Src-family kinase–dependent disruption of endothelial barrier function by Plasmodium falciparum merozoite proteins

Abstract

Pulmonary complication in severe Plasmodium falciparum malaria is manifested as a prolonged impairment of gas transfer or the more severe acute respiratory distress syndrome (ARDS). In either clinical presentation, vascular permeability is a major component of the pathologic process. In this report, we examined the effect of clinical P falciparum isolates on barrier function of primary dermal and lung microvascular endothelium in vitro. We showed that parasite sonicates but not intact infected erythrocytes disrupted endothelial barrier function in a Srcfamily kinase-dependent manner. The abnormalities were manifested both as discontinuous immunofluorescence staining of the junctional proteins ZO-1, claudin 5, and VE-cadherin and the formation of interendothelial gaps in monolayers. These changes were associated with a loss in total protein content of claudin 5 and redistribution of ZO-1 from the cytoskeleton to the membrane and the cytosolic and nuclear fractions. There was minimal evidence of a proinflammatory response or direct cellular cytotoxicity or cell death. The active component in sonicates appeared to be a merozoite-associated protein. Increased permeability was also induced by P falciparum glycophosphatidylinositols (GPIs) and food vacuoles. These results demonstrate that parasite components can alter endothelial barrier function and thus contribute to the pathogenesis of severe falciparum malaria.

Dynamic interactions ofPlasmodiumspp. with vascular endothelium

“…[45][46][47][48][49] Permeability is assessed either as a change in transendothelial resistance, or the flux of fluorescein-labeled solutes such as dextran or albumin. While there is general agreement that IRBC do induce permeability, the mechanisms appear to differ depending on the experimental design and cell types used.…”

“…115 The effect of GPI can be inhibited by the Src-family kinase antagonist herbimycin A. Merozoite proteins, independently of TLR2 stimulation, can also increase endothelial permeability in a Src family kinase-dependent manner by inducing the redistribution of ZO-1, VE-cadherin and claudin-5 away from cell-cell junctions in HDMEC. 49 As part of hemoglobin degradation, P. falciparum generates a relatively insoluble crystal of heme monomers called hemozoin or malaria pigment in parasitophorous food vacuoles. Similar to merozoites, food vacuoles are released every 48 hours at the time of IRBC rupture.…”

“…Purified food vacuoles have been found to induce endothelial cell death and barrier dysfunction in HDMEC. 49 Food vacuoles may also activate complement and coagulation pathways, 116 both of which could increase endothelial permeability through the production of C5a 117 and thrombin, respectively. Although hemozoin itself does not induce endothelial barrier dysfunction, 47,49 it has been shown to activate NF-kB signaling pathways as shown by increased IL-8 and MCP-1 (CCL2) production in HUVEC.…”

“…49 Food vacuoles may also activate complement and coagulation pathways, 116 both of which could increase endothelial permeability through the production of C5a 117 and thrombin, respectively. Although hemozoin itself does not induce endothelial barrier dysfunction, 47,49 it has been shown to activate NF-kB signaling pathways as shown by increased IL-8 and MCP-1 (CCL2) production in HUVEC. 118 Other parasite derived products such as DNA, 119,120 histones, 121 tRNA synthetase, 120 uric acid 122 and heat shock proteins (HSP) 123 have been shown to activate the host immune system.…”

“…These studies are consistent with previous results showing late stage (schizont) parasite extracts and merozoite proteins decreased endothelial claudin-5 production in conjunction with disruption in VE-cadherin localization to cell-cell junctions. 49 Interestingly, the blockade of the angiotensin II type 1 receptor (AT1) or stimulation of the type 2 receptor (AT2) abrogated IRBCinduced activation of b-catenin and prevented the disruption of brain endothelial monolayers.…”