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Plasmodium falciparum-infected erythrocytes induce NF-kappaB regulated inflammatory pathways in human cerebral endothelium.

ABSTRACT: Cerebral malaria is a severe multifactorial condition associated with the interaction of high numbers of infected erythrocytes to human brain endothelium without invasion into the brain. The result is coma and seizures with death in more than 20% of cases. Because the brain endothelium is at the interface of these processes, we investigated the global gene responses of human brain endothelium after the interaction with Plasmodium falciparum-infected erythrocytes with either high- or low-binding phenotypes. The most significantly up-regulated transcripts were found in gene ontology groups comprising the immune response, apoptosis and antiapoptosis, inflammatory response, cell-cell signaling, and signal transduction and nuclear factor kappaB (NF-kappaB) activation cascade. The proinflammatory NF-kappaB pathway was central to the regulation of the P falciparum-modulated endothelium transcriptome. The proinflammatory molecules, for example, CCL20, CXCL1, CXCL2, IL-6, and IL-8, were increased more than 100-fold, suggesting an important role of blood-brain barrier (BBB) endothelium in the innate defense during P falciparum-infected erythrocyte (Pf-IRBC) sequestration. However, some of these diffusible molecules could have reversible effects on brain tissue and thus on neurologic function. The inflammatory pathways were validated by direct measurement of proteins in brain endothelial supernatants. This study delineates the strong inflammatory component of human brain endothelium contributing to cerebral malaria.

SUBMITTER: Tripathi AK

PROVIDER: S-EPMC2925626 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature

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Plasmodium falciparum-infected erythrocytes induce NF-kappaB regulated inflammatory pathways in human cerebral endothelium.

Tripathi Abhai K AK Sha Wei W Shulaev Vladimir V Stins Monique F MF Sullivan David J DJ

Blood 20090827 19

Cerebral malaria is a severe multifactorial condition associated with the interaction of high numbers of infected erythrocytes to human brain endothelium without invasion into the brain. The result is coma and seizures with death in more than 20% of cases. Because the brain endothelium is at the interface of these processes, we investigated the global gene responses of human brain endothelium after the interaction with Plasmodium falciparum-infected erythrocytes with either high- or low-binding ...[more]

PMID: 19713460

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Project description:BackgroundThe intra-erythrocytic development of the malaria parasite Plasmodium falciparum depends on the uptake of a number of essential nutrients from the host cell and blood plasma. It is widely recognized that the parasite imports low molecular weight solutes from the plasma and the consumption of these nutrients by P. falciparum has been extensively analysed. However, although it was already shown that the parasite also imports functional proteins from the vertebrate host, the internalization route through the different infected erythrocyte membranes has not yet been elucidated. In order to further understand the uptake mechanism, the study examined the trafficking of human plasminogen from the extracellular medium into P. falciparum-infected red blood cells.MethodsPlasmodium falciparum clone 3D7 was cultured in standard HEPES-buffered RPMI 1640 medium supplemented with 0.5% AlbuMAX. Exogenous human plasminogen was added to the P. falciparum culture and the uptake of this protein by the parasites was analysed by electron microscopy and Western blotting. Immunoprecipitation and mass spectrometry were performed to investigate possible protein interactions that may assist plasminogen import into infected erythrocytes. The effect of pharmacological inhibitors of different cellular physiological processes in plasminogen uptake was also tested.ResultsIt was observed that plasminogen was selectively internalized by P. falciparum-infected erythrocytes, with localization in plasma membrane erythrocyte and parasite's cytosol. The protein was not detected in parasitic food vacuole and haemoglobin-containing vesicles. Furthermore, in erythrocyte cytoplasm, plasminogen was associated with the parasite-derived membranous structures tubovesicular network (TVN) and Maurer's clefts. Several proteins were identified in immunoprecipitation assay and may be involved in the delivery of plasminogen across the P. falciparum multiple compartments.ConclusionThe findings here reported reveal new features regarding the acquisition of plasma proteins of the host by P. falciparum-infected erythrocytes, a mechanism that involves the exomembrane system, which is distinct from the haemoglobin uptake, clarifying a route that may be potentially targeted for inhibition studies.

Project description:In human erythrocytes (h-RBCs) various stimuli induce increases in [cAMP] that trigger ATP release. The resulting pattern of extracellular ATP accumulation (ATPe kinetics) depends on both ATP release and ATPe degradation by ectoATPase activity. In this study we evaluated ATPe kinetics from primary cultures of h-RBCs infected with P. falciparum at various stages of infection (ring, trophozoite and schizont stages). A "3V" mixture containing isoproterenol (?-adrenergic agonist), forskolin (adenylate kinase activator) and papaverine (phosphodiesterase inhibitor) was used to induce cAMP-dependent ATP release. ATPe kinetics of r-RBCs (ring-infected RBCs), t-RBCs (trophozoite-infected RBCs) and s-RBCs (schizont-infected RBCs) showed [ATPe] to peak acutely to a maximum value followed by a slower time dependent decrease. In all intraerythrocytic stages, values of ?ATP1 (difference between [ATPe] measured 1 min post-stimulus and basal [ATPe]) increased nonlinearly with parasitemia (from 2 to 12.5%). Under 3V exposure, t-RBCs at parasitemia 94% (t94-RBCs) showed 3.8-fold higher ?ATP1 values than in h-RBCs, indicative of upregulated ATP release. Pre-exposure to either 100 µM carbenoxolone, 100 nM mefloquine or 100 µM NPPB reduced ?ATP1 to 83-87% for h-RBCs and 63-74% for t94-RBCs. EctoATPase activity, assayed at both low nM concentrations (300-900 nM) and 500 µM exogenous ATPe concentrations increased approx. 400-fold in t94-RBCs, as compared to h-RBCs, while intracellular ATP concentrations of t94-RBCs were 65% that of h-RBCs. In t94-RBCs, production of nitric oxide (NO) was approx. 7-fold higher than in h-RBCs, and was partially inhibited by L-NAME pre-treatment. In media with L-NAME, ?ATP1 values were 2.7-times higher in h-RBCs and 4.2-times higher in t94-RBCs, than without L-NAME. Results suggest that P. falciparum infection of h-RBCs strongly activates ATP release via Pannexin 1 in these cells. Several processes partially counteracted ATPe accumulation: an upregulated ATPe degradation, an enhanced NO production, and a decreased intracellular ATP concentration.

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Plasmodium falciparum-infected erythrocytes induce NF-kappaB regulated inflammatory pathways in human cerebral endothelium.

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Plasmodium falciparum-infected erythrocytes induce NF-kappaB regulated inflammatory pathways in human cerebral endothelium.

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