Activated Protein C Strengthens Cardiac Tolerance to Ischemic Insults in Aging.

BACKGROUND: APC (activated protein C) is a plasma serine protease with anticoagulant and anti-inflammatory activities. EPCR (Endothelial protein C receptor) is associated with APC's activity and mediates its downstream signaling events. APC exerts cardioprotective effects during ischemia and reperfusion (I/R). This study aims to characterize the role of the APC-EPCR axis in ischemic insults in aging. METHODS: Young (3-4 months) and aged (24-26 months) wild-type C57BL/6J mice, as well as EPCR point mutation (EPCRR84A/R84A) knockin C57BL/6J mice incapable of interaction with APC and its wild type of littermate C57BL/6J mice, were subjected to I/R. Wild-type APC, signaling-selective APC-2Cys, or anticoagulant-selective APC-E170A were administrated before reperfusion. RESULTS: The results demonstrated that cardiac I/R reduces APC activity, and the APC activity was impaired in the aged versus young hearts possibly attributable to the declined EPCR level with aging. Serum EPCR measurement showed that I/R triggered the shedding of membrane EPCR into circulation, while administration of APC attenuated the I/R-induced EPCR shedding in both young and aged hearts. Subsequent echocardiography showed that APC and APC-2Cys but not APC-E170A ameliorated cardiac dysfunction during I/R in both young and aged mice. Importantly, APC elevated the resistance of the aged heart to ischemic insults through stabilizing EPCR. However, all these cardioprotective effects of APC were blunted in the EPCRR84A/R84A mice versus its wild-type littermates. The ex vivo working heart and metabolomics results demonstrated that AMPK (AMP-activated protein kinase) mediates acute adaptive response while AKT (protein kinase B) is involved in chronic metabolic programming in the hearts with APC treatment. CONCLUSIONS: I/R stress causes shedding of the membrane EPCR in the heart, and administration of APC prevents I/R-induced cardiac EPCR shedding that is critical for limiting cardiac damage in aging.

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.

Soluble endothelial protein C is associated with blood pressure variability and salt consumption but not mean blood pressure in patients with newly diagnosed primary hypertension.

BACKGROUND: Hypertension is a widespread disease involving frequent thrombotic complications. Blood pressure variability (BPV) has recently been shown to be associated with end-organ damage and cardiovascular events. However, the pathogenesis of the relation between BPV and cardiovascular events has not yet been explained. Soluble endothelial protein C (sEPCR) exhibits a procoagulant effect by reducing the anticoagulant and anti-inflammatory effects of protein C and activated protein C. The purpose of this study was to evaluate sEPCR levels in hypertensive individuals and the parameters affecting that level, particularly BPV. METHODS: Fifty-one newly diagnosed hypertensive subjects and 31 healthy individuals were included in the study. Twenty-four-hour ambulatory blood pressure monitoring (ABPM) was performed after office control, and simultaneous 24-h urine was collected. BPV was calculated with average real variability (ARV) from ABPM data. Blood specimens were collected under appropriate conditions for sEPCR levels and biochemical tests. sEPCR levels were compared between the patient and healthy groups, after which parameters affecting sEPCR elevation in the hypertensive group were evaluated. RESULTS: sEPCR levels were significantly high in the hypertensive group (p < 0.05). At multivariate regression analysis in the hypertensive group, sEPCR was determined to be independently associated with 24-h systolic ARV (ß = 0.572, p < 0.05) and 24-h urine Na (ß = 0.428, p < 0.05). CONCLUSION: In our study, sEPCR was high in hypertensive individuals, and this elevation was related to ARV and urine Na excretion independently of mean blood pressure.

Alterations of anticoagulant proteins and soluble endothelial protein C receptor in thalassemia patients of Chinese origin.

BACKGROUND: Thalassemia is characterized by a hypercoagulable state in which the protein C (PC) pathway controls thrombosis. We investigated changes in PC, protein S (PS), antithrombin III (AT III) and soluble endothelial protein C receptor (sEPCR) in thalassemia. METHODS: A group of 129 patients with ß-thalassemia major (ß-TM), ß-thalassemia intermedia (ß-TI), α-thalassemia intermedia (α-TI) and combined α-/ß-thalassemia (α + ß-thal) were compared with 32 gender- and age-matched controls. PC, PS, AT III, sEPCR, thrombin-antithrombin complex (TAT), and intercellular adhesion molecule1 (ICAM-1) antigens were measured by enzyme-linked immunosorbent assay. PC, AT III, and PS activity were assayed by substrate chromatography and a prothrombin time (PT)-based free protein S assay. RESULTS: PC deficiency was seen in 95.3% of the patients and PS deficiency was seen in 77.5%. Concomitant reductions in PC and AT III antigen and activity were observed in ß-TM, ß-TI, and α-TI than in controls (p < 0.005). PC activity was lower in ß-TM than in α-TI (p = 0.004). PS antigen was elevated in ß-TM (p = 0.011) and sEPCR was elevated in α-TI (p = 0.018). Nonsplenectomized patients had lower PC (p = 0.001) and PS (p = 0.006) and higher sEPCR (p = 0.021) than postsplenectomy patients. Transfusion dependent thalassemia (TDT) patients had lower PC levels (p < 0.005) than those with nontransfusion dependent thalassemia (NTDT). ICAM-1 was increased in patient subgroups (p < 0.001), especially those with splenectomies (p = 0.009), and TAT was increased in all patient subgroups compared with controls (p < 0.001) except for α + ß-thal. CONCLUSIONS: Deficiencies of anticoagulant proteins and elevated sEPCR contributed to chronic hypercoagulability in these thalassemia patients of Chinese origin. Splenectomy alleviated these alterations in this patient cohort with the median duration since splenectomy of two years. Blood transfusion was not ideal for avoiding thrombosis.

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.

Human platelets express endothelial protein C receptor, which can be utilized to enhance localization of factor VIIa activity.

Essentials Factor VIIa binds activated platelets to promote hemostasis in hemophilia patients with inhibitors. The interactions and sites responsible for platelet-FVIIa binding are not fully understood. Endothelial cell protein C receptor (EPCR) is expressed on activated human platelets. EPCR binding enhances the efficacy of a FVIIa variant and could impact design of new therapeutics. SUMMARY: Background High-dose factor VIIa (FVIIa) is routinely used as an effective bypassing agent to treat hemophilia patients with inhibitory antibodies that compromise factor replacement. However, the mechanism by which FVIIa binds activated platelets to promote hemostasis is not fully understood. FVIIa-DVQ is an analog of FVIIa with enhanced tissue factor (TF)-independent activity and hemostatic efficacy relative to FVIIa. Our previous studies have shown that FVIIa-DVQ exhibits greater platelet binding, thereby suggesting that features in addition to lipid composition contribute to platelet-FVIIa interactions. Objectives Endothelial cell protein C receptor (EPCR) also functions as a receptor for FVIIa on endothelial cells. We therefore hypothesized that an interaction with EPCR might play a role in platelet-FVIIa binding. Methods/results In the present study, we used flow cytometric analyses to show that platelet binding of both FVIIa and FVIIa-DVQ is partially inhibited in the presence of excess protein C or an anti-EPCR antibody. This decreased binding results in a corresponding decrease in the activity of both molecules in FXa and thrombin generation assays. Enhanced binding to EPCR was sufficient to account for the increased platelet binding of FVIIa-DVQ compared with wild-type FVIIa. As EPCR protein expression has not previously been shown in platelets, we confirmed the presence of EPCR in platelets using immunofluorescence, flow cytometry, immunoprecipitation, and mass spectrometry. Conclusions This work represents the first demonstration that human platelets express EPCR and suggests that modulation of EPCR binding could be utilized to enhance the hemostatic efficacy of rationally designed FVIIa analogs.

Inflammatory and related biomarkers are associated with post-transplant diabetes mellitus in kidney recipients: a retrospective study.

In this study, we investigate the association between selected inflammatory-related biomarkers and post-transplant hyperglycemia in kidney transplant recipients. This retrospective analysis comprises 852 patients receiving a kidney transplant at the Norwegian national transplant center between 2007 and 2012, all having a normal oral glucose tolerance test (OGTT) before transplantation. A diagnostic OGTT was performed 10 weeks post-transplant to examine the association between inflammation-related biomarkers and two-hour plasma glucose (2HPG) by multivariable linear regression models adjusting for BMI, age, graft function, fasting insulin levels, dosage of prednisolone, and concentration of calcineurin inhibitors. Six of 20 biomarkers were significantly associated with 2HPG in multivariate analyses showing strong associations with soluble tumor necrosis factor type 1 (P = 0.027), Pentraxin 3 (P = 0.019), macrophage migration inhibitory factor (P = 0.024), and endothelial protein C receptor (P = 0.001). These associated markers reflect several distinct but also overlapping pathways including activation of tumor necrosis factor, macrophages, and endothelial cells. The multinomial logistic regression model showed a clear association between the inflammatory biomarkers and post-transplant diabetes mellitus (PTDM). The association between a range of inflammation markers and PTDM suggests that these markers may be target for future studies on pathogenesis and perhaps also treatment of PTDM.

Alteration of haemostatic parameters in uncomplicated canine babesiosis.

Babesiosis is a tick-borne zoonotic disease caused by haemoprotozoan parasites. The aim of this study were to assess markers of coagulation pathways in 25 dogs with naturally occurring babesiosis caused by B. canis, compared to 10 healthy controls. Protein C (PC) and antithrombin III (AT III) activity were assessed using a chromogenic substrate test, while levels of thrombin-antithrombin (TAT) complexes, activated protein C (APC) and endothelial protein C receptor were assessed using canine-specific ELISA. AT III activity was decreased as a result of a negative acute phase response, degradation by elastase, reduced availability of glycosaminoglycans, and, most importantly, consumption as a consequence of thrombin formation. Procoagulant state and haemostatic shift towards thrombin formation are also demonstrated by elevated TAT levels. Regarding PC pathway only significant difference was found for APC. Taken together, haemostatic alterations in uncomplicated babesiosis represent a procoagulant state that is mostly reversed during treatment.

Decreased Activity of the Protein C Anticoagulant Pathway in the Early Hours of Paroxysmal Atrial Fibrillation.

BACKGROUND: Increased coagulation activity has been established in paroxysmal atrial fibrillation (PAF), but data on the anticoagulant system are scarce. PURPOSE: To examine the protein C anticoagulant pathway in the early hours of the disease. MATERIALS AND METHODS: Fifty-one patients (26 men and 25 women; mean age 59.84 ± 1.60 years) and 52 controls (26 men and 26 women; mean age 59.50 ± 1.46 years) were selected for the study. Protein C antigen and its activity, total protein S, free protein S and its activity, soluble forms of endothelial protein C receptor (sEPCR), and thrombomodulin (sTM) were examined in the plasma. RESULTS: The indicators were studied in patients between the 2nd and the 24th hour after the onset of arrhythmia. Levels of protein C were significantly elevated in patients compared to controls (111.40% ± 6.66% vs 94.83% ± 4.47%; P = .039). Protein C activity showed significant reduction in PAF (73.13% ± 5.80% vs 103.3% ± 3.80%; P < .001). Total protein S levels did not differ significantly (108.20% ± 4.07% vs 102.40% ± 3.65%; P = .30). Free protein S (76.81% ± 6.01% vs 122.10% ± 3.97%; P < .001) and its activity (71.39% ± 6.27% vs 119.50% ± 6.54%; P < .001) were reduced in patients. Higher levels of sEPCR (203.10 ± 10.33 vs 133.10 ± 7.37 ng/mL; P < .001) and sTM (6.50±0.40 vs 4.48±0.28 ng/mL; P < .001) were measured in PAF. CONCLUSION: Protein C activity is reduced still in the first hours (until the 24th hour) of PAF clinical manifestation, determining reduced activity of the anticoagulant pathway as a whole. The established low levels of free protein S and its activity as well as low sEPCR and sTM levels are a possible explanation of the changes in protein C activity.

Plasma Ang2 and ADAM17 levels are elevated during clinical malaria; Ang2 level correlates with severity and expression of EPCR-binding PfEMP1.

The pathogenesis of Plasmodium falciparum malaria involves a complex interplay between parasite adhesion and inflammatory response that includes release of cytokines and activation of the endothelium with accompanying release of Angiopoitin 2 (Ang2) to the plasma. A-disintegrin and metalloproteinase 17 (ADAM17) is a protein responsible for releasing cytokines, including Tumor Necrosis Factor α (TNFα), and shedding of adhesion proteins. In this study, we show that plasma levels of ADAM17 are increased in Tanzanian children hospitalized with a malaria infection compared with asymptomatic children but similar to children hospitalized with other infectious diseases. The plasma levels of ADAM17 decreased during recovery after an acute malaria episode. Plasma levels of Ang2 were associated with markers of malaria severity and levels of var transcripts encoding P. falciparum Erythrocyte Membrane Protein 1 (PfEMP1) containing Cysteine Rich Inter Domain Region α1 (CIDRα1) domains predicted to bind Endothelial Protein C receptor (EPCR). ADAM17 levels were not associated with expression of var genes encoding different PfEMP1 types when controlling for age. These data are the first to report ADAM17 plasma levels in malaria-exposed individuals, and support the notion that parasite sequestration mediated by EPCR-binding PfEMP1 is associated with endothelial activation and pathology in severe paediatric malaria.

The endothelial protein C receptor rs867186-GG genotype is associated with increased soluble EPCR and could mediate protection against severe malaria.

The endothelial protein C receptor (EPCR) appears to play an important role in Plasmodium falciparum endothelial cell binding in severe malaria (SM). Despite consistent findings of elevated soluble EPCR (sEPCR) in other infectious diseases, field studies to date have provided conflicting data about the role of EPCR in SM. To better define this role, we performed genotyping for the rs867186-G variant, associated with increased sEPCR levels, and measured sEPCR levels in two prospective studies of Ugandan children designed to understand immunologic and genetic factors associated with neurocognitive deficits in SM including 551 SM children, 71 uncomplicated malaria (UM) and 172 healthy community children (CC). The rs867186-GG genotype was more frequent in CC (4.1%) than SM (0.6%, P = 0.002). The rs867186-G variant was associated with increased sEPCR levels and sEPCR was lower in children with SM than CC (P < 0.001). Among SM children, those who had a second SM episode showed a trend toward lower plasma sEPCR both at initial admission and at 6-month follow-up compared to those without repeated SM (P = 0.06 for both). The study findings support a role for sEPCR in severe malaria pathogenesis and emphasize a distinct role of sEPCR in malaria as compared to other infectious diseases.