Mechanisms of anticoagulant and cytoprotective actions of the protein C pathway

Heme-induced loss of renovascular endothelial protein C receptor promotes chronic kidney disease in sickle mice

ABSTRACT

Chronic kidney disease (CKD) is a major contributor to morbidity and mortality in sickle cell disease (SCD). Anemia, induced by chronic persistent hemolysis, is associated with the progressive deterioration of renal health, resulting in CKD. Moreover, patients with SCD experience acute kidney injury (AKI), a risk factor for CKD, often during vaso-occlusive crisis associated with acute intravascular hemolysis. However, the mechanisms of hemolysis-driven pathogenesis of the AKI-to-CKD transition in SCD remain elusive. Here, we investigated the role of increased renovascular rarefaction and the resulting substantial loss of the vascular endothelial protein C receptor (EPCR) in the progressive deterioration of renal function in transgenic SCD mice. Multiple hemolytic events raised circulating levels of soluble EPCR (sEPCR), indicating loss of EPCR from the cell surface. Using bone marrow transplantation and super-resolution ultrasound imaging, we demonstrated that SCD mice overexpressing EPCR were protective against heme-induced CKD development. In a cohort of patients with SCD, plasma sEPCR was significantly higher in individuals with CKD than in those without CKD. This study concludes that multiple hemolytic events may trigger CKD in SCD through the gradual loss of renovascular EPCR. Thus, the restoration of EPCR may be a therapeutic target, and plasma sEPCR can be developed as a prognostic marker for sickle CKD.

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.

Therapeutic management of ischemic stroke

Stroke is the third leading cause of years lost due to disability and the second-largest cause of mortality worldwide. Most occurrences of stroke are brought on by the sudden occlusion of an artery (ischemic stroke), but sometimes they are brought on by bleeding into brain tissue after a blood vessel has ruptured (hemorrhagic stroke). Alteplase is the only therapy the American Food and Drug Administration has approved for ischemic stroke under the thrombolysis category. Current views as well as relevant clinical research on the diagnosis, assessment, and management of stroke are reviewed to suggest appropriate treatment strategies. We searched PubMed and Google Scholar for the available therapeutic regimes in the past, present, and future. With the advent of endovascular therapy in 2015 and intravenous thrombolysis in 1995, the therapeutic options for ischemic stroke have expanded significantly. A novel approach such as vagus nerve stimulation could be life-changing for many stroke patients. Therapeutic hypothermia, the process of cooling the body or brain to preserve organ integrity, is one of the most potent neuroprotectants in both clinical and preclinical contexts. The rapid intervention has been linked to more favorable clinical results. This study focuses on the pathogenesis of stroke, as well as its recent advancements, future prospects, and potential therapeutic targets in stroke therapy.

Natural Anticoagulant Protein Levels in Patients With Beta-Thalassemia Major: A Case-Control Study

Background

β-thalassemia is a group of inherited blood disorders that affect the production of β-globin chains, leading to the reduction or absence of these chains. One of the complications observed in patients with β-thalassemia major (β-TM) is thrombosis, especially in those who receive frequent blood transfusions. This may be due to a decrease in the levels of the natural anticoagulants: protein C (PC), total protein S (PS), and antithrombin (AT).

Methods

In this case-control study, patients with β-TM, who had received at least 20 packed cell transfusions during their lifetime, were included. Patients with other underlying diseases like bleeding or thrombotic disorders were excluded. Totally, 118 patients with β-TM and 120 healthy individuals were included.

Results

The mean level of PC and AT was significantly lower in patients with β-TM (48.2 ± 65.4 and 57.42 ± 13.6, respectively) compared to the control group (97.1 ± 21.46 and 81.79 ± 14.3, respectively), with P value of 0.001 and 0.01, respectively. Although the difference was not statistically significant (P = 0.1), a similar trend was observed for total PS (61.12 ± 21.12 for patients versus 72.2 ± 35.2 for the control group). Of note, the decrease in PC, AT, and total PS levels compared to the control group was 50.36%, 27.5%, and 15.34%, respectively.

Conclusions

It seems that β-TM patients who receive prolonged blood transfusions frequently are at an increased risk of decreased in natural anticoagulants levels and therefore potentially are at risk of thrombosis.

Unraveling the Molecular Mechanisms of Activated Protein C (APC) in Mitigating Reperfusion Injury and Cardiac Ischemia: a Promising Avenue for Novel Therapeutic Interventions

Ischemic heart disease, which results from plaque formation in the coronary arteries, hinders the flow of oxygenated blood to the heart, leading to ischemia. Reperfusion injury remains a significant challenge for researchers, and the mechanisms underlying myocardial ischemia-reperfusion injury (MIRI) are not entirely understood. The review directs future research into potential targets in clinical treatment based on our present understanding of the pathophysiological mechanisms of MIRI. The study provides insights into the mechanisms underlying MIRI and offers direction for future research in this area. The use of targeted therapies may hold promise in improving cardiac function in the elderly and minimizing the adverse effects of revascularization therapies. The purpose of this review is to analyze the role of activated protein C (APC) in the pathogenesis of ischemic heart disease, heart failure, and myocardial ischemia-reperfusion injury, and discuss the potential of APC-based therapeutics.

Effect of prior anticoagulation therapy on outcomes of traumatic brain injury: A systematic review and meta‑analysis

Anticoagulants are commonly prescribed for multiple conditions. However, their influence on traumatic brain injury (TBI) outcomes, especially mortality, is not clear. The present study aimed to explore the effect of prior anticoagulation treatment on the outcomes of TBI. PubMed, Embase, Cochrane Central Register of Controlled Trials, Scopus and CINAHL databases were systematically searched for studies on individuals diagnosed with TBI, with a subgroup on prior anticoagulation therapy. Outcomes of interest included overall mortality, in-hospital mortality, length of hospital and intensive care unit stay, need for neurosurgical intervention and discharge rate. Cohort and case-control studies, published up to September 2023, were examined. Analysis was performed using STATA version 14.2 software and the Newcastle Ottawa Scale was used for bias assessment. A total of 22 studies (102,036 participants) were included in the analysis. Patients with TBI with prior anticoagulation treatment showed a statistically higher overall mortality risk [odds ratio (OR): 1.967, 95% confidence interval (CI): 1.481-2.613]. Subgroup analyses revealed age-specific and TBI severity-specific variations. Prior anticoagulation treatment was associated with a 1.860-times higher rate of in-hospital mortality and a significantly increased likelihood of requiring neurosurgical intervention (OR: 1.351, 95%CI: 1.068-1.708). However, no significant difference was noted in lengths of hospital or ICU stays. Patients with TBI and prior anticoagulation therapy are at higher risk of overall and in-hospital mortality and have significantly higher likelihood of needing neurosurgical interventions. The results emphasized the need for tailored therapeutic approach and more comprehensive clinical guidelines. Future investigations on specific anticoagulant types and immediate post-TBI interventions could offer further insights.

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.

Research into New Molecular Mechanisms in Thrombotic Diseases Paves the Way for Innovative Therapeutic Approaches

Thrombosis is a multifaceted process involving various molecular components, including the coagulation cascade, platelet activation, platelet-endothelial interaction, anticoagulant signaling pathways, inflammatory mediators, genetic factors and the involvement of various cells such as endothelial cells, platelets and leukocytes. A comprehensive understanding of the molecular signaling pathways and cell interactions that play a role in thrombosis is essential for the development of precise therapeutic strategies for the treatment and prevention of thrombotic diseases. Ongoing research in this field is constantly uncovering new molecular players and pathways that offer opportunities for more precise interventions in the clinical setting. These molecular insights into thrombosis form the basis for the development of targeted therapeutic approaches for the treatment and prevention of thrombotic disease. The aim of this review is to provide an overview of the pathogenesis of thrombosis and to explore new therapeutic options.

Cytoprotective E-WE thrombin reduces disease severity in a murine model of relapsing-remitting multiple sclerosis

The blood-brain barrier is composed of microvascular endothelial cells, immune cells, and astrocytes that work in concert with the coagulation cascade to control inflammation and immune cell infiltration into the central nervous system. Endothelial cell dysfunction leading to increased permeability and compromised barrier function are hallmarks of neuroinflammatory and autoimmune disorders, including multiple sclerosis (MS). Therapeutic strategies that improve or protect endothelial barrier function may be beneficial in the treatment or prevention of neuroinflammatory diseases. We therefore tested the hypothesis that biasing thrombin toward anticoagulant and cytoprotective activities would provide equivalent or even additive benefit compared with standard-of-care therapeutic strategies, including corticosteroids. In a mouse model of relapsing-remitting MS, treatment with the thrombin mutant, E-WE thrombin, an engineered thrombin mutant with cytoprotective activities that is biased toward anticoagulant and cytoprotective activity, reduced neuroinflammation and extracellular fibrin formation in SJL mice inoculated with proteolipid protein (PLP) peptide. When administered at the onset of detectable disease, E-WE thrombin significantly improved the disease severity of the initial attack as well as the relapse and delayed the onset of relapse to a similar extent as observed with methylprednisolone. Both methylprednisolone and E-WE thrombin reduced demyelination and immune cell recruitment. These results provide rationale for considering engineered forms of thrombin biased toward anticoagulant and cytoprotective activity as a therapeutic strategy and perhaps an effective alternative to high-dose methylprednisolone for the management of acute relapsing MS attacks.NEW & NOTEWORTHY There are limited treatment options for mitigating acute relapsing attacks for patients with multiple sclerosis. We tested the hypothesis that harnessing the cytoprotective activity of the blood coagulation enzyme, thrombin, would provide benefit and protection against relapsing disease in a mouse model of MS. Our results provide rationale for considering engineered forms of thrombin biased toward cytoprotective activity as a therapeutic strategy and perhaps an alternative to steroids for the management of relapsing MS attacks.

E-WE thrombin, a protein C activator, reduces disease severity and spinal cord inflammation in relapsing-remitting murine experimental autoimmune encephalomyelitis

Objective

Relapses in patients with relapsing-remitting multiple sclerosis (RRMS) are typically treated with high-dose corticosteroids including methylprednisolone. However, high-dose corticosteroids are associated with significant adverse effects, can increase the risk for other morbidities, and often do not impact disease course. Multiple mechanisms are proposed to contribute to acute relapses in RRMS patients, including neuroinflammation, fibrin formation and compromised blood vessel barrier function. The protein C activator, E-WE thrombin is a recombinant therapeutic in clinical development for its antithrombotic and cytoprotective properties, including protection of endothelial cell barrier function. In mice, treatment with E-WE thrombin reduced neuroinflammation and extracellular fibrin formation in myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE). We therefore tested the hypothesis that E-WE thrombin could reduce disease severity in a relapsing-remitting model of EAE.

Methods

Female SJL mice were inoculated with proteolipid protein (PLP) peptide and treated with E-WE thrombin (25 μg/kg; iv) or vehicle at onset of detectable disease. In other experiments, E-WE thrombin was compared to methylprednisolone (100 mg/kg; iv) or the combination of both.

Results

Compared to vehicle, administration of E-WE thrombin significantly improved disease severity of the initial attack and relapse and delayed onset of relapse as effectively as methylprednisolone. Both methylprednisolone and E-WE thrombin reduced demyelination and immune cell recruitment, and the combination of both treatments had an additive effect.

Conclusion

The data presented herein demonstrate that E-WE thrombin is protective in mice with relapsing-remitting EAE, a widely used model of MS. Our data indicate that E-WE thrombin is as effective as high-dose methylprednisolone in improving disease score and may exert additional benefit when administered in combination. Taken together, these data suggest that E-WE thrombin may be an effective alternative to high-dose methylprednisolone for managing acute MS attacks.

Host-directed therapies for malaria: possible applications and lessons from other indications

Host-directed therapies (HDT) are rapidly advancing as a new and clinically relevant strategy to treat infectious disease. The application of HDT can be broadly used to (i) inhibit host factors essential for pathogen development, including host protein kinases, (ii) control detrimental immune signalling, resulting from excessive release of cytokines, chemokines and extracellular vesicles and (iii) strengthen host defence mechanisms, such as tight junctions in the endothelium. For malaria and other eukaryotic parasite-causing diseases, HDTs could provide a novel avenue to combat the growing resistance seen across all antimicrobials and provide protection against the severe forms of disease through modulation of the host immune response.

Dysregulated Hemostasis and Immunothrombosis in Cerebral Cavernous Malformations

Cerebral cavernous malformation (CCM) is a neurovascular disease that affects 0.5% of the general population. For a long time, CCM research focused on genetic mutations, endothelial junctions and proliferation, but recently, transcriptome and proteome studies have revealed that the hemostatic system and neuroinflammation play a crucial role in the development and severity of cavernomas, with some of these publications coming from our group. The aim of this review is to give an overview of the latest molecular insights into the interaction between CCM-deficient endothelial cells with blood components and the neurovascular unit. Specifically, we underscore how endothelial dysfunction can result in dysregulated hemostasis, bleeding, hypoxia and neurological symptoms. We conducted a thorough review of the literature and found a field that is increasingly poised to regard CCM as a hemostatic disease, which may have implications for therapy.

Investigations of the effectiveness of heparin variants as inhibitors of histones

BACKGROUND

Extracellular histones exert cytotoxic and procoagulant effects which contribute to immunothrombosis in vascular diseases such as sepsis. Heparin has been shown to neutralize the pathologic effects of histones in vitro and in animal models.

OBJECTIVES

To compare the effectiveness of unfractionated heparin (UFH), low-molecularweight heparin (LMWH), Vasoflux (lacks anticoagulant activity), and fondaparinux in neutralizing the cytotoxic and procoagulant activities of histones METHODS: Binding affinities between heparin variants and histone subunits were determined by Bio-layer Interferometry. The ability of heparin variants to diminish the cytotoxic and procoagulant effects of histones was studied by treating endothelial cells or monocytic THP-1 cells with histones ± heparin variants.

RESULTS

Unfractionated heparin, LMWH, and Vasoflux bind histone subunits with high affinities (Kd <1 pM-66.7 nM) whereas fondaparinux exhibited a low affinity (Kd of 3.06 µM-81.1 mM). UFH, LMWH, and Vasoflux neutralize histone-mediated cytotoxicity as well as monocytic procoagulant activity (as assessed by cell surface tissue factor and phosphatidylserine). In contrast, fondaparinux has no effect on these activities. All four heparin variants reverse histone-mediated impairment of APC generation in a dose-dependent manner.

CONCLUSIONS

The ability of heparin to neutralize the cytotoxic and procoagulant effects of histones require heparin fragments >1.7 kDa and is independent of the antithrombin-binding pentasaccharide. In contrast, the ability of heparin to neutralize histone-mediated impairment of APC generation is independent of size and anticoagulant activity. These findings suggest that heparin variants may have differential therapeutic potential in vascular diseases associated with elevated levels of histones.

CircRNA-miRNA interactions in atherogenesis

Atherosclerosis is the major cause of coronary artery disease (CAD) which includes unstable angina, myocardial infarction, and heart failure. The onset of atherogenesis, a process of atherosclerotic lesion formation in the intima of arteries, is driven by lipid accumulation, a vicious cycle of reactive oxygen species (ROS)-induced oxidative stress and inflammatory reactions leading to endothelial cell (EC) dysfunction, vascular smooth muscle cell (VSMC) activation, and foam cell formation which further fuel plaque formation and destabilization. In recent years, there is a surge in the number of publications reporting the involvement of circular RNAs (circRNAs) in the pathogenesis of cardiovascular diseases, cancers, and metabolic syndromes. These studies have advanced our understanding on the biological functions of circRNAs. One of the most common mechanism of action of circRNAs reported is the sponging of microRNAs (miRNAs) by binding to the miRNAs response element (MRE), thereby indirectly increases the transcription of their target messenger RNAs (mRNAs). Individual networks of circRNA-miRNA-mRNA associated with atherogenesis have been extensively reported, however, there is a need to connect these findings for a complete overview. This review aims to provide an update on atherogenesis-related circRNAs and analyze the circRNA-miRNA-mRNA interactions in atherogenesis. The atherogenic mechanisms and clinical relevance of each atherogenesis-related circRNA were systematically discussed for better understanding of the knowledge gap in this area.

The Association between Protein C and Antithrombin III Levels with the Severity of Coronavirus Disease-2019 Symptoms

BACKGROUND: Coronavirus disease-2019 (COVID-19) has various symptoms ranging from mild to critical. Hypercoagulation state is often observed in severe and critical COVID-19. Both coagulation and inflammation are interrelated and amplifying each other, with protein C and antithrombin (AT) III as two important mediators. OBJECTIVE: To determine the association between protein C and AT III levels with the severity of COVID-19 symptoms. METHODS: This analytical study was conducted at Haji Adam Malik Hospital from April to July 2021. Subjects were obtained by consecutive sampling method. Inclusion criteria were patients with confirmed COVID-19 using RT-PCR and willing to participate. Subjects were divided into 2 groups: mild-moderate and severe-critical symptom groups. Demographic and blood sample were obtained from each subject. Blood samples underwent examination for leukocyte, thrombocyte, PT, aPTT, protein C, and AT III. RESULTS: A total of 50 patients were obtained with female domination (58%) and mean age of 41.44 (SD 20.90) years. Most subjects (86%) were in mild-moderate symptom group. There were significant differences in the level of protein C and AT III in both group (p= 0.029 and 0.034, respectively). Using the cut-off values for protein C of 5.36 ng/mL and AT III of 45.6%, subjects who had mediators level below the value tend to develop severe and critical symptoms compared to their counterparts (OR= 5.769 and 6.458, respectively). CONCLUSION: Protein C and AT III are associated with severity of COVID-19 symptoms. Lower protein C and AT III levels increase the risk for developing severe and critical symptoms.

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.

Osteonecrosis of the Jaws in Patients with Hereditary Thrombophilia/Hypofibrinolysis-From Pathophysiology to Therapeutic Implications

Osteonecrosis of the jaws (ONJ) usually has a clear etiology. Local infection or trauma, radiotherapy and drugs that disrupt the vascular supply or bone turnover in the jaws are its major contributors. The thrombotic occlusion of the bone’s venous outflow that occurs in individuals with hereditary thrombophilia and/or hypofibrinolysis has a less known impact on jaw health and healing capability. Our research provides the most comprehensive, up-to-date and systematized information on the prevalence and significance of hereditary thrombophilia and/or hypofibrinolysis states in ONJ. We found that hereditary prothrombotic abnormalities are common in patients with ONJ refractory to conventional medical and dental treatments. Thrombophilia traits usually coexist with hypofibrinolysis traits. We also found that frequently acquired prothrombotic abnormalities coexist with hereditary ones and enhance their negative effect on the bone. Therefore, we recommend a personalized therapeutic approach that addresses, in particular, the modifiable risk factors of ONJ. Patients will have clear benefits, as they will be relieved of persistent pain and repeated dental procedures.

Comparison of Acquired Activated Protein C Resistance, Using the CAT and ST-Genesia® Analysers and Three Thrombin Generation Methods, in APS and SLE Patients

Background: Acquired activated protein C resistance (APCr) has been identified in antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE). Objective: To assess agreement between the ST-Genesia^® and CAT analysers in identifying APCr prevalence in APS/SLE patients, using three thrombin generation (TG) methods. Methods: APCr was assessed with the ST-Genesia using STG-ThromboScreen and with the CAT using recombinant human activated protein C and Protac^® in 105 APS, 53 SLE patients and 36 thrombotic controls. Agreement was expressed in % and by Cohen’s kappa coefficient. Results: APCr values were consistently lower with the ST-Genesia^® compared to the CAT, using either method, in both APS and SLE patients. Agreement between the two analysers in identifying APS and SLE patients with APCr was poor (≤65.9%, ≤0.20) or fair (≤68.5%, ≥0.29), regardless of TG method, respectively; no agreement was observed in thrombotic controls. APCr with both the ST Genesia and the CAT using Protac^®, but not the CAT using rhAPC, was significantly greater in triple antiphospholipid antibody (aPL) APS patients compared to double/single aPL patients (p < 0.04) and in thrombotic SLE patients compared to non-thrombotic SLE patients (p < 0.05). Notably, the ST-Genesia^®, unlike the CAT, with either method, identified significantly greater APCr in pregnancy morbidity (median, confidence intervals; 36.9%, 21.9–49.0%) compared to thrombotic (45.7%, 39.6–55.5%) APS patients (p = 0.03). Conclusion: Despite the broadly similar methodology used by CAT and ST-Genesia^®, agreement in APCr was poor/fair, with results not being interchangeable. This may reflect differences in the TG method, use of different reagents, and analyser data handling.

Gene Analysis, Cloning, and Heterologous Expression of Protease from a Micromycete Aspergillus ochraceus Capable of Activating Protein C of Blood Plasma

Micromycetes are known to secrete numerous enzymes of biotechnological and medical potential. Fibrinolytic protease-activator of protein C (PAPC) of blood plasma from micromycete Aspergillus ochraceus VKM-F4104D was obtained in recombinant form utilising the bacterial expression system. This enzyme, which belongs to the proteinase-K-like proteases, is similar to the proteases encoded in the genomes of Aspergillus fumigatus ATCC MYA-4609, A. oryzae ATCC 42149 and A. flavus 28. Mature PAPC-4104 is 282 amino acids long, preceded by the 101-amino acid propeptide necessary for proper folding and maturation. The recombinant protease was identical to the native enzyme from micromycete in terms of its biological properties, including an ability to hydrolyse substrates of activated protein C (pGlu-Pro-Arg-pNA) and factor Xa (Z-D-Arg-Gly-Arg-pNA) in conjugant reactions with human blood plasma. Therefore, recombinant PAPC-4104 can potentially be used in medicine, veterinary science, diagnostics, and other applications.

Anti-protein C antibodies and acquired protein C resistance in SLE: novel markers for thromboembolic events and disease activity?

OBJECTIVES

Risk factors for thromboembolism in SLE are poorly understood. We hypothesized a possible role for protein C, based on its dual activity in inflammation and haemostasis and on the evidence of an association between acquired activated protein C (APC) resistance (APCR) and high-avidity anti-protein C antibodies (anti-PC) with a severe thrombotic phenotype in venous thrombosis APS patients.

METHODS

In a cross-sectional study of 156 SLE patients, the presence and avidity of IgG anti-PC was established by in house-ELISA, and APCR to exogenous recombinant human APC (rhAPC) and Protac (which activates endogenous protein C) was assessed by thrombin generation-based assays. Associations with aPL profile, thrombotic history and disease activity (BILAG and SLEDAI-2K) were also established.

RESULTS

Anti-PC were detected in 54.5% of patients and APCR in 59%. Anti-PC positivity was associated with APCR to both rhAPC (P <0.0001) and Protac (P =0.0001). High-avidity anti-PC, detected in 26.3% of SLE patients, were associated with APCR in patients with thrombosis only (P <0.05), and with the development of thrombosis over time (range: 0-52 years; P =0.014). High-avidity anti-PC levels correlated with SLEDAI-2K (P =0.033) and total BILAG (P =0.019); SLEDAI-2K correlated inversely with APCR to Protac (P =0.004).

CONCLUSION

Anti-PC occur in patients with SLE, independently of aPL profile, and are associated with APCR. High-avidity anti-PC are associated with thrombosis and with active disease and might prove a novel marker to monitor the risk of thrombosis and disease progression in SLE.

Sickle-trait hemoglobin reduces adhesion to both CD36 and EPCR by Plasmodium falciparum-infected erythrocytes

Sickle-trait hemoglobin protects against severe Plasmodium falciparum malaria. Severe malaria is governed in part by the expression of the Plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1) that are encoded by var genes, specifically those variants that bind Endothelial Protein C Receptor (EPCR). In this study, we investigate the effect of sickle-trait on parasite var gene expression and function in vitro and in field-collected parasites. We mapped var gene reads generated from RNA sequencing in parasite cultures in normal and sickle-cell trait blood throughout the asexual lifecycle. We investigated sickle-trait effect on PfEMP1 interactions with host receptors CD36 and EPCR using static adhesion assays and flow cytometry. Var expression in vivo was compared by assembling var domains sequenced from total RNA in parasites infecting Malian children with HbAA and HbAS. Sickle-trait did not alter the abundance or type of var gene transcripts in vitro, nor the abundance of overall transcripts or of var functional domains in vivo. In adhesion assays using recombinant host receptors, sickle-trait reduced adhesion by 73-86% to CD36 and 83% to EPCR. Similarly, sickle-trait reduced the surface expression of EPCR-binding PfEMP1. In conclusion, Sickle-cell trait does not directly affect var gene transcription but does reduce the surface expression and function of PfEMP1. This provides a direct mechanism for protection against severe malaria conferred by sickle-trait hemoglobin. Trial Registration: ClinicalTrials.gov Identifier: NCT02645604.

Sex-dependent effects of genetic upregulation of activated protein C on delayed effects of acute radiation exposure in the mouse heart, small intestine, and skin

Accidental exposure to ionizing radiation may lead to delayed effects of acute radiation exposure (DEARE) in many organ systems. Activated protein C (APC) is a known mitigator of the acute radiation syndrome. To examine the role of APC in DEARE, we used a transgenic mouse model with 2- to 3-fold increased plasma levels of APC (high in APC, APCHi). Male and female APCHi mice and wild-type littermates were exposed to 9.5 Gy γ-rays with their hind-legs (bone marrow) shielded from radiation to allow long-term survival. At 3 and 6 months after irradiation, cardiac function was measured with ultrasonography. At 3 months, radiation increased cardiac dimensions in APCHi males, while decreases were seen in wild-type females. At this early time point, APCHi mice of both sexes were more susceptible to radiation-induced changes in systolic function compared to wild-types. At 6 months, a decrease in systolic function was mainly seen in male mice of both genotypes. At 6 months, specimens of heart, small intestine and dorsal skin were collected for tissue analysis. Female APCHi mice showed the most severe radiation-induced deposition of cardiac collagens but were protected against a radiation-induced loss of microvascular density. Both male and female APCHi mice were protected against a radiation induced upregulation of toll-like receptor 4 in the heart, but this did not translate into a clear protection against immune cell infiltration. In the small intestine, the APCHi genotype had no effect on an increase in the number of myeloperoxidase positive cells (seen mostly in females) or an increase in the expression of T-cell marker CD2 (males). Lastly, both male and female APCHi mice were protected against radiation-induced epidermal thickening and increase in 3-nitrotyrosine positive keratinocytes. In conclusion, prolonged high levels of APC in a transgenic mouse model had little effects on indicators of DEARE in the heart, small intestine and skin, with some differential effects in male compared to female mice.

Increased expression of Protein S in eyes with diabetic retinopathy and diabetic macular edema

Protein S (PS) is a multifunctional glycoprotein that ameliorates the detrimental effects of diabetes mellitus (DM). The aim of this study was to evaluate the distribution of PS in diabetic retinopathy (DR) and diabetic macular edema (DME). This was a study of 50 eyes with DM (37 with DME, 6 with proliferative DR, and 7 with no DR) and 19 eyes without DM. The level of PS was measured by enzyme immunoassay and was compared between eyes with or without DM, with or without DME, and with severe DME (≥ 350 μm) or mild DME (< 350 μm). We also performed immunohistopathologic evaluations of post-mortem eyes and the cystoid lesions excised during surgery. The aqueous free PS was significantly higher with DM (7.9 ± 1.2 ng/ml, P < 0.01) than without DM (6.1 ± 0.7). The aqueous free PS was significantly elevated with DME (8.2 ± 1.2, P < 0.05) compared to proliferative DR (7.0 ± 1.0) and no DR (7.0 ± 0.7). Eyes with severe DME had significantly higher aqueous free PS than mild DME (8.5 ± 1.3 vs. 7.7 ± 1.0, P < 0.05). Immunohistochemistry showed PS in the outer plexiform layer of the retina and cystoid lesion. The higher expression of PS with DR and DME suggests that PS is involved in their pathogenesis.

X chromosome-dependent disruption of placental regulatory networks in hybrid dwarf hamsters

Embryonic development in mammals is highly sensitive to changes in gene expression within the placenta. The placenta is also highly enriched for genes showing parent-of-origin or imprinted expression, which is predicted to evolve rapidly in response to parental conflict. However, little is known about the evolution of placental gene expression, or if divergence of placental gene expression plays an important role in mammalian speciation. We used crosses between two species of dwarf hamsters (Phodopus sungorus and Phodopus campbelli) to examine the genetic and regulatory underpinnings of severe placental overgrowth in their hybrids. Using quantitative genetic mapping and mitochondrial substitution lines, we show that overgrowth of hybrid placentas was primarily caused by genetic differences on the maternally inherited P. sungorus X chromosome. Mitochondrial interactions did not contribute to abnormal hybrid placental development, and there was only weak correspondence between placental disruption and embryonic growth. Genome-wide analyses of placental transcriptomes from the parental species and first- and second-generation hybrids revealed a central group of co-expressed X-linked and autosomal genes that were highly enriched for maternally biased expression. Expression of this gene network was strongly correlated with placental size and showed widespread misexpression dependent on epistatic interactions with X-linked hybrid incompatibilities. Collectively, our results indicate that the X chromosome is likely to play a prominent role in the evolution of placental gene expression and the accumulation of hybrid developmental barriers between mammalian species.

Borrelia burgdorferi infection modifies protein content in saliva of Ixodes scapularis nymphs

BACKGROUND

Lyme disease (LD) caused by Borrelia burgdorferi is the most prevalent tick-borne disease. There is evidence that vaccines based on tick proteins that promote tick transmission of B. burgdorferi could prevent LD. As Ixodes scapularis nymph tick bites are responsible for most LD cases, this study sought to identify nymph tick saliva proteins associated with B. burgdorferi transmission using LC-MS/MS. Tick saliva was collected using a non-invasive method of stimulating ticks (uninfected and infected: unfed, and every 12 h during feeding through 72 h, and fully-fed) to salivate into 2% pilocarpine-PBS for protein identification using LC-MS/MS.

RESULTS

We identified a combined 747 tick saliva proteins of uninfected and B. burgdorferi infected ticks that were classified into 25 functional categories: housekeeping-like (48%), unknown function (18%), protease inhibitors (9%), immune-related (6%), proteases (8%), extracellular matrix (7%), and small categories that account for <5% each. Notably, B. burgdorferi infected ticks secreted high number of saliva proteins (n=645) than uninfected ticks (n=376). Counter-intuitively, antimicrobial peptides, which function to block bacterial infection at tick feeding site were suppressed 23-85 folds in B. burgdorferi infected ticks. Similar to glycolysis enzymes being enhanced in mammalian cells exposed to B. burgdorferi : eight of the 10-glycolysis pathway enzymes were secreted at high abundance by B. burgdorferi infected ticks. Of significance, rabbits exposed to B. burgdorferi infected ticks acquired potent immunity that caused 40-60% mortality of B. burgdorferi infected ticks during the second infestation compared to 15-28% for the uninfected. This might be explained by ELISA data that show that high expression levels of immunogenic proteins in B. burgdorferi infected ticks.

CONCLUSION

Data here suggest that B. burgdorferi infection modified protein content in tick saliva to promote its survival at the tick feeding site. For instance, enzymes; copper/zinc superoxide dismutase that led to production of H2O2 that is toxic to B. burgdorferi were suppressed, while, catalase and thioredoxin that neutralize H2O2, and pyruvate kinase which yields pyruvate that protects Bb from H2O2 killing were enhanced. We conclude data here is an important resource for discovery of effective antigens for a vaccine to prevent LD.

Validation of the Role of Thrombin Generation Potential by a Fully Automated System in the Identification of Breast Cancer Patients at High Risk of Disease Recurrence

Background  The measurement of thrombin generation (TG) potential by the calibrated automated thrombogram (CAT) assay provides a strong contribution in identifying patients at high risk of early disease recurrence (E-DR). However, CAT assay still needs standardization and clinical validation.

Objective  In this study, we aimed to validate the role of TG for E-DR prediction by means of the fully automated ST Genesia system.

Methods  A prospective cohort of 522 patients from the HYPERCAN study with newly diagnosed resected high-risk breast cancer was included. Fifty-two healthy women acted as controls. Plasma samples were tested for protein C, free-protein S, and TG by ST Genesia by using the STG-ThromboScreen reagent with and without thrombomodulin (TM).

Results  In the absence of TM, patients showed significantly higher peak and ETP compared with controls. In the presence of TM, significantly lower inhibition of ETP and Peak were observed in patients compared with controls. E-DR occurred in 28 patients; these patients had significantly higher peak and endogenous thrombin potential (ETP) in the absence of TM compared with disease-free patients. Multivariable analysis identified mastectomy, luminal B HER2-neg, triple negative subtypes, and ETP as independent risk factors for E-DR. These variables were combined to generate a risk assessment score, able to stratify patients in three-risk categories. The E-DR rates were 0, 4.7, and 13.5% in the low-, intermediate-, and high-risk categories (hazard ratio = 8.7; p  < 0.05, low vs. high risk).

Conclusion  Our data validate the ETP parameter with a fully automated standardized system and confirm its significant contribution in identifying high-risk early breast cancer at risk for E-DR during chemotherapy.

Immunogenetics of xenotransplantation

Xenotransplantation may become the highly desired solution to close the gap between the availability of donated organs and number of patients on the waiting list. In recent years, enormous progress has been made in the development of genetically engineered donor pigs. The introduced genetic modifications showed to be efficient in prolonging xenograft survival. In this review, we focus on the type of immune responses that may target xeno-organs after transplantation and promising immunogenetic modifications that show a beneficial effect in ameliorating or eliminating harmful xenogeneic immune responses. Increasing histocompatibility of xenografts by eliminating genetic discrepancies between species will pave their way into clinical application.

Neuroprotective Effects of Activated Protein C Involve the PARP/AIF Pathway against Oxygen-Glucose Deprivation in SH-SY5Y Cells

Protein C, a member of the zymogen family of serine proteases in plasma, is one of the several vitamin K dependent glycoproteins known to induce anti-apoptotic activity. However, the target molecule involved in the mechanism needs to be investigated. We sought to investigate the pathways involved in the anti-apoptotic role of activated protein C (APC) on oxygen-glucose deprivation (OGD) induced ischemic conditions in in-vitro SH-SY5Y cells. SH-SY5Y cells were exposed to OGD in an airtight chamber containing 95% N₂ and 5% CO₂ and media deprived of glucose for 4 h following 24 h of reoxygenation. The cell toxicity, viability, expression of receptors such as endothelial cell protein C receptor (EPCR), protease-activated receptor (PAR)1, PAR3, and apoptosis-related proteins B-cell lymphoma 2 (BCL-2), BCL-2-like protein 4 (Bax), Poly [ADP-ribose] polymerase-1 (PARP-1) were assessed. Administration of APC decreased the cellular injury when compared to the OGD exposed group in a dose-dependent manner and displayed increased expression of PAR-1, PAR-3, and EPCR. The APC treatment leads to a reduction in PARP-1 expression and cleavage and apoptosis-inducing factor (AIF) expression. The reduction of caspase-3 activity and PARP-1 and AIF expression following APC administration results in restoring mitochondrial function with decreased cellular injury and apoptosis. Our results suggested that APC has potent protective effects against in-vitro ischemia in SH-SY5Y cells by modulating mitochondrial function.

Impact of Acute and Chronic Stress on Thrombosis in Healthy Individuals and Cardiovascular Disease Patients

Psychological stress induces different alterations in the organism in order to maintain homeostasis, including changes in hematopoiesis and hemostasis. In particular, stress-induced hyper activation of the autonomic nervous system and hypothalamic–pituitary–adrenal axis can trigger cellular and molecular alterations in platelets, coagulation factors, endothelial function, redox balance, and sterile inflammatory response. For this reason, mental stress is reported to enhance the risk of cardiovascular disease (CVD). However, contrasting results are often found in the literature considering differences in the response to acute or chronic stress and the health condition of the population analyzed. Since thrombosis is the most common underlying pathology of CVDs, the comprehension of the mechanisms at the basis of the association between stress and this pathology is highly valuable. The aim of this work is to give a comprehensive review of the studies focused on the role of acute and chronic stress in both healthy individuals and CVD patients, focusing on the cellular and molecular mechanisms underlying the relationship between stress and thrombosis.

Severe Protein C Deficiency due to Novel Biallelic Variants in PROC and Their Phenotype Correlation

Severe protein C deficiency due to biallelic PROC mutations is an extremely rare thrombophilia, most commonly presenting during the neonatal period as purpura fulminans. Despite treatment, severe morbidity and mortality are frequent. The current study reports 3 unrelated patients harboring novel homozygous PROC mutations and their clinical phenotypes. We discuss how the cytoprotective activity of protein C and its role in the stabilization of endothelial barriers may account for the unique symptoms of this thrombophilia.

Expression Characteristics of Genes Hypermethylated and Downregulated in Rat Liver Specific to Nongenotoxic Hepatocarcinogens

This study examined hypermethylated and downregulated genes specific to carbon tetrachloride (CCl₄) by Methyl-Seq analysis combined with expression microarray analysis in the liver of rats treated with CCl₄ or N-nitrosodiethylamine (DEN) for 28 days, by excluding those with DEN. Among 52 genes, Ldlrad4, Proc, Cdh17, and Nfia were confirmed to show promoter-region hypermethylation by methylation-specific quantitative PCR analysis on day 28. The transcript levels of these 4 genes decreased by real-time reverse transcription-PCR analysis in the livers of rats treated with nongenotoxic hepatocarcinogens for up to 90 days compared with untreated controls and genotoxic hepatocarcinogens. Immunohistochemically, LDLRAD4 and PROC showed decreased immunoreactivity, forming negative foci, in glutathione S-transferase placental form (GST-P)⁺ foci, and incidences of LDLRAD4⁻ and PROC⁻ foci in GST-P⁺ foci induced by treatment with nongenotoxic hepatocarcinogens for 84 or 90 days were increased compared with those with genotoxic hepatocarcinogens. In contrast, CDH17 and NFIA responded to hepatocarcinogens without any relation to the genotoxic potential of carcinogens. All 4 genes did not respond to renal carcinogens after treatment for 28 days. Considering that Ldlrad4 is a negative regulator of transforming growth factor-β signaling, Proc participating in p21^WAF1/CIP1 upregulation by activation, Cdh17 inducing cell cycle arrest by gene knockdown, and Nfia playing a role in a tumor-suppressor, all these genes may be potential in vivo epigenetic markers of nongenotoxic hepatocarcinogens from the early stages of treatment in terms of gene expression changes. LDLRAD4 and PROC may have a role in the development of preneoplastic lesions produced by nongenotoxic hepatocarcinogens.

Immunization with virus-like particles conjugated to CIDRα1 domain of Plasmodium falciparum erythrocyte membrane protein 1 induces inhibitory antibodies

BACKGROUND

During the erythrocytic cycle, Plasmodium falciparum malaria parasites express P. falciparum Erythrocyte Membrane Protein 1 (PfEMP1) that anchor the infected erythrocytes (IE) to the vascular lining of the host. The CIDRα1 domain of PfEMP1 is responsible for binding host endothelial protein C receptor (EPCR), and increasing evidence support that this interaction triggers severe malaria, accounting for the majority of malaria-related deaths. In high transmission regions, children develop immunity to severe malaria after the first few infections. This immunity is believed to be mediated by antibodies targeting and inhibiting PfEMP1, causing infected erythrocytes to circulate and be cleared in the spleen. The development of immunity to malaria coincides with acquisition of broad antibody reactivity across the CIDRα1 protein family. Altogether, this identifies CIDRα1 as an important vaccine target. However, the antigenic diversity of the CIDRα1 domain family is a challenge for vaccine development.

METHODS

Immune responses in mice vaccinated with Virus-Like Particles (VLP) presenting CIDRα1 antigens were investigated. Antibody reactivity was tested to a panel of recombinant CIDRα1 domains, and the antibodies ability to inhibit EPCR binding by the recombinant CIDRα1 domains was tested in Luminex-based multiplex assays.

RESULTS

VLP-presented CIDRα1.4 antigens induced a rapid and strong IgG response capable of inhibiting EPCR-binding of multiple CIDRα1 domains mainly within the group A CIDRα1.4-7 subgroups.

CONCLUSIONS

The study observations mirror those from previous CIDRα1 vaccine studies using other vaccine constructs and platforms. This suggests that broad CIDRα1 antibody reactivity may be achieved through vaccination with a limited number of CIDRα1 variants. In addition, this study suggest that this may be achieved through vaccination with a human compatible VLP vaccine platform.

Cerebral Plasmodium falciparum malaria: The role of PfEMP1 in its pathogenesis and immunity, and PfEMP1-based vaccines to prevent it

Malaria, a mosquito-borne infectious disease caused by parasites of the genus Plasmodium continues to be a major health problem worldwide. The unicellular Plasmodium-parasites have the unique capacity to infect and replicate within host erythrocytes. By expressing variant surface antigens Plasmodium falciparum has evolved to avoid protective immune responses; as a result in endemic areas anti-malaria immunity develops gradually over many years of multiple and repeated infections. We are studying the role of Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) expressed by asexual stages of P. falciparum responsible for the pathogenicity of severe malaria. The immunopathology of falciparum malaria has been linked to cyto-adhesion of infected erythrocytes to specific host receptors. A greater appreciation of the PfEMP1 molecules important for the development of protective immunity and immunopathology is a prerequisite for the rational discovery and development of a safe and protective anti-disease malaria vaccine. Here we review the role of ICAM-1 and EPCR receptor adhering falciparum-parasites in the development of severe malaria; we discuss our current research to understand the factors involved in the pathogenesis of cerebral malaria and the feasibility of developing a vaccine targeted specifically to prevent this disease.

Re-Evaluating Biologic Pharmacotherapies that Target the Host Response during Sepsis

Multiple organ dysfunction syndrome (MODS) caused by the systemic inflammatory response during sepsis is responsible for millions of deaths worldwide each year, and despite broad consensus concerning its pathophysiology, no specific or effective therapies exist. Recent efforts to treat and/or prevent MODS have included a variety of biologics, recombinant proteins targeting various components of the host response to the infection (e.g., inflammation, coagulation, etc.) Improvements in molecular biology and pharmaceutical engineering have enabled a wide range of utility for biologics to target various aspects of the systemic inflammatory response. The majority of clinical trials to date have failed to show clinical benefit, but some have demonstrated promising results in certain patient populations. In this review we summarize the underlying rationale and outcome of major clinical trials where biologics have been tested as a pharmacotherapy for MODS in sepsis. A brief description of the study design and overall outcome for each of the major trials are presented. Emphasis is placed on discussing targets and/or trials where promising results were observed. Post hoc analyses of trials where therapy demonstrated harm or additional risk to certain patient subgroups are highlighted, and details are provided about specific trials where more stringent inclusion/exclusion criteria are warranted.

Protease-activated receptor signaling in intestinal permeability regulation

Protease-activated receptors (PARs) are a unique class of G-protein-coupled transmembrane receptors, which revolutionized the perception of proteases from degradative enzymes to context-specific signaling factors. Although PARs are traditionally known to affect several vascular responses, recent investigations have started to pinpoint the functional role of PAR signaling in the gastrointestinal (GI) tract. This organ is exposed to the highest number of proteases, either from the gut lumen or from the mucosa. Luminal proteases include the host's digestive enzymes and the proteases released by the commensal microbiota, while mucosal proteases entail extravascular clotting factors and the enzymes released from resident and infiltrating immune cells. Active proteases and, in case of a disrupted gut barrier, even entire microorganisms are capable to translocate the intestinal epithelium, particularly under inflammatory conditions. Especially PAR-1 and PAR-2, expressed throughout the GI tract, impact gut permeability regulation, a major factor affecting intestinal physiology and metabolic inflammation. In addition, PARs are critically involved in the onset of inflammatory bowel diseases, irritable bowel syndrome, and tumor progression. Due to the number of proteases involved and the multiple cell types affected, selective regulation of intestinal PARs represents an interesting therapeutic strategy. The analysis of tissue/cell-specific knockout animal models will be of crucial importance to unravel the intrinsic complexity of this signaling network. Here, we provide an overview on the implication of PARs in intestinal permeability regulation under physiologic and disease conditions.

The parmodulin NRD-21 is an allosteric inhibitor of PAR1 Gq signaling with improved anti-inflammatory activity and stability

Novel analogs of the allosteric, biased PAR1 ligand ML161 (parmodulin 2, PM2) were prepared in order to identify potential anti-thrombotic and anti-inflammatory compounds of the parmodulin class with improved properties. Investigations of structure-activity relationships of the western portion of the 1,3-diaminobenzene scaffold were performed using an intracellular calcium mobilization assay with endothelial cells, and several heterocycles were identified that inhibited PAR1 at sub-micromolar concentrations. The oxazole NRD-21 was profiled in additional detail, and it was confirmed to act as a selective, reversible, negative allosteric modulator of PAR1. In addition to inhibiting human platelet aggregation, it showed superior anti-inflammatory activity to ML161 in a qPCR assay measuring the expression of tissue factor in response to the cytokine TNF-alpha in endothelial cells. Additionally, NRD-21 is much more plasma stable than ML161, and is a promising lead compound for the parmodulin class for anti-thrombotic and anti-inflammatory indications.

Lower plasma protein C activity is associated with early myocardial necrosis and no-reflow phenomenon in patients with ST elevation myocardial infarction

Background: Activity of protein C has important role in the development of early necrosis and no-reflow phenomenon in patients with ST-segment elevation myocardial infarction (STEMI) after successful primary percutaneous coronary intervention (pPCI). Methods: We examined association between plasma activity of protein C, antithrombin, coagulation factors II, VII, VIII and fibrinogen to early formation of new Q-waves (myocardial necrosis) before pPCI and early ST-segment resolution (microcirculatory reperfusion) after pPCI in patients with acute STEMI. According to ischaemic time, patients were considered as early or late presenters. 12-lead ECG was analysed for the presence of new Q-wave at admission and for significant ST-segment resolution 60 minutes after primary PCI. Results: In early presenters' group, protein C activity was significantly lower in patients who did not achieve significant ST-segment resolution after pPCI compared to patients who did (1.11 IU/L vs. 0.99 IU/L, p = .006) and in patients who had new Q-waves compared to group who had not (1.04 UI/l vs. 1.11 IU/L, p = .038). There was significant negative correlation between protein C activity and maximal CK-MB levels (R² = 0.06, p = .009) and BNP levels (R² = 0.109, p = .003) and significant positive correlation between protein C activity with LVEF (R² = 0.065, constant = 33.940, b = 11.968, p = .007) in early STEMI presenters. There were no differences between the activity of other examined haemostasis factors. Conclusion: Therefore we concluded that STEMI patients with early myocardial necrosis and no-reflow phenomenon after pPCI have lower activity of plasma protein C levels.

Increased Activated Protein C Response Rates Reduce the Thrombotic Risk of Factor V Leiden Carriers But Not of Prothrombin 20210G>A Carriers

RATIONALE

Carriers of the most common prothrombotic mutations FVL (factor V Leiden) and FII (prothrombin) 20210G>A show a highly variable clinical phenotype. Using standardized in vivo coagulation activation followed by activity pattern analysis we have recently shown, that the FVL mutation accelerates thrombin and APC (activated protein C) formation in carriers without a history of venous thromboembolism (VTE).

OBJECTIVE

The aim of this prospective cohort study was to investigate, if the FII 20210G>A mutation induces a similar reaction pattern, and if the response rates differ in FVL and FII 20210G>A mutation carriers with prior VTE (VTE+).

METHODS AND RESULTS

We comparatively analyzed 30 FVL carriers, 28 FII 20210G>A carriers (thereof 13 VTE+ each) and 15 healthy controls. Changes in plasma levels of thrombin, prothrombin activation fragment 1+2 (F1+2), TAT (thrombin-antithrombin complex), APC, and D-dimer were monitored over 8 hours after infusion of recombinant factor VIIa (15 µg/kg). An increase of F1+2 and TAT levels was observed, that did neither differ between FVL and FII 20210G>A carriers nor between asymptomatic and VTE+ carriers of these mutations. Median plasma levels of APC increased more (P=0.008) in FVL carriers (from 1.39 to 7.79 pmol/L) than in FII 20210G>A carriers (from 1.03 to 5.79 pmol/L), and more in FII 20210G>A carriers (P=2×10^-4) than in healthy controls (from 0.86 to 3.00 pmol/L). Most importantly, however, the APC response was greater (P=0.015) in asymptomatic (n=13) than in VTE+ (n=12) heterozygous FVL carriers, with an increase of APC levels from 1.44 to 8.11 pmol/L versus 1.27 to 5.62 pmol/L.

CONCLUSIONS

These in vivo data demonstrate that the FII 20210G>A and FVL mutations share an intermediate phenotype that is characterized by increased thrombin formation after coagulation activation. Furthermore, our data support the conclusion that the APC activating capacity of FVL carriers modifies the thrombotic risk of this common prothrombotic mutation.

Activated protein C induces suppression and regression of choroidal neovascularization- A murine model

Activated protein C (APC) exerts diverse cell signaling pathways which results in multiple distinct cytoprotective actions. These include anti-apoptotic and anti-inflammatory activities and stabilization of endothelial and epithelial barriers. We studied the ability of APC to inhibit the leakage and the growth of newly formed as well as pre-existing choroidal neovascularization (CNV) and examined the ability of APC to stabilize the Retinal Pigmented Epithelium (RPE). We explored the contribution of Tie2 receptor to the protective effects of APC. CNV was induced by laser photocoagulation in C57BL/6J mice. APC was injected intravitreally immediately or 7 days after CNV induction. Neovascularization was evaluated on RPE-choroidal flatmounts using FITC-dextran perfusion and CD31 immunofluorescence. CNV leakage was measured by fluorescein angiography (FA). The ability of APC to stabilize the RPE barrier was evaluated in-vitro by dextran permeability and zonula occludens 1 (ZO1) immunostaining. Tie2 blocking was induced in-vivo by intraperitoneal injection of Tie2 kinase inhibitor and in-vitro by incubation with anti Tie2 antibodies. APC treatment dramatically inhibited the generation of newly formed CNV leakage sites and reversed leakage in 85% of the pre-existing CNV leaking sites. In RPE cell culture, APC induced translocation of ZO1 to the cell membrane, accompanied by reduction in permeability of the monolayer. Inhibition of Tie2 significantly decreased APC protective activities in both the mouse model and the RPE cell culture. Our results show that APC treatment significantly inhibits the leakage and growth of newly formed, as well as pre-existing CNV, and its protective activities are partially mediated via the Tie2 receptor. The data suggest that APC should be further investigated as a possible effective treatment for CNV.

The bacterial protein CNF1 as a new strategy against Plasmodium falciparum cytoadherence

Plasmodium falciparum severe malaria causes more than 400,000 deaths every year. One feature of P. falciparum-parasitized erythrocytes (pRBC) leading to cerebral malaria (CM), the most dangerous form of severe malaria, is cytoadherence to endothelium and blockage of the brain microvasculature. Preventing ligand-receptor interactions involved in this process could inhibit pRBC sequestration and insurgence of severe disease whilst reversing existing cytoadherence could be a saving life adjunct therapy. Increasing evidence indicate the endothelial Rho signaling as a crucial player in malaria parasite cytoadherence. Therefore, we have used the cytotoxic necrotizing factor 1 (CNF1), an Escherichia coli protein able to modulate the activity of Cdc42, Rac, and Rho, three subfamilies of the Rho GTPases family, to study interactions between infected erythrocytes and cerebral endothelium in co-culture models. The main results are that CNF1 not only prevents cytoadherence but, more importantly, induces the detachment of pRBCs from endothelia monolayers. We first observed that CNF1 does affect neither parasite growth, nor the morphology and concentration of knobs that characterize the parasitized erythrocyte surface, as viewed by scanning electron microscopy. On the other hand, flow cytometry experiments show that cytoadherence reversion induced by CNF1 occurs in parallel with a decreased ICAM-1 receptor expression on the cell surface, suggesting the involvement of a toxin-promoted endocytic activity in such a response. Furthermore, since the endothelial barrier functionality is compromised by P. falciparum, we conducted a permeability assay on endothelial cells, revealing the CNF1 capacity to restore the brain endothelial barrier integrity. Then, using pull-down assays and inhibitory studies, we demonstrated, for the first time, that CNF1 is able not only to prevent but also to cause the parasite detachment by simultaneously activating Rho, Rac and Cdc42 in endothelial cells. All in all our findings indicate that CNF1 may represent a potential novel therapeutic strategy for preventing neurological complications of CM.

Activated Protein C in Cutaneous Wound Healing: From Bench to Bedside

Independent of its well-known anticoagulation effects, activated protein C (APC) exhibits pleiotropic cytoprotective properties. These include anti-inflammatory actions, anti-apoptosis, and endothelial and epithelial barrier stabilisation. Such beneficial effects have made APC an attractive target of research in a plethora of physiological and pathophysiological processes. Of note, the past decade or so has seen the emergence of its roles in cutaneous wound healing-a complex process involving inflammation, proliferation and remodelling. This review will highlight APC's functions and mechanisms, and detail its pre-clinical and clinical studies on cutaneous wound healing.

Plasma From Patients Undergoing Liver Transplantation Is Resistant to Anticoagulant Activity of Soluble Thrombomodulin

Recombinant human soluble thrombomodulin (ART-123) is an anticoagulant and anti-inflammatory agent clinically used for treatment of disseminated intravascular coagulation. Preclinical studies have shown that ART-123 reduces hepatic ischemia/reperfusion. Although ART-123 may therefore have clinical benefit in orthotopic liver transplantation, the substantial alterations in the hemostatic system may complicate its use in this setting. Here, we studied the in vitro effect of ART-123 on coagulation of patients with end-stage liver disease undergoing liver transplantation. Ten patients with end-stage liver disease undergoing liver transplantation were included in this study. Plasma samples of 10 healthy individuals were included to establish reference values. Different concentrations of ART-123 were added to plasma samples, and peak thrombin generation and clot lysis times (CLTs) were determined. In patient samples, plasma was profoundly resistant to the anticoagulant action of ART-123, as reflected by significantly higher median inhibitory concentration (IC₅₀ ) values of peak thrombin generation compared with controls. This might be partially explained by low levels of protein C, protein S, and elevated levels of factor VIII during transplantation. Intraoperative levels of thrombin activatable fibrinolysis inhibitor were significantly lower when compared with controls. However, ART-123-dependent prolongation of CLTs was not significantly different from healthy controls. In conclusion, this study suggests that ART-123 is unlikely to provoke bleeding in patients undergoing liver transplantation because proposed clinical dosages have a virtually absent anticoagulant effect in these patients. Clinical studies are required to confirm the safety of ART-123 and efficacy on alleviating ischemia/reperfusion injury during liver transplantation.