Differential regulation of angiopoietin 1 and angiopoietin 2 during dengue virus infection of human umbilical vein endothelial cells: implications for endothelial hyperpermeability

Sevoflurane alleviates inflammation, apoptosis and permeability damage of human umbilical vein endothelial cells induced by lipopolysaccharide by inhibiting endoplasmic reticulum stress via upregulating RORα

Endothelial dysfunction often accompanies sepsis. Sevoflurane (Sev) is a widely used inhaled anesthetic that has a protective effect on sepsis-associated damage. We aimed to elucidate the role of Sev in endothelial dysfunction by using a model of LPS induced HUVECs. Sev increased the viability and decreased the apoptosis of HUVECs exposed to LPS. Inflammation and endothelial cell adhesion were improved after Sev addition. Besides, Sev alleviated LPS-induced endothelial cell permeability damage in HUVECs. RORα served as a potential protein that bound to Sev. Importantly, Sev upregulated RORα expression and inhibited endoplasmic reticulum (ER) stress in LPS-treated HUVECs. RORα silencing reversed the impacts of Sev on ER stress. Moreover, RORα deficiency or tunicamycin (ER stress inducer) treatment restored the effects of Sev on the viability, apoptosis, inflammation and endothelial permeability damage of HUVECs exposed to LPS. Taken together, Sev ameliorated LPS-induced endothelial cell damage by targeting RORα to inhibit ER stress.

Fingolimod (FTY720), an FDA-approved sphingosine 1-phosphate (S1P) receptor agonist, restores endothelial hyperpermeability in cellular and animal models of dengue virus serotype 2 infection

Extensive vascular leakage and shock is a major cause of dengue-associated mortality. At present, there are no specific treatments available. Sphingolipid pathway is a key player in the endothelial barrier integrity; and is mediated through the five sphingosine-1-phosphate receptors (S1PR1-S1PR5). Signaling through S1PR2 promotes barrier disruption; and in Dengue virus (DENV)-infection, there is overexpression of this receptor. Fingolimod (FTY720) is a specific agonist that targets the remaining barrier-protective S1P receptors, without targeting S1PR2. In the present study, we explored whether FTY720 treatment can alleviate DENV-induced endothelial hyperpermeability. In functional assays, in both in vitro systems and in AG129 animal models, FTY720 treatment was found effective. Upon treatment, there was complete restoration of the monolayer integrity in DENV serotype 2-infected human microvascular endothelial cells (HMEC-1). At the molecular level, the treatment reversed activation of the S1P pathway. It significantly reduced the phosphorylation of the key molecules such as PTEN, RhoA, and VE-Cadherin; and also, the expression levels of S1PR2. In DENV2-infected AG129 mice treated with FTY720, there was significant improvement in weight gain, in overall clinical symptoms, and in survival. Whereas 100% of the DENV2-infected, untreated animals died by day-10 post-infection, 70% of the FTY720-treated animals were alive; and at the end of the 15-day post-infection observation period, 30% of them were still surviving. There was a significant reduction in the Evan's-blue dye permeability in the organs of FTY720-treated, DENV-2 infected animals; and also improvement in the hemogram, with complete restoration of thrombocytopenia and hepatic function. Our results show that the FDA-approved molecule Fingolimod (FTY720) is a promising therapeutic intervention in severe dengue.

miR-573 rescues endothelial dysfunction during dengue infection under PPARγ regulation

Early prognosis of abnormal vasculopathy is essential for effective clinical management of severe dengue patients. An exaggerated interferon (IFN) response and release of vasoactive factors from endothelial cells cause vasculopathy. This study shows that dengue 2 (DENV2) infection of human umbilical vein endothelial cells (HUVEC) results in differentially regulated miRNAs important for endothelial function. miR-573 was significantly down-regulated in DENV2-infected HUVEC due to decreased Peroxisome Proliferator Activator Receptor Gamma (PPARγ) activity. Restoring miR-573 expression decreased endothelial permeability by suppressing the expression of vasoactive angiopoietin 2 (ANGPT2). We also found that miR-573 suppressed the proinflammatory IFN response through direct downregulation of toll like receptor 2 (TLR2) expression. Our study provides a novel insight into miR-573 mediated regulation of endothelial function during DENV2 infection which can be further translated into a potential therapeutic and prognostic agent for severe dengue patients. IMPORTANCE: We need to identify molecular factors which can predict the onset of endothelial dysfunction in dengue patients. Increase in endothelial permeability during severe dengue infections is poorly understood. In this study we focus on factors which regulate endothelial function and are dysregulated during DENV2 infection. We show that miR-573 rescues endothelial permeability and is downregulated during DENV2 infection in endothelial cells. This finding can have diagnostic as well as therapeutic applications.

Multifaceted Pathomolecular Mechanism of a VWF Large Deletion Involved in the Pathogenesis of Severe VWD

The present study demonstrates the dominant-negative impact of an in-frame large deletion on VWF biosynthesis and biogenesis of the WPBs.

The malformed WPBs/altered trafficking of its inflammatory cargos cause distresses in endothelial cell signaling pathways and phenotype.

An in-frame heterozygous large deletion of exons 4 through 34 of the von Willebrand factor (VWF) gene was identified in a type 3 von Willebrand disease (VWD) index patient (IP), as the only VWF variant. The IP exhibited severe bleeding episodes despite prophylaxis treatment, with a short VWF half-life after infusion of VWF/factor VIII concentrates. Transcript analysis confirmed transcription of normal VWF messenger RNA besides an aberrant deleted transcript. The IP endothelial colony-forming cells (ECFCs) exhibited a defect in the VWF multimers and Weibel-Palade bodies (WPBs) biogenesis, although demonstrating normal VWF secretion compared with healthy cells. Immunostaining of IP-ECFCs revealed subcellular mislocalization of WPBs pro-inflammatory cargos angiopoietin-2 (Ang2, nuclear accumulation) and P-selectin. Besides, the RNA-sequencing (RNA-seq) analysis showed upregulation of pro-inflammatory and proangiogenic genes, P-selectin, interleukin 8 (IL-8), IL-6, and GROα, copackaged with VWF into WPBs. Further, whole-transcriptome RNA-seq and subsequent gene ontology (GO) enrichment analysis indicated the most enriched GO-biological process terms among the differentially expressed genes in IP-ECFCs were regulation of cell differentiation, cell adhesion, leukocyte adhesion to vascular endothelial, blood vessel morphogenesis, and angiogenesis, which resemble downstream signaling pathways associated with inflammatory stimuli and Ang2 priming. Accordingly, our functional experiments exhibited an increased endothelial cell adhesiveness and interruption in endothelial cell–cell junctions of the IP-ECFCs. In conclusion, the deleted VWF has a dominant-negative impact on multimer assembly and the biogenesis of WPBs, leading to altered trafficking of their pro-inflammatory cargos uniquely, which, in turn, causes changes in cellular signaling pathways, phenotype, and function of the endothelial cells.

The emerging role of perivascular cells (pericytes) in viral pathogenesis

Viruses may exploit the cardiovascular system to facilitate transmission or within-host dissemination, and the symptoms of many viral diseases stem at least in part from a loss of vascular integrity. The microvascular architecture is comprised of an endothelial cell barrier ensheathed by perivascular cells (pericytes). Pericytes are antigen-presenting cells (APCs) and play crucial roles in angiogenesis and the maintenance of microvascular integrity through complex reciprocal contact-mediated and paracrine crosstalk with endothelial cells. We here review the emerging ways that viruses interact with pericytes and pay consideration to how these interactions influence microvascular function and viral pathogenesis. Major outcomes of virus-pericyte interactions include vascular leakage or haemorrhage, organ tropism facilitated by barrier disruption, including viral penetration of the blood-brain barrier and placenta, as well as inflammatory, neurological, cognitive and developmental sequelae. The underlying pathogenic mechanisms may include direct infection of pericytes, pericyte modulation by secreted viral gene products and/or the dysregulation of paracrine signalling from or to pericytes. Viruses we cover include the herpesvirus human cytomegalovirus (HCMV, Human betaherpesvirus 5), the retrovirus human immunodeficiency virus (HIV; causative agent of acquired immunodeficiency syndrome, AIDS, and HIV-associated neurocognitive disorder, HAND), the flaviviruses dengue virus (DENV), Japanese encephalitis virus (JEV) and Zika virus (ZIKV), and the coronavirus severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2; causative agent of coronavirus disease 2019, COVID-19). We touch on promising pericyte-focussed therapies for treating the diseases caused by these important human pathogens, many of which are emerging viruses or are causing new or long-standing global pandemics.

Arginine vasopressin receptor 2 activation promotes microvascular permeability in sepsis

Methicillin-resistant Staphylococcus aureus (MRSA) sepsis is a severe condition associated with vascular leakage and poor prognosis. The hemodynamic management of sepsis targets hypotension, but there is no specific treatment available for vascular leakage. Arginine vasopressin (AVP) has been used in sepsis to promote vasoconstriction by activating AVP receptor 1 (V₁R). However, recent evidence suggests that increased fluid retention may be associated with the AVP receptor 2 (V₂R) activation worsening the outcome of sepsis. Hence, we hypothesized that the inhibition of V₂R activation ameliorates the severity of microvascular hyperpermeability during sepsis. The hypothesis was tested using a well-characterized and clinically relevant ovine model of MRSA pneumonia/sepsis and in vitro assays of human lung microvascular endothelial cells (HMVECs). in vivo experiments demonstrated that the treatment of septic sheep with tolvaptan (TLVP), an FDA-approved V₂R antagonist, significantly attenuated the sepsis-induced fluid retention and markedly reduced the lung water content. These pathological changes were not affected by the treatment with V₂R agonist, desmopressin (DDAVP). Additionally, the incubation of cultured HMVECs with DDAVP, and DDAVP along with MRSA significantly increased the paracellular permeability. Finally, both the DDAVP and MRSA-induced hyperpermeability was significantly attenuated by TLVP. Subsequent protein and gene expression assays determined that the V₂R-induced increase in permeability is mediated by phospholipase C beta (PLCβ) and the potent permeability factor angiopoietin-2. In conclusion, our results indicate that the activation of the AVP-V₂R axis is critical in the pathophysiology of severe microvascular hyperpermeability during Gram-positive sepsis. The use of the antagonist TLVP should be considered as adjuvant treatment for septic patients. The results from this clinically relevant animal study are highly translational to clinical practice.

Transcriptome Analysis Revealed Inflammation Is Involved in the Impairment of Human Umbilical Vein Endothelial Cells Induced by Post-hemorrhagic Shock Mesenteric Lymph

Vascular endothelial injury caused by post-hemorrhagic shock mesenteric lymph (PHSML) return is an important manifestation during refractory hemorrhagic shock. Using human umbilical vein endothelial cells (HUVECs) and transcriptome analysis, this study sought to investigate the molecular mechanism underlying the adverse effect of PHSML on vascular endothelium. Post-hemorrhagic shock mesenteric lymph was collected from male rats after they underwent hemorrhagic shock and following resuscitation, while normal mesenteric lymph (NML) was harvested from sham rats. Human umbilical vein endothelial cells were incubated with the culture medium containing either 10% phosphate buffered saline (Control), NML, or PHSML for 3 h, and then were harvested for RNA sequencing. In comparison with NML treated cells, 37 genes were differentially expressed in PHSML-treated HUVECs, including 32 upregulated genes and five downregulated genes. These differentially expressed genes were mainly enriched in inflammatory pathways, including signaling pathways for activation of the NOD-like receptors, NF-κB, and TNF. Furthermore, we found that C-C motif chemokine ligand 2 (CCL2) was increased significantly after PHSML treatment, and Bindarit, a CCL2 production inhibitor, attenuated the damage of HUVECs induced by PHSML. The results provide molecular evidence on vascular endothelium damage caused by PHSML. C-C motif chemokine ligand 2 might represent a new target for reducing vascular injury after severe hemorrhagic shock.

High Levels of Serum Angiopoietin 2 and Angiopoietin 2/1 Ratio at the Critical Stage of Dengue Hemorrhagic Fever in Patients and Association with Clinical and Biochemical Parameters

Longitudinal changes of serum angiopoietin 1 (Ang-1) and angiopoietin 2 (Ang-2) associated with endothelial stability in dengue patients with different disease stages were studied. Serum Ang-1 and Ang-2 levels were measured in confirmed dengue fever (DF) patients on admission (DFA, n = 40) and discharge (DFD, n = 20); in dengue hemorrhagic fever (DHF) patients on admission (DHFA, n = 40), at critical stage (DHFC, n = 36), and on discharge (DHFD, n = 20); and in healthy controls (HC, n = 25). DHFC had the highest serum Ang-2 and lowest Ang-1 levels compared to DFA, DHFA, and HC (P < 0.050). The ratio of serum Ang-2/Ang-1 in DHFC was the highest among all study categories tested (P < 0.001). Significant positive correlations were observed between serum Ang-1 and platelet count in DHFA (Pearson r = 0.653, P < 0.001) and between Ang-1 and pulse pressure in DHFC (r = 0.636, P = 0.001). Using a cutoff value of 1.01 for the Ang-2/Ang-1 ratio for DHFC, a sensitivity of 83.2% and a specificity of 81.2% discerning DF from DHF were obtained. Therefore, serum Ang-2/Ang-1 could be used as a biomarker for endothelial dysfunction in severe dengue at the critical stage.

The identification of differentially expressed genes between extremes of placental efficiency in maternal line gilts on day 95 of gestation

Background

Placental efficiency (PE) describes the relationship between placental and fetal weights (fetal wt/placental wt). Within litters, PE can vary drastically, resulting in similarly sized pigs associated with differently sized placentas, up to a 25% weight difference. However, the mechanisms enabling the smaller placenta to grow a comparable littermate are unknown. To elucidate potential mechanisms, morphological measurements and gene expression profiles in placental and associated endometrial tissues of high PE and low PE feto-placental units were compared. Tissue samples were obtained from eight maternal line gilts during gestational day 95 ovario-hysterectomies. RNA was extracted from tissues of feto-placental units with the highest and lowest PE in each litter and sequenced.

Results

Morphological measurements, except placental weight, were not different (P > 0.05) between high and low PE. No DEG were identified in the endometrium and 214 DEG were identified in the placenta (FDR < 0.1), of which 48% were upregulated and 52% were downregulated. Gene ontology (GO) analysis revealed that a large percentage of DEG were involved in catalytic activity, binding, transporter activity, metabolism, biological regulation, and localization. Four GO terms were enriched in the upregulated genes and no terms were enriched in the downregulated genes (FDR < 0.05). Eight statistically significant correlations (P < 0.05) were identified between the morphological measurements and DEG.

Conclusion

Morphological measures between high and low PE verified comparisons were of similarly sized pigs grown on different sized placentas, and indicated that any negative effects of a reduced placental size on fetal growth were not evident by day 95. The identification of DEG in the placenta, but absence of DEG in the endometrium confirmed that the placenta responds to the fetus. The GO analyses provided evidence that extremes of PE are differentially regulated, affecting components of placental transport capacity like nutrient transport and blood flow. However, alternative GO terms were identified, indicating the complexity of the relationship between placental and fetal weights. These findings support the use of PE as a marker of placental function and provide novel insight into the genetic control of PE, but further research is required to make PE production applicable.

Dengue virus or NS1 protein induces trans-endothelial cell permeability associated with VE-Cadherin and RhoA phosphorylation in HMEC-1 cells preventable by Angiopoietin-1

A transient increase in trans-endothelial cell permeability in dengue patients leads to vascular leakage and shock syndrome. Here, we analysed the molecular mechanisms that cause permeability changes in human dermal microvascular endothelial cells (HMEC-1) using a direct dengue virus (DENV) infection model or treatment with NS1, a secreted DENV non-structural protein. In HMEC-1 cells, both treatments increase permeability with a concordant increase in the secretion of angiopoietin-2 (Ang-2). There is phosphorylation and loss of the junction protein VE-Cadherin from the inter-endothelial cell junctions and phosphorylation of RhoA. Direct virus infection results in activation of Src by phosphorylation, whereas NS1 treatment alone does not lead to Src activation. Furthermore, treatment with recombinant Ang-1, a physiological antagonist of Ang-2, prevents Ang-2 release, VE-Cadherin phosphorylation and internalization, and phosphorylation of RhoA and Src, resulting in restoration of barrier function. The permeability increase could also be prevented by blocking the Ang1/2 signalling receptor, Tie-2, or using a Rho/ROCK-specific inhibitor. Dasatinib, a Src-family kinase (SFK) inhibitor that inhibits Src phosphorylation, prevents enhanced permeability induced by direct DENV infection whereas in NS1 protein-treated cells its effect is less significant. The results provide important insights on the mechanisms of increased trans-endothelial permeability in DENV infection, and suggest the therapeutic potential of using recombinant Ang-1 or targeting these key molecules to prevent vascular leakage in dengue.

High dengue virus load differentially modulates human microvascular endothelial barrier function during early infection

Plasma leakage is the main pathophysiological feature in severe dengue, resulting from altered vascular barrier function associated with an inappropriate immune response triggered upon infection. The present study investigated functional changes using an electric cell-substrate impedance sensing system in four (brain, dermal, pulmonary and retinal) human microvascular endothelial cell (MEC) lines infected with purified dengue virus, followed by assessment of cytokine profiles and the expression of inter-endothelial junctional proteins. Modelling of changes in electrical impedance suggests that vascular leakage in dengue-infected MECs is mostly due to the modulation of cell-to-cell interactions, while this loss of vascular barrier function observed in the infected MECs varied between cell lines and DENV serotypes. High levels of inflammatory cytokines (IL-6 and TNF-α), chemokines (CXCL1, CXCL5, CXCL11, CX3CL1, CCL2 and CCL20) and adhesion molecules (VCAM-1) were differentially produced in the four infected MECs. Further, the tight junctional protein, ZO-1, was down-regulated in both the DENV-1-infected brain and pulmonary MECs, while claudin-1, PECAM-1 and VE-cadherin were differentially expressed in these two MECs after infection. Non-purified virus stock was also studied to investigate the impact of virus stock purity on dengue-specific immune responses, and the results suggest that virus stock propagated through cell culture may include factors that mask or alter the DENV-specific immune responses of the MECs. The findings of the present study show that high DENV load differentially modulates human microvascular endothelial barrier function and disrupts the function of inter-endothelial junctional proteins during early infection with organ-specific cytokine production.

Exposure to endosulfan increases endothelial permeability by transcellular and paracellular pathways in relation to cardiovascular diseases

Exposure to environmental pollutants results in out-of-balance of vascular homeostasis. Endothelial dysfunction leads to a disruption of the endothelial permeability characteristics, associated with cardiovascular diseases. We previously reported that endosulfan could cause endothelial dysfunction, but the role of endosulfan in permeability of endothelial cells has been unexplored. To elucidate molecular mechanism of endosulfan-induced changes in endothelial permeability, human umbilical vein endothelial cells (HUVECs) were exposed to endosulfan, followed by endothelial permeability analysis. The results showed that permeability of HUVECs was enhanced at 48 h after exposure to endosulfan in a dose-dependent manner. Immunofluorescence analysis demonstrated the disruptions of actin cytoskeleton and focal adhesion in endosulfan-exposed cells. Endosulfan activated MMP3/LAMC1/FAK signaling pathway, and downregulated ROCK and PXN in transcellular pathway. Endosulfan affected adherens junctions via E-cadherin and β-catenin, and impaired gap junctions through downregulation of Cx43 in paracellular pathway. We predicted four closely related human cardiovascular diseases in Nextbio, including shock, coronary arteriosclerosis, disorder of cardiac function and hypertensive disorder in relation to endosulfan exposure. Some genes such as ROCK2 and PXN were predicted to be key genes in these diseases. These findings suggest that endosulfan increased endothelial permeability by paracellular and transcellular pathways, implicating the potential correlation between endosulfan and cardiovascular diseases.

Association of Microvascular Function and Endothelial Biomarkers With Clinical Outcome in Dengue: An Observational Study

Background. The hallmark of severe dengue is increased microvascular permeability, but alterations in the microcirculation and their evolution over the course of dengue are unknown.

Methods. We conducted a prospective observational study to evaluate the sublingual microcirculation using side-stream dark-field imaging in patients presenting early (<72 hours after fever onset) and patients hospitalized with warning signs or severe dengue in Vietnam. Clinical findings, microvascular function, global hemodynamics assessed with echocardiography, and serological markers of endothelial activation were determined at 4 time points.

Results. A total of 165 patients were enrolled. No difference was found between the microcirculatory parameters comparing dengue with other febrile illnesses. The proportion of perfused vessels (PPV) and the mean flow index (MFI) were lower in patients with dengue with plasma than those without leakage (PPV, 88.1% vs 90.6% [P = .01]; MFI, 2.1 vs 2.4 [P = .007]), most markedly during the critical phase. PPV and MFI were correlated with the endothelial activation markers vascular cell adhesion molecule 1 (P < .001 for both) and angiopoietin 2 (P < .001 for both), negatively correlated.

Conclusions. Modest microcirculatory alterations occur in dengue, are associated with plasma leakage, and are correlate with molecules of endothelial activation, angiopoietin 2 and vascular cell adhesion molecule 1.

Regulators of endothelial integrity as severity predictors in dengue

INTRODUCTION

Dengue is currently among the mosquito-borne diseases of greatest global impact. The clinical course of the disease can be unpredictable, so proper handling in its early stages is critical to ensure optimal outcomes. 

OBJECTIVE

To evaluate serum regulators of endothelial integrity (VEGF, sICAM-1, sEndoglina, Ang-1, and Ang-2) as predictive markers of dengue severity. 

MATERIALS AND METHODS

We conducted a case-control study nested in an appropriate cohort. Endothelial regulator levels were first measured by ELISA, after which analysis was performed using logistic regression of clinical and regulatory variables, with severity as an output variable. A possible severity prediction model, based on the variables of interest and output, was defined using the best area under the ROC curve. 

RESULTS

The median subject age was 24 years. Severe cases were associated with Ang-2 serum levels of ≥1,490 ng/ml (OR=3.1; p=0.015). Serum levels of Ang-2 (≥1,490 ng/ml) contributed to the severity prediction model, as did a 0.73 area under the ROC curve, together with the variables rash, impaired consciousness and abdominal pain, with an OR of 3.2 (CI 95%: 1.16 to 8.9; p=0.024). 

CONCLUSION

The endothelial regulator Ang-2 could be a predictor of severity in dengue.

Posthemorrhagic shock mesenteric lymph enhances monolayer permeability via F-actin and VE-cadherin

BACKGROUND

Vascular hyperpermeability plays a critical role in the development of refractory hypotension after severe hemorrhagic shock. Posthemorrhagic shock mesenteric lymph (PHSML) return has been shown to be involved in regulation of vascular hyperpermeability. The present study was conducted to investigate the effect of PHSML on permeability of endothelial cells in vitro.

MATERIALS AND METHODS

A hemorrhagic shock model (40 ± 2 mm Hg for 90 min, followed by fluid resuscitation) was used for collection of PHSML. Two separated PHSMLs were collected from period 0-3 h (early) and period 3-6 h (late) after resuscitation and diluted into concentration of 4% or 10%. The human umbilical vein endothelial cells (HUVECs) were then treated with these PHSMLs for 6 h. The monolayer cellular permeability to FITC-albumin was observed by using the costar transwell system. The multiple approaches including scanning electron microscope, fluorescent cytochemistry staining, and Western blotting were also used to assess the changes in cellular morphologic and the expressions of F-actin and VE-cadherin.

RESULTS

The treatments with either early or late PHSML resulted in morphologic injuries, increased cellular permeability, and decreased expression of F-actin in HUVECs. In contrast, only early PHSML, but not late PHSML, reduced the VE-cadherin expression.

CONCLUSIONS

These results indicate that the PHSML in vitro increases the cellular permeability of HUVECs through suppression of F-actin and VE-cadherin.

Potential prognostic markers for predicting onset of dengue hemorrhagic fever

Dengue is fast evolving as a global infectious disease with more than 390 million infections reported annually. Despite the considerable amount of research, there are no effective vaccines for dengue and the clinical management of the disease solely relies on the effective medical care and supportive treatment of the patients. Rapid diagnosis and early prediction of the severity of the disease will not only aid the clinical management of the disease but also enable efficient utilization of the medical resources in the resource-poor dengue endemic regions. In this review, we have focused on certain diagnostic and prognostic biomarkers for dengue infection which could have a predictive potential for disease severity in the clinical scenario.

Endothelial dysfunction in dengue virus pathology

Dengue virus (DENV) is a leading cause of illness and death, mainly in the (sub)tropics, where it causes dengue fever and/or the more serious diseases dengue hemorrhagic fever and dengue shock syndrome that are associated with changes in vascular permeability. Despite extensive research, the pathogenesis of DENV is still poorly understood and, although endothelial cells represent the primary fluid barrier of the blood vessels, the extent to which these cells contribute to DENV pathology is still under debate. The primary target cells for DENV are dendritic cells and monocytes/macrophages that release various chemokines and cytokines upon infection, which can activate the endothelium and are thought to play a major role in DENV-induced vascular permeability. However, recent studies indicate that DENV also replicates in endothelial cells and that DENV-infected endothelial cells may directly contribute to viremia, immune activation, vascular permeability and immune targeting of the endothelium. Also, the viral non-structural protein-1 and antibodies directed against this secreted protein have been reported to be involved in endothelial cell dysfunction. This review provides an extensive overview of the effects of DENV infection on endothelial cell physiology and barrier function.

Serum angiopoietin-2 and soluble VEGF receptor 2 are surrogate markers for plasma leakage in patients with acute dengue virus infection

BACKGROUND

Endothelial cell dysfunction is believed to play an important role in the pathogenesis of plasma leakage in patients with acute dengue virus (DENV) infection. Several factors, produced by activated endothelial cells, have been associated with plasma leakage or severe disease in patients with infectious diseases.

OBJECTIVES

The aim of this study was to investigate which of these markers could serve as a surrogate marker for the occurrence of plasma leakage in patients with acute DENV infection.

STUDY DESIGN

A case-control study was performed in patients with acute DENV infection in Santos, Brazil. Plasma leakage was detected with X-ray and/or ultrasound examination at admission. Serum levels of soluble endoglin, endothelin-1, angiopoietin-2, VEGF, soluble VEGFR-2, MMP-2, MMP-9, TIMP-1 and TIMP-2 were determined using commercially available ELISAs.

RESULTS

Increased levels of angiopoietin-2, endothelin-1 and MMP-2 and decreased levels of soluble VEGFR-2 were significantly associated with the occurrence of plasma leakage. An unsupervised cluster analysis confirmed that angiopoietin-2 and soluble VEGFR-2 were strongly associated with clinical apparent vascular leakage.

CONCLUSION

Angiopoietin-2 and soluble VEGFR-2 can serve as surrogate markers for the occurrence of plasma leakage in patients with acute DENV infection.