Vascular Functions of the Plasminogen Activation System

Dual surface modification of polydimethylsiloxane (PDMS) with antithrombin-heparin complex (ATH) and tissue plasminogen activator (t-PA) for enhanced antithrombotic activity

Medical devices used in contact with blood trigger coagulation and activate platelets leading to thrombotic complications. To prevent these effects, systemic anticoagulants and antiplatelet agents are typically prescribed, but these agents tend to increase the risk of bleeding. Modification of the surface of the blood-contacting material is an alternative approach to the inhibition of coagulation and thrombosis. In this work, the dual surface modification of polydimethylsiloxane (PDMS) with an antithrombin-heparin complex (ATH) to inhibit coagulation, and tissue plasminogen activator (t-PA) to lyse incipient clot, was investigated. Three different modification processes were used to immobilize ATH and t-PA: sequentially, with one component followed by the other; and with both components present simultaneously. Polydopamine (PDA) was used as a "bioglue" to enhance adhesion of the modifiers. The surface hydrophilicity and roughness were found to increase with increasing extent of modification. The surface density of the modifiers and their stability in plasma were significantly influenced by the modification process. The sequential method with t-PA first followed by ATH led to increased heparin activity. Data from plasma clotting time experiments showed that the combination of ATH and t-PA provides a synergistic effect, wherein both the anticoagulant activity of ATH and the clot lysis activity of t-PA on the surface are enhanced. This dual modification approach using both an anticoagulant and a thrombolytic agent shows promise to improve the blood compatibility of PDMS. The strategy can be applied to materials other than PDMS since the PDA coating is generic, thus providing a method for improving the performance of many blood-contacting devices.

Exploring the Diversity and Function of Serine Proteases in Toxicofera Reptile Venoms: A Comprehensive Overview

Toxicofera reptile venoms are composed of several toxins, including serine proteases. These proteases are glycosylated enzymes that affect the prey's hemostatic system. Their actions extend across the coagulation cascade, the kallikrein-kinin system, and platelet activation. Despite their specificity for different substrates, these enzymes are homologous across all toxicoferans and display high sequence similarity. The aim of this review is to compile decades of knowledge about venom serine proteases, showing the diversity of biochemically and biophysically characterized enzymes, their structural characteristics, advances in understanding their origin and evolution, as well as methods of obtaining enzymes and their biotechnological applications.

PAI-1 Regulates the Cytoskeleton and Intrinsic Stiffness of Vascular Smooth Muscle Cells

BACKGROUND

Plasma concentration of PAI-1 (plasminogen activator inhibitor-1) correlates with arterial stiffness. Vascular smooth muscle cells (SMCs) express PAI-1, and the intrinsic stiffness of SMCs is a major determinant of total arterial stiffness. We hypothesized that PAI-1 promotes SMC stiffness by regulating the cytoskeleton and that pharmacological inhibition of PAI-1 decreases SMC and aortic stiffness.

METHODS

PAI-039, a specific inhibitor of PAI-1, and small interfering RNA were used to inhibit PAI-1 expression in cultured human SMCs. Effects of PAI-1 inhibition on SMC stiffness, F-actin (filamentous actin) content, and cytoskeleton-modulating enzymes were assessed. WT (wild-type) and PAI-1-deficient murine SMCs were used to determine PAI-039 specificity. RNA sequencing was performed to determine the effects of PAI-039 on SMC gene expression. In vivo effects of PAI-039 were assessed by aortic pulse wave velocity.

RESULTS

PAI-039 significantly reduced intrinsic stiffness of human SMCs, which was accompanied by a significant decrease in cytoplasmic F-actin content. PAI-1 gene knockdown also decreased cytoplasmic F-actin. PAI-1 inhibition significantly increased the activity of cofilin, an F-actin depolymerase, in WT murine SMCs, but not in PAI-1-deficient SMCs. RNA-sequencing analysis suggested that PAI-039 upregulates AMPK (AMP-activated protein kinase) signaling in SMCs, which was confirmed by Western blotting. Inhibition of AMPK prevented activation of cofilin by PAI-039. In mice, PAI-039 significantly decreased aortic stiffness and tunica media F-actin content without altering the elastin or collagen content.

CONCLUSIONS

PAI-039 decreases intrinsic SMC stiffness and cytoplasmic stress fiber content. These effects are mediated by AMPK-dependent activation of cofilin. PAI-039 also decreases aortic stiffness in vivo. These findings suggest that PAI-1 is an important regulator of the SMC cytoskeleton and that pharmacological inhibition of PAI-1 has the potential to prevent and treat cardiovascular diseases involving arterial stiffening.

C-peptide in diabetes: A player in a dual hormone disorder?

C-peptide, a byproduct of insulin synthesis believed to be biologically inert, is emerging as a multifunctional molecule. C-peptide serves an anti-inflammatory and anti-atherogenic role in type 1 diabetes mellitus (T1DM) and early T2DM. C-peptide protects endothelial cells by activating AMP-activated protein kinase α, thus suppressing the activity of NAD(P)H oxidase activity and reducing reactive oxygen species (ROS) generation. It also prevents apoptosis by regulating hyperglycemia-induced p53 upregulation and mitochondrial adaptor p66shc overactivation, as well as reducing caspase-3 activity and promoting expression of B-cell lymphoma-2. Additionally, C-peptide suppresses platelet-derived growth factor (PDGF)-beta receptor and p44/p42 mitogen-activated protein (MAP) kinase phosphorylation to inhibit vascular smooth muscle cells (VSMC) proliferation. It also diminishes leukocyte adhesion by virtue of its capacity to abolish nuclear factor kappa B (NF-kB) signaling, a major pro-inflammatory cascade. Consequently, it is envisaged that supplementation of C-peptide in T1DM might ameliorate or even prevent end-organ damage. In marked contrast, C-peptide increases monocyte recruitment and migration through phosphoinositide 3-kinase (PI-3 kinase)-mediated pathways, induces lipid accumulation via peroxisome proliferator-activated receptor γ upregulation, and stimulates VSMC proliferation and CD4+ lymphocyte migration through Src-kinase and PI-3K dependent pathways. Thus, it promotes atherosclerosis and microvascular damage in late T2DM. Indeed, C-peptide is now contemplated as a potential biomarker for insulin resistance in T2DM and linked to increased coronary artery disease risk. This shift in the understanding of the pathophysiology of diabetes from being a single hormone deficiency to a dual hormone disorder warrants a careful consideration of the role of C-peptide as a unique molecule with promising diagnostic, prognostic, and therapeutic applications.

Effects of copy number variations on longevity in late-onset Alzheimer's disease patients: insights from a causality network analysis

Alzheimer's disease (AD), particularly late-onset Alzheimer's disease (LOAD), is a prevalent form of dementia that significantly affects patients' cognitive and behavioral capacities and longevity. Although approximately 70 genetic risk factors linked with AD have been identified, their influence on patient longevity remains unclear. Further, recent studies have associated copy number variations (CNVs) with the longevity of healthy individuals and immune-related pathways in AD patients. This study aims to investigate the role of CNVs on the longevity of AD patients by integrating the Whole Genome Sequencing (WGS) and transcriptomics data from the Religious Orders Study/Memory and Aging Project (ROSMAP) cohort through causality network inference. Our comprehensive analysis led to the construction of a CNV-Gene-Age of Death (AOD) causality network. We successfully identified three key CNVs (DEL5006, mCNV14192, and DUP42180) and seven AD-longevity causal genes (PLGRKT, TLR1, PLAU, CALB2, SYTL2, OTOF, and NT5DC1) impacting AD patient longevity, independent of disease severity. This outcome emphasizes the potential role of plasminogen activation and chemotaxis in longevity. We propose several hypotheses regarding the role of identified CNVs and the plasminogen system on patient longevity. However, experimental validation is required to further corroborate these findings and uncover precise mechanisms. Despite these limitations, our study offers promising insights into the genetic influence on AD patient longevity and contributes to paving the way for potential therapeutic interventions.

Direct delivery of plasmin using clot-anchoring thrombin-responsive nanoparticles for targeted fibrinolytic therapy

BACKGROUND

Fibrin-rich clot formation in thrombo-occlusive pathologies is currently treated by systemic administration of plasminogen activators (e.g. tPA), to convert fibrin-associated plasminogen to plasmin for fibrinolytic action. However, this conversion is not restricted to clot site only but also occurs on circulating plasminogen, causing systemic fibrinogenolysis and bleeding risks. To address this, past research has explored tPA delivery using clot-targeted nanoparticles.

OBJECTIVES

We designed a nanomedicine system that can (1) target clots via binding to activated platelets and fibrin, (2) package plasmin instead of tPA as a direct fibrinolytic agent, and (3) release this plasmin triggered by thrombin for clot-localized action.

METHODS

Clot-targeted thrombin-cleavable nanoparticles (CTNPs) were manufactured using self-assembly of peptide-lipid conjugates. Plasmin loading and its thrombin-triggered release from CTNPs were characterized by UV-visible spectroscopy. CTNP-targeting to clots under flow was studied using microfluidics. Fibrinolytic effect of CTNP-delivered plasmin was studied in vitro using BioFlux imaging and D-dimer analysis and in vivo in a zebrafish thrombosis model.

RESULTS

Plasmin-loaded CTNPs significantly bound to clots under shear flow and showed thrombin-triggered enhanced release of plasmin. BioFlux studies confirmed that thrombin-triggered plasmin released from CTNPs rendered fibrinolysis similar to free plasmin, further corroborated by D-dimer analysis. In the zebrafish model, CTNP-delivered plasmin accelerated time-to-recanalization, or completely prevented occlusion when infused before thrombus formation.

CONCLUSION

Considering that the very short circulation half-life (<1 second) of plasmin prevents its systemic use but also makes it safer without off-target drug effects, clot-targeted delivery of plasmin using CTNPs can enable safer and more efficacious fibrinolytic therapy.

PAI-1: A Major Player in the Vascular Dysfunction in Obstructive Sleep Apnea?

Obstructive sleep apnea is a chronic and prevalent condition that is associated with endothelial dysfunction, atherosclerosis, and imposes excess overall cardiovascular risk and mortality. Despite its high prevalence and the susceptibility of CVD patients to OSA-mediated stressors, OSA is still under-recognized and untreated in cardiovascular practice. Moreover, conventional OSA treatments have yielded either controversial or disappointing results in terms of protection against CVD, prompting the need for the identification of additional mechanisms and associated adjuvant therapies. Plasminogen activator inhibitor-1 (PAI-1), the primary inhibitor of tissue-type plasminogen activator (tPA) and urinary-type plasminogen activator (uPA), is a key regulator of fibrinolysis and cell migration. Indeed, elevated PAI-1 expression is associated with major cardiovascular adverse events that have been attributed to its antifibrinolytic activity. However, extensive evidence indicates that PAI-1 can induce endothelial dysfunction and atherosclerosis through complex interactions within the vasculature in an antifibrinolytic-independent matter. Elevated PAI-1 levels have been reported in OSA patients. However, the impact of PAI-1 on OSA-induced CVD has not been addressed to date. Here, we provide a comprehensive review on the mechanisms by which OSA and its most detrimental perturbation, intermittent hypoxia (IH), can enhance the transcription of PAI-1. We also propose causal pathways by which PAI-1 can promote atherosclerosis in OSA, thereby identifying PAI-1 as a potential therapeutic target in OSA-induced CVD.

Plg-RKT Expression in Human Breast Cancer Tissues

The plasminogen activation system regulates the activity of the serine protease, plasmin. The role of plasminogen receptors in cancer progression is being increasingly appreciated as key players in modulation of the tumor microenvironment. The interaction of plasminogen with cells to promote plasminogen activation requires the presence of proteins exposing C-terminal lysines on the cell surface. Plg-R_KT is a structurally unique plasminogen receptor because it is an integral membrane protein that is synthesized with and binds plasminogen via a C-terminal lysine exposed on the cell surface. Here, we have investigated the expression of Plg-R_KT in human breast tumors and human breast cancer cell lines. Breast cancer progression tissue microarrays were probed with anti-Plg-R_KT mAB and we found that Plg-R_KT is widely expressed in human breast tumors, that its expression is increased in tumors that have spread to draining lymph nodes and distant organs, and that Plg-R_KT expression is most pronounced in hormone receptor (HR)-positive tumors. Plg-R_KT was detected by Western blotting in human breast cancer cell lines. By flow cytometry, Plg-R_KT cell surface expression was highest on the most aggressive tumor cell line. Future studies are warranted to address the functions of Plg-R_KT in breast cancer.

Adipokines and Arterial Stiffness in Obesity

Adipokines are active molecules with pleiotropic effects produced by adipose tissue and involved in obesity-related metabolic and cardiovascular diseases. Arterial stiffness, which is a consequence of arteriosclerosis, has been shown to be an independent predictor of cardiovascular morbidity and mortality. The pathogenesis of arterial stiffness is complex but incompletely understood. Adipokines dysregulation may induce, by various mechanisms, vascular inflammation, endothelial dysfunction, and vascular remodeling, leading to increased arterial stiffness. This article summarizes literature data regarding adipokine-related pathogenetic mechanisms involved in the development of arterial stiffness, particularly in obesity, as well as the results of clinical and epidemiological studies which investigated the relationship between adipokines and arterial stiffness.

Coagulation disorders in Chagas disease: A pathophysiological systematic review and meta-analysis

BACKGROUND

Currently, Chagas disease (CD) constitutes one of the main public health problems in Latin America. However, little is known about potential mechanisms of disease different from cardiac or digestive involvement, such as the coagulation disorders elicited by the parasite persistence in the tissues. The aim of this systematic review was to describe and characterize all the published literature that evaluated the pathophysiological aspects of coagulation disorders in CD.

METHODS

Searches in Medline, EMBASE, and LILACS databases (from inception to July 28th, 2020) were performed. Articles of any language reporting the levels of different coagulation factors/markers or the prevalence of abnormal levels of the mentioned molecules in patients with CD were included. Two reviewers independently selected the studies, extracted the data, and assessed the quality of evidence. Estimates were pooled using random-effects meta-analyses.

RESULTS

Seven studies evaluating a total of 676 participants fulfilled the criteria and were included, while only six were suitable for meta-analyzing (544 participants, 52% men, mean age: 49 ± 8 years). 57.16% of the patients in the meta-analysis had a serological confirmed diagnosis of CD, while 97% of these were in the indeterminate stage of the disease. Patients in the CD group had higher levels of F 1 + 2 (SMD 5.15. 95% CI 1.92, 8.38), PAI-1 (SMD 0.46. 95% CI 0.07; 0.89), and P-selectin (SMD 1.8; 95% CI 0.13-3.47) compared to healthy controls. Furthermore, benznidazole therapy was associated with a reduction in the levels of these biomarkers after treatment.

CONCLUSION

The results of the present study suggest that patients with chronic T. cruzi infection are affected by a potential hypercoagulable state irrespective of the development of cardiac or digestive disease. Furthermore, the reduction in the levels of the coagulation markers after benznidazole therapy may suggest a significant role of the parasite load in the development of these coagulation disorders. There is a scarcity of research assessing the molecular and pathophysiological mechanisms of coagulation disorders in Chagas disease. Further research is needed to assess the benefit of benznidazole therapy on this hypercoagulable state in the long-term, along with its impact on the risk of thromboembolic events in CD patients.

Dissecting molecular details and functional effects of the high-affinity copper binding site in plasminogen activator Inhibitor-1

Plasminogen activator inhibitor-1 (PAI-1) is the primary inhibitor for plasminogen activators, tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA). As a unique member in the serine protease inhibitor (serpin) family, PAI-1 is metastable and converts to an inactive, latent structure with a half-life of 1-2 hr under physiological conditions. Unusual effects of metals on the rate of the latency conversion are incompletely understood. Previous work has identified two residues near the N-terminus, H2 and H3, which reside in a high-affinity copper-binding site in PAI-1 [Bucci JC, McClintock CS, Chu Y, Ware GL, McConnell KD, Emerson JP, Peterson CB (2017) J Biol Inorg Chem 22:1123-1,135]. In this study, neighboring residues, H10, E81, and H364, were tested as possible sites that participate in Cu(II) coordination at the high-affinity site. Kinetic methods, gel sensitivity assays, and isothermal titration calorimetry (ITC) revealed that E81 and H364 have different roles in coordinating metal and mediating the stability of PAI-1. H364 provides a third histidine in the metal-coordination sphere with H2 and H3. In contrast, E81 does not appear to be required for metal ligation along with histidines; contacts made by the side-chain carboxylate upon metal binding are perturbed and, in turn, influence dynamic fluctuations within the region encompassing helices D, E, and F and the W86 loop that are important in the pathway for the PAI-1 latency conversion. This investigation underscores a prominent role of protein dynamics, noncovalent bonding networks and ligand binding in controlling the stability of the active form of PAI-1.

The Role of Immunomodulation in Vein Graft Remodeling and Failure

Obstructive arterial disease is a major cause of morbidity and mortality in the developed world. Venous bypass graft surgery is one of the most frequently used revascularization strategies despite its considerable short and long time failure rate. Due to vessel wall remodeling, inflammation, intimal hyperplasia, and accelerated atherosclerosis, vein grafts may (ultimately) fail to revascularize tissues downstream to occlusive atherosclerotic lesions. In the past decades, little has changed in the prevention of vein graft failure (VGF) although new insights in the role of innate and adaptive immunity in VGF have emerged. In this review, we discuss the pathophysiological mechanisms underlying the development of VGF, emphasizing the role of immune response and associated factors related to VG remodeling and failure. Moreover, we discuss potential therapeutic options that can improve patency based on data from both preclinical studies and the latest clinical trials. This review contributes to the insights in the role of immunomodulation in vein graft failure in humans. We describe the effects of immune cells and related factors in early (thrombosis), intermediate (inward remodeling and intimal hyperplasia), and late (intimal hyperplasia and accelerated atherosclerosis) failure based on both preclinical (mouse) models and clinical data.

Redox control of vascular biology

Redox control is lost when the antioxidant defense system cannot remove abnormally high concentrations of signaling molecules, such as reactive oxygen species (ROS). Chronically elevated levels of ROS cause oxidative stress that may eventually lead to cancer and cardiovascular and neurodegenerative diseases. In this review, we focus on redox effects in the vascular system. We pay close attention to the subcompartments of the vascular system (endothelium, smooth muscle cell layer) and give an overview of how redox changes influence those different compartments. We also review the core aspects of redox biology, cardiovascular physiology, and pathophysiology. Moreover, the topic-specific knowledgebase DES-RedoxVasc was used to develop two case studies, one focused on endothelial cells and the other on the vascular smooth muscle cells, as a starting point to possibly extend our knowledge of redox control in vascular biology.

GLUT10 maintains the integrity of major arteries through regulation of redox homeostasis and mitochondrial function

Glucose transporter 10 (GLUT10) is a member of the GLUT family of membrane transporters, and mutations in this gene cause arterial tortuosity syndrome (ATS). However, the physiological role and regulation of GLUT10 in arteries remains unclear. To further understand its physiological roles in major arteries, we examined the regulatory mechanisms of GLUT10 in ASMCs and aortic tissues. Interestingly, we find that targeting of GLUT10 to mitochondria is increased in ASMCs under both stress and aging conditions, which enhances dehydroascorbic acid (DHA) uptake and maintains intracellular ascorbic acid (AA) levels. We further demonstrate that the targeting of GLUT10 to mitochondria is important to maintain redox homeostasis, mitochondrial structure and mitochondrial function in ASMCs. A missense mutation of GLUT10 (Glut10G128E) impairs mitochondrial targeting in ASMCs. Consequently, ASMCs isolated from Glut10G128E mice exhibit increased reactive oxygen species (ROS) levels, fragmented mitochondria and impaired mitochondrial function, as well as enhanced cell proliferation and migration. In vivo, mitochondrial structure is altered, and ROS levels are heightened in aortic tissues of Glut10G128E mice. Furthermore, increased number and disorganization of ASMCs, along with progressive arterial wall remodeling were observed in aortic tissues of Glut10G128E mice. These defects were coincident with elevated systolic blood pressure in aged Glut10G128E animals. Our results describe a novel mechanism that GLUT10 targeting to mitochondria under stress and aging condition has a critical role in maintaining AA levels, redox homeostasis and mitochondrial structure and function in ASMCs, which is likely to contribute to the maintenance of healthy vascular tissue.

Production of human tissue-type plasminogen activator (htPA) using in vitro cultured transgenic pig mammary gland cells

Tissue plasminogen activator (tPA) is a protein involved in the breakdown of blood clots. We have previously produced a human tPA (htPA)-overexpressing transgenic pig using a mammary gland-specific promoter. In this study, we have established a transgenic pig mammary gland cell line that produces recombinant htPA. The mammary gland cells grew well and retained their character over long periods of culture. There was no difference in the extent of apoptosis in transgenic cells compared to wild-type mammary gland cells. In addition, the transgenic mammary gland cells expressed and secreted htPA into the conditioned media at a concentration similar to that in milk. This transgenic cell line represents a simple and ethical method for recombinant htPA production.

PAI-1 is a novel component of the miR-17~92 signaling that regulates pulmonary artery smooth muscle cell phenotypes

We have previously reported that miR-17~92 is critically involved in the pathogenesis of pulmonary hypertension (PH). We also identified two novel mR-17/20a direct targets, PDZ and LIM domain protein 5 (PDLIM5) and prolyl hydroxylase 2 (PHD2), and elucidated the signaling pathways by which PDLIM5 and PHD2 regulate functions of pulmonary artery smooth muscle cells (PASMCs). In addition, we have shown that plasminogen activator inhibitor-1 (PAI-1) is also downregulated in PASMCs that overexpress miR-17~92. However, it is unclear whether PAI-1 is a direct target of miR-17~92 and whether it plays a role in regulating the PASMC phenotype. In this study, we have identified PAI-1 as a novel target of miR-19a/b, two members of the miR-17~92 cluster. We found that the 3'-untranslated region (UTR) of PAI-1 contains a miR-19a/b binding site and that miR-19a/b can target this site to suppress PAI-1 protein expression. MiR-17/20a, two other members of miR-17~92, may also indirectly suppress PAI-1 expression through PDLIM5. PAI-1 is a negative regulator of miR-17~92-mediated PASMC proliferation. Silencing of PAI-1 induces Smad2/calponin signaling in PASMCs, suggesting that PAI-1 is a negative regulator of the PASMC contractile phenotype. We also found that PAI-1 is essential for the metabolic gene expression in PASMCs. Furthermore, although there is no significant change in PAI-1 levels in PASMCs isolated from idiopathic pulmonary arterial hypertension and associated pulmonary arterial hypertension patients, PAI-1 is downregulated in hypoxia/Sugen-induced hypertensive rat lungs. These results suggest that miR-17~92 regulates the PASMC contractile phenotype and proliferation coordinately and synergistically by direct and indirect targeting of PAI-1.

Inflammation in Vein Graft Disease

Bypass surgery is one of the most frequently used strategies to revascularize tissues downstream occlusive atherosclerotic lesions. For venous bypass surgery the great saphenous vein is the most commonly used vessel. Unfortunately, graft efficacy is low due to the development of vascular inflammation, intimal hyperplasia and accelerated atherosclerosis. Moreover, failure of grafts leads to significant adverse outcomes and even mortality. The last couple of decades not much has changed in the treatment of vein graft disease (VGD). However, insight is the cellular and molecular mechanisms of VGD has increased. In this review, we discuss the latest insights on VGD and the role of inflammation in this. We discuss vein graft pathophysiology including hemodynamic changes, the role of vessel wall constitutions and vascular remodeling. We show that profound systemic and local inflammatory responses, including inflammation of the perivascular fat, involve both the innate and adaptive immune system.

Resolving distinct molecular origins for copper effects on PAI-1

Components of the fibrinolytic system are subjected to stringent control to maintain proper hemostasis. Central to this regulation is the serpin plasminogen activator inhibitor-1 (PAI-1), which is responsible for specific and rapid inhibition of fibrinolytic proteases. Active PAI-1 is inherently unstable and readily converts to a latent, inactive form. The binding of vitronectin and other ligands influences stability of active PAI-1. Our laboratory recently observed reciprocal effects on the stability of active PAI-1 in the presence of transition metals, such as copper, depending on the whether vitronectin was also present (Thompson et al. Protein Sci 20:353–365, 2011). To better understand the molecular basis for these copper effects on PAI-1, we have developed a gel-based copper sensitivity assay that can be used to assess the copper concentrations that accelerate the conversion of active PAI-1 to a latent form. The copper sensitivity of wild-type PAI-1 was compared with variants lacking N-terminal histidine residues hypothesized to be involved in copper binding. In these PAI-1 variants, we observed significant differences in copper sensitivity, and these data were corroborated by latency conversion kinetics and thermodynamics of copper binding by isothermal titration calorimetry. These studies identified a copper-binding site involving histidines at positions 2 and 3 that confers a remarkable stabilization of PAI-1 beyond what is observed with vitronectin alone. A second site, independent from the two histidines, binds metal and increases the rate of the latency conversion.

Functional Regulation of the Plasma Protein Histidine-Rich Glycoprotein by Zn2+ in Settings of Tissue Injury

Divalent metal ions are essential nutrients for all living organisms and are commonly protein-bound where they perform important roles in protein structure and function. This regulatory control from metals is observed in the relatively abundant plasma protein histidine-rich glycoprotein (HRG), which displays preferential binding to the second most abundant transition element in human systems, Zinc (Zn²⁺). HRG has been proposed to interact with a large number of protein ligands and has been implicated in the regulation of various physiological and pathological processes including the formation of immune complexes, apoptotic/necrotic and pathogen clearance, cell adhesion, antimicrobial activity, angiogenesis, coagulation and fibrinolysis. Interestingly, these processes are often associated with sites of tissue injury or tumour growth, where the concentration and distribution of Zn²⁺ is known to vary. Changes in Zn²⁺ levels have been shown to modify HRG function by altering its affinity for certain ligands and/or providing protection against proteolytic disassembly by serine proteases. This review focuses on the molecular interplay between HRG and Zn²⁺, and how Zn²⁺ binding modifies HRG-ligand interactions to regulate function in different settings of tissue injury.

Streptokinase@alumina nanoparticles as a promising thrombolytic colloid with prolonged action

The present study is devoted to the development of a new class of thrombolytic systems - nanocolloids. A non-direct plasminogen activator, streptokinase, was entrapped in a sol-gel matrix based on boehmite nanoparticles used in medical practice as the most common vaccine adjuvant. It is shown that when the enzyme content in the composite is less than 10%, only minor release is observed, while thrombolytic properties are maintained at a relatively high level, demonstrating the prolonged effect. Based on the obtained composites, thrombolytic nanocolloids containing nanoparticles of less than 500 nm size and suitable for parenteral administration were produced. The thrombolytic properties were studied using the plasminogen activation tests, human plasma clots and a model thrombus made from a whole human blood. Based on the obtained results, the structure of the composites and the mechanism of their action are suggested.

Increased Urokinase-Type Plasminogen Activator Receptor Expression on Circulating Monocytes Is Correlated with Clinical Instability and Long-Term Adverse Cardiac Events in Patients with Coronary Artery Disease

OBJECTIVES

This study sought to investigate the clinical correlates and prognostic roles of urokinase-type plasminogen activator receptor (uPAR) on circulating monocytes in patients with coronary artery disease (CAD).

METHODS

263 angina patients were included in this study. The percentage of uPAR expressing monocytes (PUEM) and the mean fluorescence intensity (MFI) index of uPAR were measured using flow cytometry. Patient follow-up was on average 604 days. Major adverse cardiac events (MACE) were defined as a composite of cardiac death, reinfarction, acute heart failure and hospitalization for revascularization.

RESULTS

The PUEM and MFI index levels were significantly more elevated in acute coronary syndrome patients than in stable ones. uPAR expressions on circulating monocytes at admission were correlated to inflammatory biomarkers and myocardial necrosis. Logistic regression analysis revealed that PUEM ≥15% (OR 21.96, 95% CI 7.31-65.98, p < 0.001) and uPAR MFI index ≥3.00 (OR 3.54, 95% CI 1.18-10.59, p = 0.024) were independent determinants of clinical instability in patients with CAD. When followed up, a high PUEM level at admission was an independent prognostic parameter for long-term MACE (HR 3.99, 95% CI 1.31-12.11, p = 0.015).

CONCLUSIONS

uPAR expression on circulating monocytes is associated with clinical instability and myocardial necrosis and independently predicts the risk of MACE in patients with CAD.

Vein graft failure: from pathophysiology to clinical outcomes

Occlusive arterial disease is a leading cause of morbidity and mortality worldwide. Aside from balloon angioplasty, bypass graft surgery is the most commonly performed revascularization technique for occlusive arterial disease. Coronary artery bypass graft surgery is performed in patients with left main coronary artery disease and three-vessel coronary disease, whereas peripheral artery bypass graft surgery is used to treat patients with late-stage peripheral artery occlusive disease. The great saphenous veins are commonly used conduits for surgical revascularization; however, they are associated with a high failure rate. Therefore, preservation of vein graft patency is essential for long-term surgical success. With the exception of 'no-touch' techniques and lipid-lowering and antiplatelet (aspirin) therapy, no intervention has hitherto unequivocally proven to be clinically effective in preventing vein graft failure. In this Review, we describe both preclinical and clinical studies evaluating the pathophysiology underlying vein graft failure, and the latest therapeutic options to improve patency for both coronary and peripheral grafts.

Why Do Patients Bleed?

Patients undergoing surgical procedures can bleed for a variety of reasons. Assuming that the surgical procedure has progressed well and that the surgeon can exclude surgical reasons for the unexpected bleeding, then the bleeding may be due to structural (anatomical) anomalies or disorders, recent drug intake, or disorders of hemostasis, which may be acquired or congenital. The current review aims to provide an overview of reasons that patients bleed in the perioperative setting, and it also provides guidance on how to screen for these conditions, through consideration of appropriate patient history and examination prior to surgical intervention, as well as guidance on investigating and managing the cause of unexpected bleeding.

Proteolytic degradation of neuropeptide Y (NPY) from head to toe: Identification of novel NPY-cleaving peptidases and potential drug interactions in CNS and Periphery

The bioactivity of neuropeptide Y (NPY) is either N-terminally modulated with respect to receptor selectivity by dipeptidyl peptidase 4 (DP4)-like enzymes or proteolytic degraded by neprilysin or meprins, thereby abrogating signal transduction. However, neither the subcellular nor the compartmental differentiation of these regulatory mechanisms is fully understood. Using mass spectrometry, selective inhibitors and histochemistry, studies across various cell types, body fluids, and tissues revealed that most frequently DP4-like enzymes, aminopeptidases P, secreted meprin-A (Mep-A), and cathepsin D (CTSD) rapidly hydrolyze NPY, depending on the cell type and tissue under study. Novel degradation of NPY by cathepsins B, D, L, G, S, and tissue kallikrein could also be identified. The expression of DP4, CTSD, and Mep-A at the median eminence indicates that the bioactivity of NPY is regulated by peptidases at the interphase between the periphery and the CNS. Detailed ex vivo studies on human sera and CSF samples recognized CTSD as the major NPY-cleaving enzyme in the CSF, whereas an additional C-terminal truncation by angiotensin-converting enzyme could be detected in serum. The latter finding hints to potential drug interaction between antidiabetic DP4 inhibitors and anti-hypertensive angiotensin-converting enzyme inhibitors, while it ablates suspected hypertensive side effects of only antidiabetic DP4-inhibitors application. The bioactivity of neuropeptide Y (NPY) is either N-terminally modulated with respect to receptor selectivity by dipeptidyl peptidase 4 (DP4)-like enzymes or proteolytic degraded by neprilysin or meprins, thereby abrogating signal transduction. However, neither the subcellular nor the compartmental differentiation of these regulatory mechanisms is fully understood. Using mass spectrometry, selective inhibitors and histochemistry, studies across various cell types, body fluids, and tissues revealed that most frequently DP4-like enzymes, aminopeptidases P, secreted meprin-A (Mep-A), and cathepsin D (CTSD) rapidly hydrolyze NPY, depending on the cell type and tissue under study. Novel degradation of NPY by cathepsins B, D, L, G, S, and tissue kallikrein could also be identified. The expression of DP4, CTSD, and Mep-A at the median eminence indicates that the bioactivity of NPY is regulated by peptidases at the interphase between the periphery and the CNS. Detailed ex vivo studies on human sera and CSF samples recognized CTSD as the major NPY-cleaving enzyme in the CSF, whereas an additional C-terminal truncation by angiotensin-converting enzyme could be detected in serum. The latter finding hints to potential drug interaction between antidiabetic DP4 inhibitors and anti-hypertensive angiotensin-converting enzyme inhibitors, while it ablates suspected hypertensive side effects of only antidiabetic DP4-inhibitors application.

Retinoic acid inhibits tissue factor and HMGB1 via modulation of AMPK activity in TNF-α activated endothelial cells and LPS-injected mice

OBJECTIVE

Retinoic acid (RA) is the active vitamin A derivative and has diverse immunomodulatory actions. We hypothesized that RA reduces prothrombotic mediators such as tissue factor (TF) in endothelial cells during inflammatory conditions via an AMPK-dependent pathway, which attenuates cardiovascular complications.

RESULTS

RA significantly increased AMPK and Akt phosphorylation in a time- and concentration-dependent manner in endothelial cells (EC). RA downregulated TF expression at the transcriptional and translational levels in TNF-α activated ECs, which was reversed by the silencing of AMPK and transfection of DN-AMPK. Interestingly, the PI3-kinase inhibitor LY294002 reversed the RA effect on TF expression. Increased AMPK phosphorylation by RA was inhibited by LY294002. However, increased Akt phosphorylation was not reduced by compound C, indicating that PI3K/Akt signaling modulates AMPK activity. In addition, RA reduced HMGB1 release in TNF-α activated ECs, which was reversed by both LY294001 and siAMPK. Importantly, administration of RA (1 mg/kg) significantly reduced blood TF activity, circulating HMGB1 and PAI-1 levels and expression of hepatic TF mRNA as well as fibrin deposition in LPS (5 mg/kg)-injected mice.

CONCLUSIONS

Taken together, the activation of PI3K/Akt by RA modulates AMPK activity in ECs and plays a crucial role in the inhibition of coagulatory factors such as TF, PAI-1, and HMGB1 in inflammatory conditions.

The 4G/4G Genotype of PAI-1 Polymorphism Is Associated with Higher Plasma PAI-1 Concentrations and Mortality in Patients with Severe Sepsis

Objective

Two studies have reported that patients with the 4G/4G genotype of the plasminogen activator inhibitor-1 (PAI-1) genetic polymorphism had higher plasma PAI-1 concentrations and higher risk of death than those with the 4G/5G or 5G/5G genotypes; one study involved 175 children with meningococcal disease, and the other included 88 adult patients with septic shock. Thus, the objective of this study was to determine whether there is an association between carriage of the 4G/4G genotype, plasma PAI-1 concentrations and mortality in a large series of adult septic patients.

Methods

An observational, prospective, multicenter study was carried out in six Spanish Intensive Care Units including severe septic patients. We determined the PAI-1 4G/5G polymorphism and plasma PAI-1 concentrations in all patients. The end-points of the study were 30-day and 6-month mortality.

Results

We included a total of 260 patients, 82 (31.5%) with 4G/4G, 126 (48.5%) with 4G/5G and 52 (20.0%) with 5G/5G genotype. Multivariate logistic regression analysis showed that the 4G/4G genotype was associated with higher mortality at 30 days (Odds Ratio = 1.95; 95% CI = 1.063–3.561; p = 0.03) and at 6 months (Odds Ratio = 2.19; 95% CI = 1.221–3.934; p = 0.01), and that higher plasma PAI-1 concentrations were associated with higher mortality at 30 days (Odds Ratio = 1.01; 95% CI = 1.002–1.022; p = 0.02) at 6 months (Odds Ratio = 1.01; 95% CI = 1.003–1.023; p = 0.01). Multivariate linear regression analysis showed that increased plasma PAI-1 concentrations were associated with the PAI-1 4G/4G genotype (regression coefficient = 4.82; 95% CI = 3.227 to 6.406; p<0.001).

Conclusions

The major findings of our study, to our knowledge the largest series reporting data about 4G/5G polymorphism of the PAI-1 gene, plasma PAI-1 concentrations and mortality in septic patients, were that septic patients with the 4G/4G genotype had higher plasma PAI-1 concentrations and higher risk of death than those with 4G/5G or 5G/5G genotypes.

The inflammatory actions of coagulant and fibrinolytic proteases in disease

Aside from their role in hemostasis, coagulant and fibrinolytic proteases are important mediators of inflammation in diseases such as asthma, atherosclerosis, rheumatoid arthritis, and cancer. The blood circulating zymogens of these proteases enter damaged tissue as a consequence of vascular leak or rupture to become activated and contribute to extravascular coagulation or fibrinolysis. The coagulants, factor Xa (FXa), factor VIIa (FVIIa), tissue factor, and thrombin, also evoke cell-mediated actions on structural cells (e.g., fibroblasts and smooth muscle cells) or inflammatory cells (e.g., macrophages) via the proteolytic activation of protease-activated receptors (PARs). Plasmin, the principle enzymatic mediator of fibrinolysis, also forms toll-like receptor-4 (TLR-4) activating fibrin degradation products (FDPs) and can release latent-matrix bound growth factors such as transforming growth factor-β (TGF-β). Furthermore, the proteases that convert plasminogen into plasmin (e.g., urokinase plasminogen activator) evoke plasmin-independent proinflammatory actions involving coreceptor activation. Selectively targeting the receptor-mediated actions of hemostatic proteases is a strategy that may be used to treat inflammatory disease without the bleeding complications of conventional anticoagulant therapies. The mechanisms by which proteases of the coagulant and fibrinolytic systems contribute to extravascular inflammation in disease will be considered in this review.

[Expression of plasminogen activator system components in the gastric mucosa in portal hypertensive gastropathy]

OBJECTIVE

to study the expression of urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) in the gastric mucosal (GM) vascular endothelium and epithelial cells of patients with portal hypertensive gastropathy (PHG) and those with portal hypertension (PH) without signs of PHG as compared to a control group.

MATERIAL AND METHODS

GM biopsy specimens from patients with PHG, those with PH without signs of PHG, and controls with the normal gastric mucosa were immunohistochemically examined.

RESULTS

Comparison of the expression of uPA in the GM vascular endothelium and epithelial vessels revealed no significant differences in the patient groups. The level of PAI-1 in the GM vessels was statistically significantly higher in the control group than in the groups of patients with PHG and PH without PHG. PAI-1 expression in the GM epithelial cells was significantly more commonly absent in the PHG group than in the control group. An analysis of an uPA and PAI-1 expression ratio showed a statistically significant predominance of the expression of uPA over its inhibitor in the GM vascular endothelium of the patients with PHG and those with PH without PHG as compared to the controls.

CONCLUSION

The predominance of uPA over PAI-1 in the GM vessels and epithelial cells can play a role in the development of GM bleeding.

Plasminogen-stimulated airway smooth muscle cell proliferation is mediated by urokinase and annexin A2, involving plasmin-activated cell signalling

BACKGROUND AND PURPOSE

The conversion of plasminogen into plasmin by interstitial urokinase plasminogen activator (uPA) is potentially important in asthma pathophysiology. In this study, the effect of uPA-mediated plasminogen activation on airway smooth muscle (ASM) cell proliferation was investigated.

EXPERIMENTAL APPROACH

Human ASM cells were incubated with plasminogen (0.5-50 μg·mL(-1) ) or plasmin (0.5-50 mU·mL(-1) ) in the presence of pharmacological inhibitors, including UK122, an inhibitor of uPA. Proliferation was assessed by increases in cell number or MTT reduction after 48 h incubation with plasmin(ogen), and by earlier increases in [(3) H]-thymidine incorporation and cyclin D1 expression.

KEY RESULTS

Plasminogen (5 μg·mL(-1) )-stimulated increases in cell proliferation were attenuated by UK122 (10 μM) or by transfection with uPA gene-specific siRNA. Exogenous plasmin (5 mU·mL(-1) ) also stimulated increases in cell proliferation. Inhibition of plasmin-stimulated ERK1/2 or PI3K/Akt signalling attenuated plasmin-stimulated increases in ASM proliferation. Furthermore, pharmacological inhibition of cell signalling mediated by the EGF receptor, a receptor trans-activated by plasmin, also reduced plasmin(ogen)-stimulated cell proliferation. Knock down of annexin A2, which has dual roles in both plasminogen activation and plasmin-signal transduction, also attenuated ASM cell proliferation following incubation with either plasminogen or plasmin.

CONCLUSIONS AND IMPLICATIONS

Plasminogen stimulates ASM cell proliferation in a manner mediated by uPA and involving multiple signalling pathways downstream of plasmin. Targeting mediators of plasminogen-evoked ASM responses, such as uPA or annexin A2, may be useful in the treatment of asthma.

Extracellular matrix biomarker, fibulin-1, is closely related to NT-proBNP and soluble urokinase plasminogen activator receptor in patients with aortic valve stenosis (the SEAS study)

Background

Fibulin-1, a circulating extracellular matrix glycoprotein, has been associated with arterial disease and elevated N-terminal prohormone B-type natriuretic peptide (NT-proBNP) in diabetes. Soluble urokinase plasminogen activator receptor (suPAR), a marker of inflammation, has been associated with subclinical atherosclerosis. Therefore, we aimed to explore the interplay between these biomarkers and mild to moderate aortic valve stenosis (AS).

Methods

In 374 patients with mild to moderate AS, we investigated the relationship of fibulin-1 with NT-proBNP, levels of suPAR and the degree of AS at baseline and after one and four years of treatment with Simvastatin 40 mg and Ezetimibe 10 mg or placebo.

Results

During treatment, fibulin-1 became more closely associated with NT-proBNP (β_year0 = 0.10, p = 0.08, β_year1 = 0.16, p = 0.005, β_year4 = 0.22, p<0.001) and suPAR (β_year0 = 0.05, p = 0.34, β_year1 = 0.16, p = 0.006, β_year4 = 0.13, p = 0.03) at the expense of the association to aortic valve area index (AVAI) (β_year0 = −0.14, p = 0.005, β_year1 = −0.08, p = 0.11, β_year4 = −0.06, p = 0.22) independently of age, gender, creatinine, and serum aspartate aminotransferase (Adj.R_year0² = 0.19, Adj.R_year1² = 0.22, Adj.R_year4² = 0.27). Fibulin-1 was unrelated to aortic regurgitation, left ventricular mass, and ejection fraction. In patients with baseline AVAI<0.58 cm²/m² (median value), fibulin-1 was more closely associated to NT-proBNP (β_year0 = 0.25, β_year1 = 0.21, β_year4 = 0.22, all p<0.01), and suPAR (β_year0 = 0.09, p = 0.26, β_year1 = 0.23, β_year4 = 0.21, both p<0.01) independently of age, gender, AST and treatment allocation.

Conclusions

Increased levels of fibulin-1 were independently associated with higher levels of suPAR and NT-proBNP especially in patients with lower AVAI, suggesting that fibulin-1 may be an early marker of AS as well as cardiac fibrosis secondarily to elevated left ventricular hemodynamic load.

Development and characterization of highly selective target-sensitive liposomes for the delivery of streptokinase: in vitro/in vivo studies

Streptokinase is one of the most commonly used thrombolytic agents for the treatment of thromboembolism. Short half-life of the streptokinase requires administration of higher dose which results in various side effects including systemic haemorrhage due to activation of systemic plasmin. To increase the selectivity of the streptokinase and hence to reduce side effects, various novel carriers have been developed. Among these carriers, liposomes have been emerged as versatile carrier. In the present study, highly selective target-sensitive liposomes were developed and evaluated by in vitro and in vivo studies. Prepared liposomes were found to release streptokinase in vitro following binding with activated platelets. Intravital microscopy studies in thrombosed murine model revealed higher accumulation of liposomes in the thrombus area. In vivo thrombolysis study was performed in the human clot inoculated rat model. Results of the study showed that target-sensitive liposomes dissolved 28.27 ± 1.56% thrombus as compared to 17.18 ± 1.23% of non-liposomal streptokinase. Further, it was also observed that target-sensitive liposomes reduced the clot dissolution time as compared to streptokinase solution. Studies concluded that developed liposomes might be pragmatic carriers for the treatment of thromboembolism.

Sustained high plasma plasminogen activator inhibitor-1 levels are associated with severity and mortality in septic patients

BACKGROUND

Higher plasma plasminogen activator inhibitor-1 (PAI-1) levels have been reported in septic patients. However, some questions remain unanswered, such as whether there is an association between plasma PAI-1 levels and sepsis severity and mortality, and inflammation state during the first week.

METHODS

Multicenter, observational and prospective study carried out in six Spanish Intensive Care Units of 260 patients with severe sepsis. Circulating levels of PAI-1 and tumour necrosis factor (TNF)-α were measured at day 1, 4 and 8. End-point was 30-day mortality.

RESULTS

Nonsurviving septic patients (n=89) presented higher PAI-1 levels than surviving (n=171) at day 1 (58.4 (33.3-83.8) vs 36.5 (21.1-62.5) ng/mL; p<0.001), 4 (34.0 (14.7-53.3) vs 16.2 (10.2-27.4) ng/mL; p<0.001) and 8 (30.6 (16.2-47.8) vs 18.9 (10.4-29.5) ng/mL; p=0.004). We found a positive correlation of PAI-1 levels with SOFA, lactic acid, aPTT, INR and TNF-α, and negative with platelet count at day 1, 4 and 8. Logistic regression analyses showed that PAI-1 levels at day 1 (p<0.001), 4 (p<0.001) and 8 (p=0.001) were associated with 30-day mortality. On ROC curve analysis to predict 30- day survival, the area under the curve of PAI-1 levels at day 1, 4 and 8 were 0.65 (95% CI=0.58-0.72; p<0.001), 0.69 (95% CI=0.60-0.78; p<0.001) and 0.65 (95% CI=0.54-0.75; p=0.005) respectively.

CONCLUSIONS

The most interesting findings of our study, to our knowledge the largest series reporting PAI-1 levels during follow-up in septic patients, were that plasma PAI-1 levels during the first week were associated with inflammation, severity and mortality.

Expression of uPA, tPA, and PAI-1 in Calcified Aortic Valves

Purpose. Our physiopathological assumption is that u-PA, t-PA, and PAI-1 are released by calcified aortic valves and play a role in the calcification of these valves. Methods. Sixty-five calcified aortic valves were collected from patients suffering from aortic stenosis. Each valve was incubated for 24 hours in culture medium. The supernatants were used to measure u-PA, t-PA, and PAI-1 concentrations; the valve calcification was evaluated using biphotonic absorptiometry. Results. Aortic stenosis valves expressed normal plasminogen activators concentrations and overexpressed PAI-1 (u-PA, t-PA, and PAI-1 mean concentrations were, resp., 1.69 ng/mL ± 0.80, 2.76 ng/mL ± 1.33, and 53.27 ng/mL ± 36.39). There was no correlation between u-PA and PAI-1 (r = 0.3) but t-PA and PAI-1 were strongly correlated with each other (r = 0.6). Overexpression of PAI-1 was proportional to the calcium content of the AS valves. Conclusions. Our results demonstrate a consistent increase of PAI-1 proportional to the calcification. The overexpression of PAI-1 may be useful as a predictive indicator in patients with aortic stenosis.

Evaluation of coagulation activation after rhinovirus infection in patients with asthma and healthy control subjects: an observational study

Background

Asthma exacerbations are frequently triggered by rhinovirus infections. Both asthma and respiratory tract infection can activate haemostasis. Therefore we hypothesized that experimental rhinovirus-16 infection and asthmatic airway inflammation act in synergy on the haemostatic balance.

Methods

28 patients (14 patients with mild allergic asthma and 14 healthy non-allergic controls) were infected with low-dose rhinovirus type 16. Venous plasma and bronchoalveolar lavage fluid (BAL fluid) were obtained before and 6 days after infection to evaluate markers of coagulation activation, thrombin-antithrombin complexes, von Willebrand factor, plasmin-antiplasmin complexes, plasminogen activator inhibitor type-1, endogenous thrombin potential and tissue factor-exposing microparticles by fibrin generation test, in plasma and/or BAL fluid. Data were analysed by nonparametric tests (Wilcoxon, Mann Whitney and Spearman correlation).

Results

13 patients with mild asthma (6 females, 19-29 y) and 11 healthy controls (10 females, 19-31 y) had a documented Rhinovirus-16 infection. Rhinovirus-16 challenge resulted in a shortening of the fibrin generation test in BAL fluid of asthma patients (t = -1: 706 s vs. t = 6: 498 s; p = 0.02), but not of controls (t = -1: 693 s vs. t = 6: 636 s; p = 0.65). The fold change in tissue factor-exposing microparticles in BAL fluid inversely correlated with the fold changes in eosinophil cationic protein and myeloperoxidase in BAL fluid after virus infection (r = -0.517 and -0.528 resp., both p = 0.01).

Rhinovirus-16 challenge led to increased plasminogen activator inhibitor type-1 levels in plasma in patients with asthma (26.0 ng/mL vs. 11.5 ng/mL in healthy controls, p = 0.04). Rhinovirus-16 load in BAL showed a linear correlation with the fold change in endogenous thrombin potential, plasmin-antiplasmin complexes and plasminogen activator inhibitor type-1.

Conclusions

Experimental rhinovirus infection induces procoagulant changes in the airways of patients with asthma through increased activity of tissue factor-exposing microparticles. These microparticle-associated procoagulant changes are associated with both neutrophilic and eosinophilic inflammation. Systemic activation of haemostasis increases with Rhinoviral load.

Trial registration

This trial was registered at the Dutch trial registry (http://www.trialregister.nl): NTR1677.

Plasminogen-stimulated inflammatory cytokine production by airway smooth muscle cells is regulated by annexin A2

Plasminogen has a role in airway inflammation. Airway smooth muscle (ASM) cells cleave plasminogen into plasmin, a protease with proinflammatory activity. In this study, the effect of plasminogen on cytokine production by human ASM cells was investigated in vitro. Levels of IL-6 and IL-8 in the medium of ASM cells were increased by incubation with plasminogen (5-50 μg/ml) for 24 hours (P < 0.05; n = 6-9), corresponding to changes in the levels of cytokine mRNA at 4 hours. The effects of plasminogen were attenuated by α2-antiplasmin (1 μg/ml), a plasmin inhibitor (P < 0.05; n = 6-12). Exogenous plasmin (5-15 mU/ml) also stimulated cytokine production (P < 0.05; n = 6-8) in a manner sensitive to serine-protease inhibition by aprotinin (10 KIU/ml). Plasminogen-stimulated cytokine production was increased in cells pretreated with basic fibroblast growth factor (300 pM) in a manner associated with increases in urokinase plasminogen activator expression and plasmin formation. The knockdown of annexin A2, a component of the putative plasminogen receptor comprised of annexin A2 and S100A10, attenuated plasminogen conversion into plasmin and plasmin-stimulated cytokine production by ASM cells. Moreover, a role for annexin A2 in airway inflammation was demonstrated in annexin A2-/- mice in which antigen-induced increases in inflammatory cell number and IL-6 levels in the bronchoalveolar lavage fluid were reduced (P < 0.01; n = 10-14). In conclusion, plasminogen stimulates ASM cytokine production in a manner regulated by annexin A2. Our study shows for the first time that targeting annexin A2-mediated signaling may provide a novel therapeutic approach to the treatment of airway inflammation in diseases such as chronic asthma.

The plasminogen activation system: new targets in lung inflammation and remodeling

The plasminogen activation system (PAS) and the plasmin it forms have dual roles in chronic respiratory diseases including asthma, chronic obstructive pulmonary disease and interstitial lung disease. Whilst plasmin-mediated airspace fibrinolysis is beneficial, interstitial plasmin contributes to lung dysfunction because of its pro-inflammatory and tissue remodeling activities. Recent studies highlight the potential of fibrinolytic agents, including small molecule inhibitors of plasminogen activator inhibitor-1 (PAI-1), as treatments for chronic respiratory disease. Current data also suggest that interstitial urokinase plasminogen activator is an important mediator of lung inflammation and remodeling. However, further preclinical characterization of uPA as a drug target for lung disease is required. Here we review the concept of selectively targeting the contributions of PAS to treat chronic respiratory disease.

Plasmin promotes foam cell formation by increasing macrophage catabolism of aggregated low-density lipoprotein

OBJECTIVE

The plasmin/plasminogen system is involved in atherosclerosis. However, the mechanisms by which it stimulates disease are not fully defined. A key event in atherogenesis is the deposition of low-density lipoprotein (LDL) on arterial walls where it is modified, aggregated, and retained. Macrophages are recruited to clear the lipoproteins, and they become foam cells. The goal of this study was to assess the role of plasmin in macrophage uptake of aggregated LDL and foam cell formation.

APPROACH AND RESULTS

Plasminogen treatment of macrophages catabolizing aggregated LDL significantly accelerated foam cell formation. Macrophage interaction with aggregated LDL increased the surface expression of urokinase-type plasminogen activator receptor and plasminogen activator activity, resulting in increased ability to generate plasmin at the cell surface. The high local level of plasmin cleaves cell-associated aggregated LDL, allowing a portion of the aggregate to become sequestered in a nearly sealed, yet extracellular, acidic compartment. The low pH in the plasmin-induced compartment allows lysosomal enzymes, delivered via lysosome exocytosis, greater activity, resulting in more efficient cholesteryl ester hydrolysis and delivery of a large cholesterol load to the macrophage, thereby promoting foam cell formation.

CONCLUSIONS

These findings highlight a critical role for plasmin in the catabolism of aggregated LDL by macrophages and provide a new context for considering the atherogenic role of plasmin.

Statins as a novel therapeutic strategy in acute lung injury

Acute lung injury (ALI) is a devastating clinical condition associated with pulmonary and systemic inflammation and characterized by incompetence of the pulmonary microvascular barrier culminating in noncardiogenic pulmonary edema. An understanding of the mechanisms underlying endothelial barrier dysfunction in ALI has been facilitated by study of the effects of statins in relevant cellular and animals models. Many of the pleotropic properties of these drugs, including direct effects on endothelial cell (EC) cytoskeletal rearrangement, NADPH oxidase, and nitric oxide activity, as well as effects on differential EC gene expression, are relevant to the pathobiology of ALI and suggest a potential therapeutic role for statins in this context. Moreover, results from preclinical studies and observations in relevant patient populations support the protective potential of statins in ALI, paving the way now for definitive clinical trials.

The changes in the endothelial function and haemostatic and inflammatory parameters in subclinical and overt hyperthyroidism

Introduction. The aim of the present study was to compare the levels of circulating markers of endothelial function and low-grade inflammation in patients with subclinical and overt hyperthyroidism (OH) due to Graves disease (GD) and toxic nodular goiter (TNG). Material and Methods. The group studied consisted of 42 patients with GD, 75 patients with TNG, and 39 healthy controls. Results. Circulating markers of endothelial dysfunction were elevated in the patients with both SH and OH, but the concentrations of interleukin-12 (IL-12) (P < 0.05), IL-18 (P < 0.05), fibrinogen (P < 0.01), and von Willebrand factor (vWF) (P < 0.05) were significantly higher in the OH than in the SH group. The highest levels of IL-6, IL-12, IL-18, vWF, sVCAM-1, and fibrinogen were found in the patients with GD, but the differences between the GD, and TNG groups were not significant. In the subjects with OH serum IL-6 was positively associated with FT3 (R = 0.276, P < 0.05), FT4 (R = 0.273, P < 0.05), and thyroid peroxidase antibodies (R = 0.346, P < 0.01) levels. Conclusion. Our results may suggest that both SH and OH may be associated with endothelial dysfunction, which is reflected by decreased fibrinolytic activity, hypercoagulability, and increased levels of IL-6, IL-12, and IL-18 and depends not only on the cause but also on the degree of hyperthyroidism.

The biochemistry and regulation of S100A10: a multifunctional plasminogen receptor involved in oncogenesis

The plasminogen receptors mediate the production and localization to the cell surface of the broad spectrum proteinase, plasmin. S100A10 is a key regulator of cellular plasmin production and may account for as much as 50% of cellular plasmin generation. In parallel to plasminogen, the plasminogen-binding site on S100A10 is highly conserved from mammals to fish. S100A10 is constitutively expressed in many cells and is also induced by many diverse factors and physiological stimuli including dexamethasone, epidermal growth factor, transforming growth factor-α, interferon-γ, nerve growth factor, keratinocyte growth factor, retinoic acid, and thrombin. Therefore, S100A10 is utilized by cells to regulate plasmin proteolytic activity in response to a wide diversity of physiological stimuli. The expression of the oncogenes, PML-RARα and KRas, also stimulates the levels of S100A10, suggesting a role for S100A10 in pathophysiological processes such as in the oncogenic-mediated increases in plasmin production. The S100A10-null mouse model system has established the critical role that S100A10 plays as a regulator of fibrinolysis and oncogenesis. S100A10 plays two major roles in oncogenesis, first as a regulator of cancer cell invasion and metastasis and secondly as a regulator of the recruitment of tumor-associated cells, such as macrophages, to the tumor site.

Gender specifics of the association between blood fibrinolytic activity and cardiovascular disease or diabetes mellitus in a cohort of Muscovites aged 55 years or older

Aim. To investigate potential gender differences in the association between plasma fibrinolytic activity (FLA) and atherosclerotic pathology in elderly people. Material and methods. This analysis was performed as a part of the prospective population-based cohort study “Stress, Ageing, and Health in Russia”. The study included randomly selected Moscow residents of both genders and age of ≥55 years (n=1863; 889 men and 974 women). Based on the levels of blood FLA (time of spontaneous lysis of euglobin blood fraction, or euglobin lysis time, ELT), all participants were divided into three groups: with normofibrinolysis (ELT 180-260 minutes), hypofibrinolysis (ELT >260 minutes), and hyperfibrinolysis (ELT <180 minutes). Results. In this cohort of elderly Muscovites, the association between FLA and the presence of cardiovascular disease (CVD) or Type 2 diabetes mellitus (DM-2) differed in men and women. The link between hypofibrinolysis, atherogenic changes in lipid profile, or high fasting levels of insulin and arterial hypertension (AH), myocardial infarction (MI), or DM-2 was present only in men. In women, either reduced or increased FLA was not related to DM-2. Men with hyperfibrinolysis demonstrated lower odds of AH and DM-2, while women with hyperfibrinolysis had lower odds of AH, coronary heart disease, or angina. Conclusion. In elderly people, high FLA appears to provide protection against atherothrombotic pathology, regardless of gender. Low FLA was associated with higher odds of CVD and DM-2 in men only.