Candida albicans internalization by host cells is mediated by a clathrin-dependent mechanism

Candida albicans is a major cause of oropharyngeal, vulvovaginal and haematogenously disseminated candidiasis. Endocytosis of C. albicans hyphae by host cells is a prerequisite for tissue invasion. This internalization involves interactions between the fungal invasin Als3 and host E- or N-cadherin. Als3 shares some structural similarity with InlA, a major invasion protein of the bacterium Listeria monocytogenes . InlA mediates entry of L. monocytogenes into host cells through binding to E-cadherin. A role in internalization, for a non-classical stimulation of the clathrin-dependent endocytosis machinery, was recently highlighted. Based on the similarities between the C. albicans and L. monocytogenes invasion proteins, we studied the role of clathrin in the internalization of C. albicans . Using live-cell imaging and indirect immunofluorescence of epithelial cells infected with C. albicans , we observed that host E-cadherin, clathrin, dynamin and cortactin accumulated at sites of C. albicans internalization. Similarly, in endothelial cells, host N-cadherin, clathrin and cortactin accumulated at sites of fungal endocytosis. Furthermore, clathrin, dynamin or cortactin depletion strongly inhibited C. albicans internalization by epithelial cells. Finally, beads coated with Als3 were internalized in a clathrin-dependent manner. These data indicate that C. albicans , like L. monocytogenes, hijacks the clathrin-dependent endocytic machinery to invade host cells.     

Activation of human T cells is associated with tyrosine phosphorylation of several cellular proteins

Human T lymphocytes are activated to proliferate after triggering the T Cell Antigen Receptor Complex. CD3-Ti, with either antigen, mitogenic lectins or monoclonal antibodies against its different subunits. Stimulation of Jurkat leukemic human T cells with anti-CD3 or anti-Ti monoclonal antibodies was found to induce, within 1 min, an increase in the phosphorylation of a set of cellular proteins that can be precipitated with anti-phosphotyrosine antibodies. Seven phosphotyrosine-containing proteins were separated with respective mol. wt of 21, 25, 38, 55, 70, 80 and 110 kDa, among which the 38 kDa species is predominant. Moreover, incubation of Jurkat T cells with sodium orthovanadate, a potent inhibitor of phosphotyrosine protein-phosphatases, was found to potentiate the effects of anti-CD3 mAb on tyrosine phosphorylation. In addition vanadate also induced IL-2 secretion in Jurkat cells when associated with the phorbol ester TPA, further demonstrating the importance of these phosphorylation reactions in the process of T cell activation. Our results therefore allow us to identify several protein substrates of a tyrosine kinase activity, whose stimulation appears to be an early event in human T cell activation through the antigen receptor pathway.     

Activation of Helicobacter pylori CagA by tyrosine phosphorylation is essential for dephosphorylation of host cell proteins in gastric epithelial cells

Helicobacter pylori type I strains harbour the cag pathogenicity island (cag-PAI), a 37 kb sequence,which encodes the components of a type IV secretion system. CagA, the first identified effector protein of the cag-PAI, is translocated into eukaryotic cells and tyrosine phosphorylated (CagAP-tyr) by a host cell tyrosine kinase. Translocation of CagA induces the dephosphorylation of a set of phosphorylated host cell proteins of unknown identity. CagA proteins of independent H. pylori strains vary in sequence and thus in the number and composition of putative tyrosine phosphorylation motifs (TPMs). The CagA protein of H. pylori strain J99 (CagAJ99) does not carry any of three putative tyrosine phosphorylation motifs (TPM-A, TPM-B or TPM-C) predicted by the MOTIF algorithm in CagA proteins. CagA,n is not tyrosine phosphorylated and is inactive in the dephosphorylation of host cell proteins. By site-specific mutagenesis,we introduced a TPM-C into CagA,. by replacing a single lysine with a tyrosine. This slight modification resulted in tyrosine phosphorylation of CagAJ99 and host cell protein dephosphorylation. In contrast, the removal of the indigenous TPM-C from CagAP12 did not abolish its tyrosine phosphorylation, suggesting that further phosphorylated sites are present in CagAP12. By generation of hybrid CagA proteins, a phosphorylation of the most N-terminal TPM-A could be excluded. Our data suggest that tyrosine phosphorylation at TPM-C is sufficient, but not exclusive,to activate translocated CagA. Activated CagAPtr might either convert into a phosphatase itself or activate a cellular phosphatase to dephosphorylate cellular phosphoproteins and modulate cellular signalling cascades of the host.     

Capacitation is associated with tyrosine phosphorylation and tyrosine kinase-like activity of pig sperm proteins

Capacitation represents the final maturational steps that render mammalian sperm competent to fertilize, either in vivo or in vitro. Capacitation is defined as a series of events that enables sperm to bind the oocyte and undergo the acrosome reaction in response to the zona pellucida. Although the molecular mechanisms involved are not fully understood, sperm protein phosphorylation is associated with capacitation. The hypothesis of this study is that protein tyrosine phosphorylation and kinase activity mediate capacitation of porcine sperm. Fresh sperm were incubated in noncapacitating or capacitating media for various times. Proteins were extracted with SDS, subjected to SDS-PAGE, and immunoblotted with an antiphosphotyrosine antibody. An M(r) 32 000 tyrosine-phosphorylated protein (designated as p32) appeared only when the sperm were incubated in capacitating medium and concomitant with capacitation as assessed by the ionophore-induced acrosome reaction. The p32 was soluble in Triton X-100. Fractionation of sperm proteins with Triton X-114 demonstrated that after capacitation, this tyrosine phosphoprotein is located in both the cytosol and the membrane. Enzyme renaturation of sperm proteins was conducted in gels with or without either poly glu:tyr (a tyrosine kinase substrate) or kemptide (a protein kinase A substrate). An M(r) 32 000 enzyme with kinase behavior was observed in all gels but was preferentially phosphorylated on tyrosine, as assessed by phosphorimagery and by thin layer chromotography to identify the phosphoamino acids. Indirect immunolocalization showed that the phosphotyrosine residues redistribute to the acrosome during capacitation, which is an appropriate location for a protein involved in the acquisition of fertility.     

Adherence of Candida albicans to host cells

Abstract Research devoted to uncovering the mechanisms of adherence of Candida albicans to human tissue is reviewed. The physical aspects of adherence of the fungus to host cells and the biochemical and molecular features, as far as they are known, are discussed. Relevant pre- and post-adherence events in the pathogenesis of disease caused by this fungus are also noted. Putative adhesins and surface receptors of C. albicans for host proteins are discussed in detail.     

Candida albicans Ecm33p is important for normal cell wall architecture and interactions with host cells

Candida albicans ECM33 encodes a glycosylphosphatidylinositol-linked cell wall protein that is important for cell wall integrity. It is also critical for normal virulence in the mouse model of hematogenously disseminated candidiasis. To identify potential mechanisms through which Ecm33p contributes to virulence, we investigated the interactions of C. albicans ecm33Delta mutants with endothelial cells and the FaDu oral epithelial cell line in vitro. The growth rate of blastospores of strains containing either one or no intact copies of ECM33 was 50% slower than that of strains containing two intact copies of ECM33. However, all strains germinated at the same rate, forming similar-length hyphae on endothelial cells and oral epithelial cells. Strains containing either one or no intact copies of ECM33 had modestly reduced adherence to both types of host cells, and a markedly reduced capacity to invade and damage these cells. Saccharomyces cerevisiae expressing C. albicans ECM33 did not adhere to or invade epithelial cells, suggesting that Ecm33p by itself does not act as an adhesin or invasin. Examination of ecm33Delta mutants by transmission electron microscopy revealed that the cell wall of these strains had an abnormally electron-dense outer mannoprotein layer, which may represent a compensatory response to reduced cell wall integrity. The hyphae of these mutants also had aberrant surface localization of the adhesin Als1p. Collectively, these results suggest that Ecm33p is required for normal cell wall architecture as well as normal function and expression of cell surface proteins in C. albicans.     

N-cadherin mediates endocytosis of Candida albicans by endothelial cells

Candida albicans is the most common cause of fungal bloodstream infections. To invade the deep tissues, blood-borne organisms must cross the endothelial cell lining of the vasculature. We have found previously that C. albicans hyphae, but not blastospores, invade endothelial cells in vitro by inducing their own endocytosis. Therefore, we set out to identify the endothelial cell receptor that mediates the endocytosis of C. albicans. We determined that endocytosis of C. albicans was not mediated by bridging molecules in the serum and that it was partially dependent on the presence of extracellular calcium. Using an affinity purification procedure, we discovered that endothelial cell N-cadherin bound to C. albicans hyphae but not blastospores. N-cadherin also co-localized with C. albicans hyphae that were being endocytosed by endothelial cells. Chinese hamster ovary (CHO) cells expressing human N-cadherin endocytosed significantly more C. albicans hyphae than did CHO cells expressing either human VE-cadherin or no human cadherins. The expression of N-cadherin by the CHO cells resulted in enhanced endocytosis of hyphae, but not blastospores, indicating the selectivity of the N-cadherin-mediated endocytosis. Down-regulation of endothelial cell N-cadherin expression with small interfering RNA significantly inhibited the endocytosis of C. albicans hyphae. Therefore, a novel function of N-cadherin is that it serves as an endothelial cell receptor, which mediates the endocytosis of C. albicans.     

Proteomic analysis of Candida albicans yeast and hyphal cell wall and associated proteins

Candida albicans is an important human pathogen that causes systemic infections, predominantly among populations with weakened immune systems. The morphological transition from the yeast to the hyphal state is one of the key factors in C. albicans pathogenesis. Owing to their location at the host-pathogen interface, the cell wall and associated proteins are of interest, especially with respect to the yeast to hyphal transition. This study entailed the proteomic analysis of differentially regulated proteins involved in this transition. The protein profiles of C. albicans DTT/SDS-extractible proteins and the cyanogen bromide (CNBr)/trypsin-extractable proteins of a cell wall-enriched fraction from yeast and hyphae were compared. In total, 107 spots were identified from the DTT/SDS-extractible cell wall-enriched fraction, corresponding to 82 unique proteins. Of these DTT/SDS-extractible proteins, 14 proteins were upregulated and 10 were downregulated in response to hyphal induction. Approximately 6-9% of total cell wall-protein-enriched fraction was found to be resistant to DTT/SDS extraction. Analysis of the DTT/SDS-resistant fraction using a CNBr/trypsin extraction resulted in the identification of 29 proteins. Of these, 17 were identified only in the hyphae, four were identified only in the yeast, and eight were identified in both the yeast and hyphae.     

Atorvastatin preserves the integrity of endothelial adherens junctions by inhibiting vascular endothelial cadherin tyrosine phosphorylation

Vascular endothelial cadherin (VE-cad) tyrosine (Tyr) phosphorylation has been implicated in the disruption of adherens junctions (AJs) induced by inflammatory reactions. The impacts of statins on integrity of AJs and VE-cad Tyr phosphorylation have not been explored. The effects of atorvastatin on IL-1β and monocyte-induced VE-cad Tyr phosphorylation in human umbilical vein endothelial cells (ECs) were studied. In ECs treated with interleukin (IL)-1β for 30 min, VE-cad Tyr phosphorylation, dissociation of the VE-cad/β-catenin complex and transendothelial migration (TEM) of monocytes were increased. These processes were mediated by activation of HRas and RhoA that leads to phosphorylation of myosin light chain (MLC). Atorvastatin inhibited IL-1β-induced Tyr phosphorylation of VE-cad by inhibiting RhoA and by dephosphorylating MLC. The attenuating effect of atorvastatin on VE-cad Tyr phosphorylation was reversed when RhoA was activated or MLC phosphatase was inhibited. Furthermore, inhibiting farnesyl transferase or geranylgeranyl transferase reproduced the inhibitory effects of atorvastatin on VE-cad Tyr phosphorylation. In addition, atorvastatin inhibited monocyte-induced VE-cad Tyr phosphorylation in ECs and attenuated IL-1β-induced TEM of monocytes. Our study introduces a novel pleiotropic effect of atorvastatin and suggests that statins protect the integrity of AJs in ECs by inhibiting RhoA-mediated Tyr phosphorylation of VE-cad.     

Candida albicans biofilm formation is associated with increased anti-oxidative capacities

Candida albicans is a common, opportunistic, human fungal pathogen that causes a variety of mucosal and systemic afflictions. It exists in nature both in the biofilm or the sessile phase, as well as in the free-floating or the planktonic phase. Candida biofilms, in particular, display unique characteristics that confer survival advantages over their planktonic counterparts, such as their recalcitrance to common antifungals. The mechanisms underlying Candida biofilm formation and their attributes are poorly understood. In this study, we used a 2-DE-based approach to characterize the protein markers that are differentially expressed in Candida biofilms in comparison to their planktonic counterparts. Using tandem mass spectrometric analysis, we have identified a significant number of proteins including alkyl hydroperoxide reductase, thioredoxin peroxidase, and thioredoxin involved in oxidative stress defenses that are upregulated in the biofilm phase. These proteomic findings were further confirmed by real-time PCR and lucigenin-based chemiluminescence assays. In addition, we demonstrate that a drug target for the new antifungal agent echinocandin, is abundantly expressed and significantly upregulated in Candida biofilms. Taken together, these data imply that the biofilm mode, Candida, compared with their planktonic counterparts, exhibits traits that can sustain oxidative stress (anti-oxidants), and thereby exert resistance to commonly used antifungals.     

Changes associated with tyrosine phosphorylation during short-term hypoxia in retinal microvascular endothelial cells in vitro

The occlusion of capillary vessels results in low oxygen tension in adjacent tissues which triggers a signaling cascade that culminates in neovascularization. Using bovine retinal capillary endothelial cells (BRCEC), we investigated the effects of short-term hypoxia on DNA synthesis, phosphotyrosine induction, changes in the expression of basic fibroblast growth factor receptor (bFGFR), protein kinase C (PKCα), heat shock protein 70 (HSP70), and SH2-containing protein (SHC). The effect of protein tyrosine kinase (PTK) and phosphatase inhibitors on hypoxia-induced phosphotyrosine was also studied. Capillary endothelial cells cultured in standard normoxic (pO₂ = 20%) conditions were quiesced in low serum containing medium and then exposed to low oxygen tension or hypoxia (pO₂ = 3%) in humidified, 5% CO₂, 37°C, tissue culture chambers, on a time-course of up to 24 h. DNA synthesis was potentiated by hypoxia in a time-dependent manner. This response positively correlated with the cumulative induction of phosphotyrosine and the downregulation of bFGFR (M_r ～ 85 kDa). Protein tyrosine kinase inhibitors, herbimycin-A, and methyl 2,5-dihydroxycinnamate, unlike genistein, markedly blocked hypoxia-induced phosphotyrosine. Prolonged exposure of cells to phosphatase inhibitor, sodium orthovanadate, also blocked hypoxia-induced phosphotyrosine. The expression of HSP70, PKCα, and SHC were not markedly altered by hypoxia. Taken together, these data suggest that short-term hypoxia activates endothelial cell proliferation in part via tyrosine phosphorylation of cellular proteins and changes in the expression of the FGF receptor. Thus, endothelial cell mitogenesis and neovascularization associated with low oxygen tension may be controlled by abrogating signaling pathways mediated by protein tyrosine kinase and phosphatases. © 1995 Wiley-Liss, Inc.     

Secretion of micronemal proteins is associated with toxoplasma invasion of host cells

Toxoplasma gondii is an obligate intracellular parasite that actively invades a wide variety of vertebrate cells, although the basis of its pervasive cell invasion is not completely understood. Here, we demonstrate, using several independent assays, that Toxoplasma invasion of host cells is tightly coupled to the release of proteins stored within apical secretory granules called micronemes. Both microneme secretion and cell invasion were highly temperature dependent, and partial depletion of microneme resulted in a transient loss of infectivity. Chelation of parasite intracellular calcium strongly inhibited both microneme release and invasion of host cells, and this effect was partially reversed by raising intracellular calcium using the ionophore A23187. We also provide evidence that a staurosporine-sensitive kinase activity regulates microneme discharge and is required for parasite invasion of host cells. Additionally, we demonstrate that, during apical attachment to the host cell, the micronemal protein MIC2 is released at the junction between the parasite and the host cell. During invasion, MIC2 is successively translocated towards the posterior end of the parasite and is shed before entry of the parasite into the vacuole. Furthermore, we show that the full-length cellular form of MIC2, but not the proteolytically modified secreted form of MIC2, binds specifically to host cells. Collectively, these observations strongly imply that micronemal proteins play a role in Toxoplasma invasion of host cells.     

Involvement of host cell tyrosine phosphorylation in the invasion of HEp-2 cells by Bartonella bacilliformis

We have provided evidence that exposure of human cells to protein kinase inhibitors results in decreased invasion of these cells by Bartonella bacilliformis in a dose-dependent manner. Preincubation of human laryngeal epithelial cells in the presence of genistein, a tyrosine protein kinase inhibitor, decreased the invasion of these cells by B. bacilliformis significantly. Further, exposure of normal human umbilical vein endothelial cells to staurosporine, a potent inhibitor of protein kinase C and some tyrosine protein kinases, resulted in a considerable reduction in the number of organisms internalized by these cells. Moreover, Bartonella infection of HEp-2 cells induced tyrosine phosphorylation of several Triton X-100 soluble proteins with approximate molecular masses of 243, 215 179, 172 (doublet), 160, 145 and 110 kDa that were absent or reduced in the presence of genistein in cells after 1 h of infection. Exposure of HEp-2 cell monolayers to anti-alpha 5 and anti-beta 1 chain integrin monoclonal antibodies resulted in a moderate decrease in the invasion of these cells, suggesting a possible role of alpha 5 beta 1 integrins in the uptake of Bartonella into nucleated cells.     

Production of IGF-binding proteins by vascular endothelial cells

Conditioned serum-free media from cultured human, bovine and rodent endothelial cells contained binding proteins with high affinity for the insulin-like growth factors (IGFs). After partial purifications on heparin or Multiplication Stimulating Activity (MSA)-affinity columns, 2 species of binding protein were identified, a major protein having Mr approximately 35,000 and a minor 22-28,000 protein. The binding proteins had greater affinity for IGF-I than IGF-II with no affinity for insulin or proinsulin. Substantial amounts of the binding proteins remained cell-associated, loosely bound to the outer cell surface of the endothelial cell. Binding protein(s) from human endothelial cells cross-reacted with antibodies to the 53,000 dalton acid-stable human serum binding protein. Production of endothelial binding proteins was not stimulated by growth hormone or insulin. We conclude that endothelial cells in culture produce large quantities of specific IGF binding proteins. Such binding proteins should be relevant in understanding the complex metabolism and function of the IGFs in the intact host.     

Stimulation of endothelial cell proliferation by vanadate is specific for microvascular endothelial cells.

Micromolar concentrations of sodium orthovanadate stimulated the proliferation of bovine capillary endothelial cells, but not bovine aortic endothelial cells. Vanadate was equally potent at inducing protein tyrosine phosphorylation and changes in morphology in both types of cells. However, vanadate treatment lead to an inhibition of protein tyrosine kinase activity in the aortic endothelial cells, but not the capillary endothelial cells. In capillary endothelial cells, the effect of vanadate was additive with basic FGF (bFGF) at low concentrations of bFGF. There was no interaction between bFGF and vanadate in aortic endothelial cells. TGF-beta, which inhibits the induction of endothelial cell proliferation by bFGF, appeared to shift the dose response curve to vanadate in capillary endothelial cells, increasing the proliferative effect of vanadate at low vanadate concentrations, but decreasing the proliferative effect at higher vanadate concentrations.     

Als3 is a Candida albicans invasin that binds to cadherins and induces endocytosis by host cells

Candida albicans is the most common cause of hematogenously disseminated and oropharyngeal candidiasis. Both of these diseases are characterized by fungal invasion of host cells. Previously, we have found that C. albicans hyphae invade endothelial cells and oral epithelial cells in vitro by inducing their own endocytosis. Therefore, we set out to identify the fungal surface protein and host cell receptors that mediate this process. We found that the C. albicans Als3 is required for the organism to be endocytosed by human umbilical vein endothelial cells and two different human oral epithelial lines. Affinity purification experiments with wild-type and an als3Δ/als3Δ mutant strain of C. albicans demonstrated that Als3 was required for C. albicans to bind to multiple host cell surface proteins, including N-cadherin on endothelial cells and E-cadherin on oral epithelial cells. Furthermore, latex beads coated with the recombinant N-terminal portion of Als3 were endocytosed by Chinese hamster ovary cells expressing human N-cadherin or E-cadherin, whereas control beads coated with bovine serum albumin were not. Molecular modeling of the interactions of the N-terminal region of Als3 with the ectodomains of N-cadherin and E-cadherin indicated that the binding parameters of Als3 to either cadherin are similar to those of cadherin–cadherin binding. Therefore, Als3 is a fungal invasin that mimics host cell cadherins and induces endocytosis by binding to N-cadherin on endothelial cells and E-cadherin on oral epithelial cells. These results uncover the first known fungal invasin and provide evidence that C. albicans Als3 is a molecular mimic of human cadherins.     

Posttranslational regulation of cyclooxygenase by tyrosine phosphorylation in cerebral endothelial cells

Endothelium-derived cyclooxygenase (COX) products regulatecerebral vascular tone in newborn pigs. Both COX-1 and COX-2 are constitutively expressed in endothelial cells from newborn pig cerebralmicrovessels. We investigated the role of protein phosphorylation inthe regulation of COX activity. The protein tyrosine phosphatase (PTP)inhibitors phenylarsine oxide, vanadate, and benzylphosphonic acidrapidly stimulated COX activity, whereas the protein tyrosine kinaseinhibitors, genistein and tyrphostins, inhibited it. Protein synthesisinhibitors did not reverse the stimulation of COX activity evoked byPTP inhibitors. Similar changes were observed in other vascular cellsfrom newborn pigs that also express COX-1 and COX-2 (cerebralmicrovascular smooth muscle cells and aortic endothelial cells) but notin human umbilical vein endothelial cells or Swiss 3T3 fibroblasts thatexpress COX-1 only. Tyrosine-phosphorylated proteins wereimmunodetected in endothelial cell lysates. COX-2 immunoprecipitatedfrom ³²P-loaded endothelial cellsincorporated ³²P that wasincreased by PTP inhibitors. COX-2, but not COX-1, was detected inendothelial fractions immunoprecipitated with anti-phosphotyrosine.These data indicate that tyrosine phosphorylation posttranslationallyregulates COX activity in newborn pig vascular cells and that COX-2 isa substrate for phosphorylation.

     

Immunochemical characterization of Candida albicans cell wall antigens: specific determinant of Candida albicans serotype A mannan

We investigated the chemical structure of the specific determinant in the mannan of Candida albicans M-1012 (serotype A) strain. Acetolysis of the mannan, obtained by alkali extraction and purified as the copper complex, gave mannose and six oligosaccharides (from di- to hexasaccharide) and a small amount of a heptasaccharide. We examined the inhibition by these oligosaccharides up to hexaose of the precipitin reaction between anti-factor 6 serum specific for serotype A and homologous mannan, and found that the mannohexaose was the most effective inhibitor. These, and results obtained by proton magnetic resonance (PMR) spectroscopy, methylation analysis, and other structural studies, suggest that the main component of this hexaose consists of one terminal alpha (1-3) linkage in addition to four alpha (1-2) linkages, and that this alpha (1-3)-containing mannohexaose may be responsible for the specificity of antigenic factor 6. Further results obtained by analyses of polarimetry, PMR spectroscopy, and chromium trioxide oxidation-methylation of C. albicans M-1012 mannan has a beta-linkage in addition to alpha-linkages, and that the mode of the beta-linkage is mainly (1-6) linkage. Further evidence obtained by Smith degradation-methylation analysis and by quantitative precipitin reactions of intact and acid-degraded mannan suggests that the antigenic determinant of antigenic factor 6 may be bound, via the beta (1-6) linkage, to C-6 of mannose residues involved in oligosaccharide side chains of serotype A mannan.     

Focal adhesion kinase tyrosine phosphorylation is associated with myogenesis and modulated by insulin

Focal adhesion kinase (FAK) was heavily phosphorylated as a function of differentiation of C2C12 mouse skeletal muscle cells. Insulin caused increases in FAK phosphorylation before stabilization in proliferated cells, while in differentiated cells there was a consistent transient inhibition of FAK phosphorylation before stimulation. The expression level of FAK was unaltered. Specific inhibition of insulin receptor tyrosine kinase activity abolished the insulin-mediated dephosphorylation of FAK. The data strongly indicate that FAK tyrosine phosphorylation, necessary for skeletal muscle differentiation, is modulated by insulin. Thus, for the first time, we report the differential regulation of FAK tyrosine phosphorylation by insulin during skeletal muscle differentiation.     

Dysregulation of vascular endothelial growth factor receptor 2 phosphorylation is associated with disruption of the blood-brain barrier and brain endothelial cell apoptosis induced by plasma from women with preeclampsia

Disruption of the blood-brain barrier (BBB) is central in the pathophysiology of acute cerebral complications in women who have preeclampsia. Underling mechanisms are unclear.Using female human brain endothelial cells as an in vitro model of BBB, we show that plasma of women with preeclampsia increases cell apoptosis and permeability via activation of the vascular endothelial growth factor receptor 2 (VEGFR2).Since plasma of women with preeclampsia also enhanced VEGFR2 phosphorylation in the tyrosine 951 but decreased phosphorylation at the tyrosine 1175, we propose the former would be the more likely active form of VEGFR2 responsible for BBB alterations.