ICAM-1 and CSA, expressing single and distinct var gene variants. This technique has established the framework for examining var gene expression, its regulation and switching. It was found that var gene switching occurs in situ. Ubiquitous transcription of all var gene variants appears to occur in early ring stages. However, var gene expression is tightly regulated in trophozoites and is exerted through a silencing mechanism. Transcriptional control is mutually exclusive in parasites that express defined adhesive phenotypes. In situ var gene switching is apparently mediated at the level of transcriptional initiation, as demonstrated by nuclear run-on analyses. Our results suggest that an epigenetic mechanism(s) is involved in var gene regulation.
 ...
PMID:Antigenic variation in malaria: in situ switching, relaxed and mutually exclusive transcription of var genes during intra-erythrocytic development in Plasmodium falciparum. 973 19

The ability of Plasmodium falciparum infected erythrocytes from 162 Thai patients with uncomplicated malaria, 82 patients with severe malaria and 19 patients with cerebral malaria to form rosettes in vitro was studied. Of 263 isolates, 62 were evaluated for their adherence to different target molecules. We found that wide variation occurred in isolates from all groups in the level of rosette formation and adherence to CD36, intracellular adhesion molecule-1, thrombospondin and chondroitin sulfate A. No statistically significant correlation between the magnitude of rosette formation and disease severity was found (p > 0.05). In addition, our results from the use of purified CD36 as an adherence receptor showed no association between the degree rosetting and level of cytoadherence (p > 0.05, r = -0.04). Our data provide evidence that rosette formation and cytoadherence involve different molecular mechanisms and both phenomena can occur in all manifestations of the disease.
 ...
PMID:Lack of significant association between rosette formation and parasitized erythrocyte adherence to purified CD36. 974 Feb 66

During falciparum malaria infection, severe complications ensue because parasitized red blood cells (PRBCs) adhere to endothelial cells and accumulate in the microvasculature. At the molecular level, adhesion is mediated by interaction of Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP-1) on the PRBC surface with receptors on the surface of endothelial cells, including CD36. We have shown that a recombinant 179-residue subfragment of PfEMP-1 (rC1-2[1-179]), which encompasses the CD36-binding region, inhibits and reverses adhesion of PRBCs to CD36 under physiologically relevant flow conditions. rC1-2[1-179] inhibited adhesion in a concentration-dependent manner over the range 100 pM to 2 microM, with up to 99% of adhesion blocked at the highest concentration tested. The antiadhesive activity of rC1-2[1-179] was not strain specific and almost totally ablated adhesion of four different parasite lines. Furthermore, rC1-2[1-179] showed remarkable ability to progressively reverse adhesion when flowed over adherent PRBCs for 2h. The effect of rC1-2[1-179] was, however, specific for CD36-mediated adhesion and had no effect on adhesion mediated by CSA. Interference with binding of PRBCs to the vascular endothelium using rC1-2[1-179] or smaller organic mimetics may be a useful therapeutic approach to ameliorate severe complications of falciparum malaria.
 ...
PMID:A recombinant peptide based on PfEMP-1 blocks and reverses adhesion of malaria-infected red blood cells to CD36 under flow. 978 87

Adhesion molecules on the endothelial surface of the blood-brain barrier (BBB) play an important role in the pathogenesis of many encephalopathies, including multiple sclerosis (MS) and cerebral malaria (CM). The expression of four surface molecules of relevance to MS and CM on the immortalized human umbilical vein endothelial cell line, ECV304, was investigated using immunofluorescence flow cytometry. We found that ECV304 cells express intercellular adhesion molecule-1 (ICAM-1) and low levels of CD36, but not vascular cell adhesion molecule-1 (VCAM-1) or E-selectin. This expression pattern was unaltered on ECV304 cells which were co-cultured with C6 glioma cells; conditions under which the endothelial cells display enhanced barrier formation. Tumour necrosis factor-alpha (TNF-alpha), which is elevated in MS and CM, decreased the integrity of the barrier in co-cultured endothelial cells and upregulated the expression of ICAM-1 nine-fold. The significance of elevated ICAM-1 expression in relation to the binding of parasitised erythrocytes at the BBB in CM is discussed.
 ...
PMID:Upregulation of intercellular adhesion molecule-1 expression on human endothelial cells by tumour necrosis factor-alpha in an in vitro model of the blood-brain barrier. 1036 90

CD36 is one of the major glycoproteins of platelets and known as GPIV. Besides platelets, CD36 is distributed in megakaryocytes, monocytes, capillary endothelium and mammary epithelial cells. In vitro analyses, CD36 is reported to act as receptors to a variety of ligands including collagen, thrombospondin, malaria-infected erythrocytes and oxidized LDL. However, it remains unclear to which of these functions CD36 is critical in vivo. CD36-deficient individuals can be the key to answer this question. In calcium-deficient state, CD36-deficient platelets exhibited a delay and decline of irreversible aggregation on agonist stimulation. Irreversible aggregation of platelets depends on intake of arachidonic acid once-secreted from platelets and production of its metabolite Eps/TxA2. The calcium influx in response to U46619 (TxA2 analogue) of CD36-deficient platelets was not different from normal platelets in the presence of indomethacin and ETYA. Defective aggregation of CD36-deficient platelets in calcium-deficient state seemed to be derived from defective intake of arachidonic acid. This assumption was verified by our results that inhibitory effect of arachidonic acid in aggregation depended on the presence of platelet CD36. Intake of arachidonic acid through CD36 may have an effect in low concentration state of arachidonic acid. The CD36 deficiency is present in several % in Japanese and approximately 0.3% in Caucasians and is divided in type I (deficient in platelets and monocytes) and type II (deficient only in platelets). Analyses of CD36 cDNA revealed that codon 90 (proline/serine) was critical as to the surface expression of CD36 protein. By analyses of CD36 genomic DNA, the CD36 gene could be classified; 1) serine90 type that was not translated as CD36 protein, 2) proline90 type that was not transcribed to mRNA, 3) proline90 type that was transcribed only in monocytes and not in platelets, 4) proline90 type that was transcribed in platelets but in very small amounts and 5) wild type proline 90. The results of family studies were consistent with the assumption described above.
 ...
PMID:Platelet membrane protein CD36. 1038 59


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>