Distribution of plasminogen activator inhibitor (PAI-1) in tissues

G6pdN126D Variant Increases the Risk of Developing VEGFR (Vascular Endothelial Growth Factor Receptor) Blocker-Induced Pulmonary Vascular Disease

BACKGROUND

G6PD (glucose-6-phosphate-dehydrogenase) is a key enzyme in the glycolytic pathway and has been implicated in the pathogenesis of cancer and pulmonary hypertension-associated vascular remodeling. Here, we investigated the role of an X-linked G6pd mutation (N126D polymorphism), which is known to increase the risk of cardiovascular disease in individuals from sub-Saharan Africa and many others with African ancestry, in the pathogenesis of pulmonary hypertension induced by a vascular endothelial cell growth factor receptor blocker used for treating cancer.

METHODS AND RESULTS

CRISPR-Cas9 genome editing was used to generate the G6pd variant (N126D; G6pdN126D) in rats. A single dose of the vascular endothelial cell growth factor receptor blocker sugen-5416 (SU; 20 mg/kg in DMSO), which is currently in a Phase 2/3 clinical trial for cancer treatment, was subcutaneously injected into G6pdN126D rats and their wild-type littermates. After 8 weeks of normoxic conditions, right ventricular pressure and hypertrophy, pulmonary artery remodeling, the metabolic profile, and cytokine expression were assessed. Right ventricular pressure and pulmonary arterial wall thickness were increased in G6PDN126D+SU/normoxic rats. Simultaneously, levels of oxidized glutathione, inositol triphosphate, and intracellular Ca2+ were increased in the lungs of G6PDN126D+SU/normoxic rats, whereas nitric oxide was decreased. Also increased in G6PDN126D+SU/normoxic rats were pulmonary levels of plasminogen activator inhibitor-1, thrombin-antithrombin complex, and expression of proinflammatory cytokines CCL3 (chemokine [C-C motif] ligand), CCL5, and CCL7.

CONCLUSIONS

Our results suggest G6PDN126D increases inositol triphosphate-Ca2+ signaling, inflammation, thrombosis, and hypertrophic pulmonary artery remodeling in SU-treated rats. This suggests an increased risk of vascular endothelial cell growth factor receptor blocker-induced pulmonary hypertension in those carrying this G6PD variant.

Orchestra of ligand-activated transcription factors in the molecular symphony of SERPINE 1 / PAI-1 gene regulation

Plasminogen activator inhibitor 1 (PAI-1) is a crucial serine protease inhibitor that prevents plasminogen activation by inhibiting tissue- and urokinase-type plasminogen activators (tPA, uPA). PAI-1 is well-known for its role in modulating hemocoagulation or extracellular matrix formation by inhibiting plasmin or matrix metalloproteinases, respectively. PAI-1 is induced by pro-inflammatory cytokines across various tissues, yet its regulation by ligand-activated transcription factors is partly disregarded. Therefore, we have attempted to summarize the current knowledge on the transcriptional regulation of PAI-1 expression by the most relevant xenobiotic and endocrine receptors implicated in modulating PAI-1 levels. This review aims to contribute to the understanding of the specific, often tissue-dependent regulation of PAI-1 and provide insights into the modulation of PAI-1 levels beyond its direct inhibition.

Blood PAI-1 and cardiovascular and metabolic risk factors among the middle-aged women from SWAN study

The research on the role of plasminogen activator inhibitor-1 (PAI-1) in cardiovascular and metabolic diseases is insufficient. We aimed to explore whether elevated blood PAI-1 levels are significantly related to increased cardiovascular and metabolic risk factors in a midlife women population. Data were obtained from baseline characteristics in Study of Women's Health Across the Nation (SWAN) study. Multivariable linear regression models were performed to examine for the trends of associations between PAI-1 and cardiovascular and metabolic risk factors (systolic BP, diastolic BP, fasting blood glucose, insulin, HDL-C, LDL-C, TG and TC), respectively. Smooth curve demonstrated gradual upward trends on associations of blood PAI-1 levels with LDL-C, TG, TC, fasting blood glucose, insulin, systolic BP and diastolic BP (all P < 0.05) and a gradual downward trend of PAI-1 levels with HDL-C (P < 0.05). Multivariable linear regression models still indicated that increased blood PAI-1 levels were associated with higher cardiovascular and metabolic risk after confounding factors including age, race/ethnicity, ever smoked regularly, alcohol in last 24 h, menopausal status, total family income and BMI were controlled for. Moreover, we observed that the independent associations between blood levels of PAI-1 and cardiovascular and metabolic risk factors examined by stratified analysis were not influenced by age, smoking status, menopausal status and BMI, respectively. Our analysis showed that increased blood PAI-1 levels were associated with higher level for cardiovascular and metabolic risk factors which mainly causes to higher possibility of cardio-cerebrovascular diseases in a large-sample midlife women subjects.

Obesity and prostate cancer - microenvironmental roles of adipose tissue

Obesity is known to have important roles in driving prostate cancer aggressiveness and increased mortality. Multiple mechanisms have been postulated for these clinical observations, including effects of diet and lifestyle, systemic changes in energy balance and hormonal regulation and activation of signalling by growth factors and cytokines and other components of the immune system. Over the past decade, research on obesity has shifted towards investigating the role of peri-prostatic white adipose tissue as an important source of locally produced factors that stimulate prostate cancer progression. Cells that comprise white adipose tissue, the adipocytes and their progenitor adipose stromal cells (ASCs), which proliferate to accommodate white adipose tissue expansion in obesity, have been identified as important drivers of obesity-associated cancer progression. Accumulating evidence suggests that adipocytes are a source of lipids that are used by adjacent prostate cancer cells. However, results of preclinical studies indicate that ASCs promote tumour growth by remodelling extracellular matrix and supporting neovascularization, contributing to the recruitment of immunosuppressive cells, and inducing epithelial-mesenchymal transition through paracrine signalling. Because epithelial-mesenchymal transition is associated with cancer chemotherapy resistance and metastasis, ASCs are considered to be potential targets of therapies that could be developed to suppress cancer aggressiveness in patients with obesity.

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.

Oxidative Stress and Extracellular Matrix Remodeling Are Signature Pathways of Extracellular Vesicles Released upon Morphine Exposure on Human Brain Microvascular Endothelial Cells

Morphine, a commonly used antinociceptive drug in hospitals, is known to cross the blood-brain barrier (BBB) by first passing through brain endothelial cells. Despite its pain-relieving effect, morphine also has detrimental effects, such as the potential induction of redox imbalance in the brain. However, there is still insufficient evidence of these effects on the brain, particularly on the brain endothelial cells and the extracellular vesicles that they naturally release. Indeed, extracellular vesicles (EVs) are nanosized bioparticles produced by almost all cell types and are currently thought to reflect the physiological state of their parent cells. These vesicles have emerged as a promising source of biomarkers by indicating the functional or dysfunctional state of their parent cells and, thus, allowing a better understanding of the biological processes involved in an adverse state. However, there is very little information on the morphine effect on human brain microvascular endothelial cells (HBMECs), and even less on their released EVs. Therefore, the current study aimed at unraveling the detrimental mechanisms of morphine exposure (at 1, 10, 25, 50 and 100 µM) for 24 h on human brain microvascular endothelial cells as well as on their associated EVs. Isolation of EVs was carried out using an affinity-based method. Several orthogonal techniques (NTA, western blotting and proteomics analysis) were used to validate the EVs enrichment, quality and concentration. Data-independent mass spectrometry (DIA-MS)-based proteomics was applied in order to analyze the proteome modulations induced by morphine on HBMECs and EVs. We were able to quantify almost 5500 proteins in HBMECs and 1500 proteins in EVs, of which 256 and 148, respectively, were found to be differentially expressed in at least one condition. Pathway enrichment analysis revealed that the "cell adhesion and extracellular matrix remodeling" process and the "HIF1 pathway", a pathway related to oxidative stress responses, were significantly modulated upon morphine exposure in HBMECs and EVs. Altogether, the combination of proteomics and bioinformatics findings highlighted shared pathways between HBMECs exposed to morphine and their released EVs. These results put forward molecular signatures of morphine-induced toxicity in HBMECs that were also carried by EVs. Therefore, EVs could potentially be regarded as a useful tool to investigate brain endothelial cells dysfunction, and to a different extent, the BBB dysfunction in patient circulation using these "signature pathways".

Vitronectin and Its Interaction with PAI-1 Suggests a Functional Link to Vascular Changes in AMD Pathobiology

The pathogenesis of age-related macular degeneration (AMD), a frequent disorder of the central retina, is incompletely understood. Genome-wide association studies (GWAS) suggest a strong contribution of genomic variation in AMD susceptibility. Nevertheless, little is known about biological mechanisms of the disease. We reported previously that the AMD-associated polymorphism rs704C > T in the vitronectin (VTN) gene influences protein expression and functional aspects of encoded vitronectin, a human blood and extracellular matrix (ECM) protein. Here, we refined the association of rs704 with AMD in 16,144 cases and 17,832 controls and noted that rs704 is carried exclusively by the neovascular AMD subtype. Interaction studies demonstrate that rs704 affects the ability of vitronectin to bind the angiogenic regulator plasminogen activator inhibitor 1 (PAI-1) but has no influence on stabilizing its active state. Western blot analysis and confocal imaging reveal a strong enrichment of PAI-1 in the ECM of cultured endothelial cells and RPE cell line ARPE-19 exposed to vitronectin. Large-scale gene expression of VTN and PAI-1 showed positive correlations and a statistically significant increase in human retinal and blood tissues aged 60 years and older. Our results suggest a mechanism by which the AMD-associated rs704 variant in combination with ageing may contribute to the vascular complications in AMD.

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.

Identification of the Transgene Integration Site and Host Genome Changes in MRP8-Cre/ires-EGFP Transgenic Mice by Targeted Locus Amplification

The MRP8-Cre-ires/EGFP transgenic mouse (Mrp8cre^Tg, on C57BL/6J genetic background) is popular in immunological and hematological research for specifically expressing Cre recombinase and an EGFP reporter in neutrophils. It is often crossed with other transgenic lines carrying loxP-flanked genes to achieve restricted gene knockout in neutrophils. However, due to the way in which the line was created, basic knowledge about the MRP8-Cre-ires/EGFP transgene in the host genome, such as its integration site(s) and flanking sequences, remains largely unknown, hampering robust experimental design and data interpretation. Here we used a recently developed technique, targeted locus amplification (TLA) sequencing, to fill these knowledge gaps. We found that the MRP8-Cre-ires/EGFP transgene was integrated into chromosome 5 (5qG2) of the host mouse genome. This integration led to a 44 kb deletion of the host genomic sequence, resulting in complete deletion of Serpine1 and partial deletion of Ap1s1. Having determined the flanking sequences of the transgene, we designed a new genotyping protocol that can distinguish homozygous, heterozygous, and wildtype Mrp8cre^Tg mice. To our surprise, crossing heterozygous mice produced no homozygous Mrp8cre^Tg mice, most likely due to prenatal lethality resulting from disrupted Ap1s1 gene expression.

Adipokines, Hepatokines and Myokines: Focus on Their Role and Molecular Mechanisms in Adipose Tissue Inflammation

Chronic low-grade inflammation in adipose tissue (AT) is a hallmark of obesity and contributes to various metabolic disorders, such as type 2 diabetes and cardiovascular diseases. Inflammation in ATs is characterized by macrophage infiltration and the activation of inflammatory pathways mediated by NF-κB, JNK, and NLRP3 inflammasomes. Adipokines, hepatokines and myokines - proteins secreted from AT, the liver and skeletal muscle play regulatory roles in AT inflammation via endocrine, paracrine, and autocrine pathways. For example, obesity is associated with elevated levels of pro-inflammatory adipokines (e.g., leptin, resistin, chemerin, progranulin, RBP4, WISP1, FABP4, PAI-1, Follistatin-like1, MCP-1, SPARC, SPARCL1, and SAA) and reduced levels of anti-inflammatory adipokines such as adiponectin, omentin, ZAG, SFRP5, CTRP3, vaspin, and IL-10. Moreover, some hepatokines (Fetuin A, DPP4, FGF21, GDF15, and MANF) and myokines (irisin, IL-6, and DEL-1) also play pro- or anti-inflammatory roles in AT inflammation. This review aims to provide an updated understanding of these organokines and their role in AT inflammation and related metabolic abnormalities. It serves to highlight the molecular mechanisms underlying the effects of these organokines and their clinical significance. Insights into the roles and mechanisms of these organokines could provide novel and potential therapeutic targets for obesity-induced inflammation.

Neuroprotective Effect of Plasminogen Activator Inhibitor-1 Antagonist in the Rat Model of Mild Traumatic Brain Injury

Plasminogen activator inhibitor-1 (PAI-1) antagonists are known for their neuroprotective effects. In this study, it was aimed to investigate the possible protective effects of PAI-1 antagonists in a rat mild traumatic brain injury (TBI) model. Sprague-Dawley male rats were grouped as sham (n = 7), TBI (n = 9), and TBI + PAI-1 antagonist (5 and 10 mg/kg TM5441 and TM5484; n = 6-7). Under anesthesia, TBI was induced by dropping a metal 300-g weight from a height of 1 m on the skull. Before and 24-h after trauma neurological examination, tail suspension, Y-maze, and novel object recognition tests were performed. Twenty-four hours after TBI, the rats were decapitated and activities of myeloperoxidase, nitric oxide release, luminol-, and lucigenin-enhanced chemiluminescence were measured. Also, interleukin-1β, interleukin-6, tumor necrosis factor, interleukin-10, tumor growth factor-β, caspase-3, cleaved caspase-3, and PAI levels were measured with the ELISA method in the brain tissue. Brain injury was graded histopathologically following hematoxylin-eosin staining. Western blot and immunohistochemical investigation for low-density lipoprotein receptor, matrix metalloproteinase-3, and nuclear factor-κB were also performed. Data were analyzed using GraphPad Prism 8.0 (GraphPad Software, San Diego, CA, USA) and expressed as means ± SEM. Values of p < 0.05 were considered to be statistically significant. Higher levels of myeloperoxidase activity in the TBI group (p < 0.05) were found to be suppressed in 5 and 10 mg/kg TM5441 treatment groups (p < 0.05-p < 0.01). The tail suspension test score was increased in the TBI group (p < 0.001) and decreased in all treatment groups (p < 0.05-0.001). The histologic damage score was increased statistically significantly in the cortex, dentate gyrus, and CA3 regions in the TBI group (p < 0.01-0.001), decreased in the treatment groups in the cortex and dentate gyrus (p < 0.05-0.001). PAI antagonists, especially TM5441, have antioxidant and anti-inflammatory properties against mild TBI in the acute period. Behavioral test results were also improved after PAI antagonist treatment after mild TBI.

Disorders of Fibrinogen and Fibrinolysis

Fibrinogen plays a fundamental role in coagulation through its support for platelet aggregation and its conversion to fibrin. Fibrin stabilizes clots and serves as a scaffold and immune effector before being broken down by the fibrinolytic system. Given its importance, abnormalities in fibrin(ogen) and fibrinolysis result in a variety of disorders with hemorrhagic and thrombotic manifestations. This review summarizes (i) the basic elements of fibrin(ogen) and its role in coagulation and the fibrinolytic system; (ii) the laboratory evaluation for fibrin(ogen) disorders, including the use of global fibrinolysis assays; and (iii) the management of congenital and acquired disorders of fibrinogen and fibrinolysis.

Fibrinolytic Serine Proteases, Therapeutic Serpins and Inflammation: Fire Dancers and Firestorms

The making and breaking of clots orchestrated by the thrombotic and thrombolytic serine protease cascades are critical determinants of morbidity and mortality during infection and with vascular or tissue injury. Both the clot forming (thrombotic) and the clot dissolving (thrombolytic or fibrinolytic) cascades are composed of a highly sensitive and complex relationship of sequentially activated serine proteases and their regulatory inhibitors in the circulating blood. The proteases and inhibitors interact continuously throughout all branches of the cardiovascular system in the human body, representing one of the most abundant groups of proteins in the blood. There is an intricate interaction of the coagulation cascades with endothelial cell surface receptors lining the vascular tree, circulating immune cells, platelets and connective tissue encasing the arterial layers. Beyond their role in control of bleeding and clotting, the thrombotic and thrombolytic cascades initiate immune cell responses, representing a front line, "off-the-shelf" system for inducing inflammatory responses. These hemostatic pathways are one of the first response systems after injury with the fibrinolytic cascade being one of the earliest to evolve in primordial immune responses. An equally important contributor and parallel ancient component of these thrombotic and thrombolytic serine protease cascades are the serine protease inhibitors, termed serpins. Serpins are metastable suicide inhibitors with ubiquitous roles in coagulation and fibrinolysis as well as multiple central regulatory pathways throughout the body. Serpins are now known to also modulate the immune response, either via control of thrombotic and thrombolytic cascades or via direct effects on cellular phenotypes, among many other functions. Here we review the co-evolution of the thrombolytic cascade and the immune response in disease and in treatment. We will focus on the relevance of these recent advances in the context of the ongoing COVID-19 pandemic. SARS-CoV-2 is a "respiratory" coronavirus that causes extensive cardiovascular pathogenesis, with microthrombi throughout the vascular tree, resulting in severe and potentially fatal coagulopathies.

A Narrative Review on Plasminogen Activator Inhibitor-1 and Its (Patho)Physiological Role: To Target or Not to Target?

Plasminogen activator inhibitor-1 (PAI-1) is the main physiological inhibitor of plasminogen activators (PAs) and is therefore an important inhibitor of the plasminogen/plasmin system. Being the fast-acting inhibitor of tissue-type PA (tPA), PAI-1 primarily attenuates fibrinolysis. Through inhibition of urokinase-type PA (uPA) and interaction with biological ligands such as vitronectin and cell-surface receptors, the function of PAI-1 extends to pericellular proteolysis, tissue remodeling and other processes including cell migration. This review aims at providing a general overview of the properties of PAI-1 and the role it plays in many biological processes and touches upon the possible use of PAI-1 inhibitors as therapeutics.

Elevated postischemic tissue injury and leukocyte-endothelial adhesive interactions in mice with global deficiency in caveolin-2: role of PAI-1

Ischemia/reperfusion (I/R)-induced rapid inflammation involving activation of leukocyte-endothelial adhesive interactions and leukocyte infiltration into tissues is a major contributor to postischemic tissue injury. However, the molecular mediators involved in this pathological process are not fully known. We have previously reported that caveolin-2 (Cav-2), a protein component of plasma membrane caveolae, regulated leukocyte infiltration in mouse lung carcinoma tumors. The goal of the current study was to examine if Cav-2 plays a role in I/R injury and associated acute leukocyte-mediated inflammation. Using a mouse small intestinal I/R model, we demonstrated that I/R downregulates Cav-2 protein levels in the small bowel. Further study using Cav-2-deficient mice revealed aggravated postischemic tissue injury determined by scoring of villi length in H&E-stained tissue sections, which correlated with increased numbers of MPO-positive tissue-infiltrating leukocytes determined by IHC staining. Intravital microscopic analysis of upstream events relative to leukocyte transmigration and tissue infiltration revealed that leukocyte-endothelial cell adhesive interactions in postcapillary venules, namely leukocyte rolling and adhesion were also enhanced in Cav-2-deficient mice. Mechanistically, Cav-2 deficiency increased plasminogen activator inhibitor-1 (PAI-1) protein levels in the intestinal tissue and a pharmacological inhibition of PAI-1 had overall greater inhibitory effect on both aggravated I/R tissue injury and enhanced leukocyte-endothelial interactions in postcapillary venules in Cav-2-deficient mice. In conclusion, our data suggest that Cav-2 protein alleviates tissue injury in response to I/R by dampening PAI-1 protein levels and thereby reducing leukocyte-endothelial adhesive interactions.NEW & NOTEWORTHY The role of caveolin-2 in regulating ischemia/reperfusion (I/R) tissue injury and the mechanisms underlying its effects are unknown. This study uses caveolin-2-deficient mouse and small intestinal I/R injury models to examine the role of caveolin-2 in the leukocyte-dependent reperfusion injury. We demonstrate for the first time that caveolin-2 plays a protective role from the I/R-induced leukocyte-dependent reperfusion injury by reducing PAI-1 protein levels in intestinal tissue and leukocyte-endothelial adhesive interactions in postcapillary venules.

Interacting hepatic PAI-1/tPA gene regulatory pathways influence impaired fibrinolysis severity in obesity

Fibrinolysis is initiated by tissue-type plasminogen activator (tPA) and inhibited by plasminogen activator inhibitor 1 (PAI-1). In obese humans, plasma PAI-1 and tPA proteins are increased, but PAI-1 dominates, leading to reduced fibrinolysis and thrombosis. To understand tPA–PAI-1 regulation in obesity, we focused on hepatocytes, a functionally important source of tPA and PAI-1 that sense obesity-induced metabolic stress. We showed that obese mice, like humans, had reduced fibrinolysis and increased plasma PAI-1 and tPA, due largely to their increased hepatocyte expression. A decrease in the PAI-1 (SERPINE1) gene corepressor Rev-Erbα increased PAI-1, which then increased the tPA gene PLAT via a PAI-1/LRP1/PKA/p-CREB1 pathway. This pathway was partially counterbalanced by increased DACH1, a PLAT-negative regulator. We focused on the PAI-1/PLAT pathway, which mitigates the reduction in fibrinolysis in obesity. Thus, silencing hepatocyte PAI-1, CREB1, or tPA in obese mice lowered plasma tPA and further impaired fibrinolysis. The PAI-1/PLAT pathway was present in primary human hepatocytes, and associations among PAI-1, tPA, and PLAT in livers from obese and lean humans were consistent with these findings. Knowledge of PAI-1 and tPA regulation in hepatocytes in obesity may suggest therapeutic strategies for improving fibrinolysis and lowering the risk of thrombosis in this setting.

Targeting PAI-1 in Cardiovascular Disease: Structural Insights Into PAI-1 Functionality and Inhibition

Plasminogen activator inhibitor-1 (PAI-1), a member of the serine protease inhibitor (serpin) superfamily with antiprotease activity, is the main physiological inhibitor of tissue-type (tPA) and urokinase-type (uPA) plasminogen activators (PAs). Apart from being crucially involved in fibrinolysis and wound healing, PAI-1 plays a pivotal role in various acute and chronic pathophysiological processes, including cardiovascular disease, tissue fibrosis, cancer, and age-related diseases. In the prospect of treating the broad range of PAI-1-related pathologies, many efforts have been devoted to developing PAI-1 inhibitors. The use of these inhibitors, including low molecular weight molecules, peptides, antibodies, and antibody fragments, in various animal disease models has provided ample evidence of their beneficial effect in vivo and moved forward some of these inhibitors in clinical trials. However, none of these inhibitors is currently approved for therapeutic use in humans, mainly due to selectivity and toxicity issues. Furthermore, the conformational plasticity of PAI-1, which is unique among serpins, poses a real challenge in the identification and development of PAI-1 inhibitors. This review will provide an overview of the structural insights into PAI-1 functionality and modulation thereof and will highlight diverse approaches to inhibit PAI-1 activity.

Impact of overweight/obesity on the development of hematoma following tissue expander-based breast reconstruction

BACKGROUND

Overweight and obesity are well-known risk factors for postoperative complications; however, their impacts on hematoma formation have not been clarified. Several studies have suggested that overweight/obesity could have procoagulative effects, potentially reducing a risk for developing postoperative bleeding complications. This study aimed to investigate the effects of overweight/obesity on hematoma formation following tissue expander-based breast reconstruction.

METHOD

Patients who underwent immediate tissue expander-based unilateral breast reconstruction between January 2010 and November 2018 were reviewed. They were categorized into four groups according to body mass index (BMI): underweight (<18.5 kg/m2), normal weight (18.5-25.0 kg/m2), overweight (25.0-30.0 kg/m2), and obesity (>30.0 kg/m2). The outcome was major postoperative hematoma, defined as one requiring emergent surgical intervention. Independent impacts of variables on hematoma development were evaluated via uni- and multivariable analyses.

RESULTS

A total of 1,431 patients were analyzed, including 133 cases (9.3%) with underweight, 952 (66.5%) with normal weight, 302 (21.1%) with overweight, and 44 (3.1%) with obesity. Postoperative major hematoma developed in 29 cases (2.0%). The rate of hematoma formation was 2.3%, 2.6%, 0.3%, and 0% in the underweight, normal weight, overweight, and obesity groups, respectively, showing a significantly decreasing trend (p = 0.009), while those of other complications including seroma and mastectomy flap necrosis revealed the opposite trends, being significantly elevated as patient BMI increased. Multivariate analyses found overweight to be an independent protector against major hematoma compared with normal weight (p = 0.014; odds ratio=0.071).

CONCLUSION

Overweight/obesity might have a protective effect on development of major bleeding complications following tissue expander-based breast reconstruction.

Indirect Contributions to Tumor Dynamics in the First Stage of the Avascular Phase

A continuum model for tumor invasion in a two-dimensional spatial domain based on the interaction of the urokinase plasminogen activation system with a model for cancer cell dynamics is proposed. The arising system of partial differential equations is numerically solved using the finite element method. We simulated a portion of biological tissue imposing no flux boundary conditions. We monitored the cancer cell dynamics, as well the degradation of an extra cellular matrix representative, vitronectin, and the evolution of a specific degrading enzyme, plasmin, inside the biological tissue. The computations were parameterized as a function of the indirect cell proliferation induced by a plasminogen activator inhibitor binding to vitronectin and of the indirect plasmin deactivation due to the plasminogen activator inhibitor binding to the urokinase plasminogen activator. Their role during the cancer dynamical evolution was identified, together with a possible marker helping the mapping of the cancer invasive front. Our results indicate that indirect cancer cell proliferation biases the speed of the tumor invasive front as well as the heterogeneity of the cancer cell clustering and networking, as it ultimately acts on the proteolytic activity supporting cancer formation. Because of the initial conditions imposed, the numerical solutions of the model show a symmetrical dynamical evolution of heterogeneities inside the simulated domain. Moreover, an increase of up to about 12% in the invasion speed was observed, increasing the rate of indirect cancer cell proliferation, while increasing the plasmin deactivation rate inhibits heterogeneities and networking. As cancer cell proliferation causes vitronectin consumption and plasmin formation, the intensities of the concentration maps of both vitronectin and plasmin are superimposable to the cancer cell concentration maps. The qualitative imprinting that cancer cells leave on the extra cellular matrix during the time evolution as well their activity area is identified, framing the numerical results in the context of a methodology aimed at diagnostic and therapeutic improvement.

Thrombin Provokes Degranulation of Platelet α-Granules Leading to the Release of Active Plasminogen Activator Inhibitor-1 (PAI-1)

BACKGROUND

The balance of fibrinolytic mediators is crucial to the survival of the critically ill patient, with tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) playing significant roles. While elevated levels of PAI-1 are associated with increased morbidity and mortality, the source of this PAI-1 remains elusive. Platelets contain 90% of circulating plasma PAI-1, however, their ability to release active PAI-1 is controversial. We hypothesize platelets contain active PAI-1 in α-granules capable of immediate degranulation when exposed to high concentrations of thrombin.

METHODS

In vitro apheresis platelets were stimulated with thrombin (1 IU/mL, 5 IU/mL) followed by the collection of supernatant (5-120 min). Supernatant and lysate PAI-1 was measured by ELISA. The experiment was repeated in the presence of t-PA followed by measurement of t-PA:PAI-1 complex measurement by ELISA. Finally, healthy whole blood underwent dilution with control and thrombin-treated platelet lysate followed by thrombelastography (TEG) in a t-PA-stimulated TEG.

RESULTS

Thrombin provoked immediate near-complete degranulation of PAI-1 from α-granules (median 5m 5 IU/mL thrombin 125.1 ng/mL, 1 IU/mL thrombin 114.9 ng/mL, control 9.9 ng/mL). The released PAI-1 rapidly complexed with t-PA, with a 4-fold increase in complex formation in the thrombin-treated supernatant. Conversely, PAI-1 in the control lysate demonstrated a 6-fold increase in complex formation compared with thrombin lysate. Last, control platelet lysate inhibited t-PA-induced fibrinolysis by TEG (median LY30 control 15m 7.9%), while thrombin-treated platelet lysates, after PAI-1 degranulation, were unable to affect the fibrinolysis profile (median LY30 5 IU/mL 28.5%, 1 IU/mL 12.4%).

CONCLUSION

Thrombin provokes rapid α-degranulation of active PAI-1, capable of complexing with t-PA and neutralizing t-PA-induced fibrinolysis by TEG.

Plasminogen activator inhibitor-1 augments damage by impairing fibrinolysis after traumatic brain injury

OBJECTIVE

Plasminogen activator inhibitor-1 (PAI-1) is the key endogenous inhibitor of fibrinolysis, and enhances clot formation after injury. In traumatic brain injury, dysregulation of fibrinolysis may lead to sustained microthrombosis and accelerated lesion expansion. In the present study, we hypothesized that PAI-1 mediates post-traumatic malfunction of coagulation, with inhibition or genetic depletion of PAI-1 attenuating clot formation and lesion expansion after brain trauma.

METHODS

We evaluated PAI-1 as a possible new target in a mouse controlled cortical impact (CCI) model of traumatic brain injury. We performed the pharmacological inhibition of PAI-1 with PAI-039 and stimulation by tranexamic acid, and we confirmed our results in PAI-1-deficient animals.

RESULTS

PAI-1 mRNA was time-dependently upregulated, with a 305-fold peak 12 hours after CCI, which effectively counteracted the 2- to 3-fold increase in cerebral tissue-type/urokinase plasminogen activator expression. PAI-039 reduced brain lesion volume by 26% at 24 hours and 43% at 5 days after insult. This treatment also attenuated neuronal apoptosis and improved neurofunctional outcome. Moreover, intravital microscopy demonstrated reduced post-traumatic thrombus formation in the pericontusional cortical microvasculature. In PAI-1-deficient mice, the therapeutic effect of PAI-039 was absent. These mice also displayed 13% reduced brain damage compared with wild type. In contrast, inhibition of fibrinolysis with tranexamic acid increased lesion volume by 25% compared with vehicle.

INTERPRETATION

This study identifies impaired fibrinolysis as a critical process in post-traumatic secondary brain damage and suggests that PAI-1 may be a central endogenous inhibitor of the fibrinolytic pathway, promoting a procoagulatory state and clot formation in the cerebral microvasculature. Ann Neurol 2019;85:667-680.

Genetic investigation of childhood vascular tumor biology reveals pathways for therapeutic intervention

Vascular tumors are neoplasms of endothelial cells, a significant number of which present in childhood. Recent studies have examined the mutational landscape of many subtypes of vascular tumors, identifying mutations primarily within the Ras–mitogen-activated protein kinase (MAPK) pathway and providing a unique opportunity to consider targeted therapeutics. This review will summarize the current understanding of childhood vascular tumor pathobiology.

An ATF6-tPA pathway in hepatocytes contributes to systemic fibrinolysis and is repressed by DACH1

Tissue-type plasminogen activator (tPA) is a major mediator of fibrinolysis and, thereby, prevents excessive coagulation without compromising hemostasis. Studies on tPA regulation have focused on its acute local release by vascular cells in response to injury or other stimuli. However, very little is known about sources, regulation, and fibrinolytic function of noninjury-induced systemic plasma tPA. We explore the role and regulation of hepatocyte-derived tPA as a source of basal plasma tPA activity and as a contributor to fibrinolysis after vascular injury. We show that hepatocyte tPA is downregulated by a pathway in which the corepressor DACH1 represses ATF6, which is an inducer of the tPA gene Plat Hepatocyte-DACH1-knockout mice show increases in liver Plat, circulating tPA, fibrinolytic activity, bleeding time, and time to thrombosis, which are reversed by silencing hepatocyte Plat Conversely, hepatocyte-ATF6-knockout mice show decreases in these parameters. The inverse correlation between DACH1 and ATF6/PLAT is conserved in human liver. These findings reveal a regulated pathway in hepatocytes that contributes to basal circulating levels of tPA and to fibrinolysis after vascular injury.

Plasminogen activator system homeostasis and its dysregulation by ethanol in astrocyte cultures and the developing brain

In utero alcohol exposure can cause fetal alcohol spectrum disorders (FASD), characterized by structural brain abnormalities and long-lasting behavioral and cognitive dysfunction. Neuronal plasticity is affected by in utero alcohol exposure and can be modulated by extracellular proteolysis. Plasmin is a major extracellular serine-protease whose activation is tightly regulated by the plasminogen activator (PA) system. In the present study we explored the effect of ethanol on the expression of the main components of the brain PA system in sex-specific cortical astrocyte primary cultures in vitro and in the cortex and hippocampus of post-natal day (PD) 9 male and female rats. We find that ethanol alters the PA system in astrocytes and in the developing brain. In particular, the expression of tissue-type PA (tPA), encoded by the gene Plat, is consistently upregulated by ethanol in astrocytes in vitro and in the cortex and hippocampus in vivo. Astrocytes exhibit endogenous plasmin activity that is increased by ethanol and recombinant tPA and inhibited by tPA silencing. We also find that tPA is expressed by astrocytes of the developing cortex and hippocampus in vivo. All components of the PA system investigated, with the exception of Neuroserpin/Serpini1, are expressed at higher levels in astrocyte cultures than in the developing brain, suggesting that astrocytes are major producers of these proteins in the brain. In conclusion, astrocyte PA system may play a major role in the modulation of neuronal plasticity; ethanol-induced upregulation of tPA levels and plasmin activity may be responsible for altered neuronal plasticity in FASD.

Thrombin stimulates increased plasminogen activator inhibitor-1 release from liver compared to lung endothelium

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) is a major regulator of the fibrinolytic system, covalently binding to tissue plasminogen activator and blocking its activity. Fibrinolysis shutdown is evident in the majority of severely injured patients in the first 24 h and is thought to be due to PAI-1. The source of this PAI-1 is thought to be predominantly endothelial cells, but there are known organ-specific differences, with higher levels thought to be in the liver. Thrombin generation is also elevated in injured patients and is a potent stimulus for PAI-1 release in human umbilical endothelial cells. We hypothesize that thrombin induces liver endothelial cells to release increased amounts of PAI-1, versus pulmonary endothelium, consisting of both stored PAI-1 and a larger contribution from de novo PAI-1 synthesis.

METHODS

Human liver sinusoidal endothelial cells (LSECs) and human microvascular lung endothelial cells (HMVECs) were stimulated in vitro ± thrombin (1 and 5 IU/mL) for 15-240 min, the supernatants were collected, and PAI-1 was measured by enzyme-linked immunosorbent assays. To elucidate the PAI-1 contribution from storage versus de novo synthesis, cycloheximide (10 μg/mL) was added before thrombin in separate experiments.

RESULTS

While both LSECs and HMVECs rapidly stimulated PAI-1 release, LSECs released more PAI-1 than HMVECs in response to high-dose thrombin, whereas low-dose thrombin did not provoke immediate release. LSECs continued to release PAI-1 over the ensuing 240 min, whereas HMVECs did not. Cycloheximide did not inhibit early PAI-1 release from LSECs but did at the later time points (30-240 min).

CONCLUSIONS

Thrombin elicits increased amounts of PAI-1 release from liver endothelium compared with lung, with a small presynthesized stored contribution and a later, larger increase in PAI-1 release via de novo synthesis. This study suggests that the liver may be an important therapeutic target for inhibition of the hypercoagulable surgical patient and the associated complications that result.

Everolimus for Treatment of Pseudomyogenic Hemangioendothelioma

Pseudomyogenic hemangioendothelioma (PMH) is a recently described vascular neoplasm that occurs most commonly in the soft tissue of the distal extremities of young adults. Metastatic PMH can be fatal and there are no effective medications. We describe a case of a 15-year-old boy with metastatic PMH, who responded to treatment with everolimus, a mammalian target of rapamycin inhibitor. Immunohistochemistry showed that mammalian target of rapamycin was expressed in PMH biopsy specimens, which may explain the reduction in PMH tumor size following treatment.

Advances in the Genetic Characterization of Cutaneous Mesenchymal Neoplasms: Implications for Tumor Classification and Novel Diagnostic Markers

Cutaneous mesenchymal neoplasms often pose significant diagnostic challenges; many such entities are rare or show clinical and histologic overlap with both other mesenchymal and non-mesenchymal lesions. Recent advances in the genetic classification of many cutaneous mesenchymal neoplasms have not only helped define unique pathologic entities and increase our understanding of their biology, but have also provided new diagnostic markers. This review details these recent discoveries, with a focus on their implications for tumor classification and diagnosis.

Blood markers of fibrinolysis and endothelial activation in canine babesiosis

Background

Canine babesiosis is a tick-borne disease caused by hemoprotozoan parasites of the genus Babesia. The disease can be clinically classified into uncomplicated and complicated forms. The aim of this study was to assess the level of endothelial activation and alterations in the fibrinolytic pathway during canine babesiosis.

Results

Blood samples were collected on the day of admission and on the 6th day after treatment with imidocarb propionate, from 30 dogs of various breeds and of both sexes with naturally occurring babesiosis caused by B. canis. In this prospective study, plasminogen activity was assessed using a chromogenic assay, and concentrations of high mobility group box-1 protein (HMGB-1), intercellular adhesive molecule-1 (ICAM-1), vascular adhesive molecule-1 (VCAM-1), soluble urokinase receptor of plasminogen activator (suPAR), thrombin activatable fibrinolysis inhibitor (TAFI), soluble thrombomodulin (TM) and plasminogen activator inhibitor-1 (PAI-1) were determined using a canine specific ELISA. Concentrations of TM, HMGB-1, VCAM-1 and suPAR were increased in dogs with babesiosis at admission compared to healthy dogs. After treatment, concentrations of TM were lower in infected dogs compared to healthy dogs. Dogs with babesiosis also had increased concentrations of TM, ICAM-1 and HMGB-1 and decreased plasminogen and PAI-1 at presentation compared to day 6 after treatment. Dogs with complicated babesiosis had higher concentrations of TM, HMGB1 and TAFI at admission compared to the 6th day.

Conclusions

Biomarkers of endothelial activation and fibrinolysis were altered in dogs with babesiosis. Further studies into their usefulness as biomarkers of disease severity or prognosis is warranted.

Elevated circulating PAI-1 levels are related to lung function decline, systemic inflammation, and small airway obstruction in chronic obstructive pulmonary disease

Background

Plasminogen activator inhibitor-1 (PAI-1) and soluble urokinase-type plasminogen activator receptor (suPAR) participate in inflammation and tissue remolding in various diseases, but their roles in chronic obstructive pulmonary disease (COPD) are not yet clear. This study aimed to investigate if PAI-1 and suPAR were involved in systemic inflammation and small airway obstruction (SAO) in COPD.

Methods

Demographic and clinical characteristics, spirometry examination, and blood samples were obtained from 84 COPD patients and 51 healthy volunteers. Serum concentrations of PAI-1, suPAR, tissue inhibitor of metalloproteinase-1 (TIMP-1), Matrix metalloproteinase-9 (MMP-9), and C-reactive protein (CRP) were detected with Magnetic Luminex Screening Assay. Differences between groups were statistically analyzed using one-way analysis of variance or chi-square test. Pearson’s partial correlation test (adjusted for age, sex, body mass index, cigarette status, and passive smoke exposure) and multivariable linear analysis were used to explore the relationships between circulating PAI-1 and indicators of COPD.

Results

First, we found that serum PAI-1 levels but not suPAR levels were significantly increased in COPD patients compared with healthy volunteers (125.56±51.74 ng/mL versus 102.98±36.62 ng/mL, P=0.007). Then, the correlation analysis showed that circulating PAI-1 was inversely correlated with pulmonary function parameters including the ratio of forced expiratory volume in 1 second to forced vital capacity (FEV₁/FVC), FEV₁/Pre (justified r=−0.308, P<0.001; justified r=−0.295, P=0.001, respectively) and SAO indicators such as FEV₃/FVC, MMEF25–75/Pre (justified r=−0.289, P=0.001; justified r=−0.273, P=0.002, respectively), but positively related to the inflammatory marker CRP (justified r=0.351, P<0.001), the small airway remolding biomarker TIMP-1, and MMP-9 (justified r=0.498, P<0.001; justified r=0.267, P=0.002, respectively). Besides, multivariable linear analysis showed that FEV₁/FVC, CRP, and TIMP-1 were independent parameters associated with PAI-1.

Conclusion

Our findings first illustrate that elevated serum PAI-1 levels are related to the lung function decline, systemic inflammation, and SAO in COPD, suggesting that PAI-1 may play critical roles in the pathogenesis of COPD.

Generation and in vitro characterisation of inhibitory nanobodies towards plasminogen activator inhibitor 1

Plasminogen activator inhibitor 1 (PAI-1) is the principal physiological inhibitor of tissue-type plasminogen activator (t-PA) and has been identified as a risk factor in cardiovascular diseases. In order to generate nanobodies against PAI-1 to interfere with its functional properties, we constructed three nanobody libraries upon immunisation of three alpacas with three different PAI-1 variants. Three panels of nanobodies were selected against these PAI-1 variants. Evaluation of the amino acid sequence identity of the complementarity determining region-3 (CDR3) reveals 34 clusters in total. Five nanobodies (VHH-s-a98, VHH-2w-64, VHH-s-a27, VHH-s-a93 and VHH-2g-42) representing five clusters exhibit inhibition towards PAI-1 activity. VHH-s-a98 and VHH-2w-64 inhibit both glycosylated and non-glycosylated PAI-1 variants through a substrate-inducing mechanism, and bind to two different regions close to αhC and the hinge region of αhF; the profibrinolytic effect of both nanobodies was confirmed using an in vitro clot lysis assay. VHH-s-a93 may inhibit PAI-1 activity by preventing the formation of the initial PAI-1t-PA complex formation and binds to the hinge region of the reactive centre loop. Epitopes of VHH-s-a27 and VHH-2g-42 could not be deduced yet. These five nanobodies interfere with PAI-1 activity through different mechanisms and merit further evaluation for the development of future profibrinolytic therapeutics.

Obesity and clotting: Body mass index independently contributes to hypercoagulability after injury

BACKGROUND

Although obese patients have high thrombosis rates following injury, the role of obesity in coagulation after trauma remains unknown. We hypothesized that body mass index (BMI) is independently associated with increased measures of hypercoagulability longitudinally after injury.

METHODS

Data were prospectively collected for 377 consecutive highest-level trauma activation patients with a BMI of 18.5 kg/m² or greater. Standard coagulation measures, citrated kaolin and functional fibrinogen thromboelastography, as well as clotting factors were measured at 0 hour to 120 hours. BMI categories were defined as normal weight (18.5-24.99 kg/m²), overweight (25-29.99 kg/m²), and obese (≥30 kg/m²).

RESULTS

The 377 patients were mostly male (81%) and had blunt injury (61%), with a median BMI of 25.8 kg/m². Of the patients, 42% were normal weight (median BMI, 22.5 kg/m²). There were no differences in age, sex, Injury Severity Score (ISS), or base deficit between groups. There were no differences in admission international normalized ratio/partial thromboplastin time or factors II, V, VII, VIII, and X; antithrombin III; or protein C. However, obese patients had higher admission platelet counts (303 × 10⁹/L vs. 269 × 10⁹/L, p = 0.004), lower D-dimer (1.88 μg/mL vs. 4.00 μg/mL, p = 0.004), and a trend toward higher factor IX (134% vs. 119% activity, p = 0.042) compared with normal weight patients. Measured by thromboelastography, clot strength (maximum amplitude) and functional fibrinogen level (FLEV) were also higher on admission for obese patients (maximum amplitude, 65.7 mm vs. 63.4 mm, p = 0.016; FLEV, 407 mg/dL vs. 351 mg/dL, p = 0.008). In multiple linear regression, the relationship of BMI to clot strength, FLEV, and factor IX persisted through 24 hours. Similarly, the relationship of BMI and platelet count persisted through 120 hours (all p < 0.05). In multiple logistic regression, for every 5-kg/m² increase in BMI, there was an 85% increase in odds of thromboembolic complication (odds ratio, 1.85; 95% confidence interval, 1.13-3.08; p = 0.017).

CONCLUSION

Obese trauma patients are hypercoagulable compared with their similarly injured normal-weight counterparts, which persists longitudinally after injury. The significance of this hypercoagulability requires elucidation for guidance of anticoagulation in this at-risk group.

LEVEL OF EVIDENCE

Prognostic study, level III.

Alterations in the endometrium of rats, rabbits, and Macaca mulatta that received an implantation of copper/low-density polyethylene nanocomposite

A copper/low-density polyethylene nanocomposite (nano-Cu/LDPE), a potential intrauterine device component material, has been developed from our research. A logical extension of our previous work, this study was conducted to investigate the expression of plasminogen activator inhibitor 1 (PAI-1), substance P (SP), and substance P receptor (SP-R) in the endometrium of Sprague Dawley rats, New Zealand White rabbits, and Macaca mulatta implanted with nano-Cu/LDPE composite. The influence of the nano-Cu/LDPE composite on the morphology of the endometrium was also investigated. Animals were randomly divided into five groups: the sham-operated control group (SO group), bulk copper group (Cu group), LDPE group, and nano-Cu/LDPE groups I and II. An expression of PAI-1, SP, and SP-R in the endometrial tissues was examined by immunohistochemistry at day 30, 60, 90, and 180 postimplantation. The significant difference for PAI-1, SP, and SP-R between the nano-Cu/LDPE groups and the SO group (P<0.05) was identified when the observation period was terminated, and the changes of nano-Cu/LDPE on these parameters were less remarkable than those of the Cu group (P<0.05). The damage to the endometrial morphology caused by the nano-Cu/LDPE composite was much less than that caused by bulk copper. The nano-Cu/LDPE composite might be a potential substitute for conventional materials for intrauterine devices in the future because of its decreased adverse effects on the endometrial microenvironment.

A novel SERPINE1-FOSB fusion gene results in transcriptional up-regulation of FOSB in pseudomyogenic haemangioendothelioma

Pseudomyogenic haemangioendothelioma (PHE) is an intermediate malignant vascular soft tissue tumour primarily affecting children and young adults. The molecular basis of this neoplasm is unknown. We here used chromosome banding analysis, fluorescence in situ hybridization (FISH), mRNA sequencing, RT-PCR and quantitative real-time PCR on a series of morphologically well-characterized PHEs to show that a balanced translocation, t(7;19)(q22;q13), detected as the sole cytogenetic aberration in two cases, results in fusion of the SERPINE1 and FOSB genes. This translocation has not been observed in any other bone or soft tissue tumour. Interphase FISH on sections from eight additional PHEs identified the same SERPINE1-FOSB fusion in all cases. The role of SERPINE1, which is highly expressed in vascular cells, in this gene fusion is probably to provide a strong promoter for FOSB, which was found to be expressed at higher levels in PHEs than in other soft tissue tumours. FOSB encodes a transcription factor belonging to the FOS family of proteins, which, together with members of the JUN family of transcription factors, are major components of the activating protein 1 (AP-1) complex. Further studies are needed to understand the cellular impact of the aberrant expression of the FOSB gene, but as the t(7;19) resulting in the SERPINE1-FOSB fusion seems to be pathognomonic for PHE, FISH or RT-PCR could be useful for differential diagnostic purposes.

Placental protein tyrosine nitration and MAPK in type 1 diabetic pre-eclampsia: Impact of antioxidant vitamin supplementation

AIM

To examine the role of placental protein tyrosine nitration and p38-Mitogen-Activated Protein Kinase α (p38-MAPKα), Extra Cellular-Signal Regulated Kinase (ERK) and c-Jun NH2-Terminal Kinase (JNK) activity, in the pathogenesis of type 1 diabetic pre-eclampsia, and the putative modulation of these indices by maternal vitamin C and E supplementation.

METHODS

Placental samples were obtained from a sub-cohort of the DAPIT trial: a randomised placebo-controlled trial of antioxidant supplementation to reduce pre-eclampsia in type 1 diabetic pregnancy. Placenta from placebo-treated: normotensive (NT) [n=17], gestational hypertension (GH) [n=7] and pre-eclampsia (PE) [n=6] and vitamin-treated: NT (n=20), GH (n=4) and PE (n=3) was analysed. Protein tyrosine nitration was assessed by immunohistochemistry in paraffin-embedded tissue. Catalytic activities of placental p38-MAPKα, ERK and JNK were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Nitrotyrosine immunostaining was present in placebo-treated NT, GH and PE placentae, with no significant difference observed between the groups. There was a non-significant trend towards decreased p38-MAPKα activity in PE vs NT control placentae. ERK and JNK were similar among the three outcome placebo groups and vitamin supplementation did not significantly alter their activity.

CONCLUSION

Nitrotyrosine immunopositivity in normotensive diabetic placentae indicates some degree of tyrosine nitration in uncomplicated diabetic pregnancy, possibly due to inherent oxidative stress and peroxynitrite production. Our results suggest that p38-MAPKα, ERK and JNK are not directly involved in the pathogenesis of type 1 diabetic pre-eclampsia and are not modulated by vitamin-supplementation.

Plasminogen activator inhibitor-1 gene polymorphism in Iranian Azeri Turkish patients with FMF disease and its association with amyloidosis

Familial Mediterranean fever (FMF) is an autosomal recessive disorder characterized by intermittent episodes of fever with serositis, arthritis, or eriseplemya. Plasminogen activator inhibitor 1 (PAI-1) is a key element in the inhibition of fibrinolysis by inactivating tissue-type and urokinase-type plasminogen activators. We evaluated the association of PAI-1 -675 4G/5G polymorphism with the severity of FMF disease. For this purpose, 89 FMF patients with M694V homozygous mutation and 95 healthy controls from Iranian Azeri Turks were selected. Detection of this polymorphism was performed by polymerase chain reaction using allele-specific primers. No significant association was found between patients and control group. However, these data showed that FMF patients with M694V homozygous mutation carrying 4G/4G genotype have a reduced risk for development of pleuritis (odds ratios (OR) 0.36; 95 % confidence intervals (CI) 0.5-0.85; P value = 0.007) compared with 5G/5G homozygotes who have increased risk for development of amyloidosis (OR = 2.46; 95 %CI = 1.29-4.72; P value = 0.001), pleuritis (OR = 2.55; 95 %CI = 1.31-4.99; P value = 0.001), and fever (OR = 4.68; 95 %CI = 2.04-10.96; P value = 0.000). Furthermore, the allelic frequency of the 4G among the patients with pleuritis was significantly low (OR = 0.5, 95 % CI = 0.27-0.92, P value = 0.008).

CONCLUSION

Our data suggest a protective role for the 4G allele against pleuritis in FMF patients with M694V homozygous mutation in this cohort. More evaluation of this polymorphism may be important and require further studies.

Biochemical dynamics relevant to the safety of low-dose, intraclot alteplase for deep vein thrombosis

Intraclot tissue plasminogen activator (tPA) has been shown to be an effective treatment for deep vein thrombosis (DVT) (Radiology 2008;246:619 and J Vasc Interv Radiol 2011;22:1107). We sought to correlate pharmacokinetics of tPA, fibrinogen, fibrinolytic inhibitors, and D-dimers with the safety and efficacy of intraclot tPA. Thirty subjects received intraclot tPA for lower extremity DVT by infiltrating the thrombus with ≤10 mg doses tPA in an open-label study, using a pulse-spray catheter. We measured various parameters over 8 h following a first dose of tPA. Mean tPA levels of 75 units per mL (95% confidence interval 19-131 units/mL) were seen immediately after administration of a mean tPA dose of 8.0 mg (SD 1.5 mg). tPA levels returned to baseline within 2 h of completion of treatment. Plasminogen activator inhibitor-1 (PAI-1) was consumed following tPA treatment, but rose to levels significantly greater than baseline (P < 0.001). Fibrinogen decreased slightly, but remained >125 mg/dL for all subjects. α2-antiplasmin decreased from a mean of 115 units/mL to 56 units/mL after tPA administration (P < 0.001) and remained decreased for 8 h. Plasminogen at baseline (112 units/mL) decreased to 89 units/mL immediately after tPA administration (P < 0.001) and was unchanged thereafter. D-dimer levels were >20 μg/mL in all but 4 subjects, one of whom was the only one to fail to achieve clot lysis. The safety of low-dose, intraclot tPA is due to its short persistence in the circulation, lack of hypofibrinogenemia, and a reflexive rise of PAI-1. Subjects whose D-dimers remain <20 μg/mL are at risk of not achieving thrombolysis.

Maximal PAI-1 inhibition in vivo requires neutralizing antibodies that recognize and inhibit glycosylated PAI-1

Plasminogen activator inhibitor-1 (PAI-1) regulates the activity of t-PA and u-PA and is an important inhibitor of the plasminogen activator system. Elevated PAI-1 levels have been implicated in the pathogenesis of several diseases. Prior to the evaluation of PAI-1 inhibitors in humans, there is a strong need to study the effect of PAI-1 inhibition in mouse models. In the current study, four monoclonal antibodies previously reported to inhibit recombinant PAI-1 in vitro, were evaluated in an LPS-induced endotoxemia model in mice. Both MA-33H1F7 and MA-MP2D2 exerted a strong PAI-1 inhibitory effect, whereas for MA-H4B3 and MA-124K1 no reduced PAI-1 activity was observed in vivo. Importantly, the lack of PAI-1 inhibition observed for MA-124K1 and MA-H4B3 in vivo corresponded with the absence of inhibition toward glycosylated mouse PAI-1 in vitro. Three potential N-glycosylation sites were predicted for mouse PAI-1 (i.e. N209, N265 and N329). Electrophoretic mobility analysis of glycosylation knock-out mutants before and after deglycosylation indicates the presence of glycan chains at position N265. These data demonstrate that an inhibitory effect toward glycosylated PAI-1 is a prerequisite for efficient PAI-1 inhibition in mice. Our data also suggest that PAI-1 inhibitors for use in humans must preferably be screened on glycosylated PAI-1 and not on recombinant non-glycosylated PAI-1.

Use of mouse models to study plasminogen activator inhibitor-1

Plasminogen activator inhibitor-1 (PAI-1) is the main inhibitor of tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA) and therefore plays an important role in the plasminogen/plasmin system. PAI-1 is involved in a variety of cardiovascular diseases (mainly through inhibition of t-PA) as well as in cell migration and tumor development (mainly through inhibition of u-PA and interaction with vitronectin). PAI-1 is a unique member of the serpin superfamily, exhibiting particular unique conformational and functional properties. Since its involvement in various biological and pathophysiological processes PAI-1 has been the subject of many in vivo studies in mouse models. We briefly discuss structural and physiological differences between human and mouse PAI-1 that should be taken into account prior to extrapolation of data obtained in mouse models to the human situation. The current review provides an overview of the various models, with a focus on cardiovascular disease and cancer, using wild-type mice or genetically modified mice, either deficient in PAI-1 or overexpressing different variants of PAI-1.

Curcumin down-regulates PAI-1 expression but up-regulates u-PA expression in carbon tetrachloride-induced hepatic fibrosis in rats

AIM: To investigate the effects of curcumin on the expression of plasminogen activator inhibitor-1 (PAI-1) and urokinase-type plasminogen activator (u-PA) in carbon tetrachloride-induced hepatic fibrosis in rats.

METHODS: One hundred male Sprague-Dawley rats were randomly divided into five groups: normal group, model group, low-, medium- and high-dose curcumin group. Except the normal group, the rats of the other groups were intraperitoneally injected with carbon tetrachloride for 6 wk to induce liver fibrosis. The rats of the low-, medium- and high-dose curcumin groups were administrated different doses of curcumin. On days 4, 7, 21 and 42 after treatment, five rats randomly selected from each group were sacrificed to take liver specimens for pathological examination (HE). The expression of PAI-1 and u-PA in hepatic fibrosis was detected by immunohistochemistry.

RESULTS: The expression levels of PAI-1 and u-PA were much lower in the normal group than in the model group. Compared to the model group, PAI-1 expression was significantly down-regulated (42 d: 5.60 ± 1.673, 3.40 ± 1.673, 2.40 ± 1.140 vs 8.80 ± 2.168, all P < 0.05) and u-PA expression was significantly up-regulated (42 d: 6.00 ± 1.414, 9.20 ± 1.643, 9.80 ± 2.049 vs 4.20 ± 1.095, P < 0.05) in the low-, medium- and high-dose curcumin groups. Curcumin treatment altered the expression of PAI-1 and u-PA in a dose- and time-dependent manner.

CONCLUSION: Curcumin exerts anti-fibrotic effects possibly by decreasing the expression of PAI-1 and increasing the expression of u-PA.

Placenta growth factor (PlGF), a novel inducer of plasminogen activator inhibitor-1 (PAI-1) in sickle cell disease (SCD)

Sickle cell disease (SCD) is characterized by a prothrombotic state. Plasminogen activator inhibitor-1 (PAI-1) is known to modulate fibrinolysis, lung injury/fibrosis, and angiogenesis. However, its role in SCD is less understood, and the molecular mechanisms underlying increased PAI-1 are unknown. Herein, we show a novel link between PAI-1 and sickle erythropoiesis. Plasma PAI-1 levels were high in SCD patients at steady state and in two humanized sickle mouse models, with increased PAI-1 immunolabeling in sickle mouse lung, bronchial epithelial cells, alveolar macrophages, and pulmonary microvascular endothelial cells. Placenta growth factor (PlGF), released at high levels by sickle erythroblasts, induced PAI-1 expression in primary human pulmonary microvascular endothelial cells and monocytes through activation of c-Jun N-terminal kinase (JNK), NADPH oxidase, and hypoxia-inducible factor-1alpha (HIF-1alpha). Analysis of the human PAI-1 promoter revealed this induction was mediated by hypoxia-response element (HRE)-1, HRE-2, and distal activator protein (AP-1) sites. We also identify the involvement of c-Jun, c-Jun/c-Fos, and JunD, but not JunB, in binding with AP-1 sites of the PAI-1 promoter upon PlGF induction. Consistent with these findings, levels of PAI-1 were low in PlGF knock-out mice and sickle-PlGF knock-out mice; overexpression of PlGF in normal mice increased circulating PAI-1. In conclusion, we identify a novel mechanism of PAI-1 elevation in SCD.

Impaired fibrinolysis as a risk factor for Budd-Chiari syndrome

In Budd-Chiari syndrome (BCS), thrombosis develops in the hepatic veins or inferior vena cava. To study the relationship between hypofibrinolysis and BCS, we measured plasma levels of fibrinolysis proteins in 101 BCS patients and 101 healthy controls and performed a plasma-based clot lysis assay. In BCS patients, plasminogen activator inhibitor 1 (PAI-1) levels were significantly higher than in controls (median, 6.3 vs 1.4 IU/mL, P < .001). Thrombin-activatable fibrinolysis inhibitor and plasmin inhibitor levels were lower than in controls (13.8 vs 16.9 μg/mL and 0.91 vs 1.02 U/L, both P < .001). Median plasma clot lysis time (CLT) was 73.9 minutes in cases and 73.0 minutes in controls (P = .329). A subgroup of cases displayed clearly elevated CLTs. A CLT above the 90th or 95th percentile of controls was associated with an increased risk of BCS, with odds ratios of 2.4 (95% confidence interval, 1.1-5.5) and 3.4 (95% confidence interval, 1.2-9.7), respectively. In controls, only PAI-1 activity was significantly associated with CLT. Analysis of single nucleotide polymorphisms of fibrinolysis proteins revealed no significant differences between cases and controls. This case-control study provides the first evidence that an impaired fibrinolytic potential, at least partially caused by elevated PAI-1 levels, is related to the presence of BCS.

Evidence of increased oxidative stress and a change in the plasminogen activator inhibitor (PAI)-1 to PAI-2 ratio in early-onset but not late-onset preeclampsia

OBJECTIVE

The aims of this study were to measure the degree of oxidative stress and alterations in plasminogen activator inhibitor (PAI) type 1 and PAI-2 ratio in women with early-onset and late-onset preeclampsia.

STUDY DESIGN

A case-control study was conducted in women with early-onset (24-32 weeks' gestation; n=18) and late-onset (35-42 weeks' gestation; n=20) preeclampsia and in control pregnant women at corresponding gestational weeks. Placenta, urine, and serum samples were collected.

RESULTS

In early-onset preeclampsia, the median placental concentration of 8-iso-prostaglandin (PG)-F2alpha was higher and the PAI-1 to PAI-2 ratio higher than in early controls. These values did not differ between women with late-onset preeclampsia and their corresponding controls. Serum concentrations of 8-iso-PGF2alpha and vitamins C and E did not differ between cases and controls.

CONCLUSION

Early-onset but not late-onset preeclampsia is associated with increased placental oxidative stress and increased PAI-1 to PAI-2 ratio.

Role of adipose tissue in haemostasis, coagulation and fibrinolysis

Obesity is associated with an increased incidence of insulin resistance (IR), type 2 diabetes mellitus and cardiovascular diseases. The increased risk for cardiovascular diseases could partly be caused by a prothrombotic state that exists because of abdominal obesity. Adipose tissue induces thrombocyte activation by the production of adipose tissue-derived hormones, often called adipokines, of which some such as leptin and adiponectin have been shown to directly interfere with platelet function. Increased adipose tissue mass induces IR and systemic low-grade inflammation, also affecting platelet function. It has been demonstrated that adipose tissue directly impairs fibrinolysis by the production of plasminogen activator inhibitor-1 and possibly thrombin-activatable fibrinolysis inhibitor. Adipose tissue may contribute to enhanced coagulation by direct tissue factor production, but hypercoagulability is likely to be primarily caused by affecting hepatic synthesis of the coagulation factors fibrinogen, factor VII, factor VIII and tissue factor, by releasing free fatty acids and pro-inflammatory cytokines (tumour necrosis factor-alpha, interleukin-1beta and interleukin-6) into the portal circulation and by inducing hepatic IR. Adipose tissue dysfunction could thus play a causal role in the prothrombotic state observed in obesity, by directly and indirectly affecting haemostasis, coagulation and fibrinolysis.