Platelets Potentiate Brain Endothelial Alterations Induced byPlasmodium falciparum

Abstract

Brain lesions of cerebral malaria (CM) are characterized by a sequestration of Plasmodium falciparumparasitized red blood cells (PRBC) and platelets within brain microvessels, as well as by blood-brain barrier (BBB) disruption. In the present study, we evaluated the possibility that PRBC and platelets induce functional alterations in brain endothelium. In a human brain endothelial cell line, named HBEC-5i, exhibiting most of the features demanded for a pathophysiological study of BBB, tumor necrosis factor (TNF) or lymphotoxin ␣ (LT-␣) reduced transendothelial electrical resistance (TEER), enhanced the permeability to 70-kDa dextran, and increased the release of microparticles, a recently described indicator of disease severity in CM patients. In vitro cocultures showed that platelets or PRBC can have a direct cytotoxic effect on activated, but not on resting, HBEC-5i cells. Platelet binding was required, as platelet supernatant had no effect. Furthermore, platelets potentiated the cytotoxicity of PRBC for TNF-or LT-␣-activated HBEC-5i cells when they were added prior to these cells on the endothelial monolayers. This effect was not observed when platelets were added after PRBC. Both permeability and TEER were strongly affected, and the apoptosis rate of HBEC-5i cells was dramatically increased. These findings provide insights into the mechanisms by which platelets can be deleterious to the brain endothelium during CM.

Association of cerebrospinal fluid anti–NR2 glutamate receptor antibodies with diffuse neuropsychiatric systemic lupus erythematosus

“…We have recently demonstrated that anti-P antibodies up-regulate the expression of tumor necrosis factor ␣ protein and messenger RNA in human peripheral blood monocytes (20). Since tumor necrosis factor ␣ has been found to abrogate the integrity of the blood-brain barrier (21,22), it is likely that serum anti-P antibodies might also induce blood-brain barrier impairment and thus allow anti-NR2 in the systemic circulation to enter the CNS, leading to the development of neuronal damage. However, further studies would be needed to confirm this.…”

TGF-β1 Released from Activated Platelets Can Induce TNF-Stimulated Human Brain Endothelium Apoptosis: A New Mechanism for Microvascular Lesion during Cerebral Malaria

“…Platelets may also have proapoptotic effects on TNF-activated human brain microvascular endothelial cells (HBEC-5i) 4 in vitro (25). Inflammatory mediators such as TNF are key to the pathogenesis of infectious diseases (5), and fatal CM is associated with high circulating levels of this cytokine (6,7), although other inflammatory mediators are also involved (8).…”

“…Briefly, they express stable patterns of endothelial cell markers such as VE-cadherin, von Willebrand factor VIII, and peripheral occludin, in addition to CD54, CD40, and CSA, and they show an up-regulation of CD54 and CD106 upon TNF activation. Moreover, HBEC-5i exhibit major features of cerebral endothelial cells, especially efficient tight-junction structures, as assessed by high trans endothelial electric resistance and very low permeability to 70-kDa dextran (25). HBEC-5i were cultured on 0.1% gelatin-coated 24-well culture plates (BD Falcon, BD Biosciences) and grown to confluence in DMEM:Ham's F-12 (pH 7.4), supplemented with 10% FCS, 30 g/ml endothelial cell growth supplement (E 0760; Sigma-Aldrich), and 10 g/ml gentamicin.…”

“…These brains were devoid of any pathologic abnormalities, as described, and the isolation and purification procedures were conducted according to the method developed by Bowman et al (18), with minor modifications. These cells were then immortalized (17) and characterized in our laboratory, as described elsewhere (25). Briefly, they express stable patterns of endothelial cell markers such as VE-cadherin, von Willebrand factor VIII, and peripheral occludin, in addition to CD54, CD40, and CSA, and they show an up-regulation of CD54 and CD106 upon TNF activation.…”

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.…”