Endothelial activation and repair during hantavirus infection: association with disease outcome

The Endothelial Glycocalyx in Pig-to-Baboon Cardiac Xenotransplantation-First Insights

Cardiac xenotransplantation has seen remarkable success in recent years and is emerging as the most promising alternative to human cardiac allotransplantation. Despite these achievements, acute vascular rejection still presents a challenge for long-term xenograft acceptance and new insights into innate and adaptive immune responses as well as detailed characterizations of signaling pathways are necessary. In allotransplantation, endothelial cells and their sugar-rich surface-the endothelial glycocalyx-are known to influence organ rejection. In xenotransplantation, however, only in vitro data exist on the role of the endothelial glycocalyx so far. Thus, in the current study, we analyzed the changes of the endothelial glycocalyx components hyaluronan, heparan sulfate and syndecan-1 after pig-to-baboon cardiac xenotransplantations in the perioperative (n = 4) and postoperative (n = 5) periods. These analyses provide first insights into changes of the endothelial glycocalyx after pig-to-baboon cardiac xenotransplantation and show that damage to the endothelial glycocalyx seems to be comparable or even less pronounced than in similar human settings when current strategies of cardiac xenotransplantation are applied. At the same time, data from the experiments where current strategies, like non-ischemic preservation, growth inhibition or porcine cytomegalovirus (a porcine roseolovirus (PCMV/PRV)) elimination could not be applied indicate that damage of the endothelial glycocalyx also plays an important role in cardiac xenotransplantation.

Soluble Endoglin and Syndecan-1 levels predicts the clinical outcome in COVID-19 patients

Endothelial instability is reported to be involved in the pathogenesis of COVID-19. The mechanism that regulates the endothelial dysfunction and disease virulence is not known. Studies on proteins that are released into circulation by activated endothelial cells may provide some means to understand the disease manifestation. The study investigated the circulating levels of two molecules Endoglin (Eng) and Syndecan-1 (SDC-1) that are presumed to be involved in the maintenance of endothelial integrity and their association with hypercoagulation marker in COVID-19 patients. The serum levels of Eng, SDC-1, D-mer were evaluated using ELISA at the time of admission (DOA) and day 7 post-admission among COVID-19 patients (N = 39 with 17 moderate and 22 severe cases). Compared to the time of admission, there was an increase in sEng and sSDC1 levels in all COVID-19 cases on day 7 post admission. The serum levels of sEng and sSDC-1 was significantly (P ≤ 0.001 & P ≤ 0.01 respectively) elevated in severe cases including the four deceased group compared to moderate cases on day 7 post admission. Further, the study molecules showed a strong positive association (P ≤ 0.001) with the hypercoagulation marker D-mer. The results show an early shedding of the endothelial proteins sEng and sSDC-1 into circulation as a host response to the viral infection during the febrile phase of infection. Increased levels of sEng and sSDC-1 along with D-mer could be beneficial in predicting COVID-19 disease severity.

Direct and indirect effects of Puumala hantavirus on platelet function

Thrombocytopenia is a cardinal symptom of hantavirus-induced diseases including Puumala virus (PUUV)-induced hemorrhagic fever with renal syndrome (HFRS), which is associated with impaired platelet function, bleeding manifestations and augmented thrombotic risk. However, the underlying mechanisms causing thrombocytopenia and platelet hypo-responsiveness are unknown. Thus, we investigated the direct and indirect impact of PUUV on platelet production, function and degradation. Analysis of PUUV-HFRS patient blood revealed that platelet hypo-responsiveness in PUUV infection was cell-intrinsic and accompanied by reduced platelet-leukocyte aggregates (PLAs) and upregulation of monocyte tissue factor (TF), whereas platelet vasodilator-stimulated phosphoprotein (VASP) phosphorylation was comparable to healthy controls. Plasma CXCL4 levels followed platelet count dynamics throughout disease course. PUUV activated both neutrophils and monocytes in vitro, but platelet desialylation, degranulation and GPIIb/IIIa activation as well as PLA formation and endothelial adhesion under flow remained unaltered in the presence of PUUV. Further, MEG-01 megakaryocytes infected with PUUV displayed unaltered polyploidization, expression of surface receptors and platelet production. However, infection of endothelial cells with PUUV significantly increased platelet sequestration. Our data thus demonstrate that although platelet production, activation or degradation are not directly modulated, PUUV indirectly fosters thrombocytopenia by sequestration of platelets to infected endothelium. Upregulation of immunothrombotic processes in PUUV-HFRS may further contribute to platelet dysfunction and consumption. Given the pathophysiologic similarities of hantavirus infections, our findings thus provide important insights into the mechanisms underlying thrombocytopenia and highlight immune-mediated coagulopathy as potential therapeutic target.

Circulating Syndecan-1 Levels Are Associated with Chronological Coagulofibrinolytic Responses and the Development of Disseminated Intravascular Coagulation (DIC) after Trauma: A Retrospective Observational Study

BACKGROUND

The purpose of this study was to evaluate the association between endotheliopathy represented by high levels of circulating syndecan-1 (SDC-1) and coagulofibrinolytic responses due to trauma, which can lead to disseminated intravascular coagulation (DIC).

METHODS

We retrospectively evaluated 48 eligible trauma patients immediately admitted to our hospital and assessed SDC-1 and coagulofibrinolytic parameters for 7 days after admission. We compared the longitudinal changes of coagulofibrinolytic parameters and SDC-1 levels between two groups (high and low SDC-1) according to median SDC-1 value on admission.

RESULTS

The median circulating SDC-1 level was 99.6 (61.1-214.3) ng/mL on admission, and levels remained high until 7 days after admission. Coagulofibrinolytic responses assessed by biomarkers immediately after trauma were correlated with SDC-1 elevation (thrombin-antithrombin complex, TAT: r = 0.352, p = 0.001; antithrombin, AT: r = -0.301, p < 0.001; plasmin-α₂-plasmin inhibitor complex, PIC: r = 0.503, p = 0.035; tissue plasminogen activator, tPA: r = 0.630, p < 0.001). Sustained SDC-1 elevation was associated with intense and prolonged coagulation activation, impairment of anticoagulation, and fibrinolytic activation followed by inhibition of fibrinolysis, which are the primary responses associated with development of DIC in the acute phase of trauma. Elevation of circulating SDC-1 level was also associated with consumption coagulopathy and the need for transfusion, which revealed a significant association between high SDC-1 levels and the development of DIC after trauma (area under the curve, AUC = 0.845, cut-off value = 130.38 ng/mL, p = 0.001).

CONCLUSIONS

High circulating levels of syndecan-1 were associated with intense and prolonged coagulation activation, impairment of anticoagulation, fibrinolytic activation, and consumption coagulopathy after trauma. Endotheliopathy represented by SDC-1 elevation was associated with trauma induced coagulopathy, which can lead to the development of DIC.

High levels of exfoliated fragments following glycocalyx destruction in hemorrhagic fever with the renal syndrome are associated with mortality risk

Background

The glycocalyx is a gel-like structure that covers the luminal side of vascular endothelial cells. It plays an important role in maintaining the integrity of the vascular endothelial barrier structure. However, the presence or absence of glycocalyx destruction in hemorrhagic fever with renal syndrome (HFRS) and its specific mechanism and role is still unclear.

Methods

In this study, we detected the levels of exfoliated glycocalyx fragments, namely, heparan sulfate (HS), hyaluronic acid (HA), and chondroitin sulfate (CS), in HFRS patients and investigated their clinical application value on the evaluation of disease severity and prognosis prediction.

Results

The expression of exfoliated glycocalyx fragments in plasma was significantly increased during the acute stage of HFRS. The levels of HS, HA, and CS in HFRS patients during the acute stage were significantly higher than in healthy controls and convalescent stages of the same type. HS and CS during the acute stage gradually increased with the aggravation of HFRS, and both fragments showed a significant association with disease severity. In addition, exfoliated glycocalyx fragments (especially HS and CS) showed a significant correlation with conventional laboratory parameters and hospitalization days. High levels of HS and CS during the acute phase were significantly associated with patient mortality and demonstrated an obvious predictive value for the mortality risk of HFRS.

Conclusion

Glycocalyx destruction and shedding may be closely associated with endothelial hyperpermeability and microvascular leakage in HFRS. The dynamic detection of the exfoliated glycocalyx fragments may be beneficial for the evaluation of disease severity and prognosis prediction in HFRS.

Increased Heparanase Levels in Urine during Acute Puumala Orthohantavirus Infection Are Associated with Disease Severity

Old–world orthohantaviruses cause hemorrhagic fever with renal syndrome (HFRS), characterized by acute kidney injury (AKI) with transient proteinuria. It seems plausible that proteinuria during acute HFRS is mediated by the disruption of the glomerular filtration barrier (GFB) due to vascular leakage, a hallmark of orthohantavirus–caused diseases. However, direct infection of endothelial cells by orthohantaviruses does not result in increased endothelial permeability, and alternative explanations for vascular leakage and diminished GFB function are necessary. Vascular integrity is partly dependent on an intact endothelial glycocalyx, which is susceptible to cleavage by heparanase (HPSE). To understand the role of glycocalyx degradation in HFRS–associated proteinuria, we investigated the levels of HPSE in urine and plasma during acute, convalescent and recovery stages of HFRS caused by Puumala orthohantavirus. HPSE levels in urine during acute HFRS were significantly increased and strongly associated with the severity of AKI and other markers of disease severity. Furthermore, increased expression of HPSE was detected in vitro in orthohantavirus–infected podocytes, which line the outer surfaces of glomerular capillaries. Taken together, these findings suggest the local activation of HPSE in the kidneys of orthohantavirus–infected patients with the potential to disrupt the endothelial glycocalyx, leading to increased protein leakage through the GFB, resulting in high amounts of proteinuria.

Endothelial glycocalyx degradation during sepsis: Causes and consequences

•

The endothelial glycocalyx is a ubiquitous intravascular structure essential for vascular homeostasis.

•

During sepsis, the glycocalyx is degraded via the collective action of a variety of redundant sheddases, the regulation of which remains the focus of active investigation.

•

Septic loss of the glycocalyx imparts both local vascular injury (leading to acute respiratory distress syndrome and acute kidney injury) as well as the systemic consequences of circulating glycosaminoglycan fragments (leading to cognitive dysfunction).

•

Glycocalyx degradation during sepsis is potentially shaped by clinically-modifiable factors, suggesting opportunities for therapeutic intervention to mitigate the end-organ consequences of sepsis.

The glycocalyx is a ubiquitous structure found on endothelial cells that extends into the vascular lumen. It is enriched in proteoglycans, which are proteins attached to the glycosaminoglycans heparan sulfate, chondroitin sulfate, dermatan sulfate, keratan sulfate, and hyaluronic acid. In health and disease, the endothelial glycocalyx is a central regulator of vascular permeability, inflammation, coagulation, and circulatory tonicity. During sepsis, a life-threatening syndrome seen commonly in hospitalized patients, the endothelial glycocalyx is degraded, significantly contributing to its many clinical manifestations. In this review we discuss the intrinsically linked mechanisms responsible for septic endothelial glycocalyx destruction: glycosaminoglycan degradation and proteoglycan cleavage. We then examine the consequences of local endothelial glycocalyx loss to several organ systems and the systemic consequences of shed glycocalyx constituents. Last, we explore clinically relevant non-modifiable and modifiable factors that exacerbate or protect against endothelial glycocalyx shedding during sepsis.

Coagulopathy in Acute Puumala Hantavirus Infection

Puumala hantavirus (PUUV) causes a hemorrhagic fever with renal syndrome (HFRS), also called nephropathia epidemica (NE), which is mainly endemic in Europe and Russia. The clinical features include a low platelet count, altered coagulation, endothelial activation, and acute kidney injury (AKI). Multiple connections between coagulation pathways and inflammatory mediators, as well as complement and kallikrein–kinin systems, have been reported. The bleeding symptoms are usually mild. PUUV-infected patients also have an increased risk for disseminated intravascular coagulation (DIC) and thrombosis.

The Endothelial Glycocalyx as a Double-Edged Sword in Microvascular Homeostasis and Pathogenesis

Expressed on the endothelial cell (EC) surface of blood vessels, the glycocalyx (GCX), a mixture of carbohydrates attached to proteins, regulates the access of cells and molecules in the blood to the endothelium. Besides protecting endothelial barrier integrity, the dynamic microstructure of the GCX confers remarkable functions including mechanotransduction and control of vascular tone. Recently, a novel perspective has emerged supporting the pleiotropic roles of the endothelial GCX (eGCX) in cardiovascular health and disease. Because eGCX degradation occurs in certain pathological states, the circulating levels of eGCX degradation products have been recognized to have diagnostic or prognostic values. Beyond their biomarker roles, certain eGCX fragments serve as pathogenic factors in disease progression. Pharmacological interventions that attenuate eGCX degradation or restore its integrity have been sought. This review provides our current understanding of eGCX structure and function across the microvasculature in different organs. We also discuss disease or injury states, such as infection, sepsis and trauma, where eGCX dysfunction contributes to severe inflammatory vasculopathy.

The Clinical Presentation of Puumala Hantavirus Induced Hemorrhagic Fever with Renal Syndrome Is Related to Plasma Glucose Concentration

Puumala hantavirus (PUUV) causes a hemorrhagic fever with renal syndrome characterized by thrombocytopenia, increased capillary leakage, and acute kidney injury (AKI). As glucosuria at hospital admission predicts the severity of PUUV infection, we explored how plasma glucose concentration associates with disease severity. Plasma glucose values were measured during hospital care in 185 patients with PUUV infection. They were divided into two groups according to maximum plasma glucose concentration: P-Gluc < 7.8 mmol/L (n = 134) and P-Gluc ≥ 7.8 mmol/L (n = 51). The determinants of disease severity were analyzed across groups. Patients with P-Gluc ≥7.8 mmol/L had higher hematocrit (0.46 vs. 0.43; p < 0.001) and lower plasma albumin concentration (24 vs. 29 g/L; p < 0.001) than patients with P-Gluc < 7.8 mmol/L. They presented with higher prevalence of pulmonary infiltrations and pleural effusion in chest radiograph, higher prevalence of shock and greater weight change during hospitalization. Patients with P-Gluc ≥ 7.8 mmol/L were characterized by lower platelet count (50 vs. 66 × 10⁹/L; p = 0.001), more severe AKI (plasma creatinine 272 vs. 151 µmol/L; p = 0.001), and longer hospital treatment (8 vs. 6 days; p < 0.001) than patients with P-Gluc < 7.8 mmol/L. Plasma glucose level is associated with the severity of capillary leakage, thrombocytopenia, inflammation, and AKI in patients with acute PUUV infection.

Human glycocalyx shedding: Systematic review and critical appraisal

BACKGROUND

The number of studies measuring breakdown products of the glycocalyx in plasma has increased rapidly during the past decade. The purpose of the present systematic review was to assess the current knowledge concerning the association between plasma concentrations of glycocalyx components and structural assessment of the endothelium.

METHODS

We performed a literature review of Pubmed to determine which glycocalyx components change in a wide variety of human diseases and conditions. We also searched for evidence of a relationship between plasma concentrations and the thickness of the endothelial glycocalyx layer as obtained by imaging methods.

RESULTS

Out of 3,454 publications, we identified 228 that met our inclusion criteria. The vast majority demonstrate an increase in plasma glycocalyx products. Sepsis and trauma are most frequently studied, and comprise approximately 40 publications. They usually report 3-4-foldt increased levels of glycocalyx degradation products, most commonly of syndecan-1. Surgery shows a variable picture. Cardiac surgery and transplantations are most likely to involve elevations of glycocalyx degradation products. Structural assessment using imaging methods show thinning of the endothelial glycocalyx layer in cardiovascular conditions and during major surgery, but thinning does not always correlate with the plasma concentrations of glycocalyx products. The few structural assessments performed do not currently support that capillary permeability is increased when the plasma levels of glycocalyx fragments in plasma are increased.

CONCLUSIONS

Shedding of glycocalyx components is a ubiquitous process that occurs during both acute and chronic inflammation with no sensitivity or specificity for a specific disease or condition.

Heparin prevents in vitro glycocalyx shedding induced by plasma from COVID-19 patients

The severe forms and worsened outcomes of COVID-19 (coronavirus disease 19) are closely associated with hypertension and cardiovascular disease. Endothelial cells express Angiotensin-Converting Enzyme 2 (ACE2), which is the entrance door for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The hallmarks of severe illness caused by SARS-CoV-2 infection are increased levels of IL-6, C-reactive protein, D-dimer, ferritin, neutrophilia and lymphopenia, pulmonary intravascular coagulopathy and microthrombi of alveolar capillaries. The endothelial glycocalyx, a proteoglycan- and glycoprotein-rich layer covering the luminal side of endothelial cells, contributes to vascular homeostasis. It regulates vascular tonus and permeability, prevents thrombosis, and modulates leukocyte adhesion and inflammatory response. We hypothesized that cytokine production and reactive oxygen species (ROS) generation associated with COVID-19 leads to glycocalyx degradation. A cohort of 20 hospitalized patients with a confirmed COVID-19 diagnosis and healthy subjects were enrolled in this study. Mechanisms associated with glycocalyx degradation in COVID-19 were investigated. Increased plasma concentrations of IL-6 and IL1-β, as well as increased lipid peroxidation and glycocalyx components were detected in plasma from COVID-19 patients compared to plasma from healthy subjects. Plasma from COVID-19 patients induced glycocalyx shedding in cultured human umbilical vein endothelial cells (HUVECs) and disrupted redox balance. Treatment of HUVECs with low molecular weight heparin inhibited the glycocalyx perturbation. In conclusion, plasma from COVID-19 patients promotes glycocalyx shedding and redox imbalance in endothelial cells, and heparin treatment potentially inhibits glycocalyx disruption.

Circulating Extracellular Vesicle Tissue Factor Activity During Orthohantavirus Infection Is Associated With Intravascular Coagulation

BACKGROUND

Puumala orthohantavirus (PUUV) causes hemorrhagic fever with renal syndrome (HFRS). Patients with HFRS have an activated coagulation system with increased risk of disseminated intravascular coagulation (DIC) and venous thromboembolism (VTE). The aim of the study was to determine whether circulating extracellular vesicle tissue factor (EVTF) activity levels associates with DIC and VTE (grouped as intravascular coagulation) in HFRS patients.

METHODS

Longitudinal samples were collected from 88 HFRS patients. Patients were stratified into groups of those with intravascular coagulation (n = 27) and those who did not (n = 61). We measured levels of circulating EVTF activity, fibrinogen, activated partial prothrombin time, D-dimer, tissue plasminogen activator (tPA), plasminogen activator inhibitor 1 (PAI-1), and platelets.

RESULTS

Plasma EVTF activity was transiently increased during HFRS. Levels of EVTF activity were significantly associated with plasma tPA and PAI-1, suggesting that endothelial cells could be a potential source. Patients with intravascular coagulation had significantly higher peak EVTF activity levels compared with those who did not, even after adjustment for sex and age. The peak EVTF activity value predicting intravascular coagulation was 0.51 ng/L with 63% sensitivity and 61% specificity with area under the curve = 0.63 (95% confidence interval, 0.51-0.76) and P = .046.

CONCLUSIONS

Plasma EVTF activity during HFRS is associated with intravascular coagulation.

Biodefense Implications of New-World Hantaviruses

Hantaviruses, part of the Bunyaviridae family, are a genus of negative-sense, single-stranded RNA viruses that cause two major diseases: New-World Hantavirus Cardiopulmonary Syndrome and Old-World Hemorrhagic Fever with Renal Syndrome. Hantaviruses generally are found worldwide with each disease corresponding to their respective hemispheres. New-World Hantaviruses spread by specific rodent-host reservoirs and are categorized as emerging viruses that pose a threat to global health and security due to their high mortality rate and ease of transmission. Incidentally, reports of Hantavirus categorization as a bioweapon are often contradicted as both US National Institute of Allergy and Infectious Diseases and the Centers for Disease Control and Prevention refer to them as Category A and C bioagents respectively, each retaining qualitative levels of importance and severity. Concerns of Hantavirus being engineered into a novel bioagent has been thwarted by Hantaviruses being difficult to culture, isolate, and purify limiting its ability to be weaponized. However, the natural properties of Hantaviruses pose a threat that can be exploited by conventional and unconventional forces. This review seeks to clarify the categorization of Hantaviruses as a bioweapon, whilst defining the practicality of employing New-World Hantaviruses and their effect on armies, infrastructure, and civilian targets.

Increased serum sialic acid is associated with morbidity and mortality in a murine model of dengue disease

Dengue virus (DENV) causes the most prevalent arboviral infection of humans, resulting in a spectrum of outcomes, ranging from asymptomatic infection to dengue fever to severe dengue characterized by vascular leakage and shock. Previously, we determined that DENV nonstructural protein 1 (NS1) induces endothelial hyperpermeability, disrupts the endothelial glycocalyx layer (EGL) in vitro and triggers shedding of structural components, including sialic acid (Sia) and heparan sulfate. Here, using a murine model of dengue disease disease, we found high levels of Sia and NS1 circulating in mice with DENV-induced morbidity and lethal DENV infection. Further, we developed a liquid chromatography/mass spectrometry-based method for quantifying free Sia in serum and determined that the levels of free N-glycolylneuraminic acid were significantly higher in DENV-infected mice than in uninfected controls. These data provide additional evidence that DENV infection disrupts EGL components in vivo and warrant further research assessing Sia as a biomarker of severe dengue disease.

Flavivirus NS1 Triggers Tissue-Specific Vascular Endothelial Dysfunction Reflecting Disease Tropism

Flaviviruses cause systemic or neurotropic-encephalitic pathology in humans. The flavivirus nonstructural protein 1 (NS1) is a secreted glycoprotein involved in viral replication, immune evasion, and vascular leakage during dengue virus infection. However, the contribution of secreted NS1 from related flaviviruses to viral pathogenesis remains unknown. Here, we demonstrate that NS1 from dengue, Zika, West Nile, Japanese encephalitis, and yellow fever viruses selectively binds to and alters permeability of human endothelial cells from lung, dermis, umbilical vein, brain, and liver in vitro and causes tissue-specific vascular leakage in mice, reflecting the pathophysiology of each flavivirus. Mechanistically, each flavivirus NS1 leads to differential disruption of endothelial glycocalyx components, resulting in endothelial hyperpermeability. Our findings reveal the capacity of a secreted viral protein to modulate endothelial barrier function in a tissue-specific manner both in vitro and in vivo, potentially influencing virus dissemination and pathogenesis and providing targets for antiviral therapies and vaccine development.

Puerta-Guardo et al. discover that five flavivirus NS1 proteins trigger hyperpermeability and vascular dysfunction in human endothelial cells and mice in a manner reflecting disease tropism. This tissue-specific tropism is partially determined by the capacity of NS1 to bind endothelial cells and is characterized by disruption of endothelial glycocalyx components.

Motility of human renal cells is disturbed by infection with pathogenic hantaviruses

Background

Hemorrhagic fever with renal syndrome (HFRS) caused by pathogenic hantaviruses in Europe and Asia is often characterized by acute kidney injury (AKI) with massive proteinuria. Renal filtration depends on the integrity of epithelial and endothelial monolayers in the tubular and glomerular apparatus. Tubular and glomerular cells represent target cells of hantavirus infection. However, the detailed mechanisms of renal impairment induced by hantaviruses are not well understood.

Methods

We analyzed the cellular consequences of hantavirus infection by measuring adhesion and migration capacity of human renal cells infected with Puumala (PUUV) or Hantaan (HTNV) virus. The impact of hantaviral nucleocapsid proteins (N proteins) on motility was examined by transfection of podocytes.

Results

Infection of kidney cells with hantavirus species PUUV and HTNV causes a significant reduction of migration capacity. The impaired motility depends on viral replication and transfection of podocytes with N protein of PUUV or HTNV reveals that the expression of N protein alone is sufficient to deteriorate podocyte function. The cellular effects are more pronounced for the more pathogenic HTNV than for PUUV that causes a milder form of HFRS.

Conclusions

The direct impairment of migration capacity of renal cells by hantaviral N proteins may contribute substantially to proteinuria observed in the clinical picture of hantavirus infection.

Soluble syndecans: biomarkers for diseases and therapeutic options

Syndecans are important mediators of signalling by transmitting external stimuli into the cells. This role in signal transduction has been attributed mainly to the membrane-bound syndecans. In the last years, however, the soluble ectodomain of syndecans generated by shedding has come into the focus of research as this process has been show to modulate the syndecan-dependent signalling pathways, as well as other pathways. This review summarizes the current knowledge about the induction of syndecan shedding and the different pathways modulated by shed syndecan proteins. This review summarizes the known and putative sheddases for each syndecan and describes the exemplary conditions of sheddase activity for some syndecans. This review summarizes the proposed use of shed syndecans as biomarkers for various diseases, as the shedding process of syndecans depends crucially on tissue- and disease-specific activation of the sheddases. Furthermore, the potential use of soluble syndecans as a therapeutic option is discussed, on the basis of the current literature. LINKED ARTICLES: This article is part of a themed section on Translating the Matrix. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.1/issuetoc.

Endothelial Glycocalyx as a Shield Against Diabetic Vascular Complications: Involvement of Hyaluronan and Hyaluronidases

The endothelial glycocalyx (EG), which covers the apical surface of the endothelial cells and floats into the lumen of the vessels, is a key player in vascular integrity and cardiovascular homeostasis. The EG is composed of PGs (proteoglycans), glycoproteins, glycolipids, and glycosaminoglycans, in particular hyaluronan (HA). HA seems to be implicated in most of the functions described for EG such as creating a space between blood and the endothelium, controlling vessel permeability, restricting leukocyte and platelet adhesion, and allowing an appropriate endothelial response to flow variation through mechanosensing. The amount of HA in the EG may be regulated by HYAL (hyaluronidase) 1, the most active somatic hyaluronidase. HYAL1 seems enriched in endothelial cells through endocytosis from the bloodstream. The role of the other main somatic hyaluronidase, HYAL2, in the EG is uncertain. Damage to the EG, accompanied by shedding of one or more of its components, is an early sign of various pathologies including diabetes mellitus. Shedding increases the blood or plasma concentration of several EG components, such as HA, heparan sulfate, and syndecan. The plasma levels of these molecules can then be used as sensitive markers of EG degradation. This has been shown in type 1 and type 2 diabetic patients. Recent experimental studies suggest that preserving the size and amount of EG HA in the face of diabetic insults could be a useful novel therapeutic strategy to slow diabetic complications. One way to achieve this goal, as suggested by a murine model of HYAL1 deficiency, may be to inhibit the function of HYAL1. The same approach may succeed in other pathological situations involving endothelial dysfunction and EG damage.

Sequential assessment of clinical and laboratory parameters in patients with hemorrhagic fever with renal syndrome

Background

Information on the sequential appearance, duration, and magnitude of clinical and laboratory parameters in hemorrhagic fever with renal syndrome (HFRS) is limited.

Methods

Analysis of clinical and laboratory parameters obtained serially in 81 patients with HFRS, of whom 15 were infected with Dobrava virus and 66 with Puumala virus.

Results

The initial signs/symptoms, appearing on median day 1 of illness, were fever, headache, and myalgia. These were present in 86%, 65%, and 40% of patients and had a median duration of 4, 4, and 5.5 days, respectively. The signs/symptoms were followed by myopia (appearance on day 5), insomnia (day 6), oliguria/anuria (day 6), polyuria (day 9), and sinus bradycardia (day 9.5). These were present in 35%, 30%, 28%, 91%, and 35% of patients; their median duration was 2, 2, 2, 7, and 1 day, respectively. Laboratory abnormalities, including thrombocytopenia, elevated alanine aminotransferase, CRP, procalcitonin, creatinine, diminished glomerular filtration rate, and leukocytosis, were ascertained on admission to hospital or on the following day (day 5 or 6 of illness) and were established in 95%, 87%, 99%, 91%, 94%, 87%, and 55% of patients, and had a median duration of 4, 3, 7, 3, 9, 8, and 2 days, respectively. Comparison of patients infected with Dobrava and Puumala viruses found several differences in the frequency, magnitude, and duration of abnormalities, indicating that Dobrava virus causes the more severe HFRS.

Conclusions

In the majority of patients, the classic clinical distinction into febrile, hypotonic, oliguric, polyuric, and convalescent phases of illness is unclear.

Relationship between circulating vascular endothelial growth factor and its soluble receptor in patients with hemorrhagic fever with renal syndrome

Hemorrhagic fever with renal syndrome (HFRS) is characterized by endothelial dysfunction with capillary leakage without obvious cytopathology in the capillary endothelium. The aim of the study was to analyze the kinetics of vascular endothelial growth factor (VEGF) and its soluble receptor (sVEGFR-2) in HFRS patients infected with Dobrava (DOBV) or Puumala virus (PUUV). VEGF and sVEGFR-2 levels were measured in daily plasma and urine samples of 73 patients with HFRS (58 with PUUV, 15 with DOBV) and evaluated in relation to clinical and laboratory variables. In comparison with the healthy controls, initial samples (obtained in the first week of illness) from patients with HFRS had higher plasma and urine VEGF levels, whereas sVEGFR-2 levels were lower in plasma but higher in urine. VEGF levels did not differ in relation to hantavirus species, viral load, or the severity of HFRS. The comparison of VEGF dynamics in plasma and urine showed the pronounced secretion of VEGF in urine. Significant correlations were found between daily VEGF/sVEGFR-2 levels and platelet counts, as well as with diuresis: the correlations were positive for plasma VEGF/sVEGFR-2 levels and negative for urine levels. In addition, patients with hemorrhagic manifestations had very high plasma and urine VEGF, together with high urine sVEGFR-2. Measuring the local secretion of sVEGFR-2 in urine might be a useful biomarker for identifying HFRS patients who will progress to severe disease.

Risk of Venous Thromboembolism Following Hemorrhagic Fever With Renal Syndrome: A Self-controlled Case Series Study

Background

Bleeding is associated with viral hemorrhagic fevers; however, thromboembolic complications have received less attention. Hemorrhagic fever with renal syndrome (HFRS) is a mild viral hemorrhagic fever caused by Puumala hantavirus. We previously identified HFRS as a risk factor for myocardial infarction and stroke, but the risk for venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), is unknown.

Methods

Personal identity numbers from the Swedish HFRS database were cross-linked with the National Patient register to obtain information on all causes for hospitalization during 1964 to 2013. The self-controlled case series method was used to calculate the incidence rate ratio (IRR) for first VTE, DVT, and PE during 1998 to 2013.

Results

From 7244 HFRS patients, there were 146 with a first VTE of which 74 were DVT and 78 were PE, and 6 patients had both DVT and PE. The overall risk for a VTE was significantly higher during the first 2 weeks following HFRS onset, with an IRR of 64.3 (95% confidence interval [CI], 36.3-114). The corresponding risk for a DVT was 45.9 (95% CI, 18-117.1) and for PE, 76.8 (95% CI, 37.1-159). Sex interacted significantly with the association between HFRS and VTE, with females having a higher risk compared with males.

Conclusions

A significantly increased risk for VTE was found in the time period following HFRS onset. It is important to keep this in mind and monitor HFRS patients, and possibly other viral hemorrhagic fever patients, for early symptoms of VTE.

Deregulation of levels of angiopoietin-1 and angiopoietin-2 is associated with severe courses of hantavirus infection

BACKGROUND

Hantavirus disease is characterized by endothelial dysfunction. Angiopoietin-1 (Ang-1) and its antagonist angiopoietin-2 (Ang-2) play a key role in the control of capillary permeability. Ang-1 is responsible for maintenance of cell-to-cell contacts whereas Ang-2 destabilizes monolayers. An imbalance of Ang-1 and Ang-2 levels results in enhanced permeability and capillary leakage.

OBJECTIVES

To analyze the involvement of angiopoietins in hantavirus-induced disruption of endothelia, we measured the levels of Ang-1 and Ang-2 in hantavirus infection.

STUDY DESIGN

Levels of angiopoietins of 31 patients with acute Puumala virus (PUUV) infection and a patient infected with Dobrava-Belgrade virus genotype Sochi (DOBV-Sochi) were analyzed. An age-matched group of 16 healthy volunteers served as control. The ratios of Ang-2 to Ang-1 levels were calculated and correlated with laboratory parameters.

RESULTS

Patients with PUUV and DOBV-Sochi infection exhibited elevated ratios of Ang-2/Ang-1 compared to the control group. The imbalance of Ang-2 to Ang-1 levels was observed early after onset of symptoms and lasted for the acute phase of infection. The deregulation in DOBV-Sochi infection was more prominent than in PUUV infection. Analysis of Ang-2/Ang-1 ratio and laboratory parameters in the PUUV cohort revealed a positive correlation with serum creatinine and a negative correlation with serum albumin and thrombocyte levels.

CONCLUSIONS

We observed an imbalance between levels of Ang-1 and Ang-2 in patients infected with PUUV and DOBV-Sochi. Elevated Ang-2/Ang-1 ratios correlate with disease severity. The virus-induced deregulation of angiopoietin levels may enhance capillary permeability and contribute to the pathogenesis of hantavirus disease.

Increased Serum Hyaluronic Acid and Heparan Sulfate in Dengue Fever: Association with Plasma Leakage and Disease Severity

Plasma leakage is a major pathogenic mechanism of severe dengue, but the etiology remains unclear. The association between endothelial glycocalyx integrity and vascular permeability in older adults with dengue has not been evaluated. A prospective cohort study of adults with undifferentiated fever screened for dengue by RT-PCR or NS1 antigen testing was performed. Patients were assessed daily while symptomatic and at convalescence. Serum hyaluronic acid (HA), heparan sulfate (HS) and selected cytokines (TNF-α, IL-6, IL-10) were measured on enrollment and convalescence. Patients were diagnosed as dengue fever (DF, n = 30), dengue hemorrhagic fever (DHF, n = 20) and non-dengue (ND) febrile illness (n = 11). Acute HA and HS levels were significantly higher in all dengue patients compared to ND (p = 0.0033 and p = 0.0441 respectively), but not different between DF and DHF (p = 0.3426 and p = 0.9180 respectively). Enrolment HA inversely correlated with serum albumin, protein and platelets in all dengue and DHF (p < 0.05). HA and HS in all dengue patients decreased significantly at convalescence. Serum IL-10 was significantly associated with HA in all dengue patients (p = 0.002). Serum HA and HS levels were increased in adult dengue and HA was associated with markers of disease severity. Endothelial glycocalyx damage may have a role in vascular leakage in dengue.

Shock induced endotheliopathy (SHINE) in acute critical illness - a unifying pathophysiologic mechanism

One quarter of patients suffering from acute critical illness such as severe trauma, sepsis, myocardial infarction (MI) or post cardiac arrest syndrome (PCAS) develop severe hemostatic aberrations and coagulopathy, which are associated with excess mortality. Despite the different types of injurious “hit”, acutely critically ill patients share several phenotypic features that may be driven by the shock. This response, mounted by the body to various life-threatening conditions, is relatively homogenous and most likely evolutionarily adapted. We propose that shock-induced sympatho-adrenal hyperactivation is a critical driver of endothelial cell and glycocalyx damage (endotheliopathy) in acute critical illness, with the overall aim of ensuring organ perfusion through an injured microvasculature. We have investigated more than 3000 patients suffering from different types of acute critical illness (severe trauma, sepsis, MI and PCAS) and have found a potential unifying pathologic link between sympatho-adrenal hyperactivation, endotheliopathy, and poor outcome. We entitled this proposed disease entity, shock-induced endotheliopathy (SHINE). Here we review the literature and discuss the pathophysiology of SHINE.

Clinical characterization of two severe cases of hemorrhagic fever with renal syndrome (HFRS) caused by hantaviruses Puumala and Dobrava-Belgrade genotype Sochi

BACKGROUND

Hantavirus disease belongs to the emerging infections. The clinical picture and severity of infections differ between hantavirus species and may even vary between hantavirus genotypes. The mechanisms that lead to the broad variance of severity in infected patients are not completely understood. Host- and virus-specific factors are considered.

CASE PRESENTATION

We analyzed severe cases of hantavirus disease in two young women. The first case was caused by Puumala virus (PUUV) infection in Germany; the second case describes the infection with Dobrava-Belgrade virus (DOBV) in Russia. Symptoms, laboratory parameters and cytokine levels were analyzed and compared between the two patients. Serological and sequence analysis revealed that PUUV was the infecting agent for the German patient and the infection of the Russian patient was caused by Dobrava-Belgrade virus genotype Sochi (DOBV-Sochi). The symptoms in the initial phase of the diseases did not differ noticeably between both patients. However, deterioration of laboratory parameter values was prolonged and stronger in DOBV-Sochi than in PUUV infection. Circulating endothelial progenitor cells (cEPCs), known to be responsible for endothelial repair, were mobilized in both infections. Striking differences were observed in the temporal course and level of cytokine upregulation. Levels of angiopoietin-2 (Ang-2), vascular endothelial growth factor (VEGF), and stromal derived factor-1 (SDF-1α) were increased in both infections; but, sustained and more pronounced elevation was observed in DOBV-Sochi infection.

CONCLUSIONS

Severe hantavirus disease caused by different hantavirus species did not differ in the general symptoms and clinical characteristics. However, we observed a prolonged clinical course and a late and enhanced mobilization of cytokines in DOBV-Sochi infection. The differences in cytokine deregulation may contribute to the observed variation in the clinical course.

Electrocardiographic abnormalities and relative bradycardia in patients with hantavirus-induced nephropathia epidemica

BACKGROUND

Nephropathia epidemica (NE), caused by Puumala virus (PUUV), is characterized by acute kidney injury (AKI) and thrombocytopenia. Cardiac involvement with electrocardiographic (ECG) abnormalities has been previously reported in NE; however, its prognostic value is unknown. Relative bradycardia is an important clinical sign in various infectious diseases, and previous smaller studies have described pulse-temperature deficit in patients with PUUV infection.

METHODS

We performed a cross-sectional survey of 471 adult patients with serologically confirmed NE. Data were collected retrospectively from medical records and prospectively at follow-up visits. Patients for whom ECGs were recorded during the acute phase of disease were enrolled retrospectively (n=263). Three patients were excluded because of documented pre-existing ECG abnormalities prior to NE. All patients with ECG abnormalities during the acute phase underwent follow-up.

RESULTS

A total of 46 patients had ECG abnormalities at the time of admission to hospital (18%). T-wave inversion was the most frequent ECG abnormality (n=31 patients), followed by ST segment changes (nine patients with elevation and six with depression). No major adverse cardiac events occurred during follow-up (median 37months; range 34-63months). Of note, ECG abnormalities reverted to normal in the majority of the patients during follow-up. During the acute phase of NE, 149 of 186 patients had relative bradycardia, without implications for disease course.

CONCLUSIONS

Transient ECG abnormalities were detected in 18% of patients during acute NE but were not associated with negative cardiovascular outcome. Relative bradycardia was identified in 80% of the patients with acute NE.

Meeting report: Tenth International Conference on Hantaviruses

The 10th International Conference on Hantaviruses, organized by the International Society on Hantaviruses, was held from May 31-June 3, 2016 at Colorado State University, Fort Collins, CO, USA. These conferences have been held every three years since 1980. The current report summarizes research presented on all aspects of hantavirology: ecology and epidemiology, virus replication, phylogeny, pathogenesis, immune response, clinical studies, vaccines and therapeutics.

What Do We Know about How Hantaviruses Interact with Their Different Hosts?

Hantaviruses, like other members of the Bunyaviridae family, are emerging viruses that are able to cause hemorrhagic fevers. Occasional transmission to humans is due to inhalation of contaminated aerosolized excreta from infected rodents. Hantaviruses are asymptomatic in their rodent or insectivore natural hosts with which they have co-evolved for millions of years. In contrast, hantaviruses cause different pathologies in humans with varying mortality rates, depending on the hantavirus species and its geographic origin. Cases of hemorrhagic fever with renal syndrome (HFRS) have been reported in Europe and Asia, while hantavirus cardiopulmonary syndromes (HCPS) are observed in the Americas. In some cases, diseases caused by Old World hantaviruses exhibit HCPS-like symptoms. Although the etiologic agents of HFRS were identified in the early 1980s, the way hantaviruses interact with their different hosts still remains elusive. What are the entry receptors? How do hantaviruses propagate in the organism and how do they cope with the immune system? This review summarizes recent data documenting interactions established by pathogenic and nonpathogenic hantaviruses with their natural or human hosts that could highlight their different outcomes.

Hantavirus Infection Suppresses Thrombospondin-1 Expression in Cultured Endothelial Cells in a Strain-Specific Manner

Hantavirus infection is associated with two frequently fatal diseases in humans: Hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). The pathogenesis of hantavirus infection is complex and not fully understood; however, it is believed to involve virus-induced hyperinflammatory immune responses. Thrombospondin-1 (THBS1) is a large homotrimeric protein that plays a putative role in regulating blood homeostasis. Hyperresponsiveness to inflammatory stimuli has also been associated with defects in the THBS1 gene. Our data suggest that hantavirus infection of human umbilical cord vein endothelial cells (HUVEC) suppress the accumulation of THBS1 in the extracellular matrix. Additionally, this suppression is dependent on virus replication, implying a direct mechanism of action. Our data also imply that the pathogenic Andes and Hantaan strains inhibit THBS1 expression while the non-pathogenic Prospect Hill strain showed little inhibition. These observations suggest that a dysregulation of THBS1 may contribute to the pathogenesis of hantavirus infection.

Thrombocytopenia associates with the severity of inflammation and variables reflecting capillary leakage in Puumala Hantavirus infection, an analysis of 546 Finnish patients

BACKGROUND

Hantaviruses cause hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS) in humans. Hantavirus infections are characterized by thrombocytopenia. Our objective was to assess the association of thrombocytopenia with disease severity in HFRS induced by Puumala hantavirus (PUUV).

METHODS

Altogether 546 patients treated for acute serologically confirmed PUUV infection during 1982-2013 at Tampere University Hospital, Finland, were examined. Blood platelet count was determined daily and analysed in relation to different variables reflecting disease severity. The patients were divided into two groups according to the minimum platelet count: severe thrombocytopenia (<69 × 10(9)/L, i.e. below median) and no severe thrombocytopenia (≥69 × 10(9)/L).

RESULTS

Thrombocytopenia (platelet count <150 × 10(9)/L) was detected in 90% of patients, and in 28% of patients platelet count was <50 × 10(9)/L. Patients with severe thrombocytopenia had longer stay (8 versus 7 days, p = 0.002) and greater weight gain (2.8 versus 2.0 kg, p < 0.001) at the hospital, higher blood leukocyte count (11.2 × 10(9)/L versus 9.6 × 10(9)/L, p < 0.001), plasma C-reactive protein (81 versus 59 mg/L, p < 0.001), maximum hematocrit (0.44 versus 0.42, p < 0.001), urinary protein excretion (1.7 versus 1.1 g/24 h, p = 0.002), and lower plasma albumin concentration (27 versus 32 g/L, p < 0.001) than patients without severe thrombocytopenia (comparisons between medians). Maximum creatinine concentration did not differ between patients with or without severe thrombocytopenia (median 235 versus 214 μmol/L, p = 0.217).

CONCLUSIONS

The severity of thrombocytopenia associates with the degree of inflammation and variables reflecting capillary leakage, but not with the severity of acute kidney injury in PUUV infected Finnish patients.

Host biomarkers are associated with progression to dengue haemorrhagic fever: a nested case-control study

OBJECTIVES

Dengue represents the most important arboviral infection worldwide. Onset of circulatory collapse can be unpredictable. Biomarkers that can identify individuals at risk of plasma leakage may facilitate better triage and clinical management.

DESIGN

Using a nested case-control design, we randomly selected subjects from a prospective cohort study of dengue in Colombia (n=1582). Using serum collected within 96 hours of fever onset, we tested 19 biomarkers by ELISA in cases (developed dengue hemorrhagic fever or dengue shock syndrome (DHF/DSS); n=46), and controls (uncomplicated dengue fever (DF); n=65) and healthy controls (HC); n=15.

RESULTS

Ang-1 levels were lower and angptl3, sKDR, sEng, sICAM-1, CRP, CXCL10/IP-10, IL-18 binding protein, CHI3L1, C5a and Factor D levels were increased in dengue compared to HC. sICAM-1, sEng and CXCL10/IP-10 were further elevated in subjects who subsequently developed DHF/DSS (p=0.008, p=0.028 and p=0.025, respectively). In a logistic regression model, age (odds ratio (OR) (95% CI): 0.95 (0.92-0.98), p=0.001), hyperesthesia/hyperalgesia (OR; 3.8 (1.4-10.4), p=0.008) and elevated sICAM-1 (>298ng/mL: OR; 6.3 (1.5-25.7), p=0.011) at presentation were independently associated with progression to DHF/DSS.

CONCLUSIONS

These results suggest that inflammation and endothelial activation are important pathways in the pathogenesis of dengue and sICAM-1 levels may identify individuals at risk of plasma leakage.

Degradation of the endothelial glycocalyx in clinical settings: searching for the sheddases

The endothelial glycocalyx has a profound influence at the vascular wall on the transmission of shear stress, on the maintenance of a selective permeability barrier and a low hydraulic conductivity, and on attenuating firm adhesion of blood leukocytes and platelets. Major constituents of the glycocalyx, including syndecans, heparan sulphates and hyaluronan, are shed from the endothelial surface under various acute and chronic clinical conditions, the best characterized being ischaemia and hypoxia, sepsis and inflammation, atherosclerosis, diabetes, renal disease and haemorrhagic viral infections. Damage has also been detected by in vivo microscopic techniques. Matrix metalloproteases may shed syndecans and heparanase, released from activated mast cells, cleaves heparan sulphates from core proteins. According to new data, not only hyaluronidase but also the serine proteases thrombin, elastase, proteinase 3 and plasminogen, as well as cathepsin B lead to loss of hyaluronan from the endothelial surface layer, suggesting a wide array of potentially destructive conditions. Appropriately, pharmacological agents such as inhibitors of inflammation, antithrombin and inhibitors of metalloproteases display potential to attenuate shedding of the glycocalyx in various experimental models. Also, plasma components, especially albumin, stabilize the glycocalyx and contribute to the endothelial surface layer. Though symptoms of the above listed diseases and conditions correlate with sequelae expected from disturbance of the endothelial glycocalyx (oedema, inflammation, leukocyte and platelet adhesion, low reflow), therapeutic studies to prove a causal connection have yet to be designed. With respect to studies on humans, some clinical evidence exists for benefits from application of sulodexide, a preparation delivering precursors of the glycocalyx constituent heparan sulphate. At present, the simplest option for protecting the glycocalyx seems to be to ensure an adequate level of albumin. However, also in this case, definite proof of causality needs to be delivered.