Mechanisms by which soluble endothelial cell protein C receptor modulates protein C and activated protein C function

Dysregulated Coagulation and Fibrinolysis Are Present in Patients Admitted to the Emergency Department with Acute Hypoxemic Respiratory Failure: A Prospective Study

Acute hypoxemic respiratory failure (AHRF) is defined as acute and progressive, and patients are at a greater risk of developing acute respiratory distress syndrome (ARDS). Until now, most studies have focused on prognostic and diagnostic biomarkers in ARDS. Since there is evidence supporting a connection between dysregulated coagulant and fibrinolytic pathways in ARDS progression, it is plausible that this dysregulation also exists in AHRF. The aim of this study was to explore whether levels of soluble endothelial protein C receptor (sEPCR) and plasminogen differentiate patients admitted to the emergency department (ED) with AHRF. sEPCR and plasminogen levels were measured in 130 AHRF patients upon ED presentation by ELISA. Our results demonstrated that patients presenting to the ED with AHRF had elevated levels of sEPCR and plasminogen. It seems that dysregulation of coagulation and fibrinolysis occur in the early stages of respiratory failure requiring hospitalisation. Further research is needed to fully comprehend the contribution of sEPCR and plasminogen in AHRF.

Endothelial Protein C Receptor and Its Impact on Rheumatic Disease

Endothelial Protein C Receptor (EPCR) is a key regulator of the activated protein C anti-coagulation pathway due to its role in the binding and activation of this protein. EPCR also binds to other ligands such as Factor VII and X, γδ T-cells, plasmodium falciparum erythrocyte membrane protein 1, and Secretory group V Phospholipases A2, facilitating ligand-specific functions. The functions of EPCR can also be regulated by soluble (s)EPCR that competes for the binding sites of membrane-bound (m)EPCR. sEPCR is created when mEPCR is shed from the cell surface. The propensity of shedding alters depending on the genetic haplotype of the EPCR gene that an individual may possess. EPCR plays an active role in normal homeostasis, anti-coagulation pathways, inflammation, and cell stemness. Due to these properties, EPCR is considered a potential effector/mediator of inflammatory diseases. Rheumatic diseases such as rheumatoid arthritis and systemic lupus erythematosus are autoimmune/inflammatory conditions that are associated with elevated EPCR levels and disease activity, potentially driven by EPCR. This review highlights the functions of EPCR and its contribution to rheumatic diseases.

Circulating Soluble EPCR Levels Are Reduced in Patients with Ischemic Peripheral Artery Disease and Associated with Markers of Endothelial and Vascular Function

(1) Background: Endothelial dysfunction initiates cardiovascular pathologies, including peripheral artery disease (PAD). The pathophysiology of impaired new vessel formation in the presence of angiogenic stimuli, such as ischemia and inflammation, is unknown. We have recently shown in mice that reduced endothelial protein C receptor (EPCR) expression results in defective angiogenesis following experimental hindlimb ischemia. (2) Purpose: To determine soluble (s)EPCR levels in the plasma of patients with PAD and to compare them with the protein C activity and biomarkers of endothelial function, inflammation, and angiogenesis. (3) Methods and Results: Clinical tests of vascular function and immunoassays of plasma from patients with PAD stage II were compared to age- and sex-matched individuals with and without cardiovascular risk factors or PAD stage III/IV patients. sEPCR levels were significantly lower in PAD stage II patients compared to subjects with risk factors, but no PAD, and further decreased in PAD stage III/IV patients. Plasma protein C activity or levels of ADAM17, a mediator of EPCR shedding, did not differ. Significant associations between sEPCR and the ankle-brachial index (p = 0.0359), age (p = 0.0488), body mass index (p = 0.0110), and plasma sE-selectin levels (p = 0.0327) were observed. High-sensitive CRP levels and white blood cell counts were significantly elevated in PAD patients and associated with serum glucose levels, but not sEPCR. In contrast, plasma TNFα or IL1β levels did not differ. Circulating levels of VEGF were significantly elevated in PAD stage II patients (p = 0.0198), but not associated with molecular (sE-selectin) or functional (ankle-brachial index) markers of vascular health. (4) Conclusions: Our findings suggest that circulating sEPCR levels may be useful as biomarkers of endothelial dysfunction, including angiogenesis, in persons older than 35 years and that progressive loss of endothelial protein C receptors might be involved in the development and progression of PAD.

Status of major hemostatic components in the setting of COVID-19: the effect on endothelium, platelets, coagulation factors, fibrinolytic system, and complement

The coagulation, fibrinolytic, anticoagulation, and complement systems are in delicate balance with the vessel wall endothelium ensuring appropriate hemostasis. Coagulopathy in coronavirus disease 2019 (COVID-19) is not a simple disorder of one hemostatic component but a complicated process affecting most of the hemostasis system. COVID-19 disturbs the balance between the procoagulant systems and the regulatory mechanisms. Here, we investigate the effect of COVID-19 on key hemostatic components, including platelets, endothelial cells, coagulation factors, fibrinolytic system, anticoagulant protein system, and complement system, to improve our understanding of the pathophysiological processes underlying COVID-19 coagulopathy based on evidence.

Biomarkers Assessing Endothelial Dysfunction in Alzheimer's Disease

Alzheimer's disease (AD) is the most common degenerative disorder in the elderly in developed countries. Currently, growing evidence is pointing at endothelial dysfunction as a key player in the cognitive decline course of AD. As a main component of the blood-brain barrier (BBB), the dysfunction of endothelial cells driven by vascular risk factors associated with AD allows the passage of toxic substances to the cerebral parenchyma, producing chronic hypoperfusion that eventually causes an inflammatory and neurotoxic response. In this process, the levels of several biomarkers are disrupted, such as an increase in adhesion molecules that allow the passage of leukocytes to the cerebral parenchyma, increasing the permeability of the BBB; moreover, other vascular players, including endothelin-1, also mediate artery inflammation. As a consequence of the disruption of the BBB, a progressive neuroinflammatory response is produced that, added to the astrogliosis, eventually triggers neuronal degeneration (possibly responsible for cognitive deterioration). Recently, new molecules have been proposed as early biomarkers for endothelial dysfunction that can constitute new therapeutic targets as well as early diagnostic and prognostic markers for AD.

Markers of Hereditary Thrombophilia with Unclear Significance

Thrombophilia leads to an increased risk of venous thromboembolism. Widely accepted risk factors for thrombophilia comprise deficiencies of protein C, protein S, and antithrombin, as well as the factor V "Leiden" mutation, the prothrombin G20210A mutation, dysfibrinogenemia, and, albeit less conclusive, increased levels of factor VIII. Besides these established markers of thrombophilia, risk factors of unclear significance have been described in the literature. These inherited risk factors include deficiencies or loss-of-activity of the activity of ADAMTS13, heparin cofactor II, plasminogen, tissue factor pathway inhibitor (TFPI), thrombomodulin, protein Z (PZ), as well as PZ-dependent protease inhibitor. On the other hand, thrombophilia has been linked to the gain-of-activity, or elevated levels, of α2-antiplasmin, angiotensin-converting enzyme, coagulation factors IX (FIX) and XI (FXI), fibrinogen, homocysteine, lipoprotein(a), plasminogen activator inhibitor-1 (PAI-1), and thrombin-activatable fibrinolysis inhibitor (TAFI). With respect to the molecular interactions that may influence the thrombotic risk, more complex mechanisms have been described for endothelial protein C receptor (EPCR) and factor XIII (FXIII) Val34Leu. With focus on the risk for venous thrombosis, the present review aims to give an overview on the current knowledge on the significance of the aforementioned markers for thrombophilia screening. According to the current knowledge, there appears to be weak evidence for a potential impact of EPCR, FIX, FXI, FXIII Val34Leu, fibrinogen, homocysteine, PAI-1, PZ, TAFI, and TFPI on the thrombotic risk.

Identification of 969 protein quantitative trait loci in an African American population with kidney disease attributed to hypertension

Investigations into the causal underpinnings of disease processes can be aided by the incorporation of genetic information. Genetic studies require populations varied in both ancestry and prevalent disease in order to optimize discovery and ensure generalizability of findings to the global population. Here, we report the genetic determinants of the serum proteome in 466 African Americans with chronic kidney disease attributed to hypertension from the richly phenotyped African American Study of Kidney Disease and Hypertension (AASK) study. Using the largest aptamer-based protein profiling platform to date (6,790 proteins or protein complexes), we identified 969 genetic associations with 900 unique proteins; including 52 novel cis (local) associations and 379 novel trans (distant) associations. The genetic effects of previously published cis-protein quantitative trait loci (pQTLs) were found to be highly reproducible, and we found evidence that our novel genetic signals colocalize with gene expression and disease processes. Many trans- pQTLs were found to reflect associations mediated by the circulating cis protein, and the common trans-pQTLs are enriched for processes involving extracellular vesicles, highlighting a plausible mechanism for distal regulation of the levels of secreted proteins. Thus, our study generates a valuable resource of genetic associations linking variants to protein levels and disease in an understudied patient population to inform future studies of drug targets and physiology.

The interplay between inflammation and thrombosis in COVID-19: Mechanisms, therapeutic strategies, and challenges

Coronavirus disease 2019 (COVID-19), caused by a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), can cause life-threatening pathology characterized by a dysregulated immune response and coagulopathy. While respiratory failure induced by inflammation is the most common cause of death, micro-and macrovascular thrombosis leading to multiple organ failure are also causes of mortality. Dysregulation of systemic inflammation observed in severe COVID-19 patients is manifested by cytokine release syndrome (CRS) - the aberrant release of high levels of proinflammatory cytokines, such as IL-6, IL-1, TNFα, MP-1, as well as complement. CRS is often accompanied by activation of endothelial cells and platelets, coupled with perturbation of the balance between the pro-and antithrombotic mechanisms, resulting in thrombosis. Inflammation and thrombosis form a vicious circle, contributing to morbidity and mortality. Treatment of hyperinflammation has been shown to decrease thrombosis, while anti-thrombotic treatment also downregulates cytokine release. This review highlights the relationship between COVID-19-mediated systemic inflammation and thrombosis, the molecular pathways involved, the therapies targeting these processes, and the challenges currently encountered.

Are H1 and H3 haplotypes of endothelial protein C receptor (PROCR) an important factor in contracting COVID-19?

The development of cardiovascular disease shows increase after contracting coronavirus 2019 (COVID-19) disease and myocardial damage is observed in patients who have had the disease severely. The relationship between genetic cardiovascular risk factors with COVID-19 infection was investigated in our study. One hundred thirty-five patients, 27 of whom were COVID-19 (-) and 108 were COVID-19 (+) patients, were included in the study. Patients were divided into three groups ([COVID-19 [-], COVID-19 [+] asymptomatic, and COVID-19 [+] symptomatic + patients with pulmonary involvement]). Genetic cardiovascular risk factors were examined in blood samples taken from the patients with new generation sequencing analysis. In the clinical classification, there were no significant differences between the three groups in fibrinogen beta chain-455G>A, human platelet antigen 1 (HPA1b)/platelet receptor GPIIIa/(ITGB3) (HPA1a/b; GpIIIa; integrin beta 3 L33P), ACE I/D, AGT (M268T), AGTR1 (1166A>C), Apo E (E2/E3/E4) (rs7412, rs429358), eNOS (786T>C), eNOS (894G>T) genes (p > 0.05). However, significant differences were observed in PROCR H3 haplotype/G (endothelial protein C receptor gene [EPCR] 4600A>G [A3 haplotype]), PROCR H1 haplotype/C (EPCR 4678G>C [A1 haplotype]) genes (p < 0.05). When COVID-19 (+) and COVID-19 (-) groups were compared, it was observed that the infection was more common in people with PROCR H1 haplotype/C and PROCR H3 haplotype/G genotypes (p < 0.05). PROCR H1 and PROCR H3 haplotypes may be an important factor in contracting COVID-19 disease. In people with COVID-19 disease, revealing PROCR genetic differences and measuring sEPCR levels will be beneficial in the follow-up of the disease.

Elucidating mechanisms of genetic cross-disease associations at the PROCR vascular disease locus

Many individual genetic risk loci have been associated with multiple common human diseases. However, the molecular basis of this pleiotropy often remains unclear. We present an integrative approach to reveal the molecular mechanism underlying the PROCR locus, associated with lower coronary artery disease (CAD) risk but higher venous thromboembolism (VTE) risk. We identify PROCR-p.Ser219Gly as the likely causal variant at the locus and protein C as a causal factor. Using genetic analyses, human recall-by-genotype and in vitro experimentation, we demonstrate that PROCR-219Gly increases plasma levels of (activated) protein C through endothelial protein C receptor (EPCR) ectodomain shedding in endothelial cells, attenuating leukocyte-endothelial cell adhesion and vascular inflammation. We also associate PROCR-219Gly with an increased pro-thrombotic state via coagulation factor VII, a ligand of EPCR. Our study, which links PROCR-219Gly to CAD through anti-inflammatory mechanisms and to VTE through pro-thrombotic mechanisms, provides a framework to reveal the mechanisms underlying similar cross-phenotype associations.

Thrombotic risk determined by protein C receptor (PROCR) variants among middle-aged and older adults: a population-based cohort study

BACKGROUND

The protein C (PC) anticoagulant system has a key role in maintaining hemostatic balance. One missense (Ser219Gly) variant in the protein C receptor (PROCR) was associated with venous thromboembolism (VTE) in genome-wide association studies.

OBJECTIVES

This study aimed to determine the thrombotic risk of rare and common PROCR variants in a large population-based cohort of middle-aged and older adults.

PATIENTS/METHODS

The exonic sequence of PROCR was analyzed for the Ser219Gly variant and other qualifying variants in 28,794 subjects (born 1923-1950, 60% women) without previous VTE, who participated in the Malmö Diet and Cancer study (1991-1996). Incidence of VTE was followed up until 2018. Qualifying variants were defined as loss-of-function or non-benign (PolyPhen-2) missense variants with minor allele frequencies (MAF) < 0.1%.

RESULTS

Resequencing identified 36 PROCR variants in the study population (26,210 non-VTE exomes and 2584 VTE exomes), 11 synonymous, 22 missense and three loss-of-function variants. Kaplan-Meier analysis of the known Ser219Gly variant (rs867186) showed that homozygosity for this variant increased the risk of disease whereas heterozygosity showed no effect. Cox multivariate regression analysis revealed an adjusted hazard ratio of 1.5 (95%CI 1.1-2.0). Fifteen rare variants were classified as qualifying and were included in collapsing analysis (burden test and SKAT-O). They did not contribute to risk. However, a Arg113Cys missense variant (rs146420040; MAF=0.004) showed an increased VTE risk (HR=1.3; 95%CI 1.0-1.9).

CONCLUSIONS

Homozygosity for the Ser219Gly variant and a previously identified functional PROCR variant (Arg113Cys) was associated with VTE. Other variants did not contribute to VTE.

Relationship between serum soluble endothelial protein C receptor level and COVID-19 findings

Coronavirus-related disease-2019 (COVID-19)-associated coagulopathy presents predominantly with thrombosis and leads to complications in close association with inflammatory process. Soluble endothelial protein C receptor (sEPCR), which is the soluble form of EPCR, reduces the anticoagulant and anti-inflammatory activity of activated protein C. The purpose of this study is to investigate the relationship between sEPCR and the laboratory parameters and thorax computed tomography (CT) findings in the course of COVID-19. Twenty-five laboratory-confirmed [reverse transcription-quantitative polimerase chain reaction (RT-qPCR) positive] and 24 clinically diagnosed (RT-qPCR negative) COVID-19 patients were enrolled in the study. Blood specimens were collected for sEPCR and haematological and biochemical parameter measurement. Thorax CT was performed to detect COVID-19 findings. These parameters from RT-qPCR positive and negative patients were then compared. Although there was no difference between the groups in terms of symptoms, the time between the onset of symptoms and the admission time was shorter in RT-qPCR positive group (P = 0.000). sEPCR levels were significantly higher in the RT-qPCR positive group (P = 0.011). Patients with ground-glass opacity and bilateral involvement on thorax CT have higher serum sEPCR levels (P = 0.012 and 0.043, respectively). This study has shown for the first time that serum sEPCR levels, which is a member of coagulation cascade and has also been reported to be associated with inflammation, is higher in patients with positive RT-qPCR test and patients with GGO or bilateral involvement on thorax CT regardless of the PCR result.

Could Soluble Endothelial Protein C Receptor Levels Recognize SARS-CoV2-Positive Patients Requiring Hospitalization?

INTRODUCTION

The endothelial protein C receptor (EPCR) is a protein that regulates the protein C anticoagulant and anti-inflammatory pathways. A soluble form of EPCR (sEPCR) circulates in plasma and inhibits activated protein C (APC) activities. The clinical impact of sEPCR and its involvement in COVID-19 has not been explored. In this study, we investigated whether sEPCR levels were related to COVID-19 patients' requirement for hospitalization.

METHODS

Plasma sEPCR levels were measured on hospital admission in 84 COVID-19 patients, and in 11 non-hospitalized SARS-CoV2-positive patients approximately 6 days after reported manifestation of their symptoms. Multiple logistic regression analysis was performed to identify potential risk factors for hospitalization and receiver operating characteristic (ROC) curves were generated to assess their value.

RESULTS

In our cohort, hospitalized patients had considerably higher sEPCR levels upon admission compared with outpatients [107.5 (76.7-156.3) vs. 44.6 (12.1-84.4) ng/mL; P < 0.0001)]. The ROC curve using hospitalization as the classification variable and sEPCR levels as the prognostic variable generated an area under the curve at 0.845 (95% CI = 0.710-0.981, P < 0.001). Additionally, we investigated the predictive value of sEPCR combined with BMI, age, or D-dimers.

CONCLUSIONS

In our cohort, sEPCR levels in COVID-19 patients upon hospital admission appear considerably elevated compared with outpatients; this could lead to impaired APC activities and might contribute to the pro-coagulant phenotype reported in such patients. sEPCR measurement might be useful as a point-of-care test in SARS-CoV2-positive patients.

Lentiviral CRISPR-guided RNA library screening identified Adam17 as an upstream negative regulator of Procr in mammary epithelium

BACKGROUND

Protein C receptor (Procr) has recently been shown to mark resident adult stem cells in the mammary gland, vascular system, and pancreatic islets. More so, high Procr expression was also detected and used as indicator for subsets of triple-negative breast cancers (TNBCs). Previous study has revealed Procr as a target of Wnt/β-catenin signaling; however, direct upstream regulatory mechanism of Procr remains unknown. To comprehend the molecular role of Procr during physiology and pathology, elucidating the upstream effectors of Procr is necessary. Here, we provide a system for screening negative regulators of Procr, which could be adapted for broad molecular analysis on membrane proteins.

RESULTS

We established a screening system which combines CRISPR-Cas9 guided gene disruption with fluorescence activated cell sorting technique (FACS). CommaDβ (murine epithelial cells line) was used for the initial Procr upstream effector screening using lentiviral CRISPR-gRNA library. Shortlisted genes were further validated through individual lentiviral gRNA infection followed by Procr expression evaluation. Adam17 was identified as a specific negative inhibitor of Procr expression. In addition, MDA-MB-231 cells and Hs578T cells (human breast cancer cell lines) were used to verify the conserved regulation of ADAM17 over PROCR expression.

CONCLUSION

We established an efficient CRISPR-Cas9/FACS screening system, which identifies the regulators of membrane proteins. Through this system, we identified Adam17 as the negative regulator of Procr membrane expression both in mammary epithelial cells and breast cancer cells.

Early protein C activation is reflective of burn injury severity and plays a critical role in inflammatory burden and patient outcomes

BACKGROUND

Navigating the complexities of a severe burn injury is a challenging endeavour where the natural course of some patients can be difficult to predict. Straddling both the coagulation and inflammatory cascades that feature strongly in the burns systemic pathophysiology, we propose the pleiotropic protein C (PC) system may produce a viable biomarker to assist traditional evaluation methods for diagnostic and prognostic purposes.

METHODS

We enrolled 86 patients in a prospective observational cohort study. Over three weeks, serial blood samples were taken and measured for PC, activated (A)PC, their receptor endothelial protein C receptor (EPCR), and a panel of inflammatory cytokines including C-reactive protein (CRP), tumour necrosis factor-α, interleukin (IL)-1β, IL-6, IL-8, and IL-17. Their temporal trends were analysed alongside clinical factors including burn size, burn depth, presence of inhalational injury, and a composite outcome of requiring increased support.

RESULTS

(i) APC increased from a nadir on Day 3 (2.3±2.1ng/mL vs 4.1±2.5ng/mL by Day 18, p<0.0005), only becoming appropriately correlated to PC from Day 6 onwards (r=0.412-0.721, p<0.05 for all Days 6-21). (ii) This early disturbance in the PC system was amplified in the more severe burns (≥30% total body surface area, predominantly full thickness, or with inhalational injury), which were characterised by a marked fall in PC activation (approximated by APC/PC ratio) and APC levels during Days 0-3 with low unchanged PC levels. Critically low levels of this cytoprotective agent was associated with greater inflammatory burden, as reflected by significantly elevated CRP, IL-6, and IL-8 levels in the more severe compared to less severe burns, and by negative correlations between both PC and APC with most inflammatory cytokines. (iii) Alongside clinical markers of severity at admission (burn size, burn depth, and presence of inhalational injury), only Day 0 APC/PC ratio (OR 1.048 (1.014-1.083), p=0.006), APC (OR 1.364 (1.032-1.803), p=0.029), PC (OR 0.899 (0.849-0.953), p<0.0005), and not any inflammatory cytokines were predictive markers of requiring increased support. Uniquely, decreased Day 0 PC was further individually associated with each increased total length of stay, ICU length of stay, intravenous fluid resuscitation, and total surgeries, as well as possibly mortality.

CONCLUSION

An early functional depletion of the cytoprotective PC system provides a physiological link between severe burns and the cytokine storm, likely contributing to worse outcomes. Our findings on the changes in APC, PC and PC activation during this pathological state support APC and PC as early diagnostic and prognostic biomarkers, and provides a basis for their therapeutic potential in severe burn injuries.

Endothelial Microparticle as an early Marker of Endothelial Dysfunction in Patients with Essential Hypertension: A Pilot Study

Hypertension is a global health burden causing immense morbidity and mortality especially from the complications of end-organ damage. It is expected to affect 29% of the population by the year 2025. Hypertension is usually asymptomatic; it is diagnosed by a disease of exclusion. Numerous factors such as inflammation, oxidative stress, genetic predisposition etc. play roles in the pathogenesis of hypertension. Endothelial microparticles (EMPs) are released into the circulation with the onset of changes in endothelium, even before the release of other routine vascular endothelial markers. EMPs mediate inflammation, thrombosis and vasoconstriction of blood vessels in hypertensives. This pilot study was undertaken to assess whether EMPs are early markers of endothelial dysfunction in essential hypertensive patients. The study was conducted as a large case control study in which 525 individuals were involved. It consisted of three study groups: Group I: individuals with normal blood pressure (JNC8), group II: hypertensives without evidence of end-organ damage and group III: hypertensives with evidence of end-organ damage. Homocysteine, hsCRP, fibrinogen, eNOS, oxLDL and other markers were measured. For analysis of EMPs a subset of individuals are taken from each group. Control group of 10 individuals who had homocysteine level more than15μmol/L was taken as Group I. Another 10 individuals were taken randomly of five each from groups II and III. EMPs were analyzed by flow cytometry and were identified as CD31 +, CD42 - microparticles with diameters < 1.0 mm. There was significant increase in EMPs (p = 0.035) in hypertensive individuals with end organ damage. Measurement of EMPs in hypertensive individuals could help physicians in identifying and initiating therapeutic interventions at a very early stage of the disease, thus improving the quality of life.

An early increase in endothelial protein C receptor is associated with excess mortality in pneumococcal pneumonia with septic shock in the ICU

BACKGROUND

This study investigated changes in plasma level of soluble endothelial protein C receptor (sEPCR) in association with outcome in patients with septic shock. We explored sEPCR for early sepsis prognosis assessment and constructed a scoring system based on clinical and biological data, in order to discriminate between surviving at hospital discharge and non-surviving patients.

METHODS

Clinical data and samples were extracted from the prospective "STREPTOGENE" cohort. We enrolled 278 patients, from 50 intensive care units (ICUs), with septic shock caused by pneumococcal pneumonia. Patients were divided into survivors (n = 194) and non-survivors (n = 84) based on in-hospital mortality. Soluble EPCR plasma levels were quantified at day 1 (D1) and day 2 (D2) by ELISA. The EPCR gene A3 haplotype was determined. Patients were followed up until hospital discharge. Univariate and multivariate analyses were performed. A scoring system was constructed using least absolute shrinkage and selection operator (lasso) logistic regression for selecting predictive variables.

RESULTS

In-hospital mortality was 30.2% (n = 84). Plasma sEPCR level was significantly higher at D1 and D2 in non-surviving patients compared to patients surviving to hospital discharge (p = 0.0447 and 0.0047, respectively). Early increase in sEPCR at D2 was found in non-survivors while a decrease was observed in the survival group (p = 0.0268). EPCR A3 polymorphism was not associated with mortality. Baseline sEPCR level and its variation from D1 to D2 were independent predictors of in-hospital mortality. The scoring system including sEPCR predicted mortality with an AUC of 0.75.

CONCLUSIONS

Our findings confirm that high plasma sEPCR and its increase at D2 are associated with poor outcome in sepsis and thus we propose sEPCR as a key player in the pathogenesis of sepsis and as a potential biomarker of sepsis outcome.

The H1 haplotype of the endothelial protein C receptor protects against arterial thrombosis in patients with antiphospholipid syndrome

INTRODUCTION

Genetic variants in the endothelial protein C receptor gene (PROCR) may contribute to the thrombosis risk by regulating levels of the soluble form of this protein (sEPCR). We evaluated whether PROCR polymorphisms and sEPCR levels play a role in the thrombotic manifestations of antiphospholipid syndrome.

MATERIALS AND METHODS

One hundred and seventy-five patients (62 with primary antiphospholipid syndrome, 30 with antiphospholipid syndrome associated with systemic lupus erythematosus, 40 with systemic lupus erythematosus without antiphospholipid antibodies and 43 with systemic lupus erythematosus and antiphospholipid antibodies) and 66 healthy controls were included. PROCR H1 and H3 haplotypes were determined by genotyping 7014G/C and 1651C/G tag-polymorphisms, respectively. sEPCR levels were determined by enzyme-linked immunosorbent assay.

RESULTS

PROCR haplotype distribution was similar among groups of patients and controls. PROCR H1 and H3 haplotypes were less prevalent in antiphospholipid syndrome patients with arterial thrombosis than those without arterial thrombosis, but statistical significance was only reached for the H1 haplotype (58.0% vs. 85.7%, p = 0.003; odds ratio: 0.23 [95% CI 0.08-0.65]). No relationship between the PROCR H1 and H3 haplotypes and venous thrombosis was found. sEPCR levels were higher in H3 than in H1 carriers (175.5 [95% CI 60.9-290.1] ng/ml vs. 69.1 [95% CI 61.5-76.9] ng/ml, p < 0.01). No relationship of sEPCR with arterial or venous thrombosis was found.

CONCLUSION

The PROCR H1 haplotype was less frequently found in APS patients with arterial thrombosis, suggesting a protective effect of PROCR H1 against arterial thrombosis in these patients. No relationship between sEPCR and thrombosis was found.

The H3 Haplotype of the EPCR Gene Determines High sEPCR Levels in Critically Ill Septic Patients

Introduction

A soluble (s) form of the endothelial protein C receptor (EPCR) circulates in plasma and inhibits activated protein C (APC) activities. The clinical impact of sEPCR and its involvement in the septic process is under investigation. This study determined the frequencies of EPCR haplotypes H1 and H3 to investigate possible associations with plasma admission levels of sEPCR in an intensive care unit (ICU) cohort of septic patients.

Methods

Three polymorphisms in the EPCR gene were genotyped in 239 Caucasian critically ill patients, and their plasma sEPCR levels were also measured at the time of admission to the ICU. Multivariate logistic regression analysis controlling for sepsis severity, age, acute physiology and chronic health evaluation (APACHE II) and sequential organ failure assessment (SOFA) scores, lactate level, sex, diagnostic category, length of ICU stay and hospital mortality was performed to determine the effect of EPCR haplotypes H1 and H3 on the levels of sEPCR.

Results

Individuals carrying at least one H3 allele had significantly higher levels of sEPCR than individuals with no H3 alleles (p < 0.001). No differences were found in the distribution of the H3 allele in the patient groups categorized using the pre-existing and current sepsis-3 definitions.

Conclusion

Using the preceding and current sepsis definitions, sEPCR levels and the H3 haplotype were not associated with sepsis severity and the risk of poor outcomes in septic patients; however, the EPCR H3 allele contributed to higher levels of sEPCR.

Zingerone Suppresses the Shedding of Endothelial Protein C Receptor

Zingerone (ZGR), a phenolic alkanone found in Zingiber officinale, has been reported to have various pharmacological activities including anti-inflammatory and anti-apoptotic activities. The endothelial cell protein C receptor (EPCR) plays an important role in the cytoprotective pathway and activation of protein C EPCR can be shed from the cell surface, which is mediated by tumor necrosis factor-α converting enzyme (TACE). However, little is known about the effects of ZGR on EPCR shedding. We investigated this by monitoring the effects of ZGR on phorbol-12-myristate 13-acetate (PMA)-, tumor necrosis factor (TNF)-a, and interleukin (IL)-1p-induced EPCR shedding in human umbilical vein endothelial cells (HUVECs), and cecal ligation and puncture (CLP)-mediated EPCR shedding in mice, as well as by analyzing the underlying mechanisms. Here, ZGR triggered potent inhibition of PMA-, TNF-α-, IL-1β-and CLP-induced EPCR shedding through the inhibition of phosphorylation of mitogen-activated protein kinases (MAPKs) such as p38, janus kinase (JNK), and extracellular signal-regulated kinase (ERK) 1/2. ZGR also inhibited PMA-induced TACE expression and activity in HUVECs, suggesting that p38, ERK1/2, and JNK could be molecular targets of ZGR. These results demonstrate the potential of ZGR as an agent against PMA- and CLP-mediated EPCR shedding.

EPCR Gene Ser219Gly Polymorphism and Venous Thromboembolism: A Meta-Analysis of 9,494 Subjects

Background: Although endothelial cell protein C receptor (EPCR) gene Ser219Gly polymorphism has been associated with venous thromboembolism (VTE) susceptibility, no clear consensus has yet been reached.

Objective and methods: A meta-analysis of 9,494 subjects from 13 individual studies was conducted to better elucidate the potential relationship between the EPCR gene Ser219Gly polymorphism and VTE. Pooled odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were evaluated by using fixed or random effect models.

Results: The current meta-analysis suggested that there was a significant association between EPCR gene Ser219Gly polymorphism and VTE under allelic (OR: 1.42, 95% CI: 1.21–1.66, P = 1.30 × 10⁻⁵), recessive (OR: 2.02, 95% CI: 1.44–2.85, P = 5.35 × 10⁻⁵), homozygous (OR: 2.24, 95% CI: 1.59–3.16, P = 3.66 × 10⁻⁶), and additive genetic models (OR: 1.63, 95% CI: 1.30–2.04, P = 2.24 × 10⁻⁵).

Conclusions:EPCR gene Ser219Gly polymorphism was associated with an elevated risk of VTE and the Gly residue carriers of the EPCR gene might be predisposed to VTE.

Astragaloside IV inhibits PMA-induced EPCR shedding through MAPKs and PKC pathway

Astragaloside IV (AS-IV), a main active substance isolated from Astragalus membranaceus Bunge, has been shown to have multiple pharmacological effects. Endothelial cell protein C receptor (EPCR) is a marker of inflammation, and is also a major member of protein C (PC) anti-coagulation system. EPCR can be cut off from the cell surface by tumor necrosis factor-α converting enzyme (TACE), which is controlled through mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) pathways. To develop novel therapeutic drug for EPCR shedding, the effect of AS-IV was studied in phorbol-12-myristate 13-acetate (PMA)-induced human umbilical vein endothelial cells (HUVECs) and the potential molecular mechanism of AS-IV action was investigated. The results showed that AS-IV could significantly inhibit PMA-induced EPCR shedding. In further study, AS-IV suppressed the expression and activity of TACE. In addition, AS-IV could decrease the phosphorylation of MAPK such as janus kinase (JNK) and p38, and inhibit activation of PKC through the prevention of non-phosphorylation and phosphorylation of specific PKC isoforms in PMA-stimulated HUVECs. These findings indicate that AS-IV may be used as a natural medicine to treat EPCR-related systemic inflammation and cardiovascular diseases by targeting MAPK and PKC pathway.

Coagulation and inflammation

The protein C anticoagulant pathway is critical for controlling microvascular thrombosis and is initiated when thrombin binds to thrombomodulin (TM) on the surface of the endothelium. Protein C activation is augmented by an endothelial cell protein C receptor (EPCR). EPCR is shed from the vasculature by inflammatory mediators and thrombin. EPCR binds to activated neutrophils in a process that involves proteinase 3 and Mac-1 and appears to inhibit leukocyte extravasation. EPCR can undergo translocation from the plasma membrane to the nucleus where it re-directs gene expression. During translocation, EPCR can carry activated protein C (APC) to the nucleus, possibly accounting for the ability of APC to modulate inflammatory mediator responses in the endothelium. TNF-α and other inflammatory mediators can down-regulate EPCR and TM. Inhibition of protein C pathway function increases cytokine elaboration, endothelial cell injury and leukocyte extravasation in response to endotoxin and infusion of APC reverses these processes. In vitro, APC has been reported to inhibit TNF-α elaboration from monocytes and to block leukocyte adhesion to selectins. Since thrombin can elicit many inflammatory responses in microvascular endothelium, loss of control of microvascular thrombin generation due to impaired protein C pathway function probably contributes to microvascular dysfunction in sepsis.

Inhibitory effects of lysozyme on endothelial protein C receptor shedding in vitro and in vivo

Lysozyme protects us from the ever-present danger of bacterial infection and binds to bacterial lipopolysaccharide (LPS) with high affinity. Beyond its role in the activation of protein C, the endothelial cell protein C receptor (EPCR) plays an important role in the cytoprotective pathway. EPCR can be shed from the cell surface, which is mediated by tumor necrosis factor-α converting enzyme (TACE). However, little is known about the effects of lysozyme on EPCR shedding. We investigated this issue by monitoring the effects of lysozyme on phorbol-12-myristate 13-acetate (PMA)-, tumor necrosis factor (TNF)-α-, interleukin (IL)-1βand cecal ligation and puncture (CLP)-mediated EPCR shedding and underlying mechanism. Data demonstrate that lysozyme induced potent inhibition of PMA-, TNF-α-, IL-1β-, and CLP-induced EPCR shedding. Lysozyme also inhibited the expression and activity of PMA-induced TACE in endothelial cells. These results demonstrate the potential of lysozyme as an anti-EPCR shedding reagent against PMA-mediated and CLP-mediated EPCR shedding. [BMB Reports 2015; 48(11): 624-629]

Renal endothelial protein C receptor expression and shedding during diabetic nephropathy

Essentials Endothelial protein C receptor (EPCR) promotes diabetic nephropathy (DN) outcome improvement. Renal expression and shedding of EPCR were measured in diabetic patients with or without DN. Inhibition of metalloproteinase-driven EPCR shedding restored glomerular endothelium phenotype. EPCR shedding through metalloproteinase ADAM17 contributes to the worsening of DN.

SUMMARY

Background Diabetic nephropathy (DN) represents the leading cause of end-stage renal disease. The endothelial protein C receptor (EPCR) and its ligand (activated protein C) have been shown to ameliorate the phenotype of DN in mice. EPCR activity can be regulated by proteolytic cleavage involving ADAMs, yielding a soluble form of EPCR (sEPCR). Objective To characterize the renal expression and shedding of EPCR during DN. Methods EPCR levels were measured in plasma, urine and biopsy samples of diabetic patients with (n = 73) or without (n = 63) DN. ADAM-induced cleavage of EPCR was investigated in vitro with a human glomerular endothelium cell line. Results DN patients showed higher plasma and urinary levels of sEPCR than diabetic controls (112.2 versus 135.2 ng mL(-1) and 94.35 versus 140.6 ng mL(-1) , respectively). Accordingly, glomerular endothelial EPCR expression was markedly reduced in patients with DN, and this was associated with increased glomerular expression of ADAM-17 and ADAM-10. In vitro, EPCR shedding was induced by incubation of glomerular endothelium in high-glucose medium, and this shedding was suppressed by ADAM-17 inhibition or silencing, which led to improved vascular endothelial cadherin (VE-cadherin) expression and reduced mRNA expression of transforming growth factor (TGF)-β. In addition, EPCR silencing led to minor effects on VE-cadherin but to a significant increase in TGF-β mRNA expression. Conclusion Inhibition of ADAM-driven glomerular EPCR shedding restored the endothelial phenotype of glomerular endothelium, whereas EPCR silencing led to enhanced expression of TGF-β, a marker of endothelial-mesenchymal transition. These findings demonstrate that EPCR shedding driven by ADAMs contributes to the worsening of DN.

Suppressive Effects of Pelargonidin on Endothelial Protein C Receptor Shedding via the Inhibition of TACE Activity and MAP Kinases

Beyond its role in the activation of protein C, the endothelial cell protein C receptor (EPCR) plays an important role in the cytoprotective pathway. EPCR can be shed from the cell surface, which is mediated by tumor necrosis factor-[Formula: see text] converting enzyme (TACE). Pelargonidin is a well-known red pigment found in plants, and has been reported to have important biological activities that are potentially beneficial to human health. However, little is known about the effects of pelargonidin on EPCR shedding. We investigated this issue by monitoring the effects of pelargonidin on phorbol-12-myristate 13-acetate (PMA)-, tumor necrosis factor (TNF)-[Formula: see text]-, interleukin (IL)-1β-, and cecal ligation and puncture (CLP)-mediated EPCR shedding and by investigating the underlying mechanism of pelargonidin action. Data demonstrate that pelargonidin induced potent inhibition of PMA-, TNF-[Formula: see text]-, IL-1β-, and CLP-induced EPCR shedding by inhibiting the phosphorylation of mitogen-activated protein kinases (MAPKs) such as p38, janus kinase (JNK), and extracellular signal-regulated kinase (ERK) 1/2. Pelargonidin also inhibited the expression and activity of PMA-induced TACE in endothelial cells. These results demonstrate the potential of pelargonidin as an anti-EPCR shedding reagent against PMA- and CLP-mediated EPCR shedding.

Inhibitory effects of three diketopiperazines from marine-derived bacteria on endothelial protein C receptor shedding in human endothelial cells and mice

Diketopiperazine is a natural products found from bacteria, fungi, marine sponges, gorgonian and red algae. They are cyclic dipeptides possessing relatively simple and rigid structures with chiral nature and various side chains. The compounds in this structure class have been known to possess diverse bioactivities including antibiotic activity, anti-cancer activity, neuroprotective activity, and anti-inflammatory activity. The endothelial cell protein C receptor (EPCR) plays an important role in the cytoprotective pathway and in the activation of protein C. Endothelial cell protein C receptor (EPCR) can be shed from the cell surface, which is mediated by tumor necrosis factor-α converting enzyme (TACE). However, little is known about the effects of diketopiperazine on EPCR shedding. We investigated this issue by monitoring the effects of diketopiperazine on phorbol-12-myristate 13-acetate (PMA)-, tumor necrosis factor (TNF)-α, and interleukin (IL)-1β-induced EPCR shedding in human umbilical vein endothelial cells (HUVECs), and cecal ligation and puncture (CLP)-mediated EPCR shedding in mice and underlying mechanism. Here, three (1-3) of diketopiperazines were isolated from two strains of marine-derived bacteria and 1-3 induced potent inhibition of PMA-, TNF-α-, IL-1β (in HUVECs), and CLP-induced EPCR shedding (in mice) via inhibition of phosphorylation of mitogen-activated protein kinases (MAPKs) such as p38, janus kinase (JNK), and extracellular signal-regulated kinase (ERK) 1/2. 1-3 also inhibited the expression and activity of PMA-induced TACE in HUVECs suggesting that p38, ERK1/2, and JNK could be molecular targets of 1-3. These results demonstrate the potential of 1-3 as an anti-EPCR shedding reagent against PMA-mediated and CLP-mediated EPCR shedding.

Anti-inflammatory effects of Baicalin, Baicalein, and Wogonin in vitro and in vivo

Here, three structurally related polyphenols found in the Chinese herb Huang Qui, namely baicalin, baicalein, and wogonin, were examined for its effects on inflammatory responses by monitoring the effects of baicalin, baicalein, and wogonin on lipopolysaccharide (LPS)-mediated vascular inflammatory responses. We found that each compound inhibited LPS-induced barrier disruption, expression of cell adhesion molecules (CAMs), and adhesion/transendothelial migration of monocytes to human endothelial cells. Each compound induced potent inhibition of phorbol-12-myristate 13-acetate and LPS-induced endothelial cell protein C receptor shedding. It also suppressed LPS-induced hyperpermeability and leukocytes migration in vivo. Furthermore, each compound suppressed the production of tumor necrosis factor-α or interleukin-6 and the activation of nuclear factor-κB or extracellular regulated kinases 1/2 by LPS. Moreover, treatment with each compound resulted in reduced LPS-induced lethal endotoxemia. These results suggest that baicalin, baicalein, and wogonin posses anti-inflammatory functions by inhibiting hyperpermeability, expression of CAMs, and adhesion and migration of leukocytes, thereby endorsing its usefulness as a therapy for vascular inflammatory diseases.

Suppressive effects of polyozellin on endothelial protein C receptor shedding via inhibiting TACE activity and MAP kinases

Beyond its role in the activation of protein C, the endothelial cell protein C receptor (EPCR) plays an important role in the cytoprotective pathway. EPCR can be shed from the cell surface, which is mediated by tumor necrosis factor-α converting enzyme (TACE). Polyozellin, a major constituent of a Korea edible mushroom Polyozellus multiplex, has been known to exhibit the biological activities such as anti-oxidative and anti-inflammatory effects. However, little is known about the effects of polyozellin on EPCR shedding. We investigated this issue by monitoring the effects of polyozellin on phorbol-12-myristate 13-acetate (PMA)-, tumor necrosis factor (TNF)-α-, interleukin (IL)-1β-induced EPCR shedding in human umbilical vein endothelial cells (HUVECs), and cecal ligation and puncture (CLP)-mediated EPCR shedding in mice and underlying mechanism. Data demonstrate that polyozellin induced potent inhibition of PMA-, TNF-α-, IL-1β- (in HUVECs), and CLP-induced EPCR shedding (in mice) via inhibition of phosphorylation of mitogen-activated protein kinases (MAPKs) such as p38, janus kinase (JNK), and extracellular signal-regulated kinase (ERK) 1/2. Polyozellin also inhibited the expression and activity of PMA-induced TACE in HUVECs suggesting that p38, ERK1/2, and JNK could be the molecular targets of POZ. These results demonstrate the potential of polyozellin as an anti-EPCR shedding reagent against PMA-mediated and CLP-mediated EPCR shedding.

Endothelial protein C receptor gene 6936A/G single-nucleotide polymorphism as a possible biomarker of thrombotic risk in acute myeloid leukemia

Protein C (PC) is a natural anticoagulant, which interacts with the endothelial PC receptor (EPCR). EPCR single-nucleotide polymorphism (SNP) 6936A/G results in high levels of a free soluble form of EPCR (sEPCR) and may affect the risk of coagulation. The objective of this study was to assess whether the 6936A/G SNP of the EPCR gene is involved in the procoagulant activity displayed by hematological malignancies. EPCR 6936A/G polymorphism analysis was performed in 205 patients with hematological malignancies and in 63 healthy controls. All the subjects were genotyped for the EPCR 6936A/G SNP (AA, AG and GG genotypes). The 6936A/G polymorphism distribution was similar between healthy donors and patients. The association between EPCR 6936A/G SNP and thrombosis was investigated in 110 patients. The disease-wise break-up revealed that 55 of the patients suffered from acute myeloid leukemia (AML). In AML patients, the incidence of thrombosis was 28.3% and significantly higher in the 6936AG compared with that in the 6936AA genotype (50 vs. 22%, respectively). In conclusion, this study revealed a significant association of the 6936AG genotype of EPCR with thrombotic events in AML. Therefore, the presence of the 6936AG genotype in AML patients may be considered as a risk indicator of thrombosis.

Association of ambulatory arterial stiffness index with sEPCR in newly diagnosed hypertensive patients

AIM

Increased arterial stiffness is strongly associated with cardiovascular diseases, while thrombotic events are more common than hemorrhagic events in hypertensive patients. Markers of a hypercoagulable state may also predict future cardiovascular events in hypertensive patients. Here, we speculated that increased arterial stiffness might lead to the development of a hypercoagulable state that can play a role in the thrombotic complications of hypertension. Soluble endothelial protein C receptor (sEPCR) is one such marker of hypercoagulation. The ambulatory arterial stiffness index (AASI) could be accepted as a non-invasive measure of arterial stiffness. The aim of this study was to investigate association of AASI with levels of sEPCR in newly diagnosed hypertensive patients.

MATERIALS AND METHODS

The study included 263 newly diagnosed essential hypertensive patients and 55 healthy normotensive controls. All subjects underwent 24 h ambulatory blood pressure monitoring (ABPM); the AASI was derived from ABPM tracings. Plasma sEPCR was measured by ELISA.

RESULTS

Hypertensive patients (n = 263) had higher AASI, C-reactive protein (CRP) and sEPCR versus the normotensive healthy group (n = 55). Univariate analysis showed that AASI was positively associated with age (r = 0.212, p <  0.001) body mass index (r = 0.412, p < 0.001), pulse pressure (r = 0.350, p < 0.001), plasma sEPCR (r = 0.894, p < 0.001), 24-h heart rate (r = 0.176, p = 0.001) and inversely related to high-density lipoprotein (HDL) (r = -0.293, p < 0.001). Multivariate analyses revealed that sEPCR and HDL are independently correlated to AASI.

CONCLUSION

We suggest that increased AASI is associated with elevated sEPCR. It might be responsible for subsequent thrombotic events in newly diagnosed hypertensive patients.

Serum sEPCR levels are elevated in patients with Alzheimer's disease

Blood-brain barrier impairment and endothelial cell dysfunction have both been implicated in the pathogenesis of Alzheimer's disease (AD). The presence of vascular risk factors is also known to increase the risk of AD. Soluble endothelial protein C receptor (sEPCR) should thus produce procoagulant and proinflammatory effects. Serum sEPCR levels have been found to be associated with several diseases. To date, no reports have been published regarding serum sEPCR levels in AD. In this study, we found that serum sEPCR levels were significantly increased in patients with AD when compared to control participants (P = .0005). There was no significant difference between patients with mild cognitive impairment (MCI) and healthy controls (P = .055) or between patients with AD and MCI (P = .054). Importantly, our results also indicate that the degree of cognitive impairment is significantly correlated with serum sEPCR levels in all patients and healthy controls. These findings suggest that serum sEPCR levels could be a potential candidate for a biomarker panel for AD diagnosis.

Protein C system defects inflicted by the malaria parasite protein PfEMP1 can be overcome by a soluble EPCR variant

The Endothelial Protein C receptor (EPCR) is essential for the anticoagulant and cytoprotective functions of the Protein C (PC) system. Selected variants of the malaria parasite protein, Plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1) associated with severe malaria, including cerebral malaria, specifically target EPCR on vascular endothelial cells. Here, we examine the cellular response to PfEMP1 engagement to elucidate its role in malaria pathogenesis. Binding of the CIDRα1.1 domain of PfEMP1 to EPCR obstructed activated PC (APC) binding to EPCR and induced a loss of cellular EPCR functions. CIDRα1.1 severely impaired endothelial PC activation and effectively blocked APC-mediated activation of protease-activated receptor-1 (PAR1) and associated barrier protective effects of APC on endothelial cells. A soluble EPCR variant (E86A-sEPCR) bound CIDRα1.1 with high affinity and did not interfere with (A)PC binding to cellular EPCR. E86A-sEPCR used as a decoy to capture PfEMP1, permitted normal PC activation on endothelial cells, normal barrier protective effects of APC, and greatly reduced cytoadhesion of infected erythrocytes to brain endothelial cells. These data imply important contributions of PfEMP1-induced protein C pathway defects in the pathogenesis of severe malaria. Furthermore, the E86A-sEPCR decoy provides a proof-of-principle strategy for the development of novel adjunct therapies for severe malaria.

Inhibitory effects of rutin on the endothelial protein C receptor shedding in vitro and in vivo

Endothelial cell protein C receptor (EPCR) has important functions in regulation of coagulation and inflammation. EPCR shedding from the cell surface is mediated by tumor necrosis factor-α converting enzyme (TACE). Rutin is one of the major flavonoids from the buckwheat plant Fagopyrum tataricum. In this study, we investigated the effects of rutin on phorbol-12-myristate 13-acetate (PMA), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and on cecal ligation and puncture (CLP)-mediated EPCR shedding. We used a CLP model because this model more closely resembles human sepsis. Data showed rutin was a potent inhibitor of PMA, TNF-α, IL-1β, and CLP-induced EPCR shedding by suppression of TACE expression. Treatment with rutin resulted in a decrease of PMA-stimulated phosphorylation of p38, extracellular regulated kinases 1/2, and c-Jun N-terminal kinase. These results suggest the potential application of rutin for treatment of PMA and CLP-mediated EPCR shedding.

Soluble endothelial protein C receptor and high sensitivity C reactive protein levels as markers of endothelial dysfunction in patients with type 1 and type 2 diabetes mellitus: their role in the prediction of vascular complications

BACKGROUND AND OBJECTIVE

Endothelial dysfunction in diabetes mellitus (DM) is an important factor in the pathogenesis of micro and macrovascular complications. We aimed to measure soluble endothelial protein C receptor (sEPCR) and high sensitivity C reactive protein (hsCRP) levels as markers of endothelial damage in both types of diabetes mellitus and to determine if they can be used as predictors of vascular complications.

METHODS

Fifty patients with DM, 20 with type 1 and 30 with type 2 as well as 30 healthy subjects were included. All were subjected to measurement of sEPCR and hsCRP by enzyme linked immunosorbent assay.

RESULTS

sEPCR and hsCRP were significantly increased when compared to the control group in both types of DM. sEPCR was a significant predictor of macrovascular complications and thrombosis in type 1 p=0.02, and p=0.015, respectively. hsCRP was a significant predictor of macrovascular complications in type 2 p=0.04.

CONCLUSION

Patients with type 1 and type 2 DM exhibit higher sEPCR and hsCRP levels compared to healthy controls which suggesting endothelial damage. sEPCR could be used as a predictor of macrovascular complications and thrombosis in type 1 DM, whereas, hsCRP might be used as a predictor of macrovascular complications in type 2 DM.

Endothelial Protein C Receptor Gene Variants and Risk of Thrombosis

Endothelial protein C receptor (EPCR) is a candidate mediator in the pathogenesis of thrombosis, as several data in the literature indicate that polymorphisms such as EPCR 4678G/C and 4600A/G are associated with either protective effect or increased risk of thrombosis, respectively. We investigated the prevalence of these polymorphisms in patients with thrombotic disorders as well as their impact on the risk of thrombosis, the age of first thrombotic episode, and recurrence. The prevalence of the rare EPCR alleles 4600G and 4678C was comparable in patients and controls. However, in a subset analysis, we observed that 4600G allele was more prevalent among patients who developed thrombosis at younger age (<35 years). Moreover, the prevalence of 4678C allele was significantly lower in younger patients compared to older patients. Neither polymorphism seemed to have an impact on recurrence regardless of age. Soluble EPCR levels were elevated in 4600AG patients compared to controls while 4678CC patients presented with lower levels of soluble form of EPCR compared to carriers of at least 1 4678G allele. Our data suggest that either the lack of the protective EPCR 4678C allele or the presence of EPCR 4600G allele may be associated with earlier development of thrombosis.

sEPCR Levels in Chronic Myeloproliferative Diseases and Their Association with Thromboembolic Events: A Case-Control Study

Objective: Venous, arterial, and microcirculatory events are frequently encountered in the clinical course of essential thrombocytosis and polycythemia vera. We aimed to investigate the levels of soluble endothelial protein C receptor (sEPCR) in myeloproliferative diseases to see whether there was a difference between the patients with and without history of thromboembolism.

Materials and Methods: The study included patients with polycythemia vera (n=12), patients with essential thrombocytosis (n=13), and controls (n=29). In all groups, we measured proteins C and S, antithrombin and sEPCR levels, and plasma concentrations of thrombin-antithrombin complex, prothrombin fragments 1+2, and D-dimer.

Results: Comparing the patients with and without history of thromboembolic attack, statistically significant differences were not observed in terms of sEPCR, D-dimer, thrombin-antithrombin complex, prothrombin fragments 1+2, and hematocrit levels (p=0.318, 0.722, 0.743, 0.324, and 0.065, respectively).

Conclusion: Significant increase in the parameters that reflect activation of coagulation, such as sEPCR, thrombin-antithrombin complex, prothrombin fragments 1+2, and D-dimer, reflects the presence of a basal condition that leads to a tendency toward thrombosis development in ET and PV when compared to healthy controls.

Comparative response of platelet fV and plasma fV to activated protein C and relevance to a model of acute traumatic coagulopathy

Background

Acute traumatic coagulopathy (ATC) has been linked to an increase in activated protein C (aPC) from 40 pM in healthy individuals to 175 pM. aPC exerts its activity primarily through cleavage of active coagulation factor Va (fVa). Platelets reportedly possess fVa which is more resistant to aPC cleavage than plasma fVa; this work examines the hypothesis that normal platelets are sufficient to maintain coagulation in the presence of elevated aPC.

Methods

Coagulation responses of normal plasma, fV deficient plasma (fVdp), and isolated normal platelets in fVdp were conducted: prothrombin (PT) tests, turbidimetry, and thromboelastography (TEG), including the dose response of aPC on the samples.

Results

PT and turbidimetric assays demonstrate that normal plasma is resistant to aPC at doses much higher than those found in ATC. Additionally, an average physiological number of washed normal platelets (200,000 platelets/mm³) was sufficient to eliminate the anti-coagulant effects of aPC up to 10 nM, nearly two orders of magnitude above the ATC concentration and even the steady-state pharmacological concentration of human recombinant aPC, as measured by TEG. aPC also demonstrated no significant effect on clot lysis in normal plasma samples with or without platelets.

Conclusions

Although platelet fVa shows slightly superior resistance to aPC's effects compared to plasma fVa in static models, neither fVa is sufficiently cleaved in simulations of ATC or pharmacologically-delivered aPC to diminish coagulation parameters. aPC is likely a correlative indicator of ATC or may play a cooperative role with other activity altering products generated in ATC.

Exendin-4 inhibits endothelial protein C receptor shedding in vitro and in vivo

Exendin-4 (EX4), a glucagon-like peptide-1 receptor agonist, has been reported to attenuate myocardial ischemia and reperfusion (I/R) injury, inflammatory and oxidative responses. Increasing evidence has demonstrated that beyond its role in activation of protein C, endothelial cell protein C receptor (EPCR) is involved in vascular inflammation. EPCR activity is markedly decreased by ectodomain cleavage and release as the soluble EPCR. EPCR can be shed from the cell surface, which is mediated by tumor necrosis factor-α converting enzyme (TACE). However, little is known about the effects of EX4 on EPCR shedding. Data from this study showed that EX4 induced potent inhibition of phorbol-12-myristate 13-acetate (PMA), tumor necrosis factor (TNF)-α, and interleukin (IL)-1β-induced EPCR shedding in human umbilical vein endothelial cells (HUVECs), and cecal ligation and puncture (CLP)-induced EPCR shedding in mice. EX4 also inhibited expression and activity of TACE induced by PMA in HUVECs. In addition, treatment with EX4 resulted in reduced PMA-stimulated phosphorylation of p38, extracellular regulated kinases (ERK) 1/2, and c-Jun N-terminal kinase (JNK). These results demonstrate the potential of EX4 as an anti-sEPCR shedding reagent against PMA and CLP-mediated EPCR shedding.

Withaferin A is an inhibitor of endothelial protein C receptor shedding in vitro and in vivo

Withaferin A (WFA), an active compound from Withania somnifera, has been widely researched for its anti-inflammatory and cardioactive properties and effects on the central nervous system. The endothelial cell protein C receptor (EPCR) plays important roles in blood coagulation and inflammation. EPCR activity is markedly changed by ectodomain cleavage and release as the soluble EPCR. EPCR is shed from the cell surface, mediated by tumor necrosis factor-α converting enzyme (TACE). In this study, we investigated the effects of WFA on the EPCR shedding in human umbilical vein endothelial cells (HUVECs) and in mice and the associated signaling pathways. WFA was found to induce inhibition of phorbol-12-myristate 13-acetate (PMA), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and on cecal ligation and puncture (CLP)-induced EPCR shedding and WFA suppressed the expression and activity of TACE. In addition, treatment with WFA resulted in reduced PMA-stimulated phosphorylation of p38, extracellular regulated kinases (ERK) 1/2, and c-Jun N-terminal kinase (JNK). These results demonstrate a therapeutic potentiality of WFA as an anti-sEPCR shedding reagent against PMA and CLP-mediated EPCR shedding.

Endothelial protein C receptor-associated invasiveness of rheumatoid synovial fibroblasts is likely driven by group V secretory phospholipase A2

INTRODUCTION

Rheumatoid synovial fibroblasts (RASFs) mediate joint inflammation and destruction in rheumatoid arthritis (RA). Endothelial protein C receptor (EPCR) is a specific receptor for the natural anticoagulant activated protein C (APC). It mediates the cytoprotective properties of APC and is expressed in rheumatoid synovial tissue. A recent report shows that group V secretory phospholipase A2 (sPLA₂V) prevents APC from binding to EPCR in endothelium and inhibits EPCR/APC function. The aim of this study was to investigate the expression and function of EPCR on RASFs.

METHODS

Human synovial fibroblasts (SFs) were isolated from RA or osteoarthritis (OA) synovial tissues and treated with control, EPCR, or sPLA₂V small interfering RNA (siRNA); recombinant human APC, tumor necrosis factor-alpha (TNF-α), or sPLA₂V. RASF viability and migration/invasion were measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and collagen gel migration/invasion assays, respectively, and cartilage degradation by 1,9-dimethylmethylene blue (DMMB) assay in the presence of human OA articular cartilage explants. The expression or activation of cytokines, EPCR, cadherin-11, mitogen-activated protein (MAP) kinases, and nuclear factor-kappa-B (NF-κB) or both were detected by enzyme-linked immunosorbent assay, Western blotting, or immunostaining.

RESULTS

EPCR was expressed by both OASFs and RASFs but was markedly increased in RASFs. When EPCR was suppressed by siRNA or blocking antibody cell viability, cell invasion and cartilage degradation were reduced by more than 30%. Inflammatory mediators interleukin-1-beta (IL-1β), cadherin-11, and NF-κB were significantly reduced by EPCR suppression under control or TNF-α-stimulated conditions. The expression or activation (or both) of MAP kinases ERK, p38, and JNK were also markedly decreased in cells transfected with EPCR siRNA. Further analysis revealed that sPLA₂V co-localized with EPCR on RASFs. Suppression of sPLA₂V reduced cell viability and cartilage degradation and increased APC binding to RASFs. Conversely, recombinant sPLA₂V increased cartilage degradation, blocked APC binding to RASFs, and could not rescue the effects induced by EPCR suppression.

CONCLUSIONS

Our results demonstrate that EPCR is overexpressed by RASFs and mediates the aggressive behavior of RASFs. This function of EPCR is contrary to its cytoprotective role in other settings and is likely driven by sPLA₂V.