Differential induction of malaria liver pathology in mice infected with Plasmodium chabaudi AS or Plasmodium berghei NK65.

Background: Cerebral malaria and severe anaemia are the most common deadly complications of malaria, and are often associated, both in paediatric and adult patients, with hepatopathy, whose pathogenesis is not well characterized, and sometimes also with acute respiratory distress syndrome (ARDS). Here, two species of murine malaria, the lethal Plasmodium berghei strain NK65 and self-healing Plasmodium chabaudi strain AS which differ in their ability to cause hepatopathy and/or ARDS were used to investigate the lipid alterations, oxidative damage and host immune response during the infection in relation to parasite load and accumulation of parasite products, such as haemozoin.

Methods: Plasma and livers of C57BL/6J mice injected with PbNK65 or PcAS infected erythrocytes were collected at different times and tested for parasitaemia, content of haemozoin and expression of tumour necrosis factor (TNF).

Altered Lipid Composition of Surfactant and Lung Tissue in Murine Experimental Malaria-Associated Acute Respiratory Distress Syndrome.

Malaria-associated acute lung injury (MA-ALI) and its more severe form malaria-associated acute respiratory distress syndrome (MA-ARDS) are common, often fatal complications of severe malaria infections. However, little is known about their pathogenesis. In this study, biochemical alterations of the lipid composition of the lungs were investigated as possible contributing factors to the severity of murine MA-ALI/ARDS.

Chronic deficiency of nitric oxide affects hypoxia inducible factor-1α (HIF-1α) stability and migration in human endothelial cells.

Background: Endothelial dysfunction in widely diffuse disorders, such as atherosclerosis, hypertension, diabetes and senescence, is associated with nitric oxide (NO) deficiency. Here, the behavioural and molecular consequences deriving from NO deficiency in human umbilical vein endothelial cells (HUVECs) were investigated.

Results: Endothelial nitric oxide synthase (eNOS) was chronically inhibited either by N(G)-Nitro-L-arginine methyl ester (L-NAME) treatment or its expression was down-regulated by RNA interference.

The lipid moiety of haemozoin (Malaria Pigment) and P. falciparum parasitised red blood cells bind synthetic and native endothelin-1.

Endothelin1 (ET-1) is a 21-amino acid peptide produced by the vascular endothelium under hypoxia, that acts locally as regulator of vascular tone and inflammation. The role of ET-1 in Plasmodium falciparum malaria is unknown, although tissue hypoxia is frequent as a result of the cytoadherence of parasitized red blood cell (pRBC) to the microvasculature. Here, we show that both synthetic and endothelial-derived ET-1 are removed by parasitized RBC (D10 and W2 strains, chloroquine sensitive, and resistant, resp.

Novel antimalarial aminoquinolines: heme binding and effects on normal or Plasmodium falciparum-parasitized human erythrocytes.

Two new quinolizidinyl-alkyl derivatives of 7-chloro-4-aminoquinoline, named AM-1 and AP4b, which are highly effective in vitro against both the D10 (chloroquine [CQ] susceptible) and W2 (CQ resistant) strains of Plasmodium falciparum and in vivo in the rodent malaria model, have been studied for their ability to bind to and be internalized by normal or parasitized human red blood cells (RBC) and for their effects on RBC membrane stability. In addition, an analysis of the heme binding properties of these compounds and of their ability to inhibit beta-hematin formation in vitro has been performed. Binding of AM1 or AP4b to RBC is rapid, dose dependent, and linearly related to RBC density.

Two complementary fluorimetric assays for the determination of aminoquinoline binding and uptake by human erythrocytes in vitro.

We provide two simple low-cost and low-tech procedures to measure with good precision and accuracy the binding and internalization into human erythrocytes of chloroquine and other aminoquinolines. The methods are based on the high fluorescence of the quinoline ring and are complementary. Method A evaluates residual drugs in the supernatants of treated erythrocytes, whereas method B quantifies the total uptake by whole cells and the fraction bound to the membranes.

Effects of malaria heme products on red blood cell deformability.

In falciparum malaria, the deformability of the entire erythrocyte population is reduced in proportion to disease severity, and this compromises microcirculatory blood flow through vessels partially obstructed by cytoadherent parasitized erythrocytes. The cause of rigidity of uninfected erythrocytes in not known but could be mediated by malaria heme products. In this study, we show that red blood cell deformability (RBC-D), measured by laser-assisted optical rotational cell analyzer, decreased in a dose-dependent manner after incubation with hemin and hydrogen peroxide but not with hemoglobin or beta-hematin.

Modulation of glyceraldehyde 3 phosphate dehydrogenase activity and tyr-phosphorylation of Band 3 in human erythrocytes treated with ferriprotoporphyrin IX.

Erythrocyte glyceraldehyde-3-phosphate dehydrogenase (G3PD), is a glycolytic enzyme normally inhibited upon binding to the anion transporter Band 3 and activated when free in the cytosol. We have previously reported that ferric protoporphyrin IX (FP) enhances G3PD activity in human erythrocytes (RBC). This could be due to two mechanisms considered in this work: Band 3 tyrosine phosphorylation or oxidative damage of specific G3PD binding sites in the membrane.

Regulation of human erythrocyte glyceraldehyde-3-phosphate dehydrogenase by ferriprotoporphyrin IX.

Erythrocyte glyceraldehyde-3-phosphate dehydrogenase (G3PD) is a glycolytic enzyme containing critical thiol groups and whose activity is reversibly inhibited by binding to the cell membrane. Here, we demonstrate that the insertion of ferriprotoporphyrin IX (FP) into the red cell membranes exerts two opposite effects on membrane bound G3PD. First, the enzyme is partially inactivated through oxidation of critical thiols.

Major artifacts encountered in studying biological samples containing ferric protoporphyrin IX.

Heme (ferric protoporphyrin IX, FP) dissolves very rapidly into the lipid phase of membranes, and a large number of studies have focused attention on its possible toxic effect in whole cells or isolated membranes. However, because of its molecular structure and reactivity, different problems can be encountered during the course of studying biological samples containing FP. In this article, we discuss important interferences by FP and artifacts that can affect the experimental values.

Destabilisation and subsequent lysis of human erythrocytes induced by Plasmodium falciparum haem products.

In falciparum malaria, both infected and uninfected red cells have structural and functional alterations. To investigate the mechanisms of these modifications, we studied the effects of two Plasmodium falciparum haem products (haematin and malaria pigment in the synthetic form beta-haematin) on isolated human red blood cells (RBCs) and purified RBC ghosts. A dose- and time-dependent incorporation of haematin into RBC ghosts and intact cells was observed, which was in proportion to the extent of haematin- induced haemolysis.

Accelerated senescence of human erythrocytes cultured with Plasmodium falciparum.

Red blood cells infected withPlasmodium falciparum(IRBCs) undergo changes primarily in their membrane composition that contribute to malaria pathogenesis. However, all manifestations (eg, anemia) cannot be accounted for by IRBCs alone. Uninfected erythrocytes (URBCs) may play a role, but they have been under-researched.