Plasminogen and plasmin activity in patients with coronary artery disease

A genomic mutational constraint map using variation in 76,156 human genomes

The depletion of disruptive variation caused by purifying natural selection (constraint) has been widely used to investigate protein-coding genes underlying human disorders1-4, but attempts to assess constraint for non-protein-coding regions have proved more difficult. Here we aggregate, process and release a dataset of 76,156 human genomes from the Genome Aggregation Database (gnomAD)-the largest public open-access human genome allele frequency reference dataset-and use it to build a genomic constraint map for the whole genome (genomic non-coding constraint of haploinsufficient variation (Gnocchi)). We present a refined mutational model that incorporates local sequence context and regional genomic features to detect depletions of variation. As expected, the average constraint for protein-coding sequences is stronger than that for non-coding regions. Within the non-coding genome, constrained regions are enriched for known regulatory elements and variants that are implicated in complex human diseases and traits, facilitating the triangulation of biological annotation, disease association and natural selection to non-coding DNA analysis. More constrained regulatory elements tend to regulate more constrained protein-coding genes, which in turn suggests that non-coding constraint can aid the identification of constrained genes that are as yet unrecognized by current gene constraint metrics. We demonstrate that this genome-wide constraint map improves the identification and interpretation of functional human genetic variation.

Past, Present, and Future Perspectives of Plasminogen Activator Inhibitor 1 (PAI-1)

Plasminogen activator inhibitor 1 (PAI-1), a SERPIN inhibitor, is primarily known for its regulation of fibrinolysis. However, it is now known that this inhibitor functions and contributes to many (patho)physiological processes including inflammation, wound healing, cell adhesion, and tumor progression.This review discusses the past, present, and future roles of PAI-1, with a particular focus on the discovery of this inhibitor in the 1970s and subsequent characterization in health and disease. Throughout the past few decades diverse functions of this serpin have unraveled and it is now considered an important player in many disease processes. PAI-1 is expressed by numerous cell types, including megakaryocytes and platelets, adipocytes, endothelial cells, hepatocytes, and smooth muscle cells. In the circulation PAI-1 exists in two pools, within plasma itself and in platelet α-granules. Platelet PAI-1 is secreted following activation with retention of the inhibitor on the activated platelet membrane. Furthermore, these anucleate cells contain PAI-1 messenger ribonucleic acid to allow de novo synthesis.Outside of the traditional role of PAI-1 in fibrinolysis, this serpin has also been identified to play important roles in metabolic syndrome, obesity, diabetes, and most recently, acute respiratory distress syndrome, including coronavirus disease 2019 disease. This review highlights the complexity of PAI-1 and the requirement to ascertain a better understanding on how this complex serpin functions in (patho)physiological processes.

Taipan Natriuretic Peptides Are Potent and Selective Agonists for the Natriuretic Peptide Receptor A

Cardiovascular ailments are a major cause of mortality where over 1.3 billion people suffer from hypertension leading to heart-disease related deaths. Snake venoms possess a broad repertoire of natriuretic peptides with therapeutic potential for treating hypertension, congestive heart failure, and related cardiovascular disease. We now describe several taipan (Oxyuranus microlepidotus) natriuretic peptides TNPa-e which stimulated cGMP production through the natriuretic peptide receptor A (NPR-A) with higher potencies for the rat NPR-A (rNPR-A) over human NPR-A (hNPR-A). TNPc and TNPd were the most potent, demonstrating 100- and 560-fold selectivity for rNPR-A over hNPR-A. In vivo studies found that TNPc decreased diastolic and systolic blood pressure (BP) and increased heart rate (HR) in conscious normotensive rabbits, to a level that was similar to that of human atrial natriuretic peptide (hANP). TNPc also enhanced the bradycardia due to cardiac afferent stimulation (Bezold-Jarisch reflex). This indicated that TNPc possesses the ability to lower blood pressure and facilitate cardiac vagal afferent reflexes but unlike hANP does not produce tachycardia. The 3-dimensional structure of TNPc was well defined within the pharmacophoric disulfide ring, displaying two turn-like regions (RMSD = 1.15 Å). Further, its much greater biological stability together with its selectivity and potency will enhance its usefulness as a biological tool.

A Serpin With a Finger in Many PAIs: PAI-1's Central Function in Thromboinflammation and Cardiovascular Disease

Plasminogen activator inhibitor 1 (PAI-1) is a member of the serine protease inhibitor (serpin) superfamily. PAI-1 is the principal inhibitor of the plasminogen activators, tissue plasminogen activator (tPA), and urokinase-type plasminogen activator (uPA). Turbulence in the levels of PAI-1 tilts the balance of the hemostatic system resulting in bleeding or thrombotic complications. Not surprisingly, there is strong evidence that documents the role of PAI-1 in cardiovascular disease. The more recent uncovering of the coalition between the hemostatic and inflammatory pathways has exposed a distinct role for PAI-1. The storm of proinflammatory cytokines liberated during inflammation, including IL-6 and TNF-α, directly influence PAI-1 synthesis and increase circulating levels of this serpin. Consequently, elevated levels of PAI-1 are commonplace during infection and are frequently associated with a hypofibrinolytic state and thrombotic complications. Elevated PAI-1 levels are also a feature of metabolic syndrome, which is defined by a cluster of abnormalities including obesity, type 2 diabetes, hypertension, and elevated triglyceride. Metabolic syndrome is in itself defined as a proinflammatory state associated with elevated levels of cytokines. In addition, insulin has a direct impact on PAI-1 synthesis bridging these pathways. This review describes the key physiological functions of PAI-1 and how these become perturbed during disease processes. We focus on the direct relationship between PAI-1 and inflammation and the repercussion in terms of an ensuing hypofibrinolytic state and thromboembolic complications. Collectively, these observations strengthen the utility of PAI-1 as a viable drug target for the treatment of various diseases.

Advances in Analysis of Milk Proteases Activity at Surfaces and in a Volume by Acoustic Methods

This review is focused on the application of surface and volume-sensitive acoustic methods for the detection of milk proteases such as trypsin and plasmin. While trypsin is an important protein of human milk, plasmin is a protease that plays an important role in the quality of bovine, sheep and goat milks. The increased activity of plasmin can cause an extensive cleavage of β-casein and, thus, affect the milk gelation and taste. The basic principles of surface-sensitive acoustic methods, as well as high-resolution ultrasonic spectroscopy (HR-US), are presented. The current state-of-the-art examples of the application of acoustic sensors for protease detection in real time are discussed. The application of the HR-US method for studying the kinetics of the enzyme reaction is demonstrated. The sensitivity of the acoustics biosensors and HR-US methods for protease detection are compared.

Elevated Plasmin(ogen) as a Common Risk Factor for COVID-19 Susceptibility

Patients with hypertension, diabetes, coronary heart disease, cerebrovascular illness, chronic obstructive pulmonary disease, and kidney dysfunction have worse clinical outcomes when infected with SARS-CoV-2, for unknown reasons. The purpose of this review is to summarize the evidence for the existence of elevated plasmin(ogen) in COVID-19 patients with these comorbid conditions. Plasmin, and other proteases, may cleave a newly inserted furin site in the S protein of SARS-CoV-2, extracellularly, which increases its infectivity and virulence. Hyperfibrinolysis associated with plasmin leads to elevated D-dimer in severe patients. The plasmin(ogen) system may prove a promising therapeutic target for combating COVID-19.

The need to manage the risk of thromboembolism in COVID-19 patients

COVID-19 first appeared in Wuhan, Hubei Province, China, in December 2019. Thought to be of zoonotic origin, it has been named SARS-CoV-2 (COVID-19) and has spread rapidly. As of April 20, 2020, there have been >2.4 million cases recorded worldwide. The inflammatory process, cytokine storm, and lung injury that are associated with COVID-19 can put patients at an increased risk of thrombosis. The total incidence of thrombotic events in COVID-19 patients is currently uncertain. Those with more severe disease and with other risk factors, including increasing age, male sex, obesity, cancer, comorbidities, and intensive care unit admission, are at higher risk of these events. However, there is little international guidance on managing these risks in COVID-19 patients. In this paper, we explore the current evidence and theories surrounding thrombosis in these unique patients and reflect on experience from our center.

Patho- physiological role of BDNF in fibrin clotting

Circulating levels of Brain Derived Neurotrophic Factor (BDNF) are lower in coronary heart disease (CHD) than in healthy subjects and are associated with coronary events and mortality. However, the mechanism(s) underling this association is not fully understood. We hypothesize that BDNF may influence fibrin fiber structure and clot stability, favoring clot lysis and thrombus resolution. We showed that recombinant BDNF (rh-BDNF) influenced with clot formation in a concentration-dependent manner in both purified fibrinogen and plasma from healthy subjects. In particular, rh-BDNF reduced the density of fibrin fibers, the maximum clot firmness (MCF) and the maximum clot turbidity, and affected the lysis of clot. In addition, both thrombin and reptilase clotting time were prolonged by rh-BDNF, despite the amount of thrombin formed was greater. Intriguingly, CHD patients had lower levels of BDNF, greater fibrin fibers density, higher MCF than control subjects, and a negative correlation between BDNF and MCF was found. Of note, rh-BDNF markedly modified fibrin clot profile restoring physiological clot morphology in CHD plasma. In conclusion, we provide evidence that low levels of BDNF correlate with the formation of bigger thrombi (in vitro) and that this effect is mediated, at least partially, by the alteration of fibrin fibers formation.

Searching for tryptase in the RBL-2H3 mast cell model: Preparation for comparative mast cell toxicology studies with zebrafish

Mast cells comprise a physiologically and toxicologically important cell type that is ubiquitous among species and tissues. Mast cells undergo degranulation, in which characteristic intracellular granules fuse with the plasma membrane and release many bioactive substances, such as enzymes β-hexosaminidase and tryptase. Activity of mast cells in the toxicology model organism, zebrafish, has been monitored via tryptase release and cleavage of substrate N-α-benzoyl-dl-Arg-p-nitroanilide (BAPNA). An extensively used in vitro mast cell model for studying toxicant mechanisms is the RBL-2H3 cell line. However, instead of tryptase, granule contents such as β-hexosaminidase have usually been employed as RBL-2H3 degranulation markers. To align RBL-2H3 cell toxicological studies to in vivo mast cell studies using zebrafish, we aimed to develop an RBL-2H3 tryptase assay. Unexpectedly, we discovered that tryptase release from RBL-2H3 cells is not detectable, using BAPNA substrate, despite optimized assay that can detect as little as 1 ng tryptase. Additional studies performed with another substrate, tosyl-Gly-Pro-Lys-pNA, and with an enzyme-linked immunosorbent assay, revealed a lack of tryptase protein released from stimulated RBL-2H3 cells. Furthermore, none of the eight rat tryptase genes (Tpsb2, Tpsab1, Tpsg1, Prss34, Gzmk, Gzma, Prss29, Prss41) is expressed in RBL-2H3 cells, even though all are found in RBL-2H3 genomic DNA and even though β-hexosaminidase mRNA is constitutively expressed. Therefore, mast cell researchers should utilize β-hexosaminidase or another reliable marker for RBL-2H3 degranulation studies, not tryptase. Comparative toxicity testing in RBL-2H3 cells in vitro and in zebrafish mast cells in vivo will require use of a degranulation reporter different from tryptase.

Markers of Atherosclerosis: Part 1 - Serological Markers

Atherosclerosis is a major contributor to morbidity and mortality worldwide. With therapeutic consequences in mind, several risk scores are being used to differentiate individuals with low, intermediate or high cardiovascular (CV) event risk. The most appropriate management of intermediate risk individuals is still not known, therefore, novel biomarkers are being sought to help re-stratify them as low or high risk. This narrative review is presented in two parts. Here, in Part 1, we summarise current knowledge on serum (serological) biomarkers of atherosclerosis. Among novel biomarkers, high sensitivity C-reactive protein (hsCRP) has emerged as the most promising in chronic situations, others need further clinical studies. However, it seems that a combination of serum biomarkers offers more to risk stratification than either biomarker alone. In Part 2, we address genetic and imaging markers of atherosclerosis, as well as other developments relevant to risk prediction.

The roles of PAI-1 gene polymorphisms in atherosclerotic diseases: A systematic review and meta-analysis involving 149,908 subjects

BACKGROUND

The roles of plasminogen activator inhibitor-1 (PAI-1) gene polymorphisms in atherosclerotic diseases were intensively analyzed, but the results of these studies were inconsistent. Therefore, we performed this study to better assess the relationship between PAI-1 genetic variations and atherosclerosis.

METHODS

Eligible studies were searched in PubMed, Medline, Embase and Web of Science. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess relationship between PAI-1 polymorphisms and atherosclerotic diseases.

RESULTS

Ninety-nine studies involving 62,739 cases and 87,169 controls were finally included. Significant associations with the risk of atherosclerosis were detected for the rs2227631 polymorphism in the dominant model (95% CI 0.84-1.00), for the rs1799889 polymorphism in the dominant (95% CI 1.01-1.18), recessive (95% CI 0.90-0.98) and allele (95% CI 1.01-1.12) models. Further subgroup analyses based on type of disease and ethnicity of participants suggested that the rs2227631 polymorphism was significantly associated with the risk of coronary artery disease in the dominant (95% CI 0.71-0.94) and allele (95% CI 0.80-0.94) models, whereas the rs1799889 polymorphism was significantly associated with the risk of myocardial infarction (dominant model: 95% CI 1.09-1.57; recessive model: 95% CI 0.71-0.96; allele model: 95% CI 1.05-1.28) and cerebral infarction (dominant model: 95% CI 1.68-3.51; additive model: 95% CI 0.39-0.77; allele model: 95% CI 1.23-2.00). Moreover, the rs1799889 polymorphism was also significantly correlated with the risk of atherosclerosis in both Asians (dominant model: 95% CI 1.10-1.83; allele model: 95% CI 1.03-1.41) and Caucasians (recessive model: 95% CI 0.87-0.97; allele model: 95% CI 1.01-1.12).

CONCLUSION

In conclusion, our findings indicate that PAI-1 rs2227631 and rs1799889 polymorphisms may serve as genetic biomarkers of atherosclerotic diseases.

Protein biomarkers and coronary microvascular dilatation assessed by rubidium-82 PET in women with angina pectoris and no obstructive coronary artery disease

BACKGROUND AND AIMS

While a plethora of biomarkers have been shown to be associated with coronary artery disease, studies assessing biomarkers in coronary microvascular dysfunction (CMD) are few. We investigated associations between cardiovascular protein biomarkers and non-endothelium dependent CMD assessed by positron emission tomography (PET).

METHODS

In 97 women with angina pectoris and no significant obstructive coronary artery disease (<50% stenosis on invasive coronary angiography), CMD was defined as myocardial blood flow reserve (MBFR) < 2.5 by rubidium-82 PET. Blood samples were analyzed with a cardiovascular disease proteomic panel encompassing 92 biomarkers. The relation between MBFR and biomarkers was evaluated with age-adjusted regression analysis.

RESULTS

Median age was 62 years (range 31-79), median MBFR was 2.7 (range 1.2-4.7) and 32% had non-endothelium dependent CMD (MBFR<2.5). Four biomarkers were significantly correlated with MBFR: Galectin-4 (Gal4, p = 0.008), growth differentiation factor 15 (GDF15, p = 0.026), tissue-type plasminogen activator (tPA, p = 0.030) and von Willebrand factor (vWF, p = 0.018), while 12 biomarkers showed a trend for correlation (0.05 ≤ p < 0.15). Of the 16 identified biomarkers, 10 are involved in pro-inflammatory pathways.

CONCLUSIONS

In a panel of 92 cardiovascular protein biomarkers, 4 were significantly associated with non-endothelium dependent CMD in women: Gal4, GDF15, tPA and vWF, suggesting that inflammatory status and coagulation changes are associated with impaired microvascular dilatation. Further confirmatory studies are needed to corroborate these findings.

Unusual clotting dynamics of plasma supplemented with iron(III)

Iron salts are used in the treatment of iron deficiency anemia. Diabetic patients are frequently anemic and treatment includes administration of iron. Anemic patients on hemodialysis are at an increased risk of thromboembolic coronary events associated with the formation of dense fibrin clots resistant to fibrinolysis. Moreover, in chronic kidney disease patients, high labile plasma iron levels associated with iron supplementation are involved in complications found in dialyzed patients such as myocardial infarction. The aim of the present study was to investigate whether iron treatment is involved in the formation of the fibrin clots. Clotting of citrated plasma supplemented with Fe(3+) was investigated by thromboelastometry and electron microscopy. The results revealed that iron modifies coagulation in a complex manner. FeCl(3) stock solution underwent gradual chemical modification during storage and altered the coagulation profile over 29 days, suggesting that Fe(3+) interacts with both proteins of the coagulation cascade as well as the hydrolytic Fe(3+) species. Iron extends clotting of plasma by interacting with proteins of the coagulation cascade. Fe(3+) and/or its hydrolytic species interact with fibrinogen and/or fibrin changing their morphology and properties. In general FeCl(3) weakens the fibrin clot while at the same time precipitating plasma proteins immediately after application. Fe(3+) or its derivatives induced the formation of insoluble coagulums in non-enzymatic reactions including albumin and transferrin. Iron plays a role in coagulation and can precipitate plasma proteins. The formation of coagulums resistant to lysis in non‑enzymatic reactions can increase the risk of thrombosis, and extending clotting of plasma can prolong bleeding.

Antiangiogenic activity of rPAI-1(23) promotes vasa vasorum regression in hypercholesterolemic mice through a plasmin-dependent mechanism

RATIONALE

The antiangiogenic activity of rPAI-1(23), a truncated plasminogen activator inhibitor-1 (PAI-1) protein, induces vasa vasorum collapse and significantly reduces plaque area and plaque cholesterol in hypercholesterolemic low-density lipoprotein receptor-deficient/apolipoprotein B48-deficient mice.

OBJECTIVE

The objective of this study was to examine rPAI-1(23)-stimulated mechanisms that cause vasa vasorum collapse.

METHODS AND RESULTS

The rPAI-1(23) protein opposed PAI-1 antiproteolytic function by stimulating a 1.6-fold increase in plasmin activity compared with the saline-treated counterpart. The increased proteolytic activity corresponded to increased activity of matrix metalloproteinase-3 and degradation of fibrin(ogen), nidogen, and perlecan in the adventitia of descending aortas. PAI-1 activity was reduced by 48% in response to rPAI-1(23); however, PAI-1 protein expression levels were similar in the rPAI-1(23)- and saline-treated hypercholesterolemic mice. Coimmunoprecipitation assays demonstrated a novel PAI-1-plasminogen complex in protein from the descending aorta of rPAI-1(23)- and saline-treated mice, but complexed PAI-1 was 1.6-fold greater in rPAI-1(23)-treated mice. Biochemical analyses demonstrated that rPAI-1(23) and PAI-1 binding interactions with plasminogen increased plasmin activity and reduced PAI-1 antiproteolytic activity.

CONCLUSIONS

We conclude that rPAI-1(23) causes regression or collapse of adventitial vasa vasorum in hypercholesterolemic mice by stimulating an increase in plasmin activity. The rPAI-1(23)-enhanced plasmin activity was achieved through a novel mechanism by which rPAI-1(23) and PAI-1 bound plasminogen in a cooperative manner to increase plasmin activity and reduce PAI-1 activity.

Very long half-life plasminogen activator inhibitor type 1 reduces bleeding in a mouse model

OBJECTIVE

To investigate the potential for the future clinical use of a very long half-life plasminogen activator inhibitor type 1 (VLHL PAI-1) as a haemostatic agent.

MATERIALS AND METHODS

We developed a VLHL PAI-1 (half-life >700 h) recombinant mutant of PAI-1 and assessed VLHL PAI-1 for its ability to inhibit fibrinolysis in vitro using human, rabbit, mouse and rat blood. Fibrin clot lysis time, monitored by thromboelastometry, was determined at various concentrations of VLHL PAI-1. Also, we determined total bleeding time and total blood loss of control, VLHL PAI-1-, tissue-type plasminogen activator (tPA)- and tPA + VLHL PAI-1-treated mice.

RESULTS

Using a thromboelastometer, mouse blood was most similar to human blood in its coagulation and fibrinolytic characteristics. We evaluated the affect of VLHL PAI-1 on haemostasis using the mouse model and showed that VLHL PAI-1 is an effective inhibitor of fibrin clot degradation. It reduced time of bleeding and total blood loss.

CONCLUSION

VLHL PAI-1 may provide an important physiological mechanism to protect clots from premature dissolution in surgical and trauma settings.

Cardiovascular diseases (CVD) risk factors, physical activity (PA) and plasma plasminogen (Plg) in a random sample of community-dwelling elderly

The aim of this study was to evaluate the association between plasma Plg levels and coexisting CVD risk factors, comorbidities, PA, functional status and cognitive function in a random sample of 298 (179 women and 119 men) community-dwelling elderly aged 65-79 years. The average plasma Plg level was 91.4+/-19.7% and was lower in men (86.6+/-20.7%) than in women (94.6+/-18.5%). In women, Plg levels were higher in individuals with diagnosed ischemic heart disease (IHD) and increased with triglycerides (TG) and glucose level. In men, Plg levels decreased with advancing age, were higher in current smokers, decreased with the percentage of body fat, increased with total cholesterol (T-CH), low density lipoprotein cholesterol (LDL-CH) and high density lipoprotein cholesterol (HDL-CH) levels, and were directly correlated with two different PA indices. Multivariate analysis revealed that gender, current smoking, IHD, T-CH and the Seven Day Recall PA Questionnaire Hard score independently predict plasma Plg levels in the whole group of elderly people. In conclusion, Plg seems to be directly related to CVD and metabolic risk profile as well as PA level but not to functional status or cognitive function of older individuals.