Urokinase-type plasminogen activator (uPA) modulates monocyte-to-macrophage differentiation and prevents Ox-LDL-induced macrophage apoptosis

Immune cell-mediated venous thrombus resolution

Herein, we review the current processes that govern experimental deep vein thrombus (DVT) resolution. How the human DVT resolves at the molecular and cellular level is not well known due to limited specimen availability. Experimentally, the thrombus resolution resembles wound healing, with early neutrophil-mediated actions followed by monocyte/macrophage-mediated events, including neovascularization, fibrinolysis, and eventually collagen replacement. Potential therapeutic targets are described, and coupling with site-directed approaches to mitigate off-target effects is the long-term goal. Similarly, timing of adjunctive agents to accelerate DVT resolution is an area that is only starting to be considered. There is much critical research that is needed in this area.

All tangled up: interactions of the fibrinolytic and innate immune systems

The hemostatic and innate immune system are intertwined processes. Inflammation within the vasculature promotes thrombus development, whilst fibrin forms part of the innate immune response to trap invading pathogens. The awareness of these interlinked process has resulted in the coining of the terms "thromboinflammation" and "immunothrombosis." Once a thrombus is formed it is up to the fibrinolytic system to resolve these clots and remove them from the vasculature. Immune cells contain an arsenal of fibrinolytic regulators and plasmin, the central fibrinolytic enzyme. The fibrinolytic proteins in turn have diverse roles in immunoregulation. Here, the intricate relationship between the fibrinolytic and innate immune system will be discussed.

PLAUR splicing pattern in hereditary angioedema patients' monocytes and macrophages

BACKGROUND

The PLAUR gene encodes the urokinase-like plasminogen activator receptor (uPAR) and may undergo alternative splicing. Excluding cassette exons 3, 5 and 6 from the transcript results in truncated protein variants whose precise functions have not been elucidated yet. The PLAUR gene is one of several expressed in myeloid cells, where uPAR participates in different cellular processes, including the contact activation system and kallikrein-kinin system, which play an important role in hereditary angioedema (HAE) pathogenesis. A hypothesis about the PLAUR splicing pattern impact on HAE severity was tested.

METHODS AND RESULTS

The RT-PCR quantified by capillary electrophoresis was used. Although no significant difference in alternative transcript frequency was observed between healthy volunteers and HAE patients, a significant increase in all cassette exon inclusion variants was revealed during monocyte-to-macrophage differentiation.

CONCLUSIONS

PLAUR alternative splicing in monocytes and macrophages neither was different between HAE patients and healthy controls, nor reflected disease severity. However, the results showed an PLAUR splicing pattern was changing during monocyte-to-macrophage differentiation, but the significance of these changes is unknown and awaits future clarification.

Common Genetic Factors and Pathways in Alzheimer's Disease and Ischemic Stroke: Evidences from GWAS

Alzheimer's disease (AD) and ischemic stroke (IS) are common neurological disorders, and the comorbidity of these two brain diseases is often seen. Although AD and IS were regarded as two distinct disease entities, in terms of different etiologies and clinical presentation, recent genome-wide association studies (GWASs) revealed that there were common risk genes between AD and IS, indicating common molecular pathways and their common pathophysiology. In this review, we summarize AD and IS risk single nucleotide polymorphisms (SNPs) and their representative genes from the GWAS Catalog database, and find thirteen common risk genes, but no common risk SNPs. Furthermore, the common molecular pathways associated with these risk gene products are summarized from the GeneCards database and clustered into inflammation and immunity, G protein-coupled receptor, and signal transduction. At least seven of these thirteen genes can be regulated by 23 microRNAs identified from the TargetScan database. Taken together, the imbalance of these molecular pathways may give rise to these two common brain disorders. This review sheds light on the pathogenesis of comorbidity of AD and IS, and provides molecular targets for disease prevention, manipulation, and brain health maintenance.

Epithelial sodium channels in macrophage migration and polarization: role of proinflammatory cytokines TNFα and IFNγ

Migration of monocytes-macrophages plays an important role in phagocytosis of pathogens and cellular debris in a variety of pathophysiological conditions. Although epithelial Na+ channels (ENaCs) are required for normal migratory responses in other cell types, their role in macrophage migration signaling is unknown. To address this possibility, we determined whether ENaC message is present in several peripheral blood monocyte cell populations and tissue-resident macrophages in healthy humans using the Human Protein Atlas database (www.proteinatlas.org) and the mouse monocyte cell line RAW 264.7 using RT-PCR. We then determined that selective ENaC inhibition with amiloride inhibited chemotactic migration (∼50%), but not phagocytosis, of the mouse monocyte-macrophage cell line RAW 264.7. Furthermore, we generated a cell line stably expressing an NH2-terminal truncated αENaC to interrupt normal channel trafficking and found it suppressed migration. Prolonged exposure (48 h) of RAW 264.7 cells to proinflammatory cytokines interferon γ (IFNγ) and/or tumor necrosis factor α (TNFα) inhibited RAW 264.7 migration and abolished the amiloride (1 µM)-sensitive component of migration, a finding consistent with ENaC downregulation. To determine if proinflammatory cytokines regulate αENaC protein expression, cells were exposed to proinflammatory cytokines IFNγ (10 ng/mL, last 48 h) and TNFα (10 ng/mL, last 24 h). By Western blot analysis, we found whole cell αENaC protein is reduced ≥50%. Immunofluorescence demonstrated heterogeneous αENaC inhibition. Finally, we found that overnight exposure to amiloride stimulated morphological changes and increased polarization marker expression. Our findings suggest that ENaC may be a critical molecule in macrophage migration and polarization.

Urokinase-Type Plasminogen Activator Enhances the Neuroprotective Activity of Brain-Derived Neurotrophic Factor in a Model of Intracerebral Hemorrhage

Brain-derived neurotrophic factor (BDNF) is a classic neuroprotective and pro-regenerative factor in peripheral and central nervous tissue. Its ability to stimulate the restoration of damaged nerve and brain tissue after ischemic stroke and intraventricular hemorrhage has been demonstrated. However, the current concept of regeneration allows us to assert that one factor, even if essential, cannot be the sole contributor to this complex biological process. We have previously shown that urokinase-type plasminogen activator (uPA) complements BDNF activity and stimulates restoration of nervous tissue. Using a model of intracerebral hemorrhage in rats, we investigated the neurotrophic and neuroprotective effect of BDNF combined with uPA. The local simultaneous administration of BDNF and uPA provided effective neuroprotection of brain tissue after intracerebral hemorrhage, promoted survival of experimental animals and their neurological recovery, and decreased lesion volume. The study of cellular mechanisms of the observed neurotrophic effect of BDNF and uPA combination revealed both known mechanisms (neuronal survival and neurite growth) and new ones (microglial activation) that had not been shown for BDNF and uPA. Our findings support the concept of using combinations of biological factors with diverse but complementary mechanisms of action as a promising regenerative approach.

Modulation of Cellular Function by the Urokinase Receptor Signalling: A Mechanistic View

Urokinase-type plasminogen activator receptor (uPAR or CD87) is a glycosyl-phosphatidyl-inositol anchored (GPI) membrane protein. The uPAR primary ligand is the serine protease urokinase (uPA), converting plasminogen into plasmin, a broad spectrum protease, active on most extracellular matrix components. Besides uPA, the uPAR binds specifically also to the matrix protein vitronectin and, therefore, is regarded also as an adhesion receptor. Complex formation of the uPAR with diverse transmembrane proteins, including integrins, formyl peptide receptors, G protein-coupled receptors and epidermal growth factor receptor results in intracellular signalling. Thus, the uPAR is a multifunctional receptor coordinating surface-associated pericellular proteolysis and signal transduction, thereby affecting physiological and pathological mechanisms. The uPAR-initiated signalling leads to remarkable cellular effects, that include increased cell migration, adhesion, survival, proliferation and invasion. Although this is beyond the scope of this review, the uPA/uPAR system is of great interest to cancer research, as it is associated to aggressive cancers and poor patient survival. Increasing evidence links the uPA/uPAR axis to epithelial to mesenchymal transition, a highly dynamic process, by which epithelial cells can convert into a mesenchymal phenotype. Furthermore, many reports indicate that the uPAR is involved in the maintenance of the stem-like phenotype and in the differentiation process of different cell types. Moreover, the levels of anchor-less, soluble form of uPAR, respond to a variety of inflammatory stimuli, including tumorigenesis and viral infections. Finally, the role of uPAR in virus infection has received increasing attention, in view of the Covid-19 pandemics and new information is becoming available. In this review, we provide a mechanistic perspective, via the detailed examination of consolidated and recent studies on the cellular responses to the multiple uPAR activities.

Discovery of a novel inhibitor against urokinase-type plasminogen activator, a potential enzyme with a role in atherosclerotic plaque instability

The buildup of lipids, cholesterol, and other substances in and on the walls of the arteries is known as atherosclerosis and deposition is known as atherosclerotic plaque. Urokinase-type plasminogen activator (uPA) has multiple roles in the atherosclerotic plaque formation and even work simultaneously in making the atherosclerotic plaque unstable. Extracellular matrix plays a major role in the plaque remodeling and rapture. In this study, we have accessed that a higher interaction was observed in the molecular interaction score for uPA with ZINC380065722 having a GOLD fitness score of about 67.60, which is much higher as compared to the known standard inhibitor UK 122 which has reported an interaction score of 59.14. Ser217 and Asp192 are found to be the key amino acid residues in almost all the interactions. Protein frustration analysis has shown that these amino acid residues play a crucial role in the retention of the active pocket conformation and any mutation of these two residues can causes serious decrease in the overall function of the protein. It was observed that the molecule ZINC380065722 remained bound to the protein till 100 ns of simulation time. The average SASA for the apo-uPA and uPA-ligand complex was found to be stable. The network of hydrogen bonds for the intramolecular protein secondary structure and with the solvent system for the apo-protein and the uPA-ligand complex was found to be consistent.Communicated by Ramaswamy H. Sarma.

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.

Gene Expression Profiling of Apoptotic Proteins in Circulating Peripheral Blood Mononuclear Cells in Type II Diabetes Mellitus and Modulation by Metformin

INTRODUCTION

Insulin resistance in obesity and type 2 diabetes mellitus (T2DM) is associated with cardiovascular complications such as atherosclerosis. On the other hand, the reduction of apoptosis in macrophages has been linked with accelerated atherosclerosis. Apoptosis is controlled by a different family of proteins including Bcl-2 and caspases.

METHODS

To examine apoptosis in insulin resistance, we assessed the mRNA expression by qRT-PCR of several Bcl-2 family members, as well as caspase-3, -7, -8, and -9 in peripheral blood mononuclear cells (PBMCs) isolated from lean, obese, diabetic, and diabetic on metformin individuals.

RESULTS

PBMCs of diabetic individuals exhibited reduced expression of caspase-7 and increased expression of Bcl-10, Bad, Bax, Bid, and caspase-3. T2DM on metformin group had significantly higher Bad, Bax, and caspase-7 expression.

DISCUSSION

The moderate up-regulation of pro-apoptotic Bcl-10, Bax, Bad, Bid, and the effector caspase-3 coupled with inhibition of caspase-7 in circulating PBMCs of T2DM could be the result of increased inflammation in T2DM. Metformin treatment significantly inhibited the expression of Bcl-10, Bid, and caspase-3 and upregulated Bad/Bax/caspase-7 pathway suggesting the activation of Bad/Bax/caspase-7 apoptotic pathway. Further studies are warranted to elicit the underlying apoptotic pathways of PBMCs in T2DM and following metformin treatment.

Resolution of Deep Venous Thrombosis: Proposed Immune Paradigms

Venous thromboembolism (VTE) is a pathology encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE) associated with high morbidity and mortality. Because patients often present after a thrombus has already formed, the mechanisms that drive DVT resolution are being investigated in search of treatment. Herein, we review the current literature, including the molecular mechanisms of fibrinolysis and collagenolysis, as well as the critical cellular roles of macrophages, neutrophils, and endothelial cells. We propose two general models for the operation of the immune system in the context of venous thrombosis. In early thrombus resolution, neutrophil influx stabilizes the tissue through NETosis. Meanwhile, macrophages and intact neutrophils recognize the extracellular DNA by the TLR9 receptor and induce fibrosis, a complimentary stabilization method. At later stages of resolution, pro-inflammatory macrophages police the thrombus for pathogens, a role supported by both T-cells and mast cells. Once they verify sterility, these macrophages transform into their pro-resolving phenotype. Endothelial cells both coat the stabilized thrombus, a necessary early step, and can undergo an endothelial-mesenchymal transition, which impedes DVT resolution. Several of these interactions hold promise for future therapy.

SerpinB2 inhibits migration and promotes a resolution phase signature in large peritoneal macrophages

SerpinB2 (plasminogen activator inhibitor type 2) has been called the “undecided serpin” with no clear consensus on its physiological role, although it is well described as an inhibitor of urokinase plasminogen activator (uPA). In macrophages, pro-inflammatory stimuli usually induce SerpinB2; however, expression is constitutive in Gata6+ large peritoneal macrophages (LPM). Interrogation of expression data from human macrophages treated with a range of stimuli using a new bioinformatics tool, CEMiTool, suggested that SerpinB2 is most tightly co- and counter-regulated with genes associated with cell movement. Using LPM from SerpinB2^−/− and SerpinB2^R380A (active site mutant) mice, we show that migration on Matrigel was faster than for their wild-type controls. Confocal microscopy illustrated that SerpinB2 and F-actin staining overlapped in focal adhesions and lamellipodia. Genes associated with migration and extracellular matrix interactions were also identified by RNA-Seq analysis of migrating RPM from wild-type and SerpinB2^R380A mice. Subsequent gene set enrichment analyses (GSEA) suggested SerpinB2 counter-regulates many Gata6-regulated genes associated with migration. These data argue that the role of SerpinB2 in macrophages is inhibition of uPA-mediated plasmin generation during cell migration. GSEA also suggested that SerpinB2 expression (likely via ensuing modulation of uPA-receptor/integrin signaling) promotes the adoption of a resolution phase signature.

Estramustine Phosphate Inhibits TGF-β-Induced Mouse Macrophage Migration and Urokinase-Type Plasminogen Activator Production

Transforming growth factor-beta (TGF-β) has been demonstrated as a key regulator of immune responses including monocyte/macrophage functions. TGF-β regulates macrophage cell migration and polarization, as well as it is shown to modulate macrophage urokinase-type plasminogen activator (uPA) production, which also contributes to macrophage chemotaxis and migration toward damaged or inflamed tissues. Microtubule (MT) cytoskeleton dynamic plays a key role during the cell motility, and any interference on the MT network profoundly affects cell migration. In this study, by using estramustine phosphate (EP), which modifies MT stability, we analysed whether tubulin cytoskeleton contributes to TGF-β-induced macrophage cell migration and uPA expression. We found out that, in the murine macrophage cell line RAW 264.7, EP at noncytotoxic concentrations inhibited cell migration and uPA expression induced by TGF-β. Moreover, EP greatly reduced the capacity of TGF-β to trigger the phosphorylation and activation of its downstream Smad3 effector. Furthermore, Smad3 activation seems to be critical for the increased cell motility. Thus, our data suggest that EP, by interfering with MT dynamics, inhibits TGF-β-induced RAW 264.7 cell migration paralleled with reduction of uPA induction, in part by disabling Smad3 activation by TGF-β.

The Inhibition of Oxidised Low-Density Lipoprotein-Induced Apoptosis of Macrophages by Recombinant Human Brain Natriuretic Peptide and the Underlying Mechanism

OBJECTIVE

Macrophage apoptosis plays a key role in atherosclerotic plaque rupture. This study investigated the effects of recombinant human brain natriuretic peptide (BNP) on oxidised low-density lipoprotein (ox-LDL)-induced macrophage apoptosis and explored the underlying mechanism.

METHODS

A model of ox-LDL-induced macrophage injury was established to evaluate the role of BNP. Flow cytometry was employed to detect apoptosis and changes in mitochondrial membrane potential (x0394;x03A8;m), and confocal microscopy was used to determine cellular reactive oxygen species (ROS) levels. Additionally, reverse transcription-polymerase chain reaction and colourimetry were used to detect the mRNA expression and activity, respectively, of superoxide dismutase (SOD) and malondialdehyde (MDA).

RESULTS

Ox-LDL induced macrophage apoptosis in a concentration-dependent manner, and maximum apoptosis occurred at 100 μg/ml ox-LDL (45.62 ± 2.76 vs. 6.84 ± 1.94%; p < 0.05). Conversely, BNP suppressed macrophage apoptosis, with a maximal effect at 10-9 mol/l (18.56 ± 1.79%; p < 0.05). Compared with the control group, intracellular ROS levels increased, x0394;x03A8;m decreased, SOD mRNA expression and activity decreased and MDA mRNA expression and content increased in the 100-μg/ml ox-LDL group (527.30 ± 36.20 vs. 100.00 ± 0.00%, 3.01 ± 0.52 vs. 9.67 ± 0.51%, 0.53 ± 0.18 vs. 1.00 ± 0.00, 256.6 ± 8.20 vs. 355.8 ± 9.58 U/ml, 1.59 ± 0.23 vs. 1.00 ± 0.00 and 29.4 ± 1.68 vs. 5.94 ± 0.51 nmol/ml; p < 0.05); these effects were significantly counteracted by 10-9 mol/l BNP (237.30 ± 30.62%, 6.55 ± 1.57%, 0.90 ± 0.07, 310.4 ± 2.97 U/ml, 1.14 ± 0.10, 20.54 ± 1.55 nmol/ml; p < 0.05).

CONCLUSION

BNP attenuates ox-LDL-induced macrophage apoptosis by suppressing oxidative stress and preventing x0394;x03A8;m loss.

Tissue invasion and metastasis: Molecular, biological and clinical perspectives

Cancer is a key health issue across the world, causing substantial patient morbidity and mortality. Patient prognosis is tightly linked with metastatic dissemination of the disease to distant sites, with metastatic diseases accounting for a vast percentage of cancer patient mortality. While advances in this area have been made, the process of cancer metastasis and the factors governing cancer spread and establishment at secondary locations is still poorly understood. The current article summarizes recent progress in this area of research, both in the understanding of the underlying biological processes and in the therapeutic strategies for the management of metastasis. This review lists the disruption of E-cadherin and tight junctions, key signaling pathways, including urokinase type plasminogen activator (uPA), phosphatidylinositol 3-kinase/v-akt murine thymoma viral oncogene (PI3K/AKT), focal adhesion kinase (FAK), β-catenin/zinc finger E-box binding homeobox 1 (ZEB-1) and transforming growth factor beta (TGF-β), together with inactivation of activator protein-1 (AP-1) and suppression of matrix metalloproteinase-9 (MMP-9) activity as key targets and the use of phytochemicals, or natural products, such as those from Agaricus blazei, Albatrellus confluens, Cordyceps militaris, Ganoderma lucidum, Poria cocos and Silybum marianum, together with diet derived fatty acids gamma linolenic acid (GLA) and eicosapentanoic acid (EPA) and inhibitory compounds as useful approaches to target tissue invasion and metastasis as well as other hallmark areas of cancer. Together, these strategies could represent new, inexpensive, low toxicity strategies to aid in the management of cancer metastasis as well as having holistic effects against other cancer hallmarks.

A urokinase receptor-Bim signaling axis emerges during EGFR inhibitor resistance in mutant EGFR glioblastoma

EGFR is the most common genetically altered oncogene in glioblastoma (GBM), but small-molecule EGFR tyrosine kinase inhibitors (TKI) have failed to yield durable clinical benefit. Here, we show that in two novel model systems of acquired resistance to EGFR TKIs, elevated expression of urokinase plasminogen activator (uPA) drives signaling through the MAPK pathway, which results in suppression of the proapoptotic BCL2-family member protein BIM (BCL2L11). In patient-derived GBM cells and genetic GBM models, uPA is shown to suppress BIM levels through ERK1/2 phosphorylation, which can be reversed by siRNA-mediated knockdown of uPA. TKI-resistant GBMs are resensitized to EGFR TKIs by pharmacologic inhibition of MEK or a BH3 mimetic drug to replace BIM function. A link between the uPA-uPAR-ERK1/2 pathway and BIM has not been previously demonstrated in GBM, and involvement of this signaling axis in resistance provides rationale for a new strategy to target EGFR TKI-resistant GBM.

Urokinase-type plasminogen activator (uPA) stimulates triglyceride synthesis in Huh7 hepatoma cells via p38-dependent upregulation of DGAT2

OBJECTIVE

The liver is the central organ of fatty acid and triglyceride metabolism. Oxidation and synthesis of fatty acids and triglycerides is under the control of peroxisome-proliferator-activated receptors (PPAR) α. Impairment of these receptors' function contributes to the accumulation of triglycerides in the liver resulting in non-alcoholic fatty liver disease. Urokinase-type plasminogen activator (uPA) was shown to regulate gene expression in the liver involving PPARγ transcriptional activity. In this study we questioned whether uPA modulates triglyceride metabolism in the liver, and investigated the mechanisms involved in the observed processes.

METHODS AND RESULTS

Huh7 hepatoma cells were incubated with increasing concentrations of uPA for 24 h uPA dose-dependently increased the cellular triglyceride mass, and this effect resulted from increased de novo triglyceride synthesis mediated by the enzyme diglyceride acyltransferase 2 (DGAT2). Also, the amount of free fatty acids was highly up regulated by uPA through activation of the transcription factor SREBP-1. Chemical activation of PPARα further increased uPA-stimulated triglyceride synthesis, whereas inhibition of p38, an upstream activator of PPARα, completely abolished the stimulatory effect of uPA on both triglyceride synthesis and DGAT2 upregulation. The effect of uPA on triglyceride synthesis in Huh7 cells was mediated via binding to its receptor, the uPAR. In vivo studies in uPAR(-/-) mice demonstrated that no lipid droplets were observed in their livers compared to C57BL/6 mice and the triglyceride levels were significantly lower.

CONCLUSION

This study presents a new biological function of the uPA/uPAR system in the metabolism of triglycerides and might present a new target for an early therapeutic intervention for NAFLD.