Plasminogen activator inhibitor-1 and vitronectin expression level and stoichiometry regulate vascular smooth muscle cell migration through physiological collagen matrices

Interleukin-1β and plasminogen activating system members in endometriotic stromal cell migration/invasion

OBJECTIVE

To study the role of interleukin (IL)-1β and the plasminogen activating (PA) system members in endometriotic stromal cell (ESC) migration/invasion.

DESIGN

Primary cultures of ESCs.

SETTING

Tertiary referral center for endometriosis and pelvic pain.

PATIENT(S)

Patients with surgically excised endometriosis.

INTERVENTION(S)

Interleukin-1β stimulation of primary cultures of ESCs and knockdown of the PA system members urokinase plasminogen activator (uPA), uPA receptor, and plasminogen activator inhibitor-1 (PAI-1).

MAIN OUTCOME MEASURE(S)

Invasion/migration assays.

RESULT(S)

In primary cultures, IL-1β-stimulated ESC production of the PA system members uPA, uPA receptor, and PAI-1. Interleukin-1β also enhanced ESC migration and invasion, and these effects were inhibited by the IL-1 receptor-1 antagonist anakinra. Knockdown of each of the 3 PA system members also inhibited ESC migration and invasion. Knockdown of these PA system members further attenuated the impact of IL-1β on migration and invasion, suggesting that they mediated the promigration and proinvasion effects of IL-1β. To supplement the cell culture work, immunohistochemistry was performed on tissue sections of endometriotic epithelium/stroma: uPA, PAI-1, and IL-1β histoscores were not found to be correlated with each other.

CONCLUSION(S)

In primary cultures of ESCs, IL-1β induces migration and invasion, which is mediated by PA system members and inhibited by the drug anakinra. However, the immunohistochemistry expression of IL-1β, urokinase plasminogen inhibitor-1, and PAI-1 were not correlated, suggesting other regulatory mechanisms for PA system members. Inhibition of IL-1β (e.g., with anakinra) may have potential as a novel treatment approach for the migration/invasion of endometriosis.

"Super" SERPINs-A stabilizing force against fibrinolysis in thromboinflammatory conditions

The superfamily of serine protease inhibitors (SERPINs) are a class of inhibitors that utilise a dynamic conformational change to trap and inhibit their target enzymes. Their powerful nature lends itself well to regulation of complex physiological enzymatic cascades, such as the haemostatic, inflammatory and complement pathways. The SERPINs α2-antiplasmin, plasminogen-activator inhibitor-1, plasminogen-activator inhibitor-2, protease nexin-1, and C1-inhibitor play crucial inhibitory roles in regulation of the fibrinolytic system and inflammation. Elevated levels of these SERPINs are associated with increased risk of thrombotic complications, obesity, type 2 diabetes, and hypertension. Conversely, deficiencies of these SERPINs have been linked to hyperfibrinolysis with bleeding and angioedema. In recent years SERPINs have been implicated in the modulation of the immune response and various thromboinflammatory conditions, such as sepsis and COVID-19. Here, we highlight the current understanding of the physiological role of SERPINs in haemostasis and inflammatory disease progression, with emphasis on the fibrinolytic pathway, and how this becomes dysregulated during disease. Finally, we consider the role of these SERPINs as potential biomarkers of disease progression and therapeutic targets for thromboinflammatory diseases.

Correlations between vitronectin, miR-520, and miR-34 in patients with stenosis of coronary arteries

BACKGROUND

In-stent restenosis usually occurs by platelet activation, neointima formation, VSMC migration, and proliferation in the position of the vessel stent. The monocytes have a magnificent role in neointimal hyperplasia since these cells recruit to the site of vessel injury through chemokines and other secretion proteins. This study is focused on the investigation of vitronectin, miR-193, miR-34, and miR-520 expression levels in PBMCs isolated from stenosed patients.

METHODS

A total of sixty subjects undergoing coronary artery angiography containing patients with stent no restenosis (n = 20), in-stent restenosis (n = 20), and healthy participants (n = 20) participated in the study. The vitronectin, miR-193, miR-34, and miR-520 expression levels were measured by the RT-qPCR technique. Data were analyzed by SPSS software.

RESULTS

The vitronectin, miR-34, and miR-520 expression levels changed significantly in patients with vessel in-stent restenosis (p = 0.02, p = 0.02, and p = 0.01, respectively). Furthermore, there were inverse correlations between the expression levels of vitronectin gene and miR-34 (r =  - 0.44, p = 0.04) as well as miR-520 (r =  - 0.5, p=0.01).

CONCLUSIONS

The molecular events in the vessel stenosis may be affected by targeting vitronectin with miR-520 and miR-34.

A risk model developed based on tumor microenvironment predicts overall survival and associates with tumor immunity of patients with lung adenocarcinoma

Tumor microenvironment (TME) has been reported to exhibit a crucial effect in lung cancer. Therefore, this study was aimed to investigate the genes associated with TME and develop a risk score to predict the overall survival (OS) of patients with lung adenocarcinoma (LUAD) based on these genes. The immune and stromal scores were generated by the ESTIMATE algorithm for LUAD patients in The Cancer Genome Atlas (TCGA) database. Differentially expressed gene and weighted gene co-expression network analyses were used to derive immune- and stromal-related genes. The Least Absolute Shrinkage and Selection Operator (LASSO)-Cox regression was applied for further selection and the selected genes were inputted into stepwise regression to develop TME-related risk score (TMErisk) which was further validated in Gene Expression Omnibus (GEO) datasets. TMErisk-related biological phenotypes were analyzed in function enrichment, tumor immune signature, and tumor mutation signature. The patient's response to immunotherapy was inferred by the tumor immune dysfunction and exclusion (TIDE) score and immunophenoscore (IPS). According to our results, TMErisk was developed based on SERPINE1, CX3CR1, CD200R1, GBP1, IRF1, STAP1, LOX, and OR7E47P. Furthermore, high TMErisk was identified as a poor factor for OS in TCGA and GEO datasets, as well as in subgroup analysis with different gender, smoking status, age, race, anatomic site, therapies, and tumor-node-metastasis (TNM) stages. Higher TMErisk is also associated negatively with the abundance of B cells, CD4+ T cells, CD8+ T cells, neutrophils, macrophages, and other stromal or immune cells. Several genes of the human leukocyte antigen (HLA) family and immune checkpoints were less expressed in the high-TMErisk group. Mutations of 19 genes occurred more frequently in the high-TMErisk group. These mutations may be associated with TME change and indicate patients' response to immunotherapy. According to our analyses, a lower TMErisk score may indicate better response and OS outcome of immunotherapy.

Circulating miR-30c as a predictive biomarker of type 2 diabetes mellitus with coronary heart disease by regulating PAI-1/VN interactions

AIMS

Type 2 diabetes mellitus (DM2) is associated with coronary heart disease (CHD) and is characterized by high levels of plasminogen activator inhibitor (PAI)-1. Circulating microRNAs have been reported as potential diagnostic biomarkers for DM2 and CHD. However, the underlying mechanisms have largely remained unclear.

MAIN METHODS

The changes of circulating miR-30c, PAI-1 and vitronetin (VN) in plasma from CHD, noncomplicated (NC) + DM2, CHD + DM2 subjects and control individuals were assessed by quantitative reverse transcription PCR (qRT-PCR) and ELISA assays, respectively. The effects of miR-30c on VN expression by targeting PAI-1 were assessed in vitro SMC and in ex vivo plasma, using bioinformatic analysis, miRNA transfection, luciferase assays, qRT-PCR and western blot, respectively.

KEY FINDINGS

We found that decreased circulating miR-30c was negatively correlated with the severity of coronary lesions and the resulting elevated PAI-1 and VN levels. Circulating miR-30c significantly distinguished between patients with CHD + DM2, NC + DM2, CHD and control subjects, and that were significantly associated with certain risk factors for progression from a normal individual to one with CHD + DM2. Furthermore, we also showed that miR-30c plays a previously unrecognized role in regulating the expression of VN levels via regulating PAI-1 levels in vitro SMC and in ex vivo plasma.

SIGNIFICANCE

These findings provide a novel regulatory mechanism of miR-30c in regulating PAI-1/VN interactions and that may serve as a diagnostic biomarker of DM2 that is complicated with CHD.

Identification of SERPINE1 as a Regulator of Glioblastoma Cell Dispersal with Transcriptome Profiling

High mortality rates of glioblastoma (GBM) patients are partly attributed to the invasive behavior of tumor cells that exhibit extensive infiltration into adjacent brain tissue, leading to rapid, inevitable, and therapy-resistant recurrence. In this study, we analyzed transcriptome of motile (dispersive) and non-motile (core) GBM cells using an in vitro spheroid dispersal model and identified SERPINE1 as a modulator of GBM cell dispersal. Genetic or pharmacological inhibition of SERPINE1 reduced spheroid dispersal and cell adhesion by regulating cell-substrate adhesion. We examined TGFβ as a potential upstream regulator of SERPINE1 expression. We also assessed the significance of SERPINE1 in GBM growth and invasion using TCGA glioma datasets and a patient-derived orthotopic GBM model. SERPINE1 expression was associated with poor prognosis and mesenchymal GBM in patients. SERPINE1 knock-down in primary GBM cells suppressed tumor growth and invasiveness in the brain. Together, our results indicate that SERPINE1 is a key player in GBM dispersal and provide insights for future anti-invasive therapy design.

Pancreatic stellate cells activated by mutant KRAS-mediated PAI-1 upregulation foster pancreatic cancer progression via IL-8

Background: The dense fibrotic stroma enveloping pancreatic tumors is a major cause of drug resistance. Pancreatic stellate cells (PSCs) in the stroma can be activated to induce intra-tumor fibrosis and worsen patient survival; however, the molecular basics for the regulation of PSC activation remains unclear.

Methods: The in vitro coculture system was used to study cancer cell-PSC interactions. Atomic force microscopy was used to measure the stiffness of tumor tissues and coculture gels. Cytokine arrays, qPCR, and Western blotting were performed to identify the potential factors involved in PSC activation and to elucidate underlying pathways.

Results: PSC activation characterized by α-SMA expression was associated with increased pancreatic tumor stiffness and poor prognosis. Coculture with cancer cells induced PSC activation, which increased organotypic coculture gel stiffness and cancer cell invasion. Cancer cells-derived PAI-1 identified from coculture medium could activate PSCs, consistent with pancreatic cancer tissue microarray analysis showing a strong positive correlation between PAI-1 and α-SMA expression. Suppression by knocking down PAI-1 in cancer cells demonstrated the requirement of PAI-1 for coculture-induced PSC activation and gel stiffness. PAI-1 could be upregulated by KRAS in pancreatic cancer cells through ERK. In PSCs, inhibition of LRP-1, ERK, and c-JUN neutralized the effect of PAI-1, suggesting the contribution of LRP-1/ERK/c-JUN signaling. Furthermore, activated PSCs might exacerbate malignant behavior of cancer cells via IL-8 because suppression of IL-8 signaling reduced pancreatic tumor growth and fibrosis in vivo.

Conclusions: KRAS-mutant pancreatic cancer cells can activate PSCs through PAI-1/LRP-1 signaling to promote fibrosis and cancer progression.

Association between plasminogen activator inhibitor-1 and cardiovascular events: a systematic review and meta-analysis

Background

Small studies have implicated plasminogen activator inhibitor-1 (PAI-1) as a predictor of cardiovascular events; however, these findings have been inconsistent.

We sought out to examine the potential role of PAI-1 as a marker for major adverse cardiovascular events (MACE).

Methods

We systematically reviewed all indexed studies examining the association between PAI-1 and MACE (defined as death, myocardial infarction, or cerebrovascular accident) or restenosis. EMBASE, Web of Science, Medline, and the Cochrane Library were searched through October 2016 to identify relevant studies, supplemented by letters to authors and review of citations. Studies reporting the results of PAI-1 antigen and/or activity levels in association with MACE in human subjects were included.

Results

Of 5961 articles screened, we identified 38 articles published between 1991 to 2016 that reported PAI-1 levels in 11,557 patients. In studies that examined PAI-1 antigen and activity levels, 15.1% and 29.6% of patients experienced MACE, respectively. Patients with MACE had higher PAI-1 antigen levels with a mean difference of 6.11 ng/mL (95% CI, 3.27-8.96). This finding was similar among patients with and without known coronary artery disease. Comparatively, studies that stratified by PAI-1 activity levels were not associated with MACE. In contrast, studies of coronary restenosis suggest PAI-1 antigen and activity levels are negatively associated with MACE.

Conclusions

Elevated plasma PAI-1 antigen levels are associated with MACE. Definitive studies are needed to ascertain if PAI-1 acts simply as a marker of risk or if it is indeed a bona fide therapeutic target.

Electronic supplementary material

The online version of this article (10.1186/s12959-018-0166-4) contains supplementary material, which is available to authorized users.

Platelets, inflammation and tissue regeneration

Blood platelets have long been recognised to bring about primary haemostasis with deficiencies in platelet production and function manifesting in bleeding while upregulated function favourises arterial thrombosis. Yet increasing evidence indicates that platelets fulfil a much wider role in health and disease. First, they store and release a wide range of biologically active substances including the panoply of growth factors, chemokines and cytokines released from α-granules. Membrane budding gives rise to microparticles (MPs), another active participant within the blood stream. Platelets are essential for the innate immune response and combat infection (viruses, bacteria, micro-organisms). They help maintain and modulate inflammation and are a major source of pro-inflammatory molecules (e.g. P-selectin, tissue factor, CD40L, metalloproteinases). As well as promoting coagulation, they are active in fibrinolysis; wound healing, angiogenesis and bone formation as well as in maternal tissue and foetal vascular remodelling. Activated platelets and MPs intervene in the propagation of major diseases. They are major players in atherosclerosis and related diseases, pathologies of the central nervous system (Alzheimers disease, multiple sclerosis), cancer and tumour growth. They participate in other tissue-related acquired pathologies such as skin diseases and allergy, rheumatoid arthritis, liver disease; while, paradoxically, autologous platelet-rich plasma and platelet releasate are being used as an aid to promote tissue repair and cellular growth. The above mentioned roles of platelets are now discussed.

Plasminogen activator inhibitor-1 regulates the vascular expression of vitronectin

Essentials Vitronectin (VN) is produced by smooth muscle cells (SMCs) and promotes neointima formation. We studied the regulation of vascular VN expression by plasminogen activator inhibitor-1 (PAI-1). PAI-1 stimulates VN gene expression in SMCs by binding LDL receptor-related protein 1. Stimulation of VN gene expression may be a mechanism by which PAI-1 controls vascular remodeling.

SUMMARY

Background Increased expression of vitronectin (VN) by smooth muscle cells (SMCs) promotes neointima formation after vascular injury, and may contribute to chronic vascular diseases, such as atherosclerosis. However, the molecular regulation of vascular VN expression is poorly defined. Given the overlapping expression profiles and functions of VN and plasminogen activator inhibitor (PAI)-1, we hypothesized that PAI-1 regulates vascular VN expression. Objectives To determine whether PAI-1 regulates VN expression in SMCs and in vivo. Methods The effects of genetic alterations in PAI-1 expression, pharmacologic PAI-1 inhibition and recombinant PAI-1 on SMC VN expression were studied, and vascular VN expression in wild-type (WT) and PAI-1-deficient mice was assessed. Results VN expression was significantly lower in PAI-1-deficient SMCs and significantly increased in PAI-1-overexpressing SMCs. PAI-1 small interfering RNA and pharmacologic PAI-1 inhibition significantly decreased SMC VN expression. Recombinant PAI-1 stimulated VN expression by binding LDL receptor-related protein-1 (LRP1), but another LRP1 ligand, α2 -macroglobulin, did not. As compared with WT controls, carotid artery VN expression was significantly lower in PAI-1-deficient mice and significantly higher in PAI-1-transgenic mice. In a vein graft (VG) model of intimal hyperplasia, VN expression was significantly attenuated in PAI-1-deficient VGs as compared with WT controls. The plasma VN concentration was significantly decreased in PAI-1-deficient mice versus WT controls at 4 weeks, but not at 5 days or 8 weeks, after surgery. Conclusions PAI-1 stimulates SMC VN expression by binding LRP1, and controls vascular VN expression in vivo. Autocrine regulation of vascular VN expression by PAI-1 may play important roles in vascular homeostasis and pathologic vascular remodeling.

Mechanisms of plasminogen activator inhibitor 1 action in stromal remodeling and related diseases

Plasminogen activator inhibitor type 1 (PAI-1) is the main physiologic inhibitor of fibrinolysis. However, it is also involved in many physiological processes such as extracellular matrix (ECM) proteolysis and remodeling, cell adhesion, motility, and apoptosis, angiogenesis, etc. The aim of the study was to summarize current knowledge and gain insights into the mechanisms of PAI-1 action in the processes of stromal remodeling and diseases with considerable matrix pathologies (atherosclerosis, tissue fibrosis, cancer metastasis, pregnancy related complications, etc). As a component of an early cellular response to injury, PAI-1 reacts with membrane surface proteins and participates in the initiation of intracellular signaling, specifically cytoskeletal reorganization and motility. Complexity of ECM homeostasis resides in varying relation of the plasminogen system components and other matrix constituents. Inflammatory mediators (transforming growth factor-β and interferon-γ) and hormones (angiotensin II) are in the close interdependent relation with PAI-1. Also, special attention is devoted to the role of increased PAI-1 concentrations due to the common 4G/5G polymorphism. Some of the novel mechanisms of ECM modification consider PAI-1 dependent stabilization of urokinase mediated cell adhesion, control of the vascular endothelial cadherin trafficking and interaction with endothelial cells proteasome, its relation to matrix metalloproteinase 2 and osteopontin, and oxidative inhibition by myeloperoxidase. Targeting and/or alteration of PAI-1 functions might bring benefit to the future therapeutic approaches in diseases where ECM undergoes substantial remodeling.

Resolving distinct molecular origins for copper effects on PAI-1

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

The nuclear receptor NOR-1/NR4A3 regulates the multifunctional glycoprotein vitronectin in human vascular smooth muscle cells

The nuclear receptor NOR-1 (NR4A3) has recently been involved in the regulation of extracellular matrix (ECM) proteins associated with neointimal thickening and the vascular control of hemostasis. We sought to find as-yet unidentified NOR-1 target genes in human vascular smooth muscle cells (VSMCs). An in silico analysis identified putative NOR-1 response elements in the proximal promoter region of several genes encoding for ECM proteins, including vitronectin (VTN). Lentiviral overexpression of NOR-1 strongly increased VTN mRNA and protein levels, whereas NOR-1 silencing significantly reduced VTN expression. Deletion and site-directed mutagenesis studies, as well as EMSA and chromatin immunoprecipitation, identified the NBRE(-202/-195) site in the VTN promoter as an essential element for NOR-1 responsiveness. Furthermore, NOR-1 and VTN colocalized in VSMCs in human atherosclerotic lesions. VTN levels were increased in cell supernatants from VSMCs that overexpress NOR-1. Cell supernatants from VSMCs overexpressing NOR-1 induced cell migration to a greater extent than supernatants from control cells, and this effect was attenuated when cell supernatants were preincubated with anti-VTN blocking antibodies or VTN was silenced in supernatant-generating cells. These results indicate that VTN is a target of NOR-1 and suggest that this multifunctional glycoprotein may participate in vascular responses mediated by this nuclear receptor.-Martí-Pàmies, I., Cañes, L., Alonso, J., Rodríguez, C., Martínez-González, J. The nuclear receptor NOR-1/NR4A3 regulates the multifunctional glycoprotein vitronectin in human vascular smooth muscle cells.

Extracellular Vesicles Derived from Adipose Mesenchymal Stem Cells Regulate the Phenotype of Smooth Muscle Cells to Limit Intimal Hyperplasia

PURPOSE

Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) play important roles in the reduction of inflammation in multiple disease models. However, their role in vein graft (VG) remodeling is undefined. We aimed to investigate the effect of EVs from adipose MSCs (ADMSC-EVs) on VG intimal hyperplasia and to explore the possible mechanisms.

METHODS

After generation and characterization of control-EVs and ADMSC-EVs in vitro, we investigated their effect on the proliferation and migration of vascular smooth muscle cells (VSMCs) in vitro. Next, we established a mouse model of VG transplantation. Mice underwent surgery and received control-EVs or ADMSC-EVs by intraperitoneal injection every other day for 20 days. VG remodeling was evaluated after 4 weeks. We also assessed the effect of ADMSC-EVs on macrophage migration and inflammatory cytokine expression.

RESULTS

Significant inhibitory effects of ADMSC-EVs on in vitro VSMC proliferation (p < 0.05) and migration (p < 0.05) were observed compared with control-EVs. The extent of intimal hyperplasia was significantly decreased in ADMSC-EV-treated mice compared with control-EV-treated mice (26 ± 8.4 vs. 45 ± 9.0 μm, p < 0.05). A reduced presence of macrophages was observed in ADMSC-EV-treated mice (p < 0.05). Significantly decreased expression of inflammatory cytokines interleukin (IL)-6 and monocyte chemoattractant protein-1 (MCP-1) was also found in the ADMSC-EV-treated group (both p < 0.05). In addition, phosphorylation of Akt, Erk1/2, and p38 in VGs was decreased in the ADMSC-EV-treated group.

CONCLUSIONS

We demonstrated that ADMSC-EVs exert an inhibitory effect on VG neointima formation by regulating VSMC proliferation and migration, macrophage migration, inflammatory cytokine expression, and the related signaling pathways.

Pharmacological Targeting of Plasminogen Activator Inhibitor-1 Decreases Vascular Smooth Muscle Cell Migration and Neointima Formation

OBJECTIVE

Plasminogen activator inhibitor-1 (PAI-1), a serine protease inhibitor that promotes and inhibits cell migration, plays a complex and important role in adverse vascular remodeling. Little is known about the effects of pharmacological PAI-1 inhibitors, an emerging drug class, on migration of vascular smooth muscle cells (SMCs) and endothelial cells (ECs), crucial mediators of vascular remodeling. We investigated the effects of PAI-039 (tiplaxtinin), a specific PAI-1 inhibitor, on SMC and EC migration in vitro and vascular remodeling in vivo.

APPROACH AND RESULTS

PAI-039 inhibited SMC migration through collagen gels, including those supplemented with vitronectin and other extracellular matrix proteins, but did not inhibit migration of PAI-1-deficient SMCs, suggesting that its antimigratory effects were PAI-1-specific and physiologically relevant. However, PAI-039 did not inhibit EC migration. PAI-039 inhibited phosphorylation and nuclear translocation of signal transducers and activators of transcription-1 in SMCs, but had no discernable effect on signal transducer and activator of transcription-1 signaling in ECs. Expression of low-density lipoprotein receptor-related protein 1, a motogenic PAI-1 receptor that activates Janus kinase/signal transducers and activators of transcription-1 signaling, was markedly lower in ECs than in SMCs. Notably, PAI-039 significantly inhibited intimal hyperplasia and inflammation in murine models of adverse vascular remodeling, but did not adversely affect re-endothelialization after endothelium-denuding mechanical vascular injury.

CONCLUSIONS

PAI-039 inhibits SMC migration and intimal hyperplasia, while having no inhibitory effect on ECs, which seems to be because of differences in PAI-1-dependent low-density lipoprotein receptor-related protein 1/Janus kinase/signal transducer and activator of transcription-1 signaling between SMCs and ECs. These findings suggest that PAI-1 may be an important therapeutic target in obstructive vascular diseases characterized by neointimal hyperplasia.

Intra- and extracellular plasminogen activator inhibitor-1 regulate effect of vitronectin against radiation-induced endothelial cell death

Plasminogen activator inhibitor-1 (PAI-1) is induced by radiation resulting in endothelial cell impairment, potentially leading to multiple organ failure. Vitronectin (VN) is a 75-kDa glycoprotein (VN₇₅) cleaved into two forms (VN₇₅ or VN_65/10) by furin, which is regulated by intracellular PAI-1. VN protects against radiation-induced endothelial cell death, but the mechanisms involved in VN processing and its interactions with intra- and extracellular PAI-1 remain unclear. We examined these processes in cells in vitro using recombinant proteins or overexpression of VN and PAI-1 genes, including furin-susceptible (T³⁸¹) and furin-resistant VN (A³⁸¹). VN processing was analyzed using a mutant PAI-1 with relatively weaker binding to VN. VN function was evaluated by survival of radiation-damaged endothelial cells. Wild-type, but not mutant PAI-1 inhibited furin-dependent VN processing. Gene transfer revealed that furin-susceptible VN was processed more than the furin-resistant form, but processing of both was inhibited by PAI-1 overexpression. Intracellular PAI-1 formed a complex with VN₇₅ (T³⁸¹) in cells and media, and the VN₇₅ form was secreted preferentially. Only VN₇₅ protected against radiation-induced endothelial cell death, in which its effect was abolished by wild-type but not mutant PAI-1. These findings indicate that intracellular PAI-1 inhibits VN processing and protects against radiation-induced endothelial cell death.

TGF-β1-induced PAI-1 contributes to a profibrotic network in patients with eosinophilic esophagitis

BACKGROUND

Eosinophilic esophagitis (EoE) is an allergic disease of increasing worldwide incidence. Complications are due to tissue remodeling and involve TGF-β1-mediated fibrosis. Plasminogen activator inhibitor 1 (PAI-1/serpinE1) can be induced by TGF-β1, but its role in EoE is not known.

OBJECTIVE

We sought to understand the expression and role of PAI-1 in patients with EoE.

METHODS

We used esophageal biopsy specimens and plasma samples from control subjects and patients with EoE, primary human esophageal epithelial cells, and fibroblasts from patients with EoE in immunohistochemistry, quantitative PCR, and immunoassay experiments to understand the induction of PAI-1 by TGF-β1, the relationship between PAI-1 and esophageal fibrosis, and the role of PAI-1 in fibrotic gene expression.

RESULTS

PAI-1 expression was significantly increased in epithelial cells of biopsy specimens from patients with active EoE compared with that seen in biopsy specimens from patients with inactive EoE or control subjects (P < .001). Treatment of primary esophageal epithelial cells with recombinant TGF-β1 increased PAI-1 transcription, intracellular protein expression, and secretion. Esophageal PAI-1 expression correlated with basal zone hyperplasia, fibrosis, and markers of esophageal remodeling, including vimentin, TGF-β1, collagen I, fibronectin, and matrix metalloproteases, and plasma PAI-1 levels correlated with plasma TGF-β1 levels. PAI-1 inhibition significantly decreased baseline and TGF-β1-induced fibrotic gene expression.

CONCLUSIONS

PAI-1 expression is significantly increased in the epithelium in patients with EoE and reflects fibrosis, and its inhibition decreases TGF-β1-induced gene expression. Epithelial PAI-1 might serve as a marker of EoE severity and form part of a TGF-β1-induced profibrotic network.

The ADP antagonist MRS2179 regulates the phenotype of smooth muscle cells to limit intimal hyperplasia

PURPOSE

ADP plays an important part in platelet aggregation by activating P2Y1 and P2Y12 receptors. The ADP antagonist MRS2179 has been used in thrombosis-related treatments but its effects on vein graft (VG) remodeling is undefined. We examined the effect of MRS2179 on VG intimal hyperplasia and explored the mechanism of action.

METHODS

A mouse model of VG transplantation was established. Mice underwent surgery and received MRS2179 by intraperitoneal injection every other day for 3 weeks. VG remodeling was assessed 4-weeks later. Vascular smooth muscle cells (VSMCs) were isolated and treated with MRS2179. The effect of MRS2179 on the proliferation, migration and inflammatory-cytokine expression of VSMCs was also evaluated.

RESULTS

MRS2179 significantly inhibited VSMC proliferation compared with the control group. Significant inhibitory effects of MRS2179 on VSMC migration was observed in two-dimensional and three-dimensional models. The extent of intimal hyperplasia was significantly less in MRS2179 treated mice than in controls. Reduced migration of macrophage was found in MRS2179 treated mice. Expression of the inflammatory cytokines IL-1β and TNF-α was decreased significantly in the MRS2179 treated group. In addition, decreased phosphorylation was found on Akt, Erk1/2 and p38.

CONCLUSIONS

These data demonstrate that MRS2179 inhibits neointima formation in VGs by regulating the proliferation, and migration of VSMCs, macrophage migration, inflammatory-cytokine secretion and related signaling pathway. Our study provides novel insights regarding purinergic signaling in SMCs in vivo. The P2Y1 receptor may serve as a therapeutic target in neointima formation.

Distinct encounter complexes of PAI-1 with plasminogen activators and vitronectin revealed by changes in the conformation and dynamics of the reactive center loop

Plasminogen activator inhibitor-1 (PAI-1) is a biologically important serine protease inhibitor (serpin) that, when overexpressed, is associated with a high risk for cardiovascular disease and cancer metastasis. Several of its ligands, including vitronectin, tissue-type and urokinase-type plasminogen activator (tPA, uPA), affect the fate of PAI-1. Here, we measured changes in the solvent accessibility and dynamics of an important unresolved functional region, the reactive center loop (RCL), upon binding of these ligands. Binding of the catalytically inactive S195A variant of tPA to the RCL causes an increase in fluorescence, indicating greater solvent protection, at its C-terminus, while mobility along the loop remains relatively unchanged. In contrast, a fluorescence increase and large decrease in mobility at the N-terminal RCL is observed upon binding of S195A-uPA to PAI-1. At a site distant from the RCL, binding of vitronectin results in a modest decrease in fluorescence at its proximal end without restricting overall loop dynamics. These results provide the new evidence for ligand effects on RCL conformation and dynamics and differences in the Michaelis complex with plasminogen activators that can be used for the development of more specific inhibitors to PAI-1. This study is also the first to use electron paramagnetic resonance (EPR) spectroscopy to investigate PAI-1 dynamics.

SIGNIFICANCE

Balanced blood homeostasis and controlled cell migration requires coordination between serine proteases, serpins, and cofactors. These ligands form noncovalent complexes, which influence the outcome of protease inhibition and associated physiological processes. This study reveals differences in binding via changes in solvent accessibility and dynamics within these complexes that can be exploited to develop more specific drugs in the treatment of diseases associated with unbalanced serpin activity.

Activation of the D4 dopamine receptor attenuates proliferation and migration of vascular smooth muscle cells through downregulation of AT1a receptor expression

Angiotensin (Ang) II has an important role in the vascular smooth muscle cell (VSMC) proliferation and migration and subsequently in the development of vascular diseases, whereas dopamine has the opposite effect. Previous studies have shown an interaction between dopamine and AT(1) receptors in the kidney. The dopamine D(4) receptor is expressed in arteries and has an inhibitory effect on VSMC proliferation. We hypothesized that the D(4) receptor, through its interaction with the AT(1a) receptor, may have an inhibitory effect on Ang II-mediated VSMC proliferation and migration, which could have a pivotal role in hypertension-induced vascular remodeling. In the current study, we found that Ang II markedly induced the proliferation and migration of A10 cells, which was inhibited by the D(4) receptor agonist PD168077. The activation of the D(4) receptor by PD168077 inhibited AT(1a) receptor expression in a concentration- and time-dependent manner. These effects were attenuated by silencing the D(4) receptor with a D(4) receptor-targeting small interfering RNA. The D(4) receptor-mediated inhibition of AT(1) receptor function involved protein kinase A (PKA). The activation of the D(4) receptor by PD168077 increased PKA activity in A10 cells, and the presence of a PKA inhibitor (PKA inhibitor 14-22, 10(-7) mol l(-1) per 24 h) blocked the inhibitory effect of the D(4) receptor on AT(1) receptor expression and function. The inhibitory effect of the D(4) receptor on AT(1) receptor expression and function was preserved in VSMCs (primary culture) from spontaneously hypertensive rats relative to VSMCs from Wistar-Kyoto rats. In conclusion, our data provide insight into the regulatory role of the D(4) receptor on AT(1a) receptor expression and function in VSMCs and suggest that targeting the action of the D(4) receptor may represent an effective therapeutic approach for the treatment of cardiovascular diseases.

FZD2 inhibits the cell growth and migration of salivary adenoid cystic carcinomas

Several studies have reported that FZD2 regulates tumor biology in a complex manner. The aim of the present study was to identify the role of FZD2 in the cell growth and metastasis of salivary adenoid cystic carcinomas (SACCs). The expression of FZD2 in ACC-83 and ACC-LM cells were measured with real-time PCR. Immunohistochemical staining was used to detect the expression of FZD2 in clinical SACC samples with or without metastasis. Cell proliferation and Transwell assays were performed to explore the effects of FZD2 on cell growth and migration following the silencing of FZD2 with small interference RNAs and the overexpression of FZD2 with plasmid. Our data showed that FZD2 was downregulated in ACC-LM cells, which are an adenoid cystic carcinoma cell line with high metastatic potential, compared to ACC-83 cells, which have low metastatic potential. Additionally, the expression of FZD2 was lower in SACC tissues with metastasis compared to SACC tissues without metastasis (P<0.05). Cell proliferation and migration of ACC-83 cells were increased after the knockdown of FZD2 and decreased following overexpression of FZD2. Knockdown of FZD2 downregulated the expression of PAI-1. Our results suggest that FZD2 may be a tumor suppressor gene in SACCs that inhibits cell growth and migration.

Functionally stable plasminogen activator inhibitor-1 in a family with cardiovascular disease and vitiligo

Vitiligo is a common skin condition with a complex pathophysiology characterized by the lack of pigmentation due to melanocyte degeneration. In this study, we investigated PAI-1 antigen (Ag) and activity levels in a 34 year old male with extensive vascular disease, alopecia areata and vitiligo. Fasting PAI-1 Ag and activity levels were measured at 9 a.m. in the subject and family members. Both PAI-1 Ag (67 ± 38 vs. 18.6 ± 6.5 ng/ml, P < 0.001) and specific activity (15.8 ± 10.0 vs. 7.6 ± 6.0 IU/pmol, P < 0.04) levels of PAI-1 were moderately elevated in subjects compared to the controls. PAI-1 kinetic studies demonstrated a markedly enhanced stability of plasma PAI-1 activity in the family members. Specific activity at 16 h was significantly higher than expected activity levels (0.078 ± 0.072 vs. 0.001 ± 0.001 IU/ng/ml, P < 0.001). While the exact mechanism of increased stability of PAI-1 activity in vitiligo is not known, it is likely due to post-translational modifications or increased binding affinity for a stabilizing cofactor. In conclusion, enhanced stability of PAI-1 may contribute to the pathophysiology of vascular disease and associated melanocyte degeneration. Systemic or local treatment with PAI-1 inhibitors may offer a potential treatment alternative to the near orphan status for vitiligo drug development.

Plasminogen activator inhibitor-1 regulates infiltration of macrophages into melanoma via phosphorylation of FAK-Tyr⁹²⁵

Tumor-infiltrating macrophages are potential candidates for cancer immunotherapy. However, the detailed molecular mechanism underlying macrophage infiltration into tumors is poorly understood. Based on our previous finding that plasminogen activator inhibitor-1 (PAI-1) enhances vitronectin-dependent migration of macrophages, we investigated the potential role of PAI-1 in macrophage invasion into melanoma. Experimental evidence obtained from spheroid confrontation assay clearly showed that PAI-1 overexpression significantly enhanced the invasion of RAW 264.7 cells into B16F10 melanoma. We further demonstrated that PAI-1 induces phosphorylation of focal adhesion kinase (FAK) at Tyr(925), which, in turn, mediated the invasion of macrophages into the melanoma. This work further illustrates that low-density lipoprotein receptor related-protein 1 (LRP1) is essential for PAI-1-mediated FAK phosphorylation and macrophage invasion into melanoma. In conclusion, our study demonstrates a novel role of PAI-1 in macrophage invasion into melanoma and provides insights into the underlying molecular mechanism.

Dopamine D₄ receptors inhibit proliferation and migration of vascular smooth muscle cells induced by insulin via down-regulation of insulin receptor expression

Vascular smooth muscle cells (VSMCs) proliferation and migration, which are central in the development of vascular diseases, are regulated by numerous hormones and humoral factors. Activation of the insulin receptor stimulates VSMCs proliferation while dopamine receptors, via D₁ and D₃ receptors, inhibit the stimulatory effects of norepinephrine on VSMCs proliferation. We hypothesize that activation of the D₄ dopamine receptor may also inhibit the proliferation and migration of VSMCs, therefore, inhibit atherosclerosis. Our current study found that insulin increased the proliferation and migration of A10 cells, an effect that was reduced in the presence of a D₄ receptor agonist, PD168077. The negative effect of the D₄ receptor on insulin’s action may be via decreasing insulin receptor expression, because activation of the D₄ receptor inhibited insulin receptor protein and mRNA expressions, indicating that the regulation occured at the transcriptional or post-transcriptional levels. To determine whether or not the inhibition of D₄ receptor on insulin-mediated proliferation and migration of VSMCs has physiological significance, hyper-insulinemic Sprague–Dawley rats with balloon-injured carotid artery were treated with a D₄ agonist, PD168077, (6 mg/kg/d) for 14 days. We found that PD168077 significantly inhibited neointimal formation by inhibition of VSMC proliferation. This study suggests that activation of the D₄ receptor suppresses the proliferation and migration of VSMCs, therefore, inhibit atherosclerosis. The D₄ receptor may be a potential therapeutic target to reduce the effects of insulin on artery remodeling.

The LRP1-independent mechanism of PAI-1-induced migration in CpG-ODN activated macrophages

CpG-oligodeoxynucleotides (CpG-ODNs) induces plasminogen activator inhibitor type-1 (PAI-1) expression in macrophages, leading to enhanced migration through vitronectin. However, the precise role of low-density lipoprotein receptor-related protein 1 (LRP1) in PAI-1 induced migration of macrophages in the inflammatory environment is not known. In this study, we elucidated a novel mechanism describing the altered role of LRP1 in macrophage migration depending on the activation state of the cells. Experimental evidence clearly shows that the blocking of LRP1 function inhibited the PAI-induced migration of resting RAW 264.7 cells through vitronectin but exerted a pro-migratory effect on CpG-ODN-activated cells. We also demonstrate that CpG-ODN downregulates the protein and mRNA levels of LRP1 both in vivo and in vitro, a function that depends on the NF-κB signaling pathway, resulting in reduced internalization of PAI-1. This work illustrates the distinct mechanism that PAI-1-induced migration of CpG-ODN-activated cells through vitronectin depends on the interaction of PAI-1 with vitronectin but not LRP1 unlike in the resting cells, where the migration is LRP1 dependent and vitronectin independent. In conclusion, our experimental results demonstrate the altered function of LRP1 in the migration of resting and activated macrophages in the context of microenvironmental extracellular matrix components.

SERPINE1 expression discriminates site-specific metastasis in human melanoma

Depth of invasion, a quantifier of vertical growth, is a major cutaneous melanoma staging factor. Stromal penetrance requires pericellular proteolysis regulated by the serine protease and matrix metalloproteinase cascades. The serine protease inhibitor SERPINE1, a poor prognosis biomarker in various cancers, promotes tumor progression likely by titrating the extent and local of plasmin-initiated matrix remodelling. SERPINE1 in human melanoma was assessed using tissue arrays that included primary/metastatic tumors and normal skin. SERPINE1 was basal layer-restricted in the normal epidermis. SERPINE1 immunoreactivity was evident in 27/28 primary (96%) and 24/26 metastatic tumors (92%); cutaneous metastases (80%) had significantly elevated SERPINE1 levels compared with low signals characteristic of lymph node lesions. Moderate SERPINE1 expression was a general finding in primary melanoma, whereas reduced or increased SERPINE1 immunolocalization typified metastatic deposits. The amplitude of SERPINE1 expression may impact melanoma site-specific dissemination, with cutaneous metastases representing a high-SERPINE1 tumor subtype.

Plasminogen activator inhibitor type 1 regulates microglial motility and phagocytic activity

Background

Plasminogen activator inhibitor type 1 (PAI-1) is the primary inhibitor of urokinase type plasminogen activators (uPA) and tissue type plasminogen activators (tPA), which mediate fibrinolysis. PAI-1 is also involved in the innate immunity by regulating cell migration and phagocytosis. However, little is known about the role of PAI-1 in the central nervous system.

Methods

In this study, we identified PAI-1 in the culture medium of mouse mixed glial cells by liquid chromatography and tandem mass spectrometry. Secretion of PAI-1 from glial cultures was detected by ELISA and western blotting analysis. Cell migration was evaluated by in vitro scratch-wound healing assay or Boyden chamber assay and an in vivo stab wound injury model. Phagocytic activity was measured by uptake of zymosan particles.

Results

The levels of PAI-1 mRNA and protein expression were increased by lipopolysaccharide and interferon-γ stimulation in both microglia and astrocytes. PAI-1 promoted the migration of microglial cells in culture via the low-density lipoprotein receptor-related protein (LRP) 1/Janus kinase (JAK)/signal transducer and activator of transcription (STAT)1 axis. PAI-1 also increased microglial migration in vivo when injected into mouse brain. PAI-1-mediated microglial migration was independent of protease inhibition, because an R346A mutant of PAI-1 with impaired PA inhibitory activity also promoted microglial migration. Moreover, PAI-1 was able to modulate microglial phagocytic activity. PAI-1 inhibited microglial engulfment of zymosan particles in a vitronectin- and Toll-like receptor 2/6-dependent manner.

Conclusion

Our results indicate that glia-derived PAI-1 may regulate microglial migration and phagocytosis in an autocrine or paracrine manner. This may have important implications in the regulation of brain microglial activities in health and disease.

Complex Regulation of the Pericellular Proteolytic Microenvironment during Tumor Progression and Wound Repair: Functional Interactions between the Serine Protease and Matrix Metalloproteinase Cascades

Spatial and temporal regulation of the pericellular proteolytic environment by local growth factors, such as EGF and TGF-β, initiates a wide repertoire of cellular responses coupled to a plasmin/matrix metalloproteinase (MMP) dependent stromal-remodeling axis. Cell motility and invasion, tumor metastasis, wound healing, and organ fibrosis, for example, represent diverse events controlled by expression of a subset of genes that encode various classes of tissue remodeling proteins. These include members of the serine protease and MMP families that functionally constitute a complex system of interacting protease cascades and titrated by their respective inhibitors. Several structural components of the extracellular matrix are upregulated by TGF-β as are matrix-active proteases (e.g., urokinase (uPA), plasmin, MMP-1, -3, -9, -10, -11, -13, -14). Stringent controls on serine protease/MMP expression and their topographic activity are essential for maintaining tissue homeostasis. Targeting individual elements in this highly interactive network may lead to novel therapeutic approaches for the treatment of cancer, fibrotic diseases, and chronic wounds.

PAI-1: An Integrator of Cell Signaling and Migration

Cellular migration, over simple surfaces or through complex stromal barriers, requires coordination between detachment/re-adhesion cycles, involving structural components of the extracellular matrix and their surface-binding elements (integrins), and the precise regulation of the pericellular proteolytic microenvironment. It is now apparent that several proteases and protease inhibitors, most notably urokinase plasminogen activator (uPA) and plasminogen activator inhibitor type-1 (PAI-1), also interact with several cell surface receptors transducing intracellular signals that significantly affect both motile and proliferative programs. These events appear distinct from the original function of uPA/PAI-1 as modulators of the plasmin-based proteolytic cascade. The multifaceted interactions of PAI-1 with specific matrix components (i.e., vitronectin), the low-density lipoprotein receptor-related protein-1 (LRP1), and the uPA/uPA receptor complex have dramatic consequences on the migratory phenotype and may underlie the pathophysiologic sequalae of PAI-1 deficiency and overexpression. This paper focuses on the increasingly intricate role of PAI-1 as a major mechanistic determinant of the cellular migratory phenotype.

Multifaceted role of plasminogen activator inhibitor-1 in regulating early remodeling of vein bypass grafts

OBJECTIVE

The role of plasminogen activator inhibitor-1 (PAI-1) in vein graft (VG) remodeling is undefined. We examined the effect of PAI-1 on VG intimal hyperplasia and tested the hypothesis that PAI-1 regulates VG thrombin activity.

METHODS AND RESULTS

VGs from wild-type (WT), Pai1(-/-), and PAI-1-transgenic mice were implanted into WT, Pai1(-/-), or PAI-1-transgenic arteries. VG remodeling was assessed 4 weeks later. Intimal hyperplasia was significantly greater in PAI-1-deficient mice than in WT mice. The proliferative effect of PAI-1 deficiency was retained in vitronectin-deficient mice, suggesting that PAI-1's antiproteolytic function plays a key role in regulating intimal hyperplasia. Thrombin-induced proliferation of PAI-1-deficient venous smooth muscle cells (SMC) was significantly greater than that of WT SMC, and thrombin activity was significantly higher in PAI-1-deficient VGs than in WT VGs. Increased PAI-1 expression, which has been associated with obstructive VG disease, did not increase intimal hyperplasia.

CONCLUSIONS

Decreased PAI-1 expression (1) promotes intimal hyperplasia by pathways that do not require vitronectin and (2) increases thrombin activity in VG. PAI-1 overexpression, although it promotes SMC migration in vitro, did not increase intimal hyperplasia. These results challenge the concept that PAI-1 drives nonthrombotic obstructive disease in VG and suggest that PAI-1's antiproteolytic function, including its antithrombin activity, inhibits intimal hyperplasia.